【作者】 马静文；

【导师】 周政；

【作者基本信息】 南京大学 ， 应用化学， 2012， 硕士

【摘要】 二氧化碳作为一种主要的“温室气体”过量排放,给全球气候环境造成了严重的负面影响。但同时二氧化碳也是一种潜在的资源,二氧化碳是与氢气合成甲醇的重要原料。超临界二氧化碳也得到愈来愈广泛的应用,如作为石油开采的助采剂,能够有效的提高的石油的开采率。因此,脱碳技术的研究显得尤为重要和迫切。目前工业上使用较多的有机胺吸收法存在诸多的缺点,如MEA虽然吸收CO2速率快,但腐蚀性强且再生能耗高，MDEA有较高的CO2吸收负荷,但吸收速率较慢。离子液体的特殊优良性能使其可作为一种环境友好的脱碳吸收剂,其中氨基酸离子液体对CO2有较高的吸收速率。因此将离子液体和有机胺复配使用成为新型的脱碳吸收剂研究热点。本课题组张等人合成了四种季铵类的离子液体：[N1111][Gly],[N2222][Gly][N1111][Lys]和[N2222][Lys],并将其与MDEA以总胺量为30w%复配进行吸收CO2实验,发现复合吸收剂能够有效地克服MDEA吸收度率慢的缺陷,并且15w%IL+15w%MDEA具有比其他比例复合吸收剂更大的吸收容量和更快的吸收速率。在实际生产过程中,高吸收容量的吸收剂有利于减少吸收剂的用量及吸收设备的投入,从而降低成本。对于复配溶液提高其吸收容量通常有两种方法：第一种方法是提高主体吸收剂的吸收容量；第二种方法是提高离子液体的吸收容量。本文主要就从这两个方面来开展研究工作。首先通过提高MDEA的浓度来研究其对于吸收容量的影响,另一方面通过合成一种新的高吸收容量的离子液体并将其与MDEA复配成复合吸收剂来研究其吸收性能。本文根据文献合成了四甲基铵甘氨酸离子液体[N1111][Gly]),并以不同比例与较高浓度的MDEA(30w%、40w%、50w%)和水复配成混合吸收剂,测定了混合吸收剂的密度、黏度和表面张力等物性参数。为新型吸收剂在设计模型时提供了物性参数。本文对各种不同比例的复合吸收剂进行了吸收实验,发现复合吸收剂的吸收速率主要受离子液体浓度和溶液粘度这两个互相矛盾的因素影晌.离子液体浓度的增大对吸收速率有促进作用,但浓度的提高也导致了溶液黏度的增大,而黏度对于传质速率有负面的影响。从而离子液体浓度在0-15w%范围内的复合吸收剂的吸收速率存在两个极值点,极小值点在离子液体浓度为5w%时达到,而10w%的离子液体浓度为复合吸收剂吸收速率的极大值点。同时,发现对于高浓度的复合吸收剂的吸收容量而言,MDEA的浓度是吸收容量的主导因素,IL浓度对吸收容量的影响较小。综合吸收容量和吸收速率这两方面考虑,我们可以确定在一定浓度范围内最佳吸收剂的比例。为提高吸收剂的吸收容量,本文的还设计合成了一批新型的双季铵型的氨基酸离子液体,并对产物进行了1HNMR表征。选择产物四甲基二乙基乙二铵二甘氨酸(C2(N112)2Gly2)和产物四甲基二丁基乙二铵二甘氨酸(C2(N114)2Gly2)配制成不同浓度的水溶液,用于CO2吸收实验中。实验结果显示,对于不同浓度的双季铵型的氨基酸离子液体溶液,浓度和吸收剂粘度均对吸收速率有影响,增大吸收剂中离子液体的浓度可以提高吸收速率,但离子液体浓度过大会使吸收剂粘度增大,反而降低吸收速率。更多还原

【Abstract】 Excessive emission of carbon dioxide has caused serious negative effect to global climate environment. However, CO2is not just a major "greenhouse gas" but also an important potential resource. For example, Carbon dioxide can be transformed into environmental-friendly extraction solvent for green chemical industries. Moreover, as a Cl resource, CO2can be some basic chemical materials, such as CO, syngas and methanol[3,8].Thus the research about decarbonization technology is particularly important and urgent. At present,aqueous alkanolamines have been widely used as chemical absorbents for removal carbon dioxide. For example, MEA has been widely used as industrially important absorbent because of its rapid reaction rate while the MEA has a disadvantage due to its degradation through oxidation of the amine,high enthalpy of reaction and it causes operational problem; MDEA has high loading capacity,less regeneration energy, but the absorption rate is low. Ionic liquids (ILs) as good environmentally friendly decarburization absorbent have some special properties such as low vapor, high stability and easy assembly. However, the cost and viscosity of ILs was too high to be used as industrially important absorbent. Therefore, the hybrid of MDEA and IL become a hot research topic in the area of CO2removal.Zhang et al.[6] prepared four amino acid based ILs:tetramethylammonium glycinate([N1111][Gly]), tetraethylammonium glycinate([N2222][Gly]),tetramethylammoniumlysinate([N1111][Lys]) and tetraethylammonium lysinate([N2222][Lys]) and blended them and MDEA to create a new absorbent with the total amine concentration at30w%. They found that adding a certain amount of ILs in MDEA aqueous solution could greatly improve the absorption rate of CO2,and the aqueous solutions of15wt%IL and15wt%MDEA had higher absorption rate and larger uptake capacity than the other IL+MDEA solutions.In practice, large absorption capacity of the absorbent leads to smaller amount of absorbent and size of device, resulting in lower cost in CO2removal.There usually have two kinds of methods to improve the absorption capacity for mixture absorbents, either improve the absorption capacity of main absorption agent or enhance the IL’s.In this work,we have tried to improve the concentration of MDEA in the blended aqueous liquids,and also we synthesized a new kind of IL, dual-cations amino acid ILs, blended with MDEA to explore the effect of carbon structure and two positive charge centers on CO2uptake.In the present work, different amounts of [N1111][Gly] were added in MDEA aqueous solutions of higher concentration (above30wt%) to obtain a series of CO2absorbents. The absorbents prepared were suggested to have large absorption capacity and high absorption rate. By evaluating the absorption performance of CO2in these absorbents, the influence factors of absorption rate and absorption load were determined. The solution formulation with higher absorption rate and larger capacity could also be presented according to the conflicting impact of concentration and viscosity.The absorption mechanism of the amino acid based IL+MDEA aqueous solution would be verified by analyzing the experimental results. Besides, the physical properties necessary to industrial design, such as the density, viscosity and surface tension of the solution, were measured for all the tested solutions.For the first time, dual-cations amino acid ILs were synthesized, in which the cation was equipped with two charges and the anions were functionalized with two appended amine groups. In our work, DILs and their solutions were first applied in the absorption of CO2gas. Then, absorption of CO2in the DIL aqueous solutions and the DIL+MDEA aqueous solutions was investigated respectively to explore the effect of carbon structure and two positive charge centers on CO2uptake.更多还原