IICPT Inqi Journal of Chcmicel.rd P.trolcum Enginccritrg                             lraqi       Chemical Petroleum       ...
otin,     ultimately lead to the design of inherently stable diameter,3 cm externaldiameter                               ...
Khalid A. Suk*ar et oIbtd                                                                        1-lI eteringburettetr    ...
Study of catalysts dea9lry!!!9n in isomerizationprocess Io produce high octane gasolinestrontium chloride in 500m1 distill...
Khalid A. Sukko a aI                                                        show fast catalystdeactivation  causedby depos...
Study of catalysts deactivation in isomerizationprocess to produce high octanegasoline  Membrane  Packed    with pt-loaded...
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  1. 1. IICPT Inqi Journal of Chcmicel.rd P.trolcum Enginccritrg lraqi Chemical Petroleum Journalof and Vol.8No.3(September ISSN: Engineering 2007)43-48 1997-4884 Univcnity ofBrgbdd Coll€c of EDtinE iog Deactivation lsomerization Studyof Catalysts in Process to ProduceHigh OctaneGasoline Khalid A. Sukkar,HayamM. Abrlul-Raheemo Amel Th. Jubern and Jabir Sh.Jurnaly ChemicalEngineering - University Technolog,t Department of - Iraq * College Engineering * - University Al-Nahrain Iraq Chemical Department Engineering of ofAbstract In this study the isomerization desulfuerized of light lraqi petroleumnaphtha(Al-DuraRefinery)with boilingpointrange of 37 to 124 oC , 80.5API specificgravity and 68.2 octanenumber has beenirwestigated.Two typesofcatolystswereprepared (P1/HXand Pt/SrX) by impregnationof 0.8 wt%o on l3X-zeolite. The catalyst activity and Ptselectivitytowardisomerization, catalyt deactivation and wereinvestigated. Theisomerization consisled a vertical tubular stainless unit of steelreactorof 2 cm internaldiameter, cm external 3diameter and 68 cm height.Theoperating pressure was atmospheric all experimental for runs. Theliquidflow of light-naphtha was A.4 IJh, and the catalystweight was 50 gm, H/H.C ratio usedwas 4 for all experimental runs. Theisomerizationprocess studiedat dfurent tenperatures 250, 270, 275, 300,325, and 350oC , Itwasfound that, was ofthe optimum isomerization is temperature 270"C Theisomerizationactivities snd selectivities afunction of timeshowedhigh activity at the beginningof the reaction osord were deactivated rapidly. This indicatesthat the deactivationof PI/HX and Pt/SrX results from the blocking of porenouth by the depositedcarbon. Thefollowing deaeliv;ation decreasingorder, PI/HX > Pt/SrX wasfound. On the other,nnd, PI/HX cotalyst shows higher activity and selectivitythqn that of Pt/SrX. It waseoncluded that,only an cverage 90 wt% of the carbonatoms of feed into thereactor(light naphtha)is detectedin theproductstreamduetoformation of cokedeposits which leadsto cqtalystdeactivation. resultsclearlyshowed Thethot hydrogenis necessary the ltydrogenation olefinsin order to preventoligonerizationreactionthat leadslo for ofcoke formation and catalystdeactivation. light-napgtha,PIJHX PVSrXcatalysts,Icywortls; catalyticisomerization, and deactivation.lnboduction In general,a catalystmay lose its activity or its selectivity to poisoning, due fouling,sintering lossof and Due to a heightened awareness the environrnental of activespecies Oneof the mostchallenging [], tasksinpoblem worldwide,expectations cleanand unleaded of the designand operation industrialcatalyticprocesses ofgasoline and world demand for gasoline have been is the prevention,or