保温时间对废催化裂化平衡剂合成莫来石的影响

Influence of holding time on microstructures of mullite synthesized by spent FCC equilibrium catalyst

采用X射线粉末衍射和扫描电子显微镜研究了保温时间对废催化裂化平衡剂合成莫来石的影响。结果表明,二次莫来石化反应发生在1 450℃,保温3 h后,莫来石质量分数达94%,晶体发育良好;当保温时间超过4 h,由于反应物中Si4+被Al3+取代,导致空位增多,过渡金属进入结构的空位,使莫来石熔点降低,表现为保温时间越长,液相越多,莫来石晶体粘结于液相之中,使机械性能降低。由此可见,保温时间对二次莫来石生成反应影响较大。

The influence of holding time on microstructures of mullite synthesized by spent FCC equilibri- um catalyst were investigated by means of XRD and SEM techniques. The results showed that using spent FCC equilibrium catalyst and commercial A1203 as the raw materials, mullite synthesized by solid phase reaction at high temperature was mainly Al4.59 Si1.41O9.7, and secondary mullitizatioin took place at the temperature 1 450 ℃ ;the amount of mullite reached 94wt% within holding time 3 h, and mullite crystal exhibited column shapes. When the holding time was more than 4 h, transition metals integrated into the structural vacancy that increased due to the replacement of Si4＋ by Al3＋ , which resulted in reducing the melting point of mullite. Therefore, the holding time was proportional to liquid phase that bonded with mullite,which lead to decreasing the mechanical performance. The holding time had great influence on microstructures of the secondary mullite.