Premium
Isoconversional Kinetics of Thermal Processes in Mixtures Based on Metakaolin and Sodium Hydroxide
Author(s) -
Prokof'ev Valery Yu.,
Gorditalya E.,
Khramtsova Alexandra P.,
Konstantinova Ekaterina M.,
Voynova Viktoriya V.
Publication year - 2018
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.21177
Subject(s) - metakaolin , chemistry , activation energy , nepheline , sodium hydroxide , mullite , crystallization , atmospheric temperature range , chemical engineering , nuclear chemistry , mineralogy , thermodynamics , ceramic , fly ash , physics , organic chemistry , engineering
This study investigated the thermal behavior of the mixtures 6Al 2 Si 2 O 7 : 12NaOH and 6Al 2 Si 2 O 7 : 12NaOH: 2Al 2 O 3 which are designed for synthesis of LTA (Linde type A) zeolite. XRD, SEM, and Synchronous thermal analysis (STA) have been used. It was found that after evaporating suspensions, molding pellets, and drying, small amounts of LTA and sodium hydroaluminates have been formed in the sample. The removal of crystallization water occurs on heating up to 400°C. In the temperature range from 400 to 850°C, Na 6 Al 4 Si 4 O 17 and Na 8 Al 4 Si 4 O 18 are synthesized by interaction of metakaolin with sodium hydroxide. The formation of mullite and nepheline is also observed. It was shown that preactivation of powders in the vibratory mill allows reducing the starting temperature of synthesis at 50–100°C. For the range 400–850°C using Ozawa–Flynn–Wall analysis, the values of apparent activation energy and preexponential factor have been calculated. It was established that the apparent activation energy for mixtures without preactivation made 200–290 kJ mol −1 . After preactivation, E values decreased to 130–170 kJ mol −1 . Also it was shown that alumina excess inhibits nepheline and mullite formation.