Organic nitrogen compounds in gas oil blends, their hydrotreated products and the importance to hydrotreatment

In the pretreatment of feeds for catalytic cracking and for HDA, the primar y objective is to reduce the amount of organic sulfur and nitrogen compound s in the feedstock [Catal. Rev. Sci. Eng. 36 (1994) 75] [1]. Organic nitrog en compounds have a significantly negative kinetic effect on hydrotreating reactions. The distribution of the organic nitrogen compounds in feed and h ydrotreated products is discussed. Alkyl-substituted carbazoles are found t o be the dominant and most refractive organic nitrogen compound in the feed . Our results show that indoles and quinolines are very reactive as compare d with carbazoles. From the characterization of the pyrrole benzologues, it is concluded that the more the substituents,the lesser the reactivity. It is well known that conversion of organic sulfur occurs via two different me chanistic routes: the direct and the hydrogenation route [J. Catal. 61 (198 1) 523; AIChE J. 27 (1981) 663; J. Catal. 97 (1986) 52; Catal. Today, in pr ess; Polyhedron 16 (1997) 3213] [2-6]. The hydrogenation route converts the most refractive S-molecules and plays a very important role in the convers ion of N-compounds. N-containing molecules often show a very low reactivity as compared with the analogous sulfur compounds. Several studies using mod el feedstocks show that nitrogen-containing molecules, and in particular, b asic organic nitrogen compounds inhibit the HDS reaction [Appl. Catal. A 17 0 (1998) 1] [7]. In this study, real feed experiments have demonstrated tha t even though carbazoles are slow to react and are among the predominant N- compounds, it is the basic N-compounds that are the major inhibiting specie s in diesel fuels. (C) 2001 Elsevier Science B.V. All rights reserved.