New catalysts and strategies for the transformation of bioethanol into fuels and chemicals

The exploitation of fossil resources has led to a massive release of greenhouse gases and the increase of the earth’s temperature. Additionally, the contention of fossil reservoirs has triggered international conflicts and wars. Bioethanol refinery was identified as a valuable approach to develop a circular economy and fragment fuels and chemicals production, thus reducing global warming and alleviating international tension. In this work, three strategies are presented to upgrade the properties of bioethanol and broaden the domain of biorefinery products. The Guerbet reaction provides an ideal mechanism for ethanol homologation to butanol and higher alcohols with excellent properties. The catalytic activity of ruthenium-based complexes in the liquid-phase Guerbet reaction is reported. The employment of p-benzoquinones as co-catalysts led to ethanol conversions up to 88%, with a selectivity of 97% for higher alcohols. The catalytic systems can be recycled and show comparable efficiency on real matrices of waste bioethanol. The gas-phase, continuous flow catalytic upgrading of ethanol is tackled. A simple and cheap catalytic system consisting of copper nanoparticles supported on zirconium (and lanthanum) oxides was found to promote a one-pot cascade reaction scheme leading to the production of a blend of adducts in the C6-C14 range with promising jet fuel properties. By tailoring the features of the non-innocent support and the reaction conditions, up to 40% selectivity for the jet fuel range fraction, with ethanol conversion above 85%, was achieved. Acetaldehyde is an important commodity and its manufacture currently relies almost exclusively on fossil ethylene. A selection of W-V-O mixed oxide catalysts with hexagonal tungsten bronze structure incorporating alkali and alkaline earth metals was synthesized, characterized, and tested in the gas-phase, continuous flow catalytic aerobic oxidation of ethanol to acetaldehyde. The introduction of Cs in the bronze backbone allowed for the achievement of 33% EtOH conversion and 97% acetaldehyde selectivity.