華南理工大學(xué)學(xué)報(bào)(自然科學(xué)版)第42卷第10期Journal of South China University of TechnologyVol 42 No. 102014年10月Natural Science Edition)October 2014文章編號(hào):1000-565X(2014)10-0070-05木質(zhì)素單體?；餆峤膺^程的理論分析武書彬鄧裕斌劉超(華南理工大學(xué)制漿造紙工程國(guó)家重點(diǎn)實(shí)驗(yàn)室,廣東廣州510640)摘要:為了深入研究木質(zhì)素的熱解機(jī)理,選用香草醛、香草醇和香草酸作為木質(zhì)素單體模化物模擬熱解過程.運(yùn)用密度泛函理論探討不冋化學(xué)連接鍵的解離順序,并設(shè)計(jì)了4條反應(yīng)路徑(Path1-Path4):Path1和Pah2都生成愈創(chuàng)木酚,但中間過程不同,Path3和Path4則分別以優(yōu)先過程生成鄰苯二酚和苯酚.結(jié)果表明:?；锏膫?cè)鏈甲基會(huì)優(yōu)先解離生成CH4,C1取代基的解離順序取決于其吸電子能力;在熱解過程中,C1取代基不易直接解離,而是會(huì)優(yōu)先發(fā)生外界參與下的解離;3種目標(biāo)產(chǎn)物(愈創(chuàng)木酚、鄰苯二酚和苯酚)都是可能的,且會(huì)優(yōu)先生成鄰苯二酚,其次是苯酚,較難生成愈創(chuàng)木酚;從動(dòng)力學(xué)角度分析,Path2和Path4要優(yōu)于Path1和Path3進(jìn)行;生成同種目標(biāo)產(chǎn)物時(shí)總是香草醇最易進(jìn)行香草醛次之,最難進(jìn)行的是香草酸關(guān)鍵詞:木質(zhì)素;單體?；?熱解;密度泛函理論中圖分類號(hào):TK6;0641.12doi:10.3969/jiss.1000-565X.2014.10.012近年來,世界各國(guó)都在研究生物質(zhì)能的開發(fā)和理;Li等8以木質(zhì)素BO-4高聚模化物為原料進(jìn)行利用,生物質(zhì)熱化學(xué)轉(zhuǎn)化是生物質(zhì)轉(zhuǎn)化利用中的一了熱解實(shí)驗(yàn)但這些都是從原料到產(chǎn)物的宏觀變化個(gè)重點(diǎn),而熱解在其中發(fā)揮著重要的作用2.由于推測(cè),并未真正解釋清楚木質(zhì)素的熱解過程.黃曉生物質(zhì)原料組成的復(fù)雜性,在熱解過程中可能發(fā)生露9和王華靜等0則結(jié)合量化計(jì)算的方法,從理論的化學(xué)反應(yīng)也非常復(fù)雜鑒于這種復(fù)雜性,對(duì)組成生上解釋了木質(zhì)素?；锏牧呀鈾C(jī)理,但他們的研究物質(zhì)各組分的熱解過程進(jìn)行單獨(dú)研究,把握生物質(zhì)多偏重?zé)峤獾臒崃W(xué)過程,而忽略了熱解的動(dòng)力學(xué)的總體熱解過程是非常必要的.植物生物質(zhì)主要由纖維素、半纖維素和木質(zhì)素組成,其中,木質(zhì)素的過程文中選取香草醛、香草醇和香草酸為木質(zhì)素單于結(jié)構(gòu)復(fù)雜化學(xué)鏈接形式多樣,相比于纖維素和半體?；锊捎昧炕?jì)算的方法給出了各取代基的纖維素的熱解機(jī)理更為復(fù)雜因此,了解木質(zhì)素的熱解離順序,探討了生成目標(biāo)產(chǎn)物的可能路徑解機(jī)理對(duì)探索生物質(zhì)熱解機(jī)理具有重要的意義國(guó)內(nèi)外對(duì)木質(zhì)素?zé)峤獾奈墨I(xiàn)報(bào)道很多45,筆實(shí)驗(yàn)部分者曾對(duì)木質(zhì)纖維生物質(zhì)的理化特性和熱解規(guī)律進(jìn)行了全面的研究;婁瑞則以不同種類非木材1.1計(jì)算模型原料的EMAL(酶解/溫和酸解木質(zhì)素)為原料,系選取香草醛、香草醇、香草酸為木質(zhì)素單體?；y(tǒng)地研究了不同條件下的熱解特性及其產(chǎn)物分布,物,并參考文獻(xiàn)[113]給出的實(shí)驗(yàn)構(gòu)象,以此為基并嘗試推斷了木質(zhì)素中部分化學(xué)連接鍵的斷裂機(jī)礎(chǔ)進(jìn)行后續(xù)的理論計(jì)算收稿日期:2013-12-16*基金項(xiàng)目:國(guó)家“973”計(jì)劃項(xiàng)目(2013CB228101);國(guó)家自然科學(xué)基金資助項(xiàng)中國(guó)煤化工作者簡(jiǎn)介:武書彬(1965-),男,教授,博士生導(dǎo)師,主要從事植物纖維類生物THeCNMHG質(zhì)轉(zhuǎn)化為清潔能源和化工原料等的研究E-mail:shubin@seut.edu.cn第10期武書彬等:木質(zhì)素單體?