Catalytic depolymerization of Kraft lignin to liquid fuels and guaiacol over phosphorus modified Mo/Sepiolite catalyst

Phosphorus (P) modified Mo/Sepiolite (Mo/SEP) catalysts (xP-Mo/SEP) are successfully prepared and have been certified to regulate controllably Kraft lignin conversion. The lignin oil yield and corresponding higher heating value (HHV) are obviously reduced after P addition. It attributes to P additive interplays with the skeleton structure of Mo/SEP to generate Al-PO3- and Mo-PO43- species, as a result reducing the relative surface content of Mo5+ species and impairing the strength of acid sites. However, P addition dramatically increases the productivity of phenolic compounds. Particularly, 5P-Mo/SEP has the optimized distribution between Mo5+ sites and acid strength/type. Hence, it produced lignin oil has 32.19 MJ/kg of HHV apparently higher than that of Kraft lignin (22.0 MJ/kg), and in which contains the highest amount of guaiacol monomer, 265 mg/g lignin. This ascribes to the reduction of strong Lewis acid sites over 5P-Mo/SEP surface in comparison with Mo/SEP weakens the alkylation process of reactive intermediates but enhances their demethoxylation and hydrogenation reactions. Furthermore, the plausible reaction pathways of lignin conversion over Mo/SEP and 5P-Mo/SEP are discussed in details.

Automated summary

Phosphorus-modified Mo/Sepiolite catalysts can regulate Kraft lignin conversion, reducing lignin oil yield and HHV while significantly increasing the productivity of phenolic compounds. The optimized distribution between Mo5+ sites and acid strength/type in 5P-Mo/SEP results in lignin oil with a higher HHV compared to Kraft lignin.