含超微氧化亚钴颗粒Beta分子筛的合成及其催化乙苯氧化性能（英文）
发布时间：2018-10-16 22:42
【摘要】：杂原子分子筛是指在硅铝分子筛或磷铝酸盐分子筛中含有骨架内或骨架外某种原子或其化合物的分子筛.这些杂原子可以是某些主族元素(如硼、锗、镓)或有变价特性的过渡金属元素(如钛、铁、钴、镍)等.将杂原子或其化合物通过浸渍、离子交换、水热晶化等方式引入沸石分子筛骨架中形成杂原子分子筛,往往可以改变沸石分子筛的骨架结构和理化性能,并赋予沸石分子筛新的催化反应性能.自1983年钛硅分子筛TS-1被发现能够高效催化烯烃环氧化以来,许多杂原子分子筛因其在催化烷烃类及芳烃类氧化、醛酮选择氧化及烯烃类环氧化等领域表现出的优良性能得到了广泛关注.目前,合成含不同杂原子的分子筛已成为分子筛材料开发的一个重要内容.分子筛的微孔孔道结构赋予了被引入其中作为催化中心的杂原子对反应物/产物分子独特的择形选择性;同时,分子筛骨架与杂原子之间往往存在化学键或空间限域作用,使得杂原子在高温高压等反应条件下依然保持高度的分散性,避免由于团聚导致活性降低.钴离子及含钴化合物在烷烃及芳烃类催化氧化反应中表现出很好的活性,能够利用分子氧实现对高碳烷烃及烷基苯的催化氧化.将钴离子及其化合物引入具有合适孔道结构的分子筛,可以提高催化反应的选择性.目前将对含钴分子筛的合成研究主要有后处理法及直接水热法.后处理法包括负载法及离子交换法,用于制备含有钴物种的硅铝分子筛;而直接水热法主要用于制备含有骨架钴的磷酸铝分子筛.目前为止,使用水热法合成含钴的分子筛材料的合成及其催化应用至今鲜有研究报导.这主要是由于传统的分子筛合成体系的高碱性环境会导致钴盐的沉淀,导致其无法被引入分子筛.我们通过优化合成条件,利用含氟体系直接水热法将钴引入Beta分子筛,得到含超微氧化亚钴团簇的Beta沸石分子筛.通过扫描电子显微镜、X射线粉末衍射、紫外-可见漫反射光谱、X射线光电子能谱、透射电子显微镜及H_2程序升温还原等表征手段对合成样品的物理化学性质进行了研究,并与使用浸渍、离子交换得到的含钴Beta沸石及水热合成得到的含钴AlPO-5分子筛的相关性质进行了对比.合成得到的含钴分子筛材料中,钴物种以亚纳米尺度的氧化亚钴颗粒形式存在.我们使用分子氧作为氧源,考察了该含超微氧化亚钴的Beta沸石作为催化剂催化乙苯氧化反应的活性.与浸渍、离子交换制得钴硅分子筛及含有骨架钴的磷酸铝分子筛材料相比,含超微氧化亚钴的Beta分子筛表现出更高的催化活性及对苯乙酮/醛的选择性.
[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.
【作者单位】： 中国科学院大连化学物理研究所洁净能源国家实验室(筹);中国科学院大学;中国科学院大连化学物理研究所分子反应动力学国家重点实验室;中国科学院大连化学物理研究所洁净能源国家实验室(筹)催化基础国家重点实验室;
【基金】：supported by Strategic Priority Research Program of the Chinese Academy of Sciences(XDA07020300)~~
【分类号】：O643.36
本文编号：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.
【作者单位】： 中国科学院大连化学物理研究所洁净能源国家实验室(筹);中国科学院大学;中国科学院大连化学物理研究所分子反应动力学国家重点实验室;中国科学院大连化学物理研究所洁净能源国家实验室(筹)催化基础国家重点实验室;
【基金】：supported by Strategic Priority Research Program of the Chinese Academy of Sciences(XDA07020300)~~
【分类号】：O643.36
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