Valorization of lignin in native corn stover via fractionation-hydrogenolysis process over cobalt-supported catalyst without external hydrogen

Abstract

• We presented a modified method that provides the hydrogen source in the reaction with a mixed solvent of alcohol, acid and water, replacing the original method that directly provides a hydrogen source with external hydrogen. • In addition, a new cobalt supported on nitrogen doped carbon catalyst preparation method (one-pot) was presented . • The role of the alcohol to acid and water mixed solvent not only extract lignin fragments from the matrix but also provide the hydrogen source. • Cobalt which has electronic interaction with the nitrogen reformed alcohols to obtain hydrogen and stabilized lignin intermediates during the reaction by hydrogenation of active bonds. Nearly complete delignification (91%) and high yield of target monomers (23.8%) can be obtained under the conditions (5wt% Co/Ac-N_one-pot, 10:1:1mixture solvent consist of isopropanol/water/formic acid, 235 °C, 200 min, 0.1 MPa N2), and the selectivity of target monomers was 85%. The (hemi) cellulose section is also used efficiently, and a considerable part is converted into compounds such as glucose and furfural alcohol, which realizes the effective utilization of the three components of lignocellulose. Circulation experiment of catalyst was performed directly without any operation of the residue, and it could maintain 90% activity in the first four cycles. Lignin, which represents the most abundant renewable aromatic biomass resource on the earth, is promising as an alternative for the production of chemicals. We presented a modified method that provides the hydrogen source in the reaction with a mixed solvent of alcohol, acid and water, replacing the original method that directly provides a hydrogen source with external hydrogen. In addition, a new cobalt supported on nitrogen doped carbon catalyst preparation method (one-pot) was presented. We proposed one-step method in which corn stover lignin is converted to target monomers over Co/AC-N_one-pot catalyst and mixed solvent. The role of the alcohol to acid and water mixed solvent not only extract lignin fragments from the matrix but also provide the hydrogen source. Cobalt which has electronic interaction with the nitrogen reformed alcohols to obtain hydrogen and stabilized lignin intermediates during the reaction by hydrogenation of active bonds. Different kinds of nitrogen including pyridinic and pyrrolic nitrogen functional groups plays a critical role in stabilizing Co. Nearly complete delignification (91%) and high yield of target monomers (23.8%) can be obtained under the conditions (5wt% Co/Ac-N_one-pot, 10:1:1mixture solvent consist of isopropanol/water/ formic acid, 235 °C, 200 min, 0.1 MPa N 2 ), and the selectivity of target monomers was 85%. Circulation experiment of catalyst was performed directly without any operation of the residue, and it could maintain 90% activity in the first four cycles.