Ni–Pt/H–Y Zeolite Catalysts for Disproportionation of Toluene and 1,2,4-trimethylbenzene

Abstract

Ni–Pt/H–Y zeolite catalysts with different Ni contents were prepared and applied to the disproportionation of toluene and 1,2,4-trimethylbenzene in the temperature range 250–400 °C. The line broadening XRD analysis indicates that the increasing Ni addition decreases the crystallinity of zeolites. ESCA studies show the complete reduction of Ni species up to 0.3 wt.% Ni addition over 0.1 wt.% Pt/H-Y and further addition leads to the occurrence of unreduced nickel species as NiAl2O4. A TEM study shows the formation of bimetallic (Ni–Pt) particles of nanoscale size and the average particle size is found to increase with increasing Ni loading. Acidity measurements by NH3-TPD and pyridine-adsorbed FT–IR spectroscopy show the increasing occupation of acid sites by increasing nickel loading. The catalytic activity of Ni–Pt/H–Y zeolite and Pt/H–Y catalysts was compared and it was found that addition of Ni up to 0.3 wt.% increases conversion of toluene and 1,2,4-trimethylbenzene, disproportionation selectivity and sustainability of the catalysts. Further addition of Ni leads to a decrease in conversion and disproportionation selectivity and increasing dealkylated products, which may be due to the presence of unreduced Ni species and pore blockage by large-sized bimetallic particles formed.