Enhancing sulfur tolerance of Pd catalysts by hydrogen spillover with two different zeolite supports for low-temperature hydrogenation of aromatics

Pd catalysts supported on zeolite Y and zeolite A (Pd/Y and Pd/A) were prepared separately and combined for improving sulfur tolerance based on our proposed catalyst design concept for low-temperature hydrogenation of aromatics in distillate fuels. After the external surface of Pd/A was passivated by chemical vapor deposition with silica, the resulting SiO₂-Pd/A catalyst does not show any catalytic activity for hydrogenation of tetralin. However, adding SiO₂-Pd/A to Pd/Y by physical mixing significantly enhanced sulfur tolerance of the Pd catalyst for tetralin hydrogenation in the presence of 100 ppmw sulfur as benzothiophene. The small-pore system (Pd/A) in the hybrid catalyst plays a critical role to maintain the catalytic activity of metal sites in the large-pore system (Pd/Y) in the presence of sulfur, via hydrogen spillover from metal inside the zeolite A pore channel protected by size-selective exclusion of sulfur compounds.