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Applied Catalysis A, General (v.394, #1-2)

Contents (pp. iii-xii).

Editorial Board (pp. co2).

An investigation into cyclohexanone ammoximation over Ti-MWW in a continuous slurry reactor by Song Zhao; Wei Xie; Junxia Yang; Yueming Liu; Yingtian Zhang; Biliang Xu; Jin-gang Jiang; Mingyuan He; Peng Wu (pp. 1-8).

.Display Omitted▶ The liquid-phase ammoximation of cyclohexanone has been studied for the first time with Ti-MWW as a catalyst in a continuous slurry reactor. The effects of reaction parameters on the catalytic performance of Ti-MWW in the ammoximation, the catalyst deactivation behavior as well as the regeneration method for the deactivated Ti-MWW were investigated in detail. ▶ Ti-MWW showed a much longer catalyst lifetime than TS-1 when it maintained a cyclohexanone conversion of >96% and an oxime selectivity of >99%. The deactivation of Ti-MWW was clarified to be due to the coke formation and a partial desilication of the zeolite framework. ▶ A combination of acid treatment and structure rearrangement assisted by cyclic amine is proposed to regenerate the deactivated Ti-MWW catalyst effectively. The results would be meaningful for developing cleaner processes of ketone ammoximation.In the present study, the liquid-phase ammoximation of cyclohexanone with ammonia and hydrogen peroxide was studied using a MWW-type titanosilicate (Ti-MWW) catalyst in a continuous slurry reactor to develop a clean process for producing cyclohexanone oxime. The reaction parameters, which governed the cyclohexanone conversion, oxime selectivity and catalyst deactivation, were investigated by simulating the operating conditions of an industrial process. Under optimized reaction conditions, Ti-MWW produced a cyclohexanone conversion and oxime selectivity over 96% and 99%, respectively. Moreover, Ti-MWW was extremely robust and showed a longer lifetime than the conventional titanium silicalite-1 catalyst. The causes of deactivation were elucidated to be the coke deposition and partial dissolution of the zeolite framework of Ti-MWW during ammoximation. The deactivated Ti-MWW catalyst was regenerated effectively by a combination of acid treatment and cyclic amine-assisted structural rearrangement.

Keywords: Ti-MWW; Ammoximation; Cyclohexanone oxime; Slurry reactor; Regeneration

Deactivation of HDS catalysts in deoxygenation of vegetable oils by David Kubička; Jan Horáček (pp. 9-17).

Display Omitted▶ Impurities in vegetable oils, such as alkalis and phosphorus, cause deactivation of deoxygenation catalysts. ▶ Phospholipids yield phosphoric acid that promotes quick formation of carbonaceous deposits. ▶ H₂S prevents catalyst deactivation and affects the deoxygenation pathway. ▶ Decarboxylation is promoted at the expense of hydrodeoxygenation due to H₂S.Several rapeseed oils with different degree of upgrading were used as feedstocks for deoxygenation over sulfided CoMo/γ-Al₂O₃ catalyst. The rapeseed oil samples differed in the concentration of inorganic impurities, water, free fatty acids and phospholipids. The catalytic experiments were carried out in a fixed bed reactor at constant reaction conditions (310°C, WHSV=2h⁻¹, hydrogen pressure 3.5MPa). Refined rapeseed oils were converted to hydrocarbons more efficiently than neat rapeseed oil, trap grease and waste oil. The high concentration of phospholipids in trap grease was the most likely cause of catalyst deactivation by coking. Decomposition of phospholipids as well as oligomerization of rapeseed oil by phosphoric acid at 310°C was confirmed by separate laboratory experiments. The high concentration of alkalis in waste rapeseed oil was the main reason for increased deactivation in comparison with neat rapeseed oil. Sulfur removal from catalyst active sites affected adversely the deoxygenation of triglycerides. The catalyst deoxygenation activity was partially restored by pulse addition of dimethyldisulfide (DMDS) to the feedstock, however the degradation of active sites by loss of sulfur was not fully reversible. In contrast, continually added sulfur agent (DMDS) ensured significantly slower catalyst deactivation. Moreover, presence of H₂S lowered considerably hydrodeoxygenation/decarboxylation ratio.

Keywords: Deoxygenation; Deactivation; Hydrotreating catalysts; Biofuels; Vegetable oils

Hydrodesulfurization of 4,6-DMDBT on a multi-metallic sulfide catalyst with layered structure by Lu Wang; Yongna Zhang; Yuliang Zhang; Peng Liu; Hongxian Han; Min Yang; Zongxuan Jiang; Can Li (pp. 18-24).

Display Omitted▶ The novel multi-metallic NiAlMoW catalyst has a layered structure. ▶ NiAl-LDH acts as the structure-directing template in the preparation of catalyst. ▶ NiAl₃MoW-5 shows two times higher intrinsic HDS activity than commercial catalyst. ▶ The active species are highly dispersed on the surfaces and the edges of the layers. ▶ The layered structure has a great impact on the HDS activity of the catalyst.A multi-metallic NiAlMoW catalyst with layered structure was prepared by surfactant-assisted co-precipitation method using NiAl-layered double hydroxide (NiAl-LDH) as the structure-directing template. By carefully tuning the composition of the layered structure and the synthesis conditions, we have prepared a series of Ni_mAl_nMoW catalysts. For the HDS of 4,6-DMDBT, NiAl₃MoW-5 shows two times higher intrinsic catalytic activity (based on weight of active metals) compared to that of the commercial CoNiMoW/Al₂O₃ catalyst. The sulfur content in the model compound could be reduced from 500ppm to less than 20ppm using this catalyst under the operation conditions of 3.0MPa, 300°C, a WHSV (weight hourly space velocity) of 9h⁻¹, and H₂/oil ratio of 800Nm³/m³. The synthesized catalysts were characterized by SEM, TEM, XRD, TG/DSC, nitrogen adsorption/desorption isotherms and XRF. This NiAlMoW catalyst has retained the unique layered structure of NiAl-LDH, which can facilitate uniform dispersion of the active species on both the surface and the edge of the layer. It was found that the layered structure has a great impact on the catalytic activity of the HDS reactions.

Keywords: Ultra-deep hydrodesulfurization; Multi-metallic sulfide catalyst; NiAl-LDH; 4,6-Dimethyldibenzothiophene (4,6-DMDBT); Layered structure

Role of silica template in the preparation of sulfonated mesoporous carbon catalysts by Jidon Janaun; Naoko Ellis (pp. 25-31).

Display Omitted▶ Mesoporous and high surface area glucose char was synthesized. ▶ Mesoporous and high surface area carbon-based catalyst was synthesized. ▶ Carbon catalyst reactivity is dependent on acidity but independent of surface area.Mesoporous carbon catalysts have received considerable interest in the scientific community because of their tunable porosity, hydrophobic surface, and ease of functionalization with active groups such as –SO₃H. The formation of silica templates is a typical method to prepare a mesoporous carbon, but little is understood on its role for effective sulfonation. In this study, silica templates were used to prepare mesoporous sugar char using the confined activation process. The char was functionalized with –SO₃H groups before or after removing the silica templates. The roles of the silica templates were evaluated based on the physicochemical properties of the catalysts. The results showed that silica templates provided support to the internal porosity, but prevented the –SO₃H groups from effectively reaching the internal surface. The esterification of oleic acid showed that the reactivity of the carbon-based catalysts is dependent on the total acidity, but independent of the surface area. These findings show that carbon-based catalysts are suitable for esterification which is useful for biodiesel production.

Keywords: Biodiesel; Carbon-based catalysts; Esterification; Sulfonated mesoporous carbon catalysts; Silica templates; Sugar catalyst

Influence of sulfur on the carbon deposition in steam reforming of liquid hydrocarbons over CeO₂–Al₂O₃ supported Ni and Rh catalysts by Chao Xie; Yongsheng Chen; Yan Li; Xiaoxing Wang; Chunshan Song (pp. 32-40).

