In hydrodesulfurization (HDS) of dibenzothiophene (DBT), the catalysts prepared from silica-alumina supported molybdenum compounds showed higher yields of biphenyl, cyclohexylbenzene and bicyclohexyl than conventional sulfided molybdena-alumina. Specifically, the catalysts derived from silica-alumina supported anionic molybdenum carbonyls gave the highest yields among silica-alumina supported ones.
In the hydrodesulfurization of dibenzothiophene catalyzed by alumina-supported molybdenum carbonyls, the effect of the addition of cobalt compounds (cobalt carbonyl (Co2(CO)8), cobalt nitrate (Co(NO3)2), cobalt(II) acetylacetonate (Co(acac)2), and cobalt(III) acetylacetonate (Co(acac)3) on catalytic activity and the product selectivity were investigated.The catalytic activity increased remarkably by the addition of cobalt compounds to molybdenum carbonyl-derived catalysts, and the order of activity was Co2(CO)8>Co(NO3)2>Co(acac)2>Co(acac)3. Hydrodesulfurization catalysts were also prepared from silica-alumina and silica supported molybdenum and cobalt carbonyls. The silica-alumina supported catalyst showed higher catalytic activity in HDS of dibenzothiophene and 4-methyldibenzothiophene than the alumina-supported catalyst which showed similar activity to the conventional sulfided Co-Mo/ Al2O3. The catalysts were characterized by means of NO chemisorption, FTIR, and XPS. The result from XPS showed that the catalysts derived from alumina and silica-alumina supported molybdenum and cobalt carbonyls had a higher concentration of cobalt species on the surface at the time of their preparation than the conventional Co-Mo/Al2O3, and it was supported by the results from NO chemisorption and FTIR.
In hydrodesulfurization of dibenzothiophene (DBT) catalyzed by supported ruthenium carbonylcesium hydroxide systems after presulfidation, the effects of various supports such as Al2O3, SiO2-Al2O3, SiO2, TiO2, NaY zeolite on the catalytic activity and product selectivity were investigated. In the absence of cesium, the conversion of DBT decreased in the order SiO2-Al2O3>Al2O3>TiO2>SiO2>NaY zeolite. When cesium hydroxide was added to the catalysts derived from supported Ru3(CO)12, the conversion of DBT increased remarkably with the use of Al2O3, SiO2-Al2O3, and SiO2 and reached the maximum values at Cs/Ru=2, 3 and 2, respectively. The conversion, however, decreased in the order Al2O3>SiO2>SiO2-Al2O3. Further addition of cesium decreased the activity. In contrast to this, when NaY zeolite was used, the conversion of DBT did not increase with the addition of cesium. For obtaining a high catalytic activity, it was essential to load the ruthenium hydride complex Cs[HRu3(CO)11], obtained after reacting Ru3(CO)12 with cesium hydroxide, onto the support.In the supported Ru3(CO)12-cesium hydroxide systems, biphenyl was produced selectively. XP spectra showed that the addition of an appropriate amount of cesium stabilized the ruthenium sulfide on the support even under hydrogen pressure.
In hydrodesulfurization (HDS) of dibenzothiophene (DBT) catalyzed by a supported anionic molybdenum carbonyl, [NEt4][Mo(CO)5(CH3COO)]/support (Et=ethyl group), the effects of supports (SiO2-Al2O3, Al2O3, SiO2, TiO2, NaY zeolite, HY zeolite HZSM-5, and active carbon) on catalytic activity and product selectivity were investigated in a pressurized flow reactor. The yields of hydrodesulfurization products, biphenyl (BP), cyclohexylbenzene (CHB), and bicyclohexyl (BCH) decreased in the order, SiO2-Al2O3>Al2O3>TiO2=Active carbon>SiO2>NaY zeolite=HZSM-5>HY zeolite. The rates of HDS per amount of molybdenum loaded decreased in the order, SiO2-Al2O3>TiO2>NaY zeolite>Al2O3>SiO2. When HY zeolite was used, hydrocracking occurred significantly and BP, CHB, and BCH were not produced. When active carbon was used, a substantial amount of DBT was adsorbed on it, and the material balance could not be completely obtained.From NO chemisorption and XPS measurement of the catalysts derived from silica-alumina supported anionic molybdenum carbonyls, it was deduced that presulfidation of [NEt4][Mo(CO)5(CH3COO)]/SiO2-Al2O3 and Mo(CO)6-triethylamine(NEt3)-ethanethiol(EtSH)/SiO2-Al2O3 systems would give a silica-alumina supported MoS2-x species which was active in HDS of DBT.
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