at least the control, of catalystircreasing.Catzl5ticisomerization regardedoneof the is deactivation. Loss of catalyst activity is oftenmostimportantprocesses oil refineries in which produce accompaniedby a loss in selectivity. This leads tocleanand high octanegasoline. Isomerization convefts n- greater formation of undesired by-products such asbutane, n-pentaneand n-hexaneinto their respective wasteof carbonoxides,poor utilizationof raw rnaterials,boparaffinsof substantiallyhigher octanenumber.The energy,and increased pollution [3,4]. Thus, solvingoommon feedstocke isomerization for process the light is problems of paramount deactivation is importance the forsaight run naphtha, which consists the lighter fraction of economicand ecologic performance the process ofcs tc6Lt,2l. industry.Understanding deactivation mechanisms could Vol.8No.3(September IJCPE 2007) 43
  2. 2. otin, ultimately lead to the design of inherently stable diameter,3 cm externaldiameter and 68 cm height catalysts, considerable with benefits.Solvine deactivation (reactor volume 214 cm3).The reactor was heated -of problems requiresa detailedknowledge th. ,uny uniformlyusingan electrical furnace.Thetemperarure at causes mechanisms and involved [6,7,gJ. the reactorcenterof the catalystbed and at different , On theotherhand,foulingformation regarded of is one points in reactor and system were determinedby the most importanttypes of catalystdeictivationin manufacturingan interface system, (Computerized isomerization process.Generally,the kinetics of a Temperature Measurement System) which has ten catalyst deactivation a functionof temperature, is time, calibrated thermocouple sensors K (iron-constantan). type pressure and the concentrations of different Theinterface programmed is andrun by a computer (p4). substances l0]. [9, The reactoris fittsd with accurate meansfor controlof The principal differences between the various pressure, and liquid flow rates. The experiments gas industrial processes isomerization of relate thecatalyst were conducted atmospheric to at pressure.Feedmixtures used; this will in turn affectthe feedpretreatment steps of hydrogenand hydrocarbon were preheated reactor to and spent catalyst characterization. The two principal temperature beforeentering bed. the typesof catalystidentifiedin the industry areiplatinum on zeolite,which operates temperatures at above2OO oC, and platinum chloride on alumina, which operates at temperatures below200 oCIll, l2]. Themainadvantage of zeolites overplatinum chlorinated on alumina.atalyJtt is that they have a much betterresistance againstfeed impurities such as water, which obviates need for the expensive drying facilities.Moreover,in zeolitebased processesit is unnecessary to continuouslyadd chlorinating agents, remove hydrogen chloride from effluent steams and take precautions againstcorrosion. Manyauthon haveinvestigated catalyst the deactivation phenomenon over PVA|2O3 catalystusingn-pentane, n- hexane,and n-heptane a feedstock isomerization as for reaction 13,l4]. [ll, In order to designand optimize catalysts, detailed a undentanding of the reaction mechanism,kinetic, deactivation and catalyst properties is of primary interesl The combination between catalystperformance and understanding catalystdeactivation will enable of the designof a new catalystwith reduceddeactivation and increased acrivity and selectivity for desired products. Therefore, present the work aimsto: - providea substantiated Fig.