Highly Efficient Ethanol Upgrading to Higher Alcohols over Surface Acidity-Enhanced Cu-Based Catalysts

Currently, the economic and environmental benefits of a C–C coupling technique for upgrading ethanol to produce higher alcohols call for improved performance of catalysts due to limitations such as low reaction efficiency, high byproduct selectivity, and easy catalyst deactivation. Meanwhile, there exists a lack of understanding of the roles of active sites on catalysts, especially surface acid sites, in ethanol conversion. Herein, we developed new and cost-effective metal phosphate-supported copper catalysts. Cu-support interactions were shown to impact the dispersion and reduction of copper species. Compared to Cu/CePO4 and Cu/AlPO4, the Cu/LaPO4 catalyst having a higher copper surface area and a higher Cu+ content exhibited stronger ethanol dehydrogenation activity and achieved a considerably high selectivity of higher alcohols (81.0%) at 74.5% ethanol conversion at 250 °C, as well as a much higher space-time yield of higher alcohols (37.2 mmol·gcat–1·h–1) surpassing those for Cu-based catalysts previously reported. It was revealed that the proper ratio of acidic sites to Cu0 sites and high ratio of Lewis acid sites to Brønsted acid sites on Cu-based catalysts were conducive to ethanol dehydrogenation and C–C coupling of acetaldehyde with the help of Lewis acid sites, highlighting the metal-acid synergistic catalytic effect. This study offers a reference for designing high-performance Cu-based catalysts for the efficient upgrading of ethanol to produce higher alcohols.