GC/MS Analysis of Organic Compounds in Hot Water-Extractable Fraction from Shenfu Coal

Joumal of China Urty of Mining TechnologyVol 17 No. 3Availableonlineatwww.sciencedirect.comSCIENCEDIRECT·J China Univ Mining Technol 2007, 17(3): 0354-0357G C/MS Analysis of Organic Compoundsin Hot Water-Extractable fractionfrom shenfu coalLI Bao-min, YUAN Cheng, ZONG Zhi-min, CAO Jing-pei, LIU Guang-feng, WEI Xian-yongSchool of Chemical Engineering and Technology, China University of Mining Technology, Xuzhou, Jiangsu 221008, chinaAbstract: Shenfu Coal was extracted with hot pure water and slurry was isolated. The concentrated benzene-solublefraction(CBSF)was analyzed with GC/MS and four types of organic compounds(OCs)were detected: HACOCs,DTEs, DMDT and LCAs. The amount of benzyl benzoate which is the most abundant OC was calculated by an inter-nal standard method with an indicated amount of BP. The broken hydrogen bonds and ether bonds were responsiblefor the extraction of OCs from the coal DTEs, DMDT and LCAs are essentially insoluble in water, whereas they aresoluble, probably owing to intermolecular interaction of Ocs with HACOCsKey words: thermal extraction; GC/MS analysis; water-soluble fraction; benzene-soluble fractionCLC number: TQ 5301 Introductionhermal treatment of four Chinese bituminous coalswith water at150℃and240℃ was related to theSo far, a number of investigators have paid atten- decreases of total oxygen and hydroxyl oxygen oltion to thermal treatment of coals in water -ol, graffUnderstanding the composition and structures ofand Brandes investigated coal modification by super- water-soluble fractions from water-treated coals on acritical steam". They found that exposure of Illinois molecular level could be more helpful for revealingNo 6 coal to 5 MPa of steam at temperatures berelated mechanisms. However, such reports havetween 320C and 360C resulted in significant never been publishedhanges in the coal, i. e, the coal was depolymerizedAt present, our attention in this related investiby the exposure to steam. Subsequent work suggested tion is focused on the composition and structural fea-that the steam-treated coal became more hydrophilic tures of water-soluble fractions from coals treated bythis idea was confirmed by a model reaction".C ductive bituminous coal from western China %esentslue to the reaction of steam with the ether linkages in water under milder conditions. This paper prethe coal, which forms hydroxyl groups>.Afterwardsrelated results from Shenfu coal (SFC, a weakly re-NMR and FT-MS analyses showed that extracts ofsteam-treated coal contained significant amounts of 2 Experimentaloxygenated compounds, including dihydroxyl aronaics". lino et al suggested that the increase inI Coal sample and reagentssolubility in some organic solvents for three ArgonneSFC was pulverized to pass through a 200-meshPremium coals by water treatment at 327C migsieve(<0.074 mm). Table 1 lists the proximate andbe ascribed to the relaxation of hydrogen bonds and ultimate analyses of the coal sample. Both benzene andthe removal of functional oxygen groups, including benzopher)were commercially purchasedthe cleavage of ether bonds. Shui et al recently re- anal中国煤化工) was also comported that the enhancement in solubility in carbon mercidisulfide/N-methyl-2-pyrrolidinone mixed solvent byCNMHGReceived 05 January 2007: accepted 10 March 2007Project 90410018 supported by the National Natural Science Foundation of China.Correspondingauthor.Tel:+86-516-83885021:E-mailaddress:libaomin570125@163.comLI Bao-min et alin hot water-Extractable Fraction from Shenfu Co2.2 Thermal extraction and analysisdetector temperatures were set at 300 C. Mass specig. 1 shows the experimental procedure fortra were obtained at an electron impact potential of 70thermal extraction of SFC with Pw and subsequenteV with a range of 30-500 amuisolation and GC/MS analysis of the resulting extract.As an internal standard, an indicated amount of BPAbout 10 g of SFC and 300 mL of Pw were put intowas added into the concentrated solution for quantitaa 500 mL glass beaker. After being irradiated in an ve analysisbeaker was transferred into a 500 mL spherical glass 3 Resultsflask, A condenser was set on the flask and the flaskwas heated with a mantle heater to reflux for 4 hFigs. 