Abstract

The oxidation of lignite and bituminous coal modified with an activating additive of Fe(NO₃)₂ (5 wt %) was investigated. Iron nitrate was applied by incipient wetness impregnation with the preliminary dissolution of Fe(NO₃)₂ in a water–alcohol solution with the volume ratio C₂H₅OH : H₂O = 50 : 50. The reactivity of the samples was studied by thermogravimetric analysis in the oxidation mode at a heating rate of 2.5 K/min in a temperature range of 25–600°C at atmospheric pressure. It was established that the use of the activating additive decreased the initial temperature of intense oxidation (Δt_i = 77°C) and shifted the overall process to the low-temperature region. The qualitative analysis of the gas-phase products of bituminous coal oxidation was performed by mass spectrometry, and it was found that a decrease in the initial temperature of the release of volatile compounds was associated with the decomposition of iron nitrate. The activation energies of oxidation processes in the presence of iron nitrate were calculated using the Coats–Redfern method. A maximum decrease in E_a (from 74.0 to 64.4 kJ/mol) was observed in a modified sample of bituminous coal. A possible mechanism of the action of iron nitrate, which leads to the activation of the oxidation processes of the test coals, is discussed.

中文翻译：

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Fe（NO 3）2活化添加剂对褐煤和煤的氧化作用增强

摘要

研究了用Fe（NO ₃）₂（5 wt％）的活化添加剂改性的褐煤和烟煤的氧化。通过初期湿润浸渍法施用硝酸铁，并初步溶解Fe（NO ₃）₂在体积比为C ₂ H ₅ OH：H ₂ O = 50：50的水-醇溶液中。研究了样品的反应性通过在25-600°C的大气压下以2.5 K / min的升温速率在氧化模式下进行热重分析。已经确定，使用活化添加剂可以降低强氧化的初始温度（Δt _i= 77°C），并将整个过程转移到低温区域。通过质谱法对烟煤氧化的气相产物进行了定性分析，发现挥发性化合物释放的初始温度降低与硝酸铁的分解有关。使用Coats–Redfern方法计算了在硝酸铁存在下的氧化过程的活化能。在改性烟煤样品中观察到E _a的最大降低（从74.0到64.4 kJ / mol）。讨论了硝酸铁作用的一种可能机制，该机制导致了受试煤的氧化过程的活化。