Display Omitted► Adding sulfur increased carbon deposition on both Ni and Rh catalysts, particularly on Ni. ► Rh catalyst possesses stronger ability to gasify carbon in the presence of sulfur compared to Ni. ► XANES revealed that oxidized carbon species dominated on catalysts in the run without sulfur. ► Sulfur poisoning promoted the graphitic carbon formation on reforming catalysts.This study was performed to elucidate the influence of sulfur on the carbon deposition in steam reforming of liquid hydrocarbons over CeO₂–Al₂O₃ supported Ni and Rh catalysts at 800°C. The characteristics of the carbon deposits on the used catalysts after the reactions without and with sulfur were investigated by temperature-programmed oxidation (TPO), transmission electron microscopy (TEM), scanning transmission X-ray microscopy (STXM), temperature-programmed hydrogenation (TPH), X-ray absorption near edge structure (XANES), and scanning electron microscopy (SEM). Though abundant carbon deposits can accumulate on the pure CeO₂–Al₂O₃ support due to fuel thermal cracking, the addition of Ni or Rh metal greatly reduced the carbon deposition in the sulfur-free reaction. The presence of sulfur increased the carbon deposition on both catalysts, which has a much more significant impact for the Ni catalyst. Carbon XANES study on the used catalysts revealed that graphitic carbon was dominant in the presence of sulfur, while oxidized carbon species (quinone-like carbon, carboxyl and carbonate) prevailed without sulfur. Meanwhile, the formation of carboxyl and carbonate more dramatically dropped on the Ni catalyst than that on the Rh catalyst. Our results strongly suggest that (I) the presence of sulfur can suppress carbon gasification and promote the formation of graphitic carbon on reforming catalysts due mainly to its poisoning effect on metals, and (II) Rh catalyst possesses stronger capability to maintain carbon gasification activity than Ni catalyst in the presence of sulfur.

Keywords: Carbon deposition; Sulfur poisoning; Catalyst; CeO; ₂; –Al; ₂; O; ₃; Rh; Ni; Carbon characterization; Hydrocarbon steam reforming; Hydrogen; Deactivation

Reverse micelle synthesis and characterization of supported Pt/Ni bimetallic catalysts on γ-Al₂O₃ by Beth A. Cheney; Jochen A. Lauterbach; Jingguang G. Chen (pp. 41-47).

Display Omitted▶ Reverse micelle method was used to synthesize supported Pt–Ni bimetallic catalysts. ▶ TEM was employed to verify uniform size distribution of the nanoparticles. ▶ EXAFS was utilized to confirm the formation of Pt–Ni bimetallic bonds. ▶ The reverse micelle synthesized Pt–Ni catalysts showed higher hydrogenation activity than monometallic Pt and Ni catalysts.Reverse micelle synthesis was used to improve the nanoparticle size uniformity of bimetallic Pt/Ni nanoparticles supported on γ-Al₂O₃. Two impregnation methods were investigated to optimize the use of the micelle method: (1) step-impregnation, where Ni nanoparticles were chemically reduced in microemulsion and then supported, followed by Pt deposition using incipient wetness impregnation, and (2) co-impregnation, where Ni and Pt were chemically reduced simultaneously in microemulsion and then supported. Transmission electron microscopy (TEM) was used to characterize the particle size distribution. Atomic absorption spectroscopy (AAS) was used to perform elemental analysis of bimetallic catalysts. Extended X-ray absorption fine structure (EXAFS) measurements were utilized to confirm the formation of the Pt–Ni bimetallic bond in the step-impregnated catalyst. CO pulse chemisorption and Fourier transform infrared spectroscopy (FTIR) studies of 1,3-butadiene hydrogenation in a batch reactor were performed to determine the catalytic activity. Step-impregnated Pt/Ni catalyst demonstrated enhanced hydrogenation activity over the parent monometallic Pt and Ni catalysts due to bimetallic bond formation. The catalyst synthesized using co-impregnation showed no enhanced activity, behaving similarly to monometallic Ni. Overall, our results indicate that reverse micelle synthesis combined with incipient wetness impregnation produced small, uniform nanoparticles with bimetallic bonds that enhanced hydrogenation activity.

Keywords: Reverse micelle; Microemulsion; Pt/Ni bimetallic catalysts; Hydrogenation

Easy access to quinoxaline derivatives using alumina as an effective and reusable catalyst under solvent-free conditions by Maasoumeh Jafarpour; Abdolreza Rezaeifard; Maryam Danehchin (pp. 48-51).

Display Omitted▶ Acidic alumina under neat conditions catalyzes condensation of 1,2-diamines and 1,2-dicarbonyl compounds. ▶ The high reusability of alumina which is easily separated from the reaction media as well as easy and safe work-up procedure providing ready scalability, makes this solvent-free strategy more attractive for practical goal.Alumina as a cheap, heterogeneous and reusable catalyst can provide environmentally friendly alternatives for synthesis of quinoxaline derivatives via condensation of 1,2-diamines and 1,2-dicarbonyl compounds under solvent-free conditions. The products could be separated simply from catalyst by filtration and the catalyst could be recycled and reused for several times without noticeably decreasing in catalytic activity.

Keywords: Alumina; Heterogeneous catalyst; Quinoxalines; Solvent-free; Condensation reaction

In situ photocatalytic remediation of MTBE-contaminated water: Effects of organics and inorganics by L.L.P. Lim; R.J. Lynch (pp. 52-61).

Display Omitted► MTBE removal varied inversely with the concentration of organics. ► The presence of chloride reduced the MTBE removal efficiency. ► MTBE removal efficiency peaked at an iron concentration of 50mgL⁻¹. ► Dissolved inorganic ions have greater impact on the MTBE removal than organics. ► At least 80% MTBE was removed in the presence of both organics and dissolved ion.This investigation is part of a feasibility study which uses photocatalysis as a potential technology for cleaning up contaminated groundwater. It is likely that the presence of other constituents in groundwater may affect the performance of the process. Therefore, this study was conducted to investigate the effect of organic compounds and dissolved ions on the removal efficiency of a contaminant, methyl tert butyl ether (MTBE), using a reactor reported previously, Honeycomb II. Toluene, ethylbenzene and o-xylene (TEo-X), and iron, calcium, nitrate and chloride were used to represent organic and inorganic constituents, respectively, in this study. The MTBE removal efficiency decreased with increasing TEo-X concentration. The low MTBE removal efficiency at iron concentrations of 15 and 30mgL⁻¹ could be suppressed by the effect of chloride ion via possible mechanisms such as OH radical scavenging and/or blocking of active sites via adsorption onto the catalyst surface in acidic conditions. The MTBE removal efficiency peaked at iron concentrations of 50mgL⁻¹. When flowing through the reactor in a single pass, the MTBE removal efficiency of Honeycomb II increased with increasing hydraulic residence time (HRT), similar to a previous study but at lower efficiencies. When both TEo-X and dissolved ions were present, the MTBE removal efficiency remained circa 50% after 8h operation despite the variation of TEo-X and dissolved ion concentrations. Although the catalyst was used for six experiments prior to the double pass flow experiment, about 80% MTBE removal was achieved after two passes in 48h, in the presence of TEo-X and dissolved ions. This study demonstrated that this photocatalytic reactor can still degrade MTBE in the presence of other constituents without any process optimisation measures and reinforces its potential use for in situ groundwater remediation.

Keywords: Dissolved ions; Immobilised titanium dioxide (TiO; ₂; ); In situ groundwater remediation; Organics; Photocatalysis

Toluene hydrogenation at low temperature using a molybdenum carbide catalyst by María-Laura Frauwallner; Francisco López-Linares; J. Lara-Romero; Carlos E. Scott; Vieman Ali; Eumir Hernández; Pedro Pereira-Almao (pp. 62-70).

The activity of the synthesized molybdenum carbide catalyst, compared with a commercial carbide, hydrotreating Ni–Mo/Al₂O₃ catalyst, and molybdenum nitride, was the highest under the evaluated experimental conditions.Display Omitted▶ An alternative new methodology to prepare Mo₂C catalysts at low temperature. ▶ Excellent toluene hydrogenation activity at low temperature (473K) and pressure. ▶ Kinetics reveals a noble metal catalytic behavior. ▶ Highest hydrogenation activity compared with other formulations.A molybdenum carbide catalyst prepared with a novel methodology and its toluene hydrogenation activity tested at temperatures within 423–598K and 2.76MPa is here reported. Almost 100% hydrogenation was achieved at 473K with this catalyst. The activation energy was 58.1kJ/mol with a zero-order reaction for toluene concentration, illustrating a behavior comparable to that of noble metals. Additional catalyst formulations were tested and their activities compared between them. XRD and Raman characterization of the catalysts allowed identification of several species in the newly synthesized catalyst, namely fcc-Mo₂C and MoO₂.

Keywords: Molybdenum carbide catalyst; Hydrogenation; Toluene

Avoiding the deactivation of sulphated MoO_x/TiO₂ catalysts in the photocatalytic cyclohexane oxidative dehydrogenation by a fluidized bed photoreactor by D. Sannino; V. Vaiano; P. Ciambelli; P. Eloy; E.M. Gaigneaux (pp. 71-78).

