第58卷第5期化工Vol 58 No 52007年5月JournalChemical Industry and Engineering (China)研究簡報(bào)椰殼、椰殼渣與脫灰椰殼渣熱解及熱解動(dòng)力學(xué)姚伯元,竇智峰,黃廣民,劉仁成(海南大學(xué)海南省精細(xì)化工重點(diǎn)實(shí)驗(yàn)室,海南?？?70228)關(guān)鍵詞:椰殼;椰殼渣;脫灰椰殼渣;熱解;動(dòng)力學(xué)中圖分類號:TQ013文獻(xiàn)標(biāo)識(shí)碼:A文章編號:0438-1157(207)05-1210-0Pyrolysis and pyrolysis kinetics of coconut shell, coconut shell residueand de-ashed coconut shell residueYAO Boyuan, DOU Zhifeng, HUANG Guangmin, LIU Rencheng( Hainan Provincial Key laboraof Fine Chemicals, Hainan University, Haikou 570228, Hainan, China)Abstract: The pyrolysis of coconut shell, coconut shell residue and de-ashed coconut shell residue wasstudied with the thermogravimetric technique, and the pyrolysis kinetics models were established. It wasfound that for coconut shell residue and de-ashed coconut shell residue, pyrolysis mainly occurred between280-370C, and there was only a single peak in their DtG curves. but in the case of raw coconut shell,two stages of 230--300C and 300-350C, were involved in the pyrolysis process, which resulted in twopeaks in the DTG curve. Apparent activation energies for the pyrolysis of these three materials wereestimated, and the difference of apparent activation energies in the low temperature range was more evidentthan in the high temperature range and the highest reaction rate appeared in the high temperaturestage. When used for making activated carbon, coconut shell residue and de-ashed coconut shell residuehave more advantages than coconut shell. The pyrolysis temperature is in a narrow range. The pyrolysisprocess is easy to control and is noted for energy saving.Key words: coconut shell: coconut shell residue de-ashed coconut shell residue; pyrolysis; kinetics引言固定碳的貢獻(xiàn)較小。木質(zhì)素具有苯丙烷型、非結(jié)晶性三維高分子網(wǎng)狀結(jié)構(gòu),熱分解溫度相對較高,通海南具有豐富的椰殼資源,2004年椰殼總產(chǎn)過熱縮聚反應(yīng)形成炭骨架。因此,在以椰殼制備活量約2.42億個(gè),大多數(shù)用作制備椰殼活性炭原性炭時(shí),實(shí)際上是利用原料中的木質(zhì)素。研究表料口3。椰殼( coconut shel,Cs)組分包括纖維明+,椰殼經(jīng)酸水解處理后,其中的半纖維素等素、半纖維素和木質(zhì)素等。