表 1
褐煤的工业分析和元素分析
Table 1.
Proximate and ultimate analyses of coal samples
引用本文:
闫洁, 赵云鹏, 肖剑, 田由甲. 胜利褐煤和小龙潭褐煤在甲醇中的热溶及热溶物分析[J]. 燃料化学学报,
2016, 44(1): 15-22.
Citation: YAN Jie, ZHAO Yun-peng, XIAO Jian, TIAN You-jia. Thermal dissolution of Shengli and Xiaolongtan lignites in methanol and analysis of the soluble portions[J]. Journal of Fuel Chemistry and Technology, 2016, 44(1): 15-22.
Citation: YAN Jie, ZHAO Yun-peng, XIAO Jian, TIAN You-jia. Thermal dissolution of Shengli and Xiaolongtan lignites in methanol and analysis of the soluble portions[J]. Journal of Fuel Chemistry and Technology, 2016, 44(1): 15-22.
胜利褐煤和小龙潭褐煤在甲醇中的热溶及热溶物分析
摘要:
研究了胜利褐煤(SL) 和小龙潭褐煤(XLT) 在甲醇中的热溶行为, 并利用傅里叶变换红外光谱、气相色谱/质谱(GC/MS) 和大气压固体分析探针/飞行时间质谱(ASAP/TOF-MS) 对320 ℃热溶物的组成和结构特征进行了分析。两种褐煤热溶物产率均随温度升高而增加, 但240 ℃后XLT热溶物(SPXLT) 产率明显高于SL热溶物(SPSL)。GC/MS分析表明, 两种褐煤热溶物以含氧化合物为主, 尤其酚类的相对含量超过49%;与SPXLT相比, SPSL中烯烃、芳烃、醚类、羧酸、酯类和有机硫化合物(OSCs) 含量较高, 而烷烃、酚类、酮类和有机氮化合物含量较低; SPSL中的OSCs以噻吩为主, 而SPXLT中的OSCs以硫醇为主。ASAP/TOF-MS可检测出热溶物中大量GC/MS无法检测出的较强极性和难挥发化合物; 与SPXLT相比, SPSL中CHO和CHS族分含量较低, 而CHN、CHNO、CHOS、CHNS和CHNOS族分含量较高; 两种褐煤热溶物中化合物的碳数和双键数(double bond equivalent, DBE) 主要分布在3-15和0-10, SPXLT中化合物的碳数和DBE分布相对集中。
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关键词:
- 褐煤
- / 热溶
- / 气相色谱/质谱
- / 大气压固体分析探针/飞行时间质谱
English
Thermal dissolution of Shengli and Xiaolongtan lignites in methanol and analysis of the soluble portions
Abstract:
Thermal dissolution behaviors of Shengli (SL) and Xiaolongtan (XLT) lignite in methanol were investigated. The composition and structural characteristics of soluble portions (SPs) obtained at 320 ℃ were characterized with Fourier transform infrared spectroscopy, gas chromatograph /mass spectrometer (GC/MS) and atmospheric solid analysis probe/time of flight mass spectrometer (ASAP/TOF-MS). For the two lignites, the yield of SPs increase with temperature increasing, while the yield of SPs from XLT (SPXLT) is obvious higher than that from SL (SPSL) above 240 ℃. GC/MS analysis results show that compounds in the SPs are dominated in oxygen-containing organic species, especially the relative content of phenols is higher than 49%. The relative contents of alkenes, arenes, ethers, carboxylic acids, esters, organosulfur compounds (OSCs) in SPSL are higher, while the relative contents of alkanes, phenols, ketones and organonitrogen compounds in SPSL are lower than those in SPXLT. Additionally, the OSCs in SPSL and SPXLT are mainly composed of thiophenes and mercaptan, respectively. Many compounds with high polarity and low volatility which could not be identified by GC/MS were identified using ASAP/TOF-MS. The relative contents of CHO and CHS class species in SPSL are higher, but the relative contents of CHN, CHNO, CHOS, CHNS and CHNOS in SPSL are lower than those in SPXLT. The carbon number and double bond equivalent (DBE) of the compounds in SPSL and SPXLT mainly distribute in 0-10 and 3-15, respectively, while the distribution of carbon number and DBE of the compound in SPXLT are more concentrated than those in SPSL.
