Pyrolysis of furfural-acetone resin as matrix precursor for new carbon materials

J. Cent. South Univ. Technol. (2008) 15: 753-756包SpringerDOI: 10.1007/s11771-008-0139- zPyrolysis of furfural- acetone resin as matrix precursor fornew carbon materialsXIA Lun-gang(夏伦刚)，ZHANG Hong-bo(张红波), XI0NG Xiang(熊翔),ZUO Jjin-li(左劲旅), YIN Jian(尹健)(State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China)Abstract: In order to increase the understanding of the pyrolysis mechanism, Fourier transform infrared spectroscopy (FT-IR) andthermogravimetry-mass spectrometric coupling technique (TG-MS) were used to study the pyrolysis behavior of furfural-acetoneresin used for new carbon materials. The curing and carbonization mechanisms of furfural-acetone resin were mainly investigated;structural changes and volatile products evolved during pyrolysis were analyzed. The results indicate that, during pyrolysis offurfural-acetone resin adding 7% (mass fraction) phosphorous acid as curing agent, the rupture ofC- O bond in the five -memberedheterocycle firstly takes place to release oxygen atoms and then does the C- H bond, which enable the molecular chain to cross-linkand condense, then lead to the formation of three dimensional networking structure. With the increase of pyrolyzing temperature, thescission of methyl and the opening of furan ring are generated. As a result, the recomposition of molecular chain structure isgenerated and a hexatomic fused ring containing double bonds is built. The main volatile products during pyrolysis of furfural-acetone resin are H2O, and a small mount of CO, CO2 and CH4 At elevated temperatures, dehydrogenation takes place and hydrogengas is evolved.Key words: new carbon materials; furfural-acetone resin; pyrolysis; volatile productsduring this processing step is great due to the1 Introductionof complicated reactions during thermal degradation ofOrganic polymer is one of the most primary sourcesfuran resin. Generally, the thermal degradation process isof carbon precursors for new carbon materials, such asdivided into two stages: curing stage at lowercarbon/carbon (C/C) composites and glasslike carbontemperatures and carbonization stage at highermaterials. Currently, the main organic polymers widelytemperatures. Invariably a variety of volatile compoundsused for carbon precursors of new carbon materials arare released during the thermal degradation reaction,phenolic resins, condensed polynuclear aromaticwhich can cause great volume expansion of the sample(COPNA) resin, polyacrylonitrile and furan resinsl".and some flaws in it, such as pores and cracks4-84. So itFuran resins refer to a family of thermosetting resinsis quite important to investigate the thermal degradationcontaining furan ring likeo in their molecularmechanisms of furan resins for improving the producingprocedure and the quality of the resulting products.structure. Furan resins are commonly produced bBecause of the differences of the raw materials andpolycondensation of furfurals or furfuryl alcohols. The;producing procedures selected by the researchers, thehave not only excellent corrosion resistance andthermal degradation mechanisms of furan resins are moreheatproof characteristic, but also high carbon yields. Soor less different. The common methods of mechanismthey have been widely applied in a variety of fields for ainvestigation are Fourier transform infrared spectroscopylong time. Furfural-acetone resin is one kind of furan(FT-IR), thermogravimetry (TG), differential scanningresins and is known as an excellent polymeric precursorcalorimetry (DSC), thermal volatilization analysis (TVA),for C/C composites and glasslike carbon materials2-” .thermogravimetry-massspectrometriccouplingThe thermal degradation of matrix precursors is antechnique (TG-MS), eteIn this study, the FT-IR andimportant step in the manufacture of new carbonTG-MS techniques were used to give physical