在熱解過程中,纖維素水解為聚糖(包括木聚糖、葡聚糖、果葡聚糖等)和半纖維素?zé)岱€(wěn)定性差,在較低熱解溫度下發(fā)生熱寡糖以及葡萄糖、木糖等單糖,經(jīng)分離提純后可得分解反應(yīng),形成的小分子以揮發(fā)分的形式析出,對到具有重要經(jīng)濟(jì)價(jià)值的單糖和寡糖。椰殼酸水解2006-09—18收到初藕,2006-12-11收到修改橫Recelved date: 2006-09-18.聯(lián)系人及第一作者:姚伯元(1955-),男,教授Corresponding author: Prof, YAO Boyuan. E-mail: yby G基金項(xiàng)目:科技部重大基礎(chǔ)研究前期研究專項(xiàng) haine. edu.cn(2003cCA03600)1?？谑兄攸c(diǎn)科技項(xiàng)目(20021225)第5期姚伯元等:椰殼、椰殼渣與脫灰椰殼渣熱解及熱解動(dòng)力學(xué)1211·后,經(jīng)離心分離含糖母液后得到的固體殘?jiān)礊橐潭ㄌ寂cCSR差別不大,說明脫灰過程中減少了殼渣( coconut shell residue,CsR),主要成分為無機(jī)組分,而對有機(jī)組分含量影響不大。未降解的木質(zhì)素等,可以作為制備高性能活性炭的2.2熱解過程分析優(yōu)質(zhì)原料。對椰殼渣進(jìn)行脫灰處理后,可得到脫原料的熱失重曲線(TG曲線)見圖1,其熱灰椰殼渣( deashed coconut shell residue,失重速率曲線(DTG曲線)為TG曲線的一階微DCR)。CSR與DCSR都可以制備高性能活性炭,分曲線,見圖2用DCSR制備還可滿足GB/T138031199對木質(zhì)顆?；钚蕴恳患壠坊曳植怀^3%的要求。炭化過程是影響產(chǎn)品性能的重要因素。炭化過程中主要發(fā)生熱分解與熱縮聚反應(yīng),研究和掌握其過程與機(jī)理很有必要。椰殼熱解過程已有文獻(xiàn)報(bào)09000道3,但其熱解動(dòng)力學(xué)、CSR與DCSR的熱解及熱解動(dòng)力學(xué)研究尚無報(bào)道1實(shí)驗(yàn)部分實(shí)驗(yàn)樣品為海南CS、CSR與DCSR。DCSR為在濃度為10%的磷酸溶液中浸漬3h進(jìn)行脫灰處理后的CSR。圖1CS、CSR和DCSR的TG曲線用粒度小于74pm的原料,在氮?dú)獗Ｗo(hù)下Fig. 1 TG curves of CS, CSR and DCSR用美國TA公司Q600型熱重分析儀進(jìn)行熱重實(shí)驗(yàn)。實(shí)驗(yàn)條件為氮?dú)饬髁?0ml·min-,升溫速率5℃·min-1,樣品用量0.4~0.7mg。炭化熱CSR解實(shí)驗(yàn)在SK2-2-10型管式電阻爐上進(jìn)行。2結(jié)果與討論2.1原料的工業(yè)分析灰分按GB/T12496.3-199水分按GB/T12496.4-1999、揮發(fā)分按GB212-91等規(guī)定測定,固定碳由差減法計(jì)算,結(jié)果見表1。100200300400500600700800表1原料的工業(yè)分析2cs、CSR和DCSR的DTG曲線Table 1 Industry analysis of different coconut shellsFig 2 DtG curves of CS, CSR and DCSRM,d/% A/% V/% FCod/%由原料的TG曲線可知,其熱解過程可分為以9.180.8874.5414.52下階段。0.7970.1820.55(1)干燥階段:從室溫到150℃。失重主要由CSR7520.2371.0621.19失水引起,包括失去外在水和內(nèi)在水,一般占原料質(zhì)量(空氣干燥基)的10%以下,見表2。由表1可知,CS、CSR、DCSR雖均屬于高揮(2)熱分解階段:從250~370℃。失重主要發(fā)分、低固定碳原料,但也有差異。CSR與DSCR由于原料中有機(jī)組分的熱分解。從TG曲線可以看的灰分和揮發(fā)分含量小于椰殼,而固定碳含量高于出,3種原料在此階段失重都最大,在50%以上椰殼,說明CS經(jīng)過水解后,其中有機(jī)組分發(fā)生明見表2。由DTG曲線可知,3種原料最大失重速顯變化。研究表明,CSR與DCSR炭化收率都率峰都出現(xiàn)在該溫度范圍,這與纖維素、半纖維素比CS高。