气体中甲烷单组分的色谱—真空低温富集方法及其同位素分馏效应

刘清梅; 李嘉成; 蒋文敏; 熊永强

doi:10.11781/sysydz202403621

气体中甲烷单组分的色谱—真空低温富集方法及其同位素分馏效应

doi: 10.11781/sysydz202403621

刘清梅^{1, 2, 3,},
李嘉成^{1, 2, 3},
蒋文敏^{1, 2},
熊永强^{1, 2, ,}

1.
中国科学院广州地球化学研究所, 有机地球化学国家重点实验室, 广州 510640
2.
中国科学院深地科学卓越创新中心, 广州 510640
3.
中国科学院大学, 北京 100049

基金项目:

国家自然科学基金项目“深层油气中甲烷团簇同位素地球化学研究” 42073065

详细信息

作者简介:
刘清梅(1996—)，女，博士生，从事团簇同位素地球化学研究。E-mail: liuqingmei@gig.ac.cn

通讯作者:
熊永强(1967—)，男，博士，研究员，从事分子有机地球化学研究。E-mail: xiongyq@gig.ac.cn

中图分类号: TE135
计量
- 文章访问数: 209
- HTML全文浏览量: 83
- PDF下载量: 21
- 被引次数: 0
出版历程
- 收稿日期: 2023-06-05
- 修回日期: 2024-03-28
- 刊出日期: 2024-05-28

Chromatography-vacuum low temperature method of methane enrichment and isotopic fractionation in gas samples

LIU Qingmei^{1, 2, 3
,},
LI Jiacheng^{1, 2, 3},
JIANG Wenmin^{1, 2},
XIONG Yongqiang^{1, 2
, ,}

1.
State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, Guangdong 510640, China
2.
CAS Center for Excellence in Deep Earth Science, Guangzhou, Guangdong 510640, China
3.
University of Chinese Academy of Sciences, Beijing 100049, China

摘要

摘要: 甲烷(CH₄)团簇同位素分析在气候变化、能源勘探和行星生命等领域中发挥了重要作用。样品中CH₄的纯度直接了影响高分辨质谱团簇同位素分析的精度和准确性。针对气样中CH₄组分的富集纯化难题，根据气相色谱(GC)组分分离原理，实时监测组分峰形，进一步优化了载气线速、进样量等条件。同时，通过外标法量化回收率，GC组分分析验证纯度，保证纯化的有效性。通过优化色谱—真空低温富集制备方法，确定了IBEX系统载气最佳线速为12 mL/min，CH₄进样量需小于12 mL等实验条件，可视化GC峰形确保CH₄峰与相邻N₂干扰峰基本分离，实现了CH₄单组分的高纯富集。当气样中CH₄含量小于70%而空气含量较高时，需要进行二次纯化以提高CH₄纯度。讨论了5Å分子筛等吸附剂在纯化过程中可能引起CH₄同位素分馏的原因，并通过适当延长CH₄收集时间来消除5Å分子筛干扰。目前，该方法单次纯化过程约90 min，CH₄的回收率和纯度分别为90.1%~95.7%和97.3%~98.9%，对同位素组成(δ¹³C_VPDB和δD_VSMOW、Δ¹³CH₃D和Δ¹²CH₂D₂)的差异均小于质谱仪的分析误差，几乎可以忽略不计。
- 甲烷 /
- 气相色谱 /
- 纯度 /
- 回收率 /
- 同位素分馏
Abstract: Methane (CH₄) clumped isotope analysis plays a crucial role in the fields of climate change, energy exploration, and planetary research. The purity of CH₄ in samples directly affects the precision and accuracy of high-resolution mass spectrometry in clumped isotope analysis. Addressing the challenge associated with enriching and purifying CH₄ components in gas samples, this study optimized conditions such as carrier gas line speed and sample injection volume based on the principles of gas chromatography (GC) component separation, with real-time monitoring of component peak shapes. Additionally, the recovery rate was quantified using an external standard method and purity was verified through GC component analysis to ensure the effectiveness of the purification process. By optimizing the chromatography-vacuum low-temperature enrichment preparation method, the optimal carrier gas line speed for the IBEX system was determined to be 12 mL/min, with a CH₄ injection volume less than 12 mL. This facilitated visualization of GC peak shapes, thus ensured that the CH₄ peak was essentially separated from the adjacent N₂ interference peak, achieving high-purity enrichment of the CH₄ single component. When the CH₄ content in gas samples was less than 70% and the air content was high, secondary purification was required to improve CH₄ purity. The causes of CH₄ isotopic fractionation during purification using adsorbents like 5Å molecular sieves were discussed, and extending the CH₄ collection time was proposed to eliminate the interference from the 5Å molecular sieve. Currently, this method requires approximately 90 min for a single purification process, with CH₄ recovery and purity ranging from 90.1% to 95.7% and 97.3% to 98.9%, respectively. The differences in isotopic composition (δ¹³C_VPDB and δD_VSMOW, Δ¹³CH₃D, and Δ¹²CH₂D₂) are all less than the analytical error of the mass spectrometer, making them almost negligible.
- CH₄ /
- gas chromatography /
- purity /
- recovery rate /
- isotopic fractionation
注释:

