A Study On The Stuctural Characteristics Of Yilan,Huadian And Longkou Oil Shlae Kerogens

Oil shale is a sedimentary rock containing a complex organic substance(mainly kerogen and a little amount of asphaltene)and a series of mineral substances.Oil shale can be retorted to yield shale oil.The total China’s shale oil resource is about 47.6 billion tonnes,and the reverse is about 2 times more than that of the recoverable oil in China.The reverse of shale oil is the largest among all the unconventional resources.Therefore,oil shale is considered as a realistic alternative or supplement resource to the conventional oil and gas resource.At present,the insufficiency of oil and gas resources of our country is very large.Hence,it is of great significance to develop oil shale.In China,oil shale was mainly used for retorting to yield shale oil and burning directly as a fuel to generate electricity or heat.The most important utilization of oil shale is to be retorted to yield shale oil,however,the use efficiency of oil shale is low.As we know,the structure of a substance decides its properties and the properties decide its application.Therefore,it is of great significance to study the structure of oil shale kerogen,which can provide theoretical guide for the use of oil shale and then improve the utilization efficiency of oil shale.In this study,direct solid state measuring techniques and selective oxidation methods were used to study the structure of Yilan(YL),Huadian(HD)and Longkou(LK)oil shale kerogens.The main content and results are as follows.1.The structural characteristic of YL oil shale kerogen(YLK)was studied and a new typical average structural model of the kerogen was constructed based on the yield distribution of 12 benzene carboxylic acids(BCAs)combined with the results of ultimate analysis,13C NMR,FTIR,XRD,XPS and ion-exchange experiment of YLK.The result shows that YLK mainly consists of aliphatic and aromatic structure.The aliphaticity,aromaticity,average methylene chain length and molar fraction of aromatic bridgehead carbon of YLK is 49.7%,43.0%,2.0 and 0.174,respectively.The aromatic structure in YLK mainly consists of aromatic clusters,which are made up of single and double aromatic rings.These aromatic clusters come in two forms:convertible to BCAs and unconvertible to BCAs.The content of aromatic clusters convertible to BCAs is 0.56 mmol/g.Finally,an average structurel model of YLK was constructed based on the results obtained from above analyses.The structural model has a molecular formula of C5322H6322O1355N100S45 and a mass-average molecular weight of 94816 Da.Compared with the structural models of oil shale kerogen in the literature,the structural model proposed in this work can not only meet the results of all techniques used above,but also account for the distribution of BCAs.2.The alkali-oxygen oxidation and ruthenium ion-catalyzed oxidation(RICO)of YLK was conducted to study the structure change of YLK during the alkali-oxygen oxidation process and the distribution of aliphatic structure.The result indicates that the alkali-oxygen oxidation of YLK is a process of gradual degradation.During the alkali-oxygen oxidation process of YLK,C-O bond is easily cleaved while the condensed aromatic rings and long alkyl chains are difficult to be oxidized.There exists a small amount of aromatic clusters with 3 aromatic rings or above in YLK.Most of aliphatic carbons of YLK exist as short alky1 chains,and little exist as long alky1 chains.The average methylene chain length of these short alky chains is less than 2.2.7%aliphatic carbon exists as n-alkyl chain in the side-chain on the aromatic rings in YLK.The carbon number of the n-alkyl chain ranges from 5 to 22,C15 and C17 are predominant.3.8%aliphatic carbons exist as n-alkyl chain in bridge linkages connecting aromatic rings in YLK.The carbon number of bridge linkages connecting aromatic rings ranges from 5 to 19,and C8 is predominant.3.Alkali KMnO4 oxidation and 13C NMR of HD oil shale kerogen(HDK)were conducted to study the structural characteristic of HDK.The result shows that the aromaticity,aliphaticity,the average methylene chain lengh and molar fraction of aromatic bridgehead carbon are 19.4%,73.1%,8.0 and 0.102,respectively.The result indicats that the carbon of HDK maily exists as aliphatic structure.The aromatic structure in HDK mainly consisis of aromatic clusters,which are made up of single and double aromatic rings.The single-ring aromatic cluster was the main aromatic structure in HDK,and the aromatic clusters in the kerogen come in two forms:convertible to BCAs and unconvertible to BCAs.The content of aromatic clusters convertible to BCAs is 0.24 mmol/g.4.The contents of humic organic matters and the humic degree of LK,HD and YL oil shale kerogens were studied.]3C NMR,FTIR,XPS,XRD and ion-exchange experiment were used to study the structural characteristics of LK,HD and YL oil shale kerogens in an increasing order of humic degree.The structural characteristics of kerogens in oil shale with different humic degrees were studied from three aspects:aliphatic structure,aromatic structure and heteroatom species(O,N and S).The result indicates that the content of aromatic structure and average aromatic cluster size increase while the content of aliphatic structure,average methylene chain length and average substitutive degree of aromatic ring decrease as the humic degree of oil shales increases.As the humic degree of oil shales increases,the content of C-O(alcohol,ether and phenol)increases while that of O=C-O(carboxyl and ester)decreases;the contents of pyridinic and chemisorbed nitrogen oxides increase while those of pyrrolic and amino decrease;the contents of aromatic sulfur and sulfoxide increase while those of aliphatic sulfur and sulfone decrease.5.The structural characteristics of kerogens in LK and HD oil shales with different density grades were studied by 13C NMR,FTIR,XPS and XRD analyses.The result shows that the content of aromatic structure and average aromatic cluster size decrease while the contents of aliphatic structure and average methylene chain length increase as the density of oil shales increases.In the studied kerogens of oil shale with different density grades,the organic oxygen exists as Car-O(phenol and ethe),Cal-O(alcohol and ether),C=0 and O=C-O and the orderings for the amounts of these oxygen functional groups are different.As the density of oil shale increases,the content of amino decreases while that of chemisorbed nitrogen oxides increases;the contents of aromatic sulflur and sulfoxide decrease while those of aliphatic sulfur and sulfone increase.