【作者】 张晓文；

【导师】 梁志武；

【作者基本信息】 湖南大学 ， 化学工程与技术， 2020， 博士

【摘要】 人类活动持续排放的CO₂等温室气体导致了温室效应和全球变暖,有机胺法CO₂捕获技术是目前最为常见和高效的CO₂捕获方法。但有机胺法CO₂捕获技术存在溶剂降解、设备腐蚀及富CO₂胺溶液再生能耗高等缺陷,尤其是溶剂再生能耗过高,极大地阻碍了该技术大规模的工业化应用,因此降低富胺溶液再生能耗对于CO₂捕获技术的发展有着极为重要的科学意义。为了实现胺溶剂高效低能耗的捕获分离CO₂,本研究设计并制备了多种固体酸催化剂及酸-碱复合催化剂,并将其用于催化富CO₂胺溶液的再生过程,以标准化胺溶剂5 M单乙醇胺溶液（MEA）为反应底物,胺溶液的富液负载是0.50 mol CO₂/mol amine,解吸温度为96-98℃。采用XRD、FT-IR、XPS、SEM、N₂脱附实验、CO₂/NH₃-TPD及P y-IR等多种表征手段对制备的催化剂的结构及酸碱性等物化性质进行了表征测试。系统考察了催化剂在富CO₂的MEA溶液中催化CO₂解吸过程CO₂解吸速率、解吸量及再生能耗的影响。对催化剂的构效关系进行了探索,并提出了可能的催化解吸机理;对催化剂的循环稳定性和催化再生对胺溶液的CO₂吸收性能的影响进行了研究。主要研究内容和创新性结果如下:（1）全面考察了固体酸催化剂SAPO-34和SO₄^2-/Ti O₂催化CO₂解吸性能。结果表明,两种催化剂可以降低CO₂解吸能耗17.1-24.3%,提升其解吸速率20.0-28.3%,SAPO-34显示出更好的催化活性。探究了催化剂用量对CO₂解吸性能的影响,结果表明,催化剂和胺溶液最佳质量比在1.0-1.5 wt%之间,催化剂SAPO-34显示出较好的循环稳定性;催化剂的介孔比表面积（MSA）和B/L比值对催化性能的提升起着至关重要的影响。（2）使用沉淀-浸渍法制备了负载型催化剂SO₄^2-/Zr O₂/γ-Al₂O₃（SZA）,并考察了其催化CO₂解吸性能。结果显示,SZA催化剂可以进一步提升CO₂解吸速率,降低CO₂解吸能耗,当Zr O₂和Al₂O₃的质量比为1/1时,SZA显示出最高的催化活性,它可以提高CO₂解吸速率33.3%,降低CO₂相对解吸能耗36.9%。催化剂S ZA的循环稳定性优异。SZA催化性能的增强主要归因于其增强的B酸位点、碱性位点和MSA。（3）以超声辅助的沉淀法制备了双功能复合催化剂Al₂O₃-H ZS M-5（Al-ZSM）,并考察了其催化CO₂解吸性能。Al-ZSM表现出增强的催化CO₂解吸性能,当Al₂O₃和HZSM-5的质量比是2时,Al-ZSM表现出最佳的催化CO₂解吸性能,可以降低CO₂的相对再生能耗34.2%,提升CO₂解吸因子近3倍左右。催化剂Al-ZSM显示出了优异的重复使用性能。Al-ZSM增强的B酸位点、MSA以及碱性位点,使其表现出优异的CO₂解吸性能。（4）以超声辅助的后修饰合成法制备了三种不同金属氧化物（Fe₂O₃,Al₂O₃和Mo O₃）修饰MCM-41的复合型催化剂,并考察了它们的催化CO₂解吸性能。Fe₂O₃修饰的MCM-41催化剂显示出最佳的催化性能,当Fe₂O₃含量为10%时,催化剂表现出最佳的催化性能,它能够提升CO₂解吸因子337.1%,降低再生能耗32.5%。复合催化剂显示出了优异的循环稳定性。催化剂增强的B酸位点和碱性位点是影响复合催化剂催化解吸性能的关键因素。此外,基于以上实验结果,系统的考察了催化剂物理化学性质和CO₂催化解吸性能之间的作用规律和催化机理,通过分析可知,催化剂催化CO₂解吸过程的作用机制主要在于,固体酸催化剂的Bronsted酸性位点（B酸）可提供质子用于解吸过程氨基甲酸酯的断裂反应,而Lewis酸性位点（L酸）则可以进一步促进氨基甲酸酯的断裂过程。而酸-碱双功能复合催化剂则可以同时促进再生过程的两步反应:（1）B酸和L酸位点可以同时促进再生过程氨基甲酸酯的断裂过程;（2）碱性位点模拟碳酸氢根基团的功能用于促进再生过程质子化胺去质子化反应,通过酸-碱性位点的协同催化作用,大大促进富CO₂胺溶液的再生过程。通过对比发现具有酸碱协同催化效应的复合催化剂辅助的CO₂解吸方法相比单一的固体酸催化剂能够大幅度降低解吸过程能耗而具有广阔的潜在工业应用前景。提出了酸碱双位点催化剂催化解吸CO₂的反应机理,该机理可为合理设计制备用于低能耗捕集CO₂的高效催化剂提供基础理论参考。更多还原