DSCR的灰分明顯低于CSR,揮發(fā)分和及木質(zhì)素都在該溫度范圍內(nèi)發(fā)生熱分解反應(yīng)有關(guān)。1212·化工學(xué)報(bào)第58卷表23種椰殼原料在不同熱解階段的失重比例Table 2 Mass loss ratio of three types of coconut shells in different pyrolysis stagesDryness stageThermal pyrolysis stageThermal polycondensation stageSampleperatureMass-lossIass-lossrange/Cratio/%range/℃range/℃ratio/%0-150250-37015.130-150250-370370-80017.8DSR30-150370-80018.6由于3種原料組分中各種化學(xué)鍵對熱穩(wěn)定性存在差率相同,則熱解反應(yīng)微分速率方程為別,因此在升溫過程中,鍵能較低的各種橋鍵首先d=k(1-a)斷裂,各種含氧官能團(tuán)(一OH、-COOH、C=0、OCH2等)支鏈、脂肪族側(cè)鏈等隨者式中a表示熱解反應(yīng)轉(zhuǎn)化率;k表示反應(yīng)速率常溫度進(jìn)一步升高也開始斷裂,生成的自由基碎片最數(shù);n表示反應(yīng)級數(shù)。終生成穩(wěn)定的小分子,以揮發(fā)分形式迅速離開體轉(zhuǎn)化率a可表示為系,致使體系快速失重aa(3)熱縮聚階段:370℃以上。失重主要由于式中W、W分別為失重前后樣品質(zhì)量;W表原料中有機(jī)組分發(fā)生熱縮聚反應(yīng)。隨著反應(yīng)溫度的示熱解反應(yīng)t時(shí)反應(yīng)物質(zhì)量升高,芳環(huán)上的C—H等鍵能較大的鍵發(fā)生斷裂將 Arrhenius公式k=Aexp(一E/RT)代人生成的含有芳環(huán)結(jié)構(gòu)的自由基碎片之間發(fā)生芳環(huán)間式(1)得脫氫縮聚反應(yīng)。隨著縮聚反應(yīng)進(jìn)行,芳香分子層片di- atexp(-e/rT)J(1-a)增大,形成以石墨微晶為主的亂層堆積炭結(jié)構(gòu)。伴隨著芳環(huán)間熱縮聚反應(yīng),僅析出H2,故該階段失當(dāng)升溫速率固定時(shí),則有dT/dt=C,C為常數(shù),代入式(3)化簡得重較緩和。在DTG曲線上,CS存在明顯的重疊雙峰,出=(1-a)"exp(一E/RT)分別位于230~300℃與300~350℃兩個(gè)溫度區(qū)間。用 Coats-Redfern積分法,對式(4)進(jìn)行積分。而CSR和DCSR只存在單峰,位于280~370℃之當(dāng)n=1時(shí)間。一般認(rèn)為,半纖維素?zé)峤夥鍖?yīng)于250~00℃之間。可見230~300℃處對應(yīng)于半纖維素的叫[=](-2)]是(③熱解。CS經(jīng)酸水解后,其中的半纖維素等易降解當(dāng)n≠1時(shí)的組分比例顯著下降,因此CSR和DSCR以未降叫[==m]1類(-g)解的纖維素和木質(zhì)素為主,其DTG曲線只存在單由于E>2RT,故可令2RT/E≈0,則峰。在此溫度區(qū)間,CSR和DSCR的熱失重比例明顯小于CS的失重比例(見表2)。CSR和DSCR因木質(zhì)素含量相對增加,其炭化料收率比CS高,換成如下形式因此,當(dāng)熱解反應(yīng)視為一級反應(yīng)時(shí),式(5)可變和熱重實(shí)驗(yàn)結(jié)果吻合。炭化實(shí)驗(yàn)發(fā)現(xiàn),3種原料析出大量揮發(fā)分的溫叫m=]一最÷6度范圍有明顯區(qū)別:CS在250℃左右,而CSR和式中A為指前因子,min-;E為活化能,kJDSCR在300℃左右,說明發(fā)生劇烈熱解反應(yīng)的溫mol;R為氣體常數(shù),8.31J·mol-·K-1。度不同,顯然與CSR和DSCR中缺少半纖維素令Y=n[-hn(1-a),T2),X=1/T,由有關(guān)。式(8)可知,此時(shí)yX為線性關(guān)系,斜率為23熱解反應(yīng)動(dòng)力學(xué)E/R,截距為ln(AR/CE)。因此,由直線的斜在熱解反應(yīng)過程中,假定小分子化合物全部以率和截距即可求得E和A等動(dòng)力學(xué)參數(shù)。