Processes for the synthesis of liquid fuels from CO2 and marine energy

In Britain, wind and wave power are expected to make a significant contribution to future energy supplies, but the vast majority of the resource is located offshore, away from the mainland electricity grid. In this context, the chemical storage and transport of this energy appears to be an attractive option for the supply of fuels. On the other hand, it is not unlikely that CO2 will be recovered on a large scale in the next 10-20 years, thus making it available as a carbon source for liquid fuels. A preliminary analysis indicated that the liquid fuels that could be most readily manufactured from hydrogen (from electrolysis) and recycled CO2 were: methanol, mixed alcohols and gasoline (via methanol). In the light of developmental work at NEDO, Japan, methanol appears to be simplest to manufacture. The Mobil Methanol-to-Gasoline process also facilitates the manufacture of a very convenient automotive fuel. Mixed alcohols have the advantages both of low toxicity, and efficient Fischer-Tropsch catalysts for their synthesis (the Pearson process and the Ecalene process). This paper compares the energy efficiency of these three processes.