Effects of acid treatments on Moroccan Tarfaya oil shale and pyrolysis of oil shale and their keroge

第37卷第6期燃料化学学报Vol.37 No.62009年12月Joumal of Fuel Chemistry and TechnologyDec. 2009文章编号: 0253-2409(2009)06-0659-09Effects of acid treatments onMoroccan Tarfaya oil shale and pyrolysis of oil shale and their kerogenABOULKAS A'2, EI HARFI K!2(1. Laboratoire de Recherche sur la Reactivites des Materiaux et lOptimisation des Procedes《REMATOP> ,Deparement de chimie, Faculte des Sciences Semlalia, Universite Cadi Ayyad, BP 2390, 40001 Marrakech, Maroc .2. Laboratoire Interdisciplinaire de Recherche en Sciences et Techniques, Facultepolydisciplinaire de Beni-Mellal, Universite Sultan Moulay Slimane, BP 592 , 23000 Beni Melal, Maroc)Abstract: In this study, the kerogen of oil shale from Moroccan Tarfaya deposits was isolated and the changes in the initial organicmatter during the removal of the mineral matrix were examined. Chloroform extraction of the oil shale increases the intensity of thepeaks in the X-ray dffactograms. Infrared spectra and X-ray difractograms reveal the presence of mineral , calcite , quartz, kaolinite ,and pyrite in the mineral matrix of the oil shale. Hydrochloric and hydroluoric acids dissolution do not alter the organice matter. Thenonisothermal weight loss measurements indicate that thermal decomposition of the isolated kerogen can be described by first-orderreaction. A single kinetic expression is valid over the temperature: range of kerogenpyrolysis between 433 K and 873 K. Furthermore,the results indicate that the removal of mineral malter causes a decrease in the activation energies of the pyrolysis reactions of oil shale.Key words: oil shale; demineralization; isolated kerogen; pyrolysisThe curent energetic crisis is mainly due to theconceptual definition implies that kerogen andincreasing demand of energy and political instability ofpetroleum have complementarycharacteristics.oil-producing countries. Dependence on petroleumAccordingly, petroleum ( and more generally bitumen)could be avoided by exploiting other fossil sources of is soluble in the usual organic solvents whereas kerogenfuel, such as coal, oil shales, and tar sands. World-is the sedimentary organic matter insoluble in thesewide petroleum reserves are calculated to be 12 400solvents.milliards of barrels ( which would last for about 43In this article ，isolation and bulk characterizationyears at the present consuming rate) ，while oilof kerogen are described to define precisely thecontained in oil shales represents 3 300 000possible limitations in interpretation resulting frommilliards'various isolation procedures. Other analytical methodsIn Morocco， 90% of the energy consumed isare considered only through their applications but aredependent on imported oil. Thus， an intensivenot specifically described. In general, as a result ofprogramme was commenced for the mobilzation ofthe low concentration of kerogen in sedimentary rocks,indigenous energy sources, especially the local oithe isolation of this dispersed macromolecular organicshales. Morocco is very rich in Upper Cretaceous oilmatter from associated minerals is a prerequisite forshale deposits, the main sites of oil shale are located atapplying many of the analytical techniques first directlyTimahdit ( Middle Atlas Mountains ) and Tarfayaused for coal characterization. Several isolation or( South Morocco). The oil-shale deposits in Moroccoconcentrationprocedures have been proposed,represent about 15% of known oil shale resources independing on the desired type of organic isolate and thethe world!2). Oil-shale deposits can be considered asanalysis to be performed. These procedures can beinteresting potential sources of carbon or of organicsubdivided into physical and chemical methods.molecules which could be exploited diversely in thePhysical separation method aims at avoiding anyfuturel3-5].chemical alteration of the organic matter during theKerogen is the sedimentary organic matter whichconcentration step. Chemical methods are generallygenerates petroleum and natural gas. In this respect ，better than the physical separation methods formany efforts have been made to its isolation and to theobtaining good separation of the kerogen from thechatacterization of its chemical structure and evolutionminerals but leave more questions about structuralduring sediment burial, aiming at a better prediction ofalteration of the kerogen'Despite attempts with aoil and gas pools. Considerable advances have beennumber of chemical reagents. no general method hasachieved with respect to the prediction of oil and gasbeen中国煤化工tely separate thpotential and the simulation of petroleum systems. Thisunchai.FYTHCNMHGimentary mixture.Received date: 2009-0504; Received in rerised form: 2009 08-10.Corresponding author; ABOULKAS A: Tel.: +212 523 485122; Fax: +212 523 485201。