Ind. Eng. Chem. Res. 1992, 31, 2661-2669
2661
Hydrogenation and Hydrocracking of a Model Light Cycle Oil Feed. 1. Properties of a Sulfided NiMo Hydrotreating Catalyst Michel Bouchy,+Pierre Dufresne,t and Slavik Kasztelan* Znstitut FranGais du Pgtrole, 1 et 4 Avenue de Bois-Preau, BP 311, 92506 Rueil-Malmaison Ceder, France
A synthetic model light cycle oil feed containing 40% w/w 1-methylnaphthalene, dimethyl disulfide, and n-butylamine in n-heptane has been treated under hydrogen on a sulfided NiMoP/A1203catalyst. Reference conditions were a hydrogen pressure of 28 atm, temperature of 400 OC, and a liquid hourly space velocity (LHSV) of 1m3 h-l m-3 cat. Kinetic data for the hydrogenation of the first and second aromatic rings of 1-methylnaphthalene have been determined. Under these reference conditions, the thermodynamic equilibrium for the hydrogenation of the first ring is reached before any hydrocracking occurs. The hydrocracking yield is about 12%. The main products of hydrocracking are, on the one hand, the isomerization of the methyltetralins into C11-alkylindans and the opening of their saturated ring into C11-alkylbenzenes and, on the other hand, the demethylation and methylation of the aromatic into naphthalene and dimethylnaphthalenes. The kinetic parameters of the main hydroconversion reactions are determined according to a simplified first-order kinetic scheme.
Introduction Light cycle oil (LCO) is a by-product of fluid catalytic cracking in oil refining. It is rich in polyaromatic compounds (about 70% w/w and mainly alkylnaphthalenes), nitrogen compounds (about 0.05% N w/w) and sulfur compounds (1-2% S w/w). Considering the increasing demand for gas oil for diesel engines, the improvement of the LCO is desirable so that it can be added to the gas-oil pool. Such an improvement can be obtained by simultaneous desulfurization,denitrogenation, hydrogenation, and conversion. Hydrodenitrogenation (HDN) and hydrodesulfurization (HDS) are basically required for environmental reasons. HDN is also required to improve the gas-oil stability. Hydrogenation of the polyaromatics themselves is becoming of importance in view of the strict regulations that may be implemented in the near future. An increase of the cetane number is however needed for the hydrotreated LCO. This can be obtained by conversion of the polyaromatics into alkylbenzenes, i.e., by partial hydrogenation followed by opening of the saturated rings. Little is known about the simultaneous hydrogenation and conversion of polyaromatics in the presence of sulfur and nitrogen. The aim of this study is to improve our knowledge of the reactions of hydrogenation and hydroconversion of a model diaromatic compound on conventional hydrotreating and hydrocracking catalysts in the presence of a sulfur and a nitrogen compound. The present study has been carried out using a conventional sulfided NiMo, P doped, hydrotreating catalyst of low cracking activity in order to get a better understanding of the hydrogenation function without too much interference from the hydroconversion. We analyze in the following the effect of the reaction conditions on the products distribution and discuss the kinetics of these two reactions. An extension of this work will be dedicated to a catalyst possessing a higher cracking activity.
* To whom correspondence should be addressed.
Experimental Section Catalyst. The catalyst used was a Ni-Mo-P oxide on y-alumina in the form of extrudates containing 2.7% NiO, 16.5% MOO,, and 6.5% P205w/w with a surface area of 170 m2g-l and a bulk density of 3.4 g cm-,. Sulfurization was carried out in situ prior to use by introducing a feed rich in sulfur (the composition of this conditioning feed is similar to the reference feed described later, but ensuring a higher partial pressure in hydrogen and H2S). Model Feed Composition. The following products were used in the liquid feed without further purification: 1-methylnaphthalene (lMN), Aldrich (98%1; n-heptane, Halterman ASTM (>99.75%); dimethyl disulfide (DMDS), Aldrich (99%); n-butylamine (NBA), Merck (99%); hydrogen (impurities
