PO43– coordinated Co2+ species on yttrium phosphate boosting the valorization of ethanol to butadiene

Upgrading of sustainable ethanol into C4 olefins by C–C coupling contributes to alleviating the dependency towards petroleum. The reaction network consists several key steps, whereas dehydration often competes with dehydrogenation over acidic catalyst. Herein, we report a designed bifunctional Co-YPO4 catalyst with balanced active sites for dehydrogenation and condensation that can directly catalyze ethanol to butadiene. The YPO4 can stabilize Co2+ species to form highly dispersed [Co-O-P] sites, which catalyze ethanol dehydrogenation to acetaldehyde. Additionally, the YPO4 surface exposed Y3+ site, as Lewis acid center, which can effectively catalyze C–C coupling reaction. The addition of cobalt enhances the ethanol dehydrogenation process while reducing the surface acidity, thus inhibiting the formation of dehydration products and promoting the formation of butadiene. Kinetic measurements suggest that the rate-limiting step is the dehydrogenation of ethanol to acetaldehyde. The synthesized Co-YPO4 shows a 68.5% selectivity of butadiene under a conversion of 78.2% at 350°C and a weight hourly space velocity of 1.0 gC2H5OH·gCat.–1·h–1.