E-mail: a. aboulkas@ yahoo. fr。本文的英文电子版由Elserier出版社在ScienceDiret上出版( htp://www siencedrect. con/sience/jouma/18725813)。660燃料化学学报第37卷The conventionalhydrochloric/hydrofluoric acidGoymuk and Green River oil shale. Berkorich et al18])treatment is efective for removing most carbonate ,presented a novel technique to the thermaloxide，and monosulfide minerals from sedimentarycharacterization of oil shale. This approach involves therocks and leaves kerogen and pyrite largelyseparation of the unique components of oil shale, theunaffected-9. Effective removal of pyrite is usuallykerogen and the clay minerals, using chemical andthe main problem' 0. Petroleum geochemists have longphysical techniques. Enthalpy data for dehydration andbeen interested in obtaining pyrite free and chemicallypyrolysis of kerogen were also determined.unaltered kerogen concentrates. Quantiative removalThe aim of this study was to investigate the effectsof pyrite is not possible without alteration of the organicof hydrochloric and hydrofluoric acids treatments. Thecomposition. The magnitude of the change in thechemical changes occurring in the organic matter andorganie matter depends on the chemical nature of thein the inorganic matrix of the oil shale were studiedkerogen as well as on the reaction conditions. Pyrite ，using infrared (IR) spectroscopy and X -ray difractionfor example, may be removed from St. Hilair oil shaletechniques. The aims of this study were to obtain someby nitric acid ( HNO, ) but nitrogen content isbasic infornation on the nonisothermal decompositionincreased from 1. 33% to 2. 31%[10]. The extent ofof the oil shale or the isolated kerogen and to discussoxidation of oil shales and coals by HNO3 varies, butthe efect of the mineral matter and the heating rate onintroduction of carboxyl groups is a major cause of thethe decomposition characteristics and kinetics.increase in oxygen content!10]. The major part of theBasically, weight loss/ diferential weight loss ( TG/products formed from vigorous oxidation of kerogen isDTG) data have been used for the estimation ofusually carboxylic acids with perhaps smaller amountseffective parameters of the process.of hydrocarbons, terpenes, pyrole resins， tannin,1 Experimentalpigments, etci"0) ，but the effect can be minimized by1.1Materials In Morocco , oil-shale deposits haveusing dilute acid at moderate temperatures for shortbeen identified at 10 localities, the most important oftime period:ol. Stankiewicz et al. 11,121succeeded inwhich are Upper Cretaceous marinates9. The twoeficently eliminating pyrite from kerogen by densitydeposits that have been explored most extensively areseparation，after chemical destruction of the mainthe Timahdit and the Tarfaya deposits.minerals. The acid treatments did not significantly alterThe oil-shale deposit used in this study was fromthe kerogen structure and did not generate newlythe Tarfaya deposit located in the south westerm part offormed solvent-soluble organic material. The influenceMorocco, near the border with Westerm Sahara. Theof demineralization on a series of oil shale was testedoil-shale deposit averages 22 m in thickness and itsby Ballice'"i, the results indicate that the leaching ofgrade averages 62 /t. The total oil-shale resource ismineral matter with HCI, HNO3, and HF caused noestimaled at 86 billion tons within a 2 500 km2 area'remarkable change in the composition of volatileThis deposit is divided in five lithologic zones (P, Q,hydrocarbons.R, S, and T). Zone R has the highest organic partThermogravimetric analysis ( TGA) of the oil-with a thickness varying between 33 m and 42 m. Thisshale samples has been extensively used as a means ofzone is divided into five different sub-zones (RO, R1,determining pyrolysis characteristics and also toR2, R3, and R4). The highest amount of oil can bedetermine kinetic parameters' 14-18. Many researchersobtained by the R3 sub-zone which is therefore used inaround the world have used nonisothermal TGAthis study". The organic matter belongs to Type IItechnique to study the decomposition process andkerogen and covers a relatively wide range of maturitydecomposition kinetics of oil shale. For example ,with Rg= (0. 