Quantification of Exchanged Copper Species in Cu-Chabazite Zeolite using Cryogenic Probe Infrared Spectroscopy

The development of a low temperature (-160 degrees C) NO adsorption technique is disclosed that avoids the chemical conversion of the probe molecule at room temperature. The observed IR peaks for Cu+(NO)(2) and Cu2+(NO) species can be used to quantify the amount of exchanged copper species in a broad range of samples, including a wash-coated honeycomb. Calibration curves for Cu+(NO)(2) and Cu2+(NO) are determined for copper loadings up to 3.99 wt% with Silica-to-Alumina Ratio (SAR) of 16-22, and quantitative agreement with the complementary hydrogen Temperature Programmed Reduction (H-2-TPR) results is established. This methodology allows to identify different Cu species in Cu-CHA, such as Z(2)Cu(II), Z(1)Cu(II)OH and Cu dimers, based on their distinct IR signatures. In addition, the perturbed T-O-T framework vibration - characterized at 400 degrees C - can also be used as a complimentary method to quantify Z(2)Cu(II) species.

Automated summary

A low temperature NO adsorption technique was developed to quantify different copper species in various samples, and distinguish different Cu species in Cu-CHA based on their distinct IR signatures.