Cu–Zn–Cr2O3 Catalysts for Dimethyl Ether Synthesis: Structure and Activity Relationship

Abstract

The CuO dispersed on ZnCr 2 O 4 catalysts derived from Cu-Zn-Cr hydrotalcite like layered double hydroxide precursors with varying Zn/Cr ratios have been synthesized, characterized by BET-Surface area, X-ray diffraction (XRD), temperature programmed reduction (TPR), electron spin resonance (ESR), N 2 O titrations and the activities were evaluated for single step dimethyl ether (STD) synthesis from syngas. It is observed that the copper species were in highly dispersed state over Cu-ZnO-Cr 2 O 3 at high Zn/Cr ratios while the copper cluster were present at low Zn/Cr ratios. The ESR analysis revealed signals due to isolated Cu 2+ at high Zn/Cr ratios and clustered Cu 2+ at low Zn/Cr ratio in fresh catalysts and only Cr 3+ species in used catalysts. The TPR results indicated that the reduction peak shifted to high temperatures with an increase in chromium content due to large copper crystallites, which was supported by XRD analysis. The conversion of syngas to DME was well correlated with the copper metal surface areas, indicating that STD synthesis can be controlled by methanol synthesis rate.

The Importance of the Aging Time to Prepare Cu/ZnO/Al2O3Catalyst with High Surface Area in Methanol Synthesis

“…Although there were controversial on the promotional effects of ZnO, it was clearly shown that apparent methanol synthesis rates increased with an increase in Cu surface areas even in the case of the structure-sensitive Cu based catalysts on methanol synthesis. [21][22] Therefore, the importance of Cu surface area cannot be overemphasized in the practical aspect. It has been discussed that the structures of the precursors were related to the final activity of the resulting Cu/ZnO/Al2O3 catalysts.…”

Applications and Preparation Methods of Copper Chromite Catalysts: A Review

“…It is suggested that the sintering of Cu via brass formation could be prevented in Cu-ZnO-Cr2O3 catalysts obtained from Cu-Zn-Cr hydrotalcite-like precursor [179]. Venugopal et al [180] synthesized a series of CuZnO-Cr2O3-Al2O3 (Zn/Cr = 1.2-6.8) catalysts using hydrotalcite like layered double hydroxide precursors for conversions of synthesis gas to dimethyl ether in a single step process. Single step dimethyl ether (DME) synthesis from syngas has technological advantages over the two step process of methanol synthesis (eqn.…”

“…Venugopal et al [180] concluded that the high syngas conversion over Cu:Zn:Cr = 7:6:1.88 (mol ratios) catalyst was attributed to the high copper metal surface area as compared to the other catalysts and higher yields of DME was obtained in single step over a Cu-Zn-Cr (Zn/Cr = 3.3) with γ-Al2O3.…”

Improved Stability of Pd/Al2O3 Prepared from Palladium Nanoparticles Protected with Carbosilane Dendrons in the Dimethyl Ether Steam Reforming Reaction

“…[1,2] In addition, the synthesis gas-to-DME process has been developed recently for the direct synthesis of DME from the product of the gasification of biomass (CO and H 2 ) in a single step, [3][4][5] which thus provides the possibility to obtain hydrogen from a renewable source. One of the most attractive methods to produce hydrogen from renewable bio-derived liquids such as DME and bioalcohols is steam reforming because of its simplicity and high H 2 yield.…”

“…(3)] with the participation of the water gas shift (WGS) reaction [Eq. (4)]. However, other reactions are usually involved, such as DME decomposition [Eq.…”