Reshaping the Role of CO2 in Propane Dehydrogenation: From Waste Gas to Platform Chemical

Abstract

The valorization of CO2 appeals to the chemical industry due to the reduction in greenhouse gas emissions and the ability to offer more renewable products. Propylene production is the second largest process in the chemical industry, and it strongly depends on fossil fuel feedstocks. Coupling CO2 reduction with propane dehydrogenation boosts conversion and produces CO, a valuable platform chemical currently synthesized by fossil-methane reforming. In this work, (i) we demonstrate the environmental benefits of coupling CO2 with a life-cycle assessment under industrial conditions, potentially reducing emissions by 3 tCO2-eq per ton of propylene produced. (ii) We screen supported catalytic materials─both known and novel─with a focus on propane and CO2 reaction mechanisms under industrial reaction conditions of 400–700 °C and pressures of 1–6 barg (redox: V, Galinstan, In, Mo, Mn, Bi, Sb, Ta; nonredox: Cr, Ga, co, Al, Zn, Au, Zr, Ag, W, La, Cu; and some alloy combinations). We evaluate each material under the kinetic regime, and we quantify reaction, side reaction, and deactivation kinetics (coking, cracking, and dry-reforming), as well as the regeneration ability. We then classify them based on their dominant mechanisms (direct CO2 assistance or indirect with H2 via reverse water gas shift) and identify each catalyst’s strengths and weaknesses. Finally, (iii) we correlate our database of experimental results of 22 active metals/metal oxides with the Tamman temperature and density functional theory (DFT)-based oxygen vacancy formation energies. We discovered that oxygen mobility plays a crucial role in the kinetics of reoxidation with CO2 and the overall balance of active sites related to dehydrogenation and reoxidation.