Oxidation of lignin using aqueous polyoxometalates in the presence of alcohols.

A novel approach has been developed in order to use Kraft lignin as a renewable resource for the production of chemicals. The concept is based on the use of polyoxometalates as reversible oxidants and on the use of radical scavengers, which prevent lignin fragments from repolymerizing. The oxidation of Kraft lignin, which is a potential source of functionalized phenols, by H3PMo12O40 in water yields a relatively small amount of monomeric species detected by GC-MS. The addition of methanol to the reaction resulted in an increase in the yield of monomeric products by a factor of up to 15. Vanillin and methyl vanillate are the main products obtained, in a maximum yield of 5 wt % based on dry Kraft lignin. Methanol plays a decisive role in the prevention of repolymerization by reducing lignin-lignin condensation reactions. Furthermore, it is proposed that methanol generates small amounts of .CH3 and CH3O. radicals through the acid-catalyzed formation of dimethyl ether which couple with lignin fragments.

Hydrogenation of benzene using aqueous solution of polyoxometalates reduced by CO over gold catalysts.

Aqueous polyoxometalate (H3PMo12O40) solution reduced by CO with liquid water using gold nanoparticle catalysts at room temperature, which contains protons in liquid water and electrons associated with the reduced polyoxometalate, can produce gaseous H2 or can hydrogenate benzene over an electrochemical cell consisting of a simple carbon anode, a proton-exchange membrane, and a Pt- or Rh-based cathode. In the present cell, H2 can be produced from the reduced H3PMo12O40 solution at voltages that are lower by about 1.15 V compared to water electrolysis.