| To clarify the formation of the water-insoluble substance in the liquefaction of palm oil trunk(Elaeis guineensis Jacq.)and its non-melting mechanism of fibre thermal stabilization.The theoretical basis and data suggested preparation of activated carbon fibers for adding the high value to palm oil trunks.Oil palm trunk from southern Thailand were used as a raw material.In this study,the composition and structure differences of the different parts of trunk were analysed and the liquefaction behaviour(polyethylene glycol#400/glycerin)under the catalytic condition of the liquefaction agent acid was investigated.Formation of the water-insoluble substance is presumed.A thermal stabilisation treatment that combined sulfuric acid chemical treatment and pre-oxidation treatment was proposed to prepare the non-molten fibres.The pore structure characteristics and the electrochemical properties of the activated carbon fibers by carbon dioxide activation is also discussed.The following main conclusions were obtained:(1)The chemical composition and structure of the outer and inner zones from the middle and top parts of the oil palm trunks were different;the cellulose content at the inner zone of the top section was 11.3%,while the carbohydrates amounted to 80.9%which was beneficial to its efficient liquefaction.(2)The inner zone of the top part of the oil palm trunk is the most easily liquefied,and its liquefaction residue rate decreases with an increasing liquor ratio,liquefaction time,and liquefaction temperature.In particular,the rate of liquefaction residue obtained was as low as 3.7%under a liquefaction temperature of 180? and for a liquefaction period of 30 min.Most amorphous chemicals could be liquefied and decomposed at 140?,while the crystalline cellulose zone must be decomposed in large quantities at higher temperatures,although high temperatures can cause polymerization between the liquefaction products and increase the residue content.(3)Carbohydrates such as cellulose,starch,and hemicellulose in oil palm dehydrate during liquefaction to form 5 hydroxymethylfurfural and furfural,which is dissolved in water with liquefied products such as levulinate ester or levulinic acid,the main component of water-insoluble substances of liquefied products.Concurrently,the retractable ether bond on a small amount of lignin structure contained in palm oil breaks under acidic liquefaction conditions and binds with polyethylene glycol to form a new ether bond,which is then re-polymerized with 5 hydroxymethylfurfural or furfural in the liquefaction product.This eventually forms a higher molecular weight liquefied water-insoluble object in the water.(4)The carbon content of the water-insoluble part of liquefaction reaches 59.4%,which is a great precursor of carbon material and has good melting performance.The initial fibre is prepared by the melting spinning method at 180? temperature.The initial fiber cannot be converted into an infusible fiber under a 1?/min heating rate condition,and a new ester bond combination is produced in the initial fibre after the diluted sulfuric acid chemical treatment.Further,the cross-linked structure is formed inside the fiber to promote the fibre's thermal stability,while the ester bond increases with the mass fraction of sulfuric acid increasing,especially by 10%.After chemical treatment with sulfuric acid,the fiber can be successfully pre-oxidized into infusible fibers under a 5?/min heating rate condition,resulting in improvements to the fibre's morphology.(5)The activated carbon fibre obtained from the infusible fiber by carbon dioxide activating was mainly microporous and gradually changed to mesoporous with increased activation time and activation temperature.Meanwhile,the specific surface area and total pore volume of the activated carbon fibers reached 1291 m2/g and 0.735 cc,respectively,but with a yield of only 5%.The activated carbon fibers show stable electrical properties in the dual-electrode capacitance. |
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