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Key words:
- lignite
- / thermal dissolution
- / GC/MS
- / ASAP/TOF-MS
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中国褐煤储量约1.3×1011 t，约占中国煤炭储量的13%[1]。然而，褐煤存在高水分、高氧含量、低热值、热稳定性差和容易风化自燃等问题，限制了其在传统煤转化技术中的大规模应用[2, 3]。相对于煤热解和直接液化，煤热溶可以在温和条件下有效溶出煤中有机质，为实现褐煤资源的高效利用和从分子水平上揭示褐煤的大分子结构特征提供可能。王知彩等[4]发现，先锋褐煤在甲苯和四氢萘中300 ℃时的热溶过程不存在明显的热解反应，供氢溶剂及氢键型溶剂作用不明显，先锋褐煤热溶物中含有丰富的脂肪结构和羧酸酯，羟基和芳香结构含量较低。潘春秀等[5]认为，低于初始热解温度时煤的热溶以溶剂破坏煤中的非共价键为主，而高于初始热解温度的热溶过程伴有侧链和桥键等共价键断裂和自由基的缩聚反应。Ding等[6]研究了胜利褐煤在苯、甲醇和丙酮中的逐级热溶，发现褐煤中的烃类、酚类和含氮化合物分别富集在苯、甲醇和丙酮的热溶物中。由于具有较强的亲核性，醇类溶剂在热溶过程中可以进攻褐煤中存在的大量氧桥键，诱使煤大分子网络结构断裂，从而在较温和的条件下得到更多的煤中有机质[7, 8]。
内蒙古胜利褐煤和云南小龙潭褐煤是中国分别形成于侏罗纪和新生代第三纪的两种典型褐煤，在中国能源和化工原材料的供应中将起到重要的作用，但有关中国形成于不同时期的褐煤热溶行为及产物的组分和结构差异的研究还鲜有报道。研究考察了胜利褐煤和小龙潭褐煤在甲醇中的热溶解聚，并利用傅里叶变换红外光谱(FT-IR)、气相色谱/质谱联用仪(GC/MS) 和大气压固体分析探针飞行时间质谱(ASAP/TOF-MS) 对热溶物的组成和结构特征进行了分析。
1 实验部分
1.1 煤样和试剂
内蒙古胜利(SL) 褐煤和云南小龙潭(XLT) 褐煤破碎至200目以下( < 74 μm)，在80 ℃真空干燥24 h，储存于真空干燥器内备用。表 1为SL和XLT的工业分析和元素分析。实验所用甲醇为西陇化工股份有限公司生产的市售分析纯试剂，使用前经旋转蒸发仪精制。
表 1
褐煤的工业分析和元素分析
Table 1.
Proximate and ultimate analyses of coal samples
Sample Proximate analysis w/% Ultimate analysis wdaf/% Mad Ad Vdaf C H N S Oa SL 13.14 11.07 42.56 69.87 5.54 1.03 1.29 22.27 XLT 20.40 7.55 41.64 59.94 5.24 1.82 2.27 30.73 a: by difference 表 1 褐煤的工业分析和元素分析
Table 1. Proximate and ultimate analyses of coal samples1.2 热溶实验
图 1为SL和XLT热溶实验流程示意图。如图 1所示，取2 g煤样和40 mL甲醇放入100 mL带有磁力搅拌的高压反应釜中，利用氮气置换釜内空气后保留1 MPa的氮气作为初始压力，连接好搅拌、加热和中轴冷却水装置后，开启控制面板，使釜内温度以10 ℃/min程序升温至设定温度(220-320 ℃)，并保持1 h。反应结束后将高压反应釜迅速用水冷却至常温，开启反应釜，将反应混合物转移至抽滤装置中，并用300 mL甲醇洗涤反应混合物，滤液经旋转蒸发仪蒸出大部分溶剂后，自然晾干，得到可溶物(soluble portions，SP)，滤饼105 ℃真空干燥24 h后得到热溶残渣。热溶物产率w=WSP/Wc, daf，其中，WSP为热溶物质量，Wc, daf为干燥无灰基煤样。热溶物和溶剂的分离过程可能会造成少量热溶物中小分子化合物的损失，但用GC/MS分析回收溶剂未检测到除溶剂分子外的其他化合物存在，说明热溶物损失量极小，对热溶物产率和组成的影响可以忽略。为方便描述，SL和XLT的热溶物分别命名为SPSL和SPXLT。
图 1
SL和XLT热溶实验流程示意图
Figure 1.
Thermal dissolution procedure of SL and XLT
1.3 分析表征
利用IR-560型傅里叶变换红外光谱仪(Nicolte Magna，美国) 对两种褐煤320 ℃热溶物的官能团进行分析，热溶物用丙酮溶解后滴在溴化钾片上并烘干，400-4 000 cm-1扫描，分辨率设定为2 cm-1。利用6890/5973型气相色谱/质谱联用仪(Aglient, 美国) 对两种褐煤320 ℃热溶物进行分析。进样量在0.4 μL左右，进样口温度设为300 ℃，初始温度为60 ℃，升温速率为3 ℃/min，升温至300 ℃后保持15 min。通过对比NIST11谱图库，根据匹配度和质谱峰确定化合物的种类。利用大气压固体分析探针ASAPTM(IonSense, 美国) 和G620型飞行时间质谱仪TOF-MS (HP，美国) 对两种褐煤320 ℃热溶物进行分析。ASAP在正离子模式下操作，具体参数为：喷雾气压力0.276 MPa，操作温度350 ℃，干燥气流量为9 L/min，电晕针放电电流4 mA，毛细管电压4 000 V，质荷比扫描60-1 000。为方便描述，SL和XLT的320 ℃热溶物分别命名为SPSL和SPXLT。
2 结果与讨论
2.1 热溶物产率
图 2为SL和XLT热溶物的产率随温度的变化。由图 2可知，两种褐煤热溶物产率均随温度升高而增加；XLT热溶物产率在220 ℃时低于SL，但其随温度升高增加的幅度较大，240 ℃后明显高于SL；320 ℃时，SL和XLT在热溶物产率分别为9.95%和21.91%。根据煤的两相结构模型，煤中的有机质包括镶嵌于煤大分子网络结构中的游离的化合物和大分子网络结构本身[9]。220 ℃时褐煤热溶过程以物理萃取为主，主要溶解出褐煤大分子网络结构中游离的化合物。SL在220 ℃热溶物产率高于XLT说明其大分子网络结构中游离的化合物含量较高。温度高于240 ℃后，热溶过程逐渐从物理萃取为主转变为化学热溶为主，甲醇可以通过供氢作用进攻褐煤中的氧桥键，诱使氧桥键断裂，从而溶出更多的有机质[7]。XLT的氧含量明显高于SL，因此，XLT高温时热溶物产率明显高于SL可能是由于其大分子网络结构中含有较多的氧桥键。
图 2
SL和XLT热溶物的产率随温度的变化
Figure 2.
