《用于n2ch4和co2ch4体系分离的新型吸附剂研究》由会员分享,可在线阅读,更多相关《用于n2ch4和co2ch4体系分离的新型吸附剂研究(60页珍藏版)》请在金锄头文库上搜索。
1、河北工业大学 硕士学位论文 用于N/CH和CO/CH体系分离的新型吸附剂研究 姓名:吴彩丽 申请学位级别:硕士 专业:应用化学 指导教师:韩恩山;刘秀伍 20100401 河北工业大学硕士学位论文 i 用于用于 N2/CH4和和 CO2/CH4体系分离的新型吸附剂研究体系分离的新型吸附剂研究 摘摘 要要 抽放煤层气和垃圾填埋气的主要成分分别为 N2/CH4和 CO2/CH4。 变压吸附法用于处理 这种小规模气体非常具有优势,但关键是缺乏高选择性的吸附剂。本课题针对用于分离这 两个体系(N2/CH4和 CO2/CH4体系)的高选择性新型吸附剂进行了研究。 以 N2为强吸附组分的天然斜发沸石和 E
2、TS- 4 沸石分子筛可以通过变压吸附分离方法 直接得到 CH4产品气,是非常具有发展前景的吸附剂。本论文首先对我国不同产地的四种 天然斜发沸石进行了筛选,发现产自吉林的斜发沸石性能最好。在不同温度下对其焙烧改 性,发现在 100焙烧的沸石为 CH4选择性,而在 280焙烧的沸石为 N2选择性吸附剂; 为了进一步改善其吸附性能, 又对其进行离子交换改性研究, 发现在室温下交换 3 次的 Na- 斜发沸石效果最好,为氮气选择性吸附剂,1 个大气压下氮气/甲烷吸附量之比为 4.37;而 Ca、Mg、Li、K、Sr、NH4- 斜发沸石对 N2和 CH4的吸附量差别不大。接着又合成了 ETS- 4 钛
3、硅分子筛,对其进行了表征,其 XRD 和 SEM 结果与文献相同,说明合成样品为 ETS- 4 分子筛。对其进行了 Sr 离子交换改性,改性后其对 N2和 CH4的吸附容量不如 Na- 斜发沸 石高,但是相同大气压下 N2/CH4吸附量之比高于 Na- 斜发沸石。 将 CO2吸收剂负载在介孔分子筛上,使介孔分子筛的介孔与吸收作用结合起来,如果 对 CO2的吸附效果能大大提高,则会成为高选择性 CO2吸附剂。首先合成介孔分子筛 SBA- 15,以 DIPA、MDEA、NMP、DGDE、TEP、PC 等对其改性。研究证明,改性后的 SBA- 15 仍保持高度有序的六方结构。通过对比,发现负载 DI
4、PA 后的 SBA- 15 对 CO2和 CH4的分离因子最高,其吸附的 CH4可以完全再生,而 CO2在 6 次稳定性实验后吸附量达 到稳定, 稳定后 CO2/CH4的分离因子为 15.5。随后研究了温度对 CO2和 CH4吸脱附性能 的影响,发现高温有利于吸附,低温有利于解吸, 45时对 CO2/CH4的综合分离性能最 好。 关键词:关键词:煤层甲烷,填埋气,分离,斜发沸石,介孔分子筛 SBA- 15,改性 用于 N2/CH4和 CO2/CH4体系分离的新型吸附剂研究 ii STUDIES ON NOVEL ADSORBENTS FOR N2/CH4 AND CO2/CH4 SEPARAT
5、ION ABSTRACT The main components of coal- bed gas are methane and nitrogen, while the main components of landfill gas are methane and carbon dioxide. The pressure swing adsorption (PSA) has the superiority in dealing with these cases where the flow rate is not large, but high selectivity adsorbents
6、are unavailable. The adsorbents, used for the two systems metioned above (methane/nitrogen and methane/carbon dioxide), were investigated to increase selectivity. The N2 selectivity adsorbents (natural clinoptilolite and ETS- 4 sieves) have a promising future as CH4 can be obtained directly as produ
7、ct gas by PSA. The clinoptilolite(1) produced in Jilin was the best one screened in the four kinds obtained from different areas of China. Treated at different temperature, The clinoptilolite(1) was methane- preferred when calcined at 100, but it was nitrogen- preferred when calcined at 280. To impr
8、ove its selectivity, different ion- exchange clinoptilolites were studied. Na- clinoptilolite exchanged at room temperature for three times was the best,it was nitrogen- preferred,and its N2 and CH4 adsorption amount ratio is 4.37 at 1 atm. The adsorption amount of N2 and CH4 on Ca, Mg, Li, K, Sr an
