Ni-Pt/H-Y zeolite catalysts for disproportionation of toluene and 1,2,4-trimethylbenzene

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 degrees 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.