Mechanistic and kinetic studies of elemental mercury oxidation over a RuO₂/rutile TiO₂ catalyst

Abstract

A mechanistic study using in situ DRIFTS and a kinetic study were conducted on a ruthenium oxide based mercury oxidation catalyst.

Adsorption and Oxidation of Elemental Mercury on Chlorinated ZnS Surface

“…In this work, we further explored the oxidation from HgCl to HgCl 2 (Supporting Information), whereas an energy barrier as high as 109.25 kJ/mol was revealed. This clearly demonstrates that the oxidation of Hg 0 to HgCl 2 in the presence of Cl 2 follows the E–R mechanism rather than the Langmuir–Hinshelwood (L–H) mechanism, which is different from the process of Hg 0 oxidation on CeO 2 , RuO 2 /TiO 2 …”

Catalyst Development for HCl Oxidation to Cl2 in the Fluorochemical Industry

“…To characterize the effects of calcination temperature for preparing Al–MgF 2 supports on the catalytic properties of the resultant catalysts in the Deacon process, FT-IR characterization was carried out using HCl as the probe. As shown in Figure B, a peak at around 1880 cm –1 was observed, which could be attributed to the Ru–H asymmetric vibration as a result of the dissociation of the adsorbed HCl on the catalyst to form a Ru–H bond . However, the Ru–Cl vibration in the range of 300–400 cm –1 was not observed due to their weak intensities in an energy-starved region .…”

“…At this point, it remains an open question how the partially positive charged RuO 2 promotes the activity of a Deacon catalyst. The mechanisms of HCl oxidation to Cl 2 over RuO 2 have been widely studied by density functional theory (DFT), and different mechanisms have been proposed. ,− ,− For example, the reaction step with the highest activation barrier (228 kJ/mol) was the recombination of two neighboring adsorbed Cl atoms to form the desired product Cl 2 from DFT calculations, and the reaction conditions (mainly partial pressures and temperature) would determine whether the rate-determining step could be chlorine recombination or oxygen adsorption, as proposed by López et al . Moreover, Teschner et al reported that oxygen activation would be the rate-determining step under typical Deacon conditions, and the O 2 dissociation energy on the metal oxide surface was chosen as the descriptor in the Deacon process, as the ranking of experimental activity data showed a volcano relationship with the O 2 dissociation energy. , Furthermore, Hess and Over found that hydrogen transfer in the formation of water would determine the overall reaction rate.…”

“…As shown in Figure 8B, a peak at around 1880 cm −1 was observed, which could be attributed to the Ru−H asymmetric vibration as a result of the dissociation of the adsorbed HCl on the catalyst to form a Ru−H bond. 61 However, the Ru−Cl vibration in the range of 300−400 cm −1 was not observed due to their weak intensities in an energystarved region. 61 Either undissociated, free HCl, or undissociated HCl attached to Ru was not observed.…”

“…61 However, the Ru−Cl vibration in the range of 300−400 cm −1 was not observed due to their weak intensities in an energystarved region. 61 Either undissociated, free HCl, or undissociated HCl attached to Ru was not observed. When the incorporated amount of Al into MgF 2 reaches its maximum in the current investigation, that is, a calcination temperature of 400 °C for preparing the Al−MgF 2 support, the highest strength of Ru−H asymmetric vibration is achieved.…”