【作者】 姚婷；

【导师】 宗志敏；

【作者基本信息】 中国矿业大学 ， 化学工艺， 2012， 博士

【摘要】 天然沥青是一种稀有的非常规重质油资源，从分子水平上充分了解天然沥青中有机质的组成对有机地球化学研究和天然沥青的高效利用有重要意义。为研究天然沥青中的有机化学成分，本课题选用新疆克拉玛依天然沥青作为研究对象，对其进行了一系列有机溶剂的溶解性分析，接着根据溶解性结果依次选用甲醇、乙醇、丙酮、乙酸乙酯、石油醚、二硫化碳六种溶剂对天然沥青进行分级萃取，再结合柱层析技术对前三级分级萃取物进行精细分离纯化，重点考察了分级萃取物和柱层析分离所得部分馏分的组成结构，以期了解天然沥青中有机物的组成及其分布规律。并通过热处理手段对天然沥青中的重质组分进行了解聚研究，得到了各种结构碎片的组成特征，有助于推测天然沥青的大分子结构的原始结构组成。天然沥青在22种溶剂中的溶解性结果表明，天然沥青在溶剂中的萃取率与溶剂介电常数和溶解度参数密切相关。介电常数表示分子的极性大小，天然沥青在介电常数较小的溶剂中均显示出较好的溶解性。溶解度参数用来表征溶剂对溶质的溶解能力，天然沥青在溶解度参数较小的溶剂中表现出良好的溶解性。根据萃取效果及溶剂的价格毒性等因素，选定甲醇、乙醇、丙酮、乙酸乙酯、石油醚和二硫化碳六种溶剂为分级萃取中所用试剂。经深度萃取后，FTIR分析结果表明，原样、六级萃取物及萃余物的红外表征有明显差异，且萃余物中基本上是灰分，这说明通过分级萃取已把天然沥青中的有机质基本都萃取出来，同时可知天然沥青中含有较多的饱和烃，所以易溶于非极性溶剂中。GC/MS分析结果表明，检测出的化合物绝对含量远远小于各级萃取物的含量，各级各次萃取物都含有大量生物标志物的复杂有机质的混合物，具有重要的有机地球化学意义。甲醇萃取物中检测出119种化合物，其中萜类、甾类、醇类及邻苯二甲酸酯类含量较大，并且检测到大量的2-乙基己醇；乙醇萃取物中检测出110种化合物，主要包括萜类、甾类、正构烷烃、类异戊二烯烃、脂肪酯类及邻苯二甲酸酯类；丙酮萃取物中只检出51种化合物，其中萜烷、甾烷和邻苯二甲酸酯类的含量较大。而在乙酸乙酯、石油醚和二硫化碳萃取物中没有GC/MS信号的响应，可能是由于GC/MS技术存在局限性，大多物质超出了其检测范围，表明其中有机质的主要特点是由分子量较大的化合物组成。以柱层析技术对天然沥青的甲醇、乙醇和丙酮分级萃取物分离与纯化的结果可知，经柱层析精细分离后可检测化合物种类明显增多，三级萃取物可检测的化合物都超过了200种。同时柱层析馏分中的可检测物质的绝对含量比萃取物中的绝对含量提高很多，如丙酮萃取物柱层析馏分中可检测成分的绝对含量提高了近两个数量级，进一步说明柱层析是精细分离的一种重要的技术手段，能较好的对样品进行精细分离，有效地富集了含量较少的化合物，有利于确提供所测物种的精确的分子结构信息。甲醇柱层析馏分中出现了萃取物中未检测到的正构烷烃、支链烷烃、羧酸类化合物以及种类较多的芳烃类化合物，并且梯度洗脱中，甲醇洗脱剂馏分中富集到了甾烷，其相对含量高达80.6%，丙酮洗脱剂馏分中富集到了芳烃，其相对含量高达66.5%，而非极性二硫化碳洗脱剂馏分中未检测出GC/MS可测成分，在甲醇/氯仿混合洗脱剂馏分中检测出一系列的正构烷烃、支链烷烃和芳烃。此外，在一个甲醇柱层析馏分中富集到一种物质，通过硅胶和凝胶相结合的方法，分离纯化并确定结构为2-乙基己醇。研究表明是由于在超声波辐射作用下，天然沥青中的特定化合物与甲醇发生了反应，甲醇中的氧进攻羰基碳而导致2-乙基己醇的生成，而在乙醇萃取物中没有发现2-乙基己醇，可能是由于乙醇中的乙基位阻较大，较难发生反应。乙醇萃取物经柱层析精细分离后可检测化合物达到239种，以甲醇作洗脱剂所得的前部分馏分富集到了芳烃类化合物和邻苯二甲酸酯类化合物，后部分馏分中则富集到了大量的甾类化合物，其绝对含量为187.8mg/g，相对含量高达81.9%。丙酮萃取物经柱层析后检测到282种化合物，远远多出萃取物中的53种，并且包含萃取物中没有出现的族组分，如正构烷烃、类异戊二烯、芳烃、脂肪酸酯类及其他含杂原子化合物等，更进一步证明说明柱层析技术对于天然沥青可溶组分精细分离的可行性和有效性，可以把萃取物中含量较低的不能检测到的化合物再进行分离分析，可以获取更直观更清晰的信息，并能富集到清晰的族组分分离效果。分级萃取实现了对于天然沥青族组分粗分离，柱层析则对萃取物实现了进一步的精细分离和纯化。本研究提供了对天然沥青进行选择性的族组分分离和分析的有效方法，并进一步揭示了天然沥青中有机物的组成和分布规律，丰富了其有机地球化学知识。克拉玛依天然沥青有机质中可检测组成中出现了大量重要的生物标志物：正构烷烃、单甲基支链烷烃、无环类异戊二烯、倍半萜烷、二萜烷、长链三环萜烷、藿烷型三萜烷、非藿烷型三萜烷、甾烷、酮、醇、酯（邻苯二甲酸酯、脂肪酯及脂芳酯）、芳烃和羧酸等化合物。结合其生物标志特征可以得知，克拉玛依天然沥青的成熟度较高，在成岩过程中几乎不存在生物降解作用，生成天然沥青的地理环境可能与某些海洋或者湖泊条件有关，陆源物质、细菌、蓝藻和一些高等植物对天然沥青生源有很大的贡献，具有重要的有机地球化学意义。为进一步了解天然沥青中重质组分的化学组成，对石油醚和二硫化碳萃取物中的重质组分进行了深入研究，在400oC左右的温度下，分别比较了重质组分在三种不同时间中的热处理产物的丙酮可溶组分的结构组成，并对得到的轻质油的丙酮可溶组分的结构也进行了分析。研究表明，热处理前后的组成有较大的差别，并且轻质油和热处理产物的组成也有较大的差别。热处理原料即天然沥青的重质组分的丙酮可溶物只能检测出极少的化合物，热处理产物及轻质油中检测到的化合物较多，主要包括正构烷烃、支链烷烃、环烷烃、烯烃和芳烃，但轻质油中族组分的化合物分子量都较小，偏轻质化，而热处理产物中化合物的分子量明显高出许多。一方面为揭示天然沥青原始的大分子网状组成结构提供了一定的理论数据，另一方面对天然沥青的精细加工具有重要的工业意义。该论文有图61幅，表83个，参考文献240篇更多还原