利益冲突声明/Conflict of Interests

所有作者声明不存在利益冲突。

All authors disclose no relevant conflict of interests.

作者贡献/Authors’Contributions

刘清梅、蒋文敏参与实验设计；刘清梅、李嘉成完成实验操作；刘清梅、蒋文敏、熊永强参与论文写作和修改。所有作者均阅读并同意最终稿件的提交。

The experiment was designed by LIU Qingmei and JIANG Wenmin. The experimental operation was completed by LIU Qingmei and LI Jiacheng. The manuscript was drafted and revised by LIU Qingmei, JIANG Wenmin and XIONG Yongqiang. All authors have read the last version of the paper and consented to its submission.

HTML全文

图 1 甲烷纯化系统结构示意

Figure 1. Schematic structure of methane purification system

下载: 全尺寸图片幻灯片

图 2 甲烷同位素分析峰形

Figure 2. Peak shapes of methane isotopic analysis

下载: 全尺寸图片幻灯片

图 3 纯化气样SG-1甲烷纯化回收率

Figure 3. Methane purification recovery rate of purified gas sample SG-1

下载: 全尺寸图片幻灯片

图 4 混合气样SG-2纯化前后气相色谱(GC)组分分析

Figure 4. GC component analysis of mixed gas sample SG-2 before and after purification

下载: 全尺寸图片幻灯片

图 5 气相色谱的板高与载气线速关系

Figure 5. Relation curve between plate height and carrier gas line speed for gas chromatography

下载: 全尺寸图片幻灯片

图 6 气相色谱峰展宽效应

Figure 6. Peak broadening effect in gas chromatography

下载: 全尺寸图片幻灯片

表 1 甲烷气样SG-1纯化前后同位素组成对比

Table 1. Comparison of isotopic composition of methane gas sample SG-1 before and after purification

	δ¹³C_VPDB/‰	δD_VSMOW/‰	Δ¹³CH₃D/‰	Δ¹²CH₂D₂/‰	样品数
纯化前	-43.23	-182.78	2.65	2.14	5
纯化后	-43.30	-182.82	2.91	1.50	5

下载: 导出CSV

表 2 通过改变载气线速纯化气样后甲烷回收率及纯度数据

Table 2. Recovery and purity data of methane after purification of gas sample by varying carrier gas line speed

样品	体积/mL	柱温/℃	载气流速/(mL/min)	峰面积			回收率/%	纯度/%
样品	体积/mL	柱温/℃	载气流速/(mL/min)	O₂	N₂	CH₄	回收率/%	纯度/%
SG-1	6	30	30	80.8	310.2	22 372.9	82.1	98.3
MG-20%	6	30	30	183.4	3 020.3	18 167.3	83.6	85.0
SG-1	6	30	20	99.1	347.4	23 279.6	85.5	98.1
MG-20%	6	30	20	187.2	1 804.5	18 913.2	87.1	90.5
SG-1	6	30	15	145.9	408.3	24 157.7	88.7	97.8
MG-20%	6	30	15	195.7	1 076.7	19 235.5	88.6	93.8
SG-1	6	30	12	112.2	353.6	25 940.1	95.2	98.2
MG-20%	6	30	12	177.3	415.1	20 831.4	95.9	97.2
SG-1	6	30	10	136.8	348.1	25 673.3	94.2	98.1
MG-20%	6	30	10	189.5	394.4	20 374.8	93.8	97.2
SG-1	9	30	12	92.7	384.2	38 221.7	93.1	98.8
SG-2	9	30	12	109.8	401.1	18 284.2	95.0	97.3
SG-1	12	30	12	112.4	434.1	47 589.2	86.8	98.9
SG-2	12	30	12	87.3	397.5	24 442.7	94.8	98.1
SG-1	18	30	12	124.4	468.3	70 179.5	85.1	99.2
SG-2	18	30	12	97.6	445.8	36 950.7	95.1	98.6
MG-10%	8	30	12	128.4	331.3	30 912.2	94.4	98.5
MG-20%	8	30	12	133.6	358.2	27 098.3	93.2	98.2
MG-30%	8	30	12	115.1	3 197.8	23 289.8	91.7	87.5
MG-30%-2nd	8	30	12	88.3	405.6	22 868.9	90.0	97.9
MG-50%	8	30	12	150.9	5 266.9	16 851.1	93.4	75.7
MG-50%-2nd	8	30	12	73.6	409.4	16 491.9	91.4	97.2
注：样品名中，百分比表示气样中N₂含量，“2nd”表示二次纯化。

