Applied Catalysis A, General (v.520, #C)
Editorial Board (IFC).
Photocatalytic and electrocatalytic reduction of CO2 to methanol by the homogeneous pyridine-based systems by Wei Wang; Junxiao Zhang; Hui Wang; Lianjia Chen; Zhaoyong Bian (1-6).
Display OmittedThe visible light driven pyridine catalytic reduction of CO2 was performed in aid of ruthenium phenanthroline complex photosensitizer. The light absorbance and utilization of the catalytic system was identified using UV–vis absorption and emission spectroscopic techniques. Under the dark conditions, electrochemical properties of the catalytic system were evaluated by compared the redox properties under N2 and CO2 pressure, respectively. Then, the photocatalytic CO2 reduction with this catalytic system was studied under the visible light (λ > 420 nm) irradiation. The gaseous and liquid products of the CO2 reduction were analyzed using gas chromatography and liquid chromatography. Methanol was the main product and there were no other products determined in the present system. The photocatalytic system showed a high product selectivity and efficient productivity with 60 μmol/L of methanol as solo product under the optimized conditions.
Keywords: Photocatalysis; CO2 reduction; Methanol; Metal complex; Homogeneous catalysis;
Ammoxidation of acrolein to acrylonitrile over bismuth molybdate catalysts by Nguyen Thanh-Binh; Jean-Luc Dubois; Serge Kaliaguine (7-12).
Display OmittedThe present work deals with the potentially significant process converting acrolein of green origin to acrylonitrile using mesoporous bismuth molybdate catalysts. The ammoxidation catalysts were characterized by N2 physisorption, X-ray diffraction, and catalytic tests under various conditions at different temperatures, contact times, and reactant molar ratios. The results indicated a catalytic activity proportional to specific surface area, which depends on bismuth molybdate phases, and concentration of oxygen in the gas feed. The selectivity of the catalysts only depends on reaction temperature. ACN selectivity obtained at 350–400 °C was 100% and reduced to 97% at 450 °C.
Keywords: Ammoxidation; Acrolein; Acrylonitrile; Mesostructure; Bismuth-molybdate catalysts;
The adsorption of mercury species and catalytic oxidation of Hg0 on the metal-loaded activated carbon by Lili Fan; Lixia Ling; Baojun Wang; Riguang Zhang (13-23).
Display OmittedThe adsorption of mercury species (Hg0, HgCl and HgCl2) and catalytic oxidation of Hg0 on the metal-loaded activated carbon (AC) with single Fe, Co, Ni, Cu and Zn atom have been studied using the periodic density functional theory (DFT) method. The results indicate that Hg0 interacts with metal-loaded AC surfaces via a physical adsorption mechanism, while chemisorptions are likely adsorption mechanisms for HgCl and HgCl2. The existence forms of HgCl and HgCl2 on metal-loaded AC surfaces are dissociated or molecular, which greatly depend on initial interaction modes between mercury species and surfaces. Besides, in the presence of Cl2, Hg0 is oxidized to be HgCl2 molecule on the Fe/AC surface, while dissociatively adsorbed HgCl2 is predominant on Ni/AC, Cu/AC and Zn/AC surfaces, but both molecular and dissociated HgCl2 exist on the Co/AC surface. What’s more, the kinetic results show that the oxidation energy barrier of Hg0 on the Fe/AC surface is the lowest, implying that Fe-loaded AC is a favorable heterogeneous catalyst for Hg0 oxidation from the point of view of efficiency and cost.
Keywords: Mercury species; Metal-loaded AC; Adsorption; Catalytic oxidation;
NiMo catalysts supported on the Nb modified mesoporous SBA-15 and HMS: Effect of thioglycolic acid addition on HDS by Radostina Palcheva; Luděk Kaluža; Lubomir Dimitrov; Georgi Tyuliev; Georgi Avdeev; Květa Jirátová; Alla Spojakina (24-34).
