Cormerais, F. X.; Chen, Y.; Kern, M.; Gnep, N. S.; Perot, G.; Guisnet, M. J. Deeba, M.; Hall, W. J. Catal. 1979, 60, 417. Dejaifve, P.; Auroux, A.; Gravelle, P. C.; Vedrine, J. C.; Gabellca, Derouane, Dejaifve, P.; Vedrine, J.; Bolls, V.; Derouane, E. G. Turner, J. 0. J. Am. Derouane, E. G.; Nagy, J. 6.; Dejaitve, P.; van Hoof, J. H. C.; Spekman, B. P.; Forni, L. Catal. Rev.The effects of organic nitrogen compounds on the hydrodesulfurization of a catalytic naphtha were examined under conditions where the nitrogen compounds were generally unreactive. The nitrogen compounds tested as inhibitors included several alkylpyridines, 2,5dimethylpyrrole, 4-methylaniline, and benzylamine. Significant differences in desulfurization were observed which could be related to nitrogen compound structure. Comparison of alkylpyridines clearly shows a steric contribution of ring substituents. The lack of inhibition when methyl groups were attached to ring carbons adjacent to the nitrogen atom suggests adsorption of the pyridine molecule on the active desulfurization site through the nitrogen atom. Electronic effects, such as resonance stabilization, may account for the relatively small inhibition effect of sterically unhindered 4-methyianiline while the larger inhibition effects of the hindered 2,5dimethylpyrrole and benzylamine can be attributed to their greater reactivity to produce more strongly adsorbed polymeric materials and ammonia, respectively.
Hydrocracking has become a major oil refining process since its introduction in 1961. Developing improved catalysts for industrial processes involves the proper balance between activity, selectivity, and catalyst life. Hydrocracking catalysts consisting of combinations of nickel and tungsten oxides supported on a low (13%) alumina, silica-alumina matrix containing 35% Ultrastable Y zeolite were tested in a once-through mode. Catalyst performance was determined using a blend of light virgin and catalytic cycle oils for hydrocracking and a heavy catalytic cycle oil for denitrogenation. The best catalysts were estimated to be more than twice as active for hydrocracking as the reference catalyst; high selectivity to heavy naphtha, and near total denitrogenation and desulfurization were also achieved.
When olefins are hydrogenated over metallic catalysts, such as nickel, the normal reaction products are paraffins of the same skeletal structure as the starting olefins. If the catalyst also possesses strong paraffin isomerization capabiliiies, the product is a mixture of paraffins which i s limited b y the paraffin isomer equilibrium. The latter reaction i s pictured as occurring in two steps-olefin saturation followed by paraffin isomerization. It i s now possible to hydrogenate normal olefins to isoparaffins beyond the limit of paraffin equilibrium. Using sulfided nickel on silica-alumina as the catalyst, normal pentene has been hydrogenaied mainly to isopentane. A reaction mechanism i s suggested, involving carbonium ion intermediates, in which the tertiary carbonium ion i s selectively hydrogenated. These results demonstrate the wide scope of reaction included in the field of catalysis. When the free energy difference is favorable, the implementation of a reaction-no matter how complex-depends only on developing the proper catalyst.YDROGEKATION of olefins usually leads to paraffiis of the However, shifts in structure can result from isomerization either of the olefin before hydrogenation or of the paraffin after hydrogenation (7,9 ) . I n these cases. where hydrogenation rate of the olefin isomers are about the same, the final compositim is limited by the equilibrium distribution of the olefins or of the paraffins.Paraffin isomerization (7) in the presence of hydrogen has frequently been referred to as hydroisomerization although no net h)drogen consumption occurs. I n this article, the term hydroisomerization of olefins is used to distinguish a new reaction in which olefins are hydrogenated primarily to isoparaffins. This type of reaction is discussed in recent patent literature (70). The ratio of iso-to n-paraffins in the product is in excess of the thermodynamic iso-to-normal equilibrium ratios of either the olefins, or the paraffins. The reaction requires a catalyst with both acidity and hydrogenation ac-ti\ity. The acidity and hydrogenation activity have been studied separately. To gain insight into the mechanism of reaction. various olefins and paraffins have been subjected to hydroisomerization conditions. same skeletal structure (5). ExperimentalThe folloi\ing hydrocarbons from Phillips Petroleum Corp. 1and 2-Pentene, technical grade 2-Methyl-2-butene, pure grade Isopentane, pure grade 3-Methylpentane, pure grade Methylcyclopentane, technical grade (repurified to 99.8% were used : purity) Except Lvhere the effect of sulfur concentration was being investigated, carbon disulfide was added to these reagents to about 0.8 wt. 70 sulfur level. Electrolytic hydrogen was passed over palladium on charcoal and dried over Drierite before use.Experiments were performed in a flow s>-stem using 3 to 6 ml. of catalyst. The reactor was 3/,-inch i.d. and 14 inches long Xvith a '/,-inch 0.d. axial thermocouple well.Catalysts were prepared by impregnating either Nalco HA silica-alumina cracking catalyst or Davison Grad...
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