Supported Ni–W–O Mixed Oxides as Selective Catalysts for the Oxidative Dehydrogenation of Ethane

Mixed Ni–W–O catalysts (with a W/(Ni + W) atomic ratio of 0.3) supported on γ-Al₂O₃ or on mesoporous alumina have been prepared, characterized and tested in the oxidation of ethane. For comparison unsupported and supported NiO as well as bulk Ni–W–O mixed oxides catalysts have also been studied. Supported Ni–W–O materials show interesting catalytic performances in the oxidative dehydrogenation of ethane. They show similar catalytic activities than the corresponding unsupported Ni–W–O catalysts. However, the selectivity to ethylene over supported catalysts was higher than that achieved over unsupported samples (the selectivity to ethylene followed the trend: mesoporous-supported > γ-Al₂O₃-supported > unsupported Ni–W–O). In addition, it has also been observed that Ni–W–O catalysts are more efficient than the corresponding W-free NiO catalysts. The discussion of the catalytic results will be undertaken on the basis of the modification of active sites of NiO when incorporating WO₃ and/or metal oxide supports.     

Hydroprocessing of Aromatics Using Sulfide Catalysts Supported on Ordered Mesoporous Phenol–Formaldehyde Polymers

Ni–W sulfide catalysts for the hydroprocessing of aromatic hydrocarbons were synthesized by the in situ decomposition of tetrabutylammonium nickel thiotungstate complex supported on ordered mesoporous phenol–formaldehyde polymer. Catalysts obtained with and without additional sulfidation with dimethyl disulfide were characterized by X-ray photoelectron spectroscopy and transmission electron microscopy. The catalytic activity has been studied using naphthalene, 1-methylnaphthalene, 2-methylnaphthalene, and anthracene as examples. It is shown that the system used in this study proved to be active in hydrogenation and hydrocracking of polyaromatic hydrocarbons.     

n-Pentane Isomerization Over Pt- and Ni–Pt-Promoted Sulfated Zirconia Catalysts Supported on Alumina

Two series of sulfated zirconia catalysts promoted with Pt and Pt–Ni, respectively, were prepared and extruded with different amount of alumina binder (0, 20, 33, and 60 wt%). The catalytic activities of the two series of catalysts, SZPtA and SZNiPtA, were measured for n-pentane isomerization reaction. The reaction reaches its maximum conversion at 20 wt% of alumina for both catalyst series. Adding alumina beyond 20 wt% reduces the overall conversion and modifies the selectivity for both catalysts series from i-C4 towards i-C5 suggesting that the reaction mechanism changed from a monomolecular to a bimolecular one. However, only SZNiPtA catalysts maintain a higher catalytic activity at higher amounts of alumina. Such difference between the two catalyst series can be attributed to the combining effect of Ni and Pt promotion of the SZNiPtA catalysts and not to their acidic properties.     

CO2 Hydrogenation over Ru-NPs Supported Amine-Functionalized SBA-15 Catalyst: Structure–Reactivity Relationship Study

Catalysis Letters - We gave an effective protocol to support Ru NPs on amine-functionalized SBA-15 mesoporous silica to catalyze the CO2 hydrogenation reaction. The amine groups present in the...     

Influence of Preparation Modes on Pt–Ni/CNTs Catalysts Used in the Selective Hydrogenation of Cinnamaldehyde to Hydrocinnamaldehyde

Pt–Ni/CNTs catalysts are prepared by different impregnation techniques and different reduction methods (H₂, HCHO, and KBH₄) for the selective hydrogenation of cinnamaldehyde (CMA) to hydrocinnamaldehyde (HCMA) and investigated by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and temperature programmed reduction (H₂-TPR) techniques. The results show that the catalytic selectivity and activity of the Pt–Ni/CNTs catalysts would significantly be improved by using KBH₄ as a reducing agent, due to the electronic synergetic effect of Pt–Ni–B, and 96% for conversion of CMA and 88% for selectivity of HCMA are obtained over Pt–Ni/CNTs catalyst reduced by KBH₄. Furthermore, the hydrogenation rate of CMA and selectivity of CMA to HCMA over Pt–Ni/CNTs catalyst are significantly improved in the presence of trace base or acid promoters again. The best result (92% for conversion of CMA and 96% for selectivity of HCMA) is obtained when NaOAc is used as base promoter.     

