摘要
采用水热处理与离子交换结合的方法对ＮａＹ沸石进行了改性．ＸＲＤ、ＸＰＳ及孔结构测试结果表明，ＮａＹ沸石经水热处理和离子交换改性制得的Ｙ沸石催化剂的晶体晶型未发生变化；处理温度对催化剂的相对结晶度、孔结构及比表面积有很大影响；水热处理可以使微孔孔口产生缺陷或破裂；在一定温度下，催化剂能够形成二次孔；过高的处理温度将导致催化剂孔结构的崩坍．Ｙ沸石催化剂存在铝富集在表面的现象．采用红外光谱及吡啶、２，６－二甲基吡啶吸附和脱附的方法，对沸石催化剂酸性质进行了表征，发现催化剂主要存在两种强度的Ｂｒｎｓｔｅｄ酸中心．催化剂的活性与其结构和酸性质密切相关，较强的Ｂｒｎｓｔｅｄ酸中心是二异丙苯和苯烷基转移反应的活性中心．
The Y zeolite catalysts for transalkylation reaction of diisopropylbenzene with benzene were prepared from NaY by hydrothermal treating and ion exchanging with aqueous solution of NH 4Cl.The structure of these catalysts was studied by using XRD,XPS and adsorption/desorption methods.Experimental results showed that the hydrothermal treating temperature(>600℃) had remarkable influence on the relative crystallinity,surface area and pore size distribution.The phenomenon of aluminum enriching to the outer surface was observed during hydrothermal treating. The acidic property of these catalysts was investigated by using IR,TPD methods.Experimental results showed that two kinds of Bronsted acid sites mainly existed on these catalysts.Several types of hydroxyl groups were found in these catalysts:those from strongly acidic bridging hydroxyl groups (3633cm -1 and 3555cm -1 ),OH groups bonded to extralattice aluminum(3688-3698cm -1 and 3600cm -1 ),and terminal SiOH groups(3742cm -1 )and 'very high frequency'(VHF)absorption (3782cm -1 ).These OH bonded to 3782cm -1 ,3742cm -1 and 3688-3695cm -1 are moderate in acid strength,other OH groups are stronger in acid strength. The pore structure,acid amount and acid strength would have significant effect on the activity of catalyst.Stronger Bronsted acid center may be the active center of transalkylation.
出处
《分子催化》
EI
CAS
CSCD
北大核心
1997年第2期113-120,共8页
Journal of Molecular Catalysis(China)
关键词
Y型
沸石
烷基转移反应
孔结构
二异丙苯
催化剂
Y type zeolite,Transalkylation reaction,Pore structure,Diisopropylbenzene
