第30卷第2期高?；瘜W(xué)工程學(xué)報(bào)4月Journal of Chemical Engineering of Chinese UniversitiesN2901603-9015(2016)02-0404-06基于熱分析的亞油酸甲酯熱解動(dòng)力學(xué)研究王學(xué)春2,方建華2,陳波水2,陳爾余!,賈賢補(bǔ)1(1.武警杭州士官學(xué)校車輛維修系,浙江杭州3100232.后勤工程學(xué)院軍事油料應(yīng)用與管理工程系,重慶401311)摘要:采用熱重分析方法研究了亞油酸甲酯在氮?dú)夂脱鯕鈿夥罩械臒岱纸馓匦?并采用 Coats-Redfern積分法對(duì)亞油酸甲酯的熱解過程進(jìn)行動(dòng)力學(xué)分析,建立了熱分解動(dòng)力學(xué)模型,計(jì)算了相應(yīng)的動(dòng)力學(xué)參數(shù)。結(jié)果表明,亞油酸甲酯在j種氣氛中的熱分解均為兩步分解過程,且在氧氣氣氛中的熱安定性較差。隨著升溫速率提高,熱解區(qū)間向高溫區(qū)移動(dòng),熱解活化能和指前因子呈較好的動(dòng)力學(xué)補(bǔ)償效應(yīng),且在不同升溫速率下具有不同的熱解反應(yīng)機(jī)理函數(shù)。熱分解率計(jì)算值與實(shí)測(cè)值的誤差統(tǒng)計(jì)分析結(jié)果表明,數(shù)值模擬計(jì)算值與實(shí)測(cè)值的誤差在10%左右,動(dòng)力學(xué)模型可有效預(yù)測(cè)亞油酸甲酯的熱分解過程。關(guān)鍵詞:亞油酸甲酯:熱重分析:熱解特性;動(dòng)力學(xué)圖分類號(hào):TQ050文獻(xiàn)標(biāo)識(shí)碼:ADOI:10.3969/ L.Issn.1003-9015.201602.022Studies of Methyl Linoleate Thermo-Decomposition Kinetics by Thermal AnalysisWANG Xue-chun", FANG Jian-hua, CHEN Bo-shui, CHEN Er-yu, JIA Xian-bu(1. Department of Vehicle Maintenance, Hangzhou Academy of Non-Commisioned Officer of CAPFHangzhou 310023, China; 2. Department of Military Oil Application Administration EngineeringLogistical er401311, China)Abstract: Thermo-decomposition characteristics of methyl linoleate were investigated using agravimetric analyzer under nitrogen and oxygen atmospheres, respectively. The decomposition kineticsof methyl linoleate was analyzed by Coats-Redfern integral method. The kinetic models and parameters forthermo-decomposition of methyl linoleate were built and calculated. The results indicate thatthermo-decomposition of methyl linoleate under nitrogen or oxygen atmosphere is a two-step process, andmethyl linoleate exhibits relatively worse thermo-stability under oxygen atmosphere. Moreover, thedecomposition temperature of methyl linoleate increases with the increase of heating rates. The decompositionactivation energy and the pre-exponential factor present good kinetic compensation effects, and the kineticmechanism functions are different under different heating rates. Furthermore, statistical analysis also show thethe relative error of the decomposition rate between calculated and experimental values is about 10%demonstratesthat the kinetic models are reliable and effective in predicting thermo-decomposition processes ofmethyl linoleateKey words: methyl linoleate; thermo-gravimetric analysis; thermo-decomposition characteristics; kinetic前言隨著能源消耗量日益增加以及礦物燃料的日趨枯竭,迫切要求新型石油替代能源的快速發(fā)展,其中,生物柴油作為一種新型能源,已受到世界各國的普遍關(guān)注3。