32 +0. 04)% ( vitrinite rflectance).Rajeshwar' 6) showed that the decomposition processVitrinite rellectance ( R) value is microscopicallyinvolves two consecutive first-order reactions. Kerogendetermined on the wood-derived maceral vitrinite.decomposes to intermediate bitumen and the pyrolytic1.2 Demineralization The finely ground samplesbitumen further decomposes into oil， gas， andof the oil shale were treated with chloroform ( CHCI,)carbonaceous residue. Karabakan and Yurumto extract the bitumen until the solvent in the soxhletstudied the efect of mineral matrix of oil shale. Theyarm中国煤化Ien-free (BF) oilfound that pyrolysis reactions were catalyzed byshaleFhed. It is thenalkaline earth metal cations in carbonates and inhibitedsubseCNMHi,0=1:2,by silicates. The inhibition efct of the silicates343 K under nitrogen ) until no further carbon dioxideseemed to be greater than the catalytic effect of theevolved. The residue was washed with. hot distilledcarbonates in the pyrolysis reactions of the originalwater until the silver nitrate test for chlorides was.第6期ABOULKAS A et al; Efte of acid treatments on Moroccan Tarfaya oil shale and .. .661negative. The hydrochloric attack was repeated twice to2 Results and discussioneliminate all calcium products. The decarbonated oil2.1 Efect of CHCl, extractionCHC; treatmentshale was dried, washed with a mixture of HCV/HF (was perfommed to extract the bitumen from the oil: 1) at 343 K under a nitrogen atmosphere. Theshale. IR spectra and difractogram of the original oilsilicate-free (SF) oil shale obtained in this step wasshale and BF oil shale are almost identical ( Figuresthen washed with hot ditilldl water. After drying SF1a, 1b, 2a, and 2b) suggesting that no alteation inoil shale, a saturated boric acid solution was added andthe organic matter of the oil shale occurred during thisthe sample was stirred for 30 min. Finally， thetreatment.remaining brown solid was treated with 6 N HCl andthe kerogen was washed with hot distilled water toremove chlorides and dried ovemight at 333 K. Thepyrite was removed by the method of densitydifference. The SF oil shale is subjected to ultrasoundanalysis，at 313 K for 60 min， fllowed bycentrifugation using CHClz， likemedium of3699 .75suspension. To extract the maximum of the pyrite, this1425separation is carried out three times. The yields of theI698Idemineralization procedure of the oil shale are|364presented in Table 1.802778Table 1 Chemical composition of the R3 sub-zone25|Composition w/%Bitumen0. 80Carbonate mineral70.00Silicate mineral10.00' 16401457 1379Pyrite1.00 .23Keroger17. oc40003000200010004001.3 Instrumental techniques IR spectroscopy: .Wavenumber σ/em'IR spectra were obtained with a PERKIN-ELMER-I760Figure 1 Infrared spectra of (a) oil shale,spectrometer. All samples for IR analysis were(b) bitumen-free oil shale, (c) carbonate-free oil shale ，prepared by grinding 2. 5 mg oil shale ( or(d) silicate-free oil shale, and (e) kerogen.demineralization product) with 200 mg KBr inigrinder for 20 min. The pellets were pressed in an2.2 Effect of dissolution on the mineral matrixHydrochloric acid treatments dissolved carbonateevacuated die from a 60 mg mixture of KBr andminerals present in the oil shale. The diffractogram ofsample, at 112.8 MPa for 1 minute and dried at 60 Cthe carbonate-free oil shale ( Figure 2c) contains fewerfor 24 h under a nitrogen atmosphere to remove water.peaks than that of BF oil shale ( Figure 2b). ThSpectra were obtained with a resolution of 2 cm~'X-ray diraction; A SIEMENS D501 X-raymissing peaks in Figure 2c correspond to those 0spectrometer with Ni-filtered CuKa radiation (λ =carbonate minerals originally present in the oil shale.0.1542 nm) was used at 32 kV and 20 mA.The presence of carbonate is also confirmned by IRDiffraction patterns were