Structural And Pyrolysis Characteristics Of Fushun Oil Shale Pyrolysis Bitumen

Pyrolysis bitumen is an important intermediate product generated by organic matter kerogen reaction in the pyrolysis process of oil shale,and it is also a reactant for generating shale oil and dry distillation gas.The study of pyrolysis bitumen structure and pyrolysis characteristics can reveal the transformation law of organic matter in oil shale and the formation law of oil and gas products.Therefore,this paper mainly takes Fushun oil shale and its pyrolysis products as the research object,compares and analyzes the basic characteristics of oil shale and its pyrolysis products,and deeply studies the structure and pyrolysis characteristics of pyrolysis bitumen.Firstly,Fushun oil shale was pyrolyzed at different final temperatures,and the pyrolysis bitumen in semi-coke was extracted in three different organic solvents.The experimental results show that when the final pyrolysis temperature is 450°C and the extraction solvent is the mixed solvent of ionic liquid(1-butyl-3-methylimidazolium chloride)and NMP(N-methyl-pyrrolidone),the yield of pyrolysis bitumen is the highest,about 5.35%.Secondly,the pyrolysis bitumen,semi-coke,residual and shale oil obtained under the above conditions are taken as the research objects.The basic properties of oil shale pyrolysis products were characterized by proximate analysis,ultimate analysis,SEM,FTIR and XRD.The results show that the relative strength of methylene functional groups in oil shale,semi coke and residual ore decreases in turn,and the aliphatic carbon chain is more prone to fracture than other structures during pyrolysis.In the process of pyrolysis bitumen decomposition into shale oil,the carbon oxygen double bond structure is not easy to decompose,and it is easier to accumulate in shale oil than other structures.¹³C NMR,XPS and GC-MS were used to characterize the structural characteristics of the intermediate pyrolysis bitumen,and the average molecular formula of pyrolysis bitumen was constructed.The results show that the carbon elements in thermal bitumen are mainly composed of aliphatic carbon and aromatic carbon,and the aliphatic carbon rate and aromatic carbon rate are 88.46%and 11.54%,respectively.The main form of carbon skeleton structure of pyrolysis bitumen is methylene carbon.The degree of branching of the alkyl chain of pyrolysis bitumen is3.12%,the average number of carbon in methylene chain is about 13,and the degree of substitution of aromatic ring is about 0.71.In addition,the carbon-oxygen binding mode mainly exists in the form of carbon-oxygen double bond,carbon-oxygen single bond and carboxyl group.Nitrogen element in pyrolysis bitumen is mainly divided into pyrrole nitrogen and pyridine nitrogen in organic nitrogen,sulfur element mainly occurs in the form of thiophene,sulfone,sulfoxide,organic sulfide and inorganic sulfur containing sulfate.The main aromatic compounds in pyrolysis bitumen are monocyclic aromatic hydrocarbons,and polycyclic aromatic hydrocarbons are naphthalene and biphenyl.Finally,thermogravimetric experiments were carried out at different heating rates.The kinetic parameters of pyrolysis bitumen were calculated by coats-Redfern,Friedman and KAS methods,and the pyrolysis products of pyrolysis bitumen were analyzed by Py-GC/MS.The results show that with the increase of heating rate,the weight loss of pyrolysis bitumen decreases gradually.With the increase of temperature,the formation rate of pyrolysis bitumen first increases and then decreases,and the decomposition rate of pyrolysis bitumen increases gradually.It is found that the activation energy values calculated by the three methods are very close and increases with the increase of conversion rate,which shows that with the pyrolysis reaction,the pyrolysis of pyrolysis bitumen becomes more and more difficult.The aromatic structure in the fast pyrolysis products of pyrolysis bitumen mainly comes from the dehydrocondensation of aliphatic compounds.The relative content of non hydrocarbon products in pyrolysis bitumen is very low,mainly including alcohols,ketones and phenols,in which phenols occupy a large proportion.