Applied Catalysis A, General (v.529, #C)
Editorial Board (IFC).
Synthesis Gas Production by Catalytic Partial Oxidation of Propane on Mesoporous Nanocrystalline Ni/Al2O3 Catalysts by Mohammad Peymani; Seyed Mehdi Alavi; Mehran Rezaei (1-9).
Display OmittedPropane partial oxidation to synthesis gas at various feed conditions was investigated over nickel catalysts supported on high surface area γ-alumina. The physicochemical characteristics of the calcined, reduced and spent samples were determined by TPR, BET, XRD, TPO and SEM analyses. The influences of Ni content, reduction and reaction temperatures, gas hourly space velocity (GHSV) and feed ratio on the catalytic properties were investigated. The activity measurements revealed that the propane conversion had a direct relation with reaction temperature and nickel loading and increased with increasing of both these factors. However, there was an optimum value for nickel content and reaction temperature in which the H2 and CO yields were maximum. The 7.5 wt% Ni/Al2O3 exhibited high stability for 12 h without any decrease in activity. However, the selectivity declined gradually with reaction time due to carbon formation. The TPO analysis revealed that an increase in O2/C molar ratio from 0.25 to 0.75 caused a decrease in the amount of deposited carbon. Also, the amount of accumulated carbon slightly decreased with rising the reaction temperature. These results were confirmed by the SEM analysis and the filamentous carbon was observed on the catalyst surface. In addition, the increase in reduction temperature caused an increase in C3H8 conversion and H2/CO ratio.
Keywords: Propane partial oxidation; Coke formation; Nickel catalysts; Mesoporous; ɤ-alumina;
Calculation of MoS2 slabs morphology descriptors from transmission electron microscopy data revisited. Case study of the influence of citric acid and treatment conditions on the properties of MoS2/Al2O3 by P. Afanasiev (10-19).
Revisited method of calculation of MoS2 slabs length and stacking in the supported catalysts has been used in a systematic study of the influence of citric acid and treatment conditions on the sulfide morphology and HDS activity.Display OmittedMolybdenum sulfide MoS2 slabs length L and stacking S obtained from the transmission microscopy (TEM) images are the major characteristics of hydrotreating sulfide catalysts, widely used as morphology descriptors. In this work we demonstrate that the formulae routinely used to estimate mean L and S should be revisited. To obtain physically meaningful values L and S, both should be calculated as surface weighted averages. Moreover, correlation between L and S must be taken into account. Using surface weighted values of mean L and S, MoS2 phase morphology was studied for a series of MoS2/Al2O3 catalysts. The effects of Mo loading, addition of citric acid and sulfidation by H2S/N2 or H2S/H2 mixtures at different temperatures from 350 to 550 °C were studied. The catalysts were evaluated in hydrodesulfurization of thiophene (HDS) and studied by temperature programmed reduction (TPR). Thorough statistical treatment of TEM, HDS and TPR data suggests that the intrinsic properties of MoS2 active phase depend primarily on the treatment atmosphere and temperature rather than on the addition of citric acid. If the impregnated catalyst is dried at temperature above 120 °C, citric acid allows moderate improvement of MoS2 morphology. However the edge-specific activity of supported sulfide remains unaffected.
Keywords: Molybdenum sulfide; Citric acid; Hydrodesulfurization; Transmission microscopy; Temperature programmed reduction;
Product tunable behavior of carbon nanotubes-supported Ni–Fe catalysts for guaiacol hydrodeoxygenation by Huihuang Fang; Jianwei Zheng; Xiaolin Luo; Junmou Du; Alberto Roldan; Stefano Leoni; Youzhu Yuan (20-31).