Display OmittedNb modified mesoporous SBA-15 and HMS materials were synthesized and studied as a support of NiMo. Calcined co-impregnated NiMo catalysts were prepared using ammonium heptamolybdate and nickel nitrate. Moreover, NiMo catalysts prepared in this manner were treated with thioglycolic acid (TGA). For comparison, NiMo catalysts were prepared by a simultaneous impregnation of the supports with Ni, Mo precursors and TGA. The TGA:Mo molar ratio was 4.0. The supports and NiMo catalysts were characterized by N2 physisorption, small- and wide-angle XRD, TPD-NH3, SEM, UV–vis DRS, FTIR and XPS. Catalyst activity was examined in hydrodesulfurization (HDS) reactions of 1-benzothiophene and thiophene at 350 °C. It was found that simultaneous impregnation by Ni, Mo and TGA led to higher HDS activities than the sequential treatment of the calcined NiMo catalysts by TGA.
Keywords: Nb-SBA-15; Nb-HMS; NiMo catalyst; Hds; Complexing agent;
Immobilization Na7PW11O39 on quanternary ammonium functionalized chloromethylated polystyrene by electrostatic interactions: An efficient recyclable catalyst for alcohol oxidation by Hefang Wang; Luping Fang; Yongfang Yang; Rongbin Hu; Yanji Wang (35-43).
Na7PW11O39 (PW11) immobilized on quanternary ammonium functionalized chloromethylated polystyrene (CMPS) was synthesized in a facile method. PW11-DMA16/CMPS exhibited a considerable catalytic activity in selective oxidation of cyclohexanol with 30% H2O2, which is similar to that of homogeneous PW11. Moreover, PW11-DMA16/CMPS also showed excellent catalytic activity in oxidation of various alcohols.Display OmittedNa7PW11O39 (PW11) was immobilized on quanternary ammonium functionalized chloromethylated polystyrene (DMA16/CMPS) in a facile method and used as efficient recyclable catalyst in oxidation of alcohol. Commercially available mesopores and macropores CMPS was quaternized by N, N- dimethylhexadecylamine (DMA16) followed by immobilization of PW11 onto the pore of CMPS by electrostatic interaction. The synthesized catalyst was characterized by Fourier transform infrared spectroscopy (FT-IR), powder X-ray diffraction (XRD), thermo gravimetric analyzer (TGA), ultraviolet–visible (UV–vis), N2 adsorption–desorption, X-ray photoelectron spectroscopy (XPS), zeta potential, contact angle, 31P nuclear magnetic resonance (31P NMR), scanning electron microscope (SEM), transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). The results indicated that Na7PW11O39 was successfully immobilized by electrostatic interaction and finely dispersed on quaternary ammonium functionalized CMPS. PW11-DMA16/CMPS showed a similar catalytic activity to that of homogeneous PW11, which was attributed to the hydrophobic nature of the PW11-DMA16/CMPS and facile diffusion of reactant to the active sites provided by widely opened mesopores and macropores. The present approach provides a promising and universal strategy for the construction of hybrid catalysts based on POMs and mesopores and macropores materials.
Keywords: Chloromethylated polystyrene; Quaternization; Immobilization; Alcohol oxidation;
Ruthenium nanoparticles supported on N-containing mesoporous polymer catalyzed aerobic oxidation of biomass-derived 5-hydroxymethylfurfural (HMF) to 2,5-diformylfuran (DFF) by Kajari Ghosh; Rostam Ali Molla; Md. Asif Iqubal; Sk. Safikul Islam; Sk. Manirul Islam (44-52).
Display OmittedA mesoporous poly-melamine-formaldehyde material embedded ruthenium nanoparticles (Ru@mPMF) has been synthesized and characterized exhibits excellent catalytity in the field of aerobic oxidation of biomass derived 5-hydroxymethylfurfural (HMF) to 2,5-diformylfuran (DFF) in toluene.Ruthenium nanoparticles embedded on a mesoporous poly-melamine-formaldehyde material (Ru@mPMF) has been synthesized and characterized by powder XRD, HRTEM, TGA, SEM, EDS, UV–vis diffuse reflection spectroscopy (DRS), Raman spectroscopy, XPS and N2 adsorption/desorption study. The Ru@mPMF catalyst was excellent for selective oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-diformylfuran (DFF) in toluene. Moreover, this catalyst is easily recoverable and it is reusable upto six cycles without notable decrease in its catalytic activity. Profoundly scattered and firmly bound Ru-NPs sites in mPMF might be engaged for the excellent performance of the material. Due to strong binding with the functional groups of the polymer, no indication of ruthenium leaching was there during the reaction. This suggests the actual heterogeneous nature of the material.