【Abstract】 As a rare unconventional heavy petroleum resources, isolation and analyses of organiccomponents in natural bitumen play an important rule in organic geochemical research andnatural bitumen effcient utilization. To investigate the organic chemical compositions in naturalbitumens, Sinkiang Karamay natural bitumen was selected and solubility was compared in aseries of organic solvents. Then Karamay natural bitumen was sequentially extracted withmethanol, ethanol, acetone, ethyl acetate, petroleum ether and carbon disulfide under ultrasonicirradiation according to the solubility result, and then the fractional extracts were separated andpurified through the column chromatography. The fractional extracts and the fractions ofcolumn chromatography were analyzed by GC/MS, FTIR and so on to explore their structurefeatures. In addition, the heavy components of Karamay natural bitumen was subject to heattreatment and depolymerize, and detected structural fragmentations could help deduce theprimitive structures of macromolecules in natural bitumen.Solubility of natural bitumen was compared in22organic solvents. the solubility resultsshowed the extract yields of natural bitumen are largely related to dielectric constant andsolubility parameter. Natural bitumen tends to easily dissolve in solvents with lower dielectricconstant and smaller solubity parameter. In other words, natural bitumen tends to show bettersolubility in non-polar solvents. On the basis of extractant and price and toxicity of reagents, somethanol, ethanol, acetone, ethyl acetate, petroleum ether and carbon disulfide were selected asfractional extract reagents.After deep extraction, the GC/MS analysis results of fractional extracts demonstrate allextracts are complex mixtures and the extract yields of compounds detected in each extractwere far below the its mass. A variety of biomarkers are detected which have specialsignificance on organic geochemistry for complex organic compounds in each extract.119compounds were detected from the methanol-extractable fraction, and a large amount of2-ethylhexan-1-ol is contained.110compounds were detected from the ethanol-extractablefraction. From acetone-extractable fraction, only53compounds were detected. But noGC/MS-detectable species in the ethyl acetate-soluble, petroleum ether-extractable andCS2-extractable fraction, indicating that all the GC/MS-detectable species were extracted infirst three level solvents.With the further separation and purification of methanol-, ethanol-and acetone-fractionalextracts by cloumn chromatographies, the results demonstrate the kinds of compounds whichcould be detected by GC/MS significantly increased after extraction being separated by column chromatography, and the detected compounds are all