烟酸锌热分解动力学研究

孙秋香等:烟酸锌热分解动力学研充烟酸锌热分解动力学研究孙秋香1,张克立2,黄元乔,李彭2,袁良杰(1.湖北第二师范学院化学系,湖北武汉430205;2.武汉大学化学与分子科学学院,湖北武汉430072)摘要:采用流变相反应法合成了烟酸锌配合物,用粉灰状,越细越好),然后移到反应釜内胆(聚四氟乙热分析(TG/DTG)、X射线衍射(XRD)技术研究了固烯)中,加入适量水调成流变态,内胆密封,再放入反应态物质烟酸锌在空气中热分解的过程。热分析结果表釜的不锈钢外套中,外套旋紧密封好。将反应釜置于明,烟酸锌在空气中是一步分解,其失重率与理论计算100℃的烘箱中反应约10h,取出来,自然冷却后,打开失重率相吻合。XRD结果表明,烟酸锌分解的终产物反应釜。反应物用无水乙醇洗涤3次,沉淀物在为ZnO。用 Friedman法和 Flynn-Wall-Ozawa(FWoO)120℃的烘箱中烘干即得到无水烟酸锌Zn(Nic)2(Nic法求取了分解过程的活化能E,并用多元线性回归法为NC5H4COO)给出了可能的机理函数,由这些方法得到的动力学数2.3热分析据相互比较吻合固体配合物的热稳定性是该化合物的重要特性之关键词:烟酸锌;TG/DTG;XRD;热分解;动力学热分析研究的是物质的物理性质和化学性质随温中图分类号:O643.12文献标识码:A度变化的关系。烟酸锌的TG/DTG在 Netzsch ST文章编号:1001-9731(2009)05-0817-03449C综合热分析仪进行。样品重量约为7.50mg。升1引言温速率为5、10、20℃/min。升温范围,从室温1200℃。根据热分析曲线上的数据,进一步在综合热高活性氧化锌和超微氧化锌在磁性材料、橡胶工分析仪上收集分解产物。业、日用化工、光吸收、热阻、催化等方面具有奇特的性2.4微量X射线粉末衍射质和广泛的用途-3)。纳米级氧化锌粒子作为联系宏用微量X射线粉末衍射法,在 Bruker d8-Ad-观物质及微观粒子的桥梁,其潜在的重要性备受关 vance X射线衍射仪上测定烟酸锌分解产物的X射线注[。粉末衍射谱图。实验条件为:镍滤光片和石墨单色器近年来,对芳香族羧酸盐配合物的热分解性质做滤波,旋转阴极铜靶Ka辐射,管压40kV,管流50mA,了很多研究-7。羧酸盐配合物热分解的最终产物大波长0.154178m,扫描速率4/min,样品为热分析过多数为纳米级别尺寸的金属氧化物。本文较详细的研程中的固体残留物,质量为5mg左右。究了烟酸锌的合成和热分解过程,得到了氧化锌产品。并用等转换率法研究烟酸锌热分解过程的动力学。在3结果与讨论未知动力学方程的情况下先得到活化能,再应用多元3.1热分析线性回归法对非等温热分析数据进行拟合以确定反应图1是烟酸锌在不同升温速率下于静态空气中的的动力学方程和参数-12TG/DTG曲线。由图1可知,在不同升温速率下,样2实验品的失重率基本一致2.1试剂、仪器2.1.1试剂氧化锌(ZnO)、烟酸(NC5H4COOH或CH5O2N缩写为HNic)、无水乙醇,均为分析纯试剂2.1.2仪器Netzsch StA449综合热分析仪; Bruker D8Ad升温速率51020cmlnvance X射线衍射仪。2.2样品制备图1烟酸锌在空气中的TG/DTG曲线首先称取一定量的(按物质的量比)烟酸和氧化锌Fig(2:1)。将两种试剂放在研钵中混合均匀,研细(研成中国煤化工CH,COO)2 In air atCNMHG基金项目:国家自然科学基金资助项目(20071026);湖北第二师范学院校管重点资助课题(2007A002)收到初稿日期:2008-1020收到修改稿日期:2009-022通讯作者:张克立作者简介:孙秋香(1955-),女,湖北黄冈人,副教授,主要从事无机固体和材料化学研究818私料2009年第5期(40)卷图2是烟酸锌在5℃/min升温速率下的TG/活化能随着转化率的变化而变化不大,表明其分解过DTG曲线。由TG曲线计算可知,烟酸锌在空气中是程是个简单的一步过程。其具体数据如表1所一步分解,其分解失重率实验值为74.83%;计算值为「 Friedman analysis烟酸3TG74.90%实验值与计算值相当吻合。固体残留物呈白色,由失重率可推知分解生成ZnO。根据上述分析,烟酸锌配合物的热分解机理为:380~470℃Zn(NC H, coO)2ZnO+有机物图4用 Friedman法得到的烟酸锌热分解的表观活Mass charge:-,83%化能随反应程度的变化Fig 4 Calculated apparent activation energies of de-composition of Zn(NCs H, COO)2 using theFriedman methods plotted against the extent ofconversion图2烟酸铧在空气中的TG/DTG曲线表1烟酸酸锌热分解的活化能Fig 2 TG/DTG curves of Zn(NC H, Coo)2 in air at- Table 1 Activation energies calculated via differentmethods during the decomposition of Zn3.2X射线粉末衍射分析(NCs H, COO)2收集500℃温度下分解的残留物,进行X射线粉ECk/moD)末衍射分析。由X射线粉末衍射数据计算得ZnO的晶胞参数为a=0.325068nm,c=0.521231nm,a=90°Friedman法FWO法v=0.04770nm3,Z=2,属于六方晶系。产物ZnO的342.74峰位置、强度及计算结果与PDF卡号36-1451的六方0.4334.10298.81相ZnO的数据基本吻合,这也与热重分析的结果相311.61302.56致50.53305.493.3动力学研究30.29313.700.8在此用 Friedman法1), Ozawa- Flynn-Wall319.75平均346.54299.84法11即多扫描速率法,又称为等转化率法通过Netzsch公司的动力学软件来研究烟酸锌的分解动力最可几反应模型通过多元线性回归得到的数据如表2所示。学图3是烟酸锌热分解过程的DTG曲线,从DTG表2由多元线性回归得到的烟酸锌热分解的动力学数据曲线可看出分解过程仅有1个峰,说明其热分解过程 Table2 Fitted kinetic parameters of Zn( NCh COO)2是一步简单反应。resulting from multivariate nonlinear regression反应类型g(A/S1)(kJ/mo相关系数00.45100.99939771.00CB19.5297300.90450.999981.01Bna20.1239303.75970.99338124199881302.58110.99229871.820.7520314.94660.99914581.42R21,027032.43750.9912461.45R321.7762334.51520.99901371.63图3烟酸锌热分解过程的DTG曲线F124.4554363.42570.995164246Fig 3 DTG curves of Zn(NC H COO), different heating rates in air atmosphere中国煤化工09583512CNMH应的最可几模型为图4是用 Friedman和FWO方法得到的烟酸锌CnB,即n级自催化反应。