【作者】 谢玲玲；

【导师】 汪华林； 张章；

【作者基本信息】 四川大学 ， 环境工程（专业学位）， 2021， 硕士

【摘要】 燃烧后捕集是控制化石燃料燃烧排放二氧化碳的重要方法之一,分为吸收法、吸附法、膜分离法等。吸附法因操作灵活性高、工艺简单、无二次污染、再生能耗低等优点快速发展。固体吸附剂如生物质炭、沸石分子筛、金属有机框架（MOF）等材料具有来源广泛、再生能耗低、成本低及可调控的表面化学性质等优点,被广泛用作燃烧后捕集二氧化碳材料。单一生物质炭材料成型困难,且活化造孔过程需要强酸强碱性物质,易腐蚀设备,产生废水造成环境污染;单一沸石分子筛材料抗水性差;单一MOF存在粉末形态缺陷且不耐高温;综合利用生物质炭材料复合沸石或MOF材料能够改良上述三种单一材料缺点。微流控技术通过将沸石分子筛或MOF的配体材料混入液态生物质（炭前驱体）进行复合成型或原位合成,是实现生物质炭复合沸石分子筛或MOF的有效手段之一。本文以壳聚糖（液态生物质）、沸石分子筛和MOF为原料,微流控技术为材料复合手段,制备生物质炭、生物质炭-沸石及生物质-MOF复合炭三种材料,调控微流控系统参数,调节三种材料的表面性质与孔隙结构,研究三种材料的物化性质对二氧化碳捕集性能的影响,并对比三种材料的吸附性能,主要结论如下:（1）针对生物质炭成型困难、分散性差的缺点,采用微流控技术制备单分散球形生物质炭。两相的流速和分散相的浓度对生物质微液滴的形貌与尺寸具有较大影响,最佳分散相/连续相流速比以及分散相浓度分别为2/10与2 wt%;球形生物质炭孔隙结构较差,比表面积、总孔容以及微孔孔容分别为94.0 m²/g、0.034 cm³/g和0.032 cm³/g;球形生物质炭吸附容量低、循环再生性优、吸附热值低及CO₂/N₂选择性好。（2）针对生物质炭活化造孔过程环境友好性低,沸石分子筛抗水性差的缺点,采用微流控技术及三种沸石原料（ZSM-5、MOR及Na-X）制备球形生物质炭-沸石复合材料。ZSM-5沸石表现出优于MOR与Na-X沸石的稳定性;改变ZSM-5/壳聚糖比例,能够调控生物质炭-沸石复合材料的孔隙结构及二氧化碳吸附容量;软模板剂F127存在时,能改善复合材料的介孔孔容,提升氮含量;最佳样品的二氧化碳吸附容量为1.23 mmol/g,CO₂/N₂的选择性为6.69（1 bar,25℃）,十次循环再生稳定性在91%以上。（3）针对MOF材料耐热性差、粉末状形态缺陷的问题,采用微流控技术原位合成球形生物质-MOF复合炭材料。生物质-MOF复合炭材料具有发达的孔隙结构和高氮含量,随着MOF的Zn（NO₃）₂·9H₂O/壳聚糖比例的升高,复合材料的比表面积先增加后降低,复合材料的氮含量增加;炭化温度对生物质-MOF复合炭材料的氮形态有较大影响,温度升高促使吡啶氮朝着稳定的石墨相氮转化;最佳样品的CO₂吸附量达1.27 mmol/g,CO₂/N₂的选择性为22.7（1 bar,25℃）,十次再生后二氧化碳吸附容量为1.07 mmol/g。（4）并对比三种材料的吸附性能可知,球形生物质炭-沸石复合材料吸附容量高、循环再生性好适用于进行工业应用。更多还原