(1)General view of experimental apparatus knowledge the isomerization of reaction based on bifunctional zeolite catalystsby using light-naphthaas a feed and determiningthe optimumproc€ss conditions. Materials - test the performance, deactivationrates and catalyst Two typesof catalysts namedPt/HX and pt/SrX were stabilityunder optimum process conditions prepared. preparation the catalysts were carried The of out by impregnation extrudates x 5) mm of sodium of (3 Experimental Work typel3X zeolite, SilAl = 2.8 ( Linde Company) with 0.8 wt% platinum.Catalytic unit Dried and desulfurized Iraqi light petroleum naphtha The experimental study was carriedout to investigate deliveredby Al-Dura Refinery-Baghdad used as a wasthe catalysts activity, selectivity and catalysts feedstock. Hydrogengas was suppliedfrom Al-Mansourdeactivation rate by building an experimental rig plant (purity is 99.9 %). Various rypes of chemicalspecifiedfor isomerization reaction,as shown in Figure compounds wereused.Hexachloroplatonic H2ptCl6acid(l) whichrepresents general view of experirnental unit. (40%wtPt), strontium chloride, ammonium chloridewere Figure(2) showsa schematic diagramof a fixed bed obtained from FlukaAG.flow-typeapparatus. isomerization consists a The unit of The properties chemical and analysis light-naphtha ofvertical tubular stainless steelreactor 2 cm internal of are tabulated Tables(l) and (2) respectively. the in On otherhand,according G.C, analysis to shownin Table44 IJCPE Vol.B No.3(September 2007)
  3. 3. Khalid A. Suk*ar et oIbtd 1-lI eteringburettetr 3-Dosiug putryI 3-Liquid meter flonUd J- I iddelraltetr 5- IIJ flonmetert 6-5AlloletularSiete j- Onewa.vtalvef 8-II iringsettisrt3 9-feed preheatiug zoneI 10- Temperamre controls)-stem 1I- Pressure touttolsf$em 12- Smiuless reattor steel 13- eatiug II fiuuace 1.1- Tbermocouples 15-Co uterizetl mp iuterfares.Ystem 16-P4conp ilter l?- Cooliug slsrem 18-Gas ChronatograPhY Fig. (2) Schematic of apparatus diagram the experimental (2), the main components the light-naphthafeed are of analysis light-Iraqipetroleum Table(2) Chemical of n-hexane (35.70 and - 408 volYo naphtha n-pentane and reipectively) which indicates that, the catalytic ComDosition wl%o process n-Pentane 35.70 isomerization suchfeed may be a dominant for 40.80 n-Hexane Therefore,such processcan be used to improve the MethvlCvcloPentane l l l3 octanenumberwhen optimum operatingconditionsare Bertzene 1,40 applied. Cvclohexane 2.82 n-HeDtane 3.15 leum n-Octane 1.88 Table( I ) TheproPerlies I of t-l i t.54 Property Data Toluene t{ 604 0.665 1.22 80.5 Total 99.64 API Distillation I,B.P, 3? oc Modification 13X-Zeolite of 5 Vol.7o distilled 42C l0 Vol.o/odistilled 48"C NaX In orderto modify the NaX zeolitespecification, 20 Vol.%distilled 52c zeolite were exchangedwith two type of cations 30 Vot.%distilled 560C 40 Vol.% distilled 60.oc (Ammonium and Strontium). The Na+ ions were 50 Vol.%distilled 550C ixchanged for NH4+ ions to obtain the HX by ion 60 Vol,%distilled 68"C exchangingthe original NaX zeolite with (3 N ) 70 Vol.% distilled 760c g20c u*rotiiurn chloride-solution [4] Thus ?875gm of 80 Vol.%distilled 90 Vol.o/odistilled 86C ammonium chloride in 500m1 distillate water was 95Yol.%distilled 920C contacted with 50gmof NaX zeolitewith stirringfor I hr 124C oC . Then,the exchangingprocess continued 4 for E.B.P. at 50 oC.The exchange TotaldistiUate 96 Vol.% temperature laboratory of25 daysat Totalrecovery Residue 0.7 Yol.o/o ["oss J.3 ol.Yo reiult shows % of exchanging ofNa* by Sr- 82 rate 68.2 On other hand,SrX form zeolite was prepared ion by SulfurContent < 3 ppm(Desulfurized) exchangingthe original NaX zeolite with (3 N ) KinematicViscosity 5.4x10 mls strontium chloride solution [5, 6] Thus 80gn of at 25oC IJCPEVol.8No.3(SePtember 2007) 45