Display Omitted▶ Higher photoactivity in the fluidized bed reactor with respect to fixed bed. ▶ Activity improvement in fluidized bed due to the minimization of light scattering. ▶ No catalyst deactivation in the fluidized bed reactor. ▶ Presence of catalyst deactivation in the fixed bed reactor. ▶ Catalyst deactivation by accumulation of carbon species and sulphur disappearance.Since the relevance of deactivation phenomena in heterogeneous gas–solid photocatalytic processes, a study on the deactivation of MoO_x/TiO₂ catalysts in the oxidative photodehydrogenation of cyclohexane has been carried out in a fixed bed reactor and compared to the behaviour of catalysts used in a two-dimensional fluidized bed photoreactor.Superior photocatalytic performances were obtained in the fluidized bed reactor with respect to the fixed bed reactor both in terms of cyclohexane conversion and benzene yield. At the opposite of the fixed bed, in the fluidized bed reactor, catalyst did not deactivate. Characterization performed on catalysts after photocatalytic tests evidenced that the deactivation of the catalysts is correlated to the accumulation of carbonaceous species on catalyst surface and the sulphur disappearance. The catalysts used in fluidized conditions remained active as they maintained their initial sulphur content at the surface.

Keywords: Photocatalytic fluidized bed reactor; Photocatalytic fixed bed reactor; MoO; _x; /TiO; ₂; Catalyst deactivation; Sulphate

Catalytic oxidation of aromatic oxygenates by the heterogeneous catalyst Co-ZIF-9 by Joseph Zakzeski; Agnieszka Dębczak; Pieter C.A. Bruijnincx; Bert M. Weckhuysen (pp. 79-85).

Display Omitted▶ Co-ZIF-9 is an active catalyst for the oxidation of aromatic oxygenates. ▶ Phthalan rapidly oxidized to phthalide in 91% selectivity. ▶ Alcohol functionality rapidly and selectively oxidized to aldehydes. ▶ The catalyst is heterogeneous in nature and easily recycled.The catalytic activity of Co-ZIF-9, a zeolitic imidazolate framework of sodalite topology, in the oxidation of small aromatic molecules including phthalan, vanillyl alcohol, guaiacol, syringol, veratryl alcohol, and cinnamyl alcohol by molecular oxygen has been investigated. Co-ZIF-9 selectively oxidized the substrates and thus represents a promising heterogeneous catalyst for the oxidation of small aromatic substrates. Phthalan was converted to three different products, i.e. phthalide, phthalaldehyde, and small amounts of phthalic acid. In addition to phthalan, the alcohol functionality of vanillyl alcohol, veratryl alcohol, and cinnamyl alcohol was also similarly oxidized to yield the corresponding aldehydes in high yields and excellent selectivity. The effect of solvent, temperature and NaOH addition on the Co-ZIF-9 catalytic system has been studied. The presence of NaOH in the solution greatly enhanced the oxidation activity. The structure and stability of the heterogeneous catalyst was probed by UV–vis diffuse reflection spectroscopy, confirming the coordination geometry of cobalt in the catalyst framework, thermal gravimetric analysis, establishing the thermal stability of the structure, and XRD to monitor crystallinity of the catalyst. The heterogeneous nature of the catalyst was established by a hot filtration experiment, ICP analysis of the liquid phase, and by UV–vis absorption spectroscopy on the hot filtered reaction mixture.

Keywords: Zeolitic imidazolate framework; Cobalt; Heterogeneous catalysis; Oxidation; Aromatics

Cobalt oxide catalyst for hydrolysis of sodium borohydride and ammonia borane by V.I. Simagina; O.V. Komova; A.M. Ozerova; O.V. Netskina; G.V. Odegova; D.G. Kellerman; O.A. Bulavchenko; A.V. Ishchenko (pp. 86-92).

Display Omitted▶ Active Co₂B phase is formed from Co₃O₄ under the action of aqueous NaBH₄. ▶ Correlation between ferromagnetic properties of catalyst formed in situ and its activity was found. ▶ The reduction of Co₃O₄ in NH₃BH₃ proceeds at slower rate than in NaBH₄. ▶ The addition of NaBH₄ to NH₃BH₃ solution increases the reduction rate of Co₃O₄.The catalytic properties of Co₃O₄ in NaBH₄ and NH₃BH₃ hydrolysis have been studied. Experiments were carried out at 20–40°C using 0.12M hydride solution. According to magnetic susceptibility measurements, FTIR, XRD, and TEM studies, Co₃O₄ is reduced to the ferromagnetic catalytically active Co₂B phase under the action of the NaBH₄ hydrolysis reaction medium. A correlation was found between the content of the cobalt boride phase formed in situ and catalyst activity. The reduction of Co₃O₄ in NH₃BH₃ proceeds at slower rate than in NaBH₄. The addition to a solution of NH₃BH₃ of even a small amount of NaBH₄ increases considerably the reduction rate of Co₃O₄. Using a Co₃O₄-based precursor instead of the widely used CoCl₂ leads to the formation of a stable catalytically active phase of cobalt boride.

Keywords: Cobalt boride; Cobalt oxide; Sodium borohydride; Ammonia borane; Hydrolysis

Mesoporous zirconium phosphate: An efficient catalyst for the synthesis of coumarin derivatives through Pechmann condensation reaction by Apurba Sinhamahapatra; Narottam Sutradhar; Sandip Pahari; Hari C. Bajaj; Asit Baran Panda (pp. 93-100).

Display Omitted▶ Mesoporous zirconium phosphate (m-ZrP) is an efficient catalyst for coumarin synthesis. ▶ Microwave assisted synthesis is the most appropriate method for coumarin synthesis. ▶ 100% yield of 7-amino 4-methyl coumarin was obtained at 110°C in just 10min. ▶ m-ZrP is active towards phenol for the synthesis of 4 methyl coumarin. ▶ m-ZrP is easily recoverable from reaction system and can reuse for at least 5 times.Mesoporous zirconium phosphate (m-ZrP) is used as a solid acid catalyst for the synthesis of coumarins via Pechmann condensation reaction and gave high catalytic activity for the condensation of phenols and ethyl acetoacetate in both conventional heating as well as microwave assisted method. The condensation reaction is studied in detail by varying the reaction parameters like effect of solvent, molar ratio of the reactants, temperature, and catalyst loading. Among the substituted phenols, m-amino phenol is more reactive and 100% yield is obtained in very short time at low temperature due to the presence of ring activating amine group in meta position. The m-ZrP is also active even for simple phenol and 57% yield of 4-methyl coumarin is obtained in conventional heating method. Microwave assisted synthetic method is found to be advantageous over conventional heating for the synthesis of coumarins, as it provides improved yield in very less time.

Keywords: Mesoporous zirconium phosphate; Pechmann condensation reaction; Coumarin; Microwave-assisted synthesis

Immobilization of porcine pancreatic lipase in zeolite MCM 22 with different Si/Al ratios by Cléber Calgaroto; Robison P. Scherer; Selma Calgaroto; J. Vladimir Oliveira; Débora de Oliveira; Sibele B.C. Pergher (pp. 101-104).

Display Omitted▶ Potential of application of MCM 22 as support for enzyme immobilization. ▶ The composition of the materials influenced the immobilization process. ▶ Higher yields and enzymatic activities for MCM 22 with Si/Al ratio of 25. ▶ Significant contribution using new and cheap materials for enzyme immobilization.The use of zeolites as support for immobilization of enzymes has been a matter of great interest recently due to the potential properties of these materials. In this work, the MCM 22 zeolite with different Si/Al ratios (15, 25 and 50) was used as support for immobilization of porcine pancreatic lipase, assessing the effect of its structure on the immobilization yield and enzyme activity. Results showed that the material composition influenced significantly the immobilization process. Higher yields of immobilization and enzymatic activities were achieved when MCM 22 with Si/Al ratio of 25 was used as support. In general, results demonstrate the potential of MCM 22 as support for porcine pancreatic lipase immobilization.

Keywords: MCM 22; Zeolites; Immobilization; Lipases

Low-temperature water–gas shift: Strategy to lower Pt loading by doping ceria with Ca²⁺ improves formate mobility/WGS rate by increasing surface O-mobility by Linda Z. Linganiso; Gary Jacobs; Khalid G. Azzam; Uschi M. Graham; Burtron H. Davis; Donald C. Cronauer; A. Jeremy Kropf; Christopher L. Marshall (pp. 105-116).

