High-density pyridine-FeN4 active sites for acetylene hydrochlorination

The high price of precious metal catalysts is an important factor restricting their industrial implementation. Therefore, developing single-atom Fe-N4 catalysts with high site density is crucial. We precisely synthesize FeNC microporous catalysts (Cs-Fe-600, 600 represent pyrolysis temperature is 600 °C) by exploiting the abundant pyridine-N confinement effect. The Fe content is up to 1.9 wt%. Cs-Fe-600 with dense pyridine-FeN4 sites was used as a catalyst in acetylene hydrochlorination reaction. It showed higher acetylene conversion compared to the carbon–nitrogen material without Fe addition. Characterization showed that the high Fe density was uniformly distributed on the carrier as stable pyridine-FeN4 active sites. And the result of characterization confirmed the strong adsorption ability of pyridine-FeN4 for acetylene, the primary active site in the reaction. The Cs-Fe-600 catalyst was deactivated by the agglomeration of Fe metal and the loss of pyridine-FeN4 active site. However, pyridine-FeN4 active sites and initial acetylene conversion recovered by high temperature treatment in ammonia gas. We successfully proposed a strategy for controlling Fe sites in specific nitrogen-coordination environment.