Influence of aluminum content, crystallinity and crystallite size of zeolite Pd/H-ZSM-5 on the catalytic performance in the dehydroalkylation of toluene with ethane

Pd/H-ZSM-5 zeolites with different aluminum contents and nSi/nAl ratios between 11 and 122, different crystallinities and crystallite sizes, including a nanocrystalline sample, were used as catalysts in the dehydroalkylation of toluene with ethane to the isomeric ethyltoluenes. This reaction was chosen as an industrially relevant test reaction for the non-oxidative activation of light alkanes. The catalysts were physicochemically characterized using X-ray diffractometry, scanning electron microscopy or dynamic light scattering, elemental analysis and 1H MAS NMR spectroscopy. The catalytic experiments were carried out in a flow-through system and were analyzed with respect to the overall toluene conversion, the selectivities and yields to the desired ethyltoluene isomers and the formation of undesired byproducts. The catalytic results were compared to the results of the physicochemical characterization of the catalysts. The best catalyst was found to be Pd/H-ZSM-5 with a high crystallinity, a large crystal size and an intermediate nSi/nAl ratio around 40.