Carbon-supported hydrodesulfurization catalysts for upgrading heavy hydrocarbon fuels

A range of carbon- and alumina-supported hydrodesulfurization (HDS) catalysts has been prepared and their activities examined for the hydrogenation and HDS of a high-boiling coal-derived liquid.; The principal carbon support used in this study was Ambersorb XE-348 which was carbonized from a sulfonated styrene-divinylbenzene copolymer. Treatment of the carbon in ammonia at 873 K for 1.5 h increased its nitrogen content from 0.4 to 3.7% wt.; Toluene chemisorption and x-ray diffraction line-broadening analysis of molybdenum (3 and 15% wt) sulfide catalysts prepared on the carbons and a {dollar}gamma{dollar}-Al{dollar}sb2{dollar}O{dollar}sb3{dollar} support indicated that MoS{dollar}sb2{dollar} was better dispersed on the carriers at the low Mo loadings than at the high Mo concentrations. The hydrogenation and HDS activities of the catalysts also followed the same trend; i.e., higher activities were obtained at low Mo loadings. Ammonia pretreatment of the carbon also enhanced the hydrogenation activity of the 3% wt Mo catalyst prepared from this support. This is attributed to increased dispersion of the active MoS{dollar}sb2{dollar} phase by the nitrogen functionality. The coking propensities of the carbon-supported catalysts were substantially lower than those of the alumina-based catalysts.; Between 648 and 723 K and for short reaction times at 6.9 MPa H{dollar}sb2{dollar} (cold), apparent activation energies of 35.2 and 44.7 kcal mol{dollar}sp{lcub}-1{rcub}{dollar}, respectively, were determined for the catalyzed (by 3% wt Mo supported on the prenitrided Ambersorb XE-348) and noncatalyzed asphaltene hydrogenation to oils. The corresponding preexponential factors were 6.3 {dollar}times{dollar} 10{dollar}sp6{dollar} s{dollar}sp{lcub}-1{rcub}{dollar} and 1.3 {dollar}times{dollar} 10{dollar}sp9{dollar} s{dollar}sp{lcub}-1{rcub}{dollar}. The apparent activation energy and preexponential factor for HDS by the same catalyst were 27.9 kcal mol{dollar}sp{lcub}-1{rcub}{dollar} and 1.6 {dollar}times{dollar} 10{dollar}sp4{dollar} s{dollar}sp{lcub}-1{rcub}{dollar}, respectively.; The results of this research indicate that, at low molybdenum loadings, Ambersorb XE-348 and ammonia-treated Ambersorb XE-348 carbon-supported hydrodesulfurization catalysts have a potential advantage over alumina-based counterparts, especially with respect to the low coking propensities of the former.