Synthesis Of Silicalite-1 Zeolite Membranes And Application In Dehydrogenation Of Ethylbenzene To Styrene

Silicalite-1 zeolite is one of the MFI zeolites, has made it be of withstanding higher temperature, higher hydrophobicity compared to ZSM-5 zeolite membrane, because of no Al in its structure, which has been applied not only in gas separation, but also in the reaction system of harsh condition. So, there is still much work to do in studying the preparation of Silicalite-1 zeolite membrane with high quality and its application in dehydrogenation of ethylbenzene to styrene.The main work of this paper is: (1) Effects of some important factors on the preparation of Silicalite-1 zeolite membranes are thoroughly studied. High-penetration Silicalite-1 zeolite membrane were synthesized on the a-Al2O3 support with pores of 3-5μm; (2) High quality Silicalite-1 zeolite membranes was prepared by in situ hydrothermal synthesis on different substrates; (3) membrane reactor was used in dehydrogenation of ethylbenzene to styrene under the circumstances of industry production and got a good result.The influence of crystallization methods and synthesis times and the methods of introducing seeds and the pretreatment methods of substrate were studied thoroughly. The results showed that using self-product Silicalite-1 zeolite as seeds and introducing them to the support and crystallizing three times using the rotary methods, integrated and continuous membranes were gained. The penetration of H2 is 12.26×10-7 mol/(m2 s Pa) and the ideal selectivity of H2/C3H8 is 13.55. It was reported that high quality Silicalite-1 membrane was directly prepared on the porous support in optional conditions. The permeation of H2 is up to 2.73 × 10-6 mol/(m2 s Pa) and it is almost one order of magnitude higher than that of the literature. The ideal selectivity of H2/N2 and H2/C3H8 is 3.72 and 24.59 respectively.Two-stage varying-temperature synthesis was introduced to the synthesis of zeolite membranes. The influence of varying-temperature on zeolite membranes was studied. High quality Silicalite-1 zeolite membranes were synthesized on the porous stainless steel support with pores of 3-5 μm, the large membranes were successfully prepared on tubular supports. The permeation of H2 is 4.77×10-7 mol/(m2 s Pa), The ideal selectivity H2/C3Hg is 14.77.The membrane reactor was used in dehydrogenation of ethylbenzene to styrene under the circumstances of industry production. The experimental results indicated that the conversion of ethylbenzene in the membrane reactor increased with the pressure and temperature and thesweep gas speed increasing. Using sweep gas instead of the vacuumizing, the result under the same conditions showed that the selectivity of styrene increased and the conversion of ethylbenzene in the membrane reactor increased by 7.52% in comparison with the fixed-bed reactor, which had been tested by a long time.