Study On Catalytic Pyrolysis Characteristics Of Crop Straw With Formate Catalyst

In this study,crop straw was used as biomass raw material,cellulose powder and lignin powder were used as biomass components,the effect of formate catalyst on the pyrolysis characteristics of biomass was investigated systematically,and the effect of cellulose-lignin interaction on the catalytic effect of formate was obtained.The specific research contents are as follows:Firstly,the pyrolysis of corn straw catalyzed by formate salts（potassium/nickel/zinc formate）were evaluated and compared by using the combination of TGA and the fixed-bed reactor.The results showed that potassium formate resulting in a forward shift of the decomposition temperature of organic components in biomass and an increase of gas yield,and the apparent activation energy decreased about 13.28KJ/mol.Compared with non-catalytic pyrolysis,nickel formate increased the yield of bio-oil by about 8wt%.After adding potassium formate,the generation of phenols in the oil was enhanced,while the presence of nickel/zinc formate obtained the opposite results.The total content of oxygenated compounds was reduced for all formate salts,and the most signigicant difference among them was that the addition of potassium formate obtained the enrichment of ketones.The analysis of gas showed that the yields of CO₂ and CO were increased after adding potassium/nickel formate.Secondly,the effect of the interaction between cellulose and lignin on the catalytic pyrolysis of formate was studied.The results indicated that the presence of potassium formate affected the whole thermal decomposition process,while the effect of nickel formate was mainly manifested before 339℃.The interaction under the action of potassium formate favored the generation of carbonyl compounds,and the catalytic pyrolysis with nickel formate was better for formating phenols.The high peak intensities of CO and CH₄ were achieved by adding nickel formate and potassium formate,respectively.The evolution of a char structure further revealed that different formate salts had different effects on the interactions.The statistical method according to the distribution of the liquid component confirmed that potassium formate had the strongest effect for reducing the cellulose-lignin interactions.Finally,potassium formate,nickel formate and zinc formate were used to prepare composite catalyst,and the effect of composite catalyst on straw pyrolysis was explored.The results showed that three different composite catalysts could increase the yield of bio-oil and syngas in different degrees,and the potassium-nickel composite catalyst could increase the yield of bio-oil and syngas to the maximum.The apparent activation energy of the pyrolysis reaction was reduced by loading three kinds of composite catalysts,and the activation energy of the pyrolysis reaction was reduced most significantly by loading potassium-nickel composite catalyst,which was about 10.79KJ/mol.The composite catalyst had a remarkable effect on reducing the content of oxygenates in the bio-oil.