净化黄磷尾气中铁基高温水汽变换催化剂中毒机理

摘要

根据非均相反应体系的热力学有关理论,分析了高温水汽变换温度范围(623～803 K)内B112型铁基水汽变换催化剂在净化黄磷尾气气氛下受磷化氢、砷化氢、氟化氢和硫化氢作用而中毒可能发生的化学反应及产物,讨论了铁基高温变换催化剂的中毒机理.结果表明:磷酸盐、砷酸盐、硫酸盐、单质硫和积炭主要造成催化剂的暂时性中毒;磷铁化合物、砷铁化合物、氟铁化合物和硫铁化合物主要造成催化剂的永久性中毒.在一氧化碳变换气氛下,氮气不参与中毒反应,一氧化碳、二氧化碳、水蒸气和氧气都参与催化剂毒物与活性组分间的中毒反应,从而为催化剂中毒提供了条件,其中氧气会明显加快催化剂中毒.由热力学分析催化剂的中毒程度由强至弱为PH3,H2S,AsH3,HF.%The possible chemical reactions and products in the process of the iron-based high temperature water-gas shift catalyst B112 poisoned by PH3, AsH3, HF and H2S in the water-gas shift reaction of purified yellow phosphorous at 623-803 K was analyzed by the thermodynamics of heterogeneous reactions and the poisoning mechanisms were discussed. The results showed that the phosphate, arsenate, sulfate, sulfur and carbon deposit led to the catalyst temporary poisoning, FeP, FeP2, Fe2P, Fe3P, FeAs, FeAs2, FeF3, FeF2, Fe2S3, FeS2, Fe7Sg and FeS led to the catalyst permanent poisoning. In the water-gas shift process, N2 did not participate in toxic reactions, while CO, CO2, H2O and O2 participated poisoning reactions and provided conditions for catalyst poisoning, especially, O2 could speed up the catalyst poisoning. Based on the thermodynamic analysis, the toxicities for the water-gas shift catalyst from strong to weak was as follows:PH3, H2S, AsH3, HF.