含超微氧化亞鈷顆粒Beta分子篩的合成及其催化乙苯氧化性能（英文）
發(fā)布時間：2018-10-16 22:42
【摘要】：雜原子分子篩是指在硅鋁分子篩或磷鋁酸鹽分子篩中含有骨架內或骨架外某種原子或其化合物的分子篩.這些雜原子可以是某些主族元素(如硼、鍺、鎵)或有變價特性的過渡金屬元素(如鈦、鐵、鈷、鎳)等.將雜原子或其化合物通過浸漬、離子交換、水熱晶化等方式引入沸石分子篩骨架中形成雜原子分子篩,往往可以改變沸石分子篩的骨架結構和理化性能,并賦予沸石分子篩新的催化反應性能.自1983年鈦硅分子篩TS-1被發(fā)現(xiàn)能夠高效催化烯烴環(huán)氧化以來,許多雜原子分子篩因其在催化烷烴類及芳烴類氧化、醛酮選擇氧化及烯烴類環(huán)氧化等領域表現(xiàn)出的優(yōu)良性能得到了廣泛關注.目前,合成含不同雜原子的分子篩已成為分子篩材料開發(fā)的一個重要內容.分子篩的微孔孔道結構賦予了被引入其中作為催化中心的雜原子對反應物/產物分子獨特的擇形選擇性;同時,分子篩骨架與雜原子之間往往存在化學鍵或空間限域作用,使得雜原子在高溫高壓等反應條件下依然保持高度的分散性,避免由于團聚導致活性降低.鈷離子及含鈷化合物在烷烴及芳烴類催化氧化反應中表現(xiàn)出很好的活性,能夠利用分子氧實現(xiàn)對高碳烷烴及烷基苯的催化氧化.將鈷離子及其化合物引入具有合適孔道結構的分子篩,可以提高催化反應的選擇性.目前將對含鈷分子篩的合成研究主要有后處理法及直接水熱法.后處理法包括負載法及離子交換法,用于制備含有鈷物種的硅鋁分子篩;而直接水熱法主要用于制備含有骨架鈷的磷酸鋁分子篩.目前為止,使用水熱法合成含鈷的分子篩材料的合成及其催化應用至今鮮有研究報導.這主要是由于傳統(tǒng)的分子篩合成體系的高堿性環(huán)境會導致鈷鹽的沉淀,導致其無法被引入分子篩.我們通過優(yōu)化合成條件,利用含氟體系直接水熱法將鈷引入Beta分子篩,得到含超微氧化亞鈷團簇的Beta沸石分子篩.通過掃描電子顯微鏡、X射線粉末衍射、紫外-可見漫反射光譜、X射線光電子能譜、透射電子顯微鏡及H_2程序升溫還原等表征手段對合成樣品的物理化學性質進行了研究,并與使用浸漬、離子交換得到的含鈷Beta沸石及水熱合成得到的含鈷AlPO-5分子篩的相關性質進行了對比.合成得到的含鈷分子篩材料中,鈷物種以亞納米尺度的氧化亞鈷顆粒形式存在.我們使用分子氧作為氧源,考察了該含超微氧化亞鈷的Beta沸石作為催化劑催化乙苯氧化反應的活性.與浸漬、離子交換制得鈷硅分子篩及含有骨架鈷的磷酸鋁分子篩材料相比,含超微氧化亞鈷的Beta分子篩表現(xiàn)出更高的催化活性及對苯乙酮/醛的選擇性.
[Abstract]:Heteroatom molecular sieve is a molecular sieve that contains some atoms or its compound in the framework or outside of the framework in silica-aluminophosphate molecular sieve or aluminophosphate molecular sieve. These heteroatoms may be some of the main group elements (such as boron, germanium, gallium) or transition metals with variable valence properties (such as titanium, iron, cobalt, nickel, etc.). Hetero atoms or their compounds are introduced into the framework of zeolites by impregnation, ion exchange and hydrothermal crystallization to form hetero-atomic molecular sieves, which can change the structure and physical and chemical properties of zeolites. The new catalytic reaction properties of zeolite molecular sieves were also given. Since TS-1 was found to be able to efficiently catalyze the epoxidation of olefins in 1983, many hetero-atomic molecular sieves have been used to catalyze the oxidation of alkanes and aromatics. The excellent properties of selective oxidation of aldehydes and ketones and epoxidation of olefins have been paid more and more attention. At present, the synthesis of molecular sieves containing different heteroatoms has become an important content in the development of molecular sieve materials. The pore structure of molecular sieve endows the hetero atom which is introduced as the catalytic center with the unique form selectivity to the reactant / product molecule, at the same time, the molecular sieve skeleton often has the chemical bond or the space limit action between the hetero atom and the molecular sieve skeleton. The hetero atoms remain highly dispersed under the conditions of high temperature and high pressure so as to avoid the decrease of activity due to agglomeration. Cobalt ions and cobalt-containing compounds show good activity in the catalytic oxidation of alkanes and aromatics, and can be used to realize the catalytic oxidation of alkanes and alkylbenzene with molecular oxygen. The selectivity of catalytic reaction can be improved by introducing cobalt ion and its compounds into molecular sieve with suitable pore structure. At present, the synthesis of cobalt-containing molecular sieve will be mainly studied by post-treatment method and direct hydrothermal method. The post-treatment methods include loading method and ion exchange method, which are used to prepare silicon-aluminum molecular sieve containing cobalt species, while direct hydrothermal method is mainly used to prepare aluminophosphate molecular sieve containing skeleton cobalt. So far, the hydrothermal synthesis of cobalt-containing molecular sieve materials and their catalytic applications have not been reported. This is mainly due to the high alkalinity environment of the traditional molecular sieve synthesis system will lead to the precipitation of cobalt salt, which can not be introduced into the molecular sieve. By optimizing the synthetic conditions, cobalt was introduced into Beta molecular sieve by direct hydrothermal method in fluorine-containing system to obtain Beta zeolite containing ultrafine cobalt oxide clusters. The physical and chemical properties of the synthesized samples were studied by means of scanning electron microscope, X-ray powder diffraction, UV-Vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscope and H-2 temperature programmed reduction. The properties of cobalt-containing Beta zeolites obtained by impregnation and ion exchange were compared with those obtained by hydrothermal synthesis of cobalt-containing AlPO-5 zeolites. Cobalt species exist in the form of subnanoscale cobalt oxide particles in the synthesized cobalt-containing molecular sieve materials. The catalytic activity of Beta zeolite containing ultrafine cobalt oxide as catalyst for the oxidation of ethylbenzene was investigated using molecular oxygen as the oxygen source. Compared with impregnation and ion exchange, the Beta molecular sieve containing ultrafine cobalt oxide exhibits higher catalytic activity and selectivity for acetophenone / aldehydes than that for aluminophosphate molecular sieve containing skeleton cobalt.
