Separation of supercritical fluid mixtures with a membrane process

不对称聚酰胺Kapton^R膜是由在70 ℃ C和4分钟蒸发时间内铸造的溶液中的18重量%聚氨基酸和5重量%苯甲酸。本膜是一个分离因子alpha_<乙醇/CO2>， 8.7在373 K和15 MPa处获得，在423 K和15 MPa处获得6.5，在423 K和15 MPa处获得了分离CO_2气体混合物和乙醇与15 ： 1的浓度比率。373 K的值比423 K高1.3次，总压力增加，当423 K的分离因子在压力下仍保持不变时，对2.6 kj/mol的乙醇的渗透能量和7.1 kj/mol的超临界CO_2的活性能量都很小，与48 kj/mol的乙醇和25 kj/mol的CO_的活性能量相比。2与对称性聚酰胺膜。超临界流体渗透实验可能是确定渗透机制的最佳方法，无论是Porto流动模型还是解决方案扩散模型，对渗透的激活能量进行测量。从收集到的数据中，计算被运送到确定所需的膜区域，从90%的乙醇中恢复混合物，初始浓度为1摩尔%，饲料速率为36摩尔/小时。此区域为0.82 m^2，用于分离在10 MPa和373 K和0.28 m^2在15 MPa和373 K。还有三个四分之一的操作能量可以被拯救。因此，该过程与薄膜恢复集成，可以节省大约3/4的操作能量，而主压缩机的大小将理论上减少到1/4。

Asymmetric polyamide Kapton^R membrane was made by casting a solution of 18 wt% polyamic acid and 5 wt% phenanthrene in dimethylacetainide at 70ﾟC with a four-minutes evaporation time. Usine this membrane, a separation factor alpha_<ethanol/CO2>, 8.7 was obtained at 373 K and 15 MPa and 6.5 at 423 K and 15 MPa for the experimemt involving the separation of gaseous mixtures Of CO_2 and ethanol with a concentration ratio of 15 : 1. Its value at 373 K is 1.3 times higher than at 423 K, and increases with total pressure, while the separation factor at 423 K remains constant with pressure.The activation energies of permeability were 2.6 kj/mol for ethanol and 7.1 kj/mol for supercritical CO_2・These values are very small compared to those of 48 kj/mol for ethanol and 25 kj/mol for CO_2 with the symmetric polyamide membrane. Supercritical fluid permeation experiment might be the best method to determine the permeation mechanism whether pore flow model or solution-diffusion model, from the measurement of activation energy of permeation.From the data obtained, a calculation was carried out to determine the required membrane area for 90% recovery of ethanol from mixtures with an initial concentration of 1 mol% and a feed rate of 36 mol/h. This area is 0.82 m^2 for separations conducted at 10 MPa and 373 K and 0.28 m^2 at 15 MPa and 373 K. And three quarters of operating energy of pressurization might be saved. Therefore, the process integrated with membrane recovery could save operating energy about 3/4 and the size of the main compressor will be reduced to 1/4 theoretically.