本文關(guān)鍵詞：超薄氧化物包裹對(duì)鉑催化劑在丙三醇?xì)浣夥磻?yīng)中的催化性能調(diào)控　出處：《中國科學(xué)技術(shù)大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 原子層沉積(ALD) 鉑催化劑 丙三醇 選擇性氫解 金屬-酸性位點(diǎn)臨近效應(yīng) 金屬-氧化物界面

【摘要】：同時(shí)含有金屬和酸性位點(diǎn)的雙功能催化劑已廣泛用于石油加氫裂解和可再生生物質(zhì)轉(zhuǎn)化。這兩種位點(diǎn)之間的距離對(duì)雙功能協(xié)同作用起著至關(guān)重要的作用,進(jìn)而對(duì)催化劑的催化活性與選擇性有重大影響。近年來,由生物質(zhì)轉(zhuǎn)化生產(chǎn)生物燃料和化學(xué)品得到了廣泛的關(guān)注。相比于石油裂解工藝,金屬-酸性位點(diǎn)臨近效應(yīng)在生物質(zhì)轉(zhuǎn)化反應(yīng)中鮮有報(bào)道。甘油是來自生物柴油生產(chǎn)過程中的廉價(jià)副產(chǎn)物(約總產(chǎn)量的10%)。通過選擇性氫解將其轉(zhuǎn)化為具有高附加價(jià)值的化學(xué)品如1,2-丙二醇和1,3-丙二醇是提高其附加值的主要途徑。甘油氫解包含脫水與加氫兩個(gè)過程,分別發(fā)生于酸性位點(diǎn)與金屬位點(diǎn)上。根據(jù)文獻(xiàn)報(bào)道,Lewis酸位點(diǎn)傾向于進(jìn)攻甘油端位的羥基,而生成中間產(chǎn)物丙酮醇,而Br(?)nsted酸則更易進(jìn)攻甘油中間位的羥基產(chǎn)生3-羥基丙醛;隨后兩者進(jìn)一步加氫分別生成1,2-丙二醇和1,3-丙二醇。負(fù)載型金屬催化劑廣泛應(yīng)用于甘油氫解反應(yīng)中,在金屬催化劑中添加酸性助劑能顯著提高催化劑的活性。大量研究表明,無論是將酸性物種添加到金屬顆粒表面或者是載體上甚至是簡單的物理混合,均能有效提升催化劑的催化性能。然而據(jù)我們所知,金屬-酸性位點(diǎn)之間的臨近效應(yīng)還未在甘油氫解反應(yīng)中報(bào)道過。因此,我們選擇負(fù)載型Pt催化劑應(yīng)用于甘油氫解作為平臺(tái)反應(yīng),通過ALD技術(shù)沉積酸性多孔的氧化鋁薄膜包裹Pt催化劑來研究金屬-酸性位點(diǎn)臨近效應(yīng)對(duì)Pt催化劑在甘油氫解反應(yīng)中的作用與影響。在本課題中,我們運(yùn)用原子層沉積技術(shù)(ALD),憑借其原子層面上精確控制的技術(shù)優(yōu)勢,我們?cè)赑t納米顆粒催化劑的表面精確沉積氧化物包裹層,研究形成的金屬-氧化物界面、金屬-酸性雙功能活性位的臨近效應(yīng)對(duì)Pt催化劑在丙三醇?xì)浣夥磻?yīng)中的活性以及選擇性的調(diào)控。主要的研究成果如下:(1)我們通過濕化學(xué)浸漬法合成了負(fù)載型Pt/Al203催化劑,隨后使用ALD技術(shù)在Pt納米顆粒表面生長氧化鋁多孔薄膜,利用氧化鋁的Lewis酸性以及其與Pt金屬的臨近效應(yīng),來提高該催化劑的雙功能協(xié)同效應(yīng)從而提高了丙三醇?xì)浣夥磻?yīng)的活性和對(duì)1,2-丙二醇的選擇性。我們研究發(fā)現(xiàn)30個(gè)周期的氧化鋁包裹后催化劑具有最高的活性與選擇性,在高分辨透射電鏡(HRTEM)下能觀測到包裹層厚度為3.6 nm。通過對(duì)丙酮醇中間產(chǎn)物加氫反應(yīng)的對(duì)比實(shí)驗(yàn),我們發(fā)現(xiàn),氧化鋁酸性和Pt加氫位點(diǎn)臨近效應(yīng)在催化性能提高中,起著重要的作用。另外,通過降低Pt顆粒的粒徑,同樣有助于1,2丙二醇選擇性的提高。因此,我們初步認(rèn)為多孔氧化鋁包裹把Pt顆粒表面分割成小的Pt聚集體,是提高1,2丙二醇選擇性的主要原因。(2)此外,我們通過ALD技術(shù),在商用Pt/C催化劑上進(jìn)一步生長了不同周期的FeOx,發(fā)現(xiàn)微量的FeOx能顯著提高催化劑的活性。我們發(fā)現(xiàn)沉積三個(gè)周期的FeOx在Pt/C催化劑上具有最高的活性,相同時(shí)間內(nèi)丙三醇?xì)浣夥磻?yīng)的轉(zhuǎn)化率是Pt/C催化劑的三倍以上。
[Abstract]:The dual functional catalysts, which contain both metal and acid sites, have been widely used in petroleum hydrocracking and renewable biomass conversion. The distance between the two loci plays an important role in the dual function synergy, which has a great influence on the catalytic activity and selectivity of the catalyst. In recent years, biomass conversion and production of biofuels and chemicals have been widely concerned. Compared with the petroleum cracking process, the metal acid site proximity effect is rarely reported in the biomass conversion reaction. Glycerol is a cheap by-product of biodiesel production (about 10% of the total production). The conversion of a selective hydrogen solution into a high added value chemical, such as 1,2- propanediol and 1,3- propanediol, is the main way to increase the added value. The hydrogenolysis of glycerol consists of two processes of dehydration and hydrogenation, which occur on acid sites and metal sites, respectively. According to reports, Lewis acid sites tend to attack the hydroxyl end of glycerol, and generate intermediate acetol and Br (?) nsted Acid is easier to attack the hydroxyl glycerol intermediate to produce 3- hydroxyl propylaldehyde; then two further hydrogenation