水合物法分离气体的促进剂及促进机理研究进展

Research progress of promoters and promoting mechanisms for hydrate-based gas separation

目前添加促进剂后水合物形成机理并无统一定论,本文详细阐述了气体水合物形成的降低表面张力理论、临界胶束理论、毛细效应理论、模板效应理论和表面疏水效应理论等促进机理,综述了传统促进剂(THF、CP、SDS)、生物环保型促进剂(氨基酸、淀粉),尤其是离子液体在气体水合物形成相平衡实验、动力学规律和促进机理方面的应用研究进展,阐述了离子液体半笼型水合促进剂在混合气体分离方面的研究现状,指出应从促进剂结构性质及其在水相中的聚集形态入手,研究促进剂−气体−水之间的分子间作用力,建立各类气体水合物促进剂的筛选体系.

Unconventional natural gas is a type of high-quality clean energy,which often contains some gases as impurities that cause reductions in its combustion heat value and utilization efficiency.Therefore,developing gas separation technologies to remove or separate these impurity gases and concentrate methane content is necessary.As a newly emerging gas separation technology,hydratebased gas separation technology currently requires exploration on ways to greatly increase hydration rate to promote its industrial application.Screening green and environmentally-friendly promoters has become a research hotspot in recent decades.Amino acids,starch,and other biological substances have attracted much attention owing to their wide accessibility and environmental protection.Ionic liquids(ILs),which are a new type of lowly volatile and recyclable solvents,exhibit excellent performance in promoting gas hydrates formation and growth.Furthermore,ILs exhibit adjustable and controllable structures,which make them potential promoters in hydrate-based gas separation.Presently,no universally recognized theory on hydrate formation mechanism exists for various promoters.In this paper,different promotion mechanisms of gas hydration were described and discussed in detail,which included surface tension reduction theory,critical micelle theory,capillary effect theory,template effect theory,and surface hydrophobic effect theory.Both traditional promoters(e.g.,THF,CP,and SDS)and bio-environmental promoters(e.g.,amino acids and starch)were reviewed in the terms of gas hydration equilibrium condition,dynamic regularity,and hydrates-acceleration mechanisms.Particularly,the application of ILs,which are a type of semi-clathrate promoter,in gas hydration was elaborated.Study on the structural properties of promoters,their aggregation morphology in water,and intermolecular interactions between ILs,gases,and water is necessary for the establishment of a promoter-screening system for various gas hydrations.