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超声波处理高酸重质原油流变性研究2.rar

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    超声波 处理 高酸重质 原油 流变 研究
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    3144r2010 American Chemical Society pubs.acs.org/EFEnergy Fuels 2010, 24, 3144–3149:DOI:10.1021/ef901302yPublished on Web 05/04/2010Reduction of Paraffin Precipitation and Viscosity of Brazilian Crude Oil Exposedto Magnetic FieldsJosC19e L. Gonc-alves,*,†Antonio J. F. Bombard,†Demetrio A. W. Soares,†and Glaucia B. Alcantara‡†LaboratC19orio de Reologia Dr. Hans Martin Laun, Instituto de Ci^encias Exatas, Universidade Federal de ItajubC19a (UNIFEI),ItajubC19a, Minas Gerais (MG) 37500-001, Brazil, and‡LaboratC19orio de Resson^ancia MagnC19etica Nuclear (RMN), Instituto deQuı´mica, Universidade Federal de GoiC19as (UFG), Goi^ania, GoiC19as (GO) 74001-970, BrazilReceived November 6, 2009. Revised Manuscript Received April 9, 2010Theproblemsrelatedtoorganicdepositiononpipelinewallsarewell-knownandhavebeenchallengingthepetroleum industry since the primordial days. Some problems can result in a decrease of the productionrateorariseinthepumpingpower.Motivatedbytheseproblems,thepresentworktriedtounderstandtheinfluenceofmagneticfieldsonparaffincrystallizationandthereductionofcrudeoilviscosity.Amixtureofparaffin(C15-C58)wasdilutedinn-hexane,andthesolventwasevaporatedslowly,undertheinfluenceofa0.3 T magnetic field, and also naturally, without the influence of magnetic fields. The micrographs ofparaffin crystals show that the magnetic field influenced the crystallization process. Further, for a betterunderstandingofthereductionofcrudeoilviscosity,someexperimentsweremadetoshowtheinfluenceofamagneticfield(1.3T)ontheviscosityofthreesampleswithdifferentparaffincontents.Sample1haditsviscosityreduced.Originally,itsviscositywas69cP.Afterexposuretothemagneticfield,itsviscositywasreduced to 39 cP. The other samples maintained the same viscosity before and after magnetic fieldexposure.Therefore,thereductionofoilviscositydoesnothappenforalltypesofcrudeoils.Inanattemptto detect the factors in sample 1 that probably affect the reduction of oil viscosity, the samples wereanalyzedbythetechniquesof1Hnuclearmagneticresonance(NMR)andvibrationsamplemagnetometer(VSM) and next compared to each other.1. IntroductionTheproblemsrelatedtotheorganicresinaccumulationandthetreatment ofhigh-viscosity crudeoilsarewell-knownandhave been challenging the petroleum industry since its pri-mordial days. Recently, some researchers have claimed thatmagnetic/electric fields may affect the quality of some crudeoil beneficially.1-7Here, some authors suggest a “new physi-cal mechanism”2,3,8of viscosity reduction based on electro-and magnetorheology principles.9-14Von Flatern5reportedthat paraffinic crude oils have a reduction in their viscosityafter exposure to magnetic fields. Rocha et al.1and Tao andXu2,3performed some experiments with crude oils and mag-netic/electricfieldsandreachedtheconclusionthatparaffiniccrude oils interact with magnetic fields in a strong way.Paraffin is an organic component responsible for causingthe problems described before, and it is worth understandinga little more about the influence of magnetic fields on itsproperties.Onthebasisofthat,thepresentworkshowsthatasample of crude oil has its viscosity and wax appearancetemperature (WAT) reduced after having been exposed to a1.3 T magnetic field for 1 min. The present work also showsthat a 0.3 T magnetic field can modify the crystallizationprocess of a paraffin mixture. To acquire more informationconcerning the magnetic behavior of samples, we measuredtheir magnetization. Information about the kind of hydro-carbonmoleculespresentinsampleswasobtainedbynuclearmagnetic resonance (NMR) spectroscopy.2. Materials and