Preparation Of PDMS Pervaporation Membranes And Research On The Separation Of Ethanol Aqueous Solution

Using cellulose or lignocellulose as raw materials to produce ethanol has become an important research direction in fermentation technology. A key problem in the fermentation process is how to separate ethanol from fermentation solution. Pervaporation technology receives wide attention in the application of ethanol extraction because it has high selectivity, permeation flux, separation efficiency and other potential advantages. For the pervaporation membrane preparation, most of study use polydimethylsiloxane (PDMS) as precursor, get the silicone rubber membrane after reacting with multifunctional crosslinking agent.In order to study the effects of PDMS precursors and other factors, n-hexane was used as solvent, TEOS (tetraethyl orthosilicate) was used as the crosslinker, hydroxyl-terminated linear PDMS precursors with molecular weights of 26.6 K,35.5 K,50.2 K,71.7 K, and 110.4 K, and dibutyltin dilaurate (DBTD) as the catalyst were chosen to prepare thirty PDMS networks at room temperature in this dissertation. To study the young’s modulus, contact Angle of water and ethanol, swelling degree of PDMS membrane influenced by the toluene extraction, content of catalyst, crosslinking agent content and so on. The pervaporation performance of PDMS membrane in ethanol, water and its mixture were also studied.It was found that the molecular weight and catalyst content had a little effects on the young’s modulus. When the catalyst content was 3%, the young’s modulus increases with increasing crosslinker content. For networks prepared with 3wt% and 5 wt% crosslinker contents, except precursors with molecular weight of 110.4 K, with the increasing of catalyst content, the young’s modulus first increase then decrease, a maximum tensile strength appears for each catalyst addition. For networks prepared with 5 wt% crosslinker content, precursors with molecular weight of 50.2K, has the strongest hydrophobicity, the water contact Angle is 140°. When the catalyst content was 5%, with the molecular weight of 110.4 K, the crosslinking membrane has the best performance of ethanol and its ethanol contact angle is 25.5°.In experiments of separation of ethanol aqueous solution, it was found that when crosslinker content is small, the swelling degree is large. For networks prepared with 3 wt% crosslinker contents,5% catalyst content, precursors with molecular weight of 50.2K, has the largest swelling degree,2.9%. When the crosslinker content is small, the water flux of PDMS membranes are small. With the increasing of catalyst content, the ethanol flux first increase then decrease. For networks prepared with 1 wt% catalyst content, precursors with molecular weight of 26.6K, has the maximum value of ethanol flux 1870 kg·m-2·h-1.In the pervaporation experiments of 10% ethanol aqueous solution, it was showed that the permeation flux first increased then decreased with the increasing of precursor molecular weight. For networks prepared with molecular weight precursors of 26.6K, the permeation flux reached the maximum value of 32 kg·m-2·h-1.The trend of the separation factor is opposite of the permeation flux. For networks prepared with molecular weight precursors of 50.2 K, the separation factor reached the maximum value of 7.2.The trend of the PSI is similar to the trend of the permeation flux. When the catalyst content was 1%, PSI reached the maximum value, the membrane showed the best performance of separating the ethanol/water. For membranes prepared with molecular weight of 35.5 K, it showed the best performance of separating the ethanol/water.