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Applied Catalysis A, General (v.441-442, #)
Heterogeneous photocatalytic degradation of recalcitrant pollutants over CdS–TiO2 nanotubes: Boosting effect of TiO2 nanoparticles at nanotube–CdS interface by Winn Wilson; A. Manivannan; Vaidyanathan Ravi Subramanian (pp. 1-9).
Display Omitted► CdS deposits on TiO2 nanotubes enhance photodegradation of methyl orange and phenol. ► Interfacial TiO2 nanoparticulate film (T_NP) boosts photocatalysis in both cases. ► Optimal Na2S+toxin stabilize CdS and promotes charge separation and photocatalysis. ► Charge transfer mechanism examined with photoelectrochemical and Mott–Schottky tests.The heterogeneous photocatalytic degradation of a textile dye, over TiO2 nanotubes (T_NT) containing nanocrystals of cadmium sulfide (CdS) and an interfacial layer of TiO2 nanoparticles (T_NP) is presented. T_NT is prepared by anodization of Ti mesh. A TiCl4 treatment is implemented to deposit T_NP on T_NT when applicable. CdS nanocrystals are prepared using a successive ionic layer adsorption and reaction approach. Methyl orange (MO) and phenol conversion on the different photocatalysts follows the trend: T_NT/T_NP/CdS>T_NT/CdS>T_NT with the actual values of fractional conversion of MO being 0.94, 0.64, and 0.04 respectively. The role of Na2S in MO photodegradation and CdS stabilization is examined in detail. The addition of a limited amount of Na2S (up to a concentration of 0.02M) with MO has multiple benefits including (i) improvement in electron separation and transport, (ii) stabilization of the CdS, and (iii) enhancement of the photocatalytic degradation of MO by 35%.
Keywords: TiO; 2; -nanotubes; Anodization; CdS nanocrystals; SILAR; Photocatalysis; Methyl orange; Phenol; Mott–Schottky; Kinetics
n-Hexadecane hydrocracking Single-Event MicroKinetics on Pt/H-beta by B.D. Vandegehuchte; J.W. Thybaut; A. Martínez; M.A. Arribas; G.B. Marin (pp. 10-20).
Display Omitted► The single-event concept was successfully applied to n-alkane hydrocracking on beta. ► The beta zeolite showed minor shape selectivity in the formation of ethyl branches. ► Micropore saturation effects were induced by strong physisorption of hexadecane. ► Secondary cracking reactions were allowed by incorporating size entropy effects.The Single-Event MicroKinetic (SEMK) model constructed for gas-phase hydroconversion of light n-alkanes on large-pore USY zeolites was applied, for the first time, to the hydrocracking of n-hexadecane on a Pt/H-Beta catalyst. Despite the 12-ringed pore channels, shape selectivity was observed in the formation of ethyl side chains. Additionally, heavy feed molecules such as n-hexadecane lead to physisorption saturation of the catalyst pores by strong Van der Waals interactions of the long alkyl chains with the zeolite framework. Intermolecular interactions and packing efficiencies in the pores induce deviations from typical Henry-regime physisorption characteristics as the physisorption selectivity, which is expected to increase with increasing carbon number, appeared to be independent of the latter. Micropore saturation effects were described by the ‘size entropy’ which quantifies the difference in standard entropy loss between physisorption in the Henry regime and hindered physisorption on a saturated surface. The size entropy is proportional to the catalyst loading with physisorbed species and the adsorbate carbon number. The addition of a size entropy term in the SEMK model, amounting to 102Jmol−1K−1 for a hexadecane molecule at full saturation, allowed accurately reproducing the contribution of secondary isomerization and cracking reactions, as quantified by means of a contribution analysis.
Keywords: Hydrocracking; Single-Event MicroKinetic modeling; Beta zeolite; Micropore saturation; Size entropy
Synthesis of isoprene from formaldehyde and isobutene over phosphate catalysts by V.L. Sushkevich; V.V. Ordomsky; I.I. Ivanova (pp. 21-29).
