本文選題：CeO_2 + 過渡金屬摻雜�。� 參考：《湖南大學(xué)》2016年碩士論文

【摘要】：氧化鈰作為一種環(huán)境友好和含量豐富的稀土金屬氧化物,由于其本身固有的儲存和釋放氧特性而被廣泛應(yīng)用到環(huán)境和能源等領(lǐng)域。在各種應(yīng)用中,氧化鈰不僅可以作為活性組分,而且還能作為其他活性組分的良好載體。但是,氧化鈰納米顆粒熱穩(wěn)定性差且易團聚降低活性。采取特殊的方法將其制備成核殼結(jié)構(gòu)或空心球結(jié)構(gòu)不僅提高氧化鈰納米顆粒的分散度和比表面積,而且作為載體與其他材料相結(jié)合后可以增強催化劑的活性和穩(wěn)定性。單羧基鈷卟啉作為仿生均相催化劑在催化氧化反應(yīng)中表現(xiàn)出良好的活性,但是其易自聚、難回收等缺點限制了它的應(yīng)用。解決這個問題的一種方法是,將鈷卟啉負(fù)載到無機載體上制備出非均相催化劑。該非均相催化劑通過載體提供的微環(huán)境可大大提高其穩(wěn)定性和抗氧化能力。另一種方法是將鈷卟啉在惰性氣氛中熱解合成新型Co-N-C材料來提高卟啉的原子利用率。綜上所述,本文合成了幾種新型負(fù)載催化劑,以氧氣作為綠色氧化劑,在無溶劑條件下通過催化氧化乙苯來考察其催化性能。具體的研究內(nèi)容如下：1.通過改進(jìn)的Stober法和表面活性劑作用制備以過渡金屬摻雜氧化鈰為核二氧化硅為殼的核殼結(jié)構(gòu)載體,然后將經(jīng)過APTES改性的鈷卟啉以化學(xué)鍵鍵聯(lián)到載體上,得到一系列表面負(fù)載鈷卟啉的二氧化硅@雙金屬氧化物催化劑(CoTPP-SiO2@(MOx/CeO2) (M=Fe、Co、Mn和Cu))。以乙苯氧化反應(yīng)為探針反應(yīng)考察不同過渡金屬摻雜氧化鈰晶格所得的催化劑催化氧化乙苯反應(yīng)的催化性能及其穩(wěn)定性,結(jié)果顯示鈷金屬摻雜的催化劑(CoTPP-SiO2@(CoOx/CeO2))催化活性最好,乙苯轉(zhuǎn)化率為28.5%,苯乙酮選擇性為76.8%。2.以單羧基鈷卟啉為Co-N-C材料的前驅(qū)體,在氮氣氛下,500℃熱解CoTPP-SiO2@(CoOx/CeO2)核殼材料,得到Co-N-C/SiO2@(CoOx/CeO2)催化劑。結(jié)果顯示,催化劑熱解后出現(xiàn)Co-Nx結(jié)構(gòu),這有利于提高催化劑的活性和穩(wěn)定性。該催化劑循環(huán)催化氧化乙苯反應(yīng)6次之后,其活性損失明顯比熱解前催化劑(CoTPP-(CoOx/CeO2)活性損失小很多。單羧基鈷卟啉熱解得到的Co-N-C很大程度上提高了催化劑的穩(wěn)定性。3.采用層層包裹的策略,以SiO2微球為硬模板制備(MnOx/CeO2)@SiO2核殼結(jié)構(gòu),然后將改性的鈷卟啉化學(xué)鍵聯(lián)到表面,再在外面包裹一層SiO2,在氮氣氛下500℃焙燒處理1h后,最后用氫氧化鈉刻蝕得到Co-N-C負(fù)載在空心球MnOx/CeO2上的催化劑。該催化劑中的Co-N-C是嵌入在載體孔隙中的,提供了“納米反應(yīng)器”環(huán)境。具有高比表面積、大孔腔等特性的催化劑在乙苯氧化反應(yīng)方面表現(xiàn)出優(yōu)異的性能,乙苯轉(zhuǎn)化率達(dá)到44.5%。并依據(jù)文獻(xiàn)和特設(shè)的實驗考察了催化劑催化氧化乙苯的機理。結(jié)果顯示,Co-N-C/(MnOx/CeO2)空心球由于氧空穴造成的表面活性氧和Co-Nx結(jié)構(gòu)是其主要的活性位。
[Abstract]:As an environmentally friendly and rich rare earth metal oxide, cerium oxide has been widely used in environmental and energy fields due to its inherent storage and oxygen release properties. In various applications, cerium oxide can be used not only as active component, but also as a good carrier of other active components. However, the thermal stability of cerium oxide nanoparticles is poor and the agglomeration is easy to reduce the activity. The core-shell structure or hollow sphere structure can not only improve the dispersion and specific surface area of cerium oxide nanoparticles, but also enhance the activity and stability of the catalyst when the support is combined with other materials. Monocarboxylic cobalt porphyrins show good activity in catalytic oxidation as bionic homogeneous catalysts, but their easy self-polymerization and difficult recovery limit their application. One way to solve this problem is to prepare heterogeneous catalysts by loading cobalt porphyrin onto inorganic support. The stability and oxidation resistance of the heterogeneous catalyst can be greatly improved by the microenvironment provided by the support. Another method is to pyrolyse cobalt porphyrin in inert atmosphere to synthesize a new Co-N-C material to improve the atomic utilization ratio of porphyrin. To sum up, several novel supported catalysts were synthesized and their catalytic properties were investigated by catalytic oxidation of ethylbenzene under solvent-free conditions with oxygen as green oxidant. The specific contents of the study are as follows: 1: 1. The core-shell structure carrier with transition metal-doped cerium oxide as the core silica shell was prepared by the modified Stober method and the surfactant interaction. Then the cobalt porphyrin modified by APTES was chemically bonded onto the carrier. A series of surface supported cobalt porphyrin supported silica @ bimetallic oxide catalysts (CoTPP-SiO2 @ (MOX / CEO _ 2) (mn and Cu).) were prepared. The catalytic performance and stability of catalysts obtained from different transition metal doped cerium oxide lattices for the oxidation of ethylbenzene were investigated using ethylbenzene oxidation reaction as probe reaction. The results showed that cobalt doped catalysts (CoTPP-SiO2 @ (CoOxp / CeO2) had the best catalytic activity. The conversion rate of ethylbenzene was 28.5.The selectivity of acetophenone was 76.80.2. Co-N-C / SiO2@ (CoOxp-CeO2) core-shell materials were pyrolyzed at 500 鈩，

本文編號：2064558