Display OmittedBimetallic Ni–Fe nanoparticles supported on carbon nanotubes (CNTs) are prepared and evaluated for the catalytic hydrodeoxygenation (HDO) of a lignin-derived model compound guaiacol. Appropriate combination of Ni and Fe affords high activity and significantly enhances selectivity to cyclohexane or phenol, whereas monometallic Ni and Fe catalysts display poor activities or selectivities. The product tunable behavior of guaiacol HDO is found to be dependent on Ni/Fe atomic ratios. Cyclohexane and phenol are the major products over Ni5–Fe1/CNT with Ni/Fe atomic ratio at 5/1 and Ni1–Fe5/CNT with Ni/Fe atomic ratio at 1/5, respectively. Characterization results confirm that Ni–Fe alloys are formed and elicit synergistic effects on the HDO performance. The selectivity-switchable performance of Ni–Fe/CNT can be assigned to the synergism between Ni domains, where H2 can be easily activated, and Fe domains, which exhibited strong oxophilicity. The bimetallic catalysts give an enhanced stability without significant sintering of metal nanoparticles, while the monometallic catalysts show obvious deactivation due to the agglomeration of metal nanoparticles. Further results reveal that the conversion of guaiacol depends on not only the chemical state but also the size of the metallic nanoparticles. The catalysts with appropriate Ni/Fe atomic ratio and smaller particle perform better hydrogenolysis of C–O bonds, resulting in high selectivity to cyclohexane or phenol.
Keywords: Ni–Fe catalysts; Hydrodeoxygenation; Guaiacol; Cyclohexane; Phenol;
Metal-surfactant interaction as a tool to control the catalytic selectivity of Pd catalysts by A.M. Perez-Coronado; L. Calvo; J.A. Baeza; J. Palomar; L. Lefferts; J.J. Rodriguez; M.A. Gilarranz (32-39).
Display OmittedThe catalytic activity of Palladium nanoparticles synthesized via sodium bis[2-ethylhexyl] sulfosuccinate (AOT)/isooctane reverse microemulsion was studied in nitrite reduction. The influence of reaction conditions and the synthesis and purification of the nanoparticles was evaluated. In the nanoparticle size range studied (6.2–11.6 nm) a lower reaction rate and TOF were observed for small nanoparticles. This apparent structure sensitiveness results from surface blockage due to interaction of AOT with the surface of nanoparticles, as evidenced by purification with several solvents providing different removal of AOT. The activity loss was accompanied by negligible selectivity to ammonium. Large nanoparticles in buffered medium produced insignificant amount of ammonium ion for nitrite conversion values of ca. 80%. The selectivity control is ascribed to preferential blockage of the sites responsible for ammonium generation. The results show the potential of the interaction between the AOT and the nanoparticles as a tool to control catalytic selectivity.
Keywords: Palladium; Nanoparticles; Catalysis; AOT; Nitrite;
Novel capture and photocatalytic conversion of CO2 into solar fuels by metals co-doped TiO2 deposited on PU under visible light by Thanh-Dong Pham; Byeong- Kyu Lee (40-48).
Display OmittedIn this study, Ag and Cu co-doped TiO2 deposited on polyurethane (Ag@Cu-TiO2/PU) was synthesized for the conversion of CO2 into solar fuels under visible light. The synthesized Ag@Cu-TiO2/PU, which synergistically inherited all the advantages of both Ag and Cu doping, exhibited very high photocatalytic activity for the reduction of gaseous CO2 to produce CH4 and CO fuels. The dopants defects in the TiO2 lattice formed Ti3+ and oxygen vacancies in the lattice. The presence of Ti3+ and oxygen vacancies on the surface of the photocatalyst induced the formation of new adsorption sites to adsorb CO2. The Ag and Cu dopants also enhanced the separation of electron–hole pairs of the doped TiO2 photocatalysts. Therefore, the Ag@Cu- TiO2/PU photocatalysts generated electron–hole pairs, which could react with H2O and CO2 to produce the CO and CH4, even under visible light. 2Ag@4Cu-TiO2/PU, corresponding to the Ag/TiO2 and Cu/TiO2 ratios of 2 and 4 wt%, respectively, exhibited the highest photocatalytic reduction of CO2. The yields of CH4 and CO produced from the photocatalytic reduction of CO2 by 2Ag@4Cu-TiO2/PU under visible light were 880 and 550 (μmol/g.cat), respectively.
Keywords: Co-doping; Oxygen vacancy; CO2 conversion; Photocatalytic reduction; Solar fuels;
Bimetallic Ru:Ni/MCM-48 catalysts for the effective hydrogenation of d-glucose into sorbitol by Alberto Romero; Antonio Nieto-Márquez; Esther Alonso (49-59).
