利用再生PET、PLA與CO2之化學轉化與催化研究

Abstract

摘要 聚對苯二甲酸乙二醇酯（PET）是日常生活的重要組成部分。 然而，由於PET不易自然降解，生態系統中的大量生命在廢棄塑料中游泳，造成了嚴重的環境災難。 通過醣酵解（一種化學回收方法），PET 大部分被回收為對苯二甲酸雙（2-羥乙基）酯 (BHET) 單體。 BHET 聚合回預聚物 (~25-35 DPn)，然後縮聚以獲得更高的分子量，因此是一種能源密集型且成本低效的方法。 這項研究表明，在溫和的反應條件下，使用氨基醇 (AmOH) 進行 rPET 醣酵解，可生成 DPn 值約為 30 的低聚對苯二甲酸乙二醇酯 (OET)，收率高達 98%； 180℃溫度，常壓，具有可回收性。 通過從生成的 OET 中製備 rPET 來結束 PET 到 PET 的循環。 對苯甲酸甲酯（EG）的比較模型研究揭示了 AmOH 相對於 Hünig 鹼的效率； N,N-乙基二異丙胺 (DIPEA) 儘管鹼性更強。 同樣，N-丁基-N-甲基丁烷-1-胺 (MDBA) 的 PET 轉化速度比甲基二乙醇胺 (MDEA) AmOH 慢。 儘管 MDEA 等 AmOH 也充當親核試劑並添加到聚合物鏈中，但令我們驚訝的是，我們的 NMR 研究表明沒有 AmOH 插入的跡象，表明 AmOH 可能起到催化劑的作用。 在不同反應條件下進行的形態學研究揭示了OET的生成方法。 計算研究和動力學同位素研究解釋了 AmOH 羥基在降解過程中的促進作用。 根據收縮核心模型，計算出的降解活化能估計為 45.4 kJ mol-1。 此外，更大規模地進行了rPET酯交換成聚對苯二甲酸丁二醇酯(PBT)的反應。 合成的PBT預聚物的收率為94%。 氨基醇也被認為是降解聚乳酸（PLA）的潛在有機催化劑。 該反應在不使用任何有害溶解溶劑的情況下進行。 使用乙二醇作為酯交換反應促進劑，解聚反應在 130℃、90 分鐘的反應時間內在溫和的反應條件下產生乳酸酯。 隨着反應溫度的降低，乳酸酯的收率保持在~80%。 在 2-惡唑烷酮一鍋法合成中利用分子篩 (MS) 促進二氧化碳 (CO2) 的有效方法。 CuI/MS系統以水為反應介質，在1個大氣壓的CO2下進行芳基乙炔、芳基醛和芳基胺之間的環化反應。 4 Å 分子篩促進羧化並改善 CO2 捕獲，從而產生高產率的產品。

Abstract Polyethylene terephthalate (PET) is an essential component of daily life. However, due to PET’s resistance to natural degradation, a plethora of life in the ecosystem is swimming in discarded plastic, causing a serious environmental disaster. Using glycolysis, a chemical recycling method, PET is largely recycled to bis(2-hydroxyethyl) terephthalate (BHET) monomers. BHET is polymerized back to a pre-polymer (~25-35 DPn) followed by polycondensation for higher molecular weight, hence an energy-intensive and cost-inefficient method. This study demonstrates glycolysis of rPET using Amino alcohols (AmOH’s) for generating oligoethylene terephthalate (OET) of DPn value of ~30 in high yields (98%) under mild reaction conditions; 180 °C temperature, atmospheric pressure, with recyclability. PET-to-PET cycle was closed by preparing rPET from generated OETs. A comparative model study on methyl benzoate (in EG) revealed the efficiency of AmOH’s over Hünig’s base; N, N-Ethyldiisopropylamine (DIPEA) despite being more basic. Similarly, N-Butyl-N-methylbutane-1-amine (MDBA) demonstrated slower rPET conversion than Methyl diethanolamine (MDEA) AmOH. Although AmOH’s such as MDEA also act as nucleophile and add to the polymer chain, to our surprise, our NMR studies revealed that there is no sign of insertion of AmOH’s indicating that the AmOH’s may function as catalysts. Morphological studies conducted under different reaction conditions unveiled the method of OET generation. The computational studies and Kinetic Isotopic studies explained the facilitation of the hydroxy group of AmOH in the degradation. Following the shrinking core model, the calculated activation energy for degradation was estimated to be 45.4 kJ mol-1. Furthermore, the transesterification of PET into Polybutylene terephthalate (PBT) was conducted at a larger scale. The yield of synthesized PBT pre-polymer was recorded to be 94%. Amino alcohols are also presented as potential organic catalysts to degrade polylactic acid (PLA). The reactions were employed without using any harmful dissolving solvent. The depolymerization reactions produced lactate esters under mild reaction conditions at 130 °C in 90 minutes of reaction time using ethylene glycol as a transesterification reaction promotor. The yield of lactate ester remained ~80% with the decrease in reaction temperature. An efficient way of utilizing molecular sieves (MS) to promote carbon dioxide (CO2) in a one-pot synthesis of 2-oxazolidinone. Water as a reaction medium is used in the CuI/MS system for the cyclization reaction between arylacetylene, arylaldehyde, and arylamine under 1 atmospheric pressure of CO2. The 4 Å molecular sieves facilitated the carboxylation and improved CO2 capture to generate products with high yields.