Hydrodenitrogenation of basic and non-basic nitrogen-containing compounds in coker gas oil

Abstract

The hydrodenitrogenation (HDN) performance of a Chinese coker gas oil (CGO) was tested in a micro-fixed bed reactor over a nickel–tungsten supported on citric-treated Y zeolite mixed with a titania–silica composite catalyst (NiW/CYCTS) within the temperature range of 360–420°C, operating pressure range of 5.0–8.0MPa, liquid hour space velocity (LHSV) range of 0.5–2h−1, H2/CGO ratio range of 400–1200 (v/v), and H2S concentration range of 1–5wt.%. The effects of these parameters on the relative conversions of total nitrogen (TN), basic nitrogen (BN), and non-basic nitrogen (NBN) compounds were determined. The conversion of TN compounds enhanced as the temperature and operating pressure increased and as LHSV decreased. BN compounds were easier to be removed than NBN compounds; they were also affected more significantly by the reaction conditions. With increasing H2/CGO ratio, the conversion of BN and NBN compounds initially increased and then decreased thereafter. This finding may be attributed to the addition of phenyl-sulfide (PHS) in the feedstock. The kinetic study of the HDN reaction showed that TN, BN, and NBN compounds accorded with the pseudo-first-order kinetic model. The calculation of the rate constants and activation energies indicated that the HDN of NBN compounds controlled the removal of TN compounds. Moreover, the hydrogenation of N-heterocyclic was the controlling step for the conversion of NBN compounds. The results above can guide the development of CGO hydrotreating catalyst. With the information from this paper, the development of CGO hydrotreating catalyst can adjust the properties of the catalyst by decided technology which will favor the removal of NBN containing compounds.