O-Mobility/oxide reducibility enhanced with Ca-doping. Transport of O-bound intermediates also improves, increasing LTS rates.Display Omitted▶ X_CO during LTS increases with Ca level from 0.5% Pt/CeO₂ to 0.5% Pt/Ca_0.50Ce_0.50O_1.5. ▶ TPR–XANES demonstrates that Ca doping enhances O-mobility/reducibility. ▶ Improved O-mobility translates to increased mobility of O-bound intermediates. ▶ HR-TEM indicates that the Pt size was similar for undoped and Ca-doped catalysts. ▶ XRD/HR-TEM reveal oxide morphology changes and lattice strain with Ca-doping.In one view, the metal–oxide synergy (e.g., Pt metal and cerium oxide) has been explained in terms of the dehydrogenation of formate formed on the surface of the partially reducible oxide (PRO) by Pt across the interface, with H₂O participating in the transition state of forward formate decomposition. In this work, Ca-doping of the ceria component in Pt/ceria catalysts was demonstrated by TPR and TPR–XANES measurements to facilitate the temperature of ceria surface shell and bulk reduction steps, and by TPR–XANES to increase the extents of surface shell and bulk reduction of ceria. The results thus confirm, experimentally, past theoretical models, which suggested that divalent elements (e.g., Ca) enhance both O-mobility and reducibility of ceria by weakening the Ce–O bond through lattice strain. This strain was also detected in our XRD measurements.A recent surface diffusion model postulated that increasing oxygen surface diffusion also improves the mobility of O-bound intermediates (e.g., formates, carbonates, carboxylates). In this work, in situ DRIFTS measurements confirm that improved formate decomposition rates were realized over the Ca-doped Pt promoted ceria catalysts possessing higher O-mobility relative to undoped Pt/ceria. In turn, improved LT-WGS rates were observed over the Ca-doped Pt/ceria catalysts. While the precise mechanism is still under debate, the enhanced mobility of O-bound intermediates by Ca-doping is suggested to be responsible for the significant boosts in CO conversion levels and TOFs observed during LT-WGS. Thus, doping ceria with elements like Ca provides a path forward for lowering the precious metal content (e.g., Pt), as well as the rare earth content (e.g., Ce) – catalytic components that are becoming increasingly expensive.

Keywords: Water–gas shift; WGS; LTS; Pt/ceria; Divalent elements; Calcium doping

Biphasic hydroformylation of substituted allylbenzenes with water-soluble rhodium or ruthenium complexes by Luis G. Melean; Mariandry Rodriguez; Marynell Romero; Maria L. Alvarado; Merlin Rosales; Pablo J. Baricelli (pp. 117-123).

Display Omitted▶ Hydrosoluble Rh and Ru complexes were used in the hydroformylation of allylbenzenes. ▶ Using a phase transfer agent, CTAC, enhances the reaction conversion and selectivity. ▶ The catalytic aqueous phase can be recycled up to four times. ▶ The mercury test evidences the homogeneity of the system.The water-soluble complexes [Rh(CO)(Pz)(L)]₂ and [HRu(CO)(CH₃CN)(L)₃][BF₄] [L=TPPMS ( m-sulfonatophenyl-diphenylphosphine) and TPPTS ( tris-m-sulfonato-phenylphosphine)] were used for the first time as catalyst precursors for the hydroformylation of eugenol, estragole, safrole and trans-anethole under moderate conditions in biphasic media. Under mild reaction conditions the substrates showed the following reactivity order: eugenol>estragole≈safrole≫ trans-anethole. The use of cetyl-trimethylammonium chloride (CTAC) as phase transfer agent inhibits the isomerization reaction, reaching high selectivity for the hydroformylation products (80–94%). The catalytic phase can be recycled up to four times with a decrease in the activity over time but maintaining its high selectivity.

Keywords: Biphasic hydroformylation; Allylbenzenes; Water-soluble Rh and Ru complexes

Ni catalysts supported over MgAl₂O₄ modified with Pr for hydrogen production from ethanol steam reforming by M. Noelia Barroso; Agustín E. Galetti; M. Cristina Abello (pp. 124-131).

Display Omitted▶ The presence of Pr in Ni supported catalysts showed a positive effect in the ethanol steam reforming. ▶ The catalyst Ni/MgAl₂O₄ with 2.6wt.% of Pr showed the best performance in ethanol steam reforming. ▶ The Pr addition slowed down the rate of deactivation affecting the amount and the type of carbon deposits.MgAl₂O₄ spinel oxide-supported Ni catalysts modified with Pr have been prepared by wet impregnation method with 8wt.% Ni and variable loadings of Pr (0–7wt.%). The samples were characterized by ICP, BET, XRD, TPR, SEM, Raman and TG-TPO and they were tested in ethanol steam reforming reaction.The XRD of the samples revealed the presence of spinel phase MgAl₂O₄, NiO and weak lines of PrO₂/Pr₆O₁₁. The addition of Pr slowed down the deactivation rate affecting the amount and the type of carbon deposit. Under reactive conditions, the system with 2.6 Prwt.% showed the best performance and although it presented filamentous carbon, this catalytic system kept around 80% ethanol conversion during the reaction time (40h) under severe reforming conditions without reactor plugging.

Keywords: Ni/MgAl; ₂; O; ₄; catalysts; Hydrogen; Ethanol steam reforming; Carbon deposits

Epoxidation of jatropha oil using heterogeneous catalysts suitable for the Prileschajew reaction: Acidic resins and immobilized lipase by Luis A. Rios; David A. Echeverri; Alexander Franco (pp. 132-137).

Display Omitted▶ Amberlite IR-120 was the best catalyst, yielding 70% epoxide selectivity. ▶ Amberlite IR-120 was stable through five re-uses. ▶ Low-accessible acid sites increase epoxide selectivity. ▶ Highly accessible acid sites increase glycol selectivity. ▶ Epoxidation rate is favored by acid strength.Sulphonated polystyrene resins, Nafion-silica and immobilized lipase were used as heterogeneous catalysts for the epoxidation of jatropha oil. Immobilized lipase showed ca. 100% conversion and 100% epoxide selectivity at 24h. However, this catalyst cannot be reused because it completely deactivates after one use. For the selective epoxidation of vegetable oils with percarboxylic acids the most crucial feature to prevent the formation of glycols is to minimize the exposure of the epoxide to the acidic sites of the catalyst. This can be achieved using resins with a high level of cross-linking and with low external surface area. Activity can be increased by increasing the strength of the acid sites. Amberlite IR-120 was the best heterogeneous catalysts, yielding ca. 90% conversion and 70% epoxide selectivity, both stable through five re-uses. Dowex 50WX2 afforded the production of glycols with more than 90% selectivity at conversions of ca. 90%.

Keywords: Epoxidation; Vegetable oils; Jatropha; Acidic resins; Lipase

Mixed salts of cesium and ammonium derivatives of 12-tungstophosphoric acid: Synthesis and structural characterization by Joicy S. Santos; José A. Dias; Sílvia C.L. Dias; Fillipe A.C. Garcia; Julio L. Macedo; Flávia S.G. Sousa; Liana S. Almeida (pp. 138-148).

.Display Omitted▶ New salts of cesium and ammonium derivatives of H₃PW₁₂O₄₀ were synthesized by precipitation. ▶ The properties of the mixed salts depend on the order of precipitation. ▶ The salts precipitated by ammonium followed by cesium have areas four times than the opposite. ▶ The nanocrystals aggregated forming mesoporous–microporous structures. ▶ The structures are formed by partial unidirectional growth.Mixed salts of cesium and ammonium derivatives of H₃PW₁₂O₄₀ ((NH₄)_xCs_yH_0.5PW) were synthesized by a precipitation/ion exchange method with a different addition order for each cation. The produced salts were characterized by FTIR, XRD,³¹P MAS NMR, SEM, pore size and the BET method. FTIR demonstrated that the materials maintained the Keggin structure under all tested conditions. BET results showed that salts formed by proton substitution from ammonium to cesium had much higher surface areas. Characterization by³¹P MAS NMR and XRD, demonstrated that the salt structures varied sharply with the degree of hydration. After calcination, the materials were confirmed to have characteristics of solid solutions with random distribution of the cations with similar crystallographic patterns. The primary nanocrystals aggregated to form solids with mesoporous and microporous structures, created by partial unidirectional growth of the nanocrystals during formation of the bigger, round microcrystallites about 0.3–1μm in size.

Keywords: Polyoxometalate; Heteropoly salts of cesium and ammonium; 12-Tugstophosphoric acid; Mixed cationic salt; Nanostructured catalyst

Co-production of butyrate methyl ester and triacetylglycerol from tributyrin and methyl acetate by Ezio Battistel; Chiara Calaprice; Enrico Gualdi; Elena Rebesco; Elisabetta Maria Usai (pp. 149-157).

