Due to environmental concerns, worries about fossil fuel supplies and control of large oil reserves by dictatorships, biofuels from biomass have been the subject of much attention; renewable resources, such as specially cultivated plants, wood scraps, and other plant waste, could be a key component in solving future energy issues. Processes such as pyrolysis or liquefaction allow the conversion of biomass into bio-oil, a highly promising renewable source of energy but the process to use bio-oil remains unacceptable.
A team of German and Chinese scientists led by Johannes A. Lercher at the Technical University of Munich has now developed a new catalytic process to convert components of bio-oil directly into alkanes and methanol. As reported in the journal Angewandte Chemie, the process is based on a "one-pot" reaction catalyzed by a precious metal on a carbon support combined with an inorganic acid.
Bio-oil contains a phenolic fraction consisting of compounds with the main framework being an aromatic ring made of six carbon atoms with some hydroxy (-OH) groups attached. With the new process, the phenolic components of bio-oil can be converted with high selectivity to cycloalkanes (ring-shaped alkanes) and methanol. The researchers were able to demonstrate this with various model substances. As catalyst, they used palladium metal on a carbon support, with phosphoric acid as the proton source for the reaction.
The reaction is a "one-pot" reaction, meaning a one-step reaction whose partial reactions (hydrogenation, hydrolysis, and dehydration) occur in the same reactor, with no intermediate work-up. The secret is in the catalyst, which works on all of these different reactions. The end result is a mixture of various alkanes that separates into a second phase, making it easy to separate from the aqueous bio-oil phase. The new process is a practical approach for the direct use of bio-oil for the production of alkanes.
Article: Johannes A. Lercher, 'Highly Selective Catalytic Conversion of Phenolic Bio-Oil to Alkanes', Angewandte Chemie International Edition 2009, 48, No. 22, 4047-4050, doi: 10.1002/anie.200900404