Display Omitted► Formaldehyde condensation with isobutene has been studied over phosphate catalysts. ► The reactivity of phosphates increases in the following order: BP≪AlPδ+Oδ− ion pairs are responsible for competitive carbon monoxide formation. The high resistance of ZrP and NbP catalysts to deactivation is accounted for by the in situ restoration of the Brønsted acid sites in the presence of water directly during the time course of the reaction.
Keywords: Prins condensation; Isoprene; Phosphates; Deactivation
Oxidative dehydrogenation of propane with N2O over Fe-ZSM-5 and Fe–SiO2: Influence of the iron species and acid sites by Ayten Ates; Christopher Hardacre; Alexandre Goguet (pp. 30-41).
Display Omitted► Fe-ZSM-5 zeolites prepared with solid-state show high stability for ODHP. ► The acidity degree of Fe-ZSM-5 is important for high propene selectivity. ► The acidity of Fe-ZSM-5 can be controlled by the treatment conditions and Si/Al ratio. ► Highly selective propane dehydrogenation to propene over Fe–SiO2 is obtained.A series of iron containing zeolites with varying Si/Al ratios (11.5–140) and low iron content (∼0.9wt.% Fe) have been synthesised by solid-state ion exchange with commercially available zeolites and tested, for the first time, in the oxidative dehydrogenation of propane (ODHP) with N2O. The samples were characterised by XRD, N2-Adsorption, NH3-TPD and DR-UV–vis spectroscopy. The acidity of the Fe-ZSM-5 can be controlled by high temperature and steam treatments and Si/Al ratio. The selectivity and yield of propene were found to be the highest over Fe-ZSM-5 with low Al contents and reduced acidity. The initial propene yield over Fe-ZSM-5 was significantly higher than that of Fe–SiO2 since the presence of weak and/or medium acid sites together with oligonuclear iron species and iron oxides on the ZSM-5 are found to enhance the N2O activation. The coking of Fe-ZSM-5 catalysts could also be controlled by reduction of the surface acidity of ZSM-5 and by the use of O2 in addition to N2O as the oxidant. Fe-ZSM-5 zeolites prepared with solid-state method have been shown to have comparable activity and better stability towards coking compared with Fe-ZSM-5 zeolites prepared by liquid ion exchange and hydrothermal synthesis methods.
Keywords: Fe-ZSM-5; Dehydrogenation of propane; Propene; Nitrous oxide; Fe–SiO; 2
Sequential deracemization of sulfoxides via whole-cell resolution and heterogeneous oxidation by Madalina Tudorache; Simona Nica; Emerich Bartha; Iulia Lupan; Vasile I. Parvulescu (pp. 42-46).
Display Omitted► Enantioreduction of rac-sulfoxide was performed using Escherichia coli biocatalyst. ► Optimum growth conditions of E. coli biocatalyst have been set up. ► Selectivity of the biocatalyst was tested for different rac-sulfoxides. ► Sequential two-step deracemization was performed for rac-sulfoxides.A new concept for the synthesis of asymmetric sulfoxides exploiting sequential deracemization of racemic ( rac) sulfoxides using a two-stage protocol had been developed. Enantio-pure sulfoxide was obtained using Escherichia coli ( E. coli) cells to catalyze the reduction of ( R)-sulfoxide to the thioether, and then using a heterogeneous Ta2O5–SiO2 catalyst for catalyzing the oxidation of the ethers to the rac-sulfoxide. The performance of E. coli depended on the strain and the conditions under which the bacteria growth was carried out ( e.g. source of carbon, presence of vitamins, and concentration of dimethyl sulfoxide, DMSO). Under optimized conditions, the E. coli cells performed the rac-sulfoxide resolution for different sufoxides leading to the best enantiomeric excess (ee) of around 62% ( S)-MTSO (methyl tolyl sulfoxide) with 49% conversion of the rac-MTSO. The sequential deracemization process applied for rac-MTSO was cyclically performed leading to 97.5% ee of ( S)-sulfoxide and a 56% yield in ( S)-sulfoxide after three deracemization cycles of rac-MTSO.