【Abstract】 Post-combustion capture is one of the most important methods to control carbon dioxide emissions from fossil fuel combustion.It is divided into absorption method,adsorption method,membrane separation method and so on.The adsorption method is developing rapidly due to the advantages of high flexibility of operation,simple process,no secondary pollution,and low energy consumption for regeneration.Solid adsorbents such as biomass charcoal,zeolite molecular sieve,metal organic framework（MOF）and other materials have the advantages of a wide range of sources,low regeneration energy consumption,low cost,and controllable surface chemistry.They are widely used as materials for capturing carbon dioxide after combustion.It is difficult to form a porous biomass-based carbon material,and the process of pore-making process requires strong acid and strong alkaline substances,which is easy to corrode equipment and produces waste water which causes environmental pollution;a single zeolite molecular sieve material has poor water resistance;a single MOF has powder defects and is not resistant to high temperatures;The use of biomass carbon material composite zeolite or MOF material can improve the shortcomings of the above three single materials.Microfluidic technology is one of the effective means to achieve biomass charcoal composite zeolite or MOF by mixing zeolite or MOF material into liquid biomass（carbon precursor）for molding or in-situ synthesis.In this paper,chitosan（liquid biomass）,zeolite and MOF are used as raw materials,and microfluidic technology is used as a material composite method to prepare three materials.Control system parameters,adjust the surface properties and pore structure of the three materials,study the influence of the physical and chemical properties of the three materials on the carbon dioxide capture performance,and compare the adsorption performance of the three materials.The main conclusions are as follows:（1）Aiming at the shortcomings of difficult molding of biomass charcoal and poor dispersibility,microfluidic technology is used to prepare monodisperse spherical biomass charcoal.The flow rate of the two phases and the concentration of the dispersed phase have greater impact on the morphology and size of the biomass microdroplets.The best dispersed phase/continuous phase flow rate ratio and the dispersed phase concentration are 2:10 and 2 wt%,respectively;The pore structure of the material carbon is poor,and the specific surface area,total pore volume and micropore volume are 94.0 m²/g,0.034cm³/g and 0.032 cm³/g respectively;the spherical biomass carbon has low adsorption capacity,excellent reproducibility,and adsorption heat.Low value and good CO₂/N₂ selectivity.（2）Aiming at the disadvantages of low environmental friendliness and poor water resistance of zeolite molecular sieve,microfluidic technology and three zeolite raw materials（ZSM-5,MOR and Na-X）are used to prepare spherical biomass-based carbon-Zeolite composite material.ZSM-5 zeolite shows better stability than MOR and Na-X zeolite;changing the ratio of ZSM-5/chitosan can control the pore structure and carbon dioxide adsorption capacity of the biomass-based carbon-zeolite composite;the presence of soft template agent F127 can improve the mesoporous volume and nitrogen content of the composite material.The carbon dioxide adsorption capacity of the best sample is 1.23 mmol/g,the selectivity of CO₂/N₂ is 6.69（1 bar,25℃）,and the stability of ten cycles of regeneration is above 91%.（3）Aiming at the problems of poor heat resistance and powdery morphology of MOF materials,microfluidic technology is used to synthesize spherical biomass-MOF composite carbon materials in situ.Biomass-MOF composite carbon materials have developed pore structure and high nitrogen content.As the ratio of Zn（NO3）2·9H2O/chitosan of MOF increases,the specific surface area of the composite material first increases and then decreases,and the nitrogen content of the composite material increases;The carbonization temperature has a great influence on the nitrogen form of the biomass-MOF composite carbon material.The increase in temperature promotes the conversion of pyridine nitrogen to the stable graphite phase nitrogen;the CO₂adsorption capacity of the best sample is 1.27 mmol/g,and the CO₂/N₂selectivity is 22.7（1 bar,25℃）,and the carbon dioxide adsorption capacity is1.07 mmol/g after ten regenerations.（4）Comparing the adsorption performance of the three materials shows that the spherical biomass-based carbon-zeolite composite material has high adsorption capacity and good recyclability and is suitable for industrial applications.更多还原