研究表明4,發(fā)動(dòng)機(jī)在高溫條件下工作收稿日期:2014-12-17;修訂日期:2015-0409中國煤化工基金項(xiàng)目:國家自然科學(xué)基金(51375491):重慶市自然科學(xué)基金CSTC,2014 ICYJAA50021):后勤作者簡(jiǎn)介:王學(xué)春(1990-),男,甘肅宕昌人,武警杭州士官學(xué)校助教,碩士。通訊聯(lián)系人:方建華HaCNMHG30卷第2王學(xué)春熱分析的亞油酸甲酯熱解動(dòng)力學(xué)研究過程中,燃料會(huì)通過滲流或燃?xì)鈯A帶進(jìn)入曲軸箱,造成發(fā)動(dòng)?xùn)i油持續(xù)稀釋和污染等問題。然而,由于生物柴油熱解化學(xué)行為和機(jī)制的復(fù)雜性,致使學(xué)者對(duì)生物柴油誘導(dǎo)發(fā)動(dòng)機(jī)潤(rùn)滑油品質(zhì)衰變的熱分解特性和動(dòng)力學(xué)研究至今還沒有深入的開展。實(shí)際上,生物柴油的熱不穩(wěn)定性是受其組成中不飽和脂肪酸的甲酯結(jié)構(gòu)的影響,因此,研究和揭示不飽和脂肪酸甲酯的熱分解行為及動(dòng)力學(xué)特性,對(duì)了解生物柴油誘導(dǎo)發(fā)動(dòng)機(jī)油劣化的本質(zhì)具有十分重要的理論意義和工程應(yīng)用價(jià)值。本文采用熱分析法對(duì)亞油酸甲酯的熱分解特性及其動(dòng)力學(xué)規(guī)律進(jìn)行初步的研究,以期進(jìn)一步了解生物柴油的熱分解特性及其對(duì)發(fā)動(dòng)機(jī)油的影響2實(shí)驗(yàn)部分2.1材料與儀器(1)亞油酸甲酯:分析純,昊?；瘜W(xué)(上海)有限公司。(2)SDTQ600型熱分析儀(TG-DSC:美國范德比爾特公司生產(chǎn)。22實(shí)驗(yàn)方法采用SDrQ600熱分析儀對(duì)亞油酸甲酯進(jìn)行熱重分析。取試樣7mg置于熱天平的托盤內(nèi),選擇4個(gè)不同升溫速率,從室溫至600℃進(jìn)行熱重分析,自動(dòng)記錄熱解過程的質(zhì)量變化,可以得到連續(xù)熱重(TG)記錄曲線和微分質(zhì)量損失熱解(DTG)曲線。熱天平的操作條件為:分別以高純氮?dú)夂脱鯕鉃檩d氣,氣體流速為50 mL min-1,程序升溫3結(jié)果與討論3.1亞油酸甲酯熱解特性不同性質(zhì)的熱解氣氛對(duì)試樣熱解特性的影響很大。在升溫速率B=10℃min4的條件下,考察亞油酸甲酯在氧氣氛下的熱氧化分解特性。為對(duì)比相同條件下,反應(yīng)氣氛對(duì)亞油酸甲酯的熱分解特性的影響,在氮?dú)夥障峦瑫r(shí)進(jìn)行熱解實(shí)驗(yàn)。兩種不同氣氛下亞油酸甲酯 TG/DTG曲線見圖1,熱解特性參數(shù)見表1。4.11%DIGDIG喜60|17c165℃-84.7%269℃0100200300400500600100emperature/℃(a)N2 atmosphere(b)O2 atmosphe圖1油酸甲酯在不同氣氛下的 TG/DTG曲線(B=10℃min2)Fig 1 TG/DTG curves of methyl linoleate at different atmospheres(B= 10C.min表1亞油酸甲酯在不同氣氛下熱解特性參數(shù)Table 1is parameters of methyl linoleate at different atmosphereTemperatureAtmosphere(dMldr)max Loss mass Temperature Tma(dm/d r)matLoss massange/℃rae/% range/℃rate /%o170l10~1450.1654.11ak temperature of DTG curve. C:(dM/d t)max the maximum weight loss rate.r-7269Stage II 210-30094.9由圖1和表1可以看出,亞油酸甲酯在兩種保護(hù)氣氛下的熱解特性相似。氮?dú)夥諊?圖1a),在170°℃和297℃處,DTG曲線上出現(xiàn)兩個(gè)大的吸熱峰,分別與TG曲線上的兩個(gè)失重臺(tái)階相對(duì)應(yīng),質(zhì)量26H中國煤化工269℃),CNMHG甲酯在兩406高?；瘜W(xué)工程學(xué)報(bào)2016年4月種保護(hù)氣氛中的熱解特性有一定區(qū)別,在氧氣氛圍中起始失重溫度、終止失重溫度、失重速率峰值溫度均較在氮?dú)夥諊械?說明亞油酸甲酯在氧氣氣氛中具有較差的熱安定性,這是因?yàn)閬営退峒柞シ肿又泻袃蓚€(gè)不飽和雙鍵,在氧氣氛圍中不僅發(fā)生熱分解反應(yīng),還可能發(fā)生由雙鍵誘導(dǎo)引發(fā)的系列熱氧化反3.2升溫速率對(duì)亞油酸甲酯熱解特性影響分別在氮?dú)夂脱鯕鈿夥?