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Applied Catalysis A, General (v.453, #)

Contents (pp. iii-xiv).

Editorial Board (pp. co2).

Catalytic VOCs elimination over copper and cerium oxide modified mesoporous SBA-15 silica by Tanya Tsoncheva; Gloria Issa; Teresa Blasco; Momtchil Dimitrov; Margarita Popova; Selene Hernández; Daniela Kovacheva; Genoveva Atanasova; José M. López Nieto (pp. 1-12).

Display Omitted► The mode of copper–ceria interaction regulates catalytic activity. ► Porous silica support controls the interaction between metal oxide particles. ► Silica porous support changes the effect of Cu/Ce composition.Copper and cerium oxide bi-component materials with different Cu/Ce ratio were prepared using ordered SBA-15 silica as a support and compared with their bulk analogs. The samples were characterized by nitrogen physisorption, XRD, UV-Vis, FTIR, XPS, Raman spectroscopy and TPR with hydrogen. Cyclohexanol conversion was used as a catalytic test to obtain more information for the surface properties of the supported materials. The catalytic properties of the samples were studied in VOCs oxidation using toluene and ethyl acetate as probe molecules. A strong effect of mesoporous silica support and samples composition on the formation of catalytic sites was established.

Keywords: VOCs oxidation; Copper and cerium oxide catalysts; SBA-15 support; Catalytic sites

Selective hydrogenation ofd-mannose tod-mannitol using NiO-modified TiO₂ (NiO-TiO₂) supported ruthenium catalyst by Dinesh Kumar Mishra; Jin-Soo Hwang (pp. 13-19).

Display Omitted► Preparation of a new class of NiO-modified TiO₂ supported ruthenium novel catalyst_. ► Tentative mechanism for reduction ofd-mannose tod-mannitol. ► Kinetics study ofd-mannose hydrogenation tod-mannitol using Ru/NiO-TiO₂ catalyst. ► Deactivation test for the possibility of reusing catalyst Ru/NiO-TiO₂.NiO-modified TiO₂ (NiO-TiO₂) supported ruthenium catalyst Ru/(NiO-TiO₂) is prepared by simple impregnation method and characterized by using energy dispersive X-ray analysis (EDX/EDS), temperature- programmed reduction (TPR), inductively coupled plasma (ICP) mass spectrometry, transmission electron microscopy (TEM), X-ray powder diffraction (XRD) and CO chemisorption. The catalyst Ru/(NiO-TiO₂) is evaluated ind-mannose hydrogenation and hydrogenation experiments to produce a selective productd-mannitol were carried out batch wise in a three-phase laboratory scale reactor. A tentative mechanism for reduction ofd-mannose is presented. The kinetics ofd-mannose hydrogenation tod-mannitol using catalyst Ru/(NiO-TiO₂) was studied. The kinetic data were modeled by zero, first and second-order reaction equations. A set of four experiments was also carried out to test the deactivation of the catalyst. For affording maximumd-mannose conversion, yield and selectivity tod-mannitol, the reaction conditions are optimized.

Keywords: d; -mannose; d; -mannitol; Kinetics; Hydrogenation; Ruthenium; NiO-modified TiO; ₂

High specific surface area metal fluorides as catalysts for the fluorination of 2-chloropyridine by HF by Arnaud Astruc; Cindy Cochon; Samuel Dessources; Stéphane Célérier; Sylvette Brunet (pp. 20-27).

Display Omitted► Heterogeneous catalytic process with HF gas used to prepare 2-fluoropyridine. ► High specific surface area metal fluorides used as catalyst. ► Thermal decomposition of metal trifluoroacetates synthesis used to prepare metal fluoride catalysts. ► Fluorination of 2-chloropyridine involving unsatured metals as active sites with a weak or moderate Lewis acidity.The catalytic fluorination of 2-chloropyridine into 2-fluoropyridine by Cl/F exchange in presence of HF and a metal fluoride as catalyst was investigated. Crystallized metal fluorides (BaF₂, MgF₂, CaF₂, ZnF₂, LaF₃ and CeF₃) with significant specific surface area between 65 and 125m²g⁻¹ were prepared by thermal decomposition of corresponding metal trifluoroacetates at 350°C under nitrogen. These solids were stable under fluorination operating conditions involved in the formation of 2-fluoropyridine. An important gain in activity for the catalytic fluorination of 2-chloropyridine was obtained with these metal fluorides compared to corresponding oxides used as catalyst. BaF₂ and MgF₂ were the most active catalysts for the fluorination of 2-chloropyridine. The higher activities are in relation with the weak or moderate strength of Lewis acidity of the active sites, measured by CO adsorption followed by IR spectroscopy.

Keywords: Fluoride metal catalyst; Trifluoroacetate metal fluoride; Fluorination; 2-Chloropyridine; 2-Fluoropyridine

Regeneration of deactivated catalysts coated on foam and monolith: Example of Pd/C for nitrobenzene hydrogenation by Florica Simescu-Lazar; Valérie Meille; Stéphanie Pallier; Eric Chaînet; Claude De Bellefon (pp. 28-33).

Display Omitted► Simple methods to regenerate the used Pd/carbon-coated catalysts are described. ► Three methods have been tested: electrochemical, oxidation and oxygen plasma. ► The electrochemical treatment allows the complete regeneration of the Pd/C catalyst. ► Complete recovery of initial activities for nitrobenzene hydrogenation is obtained. ► No modification and no degradation of the textural properties of carbon are observed.The deactivation and regeneration of Pd/carbon coated support catalysts, used during nitrobenzene hydrogenation, were studied. Three methods have been tested: electrochemical treatment, chemical oxidation and oxygen plasma treatment. The regenerated catalysts were characterized by physisorption of nitrogen (BET method) and were compared with the activities of fresh catalysts. It was found that the electrochemical treatment allows the complete regeneration of the catalyst, without any modification of textural properties. Simple chemical oxidation did not allow the activity recovery of Pd catalysts and led to modification of the textural properties of carbon. Finally, the catalyst may be regenerated also by plasma method, albeit with some increase of the pore diameter.

Keywords: Carbon washcoating; Palladium; Deactivation; Electrochemical regeneration; Oxidation; Plasma regeneration; Structured catalytic reactors

Methanol steam reforming: CO₂-selective Pd₂Ga phases supported on α- and γ-Ga₂O₃ by Harald Lorenz; Ramona Thalinger; Eva-Maria Köck; Michaela Kogler; Lukas Mayr; Daniela Schmidmair; Thomas Bielz; Kristian Pfaller; Bernhard Klötzer; Simon Penner (pp. 34-44).

Display Omitted► Formation of catalytically active intermetallic Pd₂Ga phases on α-Ga₂O₃ and γ-Ga₂O₃. ► CO₂-selective state in methanol steam reforming after entering the intermetallic state. ► Polymorph-dependent catalytic performance in methanol steam reforming. ► Reduction of Ga₂O₃ polymorphs has no influence on the catalytic performance. ► A bi-functional synergism between Pd₂Ga phase and support is prevalent.A set of different Pd/Ga₂O₃ catalysts has been tested as suitable CO₂-selective catalysts in methanol steam reforming, formaldehyde steam reforming and formic acid decomposition. Special focus was put on two different polymorphic forms of Ga₂O₃, namely α-Ga₂O₃ and γ-Ga₂O₃ and their comparison to the use of the more common β-Ga₂O₃ as oxide support of small Pd particles. The formation of eventually CO₂-selective intermetallic Pd–Ga phases started at around 523K on both supports. Pd₂Ga at low temperatures (between 523K and 673K) and generally PdGa at higher temperatures (at and above 673K) were the only intermetallic phases observed. Both thermodynamically metastable oxide supports transformed into the stable β-Ga₂O₃ structure at 873K reduction temperature. In contrast to previous studies, a highly CO₂-selective state in methanol steam reforming (CO₂ selectivity>70%) could be established on both catalysts after reduction at 673K (α-Ga₂O₃) and 523K (γ-Ga₂O₃), where the active state of the catalysts can be characterised as Pd₂Ga/α-Ga₂O₃ and Pd₂Ga/γ-Ga₂O₃, respectively. α-Ga₂O₃ itself is reasonably CO₂-selective in methanol steam reforming (∼80%), although not very active. In contrast, the γ-Ga₂O₃ polymorph is neither CO₂-selective, nor active and resembles the behaviour of β-Ga₂O₃. The high CO₂-selectivity of α-Ga₂O₃ is explained in terms of a higher surface basicity alongside efficient decarboxylation of intermediary formed formic acid. As crucial parameters for the observed CO₂-selectivity in methanol steam reforming, decarboxylation of formic acid and oxidation of formaldehyde proceeding efficiently via a low-temperature reaction channel over either oxide-supported Pd₂Ga intermetallic catalysts were identified.

Keywords: Intermetallic compounds; Formic acid decomposition; X-ray diffraction; CO; ₂; selectivity; Pd; ₂; Ga

Catalytic photodegradation of Congo red in aqueous solution by Ln(OH)₃ (Ln=Nd, Sm, Eu, Gd, Tb, and Dy) nanorods by Shuyang Liu; Yun Cai; Xiaoyan Cai; He Li; Fei Zhang; Qiuying Mu; Yongjun Liu; Yude Wang (pp. 45-53).

Display Omitted► Ln(OH)₃ nanorods are fabricated by a facile hydrothermal method. ► The Ln(OH)₃ nanorods are crystalline with hexagonal crystal structure. ► The Ln(OH)₃ nanorods exhibit outstanding catalyzed degradation performance for Congo red.The stable and crystalline phase pure Ln(OH)₃ (Ln=Nd, Sm, Eu, Gd, Tb, and Dy) nanorods were synthesized by a facile hydrothermal method starting with corresponding rare-earth chloride hexahydrate LnCl₃·6H₂O, ammonia NH₃·H₂O and cationic surfactantcetyltrimethylammonium bromide (CTAB). X-ray powder diffraction (XRD) and transmission electron microscopy (TEM) were used as the structural probes in order to check the phase purity, and to examine the morphologies and microstructures of the synthesized compounds. The structural analysis reveals that the obtained compounds are rare-earth hydroxides with one-dimensional (1D) rod-like nanostructures. The formation mechanism of the Ln(OH)₃ nanorods was also proposed. The photoactivity of Ln(OH)₃ (Ln=Nd, Sm, Eu, Gd, Tb, and Dy) nanorods was tested by measuring the degradation of azo dye Congo red (CR). The results show an excellent removal capacity for organic pollutants CR from wastewater, making them promising candidates for the wastewater treatment.

Keywords: Ln(OH); ₃; nanorods; Crystalline; Congo red; Catalyzed degradation; Transmission electron microscopy

Fabrication of smalll-threonine capped nickel nanoparticles and their catalytic application by Nazar Hussain Kalwar; Sirajuddin; Syed Tufail Hussain Sherazi; Abdul Rauf Khaskheli; Keith Richard Hallam; Thomas Bligh Scott; Zulfiqar Ali Tagar; Syeda Sara Hassan; Razium Ali Soomro (pp. 54-59).

