无烟煤厌氧代谢产物对其纳米孔隙的影响

Effects of microbial anaerobic metabolites on nanoporosity of anthracite

为研究厌氧代谢产物对煤纳米孔隙发育的影响,选用山西沁水盆地寺河矿无烟煤作为底物,以寺河矿煤层气井产出水中富集并驯化获得的原位真菌与产甲烷菌混合菌群为菌源,开展微生物厌氧降解煤产甲烷实验。通过额外添加2-溴乙烷磺酸钠(BES)抑制生物甲烷生成,促进煤生物厌氧降解代谢产物的积累;利用低温氮气吸附、有机溶剂萃取、气质联用(GC/MS)等方法,分析微生物降解作用下的煤孔隙结构和有机物组成变化规律。研究发现,微生物厌氧降解后,残煤总孔容与比表面积降低,孔隙分形维数D1(<2 nm)和D2(2~10 nm)增大。说明生物降解导致煤孔隙发育降低,孔隙表面粗糙程度和孔隙结构复杂程度增加。添加BES增强了微生物厌氧降解对煤孔隙的作用。同时,微生物厌氧降解后煤中可溶有机组成及含量发生显著变化,降解残煤中芳香族含氧衍生物和杂环有机物含量明显增加。添加BES促进更多新产生的可溶有机质滞留于煤中,尤其是芳香族含氧衍生物中的对甲酚。此外,煤中芳香族含氧衍生物含量与煤的总孔容和比表面积具有显著负相关性,而与煤孔隙分形维数D1和D2具有显著正相关性。以上研究结果表明,厌氧代谢产物在微生物降解对煤孔隙影响中发挥重要作用;微生物代谢产生的可溶有机质,尤其是芳香族含氧衍生物在煤中的滞留积累是微生物厌氧降解影响煤孔隙发育的主要途径。

To study the effect of anaerobic metabolites on the evolution of coal nanopores,the anaerobically de-grading anthracite to produce biogas was performed using the anthracite obtained from Sihe in Qinshui basin,and the in-situ mixed microflora of fungi and methanogens enriched from produced water associated with Qinshui Basin.Sodium 2-bromoethanesulfonate(BES)was added to inhibit the biomethane formation and promote the accumulation of metabolites in coal biodegradation.Low-temperature nitrogen adsorption,organic solvent extraction,and gas chromatograph/mass spectrometer(GC/MS)were used to analyze the changes of pore structure and organic matter composition of coal under microbial degradation.The results showed that the total pore volume and specific surface area of coal decreased,the pore fractal dimension D1(<2 nm)and D2(2-10 nm)increased,and the roughness of pore surface and the complexity of pore structure increased after anaerobic biodegradation.The addition of BES enhanced the effect of anaerobically microbial degradation on coal pore structure.Meanwhile,the soluble organic composition and content in coal changed significantly,and the content of oxygen-containing aromatic derivatives and heterocyclic organics increased after anaerobic biodegradation.The addition of BES promoted more soluble organic matter,especially the p-cresol in oxygen-containing aromatic derivatives trapping in the coal.Besides,the content of oxygen-containing aromatic derivatives showed significantly negative correlations with the total pore volume and specific surface area of coal,whereas there was a positive relationship with coal pore fractal dimension D1 and D2.These results indicated that the anaerobic metabolites played an important role in the effect of microbial degradation on coal pore structure.The accumulation of soluble organic matter,especially oxygen-containing aromatic derivatives in coal,was the main way in the reduction of the pore evolution of coal by anaerobic biodegradation.