Dual effect of TiO2 vacancy on Pd catalyst in acetylene hydrogenation: Boosting performance and capturing reaction heat

Selective acetylene hydrogenation is a strongly exothermic process, easy to cause coking and metal agglomeration, and thus leads to deactivation. In this work, Pd/TiO2 with different oxygen vacancies (V-o) were synthesized by controlling reduction tem-perature in 300-700 degrees C, in which Pd/TiO2-HT300 (HT is reduction temperature) pos-sessed the highest V-o content. It was found highly dispersed Pd nanoparticles adjacent to more Vo exhibited enhanced catalytic behavior (near 100% conversion at 55 degrees C with 80% selectivity and turnover frequency of 0.12 s-1) due to hydrogen spillover generation and electron donation originating from V-o sites, confirmed by in situ x-ray photoelectron spectroscopy, in situ Raman, and H-2-temperature programmed desorp-tion. More importantly, the increasing Vo sites trap the released heat and devote to a decrease of heat accumulation over a single active Pd site, and consequently inhibit Pd agglomeration and polymerization, affirmed by high-resolution transmission electron microscopy, CO chemisorption, and thermogravimetric analysis.