2 and 3 display the total ion chromatogram ofThen the PW-treated slurry was filtered throughCBSF from SFC and possible structures of organicmembrane filter with qualitative filter paper. The fil- compounds(Ocs)detected In total twenty OCs weretrate was repeatedly extracted with benzene. The ex- detected. The OCs can be classified into four typestraction solution, including benzene and the bheteroatom-containing OCS(HACOCs, peaks 1, 4-9,zene-soluble fraction (BSF), was concentrated by12, 14-16, 19 and 20), arenes, i.e 1, 2-di-o-tolyledistillation with a Buchi R-134 evaporatorthenes(DTEs, peaks 2 and 3), a long-chaini.e (E)-3, 4-dimethyltridec-5-ene(DMTD, peak 13)10. g SFC, Ultrasonic imadiationSFCPand long-chain alkanes(LCAs, peaks 10, 11, andExtraction with benzeneBenzene-insolublBenzene-soluble fraction(BSFRetention time(min)Concentrated BSF(CBSF(0. 4257gFig 2 TIC of CBSF from SFCGCMS analysisk款与Fig. 1 Procedure for thermal extraction of SFC with PWand subsequent isolation and GC/MS analysisof the resulting extractTable 1 Proximate and ultimate analyses of SFC (%Proximate analysisUltimate analysis( daf)o{8810.19140.37The concentrated BSF(CBSF)was analyzed with aHewlett-Packard 6890/5973 GC/MS equipped with acapillary column coated with HP-5MS (30 m x 0. 25mm inner diameter(ID), film thickness of 0. 25 umand with a gas chromatograph equipped with a capil-nf oreanic compounds detectedlary column that was coated with HP-101(30 m x中国煤化工nSFC0.32 mm ID. film thickness of 0.3 m). The columnsN M H Gm of benzoic acidwere heated at a rate of 5 C/min from 80C (and (peak 1)detected in CBSF from SFC with a corre-held at this temperature for 2 min) to 300 C(and sponding library mass spectrum. Mass spectra of OCsheld at this temperature for 5 min). Both injector and 2, 3, 4, 12 and 14 are also almost completely consis-Journal of China Unof Mining Techol. 17 No. 3tent with their library spectra, while those of most 5a or b. BB was used as a model compound contain-other OCs are fairly or largely consistent with their ing a functional group la), but this is the first time tocorresponding library ones, but structures of some report the detection of BB from coals and their reacOCs were presumed only according to their mass tion productsspectra (e.g, peak 20)because no proper libraryThree dialkyl phthalates (peaks 5, 7 and 15)werespectra were available for comparisondetected. Their precursor, phthalic acid, was identi-fied in oxidation products reported by Bergh et al7.Scan 131(3455 min)These dialkyl phthalates also contain c=o doublebonds, thus they may come from the relaxation ofhydrogen bonds, described as Figs. 5a and b1, 3-Diphenylbutan-l-one(peak 6) was reported asa product from the reaction of sodium tetraphenylbo-#64648: BenzDic acidrate with crotonic anhydride. Gaber investigated thethermolysis of aryl desyl ethers to elucidate the coalliquefaction mechanism". He isolated benzil(peak 8)in the mixtures from the reactions of both2-phenoxy-1, 2-diphenyl-ethanone and 1, 2-diphenyl2-(p-tolyloxy) ethanone. The formation of 1Fig 4 Comparison of mass spectrum(black)of benzoic3-Diphenylbutan-l-one(peak 6)and benzyl(peak 8)acid detected in CBSF from SFC with correspondingmay be attributed to the relaxation of hydrogen bondslibrary mass spectrum(green)as described above. One organic compound with ahydroxyl group(peak 12)was detected, which can be4 Discussionformed either through the relaxation of hydrogenbonds(Figs. 5a, b and e)or the scission of ether4.1 HACOCsbonds catalyzed by water. The two N-containincompounds may arise from the relaxation of hydro-As Figs. 2 and 3 show, most of the OCs detected gen bonds(Fig. 5e)caused by hot water. Much lessmpounds and all theCOCs, except for (Ep-hepta-dec-1-en-1-amine reports have been published on the detection of the(peak 16), contain aromatic ring(s). We suggest that OCs from coals and their reaction products.Fig. 5 shows, through the relaxation of hydrogenbonds and the removal of oxygen functional groups,such as the breaking of ether bonds, that hot water8①can disrupt the crossing-linking structure of coal toform smaller molecular compounds. Informationabout chemical structures of the extractedcan be inferred by analyzing solvent-soluble organiccompounds from GC/MSBergh et al investigated non-catalytic oxidation ofR8①water-slurried coal with oxygen at 180 C under 4MPa of pressure. They identified ca. 50 differentacids in aqueous solutions isolated from the reactionmixture. Most of the species they identified are fattyacids. Benzoic acid(peak 1)is the only OC identifiedboth in CBSF from SFC and