Lamberti Fabio M, Román-Ramírez Luis A, Dove Andrew P, Wood Joseph
School of Chemical Engineering, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
Division of Chemical and Energy Engineering, London South Bank University, 103 Borough Road, London SE1 0AA, UK.
Polymers (Basel). 2022 Apr 26;14(9):1763. doi: 10.3390/polym14091763.
Polylactic acid (PLA) is a leading bioplastic of which the market share is predicted to increase in the future; its growing production capacity means its end-of-life treatment is becoming increasingly important. One beneficial disposal route for PLA is its chemical recycling via alcoholysis. The alcoholysis of PLA leads to the generation of value-added products alkyl lactates; this route also has potential for a circular economy. In this work, PLA was chemically recycled via methanolysis to generate methyl lactate (MeLa). Four commercially available catalysts were investigated: zinc acetate dihydrate (Zn(OAc)), magnesium acetate tetrahydrate (Mg(OAc)), 4-(dimethylamino)pyridine (DMAP), and triazabicyclodecene (TBD). Dual catalyst experiments displayed an increase in reactivity when Zn(OAc) was paired with TBD or DMAP, or when Mg(OAc) was paired with TBD. Zn(OAc) coupled with TBD displayed the greatest reactivity. Out of the single catalyst reactions, Zn(OAc) exhibited the highest activity: a higher mol% was found to increase reaction rate but plateaued at 4 mol%, and a higher equivalent of methanol was found to increase the reaction rate, but plateaued at 17 equivalents. PLA methanolysis was modelled as a two-step reversible reaction; the activation energies were estimated at: = 25.23 kJ∙mol, = 34.16 kJ∙mol and = 47.93 kJ∙mol.
聚乳酸（PLA）是一种领先的生物塑料，预计其市场份额在未来会增加；其不断增长的生产能力意味着其生命周期末期的处理变得越来越重要。PLA的一种有益处置途径是通过醇解进行化学回收。PLA的醇解会产生增值产品乳酸烷基酯；这条途径也具有循环经济的潜力。在这项工作中，PLA通过甲醇解进行化学回收以生成乳酸甲酯（MeLa）。研究了四种市售催化剂：二水合醋酸锌（Zn(OAc)）、四水合醋酸镁（Mg(OAc)）、4-（二甲基氨基）吡啶（DMAP）和三氮杂双环癸烯（TBD）。双催化剂实验表明，当Zn(OAc)与TBD或DMAP配对时，或者当Mg(OAc)与TBD配对时，反应活性会增加。Zn(OAc)与TBD配对时显示出最大的反应活性。在单催化剂反应中，Zn(OAc)表现出最高的活性：发现较高的摩尔百分比会提高反应速率，但在4摩尔百分比时趋于平稳，并且发现较高当量的甲醇会提高反应速率，但在17当量时趋于平稳。PLA甲醇解被模拟为两步可逆反应；估计的活化能为： = 25.23 kJ∙mol， = 34.16 kJ∙mol和 = 47.93 kJ∙mol。
