Promising catalytic synthesis pathways towards higher alcohols as suitable transport fuels based on H-2 and CO2

To address the pressing challenges of energy security and global warming, the coupling of the energy generation and transport sectors using Power-to-Fuel (PtF) technologies is an attractive strategy. PtF means the synthesis of transport fuels based on CO2 from industrial exhaust gases and H-2 produced from renewable electricity via electrolysis. This paper provides a comprehensive overview of the synthesis possibilities and potentials of H2 and CO2-based methanol and higher alcohols (C-1-C-8; from methanol up to octanol) as alternative transport fuels by adapting established and novel alcohol synthesis pathways to the PtF concept and assessing their technical maturity using the Technology Readiness Level (TRL) method. A literature review reveals that among the alcohols, methanol, ethanol, 1-/2-/iso-butanol and 1-octanol have the highest relevance for fuel blending. With the aim to give a first impression, we roughly estimated and discussed the production costs depending on the H-2 costs. We estimated the TRL of promising synthesis pathways towards alcohols at 8 for methanol and at 4 for ethanol, 1-butanol and iso-octanol. For 1-octanol, no suitable synthetic pathway is currently known.