Research On The Structure Of Huadian Oil Shale Organic Matter And Its Interaction With Minerals With Supercritical Ethanolysis

Oil shale,with abundant storage,is a kind of potential alternative fossil energy.As we know,the chemical structure of oil shale kerogen is the basis of its application.Ethanolysis is an effective method to study the structure of organic compounds.In this work,the structure of Huadian oil shale organic matter and the interaction of organic matter with minerals were studied mainly using supercritical ethanolysis.The main contents and conclusions are shown as follows.(1)Huadian organic matter(HDOM)was subjected to ethanolysis at different ethanolysis conditions,and the products were analyzed with gas chromatography/mass spectrometry(GC/MS).The residues were studied by Fourier transform infrared(FTIR)and solid-state 13C nuclear magnetic resonance(13C NMR),to further show the evolution of weak bonds(oxygen-containing functional groups)and the carbon structural parameters of residues after ethanolysis.The results indicated that with an increase in ethanolysis temperature,the conversion of HDOM increased and the number of weak bonds(including O-containing,N-containing and S-containing functional groups)broken increased.After extracted at 375 ℃,the content of O-C=O decreased from 26.3%to 4.3%and 81.3%of the organic matter of HDOM was soluble in ethanol.During the process of ethanolysis,the cleavage of weak bonds occurred,and then small molecular products were formed,including aliphatic acid esters,aliphatic acids,alkanes,alcohols,aromatics,N-containing organic compounds(NCOs),and S-containing organic compounds(SCOs).These small molecular compounds can reflect the information of primary products during pyrolysis of oil shale.During pyrolysis of oil shale,the primary products can readily suffer the secondary reactions and are difficult to be detected,while they can be easily obtained through supercritical ethanolysis.(2)It is well known that oil shale is a sedimentary shale with a large proportion of inorganic minerals.The relationship between of organic matter and minerals in Huadian oil shale was studied in this work using the methods of supercritical ethanolysis and stepwise acid treatment.HCl,HNO3,HF acid was used to dissolve carbonate,pyrite and silicate,respectively.After each acid treatment,residues were extracted by supercritical ethanolysis.Based on the analysis of SEM and BET,minerals exist in different forms in the oil shale.Carbonates are tiny particles in the oil shale particles,which is smaller then pyrite,while the silicates play a supporting role in the oil shale.After washing out all the minerals,organic matter recombines with each other to form very dense particles which are of no micropores.Compared BET parameters of the oil shale and residues after ethanolysis,it is found that a portion of organic matter was trapped in pores formed by minerals.Besides physical trapping,there are chemical bonding interactions between organic matter and minerals.The interaction of organic matter with minerals depends on the species of minerals.Carbonates of minerals in the oil shale have a strong chemical interaction with carboxylic acids of organic matter via carbonating between-COOH on carboxylic acids and cations in the carbonates(such as Ca,Mg,Fe).There are strong bonding interactions between pyrite and alkanoic acids via carbonating.After HF acid treatment of dissolving silicates and supercritical ethanolysis,there are a large number of alcohols and ethers,as well as fatty acid,in the ethanolysis products,and Si-containing compounds have also been detected in the ethanolysis products.These organic compounds mainly exist via forming Si-O ethers with silicates in the oil shale.