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Alternative TitleFundamental Research on the Efficient Materials for CO2 Adsorptive Separation from Metallurgic Flue Gas
Thesis Advisor唐清
Degree Grantor中国科学院研究生院
Degree Discipline化学工艺
Keyword二氧化碳   吸附   金属有机骨架   介孔分子筛   氨基修饰
Abstract我国CO2减排压力巨大。钢铁行业是过程工业CO2排放大户,其中高炉煤气含有大量CO2,现有以燃烧发电为主的利用方式未能实现煤气碳氢资源高值利用,而且造成CO2的集中排放。开发高效低成本CO2分离技术是实现钢铁行业碳氢烟气资源高值利用的迫切需求。本文针对高炉煤气温度高、CO2浓度低、组成复杂的特点,以研发高温条件下具有高吸附量和高选择性的新型CO2吸附剂为目标,通过向金属有机骨架MIL-101以及MSU、白炭黑等硅基多孔材料中引入氨基来增强材料表面碱性,系统开展了吸附剂制备、孔道结构与表面基团表征、吸附性能评价等研究工作。主要研究内容和创新点如下: (1)确定了MIL-101水热合成条件和氟化铵提纯方法,通过多种表征手段证明合成产物具有MIL-101的特有结构。实验研究表明,不同的Cr配位基团影响Cr空位对CO2的吸附能力,羟基中的氢原子与CO2形成弱氢键作用,导致MIL-101-OH的吸附焓较大。通过考察不同气体的吸附等温线,发现低压下MIL-101对CO的吸附能力较强,难以实现CO2/CO体系中CO2的高效分离。 (2)首次制备了MIL-101负载有机胺吸附剂,考察有机胺种类和负载量对CO2吸附量的影响。结果表明,负载四乙烯五胺(TEPA)的CO2吸附效果最好,当负载量达到70%时,在75℃、CO2分压10kPa条件下,CO2吸附量达到了3.8mmol/g。考察不同气体的吸附等温线,发现吸附剂对CO和N2基本没有吸附作用,可以实现CO2、CO、N2体系中CO2的高选择性分离。开展了吸附剂再生研究,结果表明在145℃下CO2可以实现完全脱附;但TEPA高温条件下容易流失,随着循环次数增加,CO2吸附量呈现逐渐下降趋势。 (3)为改善吸附剂稳定性,首次制备了MIL-101嫁接TEPA吸附剂。光谱表征分析研究表明,TEPA通过与金属Cr不饱和空位发生配位反应连接到MIL-101上。实验研究表明,嫁接TEPA后,由于Cr不饱和空位被TEPA占据,CO吸附得到了明显抑制,CO2/CO选择性由1.77提高到70.2;循环实验表明吸附剂循环稳定性较好,多次循环后吸附量保持在1.2mmol/g左右。通过分子模拟计算,初步揭示了CO2与TEPA的作用机理为酸碱作用与弱氢键作用。 (4)首次制备了未煅烧MSU负载TEPA吸附剂,研究了模板剂对吸附性能的影响,发现模板剂的存在有利于提高CO2吸附量,同时可以降低CO2的脱附温度。实验研究表明,当TEPA负载量为50%时,具有CO2最佳吸附效果,在75℃,10kPa条件下可达到3.87mmol/g。吸附剂对CO和N2基本不吸附,CO2选择性高。考察了温度、压力对CO2吸附量的影响,表明最佳吸附温度为75℃,压力对CO2吸附量影响较小;探索了吸附剂的再生条件,结果表明吸附剂在100℃吹扫1小时即可完成再生,适合应用于变温吸附过程。通过红外光谱分析发现,吸附剂通过TEPA和CO2反应生成氨基甲酸铵的形式来捕获CO2。
Other AbstractThere is high pressure of CO2 reduction in China. Large amount of CO2 exists in blast furnace gas from iron and steel industry . Power generation through the combusion of the blast furnace gas causes huge emmision of CO2 and less effective utilization of CO resource. The development of effective and low cost CO2 separation technology is necessary for improving the utilization efficiency of flue gas. In this paper, amine was introduced to the pores of porous materials such as metal organic framework MIL-101, mesopous silica MSU and precipitated silica in order to increae the basicity of surface and improve the capacity and selectivity, making the adsorbents suitable for CO2 separation from blast furnace gas with high temperature, low CO2 concentration and complicated composition. The adsorbents preparation, characterization and eveluation of adsorption properties were conducted systematically and the important results are showed as follows: (1) The condition of hydrothermal synthesis and purification with NH4F for MIL-101 were determined. The product had the specific structure of MIL-101 proved by characterization. The results showed that the effect of group connected with Cr on CO2 adsorption was investigated. Hydrogen bond was formed between CO2 can OH, which resulted in a higher adsorption enthalpy of MIL-101-OH. By comparing the adsorption isotherms of different gases, it was found that the adsorption of CO is also available at low pressure on MIL-101, namely the selectivity of CO2 over CO is low. (2) In order to improve the CO2 selectivity, amines were introduced to MIL-101 by impragnance for the first time. The evaluation of CO2 adsorption capacity on MIL-101 loaded with different amines and content was conducted. It was found that TEPA loaded adsorbent has the higheset capacity and the optimal loading amount was 70%. The CO2 adsorption capacity is up to 3.8mmol/g at 75 oC and 10kPa. Comparison of the isotherms of different gases showed that no CO and N2 are captured on this adsorbent, resulting in excellent selectivity. Regeneration research was conducted and the adsorbent could be thoroughly regenerated at 145℃. Adsorption capacity decreased after several cycle of adsorption-desorption because of the loss of TEPA. (3) Amine-grafted metal organic framework was prepared by grafting TEPA on the coordinatively unsaturated Cr sites of MIL-101 in order to improve the cyclic stability. TEPA molecule was successfully grafted on Cr proved by UV-vis spectroscopy. After TEPA grafted, the CO capacity sharply decreased as the Cr coordination unsaturated sites were occupied by TEPA. The selectivity for CO2 over CO was clearly improved from 1.77 to 70.2. Cyclic adsorption evaluation showed that capacity is 1.2 mmol/g during several cycles, indicating high stability of the adsorbent. The density functional theory calculation for the adsorption of CO2 and CO on TEPA indicates that CO2 captured by TEPA through acid-base interaction and hydrogen bond and the bonding energy of CO2 is obviously higher than that of CO. (4) Tetraethylenepentamine (TEPA) was incorporated into as-synthesized mesoporous silica MSU-1 for the first time. It was found that the template in the pores of MSU could increase the adsorption capacity of CO2 and decrease the regeneration temperature. 50 wt% of TEPA supported on as-synthesized MSU-1 achieved the highest capacity at 3.87 mmol/g at 75 oC and 10kPa. Excellent selectivity of CO2 was achieved as no CO and N2 were captured. CO2 adsorption isotherms measured at different temperatures revealed that the optimal adsorption temperature is 75 oC. Temperature-programmed desorption (TPD) of CO2 showed that the desorption of CO2 achieved maximal desorption rate at about 100 oC, and so is appropriate for thermal swing adsorption of CO2 from flue gas. The FTIR results suggested that CO2 interacts with TEPA to form alkalammonium carbamate.
Document Type学位论文
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王兴瑞. 冶金烟气二氧化碳高效吸附分离材料的基础研究[D]. 中国科学院研究生院,2013.
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