介孔二氧化硅调控合成及其在乙醇水蒸气重整制氢中的应用

发布时间：2018-05-12 00:10

  本文选题：介孔二氧化硅 + 乙醇水蒸气重整制氢　； 参考：《太原理工大学》2015年硕士论文

【摘要】：有序介孔二氧化硅属于分子筛范畴，因其比表面积高、孔容量大、孔径可调、耐热性好等特点而成为研究的热点。现阶段对有序介孔二氧化硅的研究主要围绕着用有机物扩孔、以其为模板剂制备其它纳米线或纳米丝材料等方面来进行。然而，因其形貌、孔道的单一性以及有机物扩孔方法的不环保性等缺点，在一定程度上限制了其应用。 本文基于研究现状的局限性，从有序介孔二氧化硅合成（S0H+X-I+）机理入手，调节合成过程中母液的种类和浓度（H+X-来源），将传统盐酸母液换作硝酸、硫酸和磷酸母液，合成出的SBA-15的形貌分别为“麦穗”状、“铜钱”状、长程连续“糖块”状和高度分散“糖块”状，形貌间差别很大。考虑到合成过程最为重要的两个步骤就是水浴和水热处理。水浴过程主要是模板剂与硅源间的相互作用合成出初始二氧化硅材料，晶化过程主要是将合成出的初始材料进一步晶化，孔壁变薄变坚硬。将合成过程的两个步骤分别调控酸度，再结合母液种类的不同，最终合成出了双介孔二氧化硅材料。通过以上简单环保的方法，在一定条件下就可以制备不同形貌和双介孔状的二氧化硅材料。 镍对乙醇水蒸气重整制氢反应有较好的活性，但镍易烧结，尤其在通常选择的酸性或表面积较小的载体中更易烧结。载体若显酸性还会使气体产物有乙烯，乙烯的存在又会使氢气产率降低。本论文中制备的SBA-15，比表面积较大且为中性，比表面积较大就会使得负载金属量较大而不发生烧结，是很好的用在该反应的催化剂载体。本实验的另一部分就是以SBA-15为催化剂载体，采用两种不同的镍源（硝酸镍、氨基磺酸镍）制备催化剂，通过XPS、TEM等手段表征催化剂的物化性能的差异，最终发现两种镍源负载到载体的位置不同，硝酸镍主要负载到催化剂孔道，氨基磺酸镍主要负载到载体表面，并且经还原后镍的晶型不同，，导致了催化后产物相差很大。通过改变反应过程的进料量和温度得到实验数据，并通过MATLAB程序中的LevenbergMarquardt和lsqcurvefit算法对实验数据进行拟合，最终得到对催化剂Ni(1)7.5SBA在550℃左右反应活化能为25.345KJ mol-1，对催化剂Ni(2)7.5SBA在500℃左右反应活化能为41.449KJ mol-1等本征动力学数据。从物化性能参数和本征动力学数据两个方面说明两种镍源催化剂催化效果差异的原因。进一步考查了两种催化剂的活性金属负载量、寿命、进料中水醇比等工艺参数，为其进一步工业的应用提供了基础研究。
[Abstract]:Ordered mesoporous silica belongs to molecular sieve and has become a hot research area due to its high specific surface area, large pore capacity, adjustable pore size and good heat resistance. At present, the study of ordered mesoporous silica is mainly focused on the preparation of other nanowires or nanowires using organic compounds as templates. However, its application is limited to some extent because of its morphology, the uniqueness of the pore channel and the unenvironmental protection of the organic pore expansion method. In this paper, based on the limitation of the present research situation, starting with the synthesis mechanism of ordered mesoporous silica, we adjust the type and concentration of mother liquor and change the traditional hydrochloric acid mother liquor into nitric acid, sulfuric acid and phosphoric acid mother liquor. The morphology of the synthesized SBA-15 is "wheat spike" shape, "copper money" shape, long range continuous "sugar block" shape and highly dispersed "sugar block" shape. Considering that the two most important steps in the synthesis process are water bath and hydrothermal treatment. The main process of water bath is the interaction between the template and the silicon source to synthesize the initial silica material. The crystallization process is mainly to further crystallize the synthesized initial material and the pore wall becomes thinner and harder. The dimesoporous silica materials were synthesized by adjusting the acidity of the two steps of the synthesis process and combining with the different kinds of mother liquor. Under certain conditions, silicon dioxide with different morphology and double mesoporous structure can be prepared by the simple environmental protection method mentioned above. Nickel has good activity for ethanol steam reforming to produce hydrogen, but nickel is easy to sintered, especially in usually selected carriers with less acid or surface area. If the carrier is acidic, the gas product will have ethylene, and the presence of ethylene will reduce the hydrogen yield. The SBA-15 prepared in this paper has a large specific surface area and a neutral surface area, which will lead to a large amount of supported metals without sintering, so it is a good catalyst carrier for this reaction. The other part of this experiment is to prepare the catalyst with two different nickel sources (nickel nitrate and nickel aminosulfonic acid) using SBA-15 as the catalyst carrier, and to characterize the difference of the physical and chemical properties of the catalyst by means of XPS Tem. Finally, it was found that the two kinds of nickel sources were loaded to the carrier in different positions. Nickel nitrate was mainly supported on the catalyst pore, and nickel aminosulfonic acid was mainly loaded on the surface of the carrier. After the reduction, the crystal form of nickel was different, which led to the great difference of the product after the catalyst. The experimental data are obtained by changing the feed amount and temperature of the reaction process, and the experimental data are fitted by the LevenbergMarquardt and lsqcurvefit algorithms in the MATLAB program. Finally, the activation energy of the reaction of the catalyst Ni(1)7.5SBA at 550 鈩

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