Liquid Organic Hydrogen Carriers (LOHCs) as H-Source for Bio-Derived Fuels and Additives Production

Abstract

Liquid organic hydrogen carriers (LOHCs) are attractive materials for their ability to generate in situ hydrogen that may be directly used to produce target biofuel precursors, fuels or fuel additives. Indeed, the replacement of fossil feedstock is an urgent necessity for shifting toward a carbon neutral energy economy. Several desired chemicals and fuels derived from renewable sources can be accessed by hydrogenation reactions and among the LOHCs used for this purpose, formic acid and small-sized alcohols (methanol or isopropanol) represent very promising alternatives to classic dangerous molecular hydrogen. In this review article, a comprehensive overview about the mechanisms of hydrogen-transfer processes for different LOHCs is given. This evaluation is necessary for large-scale implementation of LOHCs in sustainable fuel production. The catalysts’ design rationale and the criteria behind the choice of appropriate reaction conditions are reviewed in detail, since they represent crucial parameters for in situ hydrogen generation. Also the domino/cascade-type processes influence the LOHC selection, promoting the realization of energy and cost saving protocols in a step and atom economical way.