煅烧温度对高岭石相转变过程及Si、Al活性的影响

INFLUENCE OF TEMPERATURE ON HPASE TRANSFORMATION OF CALCINED KAOLINITE AND Si,Al ACTIVITY

通过对吉林通化煤系高岭石和美国Georgia高岭石在200～1300 ℃热处理产物的MAS NMR谱和XRD,IR,DTA等的研究,主要获得如下结论:①煅烧高岭石的相转变经历了四个阶段--脱羟阶段(约550 ℃),偏高岭石阶段(550～850 ℃),SiO2分凝(850～1100 ℃)及Al2O3分凝阶段(950～1100 ℃),莫来石、方英石形成阶段(1100 ℃以上);②偏高岭石-莫来石的相转变过程中存在SiO2和Al2O3的分凝,其中SiO2的分凝温度是850 ℃,而Al2O3的分凝温度是950 ℃;③1100 ℃开始,由偏高岭石分凝形成的非晶质SiO2一部分和Al2O3-γ发生反应生成了莫来石,一部分结晶为方英石;④煅烧高岭石Si、Al活性总体上随着煅烧温度的增高逐渐增强,其中Al的活性在900 ℃时达到最高,Si在1100 ℃时达到最高,当温度超过这两个临界点时,Si、Al活性将迅速下降.

From the MAS, NMR, XRD, IR and EDS data of calcined coal kaolinite from Tonghua of Jilin Province, China and one sample from Georgia, USA, which were under thermal treatment respectively from 200℃ to 1300℃, some conclusions are drawn： （1） phase transformation of calcined kaolinite involved 4 stages, including kaolinite dehydroxylation （～550℃）,meta-kaolinite （550-850℃）, segregation of SiO2（850-1100℃） and Al2O3（950-1100℃） and the formation of mullite and calcite （〉1100℃）; （2） there occurred segregation of SiO2 and Al2O3 during the phase transformation of meta-kaolinite and mullite. The temperature is 850℃ for segregation of SiO2, and 950℃ for segregation of Al2O3; （3） starting from 1100℃, a part of non-crystal SiO2-segregated meta-kaolinite reacted with Al2O3-γ to form mullite, the rest crystallized as cristobalite; （4） the activity of Si and Al from calcined kaolinite varies with temperature, and increases with the rise of temperature; AI activity can reach its maximum at 990℃, and Si activity can reach its maximum at 1100℃. At the same time, the activity will decrease suddenly while the temperature exceeds the two critical points, respectively.