Display OmittedThree different bimetallic Ru:Ni catalysts supported on a mesoporous silica MCM-48 were prepared by consecutive wet impregnations, with a total metal loading of ca. 3% (w w−1). Ru:Ni ratios spanned in the range of 0.15–1.39 (w w−1) and were compared with the corresponding monometallic Ni/MCM-48. The catalysts so prepared were characterized by X-Ray Diffraction, Transmission Electron Microscopy, adsorption/desorption of N2, Temperature Programmed Reduction, NH3 − TPD and Atomic Absorption, and tested in the liquid phase hydrogenation of d-glucose into sorbitol in the temperature range 120–140 °C under 2.5 MPa of H2 pressure. Bimetallic catalysts with Ru:Ni ratios higher than 0.45 enhanced the catalytic behavior of the monometallic Ni/MCM-48 in the reaction, increasing the reaction rate and showing complete selectivity to sorbitol by minimizing the production of mannitol. Ru:Ni/MCM-48 (0.45) was recovered from the reaction media and tested for three reaction cycles, showing good stability under the selected experimental conditions.
Keywords: Hydrogenation of sugars; Sorbitol; Ruthenium-nickel bimetallic catalysts; MCM-48; d-Glucose;
A highly active and anti-coking Pd-Pt/SiO2 catalyst for catalytic combustion of toluene at low temperature by Hui Wang; Wei Yang; Penghui Tian; Jie Zhou; Rui Tang; Shengji Wu (60-67).
Display OmittedCatalytic combustion has been identified as one of the most efficient and economically feasible routes for removing volatile organic compounds. In this work, supported noble-metal (Pd and Pt) catalysts for catalytic combustion of toluene were prepared by an improved incipient wetness impregnation method. Controlled amounts of oleic acid (OA) were introduced into the aqueous solution of metal salts in this new preparation method, which improved Pd and Pt dispersion remarkably on SiO2, as confirmed by XRD and TEM. XPS results showed that introduction of OA in the catalyst preparation resulted in increased proportion of metallic palladium. All of the activities in catalysts with OA were much higher than those of the catalysts without OA in the same catalyst system. Among the catalysts prepared, the 0.25%Pd-0.25%Pt/SiO2–OA catalyst exhibited the best catalytic activity for toluene oxidation, and the T98 of toluene was only 160 °C under the conditions of toluene concentration at 1000 ppm and SV at 60,000 mL/(g h). Furthermore, the 0.25%Pd-0.25%Pt/SiO2–OA catalyst maintained high catalytic activity in the active stability test at 160 °C, and the result of TG indicated that no coke was formed on the spent catalyst.
Keywords: Catalytic combustion; Platinum; Palladium; Volatile organic compounds (VOCs); Toluene;
Elucidating the effect of desilication on aluminum-rich ZSM-5 zeolite and its consequences on biomass catalytic fast pyrolysis by Thomas C. Hoff; David W. Gardner; Rajeeva Thilakaratne; Juan Proano-Aviles; Robert C. Brown; Jean-Philippe Tessonnier (68-78).
Display OmittedCatalytic fast pyrolysis (CFP) offers a simple and robust route to convert raw lignocellulosic biomass to aromatic hydrocarbons. During CFP, cellulose, hemicellulose, and lignin are first thermally decomposed to bio-oil vapors that are further converted to aromatics in the presence of a ZSM-5 zeolite catalyst. The high temperatures required for CFP also favor coke formation, an undesired byproduct, through condensation of the oxygenated intermediates on ZSM-5′s outer surface and/or secondary reactions inside its micropores. Introducing mesopores through desilication represents a possible strategy to enhance mass transport and intracrystalline diffusion, and consequently favor aromatic production over undesired coke formation. Here, we study the effect of desilication on the structure, acidity, and performance of aluminum-rich ZSM-5. Detailed characterization of the obtained zeolite catalysts indicates that mild desilication conditions do not significantly affect the elemental composition, crystallographic structure, microporosity, and distribution of aluminum atoms in framework and extraframework sites. However, the number of accessible Brønsted acid sites increased by ∼50% as a result of the enhanced mesoporosity. Desilication increased the aromatic yields obtained for red oak pyrolysis (27.9%) compared to the parent zeolite (23.9%), without impacting the liquid product distribution (67.4% selectivity to benzene, toluene, and xylene). Our results suggest the catalytic performance could be further improved by enlarging the mouth of ink bottle shaped mesopores in order to further enhance mass transport between the gas phase and the zeolite’s micropore network.