；餆峤膺^程的理論分析1.2路徑設(shè)計(jì)量極小值的穩(wěn)定結(jié)構(gòu);過渡態(tài)經(jīng)過頻率驗(yàn)證均有唯大量的實(shí)驗(yàn)結(jié)果表明,木質(zhì)素及其模化物在熱虛頻且通過了內(nèi)稟反應(yīng)坐標(biāo)(IRC)方法的驗(yàn)證解過程中會(huì)產(chǎn)生較高含量的愈創(chuàng)木酚、鄰苯二酚和鍵解離能(BDE)利用以下公式15進(jìn)行計(jì)算苯酚67.為解釋這一過程,以木質(zhì)素單體模化物為BDE=△r=H(A·)+H(B·)-H(A-B)起始物設(shè)計(jì)了以下4條反應(yīng)路徑:Pth1,C1取代基式中,A-B代表反應(yīng)物,A,和B,代表均裂A-B鍵在熱解過程中均裂離去,生成愈創(chuàng)木酚;Pah2,C1所得的自由基產(chǎn)物,rH是物質(zhì)的標(biāo)準(zhǔn)摩爾反應(yīng)取代基在H的協(xié)助下離去,生成愈創(chuàng)木酚;Path3焓變和Path4則是以優(yōu)先過程分別生成鄰苯二酚和苯反應(yīng)能壘(E)為過渡態(tài)能量E(TS)與反應(yīng)物酚.其中,R=—CHO/CH, OH/-COOH,R·=能量E(R)之差即CHO′·CH2OH:CoOHE。=E(TS)-E(R)式中,TS為過渡態(tài)對(duì)于沒有過渡態(tài)的均裂反應(yīng),這里用鍵解離能Path 1:BDE來作為反應(yīng)能壘ETOCHIMI2結(jié)果與討論H2.1不同基團(tuán)解離能力的比較Path 2:熱解時(shí),木質(zhì)素主要發(fā)生結(jié)構(gòu)單元中C1取代基OCHOCH,OCH的裂解和苯環(huán)上取代基的脫落,為探討不同取代基的解離能力,文中計(jì)算了3種木質(zhì)素單體?；镏械闹饕B接鍵CC1、C30、0-CH3、C4-0和+H.O—H的鍵解離能,并將數(shù)據(jù)列于表1中Path 3:FOCH表1木質(zhì)素單體?；镏兄饕B接鍵的鍵解離能Table 1. Bond dissociation energy of main connections in mono-meric model compounds of ligninkJ/mol連接鍵香草醛香草醇香草酸414.690395.345443.8650—CH3216.278IM3-2IM3-362.92933l.806321.049Path 4S4-1H認(rèn)2從表1中可以看出,模化物中不同連接鍵鍵解OCH離能的相對(duì)大小具有一致的規(guī)律,總是OCH3的IM4-1鍵解離能最低,其次是OH,最高的是C4-0,這表明在熱解過程中側(cè)鏈甲基會(huì)優(yōu)先斷裂,生成CH3和C3位上的酚氧自由基,而后分別被H中和?；镏蠧。C1連接鍵鍵解離能的排序?yàn)橄悴菟?香草醛>香草醇,這取決于C1取代基的吸電IM4-2IM4-3子能力.其他各連接鍵的鍵解離能雖然差別不大,但1.3計(jì)算方法在C1取代基的影響下表現(xiàn)出了一定的規(guī)律性,總是文中所有的計(jì)算均在Casn093中進(jìn)行,方香草醛>香草酸>香草醇這說明不同C取代基對(duì)法與基組均選用B3LYP/6-31G(d).首先對(duì)文獻(xiàn)給?；锏臒峤庑袨橛幸欢ǔ潭鹊挠绊懗龅膶?shí)驗(yàn)構(gòu)象進(jìn)行優(yōu)化然后計(jì)算其單點(diǎn)能與頻率,22熱解V凵中國(guó)煤化工得到經(jīng)振動(dòng)零點(diǎn)能(ZPE)校正的單點(diǎn)能文中出現(xiàn)的表2列∏ CNMHG法計(jì)算所得的反應(yīng)物、中間體和產(chǎn)物經(jīng)過頻率驗(yàn)證均無虛頻,為能反應(yīng)各駐點(diǎn)(反應(yīng)物R、中間體MM、過渡態(tài)T和產(chǎn)華南理工大學(xué)學(xué)報(bào)(自然科學(xué)版)第42卷物P)經(jīng)過零點(diǎn)能校正的總能量其中,過渡態(tài)能量一香草醛值都是基于過渡態(tài)理論按照前述方法計(jì)算得到的香草醇一香草酸表2反應(yīng)物、中間體、過渡態(tài)及產(chǎn)物在B3LYP/6-31G(d)水443.865平下的總能量414.690Table 2 The energy of the reactant, intermediates, transition states95.345and products at B3LYP/6-31G(d)levelHartree路徑駐點(diǎn)香草醛香草醇香草酸-64.56535.1705-536.3406-610.4119Path I421.1755-421.1755-421.1755反應(yīng)進(jìn)程-421.8510-421.8510-421.8510535.1705-536.3406-610.4119TS2-1-535.6620-536.833610.Path 2535.6946-536.8756-610535.6729-536.8477-610.9086421.8510-421.8510-421.8510-16.042-535.1705-536.3406-610.4119942IM3-1-495.2767-496.4529-570.521012::;73.162495.8918-497.0624-571.13346230:1÷2:,67}·64T3-1496.3831-497.5548-571.6238-91.092IM3-3496.4159反應(yīng)進(jìn)程496.39435694-571.6302b)Path 