The influence of support on the performance of molybdenum sulfide catalysts used to hydrotreat coal liquids.

摘要

The research described herein involves the development of catalysts for use in hydrotreating coal liquids. A variety of supports for molybdenum sulfide hydrotreating catalysts were studied. These materials included silica, silica-magnesia, titania, chromia-alumina, activated carbon and nitrided activated carbon. The alumina supported, commercial catalysts Amocat 1A and Amocat 1C as well as the silica-alumina supported, commercial catalyst Harshaw CoMo-0402 were also studied.; Catalysts were characterized by BET surface area, mercury porosimetry and x-ray powder diffraction. Acidity was measured by the temperature programmed desorption of tert-butyl amine. Initial activity screening studies were conducted in a stirred autoclave batch reactor to determine appropriate metals loadings for the various supports. Initially active catalysts were then tested in a bench scale, trickle bed reactor to determine activity maintenance, coking tendency and selectivity at lined out conditions. Selectivities for hydrodenitrogenation and for the production of hydrogen donor molecules were of interest. The donatable hydrogen content of the product was determined by {dollar}sp1{dollar}H and {dollar}sp{lcub}13{rcub}{dollar}C NMR spectroscopy.; The results indicated a strong correlation between lined out hydrogenation activity and the volume in 60-200 A diameter pores. It is thought that pores of this size can accommodate the equilibrium coke content without blockage of the active sites. A second correlation was observed between HDN activity and acid site density, indicating the importance of acid sites in denitrogenation. Low acidity catalysts appeared to produce a greater hydrogen donor content in the product oil than did high acidity catalysts but the results were not conclusive. The results also suggest that Bronsted acid sites can markedly reduce coking tendency but that in general, coke formation is related in a complex way to the acid/base chemistry of the surface.