Hydrogenolysis Of Lignin To Phenolic Compounds Over The Molybdenum Catalyst

Lignin is one of the main components of biomass,and is a three dimensional network structure consisting of different methoxylated phenylpropane units,which are linked by C-C bonds or ether linkages.Lignin is the only natural,renewable aromatic hydrocarbon resource.It is an importantly strategic significance for sustainable development by converting lignin into aromatic compounds and materials,which is used in energy,chemistry,pharmaceutical,material and other fields.In this paper,we studied the preparation of lignin by enzymatic and acid hydrolysis of Betula alnoides and Pinus yunnanensisand lignin,which is called EMAL.It is confirmed that the extracted EMAL had high purity and retained the original structure characteristics of lignin through fourier transform infrared spectroscopy(FT-IR)and 2D HSQC NMR spectroscopy for structural characterization.The birch lignin is mainly composed of S and G type structure,while the pine lignin is G type structure.Pine EMAL was converted into phenolic compound over the molybdenum catalyst.Different metal catalyst,reaction time,reaction temperature and additives were researched in the depolymerization of pine EMAL.The results showed that the catalyst supported on carbon nanotubes was better than other supporters.Under the condition of 200?,only ?y-methoxyisobutyrateis occurred,and the selectivity was up to 90%;but when the temperature rose up to 260?,the products were mainly 4-propenyl-2-methoxyphenol and 4-propyl-2-methoxyphenol,which indicated that temperature had an obvious impact on the experiment.By comparing the degradation of two lignin under the same conditions,we found that the birch lignin yield of aromatic compounds was higher,and the products were mainly 4-propenyl-2,6-dimethoxyphenol(S type)and 4-propenyl-2-methoxyphenol(G type).And the yield of aromatic compounds degraded by pine lignin was lower,and the products were mainly y-methoxyisobutylphenol(G type)and 4-propenyl-2-methoxyphenol(G Type).That was,the composition of the raw material directly determined the product structure type.Based on these data,a series of monomer compounds were synthesized,and their purity were confirmed by NMR and GC.The monomer yield was calculated by the standard curve to evaluate the reaction efficiency.