Display Omitted► Present study describes a new and simple approach to fabricatel-threonine capped Ni NPs. ► Our experiments showed development of highly efficient heterogeneous catalysts for reduction degradation of congo red dye. ► Congo red dye has been used as model compound as it gives different color shades in degraded and undegraded forms. ► Electron microscopy results in the formation of very small Ni NPs with homogeneous sizes and shapes and narrower size distributions.A facile and green seed mediated growth approach for fabrication of well dispersedl-threonine derived nickel nanoparticles (Ni NPs) in an aqueous medium via a modified borohydride reduction method is described.l-Threonine molecules served to organize the nanoscale composites in the form of well dispersed Ni NPs. The basic pH 8.5 was found to favor the formation of spherical and well dispersed Ni NPs as shown in transmission electron microscopy (TEM) micrographs. Freshly prepared Ni NPs possess the nanoscale dimension of 1.68–5.06nm, as determined from atomic force microscopy (AFM) and TEM data. The Ni NPs thus prepared were used for their catalytic potential in the reduction of congo red (CR) dye selected as a model reagent. The results revealed negligible reduction of dye in the absence of Ni NPs. Conversely the addition of only 0.2mg Ni NPs produced 100% reduction/degradation efficiency. The used Ni NPs were recovered and reutilized several times for reducing CR without any loss of activity. The current findings are equally extendable for safeguarding the aquatic environment against the pollution caused by other dyes via a facile, highly economical, rapid and efficient reduction/degradation method based on the catalytic potential of Ni NPs.

Keywords: l; -Threonine; Sodium borohydride; Nickel nanoparticles; Catalytic degradation; Congo red

Role of support lattice oxygen on steam reforming of toluene for hydrogen production over Ni/La_0.7Sr_0.3AlO3−_δ catalyst by D. Mukai; S. Tochiya; Y. Murai; M. Imori; T. Hashimoto; Y. Sugiura; Y. Sekine (pp. 60-70).

Display Omitted► Catalytic steam reforming of toluene for hydrogen production over Ni/perovskite. ► Higher activity and lower coke formation on Ni/La_0.7Sr_0.3AlO3−_δ catalyst. ► Transient response using H₂¹⁸O revealed lattice oxygen played an important role. ► The rate-determining step of the reaction depended on the activity of lattice oxygen. ► Coke deposited was removed oxidatively by lattice oxygen in/on the perovskite support.Catalytic steam reforming of aromatic hydrocarbon using toluene as a model compound for hydrogen production over Ni catalyst supported on perovskite oxide was investigated. Ni/La_0.7Sr_0.3AlO3−_δ catalyst showed higher activity and lower coke formation than other Ni-supported catalysts on hydrogen production by toluene steam reforming. Transient response using H₂¹⁸O revealed that the surface lattice oxygen of La_0.7Sr_0.3AlO3−_δ worked as active oxygen by redox mechanism at 873K. Coke deposited on the catalyst surface after the reaction was removed oxidatively by lattice oxygen in/on the perovskite support. The working temperature of the lattice oxygen depended on the catalyst support characteristics. Analyses of the support structure by XRD and XPS revealed that the lattice distortion and the increasing of oxygen vacancies by partial Sr substitution enhanced the redox ability of lattice oxygen. Arrhenius plots showed that the rate-determining step of the reaction changed at a certain temperature at which the lattice oxygen was able to contribute to reaction over Ni/La_0.7Sr_0.3AlO3−_δ and Ni/LaAlO₃. The dependence of the reaction rate on the partial pressure of H₂O and toluene revealed that the rate-determining step might be the formation of hydroxyl group on the support surface in a lower temperature region and the adsorption of toluene on the Ni surface in a higher temperature region.

Keywords: Steam reforming of toluene; Ni catalyst; Perovskite-type oxide support; Partial Sr substitution; Lattice oxygen; Low coke formation

Carbonization of nickel catalysts and its effect on methane dry reforming by V.Yu. Bychkov; Yu.P. Tyulenin; A.A. Firsova; E.A. Shafranovsky; A.Ya. Gorenberg; V.N. Korchak (pp. 71-79).

Display Omitted► Conditions of Ni catalysts carbonization during methane dry reforming were established. ► Temperature hysteresis of carbon accumulation was observed. ► At least, two carbon forms cause complicated deactivation behavior. ► Carbonization rate depends on Ni particle size.Formation and reactivity of carbon in Ni/Al₂O₃ catalysts of methane dry reforming (MDR) have been studied at their interaction with CH₄, CO₂, H₂ or CH₄–CO₂ mixture using thermogravimetry and mass-spectrometry. Temperature ranges of carbon accumulation and removal have been established, with a temperature hysteresis of carbon accumulation being observed in CH₄–CO₂ mixture. The primary deposited carbon blocks MDR activity, but the deactivation is reversible under MDR conditions. The primary carbon transforms into the secondary nanofiber carbon which is stable under MDR conditions and less blocks MDR activity. Effect of Ni catalysts deactivation because of carbonization can be reduced, if at the initial stage the catalyst does not contact with the reaction mixture at temperatures below 700°C. The rate of carbon accumulation was increased with increasing Ni particle size from 2 to 5nm.

Keywords: CO; ₂; reforming of methane; Nickel catalysts; Thermogravimetry; Carbon deposition; Catalyst deactivation; Carbon nanofibers

Preparation and characterization of TiO₂ coated with a thin carbon layer for enhanced photocatalytic activity under fluorescent lamp and solar light irradiations by M.A. Nawi; I. Nawawi (pp. 80-91).

Display Omitted► Carbon coated TiO₂ was prepared by using ENR-50 as carbon precursor. ► Uniform thin graphitic C coating of 0.68nm on TiO₂ particles. ► Photocatalytic activity was greatly improved under 45-W fluorescent and solar light. ► Enhanced photocatalytic activity was due to low recombination ofecb− and h⁺. ► Possess stable photocatalytic efficiency over extended recycled applications.Carbon (C) coated TiO₂ with C content between 0.20% and 1.09% were prepared by calcination of various mixtures of TiO₂ and epoxidized natural rubber (ENR-50) under N₂ atmosphere between 470°C and 620°C. The optimum calcination temperature and C content was 560°C and 0.25±0.01%, respectively with the estimated C coating thickness of 0.68nm. The process did not change its BET surface area and induce any phase transformation. Photocatalytic activity of C coated TiO₂ was better than pristine TiO₂ for the degradation of anionic reactive red 4 (RR4) dye by more than 3 times, phenol by 1.1 times and cationic methylene blue (MB) by 1.5 times under a 45-W household fluorescent lamp irradiation while under solar irradiation, its photocatalytic activity with respect to pristine TiO₂ improved by 5.5, 3.5 and 2 times, respectively. Coating of more than 1% C on TiO₂ changed its photocatalytic activity either at par or less than that of the pristine TiO₂. The observed photocatalytic improvement was due to the significant decrease in the electron–hole recombination process as observed for the optimum C coated sample.

Keywords: Carbon coated TiO; ₂; Epoxidized natural rubber; Reactive red 4 dyes; Ethylene blue and phenol

Synthesis and characterization of MEL and FAU zeolites doped with transition metals for their application to the fine chemistry under microwave irradiation by Federico Azzolina Jury; Isabelle Polaert; Lionel Estel; Liliana B. Pierella (pp. 92-101).

Display Omitted► MEL and FAU zeolites were synthesized and doped with transition metals. ► The doped zeolites were characterized. ► The doped zeolites dielectric properties were measured and interpreted. ► The catalytic activity of zeolites was evaluated under microwave heating. ► Microwave and conventional heating were compared for the studied reaction.Doped zeolites with transition metals were prepared for their application to the synthesis of chemical compounds under microwave irradiation. The zeolite crystalline structures were verified by XRD. Their surface areas were determined by the BET method. Lewis and Brönsted acid sites were quantified by FTIR of adsorbed pyridine in zeolites. The characterization of acidic properties revealed the generation of new Lewis acid sites after transition metal incorporation into zeolites. The dielectric properties of compacted zeolites were measured by using a reflection method. The temperature profiles of these compacted beds were measured during heating under microwave irradiation. Heating phenomena in zeolites were interpreted using a modified Debye model. Two main dielectric mechanisms were determined in zeolites: rotational polarization phenomenon and interfacial polarization. The selective catalytic oxidation of styrene with hydrogen peroxide was studied over zeolites doped with transition metals in a batch system, under conventional and microwave heating. Benzaldehyde was the main product in all the samples under study. Styrene conversion showed an important influence of the transition metal nature and content and so, the kind of zeolite structure used. With the present experimental conditions, no difference was proved between microwave and conventional heating neither on activity nor on selectivity.

Keywords: Zeolites; Dielectric properties; Microwave; Styrene oxidation

Steam reforming and oxidative steam reforming of methanol and ethanol: The behaviour of LaCo_0.7Cu_0.3O₃ by A. Glisenti; A. Galenda; M.M. Natile (pp. 102-112).

Display Omitted► For the first time the reactivity of a Cu doped LaCoO₃ (LaCo_0.7Cu_0.3O₃) with alcohols is investigated. ► The reactivity in steam reforming and oxidative steam reforming is compared. ► The reactivity is very promising and high conversions are obtained. ► LaCo_0.7Cu_0.3O₃ is a promising active material for the anodic compartment of IT-SOFCs. ► LaCo_0.7Cu_0.3O₃ allows obtaining hydrogen from simple alcohols, in sustainable way.LaCo_0.7Cu_0.3O₃ perovskite powder was prepared by means of the citrate method and treated at different temperatures from 873 to 1323K. The samples were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), temperature programmed reduction (TPR), temperature programmed desorption (TPD, O₂-TPD), and scanning electron microscopy (SEM); the BET specific surface area was also determined. The reactivity of the perovskite with methanol and ethanol was investigated under steam reforming and oxidative steam reforming conditions and correlated to its chemical and structural properties. Different oxygen/alcohol molar ratios were used to study the influence of oxygen on catalytic activity and products distribution. LaCo_0.7Cu_0.3O₃ begins to be active in alcohol steam reforming at about 523K. The catalyst calcined at 873K shows the higher conversion in methanol steam reforming. Ethanol steam reforming conversion, in contrast, is rather low and not significantly affected by the catalyst calcination temperature. The conversions increase when oxygen is present reaching 93% for methanol and 78% for ethanol. Beside the steam reforming and oxidative steam reforming, other secondary reaction paths occur: methanol decomposition and ethanol dehydrogenation.

Keywords: Perovskite; Oxidation; Hydrogen; SOFC; Oxidative steam reforming; Methanol; Ethanol

Microstructure and size effects in Pt/C and Pt₃Ni/C electrocatalysts synthesized in solutions based on binary organic solvents by V.E. Guterman; A.Yu Pakharev; N.Yu Tabachkova (pp. 113-120).