Display Omitted▶ Simultaneous synthesis of butyrate methyl ester, BuMe, and glycerol triacetate, TAG. ▶ Synthesis of biofuel (BuMe) and diesel-compatible glycerol derivatives. ▶ Quantitative yield of BuMe and 70% selectivity on TAG. ▶ Similar final products yields with either acid or base catalysts.The simultaneous synthesis of butyric acid methyl ester, the shortest component of the FAME (fatty acid methyl esters) family, and glycerol triacetate (TAG) from glycerol tributyrate (tributyrin) and methyl acetate was studied as a function of several reaction parameters, such as type of catalyst, temperature and products distribution. The reaction is an interesterification, a multistep consecutive ester interchange catalyzed by either acid or base catalyst. Under optimized conditions, a complete tributyrin conversion and an almost quantitative butyric acid methyl ester accumulation were achieved. The other reaction product, TAG, formed by the complete acetylation of the glycerol moiety, reached almost 70% yield, whereas the mono- and di-acetylated intermediates accumulated in the order of 5–8% and 24–27%, respectively. Similar final conversions and products yields were obtained with either acid or base homogeneous catalysts, suggesting that the final products mixture did not depend on the type of catalysis but might be limited by equilibrium conditions. In spite of similar final yields, base catalysis needed shorter reaction times (minutes instead of hours) and lower temperature (60°C instead of 130°C) with respect to the best acid catalyst. On the other hand, unlike heterogeneous basic catalysts, which showed low activity, a heterogeneous acid catalyst almost as active as the homogenous counterpart was found.

Keywords: Interesterification; Ester exchange; Fatty acid methyl esters; Biodiesel; Synthesis of glycerol triacetate

Dispersion and hydrogenation activity of surfactant-stabilized Rh(0) nanoparticles prepared on different mesoporous supports by Maya Boutros; Guillaume Shirley; Thomas Onfroy; Franck Launay (pp. 158-165).

Display Omitted▶ Rh loading is improved after contacting supports with a stabilizing agent, HEA16Cl. ▶ HEA16Cl is needed to get well-dispersed Rh(0) particles over Al–SBA-15 and SBA-15. ▶ There is no need to use HEA16Cl in the case of CMK-3 support. ▶ Best catalysts are Rh⁰–Na–AlSBA (w HEA16Cl) and Rh⁰–CMK–NH₃ (B) (w/o HEA16Cl). ▶ They are more active than commercial catalysts in the hydrogenation of aromatics.Supported Rh(0) colloidal particles were prepared by the reduction of Rh(III) ions by sodium borohydride in the presence of N-N-dimethyl-N-cetyl-N-(2-hydroxyethyl) ammonium chloride (HEA16Cl), usually used as a stabilizing agent in solution. Tested supports were Na–Al–SBA-15, SBA-15 and CMK-3. In each case, the influence of HEA16Cl was studied by comparison with blank samples. Surfactant and rhodium uptake were evaluated by means of elemental analysis and eventually thermogravimetry. Obtained materials were also characterized by XRD, N₂ sorption and TEM. Given the results, it appears that HEA16Cl promotes rhodium uptake in all cases. Most significant effects on the size and dispersion of particles were observed for the system combining HEA16Cl and Na–Al–SBA-15. All the solids prepared in this study were tested in the room temperature hydrogenation of styrene as well as that of a more demanding substrate, diphenylmethane, at 0.1MPa of H₂. All of them were generally more active than their commercial analogue (5wt.% Rh⁰/C). Best catalysts, i.e., those prepared from Na–Al–SBA-15 in the presence of HEA16Cl as well as CMK-3 without HEA16Cl, allowed almost 100% yield of dicyclohexylmethane within 6h (molar substrate/Rh=100).

Keywords: Rh(0) nanoparticles; SBA-15; CMK-3; Hydrogenation; Aromatic substrates

Optimisation of Ru-promoted Ir-catalysed methanol carbonylation utilising response surface methodology by Vahid Hosseinpour; Mohammad Kazemeini; Alireza Mohammadrezaee (pp. 166-175).

Display Omitted▶ Response surface methodology applied to optimise the carbonylation process. ▶ Temperature and pressure had most effects on the reaction rate. ▶ Most effective factors on methane formation are pressure and water concentration. ▶ Developed empirical correlation satisfactorily verified experimental results.In this study, central composite design (CCD) at five levels (−1.63, −1, 0, +1, +1.63) combined with response surface methodology (RSM) have been applied to optimise methanol carbonylation using a ruthenium-promoted iridium catalyst in a homogenous phase. The effect of seven process variables, including temperature, pressure, iridium, ruthenium, methyl iodide, methyl acetate and water concentrations, as well as their binary interactions, were modelled. The determined R² values greater than 0.9 for the rate and methane formation data confirmed that the quadratic equation properly fitted the obtained experimental data. The optimum conditions for maximum rate and minimum methane formation were obtained via the RSM to be: temperature of 191°C, pressure of 32.48barg, iridium concentration of 939.40ppm, ruthenium concentration of 2099.22ppm, methyl iodide concentration of 14.46wt.%, methyl acetate concentration of 17.55wt.% and water content of 7.60wt.%. The results predicted by the developed correlation at the optimum determined conditions, 28.63mol/lh for the reaction rate and 1.97mol% CH₄, were reasonably compared with the experimental data obtained for the reaction rate and methane formation of 27.10mol/lh and 3.06mol% CH₄, respectively.

Keywords: Acetic acid; Carbonylation of methanol; Iridium/ruthenium; Optimisation; RSM

Catalytic transformation of methyl benzenes over zeolite catalysts by S. Al-Khattaf; M.N. Akhtar; T. Odedairo; A. Aitani; N.M. Tukur; M. Kubů; Z. Musilová-Pavlačková; J. Čejka (pp. 176-190).

Display Omitted▶ The effect of structure architecture of novel zeolites SSZ-33 and TNU-9 is reported for toluene, m-xylene and 1,2,3-trimethylbenzene reactions. ▶ We report on the kinetic data of a riser simulator. ▶ The experimental data of catalytic studies are contrasted to the kinetic model for all reactants and catalysts tested.Catalytic transformation of three methyl benzenes (toluene, m-xylene, and 1,2,4-trimethyl benzene) has been investigated over ZSM-5, TNU-9, mordenite and SSZ-33 catalysts in a novel riser simulator at different operating conditions. Catalytic experiments were carried out in the temperature range of 300–400°C to understand the transformation of these alkyl benzenes over large pore (mordenite and SSZ-33) in contrast to medium-pore (ZSM-5 and TNU-9) zeolite-based catalysts. The effect of reaction conditions on the isomerization to disproportionation product ratio, distribution of trimethylbenzene (TMB) isomers, and p-xylene/ o-xylene ratios are reported. The sequence of reactivity of the three alkyl benzenes depends upon the pore structure of zeolites. The zeolite structure controls primarily the diffusion of reactants and products while the acidity of these zeolites is of a secondary importance. In the case of medium pore zeolites, the order of conversion was m-xylene>1,2,4-TMB>toluene. Over large pore zeolites the order of reactivity was 1,2,4-TMB> m-xylene>toluene for SSZ-33 catalyst, and m-xylene∼1,2,4-TMB>toluene over mordenite. Significant effect of pore size between ZSM-5 and TNU-9 was observed; although TNU-9 is also 3D 10-ring channel system, its slightly larger pores compared with ZSM-5 provide sufficient reaction space to behave like large-pore zeolites in transformation of aromatic hydrocarbons. We have also carried out kinetic studies for these reactions and activation energies for all three reactants over all zeolite catalysts under study have been calculated.

Keywords: ZSM-5; TNU-9; Mordenite; SSZ-33; Toluene; m; -Xylene; 1,2,4-Trimethylbenzene; Disproportionation; Isomerization

A novel improvement in ArLPdF catalytic fluorination of aromatic compounds by Bhupesh S. Samant; Sunil S. Bhagwat (pp. 191-194).

