Effective conversion of CO2 into light olefins over a bifunctional catalyst consisting of La-modified ZnZrOx oxide and acidic zeolite

Effectively promoting the formation of methanol intermediates is the key to improve the catalytic performance of a bifunctional catalyst in CO2 hydrogenation to light olefins. Herein, a series of lanthanum (La) modified zinc-zirconium oxides (ZnZrOx(nLa)) were prepared by a one-pot sol-gel method with glucose as the complexing agent. The results indicate that ZnZrOx(nLa) gives higher methanol selectivity and CO2 conversion than those on ZnZrOx in CO2 hydrogenation. XRD, Raman, N-2 sorption, TEM/HRTEM, XPS, CO2/H-2-TPD and in situ DRIFT spectroscopy measurements confirm that the addition of an appropriate amount of La can induce the formation of more oxygen vacancies on the surface of ZnZrOx, hence promoting the adsorption and activation of CO2, as well as the generation of more formate and methoxy intermediates. Upon coupling with acidic zeolites, the methanol intermediates generated on ZnZrOx(nLa) are rapidly converted into light olefins over the acid sites. As a result, ZnZrOx(0.3La)/H-SAPO-34 and ZnZrOx(0.3La)/H-SAPO-18 composite catalysts show a C-2(=)-C-4(=) selectivity in hydrocarbons as high as 83.2% and 77.5%, respectively, despite their light olefin distribution being different, due to the variation of the acid strength and strong acid content between H-SAPO-34 and H-SAPO-18.

Automated summary

This study demonstrates that modifying zinc-zirconium oxides with lanthanum can effectively promote the formation of methanol intermediates, leading to improved catalytic performance in CO2 hydrogenation to light olefins. The addition of lanthanum induces the formation of more oxygen vacancies on the surface of the catalyst, facilitating the adsorption and activation of CO2 and the generation of methanol intermediates. Coupling with acidic zeolites allows for the rapid conversion of the methanol intermediates into light olefins. The composite catalysts exhibit high selectivity for C-2(=)-C-4(=) hydrocarbons.