Display Omitted► Pt/C and Pt₃Ni/C catalysts synthesized in solutions based on two-component organic solvents. ► An electrochemical surface area of catalysts does not correlate with nanoparticle sizes. ► A downsizing the Pt and Pt–Ni alloy nanoparticles favors agglomeration processes. ► Optimal composition of binary solvent allows synthesizing optimal microstructure.Pt/C and Pt₃Ni/C electrocatalysts that contained 12–27wt.% Pt were prepared via the reduction of precursors in a binary solvent. The metal loading, average size of the Pt or Pt alloy nanoparticles, and electrochemical surface area (ECSA) of the obtained catalysts were found to be dependent on the choice of organic components and their relative amounts in the starting solution. Downsizing the nanoparticles was shown to favor the agglomeration processes that counterbalance the expected increase in the electrochemical surface area. This adverse effect of downsizing can be reduced through selection of the optimum binary solvent composition.

Keywords: Platinum alloy; Nanoparticle; Size effect; Electrochemical surface area; Fuel cell; Electrocatalyst

Role of oxygen vacancies in the basicity of ZnO: From the model methylbutynol conversion to the ethanol transformation application by Charlotte Drouilly; Jean-Marc Krafft; Frédéric Averseng; Hélène Lauron-Pernot; Delphine Bazer-Bachi; Céline Chizallet; Vincent Lecocq; Guylène Costentin (pp. 121-129).

Display Omitted► The basicity of ZnO can be tuned adapting the nature of the atmosphere of pre-treatment. ► The basic conversion correlates with the variation in oxygen vacancies concentration (EPR). ► The electronic density of the basic oxygens is increased by the formation of oxygen vacancies. ► The impact of the oxidative pretreatment on the activity level depends of the reaction temperature.The parameters governing the basic reactivity of kadox and ex-carbonate zinc oxide samples towards alcohol conversion were investigated varying the atmosphere of pre-treatment for a model reaction, the methylbutynol (MBOH) conversion, and the ethanol conversion reaction, a transformation of potential higher industrial impact. The catalytic properties of ZnO can thus be tuned: enhanced activities were measured after a pre-treatment performed under inert gas as compared to oxidative conditions. If no significant variation of residual hydroxylation nor carbonation can account for this behaviour, a quantitative correlation between the variation of MBOH conversion induced by the different atmosphere of pre-treatment with that of the concentration in oxygen vacancies characterized by in situ EPR found, showing that oxygen vacancies play a key role towards basic reactivity. In fact, the electronic density of the oxygen of the active acid/base pair is directly influenced by the electron release or capture associated to the formation or filling up of oxygen vacancies, respectively. On the kadox samples, the presence of an additional weaker active site is responsible for the residual activity of kadox sample in the absence of oxygen vacancies. The existence and location on specific crystallographic faces of these sites are discussed in relation with the different morphologies of the two samples and with their different affinity with CO₂. Even if the occurrence of oxygen vacancies still governs the conversion level for ethanol transformation, the reactivity inhibition after oxidative pre-treatment is less pronounced due to the higher reaction temperature that limits the efficiency of oxygen vacancies filling-up under oxidative atmospheres. The nature of active sites leading to the formation of acetaldehyde and ethylene is also discussed.

Keywords: ZnO; EPR; In situ; Pre-treatment; Oxygen vacancy; MBOH; Ethanol

PdCu alloy nanoparticles on alumina as selective catalysts for trichloroethylene hydrodechlorination to ethylene by Beteley T. Meshesha; Noelia Barrabés; Jordi Llorca; Anton Dafinov; Francisco Medina; Karin Föttinger (pp. 130-141).

Display Omitted► Catalyst preparation by polyol nanoparticle synthesis and conventional impregnation. ► Catalysts performance governed by Pd–Cu interaction and particle size. ► Higher selectivity to ethylene on larger Pd particles. ► Nearly complete ethylene selectivity on bimetallic Pd-Cu alloy catalysts. ► Pd-Cu alloy formation depends on synthesis protocol.PdCu bimetallic catalysts supported on alumina were prepared by different common impregnation protocols and by a polyol nanoparticles synthesis route. These materials were studied in order to establish the relationship between structure, particle size, Pd–Cu interaction and catalytic activity/selectivity in the hydrodechlorination of trichloroethylene (TCE) in gas phase. The surface properties and the interaction between Cu and Pd in the bimetallic particles, as well as their catalytic behaviour are strongly influenced by the preparation protocol. Depending on the synthesis, PdCu alloy formation or isolated phases were observed. The presence of isolated Pd particles leads to high ethane selectivity, whereas upon alloy formation or strong interaction between Pd and Cu a higher ethylene yield was obtained. By the nanoparticles polyol synthesis, Pd-Cu alloy formation was obtained, leading to total selectivity to ethylene in the TCE hydrodechlorination reaction. On the Pd monometallic catalysts larger particle size resulted in higher levels of ethylene formation.

Keywords: PdCu bimetallic catalyst; Nanoparticles; Alloy; High resolution TEM; Temperature-programmed reduction

Silica/clay organo-heterostructures to promote polyethylene–clay nanocomposites by in situ polymerization by Paula A. Zapata; Carolina Belver; Raúl Quijada; Pilar Aranda; Eduardo Ruiz-Hitzky (pp. 142-150).

Display Omitted► Organo-heterostructures were used for preparing clay–polyethylene nanocomposites by in situ polymerizations. ► The catalytic activities of supported systems were comparable to a homogeneous system. ► The polymer particles morphology improved with the presence of the clay in the polymerization. ► The molecular weight of the polymers increase for the supported systems.Two clay organo-heterostructures have been prepared and employed as fillers and catalyst supports for the development of polyethylene–clay nanocomposites. The new silica–clay organo-heterostructures have been obtained from two organoclays modified with tetramethoxysilane. In contrast to related heterostructures reported previously the organic moieties are not removed by heating and their presence intends to confer hydrophobicity to the interlayer region of the clay, even after delamination by hydrolysis-polymerization of the alkoxysilane takes place. These organo-heterostructures were used for preparing clay–polyethylene nanocomposites by in situ polymerizations in which the organo-heterostructures were added together with the metallocene catalyst, and by using the silica–clay as support for the metallocene catalysts. The polymers formed when the organo-heterostructures were used as support for the catalyst have higher molecular weights than the standard polyethylene formed under homogeneous conditions. Moreover, the presence of the inorganic silica network developed in the interlayer region of the organoclay favours the existence of a larger organophilic region in which it is possible to accommodate both the catalyst and the monomer, and hence when the polymer grows in this environment it can assist in the exfoliation of the clay layers inside the polyethylene matrix. The polymer particle morphology improved with the presence of the clay in the polymerization. The molecular weight for support systems presented an increasing ca. 40% compared to neat PE, and by TEM it was found that the clay layers were well dispersed in the PE matrix.

Keywords: Metallocene catalysts; Clay-based heterostructures; Polymer–clay nanocomposites; Polyethylene; Support catalysts

A versatile solvent-free azide–alkyne click reaction catalyzed by in situ generated copper nanoparticles by Atchutarao Pathigoolla; Ramachandra P. Pola; Kana M. Sureshan (pp. 151-158).

Display Omitted► In situ generated copper nanoparticles or their clusters catalyzed azide alkyne click reaction under ambient and open air conditions. ► This reaction is facile in organic medium, aqueous medium and solvent free conditions. ► Rate of the reaction is faster and product can be isolated by simple filtration. ► This methodology is environmentally benign and green.A general, high-yielding and efficient methodology for the copper catalyzed azide–alkyne cycloaddition (CuAAC) reaction catalyzed by in situ generated copper nanoparticles (CuNPs) or their clusters is reported. This simple reaction is facile in water, organic solvents and solvent-free conditions under ambient, open-air conditions and requires no special reaction conditions and chromatographic separation.

Keywords: Abbreviations; CuAAC; copper catalyzed azide–alkyne cycloaddition; CuNPs; copper nanoparticles; AAC; azide–alkyne cycloadditionClick reaction; Cycloaddition; Copper nanoparticles; Solvent-free; Green chemistry

Rhodium complex encapsulated functionalized hexagonal mesoporous silica for heterogeneous hydroaminomethylation by N. Sudheesh; Ram S. Shukla (pp. 159-166).

Display Omitted► HRh(CO)(PPh₃)₃ encapsulated in functionalized HMS. ► Hydroaminomethylation with high conversion and selectivity to amine. ► Recyclable upto five times without loss in activity.HRh(CO)(PPh₃)₃ complex was encapsulated into the pores of amino functionalized hexagonal mesoporous silica. The catalyst was characterized by physico-chemical techniques like P-XRD,³¹P-CPMAS NMR, FT-IR, SEM, ICP and N₂ adsorption analysis. The catalyst was active for hydroaminomethylation and a variety of alkenes and amines were used as reactants for hydroaminomethylation. The catalyst afforded to achieve 100% conversion with high (>95%) selectivity to corresponding amines. Parametric variations were performed by taking 1-hexene and morpholine as representative reactants for the study of catalyst amount, temperature, pressure and 1-hexene:morpholine ratio. Significant amounts of aldehydes and enamines were observed during the course of the reaction indicating that there could be two possible rate determining steps. The catalyst was effectively recycled up to five times without much loss in its activity and selectivity.

Keywords: Hexagonal mesoporous silica; Rhodium complex; Hydroaminomethylation; Heterogeneous catalyst

Influence of iridium content on the behavior of Pt-Ir/Al₂O₃ and Pt-Ir/TiO₂ catalysts for selective ring opening of naphthenes by María A. Vicerich; Viviana M. Benitez; Catherine Especel; Florence Epron; Carlos L. Pieck (pp. 167-174).

Display Omitted► Decalin ring opening using Pt-Ir/Al₂O₃ and Pt-Ir/TiO₂ catalysts was studied. ► Titania supported catalysts were less active than their alumina supported counterparts. ► The methylcyclopentane ring opening reaction was found to occur through a partially selective mechanism. ► The activity for decalin ring opening increased both with metal loading and reaction temperature level.The influence of Ir content on the properties of Pt-Ir/Al₂O₃ and Pt-Ir/TiO₂ catalysts for selective ring opening of naphthenes was studied. It was found that these catalysts display a strong Pt–Ir interaction but only a weak metal–support interaction. Catalyst acidities depend on the metal loading, but opposite effects were observed on alumina (decrease) or titania (increase) as the metal loading increased. The results obtained from test reactions (cyclohexane dehydrogenation and cyclopentane hydrogenolysis) showed that titania supported catalysts were less active than their alumina supported counterparts. This behavior could be due to the partial blockage of metallic sites by migrated TiO_x species and the sinterization of metallic phase during the reduction step. The methylcyclopentane ring opening reaction was found to occur through a partially selective mechanism, and an increase in activity as the Ir loading increased was observed. The selective mechanism was favored by higher total metal loadings, possibly due to an increase in the size of metallic aggregates. Alumina supported catalysts present higher ring opening selectivities. The activity for decalin ring opening increased both with metal loading and reaction temperature level.

