A new method for recycling ionic liquids (ILs) from a cellulose spinning process is suggested. The method involves the combination of freeze crystallization and evaporation of H₂O from IL + H₂O mixtures to recycle the ILs. Processes with EmimAc and EmimDep were used as references to develop this IL recycling method. EmimAc + 12.5 wt% H₂O and EmimDep + 4 wt% H₂O were selected for a quantitative mass and energy analysis of the cellulose spinning and IL recycling process (the maximal initial H₂O levels in the ILs + H₂O mixtures for cellulose dissolution were determined experimentally). The energy requirement for the freeze crystallization + evaporation method was compared to evaporation only for recycling of EmimAc and EmimDep. To produce 1 kg dry cellulose fiber, 45.4 MJ and 62.6 MJ are required for recycling EmimAc and EmimDep respectively by the freeze crystallization + evaporation recycling method. Using evaporation only, 66.9 MJ is required for EmimAc recycling and 99.9 MJ for EmimDep recycling per kg cellulose fiber produced. Thus, to fabricate 1 kg dry cellulose fiber using freeze crystallization + evaporation rather than evaporation, 21.5 MJ can be saved for EmimAc and 37.3 MJ for EmimDep recycling. We also show that compared to a classical Lyocell fiber production method using N-methylmorpholine-N-oxide (NMMO) as solvent, use of ILs is energy saving in itself. Hence, significantly less H₂O is required in the cellulose spinning process with ILs than with NMMO, and in turn less H₂O has to be evaporated for the solvent recycling.

中文翻译：

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纤维素纺丝过程中通过冷冻结晶进行离子液体的低能回收

提出了一种从纤维素纺丝工艺中回收离子液体（ILs）的新方法。该方法涉及冷冻结晶和从IL + H ₂ O混合物中蒸发H ₂ O的组合，以回收IL。EmimAc和EmimDep的工艺被用作开发这种IL回收方法的参考。选择EmimAc + 12.5 wt％H ₂ O和EmimDep + 4 wt％H ₂ O进行纤维素纺丝和IL回收过程的定量质量和能量分析（ILs + H _2中的最大初始H ₂ O水平）通过实验确定用于溶解纤维素的O混合物。将冷冻结晶+蒸发方法的能量需求与仅蒸发EmimAc和EmimDep的蒸发进行了比较。要生产1千克干纤维素纤维，需要45.4 MJ和62.6 MJ分别通过冷冻结晶+蒸发回收方法回收EmimAc和EmimDep。仅使用蒸发，每生产一公斤纤维素纤维，EmimAc循环需要66.9 MJ，EmimDep循环需要99.9 MJ。因此，使用冷冻结晶+蒸发而不是蒸发来制造1 kg干纤维素纤维，对于EmimAc可以节省21.5 MJ，对于EmimDep回收可以节省37.3 MJ。我们还表明，与使用N -methylmorpholine- N的经典莱赛尔纤维生产方法相比氧化物（NMMO）作为溶剂，使用离子液体本身就可以节省能源。因此，显著少ħ ₂ O的需要与离子液体比用NMMO纤维素纺丝工艺，进而较少ħ ₂ O具有待蒸发的溶剂回收再利用。