Yields of SPs from SL and XLT
2.2 FT-IR分析
图 3为SPSL和SPXLT热溶物红外光谱谱图。由图 3可知，两种褐煤在320 ℃的热溶物SPSL和SPXLT的FT-IR谱图相似，两者均含有归属于脂肪C-H (2 919、2 850、1 450和1 380 cm-1)，-OH (3 500-3 100 cm-1)、C=O (1 700 cm-1) 和C-O-C (1 300-1 000 cm-1) 等官能团的吸收峰，说明热溶物中含有丰富的脂肪族化合物及酚类、酮类和醚类等含氧化合物[10, 11]。
图 3
SPSL和SPXLT热溶物红外光谱谱图
Figure 3.
FT-IR spectra of SPSL and SPXLT
2.3 GC/MS分析
图 4为两种褐煤在320 ℃的热溶物SPSL和SPXLT的GC/MS分析总离子流色谱图。SPSL和SPXLT中GC/MS可检测化合物可分为烷烃、烯烃、芳烃、醇、酚、醚、醛、酮、羧酸(CAs)、酯、有机硫化合物(SOCs) 和有机氮化合物(NOCs)。图 5为各类化合物的分布图。由图 5可知，热溶物中的化合物以含氧化合物为主，尤其酚类化合物的含量超过49%，这与SPSL和SPXLT的FT-IR谱图中强的羟基吸附峰一致。
图 4
SPSL和SPXLT的GC/MS总离子流色谱图
Figure 4.
Total ion chromatograph of SPSL and SPXLT
图 5
SPSL和SPXLT中GC/MS可检测化合物分布
Figure 5.
Distributions of group components in SPSL and SPXLT identified by GC/MS
表 2为SPSL和SPXLT中GC/MS检测到的烃类化合物。由表 2可知，SPSL中芳烃和烯烃含量高于SPXLT，而烷烃含量低于SPXLT。烷烃以长的直链烷烃为主，仅在SPSL中检测到一种支链烷烃，这说明褐煤的大分子结构中存在长的烷基侧链或桥键。SPSL和SPXLT中仅检测到四种烯烃，包括两种环烯烃和两种直链烯烃。与其高的芳烃含量相一致，SPSL中检测到的芳烃种类多达17种，而SPXLT仅检测到四种芳烃。SPSL和SPXLT中未检测到三环以上的稠环芳烃，这与褐煤大分子结构芳香度较低相一致。
表 2
SPSL和SPXLT中GC/MS可检测到烃类化合物
Table 2.
Hydrocarbons identified in SPSLand SPXLT by GC/MS
Compound RC /% Compound RC /% SPSL SPXLT SPSL SPXLT Alkanes arenes 2, 6, 10, 14-tetramethylhexadecane 0.28 - 4-isopropyl-1, 2-dimethylbenzene 0.22 - Pentadecane 0.55 0.16 2-methylnaphthalene 0.24 - Tetradecane 0.44 - 1, 2, 4-trimethyl-5-(prop-1-en-2-yl) benzene 0.12 - Heptadecane - 0.25 2, 3-dihydro-1, 1, 3-trimethyl-1 H-indene 0.12 - Octadecane 0.33 0.32 trimethyl-1 H-indene 0.40 - Nonadecane - 0.63 1, 3-dimethylnaphthalene 0.62 - Eicosane 0.27 0.59 1, 2, 3, 4-tetrahydro-1, 5, 0.20 - 7-trimethylnaphthalene Heneicosane 0.28 0.80 1, 2, 3, 4, 5, 6-hexamethylbenzene 0.49 0.38 Docosane - 0.64 1, 2, 4, 5-tetraethylbenzene 1.15 - Tricosane - 0.66 1-ethyl-3, 5-diisopropylbenzene 0.51 - Tetracosane 0.11 0.36 trimethylnaphthalene 0.29 0.29 Alkenes 9-ethylphenanthrene 0.40 - 1, 2, 3, 4, 5, 6-hexamethylcyclohexa-1, 0.42 - (1 S, 4 S)-4-isopropyl-1, 6-dimethyl-1, 2, 3, 0.83 - 3-diene 4-tetrahydronaphthalene 5, 5-dimethyl-1, 2-dipropylcyclopenta-1, 3-diene 1.08 0.40 4-isopropyl-1, 6-dimethylnaphthalene 0.64 0.80 Octadec-1-ene - 0.11 1, 2, 3, 4-tetramethylnaphthalene 0.40 - (E)-henicos-10-ene 0.12 - 5, 6, 7, 8-tetramethyl-1, 2, 3, 0.77 0.19 4-tetrahydronaphthalene 1, 4-di-tert-butylbenzene 0.26 - 表 2 SPSL和SPXLT中GC/MS可检测到烃类化合物
Table 2. Hydrocarbons identified in SPSLand SPXLT by GC/MS表 3为SPSL和SPXLT中检测到的醇、酚和醚类化合物。SPSL和SPXLT分别检测到两种和三种醇类化合物，这说明褐煤中存在少量的醇羟基。SPSL和SPXLT中酚类的相对含量分别为49.48%和55.46%，且以甲基酚为主。Hodek等[12]研究表明, 煤热解过程中酚主要来自煤中芳香醚键的断裂，这说明褐煤中含有大量的芳基醚键。SPSL和SPXLT中共检测到九种醚类化合物，且以带有不同烷基侧链的芳基醚为主，进一步说明褐煤中含有大量的芳基醚键。
表 3
SPSL和SPXLT中GC/MS可检测醇、酚和醚类化合物
Table 3.