Keywords: Mesoporous; Poly-melamine-formaldehyde; RuNPs; HMF; DFF; Oxidation;
Steam reforming of ethanol over Ni-based catalysts obtained from LaNiO3 and LaNiO3/CeSiO2 perovskite-type oxides for the production of hydrogen by André Luiz A. Marinho; Raimundo C. Rabelo-Neto; Fabio B. Noronha; Lisiane V. Mattos (53-64).
Display OmittedThis work studied the performance of Ni-based catalysts derived from LaNiO3 and CeSiO2 supported LaNiO3 perovskite-type oxides for the steam reforming of ethanol. In situ XRD and TPR revealed the presence of different Ni species on both calcined samples: LaNiO3, La2NiO4 and NiO phases. Both catalysts deactivated during the reaction. Ni sintering was ruled out based on the in situ XRD experiments under reaction conditions. For LaNiO3, metallic Ni particles were partially oxidized by the water present in the feed at the beginning of the reaction. Then, NiO particles formed were reduced again by the syngas produced during the reaction. TG analysis showed significant carbon formation on LaNiO3 catalyst. However, carbon formation was significantly decreased over LaNiO3/CeSiO2 catalyst, which was due to the important role of the support on the mechanism of carbon removal for steam reforming of ethanol.
Keywords: Perovskite-type oxides; Cerium based oxides; Hydrogen production; Steam reforming; Ethanol;
Preparation and reactivity of UV light-reduced Pd/α-Fe2O3 catalyst towards the hydrogenation of o-chloronitrobenzene by Weidong Jiang; Bin Xu; Zhen Xiang; Xiaoqiang Liu; Fuan Liu (65-72).
The present work reported the convenient preparation of Pd-based catalyst over α-Fe2O3 as support via a UV light-induced reduction process. The resulting Pd/α-Fe2O3 catalyst exhibited good performance for the hydrogenation reduction of o-chloronitrobenzene (o-CNB), yielding completely o-CNB conversion and 91.4% selectivity of o-CAN at high substrate/catalyst ratio (6000:1) under mild conditions.Display OmittedA type of Pd/α-Fe2O3 catalyst was synthesized by a convenient UV light-induced reduction in the presence of Fe3+ ions. The synthesized Pd/α-Fe2O3 particles were characterized by X-ray diffraction (XRD), low-resolution transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectrum (XPS), atomic force microscope (AFM), scan electron microscopy with energy dispersion spectra (SEM-EDS), FT-IR and BET. Related characterizations confirm that UV light-induced reduction is a feasible, simply and environment-friendly method for the preparation of supported catalysts containing active metal. Furthermore, hydrogenation of o-chloronitrobenzene (o-CNB) to o-chloroaniline (o-CAN) by the selected Pd(0.5%)/α-Fe2O3 was investigated systematically. The α-Fe2O3-supported Pd catalyst was found to exhibit good catalytic activity and selectivity for the o-CNB reduction under mild conditions. The hydrogenation of o-CNB over the resulting Pd-based catalyst gave a 100% o-CNB conversion and 91.4% selectivity of o-CAN under the reaction conditions of 50 °C, 2 h, 1 MPa hydrogen pressure, n o-CNB/nPd = 6000:1. Moreover, the resulting Pd-based catalyst remained higher hydrogenation reactivity after three runs even if a sharply decrease in activity was observed at the fourth run. The obtained results reveal the as-prepared Pd/α-Fe2O3 is an efficient catalyst for the hydrogenation of o-CNB even at a high level of substrate concentration.
Keywords: Catalytic hydrogenation; o-Chloronitrobenzene; UV light-induced reduction; Pd/α-Fe2O3 catalyst;
Selective hydrogenation of aromatic carboxylic acids over basic N-doped mesoporous carbon supported palladium catalysts by Hezhan Jiang; Xiaolong Yu; Renfeng Nie; Xinhuan Lu; Dan Zhou; Qinghua Xia (73-81).