【作者單位】： 中國科學院大連化學物理研究所潔凈能源國家實驗室(籌);中國科學院大學;中國科學院大連化學物理研究所分子反應動力學國家重點實驗室;中國科學院大連化學物理研究所潔凈能源國家實驗室(籌)催化基礎國家重點實驗室;
【基金】：supported by Strategic Priority Research Program of the Chinese Academy of Sciences(XDA07020300)~~
【分類號】：O643.36
本文編號：2275853
[Abstract]:Heteroatom molecular sieve is a molecular sieve that contains some atoms or its compound in the framework or outside of the framework in silica-aluminophosphate molecular sieve or aluminophosphate molecular sieve. These heteroatoms may be some of the main group elements (such as boron, germanium, gallium) or transition metals with variable valence properties (such as titanium, iron, cobalt, nickel, etc.). Hetero atoms or their compounds are introduced into the framework of zeolites by impregnation, ion exchange and hydrothermal crystallization to form hetero-atomic molecular sieves, which can change the structure and physical and chemical properties of zeolites. The new catalytic reaction properties of zeolite molecular sieves were also given. Since TS-1 was found to be able to efficiently catalyze the epoxidation of olefins in 1983, many hetero-atomic molecular sieves have been used to catalyze the oxidation of alkanes and aromatics. The excellent properties of selective oxidation of aldehydes and ketones and epoxidation of olefins have been paid more and more attention. At present, the synthesis of molecular sieves containing different heteroatoms has become an important content in the development of molecular sieve materials. The pore structure of molecular sieve endows the hetero atom which is introduced as the catalytic center with the unique form selectivity to the reactant / product molecule, at the same time, the molecular sieve skeleton often has the chemical bond or the space limit action between the hetero atom and the molecular sieve skeleton. The hetero atoms remain highly dispersed under the conditions of high temperature and high pressure so as to avoid the decrease of activity due to agglomeration. Cobalt ions and cobalt-containing compounds show good activity in the catalytic oxidation of alkanes and aromatics, and can be used to realize the catalytic oxidation of alkanes and alkylbenzene with molecular oxygen. The selectivity of catalytic reaction can be improved by introducing cobalt ion and its compounds into molecular sieve with suitable pore structure. At present, the synthesis of cobalt-containing molecular sieve will be mainly studied by post-treatment method and direct hydrothermal method. The post-treatment methods include loading method and ion exchange method, which are used to prepare silicon-aluminum molecular sieve containing cobalt species, while direct hydrothermal method is mainly used to prepare aluminophosphate molecular sieve containing skeleton cobalt. So far, the hydrothermal synthesis of cobalt-containing molecular sieve materials and their catalytic applications have not been reported. This is mainly due to the high alkalinity environment of the traditional molecular sieve synthesis system will lead to the precipitation of cobalt salt, which can not be introduced into the molecular sieve. By optimizing the synthetic conditions, cobalt was introduced into Beta molecular sieve by direct hydrothermal method in fluorine-containing system to obtain Beta zeolite containing ultrafine cobalt oxide clusters. The physical and chemical properties of the synthesized samples were studied by means of scanning electron microscope, X-ray powder diffraction, UV-Vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscope and H-2 temperature programmed reduction. The properties of cobalt-containing Beta zeolites obtained by impregnation and ion exchange were compared with those obtained by hydrothermal synthesis of cobalt-containing AlPO-5 zeolites. Cobalt species exist in the form of subnanoscale cobalt oxide particles in the synthesized cobalt-containing molecular sieve materials. The catalytic activity of Beta zeolite containing ultrafine cobalt oxide as catalyst for the oxidation of ethylbenzene was investigated using molecular oxygen as the oxygen source. Compared with impregnation and ion exchange, the Beta molecular sieve containing ultrafine cobalt oxide exhibits higher catalytic activity and selectivity for acetophenone / aldehydes than that for aluminophosphate molecular sieve containing skeleton cobalt.
【作者單位】： 中國科學院大連化學物理研究所潔凈能源國家實驗室(籌);中國科學院大學;中國科學院大連化學物理研究所分子反應動力學國家重點實驗室;中國科學院大連化學物理研究所潔凈能源國家實驗室(籌)催化基礎國家重點實驗室;
【基金】：supported by Strategic Priority Research Program of the Chinese Academy of Sciences(XDA07020300)~~
【分類號】：O643.36
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1 奉冬文,周桂芝;利用氮氧分析儀定量分析氧化亞鈷的含量[J];冶金分析;2001年05期
，本文編號：2275853
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