A detailed study has been made of the different steps involved upon the preparation of γ-Al2O3-supported Ni-Mo HDS catalyst precursors by urea–matrix combustion (UMxC) method. Catalyst performance was evaluated using a tubular fixed-bed reactor and the hydrodesulfurization of thiophene under normal pressure as a model reaction. The oxidic and sulfurized states of the HDS catalysts were characterized by X-ray diffraction (XRD), laser Raman spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and high resolution transmission electron microscopy (HRTEM) in order to correlate their oxidic and sulfurized properties with the catalytic behaviour. During the UMxC process several consecutive stages such as melting, dissolution and chemical reactions occurred. There was no evidence of residual carbon and well-dispersed Ni- and Mo-oxo-species supported on alumina were formed.
Urea employed as fuel not only increases the combustion rate, but also undergoes a decomposition process (endothermic reaction) that could contribute to the reduction of the combustion temperature. The urea–matrix combustion method permit to synthesize highly active γ-Al2O3-supported Ni-Mo HDS catalysts with a comparable promoter effect than that of corresponding catalyst prepared by impregnation method. In addition, an opposite relation between the activity and the hydrogenation properties was observed indicating that highly active HDS catalyst requires low consumption of hydrogen. Finally, both the ignition temperature and the urea-oxidizer ratio produce no significant changes in the HDS catalytic properties of Ni-Mo-based catalysts. 相似文献
The structure of the [CpRu(PPh3)2(C6H11SH)]BF4·CH2Cl2 complex was determined by X-ray diffraction techniques; triclinic space group
,a=12.567(1),b=13.409(1),c=14.733(1) Å, =95.380(7), =111.041(7), =96.454(8)°,V=2278.5(4) Å3,Z=2,R=0.056,Rw=0.088. The Ru is attached to two triphenylphosphine ligands, a cyclopentadienyl and the S atom of the cyclohexylthiol. The Ru–S distance is 2.389(2) Å and the S–H distance is 1.23 Å. 相似文献
The performance, in thiophene HDS, of a CoMo/Al2O3 catalyst was successfully improved through chemical modification of its oxidic precursor by impregnation with 1,5-pentanediol solution. The gas phase activation with a H2/H2S mixture was followed by thermogravimetric analysis coupled with a rapid chromatograph; the catalysts were characterized at different steps of the activation using X-ray photoelectron spectroscopy (XPS). It appeared that the addition of the organic agent retards the sulfidation of the supported metals, leading to a simultaneous sulfidation of Co and Mo atoms. This induces the formation of smaller MoS2 slabs and thus an increase in the number of active CoMoS sites, directly correlated with the better HDS performance of the modified solid. The role of 1,5-pentanediol is likely to inhibit, at low temperature, the adsorption of H2S on the solid and thus the sulfidation of the supported metals. 相似文献
Applications and prospects of two-phase, tuneable solvent systems composed of ionic liquids (ILs) and supercritical fluids with an emphasis on supercritical carbon dioxide (scCO(2)) are reviewed. The IL-scCO(2) biphasic systems have increasingly been used in diverse fields of chemistry and technology, and some examples of these applications are mentioned here. Rational design of such applications can obviously benefit from pertinent data on phase equilibria including the partition coefficients of the prospective products and reactants between the two phases. Therefore, a reliable technique to measure the limiting partition coefficients would be of value. Here, the pros and cons of supercritical fluid chromatography in this respect are discussed. An overview of methods for predictive thermodynamic modelling of binary (IL-scCO(2)) and ternary (solute-IL-scCO(2)) systems is also included. 相似文献