Keywords: Selective ring opening; Pt–Ir; Decalin; Methylcyclopentane

CO₂ cycloaddition of styrene oxide over MOF catalysts by Jun Kim; Se-Na Kim; Hoi-Gu Jang; Gon Seo; Wha-Seung Ahn (pp. 175-180).

Display Omitted► Representative MOFs were prepared and tested for CO₂ cycloaddition to styrene epoxide. ► Catalytic activities were correlated with their acidity/basicity examined by NH₃- and CO₂-TPD. ► Reaction mechanism for 3 different cases were proposed. ► Catalyst stabilities were evaluated by hot-filtring and recycle test.Metal organic framework (MOF) structures of UIO-66, UIO-66-NH₂, Mg-MOF-74, MIL-101, CuBTC, ZIF-8, IRMOF-3, and MOF-5 having different acid/base properties were prepared and tested for their catalytic activity in the CO₂ cycloaddition to styrene epoxide using a high-pressure batch reactor. The high crystallinity and excellent textural properties of the prepared MOF materials were confirmed by XRD and the N₂ adsorption–desorption isotherms at 77K. Their catalytic cycloaddition activities were found to be well correlated with the Lewis acid/base distributions of the materials examined by NH₃- and CO₂-TPD, respectively, such that the concurrent presence of Lewis acid and base sites were desirable for high catalytic activity. For a given catalyst weight, UIO-66-NH₂ showed the best catalytic performance among the MOF samples tested with close to 100% selectivity to carbonate in chlorobenzene under relatively mild reaction conditions (2.0MPa, 373K). UIO-66-NH₂ could be reused 3 times without losing catalytic activity in a truly heterogeneous mode without structural deterioration, and it also exhibited excellent cycloaddition activities for different epoxide substrates as well.

Keywords: Metal organic frameworks (MOFs); CO; ₂; cycloaddition; Lewis acid/base; NH; ₃; - and CO; ₂; -TPD; UIO-66-NH; ₂

Selective oxidation of benzyl alcohol over TiO₂ nanosheets with exposed {001} facets: Catalyst deactivation and regeneration by Xiaoyang Pan; Nan Zhang; Xianzhi Fu; Yi-Jun Xu (pp. 181-187).

Display Omitted► The stability of TiO₂-001 photocatalyst is investigated. ► The TiO₂-001 photocatalyst suffers from a serious deactivation. ► The oxygen vacancies formation is responsible for the deactivation. ► A water refluxing method is able to regenerate the deactivated TiO₂-001.Increasing interest has been devoted to synthesizing TiO₂ nanocrystals with reactive {001} facets (TiO₂-001) as photocatalysts for potential applications, but relative research works on the photocatalytic stability of TiO₂-001 nanocrystals are rarely reported. Here, we have prepared TiO₂-001 using a facile hydrothermal method and studied its photocatalytic activity and stability toward selective oxidation of benzyl alcohol. The results show that TiO₂-001 suffers from a serious deactivation. By a series of joint techniques, we find that lots of oxygen vacancies have been formed on the surface of the used TiO₂-001, which is responsible for the loss in photoactivity of TiO₂-001. A possible formation mechanism of the oxygen vacancies on the TiO₂-001 surface is proposed. The regeneration of the catalyst can be realized by simply refluxing the used TiO₂-001 in water at 100°C.

Keywords: Selective oxidation; {0; 0; 1} facets of TiO; ₂; Photocatalyst deactivation; Photocatalyst regeneration

Highly efficient and selective oxidation of various substrates under mild conditions using a lanthanum-containing polyoxometalate as catalyst by Shen Zhao; Yueqing Jia; Yu-Fei Song (pp. 188-194).

Display Omitted► The DA-La(PW₁₁)₂ is highly efficient and selective for oxidation of various substrates. ► The DA-La(PW₁₁)₂ acts as a dual trapping catalyst for both substrate and the oxidizing agent. ► The catalyst of DA-La(PW₁₁)₂ is recyclable.A lanthanum-containing polyoxometalate (POM) of DA₁₁[La(PW₁₁O₃₉)₂] (denoted as DA-La(PW₁₁)₂; DA=Decyltrimethylammonium cation) is highly efficient and selective for oxidation of various substrates including alkenes, alkenols, sulfides, silane and alcohol with only one equiv. H₂O₂ as oxidant at 25°C, and the POM catalyst can be easily recovered and reused for ten times without obvious decrease of catalytic activity and the yields for catalyst recovery are all above 95%. The epoxidation of cis-cyclooctene proceeds efficiently in 98% yield with only 0.08mol% of DA-La(PW₁₁)₂, and the turnover number (TON) can reach as high as 1200 at 25°C.

Keywords: Polyoxometalate; Lanthanum; Oxidation

Shape-selective alkylation of biphenyl with propylene using zeolite and amorphous silica–alumina catalysts by Venkat Ramana Rao Pendyala; Gary Jacobs; Wilson D. Shafer; Robert A. Keogh; Jungshik Kang; Dennis E. Sparks; Burtron H. Davis (pp. 195-203).

Display Omitted► Shape-selective alkylation of biphenyl with propylene was achieved over HMOR. ► Zeolite shape selectivity was governed by geometry of channels and pore entrances. ► Biphenyl alkylation proceeds through 4-IPB in a consecutive mechanism. ► 4-IPB is only a source in step 2 for further alkylation to form 4,4′-DIPB.The influence of zeolite structure for the alkylation of biphenyl with propylene was studied over various zeolites such as HY, HZSM-5, and dealuminated mordenite (DMOR), as well as amorphous SiO₂/Al₂O₃, in a stirred tank reactor. Biphenyl conversion was found to increase with reaction time for HZSM-5 and DMOR zeolites and reach a leveling off in 4h, whereas for HY and amorphous SiO₂/Al₂O₃ a leveling off was reached within an hour. DMOR displayed the highest selectivity for 4,4′-diisopropylbiphenyl (4,4′-DIPB) even at temperatures as high as 300°C, whereas for HY, HZSM-5 and amorphous SiO₂/Al₂O₃ selectivities fell in the range of 10–35%; they were significantly lower than observed for DMOR. These differences in selectivity might be due to the structure and pore channels of the zeolites. DMOR was found to be an active catalyst, the selectivity for 4-isopropylbiphenyl (4-IPB) and (4,4′-DIPB) was high among isopropylbiphenyl (IPB) and diisopropylbiphenyl (DIPB) isomers, respectively, indicating DMOR possesses shape-selectivity. The selectivity of 4,4′-DIPB increased with time, while the corresponding selectivity of 4-IPB decreased for DMOR catalyst. Alkylation of biphenyl with propylene occurred with predominant formation of 4-IPB in the first step. 4-IPB is only a source in the second step of alkylation of biphenyl with propylene for the formation of 4,4′-DIPB, while 3-IPB does not participate in the formation of DIPB isomers.

Keywords: Alkylation; Biphenyl; Propylene; Mordenite; Zeolites; Shape-selectivity

Ruthenium-catalysed codimerisation of myrcene with methyl acrylate: Catalyst screening and mechanistic discussions by Arno Behr; Leif Johnen; Nils Rentmeister (pp. 204-212).

Display Omitted► An approach to novel C₁₃ esters for the flavour and fragrance industry was performed. ► Homogeneous catalysts containing ruthenium appeared to be very active. ► Systematic optimisations concerning the different reaction parameters were investigated. ► Selection criteria for capable ruthenium complexes could be derived.The codimerisation of 1,3-dienes and acrylic compounds is a feasible strategy for the synthesis of functionalised alkenes. In this work, a direct approach to novel C₁₃ esters for the flavour and fragrance industry was performed by codimerisation of myrcene and methyl acrylate. Thus, a further contribution was demonstrated for the use of terpenes as a biobased feedstock for fine chemicals. Different homogeneous ruthenium catalysts showed high activities in the target reaction. Systematic optimisation of the reaction parameters were carried out, resulting in high regioselectivities and yields. A comparison of codimerisation products described in the literature and the observed C₁₃ esters led to mechanistic discussions.

Keywords: Codimerisation; Homogeneous catalysis; Renewable resources; Ruthenium; Terpenoids

Stable vapor-phase conversion of tetrahydrofurfuryl alcohol into 3,4-2 H-dihydropyran by Satoshi Sato; Jun Igarashi; Yasuhiro Yamada (pp. 213-218).

Display Omitted► Conversion of tetrahydrofurfuryl alcohol to 3,4-2 H-dihydropyran was studied. ► Alumina effectively catalyzed the reaction, but along with decay in the activity. ► Supported CuO together with H₂ flow stabilizes the catalytic activity of alumina. ► The amount of coke deposited is reduced over the Al₂O₃-supported CuO in H₂ flow.Vapor-phase synthesis of 3,4-2 H-dihydropyran (DHP) from tetrahydrofurfuryl alcohol (THFA) was investigated over acidic catalysts modified with transition metals. Catalytic activity of alumina was seriously deactivated in the reaction of THFA in nitrogen at 300°C although the initial activity was high. Tetragonal ZrO₂ showed the catalytic activity to produce DHP at 350°C. Alumina modified with Cu exhibits stable catalytic activity with high selectivity to DHP under hydrogen flow conditions, and the optimum activity was obtained at CuO contents of 5–10wt.%: the selectivity to DHP was as high as 85%. Prior to the reaction, CuO was reduced to metallic Cu, which probably works as a product remover together with hydrogen to prevent coke formation. The reaction pathway from THFA to DHP was discussed: it is speculated that THFA is initially rearranged into 2-hydroxytetrahydropyran, which rapidly dehydrated to DHP.

Keywords: Dehydration; Tetrahydrofurfuryl alcohol; 3,4-2; H; -dihydropyran; Alumina catalyst; Copper; Rhodium; Inhibition of coke formation

Solvent free synthesis of coumarins using environment friendly solid acid catalysts by Shrinivas Ghodke; Uma Chudasama (pp. 219-226).

