Study On Micro-structure Of Activated Carbon On Adsorption And Desorption Of 2-Butanone

Activated carbon is environmentally-friendly and popularly applied in the recovery and adsorption of organic compounds.Among these organic compounds,2-Butanone is outstanding as an advanced organic synthetic raw material.However,the 2-butanone produced from industries can easily pollute the air and it is a waste of resources.Considering from environment and economy cost,adsorption by activated carbon is the most feasible and promising method.According to the current research work focus on the existing disadvantages in the process of 2-butanone adsorption by activated carbon,which includes wide range of pore size distribution,low selective adsorption,low purity of recovered 2-butanone recovery capacity,the research on the effects of mirco-structure of activated carbons on adsorption and desorption of 2-butanone is studied.The main research results are summarized as follows:（1）Research on adsorption and desorption of 2-butanone by activated carbonThree activated carbons with different pore size distribution were studied on the adsorption and desorption of 2-butanone,the connection between micro-structure of activated carbons and the adsorption and desorption of 2-butanone was observed.The experimental results showed that: the adsorption capacity of 2-butanone increased with the increasing of iodine value,methylene blue value,BET surface area and total pore volume;the adsorption of 2-butanone mainly happens in activated carbons of micro-pores from 0.8 to 2 nm,pores from 0.5⁰.8 nm and 1.2 nm did benefit the adsorption as well.The acidic surface functional groups such as lactonic and carboxyl groups benefited the adsorption while reduced the desorption of 2-butanone.The capacity increased during the adsorption while desorption rate decreased during desorption as the temperature was higher.The partial pressure of 2-butanone has big effect during adsorption in a positive way.The products after desorption were collected and analysized.It showed that other compounds such as esters and aldehydes were found after desorption at temperatures around 130℃,which means reactions happened during desorption of 2-butanone.（2）The study of modification on adsorption and desorption of 2-butanone by activated carbonTwo different modification methods were chosen to be used for the activated carbons,the influences by modified activated carbons were studied.The results showed that:（1）temperature modification: the iodine value and methylene blue value were increased firstly and then decreased due to the high temperature（700、800、900℃）modification,the maximum values reached 1317 mg/g and 315 mg/g at 800℃.Meanwhile,the BET surface area,total pore volume and amount of oxygen functional groups were reduced due to the high temperature,the adsorption capacity of 2-butanone was decreased to even lower than the capacity by unmodified activated carbons（0.715 g/g）.（2）H₂O₂ modification: the iodine value decreased slightly;the methylene blue value increased firstly and then went down to the lowest value of 255 mg/g while the iodine value was down to 908 mg/g when the mass fraction of H₂O₂ was 30%;the BET surface area and total pore volume decreased slightly while the amount of surface functional groups was increased,especially the oxygen functional groups;the adsorption capacity increased by the gradient mass fraction of H₂O₂（5%、10%、20%）,the highest increasing percentage is 6.7%.While the capacity of adsorption decreased with a higher mass fraction of H₂O₂.（3）the two modification methods changed the pore structure of the activated carbons,as well as the functional groups,but functioned in different ways.Modification with high temperature can have significant influence on the pore structure while the amount of functional groups on surface was changed more due to the modification with H₂O₂.（3）Study on kinetics of 2-butanone adsorption by activated carbonActivated carbons were chosen to be used in the study of 2-butanone adsorption.The effects of adsorption time,adsorption temperature and the carrier gas flow of 2-butanone were discussed.The adsorption kinetics of 2-butanone at different temperatures and at different carrier gas flow was studied.Equilibrium data were analyzed by four kinetic models which are pseudo-first-order kinetic model,pseudo-second kinetic model,Elovich kinetic model and Bangham kinetic model,thus a dynamic model on the adsorption kinetics of 2-butanone was established.The results showed that the optional adsorption temperature is 303 K and the ideal carrier gas flow is 400 mL/min.It is also found that the Bangham model is more than 0.99,therefore it can be included that the adsorption of 2-butanone by activated carbon follows Bangham kinetic model.