固相法制备金属氧化物催化材料及其消除CO、NO性能研究

发布时间：2019-05-21 12:20

【摘要】：近年来,随着经济社会的飞速发展,资源的枯竭和环境的污染已严重制约经济的进一步发展,甚至威胁到人类的生存与发展,开发新的催化剂制备方法成为解决这一问题的有力手段之一。通常的催化剂制备是在水相中进行,其不可避免会带来水环境污染等问题。与此对应的是,当催化剂的制备在无水条件下进行,可有效避免水污染。以此为立足点,在本论文中,我们选取两类具有代表性的催化剂构型(负载型催化剂和复合氧化物催化剂)为研究对象,详细考察了固相法在制备高性能催化剂方面所具有的优势,同时结合多种物理化学表征手段,系统考察制备参数对催化剂的影响,深入剖析催化剂制备的中间过程,探究催化剂结构-性能间的关联。主要研究内容如下：1、以简单硝酸盐为金属氧化物前驱体,SBA-15为载体,通过固相法制备了高含量、单分散的SBA-15孔道内装载的金属氧化物(NiO, Co3O4, CeO2)纳米颗粒催化剂。N2吸附和透射电镜表明,纳米颗粒填充在介孔孔道内。而X射线衍射和透射电镜确认了纳米粒子的单分散性。进一步以镍为研究对象,全面考察了不同氧化镍含量、不同焙烧温度、不同前驱体以及孔道对制备结果的影响,同时研究了孔道限域对客体物种分解及聚集长大的影响。结果表明,NiO颗粒大小随着含量及温度增加未发生明显变化；前驱体种类以及是否存在介孔对制备结果影响较大,使用醋酸镍为镍源不能使镍盐进入介孔孔道,最终只能得到孔道外的大颗粒NiO；孔道的限域作用使得金属盐的分解和纳米颗粒的急剧长大受到明显的抑制。结合对制备中间过程的研究结果,我们推测硝酸镍前驱体在受热过程中形成的熔盐的流动性是确保镍物种进入SBA-15孔道的前提,而熔盐的粘度性质则保证了粒子的单分散性。最后,我们考察了镍催化剂在氯苯加氢脱氯以及NH3分解制氢反应中的活性,发现相对于常规方法(浸渍法),固相法得到的催化剂具有更好的活性。这一结果显示了固相法在污染物治理和清洁能源生产方面的潜在应用。2、以硝酸铜为铜盐前驱体,SBA-15为载体,使用固相法首次将高含量(20 wt%)铜物种键合到SBA-15表面,而使用常规浸渍法主要得到大颗粒的晶相CuO。进一步对固相法制备样品进行X射线衍射,H2程序升温还原,原位红外等表征,确认了铜物种以与SBA-15表面羟基共同缩合脱水形式键合到SBA-15,其存在形式为孤立的铜二聚体。另一方面,我们还对载体的影响进行了考察,结果表明载体的比表面积不是决定铜物种能够成功键合的关键,而SBA-15的独特孔道结构带来的毛细吸附对铜物种的分散至关重要。3、通过固相法制备了负载型铜铈催化剂,同时考察了其在富氢CO选择性氧化中(CO-PROX)的性能。我们发现,CeO2颗粒大小以及铜铈间的相互作用显著地影响到反应活性。由于固相法可以减小Ce02大小,同时相比于常规浸渍法,其还可以加强铜铈间的相互作用,因此展现出优异的CO-PROX活性。另外,通过比较无定形硅胶与SBA-15这两种不同载体,发现无定形硅胶具有更高的活性,这可能与反应物分子的在孔道内扩散会受到一定限制所致。4、使用固相法制备了镍铈复合氧化物催化剂,并考察了其在NO+CO反应中的性能。通过与常规浸渍法、共沉淀法比较,发现固相法在制备镍铈复合氧化物催化剂方面具有以下优势：(1)固相法可以避免活性物种的流失；(2)固相法有利于得到高比表面积催化剂,这可能与制备过程中金属盐分解释放的NOx等气体有关,其会给催化剂带来细小孔道结构；(3)固相法制备过程有利于镍和铈作用的加强。这些加强作用的镍铈主要体现在高度分散在Ce02表面的NiO以及掺入Ce02晶格中的Ni2+。正因为这些结构和物种方面的性质,使得固相法制备催化剂在NO+CO反应中表现出优良活性。进一步考察不同镍铈比,发现当镍铈摩尔比为1：9时,催化剂的NO+CO活性最佳。过多或过少的镍都不利于催化活性的提升。
[Abstract]:In recent years, with the rapid development of the economy and society, the exhaustion of resources and the pollution of the environment have seriously restricted the further development of the economy, and even threatened the survival and development of the human, and the new preparation method of the catalyst has become one of the powerful tools to solve the problem. The usual preparation of the catalyst is carried out in the aqueous phase, which inevitably leads to problems of water environmental pollution and the like. Correspondingly, when the preparation of the catalyst is carried out under the anhydrous condition, the water pollution can be effectively avoided. In this paper, we selected two representative catalyst configurations (supported catalyst and composite oxide catalyst) as the research object, and the advantages of the solid-phase method in the preparation of high-performance catalysts were investigated in detail. At the same time, the influence of the preparation parameters on the catalyst was investigated in combination with a variety of physical and chemical characterization methods, and the intermediate process of the catalyst preparation was analyzed, and the relationship between the structure and the performance of the catalyst was investigated. The main contents of the study are as follows:1. The metal oxide (NiO, Co3O4, CeO2) nano-particle catalyst loaded in the SBA-15 channel with high content and single dispersion is prepared by the solid-phase method with the simple nitrate as the metal oxide precursor and the SBA-15 as the carrier. The N2 adsorption and transmission electron microscope show that the nano-particles are filled in the mesoporous channel. The monodispersity of the nanoparticles was confirmed by X-ray diffraction and transmission electron microscopy. The effect of different nickel oxide content, different firing temperature, different precursor and pore channel on the preparation results was further investigated with nickel as the research object, and the effect of the pore-limited region on the decomposition and aggregation of the object species was also studied. The results show that the size of NiO particles has not changed significantly with the increase of content and temperature; the type of the precursor and the existence of the mesopore have great influence on the preparation result, and the nickel acetate is used as the