Enhanced Catalytic Performance of Ru/Ammonium Oxalate Catalysts with Low Ru Content for Nonmercury Acetylene Hydrochlorination

Abstract

As a promising alternative to HgCl₂ for acetylene hydrochlorination, a novel catalyst of Ru/ammonium oxalate (NCO)-activated carbon (AC) was developed, which shows approximately 90% conversion of acetylene and over 99% selectivity for the vinyl chloride monomer (VCM). In comparison to the conventional Ru/AC catalyst, the amount of ruthenium chloride in Ru/NCO-AC was reduced to less than 0.2 wt %. In addition, the coke deposition and Ru(0) generation were decreased by approximately 18% and 50%, respectively. Characterizations indicated that the N-doped AC could inhibit the over-reduction of active Ru species and decrease the coke deposition on the catalyst. Density functional theory calculations revealed that NCO-AC could provide a synergistic environment for the Ru-based catalyst. Acetylene molecules tend to be adsorbed on carbon atoms adjacent to nitrogen atoms, which protects Ru(IV) from being reduced to Ru(0) and stabilizes the reactivity. The 0.95 eV energy barrier of Ru/NCO-AC was much lower than that of a catalyst without N atoms (1.50 eV). Moreover, the low Ru content catalyst was placed in an industrial reactor and showed excellent activity during a 500 h industrial experiment. These results may be helpful for designing efficient nonmercury catalysts and replacing existing HgCl₂ for the commercial application of acetylene hydrochlorination.