Abstract:

Traces of acetylene impurities in the feed gas during the subsequent industrial production process of polyethylene will inactivate ethylene polymerization. The semi-hydrogenation of acetylene to ethylene has been proved to be one of the most effective technologies for the purification of ethylene. Pd catalysts have been playing a leading role in industrial applications due to their excellent performance. However, as Pd is a precious metal, Pd catalysts are expensive. Thus, it is very important to design low-cost, high-selectivity, and high-conversion acetylene semi-hydrogenation catalysts. Here, we summarize the influence of single-metal catalysts based on the acetylene semi-hydrogenation mechanism. The hydrogenation ability of the catalysts should be neither too high nor too low. When other metals are added to palladium catalysts, bimetallic catalysts are formed, which can be classified into typical substitutional solid-solution alloy catalysts, intermetallic compound catalysts, and single-atom alloy catalysts. Regarding the influence of bimetallic catalysts on the performance of acetylene hydrogenation, metals other than Pd have different effects on the acetylene hydrogenation process due to the different structure and environment. While, the structure of the catalyst and the chemical environment ultimately affect the electronic structure of the active center of the catalyst. Based on this, we conclude that the key to the semi-hydrogenation of acetylene is the charge density of the active center of the catalyst, such as dual-atom sites and nano-single atoms; the electrons control the active center of the catalyst. Finely turning the electronic structure of single metal active sites will improve their catalytic activity, selectivity, and stability of the catalyst for acetylene semi-hydrogenation. Additionally, we propose a possible future direction for the development of high-performance acetylene semi-hydrogenation catalysts. Future catalysts for acetylene semi-hydrogenation able to precisely control the active sites to improve their catalytic activity, selectivity, and stability are the focus of researchers, such as the precise control of single-atom-site, dual-atom-site, and nano-single-atom-site catalysts.

Key words: Acetylene, Ethylene, Selective hydrogenation, Catalyst