Preparation And Lowtemperature Denitrification Mechanism Of Tourmaline Composite Manganese-based SCR Catalyst

Selective catalytic reduction（SCR）is the mainstream method for removing nitrogen oxides from flue gas.The iron-manganese-based low-temperature SCR denitration catalyst has high denitration catalytic activity and is considered to be one of the most promising low-temperature denitration catalysts.Research focus of external low temperature SCR denitration catalysts.In this work,a series of iron-manganese-based denitration catalysts were prepared,and the catalytic activity of the composite catalyst was tested by a fixed-bed denitration reactor;The catalysts were analyzed by X-ray diffractometry（XRD）,transmission electron microscopy（TEM）,X-ray photoelectron spectroscopy（XPS）,hydrogen temperature programmed reduction（H₂-TPR）and denitration activity test,and the silicon-aluminum ratio was analyzed.The effect of iron-manganese ratio and preparation process,and the addition amount of nano tourma powder on the crystal structure,specific surface area,micro-morphology and surface characteristics of the composite catalyst.（1）A new iron-manganese catalyst with Al₂O₃-Si O₂ composite aerogel as the new carrier was prepared.The tourmaline powder was combined with the iron-manganese catalyst by sol-gel method using tourmaline as the modified material.Modified.The study found that the best silicon-aluminum ratio is Si O₂（mol）:Al₂O₃（mol）=1:1,iron content is 20 wt%,the best preparation process is solution p H=7,the calcination temperature is 400℃.The NO_xremoval rate of the catalyst prepared under these conditions at 155℃has reached more than90%.（2）In order to optimize the performance of the catalyst,the catalyst carrier was replaced with a better-structured SAPO-34 molecular sieve according to the previous research results,and the influence of tourmaline on various aspects of the catalyst was further studied.A tourmaline composite manganese-based catalyst with excellent desulfurization performance at low temperature was obtained.It was found that the optimum preparation process was iron content of 15 wt%and tourmaline addition of 3 wt%.At this time,the composite catalytic material has the best low-temperature denitration activity,and the NOx removal rate can reach 97%or more at 140℃.（3）The effect of the amount of tourmaline powder on the performance and structure of the catalyst was studied.It was found that the addition of nano tourmaline powder can significantly improve the surface morphology of the catalyst.The reason is that during the preparation process,the tourmaline particles adsorb iron ions in the solution,restrict the ion exchange process to a certain range on the surface of the molecular sieve,reduce the damage of the molecular sieve structure by ion exchange,and ensure the integrity of the catalyst particles,thereby effectively improving the low temperature denitration performance of the catalyst.