The effects of addition of small amounts of noble metals such as Pt, Pd, and Rh to Ni/γ-Al2O3 and NiO-MgO solid solutions were investigated on the catalyst activation, catalyst bed temperature profile, and carbon formation behavior in oxidative steam reforming of methane. Addition of Pt and Pd by a sequential impregnation method to Ni/γ-Al2O3 had a much more remarkable effect than by a co-impregnation method on the resistance to deactivation by oxidation of Ni and suppression of hot-spot formation. Temperature-programmed reduction, extended X-ray absorption fine structure, and Fourier transform infrared spectroscopy suggested that the noble metal atoms introduced by the sequential impregnation method were preferably located on the surface to form an alloy. Addition of noble metals (Pt, Pd, and Rh) to Ni0.2Mg0.8O solid solution catalysts inhibited carbon formation in the oxidative steam reforming of methane under pressurized conditions.
Mesoporous materials have attracted a great deal of attention because of their controllable structures and compositions, which make them suitable for a wide range of applications in catalysis, environmental clean-up, and development of advanced materials. Various mesoporous materials can be synthesized based on the self-assembly of surfactants and inorganic precursors. We previously demonstrated a novel templating route for preparing mesoporous silicas based on the self-assembly of anionic surfactants and inorganic precursors in the presence of aminosilane or quaternized aminosilane as a co-structure-directing agent (CSDA). We continue to investigate the resultant novel mesoporous materials called anionic surfactant mesoporous silica (AMS). The latest AMS series is a novel bicontinuous cubic Pn3m mesoporous silica (AMS-10). We have also found that the assynthesized AMS is transformed into amino-functionalized mesoporous silica, by removal of only the surfactant by extraction, with potential uses as high-performance catalysts and adsorbents. Furthermore, the use of a chiral anionic surfactant derived from the amino acid, N-myristoyl-L-alanine sodium salt, provides chiral mesoporous silica. Such anionic surfactant templating routes will provide a new family of mesoporous materials as well as information on the structural behavior of anionic surfactants. This review describes the preparation, properties, and potential applications of anionic surfactant templated mesoporous silicas.
The skeletal isomerization of paraffins is effective in improving the gasoline octane number, and platinum catalyst supported on sulfated zirconia (SZ) has been practically used for light naphtha isomerization. Though the development of heavy naphtha isomerization would also be desired in future, selective isomerization is very difficult to achieve since undesirable cracking proceeds very fast and an effective process has never been reported. In this study, platinum-supported tungstated zirconia (WZ) catalyst was found to be promising in suppressing the undesirable cracking during heavy naphtha isomerization. In addition, a reaction behavior based on the difference in acidity between both the catalysts to clarify the reactivity difference between light naphtha and heavy naphtha was reported. Using an optimized Pt/WZ catalyst we successfully obtained an isomeric yield of 80% (98% of isomerization selectivity) for a conversion of 82%. Furthermore, it was proved that WZ has a greater number of weak acid sites instead of less strong and total acid sites as compared with the acidity of SZ, as analyzed by the application of NH3 adsorption-direct nitrogen analysis to the solid acids. It was concluded that the catalyst with a higher weak acid ratio has higher selectivity in n-C7 isomerization.
Newly developed CoMo titania catalysts for ultra-deep hydrodesulfurization (HDS) of diesel oil have higher activities for both HDS and hydrodenitrogenation (HDN), whereas the chemical hydrogen consumption is almost the same or lower than that of alumina supported catalysts. The HDN reaction routes of a model nitrogen compound and the hydrogenation activities of a model aromatic hydrocarbon compound over CoMo titania catalysts and commercial CoMo and NiMo alumina catalysts were investigated using carbazole dissolved in toluene as the feedstock. Toluene was used as the representative of aromatic hydrocarbon compounds which account for about 30% of diesel oil. The HDN reactions over each catalyst proceeded by the same reaction routes for hydrogenation of the aromatic rings of carbazole. However, the hydrogenation activity of toluene over the CoMo titania catalysts was lower than that over alumina supported catalysts. It is considered that the chemical hydrogen consumption of the CoMo titania catalyst is less than that of alumina supported catalysts, because hydrogenation of aromatic hydrocarbon compounds in diesel oil is selectively restricted over the CoMo titania catalyst.