Pd NPs are supported on MCN that is prepared via polymerization between ethylenediamine and carbon tetrachloride. The negative charge and the basicity on MCN surface are originated from its rich carbon nitride heterocycles. The negative charge contributes to strong N-Pd interaction and the basicity generates higher adsorption capacity for acid substrates, both of which may lead to its high activity for selective ring hydrogenation of aromatic compounds.Display OmittedMesoporous carbon nitride (MCN) has been prepared through a simple polymerization reaction between ethylenediamine (EDA) and carbon tetrachloride (CTC) by a nano hard-templating approach. The obtained MCN possesses high surface area (166.3 m2/g), average pore size of 9.2 nm and high N content (up to 18.5 wt%). The negative charge and the basicity on MCN surface are originated from its rich carbon nitride heterocycles, which notably improves the surface hydrophilicity and the adsorption of acidic molecules. Furthermore, MCN can be adopted as the proper support for highly dispersed Pd NPs with well-controlled size distribution. Compared with microporous N-doped active carbon with low N-content, the MCN-supported Pd catalyst shows an enhanced activity in water phase for the selective ring hydrogenation of benzoic acid, benzamide and phenol, in which 11.3 times higher activity in comparison to undoped catalyst is achieved. Wide characterizations reveal that big pore size, selective adsorption for acid substrate and strong interaction between N and Pd may lead to the high activity of Pd/MCN.
Keywords: Mesoporous carbon nitride; Polymerization; Basicity; Palladium; Selective hydrogenation;
Selective oxidation of CO in H2-rich stream over ZSM5 zeolites supported Ru catalysts: An investigation on the role of the support and the Ru particle size by Salvatore Scirè; Roberto Fiorenza; Antonino Gulino; Andrea Cristaldi; Paolo M. Riccobene (82-91).
Display OmittedSelective oxidation of CO in H2-rich stream was studied over ZSM5 zeolite supported Ru catalysts and the results were compared with those obtained over Ru samples supported on alumina, silica and ceria. ZSM5 zeolite supported Ru catalysts exhibited higher yields to CO2 than Ru samples on other supports. The SiO2/Al2O3 ratio of the zeolite was found to strongly affect the performance of the Ru/ZSM5 system, the Ru sample supported on the H-ZSM5 with the highest SiO2/Al2O3 ratio (280) being the most efficient towards the CO selective oxidation. The form of the zeolite (H- or Na-) had instead a lower influence. On the basis of characterization data (TEM, XPS, H2-TPR, NH3-TPD) it was pointed out that the performance of the Ru/ZSM5 samples are strongly dependent on the Lewis acidity of the zeolite and/or the Ru particle size, a lower number of Lewis acid sites and bigger Ru particles resulting in higher CO2 yields.
Keywords: PROX; Ruthenium; Zeolite; Size effect; Acidity;
Flame Spray Pyrolysis as fine preparation technique for stable Co and Co/Ru based catalysts for FT process by A. Comazzi; C. Pirola; A. Di Michele; M. Compagnoni; F. Galli; I. Rossetti; F. Manenti; C.L. Bianchi (92-98).
Display OmittedFlame spray pyrolysis (FSP) is an innovative and scalable technique, used to synthesize monometallic and bimetallic Co-Ru catalysts with 5% wt. Co, 10% wt. Co and 0.4% wt. Ru supported on SiO2 active in the Gas-to-Liquids (GTL)-Fischer-Tropsch (FT) process, which converts syngas to hydrocarbons. The catalysts were characterized by TEM, FE-SEM-EDX, TPR, XRD and N2 adsorption/desorption. All the three samples have been tested in a fixed bed FT-bench scale plant. Results demonstrated that the 5% wt. Co catalyst was not active toward FT synthesis, while samples containing 10% wt. Co and 10% wt. Co - 0.4% wt. Ru were suitable candidates for the GTL-FT process. With an increase in temperature, the CO conversion increased, the product selectivity remained unchanged, and the 10% wt. Co catalyst showed higher stability as a function of time-on-stream (TOS) with respect to traditionally prepared materials. The addition of 0.4% wt. of Ru improved the performance in terms of CO conversion and C2+ yield.
