不同AlOOH的结构及其对催化性能影响的研究
发布时间：2019-06-01 17:15
【摘要】：AlOOH是一种具有双层结构的不完整氧化铝水合物，其层内部由Al-O键连接形成网状结构，层间由羟基形成的氢键相连。AlOOH界面能高、孔隙率大、比表面大、分散性好，被广泛用于制备γ-Al2O3前驱体，，且该过程具有记忆效应，所得γ-Al2O3与AlOOH前驱体保持一致的形貌；此外AlOOH可用作吸附剂，同时可以作为催化剂载体负载Pd、Au、Ru等活性组分用于低温（120-145℃）有机合成。但是关于AlOOH作为催化剂活性组分的研究鲜有报道。 本课题组前期研究中发现采用完全液相法制备的CuZnAl催化剂中Al组分是以AlOOH的形式存在，而不是以传统Al2O3的形式存在。通过设计实验发现完全液相法制得的AlOOH作为独立的催化剂组分用于浆态相甲醇脱水反应亦具有高的活性和优异的稳定性，这一研究开创了AlOOH作为催化剂活性组分使用的先例。但是，关于AlOOH结构与性能的关系至今未进行系统研究。 本文采用完全液相法、沉淀法、水热法制备AlOOH，系统研究了AlOOH的制备方法对其结构以及催化甲醇脱水行为的影响，并将AlOOH与工业甲醇合成催化剂进行机械混合，探究复合催化剂在CO加氢反应中的催化性能。利用XRD、FT-IR、NH3-TPD-MS、CO-TPD-MS、CO2-TPD-MS、BET、SEM、TG-DTG等测试手段对有代表性的催化剂进行了表征，并与活性评价结果相关联。主要得到以下结论： 1. AlOOH不同制备方法显著影响其结构及其甲醇脱水能力，完全液相法制备的AlOOH催化剂有较多的晶格缺陷，具有适量的强、弱酸比例，使其在甲醇脱水反应中表现出良好的活性及稳定性，尤其是低温反应活性；水热法制备的AlOOH结晶度高，强酸中心量大，削弱了它的甲醇脱水能力；沉淀法制备的AlOOH晶粒度小，不仅活性低，而且稳定性差。 2. AlOOH不同制备方法显著影响复合催化剂的CO加氢反应性能。完全液相法制备的AlOOH对CO几乎没有吸附活性，复合催化剂具有较强的甲醇脱水能力；沉淀法制备的AlOOH晶粒小，易形成更多的弱碱性位，导致水煤气变换反应速度提高，产生较多的CO2；水热法制备的AlOOH结晶度高，具有完整的层间结构，对CO具有较强的解离吸附作用，可以起到碳链增长的作用，与工业甲醇合成催化剂混合可以形成较好的低碳醇催化剂。 3.水热法制备的不同形貌的AlOOH显著影响复合催化剂的CO加氢反应性能。梭形AlOOH催化剂具有较强的弱酸，晶型较弥散，主要暴露（200）晶面，有利于甲醇脱水，CO加氢产物分布主要是二甲醚；纳米棒、立方体、针形的AlOOH结晶度较高，主要暴露（020）晶面，有利于碳链增长，其产物分布主要是低碳醇。针状、立方体、纳米棒状形貌的催化剂具有起键合作用的层间结构水，但其含量不同，意味着三种形貌的催化剂层状结构的完整程度不同。 4．要提高低碳醇选择性，需要增加混合醇合成催化剂上双活性中心的含量，用于链增长和含氧化的两类活性中心需达到平衡才能构成双活性中心，而不是单一的增加其中任一活性组分的含量。较低的H2/CO的比例以及280℃的温度有利于AlOOH构成的复合催化剂低碳醇选择性的提高。
[Abstract]:AlOOH is an incomplete alumina hydrate with a double-layer structure, the inner part of which is connected by an Al-O bond to form a net structure, and the interlayer is connected with a hydrogen bond formed by hydroxyl groups. The AlOOH interface is high in interface energy, large in porosity, large in specific surface and good in dispersibility, and is widely used for preparing the Al-Al2O3 precursor, and the process has a memory effect, and the obtained Al-Al2O3 is consistent with the AlOOH precursor; in addition, AlOOH can be used as an adsorbent, and can be used as a catalyst carrier to load Pd, The active components such as Au, Ru, and the like are used for organic synthesis at a low temperature (120-145.degree. C.). However, there is little report on the study of AlOOH as the active component of the catalyst. In the earlier study of the research group, it was found that the Al component in the CuZnAl catalyst prepared by the complete liquid phase method is in the form of AlOOH, not in the form of conventional Al2O3. In this paper, AlOOH as a separate catalyst component is found to be used as a separate catalyst component in the slurry phase methanol dehydration reaction, and has high activity and excellent stability. Example. However, the relationship between the structure and performance of the AlOOH has not been systematically studied so far In this paper, AlOOH was prepared by means of a complete liquid phase method, a precipitation method and a hydrothermal method. The structure of AlOOH and the effect of the preparation of AlOOH on the structure and the dehydration of methanol were studied. Study on the Catalytic Activity of the Composite Catalyst in the Hydrogenation of CO in the Process of CO Hydrogenation The representative catalysts were characterized by XRD, FT-IR, NH3-TPD-MS, CO-TPD-MS, CO2-TPD-MS, BET, SEM and TG-DTG. To be associated with. The results of the following conclusions:1. The different preparation methods of AlOOH have a significant effect on the structure and the methanol dehydration ability. The AlOOH catalyst prepared by the method of complete liquid phase has more lattice defects, and has a moderate amount of strong and weak acid proportion, so that the AlOOH has good activity in the dehydration reaction of methanol. and the prepared AlOOH grain is small in grain size and is not only low in activity, And the stability is poor. AlOOH prepared by a complete liquid phase method has little adsorption activity to CO, and the composite catalyst has strong methanol dehydration capacity; the AlOOH grain prepared by the precipitation method is small, so that more weak alkaline sites are easy to form, and the reaction speed of the water gas shift is improved, The AlOOH prepared by the hydrothermal method has high crystallinity, has a complete interlayer structure, has a strong dissociation adsorption effect on the CO, can play the role of carbon chain growth, and can be mixed with the industrial methanol synthesis catalyst to form better 3. The AlOOH of different morphology prepared by the hydrothermal method has a significant effect on the composite catalyst. The shuttle-shaped AlOOH catalyst has a strong weak acid, the crystal form is more dispersed, the main exposed (200) crystal plane is favorable for the dehydration of the methanol, the distribution of the CO hydrogenation product is mainly dimethyl ether, the crystallinity of the nano-rod, the cube and the needle-shaped AlOOH is high, and the main exposure (020) crystal the surface is favorable for the growth of the carbon chain and the production of the carbon chain, The distribution of the material is mainly low-carbon alcohol. The catalyst with the shape of needle, cube and nanometer rod has the inter-layer structure water for bonding and cooperation, but its content is different, which means that the catalyst layer of three kinds of shapes 4. To improve the selectivity of the low-carbon alcohol, it is necessary to increase the content of the two active centers on the mixed alcohol synthesis catalyst, which can be used for both the chain growth and the oxidation-containing two types of active centers to be balanced to form the double active center, not a single increase. wherein the content of any of the active components is higher than that of the lower H2/ CO, and the temperature of 280 DEG C is favorable for the compound acceleration composed of AlOOH
