Effect of various g-C3N4 precursors on the catalytic performance of alkylorganotin-based catalysts in acetylene hydrochlorination

Abstract

A series of alkylorganotin-based catalysts (Sn-g-C3 N4 /AC) was prepared by wet impregnation in ethanolusing different g-C3 N4 precursors and alkylorganotin compounds. The structure, texture, surface composition, andadsorption properties of the as-prepared catalysts were extensively characterized. Then, the obtained samples wereevaluated for their catalytic performance in hydrochlorination of acetylene. The results provided by the X-ray photoelectron spectroscopy, acetylene temperature-programmed desorption, and HCl adsorption confirmed the nature of theactive sites (i.e. Sn-Nx) involved in the reactant adsorption, and hence in the improved catalytic performance. Theseactive sites were also related to the improved lifetime of alkylorganotin-based catalysts in the hydrochlorination of acetylene. At a constant reaction temperature of 200 °C with an acetylene gas hourly space velocity (C2 H2 -GHSV) of 30h−1, Sn-g 1 -C3 N4 /AC-550 exhibited the highest acetylene conversion (~98.0%) and selectivity toward the vinyl chloridemonomer (>98.0%). From the catalytic test results, it was reasonably concluded that the hexamethylenetetramine is themost suitable N precursor, as compared to the dicyandiamide and urea, to prepare high-performance catalysts. Fromthe BET specific surface area of fresh and used catalysts, it was suggested that, in contrast to dicyandiamide and urea,hexamethylenetetramine could delay the deposition of coke on alkylorganotin-based catalysts, which is reflected by theextended lifetime.