The Thermal Decomposition Process And Kinetic Analysis Of Light Rare Earth Carbonate

Rare earth carbonates have the advantages of low preparation cost and less pollution etc.and are widely concerned by various companies.In order to study the thermal decomposition process of light rare earth carbonate dynamics,this paper studies praseodymium carbonates prepared using three different precipitants.The theoretical basis for the industrial production of rare earth oxides with specific morphology and size from rare earth carbonates is provided.In this paper,the thermogravimetry-differential scanning?TG-DSC?technique was used to study the thermal decomposition process of light rare earth carbonates in air.The thermal decomposition process and kinetic parameters of light rare earth carbonates were studied by using O zawa-Flynm-Wall method?K issinger method?Crane method and Coats-Redfern method.Research indicates::?1?The thermal decomposition process of lanthanum carbonate is divided into three stages,the first stage is dehydration reaction,and the second and third stages are the decomposition reaction of lanthanum carbonate.The three stages of activation energy E are 31.79?173.84?195.48kJ·mol^-1.Reaction level n is 1,Pre-Factor A are8.48×10³?1.67×10¹¹?1.28×10⁹s^-1.The second and third stage reaction mechanism functions are g???=[-ln?1-??]?g???=[-ln?1-??]^1/1.5;?2?The thermal decomposition process of cerium carbonate is divided into two stages.E are 37.03?121.1 kJ·mol^-1,n are about 1.3?0.6,A are 1.03×10¹³?1.75×10⁸s^-1,The mechanism function of the second stage is g???=[1-?1-??^1/3]².;?3?The thermal decomposition process of Praseodymium carbonate with different morphology and particle size prepared from sodium bicarbonate,sodium carbonate and ammonium bicarbonate is divided into three stages.The first stage is dehydration reaction,E are 40.52?40.11?31.79 kJ·mol^-1,A are 5.8×10⁴?2.75×10⁴?4.12×10⁴s^-1,n are about 1,decomposition temperature is 418?428 and 410K.The second stage was the generation of Pr₂CO₅.E are 220.94?211.34?220.22 kJ·mol^-1,A are 1.35×10¹¹?1.51×10¹⁴?1.51×10¹⁴s^-1,n are about 1,decomposition temperature is 778?782 and768K,the mechanism function is g???=?+?1+??ln?1+??,g???=[-ln?1-??],g???=[-ln?1-??]^1/1.5,E of third stage are 120.71,146.77,94.44 kJ·mol^-1.A are 6.22×10²,6.29×10⁷,3.37×10⁶s^-1,n are about 0.9,decomposition temperature is 987?1001 and970K.The mechanism functions are g???=[-ln?1-??]^1/2,g???=?,g???=[-ln?1-??]^1/2;?4?The decomposition activation energy and decomposition temperature of praseodymium carbonate prepared by ammonium bicarbonate as precipitator are the lowest,it can reduce the energy consumption by using the stage heating roasting.