摘要
应用ＸＲＤ、ＸＰＳ、ＩＲ、２９ＳｉＭＡＳＮＭＲ、２７ＡｌＭＡＳＮＭＲ和ＮＯ－ＩＲ吸附等手段对一系列经不同温度焙烧的Ｍｏ／ＵＳＹ催化剂中ＵＳＹ骨架结构破坏过程和Ｍｏ在ＵＳＹ分子筛中的烧结行为进行了研究，结果表明，Ｍｏ在ＵＳＹ上分散和烧结时，存在一个ＭＯ对ＵＳＹ分子筛骨架铝的抽提过程．Ｍｏ在ＵＳＹ分子筛表面分散时，抽提该分子筛骨架Ｓｉ（２Ａｌ）中少量的Ａｌ，但当焙烧温度升高，Ｍｏ开始烧结时，Ｍｏ主要抽提骨架中Ｓｉ（１Ａｌ）中的Ａｌ；ＭｏＯ３在ＵＳＹ分子筛上的烧结首先表现为Ｍｏ对该分子筛骨架铝的抽提，导致分子筛严重脱铝和结构崩塌．一旦分子筛结构破坏，ＭｏＯ３则迅速与Ａｌ３＋结合并烧结成Ａｌ２（ＭｏＯ４）３。
Mo/USY samples,prepared by conventional impregnation with(NH4)6Mo7O24 solution and calcined at 300,400,500,600℃,were characterized,by XRD,XPS, 29Si MAS NMR and 27Al MAS NMR,acidity measurement with IR-TPD and NO chemisop tion.The results obviously show that Mo incorporation induces an aluminium extraction from the framework of zeolite.When molybdenum is dispersed over the support at low calcination temperature(<400℃),it mainly extracts aluminium of Si(2Al)in the framework of USY zeolite. However,sintering at a high calcined temperature,molybdenum mainly extracts aluminium of Si(1Al) from the framework.There are two steps in the process of sintering of molybdenum in Mo/USY catalysts. First, molybdenum makes USY zeolite dealuminate sharply and destroy the framework,and then immediately forms bulk Al2(MoO4)3 with the non -framework aluminium originated from the framework of USY zeolite.
出处
《高等学校化学学报》
SCIE
EI
CAS
CSCD
北大核心
1995年第4期608-612,共5页
Chemical Journal of Chinese Universities
基金
国家自然科学基金
关键词
USY
烧结
钼
分子筛
催化剂
Mo/USY,Dealumination of USY,Sintering of Mo