揮發(fā)分形式析出,即熱解反應(yīng)速率與揮發(fā)分析出速實(shí)驗(yàn)中分別選取原料主要熱解反應(yīng)溫度區(qū)間第5期姚伯元等:椰殼、椰殼渣與脫灰椰殼渣熱解及熱解動(dòng)力學(xué)1213表3回歸分析與熱解反應(yīng)表觀動(dòng)力學(xué)參數(shù)計(jì)算結(jié)果Table 3 Calculated results of apparent dynamies parameters and linear regressionSamplerange/KR/kJ·mol-1/min488-553Y=7.50-11845.2X一0.99898.432.15×1030.0275Y=-0.55-7409.5X61.574.25×1010.1286613-638Y=14.96-16882.1X0.9980.834140.295.33×10110.9905508-533Y=13.14-15080.4X0.9920.834125.327.74X10100.0197538-608Y=0.86-8548.1X-0.9990.60671.042.03×1050.0673Y=20.34-20528.7X0.9940.765138.492.21×1010.71778-543Y=18.43-18255.3X84X10130.0146548-608Y=2.72-9716.4X0.9990.64180.741.47×1060.0736Y=14.10-16664.9X0.7668Note: R-correlation coefficient: Ro-correlation cofficient critical value (a=0. 01)488~648K(215~375℃),溫度間隔為5K,見過程中,半纖維素降解為木糖等,因此CSR和圖3。對經(jīng)上述變換后的熱重實(shí)驗(yàn)數(shù)據(jù)回歸處理,DCSR以纖維素和木質(zhì)素為主,熱穩(wěn)定性相對較可得到X對Y的線性方程。在a=0.01的置信水高,除含氧官能團(tuán)和支鏈斷裂外,熱穩(wěn)定較高的主平上,均滿足R>R°,因此各段線性關(guān)系均顯著。要組分尚未發(fā)生熱分解反應(yīng),因此表觀活化能較將r=-E/R,b=ln(AR/CE)聯(lián)立后,求出3種高,平均表觀反應(yīng)速率k值較低。原料熱解反應(yīng)的表觀指前因子A及表觀活化能E在高溫段時(shí),3種原料的表觀活化能E值均較等動(dòng)力學(xué)參數(shù),見表3。低溫段高,但差別減小。CS與CSR的E值非常接CS488-553近。在此溫度段,3種原料的熱解反應(yīng)表觀速率?！铩魯?shù)k均達(dá)到最大值,分別為0.9905、0.7177、0.7668min-1,在DTG曲線上表現(xiàn)為都出現(xiàn)峰說明3種原料中熱穩(wěn)定性較高、活化能較大的化學(xué)-15.0鍵開始斷裂,主要熱解反應(yīng)激烈進(jìn)行,并達(dá)到最大日-160反應(yīng)速率。DCSR的E值高于CS和CSR,與脫灰作用有-17.0關(guān)。無機(jī)物中的堿金屬與堿土金屬在化學(xué)反應(yīng)中都-18.000016000170.00180001900020有催化作用,可降低反應(yīng)活化能。DCSR的A僅為0.23,明顯低于CS的0.88與CSR的0.79。同圖3CS、CSR和DCSR表觀動(dòng)力學(xué)樣原因造成CSR和DCSR的k值明顯低于CS模型曲線與擬合直線圖研究表明,3種原料制備高性能活性炭時(shí),炭Fig 3 Modeled and fitted curves of apparentdynamics of CS, CSR and CSR化前期熱分解有明顯差異,炭化后期基本相同。上述建立的熱解動(dòng)力學(xué)模型可較好地解釋3種原料的從表3可以看出,在低溫段,CS表觀活化能熱解反應(yīng)過程。此研究方法同樣適用于組分復(fù)雜的為98.43kJ·mol-1,明顯低于CSR的125.32其他木質(zhì)類原料。3種原料炭化過程后期的熱縮聚kJ·mol-和DCSR的151.70kJ·mol-l;Cs的階段對炭化料性質(zhì)也有影響,動(dòng)力學(xué)過程有待平均表觀反應(yīng)速率k值為0.0275,明顯大于CSR探討。