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.1;O643.36
本文编号：2490445
[Abstract]:AlOOH is an incomplete alumina hydrate with a double-layer structure, the inner part of which is connected by an Al-O bond to form a net structure, and the interlayer is connected with a hydrogen bond formed by hydroxyl groups. The AlOOH interface is high in interface energy, large in porosity, large in specific surface and good in dispersibility, and is widely used for preparing the Al-Al2O3 precursor, and the process has a memory effect, and the obtained Al-Al2O3 is consistent with the AlOOH precursor; in addition, AlOOH can be used as an adsorbent, and can be used as a catalyst carrier to load Pd, The active components such as Au, Ru, and the like are used for organic synthesis at a low temperature (120-145.degree. C.). However, there is little report on the study of AlOOH as the active component of the catalyst. In the earlier study of the research group, it was found that the Al component in the CuZnAl catalyst prepared by the complete liquid phase method is in the form of AlOOH, not in the form of conventional Al2O3. In this paper, AlOOH as a separate catalyst component is found to be used as a separate catalyst component in the slurry phase methanol dehydration reaction, and has high activity and excellent stability. Example. However, the relationship between the structure and performance of the AlOOH has not been systematically studied so far In this paper, AlOOH was prepared by means of a complete liquid phase method, a precipitation method and a hydrothermal method. The structure of AlOOH and the effect of the preparation of AlOOH on the structure and the dehydration of methanol were studied. Study on the Catalytic Activity of the Composite Catalyst in the Hydrogenation of CO in the Process of CO Hydrogenation The representative catalysts were characterized by XRD, FT-IR, NH3-TPD-MS, CO-TPD-MS, CO2-TPD-MS, BET, SEM and TG-DTG. To be associated with. The results of the following conclusions:1. The different preparation methods of AlOOH have a significant effect on the structure and the methanol dehydration ability. The AlOOH catalyst prepared by the method of complete liquid phase has more lattice defects, and has a moderate amount of strong and weak acid proportion, so that the AlOOH has good activity in the dehydration reaction of methanol. and the prepared AlOOH grain is small in grain size and is not only low in activity, And the stability is poor. AlOOH prepared by a complete liquid phase method has little adsorption activity to CO, and the composite catalyst has strong methanol dehydration capacity; the AlOOH grain prepared by the precipitation method is small, so that more weak alkaline sites are easy to form, and the reaction speed of the water gas shift is improved, The AlOOH prepared by the hydrothermal method has high crystallinity, has a complete interlayer structure, has a strong dissociation adsorption effect on the CO, can play the role of carbon chain growth, and can be mixed with the industrial methanol synthesis catalyst to form better 3. The AlOOH of different morphology prepared by the hydrothermal method has a significant effect on the composite catalyst. The shuttle-shaped AlOOH catalyst has a strong weak acid, the crystal form is more dispersed, the main exposed (200) crystal plane is favorable for the dehydration of the methanol, the distribution of the CO hydrogenation product is mainly dimethyl ether, the crystallinity of the nano-rod, the cube and the needle-shaped AlOOH is high, and the main exposure (020) crystal the surface is favorable for the growth of the carbon chain and the production of the carbon chain, The distribution of the material is mainly low-carbon alcohol. The catalyst with the shape of needle, cube and nanometer rod has the inter-layer structure water for bonding and cooperation, but its content is different, which means that the catalyst layer of three kinds of shapes 4. To improve the selectivity of the low-carbon alcohol, it is necessary to increase the content of the two active centers on the mixed alcohol synthesis catalyst, which can be used for both the chain growth and the oxidation-containing two types of active centers to be balanced to form the double active center, not a single increase. wherein the content of any of the active components is higher than that of the lower H2/ CO, and the temperature of 280 DEG C is favorable for the compound acceleration composed of AlOOH
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.1;O643.36
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