Keywords: Sequential deracemization; Racemic sulfoxides; Escherichia coli; Enantioselective reduction; Selective heterogeneous oxidation
Microwave-assisted mild-temperature preparation of neodymium-doped titania for the improved photodegradation of water contaminants by Virginia Gomez; Alina Mariana Balu; Juan Carlos Serrano-Ruiz; Silvia Irusta; Dionysios D. Dionysiou; Rafael Luque; Jesús Santamaría (pp. 47-53).
Display Omitted► Nd-doped TiO2 catalysts prepared by a microwave-assisted methodology. ► This methodology leads to high surface area and homogeneous Nd dispersion on TiO2. ► Excelling photodegradation activities for phenol and Rhodamine B removal.Nd-doped titania materials prepared using a mild microwave-assisted protocol have been found to possess excelling activities in the photodegradation of water contaminants including phenol and Rhodamine B. These materials were characterized by a number of techniques including N2 adsorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The prepared materials showed high surface area, with the highest value for the catalyst containing a Nd/Ti ratio of 0.03 (341m2/g). The dopant agent was found to be as Nd3+ ions located on the surface and in the inter-planar space of titanium oxide crystals. Effects of the surface area together with the Nd content and the adsorption ability of the material seem to be involved in the optimum photocatalytic activity found for 0.5%Nd (Nd0.005/TiO2) and 6%Nd (Nd0.06/TiO2) containing materials.
Keywords: Neodymium; Titania; Photocatalysis; Phenols; Band gap; Water treatment
Metal microfibers entrapped catalysts as effective ambient temperature CO oxidation catalysts by Shirish S. Punde; Bruce J. Tatarchuk (pp. 54-64).
Display Omitted► Pt–ceria/silica catalyst entrapment in Ni fibers was investigated for CO oxidation at ambient conditions. ► A 1-D, non-isothermal, transient reactor model was developed and validated against reactor data. ► Effect of heat/mass transport properties on activity was studied by catalyst dilution and by simulations. ► Stability of Ni microfibers entrapped catalysts was studied.CO oxidation reaction on a highly active Pt–CeO2/SiO2 catalyst was found to be diffusion controlled at ambient conditions ( T<50°C; 50–90% RH); therefore, the use of smaller catalyst particles was imperative for optimum Pt utilization. Packed beds (PBs) of smaller particles (dia.<500μm) cause problems such as flow maldistribution and channeled flow due to cluster formation. Also these PBs are susceptible to changes in orientations and vibrations resulting in catalyst bypass and reduced activity. Nickel metal microfibrous entrapped Pt–CeO2/SiO2 catalysts (MFECs) were developed to circumvent these problems with the PBs. These MFECs outperformed the conventional catalyst PB with equivalent catalyst loading over a wide range of CO concentrations (100–10,000ppm) and exhibited greater stability. The entrapment of catalyst particles has a significant impact on the heat and mass transport properties of the reactor. Therefore, the effects of transport properties on activity were investigated experimentally using diluted PBs and by reactor simulation using a transient, non-isothermal model to understand the activity improvement by MFECs. Experimental and simulation results showed that while the thermal properties significantly affect the activity, the axial mass dispersion had negligible impact on the activity. MFECs have greater thermal conductivity due to the presence of Ni fibers and the inert thermal mass of the Ni fibers was minimal (33% of the catalyst PB). MFECs have a uniform and more open (void: 0.5–0.8) structure and the entrapment of particles minimizes cluster formation. Due to these better heat and mass transport properties, MFECs outperformed PBs. Also, these MFECs are flexible and pleatable which makes them a potential candidate for CO removal applications.
Keywords: CO oxidation; Pt; Ceria; Entrapment; Metal fibers; COMSOL; Reactor model; Catalyst
Preparation, characterization, and catalysis application of nano-rods zinc oxide in the synthesis of 3-indolyl-3-hydroxy oxindoles in water by Mona Hosseini-Sarvari; Mina Tavakolian (pp. 65-71).