  4. 4. Study of catalysts dea9lry!!!9n in isomerizationprocess Io produce high octane gasolinestrontium chloride in 500m1 distillate water were aromatizationand cracking selectiviqr are low, whilecontacted with 50gm of NaX zeolite with stirr.ing l hr for isomerization light-naphtha relativelyhigh. So that,asrhe of isat 50oC. Then, the exchanging processcontinued 4for reaction temperature increases above 300 oC thedays at laboratory temperatureof 25 oC with 85% of hydrocracking aromatization and reactions accelerated are andexchanging rate of Na* by Sr*. isomerizationactivity and selectivity startedby,decreasing. Then, the exchangedsamples(HX and SrX) were Therefore, according to Figure (4) the optimum reaction .l10 oCfiltered, washedand dried at for l0 hours.The temperature isomerizationis at 270 oC for such type of forpreparedsample was washedwith deionizedwater to be catalystsand feed composition. the other hand,Figure(3) Onfree of chloride ions, and drying procedureswere indicates that, the PI/HX catalystshows higher selectiviryrepeated twice. The obtained zeoliteswere calcined air in toward isomen than that of Pr/SrX.This is amribured high toat 5000C for 6 hoursto obtainthe HX and SrX forms. surfaceareaand the eflect of cationfvne that forms the final catalyst.Preparation PVHX of andPt/SrXcatalysts Table (3) Characterization dataofprepared catalysts. The exchangedzeolires(HX and SrX) were loadedwith Pt at concentrations 0.8 wt % by impregnation Characteri;atron Pt/HX Pt/SrX ofprocess riith aqueous Source Prepared Preparcd solutionof hexachloroplatonic acid ($t%o) Platinumcontent 0.8wt% 0.8wt%H2PIC16 The prepared . solutionwas added dropwisetot h e z e o l i r e i i h m i x i n g f o r 4 h o u r sa t 2 5 C . T h e m i x t u r e Area(mlg) Surface 340 325 u ChlorineContent(wt7o) 0.25 0 .r 8was then left at room temperaturefor 24 hours, it was (si/Ai) 2.8 2.8stined interme,liately during this time. The mixture wasthen slo*lr eraporatedto drynessover a period of 8 Catalystdeactivation definedas a phenomenon which is inhours ar rsmperarure of 75oC. The resultingcatalysts the sffuctureand stateof the catalystchange,leadingto theuere driec in air ar I l0C for an additional 12 hours. loss of active sites on the catalystssuface thus causing aThen. the sanples riere calcinedin air at 500oCfor l0 decrease catalyst in performance,Therefore,eachcatalystwashours lincreaslrg ro that temperaturewith a rate of subjected an aging period.After a pretreatrnent 350 "C in to at0.5"C mir I ar: irnaili reducedat 350oCin flowing H2 flowing hydrogen the catalyst was submitted to l0 hr offcrr-l rtrurs ,1. 5,. Then. the samples are referred as to standard reaction conditions (T=270 oC and atmosphericP t H X a n dP : S : X c a t a l , s t s . pressure).The catalytic activity, expressed in terms of percentage iso-butanes, iso-pentanes iso-hexanes and yield, isProcedure plonedas a functionof onsffeam time as shown in Figure(4). B e t o r et : e e r p e r i r n e n t sh e c a t a l y s w a s d r i e d a t l l 0 t, t Both catalyss showedgood stability,however,the activity ofC in ii:rc:e; Pt/HX fell rapidly and it was even lower after l0 hr than that Jlsruicr one hour and then reduced 350 at"C in hl crLrser florv for three hours. The