MethodsInanattempttoobservetheinfluenceofthemagneticfieldonthe paraffin crystallization process, a mixture of paraffin (C15-C58)wasdilutedonn-hexane.Theparaffinwasevaporatedonanacrylic plate with the influence of a 0.3 T magnetic field andnaturally,withoutthemagneticfieldinfluence.Thecrystalswereobserved by optical microscopy.After that, we analyzed the influence of a high-intensity mag-neticfield(1.3T) ontheviscosityofparaffiniccrudeoil.Astress-controlledrheometer(PhysicaMCR-301,AntonPaar,Germany)was used to measure the viscosity of samples. The rheometerwas equipped with a Peltier cell to control the temperature and*To whom correspondence should be addressed: LaboratC19orio deReologia, Universidade Federal de ItajubC19a, Av. BPS 1303, ItajubC19a,MG 37500-903, Brazil. Telephone: þ55-35-3629-1222. Fax: þ55-35-3629-1140. E-mail: [email protected](1) Rocha, N.; Gonzalez, G.; Marques, L. C. do C.; Vaitsman, D. S.Pet. Sci. Technol. 2000, 18,33–50.(2) Tao, R.; Xu, X. Energy Fuels 2006, 20, 2046–2051.(3) Tao, R. Int. J. Mod. Phys. B 2007, 21, 4767–4773.(4) Tung,N. P.; Vinh, N. Q.; Phong, N. T. P.; Long,B. Q. K.; Hung,P. V. Phys. B 2003, 327, 443–447.(5) Von Flatern, R. Offshore 1997, 57,3.(6) Gonc-alves, J. L.; Bombard, A. J. F. Proceedings of the RioPipeline Conference and Exposition, Rio de Janeiro, Brazil, 2009;IBP1329_09.(7) Evdokimov, I. N.; Kornishin, K. A. Energy Fuels 2009, 23, 4016–4020.(8) Tao, R.; Huang, K.; Tang, H.; Bell, D. Energy Fuels 2009, 23,3339–3342.(9) G€ulder,€O. L. Energy Fuels 2009, 23, 591–592.(10) Bombard, A. J. F.; Knobel, M.; Akantara, M. R. Int. J. Mod.Phys. B 2007, 21, 4858–4867.(11) Bombard,A.J.F.;Antunes,L.S.;Gouvea,D.J.Phys.2009,149,No. 012038.(12) Fang, F. F.; Choi, H. J.; Jhon, M. S. Colloids Surf., A 2009, 351,46–51.(13) Choi, H. J.; Jhon, M. S. Soft Matter 2009, 5, 1562–1567.(14) Choi, H. J.; Jhon, M. S. Ind. Eng. Chem. Res. 1996, 35, 2993–2998.3145Energy Fuels 2010, 24, 3144–3149:DOI:10.1021/ef901302y Gonc-alves et al.cone-plate geometry (50 mm in diameter and 1C176 cone angle). Forthe reason that the magnetic field interferes with Peltier systems,an external electromagnet was used to generate the magnetic field(1.3T).Thecrudeoilsampleswereplacedin150C217mmtesttubes,and their temperatures were kept constant in a thermostatic bath.The samples were supplied by Petrobras and named samples1-3.Accordingtothesupplier,theparaffincontentforsamples1and2was11and6%(w/w),respectively.Originally,sample3was1% (w/w) paraffin content, and 10% (w/w) paraffin was added,resultinginacrudeoilmixturewith11% (w/w) paraffin.Duringall processes, the temperature of the samples was kept constantaround their WAT. Basically, the viscosity of the sample wasanalyzed before and after exposure to a 1.3 T magnetic fieldfor 1 min.The magnetic behavior of samples was analyzed by the vibra-tion sample magnetometer (VSM), Lakeshore 7404.To measure the aliphatic/aromatic hydrocarbon ratio in sam-ples,BrukerAvanceIII500(11.75T)NMRspectroscopewasused.3. Results and DiscussionInthepaper byRochaet al.1, it isshownthat themagneticfieldsalterthemorphologyofparaffincrystals.Weattempttoanalyzewhat wouldbe the influence ofa 0.3T magnetic fieldon the process of paraffin crystal formation. A blend ofaverage weight (550 g/mol) with a molecular distributionfrom C15to C58, with 75% aliphatic and 25% branched andcyclic hydrocarbons, was dissolved in n-hexane. A total of2mLofthismixturewasdepositedonanacrylicplate,andthesolvent was evaporated at ∼25 C176C and room pressure. Theprocessofsolventevaporationoccurredsometimesunderthe0.3 T magneticfieldinfluence and sometimesnaturally,with-out the magnetic field influence. The paraffin crystals wereobserved by reflected optical microscopy and are shown inFigure 1.Onecanseeinpanelsa-cofFigure1someblackpointsthatare clusters of