recorded from 5° to 60° in 2θmeasurements. IR spectra ( Figure 1a， 1b ) arewith a HP 3390 A integrator coupled to thedominated mainly by bands characteristic of carbonate;diffractometer. No significant peaks were seen betweena strong band in the range of 1 410 cm -60° and 80° in any of the analyzed samples 2x0.1430 cm~'. The presence of calcite is confirmed byTGA runs were performned in a RheometrixIR measurements in the original oil shale with a sharpScientifie STA 1500 TGA analyzer. The experimentsband at 875 cm ~ and a relatively less sharp band atfor the determination of the thermal decomposition712 cm-1[21]， These bands also occur in the IRtemperature were carried out with an initial samplespect中国煤化工ey are reduced tomass between 20 mg and 25 mg with a particle sizes inweakYCNMHG crbonat-ere oiltherangeof0.1mm~0.2mmandataheatingratesof2 K/min, 10 K/min, 20 K/min, and 50 K/min. ThHydrochloric and hydrofuoric acids were used toatmosphere used was nitrogen with a flow rate of arounddissolve silicate minerals. As it can be seen in Figure60 mL/min.2d，the peak characteristics of complex silicate_662燃料化学学报第37卷minerals disappear after hydrofluoric acid treatment.Hydrochloricacid and hydrochloric acid trealmentsQuartz- and kaolinite-type clay minerals are identifieddo not affect pyrite. The difactogram spectra in Figureas the main component of the nontreated kerogen. Th2d contain peaks， which are attributed to pyrites.quartz is the major component of silicate minerals ,These peaks are not observed in the previousdeflated by intense peaks. The presence of silicates indiffractogram because the peaks of other minerals maskthe carbonate-free oil shale was also confirmed by IRthem. The pyrite is removed by the method of densitymeasurements. Silicates generally show very intensediference.absorption bands in the 450 cm -1 ~ 550 cm ~ ' andThe X-ray diffractogram and IR spectra of the oil900cm~' ~ 1100 cm~' rangel-24).By comparingshale and its demineralized products show that theFigure 1c and Figure 1d, it can be seen that the peakmineral matrix of the oil shale is mainly composed ofcharacteristics of silicates disappear after hydrofluoriccalcite, quartz, and some clay minerals ( kaolinite andacid trealment. The sharp bands in the rangepyrite). Carbonate and silicate minerals can be3600cm -1 ~3 700 cm~, in adition to the normalremoved by acid dissolution, but pyrite is removed bysilicate absorption bands , are characteristic of kaolinitethe method of density difference. Many previousminerals'sI. The sharp bands at 690 cm' -1 ~ 790 cm~-'studies showed that HF/HCI treatments could notare attributed to quartz.eliminate pritl1726-2.2.3Effect of acid dissolution on the organicmatter of oil shale The kerogen is the organic part ofthe oil shale isolated from the mineral matrix. IRspectra make it possible to characterize the groupingfunctional major present in an organic matter, on theCother hand, to study the effect of acid dissolution on_silssSiaecS↓the chemical composition of the kerogen.The band located at 3 393 cm~' is due to 0Hstretching vibration ( Figure le). Since the pelletswere prepared under a dry nitrogen atmosphere duringgrinding and dried at 100 C for 2 h.The band at 1 376 cm -1 is atributed to methylenegroups. The band at2850 cm -1 ~3 000 cm -1 range isdue to the asymmetric and synmetric stretchings of C-esijlciiste s&tH of methylene groups. The absorption band at1456 cm~' in Figure 1e is from the asymmetricbending of methylene and methyl groups, and the bandat 1 376 cm' 1 is mainly due to the symmetric bendingof methyl groups'2. The band near 1 700 cm -1(Figure le) may be related to C二0 stretching ofNNein in 只carbonyl and/or carboxyl groups(21,29,30The band at 1 635 cm -1 in the kerogen spectrum(Figure 1e) is probably associated with aromatic ringstretching vibrations and C = 0 stretching of quinonesbridged to acidic hydroxy|25.31I. Indeed, recentworks'52-” ”support the assignment of this band to anaromatice stretching mode."hmThe kerogen spectrum contains unresolved bandswww.wnin the 1 000 em-' ~1 300 cm-' region ( Figure le)which may be due to the absorption of etheric C- -0bands, thnf which varv with the type ofsubstit中国煤化工12010607HCNMHG of the organic20/(° )matter persist atter une acia ureatment and aFigure2 X-ray dffractograms of (a) oil shale ,considerable increase in the intensity of these bands are(b) bitumen-free oil shale, (c) carbonat-free oil shale,observed. This can be illustrated by the asymmetric(d) sicateree oil shale, and (e) kerogen.and symmetric stretchings of the methylene groups CH第6期ABOULKAS A et al: Effects of acid treatments on Moroccan Tarfaya oil shale and ...