Effects of preparation conditions on the performance of simultaneous desulfurization and denitrification over SiO2-MnOx composites

SiO2-MnOx composites were prepared by sol-gel method and used to simultaneously desulfurization and denitrification. The effects of TEOS (tetraethoxysilane) concentration, H2O concentration and ammonia concentration on the performance of simultaneous desulfurization and denitrification over the SiO2-MnOx composites were investigated. The experiment results showed that all of the SiO2-MnOx composites with a desulfurization efficiency of up to 100% in the experiment, while the denitrification efficiency was decreased from nearly 100% with the increasing of time. The SiO2-MnOx composite which was synthesized with 0.054 mol TEOS, 1.111 mol H2O, and 0.208 mol ammonia (TEOS: ammonia: H2O = 1.0: 3.9: 20.6) exhibited the best adsorption capacities of SO2 and NO, and the adsorption capacities of SO2 and NO were 0.0680 mmol/g and 0.1010mmoxl/g, respectively. The structure of the SiO2-MnOx composites, SiO2 distributed uniformly on the surface of MnOx, could reduce the adsorption inhibition of SO2 on NO, which was due to most of the SO2 could be adsorbed by the outer material (SiO2), while most of the NO molecules and the remaining SO2 enter into the inner layer and be adsorbed by MnOx. The urea treatment can increase the pore structure of the material by decomposing to produce NH3 and CO2, which made it easier for the gas to enter the material inside and improved the adsorption capacity of SO2 and NO. Based on the analysis of the TPD and FTIR spectra, it was apparent that the product of chemisorption was manganese nitrate, sulfuric acid and manganese sulfate.