Use of Polyoxometalate Catalysts in Ionic Liquids to Enhance the Dissolution and Delignification of Woody Biomass

Abstract A well‐known polyoxometalate, [PV 2 Mo 10 O 40 ] 5− , in both acidic (acidic POM, H 5 [PV 2 Mo 10 O 40 ]) and ionic liquid‐compatible form ([C 2 mim]POM, [1‐ethyl‐3‐methylimidazolium] 4 H[PV 2 Mo 10 O 40 ]), has been studied as a catalyst for the dissolution and delignification of wood in the ionic liquid (IL) 1‐ethyl‐3‐methylimidazolium acetate ([C 2 mim]OAc). Differences were observed with variables such as the form of POM, POM loading, and reaction conditions. Generally, the addition of POM leads to a faster dissolution, a lower lignin content in the recovered cellulose‐rich materials (isolated pulp), and a lower isolated yield of lignin due to its oxidation. Acidic POM decreases the lignin content of the pulp without compromising the yield of the pulp. [C 2 mim]POM in the IL facilitates greater delignification (lower lignin content in pulp) than the IL with acidic POM; however, the overall pulp yield is also lower indicating some degradation of the carbohydrates. The POM can be recovered with [C 2 mim]OAc after evaporation of the reconstitution solvent (e.g., acetone/water) and can be reused, albeit with some loss of POM and loss of POM activity under the current conditions.