| Due to benefits of efficient use of energy and equipment,maneuverability,free phase inversion and excellent permeability etc.,membrane separation is widely investigated in recent years.The pore size(0.55 nm)of silicalite-1 zeolite is similar to the size of many important industrial materials.Moreover,silicalite-1 zeolite has better chemical and physical stability and stronger hydrophobic property.If the silicalite-1 zeolite membranes can be prepared,they will have potential applications in membrane separation,pervaporation and catalytic membrane reactors due to its unique properties.In a word,it is very significant to research the preparation and application of silicalite-1 zeolite and its composite membranes.Herein,the silicalite-1 zeolite particle preparation is firstly investigated using in situ hydrothermal synthesis.Silicalite-1 zeolite particles with different sizes are obtained and the recipe of the membrane preparation is found.Based on the research of conventional hydrothermal synthesis,the method of membrane synthesis is improved.First,A novel embellishing method,vacuum seeding and template-free method are used for preparation silicalite-1 zeolite membranes on tubularα-Al2O3 support.And the methods for membrane preparation are optimized,good performance of silicalite-1 zeolite membranes are prepared. Secondly,A two-stage varying-temperature in situ synthesis is developed for silicalite-1 zeolite membrane synthesis.A continues and dense membrane with a high quality is formed. Moreover,the synthesis time is shortened.Thirdly,the preparation of composite membrane is constructed,considering the intrinsic defects of a single membrane.The composite membrane may have both benefits of the two membranes.Integrated and continues silicalite-1/carbon, silicalite-1/TiO2,silicalite-1/Pd composite membranes are prepared.Lastly,the as-prepared silicalite-1 membranes are applied to pervaporation for ethanol/water mixture and catalytic membrane reactor for the dehydrogenation of ethylbenzene to styrene.Moreover,a good separation performance for ethanol/water mixture and high ethylbenzene conversion in membrane reactor are obtained.The main results achieved are as follows:(1)The influencing factors of TPABr and TPAOH as template,alkalinity content, crystallization time,crystallization temperature and stirring time on the preparation of silicalite-1 zeolite particles were investigated respectively.The results indicated that silicalite-1 zeolite crystals size within the range of 0.1～4μm were prepared.Moreover,the crystallization degree of the as-prepared zeolite is high and the size distribution is narrow. Using TPABr as template,synthesis solution experiences the gel formation and decomposing process.But using TPAOH as template does not experience the process.Lose weight of silicalite-1 zeolite is composed of three processes during calcination process:desorption of water,decomposing of organic ammonium in zeolite pores and decomposing of TPA+.(2)Defect-freeα-Al2O3-supported silicalite-1 zeolite membranes were successfully prepared by a novel embellishing method,secondary synthesis and template-free method respectively.①Hydrothermal synthesis time before polishing and type of sand paper are two important factors for membrane preparation using the novel embellishing method.The method can effectively improve the quality of as-prepared membrane.At room temperature, the H2 permeance is 1.2×10-6mol/(m2·s·Pa),and the idea selectivities of H2/n-C4H10and H2/SF6 are 30 and 84 respectively.②The influencing factors of vacuum seeding method were investigated.A homodisperse and continues seed layer was prepared by the method. Herein,the optimized condition is that the size of seed is similar to support pores and pressure is 0.06～0.07 MPa.The gas permeation tests indicate that,at room temperature,the permeance of H2 is 3.25×10-7mol/(m2·s·Pa),and idea selectivities of H2/N2 and H2/SF6 are 4.1 and 133.2 respectively,exhibiting a good separation performance.③The influencing factors of template-free method were investigated.The optimized synthesis condition is that synthesis time is 5～8 h,ratio of silica/water is 30～45 and crystallization one times.At room temperature,the permeance of H2 of as-prepared membrane is 1.72×10-7mol/(m2·s·Pa),the idea selectivities of H2/N2 and H2/SF6 are 2.76 and 18.5 respectively.