Search

The efficient utilization of biomass, the only globally available, renewable and abundant carbon-neutral source, is of high significance in green and sustainable chemistry. Polyoxometalates (POMs) and POM-based composites have been widely applied in green catalytic reactions, due to their tunable Brønsted/Lewis-acidity and redox properties enabling high reactivity in a wide range of chemical transformations. This review covers recent advances in the chemocatalytic conversion of biomass into chemicals and fuels over POMs and POM–metal composites. For biomass valorisation over POMs, the advances of acid catalysis including hydrolysis, dehydration, etherification, alcoholysis, transesterification and esterification are summarised. Furthermore, applications in chemical oxidation for the synthesis of organic acids and furan chemicals are discussed. For biomass valorisation over metal–POM composites, an overview of tandem reactions (e.g. hydrolysis–hydrogenation, hydrolysis–oxidation, and hydrogenolysis–hydrodeoxygenation) is highlighted. The future prospects of biomass valorisation over POM-based catalysts are finally presented. [ABSTRACT FROM AUTHOR]

Alkaline-assisted stannation is applied as a facile one-step post-synthetic approach for the preparation of the Lewis-acid Sn-BEA from a high-silica commercial beta (BEA) zeolite. The concentration of base, tin and protective additive tetrapropylammonium as well as the nature of the tin precursor are identified as key parameters of the metallation process determining the acidic and structural properties of the stannated zeolite and, in turn, its performance in the isomerisation of bio-based substrates. [ABSTRACT FROM AUTHOR]

Galliation of USY zeolites in alkaline media creates tetracoordinated Lewis-acid centres linked to the framework which display outstanding selectivity in the isomerisation of dihydroxyacetone to ethyl lactate and full reusability. This simple and affordable post-synthetic route enables to tune the amount of Lewis acidity in the zeolite and has great potential for application in related biomass conversions. [ABSTRACT FROM AUTHOR]