Study On The Production Of Monophenol Chemicals By Depolymerization Of Lignin Under NiPd Composite Metal Catalyst

Lignin is a kind of natural amorphous high molecular compound,which is randomly and mainly polymerized from p-hydroxyphenyl,guaiacyl and syringyl units.Lignin is the most abundant organic matter except cellulose in nature,and can replace fossil energy from three aspects of solid,liquid,gas.Linked with a large number of C-C and C-O bonds,lignin has a complex three-dimensional network structure,which makes it difficult to be destroyed during the process of separation and transformation of lignin.The decomposition products are also complex and changeable.Among the many utilization ways of lignin,catalytic hydrogenolysis is a high potential method that can transform lignin to achievem many high-value chemicals under mild reaction conditions.In this paper,a bimetallic composite catalyst Ni-Pd/SBA-15 was prepared.The catalytic hydrogenolysis of lignin under Ni-Pd/SBA-15 was investigated and a series of research results were obtained.The typical gramineous cellulolytic enzyme corn stalk lignin?CECL?was selected as the reaction substrate to investigate its hydrogenolysis under the action of Ni-Pd/SBA-15 with different molar ratio.The results showed that the catalytic hydrogenolysis of Ni₅₀Pd₅₀/SBA-15 was the best.The total yield of mono phenol was8.14 wt%after 8 hours at 220?,and the main products were 4-ethylphenol and4-propylsyringol with their yield of 1.24 wt%and 2.1 wt%.The physical and chemical properties of Ni-Pd/SBA-15 was analyzed by six modern physical characterization techniques,such as XPS,TEM,and BET.The results show that Ni and Pd are closely combined to smaller bimetallic particles to be loaded on SBA-15and reduce the oxidation of Ni and Pd metals by bimetallic interaction.Therefore,Ni₅₀Pd₅₀/SBA-15 has better catalytic activity than other Ni-Pd/SBA-15 catalyst.The hydrogenolysis of CECL was carried out by Ni₅₀Pd₅₀/SBA-15 at 200?285?.With the increase of temperature,the yield of depolymerization products increased,but the rising trendency became gentle after 245?.It was found that 245?was the best temperature for the hydrogenolysis of CECL.Ni₅₀Pd₅₀/SBA-15 was used for the hydrogenolysis of acid extracted birch lignin?ABL?with a total yield of 18.52 wt%and a high selectivity of 47.97%for 4-propyleugenol.a lignin dimer model compound,2-?2,6-dimethoxyphenoxy?-1-phenylethanol,can be efficiently cracked by Ni₅₀Pd₅₀/SBA-15 and converted into 55.46 wt%eugenol and 42.47 wt%Phenylacetyl.The repeatability experiment shows that after four cycles,the catalyst still has 87.63%catalytic effect,which showed that Ni₅₀Pd₅₀/SBA-15 had a good catalytic depolymerization effect.Ni₅₀Pd₅₀/SBA-15 was applied to hydrogenolysis research of protolignin in biomass.In this paper,birch,pine and corn stalk were selected to study.The results showed that all of them could be hydrogenated effectively by Ni₅₀Pd₅₀/SBA-15.245?made the hydrogenolysis reaction more completely than 200?.The optimal reaction temperature is 245?and depolymerization products were up to 24.71%.The yield of 4-ethyleugenol,4-propyleugenol and 4-propenyleugenol were 3.05 wt%,6.86wt%and 4.92 wt%respectively.The increase of temperature is conducive to the depolymerization of protolignin,and the yield of liquid monomer increases.According to fourier infrared spectrum,the main component of the solid residue after protolignin hydrogenolysis at 245?is the cellulose,which indicates that lignin component in the biomass has been catalyzed hydrogenolysis efficiently.