2382.5728-382.5728-382.5728-535.1705-536.3406-610.4119圖1Path1和Path2的勢(shì)能剖面圖535.66ll-536.8327-610.9032Fig. 1 Potential energy profiles along reaction Path I and Path 2IM4-1-535.6989-536.8728-610.941Ts42-535.6815-536.8552-610.9246Path2是在,H存在下,協(xié)助C1取代基解離生Pah4M2-420.678-421.8490-495.9204成愈創(chuàng)木酚.首先,H進(jìn)攻Ca,經(jīng)過渡態(tài)TS2-1生:3-421.1685-4223418-4964103成中間產(chǎn)物M2,這一步所需的活化能較低,分別為IM4-3421.2007-422.3824-496.448-421.1800-422.3566-496.416423.262、19985和25.578kJ/mol.接著中間體IM2-307.3601-307.3601031過渡態(tài)TS22生成愈創(chuàng)木酚P2,這一步所需的活反應(yīng)路徑中除了存在表2中列出的各物質(zhì)及其化能分別為56942、3.162和76.793k/m.整個(gè)過程的能量變化同樣為-45.216、-64.561和能量外,還有H、CH3、·CHO、CH2OH和·COOH這5種自由基參與,其能量分別為-0.5003、-39808516.042kJ/mol,這說明只要目標(biāo)產(chǎn)物相同,無論113.8371、-115.0145和-189.0673 Hartree.利經(jīng)過怎樣的路徑,能量變化都是相同的.Path2需要用表2中各駐點(diǎn)和上述5種自由基的能量,計(jì)算出克服兩個(gè)能壘,第一個(gè)能壘較低決定著反應(yīng)能否開各步反應(yīng)的活化能并繪制反應(yīng)路徑的勢(shì)能剖面圖.始,比較3種?；锇l(fā)現(xiàn),香草醇最易進(jìn)行,其次是Path1和Path2的目標(biāo)產(chǎn)物同為愈創(chuàng)木酚,圖1香草醛,最難的是香草酸;第二個(gè)能壘相對(duì)較高決是兩條路徑的勢(shì)能剖面圖Pah1中,C。C1連接定著反應(yīng)能否繼續(xù)進(jìn)行,是反應(yīng)的決速步驟,此步的鍵在熱化學(xué)作用下均裂成愈創(chuàng)木酚自由基M和能壘為香草醇>香草酸>香草醛,出現(xiàn)了反差,這是3種側(cè)鏈自由基,這一步所需的活化能分別為414690、由TS2-1、TS2-2和IM2的性質(zhì)和能量造成的395.345和443.865kJ/mol,接著愈創(chuàng)木酚自由基與Path 1和Path2有著相同的反應(yīng)物和產(chǎn)物,不H結(jié)合,生成愈創(chuàng)木酚P1整個(gè)過程的能量變化分同的是中間過程,由此可以看出不同路徑對(duì)同一產(chǎn)別為-45.216、-64.561和-16.042kJ/mol,其值均物生成的影響比較兩條路徑可以發(fā)現(xiàn)無論是啟動(dòng)小于零,勢(shì)能降低,說明Path1是可能的,且香草醇反應(yīng)的能壘,還是決速步驟的能壘,Path1都要遠(yuǎn)遠(yuǎn)最有可能進(jìn)行,香草醛次之,最難進(jìn)行的是香草酸.高于Path2.從動(dòng)力學(xué)角度判斷,Path2在很大程度從動(dòng)力學(xué)角度來看,Pah1只需要克服一次反應(yīng)的上優(yōu)先于PV中國(guó)煤化工愈創(chuàng)木酚的過能壘,即C.C1連接鍵均裂所需的活化能這決定程中H參∏ CNMHG很大程度上降著Path1的動(dòng)力學(xué)可能性低了反應(yīng)的活化能,說明3種?；镌跓峤鈺r(shí)側(cè)鏈第10期武書彬等:木質(zhì)素單體?；餆峤膺^程的理論分析不會(huì)直接解離,而是會(huì)優(yōu)先發(fā)生外界參與下的解離Path4是生成苯酚的過程首先,反應(yīng)物在H的Path3和Path4的設(shè)計(jì)考慮到了基團(tuán)解離方式參與下,經(jīng)過渡態(tài)T4-1生成中間體IM4-1,此步過程的優(yōu)先性圖2是其勢(shì)能剖面圖Path3是生成鄰苯的活化能分別為25543、21.351和23.582kJ/mol.