Pyrolysis
of
waste
oil
in
the
presence
of
a
spent
catalyst
Donny
Lesmana
a,b,
Ho-Shing
Wu
a,*
aDepartmentofChemicalEngineeringandMaterialScience,YuanZeUniversity,135YuanTungRoad,ChungLi,Taoyuan32003,Taiwan
bDepartmentofChemicalEngineering,FacultyofEngineering,UniversitasLampung,1SoemantriBrojonegoro,Rajabasa,BandarLampung35145,Indonesia
ARTICLE INFO
Articlehistory: Received5May2015
Receivedinrevisedform6September2015 Accepted22September2015
Availableonline26September2015
Keywords: Spentcatalyst Degradation Dieseloil Wasteoil
ABSTRACT
Aspentcatalysthasgreatpotentialtoconvertwasteoilintodieseloil.This studyinvestigatedthe pyrolysisofwasteoilsinthepresenceofaspentcatalyst,aswellastheregenerationpropertiesofthe spentcatalyst,suchasthetypeofregeneration(insituandexsitu)andtimeandtemperatureforspent catalystregeneration.Inaddition,theeffectofthespentcatalyst,typeofwasteoil,weightratioofthe spentcatalysttothewasteoil,andstabilityofthespentcatalystwereevaluated.Theyieldofdieseloil washigherthan60%whenwasteoilwaspyrolyzedat370C.
ã2015 Elsevier Ltd. All rights reserved.
1.Introduction
Currently, more than 80% of energy sources arefossil fuels, particularlycrude oil,natural gas,and coal[1].Because known fossil energy sources are being rapidly exhausted, fossil fuel sourcesarepredictedtobedepletedinthenearfuture.Crudeoil, gaseousfuels,andcoalareestimatedtolastonlyforapproximately next80,150,and230years,respectively.Theburningoffossilfuels haveresultedinareductioninthefossilfuelsources,increasein thedemandandcostofpetroleum-basedfuels,andenvironmental hazards.Therefore, manystudiesfocused onfindingalternative newenergyresourcesandutilizingthem[1,2].
The treatmentof wastehasbecomeoneof themostcrucial concerns of modern society in protecting the environment. Treatingwastehasseveral benefitsthat include utilizing waste energysources,preservingvaluablepetroleumresources, protect-ingtheenvironmentfromtoxicandhazardouschemicals,reducing petroleumimportsandthusimprovingforeignexchange,reducing greenhousegasemissions,andpromotingregionaldevelopment andsocialstructure,particularlyindevelopingcountries[3].
Inrecentyears,millionsoftonsofwasteoilhavebeendisposed through dumping on the ground or in water, land filling, or nonenergyrecovery[4].Becauseglobalreservesoffossilfuelsare limited, great efforts are being made to find alternate carbon sourcesforproducingfuels[5].Usedorwasteoilcanberefinedand treatedtoproducefuelsorlubricatingoilbasestock.Inaddition,
wasteoilsposean environmentalhazard becauseofboth their metal contentand other contaminants[4]. Therefore, recycling wasteoilsiscrucial[3].
Wastesoilinclude automotiveengineoil,machineryoil,and lubricantoil.Thewasteautomotiveengineoilproducedworldwide is estimatedat 24 million tonsper year,posing a considerable treatmentanddisposalproblemformodernsociety[6,7].
Thecompositionofwastemachineryoilchangeswithitsuse because somecontaminants, suchas sulfur and oxidized com-pounds,hydrocarbons,andmetals(chromiumorlead),arepresent inthevirginoil.Allwasteoilsofvariousoriginsareoftenmixed during collection and storage, producing a final contaminated residuethatisoftencalledwastemachineryoil[7].Wasteoilscan be reconstructed chemically by heating in an oxygen-free environment. This process is called pyrolysis, which is defined as chemicaldecomposition by theaction ofheat and generally referstothechemicaldecompositionoforganicmaterialsheated in an environment with an insufficient supply of oxygen for combustion.Pyrolysishascertainadvantagesoverothertreatment methods for wastedisposal [4].The most crucial advantageof pyrolysis is that it does not pollute the environment when performedappropriately,becausepyrolysisproductssuchasgases, oils, andcarbonaceous residuescan beused asfuels. However, pyrolyzedoilcanbepolymerizedagainbecauseitconsistsofmany unsaturatedhydrocarbons[4].
