Second row transition metal sulfides for the hydrotreatment of coal derived naphtha III. Removal of individual nitrogen compounds Original Research Article

The disappearance of individual nitrogen compounds is followed during the hydrotreatment of a coal-derived naphtha containing a mixture of nitrogen-, sulfur- and oxygen-containing heteroatom compounds over bulk second row transition metal sulfides. The naphtha contains mainly three types of nitrogen compounds: pyridines, anilines and quinolines. While quinoline is the least reactive of the three simplest compounds in these compound classes, substituted anilines are the compounds most difficult to remove from the naphtha. The presence or absence of an alkyl substituent exerts a strong influence on the reactivity of individual compounds and can over-shadow the differences between compound types. The reactivity patterns of the methyl-substituted pyridines indicate a steric hindrance about the nitrogen atom. The order of reactivity between alkyl-substituted anilines is different over the various sulfides with steric hindrance about the nitrogen atom indicated for only the higher activity catalysts. Except for molybdenum sulfide, the reactivity of quinoline is less than or equal to that of methyl-substituted quinolines. The individual nitrogen compounds do not disappear according to a first order rate expression but indicate strong product inhibition of the reaction rate. The overall removal of nitrogen does not follow simple first, zero or second order kinetics and shows similar kinetic behavior as for the disappearance of individual nitrogen compounds.