andmaterials. The pyrolysis process converts the furanchemical insights into the thermal decomposition ofmatrix to amorphous carbon. The potential for damagefufural-aceton中国煤化工carbonizationFoundation item: Prjca(2006CB600902) supported by the Major State Basic Research and DevelopMHCNMH GReeived date: 2008 -03-13; Accepted date: 2008 -05- -27Corresponding author: ZHANG Hong-bo, Professor Tel: +86- -731- -877393; E-mail: zhanghb@hnu.cn.754J. Cent. South Univ. Technol. (2008) 15: 753 -756mechanisms were primarily revealed.polymers with aromatic rings and some kinds ofreactions are able to take place. But they are more active2 Experimentalthan aromatic compounds because the participation o1one pair electrons in the conjugate system of2.1 Raw materials and sample preparationfive-membered heterocycles enables the lone paiFA-2 furfural-acetone resin was provided byelectrons to flow to the carbon atoms easily, whichChangshu Duwei Chemical Plant， China. It wasmakes them more active in electrophilic substitutionproduced by equal mole ratio of furfural to acetone usingreactions than aromatic compounds. That is to say, the .alkali as catalyzer. The viscosity (25 °C) was 40- -150hydrogen atoms are vulnerable to be substituted or tomPa/s; water content was≤1% and grey yield was≤escape. Therefore, in the same heating condition the3%. The curing agent was industrial phosphorous acidspeeds of curing and carbonization of furan resins arewith concentration of≥85%.always faster than those of other resins with aromaticThe curing agent was added and the mixture wasrings".stirreor 10 min in order to yield ahomogeneousThe FT-IR spectrum of virgin furfural -acetone resinmixture. The mixture held in a graphite pot was put in anis shown in Fig.1. The FT-IR spectra of cured andoven and cured stepwise at 90 C for 2h, then at 120 Ccarbonized samples are shown in Fig.2. According tofor4h, and at 180 °C for 2 h in the end. The apparentlyRefs.[12- 15], the peaks in the spectra can be assignedcompact and hard cured bulk sample was obtained.and listed in Table 1. Compared with the IR spectrum ofThe cured sample with the graphite pot was heatedvirgin furfural-acetone resin, in the spectrum of curedin a vacum furnace at a programmed rate up to 850"C,sample the characteristic peak of一OH group at 3 121then kept for 3 h. The carbonized sample was obtained:m' is obviously weakened; the characteristic peak ofand cooled down to room temperature.C- H bond in- plane deformation of the aromatic ringat971 cm 1 and the ones of C- H bond out-of-plane2.2 FT-IR measurementcured and carbonized samples were obtained using 8Nicolet AVATR360 spectrophotometer in the wave-number range of 4 000- -400 cm . Liquid sample wastested directly or after diluted with tetrachloromethane,and solid samples were tested with potassium bromidepressed disc method.2.3 TG-MS measurementTG-MS apparatus consisted of a SETARAMTGA92 thermal gravimetric analyzer made in Franceith accuracy of 1 μg and a Balzers Omnistar massspectrometric analyzer made in Switzerland with4000 3500 3000 2500 2000 1500 1000 500scanned molecular mass range of 1- -300.Wavenumber/cm-lAbout 19.46 mg furfural-acetone resin with 7%Fig.1 FT-IR spectrum of virgin furfural-acetone resin(mass fraction) curing agent was held in a alumina pan,then the argon gas was flowed to expel the air for certaintime until thbaseline was smooth. The sample wasCuredpyrolyzed in an argon flow of 100 mL/min at a heatingrate of 5“C/min from room temperature to 1 000 °C.3 Results and discussionCarbonized3.1 FT-IR analysisnThe main structural unit of the furan resin moleculeis furan five-membered heterocycle containing carbon,hydrogen and oxygen elements. Because in the中国煤化工heteroatom of furan ring, such as oxygen, unpaired4000 3 500CNMHG00 S500electrons can participate in the six -membered conjugateIUCI/CIIsystem, furan resins have similar characteristic ofFig.2 FT-IR spectra