Display Omitted► ZrPW(Zirconium(IV)Phosphotungstate) is used as solid acid catalyst for the first time. ► 12TPA/ZrO₂ (12Tungstophosphoric acid supported onto ZrO₂) is used for comparison. ► ZrPW, 12TPA/ZrO₂ are solid acids possessing inherent and induced acidity respectively. ► ZrPW, 12TPA/ZrO₂ have been explored as catalysts in solvent free coumarin synthesis. ► Coumarin synthesis has been performed under conventional and microwave heating.Solid acid catalysts, ZrPW (Zirconium(IV) Phosphotungstate) and 12-TPA/ZrO₂ [12-Tungstophosphoric acid (12-TPA) supported onto ZrO₂] have been synthesized. The catalysts have been characterized for chemical stability, elemental analysis by ICP-AES, TGA, FTIR, SEM, EDX, XRD, surface area (BET) and surface acidity (NH₃-TPD). The performance of these materials as solid acid catalysts has been explored by studying Pechmann condensation as a model reaction, wherein phenols have been treated with methyl acetoacetate to give coumarins, under solvent free conditions using conventional heating as well as microwave heating. Catalytic activity of both the solid acid catalysts have been compared and correlated with surface properties of the materials.

Keywords: Solid acid catalyst; Zirconium(IV) Phosphotungstate; 12-TPA supported solid acid catalyst; Coumarin derivatives; Pechmann condensation; Microwave-assisted synthesis

Structural aspects of PtSn/γ-Al₂O₃ catalysts prepared through surface-controlled reactions: Behavior in the water denitrification reaction by María A. Jaworski; Virginia Vetere; Hernán P. Bideberripe; Guillermo J. Siri; Mónica L. Casella (pp. 227-234).

Display Omitted► PtSn/γ-Al₂O₃ catalysts prepared by Surface Organometallic Chemistry on Metals techniques. ► The selectivity of the preparation reaction led to a strong interaction between Pt and Sn atoms. ► Bimetallic PtSn catalysts are active in the hydrogenation of both NO₃⁻ and NO₂⁻ in water. ► The amount of Sn added had a pronounced influence on the activity of the catalysts. ► The amount of tin added should be low enough to allow a planar adsorption of NO₃⁻ on the Pt clusters.This research focuses on the controlled preparation and characterization of PtSn/γ-Al₂O₃ catalysts and their activity and selectivity in water denitrification by reduction of NO₃⁻ and NO₂⁻ ions with hydrogen. The bimetallic PtSn catalysts were active in the hydrogenation of both NO₃⁻ and NO₂⁻ and the amount of Sn added had a pronounced influence on the activity of the catalysts, being PtSn_0.25 catalyst the one with the best performance. An explanation for this behavior is given in terms of the electronic and geometric effects that the addition of tin exerts on Pt.

Keywords: Nitrate; Nitrite; Water denitrification; PtSn catalysts; Organometallic chemistry

Structure and phase analysis of one-pot hydrothermally synthesized FePO₄-SBA-15 as an extremely stable catalyst for harsh oxy-bromination of methane by Runqin Wang; Ronghe Lin; Yunjie Ding; Jia Liu; Junhu Wang; Tao Zhang (pp. 235-243).

Display Omitted► Fe and P were simultaneously introduced into SBA-15 via a hydrothermal method. ► FePO₄ was in good crystallinity in the hydrothermally synthesized sample. ► FePO₄-SBA-15 was extremely stable for the oxy-bromination of methane reaction. ► Structure and phase evolutions were confirmed for the fresh and spent samples.FePO₄-SBA-15 (OP) was directly synthesized via a one-pot hydrothermal technique, using Fe(NO₃)₃ and H₃PO₄ as the precursors. FePO₄/SBA-15 (IMP) was also prepared as a reference, using an impregnation method and commercially available SBA-15 as the support. The yielding samples were employed to catalyze the harsh oxy-bromination of methane (OBM) reaction, showing similar initial catalytic performances. The fresh and spent samples after catalytic reaction were thoroughly characterized by N₂-physisoption, inductively coupled plasma, wide- and small-angle X-ray diffraction, transmission electron microscopy, diffuse reflectance UV–vis spectroscopy, temperature-programmed oxidation, and room temperature⁵⁷Fe Mössbauer spectroscopy. It was found that the FePO₄ was in good crystalline in the OP sample while it was in amorphous for the IMP catalyst. Despite this difference, both FePO₄ phases in the fresh samples were transformed into Fe₇(PO₄)₆ and Fe₂P₂O₇ in the spent ones. Furthermore, the OP catalyst showed excellent stability in a period of 1000h time-on-stream performance without apparent deposition of cokes. The losses of P and Fe after the catalytic evaluation were only 9.5% and 15.5%, respectively, while the ratio of P/Fe remained close to 1.0. N₂-adsorption and TEM observations confirmed that the mesoporous pores were extremely stable under the harsh reaction ambience, which might play a crucial role in the stability test.

Keywords: SBA-15; Iron phosphate; Methane; Oxy-bromination; Stability

Controlling the selectivity of the manganese/bicarbonate/hydrogen peroxide catalytic system by a biphasic pyrrolidinium ionic liquid/ n-heptane medium by Wing-Leung Wong; Kam-Piu Ho; Lawrence Yoon Suk Lee; Ming-Him So; Tak Hang Chan; Kwok-Yin Wong (pp. 244-249).

Display Omitted► An environmentally benign catalytic system for oxidation. ► Selective oxidation of alcohols to aldehydes achieved with a biphasic ionic liquid medium. ► Short reaction time at low temperature. ► Easy separation of products and convenient recycling of the medium.The Mn²⁺/HCO₃⁻/H₂O₂ catalytic system exhibits excellent aldehyde selectivity in the oxidation of various benzylic and allyic alcohols under mild conditions and short reaction time when the reactions are carried out in a biphasic dicationic pyrrolidinium ionic liquid/ n-heptane medium. The dicationic pyrrolidinium ionic liquid shows differential solubility towards alcohols and their aldehydes whereas the immiscible n-heptane instantaneously extracted and separated aldehydes from the reaction phase. This design of biphasic ionic liquid/ n-heptane catalytic system prevents the over-oxidation of aldehydes to carboxylic acids effectively. Separation and recycling can also be easily done by decantation of the n-heptane layer after reaction. With the biphasic system, high conversion of benzyl alcohol to benzaldehyde was achieved with very low loadings of H₂O₂ and Mn(OAc)₂ catalyst at room temperature and within short reaction time. Throughout 10 reaction cycles, a total turnover number (TON) of 37,600 was achieved and excellent catalytic reactivity and selectivity were maintained with an average yield of 94%.

Keywords: Ionic liquid; Manganese catalyst; Hydrogen peroxide; Oxidation; Green chemistry

Structural and synergistic effects of three-dimensionally ordered macroporous Ce_0.8Zr_0.2O₂-supported Pt nanoparticles on the catalytic performance for soot combustion by Yuechang Wei; Jian Liu; Zhen Zhao; Chunming Xu; Aijun Duan; Guiyuan Jiang (pp. 250-261).

Display Omitted► 3DOM Pt_n/CZ catalysts were firstly synthesized by GBMR method. ► The catalysts exhibited super catalytic activities and stability for soot combustion. ► The soot combustion process over 3DOM catalyst was observed by “in situ” TEM images. ► 3DOM structural effect is favorable for weakening the dependence of catalytic activity on NO_x. ► Structural and synergetic effects of 3DOM and Pt nanoparticles were systematically investigated.Three-dimensionally ordered macroporous (3DOM) Ce_0.8Zr_0.2O₂-supported Pt catalysts were firstly synthesized. All the materials possess well-defined 3DOM nanostructure and highly dispersed Pt nanoparticles on the inner walls of uniform macropores. 3DOM structure improves the contact efficiency between catalyst and soot, and the metal (Pt)–support (Ce) synergistic effect increases the amount of active oxygen species. 3DOM Pt_n/Ce_0.8Zr_0.2O₂ catalysts exhibited high catalytic activity and thermal stability for soot combustion. The structural and synergistic effects of 3DOM Pt_n/Ce_0.8Zr_0.2O₂ catalysts are favorable for weakening the NO_x constrain on the catalytic activity, e.g., the Δ T₅₀ of 3DOM Pt₄/Ce_0.8Zr_0.2O₂ catalyst is only 60°C, while that of Pt₄/Ce_0.8Zr_0.2O₂-particles catalyst is 105°C. The reaction pathways for catalyzing soot combustion can be divided into two parts: one is that active oxygen species directly oxidize soot particles; the other one is that NO₂ acts as an intermediate to catalyze soot oxidation.

Keywords: 3DOM materials; Platinum; Structural effect; Synergistic effect; Soot combustion; Heterogeneous catalysis

Palladium (0) metal clusters: Novel Krebs type polyoxoanions stabilized, extremely active hydrogenation catalyst by Lawrence D'Souza; Michael Noeske; Ryan M. Richards; Ulrich Kortz (pp. 262-271).

Display Omitted► Pd, Au and Ag metal-clusters have been synthesized by chemical reduction method. ► Krebs type polyoxoanions were employed as stabilizers. ► All colloidal system found to be very stable for up to six months. ► The Pd-Mn₄Se₂W₁₈ system showed the longest lifetime of up to 250,000 for 1-hexene. ► Catalytic activity varies with the transition metal ions present in the polyoxoanion.One-pot synthetic route has been applied for successful synthesis and stabilization of Pd, Au and Ag metal-clusters (Metal-clusters can be defined as nanoparticles of size less than 10nm.) using Krebs type polyoxoanions [(TBA)₄H₄[M₄(H₂O)₁₀(XW₉O₃₃)₂], where M=Mn, Ni, Zn, X=Te, Se; M=Fe, X=Sb, As] as stabilizers. These polyoxoanions falls under the category of heteropolyanions and possess Krebs structure. All the polyoxoanion-metal colloidal systems were found to be stable for approximately three/six months in solution media. It was found that, due to some kind of structural transformation, polyoxoanions loose their stabilizing capability.Polyoxoanions stabilized Pd metal-clusters was found to be extremely active toward hydrogenation reaction of cyclohexene and 1-hexene. The Pd-Mn₄Se₂W₁₈ system demonstrated the longest lifetime of up to 250,000 for 1-hexene and 100,000 for cyclohexene hydrogenation. The catalytic activity is found to vary with transition metal ions like Mn, Fe, Ni, Zn, As, Sb, Te, Se which are present in the polyoxoanions. All the metal-cluster systems were characterized using various instrumental techniques such as UV–vis spectroscopy, FTIR spectroscopy, X-ray diffraction, energy dispersive spectroscopy, X-ray photoelectron spectroscopy and transmission electron microscopy.

Keywords: Pd; Au and Ag metal-clusters; Polyoxoanions stabilizers; Krebs polyoxoanions; Hydrogenation

Modification of small-crystal titanium silicalite-1 with organic bases: Recrystallization and catalytic properties in the hydroxylation of phenol by Yi Zuo; Wancang Song; Chengyi Dai; Yingping He; Mengli Wang; Xiangsheng Wang; Xinwen Guo (pp. 272-279).

