Separation And Analysis Of Karamay Natural Bitumen

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.