Insitu analytical investigation of redox behavior of Cu-ZSM-5 catalysts

Abstract

The utilization of insitu DRIFT spectroscopy combined with advanced thermoanalytical techniques (temperature programmed decomposition, TPDE; temperature programmed oxidative decomposition, TPOD) allows the characterization of redox behavior of copper ions inside ZSM-5 zeolites. The oxidation of carbonaceous impurities inside the solid matrix to CO and CO₂ is demonstrated to be responsible for Cu(II)→Cu(I) reduction, since the formation of other oxidation products, namely O₂, H₂O₂ or O₂^- ions, was not detected by mass spectrometry and DRIFT. The unusual kinetics of CO evolution in thermoanalytical experiments was attributed to the formation of a relatively stable Cu⁺···CO adduct characterized by a typical IR band at 2157 cm^-1, which acts as a specific active site of a chromatographic adsorbent material.