多酸基功能离子液体催化氧化硫化氢脱硫研究

Hydrogen sulfide (H2S) which come from the burning of fossil fuels has drawn much more attention, because H2S is the main atmospheric pollution that threatens environment and human health. Polyoxometalate (POM) is a kind of novel catalysts due to their controllable and reversible redox properties. Because the properties of ionic liquids (IL) are flexibly adjusted by various cations and anions, thus POM-anions have been attracted attention in an IL context. This project is focused mainly on fabrication polyoxometalate based ionic liquids (POM-IL) which employed as catalysts for desulfurization process of hydrogen sulfide. IL has a good absorption ability of H2S, it make the selectivity for liquid phase reaction of H2S desulfurization is much better than gas phase reaction of the reaction due to the series of inevitable reactions in gas phase reaction could be suppressed. Meanwhile, it could be obtained a purer product in liquid phase reaction based on controlled oxidative capacity. The characteristic of self-separation for POM-IL in the catalytic reaction nor only could avoid catalyst poisoning during the catalytic reaction but also could obtain product by filtration sulfur precipitation for desulfurization process of H2S directly. The preparation of POM-IL with controllable oxidative capacity and recycling characterizes could be achieved through process optimization. Meanwhile, the mechanisms of H2S absorption and catalytic decomposition in POM-IL were investigated via characterization of POM-IL, monitoring the catalytic intermediates, building the reaction kinetics model. These results provide a theoretical and data support for desulfurization of H2S by polyoxometalate based ionic liquids.

H2S由于其严重污染大气环境并对人类的健康造成重大威胁而引起全球的广泛关注。本项目基于对多金属氧酸盐阴离子的氧化能力调控，离子液体对H2S的吸收溶解能力，多酸基离子液体对产物单质硫的自动相分离性质，构建高效、易操作的H2S催化氧化脱硫室温反应体系。多酸基离子液体（POM-IL）催化H2S脱硫液相反应的选择性大大优于气相反应，可抑制气相反应不可避免的连串反应，通过POM-IL氧化能力调控获得比气相反应更纯净的产物。POM-IL的产物自分离特性不仅可避免催化剂中毒，也能直接采用过滤法使产物硫磺从反应体系中分离，获取单质硫。通过对多酸基离子液体组成、催化工艺参数对H2S脱硫率的影响规律及催化动力学研究，实现POM-IL的可控制备以及循环利用，优化催化工艺，揭示功能化多酸基离子液体与H2S的作用机理，为研究多酸基离子液体处理酸性气体提供指导。

硫化氢作为一种有害气体不仅严重地威胁人们的生命安全，还会腐蚀管道与设备，引起催化剂中毒；此外硫化氢还是造成酸雨的主要原因之一。传统脱硫工艺存在着二次污染、催化剂流失等不足，不符合绿色化学理念，因此开发一种新型、绿色、高效的H2S脱硫工艺极具有研究意义与应用价值。本文基于多金属氧酸盐离子液体构建的绿色脱硫体系不仅能同时体现多酸阴离子和有机阳离子的优良特性，还具有催化活性高、产物自分离、可再生循环利用等特点，在探索构建绿色脱硫新工艺领域有很大的研究潜力。. 首先通过常规合成法和一步合成法制备出Keggin型多金属氧酸盐离子液体[C33H32N3]4[α-SiMo12O40]和Dawson型多金属氧酸盐离子液体[C32H68N]4[α-S2W18O62]，采用红外光谱法对离子液体进行表征确定产物结构。再以室温多金属氧酸盐离子离子液体为基础，构建多酸离子液体催化氧化脱硫体系，研究催化剂用量、反应溶剂、反应时间等因素对H2S脱硫率的影响规律。结果表明，外界紫外光激发对两种多酸离子液体的催化脱硫都有促进作用，其中对Keggin型多酸离子液体[C33H32N3]4[α-SiMo12O40]的促进更为显著。溶剂的极性对多酸离子液体的氧化还原性质有较大影响；对于Keggin型多酸离子液体[C33H32N3]4[α-SiMo12O40]，其在不同溶剂中的脱硫率排序如下：乙腈溶剂体系>乙醇溶剂体系>水溶剂体系，其中在乙腈溶剂体脱硫率最高可达到96%。而对于Dawson型多酸离子液体，溶剂中的脱硫率排序如下：乙腈溶剂体系>水溶剂体系>乙醇溶剂体系，其中在乙腈溶剂中的脱硫率最高可达到90%。最后，采用双氧水为氧化剂，进行多酸离子液体催化剂的“恢复”研究，发现双氧水对两种多金属氧酸盐离子液体循环利用的效果都比较理想；Keggin型多酸离子液体经过5次修复后仍具有90%左右的脱硫效率；Dawson型多酸离子液体经过5次修复后仍具有87%的脱硫效率。本文通过研究两种多酸离子液体的H2S脱硫性能，为下一步优化H2S脱硫工艺提供了参考，有效地促进了酸性气体绿色净化与资源化的整体目标的实现。