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1 wt%Rh/Ce-MCM-41 catalysts were synthesized using Ce-MCM-41 as support where Si/Ce molar ratio varied from 10 to 30 and 50. During hydrogen reduction process, metallic Rh particles were formed on the Ce-MCM-41 at around 130 °C with an average particle size 6.8 nm. These catalysts were tested in the ethanol steam reforming (ESR) under atmospheric pressure between 225 and 425 °C. Compared to Rh/MCM-41 catalyst, cerium introduction would significantly enhance both the catalytic activity and hydrogen yield by approximately 2–3 times. However, the amount and the method of Ce incorporation in the framework of MCM-41 could greatly impact the catalytic performance of the Rh/Ce-MCM-41 catalysts. The ethanol conversion at 425 °C over the Rh/Ce-MCM-41 catalysts increased from 90.0% to 95.1% and 99.9%, as the Si/Ce molar ratio increases from 10 to 30 and 50. However, product selectivity is almost independent of the cerium content. The direct hydrothermal method of introducing Ce into the framework of MCM-41 is much superior to the impregnation route in the ESR reaction. After 6 h of reaction, the catalysts remain the mesostructure and the chemical state of cerium ions unchanged. Trace coke with graphite-like structure deposited on the surface does not modify the catalytic performance. [ABSTRACT FROM AUTHOR]

Abstract: Ceria doped MCM-41 materials were synthesized by surfactant-assisted hydrothermal and wet impregnation methods. All the obtained Ce-MCM-41 materials were characterized by N2 physical adsorption, X-ray diffraction (XRD), diffuse reflectance UV–visible spectroscopy (DRUV–vis), infrared spectroscopy (IR), solid-state cross-polarization magic angle spinning nuclear magnetic resonance spectroscopy (CP/MAS-NMR), and transmission electron microscopy (TEM). The catalytic properties were evaluated in CO oxidation under atmospheric pressure and various temperatures. The results showed that in the materials synthesized by hydrothermal method, most of Ce ions were well incorporated in the tetrahedral coordinated sites into the framework of the MCM-41 as Si/Ce molar ratio is 30 and 50. High cerium content may lead to mesostructure partial collapsing and ceria particles segregation. For CO oxidation, the catalytic activity of Ce-MCM-41 synthesized by hydrothermal method was significantly greater than that of the materials prepared by impregnation route. Over the Ce-MCM-41 materials prepared via hydrothermal technique, 100% CO conversion was achieved at 504, 514 and 528 K, respectively, as the Si/Ce molar ratio decreased from 50 to 30 and 10. For the first time, we found an interesting correlation of Q 3 species relative area in the 29Si CP/MAS-NMR spectra of the Ce-MCM-41materials with the reaction rates of CO oxidation, which indicates that both surface hydroxyls and tetrahedral-coordinated Ce4+ ions in the MCM-41 take important roles in the CO oxidation. [Copyright &y& Elsevier]

Abstract: The kinetic effect of quinoline (Q) and its reaction by-products, i.e. 1,2,3,4-tetrahydroquinoline (1,4-THQ), decahydroquinoline (DHQ) and orthopropylaniline (OPA), on the hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene (4,6-DMDBT) was studied in the presence of a commercial NiMoP/Al2O3 catalyst under operating conditions relevant to industrial applications. Kinetic observations and modelling based on a Langmuir–Hinshelwood–Hougen–Watson (LHHW) mechanism, accounting for most of the observed Q and 4,6-DMDBT by-products, indicated that Q, 1,4-THQ and DHQ are the main HDS reaction inhibitors, even at nitrogen concentrations as low as 25ppm. To some extent Q and 1,4-THQ were adsorbed favorably on the HDS catalytic active sites, being more reactive than most of the sulfur and nitrogen-containing molecules. Besides, DHQ was less reactive than Q and 1,4-THQ, despite a significant adsorption affinity on the HDS catalytic active sites. As a consequence, Q and 1,4-THQ inhibited HDS reactions at lower Q conversions, whereas DHQ inhibited them at higher Q conversions. [Copyright &y& Elsevier]

Abstract: X-ray diffraction (XRD) patterns with broad background are commonly found in the characterization of materials with a certain degree of amorphicity, so the sharp intensity peaks associated with material phases are not well defined. This work used rescaled range (denoted by R/S) analysis, a method intended for fractal analysis of noisy signals, to characterize XRD patterns with broad background. It is found that XRD patterns with broad background are not random at all, but contain information on regularities expressed as autocorrelations of the intensity signal. Sol–gel alumina fired at different temperatures was used as an example to illustrate the applicability of the method. It is shown that fractal R/S analysis is able to locate angular regions that can be associated to ideal International Centre for Diffraction Data Powder Diffraction File (ICDD PDF) lines of diverse alumina phases. [Copyright &y& Elsevier]

Abstract: A study on the catalytic properties of the transition metals (Ni,Co,Mo)-carbides, -nitrides for thiophene and dibenzothiophene hydrotreating was conducted. The (Ni,Co)-Mo carbides and the corresponding (Ni,Co)-Mo nitride phases showed a catalytic activity higher than conventional bimetallic (Ni,Co)-Mo sulfides. In addition, a study was done on the effect of the atomic ratios, i.e., 0.1≤M+/(M+ +Mo)≤0.9 where M+ stands for Ni or Co, and the concentration of promoters such as phosphorous, which was a structural stabilizing agent. The catalytic performance of the bimetallic NiMo and CoMo carbides and nitrides was studied using thiophene and dibenzothiophene hydrodesulfurization (HDS) as model reactions at 623K and P =1atm. The catalytic activity of the dispersed carbide and nitride phases on the alumina carrier was more significant than that of the reference catalysts, alumina supported NiMo-S and CoMo-S. The metallic character of the NiMo and CoMo carbides was evidenced by their higher hydrogenation activity in thiophene HDS, while the nitrides favored both hydrogenation and hydrogenolysis type reactions. [Copyright &y& Elsevier]