Effect of sulfur compounds on the hydrodenitrogenation of 1,2,3,4-tetrahydroquinoline and its intermediates over NiMo/Al_2O_3 catalyst

摘要

The effect of sulfur-containing compounds on the hydrodenitrogenition (HDN) of o-propylaniline (OPA), decahydroquinoline (DHQ), 1,2,3,4-tetrahydroquinoline (14THQ) were performed at a moderate reaction conditions over NiMo/Al2O3 catalysts in a fixed-bed reactor, respectively. The presence of DMDS and DBT, converting CUS into sulfur sites (S2- and SH- group), could accelerate the ring-opening reaction (C-sp3-N bond cleavage) of DHQ/14THQ while inhibit the direct denitrogenation (C-sp2-N bond cleavage) of OPA, indicating that the C-sp3-N bond cleavage of DHQ/14THQ would require the synergistic work of S2- and SH- group, but while the C-sp2-N bond cleavage of OPA would take place on the CUS. An inhibitory effect of sulfur-containing compounds on the HDN of 14THQ was also observed. It could be ascribed to that the selectivity of 14THQ - OPA - PB/PCHA pathway in HDN of 14THQ was enhanced. However, the conversion of OPA is rather difficult for the reason that the inhibitory effect on the C-sp2-N bond cleavage and the competitive adsorption from DHQ and 14THQ. The conversion of OPA, which is a "dead end" in the presence of sulfur-containing compounds, determines the limitation HDN conversion of 1,2,3,4-tetrahydroquinoline.