Research On SSZ-13 Zeolite-based Catalyst For DeNOx Of Diesel Exhaust

Nitrogen oxides is one of the major pollutants causing environmental pollution in the world today,leading to a series of environmental pollution such as photochemical pollution and acid rain.The problem has led to restrictions on the promotion and application of diesel vehicles.In recent years,with the improvement and strictness of relevant laws and regulations in China,higher requirements have been placed on diesel vehicle exhaust emission requirements.At the same time,because the traditional three-way catalyst（TWC）used in gasoline engines is easily deactivated under oxygen-rich water vapor conditions and cannot meet the requirements of diesel exhaust emissions treatment,it is a recent search for a catalyst that can effectively treat diesel vehicle exhaust emissions.It becomes a hotspots of diesel gas after treatment.In this paper,SSZ-13 molecular were synthesized using Cu-TEPA and TMAda OH as templates,respectively.In subsequent experiments,we choose the SSZ-13 molecule synthesized by templating agent TMAda OH,and determined the influence of calcined temperature,GSHV and the ratio of NH₃/NO.It was found through experiments that when the Cu content was 3.0%,the catalyst had a wide denitration temperature window between 150～360°.The catalyst was modified by using Ce,Fe and Zr as the second metal,and the bimetallic supported catalyst was prepared by the equal volume impregnation method,and then characterized and evaluated.According to the evaluation results,the second metals Ce,Fe and Zr can significantly improve the high-temperature denitration efficiency of the denitration catalyst.When the Ce,Fe,and Zr loadings are 2%,3%,and 1%,the denitration temperature window can reach 170-400℃,150-360℃,175-375℃,respectively,while the modification of the second metal can improve the sulfur resistance of the catalyst.In order to clarify the reasons for the difference of NH₃-SCR catalytic performance at high and low temperatures,the NO oxidation performance of different catalysts at low temperatures and the adsorption and oxidation performance of different catalysts at high temperatures were characterized and evaluated.The DFT theoretical calculation was carried out with H-SSZ-13 catalyst and Cu-SSZ-13 catalyst.It was determined that the effect of metal-supported and non-metal-supported catalysts on denitrification at high and low temperatures was quite different.