Efficient synergistic catalysis of chlorinated aromatic hydrocarbons and NO over novel low-temperature catalysts: Nano-TiO modification and interaction mechanism.

For efficient and synergistic elimination of chlorinated aromatic hydrocarbons (e.g., dioxins and chlorobenzenes) and NO at low temperatures, a novel VO-CeO-WO/TiO catalyst was systemically studied, involving the nano-TiO modification and the interaction mechanism between 1,2-dichlorobenzen (1,2-DCB) catalytic oxidation (DCBCO) and NH-SCR. The VO-CeO-WO/TiO performed excellent oxygen storage/release capacity (OSRC) and desirable 1,2-DCB conversion efficiency (95.1-97.4%) at 160-200 ℃ via M‒K and L‒H mechanism. The nano-TiO modification slightly impaired the 1,2-DCB oxidation to 93.6-96.2% owing to the reduced surface area and Brønsted acidity, while it distinctly enhanced NO conversion and lowered the T (from 162 to 112 ℃) and T (from 232 to 205 ℃) by improving catalyst reducibility. Based on further synergistic catalysis evaluation and in-situ DRIFT analysis, NO enhanced the 1,2-DCB conversion and complete oxidation capacity of VO-CeO-WO/TiO by promoting active oxygen (O, O, O) generation and improving 1,2-DCB chemosorption and subsequent oxidation. In detail, the produced HCl and HO improved the catalyst acidity and promoted the formation of HONO and HNO. Moreover, their generation not only facilitated the chemisorption of NH but also participated in the NH-SCR via L‒H mechanism. The ensuing problem was the competitive chemisorption among 1,2-DCB, NH, and their subsequent intermediates. As a result, NH had distinct advantages in competing for acid sites and active oxygen species, especially at the higher temperature, resulting in the improved NO conversion with elevated reaction temperature but the reduced 1,2-DCB conversion. The results provided essential basics for developing new catalysts to synergistically control the emission of chloroaromatic organics and NO at low temperature.