煙酸鋅熱分解動(dòng)力學(xué)研究

孫秋香等:煙酸鋅熱分解動(dòng)力學(xué)研充煙酸鋅熱分解動(dòng)力學(xué)研究孫秋香1,張克立2,黃元喬,李彭2,袁良杰(1.湖北第二師范學(xué)院化學(xué)系,湖北武漢430205;2.武漢大學(xué)化學(xué)與分子科學(xué)學(xué)院,湖北武漢430072)摘要:采用流變相反應法合成了煙酸鋅配合物,用粉灰狀,越細越好),然后移到反應釜內膽(聚四氟乙熱分析(TG/DTG)、X射線(xiàn)衍射(XRD)技術(shù)研究了固烯)中,加入適量水調成流變態(tài),內膽密封,再放入反應態(tài)物質(zhì)煙酸鋅在空氣中熱分解的過(guò)程。熱分析結果表釜的不銹鋼外套中,外套旋緊密封好。將反應釜置于明,煙酸鋅在空氣中是一步分解,其失重率與理論計算100℃的烘箱中反應約10h,取出來(lái),自然冷卻后,打開(kāi)失重率相吻合。XRD結果表明,煙酸鋅分解的終產(chǎn)物反應釜。反應物用無(wú)水乙醇洗滌3次,沉淀物在為ZnO。用 Friedman法和 Flynn-Wall-Ozawa(FWoO)120℃的烘箱中烘干即得到無(wú)水煙酸鋅Zn(Nic)2(Nic法求取了分解過(guò)程的活化能E,并用多元線(xiàn)性回歸法為NC5H4COO)給出了可能的機理函數,由這些方法得到的動(dòng)力學(xué)數2.3熱分析據相互比較吻合固體配合物的熱穩定性是該化合物的重要特性之關(guān)鍵詞:煙酸鋅;TG/DTG;XRD;熱分解;動(dòng)力學(xué)熱分析研究的是物質(zhì)的物理性質(zhì)和化學(xué)性質(zhì)隨溫中圖分類(lèi)號:O643.12文獻標識碼:A度變化的關(guān)系。煙酸鋅的TG/DTG在 Netzsch ST文章編號:1001-9731(2009)05-0817-03449C綜合熱分析儀進(jìn)行。樣品重量約為7.50mg。升1引言溫速率為5、10、20℃/min。升溫范圍,從室溫1200℃。根據熱分析曲線(xiàn)上的數據,進(jìn)一步在綜合熱高活性氧化鋅和超微氧化鋅在磁性材料、橡膠工分析儀上收集分解產(chǎn)物。業(yè)、日用化工、光吸收、熱阻、催化等方面具有奇特的性2.4微量X射線(xiàn)粉末衍射質(zhì)和廣泛的用途-3)。納米級氧化鋅粒子作為聯(lián)系宏用微量X射線(xiàn)粉末衍射法,在 Bruker d8-Ad-觀(guān)物質(zhì)及微觀(guān)粒子的橋梁,其潛在的重要性備受關(guān) vance X射線(xiàn)衍射儀上測定煙酸鋅分解產(chǎn)物的X射線(xiàn)注[。粉末衍射譜圖。實(shí)驗條件為:鎳濾光片和石墨單色器近年來(lái),對芳香族羧酸鹽配合物的熱分解性質(zhì)做濾波,旋轉陰極銅靶Ka輻射,管壓40kV,管流50mA,了很多研究-7。羧酸鹽配合物熱分解的最終產(chǎn)物大波長(cháng)0.154178m,掃描速率4/min,樣品為熱分析過(guò)多數為納米級別尺寸的金屬氧化物。本文較詳細的研程中的固體殘留物,質(zhì)量為5mg左右。究了煙酸鋅的合成和熱分解過(guò)程,得到了氧化鋅產(chǎn)品。并用等轉換率法研究煙酸鋅熱分解過(guò)程的動(dòng)力學(xué)。在3結果與討論未知動(dòng)力學(xué)方程的情況下先得到活化能,再應用多元3.1熱分析線(xiàn)性回歸法對非等溫熱分析數據進(jìn)行擬合以確定反應圖1是煙酸鋅在不同升溫速率下于靜態(tài)空氣中的的動(dòng)力學(xué)方程和參數-12TG/DTG曲線(xiàn)。由圖1可知,在不同升溫速率下,樣2實(shí)驗品的失重率基本一致2.1試劑、儀器2.1.1試劑氧化鋅(ZnO)、煙酸(NC5H4COOH或CH5O2N縮寫(xiě)為HNic)、無(wú)水乙醇,均為分析純試劑2.1.2儀器Netzsch StA449綜合熱分析儀; Bruker D8Ad升溫速率51020cmlnvance X射線(xiàn)衍射儀。