| Under the background of "carbon peak by 2030,carbon neutral by 2060",the development and utilization of biomass energy has become a strategic choice for solving energy and environmental aspect and biomass will give play to role as a zero-carbon energy.High strength carbon materials are extensively used in metallurgy,mechatronics,aerospace,new energy and other fields due to their outstanding properties.At present,the raw materials of high strength carbon materials are still heavily dependent on fossil energy.It is a scientific frontier problem to develop new high-strength biomass carbon materials and expand the research field of biomass.In this paper,bio-oil and biochar from corn stalk pyrolysis were used as precursors to prepare high-strength carbon materials,optimizing the operation conditions of carbon materials preparation,expliciting the structure-activity relationship between structure and strength of high-strength carbon materials prepared by thermal conversion of corn stalk.So as to provide scientific basis for high-value utilization of corn stalk.Corn stalk-derived high strength carbon materials were prepared by mixing,pressing and heat-treatment.The effects of pyrolysis temperature of corn stalk,proportion of bio-oil,molding pressure and heat-treatment temperature on carbon materials were studied,taking compressive strength as index.The preparation parameters were optimized by orthogonal test on the basis of single factor test.The results showed that: the compressive strength of carbon material was the highest(9.78MPa)under the pyrolysis temperature of 600℃,the proportion of bio-oil of 40%,the molding pressure of 21.85 MPa,and the heat-treatment temperature of 800℃.The optimized design provides a reference for the selection of process parameters for the preparation of corn stalk-derived high strength carbon materials.The carbon materials were characterized by Elemental analysis,Scanning electron microscopy,Fourier transform infrared spectroscopy,Nitrogen adsorption-desorption and Raman spectroscopy.From the element scale,it was found that the heat-treatment temperature had little effect on the element content of carbon materials.However,the value of H/C gradually decreased with the increase of heat-treatment temperature,indicating that the aromaticity of the carbon materials gradually increased and the chemical properties tended to be stable.The structure of the carbon materials was mainly large condensed ring structure.With the increase of bio-oil addition ratio,the content of carbon increased,while the influence of hydrogen and nitrogen was relatively small.The change range of H/C value was small.The highest combustion calorific value of carbon materials can reach 30.735MJ/kg,which can be used as fuel instead of coal and has the potential to replace industrial metallurgical coke.From the surface scale,it was found that the heat-treatment temperature had a great influence on the surface functional groups of carbon materials.The heat-treatment made the polymerization between bio-oil and biochar form macromolecular ring structure,which increased the molecular size of carbon materials.Combined with the scanning electron microscope and the analysis of specific surface area and pore structure of carbon materials,it was found that the formation of coke during the heat-treatment of bio-oil was the main reason for the increase of compressive strength of carbon materials.With the increase of heat-treatment temperature and bio-oil addition ratio,the specific surface area and pore volume of carbon materials showed a downward trend.From the molecular scale,it was found that the heat-treatment of carbon materials reduced the ratio of large aromatic ring structure to small aromatic ring structure.Therefore,it was considered that there was no more large aromatic ring structure formed in the heat-treatment reaction process,and there was more likely to be the behavior of cross-linking reaction to produce fat structure. |
PDF Full Text Request