抗生素菌渣热解特性及氮迁移转化机理研究

Pyrolysis behavior of antibiotic residues and the mechanism of nitrogen evolution

  • 摘要: 在固定床上进行了不同温度下(300–700 ℃)青霉素菌渣的热解实验,研究了不同热解温度下三相产物的产率及氮的形态和分布。采用反应分子动力学模拟的方法研究了菌渣中含有的氨基酸(天冬氨酸、组氨酸和谷氨酸)和2, 5-哌嗪二酮(DKP)的热解反应机理。结果表明,随着温度的升高,热解气产率增加,热解焦产率减少,热解油的产率先增加后减少,在500 ℃达到最大为42.3%。产物中氮含量随温度的变化与产率变化趋势一致。相较于H2和烃类气体,CO2和CO更容易在低温下生成。酰胺是热解油中的主要含氮化合物,随着热解温度的升高,其占比逐渐下降。氨基酸的脱氨反应是NH3的主要来源,氨基酸分子间发生脱水环化生成DKP类化合物。DKP热解生成NH3、HCN、HNCO等气体和R-NH、R-NH-R自由基,含氮自由基通过与其他自由基结合或发生环化生成酰胺、酮等化合物存在于热解油和热解焦中。

     

    Abstract: The pyrolysis experiments of penicillin residues at different temperatures (300–700 ℃) were carried out in a fixed bed to study the yield of three-phase products and the morphology and distribution of nitrogen at different pyrolysis temperatures. The mechanism of the pyrolysis reaction of amino acids (aspartic acid, histidine and glutamic acid) contained in the bacterial residues and 2, 5-piperazinedione (DKP) was investigated by ReaxFF molecular dynamics simulations. The results show that the yield of gas increases with the increase of temperature, while the char shows a declining trend. The yield of oil increases to a maximum of 42.3% at 500 ℃ and then decreases as temperature increase. The pattern of nitrogen content in the product with temperature is consistent with the trend of yield. Compared with H2 and hydrocarbon gases, CO2 and CO aere more easily produced at low temperatures. Amides are the main nitrogenous compounds in oil, and the proportion of amides gradually decreases as the pyrolysis temperature increases. The deamination reaction of amino acids is the main source of NH3, and dehydration cyclization occurs between amino acid molecules to produce DKP-like compounds. Gases such as NH3, HCN, HNCO and R-NH, R-NH-R radicals are generated during the pyrolysis of DKP. Nitrogen-containing radicals combine with other radicals or undergo cyclization to form amides, ketones and other compounds present in oil and char.

     

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