Keywords: Heterogeneous catalysis; Biomass conversion; Catalytic fast pyrolysis; ZSM-5; Desilication;
Deoxygenation of octanoic acid catalyzed by hollow spherical Ni/ZrO2 by Hao Chen; Yulong Wu; Suitao Qi; Yu Chen; Mingde Yang (79-90).
Display OmittedA series of Ni located on hollow spherical ZrO2 catalysts was prepared, and their catalytic performances for octanoic acid deoxygenation were investigated. The ZrO2 hollow spheres saturated by the water phase served as a nanoreactor that captured octanoic acid to react with Ni located inside a hollow spherical ZrO2. The complete conversion of octanoic acid deoxygenation could be achieved by migration of reactants and products in the water-oil biphasic phase. Oxygen vacancies on ZrO2 that resulted from calcination temperature improved the catalytic activity of deoxygenation. Propionic acid was taken as a model compound instead of octanoic acid in view of their same functional group (carboxyl), to study the mechanisms of hydrodeoxygenation, decarbonylation, and decarboxylation through density functional theory of calculations. The main reaction route was decarboxylation which was consistent with the experimental results.
Keywords: Hollow spherical Ni/ZrO2 catalyst; Deoxygenation of biooil; Octanoic acid; Density functional theory; Reaction mechanism;
Photocatalytic N2 conversion to ammonia using efficient nanostructured solar-energy-materials in aqueous media: A novel hydrogenation strategy and basic understanding of the phenomenon by Mohsen Lashgari; Parisa Zeinalkhani (91-97).
Display OmittedTo reduce carbon dioxide emission and supply the nitrogen demand of living organisms, it is crucial to employ a green, solar-based strategy to produce ammonia in aqueous media under ambient conditions, via N2 reaction with transiently photogenerated H-atoms upon appropriate semiconductor materials. In this paper, by using a facile precipitation/calcination route, we synthesized some Fe2O3 and TiO2-based uniform nanoparticles and applied them in a water photosplitting setup to photosynthesize ammonia. The maximum yield was obtained for Fe2O3 and was interpreted in terms of its ability to temporarily store hydrogen atoms, adsorb nitrogen molecules, and harvest more photons in the visible region. Based on photocatalytic reduction of protons to H-atoms and stepwise hydrogenation of N ≡ N molecules on the photocatalyst surface, a reaction pathway was proposed. During this N2-photofixation process, the generation of hydrazine by-product was also predicted and confirmed by empirical evidence. Moreover, the role of hole-scavenger additive was discussed in detail from physicochemical standpoint.
Keywords: Ammonia photosynthesis & water photosplitting; Photocatalytic H-atom generation; Hydrogen-based solar fuels; Fe2O3 nanoparticles; Haber-Bosch process;
Ethanol steam reforming over Pt/Al2O3 and Rh/Al2O3 catalysts: The effect of impurities on selectivity and catalyst deactivation by Muhammad Bilal; S. David Jackson (98-107).
Display OmittedBioethanol contains different types of organic impurities which can have a significant influence on the catalytic performance during steam reforming of bioethanol. Different C3 functional group impurities were added individually to the pure ethanol to investigate the influence of different functional groups on the ethanol steam reforming reaction over 0.2% Pt/Al2O3 and 0.2% Rh/Al2O3 catalysts at 773 K. It was established that the catalytic behaviour of both of the catalysts is significantly influenced by the different impurities. The addition of 1 mol% C3 alcohols (1-propanol and isopropyl alcohol) decreased the conversion of ethanol and increased the rate of catalyst deactivation. This deactivation of the catalyst in the presence of C3 alcohols was attributed to high olefin formation and incomplete decomposition of the C3 alcohols, which deposited over the catalysts as coke. Propanal, propylamine and acetone addition to the water/ethanol mixture resulted in rapid metal deactivation and a loss of steam reforming activity over the Pt/alumina although ethanol decomposition continued. In contrast the Rh/alumina did not lose all steam reforming activity when acetone and propylamine were added as impurities. On both the catalysts alcoholic impurities produced a large number of carbon nanotubes (CNTs).
