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

Abstract

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 À1 ) 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.

Fabrication of stable and selective non‐noble metal catalysts for selective alkyne hydrogenation

“…3.9%) occurs around 400°C (Figure 6D) although this may be associated with the combustion of a harder coke deposit, 42 which may be responsible for the inconspicuous fluctuation of activity. Similar phenomena are also observed in our previous work, 43 which suggests the increasing unsaturated coordination sites in Al 2 O 3 ‐R‐V could capture the released heat and lower to heat accumulation over a single active site (Figure S15), and thus suppress the generation of hot spots and improve the ability to resist carbon deposition.…”

Construction of Highly Active Pd–Ti3+ Sites in Defective Pd/TiO2 Catalysts for Efficient Hydrogenation of Styrene–Butadiene–Styrene

“…The desorption peak of chemical adsorbed hydrogen over Pd/Def-Ti 3+ -TiO 2 shifts to a higher temperature compared to Pd/TiO 2 and Pd/ Def-Vo-TiO 2 , suggesting that the H 2 activation is more favorable on Pd/Def-Ti 3+ -TiO 2 . 48 Moreover, the intensity of the desorption peak of chemisorbed hydrogen over Pd/Def-Ti 3+ -TiO 2 (0.29 mmol/g) is larger than that of Pd/Def-Vo-TiO 2 (0.22 mmol/g) and Pd/TiO 2 (0.18 mmol/g), indicating that there are more H 2 adsorption sites on Pd/Def-Ti 3+ -TiO 2 .…”

Enhancing selectivity for semi-hydrogenation of Ni by periodic isolation in the MM′X structure

“…Heterogeneous catalysts play a pivotal role in the efficiency of many chemical processes such as the production of petrochemicals, elimination of environmental pollutants, and sustainable energy conversion. [1][2][3] In recent years, research on heterogeneous catalysis has advanced from traditional nanocatalysts to single-atom catalysts (SACs), initially driven by the appealing atomic efficiency of the latter. 2,4 Remarkable advantages of SACs over nanocatalysts have been demonstrated by achieving high selectivity, which stems from the isolation of active atoms and significantly changes the interaction with the intermediates.…”