十水草酸镧的热分解及其动力学分析
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摘要
用热重-差热(TG-DTA)技术,在不同升温速率条件下,研究了十水草酸镧在空气气氛下的热分解过程.分别采用Ozawa-Flynm-Wall法、Kissinger法、Crane法和同步热分析法确定其热分解动力学参数.TG-DTA曲线表明:十水草酸镧分解为四个阶段,前两个阶段为脱水过程,后两个阶段为La_2(C_2O_4)_3的分解过程.实验计算得出四步反应表观活化能E分别为83.92、76.04、136.26、162.61 k J·mol-1左右;指前因子A分别为4.92×10~(10)、6.1×10~7、2.1×10~9、8.46×10~6s-1左右;反应级数n均为1左右,并用Coats-Redfem积分法得出第三步分解机理受F1控制.
Thermal decomposition behavior of lanthanum oxalate was studied by the simultaneous thermal analysis technique TG-DTA in an air atmosphere. The thermal decomposition kinetics parameters of La_2(C_2O_4)_3·10H_2O was determined by using Ozawa-Flynm-Wall method、Kissinger method、Crane method and simultaneous thermal analysis method. Curve of TG showed : the thermal decomposition of La_2(C_2O_4)_3·10H_2O has 4 stages,the first two stages are the dehydration process,the succedent two stages are the thermal decomposition of La_2( C_2O_4)_3. The four stages' apparent activation energies are 83. 92、76. 04、136. 26、162. 61 kJ·mol-1,the exponential factors are about 4. 92 × 1010、6. 1 × 10~7、2. 1 × 10~9、8. 46 × 10~6 s~(-1) respectively,the reaction order is about one,and the decomposition mechanism of the third step is controlled by F1 according to Coats-Redfem method.
Thermal decomposition behavior of lanthanum oxalate was studied by the simultaneous thermal analysis technique TG-DTA in an air atmosphere. The thermal decomposition kinetics parameters of La_2(C_2O_4)_3·10H_2O was determined by using Ozawa-Flynm-Wall method、Kissinger method、Crane method and simultaneous thermal analysis method. Curve of TG showed : the thermal decomposition of La_2(C_2O_4)_3·10H_2O has 4 stages,the first two stages are the dehydration process,the succedent two stages are the thermal decomposition of La_2( C_2O_4)_3. The four stages' apparent activation energies are 83. 92、76. 04、136. 26、162. 61 kJ·mol-1,the exponential factors are about 4. 92 × 1010、6. 1 × 10~7、2. 1 × 10~9、8. 46 × 10~6 s~(-1) respectively,the reaction order is about one,and the decomposition mechanism of the third step is controlled by F1 according to Coats-Redfem method.
引文
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[3]Dent P C,Rare earth elements,Permanent magnets[J].Journal of Applied Physics,2012,111(7):07-21.)
[4]谷双,陈纪忠.竹材热解失重动力学模型研究[J].高校化学工程学报,2011,25(2):231-235.(Gu Shuang,Chen Jizhong.Study on pyrolysis kinetics of bamboo[J].Journal of Chemical Engineering of Chinese Universities,2011,25(2):231-235.)
[5]李稳.一些无机水合盐的热分解动力学研究[D].南京:南京理工大学,2012:1-10.(Li Wen.The thermal kinetics of some metal hydrated salts[D].NanJing:Nanjing University of Science and Technology,2012:1-10.)
[6]Genieva S D,Vlaev L T,Atanassov A N.Study of the thermooxidative degradation kinetics of poly(tetrafluoroethene)using iso-conversional calculation procedure[J].Journal of Thermal Analysis and Calorimetry,2010,99(2):550-560.
[7]方正东,汪敦佳.十水草酸铈分解过程和非等温动力学研究[J].稀土,2005,26(3):19-22.(Fang Zhengdong,Wang Dunjia.Study on the thermal decomposition and non-isothermal kinetic of cerium oxalate[J].Chinese Rare Earths,2005,26(3):19.)
[8]胡艳红,李梅,柳召刚,等.大颗粒氧化铈的草酸盐前驱体热分解研究[J].稀土,2009,30(4):35-37.(Hu Yanhong,Li Mei,Liu Zhaogang,et al.Study on the thermal decomposition of cerium oxalate precursor of large particle CeO2[J].Chinese Rare Earths,2009,30(4):35-37.)
[9]黄昕,李琴,杨明,等.大颗粒草酸钕热分/解特性及动力学研究[J].中国稀土学报,2016,34(1):83-92.(Huang Xin,Li Qin,Yang Ming,et al.Thermal decomposition and kinetics analysis of larger particle neodymium oxalate[J].Journal of the Chinese Society of Rare Earths,2016,34(1):83-92.)
[10]张克立,陈雄斌,席美云,等.十水草酸镧的热分解机理[J].武汉大学学报(自然科学版),1996,42(2):163-166.(Zhang Keli,Chen Xiongbin,Xi Meiyun,et al.Thermal decomposition of lanthanum oxalate decahydrate[J].Journal of Wuhan University(Natural Science Edition),1996,42(2):163-166.)
[11]Chen Jianping,Kimio IsA.Thermal decomposition of urea and urea derivatives by simultaneous TG/(DTA)/MS[J].Journal of the Mass Spectrometry Society of Japan,1998,46(4):299-303.
[12]MothéC G,de Miranda I C.Study of kinetic parameters of thermal decomposition of bagasse and sugarcane straw using friedman and ozawa-flynn-wall isoconversional methods[J].Journal of Thermal Analysis and Calorimetry,2013,113(2):497-505.
[13]Barick A K,Tripathy D K.Thermal and dynamic mechanical characterization of thermoplastic polyurethane/organoclay nanocomposites prepared by melt compounding[J].Materials Science and Engineering:A,2010,527(3):812-823.
[14]Li Chunhua,Qi Shuhua,Zhang Dongna.Thermal degradation of environmentally friendly phenolic resin/Al2O3hybrid composite[J].Journal of Applied Polymer Science,2010,115(6):3675-3679.
[15]Van Humbeeck J.Simultaneous thermal analysis[J].Handbook of Thermal Analysis and Calorimetry,1998(1):497-508.
[16]Mathew S,Nair C G R,Ninan K N.Thermal decomposition kinetics:Part XV.Kinetics and mechanism of thermal decomposition of tetrammine copper(II)sulphate monohydrate[J].Thermochimica Acta,1989,144(1):33-43.
[17]Laidler K J.The development of the arrhenius equation[J].JChem Educ,1984,61(6):494.