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/TiO 2 with different oxygen vacancies (V o ) were synthesized by controlling reduction temperature in 300–700°C, in which Pd/TiO 2 -HT300 (HT is reduction temperature) possessed the highest V o content. It was found highly dispersed Pd nanoparticles adjacent to more V o exhibited enhanced catalytic behavior (near 100% conversion at 55°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 desorption. More importantly, the increasing V o 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.