Display Omitted► Small-crystal TS-1 was modified with different organic bases. ► The recrystallization occurred along different axis, when using different bases. ► TPA⁺ and TBA⁺ showed a protection effect on the framework Ti in the crystal. ► Hydroxylation reaction mainly occurred in the crystals, but not on the surface. ► The highest phenol conversion obtained, when using 0.06mol/L TPAOH for 72h.Small-crystal titanium silicalite-1 (TS-1) with a crystal size of about 600nm×400nm×250nm, was treated with different organic bases, including ethylamine, diethylamine, tetramethyl ammonium hydroxide, tetrapropyl ammonium hydroxide and tetrabutyl ammonium hydroxide. The treated TS-1 was characterized by X-ray powder diffraction (XRD), Fourier-transform infrared spectrum (FTIR), ultraviolet–visible diffuse reflectance spectrum (UV–vis), X-ray photoelectron spectrum (XPS), n-hexane and cyclohexane physical adsorption, nitrogen physisorption, inductive coupled plasma emission (ICP), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Modification with different bases led to different molar ratios of Si/Ti on the external surface, according to the XPS data. The TEM images showed that many irregular hollows were generated during modification, due to the random dissolution of framework silicon and titanium. The dissolved amorphous silica and titania recrystallize on the external surface of the TS-1 crystals in the presence of template, and different axis-oriented recrystallization occurred for different templates. Tetrapropyl ammonium favored a-orientation and tetrabutyl ammonium favored b-orientation. Especially the modification with tetrapropyl ammonium hydroxide improved the catalytic properties of small-crystal TS-1 for the hydroxylation of phenol. The conversion of phenol reached 32.6% over small-crystal TS-1 modified with 0.06mol/L tetrapropyl ammonium hydroxide for 72h.

Keywords: Titanium silicalite-1; Organic base; Recrystallization; Hydroxylation of phenol; Modification

Nickel catalysts based on phenyl ether-pyrazol ligands: Synthesis, XPS study, and use in ethylene oligomerization by Ana H.D.P.S. Ulbrich; Roberta R. Campedelli; Jorge L. Sônego Milani; João H.Z. dos Santos; Osvaldo de L. Casagrande Jr. (pp. 280-286).

Display Omitted► Nickel complexes supported by pheny ether-pyrazol ligands. ► The probability of (co)existing dimeric species increases in the following order:Ni4<Ni1<Ni2<Ni3. ► Nickel precatalysts exhibit high activities in ethylene oligomerization. ► Selectivities for 1-butene produced varying from 57 to 92.5%.A series of nickel(II) complexes bearing phenyl ether-pyrazol ligands [NiCl₂L] (Ni1: L=3,5-dimethyl-1-(3-phenoxypropyl)-1H-pyrazole;Ni2: L=1-(3-phenoxypropyl)-3-phenyl-1H-pyrazole;Ni3: L=3,5-di-tert-butyl-1-(3-phenoxypropyl)-1H-pyrazole;Ni4: L=1-(3-phenoxypropyl)-1H-pyrazole) were synthesized and fully characterized by elemental analysis, high-resolution mass spectrometry (HRMS) and X-ray photoelectron spectroscopy (XPS). X-ray photoelectron data illustrates that the probability of (co)existing dimeric species increases in the following order:Ni4<Ni1<Ni2<Ni3. All nickel precatalysts, activated with methylaluminoxane (MAO), exhibited moderate to high activities for ethylene oligomerization [TOF=18.4–45.7×10³ mol(ethylene)(mol(Ni))⁻¹h⁻¹)] with good selectivities for 1-butene produced (62.6–80.7%). The ligand environment regarding the substituents on the pyrazolyl unit as well as the reaction parameters influence the catalytic performance and selectivity toward production of 1-butene. When activated with ethylaluminum sesquichloride (Et₃Al₂Cl₃, EASC),Ni1 displayed low catalytic activity (TOF=9300 (molC₂H₄)·(mol Ni⁻¹h⁻¹); however, the 1-butene selectivity was increased, attaining 92.5%. The use of triphenylphosphine (PPh₃) as auxiliary ligand afforded highly active catalyst system [TOF=118.3×10³mol(ethylene)(mol(Ni))⁻¹h⁻¹)] with poor selectivity for production of 1-butene (13.7%).

Keywords: Nickel(II) complexes; Phenyl ether-pyrazol ligands; Ethylene oligomerization; 1-butene; XPS studies

Catalytic decomposition of 4-phenoxyphenol over Pd/ XCs_2.5H_0.5PW₁₂O₄₀/ACA (activated carbon aerogel)-SO₃H ( X=10–30wt%) catalysts by Hai Woong Park; Jeong Kwon Kim; Ung Gi Hong; Yoon Jae Lee; Ji Hwan Song; In Kyu Song (pp. 287-294).

Display Omitted► Pd/ XCs_2.5H_0.5PW₁₂O₄₀/ACA-SO₃H ( X=10–30wt%) catalysts were prepared. ► Catalytic decomposition of 4-phenoxyphenol was conducted. ► Acidity of the catalysts played an important role in the reaction. ► Total yield for main products increased with increasing acidity of the catalysts.Activated carbon aerogel (ACA) bearing sulfonic acid group (ACA-SO₃H) was prepared by a sulfonation of activated carbon aerogel, and subsequently, Cs_2.5H_0.5PW₁₂O₄₀ was impregnated on ACA-SO₃H to form XCs_2.5H_0.5PW₁₂O₄₀/ACA-SO₃H with a variation of Cs_2.5H_0.5PW₁₂O₄₀ content ( X=10, 15, 20, 25, and 30wt%). Palladium catalysts were then supported on XCs_2.5H_0.5PW₁₂O₄₀/ACA-SO₃H by an incipient wetness impregnation method. The prepared Pd/ XCs_2.5H_0.5PW₁₂O₄₀/ACA-SO₃H catalysts were applied to the decomposition of 4-phenoxyphenol. 4-Phenoxyphenol was used as a lignin model compound for representing 4-O-5 linkage of lignin. Cyclohexanol, benzene, and phenol were mainly produced by the decomposition of 4-phenoxyphenol. Acidity of Pd/ XCs_2.5H_0.5PW₁₂O₄₀/ACA-SO₃H catalysts played an important role in the decomposition of 4-phenoxyphenol. Conversion of 4-phenoxyphenol and total yield for main products (cyclohexanol, benzene, and phenol) increased with increasing acidity of Pd/ XCs_2.5H_0.5PW₁₂O₄₀/ACA-SO₃H. Among the catalysts tested, Pd/15Cs_2.5H_0.5PW₁₂O₄₀/ACA-SO₃H with the largest acidity showed the highest conversion of 4-phenoxyphenol and total yield for main products. Conversion of 4-phenoxyphenol and total yield for main products over Pd/15Cs_2.5H_0.5PW₁₂O₄₀/ACA-SO₃H were much higher than those over palladium catalyst supported on activated carbon aerogel (Pd/ACA) and palladium catalyst supported on activated carbon aerogel bearing sulfonic acid group (Pd/ACA-SO₃H). Furthermore, Pd/15Cs_2.5H_0.5PW₁₂O₄₀/ACA-SO₃H catalyst was stable and reusable in the decomposition of 4-phenoxyphenol.

Keywords: Heteropolyacid; Activated carbon aerogel bearing sulfonic group; Pd catalyst; 4-Phenoxyphenol; Decomposition

Methane dehydroaromatization by Mo-supported MFI-type zeolite with core–shell structure by Zhonghao Jin; Su Liu; Lei Qin; Zhicheng Liu; Yangdong Wang; Zaiku Xie; Xingyi Wang (pp. 295-301).

Display Omitted► Core–shell HZ5@S1s were synthesized by epitaxial growth of Silicalite-1 on HZSM-5. ► Silicalite-1 layer covering HZSM-5 core can eliminate the Brønsted acid sites on the external surface. ► Mo/HZ5@S1s show high selectivity of aromatics and catalytic stability during MDA reaction. ► Excess growth of Silicalite-1 shell inhibits the migration of Mo species into zeolite pores.The MFI-type core–shell HZSM-5-Silicalite-1s (HZ5@S1) with various core/shell ratios were synthesized by the epitaxial growth of Silicalite-1 on HZSM-5, and the corresponding Mo/HZ5@S1 catalysts prepared by incipient wetness impregnation were tested in methane dehydroaromatization (MDA). Characterizations by XRD, ICP, NH₃-TPD, DTBPy-FTIR, H₂-TPR, SEM and²⁷Al MAS NMR showed that Silicalite-1 layer covering on HZSM-5 core can eliminate the external acid sites, and thus prevent the formation of active Mo species associated with Brønsted acid sites on the external surface of catalysts. Mo/HZ5@S1 catalysts presented high shape selectivity to aromatics and stability in MDA reaction as well as the gradual decrease in the selectivity of non-aromatic products. However, the overgrowth of Silicalite-1 shell will lead to a severe inhibition of the Mo species migrating into zeolite pores and consequent anchoring on the Brønsted acid sites of HZSM-5 core. In this sense, the catalytic performance is dependent on the core/shell ratio.

Keywords: Methane dehydroaromatization; Core–shell; Mo-supported catalyst; HZSM-5

Effects of controlled SiO₂ deposition and phosphorus and nickel doping on surface acidity and diffusivity of medium and small sized HZSM-5 for para-selective alkylation of toluene by methanol by Ping Lu; Zhaoyang Fei; Lei Li; Xinzheng Feng; Weijie Ji; Weiping Ding; Yi Chen; Weiming Yang; Zaiku Xie (pp. 302-309).

Display Omitted► Tunable SiO₂ deposition on medium (1–1.5μm) and small (200nm) sized HZSM-5. ► Change in external Brønsted acidity due to SiO₂ modification is elaborated. ► Effects of surface SiO₂ deposition and P–Ni doping on surface acidity are clarified. ► Pre-existing extra Na⁺ has impacts on zeolite surface acidity and diffusivity. ► Silylation together with P–Ni doping is highly para-selective for toluene alkylation.In this work the controlled SiO₂ deposition on the HZSM-5 of medium (M-) and small (S-) sized grains is accomplished through the mild steam-pretreatment of zeolites (to modify the density of surface OH groups) followed by chemical liquid deposition (CLD) process. The amount of deposited SiO₂ is tunable by varying the conditions of steam-pretreatment and/or CLD process, which allows quantitative correlating the changes of sample characteristics with the amount of deposited SiO₂. NH₃-TPD, pyridine and 2,6-DBT-pyridine adsorption infrared spectroscopic studies revealed the effect of surface SiO₂ deposition on strength (weak and strong), type (Brønsted and Lewis), and location (external) of acid sites of HZSM-5. The external Brønsted acid sites of more than 75% are diminished upon SiO₂ deposition of 13wt%. Due to pre-existing extra Na⁺ in S-HZSM-5, less amount of SiO₂ deposition or P-doping will cause more obvious enhancement in para-selectivity on S-HZSM-5. The present study revealed that with the integrated modifications of SiO₂ deposition and P–Ni doping on S-HZSM-5, toluene conversion of 31% and para-selectivity of 91% can be achieved. It was also found that doping of 5wt% Na and 6wt% P to M-HZSM-5 (free of silylation) can give p-xylene selectivity of ∼80% at toluene conversion of ∼26%. SiO₂ deposition can more obviously reduce the strong acid sites, and P–Ni doping seems also to affect Lewis acidity. Low density of Brønsted (external)/Lewis acid sites and controlled diffusivity of HZSM-5 would be favorable for p-xylene generation in toluene alkylation with methanol.