程序升溫30-600的條件下,考察亞油酸甲酯在不同升溫速率(10、15、20、30℃min-)下的熱解特性,結(jié)果見圖2。表2所示為不同升溫速率下的熱解特性參數(shù)。從圖2(a)可以看出,在氮?dú)夥諊?亞油酸甲酯的DTG曲線上有一個(gè)弱吸熱峰和一個(gè)強(qiáng)吸熱峰,與TG曲線上兩個(gè)失重臺(tái)階相對(duì)應(yīng),且隨著升溫速率增加,G曲線向高溫區(qū)移動(dòng),失重率逐漸增大,起始失重溫度和終止失重溫度都明顯升高,最大熱解失重速率(dM/dr)。及其對(duì)應(yīng)的峰值溫度Tmx也相應(yīng)的增大,特別是當(dāng)溫度升到300°吋亞油酸甲酯幾乎完全分解。這是因?yàn)樯郎厮俾试黾?試樣達(dá)到熱解所需溫度的響應(yīng)時(shí)間變短,從而加速熱分解反應(yīng)的進(jìn)行。另一方面,升溫速率的提高使熱解反應(yīng)活化能減小,還可能與傳熱滯后有關(guān)8。從圖2(b)可以看出,在氧氣氛圍內(nèi),亞油酸甲酯熱解曲線隨著升溫速率的提高與在氮?dú)夥諊械淖兓厔?shì)相似1000.510020030040050060005010015020025030035040045020(a)N2 atmosphere(b)O2 atmosphere圖2亞油酸甲酯在不同升溫速率下的 TG/DTG曲線Fig 2 TG/DTG curves of methyl linoleate at different heating rates10℃·min1TG15℃ min TG20℃ min tG30℃min1TG10℃ min Dto15℃min-DrG20℃ min DtG30℃ min- DTG表2不同升溫速率下亞油酸甲酯的熱解特征值Table 2 Main parameters of methyl linoleate pyrolysis at different heating ratesN2 atmosphereemperaturedM/dt)max Loss mass Temperature TLoss massrte/% range/℃/℃/%,℃rate/%Stage I05005-21017015.2110-1450.165115-2250.27913.5115-1601670.l6120-2300.280120-1701720.2073.6l0.286125-1750.212292145~285160~310283Stage ll230-3103.14170-31581175-3301.853.3亞油酸甲酯的非等溫?zé)岱纸鈩?dòng)力學(xué)3.3.1熱分解動(dòng)力學(xué)模型在程序升溫條件下,對(duì)亞油酸甲酯在氮?dú)夂脱鯕鈿夥罩械姆堑葴責(zé)岱纸鈩?dòng)力學(xué)進(jìn)行分析。假設(shè)試樣在程序升溫下進(jìn)行熱解反應(yīng),試樣初始質(zhì)量為m,當(dāng)?shù)竭_(dá)時(shí)間t時(shí)刻,試樣質(zhì)量變?yōu)閙2,試樣最終殘余質(zhì)量為m2,則試樣熱分解速率可表示為:da/dr=f(a),式中:k為反應(yīng)速率常數(shù);a為失重率,a=(m-m2)/(m-mn),假設(shè)熱分解反應(yīng)機(jī)理函數(shù)f(a)=(1-a),中國煤化工根據(jù) Arrhenius方程試樣熱分解速率可表示為CNMHG第30卷第2期。王學(xué)春等:基于熱分析的亞油酸甲酯熱解動(dòng)力學(xué)研究da/dt=Aexp(E/RTf(a)=Aexp(E/RT)(1-a)(1)將升溫速率B=dT/dt代入(1)式可得:da/dT=exp(E/RT)(1-a)3.32動(dòng)力學(xué)參數(shù)計(jì)算根據(jù) Coats- Redfern'9⑩積分法,將方程(2)整理并取近似值可得:當(dāng)n=1時(shí)In(1AR2RTE當(dāng)n≠1時(shí),AR( 2RTEInE對(duì)于一般的反應(yīng)而言,由于E比較大,2F遠(yuǎn)小于1,則方程(3)和方程4)可以簡(jiǎn)化為當(dāng)n=1時(shí),In(1-a)AR EBE RT當(dāng)n≠1時(shí),(1-a)AR EIn(6)BE RT對(duì)圖2中亞油酸甲酯在不同升溫速率下的熱分解實(shí)驗(yàn)數(shù)據(jù)進(jìn)行線性擬合,當(dāng)n=1時(shí),以hnhn(1-a)對(duì)上作圖;當(dāng)n≠1時(shí),令=(1-a),x=1,此時(shí)以Y對(duì)X作圖。表3和表4中較高的相關(guān)系數(shù)(R2)表明通過 Coats-Redfern積分法擬合的動(dòng)力學(xué)參數(shù)值是可信的。