多孔SiO_2及SiO_2＋MO催化剂载体的烧结行为研究

A Research on the Sintering of Porous Catalyst-support Sio_2 and SiO_2+MO

运用表面积测定，孔径分布，晶相检测等仪器分析方法对作为催化剂载体的多孔ＳｉＯ２的烧结行为进行了考察．发现非晶ＳｉＯ２微细颗粒在６００℃～７００℃间即开始烧结；在恒定温度下，烧结过程并非匀速，而是分成不同的快速烧结阶段．烧结后比表面积减小，但平均孔径增大．加入碱土金属氢化物ＭＯ后，原ＳｉＯ２的表面积减小，烧结后表面积的损失更大；相比而言，加入ＭｇＯ对比表面积影响较小，而加入ＢａＯ则影响较大．对第一快速烧结阶段建立了速率方程；运用分型几何模型理论较好地解释了不同快速烧结阶段问题以及与之相应的不同半径微孔收缩封堵的关系．对于烧结过程中的伴随现象亦进行了探讨．

Methods of specific surface area determination (SSA), pore size distribution (PSD) and ray diffraction (XRD) are employed to detect the sitering behaviour of the porous SiO2 and SiO2 +MO,which are used as the support of catalysts (MO means the oxides of the basic earth metals. ). It is found that the fine uncrystal SiO2 start sintering from about 700℃ ; At the same temperature sintetingdoes not carry on at the same speed. It occurs in different fast stages. After sintering the SSA decreases, but the average pore size increases. When MO are added, SSA of SiO2 decrease, and after sinter-ing SSA loses much more. Comparatively speaking, the influence of MgO on SSA of SiO2 is smaller,while that of BaO decrease SSA seriously both before and after sintering. In the present work, the speed equation is established for the first fast--sintering stage. The fractional geometry model(FGM) is used to explain the different fast-sintering stages and the relationship with shrinkage of the small different-size pores properly. The accompaning phenomena during singtering are also discussed. This port of work has some reference value for the catalysts which are supported by porous SiO2 or SiO2+MO and are used at high temperature.