of cured and carbonized samples.J. Cent. South Univ. Technol. (2008) 15: 753- -756755Table 1 Peak identification ofFT-IR spectraspeculated that new six-membered aromatic ringWavenumber/cm-Functional groupstructure emerges and it is the foundation of thetransformation into graphite structure. But further work3 121-OHis needed to confirm this statement.C-H in-plane deformation of971aromatic ring3.2 TG-MS analysisC- H out-of-plane deformation of881The results of TG-MS study are presented in Fig.3C- H out-of- plane bending vibration of(TG-DTG) and Fig.4 (MS). The TG curve of the sample750shows two main mass losses in the temperature rangefrom room temperature to 1 000 °C. They are attributed2 900XCH2 asymmetric stretching vibrationto two stages: curing and carbonization, respectively.1 714Furan ringThe curing reaction peak on the curve of DTG is highC- 0- C asymmetric stretchingand narrow, indicating that the curing reaction is very1 162vibrationacute and rapid and the curing time is very short. The1 014C- 0- -C symmetric stretching vibrationonset and terminal temperatures of curing reaction are1 620C= =C of furan ring111.27 °C and 199.8 °C, respectively. The peak value ofreactive speed is 2.332%/s at about 155 °C. It can also be1 474C=C of furan ringseen from Fig.4 that during curing process the main1 661C=O of ketone stretching vibrationvolatile products are H2O and a small amount of CO,CH4 and CO2. According to the former results of FT-IRdeformation around 881 cm”and 750 cm-' almostspectra and Ref.[16], it can be concluded that when furandisappear. These results indicate that the hydroxyl groupsresin cures in the presence of phosphorous acid, theand active hydrogen atoms in the furan moleculesC- O bond of furan ring ruptures firstly to release oxygendisappear, and that dehydration-condensation takes place.There is also characteristic peak of) >CH2 groupasymmetric stretching vibration at 2 900 cm~，whichreveals that there is still characteristic group of acetone0+2元in the cured sample. Furthermore, it can be found that theintense characteristic peak related with furan rings at1 714 cm“and the bands attributed to C- 0- Casymmetric and symmetric stretching vibration at 1 16270-and 1 014 cm 1 are all greatly weakened, which revealsDTGthe occurrence of curing reaction due to the opening of60Ffuran rings and cross-linking reaction. In addition, theG50-bands related to C= =C double bonds in furan rings at.1 620 and 1 474 cm-' almost disappear, and the peak of02004006008001000C=O of ketone stretching vibration at 1 661 cm' isTemperature/Cvery weak, demonstrating that these groups also take partFig.3 TG-DTG curves during pyrolysis of furfural-acetonein the reaction.resinIn the FT-IR spectrum of carbonized sample, most18of the characteristic peaks disappear or are greatly16weakened, which indicates that this sample is14transformed into very pristine resin carbon, and that the\H2Ocarbon structure is transformed into a more ordered type.ζICompared with the spectrum of cured sample, the bands .associated with C= =O stretching vibration of the ketone8t /COat 1 661 cm-' and the bands corresponding to C- -H out-of-plane bending vibration of aromatic rings at 750 cmCH4are further weakened. The cause is that most of theC=O bonds in the five -membered heterocycles arebroken to release oxygen atoms, the C- H bonds ar中国煤化工ruptured, which causes the recomposition of molecularYHCNMH G)01000chains. Meanwhile, it is worthy of notice that newemperature/ Labsorption peak at around 3 432 cm-' emerges. It can beFig.4 Evolution of volatile products during pyrolysis.756J. Cent. South Univ. Technol. (2008) 15: 753 -756atoms, then other C- H bonds rupture， and thecross-linking of molecular chains takes place to form aReferencesthree-dimension networking structure. Meanwhile, waterand other volatile products are evolved.