Ultra-thin ZrO₂ overcoating on CuO-ZnO-Al₂O₃ catalyst by atomic layer deposition for improved catalytic performance of CO₂ hydrogenation to dimethyl ether

Abstract

An ultra-thin overcoating of zirconium oxide (ZrO2) film on CuO-ZnO-Al2O3 (CZA) catalysts by atomic layer deposition (ALD) was proved to enhance the catalytic performance of CZA/HZSM-5 (H form of Zeolite Socony Mobil-5) bifunctional catalysts for hydrogenation of CO2 to dimethyl ether (DME). Under optimal reaction conditions (i.e., 240 °C and 2.8 MPa), the yield of product DME increased from 17.22% for the bare CZA/HZSM-5 catalysts, to 18.40% for the CZA catalyst after 5 cycles of ZrO2 ALD with HZSM-5 catalyst. All the catalysts modified by ZrO2 ALD displayed significantly improved catalytic stability of hydrogenation of CO2 to DME reaction, compared to that of CZA/HZSM-5 bifunctional catalysts. The loss of DME yield in 100 hrs of reaction was greatly mitigated from 6.20% (loss of absolute value) to 3.01% for the CZA catalyst with 20 cycles of ZrO2 ALD overcoating. Characterizations including hydrogen temperature programmed reduction, X-ray powder diffraction, and X-ray photoelectron spectroscopy revealed that there was strong interaction between Cu active centers and ZrO2.

CO2 to dimethyl ether (DME): structural and functional insights of hybrid catalysts

“…15 Recently, Fan et al have adopted the atomic layer deposition (ALD) method to fabricate an ultrathin film of ZrO 2 on CuO/ZnO/Al 2 O 3 and unleased the effect of ZrO 2 coating on the catalytic performances of CuO/ZnO/Al 2 O 3 /H-ZSM-5 catalyst. 80 The highest DME yield of 17.2% achieved at 240 °C and 2.8 MPa is mainly attributed to ZrO 2 -induced enhanced oxygen vacancies, Cu thermal stability, and decreased RWGS reaction. An et al made an effort to improve DME yield by the consideration of a simulated CO 2 hydrogenation process.…”

The lattice oxygen determines the methanol selectivity in CO2 hydrogenation over ZnZrOx catalysts

“…4b, the binding energy of Zn 2p at 1044.8 and 1021.8 eV was assigned to Zn 2+ species. 44 The binding energy centered at 184.2 and 181.8 eV were ascribed to Zr 3d 3/2 and Zr 3d 5/2 of Zr 4+ (Fig. 4c).…”

Atomic/molecular layer deposition strategies for enhanced CO2 capture, utilisation and storage materials

“…452,496 In CO 2 hydrogenation reaction, various metal oxides have also been coated over Zn or Cu-supported catalysts by the ALD technique to enhance methanol selectivity by establishing an interface between the deposited layer and active sites or providing more oxygen vacancies to activate CO 2 molecules. 497,498 Cu NPs enveloped by either a ZnO layer with non-uniformity, a single uniform atomic layer of ZnO, or multiple layers of ZnO on porous silica were investigated in CO 2 hydrogenation. 499 The catalyst activity was found to be directly related to the quantity of metallic sites present.…”