初始凝胶含水量对Cu-SSZ-13分子筛合成的影响

摘要

Cu-SSZ-13分子筛是环保、宽温型脱硝催化剂,为了研究初始凝胶含水量对Cu-SSZ-13分子筛合成的影响,分别在定NaOH量和定pH值两个条件下进行水热合成,并且采用X射线衍射、扫描电子显微镜、77 K氮吸附、X射线荧光法和氨程序升温脱附对样品进行表征,评价Cu-SSZ-13分子筛催化剂脱硝催化性能.结果表明,初始凝胶含水量对晶化过程、结晶度、比表面积、介孔、强L酸和B酸酸性均有明显影响,高含水量有利于生成高稳定性强酸并减少中强酸的生成,但会降低晶化速率影响结晶度,适宜的初始凝胶含水量有助于获得高效脱硝的Cu-SSZ-13分子筛催化剂.%Cu-SSZ-13 molecular sieve is a high-performance and environment friendly catalyst in selective catalytic reduction of NOx over wide temperature range. To explore the effect of water content of initial gel on synthesis of Cu-SSZ-13, experiments with constant NaOH amount and at constant pH were conducted respectively. The catalysts were characterized by X-ray diffraction, scanning electron microscope, nitrogen adsorption at 77 K, X-ray fluorescence, and NH3 temperature programmed desorption, and the catalysts were evaluated in a micro fixed bed reactor for selective catalytic reduction of NOx.Results show that water content in initial gel has impact on the crystallization process, crystallinity, surface area, mesopore, strong Lewis acids and Bronsted acids of the SSZ-13. Higher water content in initial gel is favorable for the formation of strong Bronsted acids with high stability and reduces the formation of acid with medium strength. However, crystallization rate is reduced with too much water in the gel. Conclusively, Cu-SSZ-13 catalysts from initial gel with moderate water content have higher catalytic performance for reduction of NOx.