Evaluation of hydrogen transfer in FCC catalysts. A new approach for cyclohexene as a test reactant

The conversion of cyclohexene over different commercial FCC catalysts in a batch fluidized-bed reactor under very short contact times at 300 degrees C , was described by means of a simple lumped kinetic model that accounted fo r the observed yield patterns. The main branch of reaction starting from th e adsorption of cyclohexene was used to assess an index based on kinetic pa rameters that defines the relative significance of hydrogen transfer reacti ons in a set that also includes proton transfer and cracking reactions. Com plementary experiments with pulses of reactant on a fixed-bed reactor allow ed to establish the best temperature to obtain maximum sensitivity to hydro gen transfer. The same evolutions were observed for the relationships betwe en the index of hydrogen transfer and the paired acid site density with the Y zeolite unit cell size, confirming that two regions can be defined separ ated by unit cell sizes of about 24.28-24.30 Angstrom, the correlations bei ng stronger at low values of this parameter. (C) 1999 Elsevier Science Ltd. All rights reserved.