Keywords: Fischer-Tropsch; Cobalt; Ruthenium; Flame spray pyrolysis; Characterization; GTL;
Remarkably enhanced stability of HZSM-5 zeolite co-modified with alkaline and phosphorous for the selective conversion of bio-ethanol to propylene by Jiaojiao Huangfu; Dongsen Mao; Xiaolong Zhai; Qiangsheng Guo (99-104).
Dual modifications with alkaline and phosphorous significantly enhanced the catalytic stability of HZSM-5 zeolite for the selective conversion of bio-ethanol to propylene.Display OmittedThe effects of alkaline, phosphorous and dual alkaline-phosphorous modifications on the selective conversion of bio-ethanol to propylene over HZSM-5 zeolite catalysts were investigated. The results demonstrate that the doubly modified HZSM-5 zeolite catalyst offers higher propylene selectivity and remarkably improved catalytic stability than the parent and singly modified counterparts, which can be contributed to the formation of new mesoporous and decreased amount of strong acid sites induced by the alkaline treatment and phosphorous modification, respectively. The deactivation of the phosphorous and dual alkaline-phosphorous modified HZSM-5 zeolite catalysts was caused by carbon deposition but not by dealumination, which can be attributed to the enhanced hydrothermal stability of the framework aluminum by the modification of ZSM-5 zeolite with phosphorus.
Keywords: Alkali treatment; Phosphorous modification; HZSM-5 zeolite; Bio-ethanol; Propylene;
Selective etherification of hydroxymethylfurfural to biofuel additives over Cs containing silicotungstic acid catalysts by G. Raveendra; A. Rajasekhar; M. Srinivas; P.S. Sai Prasad; N. Lingaiah (105-113).
Display OmittedA series of Cs exchanged silicotungstic acid (STA) catalysts were prepared and their physico-chemical properties were derived from FT-Infrared, X-ray diffraction, Laser Raman, temperature programmed desorption of ammonia and BET surface area. The characterization results revealed that the Keggin structure of STA remained intact even after Cs ions replaced its protons. The catalysts activity was evaluated for the selective etherification of 5-hydroxymethylfurfural (HMF) with ethanol for the synthesis of 5-ethoxymethylfurfural (EMF). The partial exchange of Cs ions with protons of STA resulted an increase in acidity and the catalysts with two Cs ions in STA showed highest acidity. The activity was explained based on the acidity, surface and structural properties of the catalysts. A detailed study was made on the effect of various reaction parameters such as influence of reaction temperature, reaction time, Cs content on STA to unveil the optimize reaction conditions. The catalyst was recovered easily from the reaction mixture and reused at least four times with constant activity.
Keywords: Silicotungstic acid; Cesium nitrate; Etherification; Ethanol; HMF; EMF;
Low temperature dry reforming of methane on rhodium and cobalt based catalysts: Active phase stabilization by confinement in mesoporous SBA-15 by N. El Hassan; M.N. Kaydouh; H. Geagea; H. El Zein; K. Jabbour; S. Casale; H. El Zakhem; P. Massiani (114-121).
Display OmittedTwo silica supports either non porous (SiO2) or mesoporous (SBA-15) were impregnated with cobalt (12 wt%) in order to study the confinement effect on catalytic performances in dry reforming of methane. Further increase of activity was obtained by adding small amounts of rhodium (0.2 and 0.5 wt%) to the Co/SBA-15 catalyst. The structural and morphological properties of the calcined samples were characterized by N2 sorption, X-ray diffraction and high-resolution transmission electron microscopy (ultra-thin sections). Their reducibility was studied by temperature-programmed reduction. After in situ reduction of the materials, their catalytic activity was tested in dry reforming of methane up to 800 °C followed by stability testing at 550 °C for 550 min. Cobalt confinement in the mesopores of SBA-15 is shown to be highly beneficial towards not only activity but also stability, the reduced nanoparticles being then more resistant against sintering under stream. Rh plays a role as an additional active phase. It also strongly favors cobalt stabilization in the mesopores by permitting its reduction at a much lower temperature, which allows avoiding metal migration to the surface of the silica grains. The nature of coke is also shown to depend on rhodium addition, with less amount of carbon gamma (graphitic and destructive form) formed on the Rh-containing sample compared to the Rh-free Co/SBA-15 catalyst.