Pyrolysis is anoption for converting wasteoils intoa more usefulproduct.Ithasreceivedconsiderableattentionbecauseof themultiphaseproductvariationofyieldsinsolid,liquid,andgas formsdependingonprocessconditions[7].Inaddition,usingsolid catalyststofacilitatepyrolysishasbeenreported,andtheproduct
*Correspondingauthor:Fax:+88634631181. E-mailaddress:cehswu@saturn.yzu.edu.tw(H.-S.Wu).
http://dx.doi.org/10.1016/j.jece.2015.09.019 2213-3437/ã2015ElsevierLtd.Allrightsreserved.
–
ContentslistsavailableatScienceDirect
Journal
of
Environmental
Chemical
Engineering
catalystsincreasetheyieldofhighoctanegasolineobtainedfrom crude oil [13]. Mostcatalysts usedin refiningorpetrochemical
applicationsdeactivaterelatively quicklywithtime.In addition, catalystsaretypicallycomposed ofrareand expensiveprecious metals. Hence, using a simple, cost-effective, and efficient
regeneration procedure to improve catalyst performance is essential[14].
A catalyst plays a crucial role in heterogeneous chemical reactions.However,catalystshavealimitedlifetime.Catalystscan bedeactivatedbyalongdurationofreaction,thermaldegradation, poisoning, and sintering. Hence, thereuse technology of spent catalystsisaworthconsiderationbeforebecominguselesswaste. In thisstudy, spentcatalysts fromFCC processwereexamined. Spentcatalystsareexpectedtoreducetheoperatingtemperature ofwasteoildegradationandtokeepthestabilitytoproducethe dieseloil.Varioustypesofwasteoilswerepyrolyzedtoformdiesel oilinthepresenceofaspentcatalyst.
2.Experimental
2.1.Materials
Wasteoilsfromwastemotor(WM)oil(S:0.31wt%,Cu:15.4mg/ kg,Ni:0.874mg/kg,Cr:0.874mg/kg,Cd:0.485mg/kg,Zn:403mg/ kg,Pb:5.63mg/kg,Hg:0.083mg/kg,andAs:0.821mg/kg.),waste machinery engine (WME) oil (S: 0.27wt%), and waste bottom product (WBP) acquired after extracting the waste oil by distillation(S:0.77wt%)wereobtainedfromTaichinGlobalCo., Taiwan. The waste oils were not purified before use. A spent
knownamountofaspentcatalyst(0–28g)isintroducedintothe
reactorandheatedtoafixedtemperature(300–370C)forafixed
duration(30–60min)atatmosphericpressure.(iii)The
combina-tionmethodinvolvesacetoneleachingandheatingofthespent catalyst.
2.3.Testingprocedure
AschematicoftheexperimentalapparatusisshowninFig.1. Theapparatusconsistedofapreheater,magneticstirrer,reactor (conicalflask),condenser1,coldtrap1,condenser2,coldtrap2,
collectingvessel,andvacuumpump.Themainfunctionsofthese componentsareexplainedbrieflyasfollows.
Thepreheaterandmagneticstirrerwereusedtoprovideheat and stirring, respectively. The operation was set for a semi-continuous process, in which 175ml (approximately 140g) of wasteoilwasintroducedinthereactoratarateof25ml/h.The wasteoilwasmixedwithaspentcatalyst(0–28g)inareactor,and
thesolutionwasthenheated(300–370C)andstirred(0–200rpm)
usingthemagneticstirrerfor1–7hforthereactantstoreactand
producedieseloilinvaporform.
Dieseloilinvaporformwascondensedusingavacuumpumpin ethanol-cooledcondenser1at 2C,andthecondenseddieseloil
accumulatedincoldtrap1at 2C.Dieseloilvaporsthatescaped
condenser 1and cold trap1werecondensed againat 2C in
ethanol-cooled condenser 2, and the condensed diesel oil accumulatedincoldtrap2.Theelementalconcentrationsofthe
finaldieseloilproductwereanalyzed.Theresultsareasfollows:S:
0.19%,Cu:0.698mg/kg,Ni:0.0mg/kg,Cr:0.1mg/kg,Cd:0.0mg/kg,
Table1
Summaryofdieseloilproductionthroughcatalyticpyrolysisofvarioustypesofwasteoils.
