Hybrid zeolite-supported Pd catalyst with high sulfur tolerance for low-temperature hydrogenation of aromatics in diesel fuels

Zeolite-supported noble metals are potential catalysts for the low-temperature hydrogenation of aromatics in distillate fuels for producing ultra clean diesel fuels, but sulfur poisoning remains a major problem to be solved. In this study, hybrid catalyst was prepared as shape-selective and sulfur-tolerant noble metal catalyst using two zeolite supports having two different pore channel sizes (zeolite Y and A) based on our proposed new concept for catalyst design [CS Song, Chemtech, 1999, 29 (3), 26-30]. The hybrid catalyst have two different functions, hydrogenation in large-pore microporous channel such as that of Y zeolite and hydrogen spillover in small-pore microporous channels such as Zeolote A. It was found that zeolite A supported Pd catalyst itself did not show any significant catalytic activity for hydrogenation, but helped the zeolite Y supported Pd catalyst maintain the high activity of hydrogenation of tetralin by hydrogen spillover in the presence of sulfur compounds at low temperatures. Pd clusters on the external surface of Zeolite A supported Pd catalysts were passivated by chemical vapor deposition (CVD) with tetraethyl orthosilicate (TEOS) to clarify the effect of the catalytic functions and hydrogen spillover inside the small micropore of the hybrid catalyst system.