Keywords: Rhodium; Cobalt; SBA-15; Methane dry reforming; Confinement effect;
Vapor phase ethanol carbonylation over Rh supported on zeolite 13X by Sara Yacob; Beata A. Kilos; David G. Barton; Justin M. Notestein (122-131).
Display OmittedWhile methanol carbonylation has been extensively studied, higher alcohol carbonylation has received relatively little attention, even though, for example, ethanol carbonylation could be a useful route for the production of propionates. Here we use Rh/Na13X to investigate the vapor phase carbonylation of ethanol with an ethyl iodide co-feed. In the base case, the catalyst is ∼40% selective to propionates, with the remainder forming ethylene and diethyl ether. Deposition of additional alkali can increase selectivities to ∼60%. Isotopic labeling of ethyl iodide demonstrates reversible formation of ethyl iodide from ethanol, and that preferential incorporation of ethyl iodide initiates the Rh-catalyzed carbonylation cycle. XPS and in situ X-ray absorption spectroscopy are consistent an active anionic RhI iodide species at a zeolite exchange site. This proposed structure and the attendant catalytic reaction network are directly analogous to those of classic solution-phase Rh catalysts and other supported Rh catalysts. However, important differences are noted in the reaction orders and apparent activation barrier, which suggest that the rate of ethyl iodide formation is overall rate limiting under these conditions and for this catalyst.
Keywords: Ethanol; Ethyl iodide; Carbonylation; Zeolite 13X; Rhodium;
Effects of K-dopant on structure and activity of KMn/Al2O3 catalysts for CO oxidation: Experimental evidence and DFT calculation by Xiaopei Xie; Qinghu Tang; Jia Zhang; Jing Wang; Peizheng Zhao; Yi Wang; Michael B. Sullivan; Yanhui Yang (132-139).
K doping induces a structural phase transformation and there is a correlation among doping amount – manganese oxide phases – catalytic performance.Display OmittedKMn/Al2O3 catalysts with different K:Mn molar ratios were synthesized by a facile impregnation method and attempted for CO oxidation. The correlation in between potassium-dopant amount and the structure/catalytic activity of KMn/Al2O3 catalysts were investigated. Doping small amount of potassium (K:Mn mole ratio less than 1:10) to Mn/Al2O3 catalyst efficiently enhanced the catalytic activity of Mn/Al2O3 catalyst. We found that the K1Mn10/Al2O3 catalyst exhibited the best CO oxidation activity with the TOF of 1.5 × 10−3 s−1 for 100% CO conversion at 260 °C, which is 50 °C lower than that on Mn/Al2O3 catalyst. However, excessive amounts of potassium led to β-to-α-MnO2 phase transformation and poor catalytic performance. DFT calculations combined with multiple characterization techniques such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), O2 temperature-programmed desorption (O2-TPD) and hydrogen temperature-programmed reduction (H2-TPR) were performed to provide a deep insight into the K-doping effect. The results suggested that the addition of an appropriate amount of potassium to Mn/Al2O3 catalyst improved the dispersion of manganese oxide, the mobility and reactivity of surface lattice oxygen, thus significantly improved the catalyst activity.
Keywords: CO oxidation; Manganese oxide; Potassium; Phase transformation;
Nickel based mesoporous silica-ceria-zirconia composite for carbon dioxide reforming of methane by Xianmei Xiang; Huahua Zhao; Jian Yang; Jun Zhao; Liang Yan; Huanling Song; Lingjun Chou (140-150).
