高活性抗積碳新型燒綠石負載Ni催化劑用于甲烷重整制氫
發(fā)布時間：2018-11-13 15:25
【摘要】：隨著能源危機和環(huán)境污染等全球性問題的日益突出,尋找綠色新能源迫在眉睫。氫氣做為一種清潔能源,是化石燃料的良好替代品。目前,低碳烴水蒸汽重整是高效制氫的方法,且已大規(guī)模工業(yè)化。其中天然氣儲量豐富,為大規(guī)模天然氣水蒸汽重整制氫提供了保障。為提高制氫效率,降低氫氣價格以利于其作為綠色能源推廣,仍有待于開發(fā)具有更高活性和抗積碳性能的催化劑。燒綠石的通式為A2B2O7,用作甲烷氧化偶聯(lián)催化劑表現(xiàn)出高的化學穩(wěn)定性和催化活性。并且,B位被貴金屬離子取代的燒綠石已被用作干氣重整催化劑,但鮮見燒綠石型化合物用做Ni的載體制備重整制氫催化劑。本文以燒綠石做為載體負載Ni,并結合DBD等離子體處理方法,使得催化劑的活性、抗積碳性能和穩(wěn)定性得到提高。本文首先通過共沉淀方法制備了兩種不同B位元素的燒綠石—La2Sn2O7和La2Zr2O7,并負載Ni用于甲烷水蒸氣重整反應。與傳統(tǒng)的Ni/Al2O3催化劑相比,Ni/La2Sn2O7和Ni/La2Zr2O7都表現(xiàn)出了良好的抗積碳性能。但La2Sn2O7的活性非常的低,而La2Zr2O7則表現(xiàn)出很高的活性。TGA-DSC和SEM結果證明在Ni/?-Al2O3表面發(fā)生了嚴重的積碳,但是在以燒綠石為載體的催化劑表面未發(fā)現(xiàn)積碳。這說明以燒綠石為載體的Ni基催化劑具有強的抗積碳性能。XRD分析表明,還原后和使用后的Ni/La2Sn2O7中存在Ni3Sn2和Ni3Sn合金相。該合金的存在雖然可以有效抑制催化劑表面積碳,但會導致Ni活性中心失活,因此使催化劑活性降低。與Ni/?-Al2O3相比,Ni/La2Zr2O7催化劑中Ni晶粒更小,因此可以維持較高的活性。同時,FTIR結果表明在Ni/La2Zr2O7催化劑表面形成了大量La2O2CO3物種,可以有效抑制積碳的形成。其次通過介質阻擋放電(DBD)方法,以不同氣氛做為等離子體激發(fā)源對溶膠凝膠法制備了的Ni/La2Zr2O7催化劑進行處理,并用于甲烷干氣重整反應。同未經等離子體處理的催化劑相比,經過DBD處理后的催化劑的活性和穩(wěn)定性都有所提高。其中,焙燒前在氫氣等離子體激發(fā)源下處理的催化劑性能提高最明顯。TGA-DSC和SEM證實經過等離子體處理后的催化劑的在反應過程中積碳受到有效抑制。并且,XRD和TEM結果證明經等離子體處理后,新鮮焙燒催化劑的NiO和還原后催化劑的Ni晶粒均明顯減小。H2-TPD結果表明,經等離子體處理后催化劑的Ni活性中心分散度明顯增大,和燒綠石載體之間的作用增強,因而使催化劑的活性和抗積碳性能得到提高。
[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.
【學位授予單位】：南昌大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TQ116.2;O643.36
本文編號：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.
【學位授予單位】：南昌大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TQ116.2;O643.36
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