Keywords: Ethanol; Steam reforming; Impurities; Pt/Al2O3; Rh/Al2O3;
Synthesis, characterization and catalytic activity of a cobalt catalyst: Silica-supported, bis(1,5-diphenyl-1,3,5-pentanetrionato)dicobalt(II) [Co2(dba)2] by S.A. Ranaweera; M.D. Rowe; K.B. Walters; W.P. Henry; M.G. White; J.M. Rodriguez (108-117).
Display OmittedModels of silica supported cobalt catalysts were formed by decorating the surface of Cab-O-Sil with the dinuclear cobalt complex, bis(1,5-diphenyl-1,3,5-pentanetrionato) dicobalt(II), [Co2(dba)2]. To confirm the formation of a monolayer and multilayer of the complex on Cab-O-Sil, various loadings of [Co2(dba)2] were combined with Cab-O-Sil by batch impregnation. The supported samples were characterized by elemental analysis, DRIFTS, and TGA to show that the Co2(dba)2 complex was adsorbed on the silica surface intact and DRIFTS confirmed the loading of the Co2(dba)2 as a monolayer on the Cab-O-Sil up to a loading <2.09 wt% Co. This experimental monolayer loading confirmed the predicted loading (2.06 wt% Co metal) based on the surface area of the support, 200 m2/g, and the footprint area of the complex (1.866 nm2). When this precatalyst was decomposed in air and reduced in hydrogen, the morphology of the resulting particles depended upon the initial disposition of the metal complex on the support. Monolayer films of the metal complex decomposed into metal or metal oxide particles which are too small to give XRD reflections (2.09 wt% Co); whereas, catalyst derived from a multilayer film (4.1 wt% Co) showed large metal particles developing a very sharp XRD reflection from the Co(111) index. Both catalysts were active for the Fischer-Trøpsch reaction at 350 °C with the catalyst derived from the multilayers of complex showing an activity, as characterized by first order rate constants, about 33 times that of the catalyst derived from a monolayer of the complex:71.4 vs 2.16 (mol Co-hour)−1. The selectivity to liquid hydrocarbons showed a remarkably narrow distribution of molecular weights, comprised of mainly iso- and cycloalkanes having 6–8 carbons.
Keywords: Batch impregnation; Bis(1,5-diphenyl-1,3,5-pentanetrionato)dicobalt(II); Silica supported; Dicobalt; Fischer-Trøpsch;
Multicomponent NiSnCeO2/C catalysts for the low-temperature glycerol steam reforming by L. Pastor-Pérez; A. Sepúlveda-Escribano (118-126).
Display OmittedIn this work, the low-temperature hydrogen production via glycerol steam reforming over activated carbon-supported Ni and Ni-Sn catalysts promoted by ceria was studied. A combination of N2 adsorption, powder X-ray diffraction, temperature-programmed reduction with H2, X-ray photoelectron spectroscopy and TEM analysis were used to characterise the Ni-Sn-CeO2 interactions and the CeO2 dispersion over the activated carbon support. The catalytic activity results show that the presence of ceria enhances the water-gas shift reaction, thus promoting the selectivity towards hydrogen. The inclusion of Sn stresses the influence of ceria in the displayed performance. Moreover, the formation of a Ni-Sn alloy seems to be an efficient way to mitigate Ni sintering and therefore to improve the overall catalyst’s stability.
Keywords: H2 production; Nickel-tin; Glycerol; Ceria; Activated carbon;
Three-dimensional N-doped, plasma-etched graphene: Highly active metal-free catalyst for hydrogen evolution reaction by Ye Tian; Yongfei Ye; Xuejun Wang; Shuo Peng; Zhen Wei; Xiao Zhang; Wuming Liu (127-133).