Reverse micellar media was used to overcome the drawbacks of ArLMF catalytic fluorination of aromatic compounds, which not only enhanced the fluorination rate but also widened the scope of reaction for the bromoaromatics with electron donating and withdrawing functionalities at ortho position.Display Omitted▶ Fluorination of bromoaromatic compounds in reverse micellar media. ▶ Formation of fluoroaromatic compounds in high yield with excellent selectivity. ▶ The reductive elimination of ArLPdF in the anisotropic palisade layer of micelles. ▶ The use of cyclohexyl biarylphosphine ligand without formation of any dimeric product. ▶ Useful catalysis for bromoaromatics with e⁻ withdrawing and donating functionalities.In this study, we used reverse micellar medium for overcoming the disadvantages of ArLMF catalytic fluorination of aromatic compounds. It not only enhanced the fluorination rate, but also widened the scope of reaction for bromoaromatics with electron donating and withdrawing functionalities at ortho position. Various bromoaromatic compounds were fluorinated using the biarylphosphine ligand i.e. cyclohexyl BrettPhos ligand, along with [cinnamylPdCl]₂, and CsF as the fluoride source in reverse micellar media. The anisotropic palisade layer of reverse micelles provided the active site for reaction. The most crucial factor in the critical reductive elimination step could be the spatial orientation of ArLPdF complex in the palisade layer; forming ArF as the final product in high yield with excellent selectivity.

Keywords: Reverse micelles; Aromatic fluorination; Cyclohexyl BrettPhos; [CinnamylPdCl]; ₂

H-type zeolite coated iron-based multiple-functional catalyst for direct synthesis of middle isoparaffins from syngas by Jun Bao; Guohui Yang; Chie Okada; Yoshiharu Yoneyama; Noritatsu Tsubaki (pp. 195-200).

Display Omitted▶ The core–shell catalyst shows excellent performance for the direct synthesis of isoparaffin. ▶ The core–shell structure produces a spatially confined effect and shape selectivity. ▶ Especially, desirable low methane selectivity is achieved. ▶ This type of core–shell catalyst has high membrane area per unit volume and easy to be prepared.A compact, integral zeolite shell of H-ZSM-5 was directly crystallized on the surface of fused-iron catalyst pellet by a hydrothermal synthesis method. The synthesized catalyst has a core–shell structure without pinholes and cracks. For the reaction of direct synthesis of isoparaffin from syngas, the formation of C₁₀₊ hydrocarbons is suppressed completely on this core–shell catalyst, and the middle isoparaffins become the main products. Especially, desirable low methane selectivity is achieved. The core–shell structure of the catalyst provides a tailor-made confined reaction environment with spatially confined effect and shape selectivity, where isoparaffins escaping from outer surface of one core–shell catalyst hardly enter another core–shell catalyst via surface zeolite shell, due to its large steric obstacle, ensuring the elevated isoparaffin selectivity. Furthermore, this type of core–shell catalyst has very high membrane area per unit reactor volume and easy to be prepared, in contrast to the conventional membrane reactor.

Keywords: H-ZSM-5 zeolite; Core–shell structure; Isoparaffin synthesis; Spatially confined effect; Shape selectivity

Reduction potential, UV–visible absorption edge energy, and oxidation catalysis of niobium-containing H3+_xPW12−_xNb_xO₄₀ Keggin and H6+_xP₂W18−_xNb_xO₆₂ Wells-Dawson heteropolyacid catalysts by Dong Ryul Park; Jung Ho Choi; Sunyoung Park; In Kyu Song (pp. 201-208).

Display Omitted▶ H3+_xPW12−_xNb_xO₄₀ and H6+_xP₂W18−_xNb_xO₆₂ heteropolyacids were prepared. ▶ Reduction potentials and UV–visible absorption edge energies were measured. ▶ Yield for benzaldehyde increased with increasing reduction potential. ▶ Yield for benzaldehyde increased with decreasing absorption edge energy.Niobium-containing H3+_xPW12−_xNb_xO₄₀ ( x=0, 1, 2 and 3) Keggin and H6+_xP₂W18−_xNb_xO₆₂ ( x=0, 1, 2 and 3) Wells-Dawson heteropolyacids (HPAs) were prepared in this work to explore their redox properties and oxidation catalysis. Reduction potentials and absorption edge energies of H3+_xPW12−_xNb_xO₄₀ and H6+_xP₂W18−_xNb_xO₆₂ HPA catalysts were measured by an electrochemical method and UV–visible spectroscopy, respectively. The trend of reduction potential is well consistent with the trend of absorption edge energy with respect to niobium substitution in both series of H3+_xPW12−_xNb_xO₄₀ and H6+_xP₂W18−_xNb_xO₆₂ HPA catalysts. Absorption edge energy of H3+_xPW12−_xNb_xO₄₀ and H6+_xP₂W18−_xNb_xO₆₂ HPA catalysts shifted to lower value with increasing reduction potential of the HPA catalysts, regardless of the identity of HPA catalysts; an HPA catalyst with higher reduction potential exhibited lower absorption edge energy. In order to probe oxidation catalysis of H3+_xPW12−_xNb_xO₄₀ and H6+_xP₂W18−_xNb_xO₆₂ HPA catalysts, vapor-phase benzyl alcohol oxidation was carried out as a model reaction. Yield for benzaldehyde increased with increasing reduction potential and with decreasing absorption edge energy of H3+_xPW12−_xNb_xO₄₀ and H6+_xP₂W18−_xNb_xO₆₂ HPA catalysts.

Keywords: Heteropolyacid; Niobium; Reduction potential; Absorption edge energy; Oxidation catalysis

Selective catalytic oxidation of geraniol to citral with molecular oxygen in supercritical carbon dioxide by Sudhir E. Dapurkar; Hajime Kawanami; Maya Chatterjee; Chandrasekhar V. Rode; Toshirou Yokoyama; Yutaka Ikushima (pp. 209-214).

CrMCM-41 catalyst gave a good conversion of geraniol ( X=53%) and high selectivity of citral ( S=98%) in scCO₂ media at 80°C for 6h.Display Omitted▶ CrMCM-41 gave high selectivity (98%) and good yield (52%) of citral in scCO₂. ▶ Conversion of geraniol is enhanced in scCO₂. ▶ Activity of CrMCM-41 is higher than PtMCM-41 and PdMCM-41.Selective catalytic oxidation of geraniol to citral with molecular oxygen in supercritical carbon dioxide (scCO₂) has been investigated. The catalyst used was a chromium containing mesoporous molecular sieve catalyst viz. CrMCM-41. Comparison studies were performed with CoMCM-41, PtMCM-41 and PdMCM-41 catalysts. Among the various catalysts studied, CrMCM-41 showed a high conversion of geraniol and an excellent selectivity for citral. In contrast CoMCM-41, PtMCM-41 and PdMCM-41 catalysts exhibited low conversion of geraniol. However all three catalysts compared showed similar citral selectivity to CrMCM-41. The effect of CO₂ pressure and reaction temperature geraniol oxidation was studied with CrMCM-41. Supercritical CO₂ medium was found to enhance the conversion of geraniol and/or yield of citral. It was noticed that the catalyst can be recycled with negligible loss of conversion.

Keywords: Selective oxidation; Geraniol; Citral; Molecular oxygen; Supercritical carbon dioxide; Heterogeneous catalyst

Tandem dehalogenation–hydrogenation reaction of halogenoarenes as model substrates of endocrine disruptors in water: Rhodium nanoparticles in suspension vs. on silica support by Claudie Hubert; Elodie Guyonnet Bilé; Audrey Denicourt-Nowicki; Alain Roucoux (pp. 215-219).

Display Omitted► Aqueous colloidal Rh suspensions were efficiently deposited on silica, using a mild methodology. ► Both catalysts were used in water for the tandem dehalogenation–hydrogenation reaction of halogenoarenes, as model substrates for endocrine disrupting compounds. ► Interesting catalytic activities with TOFs up to 375h⁻¹ were obtained.This paper focuses on the removal of mono- and poly-halogenated arenes, as model substrates of endocrine disrupting compounds from aqueous effluents. The efficiency of catalysts based on metallic nanoparticles in the tandem dehalogenation–hydrogenation reaction as a pre-treatment for the remediation of organic halogenated pollutants was studied. Two catalytic systems – aqueous colloidal Rh⁰ dispersions and SiO₂-supported Rh⁰ nanoparticles – were easily prepared under mild conditions and were compared in the hydrodehalogenation reaction of the model substrates. Interesting results in terms of catalytic activity were obtained, particularly with Rh⁰@SiO₂ catalyst, which proved to be more stable and efficient under the reaction conditions.

Keywords: Nanoparticles; Hydrogenation; Dehalogenation; Halogenoarenes; Endocrine disrupting compounds

Formation of hydrogen and filamentous carbon over a Ni–Cu–Al₂O₃ catalyst through ethane decomposition by J.L. Pinilla; M.J. Lázaro; I. Suelves; R. Moliner (pp. 220-227).

