(74a) Process Systems Engineering Of Ionic Liquids

Ionic liquids (ILs) have been studied extensively as green solvents since the end of last century. The particular features and unique properties of ionic liquids make them have great potentials to be solvents, catalysts, electrolytes, coating materials and so on.  Due to the serious and long-term pollutions caused by the conventional volatile organic solvents, replacement of conventional solvents by ILs is regarded with large benefits for sustainable and green chemistry ¹. Owe to their excellent solubilities in supercritical CO₂, the catalytic products are easily to be separated from reactants in an homogeneous catalysis system ². Lower volatility and high absorption capacity make ILs be promising candidates for carbon capture ³, Coating ILs on some solid materials like polymer membrane, or synthesis poly-ionic liquid membrane, can improve the selectivities of gas separation so as to reduce the separation energy consumption ^{4, 5}. It was reported that Ionic liquids showed good performance as a recyclable catalyst for cycloaddition of CO₂⁶ and for the degradation of waste polymer ⁷. Recently, electroreduction of CO₂ which is a key component of artificial photosynthesis, has been proved that using ILs electrolyte can reduces CO₂ to CO at overpotentials below 0.2 volt which is just slightly above the minimum voltage of 1.33 volts ⁸. In addition, physicochemical properties of ILs and modeling of ILs-based process have been studied extensively, which provides basic knowledge on applications of ILs ^9-12. These achievements show the promising industrial applications of ionic liquids, but also raise questions. The most arresting question is whether these processes can be commercialized in the near future; however, it is hard to find an answer.

Getting answerers to this question as early as possible is important and necessary, not only for researchers, but also for industries. We should not be expected to obtain completely final study results before we know the possibilities or the feasibilities of new IL-based processes. Hence, we propose the concept of ‘Process Systems Engineering of Ionic Liquids’ with the aim of investigating the advantages and drawbacks as well as the feasibilities of a new IL-based process, here we highlight the whole system rather than a single unit or a substance, and also take into account the whole life cycle rather than a short period.  Thus, the key point of the concept is that it includes two dimensions, i.e., a spatial dimension and a temporal dimension. The former indicates the evaluated system including the whole facilities involved and the concept from molecular scale to process scale, while the latter means a whole life cycle should be considered, from resource extraction, IL production, IL utilization, IL recovery and degradation. The second point is the definition of the evaluation criteria, some are quantitative and some are qualitative, and also should be derived from the viewpoints of both academy and industry. Generally, these criteria include different aspects depending on the different requirements, such as energy efficiency, atom utilization efficiency, economic and environmental performance, and the potential risks. Moreover, how to build strict and robust models for simulation, prediction and optimization of basic properties, units, processes, costs, and environmental performance will still be a challenge.

With the methodology, some specific cases, such as carbon capture with IL, IL-based catalytic reaction, are studied. The results will be very useful for the development of new ionic liquid processes. It is also quite valuable to connect chemists with chemical engineers and promote a new idea from laboratory to br used in industries. 

*Corresponding information: Email: sjzhang@home.ipe.ac.cn; Tel/Fax: 0086-10-82627080

Acknowledgements

We would like to acknowledge the support from Key Program of National Natural Science Foundation of China (No.21036007), the National Natural Science Foundation of China (No. 51274183), and Science and Technology Innovation  "Cross and Cooperation Team" of Chinese Academy of Sciences (2013.1).

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