Preparation Of Phenolic Compounds And Activated Carbon By Catalytic Liquefaction Of Black Liquor From Pulping

Thermochemical conversion is an effective method to convert biomass into liquid fuel to solve energy problems.In this study,the black liquor was used as the raw material for direct depolymerization.The residual alkali in black liquor was used for catalytically hydrothermal liquefaction to obtain bio-oil and solid residue,and the bio-oil obtained was further catalyzed and liquefied in a mixed solution of methanol and water to obtain phenols.Activated carbon was prepared by using phosphoric acid as an activator from the solid residue produced.The main conculsion is as follows:(1)Preparation of phenols from kraft pulping black liquor by hydrothermal catalytic liquefaction.The raw material black liquor was depolymerized directly,and the effect of temperature on the alkaline catalytic liquefaction of black liquor in water was studied.Results showed that the maximum yield(36.00%)was obtained when the reaction temperature was 280℃.The highest yield of solid residue was obtained at 310℃(43.69%).When the reaction temperature increased,the intermediate was easy to condense and form more bio-char.(2)Preparation of activated carbon from solid residue.Solid residue was used as raw material and phosphoric acid as activator to prepare activated carbon.Results showed that the higher the reaction temperature,the lower the yield.It was found that 500℃was the optimal temperature for the preparation of activated carbon.The activated carbon prepared had the best specific surface area(599 m~2/g)and the maximum methylene blue adsorption value was 201 mg/g when prepared at500℃.The resulting activated carbon had a high internal porosity and high adsorption,which was expected to be used for wastewater treatment.(3)The hydrogenation of bio-oil prepared by black liquor to produce phenolic compounds.With Pd/C as catalyst and methanol/water as safe and effective hydrogen source,the effect of different molar ratios of methanol/water solution on the depolymerization of bio-oil into phenolic compounds was studied.The phenolic compounds from liquefaction with methanol/water(1:2,mol/mol)solvent had a high yield(12.3%),a concentrated distribution for phenolic compounds,and a good selectivity for 4-methyl-phenol(12.16%).The reaction effectively catalyzed the reduction reaction and inhibited the repolymerization reaction,thus obtaining phenols with a high yield.