Ethanol as a Binder to Fabricate a Highly‐Efficient Capsule‐Structured CuO−ZnO−Al₂O₃@HZSM‐5 Catalyst for Direct Production of Dimethyl Ether from Syngas

Abstract

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.

Catalytic Conversion of Carbon Oxides in Confined Spaces: Status and Prospects

“…In order to possibly avoid the destroying effect of coating zeolite, the physical coating method was proposed. [108][109][110] In this approach, the as-prepared SAPO-11 zeolite is physically coated on the millimetre-sized CuZnAl core by using silica sol as a binder. It produces 90.3 % of DME selectivity for syngas-to-DME owing to the intensified tandem reaction by confined effect of well-organized structure.…”

“…Furthermore, the compressed methanol dehydration of methanol over the ZA@HZSM-5-SS also lowers the CO conversion due to the thermodynamic equilibrium limitation. [110] This work not only generates an excellent CO-to-DME capsule catalyst, but also presents a new method for fabricating highly-efficient core-shell catalysts by a physical coating method for diverse tandem transformations.…”

Core/yolk-shell nanoreactors for tandem catalysis

“…1(c)) [29]. A series of catalysts were successfully prepared by this method, including Fe-Zn-Zr-T@HZSM-5 [30], CuZnZr@(Zn-)SAPO-34 [31], CuO-ZnO-Al2O3@HZSM-5 [32], CuO-ZnO-ZrO2@SAPO-11 [33], Zn-Cr@SAPO [34]. This method eliminates the damage to the internal metal core by the hydrothermal process.…”

“…H-ZSM-5 with more abundant acid sites was also chosen as a kind of great DME synthesis candidate. Guo et al [32] developed a highly efficient core-shell CuO-ZnO-Al2O3@H-ZSM-5 (CZA@H-ZSM-5-EtOH) nanoreactor for the direct STD reaction through PhyC strategy with the help of a variety of binders. While used methanol as binder, CZA core could not firmly be attached to H-ZSM-5 shell owing to the lower viscosity.…”

Synthesis, Types, and Applications of Zeolite Capsule Catalysts

“…In addition, it was found that, [ 105 ] compared with silica sol, ethanol showed relatively good binding properties, which eliminated the barrier effect of SiO 2 layer between core and shell on reactants entering active sites when silica sol was used as a binder, and it was expected to become a new binder instead of silica sol. Other binders (methanol and ethylene glycol) have unsatisfactory bonding effect, too low viscosity of methanol cannot make molecular sieve adhere to metal oxide, while too high viscosity of ethylene glycol can make molecular sieve separate from the surface of metal particles.…”