自具纳米亲水通道聚乙烯胍渗透蒸发膜的制备及乙醇脱水性能研究

The enhancement of membrane-technology competitiveness is critically dependent on developing high-performance membranes. Specifically speaking, the tuning of functional groups and optimizing the micro-structure play vital roles in optimizing membrane structures, intensifying mass transfer mechanisms, and then acquiring high-performance membranes. This study focuses on the important issue of fuel ethanol production in energy and environment fields. In order to intensify the pervaporation process for ethanol dehydration, the hydrophilic modification of membrane will be adoped by grafted strong hydrophilic guanidine group to polymer to increase the water solubility selectivity in membrane. Meantime, in order to intensify the water transport process, nanochannel in the membrane will be construted by micro-phase separation to provide continuous channel for water diffusion. It is desirable to obtain ethanol dehydration pervaporation membrane with high water selectivity and flux. The synthesis strategy is that polyvinylamine will be prepared by Huffman degradation of the commercialized polyacrylamide, and then modify the part of amino groups into strong hydrophilic guanidine groups. Meanwhile, other part of the amino groups will be modified by hydrophobic comb-side chain through the Schiff base reaction. As well as known, the comb-side polymeric architecture will induce well-defined phase separation by adjusting the proportion of hydrophilic and hydrophobic groups, and thus well-connected hydrophilic nanochannels will be constructed and conducive to improve the water transport. The effects of hydrophilic-hydrophobic group types and hydrophilic nanochannels on the membrane separation performance were studied. The mechanism of the transfer of water molecules in the microphase separation membrane will be proposed and the related transfer model will be established. We hope that the proposed investigations will provide the relevant theoretical basis for high performance ethanol dehydration membrane.

高性能膜材料是提高膜技术竞争力的关键，而膜功能基团调控，以及微观结构的优化是强化膜传质过程，获得高性能膜材料的重要手段。本项目面向清洁燃料生产的国家重大需求，以渗透蒸发燃料乙醇脱水的过程强化为目标，拟通过在膜中膜中接枝强亲水基团胍基以强化水分子在膜中的溶解选择性；同时通过在膜中形成微相分离的纳米通道，以强化水分子在膜中的扩散性能，从而获得兼具有高选择性和高水通量的乙醇脱水渗透蒸发膜。拟采用商业化的聚丙烯酰胺通过霍夫曼降解制备得到聚乙烯基胺，将适量氨基改性成强亲水性胍基，同时将部分氨基通过希夫碱反应在高分子中引入疏水的梳状侧链，调节亲疏水基团比例，诱导微相分离，形成利于水分子传递的纳米通道。通过研究亲疏水基团的种类、比例及微相分离纳米亲水通道对膜分离性能的影响规律，初步提出水分子在微相分离膜中的传递机理，并建立相关传递模型，为设计和制备高性能乙醇脱水膜提供相关理论依据。

本项目面向清洁燃料生产的国家重大需求，针对乙醇脱水渗透蒸发中渗透性和选择性相互制约的Trade-off问题，采用商业化聚丙烯酰胺通过霍夫曼反应制备了聚乙烯基胺，通过在聚乙烯基胺分子链上反应接枝亲疏水性质不相同的基团，调节亲疏水基团结构和数量比例，在膜中形成微相分离的纳米通道，以获得兼具有高选择性和高水通量的乙醇脱水渗透蒸发膜，研究了纳米通道形成方法、纳米通道结构与膜性能关系及传递机理。基于此，本项目分别开展了如下几方面的工作：1）以商业化的聚丙烯酰胺为原料，通过霍夫曼降解制备得到聚乙烯基胺，将适量胺基改性成强亲水性胍基，同时将部分胺基与长链醛进行席夫碱反应在聚乙烯胍侧链接枝适量的疏水性长链，通过调节亲疏水基团结构和比例形成微相分离纳米通道。优化了霍夫曼反应条件、聚乙烯胍合成条件，考察了疏水链长短和接枝量对聚乙烯胍膜结构和膜性能的影响，发现接枝有强亲水性胍基，并通过亲水性质差异形成微相分离纳米通道的改性后聚乙烯胍膜渗透蒸发性能相比于聚乙烯基胺具有显著提高，取得了良好的效果，但同时也发现在合成胍基时的高温反应，对分子链有一定程度降解作用，导致铸膜液粘度降低，使得其在制备复合膜时在基膜上铺展性有一定影响。2）为了避免高温导致分子链降解，我们直接将聚乙烯基胺中部分胺基与反应活性更高的且带有疏水性长链的酰氯进行反应，通过调节亲水性胺基和疏水长链的结构比例形成了类似第一部分工作中的微相分离通道，考察了微相分离通道对膜结构和膜性能的影响；3）在完成基金基本内容之外，我们在基金的支持下还开展了以下工作，以PVAm为模板剂，将疏水性聚苯胺改性成亲水性纳米线，并掺杂在PVAm膜中，在膜中构建亲水性通道，考察了亲水性聚苯胺的合成条件及掺杂量对膜结构及性能的影响；另外还研究以氮丙啶为交联剂的聚丙烯酸钠渗透蒸发膜的膜结构及性能关系。在本项目的支持下，在Reviews in inorganic Chemistry和 Journal of Taiwan Institute of Chemical Engineers 期刊上发表论文2篇，部分研究成果在投稿中，同时申请发明专利4项，申请实用新型专利2项。