从而可得到烟酸锌热分解热分解的表观活化能估计值。转化率以分解过程的部全部动力学数据如表3所示分质量损失表示。由图4知,在a=0.2~0.8范围内,孙秋香等烟酸锌热分解动力学研究819表3烟酸锌热分解过程的动力学数据Table 3 Fitted kinetic parameters during the decomposition of Zn(NCs H, COO)zFriedman法FwO法 ASTM E698 Model-fitting a lg4/s1)反应活化能(kJ/mol)应级数lgKa关系数性能类型346.5429984321.99300.4519.5233CnBn.102540.56583.99980(a)=(1-a)(1+Ka)4结论(4):549-552.[6]孙秋香,王丽娜李鹏,等.[J].分析科学学报,2007,23由热分析(TG/DTG)和X射线衍射(XRD)研究[7孙豪堂,王东利,张克立,等.[应用化学,19,14了固态物质烟酸锌在空气中热分解的过程。结果表(5):98-10明,烟酸锌在空气中是一步分解并生成ZnO,其实验失[8] Zhan Dan, Cong Changjie, Kahiyou D,eta.[].Ther重率为74.83%与计算值74.90%的失重率相一致。mochim Acta,2005,430(1-2):101-105.[9] Cong C J, Hong J H, Luo S T, et al. 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Department of Chemistry, Hubei University of Education, Wuhan 430205, Chinar ieasun Qiu-xiang, ZHANG Ke-li, HUANG Yuan-qiao', LI Peng, YUANG LiangCollege of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, China)ine nicotinate was synthesized with the rheological phase reaction method. The thermal decomposition processes taking place in the solid state zine nicotinate have been studied using TG-DTG and XRD techniques. TG-DTGcurves showed that the decomposition proceeds through one well-defined step in Air. Mass lossof the thermal decomposition of zinc nicotinate is in good agreement with the theoretical mass loss. XRD showedthat the final product of the thermal decomposition was ZnO. The activation energies were calculated throughthe Friedman and Flynn-Wall-Ozawa(FWO)methods, and the possible conversion functions had been estimatedthrough the multiple linear regression methodKey words: zine nicotinate: TG/DTG; XRD; thermal decomposition; kinetics(上接第816页)Effects of particle size of petroleum cokes on material andelectrochemical property of activated carbonZHANG Zhi-an, sUN Xiao-feng, LAI Yan-qing, LI Jie, LIU Ye-xiang(School of Metallurgical Science and Engineering, Central South University, Changsha 410083, China)Abstract: Taking the petroleum cokes with different distribution of particle size as raw material and KOh as ac-tivated agent, the ultra-high surface area activated carbons employed for supercapacitors were prepared bychemical activation process. The BET specific surface area and the pore structure of activated carbon were ana-lyzed by N2 adsorption method. The electrochemical properties of the activated carbons were determined usingtwoelectrode capacitors in lmol/L Et, NBF,/AN electrolyte. Results indicate that the yield and tap density in-creases then decreases with the decreasing particle size of petroleum cokes. And the petroleum cokes with narrow distribution developed lower BET specific surface area an中国煤化工 arbors. On the otherhand, the activated carbon prepared by petroleum cokes of144F/g. And activated carbon prepared by petroleum cokes ofCNMHGPecific capacitance ofdischarge behavor,the specific capacitance is 126 6F/g at the current of 1A/g and 116 2F/g at the current of 20A/g, respectivelywith the capacitance loss of 8. 2%Key words: petroleum coke; activated carbon; pore structure; chemical activation; supercapacitor