2.2樣品制備圖1煙酸鋅在空氣中的TG/DTG曲線(xiàn)首先稱(chēng)取一定量的(按物質(zhì)的量比)煙酸和氧化鋅Fig(2:1)。將兩種試劑放在研缽中混合均勻,研細(研成中國煤化工CH,COO)2 In air atCNMHG基金項目:國家自然科學(xué)基金資助項目(20071026);湖北第二師范學(xué)院校管重點(diǎn)資助課題(2007A002)收到初稿日期:2008-1020收到修改稿日期:2009-022通訊作者:張克立作者簡(jiǎn)介:孫秋香(1955-),女,湖北黃岡人,副教授,主要從事無(wú)機固體和材料化學(xué)研究818私料2009年第5期(40)卷圖2是煙酸鋅在5℃/min升溫速率下的TG/活化能隨著(zhù)轉化率的變化而變化不大,表明其分解過(guò)DTG曲線(xiàn)。由TG曲線(xiàn)計算可知,煙酸鋅在空氣中是程是個(gè)簡(jiǎn)單的一步過(guò)程。其具體數據如表1所一步分解,其分解失重率實(shí)驗值為74.83%;計算值為「 Friedman analysis煙酸3TG74.90%實(shí)驗值與計算值相當吻合。固體殘留物呈白色,由失重率可推知分解生成ZnO。根據上述分析,煙酸鋅配合物的熱分解機理為:380~470℃Zn(NC H, coO)2ZnO+有機物圖4用 Friedman法得到的煙酸鋅熱分解的表觀(guān)活Mass charge:-,83%化能隨反應程度的變化Fig 4 Calculated apparent activation energies of de-composition of Zn(NCs H, COO)2 using theFriedman methods plotted against the extent ofconversion圖2煙酸鏵在空氣中的TG/DTG曲線(xiàn)表1煙酸酸鋅熱分解的活化能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射線(xiàn)粉末衍射分析(NCs H, COO)2收集500℃溫度下分解的殘留物,進(jìn)行X射線(xiàn)粉ECk/moD)末衍射分析。由X射線(xiàn)粉末衍射數據計算得ZnO的晶胞參數為a=0.325068nm,c=0.521231nm,a=90°Friedman法FWO法v=0.04770nm3,Z=2,屬于六方晶系。產(chǎn)物ZnO的342.74峰位置、強度及計算結果與PDF卡號36-1451的六方0.4334.10298.81相ZnO的數據基本吻合,這也與熱重分析的結果相311.61302.56致50.53305.493.3動(dòng)力學(xué)研究30.29313.700.8在此用 Friedman法1), Ozawa- Flynn-Wall319.75平均346.54299.84法11即多掃描速率法,又稱(chēng)為等轉化率法通過(guò)Netzsch公司的動(dòng)力學(xué)軟件來(lái)研究煙酸鋅的分解動(dòng)力最可幾反應模型通過(guò)多元線(xiàn)性回歸得到的數據如表2所示。學(xué)圖3是煙酸鋅熱分解過(guò)程的DTG曲線(xiàn),從DTG表2由多元線(xiàn)性回歸得到的煙酸鋅熱分解的動(dòng)力學(xué)數據曲線(xiàn)可看出分解過(guò)程僅有1個(gè)峰,說(shuō)明其熱分解過(guò)程 Table2 Fitted kinetic parameters of Zn( NCh COO)2是一步簡(jiǎn)單反應。resulting from multivariate nonlinear regression反應類(lèi)型g(A/S1)(kJ/mo相關(guān)系數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圖3煙酸鋅熱分解過(guò)程的DTG曲線(xiàn)F124.4554363.42570.995164246Fig 3 DTG curves of Zn(NC H COO), different heating rates in air atmosphere中國煤化工09583512CNMH應的最可幾模型為圖4是用 Friedman和FWO方法得到的煙酸鋅CnB,即n級自催化反應。