High efficiency of phenol oxidation in a structured fixed bed over Cu-ZSM-5/PSSF prepared by ion-exchanged method

Abstract

Cu-ZSM-5 zeolite membrane catalysts coating on paper-like sintered stainless fibers (PSSF) were prepared by ion-exchanged method for the catalytic wet peroxide oxidation (CWPO) of phenol in a structured fixed bed reactor. Firstly, two types of Cu-ZSM-5/PSSF catalysts were synthesized by ion-exchanged and impregnation methods. Then, the structures and properties of the catalysts were characterized by SEM, EDS mapping, BET, FT-IR, UV–vis, H2-TPR and XPS, respectively. The SEM results showed that the continuous and compact ZSM-5 membrane (about 5 μm in average thickness) was coated well over the PSSF surface. The XPS results indicated that the catalyst prepared by ion exchanged method had more amount of Cu+ species and more lattice oxygen than that of the catalyst prepared by impregnation. In addition, the CWPO performance of phenol was independently conducted in the structured fixed bed composed of the two Cu-ZSM-5/PSSF catalysts. The experimental results showed that the phenol was entirely eliminated, and high TOC conversion (80%), CO2 selectivity (around 80%) as well as low total copper leaching rate (about 23%) were obtained over the catalyst prepared by ion-exchanged method, while TOC conversion of 51%, CO2 selectivity of 52% and high total copper leaching rate (about 60%) were achieved over the catalyst prepared by impregnation method. Finally, good durability with low Cu leaching concentration (only about 17 ppm) and complete phenol conversion were obtained after continuously operating 11 h. Meanwhile, the loss of Cu+ active component and hard coke formations over the catalysts prepared by ion-exchanged method were primary reason for the deactivation.