Display Omitted► Nano-rods ZnO catalyst has been synthesized and characterized. ► Nano-rods ZnO acts as a catalyst in water for the synthesis of 3-indolyl-3-hydroxy oxindoles. ► ZnO nano-rods is synthesized successfully by a new method.ZnO nano-rods is synthesized successfully by a new method employing Zn(OAc)2·2H2O, NH3 and polyethylene glycol (PEG, Mw=2000). X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and BET surface area measurement were used to characterize the structure and morphology of the catalyst. Nano-rods ZnO has been found highly effective and recyclable catalyst for synthesis of 3-indolyl-3-hydroxy oxindole derivatives by Friedel–Crafts reaction of indole with isatins in excellent yields, in water.
Keywords: Nano-rods ZnO; 3-Indolyl-3-hydroxy oxindole; Isatin; Indole; Water; Friedel–Crafts reaction
Effect of SiO2 pore size on partial hydrogenation of rapeseed oil-derived FAMEs by Natthida Numwong; Apanee Luengnaruemitchai; Nuwong Chollacoop; Yuji Yoshimura (pp. 72-78).
Display Omitted► Oxidative stability of fatty acid methyl esters was improved by partial hydrogenation. ► Hydrogenation activity over Pd/SiO2 catalysts strongly depends on pore sizes of SiO2. ► Hydrogenation activity was maximized around the SiO2 pore size of 45nm. ► Cis–trans selectivity depends on contact probability between reactant and catalyst.Palladium (Pd) supported on different SiO2 pore sizes: Q3, Q10, Q30, and Q50 with pore diameters of 3, 5, 30, and 50nm, respectively, were studied for the partial hydrogenation of rapeseed oil-derived fatty acid methyl esters (FAMEs). The supports and catalysts were characterized by BET, NH3-adsorption, and CO-chemisorption technique. Highest turn over frequency (TOF) was found for Pd/Q30, while Pd/Q3 exhibited the lowest TOF. The reaction rate constants for each hydrogenation step, consequently from C18:3 to C18:2, C18:1, and C18:0, i.e., k1, k2, and k3, respectively, were determined by POLYMATH Professional 6.2 and could explain the effect of SiO2 pore size on pore diffusion of FAMEs reactant and contact probability between reactant molecules and active sites. Moreover, pore size of the SiO2 support also affected on selectivity toward trans-monounsaturated FAME. The Pd/Q3 catalyst presented the lowest trans-monounsaturated FAME selectivity due to its smallest pore size and acidic properties. In addition, it was found that 0.5h of hydrogenation time using Pd/Q10, Pd/Q30, and Pd/Q50 could improve the oxidative stability to >10h.
Keywords: Partial hydrogenation; Pd/SiO; 2; Pore size; Biodiesel; Oxidative stability
Selective oxidation of phenol and benzoic acid in water via home-prepared TiO2 photocatalysts: Distribution of hydroxylation products by Marianna Bellardita; Vincenzo Augugliaro; Vittorio Loddo; Bartolomeo Megna; Giovanni Palmisano; Leonardo Palmisano; Maria Angela Puma (pp. 79-89).
Display Omitted► Photocatalytic hydroxylation of phenol and benzoic acid was carried out in the presence of TiO2 catalysts. ► Distribution of hydroxylation products was correlated with some catalysts features. ► Selectivity depended on photocatalyst hydroxylation degree. ► Satisfactory fitting of experimental data to the Langmuir–Hinshelwood kinetic model was found.The hydroxylation of phenol (a substrate containing an electron donor group) and of benzoic acid (a substrate containing an electron withdrawing group) has been carried out by the photocatalytic method in aqueous suspensions containing commercial or home prepared TiO2 samples. The aim of the work was to study the distribution of hydroxylation products when different photocatalysts were used and to correlate the selectivity to some physico-chemical features of the powders. The samples were characterized by X-ray diffraction, thermogravimetry, determination of crystalline phase percentage, specific surface area and zero charge point. The photoreactivity results indicate that the products of the primary oxidation of phenol are the ortho- and para-mono-hydroxy derivatives while those of benzoic acid are all the mono-hydroxy derivatives independently of the catalyst. The selectivity toward mono-hydroxy derivatives shows a strong dependence on catalyst hydroxylation and crystallinity degrees: the highest selectivity values were obtained by using the commercial samples that resulted the least hydroxylated and the most crystalline ones. A kinetic model, taking into account the mineralization and the partial oxidation reaction routes, is proposed by using the Langmuir–Hinshelwood model.
