Mechanisms of the hydrodenitrogenation of alkylamines with secondary and tertiary α-carbon atoms on sulfided NiMo/Al2O3

The hydrodenitrogenation (HDN) of alkylamines with secondary and tertiary α-carbon atoms (2-pentylamine, 3-methyl-2-butylamine, 3,3-dimethyl-2-butylamine, 2-methylcyclohexylamine, 2-methyl-2-butylamine) and benzylamine and the hydrodesulfurization (HDS) of corresponding alkanethiols were studied over sulfided NiMo/Al2O3. Alkanethiols and dialkylamines were primary products in the HDN of the amines with secondary α-carbon atoms, formed by substitution of the amine group by H2S or an alkylamine. Alkanes and alkenes were secondary products, formed from elimination and hydrogenolysis of the alkanethiols, as confirmed by the similar alkenes/alkane ratios in the HDN of the alkylamines and HDS of the corresponding alkanethiols. 2-Methyl-2-butylamine and benzylamine reacted much faster than the amines with secondary α-carbon atoms. Methylbutenes and methylbutane were the primary products of 2-methyl-2-butylamine, and toluene was the primary product of benzylamine. This and the different methylbutenes/methylbutane ratios in the HDN of 2-methyl-2-butylamine and HDS of 2-methyl-2-butanethiol indicate that 2-methyl-2-butylamine, with a tertiary α-carbon atom, and the activated benzylamine react by means of an E1 mechanism.