接二酚的過程首先,OCH3連接鍵在熱化學(xué)作用下著,中間產(chǎn)物IM41經(jīng)過渡態(tài)T42生成中間產(chǎn)物均裂成中間產(chǎn)物IM3-1和·CH3,這步過程的活化能M4-2,這步的活化能分別為45.626、46.041和分別為224.173、208.126和216.278kJ/m接著中4.84kJ/mol.H再次進(jìn)攻中間產(chǎn)物IM42,經(jīng)過渡態(tài)間產(chǎn)物M3與H結(jié)合生成中間產(chǎn)物MM3-2,放出S43生成中間產(chǎn)物M43,此步過程所需的活化能分能量在H存在下,中間產(chǎn)物MB2經(jīng)過渡態(tài)TS31別為2.9919.520和27148Jymo.中間產(chǎn)物a-3生成中間產(chǎn)物I3-3,此步反應(yīng)的活化能較低,分別再經(jīng)過渡態(tài)TS44轉(zhuǎn)變生成苯酚P4,這步過程所需的為23.527、20.484和25.990kJ/mo.隨后中間產(chǎn)物活化能分別為54.2596770和74798kJ/mo整個(gè)IM3-3經(jīng)過渡態(tài)TS3-2生成鄰苯二酚P3,此步過程的過程的能量變化分別為-104.254、-123.598和活化能分別為56.763、72.411和76.407kJ/mol.整個(gè)-75.0kJ/mol,均小于零勢(shì)能降低,且3種反應(yīng)物反應(yīng)過程的能量變化分別為-124018、-143.363和生成苯酚的可能性與生成愈創(chuàng)木酚和鄰苯二酚是一94844kJ/mol,勢(shì)能降低,說明這是可能的過程從致的從動(dòng)力學(xué)角度分析,雖然Path4需要克服4次勢(shì)能角度分析,3種反應(yīng)物生成鄰苯二酚的難易程度能壘才能生成苯酚,但每次需提供的能量都較低,這與愈創(chuàng)木酚是一致的從動(dòng)力學(xué)角度分析,Path3需表明有,H存在時(shí),Path4基本就能進(jìn)行到底要克服3段能壘,第一段能壘最高,是反應(yīng)的決速3種反應(yīng)物在相同條件下生成愈創(chuàng)木酚分別放出了45.21664.561和16.042kJ/mol的能量,生成鄰苯二過程酚放出了124.018、143.363和94.84kJ/mol的能量,香草醛生成苯酚放出了104.254、123.598和75.079k/mol香草醇的能量,單從勢(shì)能角度可以看出相同反應(yīng)物在同一條香草酸件下會(huì)優(yōu)先生成鄰苯二酚,其次是苯酚,最后才是愈創(chuàng)木酚從動(dòng)力學(xué)角度來看,Path2和Path4啟動(dòng)反應(yīng)所需的能量和決速步驟的能壘都比較低,是動(dòng)力學(xué)優(yōu)先的過程Path1和Path3反應(yīng)的啟動(dòng)需要克3-221627服化學(xué)連接鍵解離所需的能量,這個(gè)能量較大,也使78.02M3-產(chǎn)m得反應(yīng)的第一步成為決速步驟,相比于Path2和Path4不是動(dòng)力學(xué)優(yōu)先的反應(yīng)-168.8782.3熱解路徑的竟?fàn)幏磻?yīng)進(jìn)程(a) Path 3上述分析表明,愈創(chuàng)木酚、鄰苯二酚和苯酚都是可能的目標(biāo)產(chǎn)物,Path2和Path4會(huì)優(yōu)先于Path1一香草醛和Path3進(jìn)行,這是因?yàn)镠的參與很大程度地降低香草醇了反應(yīng)所需的活化能,但問題在于H從何而來熱香草酸解過程一般是在N2或Ar等惰性氣體保護(hù)下進(jìn)行是絕對(duì)無水無氧的熱化學(xué)過程,H的提供只能依靠熱解過程中的解離.表3列出了3種?；锝Y(jié)構(gòu)中所有不同化學(xué)環(huán)境H的鍵解離能.從表3中可以看27J48/975.079出,苯環(huán)酚羥基H最容易解離,其解離分別需要13+7023433806321049和30.756k/ml的能量,而Pah3123.598中OCH3連接鍵斷裂分別只需要224.173、208.126反應(yīng)進(jìn)程和216.278kJ/mol的能量,對(duì)比兩組數(shù)據(jù)可以發(fā)現(xiàn)(b) Path 4在熱解過程圖2Pah3和Path4的勢(shì)能剖面圖基已經(jīng)解離HH中國(guó)煤化工主之前,側(cè)鏈甲CNMHG.產(chǎn)生,當(dāng)其ig2 Potential energy profiles along reaction Path3 and Path4參與Path2和Path4反應(yīng)時(shí),Path3或已進(jìn)行完畢74華南理工大學(xué)學(xué)報(bào)(自然科學(xué)版)第42卷表3?；镏胁煌瘜W(xué)環(huán)境H的鍵解離能2002,83(1):47-54Table3 Bond dissociation energy of H in different chemical en-[2]劉榮厚,牛衛(wèi)生,張大雷生物質(zhì)熱化學(xué)轉(zhuǎn)換技術(shù)[M]vironments in model compoundskJ/ mol北京:化學(xué)工業(yè)出版社,2005連接鍵香草醛香草醇香草酸[3]姚燕,王樹榮鄭赟等.