Selective Upcycling of Polyethylene Terephthalate towards High‐valued Oxygenated Chemical Methyl p‐Methyl Benzoate using a Cu/ZrO<sub>2</sub> Catalyst
Jianian Cheng, Jin Xie, Yongjie Xi, Xiaojing Wu, Ruihui Zhang, Zhihe Mao, Hongfang Yang, Zelong Li, Can Li
Abstract
Abstract Upgrading of polyethylene terephthalate (PET) waste into valuable oxygenated molecules is a fascinating process, yet it remains challenging. Herein, we developed a two‐step strategy involving methanolysis of PET to dimethyl terephthalate (DMT), followed by hydrogenation of DMT to produce the high‐valued chemical methyl p‐methyl benzoate (MMB) using a fixed‐bed reactor and a Cu/ZrO 2 catalyst. Interestingly, we discovered the phase structure of ZrO 2 significantly regulates the selectivity of products. Cu supported on monoclinic ZrO 2 (5 %Cu/m‐ZrO 2 ) exhibits an exceptional selectivity of 86 % for conversion of DMT to MMB, while Cu supported on tetragonal ZrO 2 (5 %Cu/t‐ZrO 2 ) predominantly produces p‐xylene (PX) with selectivity of 75 %. The superior selectivity of MMB over Cu/m‐ZrO 2 can be attributed to the weaker acid sites present on m‐ZrO 2 compared to t‐ZrO 2 . This weak acidity of m‐ZrO 2 leads to a moderate adsorption capability of MMB, and facilitating its desorption. Furthermore, DFT calculations reveal Cu/m‐ZrO 2 catalyst shows a higher effective energy barrier for cleavage of second C−O bond compared to Cu/t‐ZrO 2 catalyst; this distinction ensures the high selectivity of MMB. This catalyst not only presents an approach for upgrading of PET waste into fine chemicals but also offers a strategy for controlling the primary product in a multistep hydrogenation reaction.