REACTION OF TRIMETHYLBENZENE OVER ALUMINA-PILLARED MONTMORILLONITE

The reaction of trimethylbenzene (TMB) over alumina-pillared montmorillonite (Al-PM) had been investigated in a fixed-bed flow reactor at 300-degrees-C and atmospheric pressure. Al-PM calcined in the range 300-500-degrees-C exhibited decreased layer distance, surface area and acid amount. The strong acid sites of Al-PM calcined at 500-degrees-C were greatly diminished according to measurements of ammonia temperature-programmed desorption. Under our conditions the reaction proceeded mainly via isomerization and disproportionation with little dealkylation. The conversion of reactant decreased in the order 1,2,3-TMB greater-than-or-equal-to 1,2,4-TMB > 1,3,5-TMB and the selectivity of isomerization in the order 1,2,3-TMB > 1,3,5-TMB > 1,2,4-TMB, corresponding to the order of diminishing thermal instability. Both the catalytic activity and the selectivity ratio of disproportionation to isomerization decreased with increased calcined temperature and time-on-stream. Omicron-Xylene content in the total xylene produced from 1,2,4-TMB or 1,2,3-TMB greatly exceeded the composition at thermodynamic equilibrium. These results are consistent with the decrease of both the strong acid sites and the pore size of Al-PM which exhibits the restricted transition state selectivity.