基于熱紅聯(lián)用分析的木質(zhì)素?zé)峤?59.043動(dòng)力學(xué)研究[J]燃燒科學(xué)與技術(shù),2007,13(1):50-54Cs-H468.116Yao Yan, Wang Shu-rong, Zheng Yun, et al. Kinetic re-C6-H462.183459.3467.618search of lignin pyrolysis by TGA-FTIR analysis [J]33l.80621.049Journal of Combustion Science and Technology, 2007, 13甲基H396.461397.826C-H(1):50-5468.676333.415側(cè)鏈上的-H388167407.530[4]Kotake T, Kawamoto H, Saka S Pyrolysis reactions of conife-ryl alcohol as a model of the primary structure formed熱解是一個(gè)快速升溫過程,其也能瞬間提供C1取代during lignin pyrolysis [J]. Journal of analytical and基解離所需的能量,所以某種程度上Path1、Path2Applied Pyrolysis, 2013, 104: 573-584Path3和Path4存在著競(jìng)爭(zhēng),這種競(jìng)爭(zhēng)不是單單憑5] Zhang M, Resende FL p, Moutsoglou A,etal. Pyrolysis of借連接鍵的鍵解離能及反應(yīng)過程中相差不大的能壘lignin extracted from prairie cordgrass, aspen, and Kraft能夠解釋的,還取決于反應(yīng)物或中間體與H的結(jié)合lignin by Py-GC/MS and TGA/FTIR [J].Journal of能力物料濃度、空間位阻、電子排斥等諸多因素Analytical and Applied Pyrolysis, 2012, 98: 65-713種?；锝Y(jié)構(gòu)中除酚羥基最容易斷裂提供,H[6】武書彬,胡元,婁瑞,等木質(zhì)纖維生物質(zhì)及其組分的外,就是側(cè)鏈取代基上H的解離但是此處H的產(chǎn)理化特性與熱解規(guī)律[M].北京:科學(xué)出版社,2013生需要較高的能量,幾乎與C1_C解離的能量相[7]婁瑞非木材纖維木素在不同熱化學(xué)條件下的產(chǎn)物形當(dāng),也高于部分連接鍵的鍵解離能,即當(dāng)需要裂解成規(guī)律與調(diào)控途徑[D].廣州:華南理工大學(xué)輕工與C1取代基來提供·H時(shí),Path1和Path3等或已進(jìn)食品學(xué)院,201行,4條路徑同樣存在著競(jìng)爭(zhēng).[8]Liu J, Wu S, Lou R. Chemical structure and pyrolysis re-sponse of B-0-4 lignin model polymer [J].BioResources3結(jié)論2011,6(2):1079-1093[9]黃曉露.木質(zhì)素模型化合物熱解的微觀機(jī)理研究(1)鍵解離能的計(jì)算結(jié)果表明,?；镌跓峤鈁D].重慶:重慶大學(xué)動(dòng)力工程學(xué)院,2012過程中側(cè)鏈甲基會(huì)優(yōu)先斷裂生成CH4C。C1連接[10]王華靜趙巖,王晨等木質(zhì)素二聚體模型物裂解歷鍵鍵解離能的相對(duì)大小為香草酸>香草醛>香草程的理論研究[J].化學(xué)學(xué)報(bào),2009,67(9)893900醇,這取決于C1取代基的吸電子能力受C1取代基Wang Hua-jing, Zhao Yan, Wang Chen, et al. Theoretical的影響,其他取代基的鍵解離能表現(xiàn)出了一致的規(guī)udy on the pyrolysis process of lignin dimer model com-律性,都是香草醛>香草酸>香草醇.pounds [J]. Acta Chimica Sinica, 2009, 67(9): 893-9002)Path1和Pah2的對(duì)比表明,熱解時(shí)C1取11 Velavan r, Sureshkumar p, Sivakumar K, et al. vanillin代基會(huì)優(yōu)先發(fā)生外界參與下的解離.