表3亞油酸甲酯在不同升溫速率下的熱解動(dòng)力學(xué)參數(shù)(n=1)Table 3 Kinetic parameters of methyl linoleate pyrolysis at different heating rates (n= 1)Pyrolysis stageTemperature rangeTemperature/k]. morange/c kJ me105-2104591.700.992110-14512424.60.99320-23037,7-0.00420-170120-2301.l125-171141058.2145-2855.08230-310170-315表4亞油酸甲酯在不同升溫速率下的熱解動(dòng)力學(xué)參數(shù)n≠1)Table Kinetic parameters of methyl linoleate pyrolysis at different heating rates(n+1)PyrolysisO2 atmospheretageC. Temperature Reactionrange/c order(n)/k- molIn aTemperature Reactionange/C order(n) /k-mor- InA R0990110~1456.10.9960500050115-225120~2309,1636-0,0350.997120~17020.50.2030993225~3053.320990160~3105273040.999StageⅡ230-310170-31549.6230~33043.03.33動(dòng)力學(xué)可靠性分析圖3所示為升溫速率B=10℃min時(shí)得到的亞油酸甲酯分別在兩種保護(hù)氣氛中的熱解過程失重曲線與模型預(yù)測(cè)失重曲線的對(duì)比。可以看出除了在起始處和熱解終了時(shí)模H中國煤化工外,在亞油酸甲酯主要熱解反應(yīng)階段,計(jì)算模型能夠很好地預(yù)測(cè)實(shí)際熱解過程CNMHG高?；瘜W(xué)工程學(xué)報(bào)2016年4月5000100200300400500600Temperature/℃(b)O2 atmosph圖3亞油酸甲酯熱解動(dòng)力學(xué)計(jì)算值與實(shí)驗(yàn)值對(duì)比Fig3 Comparison of experimental and calculated data of methyl linoleate pyrolysisexperimental x(n= 1)Stage I calculated X (n= 1)Stage II calculated +(n+ 1) Stage I calculated +(n+ 1)Stage Il進(jìn)一步采用均方根誤差(RMSE)和平均絕對(duì)百分誤差(MAPE作為評(píng)估指標(biāo),對(duì)模型的可靠性進(jìn)行分析兩種誤差表達(dá)式為RMSE=LEE-C,)". MAPE-2E-C 100其中,p為校正集樣本數(shù),E表示按照標(biāo)準(zhǔn)實(shí)驗(yàn)方法測(cè)得的校正集第i個(gè)樣本的屬性真實(shí)值,C表示模型預(yù)測(cè)的屬性值表5不同計(jì)算方法數(shù)值計(jì)算統(tǒng)計(jì)誤差分析表5所示為不同升溫速率下計(jì)算值與實(shí)測(cè)Table 5 Numerical statistical error analysis of different值的統(tǒng)計(jì)誤差分析結(jié)果。分析可知,數(shù)值模擬ErrorAtmosphe計(jì)算結(jié)果與實(shí)驗(yàn)數(shù)據(jù)的誤差都在可控范圍內(nèi),RMSE7.61445.78.0方面說明本文選取的熱解機(jī)理函數(shù)MAPE6,213.7f(a)=(1-a)"與亞油酸甲酯的熱解規(guī)律是≠1RMSE13.111.62.2MAPE6.72193.85,9致的,另一方面說明采用 Coats- Redfern積分法863PE7313.78.313.1分析亞油酸甲酯熱解動(dòng)力學(xué)模型是可信n≠1RMSE6916411414.6MAPE 8.50717910.33.34動(dòng)力學(xué)補(bǔ)償效應(yīng)對(duì)亞油酸甲酯在不同升溫速率下獲得的動(dòng)力學(xué)參數(shù)進(jìn)行線性擬合,結(jié)果如圖4所示。分析發(fā)現(xiàn),亞油酸甲酯在不同升溫速率下的E-lnA曲線擬合方程線性關(guān)系顯著,線性相關(guān)系數(shù)在0.965-0.998,說明亞油酸甲酯在兩種保護(hù)氣氛中的熱解反應(yīng)活化能和指前因子呈現(xiàn)出較好的動(dòng)力學(xué)補(bǔ)償效應(yīng)關(guān)系,多)N2 atmosphere4動(dòng)力學(xué)補(bǔ)償效應(yīng)Fig 4 Kinetic compents between activation and(n= l)Stage I◆一(n=1) Stage▲-(n≠1) StageTH中國煤化工CNMHG第30卷第2期王學(xué)春等:基于熱分析的亞油酸甲酯熱解動(dòng)力學(xué)研究表6亞油酸甲酯在不同氣氛下的動(dòng)力學(xué)補(bǔ)償效應(yīng)關(guān)系Table 6 Relationship of kinetic compensation effects for methyl linoleate at different atmospheresReaction order (n)Oz atmosphereRegression equationRegression equation RlnA1=0.24343E1-9407460.96n=0.29643E1-1234367StageⅡLnA2=0.22682E2905940n1=0.28753E2-12.026200.983n≠1Stage IlnA1=0.24159E1-8.789670977n1=0.29995E1-12.407000.995Stage llLnA2=0.23063E2-12343670995Ln2=0.26454E-10.829630.9934結(jié)論Ⅰ)亞油酸甲酯在氮?dú)夂脱鯕鈨煞N保護(hù)氣氛中的熱分解過程,均包含兩步分解,且亞油酸甲酯在氧氣氛圍具有較差的熱安定性。