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۱Synthesis and characterization of T–type zeolite membrane for pervaporation of Water\Isopropanol mixtures
اطلاعات انتشار: یازدهمین کنگره ملی مهندسی شیمی ایران، سال
تعداد صفحات: ۷
Zeolite membranes have been recently more developed to employ in pervaporation, gas separation, membrane reactors and other chemical industries. In this research, T–type zeolite membranes were prepared by hydrothermal reaction on the outer surface of a tubular porous mullite support seeded with zeolite T crystals.
Effects of the most important parameters on flux and porosity of supports and zeolite layers produced by extrusion and hydrothermal methods, respectively, were evaluated. The best results were achieved by calcining for about 3.5 h at a temperature of about 1250 ºC and with a kaolinite percent of about 83 %. These supports exhibited optimum porosity and flux and smooth surfaces. Effects of Silicon module (SiO2\Al2O3), Alkalinity (relative) (OH\SiO2), Crystallization temperature (K) on the zeolite T synthesis were also investigated. Results of these experiments showed that the gel composition of 1SiO2: 0.04Al2O3: 0.26Na2O: 0.09K2O: 14H2O yields formation of the best zeolite T powders.
Effects of crystallization time and temperature on membrane characteristics and its morphology were investigated for the zeolite T membranes using SEM, XRD and pervaporation tests. PV experiments were carried out with water\Isopropanol mixtures using synthesized membranes. Composition analysis of the feed and permeate was performed by a refractometer. It was found that the membrane synthesized at a temperature of 393 K for 30 h, shows high permeation flux of 0.7 kg m–2h–1 and selectivity of 10000.<\div>

۲Comparison of T and W zeolite membranes for separation of O2\SF6 mixtures
اطلاعات انتشار: هفتمین کنگره ملی مهندسی شیمی، سال
تعداد صفحات: ۱۱
Greenhouse effect is one of the most significant dilemmas in environmental aspects that cause negative results in nature and society. SF6 is a very potent greenhouse gas. The global warming potential of the gas is 23,900 times greater than that of CO2, and its atmospheric lifetime is about 3,000 years. Two different zeolite membranes (T (0.36 – 0.67 nm) and W (0.27 – 0.51 nm) were synthesized and their performances were evaluated in separation of O2\SF6 mixtures. They were selected due to their different silicon modules (SiO2\Al2O3) and their polarities. Effect of feedpressure on separation of O2\SF6 was also investigated. The results showed that T zeolite membrane (silicon module = 25) provides higher separation factor of O2\SF6 (50) compared withW zeolite membrane (20.1). Also, increasing feed pressure from 3 up to 5 bar decreases separationfactor of O2\SF6 and increases O2 and SF6 permeances through both the zeolite membranes. From the results, it was concluded that increasing pressure decreases the surface diffusion contribution through the molecular sieve pores, and increasing the Knudsen flow and the viscous flow contributions.<\div>
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