Keywords: SiO; ₂; deposition; Phosphorus; Nickel; Doping; Alkylation; Toluene; Methanol; para-Xylene

Light-induced generation of radicals on semiconductor-free carbon photocatalysts by Leticia F. Velasco; Valter Maurino; Enzo Laurenti; Conchi Ania (pp. 310-315).

Display Omitted► UV irradiation of free-semiconductor carbons from solution generates radicals. ► Hydroxyl and superoxide radicals have been detected by ESR. ► Photoinduced reactions occur at semiconductor free carbon materials. ► Higher amounts of radicals were detected for some carbons compared to TiO₂. ► These radicals account for the photocatalytic activity of carbon materials.This work provides an experimental evidence of the photoinduced generation of radical species upon UV irradiation of aqueous suspensions of carbon materials with varied textural, structural and chemical composition. The use of a powerful spectroscopic tool as spin trapping electron spin resonance (ESR) has allowed to detect and identify these radicals (among which are hydroxyl, superoxide and other organic radicals), which are the basis of the so-called Advanced Oxidation Processes. Our results demonstrate the ability of carbon materials – including activated carbons – to interact with UV light, and also to generate highly reactive species capable of promoting the photooxidation of an aromatic pollutant. Moreover, for some of the carbons the concentration of radicals was higher than that detected for titania powders. Although the photogeneration of radicals upon irradiation is a well-known process for inorganic semiconductors such as titanium oxide or zinc oxide, our results demonstrate a similar behavior on carbon materials in the absence of semiconductor additives.

Keywords: Hydroxyl radicals; Semiconductor-free carbon photocatalysts; Electron spin resonance

Monovacant polyoxometalates incorporated into MIL-101(Cr): novel heterogeneous catalysts for liquid phase oxidation by Carlos M. Granadeiro; André D.S. Barbosa; Patrícia Silva; Filipe A. Almeida Paz; Vipin K. Saini; João Pires; Baltazar de Castro; Salete S. Balula; Luís Cunha-Silva (pp. 316-326).

Display Omitted► Novel composite materials, PW₁₁@MIL-101 and SiW₁₁@MIL-101, were isolated. ► Materials were characterized and investigated as heterogeneous catalysts. ► Sustainable oxidation of cis-cyclooctene, geraniol and R-(+)-limonene was studied. ► Both composite materials revealed to be active, selective and recyclable catalysts.Two novel hybrid composite materials, PW₁₁@MIL-101 and SiW₁₁@MIL-101, were prepared by the inclusion of the potassium salts of the monovacant polyoxotungstates, [PW₁₁O₃₉]⁷⁻ (PW₁₁) and [SiW₁₁O₃₉]⁸⁻ (SiW₁₁), into the porous Metal-Organic Framework MIL-101(Cr). Materials were characterized by a myriad of solid-state methods such as powder X-ray diffraction (XRD), vibrational (FT-IR and FT-Raman) and³¹P solid-state NMR spectroscopies, elemental analysis, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX), and textural analysis confirming the incorporation of the POMs into MIL-101(Cr). PW₁₁@MIL-101 and SiW₁₁@MIL-101 revealed to be active, selective and recyclable catalysts for the oxidation of cis-cyclooctene, geraniol and R-(+)-limonene using the H₂O₂ as oxidant. Only one product was obtained from the epoxidation of cis-cyclooctene and geraniol: 1,2-epoxycylooctane and 2,3-epoxygeraniol, respectively. In the oxidation of R-(+)-limonene the main products were limonene-1,2-epoxide and limonene-1,2-diol, however the diepoxide was also formed. Both composite materials, PW₁₁@MIL-101 and SiW₁₁@MIL-101, are recyclable for, at least, three consecutive cycles without significant loss of activity. The stability of the composites after the catalytic cycles was confirmed by several techniques. Remarkably, the MOF framework was found to play an important role in the stability of the PW₁₁ in the presence of H₂O₂.

Keywords: Polyoxometalates; Metal organic-framework; Hybrid materials; Heterogeneous catalysis; Oxidation

Transesterification of glycerol trioleate catalyzed by basic ionic liquids immobilized on magnetic nanoparticles: Influence of pore diffusion effect by Yaping Zhang; Qingze Jiao; Bin Zhen; Qin Wu; Hansheng Li (pp. 327-333).

Display Omitted► Supported basic ionic liquids were prepared and used in transesterification. ► Magnetic mesoporous nanoparticles and magnetic nanoparticles were used as carriers. ► Mesoporous structure affects catalytic activity due to mass transfer resistance. ► The two catalysts showed excellent catalytic activities higher than that of NaOH.Supported ionic liquids have become a hotspot in heterogeneous catalysis. 1-Allyl-dodecylimidazolium hydroxide ([ADIm][OH]) basic ionic liquids immobilized on magnetic mesoporous SiO₂/CoFe₂O₄ nanoparticles (SCF) and magnetic CoFe₂O₄ nanoparticles (CF) were prepared and characterized via FTIR, XRD, TEM, TG–DTA, VSM, elemental analysis and N₂ adsorption–desorption measurements. Catalytic performance of both supported ionic liquids catalysts (SILCs) was evaluated through transesterification of glycerol trioleate. The SCF carrier consisted of mesoporous silica matrix and uniformly dispersed CoFe₂O₄ nanoparticles, while CF carriers were nanosized CoFe₂O₄ particles with an average size of 15nm. All of the carriers and the supported catalysts showed excellent paramagnetism. The two SILCs showed excellent catalytic activities higher than NaOH. Furthermore, the structure of the carriers had important influence on the catalytic performance of SILCs. Compared with the two SILCs, [ADIm][OH]/SCF presented a lower catalytic activity at the beginning of the reaction but higher catalytic activity when reaction time was long enough than [ADIm][OH]/CF due to the pore diffusion effect.

Keywords: Magnetism; Mesoporous silica; Nanoparticle; Supported ionic liquid catalyst; Transesterification

An effective method for increasing the activity of nickel boride catalyst nano-particles in hydrogenation reactions: Low-temperature hydrogen treatment by Firouzeh Taghavi; Cavus Falamaki; Alimemad Shabanov; Mina Seyyedi; Mehdi Zare (pp. 334-340).

Display Omitted► A Ni₂B catalyst was treated with H₂ at T less than 100°C in ethanol medium. ► Its performance for a direct hydrogenation reaction was studied. ► The catalytic performance is highly enhanced due to the treatment. ► The effect of temperature and pressure of the treatment has been investigated. ► The mechanism of reactivity enhancement has been elucidated.It is shown that low temperature (<100°C) hydrogen treatment of nano nickel boride catalysts is an efficient process for the enhancement of their activity in the p-nitrophenol (PNP) to p-aminophenol (PAP) hydrogenation reaction. It has been shown that such a process excludes initial borate species present on the surface and within the catalyst nano-particles by promoting their dissolution in the liquid phase. The latter phenomenon is enhanced by increasing the temperature. Treatment in the absence of hydrogen results in no reaction rate enhancement. Instead, the activity falls significantly below that of the as-synthesized catalyst. The effect of hydrogen treatment on the catalyst physical properties was investigated using FTIR, XRD, nitrogen adsorption and FESEM analysis. Mathematical simulation of the PNP hydrogenation reaction rate supports the hypothesis that the rate enhancement is mainly due to the increase of the catalyst specific surface area and partial reduction of surface nickel oxide species. The mechanism by which hydrogen increases the specific surface is discussed.

Keywords: Nickel boride; Direct hydrogenation; Hydrogen treatment; Catalyst

Activity of KNbO₃ as catalyst for soot combustion: Effect of the preparation method by G. Pecchi; B. Cabrera; E.J. Delgado; X. García; R. Jimenez (pp. 341-348).

Display Omitted► The effect of the synthesis method on the KNbO₃ structure. ► The activity of KNbO₃ catalysts depends strongly on the preparation method and the calcination temperature. ► No deactivation by potassium loss is observed due to the stabilization of the alkaline metal inside the perovskite structure.The effect of the preparation method and calcination temperature on the stability and activity of KNbO₃ as catalysts for soot oxidation is reported. The solids were prepared by three different procedures: (i) by a citrate method using NbCl₅ as niobium precursor; (ii) by a citrate method using NbF₅ as niobium precursor; and (iii) by an autocombustion method using Nb₂O₅ as niobium precursor. The powders were calcined at 600°C and 700°C and characterized by N₂ physisorption, oxygen desorption profiles, XRD and SEM. The catalytic activity is discussed in terms of both the T_m value, the temperature at which combustion of carbon black occurs at the maximum rate, and the apparent activation energy. It is found that KNbO₃ calcined at 600°C shows the higher catalytic activity. Also, a strong dependence on the preparation method is observed. The solids prepared by the citrate method show the higher catalytic activities, being the most active the one that use NbCl₅ as niobium precursor. This highest catalytic activity is discussed in terms of nanosized perovskite structure and rough interfaces associated to the oxygen's vacancies. Moreover, lower apparent activation energies were obtained for the solids prepared by the citrate method. In addition, it is observed that no deactivation by metal loss after consecutive soot combustion cycles because of the stabilization of the alkaline metal inside the perovskite structure.

Keywords: Soot combustion; Potassium niobates; Perovskite

Catalytic combustion of methane over ruthenium supported on zinc aluminate spinel by Janina Okal; Mirosław Zawadzki (pp. 349-357).

Display Omitted► Zinc aluminate spinel with high surface area is promising support for catalysts used in methane combustion. ► Ru/ZnAl₂O₄ catalysts exhibit good activity for methane combustion. ► The crystallite size of the RuO₂ oxide plays important role in the combustion of methane.Activity of the Ru/ZnAl₂O₄ catalysts, H₂-reduced or air-aged at 700°C, for the combustion of methane under O₂-rich conditions was studied in this work. High surface area ZnAl₂O₄ spinel was synthesized by the unconventional co-precipitation method. Catalysts were prepared using Ru(NO)(NO₃)₃ as metal precursor and characterized by H₂ chemisorption, O₂ uptake, BET, XRD and TEM. The size of ruthenium particles in fresh catalysts varied from 1.1 to 1.5nm with the metal loading from 0.5% to 4.5wt.%. Air-aging treatment caused severe agglomeration of the Ru phase and formation of the well-crystallized RuO₂ oxide. Under reaction conditions, highly dispersed Ru species were easily oxidized and RuO₂ oxide was the active phase for methane combustion. The fresh catalysts were more effective than aged samples in terms of light-off temperature and temperature needed for the complete methane conversion. The mean crystallite size of the RuO₂, formed during combustion reaction over fresh catalysts, depended on metal loading and was lower (21–27nm) as compared to that formed during aging process (21–40nm), which leads to higher activity. However, stable catalytic activity was observed only for aged catalysts. The specific reaction rate (μmolg_Ru⁻¹s⁻¹) for the fresh catalysts was found to decrease about 50% when the Ru loading increases from 0.5% to 4.5%. The apparent activation energies E_app on Ru/ZnAl₂O₄ catalysts were in range of 120–129kJ/mol and did not depend on the metal loading and catalyst pre-treatment. Catalytic activity could be partly explained by the changes in the morphology and the crystallite size of the RuO₂ phase and may suggest a structure sensitivity of CH₄ combustion over ruthenium. Catalyst deactivation observed for the fresh catalysts, originate mainly from severe modifications of the Ru phase but not from changes in the ZnAl₂O₄ support structure.

