Polyoxometalate-mediated electron transfer–oxygen transfer oxidation of cellulose and hemicellulose to synthesis gas

Abstract

Terrestrial plants contain B70% hemicellulose and cellulose that are a significant renewable bioresource with potential as an alternative to petroleum feedstock for carbon-based fuels. The efficient and selective deconstruction of carbohydrates to their basic components, carbon monoxide and hydrogen, so called synthesis gas, is an important key step towards the realization of this potential, because the formation of liquid hydrocarbon fuels from synthesis gas are known technologies. Here we show that by using a polyoxometalate as an electron transfer-oxygen transfer catalyst, carbon monoxide is formed by cleavage of all the carboncarbon bonds through dehydration of initially formed formic acid. In this oxidation-reduction reaction, the hydrogen atoms are stored on the polyoxometalate as protons and electrons, and can be electrochemically released from the polyoxometalate as hydrogen. Together, synthesis gas is formed. In a hydrogen economy scenario, this method can also be used to convert carbon monoxide to hydrogen.

Biomass oxidation to formic acid in aqueous media using polyoxometalate catalysts – boosting FA selectivity by in-situ extraction

“…This stoichiometric method leads to a 65% yield of CO, which is consequently formed from FA by reaction with concentrated sulphuric acid. 24 Finally, heteropolyanion-based ionic liquids have been applied as a catalyst for cellulose conversion, leading to FA yields of 51%. 25 Summarizing the wealth of very recent studies on vanadiumcatalysed biomass oxidation, it can be stated that this transformation is characterized by its mild reaction temperature (compared to biomass gasification or hydrothermal reforming) and by its applicability to a wide range of biogenic raw materials, including non-edible biopolymers, complex biogenic mixtures and wet biomasses.…”

Vanadium catalyzed aerobic carbon–carbon cleavage

“…Other groups have reported that H 5 [V 2 Mo 10 O 40 ] catalyzes the oxidation of d-glucose and cellulose to formic acid and CO 2 with complete conversion of the substrate and yields up to 50%, working in acidic aqueous media, at 70-100 • C, in the presence of additives, like p-toluensolfonic acid, and under high O 2 pressure (20-40 bar) [59][60][61][62].…”

“…), and the corresponding methyl ester, formaldehyde and its derivatives (0.92 equiv.) and a minimum amount of CO 2 from over-oxidation (Scheme 7) [62].…”

Polyoxometalate‐Mediated Lignin Oxidation for Efficient Enzymatic Production of Sugars and Generation of Electricity from Lignocellulosic Biomass

“…These solubilized polysaccharides would be difficult to recover for ethanol production. However, this hydrolysate may be also oxidized by POMs, because POMs can function as an electron‐transfer/oxygen‐transfer catalyst for oxidation of cellulose and hemicellulose to form degradation products such as formic acid, CO, and even CO 2 depending on reaction conditions . Under the pretreatment conditions, POM oxidation of lignin mainly involves the oxidation of side chains, degradation of some inter‐unit linkages, partial degradation of the benzene structure to form benzoquinone, and removal of the aliphatic and phenolic hydroxyl groups .…”