paraffin surged during the volatilization ofsolvent. Panels d-f of Figure 1 show the paraffin crystallizedunder the influence of a 0.3 T magnetic field. Visually, theamount of paraffin crystals formed under the 0.3 T magneticfieldactionwaslessthancrystalsformednaturally,withoutthemagnetic field influence. Moreover, using the optical micro-scope,itwaspossibletoobserveparaffinclustersformedduringthesolventvolatilization.Inthiscase,theparaffinclusterswereobservedjustontheplatethatwasnotexposedtothemagneticfield. This experiment was repeated 3 times, and the 0.3 Tmagnetic field appeared to interfere with the paraffin crystalformation.Because paraffin is present in crude oils and the magneticfieldappearedtointerferewiththeparaffincrystalformation,wetriedtomeasuretheintensityoftheinteractionbetweenthemagnetic fields and some samples. The magnetization curveswere measured by a VSM and are shown in Figure 2.Panels a-c of Figure 2 show that the samples with aparaffin content of 11, 6, and 11% (w/w) has a diamagneticbehaviorunderhigh-intensitymagneticfields, whichmeans afeeble interaction between them, compared to paramagneticand ferromagnetic substances.Besides the interference of magnetic fields on paraffincrystallization, the literature also reports the reduction ofWAT and viscosity of paraffinic crude oils after they wereexposed to magnetic fields.1,2To corroborate that, someexperiments were performed. WAT and viscosity of threecrudeoilsweremeasuredbyrheometry,beforeandaftertheywereexposedtoa1.3Tmagneticfield.Thethreesamplesweredivided into samples 1-3, and the results are as follows.3.1. Sample 1. The paraffincontent in thissampleis 11%(w/w), and its WAT was measured by rheometry. TheFigure 1. (a-c) Paraffin crystals formed naturally, without the magnetic field influence. (d-f) Paraffin crystallized under the influence of a0.3 T magnetic field.3146Energy Fuels 2010, 24, 3144–3149:DOI:10.1021/ef901302y Gonc-alves et al.sample was heated until 80 C176C and cooled to 15 C176Cat2C176C/min, and the WAT of the sample is observed at the inflec-tionpointofthecurve.Figure3showstheWATofsample1before and after it has been exposed to a 1.3 T magneticfield.According to Figure 3, before the sample exposure, theWAT of the sample is clearly visible at approximately 45 C176Cand, after its exposure, it is observed at 41 C176C. There was afurther reduction of sample WAT of 4 C176C.Subsequently, after the WAT of sample 1 had beenmeasured, a new amount of sample 1 was prepared. It wasFigure 2. Magnetization curves of three samples: (a) sample 1, (b) sample 2, and (c) sample 3.Figure 3.WATofsample1measuredbyrheometrybeforeandafterits exposure to a 1.3 T magnetic field.Figure 4. Viscosity of sample 1 before, immediately after, and150 min after being exposed to a 1.3 T magnetic field.3147Energy Fuels 2010, 24, 3144–3149:DOI:10.1021/ef901302y Gonc-alves et al.conditioned at 45 C176C, and its viscosity was measured at aconstant shear rate of 50 s-1. The viscosity of sample 1 weremeasuredbeforeandafterbeingexposedtoa1.3Tmagneticfield for 1 min, and the result is in Figure 4.InFigure4,0,9,and2representtheaverageofmeasuredpoints and the bars represent the standard deviation. Ac-cording to the figure, the viscosity of sample 1 before itsexposure to the magnetic field was 66 cP and, immediatelyafter that, it was reduced to approximately 39cP. There wasa reduction of 40%. Nevertheless, the reduction was notstable. Slowly the sample 1 viscosity returned to the originalstate. After 150 min, the viscosity of sample 1 was measuredagain and presented at 46 cP. In the oil field, far fromlaboratory conditions, these results could have interestingapplications.Foroiltransportation,energycouldbesavedinoil pumping, and because the oil viscosity returns to theoriginal oil very slowly, it could