Display OmittedA series of mesoporous silica-ceria-zirconia composite (Si-MCeZr) with variable Si/(Ce + Zr) molar ratios are prepared by improved evaporation induced self-assemble strategy (EISA). TEM and XRD measurements show that the Si-MCeZr frameworks are made of ceria-zirconia solid solutions crystalline nanoparticles and the amorphous silica that serves as glue connecting the nanocrystals. The further heating treatment (700 °C) reveals that the thermal stability of Si-MCeZr is higher than that of Si free mesoporous ceria-zirconia solid solution (MCeZr). This might be due to the key role of the introduction of Si, which improves the thermal stability via inhibiting the growth of nanoparticles and crystallization of ceria-zirconia solid solution nanoparticles. Furthermore, the Si-MCeZr materials are applied as support to prepare nickel based catalysts (Ni/Si-MCeZr) for CO2 reforming of CH4. The XPS analyses show that the concentration of surface oxygen vacancies in Ni/Si-MCeZr increases with the increasing of Si/(Ce + Zr) molar ratios. The long term reforming test demonstrates that the catalytic stability of Ni/Si-MCeZr is improved compared to Si free nickel based catalyst (Ni/MCeZr). The obtained results indicate that enhanced durability may originate from the higher concentration of oxygen vacancies, more rapid oxygen mobility and improved nickel dispersion in Ni/Si-MCeZr, which contribute largely to higher catalytic activity and decoking ability in reforming reaction, as confirmed by TG-DSC and XRD characterizations of catalysts before and after stability tests.
Keywords: Mesoporous; Silica-ceria-zirconium composite; Oxygen vacancy; CO2 reforming; Stability;
Ni-Silicides nanoparticles as substitute for noble metals for hydrogenation of nitrobenzene to p-Aminophenol in sulfuric acid by Zhen Dong; Tao Wang; Jie Zhao; Teng Fu; Xuefeng Guo; Luming Peng; Bin Zhao; Nianhua Xue; Weiping Ding; Zaiku Xie (151-156).
Series supported Ni-silicides was prepared and used as catalyst for the hydrogenation of nitrobenzene (NB) to prepare p-aminophenol (PAP) in sulfuric acid. The Ni-silicides nanoparticles exhibit excellent acid-resistance and performances like noble metal. NiSi2 nanoparticles supported on acid-treated active carbon exhibit excellent stability in alloy structure, morphology, and catalytic performance in reuses, suggesting the Ni-silicides nanoparticles as the promising substitute for precious metal for PAP manufactures.Display OmittedThe hydrogenation of nitrobenzene (NB) in acid medium is regarded as the most promising route to prepare p-aminophenol (PAP). The noble metals such as Pt have been reported as commercial catalysts but base metals are inactive due to strong acids needed in the reaction medium. Therefore, Ni-based catalyst has been attempted using solid acids, however, the results are not attractive. In this work, in order to improve the acid-resistance of Ni in sulfuric acid, we insert Si into the Ni crystal structure to form Ni-silicides. The as-prepared supported Ni-silicides nanoparticles exhibit excellent acid-resistance and perform high activity and selectivity of the entitled reaction. NiSi2 nanoparticles supported on acid-treated active carbon are highly active and selective to convert NB to PAP in sulfuric acid. The XPS measurements show that the Ni in the Ni-silicides donates electrons to silicon, but the Ni valence is still far lower than nickel oxide, which causes its stability in acids and the activity to hydrogen activation is partially reserved. Thus, the catalysts exhibit excellent stability in alloy structure, morphology, and catalytic performance in reuses, suggesting the Ni-silicides nanoparticles as the promising substitute for precious metal for PAP manufactures.
Keywords: Ni-silicides nanoparticles; High selectivity; Acid-resistance; Hydrogenation; p-aminophenol;
Basicity and catalytic activity of porous materials based on a (Si,Al)-N framework by A.I. Saugar; C. Márquez-Álvarez; I.J. Villar-Garcia; T. Welton; J. Pérez-Pariente (157-169).
Display OmittedPorous materials based on a framework containing T-N linkages, where T represents silicon or silicon and aluminium atoms, have been prepared by the ammonolysis at low temperature of the corresponding silicon and aluminium chlorides in an ionic liquid, both in the presence and in the absence of mineralizing agents such as pyrrolidine, ammonia and sodium amide. IR spectroscopy and XPS data are consistent with these materials having a framework based on T-NH-T groups (T = Si or Al), that contain also a large fraction of T-NH2 terminal groups. Moreover, XPS evidences the presence of Si-NH-Al groups whenever aluminium is present in the solid. The basic strength of the materials has been determined by pyrrole adsorption, and it has been found that the average basic strength increases with the population of T-NH-T groups and with the aluminium content of the framework. However, this strength is lower than that of a calcined hydrotalcite (Al/(Al + Mg) = 0.33) taken as a reference. These materials are active and very selective catalysts in the Michael addition reaction between chalcone [and malononitrile (pKa 11), but turned to be inactive when diethylmalonate having a weaker acidity (pKa 13.3) is used as donor.