從勢(shì)能角度分[J]. Acta Crystallographica Section C: Crystal Structure析,生成愈創(chuàng)木酚、鄰苯二酚和苯酚都是可能的,且Communications, 1995, 51(6): 1131-1133在相同條件下會(huì)優(yōu)先生成鄰苯二酚,然后是苯酚,最12】 Wang Q,Ls.4 Hydroxymethyl2 methoxyphenc[后才是愈創(chuàng)木酚綜合4條路徑可知,生成同種目標(biāo)Acta Crystallographica Section E: Structure Reports On-ine,2009,65(11):283產(chǎn)物時(shí)總是香草醇最易進(jìn)行,其次是香草醛,最難進(jìn)(13] Kozlevear B, blazek d, Golobie A,etal. Complexes with行的是香草酸從動(dòng)力學(xué)角度分析,Path2和Path4是動(dòng)力學(xué)優(yōu)先的過程,而Path1和Pah3需要克服lignin model compound vanillic acid. Two different car-的能壘較大boxylate ligands in the same dinuclear tetracarboxylatecomplex Cu(CgH, 04)2(02 CCH,)2(CH, OH)2]3)最有可能給Path2和Path4提供啟動(dòng)所需[J]. Polyhedron,2006,25(5):1161-1166H的是酚羥基氫的解離但熱解是一個(gè)快速升溫過14 Frisch M J, Trucks G w, Schlege4HB,ta. Gaussian3程,能瞬間克服各步反應(yīng)的能壘,所以實(shí)際熱解過程CP]. Revision E. 01. Wallingford CT: Gaussian, Inc,2004并非與理論一致,各路徑之間存在著相互競(jìng)爭(zhēng)[ 15] Laarhoven L J J, Mulder P, Wayner DD M Determina-參考文獻(xiàn):tion of bond dissociation enthalpies in solution by photoa中國(guó)煤化工 hemical Research[1 Mckendry P. Energy production from biomass( Part 2)CNMHGconversion technologies [J]. Bioresource Technology(下轉(zhuǎn)第89頁(yè))第10期袁騰等:毛細(xì)力學(xué)在超親水膜分離過程中的應(yīng)用及力學(xué)模型Application of Capillary Mechanics to Separation Process ofSuperhydrophilic Membrane and Its Mechanical ModelYuan Teng Chen Zhuo Liu Wen-ji Zhou Xian-hong Tu Wei-ping Wang Feng(1. School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510640, GuangdongChina; 2. School of Light Industry and Food Sciences, South China University of Technology, Guangzhou 510640, GuangdongChina; 3. School of Chemistry and Environmental Engineering, Dongguan University of Technology, Dongguan 523808Abstract: The current oil/ water separation membrane researches based on special wettability are seldom involved inthe dynamic process of the membrane separation and the relevant quantitative calculations. In this paper, by analy-zing the physical quantities of the superhydrophilic membrane separation process based on the capillary mechanicsand by classifying the membrane pores of membrane materials based on special wettability as capillary pores,aathematical model is constructed, and it is used to analyze the force distribution condition in the separationprocess of oil-water mixture by using the superoleophilic membrane. Then, the principle of the superhydrophilicand superoleophilic membrane in the air transforming to be superoleophobic underwater is analyzed from the perspective of surface