含氧官能团热分解对褐煤结构影响的理论研究

The energy shortage is the serious challenges we faces today. The research on the dewater upgrading of lignite is expected to become the effective way to alleviate the problem. However, in the process of dehydration the chemical adsorption water, the C-C/O bond of oxygen-containing functional groups cleavage is easliy broken, the pore collapse and crosslinking reaction, will cause high energy consumption. This is the big problem which hindered the development of lignite dehydration industry. The analyse of chemical adsorption of water from the molecular level rules will reveal the essential reason for the high energy consumption of lignite, especially for providing a reliable solutions on improving the lignite dehydration rate for experimental research. In viewing this, the purpose of the project is to discover the influence of thermolysis of oxygen-containing functional groups on the structure of lignite. Taking advantage of quantum chemistry calculation, we present the density functional theory study on the thermal decomposition reaction of hydroxyl and carboxyl groups, through the analysis of thermodynamics and kinetics, the factors affect the reaction activation energy barrier will be discovered, which will provide a valuable guide for investigating the occurrence and reaction mechanism of oxygen functional groups on different pore structure. This project is focused on establishing the theoretial model through the analyse of the oxygen-containing functional groups, complex chemical environment, and pore structure. The project will provide the theory basis of the structure changes of lignite and its spectral data for experimental research. Furthermore, this study will also provide valualbe theoretical reference for the research on industrial lignite dehydration upgrading.

能源短缺是全世界各国面临的重大难题,褐煤脱水提质有望成为缓解该问题的有效途径。然而，脱除化学吸附水时,伴随着含氧官能团C-C/O键易断裂、孔隙发生崩塌交联反应等问题导致脱水提质能耗高,严重制约褐煤脱水工业的发展。从分子层面上探索褐煤脱除化学吸附水的规律，可揭示褐煤脱水能耗高的本质原因，有望为实验研究提供解决这一难题的方案。为此，本项目以揭示含氧官能团热分解对褐煤结构的影响为研究目标，借助量子化学计算优势，采用密度泛函理论方法，以褐煤中羧基和羟基基团的分解机理为切入点, 重点从反应热力学和动力学两方面, 探讨影响羧基和羟基分解反应的活化能垒因素, 在此基础上探索不同孔隙结构中含氧官能团的赋存和分解机理。本项目旨在建立基于含氧官能团热分解、复杂结构环境、孔隙结构等因素的褐煤脱水模型，为实验研究热分解后褐煤结构变化规律和红外光谱数据提供理论依据, 进而为工业降低褐煤脱水能耗提供理论参考。

褐煤脱水提质的理论研究对于提高资源高效利用率有重要的意义。本课题针对褐煤中富含水、尤其是含氧官能团热分解导致孔结构坍塌而制约脱水提质的效率这一难题开展理论研究。首先完成褐煤模型的构建，分子内弱相互作用的探究。通过以上研究，确立了理论模型和计算方法，进而阐明了含氧官能团对分子内弱相互作用的贡献。研究苯酚，苯甲酸与水簇的相互作用，计算了化学吸附的电子结构和吸附能。进而研究了弱相互租用对褐煤结构的影响，我们发现影响褐煤结构的堆积方式主要包括静电相互，诱导作用等。另外，我们进一步研究了在金属离子存在下，苯酚以及苯甲酚与水簇作用模型。通过研究相互作用能，反应活化能以及熵变，我们探索并总结了盐效应对褐煤中水分赋存规律。此外, 以煤溶剂萃取最小羧基单元-苯甲酸为切入点，采用量子化学方法详细研究可能发生反应的活性点，掌握在高温下发生的脱羧反应机理。并进一步研究在热解过程中，研究常见氧桥键和C-O键发生化学键断裂的反应动力学。在研究的过程中，不断总结含氧官能团对褐煤赋存水以及光谱的影响规律，对比实验研究的基础的同时，从理论模拟氧官能团对水的赋存，以及模型化合物热分解对褐煤提质的影响规律，本课题研究将为褐煤脱水体质的实验研究提供了必要的理论基础。