Display Omitted▶ Non oxidative catalytic decomposition of ethane over a NiCu/Al₂O₃ catalyst. ▶ Influence of temperature and space velocity on catalyst performance. ▶ At T: 700°C and WHSV: 24lg_cat⁻¹h⁻¹, 95% ethane conversion and 45% H₂ selectivity. ▶ Characterization of the produced carbon nanofibers.The non-oxidative decomposition of ethane to yield hydrogen and nanostructured carbon was carried out over a Ni–Cu–Al₂O₃ catalyst in a quartz fixed bed reactor. The effects of temperature, which ranged between 550 and 750°C, on the gas product distribution, ethane conversion, hydrogen selectivity and carbon yield were investigated. Additionally, the effect of the space velocity on the catalytic decomposition of ethane over the Ni–Cu–Al₂O₃ was studied. At low temperatures and low space velocities, H₂ and CH₄ were the only gas products detected, although low ethane conversions were obtained. As the temperature was increased, both the ethane conversion and hydrogen selectivity increased, along with the production of ethylene as a by-product. High space velocities lead to low ethane conversions and hydrogen selectivities, although the carbon yield was significantly enhanced. A plausible mechanism of product formation under the operational conditions studied is presented. Characterization of the catalysts following reaction was performed with N₂ adsorption, XRD, SEM and TEM; the results suggested that carbon was mostly deposited as fishbone-like nanofibers that differed, based on the operational conditions, on the catalyst growth mode (bi-directional growth at low temperatures vs. mono-directional growth at higher temperatures) and on the structural degree of order (higher at high temperatures and low space velocities).

Keywords: Ethane decomposition; Hydrogen production; Nickel catalyst; Carbon nanofibers

Solvent effect in the liquid-phase hydrogenation of acetophenone over Ni/SiO₂: A comprehensive study of the phenomenon by Nicolás M. Bertero; Andrés F. Trasarti; Carlos R. Apesteguía; Alberto J. Marchi (pp. 228-238).

Display Omitted▶ Solvent strongly affects acetophenone hydrogenation activity over Ni/SiO₂ catalyst. ▶ Solvent–catalyst adsorption rules the hydrogenation activity in apolar solvents. ▶ Hydrogenation rate decreases with polarity and H-bonding in protic solvents. ▶ Surface hydrogen transfer from protic solvents to acetophenone boosts activity. ▶ Both polarity and surface interactions rule the activity with aprotic polar solvents.The solvent effect on catalyst activity and selectivity for the liquid-phase hydrogenation of acetophenone (AP) to 1-phenylethanol was thoroughly investigated over Ni/SiO₂. Solvents of different nature were used: protic (C₁–C₃ primary and secondary alcohols), aprotic polar (tetrahydrofuran, γ-butyrolactone, and acetonitrile) and apolar solvents (cyclohexane, toluene, and benzene). The solvent had a strong influence on the AP hydrogenation rate but did not modify significantly the selectivity to 1-phenylethanol that was always higher than 92%. The AP hydrogenation activity followed the order: C₂–C₃ alcohols>cyclohexane>toluene>tetrahydrofuran>γ-butyrolactone>methanol≫benzene ≅ acetonitrile. In order to explain this activity pattern, the solvent–AP, solvent–H₂ and solvent–catalyst interactions were analyzed. For the analysis of the solvent–AP interactions in liquid phase, both classical measures of polarity and others based on different solvatochromic scales were considered. The H₂ availability in the liquid phase was estimated from the H₂ solubility at reaction conditions. Solvent–catalyst interactions were characterized by means of the adsorption enthalpies measured calorimetrically. A reasonable correlation between the catalyst activity and some solvatochromic parameters was found only when solvents of similar nature were compared. For protic solvents, the AP hydrogenation rate decreased with the solvent polarity and its ability for H-bond formation with AP. Instead, the solvent–AP interactions were weak when using apolar solvents and thereby the activity pattern was essentially determined by the strength of solvent–catalyst interactions. In the case of aprotic polar solvents, both the solvent–AP interactions in the liquid phase and the solvent adsorption strength on the catalyst surface influenced the hydrogenation activity. The highest catalytic activities were obtained when using C₂–C₃ alcohol solvents. These protic solvents adsorbed dissociatively on metal nickel surface increasing the number of active H available for the hydrogenation reaction; this effect was much more important in the case of 2-propanol.

Keywords: Solvent effect; Hydrogenation; Acetophenone; 1-Phenylethanol; Nickel-based catalysts

Catalytic performance of Ir/CeO₂ for NO–C₃H₆–O₂ reaction in a stoichiometric condition by Masaaki Haneda; Naoya Aoki; Motoi Sasaki; Hideaki Hamada; Masakuni Ozawa (pp. 239-244).

Display Omitted▶ Supported Ir catalysts show extremely high performance for NO reduction by C₃H₆. ▶ Ir/CeO₂ is one of the candidates applicable to three-way catalyst. ▶ The use of CeO₂ with relatively high surface area causes SMSI effect. ▶ CeO₂ with low surface area can keep Ir species in a catalytically active state.Supported iridium catalyst was found to be highly active for NO reduction with C₃H₆ in a stoichiometric condition. Among the supported iridium catalysts tested here, Ir/CeO₂ showed the highest activity. In order to examine the influence of CeO₂ support on the catalytic performance of supported iridium, we prepared CeO₂ by precipitation method using different cerium precursors. Iridium catalyst supported on CeO₂ prepared by using Ce(IV) precursor (Ce(NH₄)₂(NO₃)₆) showed higher activity for NO reduction with C₃H₆ than that by using Ce(III) precursor (Ce(NO₃)₃·6H₂O), although the former catalyst has low BET surface area and low iridium dispersion. The activity of iridium catalyst supported on CeO₂, which was prepared by using Ce(III) precursor, calcined at different temperature was also found to increase with increasing the calcination temperature of CeO₂ support. The low activity of iridium catalyst supported on CeO₂ calcined at 600°C was considered to be due to a strong metal support interaction (SMSI) effect by the reaction gas treatment at 600°C, resulting in the formation of less active Ir–CeO₂ interacting species. On the other hand, the use of CeO₂ calcined at higher temperatures was found to be important to obtain a catalytically active iridium species under the stoichiometric reaction condition.

Keywords: Ir/CeO; ₂; three-way catalyst; NO reduction; strong metal support interaction

Influence of the products of the partial oxidation of methane (POM) on the catalytic performances of Rh/Ti-modified support catalysts by C. Mateos-Pedrero; S. Duquesne; S.R.G. Carrazán; M.A. Soria; P. Ruíz (pp. 245-256).

Display Omitted▶ Co-feeding of H₂, CO or CO₂ (reaction products) affects catalytic performances. ▶ The observed results are not explained by thermodynamics but by kinetic changes. ▶ The modifications on catalytic performances induced by gas co-feeds are reversible. ▶ An optimal oxidation state of Rh could explain the high selectivity of syngas. ▶ H₂/CO ratio can be modulated by adding proper amounts of co-feeds during POM.The influence of the addition of 1, 2 or 5vol.% of CO, H₂ or CO₂ to the feed during the partial oxidation of methane (POM) was studied over Rh/Ti-modified support catalysts (Rh/Ti–SiO₂, Rh/Ti–Al₂O₃ and Rh/Ti–MgO). The changes observed in the conversion and syngas selectivity in the presence of gaseous co-feeds are due to changes in the kinetics of POM and may be mainly explained by modifications in the oxidation state of rhodium during the reaction. A higher reduction of Rh is observed when 5% of H₂ or CO is co-fed while Rh is maintained in a higher oxidation state in the presence of CO₂ co-feed. Reversibility tests show that the modifications induced by the gaseous promoters in the catalytic performances are reversible. Such changes can alter not only the kinetics of POM but also the kinetics of the other reactions involved (dry reforming and the reverse water-gas shift) during POM reaction. Results have implications in the expression of the reaction kinetics to be used in the modelling of POM reaction mechanism.

Keywords: Partial oxidation of methane; Syngas; Rh/Ti-modified catalysts; H; ₂; CO and CO; ₂; co-feeding

Dry reforming of methane in a stagnation-flow reactor using Rh supported on strontium-substituted hexaaluminate by Nicholas E. McGuire; Neal P. Sullivan; Olaf Deutschmann; Huayang Zhu; Robert J. Kee (pp. 257-265).