Keywords: Methane combustion; Ruthenium; Zinc aluminate; RuO; ₂; agglomeration; Deactivation

Effects of phosphorus and saccharide on size, shape, and reducibility of Fischer–Tropsch catalysts for slurry phase and fixed-bed reactions by Kyoung-Su Ha; Gyu-In Jung; Min-Hee Woo; Ki-Won Jun; Jong Wook Bae (pp. 358-369).

Display Omitted► Saccharide and phosphorus were incorporated into cobalt catalyst to control size, shape as well as reducibility. ► The extraordinarily enhanced hydrothermal stability as well as reducibility of P-treated catalyst was corroborated. ► Activity tests were conducted in a fixed-bed reactor as well as in a slurry phase reactor.Saccharide was incorporated into Co/Al₂O₃ by impregnating sucrose and a cobalt precursor on a phosphorus-treated γ-Al₂O₃ support (P-Al₂O₃), to control the catalyst size, shape, and reducibility. The effects of P-Al₂O₃ on the relationship between C₅₊ productivity, dispersion, and reducibility were investigated and compared with our previous work based on the high surface area γ-Al₂O₃. Powder X-ray diffraction results for Co/P-Al₂O₃ revealed that the addition of P increased the average size of the cobalt oxide crystals due to weakened interactions between the metal and the support, which led to the increased reducibility while compromising the dispersion. The extraordinarily enhanced hydrothermal stability of the catalysts was corroborated with the help of FT-IR analysis. Activity tests were conducted in a fixed-bed reactor as well as in a slurry phase reactor charged with Co/P-Al₂O₃ catalysts to investigate the reactor behavior. The addition of a saccharide, such as sucrose, efficiently increased the dispersion capability and regulated crystal shape to overcome the lowered dispersion caused by phosphorus treatment. The effect of sucrose on crystal size and shape of Co/P-Al₂O₃ was verified through TEM imaging and XRD analysis. The control of crystal size and shape was found to be crucial to attain maximum productivity, in addition to dispersion and reducibility.

Keywords: Cobalt; Dispersion; Fischer–Tropsch; Hydrogenation; Reduction

Fluoroantimonic acid hexahydrate (HSbF₆·6H₂O) catalysis: The ring-opening polymerization of epoxidized soybean oil by Zengshe Liu; Atanu Biswas (pp. 370-375).

Display Omitted► Epoxidized soybean oil was polymerized in ethyl acetate solution at room temperature. ► Fluoroantimonic acid hexahydrate (HSbF₆·6H₂O) was used as catalyst. ► The formed biodegradable polymers are highly desirable from renewable resources. ►¹H and¹³C NMR, solid NMR and GPC were used to characterize the polymers.Ring-opening polymerization of epoxidized soybean oil (ESO) catalyzed by a super acid, fluoroantimonic acid hexahydrate (HSbF₆·6H₂O) in ethyl acetate was conducted in an effort to develop useful biodegradable polymers. The resulting polymerized ESO (SA-RPESO) was characterized using infrared (IR) spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA),¹H NMR,¹³C NMR, solid state¹³C NMR, and gel permeation chromatography (GPC). The results indicated that ESO was effectively polymerized by fluoroantimonic acid and formed polymers with relatively high crosslink density. Glass transition temperatures of these polymers ranged from −13°C to −21°C. TGA results showed the SA-RPESO polymers were thermally stable at temperatures up to 200°C. Decomposition of the polymers was found to occur at temperatures greater than 350°C. GPC results indicated the extracted soluble substances from SA-RPESO polymers were oligomers of ESO. These soybean oil-based polymers will be functionalized to hydrogels and their applications explored in the personal and health care areas.

Keywords: Epoxidized soybean oil; Ring-opening polymerization; Fluoroantimonic acid hexahydrate

Deep desulfurization of diesel by ionic liquid extraction coupled with catalytic oxidation using an Anderson-type catalyst [(C₄H₉)₄N]₄NiMo₆O₂₄H₆ by Hongying Lü; Wanzhong Ren; Hongyan Wang; Yun Wang; Wei Chen; Zhanghuai Suo (pp. 376-382).

Display Omitted► A series of Anderson-type Q₄NiMo6−_xW_xO₂₄H₆ ( x=0, 2, 4, 6) catalysts was developed. ► The Q₄NiMo₆O₂₄H₆ shows high activity in ionic liquids ECODS in diesel. ► Quaternary ammonium cations can promote ODS probably owing to the mixed-valence Mo. ► The sulfur level of a commercial diesel can be decreased from 700 to about 30ppm. ► This system can be recycled ten times with an unnoticeable decrease in activity.A series of Anderson-type Q₄NiMo6−_xW_xO₂₄H₆ ( x=0, 2, 4, 6) catalysts were synthesized and employed in ionic liquids (ILs) extraction coupled with catalytic oxidation desulfurization systems (ECODS) for removal of benzothiophene (BT), dibenzothiophene (DBT) and their derivates in a model diesel and an actual commercial diesel. The catalyst [(C₄H₉)₄N]₄NiMo₆O₂₄H₆ in ECODS system, containing H₂O₂ and [Bmim]PF₆, exhibited so high catalytic activity that DBT removal can reach 98% at 30°C in 3h. The catalytic activity of the catalysts depends on the polyoxometalate anion and cation. The DBT removal gradually increases with the increasing of the molybdenum ions in the Anderson-type polyoxometalates. Quaternary ammonium cations can effectively promote the oxidative desulfurization reaction, which was confirmed by the presence of the mixed-valence molybdenum ions in the Anderson-type polyoxometalate catalyst. ILs was used as an extractant, however it also promoted the oxidative desulfurization reaction greatly. The reaction rate was so sensitive to the oxidant dosage that the removal DBT first increased and then decreased with the increasing of O/S molar ratio. The change is probably due to the introduction of excess water in the system. Sulfur removal selectivity for S-compounds followed the order of DBT>4-MDBT>4,6-DMDBT>BT>5-MBT. The reactivity of these S-compounds is sensitive to the electron density on sulfur atoms and the steric hindrance of the substituted groups of S-compounds. The sulfur level of an actual commercial diesel can be decreased from 700 to about 30ppm after desulfurization reaction. The desulfurization system for the actual commercial diesel can be recycled ten times with an unnoticeable decrease in activity.

Keywords: Ionic liquid; Oxidative desulfurization; Diesel; Anderson-type catalyst

Microwave-assisted catalysis by iron oxide nanoparticles on MCM-41: Effect of the support morphology by Adela I. Carrillo; Elena Serrano; Rafael Luque; Javier García-Martínez (pp. 383-390).

Display Omitted► MCM-41 type silica materials as supports for iron oxide nanoparticles. ► Different morphologies can influence catalytic activities. ► Different catalytic activities in oxidation and alkylation processes. ► Helical mesostructures provided optimum catalytic activities and reusabilities.Catalytically active heterogeneous catalysts have been prepared via microwave deposition of iron oxide nanoparticles (0.5–1.2wt%) on MCM-41 type silica materials with different morphologies (particles, helical and spheres). This methodology leads to iron oxide nanoparticles composed by a mixture of FeO and Fe₂O₃ species, being the Fe(II)/Fe(III) peak ratio near to 1.11 by XPS. DRUV spectroscopy indicates the presence of tetrahedral coordinated Fe³⁺ in the silica framework of the three catalysts as well as some extraframework iron species in the catalysts with particle and sphere-like morphologies. The loading of the nanoparticles does neither affect the mesopore arrangement nor the textural properties of the silica supports, as indicated by SAXS and nitrogen adsorption/desorption isotherms. A detailed investigation of the morphology of the supports in various microwave-assisted catalyzed processes shows that helical mesostructures provide optimum catalytic activities and improved reusabilities in the microwave-assisted redox (selective oxidation of benzyl alcohol) catalyzed process probably due to a combination of lower particle size and higher acidity in comparison with the supports with particle and sphere morphology.

Keywords: Microwaves; Heterogeneous catalysis; Iron oxide nanoparticles; MCM-41 type materials

Influence of the synthesis conditions on the physicochemical properties and acidity of Al-MCM-41 as catalysts for the cyclohexanone oxime rearrangement by Eliana G. Vaschetto; Gustavo A. Monti; Eduardo R. Herrero; Sandra G. Casuscelli; Griselda A. Eimer (pp. 391-402).

Display Omitted► Al-MCM-41 sieves have been successfully prepared by direct synthesis method. ► The incorporated Al depends on the hydrothermal synthesis time and stirring of gel. ► The presence of very weak acid nest silanols could be associated with framework Al. ► Beckmann rearrangement of CHO was carried out with selectivity to ξ-C of 100%. ► Acid silanol nests are proposed as the active sites for this reaction.Al-containing mesoporous catalysts with MCM-41 structure and high surface area have been successfully prepared by direct hydrothermal synthesis. Various characterization techniques including XRD, N₂ adsorption, ICP-OES, NMR, FT-IR and adsorption of pyridine coupled to FT-IR spectroscopy were employed. A detailed study about the relationships existing between the different synthesis parameters, the physico-chemical properties, the acid behavior and the catalytic performance is presented in this contribution. We have suggested that the active sites for the Beckmann rearrangement of cyclohexanone oxime are nest silanols (at structural defects) of very weak Brønsted acid character, which is associated with the introduction of Al into the mesoporous framework. In all the cases, employing soft reaction conditions, we have obtained selectivity to caprolactam of 100%. Finally, a Si/Al initial molar ratio of 20, a stirring of synthesis gel for 7h and a hydrothermal treatment of 6 days seem to be the optimum synthesis conditions to obtain the highest framework Al incorporation, more abundant weak acid sites (silanol nests) and maximum yield for ξ-caprolactam.

Keywords: Mesoporous materials; Al-MCM-41; Synthesis time; Gel stirring; ξ-Caprolactam

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Applied Catalysis A, General (v.453, #)