The 12-tungstophosphoric acid (TPA)-catalyzed oxidative desulfurization of naphtha with H2O2 was investigated. All organosulfur compounds examined were efficiently oxidized with H2O2 and TPA catalyst in acetic acid (AcOH). The order of the oxidation reactivities was sulfides, disulfides > benzothiophenes > thiophenes. Methyl substituents on benzothiophenes and thiophenes increased the reactivity of the sulfur atom. The major oxidation products from the organosulfur compounds, except a few thiophenes, were the corresponding sulfones. The organosulfur compounds in octane were also oxidized with H2O2 and TPA catalyst in an octane/AcOH biphasic system. The oxidation proceeded in the AcOH phase and most oxidation products remained in this phase, resulting in the successive removal of the sulfur compounds from the octane phase. Using this oxidative treatment effectively reduced the sulfur content of naphtha, as the sulfur content was reduced to about 0.5 mass ppm after adsorption with silica gel. Hydrodesulfurization is an effective pretreatment for oxidative desulfurization of naphtha, by which the sulfur content can be reduced to below 0.1 mass ppm.
The dehydroisomerization of butane to isobutene was investigated over platinum-loaded MFI-type ferrisilicate catalysts with various silicon-to-iron ratios. The ratios of silicon to iron were observed to affect the yield of isobutene. The highest yield (ca. 15%) was obtained with a ratio of 100, but higher ratios gave lower yields of isobutene caused by the decomposition of butane and butenes. The ratios of silicon to iron did not affect the conversion of butenes over the ferrisilicate catalysts, indicating that the platinum loaded on the ferrisilicate is responsible for the decomposition of butane and butenes. This is supported by the observation that the particle size of platinum on ferrisilicate became smaller with lower ratios of silicon to iron.
Vapor extraction (VAPEX) is an important process for recovery of heavy oil and bitumen. In this work, the VAPEX process is studied experimentally in a rectangular physical model. The setup was constructed in a manner allowing experiments in both fractured and non-fractured systems. Propane was used as the solvent in all experiments. The experiments were conducted with pure solvent and different configurations of fracture-matrix contacts. Effects of pressure and number of side fractures were studied in this work. Results showed that the oil recovery increased with pressure. In addition, we found for the first time that there is a pressure range below the solvent dew point that the process can be performed efficiently. This has an advantage to the process and prevents any pore space blocking in the system due to solvent condensation caused by sudden pressure drops in the connecting lines, as the solvent has the tendency for condensation at conditions near to its dew point pressure. It was also found that the fractures can enhance heavy oil recovery during VAPEX process by improving the contact between solvent and oil contained in the matrix block, increasing the cross flow of solvent and oil between matrix and fracture, and also by providing more area for solvent diffusion into the heavy oil. These findings increase industry confidence for application of VAPEX process in both conventional and fractured reservoirs for exploitation of heavy oil resources.
Uniform pore sizes of 10 wt%Ru-SiO2 catalysts prepared by the alkoxide method were varied in the range of 4-8 nm, by adding formamide (FA) at the sol-gel preparation stage. The prepared catalysts were used to catalyze the Fischer-Tropsch (F-T) reaction in the slurry phase under the reaction conditions of T=503 K, P=1 MPa, H2/CO=2/1, and W/F=5 g-catal.h/mol. The Ru particle sizes estimated by H2 adsorption increased with increasing pore size, although the Ru crystallite sizes evaluated by XRD line broadening were only slightly changed. The selectivity for CH4 decreased and the selectivity for higher hydrocarbons increased with increasing pore size of the catalysts, caused by diffusivity of the slurry solvent and/or the products in the uniform meso-pores, or uniform Ru particle size effects.