(3)Silicalite-1 zeolite membranes were successfully prepared onα-Al2O3 and stainless steel supports by the developed two-stage varying-temperature synthesis.The results showed that the zeolite nuclei completely formed at 403 K for 24～36 h,the compact membrane formed by the nuclei regrown at 443 K for 12～24 h and the total synthesis time greatly decreased.Single gas permeation tests at different temperatures indicated that H2 permeance changed slightly,idea selectivities of H2/N2 and H2/SF6 decreased,and H2/SF6 had a least value.At room temperature,H2 permeance is 12.25×10-7mol/(m2·s·Pa),and the idea selectivity of H2/n-C4H10is 46.Moreover,the yield of membranes with perm-selectivity of H2/n-C4H10are larger than 25 as a quality criterion reached to 70%of all preparations.The results showed that permeability and reproducibility of the membrane are good.(4)Continues silicalite-1/carbon,silicalite-1/TiO2,silicalite-1/Pd composite membranes are prepared.①The zeolite size and content(wt%),PAA content(wt%)and precursor membrane preparation were main influencing factors on permeability of the as-prepared membranes.The compact and continues silicalite-1/carbon composite membrane was prepared by a vacuum slip-casting method and the thickness of the membrane is about 2μm. At room temperature,the permeance of oxygen is 158×10-10mol/(m2·s·Pa)without decreasing the idea selectivity of O2/N2.②The silicalite-1/TiO2 composite membrane was prepared by pre-seeding silicalite-1/TiO2 layer onα-Al2O3 support.The silicalite-1 zeolite size and content (wt%),dip-coating times and H2O/SiO2 were main influencing factors on the composite membrane preparation.The optimized condition is that zeolite content is 8%(wt%),zeolite size is 900～1000 nm(similar to support pore size),dip-coating times is 6～8 and H2O/SiO2 ratio is 120.At room temperature,the permeance of H2 is 10×10-7mol/(m2·s·Pa),and the idea selectivities of n-C4H10/i-C4H10and H2/SF6 are 7.8 and 206.3 respectively.③The slicalite-1/Pd composite membrane was successfully prepared on porous stainless steel support.Moreover,the thickness of Pd membrane was less than 2μm.At 773 K,the permeance of H2 is 1.2×10-6mol/(m2·s·Pa),the idea selectivity of H2/N2 is larger than 150. And the permeance of the H2 decreased slightly with increasing Pd-plated times.So the selectivity of the composite membrane can be controlled by Pd-plated times.⑤Silicalite-1 zeolite membranes were applied in the pervaporation separation of 5% (wt%)ethanol/water mixture.The influencing factors of feed temperature,feed flow rate, H2O/SiO2 and support on pervaporation performance of the membrane were investigated.The results showed that the selectivity of ethanol/water increased without decreasing the flux by increasing the feed flow rate.The flux of the membrane increased by increasing feed temperature.The selectivity and flux of ethanol/water were about 33 and 0.62 kg/(m2·h)when the ratio of H2O/SiO2 was 50～100.Moreover,the selectivity and flux of ethanol/water for stainless-steel-supported silicalite-1 zeolite membrane were about 36.2 and 1.25 kg/(m2·h).⑥The dehydrogenation of ethylbenzene to styrene was applied in silicalite-1 zeolite membrane reactor.The influencing factors of sweep gas flow rate,ratio of water/ethylbenzene, reaction temperature and ethylbenzene feed speed(SV)were investigated.The results indicated that the conversion in membrane reactor was increased with increasing sweep gas flow rate,the conversion in both reactors was decreased with increasing the ratio of water/ethylbenzene and ethylbenzene feed speed and the conversion in both reactors was increased with increasing the reaction temperature.The benefit of the membrane reactor is due to instantaneous removal of H2 from the reaction zone.The water/ethylbenzene ratio of 2, SV of 0.5,about 6～8%higher conversion for the membrane reactor than the fixed-bed reactor above 600℃without decreasing the styrene selectivity was obtained.The stability of membrane reactor is good for about 300 h operations at different conditions,which indicated that it is a valuable work for further investigation.
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