Upgrading of PET to CHDM over base metal catalysts via tandem processes

1,4-cyclohexanedimethanol (CHDM), which has similar structural units to PET (polyethylene terephthalate), is a crucial polyester monomer. Therefore, PET can be directly oriented to synthesize CHDM through tandem alcoholysis and selective hydrogenation. However, use of precious metal catalysts such as Pd or Ru catalyst limits the industrial application. Herein, we developed a new process that converts PET into CHDM in mixed solvent of CH₃OH-1,4-dioxane via tandem three-step reactions without the involvement of precious metal catalysts or any separation or purification, including the methanolysis of PET to obtain dimethyl terephthalate (DMT) first, then DMT was hydrogenated over a NiLa-40wt% catalyst to form the intermediate dimethyl 1,4-cyclohexanedicarboxylate (DMCD), followed by the further hydrogenolysis of DMCD to CHDM over a Cu₁Fe₁Al_0.5 catalyst to yield CHMD with an overall CHDM yield of .90.2 %. Importantly, the final product CHDM could be separated easily just by distillation because there is a significant difference in the boiling point of CHDM with the by-products.