tension, and the capillary flow rate, the capillary permeation rate, the membrane flux and thecritical penetration pressure in the membrane separation process are calculated based on capillary mechanicsare validated by experiments. On this basis, the separation mechanism of superhydrophilic and underwater supleophobic oil/ water separation membrane is preliminarily discussed based on capillary mechanicsmodel; quantitative calculation; separation mechanism brane: capillary flow; membrane separation;mechanicalKey words: capillary mechanics; superhydrophilic mer賚任編輯:張娜娜(上接第74頁(yè))Theoretical Analysis on Pyrolysis Processes ofMonomeric Model Compounds of LigninWu Shu-bin Deng Yu-bin Liu Chao(State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, Guangzhou 510640, Guangdong, China)Abstract: In order to deeply investigate the pyrolysis mechanism of lignin, its pyrolysis process is simulated withvanillin, vanillic alcohol and vanillic acid being selected as monomeric model compounds of lignin. In the investigation,the density functional theory is employed to analyze the dissociation sequences of chemical connectionbonds, and four reaction paths, namely, Path 1-Path 4, are designed. Both Path I and Path 2 generate guaiacbut their intermediate processes are not the same, while Path 3 and Path 4 generate catechol and phenol with priorityprocesses respectively. The results show that(1) the methyl in the side chains of the model compounds first dissociates with CH, being released, and the dissociation sequences of the substituents on Cl depend on their ability towithdraw electrons;(2)in the pyrolysis process, it is difficult for the substituents on CI to dissociate directly, butprior dissociation occurs instead with the help of outside factors; (3)it is possible for the target products of threekinds to be obtained in the priority sequence of catechol, phenol and guaiacol;(4 )from the view of dynamicsPath 2 and Path 4 are superior to Path 1 and Path 3; and (5) whenever the target products of the same kind aremade, it is always the easiest job for vanillic alcohol, and then vanillin, whereas vanillic acid is always the mostdifficult matter to be dealt with中國(guó)煤化工Key words: lignin; monomeric model compound; pyrolysis; density furCNMHG責(zé)任編輯:張娜娜