9、d NH4- clinoptilolite was similar. ETS- 4 sieves are synthesized, and their structures are the same with the literatures by its XRD and SEM results. Modified it with Sr, and the N2 and CH4 adsorption amount on Sr- ETS- 4 is not so good as that of Na- clinoptilolite, but the adsorption amount ratio o
10、f N2 and CH4 is higher than Na- clinoptilolite. If mesoporous molecular sieves are modified by CO2 absorbents in the CH4/N2 separation system, the mesopore and absorption were combined and the adsorption capacity of CO2 can be enhanced, and it would be a CO2 capture adsorbent. Firstly, SBA- 15 mesop
11、orous molecular sieve was synthesized and modified by different CO2 absorbents such as DIPA, MDEA, NMP, DGDE, TEP, PC. The structures of SBA- 15 before and after modified all remain highly ordered hexagonal structure. The SBA- 15 modified by DIPA has a maximum selective separation coefficient for CO
12、2/CH4. Methane adsorbed on SBA- 15 modified by DIPA could be regenerated 河北工业大学硕士学位论文 iii completely, while the adsorption capability of carbon dioxide decreased and reached stable after 6 stability tests, and the separation coefficient of CO2/CH4 was 15.5. The carbon dioxide adsorption- desorption
13、performance of DIPA modified SBA- 15 were studied on temperature change. High temperature is benefit to adsorption and low temperature is advantageous to desorption, and the comprehensive performance for CO2/CH4 separation is best at 45. KEY WORDS: coal- bed methane, landfill gas, separation, clinop
14、tilolite, mesoporous molecular sieve SBA- 15, modify 用于 N2/CH4和 CO2/CH4体系分离的新型吸附剂研究 vi 符号说明 ij 分离因子 无因次 x 吸附相摩尔分数 无因次 y 气相摩尔分数 无因次 n 吸附量 mmol/g qs 饱和吸附量 mmol/g b Langmuir 常数 1/atm C0 原料气中 CO2的浓度 mol/L C 脱附气中 CO2的浓度 mol/L iii 河北工业大学硕士学位论文 1 第一章第一章 文献综述文献综述 1- 1 研究背景和意义研究背景和意义 大气“温室效应”与地球变暖是 21 世纪人类面临
15、的最大的环境问题。人类在能源系统中产生并直 接排放的大量 CO2是导致该现象的主要原因,另外 CH4的排放也是产生温室效应的重要因素,其温室 效应为 CO2的 20- 24 倍。不论从环境保护还是节约能源的角度来看,在全世界范围内对排放的 CH4 和 CO2 进行回收和利用是非常必要的。同时,随着煤、石油和石油天然气等这些不可再生性资源的日渐 匮乏,迫使人们寻求新能源和可再生能源。 而我国的煤层气(瓦斯)资源十分丰富(据 2006 年煤层气资源评价结果,2000m 以浅的煤层气约有 36.811012m3,与剩余的天然气储量相当,可采集量约为 10.871012m31),煤层气中的 CH4是一种优质 的清洁能源,其在 21 世纪的能源结构中将会占很大的份额。另外,CH4也是造成煤矿爆炸事故的重要 因素,因为当空气中甲烷浓度达到 515%时就可能会发生燃烧或爆炸。因此,加大对煤层气中的 CH4 的回收和利用是一项具有如下战略意义的举措: (1)变废为宝:我国每年排掉的煤层气相当于两年的天然气产量,在 0,101.325kPa 下 1m3的煤层 气(甲烷含量 100%)的热能产值相当于 1kg 石油,可发电 3kWh2。经过处理的煤层 CH4可以替代常规液 化石油气作