從而可得到煙酸鋅熱分解熱分解的表觀(guān)活化能估計值。轉化率以分解過(guò)程的部全部動(dòng)力學(xué)數據如表3所示分質(zhì)量損失表示。由圖4知,在a=0.2~0.8范圍內,孫秋香等煙酸鋅熱分解動(dòng)力學(xué)研究819表3煙酸鋅熱分解過(guò)程的動(dòng)力學(xué)數據Table 3 Fitted kinetic parameters during the decomposition of Zn(NCs H, COO)zFriedman法FwO法 ASTM E698 Model-fitting a lg4/s1)反應活化能(kJ/mol)應級數lgKa關(guān)系數性能類(lèi)型346.5429984321.99300.4519.5233CnBn.102540.56583.99980(a)=(1-a)(1+Ka)4結論(4):549-552.[6]孫秋香,王麗娜李鵬,等.[J].分析科學(xué)學(xué)報,2007,23由熱分析(TG/DTG)和X射線(xiàn)衍射(XRD)研究[7孫豪堂,王東利,張克立,等.[應用化學(xué),19,14了固態(tài)物質(zhì)煙酸鋅在空氣中熱分解的過(guò)程。結果表(5):98-10明,煙酸鋅在空氣中是一步分解并生成ZnO,其實(shí)驗失[8] Zhan Dan, Cong Changjie, Kahiyou D,eta.[].Ther重率為74.83%與計算值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. [J]. Chinese J of用無(wú)模式法分別對煙酸鋅的分解反應求取了活化能Chemistry,2006,24(4):499-503E,并用多元線(xiàn)性回歸給出了分解反應的可能的機理函[10] Zhang Keli, Hong Jianhe, Cao Guihua, et aL.[門(mén)].Ther數f(a)=(1-a)"(1+Kaa),用這些方法得到的動(dòng)力mochim Acta,2005,437(1-2):145-9[11] Hong Jianhe, Zhang Zhiguo, Cong Changjie, et al. [J]學(xué)數據相當吻合。Thermochim Acta, 2006, 440(1):31-35.參考文獻[12]孫秋香,張克立,李鵬,等.[J].華中師范大學(xué)學(xué)報(自然科學(xué)版),2008,42(2):247-251[1]張振逵.[J].無(wú)機鹽工業(yè),1996,5:33-35[2]徐航,張東翔,徐文國.[J].功能材料,2008,39(4),[13] Friedman H L.[n]. J Polym Sci Part C,1963,6:183673-676[3]洪廣盲等,[冂.無(wú)機材料學(xué)報1987,6;97-104.[4]余建群,賈殿增.[冂].化學(xué)通報,1995,613031.d FlvaaT.[J]. Bull Chem Soc Jpn,1965,38:1881-1886.J H, Wall L A. UJ]. J Polym Sci Part B, 1966,4r[5]張克立袁繼兵,哀良杰,等.[冂].無(wú)機化學(xué)學(xué)報,1999,15Study on the kinetics of thermal decomposition of zine nicotinateAbstrac a :(1. 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頁(yè))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中國煤化工 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