in oxidation products, as+H2O一reported by Bergh et al". The formation of benzoicacid can be ascribed to the relaxation of hydro dscbonds(Figs. 5a and b)or the cleavage of C-O bonds(Fig. 5c)promoted by water and confirmed by estermodel compounds 4t Ar-OHBenzyl benzoate(BB, peak 4)is the most abundin all the compounds detected in CBSF from SFCThe amount of BB, calculated according to the中国煤化工+Ar-oHamount of BP, was 8.3 g/(g SFC, daf). Since there isonly one c=o double bond in BB which can formCNMHGhydrogen bonds with a hydroxyl group, the detectionFig 5 possible schemes of some organic compounof BB may result from the relaxation of the hydrogenreleased from SFC (R and Ar denote alkyl andbond. The related mechanism is similar to that of Fiing,respectively)igLIBGC/S Analysis of Organic Compounds in Hot Water-Extractable Fraction from Shenfu Coal4.2 DTEs2)The water-soluble fraction was extracted re-Both(E -(peak 2)and( Z)-(peak 3)DTEs were de- peatedly with benzene and Ocs were rich in the benzene-soluble fraction. The most abundant oc istected with almost the same amount. These twocompounds may arise from the scission of C-o bond Benzyl benzoate and reached an amount of 8.3 g/gdescribed as Fig 5d. No more information is avail- SFC,daf)able about them in relation to coal science3)During hotand ether bonds in macromolecular networks of coal4.3 DMTDare broken and the oxygen and hydroxyl oxygen re-Yoshioka and Takeda investigated infrared lasemoved, followed by a generation of small moleculesnicropyrolysis of coal macerals with GC/SIDTEs, DMTD and LCAs are essentially insoluble inwater. so their detection in CBSF from SFC seems toThey detected a series of normal alkenes in products be inconceivable. Intermolecular interaction of thend cutinite. Maybe they are material that is absorbedOCs with HACOCs in terms of codissolution maymake them solublein coal pores. However, reports on detection of alkenes(e.g, DMTD) inherently present in coals are acknowledgements4.4 LCASThis work was subsidized by the National NaturalLCAs, including normal and branched ones, areScience Foundation of China(Project 90410018), theResearch Fund for the Doctoral Program of Higheroften detected in coal extracts, but few reports on Education(Project 20020290007), the Key Project oftheir detection in aqueous solution havethe Chinese Ministry of Education( Project 104031)the Special Fund for Major State Basic Research5 ConclusionsProject(Project 2004CB217601)and the Program ofthe Universities in Jiangsu Province for Development1)Shenfu coal was extracted with hot pure water.of High-Tech Industries(Project JHB05-33).Four types of OCs were detectedReferencesGraff A, Brandes S D. Modification of coal by subcritical steam: pyrolysis and extraction yields. Energy Fuels, 1987,1(1):8488[2]Bienkowski P R, Narayan R, Greenkom R A, et al. Enhanced coal liquefaction with steam pretreatment Industrial engi-neering Chemistry Research, 1987, 26(2): 202-205[3] Brandes S D, Graff R A, Gorbaty M L, et al. Modification of coal by subcritical steam: an examination of modified nlinoisNo, 6 coal Energy& Fuels, 1989, 3(4): 494498ffect of water addition on C-o bond clehydrogenation of dinaphthylMoS2 catalyst in situ generated from ammonium tetrathiomolybdate. Energy& Fuels, 2002, 16(3): 767-773[5] lino M, Takanohashi T, Li C, et al. Increase in extraction yields of coals by water treatment. Energy Fuels, 2004, 18(5)1414-1418[6] Shui H, Wang Z, Wang G. Effect of hydrothermal treatment on the extraction of coal in the CS/NMP mixed solvent. Fuel,[7 Bergh JJ. Cronje I J, Dekker J, et al. Non-catalytic oxidation of water-slurmied coal with oxygen: identification of fulvic acidsand acute toxicity. Fuel, 1997, 76(2): 149-154[8] Cagniant D. Gruber R, Lacordaire C, et al. Solvolysis of three polish coal samples by treatment with N-methyl-2-pyrrolidinone and an sodium hydroxide/methanol mixture. Fuel, 1990, 69(7): 902-910.[9] Oguma K, Miura M, Satoh T, et al. Rhodium-catalyzed coupling of sodium tetraphenylborate with acid anhydrides in thepresence or absence of norbomene. Journal of Organometallic Chemistry, 2002, 648(1-2): 297-301[10] Gaber A E A M. The thermolysis of aryl desyl ethers: formation of furan derivatives Joumal of Analytical and Applied Py-1998,47(1):65-76[11] Yoshioka H, Takeda N. Analysis of organic compounds in coal macerals by infrared laser micropyrolysis. Journal of Ana-and Applied Pyrolysis, 2004, 71(1): 137-149中国煤化工CNMHG