(77a) Hydrocracking of Aromatics and Naphtheno-Aromatics

Advanced kinetic models for the development and simulation of hydrocarbon processes require detailed information on the reaction network for a variety of potential catalysts. The present work deals with the hydrocracking of aromatics and naphtheno-aromatics on a PtPd/US Y zeolite

Experiments on the hydrocracking of respectively tetralin and 1-methylnaphthalene, diluted with n-heptane, were conducted in a fixed bed catalytic reactor in the temperature range 275^oC to 350^oC, at pressures between 28 and 35 bar, space times between 21 to 69 gcat h/mol of reactant and with hydrogen/hydrocarbon molar ratios ranging from 100 to 340.

With tetralin feed as many as 10 components were detected and identified in the reactor effluent, with 1-methylnaphthalene up to 30.  Following the rules of carbenium ion chemistry very detailed networks of elementary steps were generated for each feed. The network for tetralin contains a total of 96 elementary steps, that for 1-methylnaphthalene 230. Typical pathways to a given product include dehydrogenation/hydrogenation of ring structures on the metal sites and protonation/deprotonation, ring contraction/expansion, PCP branching of side chains, and endocyclic β-scission on the acid sites. The presence of Pt in the catalyst also led to side chain and ring-opening hydrogenolysis.

A significant decay of the conversion of the feed component with process time was observed, more pronounced with 1-methylnaphthalene. It is attributed to irreversible adsorption of the basic feed species on the strongest acid sites. For the kinetic modeling the data were extrapolated to zero process time.