无模板剂水热合成PHI分子筛OA

Using a template-free hydrothermal synthesis method with conventional silica,alumina,and alkali sources as raw materials,the effect of the feed n(SiO2)∶n(Al2O3),[n(Na2O)+n(K2O)]∶n(SiO2),n(H2O)∶n(SiO2),n(K2O)∶[n(Na2O)+n(K2O)],crystallization temperature,and crystallization time on the synthesis of PHI zeolite was systematically investigated.The synthesized PHI zeolite was processed into PHI extrudates for the acid resistance testing.The experimental results indicate that the feed n(SiO2)∶n(Al2O3)has a certain effect on the morphology,particle size,and crystallinity of the PHI zeolite.Without template agent,the higher feed n(SiO2)∶n(Al2O3)can only alter the product n(SiO2)∶n(Al2O3)within a narrow range.A pure-phase PHI zeolite can only be synthesized when[n(Na2O)+n(K2O)]∶n(SiO2)is above 0.5.Both an excessively low n(K2O)∶[n(Na2O)+n(K2O)]and an excessively high n(H2O)∶n(SiO2)negatively affect the crystallinity of the PHI zeolite.KOH plays a structure-directing role in the synthesis system,and its concentration directly influences the structural type of the product,making it one of the key factors for the successful synthesis of PHI zeolite.Within the temperature range of 95-170℃,the higher crystallization temperature accelerates crystal growth and significantly shortens the crystallization time.However,excessively high crystallization temperatures lead to a reduction in crystallinity.Neither macrostructure nor microstructure of the PHI extrudates is significantly damaged,demonstrating superior acid resistance compared to 3A zeolite.This suggests its potential application in the deep dehydration of acidic substances.