纳米Pt基核壳催化剂的制备及性能研究
发布时间：2019-05-27 17:35
【摘要】：负载型Pt基核壳催化剂在烷烃脱氢、CO氧化、氮氧化物还原等反应中具有较好的催化性能,在催化领域得到了广泛的应用,负载型Pt基核壳催化剂的催化性能主要取决于金属粒径的大小以及载体的种类,Pt纳米颗粒具有较高的表面能,高温条件下容易发生团聚现象,随着Pt颗粒粒径的增大催化剂的催化性能迅速降低。本论文从提高Pt纳米催化剂的热稳定性出发,利用Si02封装金属粒子的方法限制Pt粒子的团聚,提高了催化剂的热稳定性,采用XRD、BET、TEM、SEM和TGA等方法对催化剂进行表征,以对硝基苯酚的还原反应为探针考察了Ptencap/mSiO2 (HSC550)、mSiO2/Pt/MOx/Fe和Fe@Pt/Ti(OH)4的催化性能,并取得了一些结论,具体内容如下：1、通过NaBH4还原K2PtCl4制得Pt纳米颗粒,负载于水热法制得的碳球表面得到Pt/C,以CTAB为模板剂,TEOS为硅源在Pt/C表面封装mSiO2层制得mSiO2/Pt/C,焙烧除去mSiO2/Pt/C中的碳球制备了HSC550中空催化剂。350℃焙烧后Pt/C表面的Pt颗粒己发生团聚,mSiO2/Pt/C经550℃焙烧后其中的Pt粒子并未发生明显的团聚现象,说明mSiO2对Pt粒子具有较好的保护作用,能有效提高催化剂的热稳定性。随着焙烧温度的升高,mSiO2/Pt/C中的碳球不断除去,逐渐形成中空结构,HSC550催化对硝基苯酚还原反应的催化活性最好,说明中空结构可以提高HSC550的催化性能。HSC550重复使用5次之后催化对硝基苯酚还原反应的催化活性并未明显降低,该催化剂可以重复使用。2、分别以TBOT为前驱体制得纳米TiO2、CeO2,负载于a-Fe2O3表面得到MOx/a-Fe2O3(M为Ti或Ce),将Pt纳米颗粒负载于MOx/a-Fe2O3表面制得Pt/MOx/a-Fe2O3,在Pt/MOx/a-Fe2O3表面封装mSiO2层制备了mSiO2/Pt/MOx/a-Fe2O3,对其进行氢还原制得mSiO2/Pt/MOx/Fe核壳催化剂。在这个催化系统中,Pt颗粒被封装在mSiO2层中,提高了mSiO2/Pt/MOx/Fe的热稳定性。500℃焙烧的mSi02/Pt/Ce02/Fe催化对硝基苯酚还原反应的催化活性最好,随着焙烧温度升至700℃,mSiO2/Pt/CeO2/Fe中的纳米Ce02和Pt颗粒部分发生团聚,mSi02/Pt/Ce02/Fe催化对硝基苯酚还原反应的催化活性明显降低,说明mSi02/Pt/Ce02/Fe的抗焙烧性能较差。mSi02/Pt/Ti02/Fe经700℃焙烧后催化活性并未明显降低,说明mSiO2/Pt/TiO2/Fe具有较好的热稳定性。Ce02的功函数比TiO2低,电子富集区电子密度更大,500℃焙烧的mSiO2/Pt/CeO2/Fe催化活性最高。3、采用水热法在α-Fe2O3表面包裹碳层得到α-Fe2O3@C,将Pt颗粒负载于α-Fe2O3@C表面得到α-Fe2O3@C/Pt,通过TBOT和TEOS的水解在a-Fe2O3@C/Pt表面先后包裹Ti02和mSiO2,制得α-Fe2O3@C/Pt/TiO2/mSiO2,焙烧除去碳层得到α-Fe2O3＠Pt/TiO2/mSiO2,利用强碱腐蚀a-Fe203@Pt/Ti02/mSi02中的Ti02得到a-Fe2O3@Pt/Ti(OH)4,对其进行氢还原制得Fe@Pt/Ti(OH)4核壳催化剂。Fe核与Ti(OH)4纳米棒之间出现空腔,Fe@Pt/Ti(OH)4中的Pt颗粒分布在Ti(OH)4纳米棒之间,500℃焙烧后Pt颗粒不易团聚,提高了Fe@Pt/Ti(OH)4的热稳定性。当焙烧温度达到700℃时,Ti(OH)4纳米棒分解为二氧化钛得到Fe@Pt/TiO2,催化剂依然保持着核壳结构。Fe@Pt/TiO2中的TiO2与Pt颗粒之间有较强的相互作用,其在对硝基苯酚的还原反应中催化性能迅速提高,约为Fe@Pt/Ti(OH)4的1.5倍。
[Abstract]:The supported Pt-based core-shell catalyst has good catalytic performance in the reaction of alkane dehydrogenation, CO oxidation, nitrogen oxide reduction and the like, has been widely applied in the catalysis field, and the catalytic performance of the supported Pt-based core-shell catalyst mainly depends on the size of the metal particle size and the type of the carrier, The Pt nanoparticles have a high surface energy and can easily be agglomerated under high temperature conditions, and the catalytic performance of the catalyst is rapidly reduced with the increase of the particle size of the Pt particles. In order to improve the thermal stability of Pt nano-catalyst, the method of Si02 encapsulation of metal particles is used to limit the agglomeration of Pt particles, and the thermal stability of the catalyst is improved. The catalyst is characterized by XRD, BET, TEM, SEM and TGA. The catalytic properties of Ptencap/ mSiO2 (HSC550), mSiO2/ Pt/ MOx/ Fe and Fe@Pt/ Ti (OH)4 were investigated by the reduction reaction of p-nitrophenol, and some conclusions were obtained. And using CTAB as a template agent, TEOS is a silicon source to encapsulate the mSiO2 layer on the Pt/ C surface to obtain mSiO2/ Pt/ C, and the carbon spheres in the mSiO2/ Pt/ C are baked to remove the carbon spheres in the mSiO2/ Pt/ C to prepare the HSC550 hollow catalyst. It is shown that mSiO2 has a good protective effect on Pt particles, and can effectively improve the thermal stability of the catalyst. With the increase of the calcination temperature, the carbon spheres in mSiO2/ Pt/ C are continuously removed, the hollow structure is gradually formed, and the catalytic activity of the HSC550 for the reduction reaction of the nitrophenol is the best, and the catalytic performance of the HSC550 can be improved by using the hollow structure. the catalytic activity of the catalytic p-nitrophenol reduction reaction is not obviously reduced after 5 times of repeated use of the HSC550, and the catalyst can be used repeatedly;2, the nano TiO2 and the CeO2 are obtained by the TBOT as a