高活性抗积碳新型烧绿石负载Ni催化剂用于甲烷重整制氢
发布时间：2018-11-13 15:25
【摘要】：随着能源危机和环境污染等全球性问题的日益突出,寻找绿色新能源迫在眉睫。氢气做为一种清洁能源,是化石燃料的良好替代品。目前,低碳烃水蒸汽重整是高效制氢的方法,且已大规模工业化。其中天然气储量丰富,为大规模天然气水蒸汽重整制氢提供了保障。为提高制氢效率,降低氢气价格以利于其作为绿色能源推广,仍有待于开发具有更高活性和抗积碳性能的催化剂。烧绿石的通式为A2B2O7,用作甲烷氧化偶联催化剂表现出高的化学稳定性和催化活性。并且,B位被贵金属离子取代的烧绿石已被用作干气重整催化剂,但鲜见烧绿石型化合物用做Ni的载体制备重整制氢催化剂。本文以烧绿石做为载体负载Ni,并结合DBD等离子体处理方法,使得催化剂的活性、抗积碳性能和稳定性得到提高。本文首先通过共沉淀方法制备了两种不同B位元素的烧绿石—La2Sn2O7和La2Zr2O7,并负载Ni用于甲烷水蒸气重整反应。与传统的Ni/Al2O3催化剂相比,Ni/La2Sn2O7和Ni/La2Zr2O7都表现出了良好的抗积碳性能。但La2Sn2O7的活性非常的低,而La2Zr2O7则表现出很高的活性。TGA-DSC和SEM结果证明在Ni/?-Al2O3表面发生了严重的积碳,但是在以烧绿石为载体的催化剂表面未发现积碳。这说明以烧绿石为载体的Ni基催化剂具有强的抗积碳性能。XRD分析表明,还原后和使用后的Ni/La2Sn2O7中存在Ni3Sn2和Ni3Sn合金相。该合金的存在虽然可以有效抑制催化剂表面积碳,但会导致Ni活性中心失活,因此使催化剂活性降低。与Ni/?-Al2O3相比,Ni/La2Zr2O7催化剂中Ni晶粒更小,因此可以维持较高的活性。同时,FTIR结果表明在Ni/La2Zr2O7催化剂表面形成了大量La2O2CO3物种,可以有效抑制积碳的形成。其次通过介质阻挡放电(DBD)方法,以不同气氛做为等离子体激发源对溶胶凝胶法制备了的Ni/La2Zr2O7催化剂进行处理,并用于甲烷干气重整反应。同未经等离子体处理的催化剂相比,经过DBD处理后的催化剂的活性和稳定性都有所提高。其中,焙烧前在氢气等离子体激发源下处理的催化剂性能提高最明显。TGA-DSC和SEM证实经过等离子体处理后的催化剂的在反应过程中积碳受到有效抑制。并且,XRD和TEM结果证明经等离子体处理后,新鲜焙烧催化剂的NiO和还原后催化剂的Ni晶粒均明显减小。H2-TPD结果表明,经等离子体处理后催化剂的Ni活性中心分散度明显增大,和烧绿石载体之间的作用增强,因而使催化剂的活性和抗积碳性能得到提高。
[Abstract]:With the increasingly prominent global problems such as energy crisis and environmental pollution, it is urgent to find new green energy. As a clean energy, hydrogen is a good substitute for fossil fuels. At present, low-carbon hydrocarbon steam reforming is an efficient method for hydrogen production and has been industrialized on a large scale. Natural gas reserves are abundant, which provides a guarantee for hydrogen production by steam reforming of large scale natural gas. In order to improve the efficiency of hydrogen production and reduce the price of hydrogen in order to promote the promotion of green energy, it is still necessary to develop catalysts with higher activity and resistance to carbon deposition. The general formula of pyrochlore is A _ 2B _ 2O _ 7, which shows high chemical stability and catalytic activity as a catalyst for oxidative coupling of methane. Moreover, the pyrochlore substituted by noble metal ions at site B has been used as dry gas reforming catalyst, but it is seldom seen that pyrochlore type compound is used as the carrier of Ni to prepare reforming catalyst for hydrogen production. In this paper, the activity, resistance to carbon deposition and stability of the catalyst were improved by using pyrochlore as the carrier to support Ni, and DBD plasma treatment. In this paper, two different B-site pyrochlore La2Sn2O7 and La2Zr2O7, were prepared by coprecipitation method and loaded with Ni for methane steam reforming. Compared with the traditional Ni/Al2O3 catalysts, both Ni/La2Sn2O7 and Ni/La2Zr2O7 showed good resistance to carbon deposition. However, the activity of La2Sn2O7 was very low, while the activity of La2Zr2O7 was very high. The results of TGA-DSC and SEM showed that there was serious carbon deposition on the surface of Ni/?-Al2O3, but no carbon deposition was found on the surface of the catalyst supported on pyrochlore. The results showed that the Ni based catalyst supported on pyrochlore had strong resistance to carbon deposition. XRD analysis showed that there were Ni3Sn2 and Ni3Sn alloy phases in Ni/La2Sn2O7 after reduction and use. The existence of the alloy can effectively inhibit the surface carbon of the catalyst, but it will lead to the deactivation of the active center of Ni, so the activity of the catalyst will decrease. Compared with Ni/?-Al2O3, the Ni grains in the Ni/La2Zr2O7 catalyst are smaller, so the higher activity can be maintained. At the same time, FTIR results show that a large number of La2O2CO3 species are formed on the surface of Ni/La2Zr2O7 catalyst, which can effectively inhibit the formation of carbon deposition. Secondly, the Ni/La2Zr2O7 catalyst prepared by sol-gel method was treated by dielectric barrier discharge (DBD) method with different atmosphere as plasma excitation source, and was used for methane dry gas reforming. Compared with the catalyst without plasma treatment, the activity and stability of the catalyst treated with DBD were improved. The catalytic properties of the catalysts treated with hydrogen plasma excitation source before calcination were the most obvious. TGA-DSC and SEM confirmed that the carbon deposition of the catalysts treated by plasma was effectively inhibited during the reaction. The results of XRD and TEM show that the NiO of the freshly calcined catalyst and the Ni grain of the catalyst after reduction are obviously decreased after plasma treatment. The results of H2-TPD show that, After plasma treatment, the dispersion of the Ni active center of the catalyst was obviously increased, and the interaction between the catalyst and the pyrochlore support was enhanced, thus the activity of the catalyst and the resistance to carbon deposition were improved.