下载: 导出CSV

表 3 甲烷不充分回收时同位素组成

Table 3. Isotopic composition of CH₄ in inadequate recovery

气样	体积/mL	采样时间/min	回收率/%	纯度/%	δ¹³C_VPDB/‰
SG-1	6	5	36.3	98.1	-41.52
SG-1	6	10	54.0	98.6	-42.22
SG-1	6	17	69.4	98.4	-42.68
SG-1	6	30	88.6	97.8	-42.89
SG-1	6	40	90.2	98.0	-43.02
SG-1	6	50	94.1	97.5	-43.39
注：SG-1初始同位素组成δ¹³C_VPDB-initial=-43.26‰。

下载: 导出CSV

参考文献(37)

[1]	DOUGLAS P M J, STOLPER D A, SMITH D A, et al. Diverse origins of arctic and subarctic methane point source emissions identified with multiply-substituted isotopologues[J]. Geochimica et Cosmochimica Acta, 2016, 188: 163-188. doi: 10.1016/j.gca.2016.05.031
[2]	BEAUDRY P, STEFÁNSSON A, FIEBIG J, et al. High temperature generation and equilibration of methane in terrestrial geothermal systems: evidence from clumped isotopologues[J]. Geochimica et Cosmochimica Acta, 2021, 309: 209-234. doi: 10.1016/j.gca.2021.06.034
[3]	GIUNTA T, YOUNG E D, LABIDI J, et al. Extreme methane clumped isotopologue bio-signatures of aerobic and anaerobic methanotrophy: insights from the Lake Pavin and the Black Sea sediments[J]. Geochimica et Cosmochimica Acta, 2022, 338: 34-53. doi: 10.1016/j.gca.2022.09.034
[4]	YOUNG E D, KOHL I E, SHERWOOD LOLLAR B, et al. The relative abundances of resolved ^l2CH₂D₂ and ¹³CH₃D and mechanisms controlling isotopic bond ordering in abiotic and biotic methane gases[J]. Geochimica et Cosmochimica Acta, 2017, 203: 235-264. doi: 10.1016/j.gca.2016.12.041
[5]	马东民, 王馨, 滕金祥, 等. 镜煤和暗煤与甲烷界面作用实验研究: 以民和盆地低阶煤为例[J]. 油气藏评价与开发, 2022, 12(4): 556-563. https://www.cnki.com.cn/Article/CJFDTOTAL-KTDQ202204002.htm MA Dongmin, WANG Xin, TENG Jinxiang, et al. Experimental study on interfacial interaction between methane and vitrinite and durain: a case study of bituminous coal in Minhe Basin[J]. Petroleum Reservoir Evaluation and Development, 2022, 12(4): 556-563. https://www.cnki.com.cn/Article/CJFDTOTAL-KTDQ202204002.htm
[6]	杨琴, 黄亮, 周文, 等. 深层页岩伊利石孔隙中甲烷吸附相密度特征[J]. 断块油气田, 2023, 30(5): 799-807. https://www.cnki.com.cn/Article/CJFDTOTAL-DKYT202305012.htm YANG Qin, HUANG Liang, ZHOU Wen, et al. Adsorption phase density characteristics of methane in illite pores of deep shale[J]. Fault-Block Oil and Gas Field, 2023, 30(5): 799-807. https://www.cnki.com.cn/Article/CJFDTOTAL-DKYT202305012.htm
[7]	毛港涛, 李治平, 王凯, 等. 全可视化双反应釜内甲烷水合物生成与分解特征研究[J]. 特种油气藏, 2023, 30(3): 73-80. https://www.cnki.com.cn/Article/CJFDTOTAL-TZCZ202303009.htm Mao Gangtao, Li Zhiping, Wang Kai, et al. Study on the generation and decomposition characteristics of methane hydrate in Fully Visible Dual Reactor[J]. Special Oil & Gas Reservoirs, 2023, 30(3): 73-80. https://www.cnki.com.cn/Article/CJFDTOTAL-TZCZ202303009.htm
[8]	史利燕, 李卫波, 康琴琴, 等. CH₄-煤吸附/解吸过程视电阻率变化的实验研究[J]. 油气藏评价与开发, 2022, 12(4): 572-579. https://www.cnki.com.cn/Article/CJFDTOTAL-KTDQ202204004.htm SHI Liyan, LI Weibo, KANG Qinqin, et al. Experimental study on variation of apparent resistivity in CH₄-coal adsorption/desorption process[J]. Petroleum Reservoir Evaluation and Development, 2022, 12(4): 572-579. https://www.cnki.com.cn/Article/CJFDTOTAL-KTDQ202204004.htm