Display OmittedExploring highly active, durable and low-cost catalysts toward hydrogen evolution reaction (HER) holds a key to clean energy technologies. Heteroatoms-doped graphene-based materials are emerging as the most promising metal-free HER catalysts, but their catalytic activity remains largely unexplored. Herein, by rationally engineering the macroscopic architecture of graphene and its chemical/defective structures, we developed a three-dimensional (3D), N-doped, plasma-etched graphene (3DNG-P) as a highly active metal-free HER catalyst. The obtained 3DNG-P combined the merits of freestanding 3D porous architecture, high-level N-doping and plasma-induced enriched defects, resulting in a highly enhanced HER activity with a low overpotential of 128 mV at 10 mA cm−2 in acidic medium. Furthermore, the 3DNG-P displayed a favorable HER activity and stability over a wide pH range. The present study thus provides a new methodology for the design of graphene-based metal-free catalysts with high HER performance.
Keywords: Hydrogen evolution reaction; Heteroatoms doping; N doped graphene; Three-dimensional graphene; Plasma-etching;
Selective epoxidation of cyclohexene with molecular oxygen on catalyst of nanoporous Au integrated with MoO3 nanoparticles by Jian Dou; Franklin (Feng) Tao (134-142).
Display OmittedSelective oxidation of olefins to desired products such as epoxides is highly demanded in chemical industry. It remains challenging to achieve high selectivity for production of epoxides over heterogeneous catalysts through using molecular oxygen as the oxidant. Nanoporous reverse catalysts (MoO3@np-Au) consisting of pure nanoporous gold (np-Au) and MoO3 nanoparticles anchored on Au ligaments were synthesized for selective oxidation of cyclohexene with molecular oxygen. By controlling the loading of molybdenum and thermal treatment condition, MoO3 nanoparticles with size of ∼5 nm were uniformly anchored on the surface of gold ligaments (30–50 nm) of pure nanoporous gold (np-Au). These synthesized MoO3@np-Au catalysts exhibited high selectivity of 58%–73% for production of cyclohexene oxide at conversion of 4%–11% of cyclohexene by using molecular oxygen as the oxidant. Compared to MoO3@np-Au, the selectivity for the production of cyclohexene oxide on pure np-Au catalyst is only 6% under the same catalytic condition as that on MoO3@np-Au. The observed high selectivity for production of cyclohexene oxide on MoO3@np-Au can be rationalized with a bi-functional mechanism of a reverse metal/oxide catalyst. The in-situ formed surface molybdenum oxo-peroxo species are suggested to be responsible for selective oxidation of cyclohexene to cyclohexene oxide, while the MoO3/Au interface activates molecular oxygen to regenerate the molybdenum oxo-peroxo active centers.
Keywords: Cyclohexene oxidation; Catalyst; Epoxidation;
Effect of Cu-doping on the structure and performance of molybdenum carbide catalyst for low-temperature hydrogenation of dimethyl oxalate to ethanol by Yanting Liu; Jian Ding; Jicheng Bi; Yanping Sun; Juan Zhang; Kefeng Liu; Fanhua Kong; Haicheng Xiao; Jiangang Chen (143-155).
Display OmittedSeveral copper-doped molybdenum carbide (Cu–Mo2C) nanomaterials for the hydrogenation of dimethyl oxalate (DMO) to ethanol at low temperature (e.g., 473 K) have been developed through a facile solid-state pyrolysis method. Characterization techniques including X-ray diffraction, scanning/transmission electron microscopy, N2-physisorption, energy-dispersive spectroscopy, and X-ray photoelectron spectroscopy were employed to reveal the morphology, structure and properties of the synthesized nanomaterials. The characterization and reaction results suggest that the incorporation of copper species in Mo2C plays a crucial role in modifying the morphologic structure of Cu–Mo2C as well as tuning the electronic state of Mo active sites, resulting in an important enhancement in the catalytic performance. Moreover, a strong synergistic effect between Cu and Mo2C is observed in DMO hydrogenation. Accordingly, the 67.2% yield of ethanol can be attained at a low temperature of 473 K over the Cu–Mo2C nanomaterials with a suitable atom ratio (e.g., Cu:Mo = 0.03:1), which are higher than those obtained by using a pure Mo2C (e.g., 13.7%) under the same reaction conditions. The Cu-doped Mo2C nanomaterials also display excellent catalytic stability during the hydrogenation of DMO to ethanol for longer than 300 h.