Keywords: Selective hydroxylation; Product distribution; Benzoic acid; Phenol; Heterogeneous photocatalysis; Reaction pathways; Kinetics; TiO; 2
Partial hydrogenation of 3-hexyne over low-loaded palladium mono and bimetallic catalysts by M. Juliana Maccarrone; Cecilia R. Lederhos; Gerardo Torres; Carolina Betti; Fernando Coloma-Pascual; Mónica E. Quiroga; Juan C. Yori (pp. 90-98).
Display Omitted► Cheaper mono and bimetallic catalysts with low Pd, Ni and W loadings are prepared. ► Catalysts are evaluated during 3-hexyne partial hydrogenation between 273 and 323K. ► Low-loaded palladium catalysts are highly selective to ( Z)-3-hexene (>93%). ► At mild conditions, catalysts are considerably more active than Lindlar catalyst. ► Palladium electron-rich species are responsible of the higher activity.Partial hydrogenation of alkynes has industrial and academic relevance on a large scale, especially those with high selectivities. To increase the activity, selectivity and lifetime of low-loaded Pd monometallic catalyst, the development of bimetallic systems has been investigated. In this work Pd mono (Pd/A) and bimetallic catalysts (PdNi/A and WPd/A) supported on γ-alumina with low metal content are prepared and evaluated during the partial hydrogenation of 3-hexyne at mild conditions. XPS, XRD, TPR and hydrogen chemisorption techniques are used for the characterization, suggesting different kind of Pd species on the mono and bimetallic catalysts. Furthermore, XPS results indicate the presence of electron rich and electron-deficient palladium species (Pd δ− and Pd n+, with δ close to 0 and 0< n<2, respectively), electron-deficient species of nickel (Ni n+, with n close to 2) and of W ρ+ (with ρ<6) on the surface of the bimetallic systems. The Lindlar commercial catalyst, commonly used in these types of reactions is used for comparative purposes. Bimetallic catalysts showed higher activities and very similar selectivities (>93%) than the monometallic system and further than the Lindlar catalyst. The rank of activity order is: WPd/A>PdNi/A>Pd/A≫Lindlar.
Keywords: Bimetallic catalysts; Alkyne; Selective hydrogenation; Lindlar
Preparation and evaluation of hydrotreating catalysts based on activated carbon derived from oil sand petroleum coke by Yu Shi; Jinwen Chen; Jian Chen; Robb A. Macleod; Marek Malac (pp. 99-107).
Display Omitted► Alberta oil sand petroleum coke was successfully converted into activated carbon. ► Ni–Mo hydrotreating catalysts were prepared using the obtained AC as support. ► Batch reactor experiments were conducted for hydrotreating heavy vacuum gas oil. ► Activity of the new AC supported catalysts was compared with 4 reference catalysts. ► The newly developed AC supported catalysts show better hydrotreating performance.Novel Ni–Mo/activated carbon (AC) hydrotreating catalysts were prepared and evaluated for upgrading heavy vacuum gas oil (HVGO). The AC supports were derived from Alberta oil sand petroleum coke, i.e. fluid coke and/or delayed coke, hereafter referred to as OSP coke, through a chemical process. The BET surface area was as high as 2194m2/g for the fluid coke derived AC and 2357m2/g for the delayed coke derived AC. Both ACs contained a large number of micropores with pore volume as high as 1.2cm3/g. Ni and Mo based active component precursors could be easily loaded on the activated carbon supports by chemical impregnation of nickel nitrate and ammonium molybdate followed by calcination in nitrogen at 773K without further modification or oxidation treatment to the activated carbons. Scanning electron microscopy (SEM) observation showed highly porous surface structure of the bare activated carbon supports and well dispersed metal (oxide) precursor nanoparticles of 30–50nm loaded on the AC supports. For comparison, two reference catalysts were also prepared by the same procedure but using commercial activated carbon and porous alumina as supports. After catalyst activation by sulfiding, the hydrotreating performance of the prepared catalysts was evaluated in a magnetically stirred autoclave with a HVGO feedstock to examine their hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) activities. Two commercial hydrotreating catalysts were also tested and compared under similar conditions with the same feed. The results showed that the catalysts based on the activated carbon supports prepared from OSP coke had better hydrotreating performance than the other catalysts. Scanning transmission electron microscopy (STEM) characterization of the catalysts after activation showed that small particles of nanostructure (2–5nm in size) were evenly embedded in the carbon matrix except for some bigger particles that were located on the catalyst surface. Energy dispersive X-ray (EDX) spectroscopy revealed that these particles were composed of Ni, Mo and S elements. The dispersed nanoparticles formed the active sites and were responsible for the observed high HDS and HDN activity. Elemental analysis and surface characterization of the spent catalysts showed that the formation of coke precursors was favored on the alumina supported catalyst, which resulted in catalyst deactivation.
