微介孔复合分子筛合成及其在汽车冷启动尾气控制中的应用  

Synthesis of Combined Micro-Mesoporous Zeolites and Their Application to Automobile Cold Start Emission Control

作　　者：张兰[1] 张振中[1] 尉继英[1] 孟弼芳[1] 江锋[1] 梁彤祥[1] 

机构地区：[1]清华大学核能与新能源技术研究院,精细陶瓷北京市重点实验室,北京100084

出　　处：《物理化学学报》2012年第6期1439-1447,共9页Acta Physico-Chimica Sinica

基　　金：国家自然科学基金(21077064)资助项目~~

摘　　要：分别采用稀溶液和浓溶液双模板剂两步水热合成法,以二氧化硅微硅粉和铝酸钠为硅源和铝源,第一步获得β分子筛晶种,第二步以β分子筛晶种为结构单元组装形成兼具MCM-41分子筛和β分子筛结构特点的复合型分子筛β/M(其中β是指β分子筛,M是指MCM-41介孔分子筛).采用X射线衍射(XRD)、傅里叶变换红外(FT-IR)光谱、氮气吸附(BET)和高分辨透射电镜(HRTEM)对样品的物相结构和微观形貌进行了表征,并对复合分子筛的合成过程进行了分析.结果表明:复合分子筛β/M的形成是微孔β结构和介孔MCM-41结构的竞争生长过程,β分子筛晶种的晶化时间和晶粒度大小对β/M复合分子筛的结构有重要影响.此外,我们以甲苯为探针分子,比较研究了三类分子筛β/M、MCM-41和β的原样以及经高温水热处理后样品的吸附性能,结果表明:β/M复合分子筛的热稳定性优于介孔分子筛MCM-41,其甲苯吸附容量比MCM-41和β分子筛的高,其中以浓溶液法合成的复合分子筛吸附容量最高.Synthesis of micro-mesoporous zeolites β/M（where β and M denote β zeolite and MCM-41 zeolite,respectively） combined with zeolites β and MCM-41 was achieved in the sodium hydroxide system using a two-step hydrothermal treatment method.Sodium aluminate and fume silica were used as the sources of aluminum and silicon,while tetraethylammonium hydroxide（TEAOH） and cetyltrimethylammonium bromide（CTAB） were used as templates for the formation of β crystal seeds and for self-assembling of β crystal seeds into mesoporous zeolites β/M,respectively.The samples were characterized by X-ray diffraction（XRD）,Fourier transform infrared（FT-IR） spectroscopy,and high resolution transmission electron microscope（HRTEM）.Reaction time and particle size of β crystal seeds were found to play an important role in the synthesis of β/M zeolites.When β seeds crystallize in a short time,a pure phase（denoted βM） can result,whose mesoporous structure resembles MCM-41,while long crystallization times can result in a phase mixture of mesoporous βM and microporous β zeolite.Due to the insertion of the secondary building units of β zeolite into the mesoporous wall,the β/M micro-mesoporous combined zeolites showed enhanced toluene adsorption performance and hydrothermal stability.

关 键 词：微介孔复合分子筛 晶化时间 晶粒度 甲苯吸附 汽车冷启动尾气控制 

分 类 号：TQ424.25[化学工程] X734.2[环境科学与工程—环境工程]