Advanced CO2- and H2S-Selective Membranes

化学和生物分离计划的NSF奖项支持Winston Ho教授及其学生通过引入新的多壁碳纳米管（MWNTs）合成先进的CO2和H2S选择性膜的工作。和二氧化硅与空间位阻胺一起引入聚合物膜基质中，并研究MWNT和二氧化硅对于改善高压下膜压缩的抵抗力和增强酸性气体。 从气体（包括合成气和天然气）中除去CO2和H2S的现有技术方法使用胺水溶液，其中蒸汽用于再生，然后冷凝含有酸性气体的蒸汽流以分离/释放酸性气体。 该过程涉及繁琐的操作、高能耗和资本密集型设备。 此外，它受到吸收过程中酸性气体溶解度的热力学平衡的限制，导致溶液循环速率增加，因此设备大型化。 因此，重要的是开发一种既节省资金又节省能源的有效方法。 这项工作的目的是开发节能膜过程，具有简单的压力驱动过程，没有移动部件。 所提出的工艺将酸性气体的吸收和汽提合并为一个步骤。 该一步法工艺简化了酸性气体的分离，克服了热力学溶解度的限制，该膜是第一种能够在相对较高的温度下具有高的CO2和H2S渗透性和对氢气和氮气的选择性的膜（100 - 120 ℃）和压力（1 - 30 atm），这是从煤和生物质中高效净化合成气以及CO2捕集所需的。 这项研究不仅是一个伟大的科学兴趣，但也可能提供重大的技术重要性的改进膜。 我们相信，这是对扩大气体分离科学知识和理解的重大贡献。 所提出的研究的潜在影响是显著的，因为这项研究的目的是新型CO2选择性膜和工艺，以克服商业气体处理技术的许多缺陷。 该一步法不仅简化了分离过程，而且消除了对吸收器、再生器、用于负载和再生胺溶液的两个泵以及吸收器和再生器之间的泵送操作的需要。 它还消除了由于水的高热容量和使用温度摆动来驱动气体解吸而导致的胺溶液的能量密集型再生。 因此，这种膜工艺将具有显著的资金和能量节省。 所提出的膜具有许多潜在的应用，包括来自煤和生物质的合成气的纯化，以产生用于燃料电池的高纯度H2，从烟道气中捕获CO2用于其封存，以及从生物气、天然气、受限空间空气和环境空气中去除CO2。 我们每年都会公布和发表这项研究。 此外，本研究还提供了1个博士学位的教育。研究生和2名本科生不仅进行了先进的膜工作，而且具有技术意义。

This NSF award by the Chemical and Biological Separations program supports work by Professor Winston Ho and his students to synthesize advanced CO2- and H2S-selective membranes by incorporating new multi-walled carbon nanotubes (MWNTs) and silica with sterically hindered amines into the polymer membrane matrix and to study the effects of MWNTs and silica for improved resistance to membrane compression under high pressures and for enhanced transport of the acid gases. The state-of-the-art process for the removal of CO2 and H2S from gases, including synthesis gas and natural gas, uses aqueous amine solutions, where steam is used for regeneration and the steam stream containing the acid gas is then condensed to separate/release the acid gas. This process involves cumbersome operations, high energy consumption, and capital-intensive equipment. Furthermore, it is limited by the thermodynamic equilibrium on acid gas solubility during absorption, resulting in an increased solution circulation rate and consequently large equipment. Thus, it is important to develop an effective process with both capital and energy savings. This work is aiming at developing the energy-efficient membrane process, featuring a simple pressure-driven process with no moving parts. The proposed process combines the absorption and stripping of acid gas into one step. This one-step process simplifies the acid gas separation and overcomes the thermodynamic solubility limitation.The proposed membrane is the first of the kind capable of possessing high CO2 and H2S permeabilities and selectivities vs. hydrogen and nitrogen at relatively high temperatures (100 - 120C) and pressures (1 - 30 atm), which is needed for energy-efficient purification of syngas from coal and biomass as well as for CO2 capture. This research not only is of a great scientific interest but also may provide improved membranes of significant technological importance. We believe that it represents a significant contribution to expanding the scientific knowledge and understanding in the gas separation. Potential impacts of the proposed research are significant as this research is aiming at the novel CO2-selective membrane and process to overcome many deficiencies of the commercial gas treating technology. This proposed one-step process not only simplifies the separation process, but also eliminates the needs for the absorber, the regenerator, two pumps for the loaded and regenerated amine solutions, and the pumping operations between the absorber and regenerator. It also eliminates the energy-intensive regeneration of the amine solution due to the high heat capacity of water and the use of temperatures swing to drive gas desorption. Thus, this membrane process will have both significant capital and energy savings. The proposed membranes have many potential applications including the purification of syngas derived from coal and biomass to produce high purity H2 for fuel cells, CO2 capture from flue gas for its sequestration, and CO2 removal from biogas, natural gas, confined space air, and ambient air. We will present and publish this research each year. Furthermore, this research provides the education of 1 Ph.D. graduate student and 2 undergraduate students for conducting not only the work on advanced membranes but also that with technological significance.