Study On Anaerobic Degradation Of Methanol Extraction Of Lignite By Sulfate-reducing Bacteria

China is rich in lignite resources.With the promotion of the " carbon peaking and carbon neutrality goals ",how to efficiently develop and clean use lignite resources has become an urgent problem to be solved in the field of coal utilization.The utilization of microorganisms to convert lignite into biological coalbed methane is an extremely effective and clean way of utilization,so it has attracted the attention of many researchers.Sulfate reduing bacteria(SRB)is an important type of microorganisms in the process of anaerobically degrading coal to form biocoalbed methane.However,it is not clear which organic components in coal can be degraded by SRB and how.In this thesis,four kinds of lignite from Shengli5hao(SL5),Mengdong(MD),Baiyinhua(BYH)and Zhaotong of Yunnan(YN)were selected as the research objects.Methanol was used as the organic solvent to extract the organic components of lignite.The methanogen communities preserved in the laboratory were used as the starting flora,and the SRB strain was isolated and purified from the mixed flora.The anaerobic degradation process of methanogen communities and SRB strain on methanol extraction components and residual coal was studied,the main conclusions were as follows:(1)The extraction rate of methanol for the four lignite from high to low was YN(9.94%)>SL5(7.93%)>BYH(7.89%)>MD(4.17%).GC/MS analysis results of four lignite methanol extracts showed that aromatic hydrocarbons were the most detectable components in methanol extract from Shengli5 hao lignite(SL5-CQY),methanol extract from Baiyinhua lignite(BYH-CQY)and methanol extract from Mengdong lignite(MD-CQY),accounting for 24%,31% and 26%,respectively.Phenolic compounds(13%)were the most detectable components in methanol extract from Zhaotong of Yunnan lignite(YN-CQY),and oxygen-containing compounds such as ketones(11%),aldehydes(6%)and carboxylate esters(9%)also dominated.The high abundance of 1,6-dimethyl-4-(1-methylethyl)-naphthalene and n-decane in SL5-CQY,1,6-caprolactam,3-oxyalkan-12-ene in YN-CQY,styrene,1,6-dimethyl-4-(1-methylethyl)-naphthalene,2-ethylacridine in BYH-CQY,1,6-caprolactam,ntetradecane,n-octadecane,pyrene and pentamethyl carbazole in MD-CQY may be utilized by SRB.1,6-dimethyl-4-(1-methylethyl)-naphthalene,styrene,1,6-caprolactam and n-octadecane can be used as model compounds to further explore the anaerobic degradation mechanism of SRB.The degradation mechanism of organic compounds in SRB strain was predicted by using the functional gene of Klebsiella Aerogenes,many functional genes of hydroenzyme and hydroformate lyase were found.These functional genes were used to predict the degradation routes of styrene and 2-haparynic acid by SRB.(2)Methanogen communities conducted bio-simulation gas production experiments on lignite methanol extract,raw coal and methanol-extracted residual coal.The results showed that the methanol-extracted residual coal of lignite was more easily used by methanogenic bacteria,and the methane yield from high to low was Methanol extraction of residual coal from Mengdong lignite(MD-CQCM)(272 μmol/g coal)>Methanol extraction of residual coal from Shengli5 hao lignite(SL5-CQCM)(37μmol/g coal)>Methanol extraction of residual coal from Baiyinhua lignite BYHCQCM(25 μmol/g coal)>Methanol extraction of residual coal from Zhaotong of Yunnan lignite(YN-CQCM)(5 μmol/gcoal).After gas production,it was found that the dominant phyla at the classification level were Firmicutes(19.47%-42.66%),Desulfobacterota(8.27%-29.75%),Spirochaetota(7.09%-24.9%),Proteobacteria(5.82%-14.84%),Bacteroidota(3.79%-13.34%),Actinobacteriota(0.17%-11.16%),the dominant phyla in methanogen communities(CJWJQ)are similar.After gas generation,it was found that the dominant species at the level of genus classification were norank＿f＿＿Spirochaetaceae(4.87%-22.92%)and norank＿f＿＿Izemoplasmataceae(3.98%-30.7%).The genus containing SRB bacteria belongs to the dominant species.Desulfosporosinus has a better share in the fermentation broth of coal samples that produce more methane,such as MD-CQCM(26.93%),BYH-CQCM(5.09%),BYH(4.19%)and SL5-CQCM(0.98%).This shows a significant positive correlation between the percentage of Desulfosporosinus and the amount of methane generated.The correlation between the Klebsiella which was isolated and purified from methanogenic bacteria and methane production was significant,indicating that Klebsiella could be used for degradation experiments.(3)Coal samples by XRD and XRF analysis showed that four kinds of lignite and methanol extracts of the content in the residual coal is more elements for Si and Al element,exists in the adherent state of quartz and kaolinite,methanogens group of SRB and after degradation,inorganic mineral components of SRB trend similar to the methane-producing bacteria,degradation of aromatic layer coal sample after condensation degree increase,SRB is more fully utilized for MD-CQCM.Coal samples of proximate analysis and ultimate analysis show that SRB degradation took advantage of the lignite and the organic components of extraction of residual coal,SRB can remove organic sulfur from coal.FTIR showed that SRB played a certain role in the degradation of methanogenic bacteria in the process of anaerobic gas production from organic matter.The functional groups of lignite extracted by methanol could be utilized more effectively.It is mainly characterized by C=O fracture,C-O formation and methyl formation,and is more easily degraded by carboxylic acid compounds.This thesis has 46 figures,32 tables and 121 references.