Lignocellulose is the most abundant sort of biomass as it is the major component of all the plant cell walls contributing structural and mechanical integrity of plants. Crude lignin is obtained in large quantities as a by-product in the pulp and paper industry, mainly as Kraft lignin and lignosulfonate. High value added chemicals, particularly aromatics can be obtained from lignin by chemical depolymerization processes. However, no practical process has been achieved commercial interest due to the inertness of the lignin structure, and the high tar and char formation tendency in the examined conditions. Besides, design of a catalyst active for Kraft lignin depolymerization and with stand sulfur is another challenge. Here, we reported that Kraft lignin can be efficiently converted into small molecular industrial commodity chemicals and valuable feedstock over nano molybdenum catalysts in pure ethanol at 280 oC using a batch reactor. A maximum yield of 1.64 g/g lignin is achieved with α-MoC1-x/AC. The higher heating value of the liquid products was estimated to be as high as 36.5 MJ kg-1, as compared to 29.7 MJ kg-1 for ethanol fuel. The main products consist of C6 to C10 esters, alcohols, arenes, phenols, and benzyl alcohols. No oligomers or char were formed in the process. The detected alcohols are mainly composed of hexyl alcohol and its isomerides, the esters are mostly ethyl esters with carboxylic acids such as hexanoic acid. The aromatics contain xylol, benzyl alcohol, guaiacol and their derivatives, no ring-opening and saturation hydrogenation products were formed in this process. The high yields of benzyl alcohols and arenes are the first observation in the one-pot heterogeneous catalytic conversion of Kraft lignin. The solvent and catalyst both play key roles and affect the molecular yields and product composition. Hydrogen was found to have a negative effect on the formation of the low-molecular weight products. This presentation will also compare the different catalyst designs and will discuss the common pathways with these catalysts.

One-pot conversion of Kraft lignin into high-valued small-molecular chemicals over nanostructured molybdenum based catalyst

249th National Meeting (2015)

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