的0.0197和DCSR的0.0146,說明CS較CSR和DCSR在低溫段更易進(jìn)行熱分解反應(yīng)。在DTG曲3結(jié)論線上,表現(xiàn)為CS有明顯的熱解峰,而CSR和(1)作為制備高性能活性炭的原料,CSR與DCSR沒有。顯然,由于CS中含有大量的半纖維DCSR比CS有更多優(yōu)點(diǎn):可形成炭骨架的組分多素,在較低溫下即可發(fā)生熱解反應(yīng),因此熱解所需熱解初期揮發(fā)分少,熱解反應(yīng)溫度集中。因此炭化活化能較低,平均表觀速率k值大。在酸水解處理過程更易控制,耗能更少,更易制備低灰優(yōu)質(zhì)品?！?214第58卷(2)利用熱重技術(shù),采用 Coats-Redfern積分5] Huang Guangmin(黃廣民), Yao Boyuan(姚伯元), Liang法求解的一級熱解反應(yīng)動(dòng)力學(xué)模型,可以解釋CSZhenyi(梁振益).TheCSR與DCSR的熱解反應(yīng)過程xylose solution prepared xylose by the coconut shell. FoodScience(食品科學(xué)),2005,26(8):242-246References[6] Wang Zhigao(王志高), Jiang Jianchun(蔣劍春),DengXianlun(鄧先倫), Yang Kaihua(楊凱華). Study ont1 Shi yinrui(施蔭銳), Tang Qifeng(唐啟風(fēng)preparation of powder activated carbon from acid-hydrolysis(趙玉明),Stulignin with H, PO. activation. Journal of Chemical Industryut shell. Chemistry and Industry of Forestof Forest Products(林產(chǎn)化工通訊),2005,39(4):15Products(林產(chǎn)化學(xué)與工業(yè)),1986,6(2):23-28[7] Xia Zhiyong(夏智勇), Guo Shucai(郭樹才). Study[2] Pandolfo A G, Amini-Amoli M, Killingley JS. Activatedthe pyrolysis of preparation of coconut shell CMS. Carboncarbons prepared from shells of different coconut varieties.Techniques(炭素技術(shù)),1998,17(2):15-17[8 Yao boyuan(姚伯元), Huang guangmin(黃廣民),Dou[3] Dai Weidi(戴偉娣), Tao Yuanbo(陶淵博), Zhangzhifeng(竇智峰), Lin baiyun(林白云), DemineralizationYanping(張燕萍), Jiang Jianchun(蔣劍賽). Studies onof Hainan coconut shell and its residue for preparing highpyrolysis of wooden material and structure of the obtainedsurface area activated carbon, Journal of Chemical Industryactivated carbon. Chemistry and Industry of Forestand engineering( China)(化工學(xué)報(bào)),2006,57(6)Products(林產(chǎn)化學(xué)與工業(yè)),2004,24(3):61-64們 Huang Guangmin(黃廣民), Yao boyuan(姚伯元),wang[9] Huang Luxian(黃律先). Technology of Wood PyrolysisHonglei(王宏磊). Study on crystal technology of the(木材熱解工藝學(xué)). Beijing; China Forest Press,1983glucose preparation from coconut shell. Food Science (gi科學(xué)),204,25(10):191-194