，663in the range 2 800 cm-1 ~3 000 cm-' and C= 0is less. Usually, the TG in this stage is considered thestretching of carbonyl at 1 700 cm-' . This is explainedmeasure of water present in oil shale and their isolatedby the high relative concentration of the organic matterkerogen.in the kerogen in comparison to the oil shale.he effect of acid dissolution on the chemicalcomposition of kerogen can be examined by the changein C二0 absorption at 1 700 cm -1[38]. The kerogen5tspectra show that the C= 0 absorption at 1 700 cm -130↑becomes more intense and well be resolved. Oxidationof the organic matter is expected when the temperature0号12个during acid dissolution is higher than 60 C[38] ，导6+especially when the reaction mixture is dry. In ourmethod of the kerogen isolation, one pays a lot ofTampeaue I425Lattention not to heat the reaction mixture above 60 C300600under nitrogen atmosphere. The hydrochloric acid andTemperature TKhydrofluoric acid dissolutions do not probably cause aFigure4 TC curves of isolaled kerogen at iferent heating rateschange in the chemical composition of the organicinset: corresponding DTG curvesmatter and the alteration reaction does not occur as1 : 2K/min;▼: 10K/min; O: 20 K/min; V: 50 K/minindicated by the stability of the C= 0 band in the IRspectrum of kerogen.The stage of mass loss from about 433 K to 873 K2.4 Thremogravimetric analysis Figures 3 and 4occurs on account of the hydrocarbon material. The oilshow the TG and DTG curves of oil shale and theirshale and its isolated kerogen exhibit a one- stepisolated kerogen samples in relation to heating rate tothermal decomposition in the main mass loss areathe final temperature of 1 273 K. The curvesattributed to hydrocarbon volatile formation that is, indemonstrate two or three stages in the mass-loss profiletemperature range, 433 K ~ 873 K suggesting a one-illustrated in the derivative curves.step evolution hydrocarbon volatiles from the oil shaleand its isolated kerogen. The one-step decomposition10has also been observed by other workers for different oilshale，for example， Huadian'41 ，Pakistan ( Kark ,Dharangi and Malgeen)(42)， and Jordanian43] oil16个” 80shales. However , Turkish oil shalel4J and Kimmeridgeoil shale45 exhibit two-stage thermal decomposition.Therefore. , whether the decomposition is a one-stage ortwo-stage process, depends on the type of the oil60shale. Usually , decomposition of kerogen to oil, gas,and char products is a two-stage process. First,Temperature TK_50300901200decomposition of kerogen to pyrolytic bitumen occursTemperature TIKand，second， decomposition of bitunen to finalproducts takes place. Though the curves show one-Figure 3 TC curves of the oil shale at diferent heating ratesstage or two-stage decomposition process of oil shales ,insel: corresponding DTG curves■:2K/min;▼: 10K/min; O: 20 K/min; V: 50 K/minthe mechanism of decomposition is a much morecomplex reaction involving a seriesof parallelThe lower temperature region of mass loss of bothreactions45,46]samples，up to approximately 443 K，has beenHeating above 873 K produces mineral matterattributed to the loss of moisture, loss of interlayerdecomposition at temperatures between 873 K andwater from clay minerals and also decomposition of1200K due to the presence of the carbonate andmineral nahcolite which is one of the minerals presentin the raw shale[39]. The mass loss has also been中国煤化工). The ol oleshowe; range due to theattributed to physical changes, such as softening andpreseYHCNMHGmolecular rearrangement associated with the release ofTable 2 shows the analysis of the TCA data ingases in kerogen prior to its decomposition to bitumenrelation to heating rate in terms of the onset of massmay occur as well40. Above all, in this stage theOSS of kerogen ( Tonset )， the temperature wherepredominant cause of mass loss is simply moisture and664燃料化学学报第37卷maximum devolatilization occurs ( T ) and therange of443 K~1200 K.maximum rates ( R, 献) of mass loss in the temperatureTable 2 Comparison of thermogravimetric data of oil shale and isolated kerogen samplesHeating rateTemperature T /KRate of mass loss w/%●min'Sample/K.min~' .LanalR0il shale253710170.182. 