No Oilsource Wo
(g)
Catalyst Wc (g)
T(oC) t Method Yield
(wt%)
References
1 Wasteengineoil – Na2CO3 10a 360 – Pyrolyticdistillation 60 [2]
2 Wasteengineoil – Zeolite 10a 360 – Pyrolyticdistillation 60 [2]
3 Wasteengineoil – Lime(CaO) 10a 360 – Pyrolyticdistillation 60 [2]
4 Wasteautomotiveengineoil 0.4–5e carbon 1b 550 2 Continuemicrowavepyrolysis(5kW) 88 [6]
5 Wastemachineryoil 3.75 HZSM5 0.5a 400
– Batchthermalpyrolysis 65 [7]
6 Vegetableoil 2d HZSM5 2c 400
– Benchhome-made5Lstainlesssteel 60 [8]
7 Malaysianrefusederivedoil – Zeolite 20a 450 4 Batchthermalpyrolysis 17.8 [12]
8 Wasteautomotiveengineoil 0.4–5e Carbon 1d 550 1 Continuemicrowavepyrolysis(5kW) 69 [11]
9 Wastemachineryoil 20 Spentcatalyst 12 370 1 Batchthermalpyrolysis 45 Thisstudy
10 Wastemachineryoil 20 Spentcatalyst 28 370 1 Batchthermalpyrolysis 73 Thisstudy
11 Wastemachineryoil 20 Spentcatalyst 12 300 1 Batchthermalpyrolysis 18.4 Thisstudy
t:reactiontime,T:operationtemperature,Wo:weightofthewasteoil,Wc:weightofthespentcatalyst. awt%.
Zn:9.57mg/kg,Pb:1.8mg/kg,Hg:0.02mg/kg,andAs:0.838mg/ kg.
2.4.Analysisoftheproduct
Dieseloilwasdrawnfromcoldtraps1and2everyhourand analyzedforitsweight,absoluteviscosity,andkinematicviscosity. Absoluteviscosity(cP)wasmeasuredusingaviscometer
(Brook-fieldLVDV-IIpro,USA)withtheASTMD4624method.Theviscosity ofthewasteoils(WMoil,WMEoil,andWBP)wasmeasuredusing aviscometerfittedwithspindlesS62,theviscosityofthedieseloil
wasmeasuredusingtheviscometerfittedwithspindlesS61,and the spindle rotational speed was 60 rpm for all samples. The viscosity reading, torque percentage, and degree of settlement wererecordedat60sintervalsforeachrotationalspeedsetting. Absoluteviscositywasmeasuredintriplicate.
Kinematic viscosity (m2/s) was measured using a
Cannon-Fenskeviscometer(300/PmT,C=0.299min,temperature= 25C),
which was calibrated with a known compound (2-propanol, chloroform,ethanol,1-butanol,or1-pentanol)at20C.Theflow
timeofaspecificvolumeoftheknowncompoundflowingthrough
the pipe capillary was measured. An equation showing the relationshipbetweenflowtimeandkinematicviscositywasthen derivedforuseasa standardcurveinmeasuringthekinematic viscosityofwasteoilanddieseloil.
2.5.Equationusedformeasuringthecatalystactivity
Based on diesel oil productionfromwaste oil (Fig.1), three typesofproductswerecollected:P1fromColdtrap1,P2fromCold trap2,andP3fromalow-boilinggasfromtheaspirator.
For measuring the catalyst activity, there was one concern aboutP1andP2.Thecatalystactivitywasmeasuredusingtheyield ofdieseloil(%):
Yieldð%Þ¼ðP1þP2Þ
Wo 100; ð1Þ
whereWoisthetotalweightofwasteoil(g).
3.Resultsanddiscussion
3.1.Effectofthespentcatalyst
The enhanced optimal use of waste engine oil would help reduceenvironmentalliability,savewasteoildisposalcosts,and reduce the burden of fuel imports [15]. The technologies for
convertingwasteoiltodieseloilarewellestablishedandinvolve usinganalkali, acid,ornocatalytic reactioninthepresenceof supercriticalmethanol.Therefore,thisstudyinvestigatedtheuse ofaspentcatalystforthedegradationofwastemachineoiltoform diesel oil. To understand the effect of a spent catalyst on the degradation of waste oil, an experiment was conducted by comparingtheyieldsof theproducts formedwithand without thepresenceofaspentcatalyst.
TheWMoil(25ml)wasreactedwith12gofaspentcatalystat 370Cand200rpmfor1hwithoutregeneration.Thetemperature
of 370C chosen is thebestregeneration temperature,and the
yieldofdieseloilfor370Cislargerthanthoseforbelowit.The
yieldsofdieseloilformedinthepresenceandabsenceofthespent catalystwere26%and15%,respectively.Thisresultshowedthat thespentcatalystincreasedtheyieldofdieseloil.
