不同硅含量多级孔SAPO-5分子筛的制备及表征

摘要

A series of hierarchical SAPO-5 molecular sieves with different silicon contents were prepared by hydrothermal synthesis using N,N-dicyclohexylmethylamine as structure directing agent,tetraethoxysilane (TEOS)as silica source,hydrated aluminum hydroxide as alumina source,phosphoric acid (85%)as phosphor-us source.The crystal structure,specific surface area,skeleton structure and acidity of SAPO-5 molecular sieves were characterized by XRD,N2-physical adsorption,FTIR and NH3-TPD,respectively.Results showed that, with the increase of silicon content,the crystallinity of hierarchical SAPO-5 molecular sieves was decreased;there was no significant alteration of the pore diameter with the silicon content increased,but the pore volume was increased;when the silicon content was 0.33,the sample was not AFI structure;the total acid amount in-creased at first and then decreased,the total acid amount reached the top value when the silicon content was 0.20.%以N-甲基二环己基胺（MCHA）为结构导向剂、正硅酸乙酯（TEOS）为硅源、氢氧化铝为铝源、85％的磷酸为磷源，采用水热法制备了不同硅含量的多级孔 SAPO-5分子筛。采用 X-射线粉末衍射（XRD）、氮气物理吸附、傅立叶变换红外光谱（FTIR）和氨程序升温脱附（NH3-TPD）等方法分别对样品的晶体结构、比表面积、骨架结构和酸性等进行表征。结果表明：随着硅含量的增加，多级孔 SAPO-5分子筛的结晶度降低；孔径无明显变化，孔容增大；当硅含量为0.33时，样品不再具有 AFI结构；总酸量随着硅含量的增加先升高后降低，当硅含量为0.20时，总酸量最大。