Display Omitted▶ Stagnation-flow reactor provides new experimental data to assist in extending previously published reaction mechanisms to a greater range of conditions. ▶ Effective modeling of dry reforming methane is most sensitive to three elementary reaction rates identified here. ▶ Reaction pathways show that the adsorbed HCO species is an important reaction step in modeling dry reforming of methane. ▶ In the present reaction pathway surface carbon is oxidized primarily by surface atomic oxygen from HCO*.A combination of experiment and modeling is used to investigate catalytic reforming of methane with carbon dioxide (dry reforming) in a stagnation-flow reactor. The catalyst surface is a porous washcoat of rhodium supported on strontium-substituted hexaaluminate. The stagnation-flow configuration enables microprobe sampling of the compositional boundary layer adjacent to the catalyst surface. This configuration also enables efficient modeling the heterogeneous chemistry, coupled with convective and diffusive transport within the gas-phase boundary layer. The measurements provide new data that assist the fundamental understanding of methane dry reforming. The modeling incorporates an elementary reaction mechanism that was developed initially to represent catalytic partial oxidation and steam reforming. Representing the new dry-reforming measurements required modification of reaction rates for CO₂ and CH₄ interactions on the catalyst surface.

Keywords: Methane; Dry reforming; Rhodium; Hexaaluminate; Stagnation flow; Modeling

Methane oxidation to methyl bisulfate in oleum at ambient pressure in the presence of iodine as a catalyst by Beata Michalkiewicz (pp. 266-268).

Display Omitted▶ I₂ catalyses CH₄ oxidations to CH₃OSO₃H in oleum at ambient pressure. ▶ High sulfur trioxide concentration and low flow of methane is recommended. ▶ The optimum of temperature is equal to 130°C. ▶ The optimum number of passes of the liquid through the reactor is equal to 5.Methane oxidation to methyl bisulfate at ambient pressure in absorption reactor packed with glass balls in presence of iodine as a catalyst was investigated. The process was performed at temperature 120–130°C, sulfur trioxide concentration in oleum 16–25wt.%, catalyst concentration 0.008–0.024moldm⁻³, methane flow: 8.69cm³min⁻¹. The optimal conditions for high ester concentration were defined.

Keywords: Methane; Oleum; Methyl bisulfate; Iodine

Photocatalytic behavior of ZnO and Pt-incorporated ZnO nanoparticles in phenol degradation by N. Morales-Flores; U. Pal; E. Sánchez Mora (pp. 269-275).

Display Omitted▶ Pt-incorporated ZnO nanoparticles are prepared by Triton assisted thermolysis. ▶ Catalytic activity of the composite particles is studied for Pheno degradation. ▶ ZnO nanoparticles decorated with tiny Pt clusters work as efficient slective catalysts.Nanostructured Pt–ZnO composite thick films were prepared using the composite nanoparticles synthesized through Triton X-100 polymer assisted thermolysis of zinc acetate. It has been observed that only a fraction of added Pt incorporates into the ZnO lattice and the rest segregates over the ZnO nanoparticle surface to form metallic nanoclusters. Morphology, crystallinity, and optical properties of the ZnO and Pt–ZnO nanostructures have been studied. Photocatalytic behavior of the samples for phenol degradation process has been studied in a high performance liquid chromatography system. It has been observed that though the phenol degradation rate is higher for pure ZnO nanostructures, Pt–ZnO nanostructures act as selective catalyst, producing only one intermediate product and dissociating it faster than ZnO.

Keywords: Photocatalysis; Phenol degradation; ZnO; Pt–ZnO; HPCL

Solvent effects in liquid-phase dehydration reaction of ethanol to diethylether catalysed by sulfonic-acid catalyst by Laurent Vanoye; Marie-Line Zanota; Audrey Desgranges; Alain Favre-Reguillon; Claude De Bellefon (pp. 276-280).

Display Omitted▶ The dehydration of ethanol to diethylether over heterogeneous sulfonic-acid catalysts. ▶ A strong dependence was found between solvent properties and initial reaction rate. ▶ Ethanol concentration has a very complex effect on the reaction rate. ▶ Such properties can be evaluated using an α scale of solvent hydrogen-bond donor (HBD). ▶ A good fit is observed using solvent scale from Kamlet–Taft.The liquid-phase dehydration of ethanol to diethylether over heterogeneous sulfonic-acid catalysts was carried out in a stirred batch reactor. The different Amberlyst catalysts were found to have similar activities for this reaction; even though Amberlyst 70 showed a lower acid capacity compensated by a higher specific activity. By comparing the conversion of ethanol as a function of reaction mixture composition, it was found that reaction rates greatly depended on ethanol concentration but also on reaction mixture polarity. The swelling of the used resins could not explain the observed variations of initial reaction rate since this effect was observed both with resins and with homogeneous catalyst, i.e. p-toluenesulfonic acid. The initial ethanol concentration has a complex effect on initial reaction rates that could not be correlated by usual kinetic models. Taking account of the intrinsic reactivity trends of the SN₂ etherification reaction, a strong dependence was found between solvent properties and initial reaction rate.

Keywords: Etherification; Sulfonic-acid catalysts; Ethanol; Solvent effect

Cu-Zr-Zn catalysts for methanol synthesis in a fluidized bed reactor by Guogao Wang; Yizan Zuo; Minghan Han; Jinfu Wang (pp. 281-286).

Display Omitted▶ Cu-Zr-Zn catalyst has suitable activity, high stability and enough attrition resistance. ▶ The particle of the catalyst is well-fluidized. ▶ Cu:Zr:Zn=4.5:3:1.5 turns out to be an optimal catalyst composition.Ten Cu-Zr-Zn catalysts prepared by reverse coprecipitation were evaluated for use for methanol synthesis at 230–270°C and 4MPa. The catalysts were characterized by N₂O-chemisorption, X-ray diffraction, scanning electron microscopy, and their attrition resistance and particle size distribution. The data showed that many of the catalysts had suitable activity, shape, size and mechanic strength. Catalyst stability during reaction at 260°C for 120h was also studied. The catalyst with the composition of Cu:Zr:Zn=4.5:3:1.5 was optimal for methanol synthesis in a fluidized bed reactor.

Keywords: Methanol synthesis; Cu-Zr-Zn catalyst; Fluidized bed reactor

A study of the redox properties and methanol oxidation rates for molybdenum-based mixed oxides by Ivan Baldychev; Ashay Javadekar; Douglas J. Buttrey; John M. Vohs; Raymond J. Gorte (pp. 287-293).

Display Omitted▶ The redox properties of Al₂(MoO₄)₃, Zr(MoO₄)₂, Cr₂(MoO₄)₃, and MgMoO₄ are identical. ▶ The redox properties of SrMoO₄ differ significantly from the other mixed oxides. ▶ Thermodynamic properties of all mixed oxides are different from that of bulk MoO₃. ▶ Mixed oxides have lower catalytic activity for CH₃OH oxidation than bulk MoO₃. ▶ The Mo⁶⁺ cations within the MoO₄²⁻ anions are inaccessible to the reactants.The equilibrium properties of bulk MgMoO₄, Zr(MoO₄)₂, Al₂(MoO₄)₃, SrMoO₄, and Cr₂(MoO₄)₃ have been characterized by coulometric titration at 873K in order to understand the effect of the mixed-cation environment on the Mo⁶⁺–Mo⁴⁺ redox properties and how this in turn affects reactivity for methanol oxidation. The structures of the oxidized and reduced phases were also characterized by XRD. With SrMoO₄, reduction resulted in the formation of SrMoO₃; however, each of the other oxides underwent a reversible decomposition. MgMoO₄ formed a mixture of crystalline MgO and Mg₂Mo₃O₈; Zr(MoO₄)₂ reduced to MoO₂ and a mixture of monoclinic and tetragonal ZrO₂; and Cr₂(MoO₄)₃ formed a new crystalline phase. For MgMoO₄, Zr(MoO₄)₂, Al₂(MoO₄)₃, and Cr₂(MoO₄)₃, removal of one O/Mo occurred at a P(O₂) of 10⁻⁶atm, corresponding to a Δ G of oxidation of −100kJ/mol-O₂; however, the equilibrium between SrMoO₄ and SrMoO₃ occurred at 10⁻²⁶atm O₂, corresponding to a Δ G of oxidation equal to −375kJ/mol-O₂. These thermodynamic properties differ significantly from oxidation of MoO₂ to MoO₃, for which Δ G is −220kJ/mol-O₂ at 873K. All of the mixed oxides were essentially inactive for the selective oxidation of methanol, with specific rates that were much lower than that observed for MoO₃.

Keywords: Coulometric titration; Redox properties; MgMoO; ₄; Zr(MoO; ₄; ); ₂; Al; ₂; (MoO; ₄; ); ₃; Cr; ₂; (MoO; ₄; ); ₃; SrMoO; ₄; Methanol oxidation

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Applied Catalysis A, General (v.394, #1-2)

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Applied Catalysis A, General (v.394, #1-2)