Study On Hullaceous Biomass Structure Evolution Of The Carbonization And Activation Process

The biomass is important preparation raw material for high-quality activated carbon.Due to the abundant carbon content,high organic oxygen content,simple structural composition and renewability.At present,High-quality activated carbon still relies heavily on imports in China,and the preparation technology of high-quality activated carbon has not yet been fully mastered.In this paper,pomegranate shell,walnut shell and coconut shell were used as rawmaterials to explore the evolution law of their micro-mesoscopic structure in the carbonization and activation process.In the experiment,the structure evolutionof the above three fruit shell biomass in carbonization process were studied by the value change of carbonization time,heating rate and carbonization temperature.The structure evolution of the above three fruit shellbiomass in activated processwere also studied by the value change of activation time,activation temperature and mass ratios of activator to carbonized substances,Thechange structure in carbonization and activation process were analyzed by iodine adsorption value,methylene blue adsorption value,FTIR,Boehm titration,SEM,XRD and elemental an alysis,respectively.The results showed that:(1)In the carbonization and activation process,the small pores and and medium pores distribution of material structure are affect by the change of experimental factor values.The pore structure are affected by the factors of time,temperature,heating rate and mass ratios of activator to carbonized substances and these factors all have critical values.When the time is 1 h,the temperature is 600℃,and the heating rate is 5-7℃/min,the corresponding iodine adsorption values and methylene blue adsorption values of carbonization and activation achieve better.(2)The molecular groups surrounding of the carbon skeleton constantly changes in the carbonization and activation process.C,H,O,N of the molecular structure are decomposing,reacting and reconstructing during the process.With the increase of experimental parameter values,The O and H content of the carbon skeleton and the total acidic groups content keeps decreasing,the ratio of C/O and C/(O+N)keeps increasing,and the hydrophilicity and polarity of carbonized substances and activated carbons decrease.(3)The carbon skeleton of activated carbon is a necessary condition for the formation of pore structure.The carbon skeleton structure is basically completed in the carbonization process,and its molecule structure changes little in the activationprocess.The used chemical activator not only plays the role of forming more new pores and changing pore size,but also participates in the activation reaction,and further changes the surrounding molecular groups binding form of the carbon skeleton.