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 .…”

Bi-modified Cu-Based Catalysts for Acetylene Hydrogenation: Leveraging Dispersion and Hydrogen Spillover

“…Two peaks at 158. 6 the electronic structure of Cu and Cu x C. In addition, the peak area of Cu δ+ species in Cu/SiO 2 (TR) is significantly smaller than that of Cu/SiO 2 (H-TR) and CuBi/SiO 2 (H-TR), indicating that the quantity of the formed Cu x C in Cu/ SiO 2 (H-TR) and CuBi/SiO 2 (H-TR) is markedly higher than that of Cu/SiO 2 (TR). Previous results have shown that the formation of Cu x C is directly related to the thermal stability of copper acetylide formed through the reaction between copper carbonate and acetylene.…”

“…The ethylene stream produced from the cracking of naphtha usually contains trace amounts of acetylene (0.5–2%), which can poison the downstream ethylene polymerization catalysts, thereby reducing the quality of the polyethylene products. − Therefore, removing the acetylene to an acceptable level (<1 ppm) is vital for the production of polymer-grade ethylene, in which hydrogenating the acetylene impurity to ethylene product is the preferred approach for ethylene purification . Traditionally, noble Pd catalysts with exceptional hydrogenation activity are most commonly used for removing the trace acetylene from the ethylene stream. − However, the poor selectivity to ethylene and high cost of Pd leave sufficient room for developing cost-effective catalysts with superior catalytic performance derived from earth-abundant metals.…”