Alcohols, phenols and ethers identified in SPSL and SPXLT by GC/MS
Compound RC /% Compound RC /% SPSL SPXLT SPSL SPXLT Alcohols 4-sec-butylphenol 0.22 - 3, 3-dimethyl-2, 3-dihydro-1 H-inden-1-ol 0.56 - 2-methyl-6-propylphenol 0.31 - (4-tert-butylphenyl) methanol 1.18 - diethylphenol 0.61 - 3, 7, 11-trimethyldodecan-1-ol - 0.80 tetramethylphenol 12.20 6.73 Henicosan-1-ol - 0.15 2-methoxy-4-propylphenol 0.27 - Docosan-1-ol - 0.19 tert-butylmethylphenol 4.94 2.14 Phenols 2-ethyl-4, 5-dimethylphenol 1.90 Phenol 0.24 - 2, 3, 5-trimethylbenzene-1, 4-diol - 4.22 o-cresol 1.09 1.00 2-tert-butyl-4, 6-dimethylphenol 0.59 0.40 2-methoxyphenol 0.43 0.76 2, 6-diisopropylphenol - 2.05 Dimethylphenol 3.91 7.57 2-tert-butylbenzene-1, 4-diol - 0.82 3-isopropylphenol 0.72 0.34 (3 S, 3a S)-3a-methyl-3, 3a, 4, 5-tetrahydro 0.36 - -2 H-cyclopenta[a]naphthalen-3-ol Ethylphenol 0.64 - (R)-2, 5, 7, 8-tetramethyl-2-((4R, 8R)-4, 8, - 0.50 12-trimethyltridecyl) chroman-6-ol Methoxymethylphenol 1.44 1.30 ethers Ethylmethylphenol 1.34 0.78 dimethoxybenzene 0.32 - 4, 5-dimethylbenzene-1, 3-diol 0.26 - methoxytrimethylbenzene 0.16 0.09 Trimethylphenol 11.14 16.97 dimethoxymethylbenzene 0.59 0.43 2-propylphenol 0.26 - 1-tert-butyl-4-methoxybenzene 0.80 - 2-ethyl-4, 5-dimethylphenol - 1.92 5-propylbenzo[ d][1, 3]dioxole 0.95 - Isopropylmethylphenol 5.15 3.47 1-sec-butyl-4-methoxybenzene 0.74 - 3-tert-butylphenol - 2.55 1-isopropyl-2-methoxy-4-methylbenzene 2.78 - 2, 3, 5-trimethylbenzene-1, 4-diol 0.47 0.53 1, 2, 3-trimethoxy-5-methylbenzene 0.91 0.76 Methoxytrimethylphenol 0.99 1.41 2, 3-dihydro-2, 2, 5, 6-tetramethylbenzofuran - 1.17 表 3 SPSL和SPXLT中GC/MS可检测醇、酚和醚类化合物
Table 3. Alcohols, phenols and ethers identified in SPSL and SPXLT by GC/MS表 4为SPSL和SPXLT中检测到的醛和酮类化合物。由表 4可知，仅在SPSL中检测到一种醛类化合物。SPSL和SPXLT共检测到15种酮类化合物，其中，11种为芳香酮。表 5为SPSL和SPXLT中检测到的CAs和酯类化合物。虽然褐煤中含有大量的羧基官能团，但SPSL和SPXLT中仅检测到三种CAs，且均为苯甲酸。SPSL和SPXLT共检测到29种酯类化合物，并且除2-isopropyl-5-methylphenyl acetate均为甲酯，特别是一系列的长链烷酸甲酯，这说明褐煤中溶出的大部分长链CAs可能与甲醇发生了酯化反应形成烷酸甲酯[7]。
表 4
SPSL和SPXLT中GC/MS可检测醛和酮类化合物
Table 4.
