To develop a new and efficient CO2‐to‐methanol catalyst is of extreme significance but still remains a challenge. Herein, an innovative indirect two‐step strategy is reported to synthesize a highly efficient capsule‐structured copper‐based CO2‐to‐methanol catalyst (CZA‐r@CZM). It consists of a structurally reconstructed millimeter‐sized Cu/ZnO/Al2O3 core (CZA‐r) with intensified Cu–ZnO interactions, which is made by a facile hydrothermal treatment in an alkaline aqueous solution, and a Cu/ZnO/MgO (CZM) shell prepared by an ethylene glycol‐assisted physical coating method. The CZA‐r core displays 2.7 times higher CO2 hydrogenation activity with 2.0 times higher CO selectivity than the previously reported Cu/ZnO/Al2O3 (CZA‐p), whereas the CZM shell can efficiently catalyze hydrogenation of the as‐formed CO from the CZA‐r core to methanol as it passes through the shell. As a result, the developed capsule‐structured CZA‐r@CZM catalyst exhibits 2.4 times higher CO2 conversion with 1.8 times higher turnover frequency and 2.3‐fold higher methanol space–time yield than the CZA‐p catalyst (729.8 vs. 312.6 gMeOH kgcat−1 h−1). In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTs) experiments reveal that the CO2 hydrogenation reaction proceeds through a reverse water–gas shift reaction followed by a CO hydrogenation pathway via an *H3CO intermediate. This work not only produces an efficient CO2‐to‐methanol catalyst, but also opens a new avenue for designing superior catalysts for other consecutive transformations.
This work reports a highly efficient capsule‐structured CuO−ZnO−Al2O3@HZSM‐5 (CZA@HZSM‐5‐EtOH) core‐shell catalyst for the direct conversion of syngas to dimethyl ether by a facile physical coating method with ethanol as a binder through coating micrometer‐sized HZSM‐5 shell on the prior‐shaped millimeter‐sized CZA core, it shows 2.9 times higher CO conversion with the 2.7 times higher turnover frequency and 9.2 times higher dimethyl ether space‐time yield of the CZA@HZSM‐5‐SS catalyst prepared by a similar process but with silica sol as a binder (315.5 vs 34.3 gDME kgcat−1 h−1). The relationship between the structure and performance was explored by a variety of characterization techniques including X‐ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X‐ray diffraction (XRD), ammonia temperature programmed desorption (NH3‐TPD), nitrogen adsorption‐desorption, H2‐temperature‐programmed reduction (H2‐TPR) and H2‐TPR after oxidation of the samples by N2O. CZA@HZSM‐5‐EtOH can be considered as a highly efficient and practical catalyst for dimethyl ether synthesis from syngas. This work presents a new avenue to design other bifunctional catalysts for the cascade reactions in which the raw materials can be converted into an intermediate over the core and then the as‐formed intermediate over the core can be subsequently converted into the final product.
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