[9]	张添锦, 王延峰, 李军, 等. 注CO2提高页岩吸附甲烷采收率核磁共振实验[J]. 特种油气藏, 2023, 30(5): 113-120. doi: 10.3969/j.issn.1006-6535.2023.05.015 Zhang Tianjin, Wang Yanfeng, Li Jun, et al. Nuclear magnetic resonance experiment for enhanced recovery af adsorbed methane from shale through carbon dioxide injection[J]. Special Oil & Gas Reservoirs, 2023, 30(5): 113-120. doi: 10.3969/j.issn.1006-6535.2023.05.015
[10]	WHITICAR M J. Carbon and hydrogen isotope systematics of bacterial formation and oxidation of methane[J]. Chemical Geology, 1999, 161(1/3): 291-314.
[11]	EILER J M. A practical guide to clumped isotope geochemistry[J]. Geochimica et Cosmochimica Acta, 2006, 70(S18): A157.
[12]	EILER J M. "Clumped-isotope" geochemistry—The study of naturally-occurring, multiply-substituted isotopologues[J]. Earth and Planetary Science Letters, 2007, 262(3/4): 309-327.
[13]	EILER J M, CLOG M, MAGYAR P, et al. A high-resolution gas-source isotope ratio mass spectrometer[J]. International Journal of Mass Spectrometry, 2013, 335: 45-56. doi: 10.1016/j.ijms.2012.10.014
[14]	YOUNG E D, RUMBLE Ⅲ D, FREEDMAN P, et al. A large-radius high-mass-resolution multiple-collector isotope ratio mass spectrometer for analysis of rare isotopologues of O₂, N₂, CH₄ and other gases[J]. International Journal of Mass Spectrometry, 2016, 401: 1-10. doi: 10.1016/j.ijms.2016.01.006
[15]	ONO S, WANG D T, GRUEN D S, et al. Measurement of a doubly substituted methane isotopologue, ¹³CH₃D, by tunable infrared laser direct absorption spectroscopy[J]. Analytical Chemistry, 2014, 86(13): 6487-6494. doi: 10.1021/ac5010579
[16]	GONZALEZ Y, NELSON D D, SHORTER J H, et al. Precise measurements of ¹²CH₂D₂ by tunable infrared laser direct absorption spectroscopy[J]. Analytical Chemistry, 2019, 91(23): 14967-14974. doi: 10.1021/acs.analchem.9b03412
[17]	GILBERT A, YAMADA K, YOSHIDA N. Exploration of intramolecular ¹³C isotope distribution in long chain n-alkanes (C₁₁-C₃₁) using isotopic ¹³C NMR[J]. Organic Geochemistry, 2013, 62: 56-61. doi: 10.1016/j.orggeochem.2013.07.004
[18]	MARTIN G J, GUILLOU C, MARTIN M L, et al. Natural factors of isotope fractionation and the characterization of wines[J]. Journal of Agricultural and Food Chemistry, 1988, 36(2): 316-322. doi: 10.1021/jf00080a019
[19]	GILBERT A, SILVESTRE V, SEGEBARTH N, et al. The intramolecular ¹³C-distribution in ethanol reveals the influence of the CO₂-fixation pathway and environmental conditions on the site-specific ¹³C variation in glucose[J]. Plant, Cell & Environment, 2011, 34(7): 1104-1112.
[20]	GILBERT A. The organic isotopologue frontier[J]. Annual Review of Earth and Planetary Sciences, 2021, 49(1): 435-464. doi: 10.1146/annurev-earth-071420-053134
[21]	STOLPER D A, SESSIONS A L, FERREIRA A A, et al. Combined ¹³C-D and D-D clumping in methane: methods and preliminary results[J]. Geochimica et Cosmochimica Acta, 2014, 126: 169-191. doi: 10.1016/j.gca.2013.10.045
[22]	STOLPER D A, LAWSON M, DAVIS C L, et al. Formation temperatures of thermogenic and biogenic methane[J]. Science, 2014, 344(6191): 1500-1503. doi: 10.1126/science.1254509
[23]	WANG D T, GRUEN D S, LOLLAR B S, et al. Nonequilibrium clumped isotope signals in microbial methane[J]. Science, 2015, 348(6233): 428-431. doi: 10.1126/science.aaa4326
