The influence of zeolite acidity for the coupled hydrogenation and ring opening of 1-methylnaphthalene on Pt/USY catalysts

The influence of framework and extraframework composition of USY zeolite on the catalytic performance of bifunctional Pt/USY (1 wt.% Pt) catalysts for the coupled hydrogenation and ring opening of 1-methylnaphthalene (1-MN) has been studied on a continuous fixed bed high pressure reactor. All Pt/USY catalysts showed very high methylnaphthalene (MN) conversions under the reaction conditions studied (T = 300-375 degreesC, P = 4.0 MPa, WHSV = 2 h(-1), H-2/1-MN = 30 mol/mol). Product yields and selectivities were mainly determined by the zeolite composition (i.e. acidity). Selectivity to products with the same number of carbon atoms than the feed (C11) increased, at constant temperature, with decreasing the Bronsted acidity of the USY zeolite, that is, with decreasing the concentration of framework Al (FAL) and increasing extraframework Al (EFAL). Selectivity to high cetane ring opening products (ROP = C11-alkylbenzenes (C11 AB) and C11-alkylcycloalkanes) within the C11 fraction was higher for the less acidic catalysts. A maximum yield of ROP of ca. 15 wt. % at a C I I yield of ca. 7 3 wt. % was obtained at 350 degreesC (P = 4.0 MPa, WHSV = 2 h-1, H-2/1-MN = 30 mol/mol) for a USY zeolite with an intermediate degree of dealumination (a(0) = 24.33 Angstrom) and containing all the EFAL (bulk Si/Al ratio of 2.6). For this catalyst, a slight increase in ROP yield (ca. 17 wt.%) at similar C11 yield (ca. 74 wt.%) was obtained by working at lower temperature (300 degreesC) and lower space velocity. Increasing the reaction pressure above 4.0 MPa had only a marginal influence on product yields and selectivities. (C) 2002 Elsevier Science B.V. All rights reserved.