over200in first three extracts. No normalparaffins, branched paraffins, carboxylic acids and various kinds of aromatic hydrocarbon weredetected in methanol extract but in eluted fractions by column chromatography. What’s more,in gradient elution, the fraction eluted with methanol enriched with sterane compounds and itsrelative content was up to80.6%. The fraction eluted with acetone enriched with aromaticcompounds and its relative content was up to66.5%. However, nothing was detected in thefraction eluted with carbon disulfide, which was non-polar solvent. A series of n-alkanes,branched alkanes and aromatic compounds were detected in the methanol/chloroform mixedelute fractions, which were not detected in extract. At the same time, with the further separationand purification of first methanol-eluted fratction by silica-gel and Sephadex LH-20gelatincolumn chromatographies, a pure compound was isolated and identified as2-ethylhexan-1-ol.239organic compounds were identified in ethanol extract by column chromatography, and thefront fractions eluted with methanol were rich in phthalates and.aromatic hydrocarbon, but thelatter fractions, which eluted with methanol enriched with a large number of steranecompounds of which the relative content was up to81.9%and the extract yield was187.8mg/g.282organic compounds were identified in acetone extract by column chromatography, whichwere far more than53compounds in extract and some special-detected species appeared ineluted fractions.A large number of biomarkers are identified in GC/MS-detected fractions, consist ofnormal paraffins, single methyl-alkanes, isoprenoids, steroids, terpenoids, alcohols, ketones,phthalates, other esters, aromatic hydrocarbon, carboxylic acid, and so on. It can be conferredthat Karamay natural bitumen was of higher maturity and there was almost no biodegradationin the process of diagenesis. The formation of Karamay natural bitumen’ geographicenvironment may be ocean or lake and the terrestrial substances, bacteria, algae and somehigher plants made a great contribution.In order to investigate further information about the chemical compounds about heavycomponents in natural bitumen, the petroleum ether and CS2-extractable fraction was subject toheating treatment in ca.400oC. Three products and two light oils acetone-soluble fractionswere detected with GC/MS, and most of compounds identified are normal alkanes, branchedalkanes, olefins, cyclic hydrocarbons and aromatic hydrocarbon. Also, properties are comparedby before and after heating treatment and heating-products and light oils. There are significantdifferences among them.61figures,83tables,240references.更多还原