Keywords: Oil sand petroleum (OSP) coke; Activated carbon (AC); Hydrotreating; Heavy vacuum gas oil (HVGO)
Synthesize 2-methylpyrazine using aqueous glycerol and ethylenediamine over zinc oxide–zinc chromite catalysts: Structure–activity relationship by Venugopal Akula; Reema Sarkari; Anjaneyulu Chatla; Krishna Vankudoth; Kotesh Kumar Mandari (pp. 108-118).
Display Omitted► Dehydrocyclization of EDA and glycerol produce 2-methylpyrazine over ZnO–ZnCr2O4. ► Nature of ZnO–ZnCr2O4 plays an important role on selectivity of 2MP and pyrazine. ► Intermolecular cyclization of EDA is predominant over crystalline Cr2O3.ZnO–ZnCr2O4 mixed oxides (Zn–Cr–O) were obtained by decomposition of Zn–Cr hydrotalcite precursors synthesized by co-precipitation method at pH∼7 and 9, with a constant Zn/Cr ratio of 2. Based on the product distribution, mechanisms were proposed. The differences in dehydrocyclization activity of Zn–Cr–O mixed oxides were established based on adsorption and spectroscopic data that emphasized changes in the structural properties of Zn–Cr–O obtained at different pHs. X-ray photoelectron (XPS) lines indicated Cr6+ and these species were reduced to Cr3+ during H2-temperature programmed reduction (H2-TPR) analysis. The higher NH3 and O2 uptakes of Zn–Cr–O (pH∼7) than Zn–Cr–O (pH∼9) are attributed to the presence of Cr6+ ions on the catalyst surface. Disorder in the cubic ZnCr2O4 sub-lattice may result in multiple Raman bands appeared in the Zn–Cr–O samples. The characteristic bands of Lewis and Bronsted acid sites at 1450 and 1540cm−1 assigned by FT-IR spectra of pyridine adsorbed on Zn–Cr–O samples, and their relative peak intensities corresponding to Lewis and Bronsted suggested higher ratios for Zn–Cr–O (pH∼7) than for Zn–Cr–O (pH∼9). It is demonstrated that the dehydrocyclization reaction proceeds on ZnO and/or ZnCr2O4 resulting in 2MP synthesis, and catalysts that possess mainly acid sites show intermolecular cyclization of EDA leading to high selectivity of pyrazine.
Keywords: Dehydrocyclization; 2-Methylpyrazine; Raman; NH; 3; uptake; UV–DRS
An efficient synthesis of α-hydroxy phosphonates and 2-nitroalkanols using Ba(OH)2 as catalyst by Muthupandi Pandi; Prem Kumar Chanani; Sekar Govindasamy (pp. 119-123).
