本文選題：貴金屬 + 多孔結構　； 參考：《中國科學院大學(中國科學院過程工程研究所)》2017年博士論文

【摘要】：揮發(fā)性有機化合物(VOCs)嚴重威脅到人類的健康及環(huán)境的安全,因而越來越多的學者致力于其凈化技術的研究。其中,催化氧化的方法因其低能耗、快速、操作安全且環(huán)境友好等特點,受到人們的廣泛關注。目前,貴金屬和金屬氧化物催化劑是降解VOCs的兩種主要典型催化劑。在近幾十年來,隨著制備、表征技術和測試手段的不斷發(fā)展,納米結構材料的合成與應用研究已經得到了蓬勃發(fā)展,這便給納米材料如何在催化凈化VOCs領域內得到高效利用,帶來了巨大的機遇與挑戰(zhàn)。對此,本文針對貴金屬基納米催化劑,以提高單位貴金屬催化劑的效率為目標,通過結構控制及界面改性的手段,探索催化劑結構、形貌與催化性能之間的關系。主要研究內容和結果如下:(1)將Co基金屬有機骨架結構(Co-MOF,Co-based ZIF-67)在不同溫度下焙燒,其有機骨架去除程度不同,因而得到的孔結構、顆粒大小及金屬的化學價態(tài)均有所不同,這將影響反應物的分布情況及催化劑表面活性氧的性質,從而影響催化劑的活性。高比表面積和豐富的孔結構有利于催化劑活性位點的暴露,即有利于反應物和表面氧的吸附及反應。在Pd/Co_3O_4-PP-350上,由Pd到O的電子轉移可以使Oads更為活躍。這也得到H2-TPR測試結果的驗證,即Pd/Co_3O_4-PP-350上的PdOx還原性最優(yōu),其上的氧活性最高。因此,Pd/Co_3O_4-PP-350對苯的完全氧化反應表現出最優(yōu)的催化活性。(2)在Pt/Al_2O_3催化劑中加入還原氧化石墨烯(rGO)助劑,可以有效提高催化劑的比表面積;同時通過XPS測試還發(fā)現催化劑的Oads軌道電子結合能低時,其T90也更低一些,當催化劑具有更高的Oads軌道電子結合能時,其T90也會高一些。這說明Oads在苯的完全氧化反應中起著至關重要的作用。而在Pt-rGO/Al_2O_3催化劑中,電子由rGO轉移至Pt和O,可降低Oads軌道電子結合能,使表面吸附氧更為活躍,從而提高催化劑的性能。(3)采用液相法對活性組分Pt的形貌進行精細調控。通過對反應溫度和Ag(或Au)添加量的控制,可以有效調控Pt的形貌,最終獲得枝狀和球形的Pt納米顆粒。將這些顆粒應用于催化劑的制備,并對得到的催化劑進行苯的催化及其他表征測試。結果表明,枝狀Pt/Al_2O_3催化劑上,表面活性氧更多,且更為活躍。因此,與球狀Pt/Al_2O_3催化劑相比,其在苯完全氧化反應中表現出更為優(yōu)異的催化活性。(4)采用液相法在油胺中還原獲得Cu含量不同的Pt-Cu顆粒,并將其負載在γ-Al_2O_3上進行活性和表征測試。由于制得的催化劑中,除Cu含量不同外,其負載量,分散度,形貌均存在較大差異,因此,很難在催化劑的性質與活性之間找到直接相關的簡單規(guī)律。但可以發(fā)現催化劑的TOF與其上Pt顆粒的模型計算粒徑正相關,進而發(fā)現催化劑的活性與其表面的Pt原子數和Pt顆粒模型計算粒徑之間存在正相關關系。因此,需找出催化劑表面Pt原子數和Pt顆粒模型計算粒徑的平衡值,以便使催化劑的活性達到最大。另外,催化劑中,lPt-lCu/Al_2O_3的活性最優(yōu)。
[Abstract]:Volatile organic compounds (VOCs) seriously threaten the safety of human health and environment, and more and more scholars have been devoted to the study of its purification technology. Among them, catalytic oxidation has attracted wide attention because of its low energy consumption, rapid operation, safe operation and environmental friendliness. It is the two major typical catalysts for the degradation of VOCs. In the past few decades, with the continuous development of preparation, characterization and testing methods, the synthesis and application of nanostructured materials have been flourishing. This has brought great opportunities and challenges on how nanomaterials can be utilized efficiently in the field of catalytic purification of VOCs. In this regard, the relationship between the structure of the catalyst and the catalytic properties of the catalyst is explored by means of structural control and interfacial modification. The main contents and results are as follows: (1) the Co based metal organic framework structure (Co-MOF, Co-based ZIF-67) is used as a result of structural control and interfacial modification. The removal of organic skeleton is different at different temperatures, thus the structure of the pores, the size of the particles and the chemical valence state of the metal are different. This will affect the distribution of the reactants and the properties of the surface active oxygen of the catalyst, thus affecting the activity of the catalyst. The high specific surface area and the rich pore structure are beneficial to the activity of the catalyst. The exposure of the loci