Sulfur-doping promoting peroxone reaction over TiO2 for highly effective NO oxidation at low temperature: Experimental and DFT studies

Abstract

The peroxone reaction between O3 and H2O2 over TiO2 exhibits bright prospects for low-temperature flue gas denitration, which effectively overcomes the limitations of traditional peroxone reaction and remains advanced poison resistant ability. In this study, sulfur-doped TiO2 was successfully adopted to improve the catalytic performance under low consumption of O3 and H2O2, making this technology take a pivotal step towards practical application. Compared with TiO2/H2O2/O3 system (68% NO conversion), the NO conversion could reach up to 85% in S-doped TiO2/H2O2/O3 system under test condition (GHSV = 1.2 × 105h−1, H2O2/NO = 1.2, and O3/NO = 0.5). Characterizations and density functional theory calculations revealed that sulfur-doping modified the local structure of the catalyst, which enables a more effective combination between Ti5c and hydroperoxyl, thus facilitating the reaction. Besides, the introduction of sulfur could increase the adsorption capacity of NOx and enhance the Lewis acidity of the catalyst, thus improving the NO conversion performance. The stability and applicability of the process were systematically tested from the following aspects: varied gas composition, H2O2 consumption, pH value, and SO2/CO concentration. Results revealed that the S-doped TiO2/H2O2/O3 system exhibited good stability and poison resistant ability, the potential for practical applications.