operating of Pt/SrX. The fast catalystdeactivation that was notedafterpressure ,r:;e he,,j constant I bar for all experimental at few hours of reaction time can be attributed to a highruns. Th: ii.:.riJ t-lo* of light-naphtha was 0.4 Llhr , hydrogenation-dehydrogenationcapacity of platinumand rhe Brnrrr.rnr of catalyst was 50 gm. A according the conclusions to submitted the work of Tomp byhrdrogerhrC:o;arbon molar ratio used was 4 for all et al. Il l] andJorgeet al. u2l. Also,Figure(4) indicates thar,experimerui i-u:rs. The isomerization process carriedout both catalysts loseapproximately35% of their initial activity.a t a r a n i e r . f : 3 n F e i a t J r ev a r i e d e f w e e n 2 5 0 , 2 7 5 , 3 0 0 , s bJi). ano _.-(_-L 80 The feec a:c :he effluent reactor were analyzed in agas chromatogiaph(Shimadzu GC-2014) FID using coiumn ( S.G.E., length=25 mm, l.D.= 0.22capillar_r 70mm, film=0.iun: t and usingN2 as a carriergas. I U)Results and Discussion 60 N Table (3) shous the rnain characterizes prepared ofcatalysts (PtlHX and Pr Sr.. Ir is clearrhat,Pr/HXcaralyst fUshowsa total surfaceareagieaterthanthat of PtSrX. 200 22s 2s0 27s 300 325 350 The reaction temperature uences infl isomerization !iN acti T e m p e r a t u r e( o C )and selectivity the catalvst a higler ertenl Figure(3) of toshows the effect of reaction temper"arure isomerzation onselectivitytoward branchedisomers hrdrocarbons. is noted lt (3) Fi_s. The influence reaction of temperature onthat, at low reaction temperatures ll,<. 2-0. l-5 oC the isomerizationselectivity46 I J C P E o l . 8N o . 3( S e p t e r n b e r 0 7 ) V 20 l
  5. 5. Khalid A. Sukko a aI show fast catalystdeactivation causedby deposition of carbonaceous materials (coke)on the catalyst surface and s 8 0 pores.The major productformedin the beginning the of reactionwas iso-butane. Higher contents iso-hexane of ! were detectedin the course of the deactivationrun. ; 6 0 However,the presence hydrogenin the reactionzone of (Hydroisomerization) essential to minimize coke is 5 5 0 formation 12,13]. [2, N Figure(6) showsaromatization selectivity a function as 4 4 0 of reactiontime. In this figure, Pt/SrX catalystshows 3 3 0 higher aromatizationselectivity than that of PI/HX This is attributed high concentration active catalyst. to of acid sitesin this type of catalysts, which promoted in aromatizationreaction take. This conclusion is in agreement theworkof Donket al. [14]. with Fig.(a)Deactivation PVHXandPVSrX of catalysts Conclusions 90 x In this paper the isomerization light-naphtha of for producing of branchedisomershas been investigated. Normal paraffin isomerization presence hydrogen in of 8 7 0 €) (hydroisomerization) an equilibrium is limitedreaction, E 6 0 in which branched paraffin isomersare favoredby low ternperatures, Therefore, was concluded it that, in order 5 5 0 to prevent the undesiredreactions of cracking and N aromatization,the isomerization process should be b 4 0 oC as an optimum operating carried out at 270 A 3 0 temperature both PI/HX andPt/SrXcatalysts. for 6 l0 t2 It was concluded that only an average 90% wt of of Time(hr) the carbonatomsfeedinto the reactor(light-naphtha) are detected in the productstream. This loss(- 10%) is due with agingtime to formation of coke depositswhich lead to catalyst selectivity Fig.(5)Loses catalysts of deactivation. the otherhand,the resultscleartyshow On that hydrogen is necessary for the hydrogenation of c 25 olefins in order to preventoligomerization reactionthat leads cokeformation catalyst to and deactivation. .: 20 In spite of the presence cske deposits of poisoningof t) the metalsites,cokedeposits alsoblock the acidsitesof a .