【Abstract】 The continuous emission of greenhouse gases such as CO₂ by human activities has caused the greenhouse effect and global warming.Amine-based CO₂ capture process is currently the most common and effective CO₂ capture method.However,this method suffers from several drawbacks such as,solvent degradation,equipment corrosion,and high solvent regeneration energy consumption,especially the excessive energy consumption for solvent regeneration,which greatly hinders the large-scale industrial application of this technology.Therefore,the reduction of the solvent regeneration heat duty has important scientific significance for the development of CO₂ capture technology.In order to achieve effective and low-energy consumption aminebased CO₂ capture process,various solid acid catalysts and acid-base bifunctional composite catalysts were designed and prepared in this study and used to catalyze the rich amine solution regeneration process.A baseline amine solvent,5 M monoethanolamine solution（MEA）was used as the reaction substrate,the rich CO₂ loading of the MEA solution is 0.50 mol CO₂/mol amine,and the CO₂ desorption temperature is 96-98℃.Various characterization methods including,XRD,FT-IR,XPS,SEM,N2 adsorptiondesorption experiment,CO₂/NH3-TPD,Py-IR were adopted to obtain the structure and physicochemical properties of the prepared catalysts.The catalytic CO₂ desorption performances of these catalysts in the CO₂-loaded MEA solution were systematically evaluated in terms of CO₂ desorption rate,the amount of desorbed CO₂ and the regeneration energy consumption.The structure-activity relationships of the catalysts were explored,and a possible catalytic CO₂ desorption mechanism was proposed.The cycle stability of catalyst and the effects of catalytic regeneration on the CO₂ absorption performance of MEA solution were studied.The main research contents and innovative results are as follows.（1）The catalytic CO₂ desorption performances of solid acid catalysts SAPO-34 and SO₄^2-/TiO2 were comprehensively investigated.The results showed that the use of the two catalysts reduced the regeneration energy consumption by 17.1-24.3% and increase the CO₂ desorption rate by 20.0-28.3%.SAPO-34 catalyst presented better catalytic activity than that of SO₄^2-/TiO2.The effect of catalyst dosage on CO₂ desorption performance was investigated,and the results showed that the optimal mass ratio of catalyst to amine solution was between 1.0-1.5 wt%.Also,the acid catalyst SAPO-34 presented good cycle stability.Mesoporous surface area（MSA）and B/L ratio of catalyst play a crucial role in improving the catalytic CO₂ desorption performance.（2）Three supported catalyst SO₄^2-/Zr O₂/γ-Al₂O₃（SZA）were prepared by the precipitation-impregnation method,and their catalytic CO₂ desorption performances were studied.The results showed that the SZA catalyst further increased the CO₂ desorption rate and reduced the regeneration heat duty.When the mass ratio of Zr O₂ and Al₂O₃ was 1/1,SZA catalytst displayed the highest catalytic activity,which could increase the CO₂ desorption rate by33.3% and lower the energy consumption by 36.9%.The supported catalyst SZA possesses superior cycle stability.The improved catalytic performance of SZA was mainly attributed to its enhanced B acid,basic site and MSA.（3）Four bifunctional composite catalysts Al₂O₃-HZSM-5（Al-ZSM）were prepared by the ultrasound-assisted precipitation method,and their catalytic CO₂ desorption performances were studied.Compared with the parent catalysts,Al-ZSM revealed enhanced catalytic CO₂ desorption performance.When the mass ratio of Al₂O₃ and HZSM-5 was 2/1,Al-ZSM showed the best catalytic CO₂ desorption performance,which decreased the energy requirement by 34.2% and increased the CO₂ desorption factor by about 3times.The bifunctional catalyst Al-ZSM showed excellent reusability.The enhanced B acid site,MSA and basic site of Al-ZSM catalysts made them presented excellent CO₂ desorption activity.（4）Three different metal oxides（Fe₂O₃,Al₂O₃ and MoO3）modified MCM-41 composite catalysts were prepared by ultrasound-as sis ted postmodification synthesis method,and their catalytic CO₂ desorption performances were evaluated.Fe₂O₃-modified MCM-41 catalyst showed the best catalytic performance.When Fe₂O₃ content was 10 wt%,the composite catalyst showed the best catalytic performance,which could increase the CO₂ desorption factor by 337.1% and reduce the regeneration energy consumption by 32.5%.The composite catalyst displayed good stability.The enhanced B acid sites and basic sites of the catalyst are the key factors to affect the catalytic CO₂ desorption performance.In addition,based on the above experimental results,the systematic investigation of the structure-activity relationships between the physical and chemical properties of the catalyst and the CO₂ catalytic desorption performance were performed.The main promotion mechanism of the solid acid catalyst is that the Br■nsted acid site（B acid）of the solid acid catalyst can provide protons to promote the breakdown of carbamate reaction in the desorption process,while the Lewis acid site（L acid）can further promote the carbamate breakdown reaction.While,the acid-base bifunctional composite catalyst can simultaneously promote the two-step reaction of the solvent regeneration process:（1）B acid and L acid sites can simultaneously promote the carbamate breakdown reaction in the solvent regeneration process;（2）basic site can mimics the role of bicarbonate to facilitate the protonated amine deprotonation reaction in the regeneration process.Through the synergistic catalysis effect of acid-basic sites,acid-base composite catalyst can greatly promote the rich amine solution regeneration process.It is found that the composite catalyst-assisted CO₂ desorption process with acid-base synergistic catalytic effect showed better catalytic CO₂ desorption performance than that of single solid acid catalyst,and has broad potential industrial application prospects for CO₂ capture field.A possible acid-base dual-site catalytic CO₂ desorption mechanism was proposed,which can provide a basic theoretical guideline for the rational design and preparation of high-efficiency catalysts for CO₂ capture with fast CO₂ desorption rate and low energy consumption.更多还原