3.2.Regenerationofthespentcatalyst
The spent catalyst used in this study was obtained from a refining petroleum oil company in Taiwan. This catalyst was unused(oritseffectivenessislow).Therefore,itcanbeusedto produce diesel oil from waste oil before its disposal in the environment.Beforeacatalystisusedfordieseloilproduction,itis regenerated. The catalyst in this study was regenerated using acetoneleaching,thermalregeneration,andacombinationofboth.
Fig. 1.Schematicoftheexperimentalapparatus.(a)Magneticstirrer,(b)positionofthermocouple,(c)conicalflask(500ml),(d)condenser1( 2C),(e)coldtrap1( 2C),(f) coldtrap2,(g)condenser2( 2C),and(h)aspirator.
Type of regeneration of catalyst
A B C D
)
%(
li
o
l
e
s
ei
d
f
o
dl
ei
Y
20 25 30 35 40 45
Themilderreactionconditionschosenfortheinsituandexsitu regeneration of the spent catalyst were regeneration tempera-ture=370C,regenerationtime=0.5h,reactiontemperature=340 C,andreactiontime=1h.Theyieldsofdieseloilobtainedusingin
situandexsituregenerationsofthecatalystwere42.5%and32.5%, respectively. Therefore, in situ regeneration is favorable for regeneratingspentcatalysts.Thisisbecauseinsituregeneration reducedtheaircontactofthecatalystinthisstudy,thusreducing thepossibilityofoxidationofthecatalyst.
Furthermore,theregenerationtimeofthecatalystaffectedthe reactionbetweenthecatalystandwasteoil.Thedieseloilyieldsat the regeneration times of 0.5 and 1h were 42.5% and 45.4%, respectively,andnotincreasedforlargerthanthegenerationtime of1h.ThisresultissimilartothatreportedbyKomvokisetal.[17], whoclaimedthataregenerationtimeof1hismorefavorablethan 0.5h.Fig.3showstheeffectofregenerationtemperatureonthe yieldofdiesel oil.Ahighregenerationtemperatureofthespent catalystdoesnotalwaysresultinahighproductyield,becausethe high temperature of the calcination of the spent catalyst can damagethetextureofthecatalyst,thusreducingthenumberof activesites.Thisleadstoawarningthatthetemperatureishigh.
3.3.Effectofagitation
Thereactionbetweenasolidcatalystandtheliquidofwasteoil isgreatlyinfluencedbyagitation,whichsubstantiallyaffectsthe uniformity of the solution in the vessel (solid, liquid, gas concentration, temperature, and pH) and increases the solid–
liquidinterfacialmasstransfer.Toobtainahighreactionyield,an optimalstirringspeedisrequired.Fig.4showsthatastirringspeed of200rpmisoptimalforproducingdieseloilinahighyield.This
revealedthatanincreaseinagitationcanincreasethereactionrate. However,afurtherincreaseinagitationcanreducethereaction ratebecausesomecatalystscansplatteronthereactorwall.
3.4.Effectofthetypeofwasteoil
Theorderofthekinematicviscositiesofvarioustypesofwaste oilsanddieseloilswasWME>WM>WBP(Table2).Fig.5shows theeffectofthetypeofwasteoil ontheyieldofdiesel oil.The results are WBP>WM>WME. The diesel oil yield was the maximum (60%) when WBP was used as the reactant. This is duetotheviscosityofWBPbeinglowerthanthoseofWMand WMEoils(Table2).Thekinematicviscosityofthedieseloilwas approximately 0.00006m2/s (60cSt). The low-boiling gas (P3)
obtainedforWMandWMEoilsandWBPwas18%,10%,and16%, respectively.Fig.6showsthedifferenceinthecolorofdieseloil producedfromvarioustypesofwasteoils.TheWMandWMEoils andWBParehomogeneousdarkbrownoils.Thecolorofproductis
Regeneration temperature (oC) 340 370 400
Fig.3.Effectofregenerationtemperatureofthespentcatalystontheyieldofdiesel oil.WMoil=25ml,spentcatalyst=12g,regenerationtime=0.5h,agitation=200 rpm,reactiontemperature=370C,andreactiontime=1h.
reactiontemperature=300C,andreactiontime=1h.
Table2
KinematicviscositiesofWBP,WMoil,WMEoil,anddieseloil.