Aldehydes and ketones identified in SPSL and SPXLT by GC/MS
Compound RC /% SPSL SPXLT Aldehydes 2-(2-methoxy-5-methylphenyl) propanal 0.60 - Ketones Trimethylcyclopent-2-enone 0.92 4.17 2, 3, 4, 5-tetramethylcyclopent-2-enone 0.69 1.04 3, 5, 5-trimethylcyclohex-2-enone - 0.63 1-(2, 6-dihydroxy-3-methylphenyl) ethanone 0.25 - 2, 3, 5, 6-tetramethylcyclohexa-2, 5-diene-1, 4-dione 0.35 0.43 1-(4-hydroxy-3-methoxyphenyl) ethanone 1.66 4.57 1-(2-hydroxy-4, 5-dimethylphenyl) ethanone 0.34 - 1-(2, 5-dimethoxyphenyl) ethanone - 0.18 Octahydro-2-(propan-2-ylidene) inden-4-one 0.56 0.49 1-(4-methoxyphenyl) butan-1-one 0.35 - 1-(5-hydroxy-2, 3, 4-trimethylphenyl) ethanone 1.26 - 2, 3-dihydro-3, 3, 5, 7-tetramethylinden-1-one 1.54 - 1-(3, 4-dichlorophenyl) ethanone 0.27 - 1-(2, 4, 5-triethylphenyl) ethanone 0.38 - 4, 4, 7, 8-tetramethylchroman-2-one - 0.37 表 4 SPSL和SPXLT中GC/MS可检测醛和酮类化合物
Table 4. Aldehydes and ketones identified in SPSL and SPXLT by GC/MS
表 5
SPSL和SPXLT中GC/MS可检测CAs和酯类化合物
Table 5.
CAs and esters identified in SPSL和SPXLT by GC/MS
Compound RC /% Compound RC /% SPSL SPXLT SPSL SPXLT CAs methyl tetradecanoate - 0.25 2-methoxybenzoic acid 0.49 - methyl 2, 3-dihydro-1, 1-dimethyl-1 H- 1.08 - indene-4-carboxylate 4-isopropylbenzoic acid 0.57 0.49 methyl 9-methyltetradecanoate 0.48 - 4-acetylbenzoic acid 1.05 - methyl palmitate - 0.55 Esters methyl heptadecanoate - 0.19 Dimethyl succinate 0.15 - methyl stearate 0.15 0.67 Dimethyl glutarate 0.22 - methyl nonadecanoate - 0.19 2-isopropyl-5-methylphenyl acetate 0.36 - methyl 12-methyltetradecanoate 0.19 - Methyl decanoate 0.17 - methyl icosanoate - 0.30 Methyl 3-methoxybenzoate 0.24 - methyl 18-methylnonadecanoate 0.14 - Methyl undecanoate 0.23 - methyl henicosanoate - 0.31 Methyl 4-(1-hydroxyethyl) benzoate 0.30 - methyl docosanoate - 0.59 Methyl 4-methoxy-3-methylbenzoate 0.61 - methyl tricosanoate - 0.36 Methyl dodecanoate - 0.31 methyl tetracosanoate 0.18 0.70 Dimethyl nonanedioate 0.51 - methyl pentacosanoate - 0.17 Dimethyl decanedioate 0.26 - methyl hexacosanoate 0.32 0.58 Methyl 7-methylcyclopenta[c] 0.40 - methyl octacosanoate 0.21 0.34 pyran-4-carboxylate 表 5 SPSL和SPXLT中GC/MS可检测CAs和酯类化合物
Table 5. CAs and esters identified in SPSL和SPXLT by GC/MS含硫和含氮化合物是煤燃料利用的主要污染物的前躯体，对其溶出和鉴定有利于从分子水平上揭示煤中硫和氮原子的赋存形态，发展有效的脱硫和脱氮工艺[13]。如表 6所示，SPSL和SPXLT共检测到五种OSCs，SPSL中以噻吩化合物为主，而SPXLT以硫醇为主。SPSL和SPXLT共检测到七种ONCs，其中, N1, N1, N4, N4-tetramethylbenzene-1, 4-diamine在SPSL和SPXLT的相对含量分别达到7.15%和10.50%，这表明两种褐煤中的氮较多的以胺基形态存在。
表 6
SPSL和SPXLT中GC/MS可检测OSCs和ONCs
Table 6.
