Atomically dispersed Co2+ on MgAlOx boosting C4-10 alcohols selectivity of ethanol valorization

Catalytic upgrading of biomass-derived ethanol to C4+ compounds through C-C coupling is an essential green and sustainable approach towards value-added fine chemicals. Developing catalysts to improve the selectivity of C4+ compounds is highly desired due to the complex transformation of ethanol affording diverse species. Here, we report atomically dispersed Co2+ on MgAlOx as catalysts derived from layered double hydroxide (LDH) precursors for the dehydrogenation coupling of ethanol to C4-10 alcohols. The selectivity for C4-10 alcohols reaches 95.4% with 32.9% ethanol conversion over the optimal catalyst, Co0.15Mg2.85AlOx, at 523 K and 0.1 MPa. A yield of 31.4% is greatly higher than that (similar to 15%) over most of the state-of-the-art catalysts. Characterization techniques including XRD, XPS, UV-Vis and CO-IR reveal that the atomically dispersed Co2+ in the lattice of MgAlOx is originated from the replacement of Mg in the LDH precursor and remain stable during the reactions. Both increments of basic and acid sites are observed after Co2+ replacement according to the TPD-MS measurements of CO2 and NH3. The introduction of an appropriate amount of Co2+ effectively facilitates the dehydrogenation step, thus, high activity under milder conditions. Meanwhile, abundant basic and acid sites boost the following aldol condensation step resulting in ultra-high C4-10 selectivity. These findings can shed light on sustainable heterogeneous catalytic processes.