Kinematicviscosity(m2/s)
Beforereaction Afterreactiona
WBP 0.00024(109) 0.0000595
WM 0.00036(150) 0.0000598
WME 0.00072(280) 0.0000601(20)
Thevaluesintheparenthesisaredynamicviscosities(cP). aItisdieseloil.
Fig.5.Effectofthetypeofwasteoilontheyieldofdieseloil.Wasteoil=25ml, spent catalyst=12g, in situ regeneration temperature=370C, regeneration time=0.5h,agitation=200rpm,reactiontemperature=370C,andreactiontime=
darkyellowish-gold.Lametal.[11]reportedthatthepyrolysisoil obtainedat550Cwasafairlypaleyellowish-goldhydrocarbon
liquidcontainingasmallamountofdarksolids.Itcorrespondsto ourresult.ThecolorofthedieseloilproducedfromtheWMEoil
was darker thanthose produced fromWMoil and WBP. Fig.7
showsthelifecycleofaspentcatalystafteritsregenerationwith varioustypesofwasteoils.25mlofwasteoilwasintroducedinto thereactoreveryhoursemicontinuously.Aftersevencycles,the
finalvolumeofthewasteoilwas175ml.Thevariationsoftheyield
Fig.6. Colorimageofthedieseloilproducedfromvarioustypesofwasteoils.(1)WBP,(2)WMoil,(3)WMEoil,(4)dieseloilproducedfromWBP,(5)dieseloilproducedfrom WMoil,and(6)dieseloilproducedfromWMEoil.
Time on strea
m (h)
0 1 2 3 4 5 6 7 8
)
%(
li
o
l
e
s
ei
d
f
o
dl
ei
Y
20 30 40 50 60 70 80
Fig.7.Effectofthelifecycleofthespentcatalystontheyieldofdieseloilproduced fromvarioustypesofwasteoils.Wasteoil=175mlatarateof25ml/h,spent catalyst=12g,insituregenerationtemperature=370C,regenerationtime=0.5h, agitation=200rpm,reactiontemperature=370C,andreactiontime=7h():WM oil,(&):WMEoil,and(D):WBP.
Time on strea
m (h)
0 1 2 3 4 5 6 7 8
)
%(
li
o
l
e
s
ei
d
f
o
dl
ei
Y
20 30 40 50 60 70 80
of diesel oil for three waste oils were within 10%. Hence, the stabilityofthespentcatalystforthethreewasteoilswashigh.For 7hofreaction,theyieldofthedieseloilproducedfromWBPwas higherthanthoseproducedfromWMandWMEoils.Theamount ofwasteoilwastreatedmorethan11.7g/gcatalyst(140gofwaste oil/12gspentcatalyst used). However,thecolorof diesel oil is graduallydarkwithincreasingthenumberofreactioncycle.
3.5.Effectoftheweightofthespentcatalyst
Fig.8showstheeffectoftheweightofthespentcatalystonthe yieldofdieseloil.Theincreaseintheweightofthespentcatalyst increasedthedieseloilyield.Thisresultcorrespondstothatof Mengetal.[18],who,reportedthatincreasingtheweightratioof the spentcatalyst to oil results in a higher reactiondegree of pyrolysis.For the first run, when 28, 20,and 12gof the spent
catalystwereused,thedieseloilyieldswere73%,57%,and43%, respectively.IfP3for 28g(weightratioofthespentcatalystto wasteoil=1.4)wasconsidered,thedieseloilyieldwashigherthan 90%.Thestabilityofthespentcatalystwasstillhighafterseven cycles.Theproducts(P1+P2+P3)forallcases(variousweightsof thespentcatalyst)weremorethan60%.Fig.9showsthatthediesel oilyieldwasproportionaltotheweightofthecatalyst.Thediesel oilyieldwascalculatedusingtheslopeofthelinearcurve;0.4gof dieseloil/hgofspentcatalystwasproducedat370C,and0.32gof
diesel oil/hg of spent catalyst was produced at 300C. The
apparent activation energy calculated using the Arrhenius equationwas 4.91kcal/mol.Theyieldsof dieseloil producedat 300 and 370C in the absence of the spent catalyst were
approximately0%and15%,respectively.
4.Conclusions
Thespentcatalystwaseffectivelyusedtotreatthewasteoil. Thespentcatalystwasmorestableatlowtemperatures(370C).
Thedieseloilyieldwashigherthan90%whenahighweightratioof
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