OSCs and ONCs identified in SPSL和SPXLT by GC/MS
Compound RC /% SPSL SPXLT OSCs Isopropylbenzenethiol 0.19 1.48 2-ethyl-7-methylbenzo[ b]thiophene 0.75 - 2-ethyl-5, 7-dimethylbenzo[ b]thiophene 1.71 - Diethylbenzo[ b]thiophene 0.57 0.46 1-(dimethylbenzo[ b]thiophen-2-yl) ethanone 1.25 - ONCs N1-ethyl-N4, N4-dimethylbenzene-1, 4-diamine - 0.33 N1, N1-diethylbenzene-1, 4-diamine - 0.55 5-methyl-5, 6, 7, 8-tetrahydroquinazoline-2, 0.53 - 4(1 H, 3 H)-dione N1, N1, N4, N4-tetramethylbenzene-1, 7.15 10.50 4-diamine (E)-4-((isopropylimino) methyl)-N, - 2.84 N-dimethylaniline 2-benzyl-1-methyl-3-nitrobenzene 0.23 - (E)-N, N-diethyl-4-(4-nitrostyryl) aniline - 0.24 表 6 SPSL和SPXLT中GC/MS可检测OSCs和ONCs
Table 6. OSCs and ONCs identified in SPSL和SPXLT by GC/MS2.4 ASAP/TOF-MS分析
ASAP是由大气压化学电离(Atmospheric Pressure Chemical Ionization) 发展而来的一种原位电离技术。研究表明，ASAP/TOF-MS可检测出煤衍生物中多种GC/MS无法检测出的较高极性和难挥发化合物[14, 15]。图 6为两种褐煤在320 ℃的热溶物SPSL和SPXLT的ASAP/TOF-MS谱图。由图 6可知，SPSL和SPXLT中存在大量60-480 Da的化合物，其中, 可精确确定分子式的化合物分别为205和120种。根据化合物中含有杂原子的种类，可将ASAP/TOF-MS可检测化合物分为CHO、CHN、CHNO、CHS、CHOS、CHNS和CHNOS等族分化合物。
图 6
SPSL和SPXLT的ASAP/TOF-MS分析质谱图
Figure 6.
Mass spectra of SPSL and SPXLT from ASAP/TOF-MS analysis
如表 7所示，SPSL和SPXLT中CHNO族分的种类和相对含量均最高，SPXLT中的CHO族分相对含量也超过30%。与SPXLT相比，SPSL中CHO和CHS族分含量较低，而CHN、CHNO、CHOS、CHNS和CHNOS族分含量较高。双键数(Double bond equivalent, DBE) 是用来表示有机化合物芳香度的重要参数[16]。如图 7所示，SPSL和SPXLT中ASAP/TOF-MS可检测化合物的DBE主要分布在0-10，而碳数目主要在分布在3-15，SPXLT的DBE和碳数分布相对集中。
表 7
SPSL和SPXLT中ASAP/TOF-MS可检测化合物族分及其分布
Table 7.
Compound classes and their distribution in SPSL and SPXLT identified by ASAP/TOF-MS
Compound class SPSL SPXLT relative peak intensity /% peak number relative peak intensity /% peak number CHO 7.17 11 34.29 17 CHN 13.64 18 7.33 19 CHNO 56.88 116 54.32 64 CHS 0.1 1 0.27 1 CHOS 2.01 4 0.05 1 CHNS 9.71 20 2.57 11 CHNOS 10.49 35 1.17 7 Total 100 205 100 120 表 7 SPSL和SPXLT中ASAP/TOF-MS可检测化合物族分及其分布
Table 7. Compound classes and their distribution in SPSL and SPXLT identified by ASAP/TOF-MS
图 7
SPSL和SPXLT中ASAP/TOF-MS可检测化合物的DBE对碳数目气泡图
Figure 7.
Iso-abundance plots of DBE versus carbon number distributions of the compounds in SPSL and SPXLT identified by ASAP/TOF-MS analysis
3 结论
两种不同地质年代的褐煤在甲醇中的热溶产率和产物组成存在较大差异。由于含有较高的氧含量，XLT在甲醇中的热溶物产率明显高于SL。GC/MS分析表明，与SPXLT相比，SPSL的烯烃、芳烃、醚类、羧酸、酯类和OSCs相对含量较高，而烷烃、酮类和ONCs相对含量较低；SPSL和SPXLT中的OSCs分别以噻吩类和硫醇类化合物为主。ASAP/TOF-MS分析表明，与SPSL相比，SPXLT中CHO和CHS族分含量较高，而CHN、CHNO、CHOS、CHNS和CHNOS族分含量较低，碳数和DBE分布相对集中。
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[1]
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图 5 SPSL和SPXLT中GC/MS可检测化合物分布
Figure 5 Distributions of group components in SPSL and SPXLT identified by GC/MS
图 6 SPSL和SPXLT的ASAP/TOF-MS分析质谱图
Figure 6 Mass spectra of SPSL and SPXLT from ASAP/TOF-MS analysis
图 7 SPSL和SPXLT中ASAP/TOF-MS可检测化合物的DBE对碳数目气泡图
Figure 7 Iso-abundance plots of DBE versus carbon number distributions of the compounds in SPSL and SPXLT identified by ASAP/TOF-MS analysis
表 1 褐煤的工业分析和元素分析
Table 1. Proximate and ultimate analyses of coal samples
Sample Proximate analysis w/% Ultimate analysis wdaf/% Mad Ad Vdaf C H N S Oa SL 13.14 11.07 42.56 69.87 5.54 1.03 1.29 22.27 XLT 20.40 7.55 41.64 59.94 5.24 1.82 2.27 30.73 a: by difference 
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表 2 SPSL和SPXLT中GC/MS可检测到烃类化合物
