2ND ROW TRANSITION-METAL SULFIDES FOR THE HYDROTREATMENT OF COAL-DERIVED NAPHTHA .2. REMOVAL OF INDIVIDUAL SULFUR-COMPOUNDS

The disappearance of individual sulfur compounds has been investigated during the hydrotreatment (simultaneous removal of sulfur, nitrogen a nd oxygen) of coal-derived naphtha over each of the bulk second row tr ansition metal sulfides. The sulfur compounds in the naphtha mainly co nsist of thiols/sulfides, thiophene and substituted thiophenes. Thiols /sulfides are, in general, more easily converted than thiophenic compo unds are. Lighter thiols/sulfides are intermediates in the conversion of higher boiling thiols/sulfides or thiophenes. Side chain alkyl C-C bond breaking is predominant during the disappearance of thiophenes ov er the Zr and Nb catalysts while C-S bond breaking is predominant over the other catalysts. Thiophenic compounds are hydrogenated prior to d esulfurization over the Mo, Ru, Rh and Pd sulfides. Highly substituted thiophenes are the compounds most difficult to convert over the Mo, R u, Rh and Pd sulfides. The substituted thiophenes exhibit different re activity trends over molybdenum sulfide, on one hand, and the Group VI II sulfides, on the other, indicating different adsorption modes and s urface mechanisms for their conversion over these catalysts. Individua l sulfur compounds do not follow first order kinetics and the disappea rance rate is limited by product inhibition. The overall removal of su lfur does not follow simple first or second order kinetics since the i ndividual compounds do not react in parallel, independent or first ord er reactions.