reach 10 km in 150 min,because the oil velocity in pipe is 4 km/h.23.2. Sample 2. According to the supplier, this oil has aparaffin content of 6% (w/w). It was exposed to a 1.3 Tmagnetic field for 1 min at 28 C176C. Its viscosity was measuredbeforeandafterbeingexposedtothemagneticfield,andtheresults are in Figure 5.In the figure,0and9are the average of measured pointsand the bars are the standard deviation. Any meaningfulalterationwasnotobservedontheviscosityofsample2afteritsexposure tothemagneticfield.Itsviscosity wasthesame,even though it presented a 6% (w/w) paraffin content.3.3.Sample3.Inacomparisonoftheresultsobtainedfromsamples 1 and 2, one can observe a reduction of 40% inviscosity for the first and nothing for the second. Accordingto some authors,1,2the reduction of the viscosity of somecrude oils is caused by the presence of paraffin in the oil andthe higher the paraffin content in the oil, the stronger theinteraction between the magnetic field and the sample.Onthebasisofthat,wepreparedamixtureofcrudeoilandparaffin (sample 3). This crude oil already had 1% (w/w),and thus, we added a 10% (w/w) blend with 550 g/molaverage weight, molecular distribution between C15andC58, with 75% (v/v) aliphatic and 25% (v/v) cyclic andbranched molecules, resulting in a mixture of crude oil with11% (w/w) paraffin content.The WAT of sample 3 was measured by rheometry, andthe inflection point became visible at 39 C176C. Similar to theothersamples,sample3wasexposedtoa1.3Tmagneticfieldfor1min,ataconstanttemperatureof39C176C,anditsviscositymeasurement is shown in Figure 6.In the figure,0and9are the average of measured pointsand the bars are the standard deviation. According to thisfigure,anymeaningfulalterationoftheviscosityofsample3was not observed, even though this sample has 11% (w/w)paraffincontent.ConsideringthementionedworksofRochaetal.1andTaoandXu,2whichreportedthatthereductionofoil viscosity is caused by the interaction of paraffin with amagnetic field,a reductionof the viscosityof sample3 wouldbe expected, as observed in sample 1.In view of the fact that the paraffin was not the crucialfactor responsible for promoting the reduction of the visco-sity of the samples, we attempted to describe the substancesand structures of molecules present in the samples thatinteract with the magnetic field. With concern to that, weanalyzed the types of major molecules in samples by NMR,as shown in Figure 7.The peaks observed in the chemical shift in Figure 7between 0 and 4 ppm correspond to the aliphatic hydro-carbons,whilepeaksobservedinthechemicalshiftbetween6and 9 ppm correspond to aromatic hydrocarbons. The peakat 4.6 ppm, more notable in sample 1, corresponds to water.Inquantitativechemicalanalysisby1HNMR,theintegralofthe peak area corresponds to the quantities of chemicalconstituents. Hence, the proportion of molecule types wasobtained by the integration and shown in Table 1.Among the samples described on Table 1, sample 1 pre-sented the biggest aromatic/aliphatic ratio and also themajor water concentration (10%, v/v). Furthermore, thiswas the unique sample which presented a significative vis-cosity reduction.The supplier of sample 1 provided some additional data,which are described in Table 2.Table 2 shows some features and properties of sample 1after its dehydration.4. ConclusionAccording to the optical micrographics of crystallizedparaffin, the magnetic field influenced the process of para-ffin crystal formation. Visually, the amount of paraffin crys-tallized under the 0.3 T magnetic field was less than thatcrystallized naturally, without the magnetic field action.Figure 6. Viscosity of sample 3 before and after exposure to a 1.3 Tmagnetic field.Figure 5. Viscosity of sample 2 before and after being exposed
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