面向生物燃料乙醇生产的高填充密度板式NaA分子筛膜合成研究

Synthesis of high packed density NaA zeolite membrane plate for biofuel ethanol production

生物燃料乙醇的推广使用为我国碳中和提供有力支持。通过粮食发酵得到生物燃料乙醇,然而发酵液中乙醇含量较低,需要进一步脱水纯化。膜法渗透汽化技术是最节能的脱水技术,其中分子筛膜是该技术核心。本文采用焙烧辅助继代晶种法于平板载体上制备出高性能NaA分子筛膜.本实验详细考察了母液涂层热处理温度和时间对NaA膜合成的影响.SEM结果显示,涂层能改善载体表面平整度,随着焙烧温度的提升,涂层逐渐平整,然而过高的焙烧温度又导致涂层粗化.因此,用500℃涂层得到的NaA膜表现出平整致密的表面,其厚度仅为1.4μm,而用700℃涂层制备的NaA膜粗糙有缺陷.另外,XRD结果显示用500℃焙烧3 h的涂层合成的NaA膜具有最高的结晶度,因此,用该合成条件得到的NaA膜具有优异的乙醇脱水性能,在60℃时,其渗透通量与渗透侧水含量分别为2.18 kg/(m^(2)·h)和近100%.本文最后利用焙烧辅助继代晶种法连续合成10代NaA膜,结果显示它们都表现出相似的形貌、厚度、结晶度,同时具有相似的乙醇脱水性能.因此,采用改进继代晶种法可以在廉价的陶瓷板式支撑体上合成重复性好、性能优异的NaA膜,有效降低了成本,为其面向生物燃料乙醇生产提供了有力支撑.

Biofuel ethanol technology is one of the most powerful carbon neutral technologies.Biofuel ethanol can be obtained by grain fermentation,but the concentration of ethanol in fermentation broth is low,further enrichment and purification are needed.Purification by pervaporation technology is the highest energy efficiency process,and the membrane is the core of this technology.A calcination modified succeeding seeding method(CMSSM)was developed for the fabrication of the high-performance NaA zeolite membrane on the ceramic plate support.The effect of thermal-treatment temperature and time of the mother liquid coating on the synthesis of NaA membrane was explored.The SEM results revealed that the coating could modified the planeness of the support,coating became smooth with the increment of calcination temperature,but the calcination temperature was too high would roughen the coating.The NaA membrane,which was prepared with the mother liquid coating calcined at 500℃for 3 h,exhibited dense and smooth surface with the thickness of 1.4 um,as well as the highest crystallinity.However,many defects can be observed for the NaA membrane prepared with calcined coating at 700℃.Thus,with the usage of coating calcined at 500℃for 3 h,the best pervaporation performance for alcohol dehydration of NaA membrane was obtained,it showed the flux of 2.18 kg/(m^(2)·h)and the water in permeation of 100%at 60℃.Ten generations of NaA zeolite membrane were continuously synthesized by CMSSM,and they all showed analogous morphology,thickness and crystallinity,as well as the pervaporation performance for alcohol dehydration.Therefore,the NaA membrane on cheap ceramic plate support with good reproducibility and prominent pervaporation property could be obtained by CMSSM,which provided technical support for the wide application of NaA zeolite membrane.