【学位授予单位】：南昌大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ116.2;O643.36
本文编号：2329555
[Abstract]:With the increasingly prominent global problems such as energy crisis and environmental pollution, it is urgent to find new green energy. As a clean energy, hydrogen is a good substitute for fossil fuels. At present, low-carbon hydrocarbon steam reforming is an efficient method for hydrogen production and has been industrialized on a large scale. Natural gas reserves are abundant, which provides a guarantee for hydrogen production by steam reforming of large scale natural gas. In order to improve the efficiency of hydrogen production and reduce the price of hydrogen in order to promote the promotion of green energy, it is still necessary to develop catalysts with higher activity and resistance to carbon deposition. The general formula of pyrochlore is A _ 2B _ 2O _ 7, which shows high chemical stability and catalytic activity as a catalyst for oxidative coupling of methane. Moreover, the pyrochlore substituted by noble metal ions at site B has been used as dry gas reforming catalyst, but it is seldom seen that pyrochlore type compound is used as the carrier of Ni to prepare reforming catalyst for hydrogen production. In this paper, the activity, resistance to carbon deposition and stability of the catalyst were improved by using pyrochlore as the carrier to support Ni, and DBD plasma treatment. In this paper, two different B-site pyrochlore La2Sn2O7 and La2Zr2O7, were prepared by coprecipitation method and loaded with Ni for methane steam reforming. Compared with the traditional Ni/Al2O3 catalysts, both Ni/La2Sn2O7 and Ni/La2Zr2O7 showed good resistance to carbon deposition. However, the activity of La2Sn2O7 was very low, while the activity of La2Zr2O7 was very high. The results of TGA-DSC and SEM showed that there was serious carbon deposition on the surface of Ni/?-Al2O3, but no carbon deposition was found on the surface of the catalyst supported on pyrochlore. The results showed that the Ni based catalyst supported on pyrochlore had strong resistance to carbon deposition. XRD analysis showed that there were Ni3Sn2 and Ni3Sn alloy phases in Ni/La2Sn2O7 after reduction and use. The existence of the alloy can effectively inhibit the surface carbon of the catalyst, but it will lead to the deactivation of the active center of Ni, so the activity of the catalyst will decrease. Compared with Ni/?-Al2O3, the Ni grains in the Ni/La2Zr2O7 catalyst are smaller, so the higher activity can be maintained. At the same time, FTIR results show that a large number of La2O2CO3 species are formed on the surface of Ni/La2Zr2O7 catalyst, which can effectively inhibit the formation of carbon deposition. Secondly, the Ni/La2Zr2O7 catalyst prepared by sol-gel method was treated by dielectric barrier discharge (DBD) method with different atmosphere as plasma excitation source, and was used for methane dry gas reforming. Compared with the catalyst without plasma treatment, the activity and stability of the catalyst treated with DBD were improved. The catalytic properties of the catalysts treated with hydrogen plasma excitation source before calcination were the most obvious. TGA-DSC and SEM confirmed that the carbon deposition of the catalysts treated by plasma was effectively inhibited during the reaction. The results of XRD and TEM show that the NiO of the freshly calcined catalyst and the Ni grain of the catalyst after reduction are obviously decreased after plasma treatment. The results of H2-TPD show that, After plasma treatment, the dispersion of the Ni active center of the catalyst was obviously increased, and the interaction between the catalyst and the pyrochlore support was enhanced, thus the activity of the catalyst and the resistance to carbon deposition were improved.
【学位授予单位】：南昌大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ116.2;O643.36
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