is beneficial to the adsorption and reaction of the reactant and surface oxygen. On Pd/Co_3O_4-PP-350, the electron transfer from Pd to O can make Oads more active. It is also verified by the results of the H2-TPR test that the PdOx reducibility on Pd/Co_3O_4-PP-350 is optimal and the highest oxygen activity on it. Therefore, the complete oxidation of Pd/Co_3O_4-PP-350 to benzene has been obtained. The reaction shows the best catalytic activity. (2) adding the reductive graphene oxide (rGO) additive in the Pt/Al_2O_3 catalyst can effectively improve the specific surface area of the catalyst. At the same time, the XPS test also found that when the Oads orbital electron binding energy of the catalyst is low, the T90 is lower, when the catalyst has a higher Oads orbital electron binding energy. The T90 will also be higher. This indicates that Oads plays a vital role in the complete oxidation of benzene. In the Pt-rGO/Al_2O_3 catalyst, the electron transfer from rGO to Pt and O can reduce the electron binding energy of the Oads orbit, make the surface adsorbed more active, and thus improve the sexual energy of the catalyst. (3) the liquid phase method is applied to the morphology of the active component Pt. Fine control. Through the control of the reaction temperature and the amount of Ag (or Au) addition, the morphology of the Pt can be effectively controlled and the Pt nanoparticles with branches and spheres are finally obtained. These particles are applied to the preparation of the catalyst, and the catalytic and other characterization tests of the obtained catalysts are carried out. The results show that the surface of the branched Pt/Al_2O_3 catalyst is on the surface. The active oxygen is more active and more active. Therefore, compared with the spherical Pt/Al_2O_3 catalyst, it has more excellent catalytic activity in the complete oxidation of benzene. (4) the Pt-Cu particles with different Cu content are obtained by the liquid phase method in the oil amine, and the activity and characterization of the particles are loaded on the gamma -Al_2O_3. In addition to the different Cu content, the load, the dispersion and the morphology of the catalyst are very different. Therefore, it is difficult to find a direct correlation between the properties and the activity of the catalyst. But it is found that the TOF of the catalyst is positively correlated with the size of the upper Pt particles, and the activity of the catalyst and the number of Pt atoms and Pt on the surface of the catalyst are also found. There is a positive correlation between particle size and particle size. Therefore, the balance between the number of Pt atoms on the surface of the catalyst and the calculation of the equilibrium value of the particle size of the Pt particle model should be found so that the activity of the catalyst can be maximum. In addition, the activity of lPt-lCu/Al_2O_3 is best in the catalyst.

【學位授予單位】：中國科學院大學(中國科學院過程工程研究所)
【學位級別】：博士
【學位授予年份】：2017
【分類號】：X505;O643.36

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