Synthesis And Application Of Mor-type Zeolite Membrane

In recent years, zeolite membrane has been used in a wide variety of applications for separation processes (especially the separation of ethanol and water) with the development of membrane technology. Pervaporation (PV) is a novel membrane-based separation technique which relies on a molecular sieving effect and on the differences between the adsorption and diffusion properties of the components to be separated. In this thesis, we focus on the synthesis of MOR-type zeolite membranes in fluoride media. Furthermore, PV performance, acid resistance and esterification reactor of MOR-type zeolite membranes were discussed respectively.1.The MOR-type zeolite powder in fluoride media was successfully synthesized by hydrothermal treatment using a molar ratio of n(Na20):n(Al2O3):n(SiO2):n(F-): n(H2O)=6:1:30:4:780 under 170℃for 24 h. The effect of fluoride source (NaF, NH4F and KF) on the synthesis of MOR-type zeolite was investigated. It was found that KF as fluoride source could not benefit the formation of pure mordenite zeolite. The influence of molar ratios of n(Na2O+NaF)/n(SiO2) and n(NaF)/n(SiO2), the synthesis time and temperature on the crystallization of MOR-type zeolite powder were also studied. The characterization of x-ray diffraction (XRD) and scanning election microscope (SEM) showed that the crystal powder crystallized in fluoride media under optimized conditions had good crystallinity.2.The MOR-type zeolite membrane was synthesized on the porous support by secondary growth,using a molar ratio of (0.15-0.35)Na2O:(0.014～0.1)Al2O3:1SiO2: (0.1～0.5)NaF:(15-60)H2O under 140～190℃for 6-26 h. The effects of molar ratios of n(NaF)/n(SiO2), n(H2O)/n(SiO2), n(Si02)/n(Al203) and n(Na20)/n(Si02) on the crystallization of MOR-type zeolite layer were investigated. The Characterization results of XRD and SEM showed that a dense MOR-type zeolite layer formed on the outer surface of porous support. Furthermore, the synthesis conditions and supports were also studied. PV performance of the resulting membranes were normally evaluated using a water/ethanol(10/90 wt.%) mixture at 75℃. Mordenite membranes prepared in fluoride media showed high flux of 1.50 kg·m-2·h-1 together with high separation factor of 1300.PV performance of membranes were also greatly influenced by the feed concentration and operation temperature. 3.PV performance of mordenite membranes were tested comparably before and after different acid treatment(0.1mol·L-1～2mol·L-1 CH3COOH (aq) and 0.1 mol·L-1 HCl (aq)) at 70℃for a certain time 24 h. It showed that the synthesized membranes were stable in 2 mol·L-1 CH3COOH solution or 0.1 mol·L-1 HCl solution for 24 h. Subsequently, the possibility of membranes in the application to the esterification reaction (used as a catalytic membrane reactor) was investigated. PV performance of the synthetic membranes in an esterification system with n(C2H5OH):n(CH3COOH)=1.5:1 was studied, it showed the membranes have better stability and that the conversion in esterification system can be increased by 30～40%, which provided a commercial application as a catalytic membrane reactor.