Synthesis And Catalytic Properties Of NaY Zeolite And Molecular Sieve Membrane

Wide attention has been drawn to the pollution of increasing discharge of phenolic wastewater which occured with the development of industry. Zeolite NaY and its membranes, have high catalytic activity and selectivity due to their unique properties of high specific surface area, uniform diameter pores, and good heat and chemical stability. Homogeneous catalysts are difficult to separate from solution, while zeolite NaY and its membranes, as new sorts of heterogeneous catalysts, can effectively solve the problem, which have great potential for application in the treatment of waste water and waste gas.In this paper, zeolite NaY was synthesized from Na2SiO3·9H2O and Na2AlO2by hydrothermal method without using templates. The influences of hydrothermal time, hydrothermal temperature and others conditions were researched to find the optimum synthesis condition. And then, zeolite NaY membranes were synthesized on supports of ceramic rasching ring, glass sheet and metal sheet separately. The effects of different seeding methods were researched. The zeolite NaY and its membranes were characterized by XRD, FE-SEM, FT-IR, TG and XRF. Catalytic wet oxidation of phenol was used to investigate the catalytic activity of zeolite NaY and its membranes. The effects of reaction time, temperature, oxidant and catalyst dosages on the catalytic performance were studied, and comparisons of catalytic performance were made between the two catalysts.The results show that factors including hydrothermal time, pH of reaction system, crystallization temperature and time, SiO2/Al2O3and feeding modes influence on the formation of zeolite NaY. The optimized conditions were as follows:gel composition of n(Na2O): n(SiO2):n(Al2O3):n(H2O)=14:10:1:800, hydrothermal temperature at60℃and hydrothermal time of3h, crystallization temperature at170℃and crystallization time of7h, zeolite synthesized under this condition has typical NaY frameworks with high crystallinity of85.04%, an average diameter of150nm and good hydrothermal stability. The factors of seeding methods and material of supports influence on the formation of zeolite membranes. The membrane synthesized on ceramic rasching ring by the pretreatment of rub-seeding displays good film-forming effect with an average crystal diameter of139nm and membrane thickness of16.7μm. Use zeolite NaY as the catalyst and H2O2as the oxidant in the reaction of phenol oxidation, when the amount of catalysts is40%of phenol, reaction temperature is80℃, reaction time is90min, the removal of phenol reached maximum,42.65%. When using zeolite membrane as catalyst, the removal of phenol reached48.80%finally, which displayed better catalytic performance.