One-Pot Synthesized Fe-AEI Zeolite Catalysts Contribute to Direct Oxidation of Methane

Abstract

CH4 and N2O are the two largest greenhouse gases after CO2. Conversion of CH4 with N2O to value-added and clean chemicals contributes to endurable development. Fe-containing zeolite catalysts, especially small-pore zeolites, are widely used and highly active in both methane conversion and N2O decomposition. The combination of direct conversion of CH4 with N2O to value-added chemicals on Fe-containing zeolite catalysts can effectively alleviate the environmental and energy problems of growing greenhouse gas emissions and the increasing demand for chemicals. Herein, we have successfully developed a method for directly and facilely crystallizing the Fe-containing aluminosilicate AEI-type zeolites (Fe-AEI) with varied Si/Fe ratios by the inter zeolite conversion method from FER zeolite. The Fe states have been carefully characterized by UV-vis, X-ray absorption spectroscopy, NO adsorption Fourier transform infrared (FTIR) spectroscopy, CO adsorption FTIR, and HADDF-STEM to demonstrate their highly dispersed properties. Thus, obtained one-pot synthesized Fe-AEI zeolites were applied to directly oxidize methane with N2O. The reaction conditions including the Si/Fe ratio, reaction temperature, ratio of CH4/N2O in feed, and H2O flow rate in feed were inspected. The catalytic activity of one-pot synthesized Fe-AEI zeolites was compared with the Fe-exchanged AEI (Fe/AEI) zeolites; the Fe-AEI zeolites exhibited much better activity due to the highly dispersed Fe species in Fe-AEI zeolites. Finally, a conceivable reaction pathway was provided based on the reaction results and FTIR spectra.