24058010410.684.9020602 .7161 0641.627. 2350626731 1104.2714.56Kerogen4606580.924786764.655239.945707227.77As the heating rate is increased, Table 2 showsreaction equation may simply be expressed as ththat there is a lateral shift to higher temperatures forfollowing formula:tomet, tma, and tme2 for both the samples. The lateraldx_= Aexp(- D.)(1-x)(1)shift is also ilustrated in Figures 3 and 4 for the DTGdtRT'curves. The rate of mass loss also reflects the lateralwhere A is the pre-exponential factor, E is thshift with an increase in the rate, as the heating rate isactivation energy, T is the temperature, t is the time,increased from 2 K/min to 50 K/min. The lateral shiftx is the TG fraction or pyrolysis conversion which canto higher temperatures for the maximum region of massbe calculated byloss has also been observed by other workers usingx=mo -m,(2)TCA to study the pyrolysis of oil shales. For example,mo-m(Gersten et al. [47) showed a lateral increase in thewhere mo is the initial mass of the sample, m, is themaximum rate of TG of about 38 C as the heating ratemass of the sample at a given time t or temperature T,was increased from5 to 50 K/ min for Israel oil-shale.mqis the final mass of the sample at the end of theKok[48] and Jaber and Probert40.43] also showed adegradation.lateral shift in the maximum rate of mass loss for theFor a constant heating rate β during the TGATGA of oil-shale samples. This can be attibuted to theexperiment,β = dT/dt，Eq. (1) can be modified byvariations in the rate of heat transfer with the change inintroducing the heating rate as follows:the heating rate and the short exposure time to adxxdT; Aexp(- )(1 -x) .(3)particular temperature at the higher heating rates'dTx duas well as the effectof thekinetics ofdecomposition' 50。Actually, at higher heating rates,the extemal surface of the shale particle will be at a= Aexp(-前)(1-x)(4)higher temperature than at its core. This will lead toBy integrating Eq. (4) and taking logarithms, wereactions occuring insidparticle at lowerobtaintemperatures and the resultant products will leave andARpass through the high-temperature region， henceln[-ln(1-x)]=In2RT(5)T[BE(1-一)] RTsecondary reactions ensue. The latter will reduce theyield of shale oil as the required product from the oil-It may be shown that for most values of E and forshale pyrolysis process.the temperature range of the pyrolysis, the expressionThe data in Table 2 also indicate that tome andIn [AR/BE(1 -2RT/E)] in Eq. (5) is esentallytmas of isolated kerogen are inferior to those of organicconstant, if the left side of Eq. (5) is plotted versusmatter of oil shale.1/T, a straight line may be oblained if the process canThe mathematical procedure used in this study, inbe ass中国煤化工From the slope,the analysis of TGA data for determining the kineticE/n be determined,parameters，activation energy， and pre-exponentialandfYHCNMH Gm,= (mo+m)/factor is based on the integral methodMany2 in the place of T in the intercept term of Eq. (5),investigators assumed that the solid fuel pyrolysis is athe pre-exponential factor A can also be determined.first-order reaction'[ 1.43.0. So the oil shale pyrolysisIn this study， the kinetic parameters are第6期ABOULKAS A et al; Elects of acid treatments on Moroccan Tarfaya oil shale and ..665 .determined for the region where the main kerogenbetween 0. 993 and 0. 998. The kinetic parameters ofdecomposition takes place (433 K ~873 K). Figures5the oil shale and its isolated kerogen are listed in Tableand 6 show the Arrhenius plots used to obtain the3. As seen from Figures5 and 6, one straight line forkinetic parameters of the decomposition processes of each heating rate of both samples, indicating a singlethe oil shale and its isolated kerogen under pyrolysis ,kinetic expression is valid over the temperature range ofrespectively.kerogen pyrolysis between the temperatures of about433 K and 873 K.-14.8-12.