Table 2. Hydrocarbons identified in SPSLand SPXLT by GC/MS
Compound RC /% Compound RC /% SPSL SPXLT SPSL SPXLT Alkanes arenes 2, 6, 10, 14-tetramethylhexadecane 0.28 - 4-isopropyl-1, 2-dimethylbenzene 0.22 - Pentadecane 0.55 0.16 2-methylnaphthalene 0.24 - Tetradecane 0.44 - 1, 2, 4-trimethyl-5-(prop-1-en-2-yl) benzene 0.12 - Heptadecane - 0.25 2, 3-dihydro-1, 1, 3-trimethyl-1 H-indene 0.12 - Octadecane 0.33 0.32 trimethyl-1 H-indene 0.40 - Nonadecane - 0.63 1, 3-dimethylnaphthalene 0.62 - Eicosane 0.27 0.59 1, 2, 3, 4-tetrahydro-1, 5, 0.20 - 7-trimethylnaphthalene Heneicosane 0.28 0.80 1, 2, 3, 4, 5, 6-hexamethylbenzene 0.49 0.38 Docosane - 0.64 1, 2, 4, 5-tetraethylbenzene 1.15 - Tricosane - 0.66 1-ethyl-3, 5-diisopropylbenzene 0.51 - Tetracosane 0.11 0.36 trimethylnaphthalene 0.29 0.29 Alkenes 9-ethylphenanthrene 0.40 - 1, 2, 3, 4, 5, 6-hexamethylcyclohexa-1, 0.42 - (1 S, 4 S)-4-isopropyl-1, 6-dimethyl-1, 2, 3, 0.83 - 3-diene 4-tetrahydronaphthalene 5, 5-dimethyl-1, 2-dipropylcyclopenta-1, 3-diene 1.08 0.40 4-isopropyl-1, 6-dimethylnaphthalene 0.64 0.80 Octadec-1-ene - 0.11 1, 2, 3, 4-tetramethylnaphthalene 0.40 - (E)-henicos-10-ene 0.12 - 5, 6, 7, 8-tetramethyl-1, 2, 3, 0.77 0.19 4-tetrahydronaphthalene 1, 4-di-tert-butylbenzene 0.26 -
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表 3 SPSL和SPXLT中GC/MS可检测醇、酚和醚类化合物
Table 3. Alcohols, phenols and ethers identified in SPSL and SPXLT by GC/MS
Compound RC /% Compound RC /% SPSL SPXLT SPSL SPXLT Alcohols 4-sec-butylphenol 0.22 - 3, 3-dimethyl-2, 3-dihydro-1 H-inden-1-ol 0.56 - 2-methyl-6-propylphenol 0.31 - (4-tert-butylphenyl) methanol 1.18 - diethylphenol 0.61 - 3, 7, 11-trimethyldodecan-1-ol - 0.80 tetramethylphenol 12.20 6.73 Henicosan-1-ol - 0.15 2-methoxy-4-propylphenol 0.27 - Docosan-1-ol - 0.19 tert-butylmethylphenol 4.94 2.14 Phenols 2-ethyl-4, 5-dimethylphenol 1.90 Phenol 0.24 - 2, 3, 5-trimethylbenzene-1, 4-diol - 4.22 o-cresol 1.09 1.00 2-tert-butyl-4, 6-dimethylphenol 0.59 0.40 2-methoxyphenol 0.43 0.76 2, 6-diisopropylphenol - 2.05 Dimethylphenol 3.91 7.57 2-tert-butylbenzene-1, 4-diol - 0.82 3-isopropylphenol 0.72 0.34 (3 S, 3a S)-3a-methyl-3, 3a, 4, 5-tetrahydro 0.36 - -2 H-cyclopenta[a]naphthalen-3-ol Ethylphenol 0.64 - (R)-2, 5, 7, 8-tetramethyl-2-((4R, 8R)-4, 8, - 0.50 12-trimethyltridecyl) chroman-6-ol Methoxymethylphenol 1.44 1.30 ethers Ethylmethylphenol 1.34 0.78 dimethoxybenzene 0.32 - 4, 5-dimethylbenzene-1, 3-diol 0.26 - methoxytrimethylbenzene 0.16 0.09 Trimethylphenol 11.14 16.97 dimethoxymethylbenzene 0.59 0.43 2-propylphenol 0.26 - 1-tert-butyl-4-methoxybenzene 0.80 - 2-ethyl-4, 5-dimethylphenol - 1.92 5-propylbenzo[ d][1, 3]dioxole 0.95 - Isopropylmethylphenol 5.15 3.47 1-sec-butyl-4-methoxybenzene 0.74 - 3-tert-butylphenol - 2.55 1-isopropyl-2-methoxy-4-methylbenzene 2.78 - 2, 3, 5-trimethylbenzene-1, 4-diol 0.47 0.53 1, 2, 3-trimethoxy-5-methylbenzene 0.91 0.76 Methoxytrimethylphenol 0.99 1.41 2, 3-dihydro-2, 2, 5, 6-tetramethylbenzofuran - 1.17
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表 4 SPSL和SPXLT中GC/MS可检测醛和酮类化合物
Table 4. Aldehydes and ketones identified in SPSL and SPXLT by GC/MS