[1 ] FU Dong-sheng, ZHANG Kang-zhu, SUN Fu-lin, YAO Dong-mei.Research progress in matrix precursors for carbon-carbon compositesWith the further increase of pyrolyzing temperature[J]. New Chemical Materials, 2003, 31(6): 19- 21. (in Chinese)from 200 °C， cured sample undergoes a gradual2] FU Xue. Resin and plastic [M]. Beiing: Chemical Industry Press,decomposition and leads to carbonization. Fig.4 shows2005. (in Chinese)slow emissions of CO2, CO, H2O, CH4 and H2, with the[3] BURKET C L， RAJAGOPALAN R， MARENCIC A P,DRONVAJJALA K, FOLEY H C. Genesis of porosity inpeaks at around 340， 359， 367， 494 and 699 °C,polyfurfuryl alcohol derived nanoporous carbon []. Carbon, 2006,respectively. The carbonization is nearly over till 850 C,44(14): 2957- 2963.obtaining51.8% carbon yieldsAccording4] GUO Hua-jun, LI Xin-hai, ZHANG Xin-min, WANG Zhi-xing,PENG Wen-jie, ZHANG Bao. Optimizing pyrolysis of resin carbonRefs.[16- 18], it can be concluded that the main reactionfor anode of lithium ion batteries []. J Cent South Univ Technol,during pyrolysis of furfural-acetone resin is thermal2006, 13(1): 58- 62.condensation. With the rupture of methyl and the5] TANABE Y, UTSUNOMIYA M, ISHIBASHI M, KYOTANI T,KABURAGI Y， YASUDA E. 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The Chinese Jourmal of Nonferrous Metals, 2003, 13(6):1430- 1434. (in Chinese)4 Conclusions[9] FIZER E, SCHAEFER w. The efet of crss-linking on theformation of glasike carbon from thermosetting resin田Carbon,1970, 8(3): 353- -364.1) The pyrolysis process of furfural-acetone resin10] WAITKUS P A, KORB L L. Process for preparing a vitreous carbon:mainly consists of two types of reaction: cross-linkingUS 4624811 [P]. 1986- 11- 25.11] WANG Shu-jun, ZHAO Fei-min. Study on the carbonized product ofwith the opening of furan rings and thermal-condensation.furfuralcohol resin as electrode materials of lithium ion batteries [J].During pyrolysis of furfural-acetone resin, the C- -ONew Carbon Materials, 2000, 15 (3): 47- -51. (in Chinese)bonds in the furan rings firstly rupture to release oxygen12] HERNANDEZ V, RAMIREZ F J, ZOTTI G, NAVARRETEJT L.Resonance Raman and FT-IR spectra of pristine and dopedatoms, then other C- H bonds rupture, and cross-linkingpolyconjugated polyfuran []. Chem Phys, 1992, 191(5): 419 -422.of molecular chains takes place tform;SOCRATES G. Infrared characteristicgroupfrequencies [M].Chicheter: John Wiley & Sons, 1980.three-dimensional networking structure. W ith the rupture14] ROBERT M, SILVERSTEIN, FRANCIS x, WEBSTER, KIEMLE D.of methyl the opening of furan rings occurs; aSpectrometric identifcation of organic compounds [M]. Hoboken,six-membered aromatic ring structure with double bondsN: John Wiley & Sons, 2005.appears after the recomposition of furan molecules.[15] LORENZ∪」, LEMAIRE J, MAITRE P, CRESTONI M E,FORNARINI s, DOPFER O, Protonation of heterocyelic aromatic2) The pyrolysis process is divided into two stages:molecules: IR signature of the protonation site of furan and prrolecuring and carbonization. Curing reaction is obviously[D]. Intermational Jourmal of Mass Spectrometry, 2007, 267(1/3):very acute and rapid, and its time is very short. Onset andterminal temperatures of curing reaction are 111.27 and16] XIA Lun-gang, ZHANG Hong-bo, XIONG Xiang, ZUO Jin-li, YINJian. Curing reaction of furfural acetone resin used for new carbon199.8 C, respectively. The peak value of reactive speedmaterals [0] The Chinese Journal of Noferrous Metals, 2008, 18(6):is 2.332%/s at around 155 °C. The speed of carbonization953- -958. (in Chinese)reaction is slower than that of curing reaction with a17] OZAKI J， OHIZUMI W，OYA A. A TG-MS study ofpoly(vinylbutyral)/phenol-formaldehyde resin blend fiber []. Carbon,wider temperature range. During the whole thermal2000, 38(10): 1515- -1519.degradation，H2O is a predominant volatile product18] BISWAS B, KANDOLA B K, HORROCKS A R, PRICE D. Afollowed by CO, CO2 and CH4. 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