Surface Property-Activity Relations of Co/Sn Oxide Nanocatalysts Evaluated Using a Model Reaction: Surface Characterization Study

An ideal hydroisomerisation reaction is expected to take place over a bifunctional catalyst, in which a balance between the number of metal sites and acid sites might lead to an optimal performance. In order to assess this relationship and the implications for n-heptane hydroisomerisation, various loadings of molybdenum oxide (1–10 wt%) were impregnated on zirconia with a view to producing samples with a range of acid and metal-like properties. The nature and amounts of the acid sites were determined using quantitative FTIR of pyridine adsorption, while the metal-like properties were determined using CO chemisorption. It was observed that zirconia alone contained only Lewis acid sites (1440 cm−1), while addition of MoO3 generated Bronsted acidity (1536 cm−1). The ratio of Bronsted to Lewis acid sites increased with loadings. Similarly, the amounts of CO taken up by the samples increased with MoO3 loadings; hence, the addition of MoO3 resulted in an improved metal like behaviour. The ratio of Bronsted acid to metal-like sites were found to range between 0.009 and 1.180 on going from 1 to 10 wt% MoO3. The materials were used for n-heptane hydroconversion. The sample with the highest amount of Bronsted acid site, which also consumed the highest amount of CO showed the highest activity. Hence, it could be concluded that the addition of MoO3 improves the Bronsted acid to metal-like site ratio, which resulted in a pronounced improvement in the activity of the samples.

Kinetic and catalytic analysis of mesoporous Co3O4 on the oxidation of morin

Physical mixtures comprising AgCeO2 and t-ZrO2 or MgO were employed as catalysts for the generation of propene from ethanol in the presence of water. The catalysts were characterized by means of several techniques such as X-ray diffraction, N2 physical adsorption, isopropanol conversion and ethanol to acetone Meerwein–Ponndorf–Verley (MPV) model reactions, NH3 temperature-programmed desorption, CO2 temperature-programmed desorption, and ethanol temperature-programmed desorption followed by diffuse reflectance infrared Fourier transform spectroscopy and mass spectrometry. Acid and strong basic sites, redox properties, and the capacity to conduct both water dissociation and MPV reduction are important characteristics for this reaction. Water is the oxidant agent; however, water may also affect the acidic–basic sites of the oxides, as demonstrated when MgO was used. The physical mixture comprising t-ZrO2 and AgCeO2 is active in the conversion of ethanol to propene, presenting the following steps. First, etha...

In this paper, three different kinds of aluminum sources (sodium aluminate, aluminum sulfate and aluminum isopropylate) were used for preparing of nano beta-zeolite. The as synthesized zeolites were mixed with the as prepared amorphous silica-alumina to produce the supports for hydrocracking catalyst. The prepared supports were used for preparation of NiMo/silica alumina-nano beta-zeolite by impregnation method. The influence of the aluminum source for preparation of beta-zeolite on the performance of the prepared catalysts has been studied. The samples were thoroughly characterized by X-Ray diffraction method (XRD), field emission-scanning electron microscopy (FE-SEM), N2 adsorption-desorption isotherms (BET), temperature programmed desorption (TPD) and temperature programmed reduction (TPR) methods. The catalysts performance was evaluated by vacuum gas oil (VGO) hydrocracking at 390 oC in a fixed bed reactor. The XRD patterns showed that the beta-zeolite samples obtained from the present methods were pure and highly crystalline and the crystal size of the prepared zeolites were in nanometer scale. Crystallite size of nano beta-zeolite synthesized by aluminum isopropylate [Al(iPrO)3] was smaller than those of prepared by the other aluminum sources. The catalyst containing this zeolite with higher surface area (231 m2/g) and more available acid sites (1.66 mmol NH3/g) possessed higher activity and selectivity to gas oil (71.9 %).

CO2 methanation over Ni-Al LDH-derived catalyst with variable Ni/Al ratio

New bi-functionalized ordered mesoporous material as heterogeneous catalyst for production of 5-hydroxymethylfurfural

The mechanism of reverse water gas shift reaction over Cu catalyst was studied by pulse reaction with QMS monitoring, temperature programmed desorption (TPD) and temperature programmed reduction (TPR) of Cu/SiO2 catalyst. The reduced and/or oxidized copper offered low catalytic activity for the dissociation of CO2 to CO in the pulse reaction study with 1 ml volume of He/CO2, but the rate of CO formation was significantly enhanced with H2 participating in the reaction. The TPD spectra of CO2 obtained by feeding H2/CO2 over copper at 773 K provided strong evidence of the formation of formate at high temperature. The formate derived from the association of H2 and CO2 is proposed to be the key intermediate for CO production. The formate dissociation mechanism is the major reaction route for CO production.

