CuZnAl@S-1 Catalyst for the Synthesis of Higher Alcohols by CO Hydrogenation

Abstract

The direct conversion of syngas to ethanol using CuZnAl catalysts is very challenging. In this paper, CuZnAl@S-1, CuZn@S-1, ZnAl@S-1, and CuAl@S-1 catalysts were prepared using a solid-phase method to prepare silicate-1 molecular sieves with Cu, Zn, and Al components encapsulated in them, and their catalytic performance for CO hydrogenation was evaluated in a fixed-bed reaction. The structural and surface properties of the catalysts were characterized using X-ray diffraction, transmission electron microscopy, N2 physisorption, and X-ray photoelectron spectroscopy and correlated with the catalytic performance. The results showed that the use of structurally simple S-1 immobilized CuZnAI nanoparticles (CZA@S-1) was effective in enhancing the conversion of ethanol, where C2+OH/ROH up to 50.63% and ROH selectivity up to 27.27% were achieved, and no deactivation was observed within six days. The characterization results indicate that the interaction between CuZn in the CZA@S-1 catalysts is stronger than that between CuAl and ZnAl, that the CuZn active component is able to supply electrons to the molecular sieve, and that the core–shell structure promotes the adsorption and dissociation of CO and enhances C–C coupling. In situ diffuse reflectance infrared Fourier transform spectroscopy measurements of the reaction intermediates for each catalyst inferred a pathway for C–C coupling to ethanol, which provides an alternative pathway to the CuZnAl conventional catalyst.