Mechanistic and kinetic studies of the heterogeneous oxidation of elemental mercury (Hg(0)) vapor by HCl gas over a RuO2/rutile TiO2 catalyst were conducted. It was found that under reaction conditions, chemically adsorbed HCl was dissociated on the catalyst surface, and the formation of Ru-H bond was observed by in-situ Fourier Transform Infrared spectroscopy (FTIR). The active chlorine species on the surface generated from HCl was found to be responsible for the Hg(0) oxidation. The intensity of the Ru-H IR signal could be used as an indicator of the available surface chlorine. Based on the in-situ FTIR and performance results, Hg(0) oxidation over the RuO2/TiO2 catalyst was proposed to follow Eley-Rideal followed by Langmuir–Hinshelwood mechanisms where HCl is an adsorbed species and reacts with gas-phase Hg(0) to form HgCl(ad), then HgCl(ad) reacts with another Cl(ad) to form HgCl2(ad). A steady-state kinetic study was conducted to determine an intrinsic reaction kinetic expression for Hg(0) oxidation over the catalyst under HCl, NH3 and SO2 gases for the first time. The kinetic expression could reasonably predict the Hg(0) oxidation performance under the competitive adsorption of NH3 and SO2 gases.

Heterogeneous reaction mechanism and kinetics of elemental mercury oxidation over RuO2/TiO2 catalyst

256th National Meeting (2018)

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