-12.5-15.213.0-.15.6E -.13.5-16.0 I-14.0-14.5 |0.001350.001500.00165 .0.0180I/T /K+0.001200.00165Figure5 ln[ --*2]versus 1/T of oil shale at1/T /K+different heaing ratesFigure6 ln[= ng -32]versus 1/T of isolated kerogen at■:2K/min;▼: 10K/min; O: 20 K/min; V: 50 K/mindifferent heating ratesThe best fit line gives a correlation cofficient■:2K/min;▼: 10 K/min; 0: 20 K/min; V: 50 K/minTable 3 Kinetic parameters of oil shale and isolated kerogen at dfferent heating ratesHeating raleKinetic paramelersCorrelationSample/K.min~'E/ k.mol-'A/ min。cofficient rOil shale2304.83x 10-30.9971364.35 x 10-0.997020501.770.9976so05.960.998 4Kerogen2408.710.9934102979. 800. 99444210.62 x 1020. 995 35314.82 x 10'0. 9985From the data in Table 3, it is found that theDembickis) examined the efect of various minerals onkinetic parameters depend on heating rate. As thethe determination of source rock kinetic parameters, byheating rate increases, the apparent activation energypyrolyzing mixtures of sedimentary minerals withand the pre -exponential factor also increase. This isvarying concentration of akerogen isolated fromprobably due to greater rates of heat transfer occurring.Kimmridgian black shale. The kinetic parametersHowever, the removal of mineral matter caused 8derived indicated that added mineral matter, such asdecrease in the activation energies of the pyrolysisquartz, calcite， and dolomite shfted the activationreactions of oil shale. It is probable that the difusionenergy to higher values than those of observed for theof the organic matter throughout the mineral matrixisolated kerogen.required a higher temperature and relatively moreComparison with literature data shows that theenergy. This is in accordance with greater Tonsetkinetic nobserved for original oil shale (Table 2). Activationoil sh中国煤化工ained an activationenergies calculated for the pyrolysis reaction of isolatedenerg,CNMH Gthermal TCA ofkerogen are lower than those of the original oil shale.Puertollano ( Span) 011 shale. Sonibare et al.[55]In this respect, the values reported here are similar toperformed nonisothermal TGA on Lokpanta oil shalesthose given in literature for oil shale',17,27,52]( Nigeria) and found the activation energies vary from666 .燃料化学学报第37卷73. 2 kJ/mol to 75 kJ/mol. Other workers haveacid and hydrofluoric acid dissolution. The pyrite isreported similar apparent activation energies for theremoved by the method of density difference.main stage of decomposition of organic matter oil shale.CHCl, extraction of the oil shale inereases thskala et al:9] performed nonisothermal TGA onintensilty of the peaks in the X-ray diffractograms. IRYugoslavian oil-shales and found overall apparentspectra and X-ray diffractograms reveal the presence ofactivation energies ranging from 42.9 kJ/mol tomineral, calcite, quartz， kaolinite, and pyrite in the114.7kJ/mol. Dogan and Uysal"4)， however,mineral matrix of the oil shale. Hydrochlorie andreported results for Turkish oil-shale of approximatelyhydrofluoric acid dissolution do not alter the organic25 kJ/ mol for the lower temperature decomposition andmatter.up to 43 kJ/mol for the main stage of decomposition.Experimental and kinetic analysis data enabled toSimiarly, Jaber and Probert43] reported apparentestablish that decomposition of Tarfaya oil shale andactivation energies for the two-stage pyrolysis oftheir kerogen samples is a frst-order reaction. A singleJordanian oil-shales with a low temperature value ofkinetic expression is valid over the temperature range of10 kJ/mol and a higher temperature value of the rangekerogen pyrolysis between 433 K and 873 K.of 40 kJ/mol ~ 68 kJ/mol.Furthermore, the results indicate that the removal ofmineral matter causes a decrease in the activation3 Conclusionsenergies of the pyrolysis reactions of oil shale. As theX-ray diffractograms and IR spectra of oil shaleheating rate increase, the activation energy and theand its demineralized products obtained by the acidpre-exponential factor increase in pyrolysis reaction ofdissolution show that the carbonate and silicateoriginal oil shale and isolated kerogen.minerals of oil shale are removed upon hydrochloricReferences[1] C-HOURCADE M L, TORRENTE C, GALAN M A. Study of the solubility of kengen from oil shales (Putollno, Spain) in supercitical tolueneand methanol[J]. Fuel, 2007 , 86(5/6): 698-705.2] BEKRI 0, ZIYAD M. 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