Catalytic Ethanolysis of Kraft Lignin into High‐Value Small‐Molecular Chemicals over a Nanostructured α‐Molybdenum Carbide Catalyst

Abstract

We report the complete ethanolysis of Kraft lignin over an a-MoC 1Àx /AC catalyst in pure ethanol at 280 8C to give high-value chemicals of low molecular weight with a maximum overall yield of the 25 most abundant liquid products (LP25) of 1.64 g per gram of lignin. The LP25 products consisted of C 6 -C 10 esters, alcohols, arenes, phenols, and benzyl alcohols with an overall heating value of 36.5 MJ kg À1 . C 6 alcohols and C 8 esters predominated and accounted for 82 wt % of the LP25 products. No oligomers or char were formed in the process. With our catalyst, ethanol is the only effective solvent for the reaction. Supercritical ethanol on its own degrades Kraft lignin into a mixture of small molecules and molecular fragments of intermediate size with molecular weights in the range 700-1400, differing in steps of 58 units, which is the weight of the branched-chain linkage C 3 H 6 O in lignin. Hydrogen was found to have a negative effect on the formation of the low-molecularweight products.

Selective catalytic conversion of guaiacol to phenols over a molybdenum carbide catalyst

“…The XRD and TEM analysis data were presented in our previous work. 2 The catalytic performance of the α-Mo 1-x C/AC catalyst was examined in a number of solvents, i.e. methanol, ethanol, isopropanol, tetralin, n-hexane and water at 340 o C under 0 MPa N 2 (gauge and being the initial pressure at room temperature) (Table 1).…”

“…1 We recently reported Kraft lignin can be completely ethanolysed to small molecules in supercritical ethanol over an α-Mo 1-x C/AC catalyst in an inert atmosphere. [2] However, the reaction pathways in the ethanolysis is complex and difficult to be followed. Furthermore, in the utilization of lignin derived compounds, the high oxygen content and poor chemical stability are often the limiting factors.…”

“…Furthermore, in the utilization of lignin derived compounds, the high oxygen content and poor chemical stability are often the limiting factors. 2,3 Therefore, obtaining information from the reactions of model compounds is often meaningful to the utilization of the lignin derived compounds. 4 Guaiacol, which contains simultaneously hydroxyl and methoxyl functional groups, has been typically used as a model compound in the study of lignin valorization.…”

Lignin Depolymerization into Aromatic Monomers over Solid Acid Catalysts

“…5 The composition of lignin varies considerably from plant to plant, particularly with regard to the type and quantity of linkages in the polymer and the number of methoxy groups present on the aromatic rings. Lignin can also be depolymerized under subcritical and supercritical conditions (> 290 o C, [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40] to yield aromatic monomers and gases. Since, lignin in large quantities is produced as a waste in many industrial processes, such as pulp production (isolation of cellulose to make paper) and in the production of bioethanol from lignocelluloses, but can be used for multiple functions such as to make lignosulfonates, or can be burnt for generation of heat or even for land filling.…”

“…Lignin can also be depolymerized under subcritical and supercritical conditions (> 290 o C, [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40] to yield aromatic monomers and gases. 33 A single step process for the hydrogenolysis and depolymerization of organosolv lignin and subsequent aromatic ring hydrogenation was studied using Cu doped porous metal oxide in supercritical methanol at 300 °C. 20 Supercritical water with p-cresol as a solvent is also used to treat organosolv lignin to yield phenols and gases.…”