{)9 l s zeolite.The followingdeactivation decreasing order of O catalysts Pt/HX > PVSrXwas found.On the otherhand o l 0 PI/HX catalystshowedhigher activity and selectivity N thanof PVSTX. Acknowledgment L ( ) The authors gratefully acknowledgethe financial supportprovided for this work by Ministry of Higher Education and Scientific Research/ Scientists and selectivity a function reaction as of Deparrment-Baghdad. CreatorsFig.(6) Aromatization time On the otherhandFigure(5) showsthe isomerization Referencesselectivity toward paraffin isomers.The isomerization l- Maloncy, J.C., M.L., Gora,L., Mcleary, E.E.,Jansen,selectivitywas reducedfrom 85% to 55o/o PtlHX for and Maschmeyeq "Hydroisomerisation Hexane T. ofcatalystand from 74Yo 46Ysfor Pt/SrXunder l0 hours to within a ReactorComposedof a Tubular Silicaliteof reactiontime. Both catalystsusedin the present work Vol.B IJCPE No.3(SePtember 2007) 47
  6. 6. Study of catalysts deactivation in isomerizationprocess to produce high octanegasoline Membrane Packed with pt-loadedChlorided Alumina 10-Ribero, F., Marcilly, C., and Guisnet, M., Catalyst", Commun., Cat, (2004). Hydroisomerization of n-Hexane on platinum Zeolite,2- Abdul Halim A. M, and Hussain, H., "Catalyic K. J. of Catalysis,Vol. 78, 267-274(1982). Aromatization Naphtha of Using DifferentCatalysts" I l-Tomp, M, van Bokhoven,J., Garriga,M., Bitter, J., IJCPE, Vol. 5, 13-19,(2004). Jong, K., and Koningsberger,D. "lnfluence of the3- MartenL.R., The development an environmental of Generation of Mesopores on the Hydroisomerization friendlycatalytic system the conversion olefins, for of . Activity and Selectivity of n-Hexane Over Catalys Today 36, 45 | -460, (1997). is PtlMordenite" J. of Catalysis , Vol. 190, 209-2144- Jabir Shanshool and Khalid A. Suker t (2000). Modification and Characterization of Platinum 12- Jorge, Timothy,J. andRavindra N., Datta,"Kinetics Supported Y-Zeolite Catalyst" Proceedingof Jordon of Deactivation Bifunctional of PyAl2O3-ClCaralysrs Int. Chem.Eng. Conference , Vol. 2, 5ep.,753-762 III by Coking",AIChE,Vol. 37, No. 6, 845-854,June, (leee). (leer).5- Jabir Shanshool and Khalid A. Sukkar (e l3- JorgeA.J., and Eduardo, V.M., "Kinetic Modelingof Modification and CatalystStudy of SomeZeolite Naphtha Catalyic Reforming Reactions",EnergV & Catalysts" Jornal Al-Nahrian of University, Vol.4, No. F u e l sV o l . 1 4 , 1 0 3 2 - 1 0 3 7 , ( 2 0 0 0 ) . . l, Dec.,79-90 (2000). 14- Donk, S., van E. Bus, A. Broersma, J.H. Bitter and6- Th.L.M. Maesenet.al.,The ShapeSelectivity of K . P . d e J o n g B u t e n e S k e l e t a lI s o m e r i z a t i o n v e r o Paraffin Hydroconversion TON-, MTT-, and AEL- on HFerrierite:a TEOM and in Situ IR Study on the Role TypeSieves, of Catalysis (1999). J. 188, of Carbonaceous Deposits and the Location of7- Martens, J.A.,Jacobs,P.A.,in "Theoretical Aspects of Brsnsted Acid Sites Appl. Catal. A: 237, 149-160 Heterogeneous (J.B.Moffat,Ed.),p. SZ-109. Catalysis" (2002). VanNostrand Reinhold,NewYork, (1991).8- Barrer,R.M.,"Zeolites andClayMinerals Sorbents as and Molecular Sieves". Academic Press,London. ( I 978).9- Hegedus, Moger,D., Szabo, and Nagy,F., M., S., "lnvestigation Isomerization n-Pentane of of Over Supported Catalyst Pt Modifiedby Adsorbed abdBi Pd",Reac. Kinet.Catal. Lett., Vol. 14,No. 3,253-258 ( re80). IJCPE Vol.B No.3(September 2007)