In situ analytical investigation of redox behavior of Cu-ZSM-5 catalysts

The utilization of in situ 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 O-2, H2O2 or O-2(-) 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.