Display Omitted► Catalytic amount of Ba(OH)2·8H2O was used as an efficient catalyst. ► Synthesis of α-hydroxy phosphonates with excellent yields in 15min at room temperature. ► The use of Ba(OH)2·8H2O avoids competing Cannizzaro and Tishchenko reactions. ► Synthesis of 2-nitroalkanols was achieved in water and high yields were obtained in 15min at room temperature.The α-hydroxy phosphonates have been synthesized using simple, inexpensive, and commonly available Ba(OH)2·8H2O at room temperature and quantitative yields were obtained in just 15min for most of the reactions. On applying the same reaction condition to aqueous mediated Henry reaction, 2-nitroalkanols were obtained in good to excellent yield within 15min.
Keywords: Barium hydroxide; Hydrophosphorylation; Pudovik reaction; α-Hydroxy phosphonates; Henry reaction; 2-Nitroalkanols
Skeletal isomerization of 1-butene over micro/mesoporous materials based on FER zeolite by Yu.P. Khitev; I.I. Ivanova; Yu.G. Kolyagin; O.A. Ponomareva (pp. 124-135).
Display Omitted► Micro/mesoporous catalysts were prepared by recrystallization of FER zeolite. ► Recrystallized FER showed improved catalytic performance in butene-1 isomerization. ► The enhanced activity is due to higher accessibility of the acid sites. ► The improved selectivity and stability is due to coating of FER with mesoporous phase.Skeletal isomerization of 1-butene has been studied over composite micro/mesoporous zeolitic catalysts prepared by the recrystallization of ferrierite (FER) in alkaline solutions in the presence of cethyltrimethylammonium bromide and by the desilication of FER in alkaline solutions. Desilication procedure led to the creation of large mesopores in zeolite crystal with broad distribution of size. Recrystallization procedure resulted in two types of mesoporosity: uniform intracrystalline mesopores homogeneously distributed along the crystal and intercrystalline ordered mesoporous layers covering zeolite crystal. Recrystallized materials showed improved catalytic performance in skeletal isomerization of 1-butene with respect to both parent and desilicated ferrierites. The effect is due to the improved accessibility of the acid sites and the creation of new pore mouths, in which the active carbonaceous species responsible for selective pseudo-monomolecular pathway can be formed. The improved stability of catalytic activity with time on stream is due to coating of ferrierite crystals with mesoporous layes, which prevent the deactivation of the catalysts. The best catalytic performance was achieved over composite micro/mesoporous materials with intermediate degree of recrystallyzation due to proper balance between zeolitic and mesoporous phases and the amount and density of the acid sites.
Keywords: Isomerization; n-Butene-1; Ferrierite; Micro/mesoporous catalysts
One-step aerobic oxidation of cyclohexane to adipic acid using an Anderson-type catalyst [(C18H37)2N(CH3)2]6Mo7O24 by Hongying Lü; Wanzhong Ren; Pengfei Liu; Shixue Qi; Wenhua Wang; Yongmei Feng; Fengxin Sun; Yuanwei Wang (pp. 136-141).
Display Omitted► One step oxidation cyclohexane to AA was attempted without additives and solvent. ► [(C18H37)2N(CH3)2]6Mo7O24 was an effective catalyst for oxidation of cyclohexane. ► The high selectivity (87.1%) at good conversion (10.2%) can be achieved. ► The TOF can reach 3.3×107.Aerobic oxidation of cyclohexane to adipic acid (AA) was performed using a series of environmentally benign Anderson-type as catalysts. It is found that the Anderson-type catalyst with metal molybdenum as the central ion, [(C18H37)2N(CH3)2]6Mo7O24, showed the highest catalytic activity and selectivity among the prepared catalysts. The effect of several reaction parameters (the amount of catalyst, oxygen pressure, reaction temperature and time) on the oxidation process was investigated and optimized. The catalyzed system (catalyst concentration: 1ppm, 160°C, 6h) demonstrated excellent reactivity that 87.1% selectivity for AA can be achieved at good conversion (10.2%) and the turnover number (TON) can reach 3.3×107. The oxidative mechanism was observed to be involved in a free radical process.
Keywords: Aerobic oxidation; Cyclohexane; Adipic acid (AA); One-step AA process