nickel source, so that the nickel salt can not enter the mesoporous channel, and the large-particle NiO outside the pore canal can only be obtained; The limited domain effect of the pore canal makes the decomposition of the metal salt and the rapid growth of the nano-particles to be obviously inhibited. In combination with the results of the preparation of the intermediate process, we speculate that the fluidity of the molten salt formed during the heating process of the nickel nitrate precursor is the premise of ensuring that the nickel species enters the SBA-15 pore canal, and the viscosity property of the molten salt ensures the monodispersity of the particles. In the end, we investigated the activity of the nickel catalyst in the hydrodechlorination of the chlorobenzene and the hydrogen production from the decomposition of NH3, and found that the catalyst obtained by the solid-phase method has better activity relative to the conventional method (impregnation method). the results show that the solid-phase method is a potential application for pollutant treatment and clean energy production.2, the copper nitrate is a copper salt precursor, the SBA-15 is a carrier, a high content (20 wt%) copper species is bonded to the SBA-15 surface for the first time by using a solid phase method, And the crystal phase cuo of the large particles is mainly obtained by using the conventional impregnation method. The samples were further characterized by X-ray diffraction, H2 program temperature-raising and reduction, in-situ IR, etc., and the copper species were bonded to SBA-15 in the form of isolated copper dimer in the form of co-condensation and dehydration with the hydroxyl group of SBA-15. The results show that the specific surface area of the carrier is not the key to the successful bonding of the copper species, and the capillary adsorption of the unique pore structure of the SBA-15 is very important to the dispersion of the copper species. Supported copper-based catalysts were prepared by solid-phase method, and the performance of CO-PROX in the selective oxidation of hydrogen-rich CO was also investigated. We have found that the size of the CeO2 particles and the interaction of the copper particles significantly affect the activity of the reaction. Due to the fact that the solid phase method can reduce the size of the Ce02, it is also possible to enhance the interaction between the copper particles as compared to the conventional impregnation method, thus exhibiting excellent CO-PROX activity. In addition, by compare that two different support of the amorphous silica gel and the SBA-15, it is found that the amorphous silica gel has a higher activity, which may be caused by a certain limit to the diffusion of the reactant molecules in the pore canal. The performance of its in NO + CO reaction was also investigated. Compared with the conventional impregnation method and the coprecipitation method, the solid-phase method has the advantages of: (1) the solid-phase method can avoid the loss of the active species; and (2) the solid-phase method is favorable for obtaining the high-specific surface area catalyst, This may be associated with a gas such as NOx released from the decomposition of the metal salt during the preparation process, which results in a fine pore structure for the catalyst; and (3) the solid phase preparation process is beneficial to the enhancement of the effect of nickel and sulfur. These reinforcing nickel alloys are mainly represented by NiO which is highly dispersed on the surface of Ce02 and Ni2 + incorporated in the Ce02 lattice. Due to the nature of these structures and species, the preparation of the catalyst in the solid phase process exhibits excellent activity in the NO + CO reaction. It was found that the NO + CO activity of the catalyst was the best when the molar ratio of nickel to nickel was 1:9. Too much or too little nickel is detrimental to the catalytic activity.
【学位授予单位】：南京大学
【学位级别】：博士
【学位授予年份】：2011
【分类号】：X505;O643.36

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