Compound RC /% SPSL SPXLT Aldehydes 2-(2-methoxy-5-methylphenyl) propanal 0.60 - Ketones Trimethylcyclopent-2-enone 0.92 4.17 2, 3, 4, 5-tetramethylcyclopent-2-enone 0.69 1.04 3, 5, 5-trimethylcyclohex-2-enone - 0.63 1-(2, 6-dihydroxy-3-methylphenyl) ethanone 0.25 - 2, 3, 5, 6-tetramethylcyclohexa-2, 5-diene-1, 4-dione 0.35 0.43 1-(4-hydroxy-3-methoxyphenyl) ethanone 1.66 4.57 1-(2-hydroxy-4, 5-dimethylphenyl) ethanone 0.34 - 1-(2, 5-dimethoxyphenyl) ethanone - 0.18 Octahydro-2-(propan-2-ylidene) inden-4-one 0.56 0.49 1-(4-methoxyphenyl) butan-1-one 0.35 - 1-(5-hydroxy-2, 3, 4-trimethylphenyl) ethanone 1.26 - 2, 3-dihydro-3, 3, 5, 7-tetramethylinden-1-one 1.54 - 1-(3, 4-dichlorophenyl) ethanone 0.27 - 1-(2, 4, 5-triethylphenyl) ethanone 0.38 - 4, 4, 7, 8-tetramethylchroman-2-one - 0.37
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表 5 SPSL和SPXLT中GC/MS可检测CAs和酯类化合物
Table 5. CAs and esters identified in SPSL和SPXLT by GC/MS
Compound RC /% Compound RC /% SPSL SPXLT SPSL SPXLT CAs methyl tetradecanoate - 0.25 2-methoxybenzoic acid 0.49 - methyl 2, 3-dihydro-1, 1-dimethyl-1 H- 1.08 - indene-4-carboxylate 4-isopropylbenzoic acid 0.57 0.49 methyl 9-methyltetradecanoate 0.48 - 4-acetylbenzoic acid 1.05 - methyl palmitate - 0.55 Esters methyl heptadecanoate - 0.19 Dimethyl succinate 0.15 - methyl stearate 0.15 0.67 Dimethyl glutarate 0.22 - methyl nonadecanoate - 0.19 2-isopropyl-5-methylphenyl acetate 0.36 - methyl 12-methyltetradecanoate 0.19 - Methyl decanoate 0.17 - methyl icosanoate - 0.30 Methyl 3-methoxybenzoate 0.24 - methyl 18-methylnonadecanoate 0.14 - Methyl undecanoate 0.23 - methyl henicosanoate - 0.31 Methyl 4-(1-hydroxyethyl) benzoate 0.30 - methyl docosanoate - 0.59 Methyl 4-methoxy-3-methylbenzoate 0.61 - methyl tricosanoate - 0.36 Methyl dodecanoate - 0.31 methyl tetracosanoate 0.18 0.70 Dimethyl nonanedioate 0.51 - methyl pentacosanoate - 0.17 Dimethyl decanedioate 0.26 - methyl hexacosanoate 0.32 0.58 Methyl 7-methylcyclopenta[c] 0.40 - methyl octacosanoate 0.21 0.34 pyran-4-carboxylate
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表 6 SPSL和SPXLT中GC/MS可检测OSCs和ONCs
Table 6. OSCs and ONCs identified in SPSL和SPXLT by GC/MS
Compound RC /% SPSL SPXLT OSCs Isopropylbenzenethiol 0.19 1.48 2-ethyl-7-methylbenzo[ b]thiophene 0.75 - 2-ethyl-5, 7-dimethylbenzo[ b]thiophene 1.71 - Diethylbenzo[ b]thiophene 0.57 0.46 1-(dimethylbenzo[ b]thiophen-2-yl) ethanone 1.25 - ONCs N1-ethyl-N4, N4-dimethylbenzene-1, 4-diamine - 0.33 N1, N1-diethylbenzene-1, 4-diamine - 0.55 5-methyl-5, 6, 7, 8-tetrahydroquinazoline-2, 0.53 - 4(1 H, 3 H)-dione N1, N1, N4, N4-tetramethylbenzene-1, 7.15 10.50 4-diamine (E)-4-((isopropylimino) methyl)-N, - 2.84 N-dimethylaniline 2-benzyl-1-methyl-3-nitrobenzene 0.23 - (E)-N, N-diethyl-4-(4-nitrostyryl) aniline - 0.24
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表 7 SPSL和SPXLT中ASAP/TOF-MS可检测化合物族分及其分布
Table 7. Compound classes and their distribution in SPSL and SPXLT identified by ASAP/TOF-MS
Compound class SPSL SPXLT relative peak intensity /% peak number relative peak intensity /% peak number CHO 7.17 11 34.29 17 CHN 13.64 18 7.33 19 CHNO 56.88 116 54.32 64 CHS 0.1 1 0.27 1 CHOS 2.01 4 0.05 1 CHNS 9.71 20 2.57 11 CHNOS 10.49 35 1.17 7 Total 100 205 100 120
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