稀土草酸盐的热分解机理及动力学研究

发布时间：2018-01-23 17:49

本文关键词： TG-DTA 热分解动力学参数稀土草酸盐　出处：《江西理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：稀土草酸盐因为结晶度高,晶型较好,常作为稀土氧化物的前驱体。为了更好的控制稀土氧化物的形貌和粒度,本文研究稀土草酸盐的热分解过程和动力学数据,为制得良好形貌和粒度的稀土氧化物提供一定的理论依据。本文采用热重-差热(TG-DTA)技术,研究了六种稀土草酸盐在空气气氛下的热分解过程。分别采用Ozawa-Flynm-Wall方程、Kissinger方程、Crane方程、同步热分析方程、Coats-Redfem积分法和二元线性拟合技术研究了六种稀土草酸盐的的热分解步骤和动力学参数。从实验的TG-DTA曲线计算得出:(1)La2(C204)3·10H20热分解过程分为四步,前两个阶段为脱水,后两个阶段为La2(C204)3 的分解过程。四步反应 E 分别为 83.92、76.04、136.26、162.61KJ·mol-1,A 分别为 4.92×1010、6.1×107、2.1×109、8.46×106s-1,n 均为 1 左右,第三步反应受F1控制,g(α)=1-α。(2)Pr2(C204)3·8H20的热分解过程分两步,第一步为脱水,第二步为Pr2(C204)3的分解过程。两步反应E分别为38.93、155.76KJ·mol-1,n分别为0.5、1.5。第一步反应受化学反应控制,g(α)=(1-α)1/3,A=1 2×1011s-1。(3)Sm2(C204)3·8H20的分解分四步进行,前两个阶段为脱水,后两个阶段是Sm2(C204)3 的分解过程。四步反应 E 分别为 40.77、85.15、56.13、69.86KJ·mol-1,n分别为0.5、0.84、1/3、0.45,第三步反应受化学反应控制,g(α)=[-ln(1-α)]2/3,A=1.26×1014s-1(4)Dy2(C204)3·6H20的分解过程分两步。两步反应E分别为36.69、83.58 KJ·mol-1,n为0.55、2/3,第二步反应受A-E方程控制,为随机形核,g(α)=[-ln(1-α)]2/3,A=967s-1。(5)Ho2(C2O4)3·4H20 的热分解过程分三步,第一步为脱水,后两步是Ho2(C2O4)3分解过程。三步反应E分别为68.13、75.56、158.77KJ·mol-1。n 均为 1 左右,A 分别为 7.2×108、8.27×108、2.3×107s-1,第二步受F1控制,为随机形核,g(α)=-ln(1-α)。(6)Y2(C2O4)3·9H20分解过程分两步,第一步是脱水,第二步是Y2(C204)3的分解过程。两步反应E分别是47.83、69.44 KJ·mol-1,n分别是0.75、2/3。第二步反应受A-E方程控制反应,g(α)=[-ln(1-α)]2/3,A= 3.6×105s-1。
[Abstract]:Rare earth oxalate is often used as the precursor of rare earth oxide because of its high crystallinity and good crystal form. In order to better control the morphology and particle size of rare earth oxide. In this paper, the thermal decomposition process and kinetic data of rare earth oxalate are studied, which provides a theoretical basis for the preparation of rare earth oxides with good morphology and particle size. In this paper, thermogravimetric differential thermogravimetric TG-DTA( TG-DTA) technique is used to prepare rare earth oxides with good morphology and particle size. The thermal decomposition of six rare earth oxalates in air atmosphere was studied. The Ozawa-Flynm-Wall equation and the Crane equation were used respectively. Synchronous thermal analysis equation. The thermal decomposition steps and kinetic parameters of six rare earth oxalates were studied by Coats-Redfem integration method and binary linear fitting technique. The thermal decomposition process of La2(C204)3 路10H20 is divided into four steps. The first two stages were dehydration and the latter two were the decomposition process of La2(C204)3. The four-step reaction E was 83.9276.04N 136.26, respectively. The values of 162.61KJ 路mol-1a were 4.92 脳 10 ~ (10), 6.1 脳 10 ~ (7), 2.1 脳 10 ~ (9) and 8.46 脳 10 ~ (6) s ~ (-1), respectively. The third step is controlled by F1 in the process of thermal decomposition. The first step is dehydration. The second step is the decomposition process of Pr2(C204)3. The E of the two-step reaction is 38.93N 155.76KJ 路mol-1n, respectively. 1.5. The first step of the reaction is controlled by a chemical reaction. The decomposition of AH12 脳 1011s-1.O3Sm ~ (2) C _ (204N) 3.8H _ (20) is divided into four steps, the first two stages are dehydration. The last two stages were the decomposition process of Sm2(C204)3, and the E of the four-step reaction was 40.77V 85.15N 56.13N 69.86KJ 路mol-1, respectively. N = 0. 5, 0. 84% 1 / 3, 0. 45, respectively. The third step reaction is controlled by chemical reaction. [The decomposition process of 2 / 3 An 1.26 脳 1014s-1C Dy 2N C 204N 3 路6H 20 is divided into two steps, and the reaction E is 36.69, respectively. 83.58 KJ 路mol -1 n is 0.55N / 2 / 3, the second step reaction is controlled by A-E equation, which is a random nucleation g (伪) =. [There are three steps in the thermal decomposition of -ln ~ 1- 伪) ~ (2 / 3) ~ (3 / 3) A ~ (96 7s) ~ (1) ~ (5) H _ (2) O _ (2) C _ 2O _ 4 ~ (3 路4H _ (20)), the first step is dehydration. The last two steps are Ho2(C2O4)3 decomposition process, and the E of the three-step reaction is 68.13 ~ 75.56 ~ 158.77 KJ 路mol-1.n, respectively. The A is 7.2 脳 108U 8.27 脳 108N 2.3 脳 107s-1.The second step is controlled by F1 and is a random nucleation. There are two steps in the decomposition process of g (伪) -ln ~ 1- 伪 ~ (- 伪) ~ (?) ~ (6) ~ (6) C _ (2) C _ (2) C _ (2) O _ (4) H _ (3) H _ (20). The second step is the decomposition process of Y2C204N3.The two step reaction E is 47.83KJ 路mol-1n, which is 0.75, respectively. The second step reaction is controlled by A-E equation. [2 / 3 A = 3.6 脳 105s-1.
【学位授予单位】：江西理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ133.3

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