Array Modified Molded Alumina Supported PdAg Catalyst for Selective Acetylene Hydrogenation: Intrinsic Kinetics Enhancement and Thermal Effect Optimization

Abstract

High temperature calcined spherical alumina material with macroporous structure is widely used in the typical strong exothermic industrial catalytic process due to its good heat transfer ability. Aiming at the problem that its low surface area limits the dispersion of active metals, an in situ growth method is applied to fabricate an alumina array on spherical alumina, while maintaining the heat transfer advantages. Taking the as-obtained modified alumina as support, a highly dispersed PdAg catalyst for selective hydrogenation of acetylene is synthesized, which exhibits a remarkable enhanced intrinsic activity. Moreover, when the conversion of acetylene reaches 90%, the selectivity toward ethylene still remains 89%. Preferred selectivity is assigned to more isolated Pd sites as well as high electronic density, which facilitates the desorption of the resulting ethylene. More importantly, the array modified catalyst exhibits good structural stability and resistance to carbon deposition. From one aspect, the decrease of the heat production rate over a single active site is conducive to reducing the reaction heat accumulation, thereby avoiding the formation of hot spots over the catalyst, which is a necessary condition for the endothermic reaction of carbon deposition. From another point of view, both the new generated outer opening pore structure and the original macroporous structure of the molded alumina are beneficial for the heat transfer.

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

“…68 Consequently, these peaks are reasonably considered to be caused by the desorption of H 2 , in which the former at 300-330 C is assigned to the desorption of chemical adsorbed hydrogen, while the latter at 410 C is ascribed to the spillover of hydrogen. 69 Compared with other catalysts, the desorption peak over Pd/TiO 2 -HT300 shifts to lower temperature of 360 C. Moreover, the peak intensity of hydrogen spillover over Pd/TiO 2 -HT300 is the strongest among all samples. Therefore, it can be concluded that more V o contributes to the occurrence of hydrogen spillover to provide more active hydrogen species during the reaction process.…”

Rational Design of PdAg Catalysts for Acetylene Selective Hydrogenation via Structural Descriptor-based Screening Strategy

“…Pd-based-catalyzed C 2 H 2 selective hydrogenation is a typical example, which is crucial to reduce the trace (0.5–2%) of C 2 H 2 content in naphtha pyrolysis products to a level of ppm while retaining large amounts of C 2 H 4 . ,,− The modification of Pd catalysts with Ag − has been reported as an important way to improve the C 2 H 4 yield of C 2 H 2 semihydrogenation catalysts. To improve PdAg catalytic performance in C 2 H 2 selective hydrogenation, researchers have synthesized many PdAg catalysts with different surface structures, such as the core–shell structure and single-atom catalysts.…”

Recent research advances on catalysts for selective hydrogenation of ethyne

“…Since VIII metals such as Pd and Ni are strong in ethyne activation and IB metal-based catalysts are selective for ethylene formation, VIII-IB bimetallic catalysts have been widely constructed to achieve high ethyne conversion and high selectivity towards ethylene simultaneously. Pd-Ag, 20,[101][102][103][104][105][106][107][108][109][110][111][112][113] Pd-Au, 114,115 Pd-Cu, [116][117][118] Ni-Cu, 119 Pt-Cu, 120 Ni-Ag, 121 and Ni-Au (ref. 122) have been developed.…”