燃煤固体废物制备介孔硅基材料

发布时间：2018-07-25 17:15

【摘要】：粉煤灰和煤气化渣是我国煤炭能源利用过程中产生的两种典型燃煤固体废物。我国所面临的燃煤固体废物的处理压力十分巨大,既要消纳历史积压而来的数量巨大的粉煤灰,又要为排放量日益增加的煤气化渣寻找处置途径。传统的资源化消纳途径如建筑材料、农用土壤等领域的市场已经趋于饱和,且随着这些领域原料价格的下滑和应用标准的提升,燃煤固体废物在其中已不占据优势。因此,燃煤固体废物的资源化势必向高附加值和创新型的应用方向发展。本研究针对燃煤固体废物的高硅特性,将其应用到介孔硅基材料的制备上,从而借助介孔硅基材料广泛的应用范围,将燃煤固体废物的资源化提升到一个新的平台,这对燃煤固体废物的永续消纳具有十分深刻的意义。本研究的内容分为两大部分。一部分是针对粉煤灰和煤气化渣化学性质的差异,分别通过不同的合成方法制备出介孔硅基材料。另一部分是对所获取的介孔硅基材料热稳定性和应用性能的检测。在介孔硅基材料的合成中,通过对煤气化渣的酸预处理和碱熔处理获得了化学活性高的高硅原料,然后通过溶胶-凝胶工艺成功制备出具有超大比表面积(1347 m2/g)和较大孔容(0.83 cm3/g)的有序介孔硅基材料MCM-41。然而溶胶-凝胶工艺由于前驱体组分和均一性难以控制,在工业放大上存在困难。故在以粉煤灰为原料合成介孔硅基材料的过程中,本研究首次提出了化学酸溶蚀法制备介孔材料。针对酸溶蚀反应强度与所获得硅基材料比表面积间的关系,本研究提出了反应强度数值模型,并借助此模型讨论了酸溶蚀法的成孔过程和机制。随模型定义的反应强度值(RI)的升高,所获得的硅基材料的孔结构按以下顺序发生变化：无孔、楔形介孔、平行板形介孔、圆筒形介孔、微孔和楔形介孔。在最佳反应强度(RI=5327)下,所制备出的新型介孔硅基材料为圆筒形介孔结构,且具有大的比表面积(585.02m2/g)和孔容(0.54 cm3/g)。这证明了酸溶蚀法可以制备出与溶胶-凝胶法相媲美的介孔硅基材料,而酸溶蚀法所具备的工艺简单,工业化难度低等特点,将会给介孔材料的合成领域带来变革。通过对溶胶-凝胶法和酸溶蚀法获得的两种介孔硅基材料热稳定性的对比发现,后者的热稳定性要明显优于前者。在900℃下处理1h后,溶胶-凝胶法获得的MCM-41的孔容仅剩余15%,而酸溶蚀法获得的孔容还保留有55%。在介孔硅基材料于相变材料载体和重金属吸附的应用研究中,同时讨论了孔形对应用性能的影响。具有圆筒形介孔的硅基材料在作为相变材料载体时,其有效负载率(54.85%)最大,所获得的定型相变材料相变热为50.65 J/g,相变温度为30.9℃在循环热稳定性和泄露性检测中均表现优越,具有极强的应用价值。所合成的介孔硅基材料直接应用于重金属Cr和Pb吸附时,其吸附量较低。经螯合基团EDTA和DTPA改性后,圆筒形介孔硅基材料对Pb的吸附量大幅上升(17.30 mg/g和16.90 mg/g),成为三种孔形中的最佳选择。改性后的介孔硅基材料在重金属吸附领域具备很强的竞争力。
[Abstract]:Coal ash and coal gasification slag are two typical solid wastes produced in the process of coal energy utilization in China. The pressure of the treatment of solid waste in China is very huge. It is necessary to eliminate the huge amount of coal ash from the historical backlog, and to find the way to deal with the coal gasification slag. The market for source reduction, such as building materials, agricultural soil and other fields, has become saturated, and with the decline of the price of raw materials and the improvement of application standards, the coal solid waste has not taken advantage of it. Therefore, the resource of coal solid waste is bound to develop to high value-added and innovative application. In view of the high silicon characteristics of coal burning solid waste, it is applied to the preparation of mesoporous silica based materials. With the wide application range of mesoporous silica based materials, the resource of solid waste is promoted to a new platform, which is of ten profound significance to the sustainable consumption of solid waste. The content of this study is divided into two parts. Part. One part is the preparation of mesoporous silica based materials by different synthetic methods for the chemical properties of fly ash and coal gasification slag. The other part is to detect the thermal stability and application performance of the mesoporous silica based materials. In the synthesis of mesoporous silica, the acid pretreatment and alkali melt treatment of coal gasification slag have been passed. High silicon materials with high chemical activity were obtained, and the ordered mesoporous silica based materials with super specific surface area (1347 m2/g) and larger Kong Rong (0.83 cm3/g) were successfully prepared by sol-gel process. However, the sol-gel process was difficult to control in the industrial amplification due to the difficulty of controlling the precursor composition and homogeneity. In the process of synthesizing mesoporous silica based materials from raw materials, the mesoporous materials were prepared by chemical acid dissolution method for the first time. In view of the relationship between the strength of acid dissolution reaction and the specific surface area of the silicon base material obtained, a numerical model of the reaction strength was put forward in this study, and the pore forming process and mechanism of acid dissolution method were discussed with the model. The pore structure of the silicon based material is changed in the following order: no hole, wedge mesoporous, parallel plate mesoporous, cylindrical mesoporous, microporous and wedge-shaped mesoporous. Under the best reaction strength (RI=5327), the new mesoporous silicon-based material is a cylindrical mesoporous structure with large RI. Specific surface area (585.02m2/g) and Kong Rong (0.54 cm3/g). This proves that acid dissolution method can produce mesoporous silica based on sol-gel method. The acid dissolution process is simple, and the difficulty of industrialization will bring about changes in the synthesis field of mesoporous materials. The sol-gel method and acid dissolution method are obtained. The thermal stability of the two mesoporous silica based materials shows that the thermal stability of the latter is obviously superior to the former. After the treatment of 1H at 900 C, the pore volume of the MCM-41 obtained by the sol-gel method is only 15%, while the pore volume obtained by the acid dissolution method still holds 55%. in the application of mesoporous silica based materials for phase variable materials and the adsorption of heavy metals. At the same time, the influence of the pore shape on the application performance is discussed. The effective load rate (54.85%) of the silicon based material with a cylindrical mesoporous material is the largest when it is used as a phase change material carrier. The phase change heat of the fixed phase change material is 50.65 J/g, the phase change temperature is 30.9, and it has excellent performance in the cyclic thermal stability and leakage detection. The adsorption capacity of the mesoporous silica based materials synthesized directly on Cr and Pb adsorption is low. After the modification of chelating group EDTA and DTPA, the adsorption of cylindrical mesoporous silica based materials on Pb is greatly increased (17.30 mg/g and 16.90 mg/g), which is the best choice in the three pores. The modified mesoporous silica based materials are in heavy metals. The field of adsorption is very competitive.
【学位授予单位】：华东理工大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TQ127.2;X705

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