Cascade catalytic strategy based on Fe/Pd bimetallic tandem active sites for efficient removal of acetylene and ethylene impurities from high-purity hydrogen chloride gas

The production of high-purity hydrogen chloride from petrochemical by-product hydrogen chloride gas represents the primary industrial approach for manufacturing electronic-grade hydrogen chloride. However, trace acetylene and ethylene impurities in the feedstock severely compromise product quality. This study innovatively proposes a "stepwise conversion-deep chlorination" synergistic mechanism and successfully develops a bimetallic catalyst (10 %Fe/0.5 %Pd/AC). By tailoring the preparation processes, we precisely controlled the distribution of Fe and Pd active sites, while systematically comparing the performance between Single-metal tandem catalytic system (Pd/AC + Fe/AC) and the bimetallic catalyst. Experimental results combined with DFT calculations demonstrate the superior performance of the 10 %Fe/0.5 %Pd/AC catalyst and confirm the cascade reaction mechanism based on the synergistic tandem effect of Fe/Pd active sites: Acetylene preferentially undergoes hydrochlorination at Pd sites to form vinyl chloride, while ethylene and the resultant vinyl chloride are subsequently converted to chloroethane and more easily removable 1,1-dichloroethane at Fe sites. Under optimized conditions (120 °C, GHSV=180 h⁻¹), removal efficiencies exceeding 99 % for both acetylene and ethylene were achieved, with 1,1-dichloroethane selectivity surpassing 99 %. Comprehensive characterizations demonstrated the outstanding stability of the 10 %Fe/0.5 %Pd/AC catalyst. This study presents an innovative catalytic approach for high-efficiency purification of industrial hydrogen chloride.