褐煤高温水萃物生物产气及化学组成变化

Biogas production and variation of the chemical composition of the high temperature water extract of lignite

微生物与煤的相互作用过程复杂,为了深入分析煤中有机物在生物产气过程中的作用及变化规律,选取义马褐煤和实验室保存的产甲烷菌群作为研究对象,研究褐煤水溶性有机物产气特征及其产气前后化学组成变化。利用去离子水在70℃下萃取褐煤得到水溶性有机物、水萃余煤,分别以其作为底物开展生物产气实验,并利用甲醇对产气后的残煤进行有机萃取,采用GC、HPLC-MS和GC-MS方法分析产气量变化及发酵液和煤甲醇萃取物的化学组成。结果表明,褐煤原煤、水溶性有机物和水萃余煤的产气量分别为0.46、0.45和0.15 mmol/g。产气初期水溶性有机物化学组成复杂,分子量主要集中在200~300 Da,生物产气后化合物种类减少,分子量降至150~200 Da,并且产气后发酵液中检测到一些分子中具有苯环结构的含氮和氧杂原子的化合物。水萃余煤生物产气后的甲醇萃取物中出现少量水溶性化合物如甲酰胺、乙酰胺、亚硫酸二甲酯等。70℃萃取得到的义马褐煤水溶性有机质能被产甲烷微生物利用产气,经过生物产气后煤中非水溶性有机物会转变成水溶性有机物。本研究探索了褐煤中水溶性有机物在生物产气过程中的潜在作用,为阐明煤生物产气的物质基础提供了实验依据。

The interaction process between microorganism and coal is complicated.In order to deeply analyze the function and change rule of organic matter in coal in the process of biological gas production,taking Yima lignite and methanogens preserved in laboratory as research objects,the gas production characteristics of water-soluble organic matter of lignite and its chemical composition change before and after gas production were studied.The water-soluble organic components of Yima lignite obtained by deionized water extraction at 70℃ and the extraction residue were used as substrates for biogas production.High performance liquid chromatography-mass spectrometry(HPLC-MS),gas chromatography(GC) and gas chromatography-mass spectrometry(GC-MS) were used to analyze the change of gas production and the chemical composition of fermentation broth and coal methanol extract.The results showed that the gas production of raw coal,water-soluble organic matter and extraction residue were 0.46,0.45 and 0.15 mmol/g coal respectively.At the beginning of gas production,the chemical composition of water-soluble organic compounds of which the molecular weight was mainly concentrated in 200-300 Da was complex.After biogas production,the species of compounds decreased,and the molecular weight decreased to 150-200 Da.Some oxygen-containing and nitrogen-containing compounds with phenyl rings were detected in the fermentation broth.GC-MS analysis showed that a small number of water-soluble compounds(e.g.,formamide,acetamide and dimethyl sulfite) appeared in the methanol extract of extraction residue after biogas production.The conclusion was that the water-soluble organic matter of lignite extracted at 70 ℃ can be utilized by methanogens for biogasification and some water-insoluble organic compounds were converted into water-soluble organic compounds in the process of biodegradation.This study explored the potential role of water-soluble organic compounds in the biogasification process of lignite.