respectively generate 1,2- propylene glycol and 1,3- propylene glycol. Supported metal catalysts are widely used in the hydrogenation of glycerol. The addition of acid additives in metal catalysts can significantly increase the activity of the catalyst. A large number of studies have shown that both the acidic species added to the surface of the metal particles, or even the simple physical mixing can effectively enhance the catalytic performance of the catalyst. However, as far as we know, the proximity effect between the metal acid sites has not been reported in the glycerol hydrogenolysis reaction. Therefore, we chose the supported Pt catalyst for glycerol hydrogenolysis as a platform reaction. The ALD porous alumina membrane was used to encapsulate Pt catalyst to study the effect of the metal acid site proximity effect on the Pt catalyst in glycerol hydrogenolysis. In this paper, we use the atomic layer deposition (ALD), with the advantage of accurate control of the atomic level, we in the precise surface deposition of oxide coating Pt nanometer particle catalyst, proximity formation of metal oxide interface, metal acid bifunctional active sites of Pt catalysts in the hydrogenation of glycerol the solution in the reaction activity and selectivity control. The main results are as follows: (1) by wet chemical impregnation method synthesized Pt/Al203 catalyst, then use the ALD technology in the growth surface of porous alumina film Pt nanoparticles, using Lewis and Pt as well as its acidic alumina metal proximity effect, synergistic effect to improve the dual functional catalyst to improve the glycerol hydrogen the solution reaction activity and selectivity of propylene glycol 1,2-. Our study found that the alumina coated with 30 cycles had the highest activity and selectivity. Under the high-resolution transmission electron microscope (HRTEM), the thickness of the coating layer was observed to be 3.6 nm. By comparing the hydrogenation of acetone alcohols intermediates, we found that the acidity of alumina and the proximity effect of Pt hydrogenation sites play an important role in improving the catalytic performance. In addition, by reducing the particle size of Pt particles, it also helps to improve the selectivity of 1,2 propanediol. Therefore, we preliminarily think that porous alumina parcels divide the surface of Pt particles into small Pt aggregates, which is the main reason for improving the selectivity of 1,2 propanediol. (2) in addition, we have further grown FeOx with different cycles on commercial Pt/C catalyst through ALD technology. It is found that trace FeOx can significantly improve the activity of the catalyst. We found that the FeOx with three cycles of deposition has the highest activity on Pt/C catalyst, and the conversion rate of glycerol hydrogenolysis is three times higher than that of Pt/C catalyst in the same time.
【學(xué)位授予單位】：中國科學(xué)技術(shù)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：O643.36

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相關(guān)期刊論文 前1條

1 鄧澄浩;冷莉;周靜紅;周興貴;袁渭康;;預(yù)處理溫度對(duì)甘油氫解雙金屬Ir-Re催化劑性能的影響（英文）[J];催化學(xué)報(bào);2015年10期

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本文編號(hào)：1346867