微波辅助合成镁铝类水滑石基氧化物及其在含O2/H2S气氛下的COS水解催化行为OA

COS hydrolysis catalysis is important in industrial gas purification and desulfurization.MgAl hydrotalcite-based oxides(MgAl-MMO)can effectively catalyze COS hydrolysis in a simple atmosphere(COS+H2O).However,the catalytic effect of O2/H2S on MgAl-MMO is not clear,and the existing synthesis methods are time-consuming.The feasibility of microwave-assisted synthesis of MgAl-MMO was explored and its catalytic behavior under reaction gas containing O2/H2S was investigated.The results show that the best performance of the catalyst for COS hydrolysis is achieved by microwave crystallization at 80℃and n(Mg)/n(Al)of 2.The COS conversion rate and H2S selectivity of the catalysts are 100.0%and maintain for 540 min in in the reaction gas(O2 volume fraction of 1.0%).However,the COS conversion rate and H2S selectivity decrease significantly(by 63.2%and 68.8%,respectively)when the O2 volume fraction increases to 1.5%,which is mainly attributed to the increase of sulfur deposition on the catalyst surface due to the catalytic oxidation of H2S at high O2 volume fraction.H2S in the O2-free environment leads to catalyst poisoning during the catalytic process,and the degree of poisoning increases with the increase of H2S mass concentration:COS conversion rate and H2S selectivity with 198 mg/m3 H2S decrease to 37.4%and 5.3%after 100 mintutes,respectively.The coexistence of 1.0%O2 and 198 mg/m3 H2S further accelerate the catalyst deactivation,exacerbate the surface sulfation and the relative content of medium bases and weak bases decreased significantly,and the detrimental effect of H2S on the catalyst is significantly greater than that of O2,with the COS conversion rate and the H2S selectivity of only 20.2%and 1.4%,respectively,after 85 minutes of reaction.