Constructing metal-site isolation in phosphate-modified Sn-doped LaMnO3 for inhibiting the generation of toxic by-products in catalytic combustion of Cl-VOCs

Abstract

Efficient catalytic combustion of chlorine-volatile organic compounds (Cl-VOCs) is frequently limited by the generation of multiple chlorine by-products and poor stability of catalysts. In this research, we aim to develop a series of efficient and stable phosphate-modified Sn-doped LaMnO₃ catalysts (S-LMO/SnPx (x = 0, 3, 6, 9). S: SBA-15, as support). The experimental results demonstrate that S-LMO/SnP6 shows excellent catalytic activity of 1,2-dichloroethane (1,2-DCE, T_90%=225.2 ℃). In addition, the S-LMO/SnP6 exhibits excellent stability in 5.0 vol% H₂O and 50 h long-term tests, attributed to the protective effect of the phosphate layer on the metal active sites. Moreover, it also exhibits outstanding degradation activity for toluene (TOL), ethyl acetate (EA), and mixed VOCs, such as 1,2-DCE and TOL, 1,2-DCE and EA. Sn doping modulates the activity and mobility of lattice oxygen in LaMnO₃. Meanwhile, phosphoric acid modification can regulate the microelectronic environment of the active metal sites on the surface, which can effectively prevent contact with polychlorinated by-products through the site isolation effect, thus inhibiting the generation of toxic by-products. The reaction pathway and mechanism of 1,2-DCE oxidation are further validated, summarized as: 1,2-DCE → vinyl chloride → vinyl alcohol → acetaldehyde → acetic acid → CO₂ and H₂O. This research provides a new interfacial engineering strategy for designing catalytic materials for Cl-VOCs with high activity and low toxic by-product generation.