Grause Guido, Sutton Joseph, Dove Andrew P, Mitchell Niall A, Wood Joseph
School of Chemical Engineering, University of Birmingham, Edgbaston, Birmingham B15 2TT, U.K.
School of Chemistry, University of Birmingham, Edgbaston, Birmingham B15 2TT, U.K.
Cryst Growth Des. 2024 Aug 23;24(17):7306-7321. doi: 10.1021/acs.cgd.4c00984. eCollection 2024 Sep 4.
The chemical recycling of poly(ethylene terephthalate) (PET) is very attractive as PET bottle waste provides an abundant clean material with low levels of additives. One of the most promising processes is glycolysis, which depolymerizes PET in the presence of ethylene glycol. For this process, it is necessary to think through the whole concept, from the waste material to the newly polymerized virgin polymer. Most research ends with determining the yield of bis(2-hydroxyethyl)terephthalate (BHET) after glycolysis. Some research includes antisolvent crystallization with water to separate BHET from ethylene glycol. However, the subsequent separation of water and ethylene glycol is an energy-intensive process. Therefore, this work aims to directly crystallize BHET from ethylene glycol. For this reason, the crystallization of BHET was investigated experimentally. Crystallization was simulated using gPROMS Formulated Products with the aim of estimating kinetic parameters and using these to optimize an industrial process. Kinetic parameters were determined by model validation, including primary and secondary nucleation and crystal growth. The best-fitting set of kinetic parameters was used to optimize BHET crystallization in batch and continuous modes by minimizing equipment costs. Impeller parameters were found to have a great influence on crystallization performance. Ultimately, the continuous and batch processes gave comparable results in terms of equipment cost, with the batch process giving larger crystals and higher yields but the continuous process requiring a smaller crystallizer.
聚对苯二甲酸乙二酯（PET）的化学循环利用极具吸引力，因为PET瓶废料能提供一种添加剂含量低的丰富清洁材料。最有前景的工艺之一是乙二醇解，该工艺在乙二醇存在的情况下使PET解聚。对于此工艺，有必要全面考虑整个概念，从废料到新聚合的原生聚合物。大多数研究止于确定乙二醇解后双（2 - 羟乙基）对苯二甲酸酯（BHET）的产率。一些研究包括用水进行反溶剂结晶以从乙二醇中分离BHET。然而，随后水和乙二醇的分离是一个能源密集型过程。因此，这项工作旨在直接从乙二醇中结晶出BHET。出于这个原因，对BHET的结晶进行了实验研究。使用gPROMS配方产品对结晶进行模拟，目的是估算动力学参数并利用这些参数优化工业过程。通过模型验证确定动力学参数，包括初级和次级成核以及晶体生长。通过使设备成本最小化，使用最佳拟合的动力学参数集对间歇和连续模式下的BHET结晶进行优化。发现搅拌器参数对结晶性能有很大影响。最终，在设备成本方面，连续和间歇过程得到了可比的结果，间歇过程得到的晶体更大且产率更高，但连续过程需要的结晶器更小。