BASF NanoSelect? Technology: Innovative Supported Pd- and Pt-based Catalysts for Selective Hydrogenation Reactions

An innovative BASF catalyst manufacturing technology (NanoSelect?) is introduced which allows production of heterogeneous catalysts with excellent control over metal crystallite sizes. NanoSelect? technology enabled the development of Pd catalysts which are lead-free Lindlar catalyst replacements in alkyne-to-cis-alkene hydrogenations. NanoSelect? Pt catalysts showed excellent chemoselectivity in substituted nitro-arene hydrogenation reactions without build-up of hydroxylamine intermediates. All NanoSelect? produced catalysts show markedly higher activity per gram of metal leading to ten-fold less use of precious metal.     

Selective Hydrogenation of Benzonitrile by Alumina-Supported Ir–Pd Catalysts

The kinetics of liquid-phase hydrogenation of benzonitrile have been examined alumina supported Ir, Pd and Ir–Pd catalysts. Benzonitrile disappearance TOF is 10-fold higher for Pd catalyst than it is for Ir catalyst. Benzylamine is produced preferentially over Pd, whereas dibenzylamine is produced principally over Ir. Non-monotonic activity and selectivity relationships with bimetallic composition are obtained.     

Efficient La–Ba–MgO Supported Ru Catalysts for Ammonia Synthesis

Abstract  

Novel Ru-based catalysts were prepared by impregnating 2 wt% Ru₃(CO)₁₂ into rare earth (La, Sm, Ce) and barium doped nano-magnesia (RE–Ba–MgO) supports, which were originally prepared by chemical co-precipitation with ultrasonic treatment. The Ru/RE–Ba–MgO catalyst exhibits higher activity, more than three times of that of conventional Ba–Ru/MgO base on water impregnation. Characterization of this catalyst by various techniques reveals that the chemical and textural properties of nano Ba–MgO supports and formation state of barium in support are key factors responsible for the elevated activity of this catalyst.     

Structure and Function of the Catalyst and the Promoter in Co—Mo Hydrodesulfurization Catalysts

Simply stated, a membrane is a barrier which is capable of redistributing components in a fluid stream through a driving force such as the difference in pressure, concentration, or electrical potential. When a concentration or electrical potential gradient provides the necessary driving force, this barrier separation process is called dialysis or electrodialysis. Most of the membrane processes are based on an applied pressure difference across the membranes.     

Structure Sensitivity of NO Reduction over Iridium Catalysts in HC–SCR

Ir black with different crystallite sizes and Ir–H–ZSM-5 prepared using two different precursors were investigated for their behavior in selective catalytic reduction using hydrocarbons as reducing agents (HC–SCR). Emphasis was given to the study of the influence of time onstream on N₂ yield, the change in Ir crystallite size, and the change in the ratio of Ir : IrO₂. Under reaction conditions at 450°C Ir–H–ZSM-5 did not reach steady-state catalytic behavior within 32 h. In contrast, unsupported Ir black showed higher initial yields of nitrogen and approached steady-state considerably faster. Ir black with the largest crystallite size (45 nm) required the shortest time for reaching steady-state behavior. The influence of crystallite size on the reaction of Ir with O₂ and NO was addressed and related to the increase in N₂ yields with increasing Ir crystallite size in the reduction of NO using propene as a reducing agent. Comparative pulse thermoanalysis studies of NO and O₂ adsorption on Ir black with different crystallite sizes (5–45 nm) revealed that the relative uptake of NO (m_NO/m_O2) increases strongly with increasing crystallite size. This behavior is due to a strong structure sensitivity of NO adsorption, whereas O₂ adsorption is relatively insensitive to crystallite size. The improved yield of N₂ with increasing crystallite size under HC–SCR conditions is traced to the higher surface concentration of NO relative to O₂ with increasing crystallite size.