[24]	WANG D T, WELANDER P V, ONO S. Fractionation of the methane isotopologues ¹³CH₄, ¹²CH₃D, and ¹³CH₃D during aerobic oxidation of methane by Methylococcus capsulatus (Bath)[J]. Geochimica et Cosmochimica Acta, 2016, 192: 186-202. doi: 10.1016/j.gca.2016.07.031
[25]	JENNINGS W. Analytical gas chromatography[M]. Orlando: Academic Press Inc., 1987.
[26]	CHEN Zhigang, YIN Xijie, ZHOU Youping. Effects of GC temperature and carrier gas flow rate on on-line oxygen isotope measurement as studied by on-column CO injection[J]. Journal of Mass Spectrometry, 2015, 50(8): 1023-1030. doi: 10.1002/jms.3617
[27]	WERRES T, SCHMIDT T C, TEUTENBERG T. The influence of injection volume on efficiency of microbore liquid chromatography columns for gradient and isocratic elution[J]. Journal of Chromatography A, 2021, 1641: 461965. doi: 10.1016/j.chroma.2021.461965
[28]	STRАPOĆD, SCHIMMELMANN A, MASTALERZ M. Carbon isotopic fractionation of CH₄ and CO₂ during canister desorption of coal[J]. Organic Geochemistry, 2006, 37(2): 152-164. doi: 10.1016/j.orggeochem.2005.10.002
[29]	XIA Xinyu, TANG Yongchun. Isotope fractionation of methane during natural gas flow with coupled diffusion and adsorption/desorption[J]. Geochimica et Cosmochimica Acta, 2012, 77: 489-503. doi: 10.1016/j.gca.2011.10.014
[30]	苏现波, 陈润, 林晓英, 等. 煤吸附¹³CH₄与¹²CH₄的特性曲线及其应用[J]. 煤炭学报, 2007, 32(5): 539-543. doi: 10.3321/j.issn:0253-9993.2007.05.021 SU Xianbo, CHEN Run, LIN Xiaoying, et al. The adsorption characteristic curves of ¹³CH₄ and ¹²CH₄ on coal and its application[J]. Journal of China Coal Society, 2007, 32(5): 539-543. doi: 10.3321/j.issn:0253-9993.2007.05.021
[31]	WANG Xiaofeng, LI Xiaofu, WANG Xiangzeng, et al. Carbon isotopic fractionation by desorption of shale gases[J]. Marine and Petroleum Geology, 2015, 60: 79-86. doi: 10.1016/j.marpetgeo.2014.11.003
[32]	MASON E A, KRONSTADT B. Graham's laws of diffusion and effusion[J]. Journal of Chemical Education, 1967, 44(12): 740. doi: 10.1021/ed044p740
[33]	GUNTER B D, GLEASON J D. Isotope fractionation during gas chromatographic separations[J]. Journal of Chromatographic Science, 1971, 9(3): 191-192. doi: 10.1093/chromsci/9.3.191
[34]	CUI Xiaojun, MARC BUSTIN R, DIPPLE G. Selective transport of CO₂, CH₄, and N₂ in coals: insights from modeling of experimental gas adsorption data[J]. Fuel, 2004, 83(3): 293-303. doi: 10.1016/j.fuel.2003.09.001
[35]	WANG Xiaofeng, LIU Peng, MENG Qiang, et al. Physical selectivity on isotopologues of gaseous alkanes by shale pore network: evidence from dynamic adsorption process of natural gas[J]. Journal of Natural Gas Science and Engineering, 2022, 97: 104252. doi: 10.1016/j.jngse.2021.104252
[36]	CRANK J. The mathematics of diffusion[M]. 2nd ed. Oxford: Clarendon Press, 1975.
[37]	程付启, 金强. 成藏后天然气组分与同位素的分馏效应研究[J]. 天然气地球科学, 2005, 16(4): 522-525. doi: 10.3969/j.issn.1672-1926.2005.04.022 CHENG Fuqi, JIN Qiang. Composition and isotope fractionations of accumulated natural gas and their significance[J]. Natural Gas Geoscience, 2005, 16(4): 522-525. doi: 10.3969/j.issn.1672-1926.2005.04.022