Keywords: Copper; Molybdenum carbide; Hydrogenation; Dimethyl oxalate; Ethanol;
Theoretical analysis of CO + NO reaction mechanism on the single Pd atom embedded in γ-Al2O3 (110) surface by Hongwei Gao (156-166).
Display OmittedThe reaction mechanism of CO + NO on Pd/γ-Al2O3 (110) has been studied using periodic density functional theory (DFT) calculations in detail. Three pathways to form CO2, N2O and N2 were investigated by the kinetics and the electronic structure of catalyst. The calculated results indicate that the oxygen vacancy Ov plays an important role during the catalytic process, and Pd-Ov pair embedded in γ-Al2O3 is proposed to be an active site. The projected density of states (PDOS) analysis indicates that the formation of the oxygen vacancy Ov and the electron transfer between the surface Pd atom and CO or NO molecule are responsible for the catalytic activity of Pd/γ-Al2O3 (110).
Keywords: CO + NO; Pd nanoparticles; γ-Al2O3; DFT; Reaction mechanism;
Isostructural metal-carboxylates MIL-100(M) and MIL-53(M) (M: V, Al, Fe and Cr) as catalysts for condensation of glycerol with acetone by Maria N. Timofeeva; Valentina N. Panchenko; Nazmul Abedin Khan; Zubair Hasan; Igor P. Prosvirin; Sergey V. Tsybulya; Sung Hwa Jhung (167-174).
Display OmittedThe synthesis of solketal from acetone and glycerol (I) was investigated in the presence of the isostructural MOFs of the families MIL-100(M) and MIL-53(M) (M = V, Al, Fe and Cr) and mixed MIL-53(Al,V) (Al/V – 100/0, 75/25, 50/50, 25/75 and 0/100 atom/atom). The main products were a five-membered solketal (2,2-dimethyl-1,3-dioxane-4-methanol, (II)) and a six-membered acetal (2,2-dimethyl-dioxane-5-ol, (III)). It was demonstrated that the reaction rate and isomer selectivity depend on different parameters such as the type of metal ion, the length of the M-O bond, the rate constant for the exchange of the water molecules from the first coordination sphere of a metal ion and the value of the zero point of the surface charge (pHPZC). Investigation of mixed MIL-53(Al,V) shows that the reaction rate and selectivity towards (II) increase with increasing V3+ content in MIL-53(Al,V). V-containing MOFs possess a high activity and selectivity at 25 °C. The efficiencies of MIL-100(V) and MIL-47(V) were higher than those of H2SO4, SnCl2 and p-toluenesulfonic acid at 25 °C. The MIL-100(V) catalyst showed good reusability for 4 catalyst recycles.
Keywords: Metal-organic frameworks; MIL-53; MIL-100; Glycerol; Acetone; Solketal;
Effect of Zn/Al ratio of Ni/ZnO-Al2O3 catalysts on the catalytic deoxygenation of oleic acid into alkane by Lei Chen; Feng Zhang; Guangci Li; Xuebing Li (175-184).
Display OmittedNi-based catalysts supported on Zn-Al composite oxides have been prepared for the catalytic deoxygenation of oleic acid into diesel-ranged alkanes, and the effects of the Zn/Al ratio on the physico-chemical properties of the supports and the deoxygenation activity of the final catalyst were investigated in detail. The results showed that higher Zn/Al ratios led to lower specific surface area of the supports and weakening of the interaction between Ni species and supports thereby improving the reducibility of Ni species. However, higher Zn/Al ratios may limit the dispersion of Ni species, leading to a decrease in the exposure of metallic Ni. Because the conversion and deoxygenation of the reactants mainly depended on the hydrogenation capability of the catalysts which was controlled by the amount of exposed metallic Ni, the catalyst with a Zn/Al ratio of 2/1 showed the highest hydrogenation rate and alkane yield. Further decreasing the Zn/Al ratio led to strong metal-support interaction, making the Ni species difficult to reduce, which may also inhibit the formation of alkane products. In addition, the change in Zn/Al ratio affected intermediate type, which could affect the yield of alkane products.
Keywords: Biodiesel; Zn-Al composite oxide; Deoxygenation; Oleic acid; Alkane;