precursor, and the MOx/ a-Fe2O3 (M is Ti or Ce) is obtained on the surface of the a-Fe2O3 respectively, The Pt/ MOx/ a-Fe2O3 is prepared by loading the Pt nano-particles on the surface of the MOx/ a-Fe2O3, and the mSiO2/ Pt/ MOx/ a-Fe2O3 is prepared on the surface of the Pt/ MOx/ a-Fe2O3, and the mSiO2/ Pt/ MOx/ a-Fe2O3 is prepared by hydrogen reduction to obtain the mSiO2/ Pt/ MOx/ Fe core-shell catalyst. In this catalytic system, Pt particles are encapsulated in the mSiO2 layer, and the thermal stability of mSiO2/ Pt/ MOx/ Fe is improved. The catalytic activity of mSi02/ Pt/ Ce02/ Fe on the reduction of nitrophenol was obviously reduced, and the anti-roasting property of mSi02/ Pt/ Ce02/ Fe was poor. The catalytic activity of mSi02/ Pt/ Ti02/ Fe was not significantly reduced after calcination at 700 鈩，
本文编号：2486343
[Abstract]:The supported Pt-based core-shell catalyst has good catalytic performance in the reaction of alkane dehydrogenation, CO oxidation, nitrogen oxide reduction and the like, has been widely applied in the catalysis field, and the catalytic performance of the supported Pt-based core-shell catalyst mainly depends on the size of the metal particle size and the type of the carrier, The Pt nanoparticles have a high surface energy and can easily be agglomerated under high temperature conditions, and the catalytic performance of the catalyst is rapidly reduced with the increase of the particle size of the Pt particles. In order to improve the thermal stability of Pt nano-catalyst, the method of Si02 encapsulation of metal particles is used to limit the agglomeration of Pt particles, and the thermal stability of the catalyst is improved. The catalyst is characterized by XRD, BET, TEM, SEM and TGA. The catalytic properties of Ptencap/ mSiO2 (HSC550), mSiO2/ Pt/ MOx/ Fe and Fe@Pt/ Ti (OH)4 were investigated by the reduction reaction of p-nitrophenol, and some conclusions were obtained. And using CTAB as a template agent, TEOS is a silicon source to encapsulate the mSiO2 layer on the Pt/ C surface to obtain mSiO2/ Pt/ C, and the carbon spheres in the mSiO2/ Pt/ C are baked to remove the carbon spheres in the mSiO2/ Pt/ C to prepare the HSC550 hollow catalyst. It is shown that mSiO2 has a good protective effect on Pt particles, and can effectively improve the thermal stability of the catalyst. With the increase of the calcination temperature, the carbon spheres in mSiO2/ Pt/ C are continuously removed, the hollow structure is gradually formed, and the catalytic activity of the HSC550 for the reduction reaction of the nitrophenol is the best, and the catalytic performance of the HSC550 can be improved by using the hollow structure. the catalytic activity of the catalytic p-nitrophenol reduction reaction is not obviously reduced after 5 times of repeated use of the HSC550, and the catalyst can be used repeatedly;2, the nano TiO2 and the CeO2 are obtained by the TBOT as a precursor, and the MOx/ a-Fe2O3 (M is Ti or Ce) is obtained on the surface of the a-Fe2O3 respectively, The Pt/ MOx/ a-Fe2O3 is prepared by loading the Pt nano-particles on the surface of the MOx/ a-Fe2O3, and the mSiO2/ Pt/ MOx/ a-Fe2O3 is prepared on the surface of the Pt/ MOx/ a-Fe2O3, and the mSiO2/ Pt/ MOx/ a-Fe2O3 is prepared by hydrogen reduction to obtain the mSiO2/ Pt/ MOx/ Fe core-shell catalyst. In this catalytic system, Pt particles are encapsulated in the mSiO2 layer, and the thermal stability of mSiO2/ Pt/ MOx/ Fe is improved. The catalytic activity of mSi02/ Pt/ Ce02/ Fe on the reduction of nitrophenol was obviously reduced, and the anti-roasting property of mSi02/ Pt/ Ce02/ Fe was poor. The catalytic activity of mSi02/ Pt/ Ti02/ Fe was not significantly reduced after calcination at 700 鈩，
本文编号：2486343
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