Preparation Of Self-form Granular Activated Carbon From Lignocellulosic Material By Phosphoirc Acid Activation And Analysis Of Its Self-from Mechanism

Based on the preparation of GAC by physical activation needs using a binder, and thisprocess is high energy consumption, high cost and complicated operation. On the other hand, itis difficult for GAC prepared from chemical activation to meet high adsorption andhigh-strength simultaneously. The dissertation used model compound of cellulose, lignin andhemi-cellulose as experimental materials, analyzed the evolution of the lignocellulosiccomponent in the process of self-form by automatic specific surface area analyzer, fouriertransform infrared spectroscopy, X-ray diffractometer, thermogravimetric analysis and gaschromatography-mass spectrometry instrument, revealed the self-form mechanism of GACprepared from phosphoric acid activation, and proved the main ingredient and sources of theplasticizing and cohesive compound in the self-form process. The objective of this dissertationis to solve the problem of the preparation of GAC by chemical activation and provide atheoretical basis and methods. The main research contents and results were as follows:GAC was prepared from fir wood powder by phosphoric acid activation without additionany binder. The results showed that phosphoric acid catalysis would promote therearrangements of the structure of lignocellulosic materials and introducephosphorus-containing functional group and C＝C＝C bond in the process of heat kneading.When heat kneading time was shorter, the main effects of phosphoric acid were hydrolysis anddilation. On the other hand, when heat kneading time was longer, the main reactions oflignocellulosic materials were dehydration and polymerization. In the process of heat kneading,with the effects of acid catalysis, mechanical strength and heat, lignocellulosic materials werehydrolysis degradation and formation of the system combined a binder and antioxidant, whichprompted the self-form of lignocellulosic materials in the condition without adding extraadhesive. In the process of self-form, the main ingredient of binder is furan resin which is fromthe homo or polycondensation of furfural. The increase of impregnation ratio benefited thedevelopment of pore structure in GAC, but not the intensity of GAC. The binder formed in the process of self-form did not clog the porosity of GAC, and the self-form process could producethe GAC with development porosity.GAC was prepared from cellulose by phosphoric acid activation without addition anybinder. The results showed that free hydroxyl groups, hydrogen content, CH groups and COgroups of cellulose were increased and phosphorus-containing functional groups, C＝C＝Cbond, C＝C bond and the C＝O bond were introduced in the process of heat kneading. Whenheat kneading time was shorter, the main effects of phosphoric acid were to hydrolyze anddilate the amorphous and crystalline regions in cellulose. When heat kneading time was longer,the main effects of phosphoric acid were dehydration and polymerization. In the process ofheat kneading, with the effects of acid catalysis, mechanical strength and heat, cellulose washydrolysis degradation and formation of the system combined a binder, plasticizer andantioxidant, which prompted the self-form of cellulose in the condition without adding extraadhesive, and then produced GAC. In the process of self-form, the main ingredient of binder isfuran resin which is from the homo or polycondensation of furfural, and the main ingredient ofplasticizer is4-methylphenol. The increase of impregnation ratio benefited the development ofpore structure in GAC, but not the intensity of GAC.Xylan was used as the main model of hemi-cellulose to prepare hemi-cellulose-basedgranular activated carbon by phosphoric acid activation without addition any binder. Theresults showed that with the effects of acid catalysis, mechanical strength and heat in theprocess of heat kneading, hemi-cellulose was hydrolysis degradation and formation of thesystem combined a binder, synthesis intermediates and antioxidant, which prompted theself-form of hemi-cellulose in the condition without adding extra adhesive, and then producedGAC. In the process of self-form, the main ingredient of binder is furan resin which is from thehomo or polycondensation of furfural. The increase of carbonization/activation temperaturebenefited the development of pore structure in GAC, but not the intensity of GAC.During preparation of GAC from the mixture of cellulose/lignin and the mixture ofcellulose/hemi-cellulose, the intensity of GAC increased firstly and then decreased with the increase of the proportion of lignin and hemi-cellulose. In the process of heat kneading, thesynergistic reaction took place between the hydrolysis degradation product of cellulose andhemi-cellulose, and produced more adhesive substance, so the intensity of GAC prepared fromthe mixture of cellulose/hemi-cellulose was stronger than the GAC prepared from cellulose andhemi-cellulose alone. During preparation of GAC from cellulose/hemi-cellulose/lignin mixture,the intensity of GAC increased with the increase of cellulosic proportion. However, theincrease of the proportion of lignin and hemi-cellulose was not good for intensity increase.During the preparation of GAC from the mixture of fir wood powder and wooden modelcompound, the intensity of GAC increased with the increase of cellulosic proportion, and theincrease of the proportion of hemi-cellulose and lignin showed an opposite trend. Whencompared with the GAC prepared from fir wood powder, the addition of cellulose and ligninbenefited the increase of GAC intensity. The factor for the increase of GAC intensity derivedfrom cellulose and lignin. The increase of furfural content benefited GAC intensity increase,but the intensity would decrease when the content of furfural was too high.The application of GAC in the field of methane adsorption and vinyl acetate catalystcarrier was studied. The results showed that the amount of methane adsorption increased firstlyand then decreased with the increase of impregnation ratio, and the unit volume of methaneadsorption decreased with the increase of impregnation ratio.The apparent density, intensity and adsorption value of zinc acetate of GAC increasedwith rising carbonization/activation temperature， but the adsorption of acetate showed theopposite trend. Controlled the preparation technology of self-form GAC, it would produce thevinyl acetate catalyst carrier conformed the national standard.