Perovskite-type La2 –xSrxCoO4 mixed oxides have been prepared by calcination at various temperatures of precipitates obtained from aqueous solutions in the presence of citric or ethylenediamintetraacetic (EDTA) acids, and have been studied by X-ray diffraction (XRD), surface area (BET) measurements, temperature programmed desorption (TPD), temperature programmed reduction (TPR) and X-ray photoelectron spectroscopy (XPS). These oxides are catalysts for hexane oxidation, with the greatest activity for LaSrCoO4 calcined at 750 C. This has extensive oxygen vacancies and large internal surface area. Pt-modified LaSrCoO4 catalysts are significantly more active than the Pt-free system. Both surface and bulk phases of the preovskitetype oxides contribute to hexane oxidation. KEY WORDS: Perovskite-type A2BO4, Surface properties, Catalytic performance, Temperature programmed desorption (TPD), Temperature programmed reduction (TPR), and X-ray photoelectron spectroscopy (XPS), Hexane oxidation Bull. Chem. Soc. Ethiop. 2007, 21(2), 271-280.

Effect of supports on the structure and activity of vanadium-chromium oxide catalysts for ammoxidation of 3-picoline

Enhanced selective catalytic reduction of NO with CO over Cu/C nanoparticles synthetized from a Cu-benzene-1,3,5-tricarboxylate metal organic framework by a continuous spray drying process

Preparation of nanocrystalline NiO–MgO solid solution powders as catalyst for methane reforming with carbon dioxide: Effect of preparation conditions

Effect of different promoters on Ni/CeZrO 2 catalyst for autothermal reforming and partial oxidation of methane

An evolutionary approach in the combinatorial selection and optimization of catalytic materials

Mesoporous tin oxide: An efficient catalyst with versatile applications in acid and oxidation catalysis

The hydrogenation of CO2 at atmospheric pressure casts a direction for researchers to recycle the atmospheric carbon and subsequently reduce the greenhouse gas effect. Several efforts have been devoted to the development of an effective and stable catalyst for this reaction. Ni supported on Y2O3 catalysts were obtained from two different Y sources, Y2O3 that calcined from Y4O(OH)9(NO3) and Y4O(OH)9(NO3) directly. Compared to the ones from Y2O3 (denoted as Ni-Y2O3), the catalysts prepared from Y4O(OH)9(NO3) (denoted as Ni/Y2O3) showed superior activity for CO2 methanation, which was attributed to the enrichment of surface medium basic sites that of great importance for CO2 activations. However, with high metal loadings such as 20%, strong basic sites appeared which resulted in a high sensitivity to coke formation. Moreover, the reaction mechanism for CO2 methanation over Ni supported on Y2O3 has been proposed involving carbonates and formates species as key intermediates. The higher reactivity towards H2 for formates over Ni/Y2O3 than that over Ni-Y2O3 was found, which probably was the rate-determining step for CH4 formations. Temperature-programmed reduction by H2 (H2-TPR) further revealed that a stronger interaction between Ni species and the support for the reference Ni-Y2O3, if compared to that of Ni/Y2O3. A W doped Ni-Mg mixed oxide catalyst (NiWMgOx) was prepared by homogeneous precipitation and employed for the methanation of CO2. The addition of W remarkably promoted the methanation activity if compared to the undoped NiMgOx catalyst with improved stability and anti-CO-poison ability. Characterization techniques including in situ diffuse reflectance infrared Fourier Transform spectroscopy (DRIFTS), temperature-programmed desorption of CO2 (CO2-TPD) and H2-TPR were applied for both NiMgOx and NiWMgOx. The superior reactivity of monodentate formate towards H2 than that of bidentate formate species was identified and doping with W favored the formation of the former during the methanation of CO2, which well agreed with the activity results. W addition also increased the formation and the stability of surface basicity sites, along with an enhancement of the Ni-Mg interaction in favor of anchoring the Ni sites, all of which were responsible for the enhanced CO2 methanation activity and the improved stability. Mechanistic studies of CO2 methanation have been carried out on Ru/Al2O3. The structural configuration of Ru species over Ru/Al2O3 catalysts at different Ru loadings has been characterized by infrared reflection absorption spectroscopy (IRAS) for CO adsorption. Supported Ru monolayers, in which metal atoms directly interacted with the support, were plentiful over 1% Ru/Al2O3, exhibiting a high CO yield for the hydrogenation of CO2 at ambient pressure. An increasing preference for methanation was observed on Ru/Al2O3 with higher Ru loadings, over which a tendency for the exclusive formation of three-dimensional (3D) nanoclusters of multilayers appeared. Density functional theory (DFT) calculations over Ru9/Al2O3, as the representative model of supported Ru monolayers, and Ru35/Al2O3, as the representative model of supported 3D nanoclusters, demonstrated that the energy barrier of reversed water gas shift (RWGS) was lower than that of the methanation on Ru monolayers while CH4 production was energetically favored on top sites of 3D Ru nanoclusters. Moreover, the incorporation of the peripheral O into the final products of CO2 hydrogenation was predicted as a critical step during the RWGS at the metal-support interfaces, which was validated by isotope exchange mass spectrometry (MS) experiments.