Preparation And Porous Structure Control Of Carbon Foams From Larch Sawdust

Carbon foams have characteristic with high porosity, light weight, acid and alkali resistant, high temperature resistant, stable structure, etc, so they demonstrate attractive application prospect in the fields of catalysis, adsorption purification, medical, aerospace, construction and military. Ordered carbon foams have ordered pore structure and regular cell morphology, they could be used as electrode material of capacitor, adsornent of macromolecule pollutants, good calalyst support, and so on. But their raw materials are limited to polyurethane. phenolic resin and mesophase pitch of coal and petroleum-base, in consideration of huge reserves and reproducibility of biomass material, if carry out preparation of ordered carbon foams by biomass material, which will have great realistic and theoretical significance. In this paper, we attempt to use agriculture and forestry residues---larch sawdust as raw material, and utilize liquefaction technique, resinification, foaming, and carbonization steps to prepare several kinds of carbon foams. We could adjust and control pore structure by adjusting dosage of foaming agent and later activation method, and adsorption and catalytic performance of obtained carbon foams are evaluated systematically. Paper,main content is as follows:The pore structure of carbon foams are controlled on the nanometer scale by combining the dispersing effect and self-assembly function of polyethylene glycol (PEG), we have prepared honeycomb controllable ordered carbon foams with high specific surface area. PEG molecules disperse and stretch in the larch resin system, occupying space, a portion of the molecules further form an ordered net and striped structure, and then interacte with the resin to form stable polymers. Integrated honeycomb cells and excellent pre-pore structures were simultaneously formed in the self-foaming process. A significant’amount of micropores and mesopores generate in ligaments, nodes and cell walls after carbonization. Ordered structure were present in samples carbonized at800℃, and the surface area and pore volume of the carbon foam were as high as1580.97m2/g and0.885cm2/g, respectively. With PEG content increasing, the amount of ordered mesopores of the carbon foams increase, honeycomb structure of carbon foams tend to be ordered. Due to coexistence of microporous and mesoporous structure, the carbon foams show excellent adsorption performance to phenol. CF-PEG-2.0-800is more conducive to the adsorption of Vitamin B12(the effective size is2.09nm). attribute to abundant mesopores concentrating at about3.89nm, they can permit large molecules into internal pore structure.Carbon foams also have good adsorption performance to soybean oil, oleic acid, liquid paraffin etc, adsorption quantity can reach to21-26g/g, oil viscosity is smaller, the stronger the polarity, the more likely it is to be adsorbed.We add triblock copolymer P123into larch resin under acid condition, to prepare microporous carbon foams with high compression strength, adjust pore structure and physical properties of carbon foams through various amount of foam agent and P123. Resuilts show that: with fewer dosage of foaming agent, desity of carbon foams increase, and compression strength of carbon foams also increase; we could prepared carbon foams with higher compression strength and lower density by using foaming agent of25ml. P123could enhance strength of carbon foams effectively under acid condition, compression strength of carbon foams with P123of7g,10g and15g were fast higher than carbon foams without P123. Compression strength of carbon foam with P123of20g was similar to carbon foams without P123, which indicate that once P123adds unduly, carbon skeleton will led to lose support, then strength decrease, when P123was removed. Some crystal salt woud be generated in the process of synthesis, they also paly a role on increasing the strength. Density of obtained carbon foams are beteen0.05～0.1g/cm3, their compression strength could reach to2.4Mpa. Though compression strength of carbon foams of CF-10p-25is similar to CF-7p-25and CF-15p-25, it has a certain toughness in the case of compression, it is not easy to be broken. CF-7p-25and CF-15p-25are much brittle, when it compressed to a certain extent, it would be fracture.We used carbon foams which previous chapter mentioned as material, and they were activated by H3PO4, then sulphonated in p-Toluene sulfonic acid, so we had prepared carbon foams with sulfo, it could catalyze the reaction of ethyl acetate as a solid acid catalyst. Resuilt indicate that resin foam of F-10p-25ml with high strength is activated with phosphoric acid at2h to obtain carbon foam of CF-10p-2h-20%P which have high specific surface area of629cm3/g, high mesoporous content of70%, and good opening structure. Obtained carbon foams with sulfonic group are used as solid acid catalyst tb catalyze esterfication reaction of acetic acid and ethanol. Carbon foams with sulfo could achieve good catalytic effect, when ethanol/acid ratio is1:2, the reaction time is2h, catalyst recycle used three times still can make the conversion rate of around90%.