(2)隨著升溫速率的增加,亞油酸甲酯在兩種保護(hù)氣氛下的TG曲線冋髙溫偏移,失重率呈現(xiàn)逐漸增大的趨勢(shì),熱分解過程的起始失重溫度和終止失重溫度都明顯向高溫方向移動(dòng),最大熱解失重速率(dM/dr)及其對(duì)應(yīng)的峰值溫度Tmx也相應(yīng)的增大,放熱量呈現(xiàn)逐漸增大的趨勢(shì)。3)利用 Coats- Redfern積分法求解亞油酸甲酯在不同升溫速率下熱分解反應(yīng)動(dòng)力學(xué)參數(shù),并將模型預(yù)測(cè)值與實(shí)驗(yàn)結(jié)果進(jìn)行對(duì)比。分析表明:亞油酸甲酯在不同保護(hù)氣氛下具有不同的熱解機(jī)理函數(shù),熱分解反應(yīng)表觀活化能和指前因子之間表現(xiàn)岀較好的動(dòng)力學(xué)補(bǔ)償效應(yīng)關(guān)系,且數(shù)值模擬計(jì)算結(jié)果與實(shí)驗(yàn)數(shù)據(jù)吻合較好,能夠很好地解釋和預(yù)測(cè)亞油酸甲酯熱解過程參考文獻(xiàn)[1 Lin L, Cunshan Z, Vittayapadung S, et al. Opportunities and challenges for biodiesel fuel [J]. Applied Energy, 2011, 88(4)1020-10312] Demirbas A Progress and recent trends in biodiesel fuels [J]. Energy Conversion and Management, 2009. 50(1): 14-34[3] Nigam P S, Singh A. Production of liquid biofuels from renewable resources [J]. Progress in Energy and Combustion Science,2011,37(1):52-68,[4] Wu J, Chen B S, Fang J H, et al. Effect of biodiesel on oxidation, detergency and lubricity of diesel oil []. China PetroleumProcessing and Petrochemical Technology, 2011, 13(4): 58-63.[5] Gili F, Igartua A, Luther R, et al. The impact of biofuels on engine oil performance [J]. Lubrication Science, 2011, 23(7): 313-330[6] Wongsiriamnuay T, Tippayawong N. Thermogravimetric analysis of giant sensitive plants under air atmosphere []. BioresourceTechnology,2010,101(23):93149320[7] Park Y H, Kim J, Kim SS, et al. Pyrolysis characteristics and kinetics of oak trees using thermogravimetric analyzer andmicro-tubing reactor [J Bioresource Technology, 2009, 100(1): 400-405HUANG Yun-ong(黃云龍), GUO Qing-jie郭慶杰, TIAN Hong-jing(田紅景),eral. Study on pyrolysis kinetics of bamboo(餐廚垃圾熱解實(shí)驗(yàn)研究)[ J]. J Chem Eng of Chinese Univ(高?；瘜W(xué)工程學(xué)報(bào),2012.,26(4):721-728[9] Guo X, Wang S, Guo Z, et al. Pyrolysis characteristics of bio-oil fractions separated by molecular distillation [J]. Applied Energy2010,87(9):2892-2898[10] Zou S P, Wu Y L, Yang M D, et al. Pyrolysis characteristics and kinetics of the marine microalgae Dunaliella tertiolecta usingthermogravimetric analyzer []. Bioresource Technology, 2010. 101(1): 359-365中國煤化工CNMHG