Keywords: Silicon-aluminium imide; Porous materials; Heterogeneous base catalyst; Michael addition; Pyrrole adsorption;
Influence of Mg modifier on cis-trans selectivity in partial hydrogenation of biodiesel using different metal types by Chachchaya Thunyaratchatanon; Jakkapong Jitjamnong; Apanee Luengnaruemitchai; Natthida Numwong; Nuwong Chollacoop; Yuji Yoshimura (170-177).
Display OmittedThe catalytic performance of Pd, Pt, and Ni supported on SiO2 catalysts was investigated for partial hydrogenation of soybean methyl esters, in terms of FAME composition and biodiesel properties, especially oxidative stability and cold flow properties. The effect of Mg modifier over SiO2-supported catalysts on cis-trans selectivity of polyunsaturated FAMEs was also examined. The catalytic testing was performed under reaction conditions of 4 bar hydrogen pressure and 80–120 °C. Hydrogenation activity was presented by turnover frequency (TOF) of diunsaturated fatty acid (C18:2) within 4 h of the reaction time. The highest TOF was obtained over Pd catalysts, while the lowest TOF was obtained from Ni catalysts. At high reaction temperature conditions showed a large amount of cis-monounsaturated fatty acid (cis-C18:1); however, it exhibited a large amount of trans-monounsaturated fatty acid (trans-C18:1) which has a negative impact on biodiesel properties. The XPS revealed that the introduction of Mg leads to a strong metal–support interaction caused by electron transfer from the support to the metal, which decreased trans-C18:1 formation and presented the higher oxidative stability than the catalysts without Mg modifier.
Keywords: Biodiesel; Partial hydrogenation; Selectivity; Oxidative stability; Cold flow properties; Mg;
Preparation of high performance nano-sized Cu/ZnO/Al2O3 methanol synthesis catalyst via aluminum hydrous oxide sol by Mohsen Bahmani; Bahman Vasheghani Farahani; Saeed Sahebdelfar (178-187).
Display OmittedTernary Cu/ZnO/Al2O3 methanol synthesis catalysts were synthesized by co-precipitation of copper and zinc hydroxycarbonates in the presence of various aluminum hydrous oxide sol preparation methods from sodium aluminate and aluminum nitrate as aluminum oxide sources. The catalysts were characterized at various stages of preparation by nitrogen adsorption-desorption, X-ray diffraction, transmission electron microscopy, temperature programmed reduction and N2O chemisorption techniques. The TPR profiles of calcined precipitates were deconvoluted into three peaks which were assigned to the reduction of copper oxide species exhibiting different crystallite size and/or different interactions with zinc oxide. All catalysts were tested for methanol synthesis activity in a fixed-bed reactor under conditions similar to that of commercial operation (503 K, 50 bar and GHSV of 17250 h−1), using H2, CO, and CO2 (80/12/8 molar ratio) mixture as the feed. The experimental results illustrated that the catalyst synthesized based on aluminum hydrous oxide sol prepared by peptization of aluminum hydroxide exhibited higher specific surface area, copper dispersion and catalytic activity for methanol synthesis. The catalysts thus prepared were shown to have less hydrotalcite-like phase, stronger interdispersion between Cu and ZnO and well-dispersed Cu nanoparticles with improved stability and activity in methanol synthesis from syngas.
Keywords: Methanol synthesis; Cu/ZnO/Al2O3 catalyst; TPR; Colloidal solution; Aluminum hydrous oxide sol;
Corrigendum to “Photocatalytic and electrocatalytic reduction of CO2 to methanol by the homogeneous pyridine-based systems” [Appl. Catal. A: Gen. 520 (2016) 1–6] by Wei Wang; Junxiao Zhang; Hui Wang; Lianjia Chen; Zhaoyong Bian (188).