";;;;
;:#ffi;1
"**,*,.t:if,:i;x,
;:,i::!,
:#,:,;:t"
i ;x:f,::
:3:,f
CuAV/HZSM-Sfor METHANE CONVERSIONTO LIQUID HYDROCARBONS
Nor Aishah Saidina Aminr
Didi Dwi Anggoro'?
lFaculry of Chemical& Natural ResourcesEnEineerins,UnivetsitiTeknologiMalatsia'
81310Studai, Johor, Malqsia
Universit, of DiponeSorc,Semamng50239,Indonesia
'zDepartnentof ChemicalEngineennS,
Abstract
of naturalgas,and in particular'the
The dhectconversion
to usefuiproduclshasbeen
principalcomponena.
methane,
inlenseiystudiedover the pastdecadesZSM-s zeolitehas
been known to be a suitable catalyst for olefln
olisomerizadon,but i! is not resistantto high temperatur$.
lnlhis work, HZSM-s was modified with copper and
lungsLenlo developa highly active and heal resisLanL
ofCu
Theperfomlances
oxidatjve-acidca!alysL.
biluncrional
modified W/HZSM-5 were comparedwith MSM-5 for the
oxida[ion of methane to liquid hydrocarbons The
chamcterizationresultsrevealedthatthe additionof tungsten
ro HZSM-s zeolite imFoved its themlal stabilitv. Response
SurfaceMethodology (RSM) was enployed to detemine
the optimum metha.neconvenion and C5' selectivity.
Numerical results indicated the optimum methane
conversionof 29.4 7owith the correspondingCi* selectivity
at 12.3vol.%ofOr,203.9mvminof
of57.27,wereachieved
total feed flow rate,and % W dopedof 3.2 wt%. The
optimumC5*seleclivity ol 70.2 qow^s andneAat 7.6 \ol.Ea
oi or, 208.9nJ/rnin of total feed flow mte, and 3.2 wt.7oof
w content with the correspondingmetharc conversion of
26.'7%. By means of variance analysis and additional
experiments,the adequacyof this model was confumed.
Keywords
T\rngsten;CoPPer;HZSM-5i Liquid
Methaneconversion;
Hyalrocarbons
Introduction
Crudeoil is a non-renewableresourceand cannotbe solely
relied as lhe feedstock or energy souce in firture New
natural gas deposits are being continuously discovered;
hence,naturalgasis a new potentialresource.Methane' the
largest component of natural gas, can be conv€rted to
valuable liquid fuels or other imPortant chemical
intermediates,In general,thereare two routesfor converting
methaneto gasoline:indirectly or/and direcdy. The indirect
route is a two-step process whereby natuml gas is fust
convertedinto synthesisgas (a rnixture of hydrogen and
carbonmonoxide),and then into gasolinerange.Tbe direct
route is the one step prccessin which the natural gasreacts
ISBN:983-2643-15-5
with oxygen (or another oxidiziog species)10 give the
desiredproductdirectly.
Zeolitesareuniquematerials.Unlike othercatalysts,zeolites
possess active sites on intracrystalline sudace
crystallo$apbicatly.For eachpafiicular zeolite stluctule the
acidity per active site reached a maximum value at a
pafiicular StAl ratio, which will determine the acidic
strengthof the zeolite. Emst andWeitkamp [l] reportedthe
prcsenceof stong acid sites in the zeolite catalyst was
detrimeotalfor ihe selectiveoxidation of methaneto higher
hyahoca$ons;otherwise oxidized products, CO" (carbon
monoxide and carbon dioxide) predominate.When the
acidity is reducedby exchangingthe zeolitewith alkali melal
cations, the selectiviry to higher hydrocarbonsis slighdy
enhanced. Han et al. {21 demonstrat€dthe successful
productionof higher hydrocarbonsfmm methaneoxidation
using ZSM-5 zeolite catalystloadedwith metal oxides.The
metal oxideswith sufficiendy high dehydrogentionand low
olefin oxidation activities reduce the acidity of ZSM_5
resultingin higherhydncarbonsproduction.
The incorDorationof two different metals could deate
mateiats ;i$ well-defined or new €atalytic and acidic
properties.One recent study has r€vealedthai acidic and
catalytic properties of these materials dependedon the
locationandsuroundings of ths metalions [3]. De Lucaset
al. t4-61discoveredthat the introductionof Cu (II) ions by an
ion-exchangemethodcould remarkablyincreasethe activity
of Mo[IZSM-5 for methanearcmatizationandimprovedits
stability to some extent. Mo species is the most acttve
conponent for methanenon-oxidalivearomatizationso far,
but its activity andstability n€€dto be improved.
Molybdenumsupportedon H-ZSM-s, is activeandselective
for benzenefornation from methaneI7-9l Il was clearly
established that at high temperaturc molybdenum in
Mo/HZSM-5 was reducedand formed MorC species[10].
Further, during the activation process of Mo/HzsM-s.
silesin
molybdenumspeciesmigratedlowads exchangeable
that
generally
reported
the zeolite framework uo,lll. It is
active
moiybdenum
on
the activation of methaneoccurred
speciesfonning ethyleneas the primary intermediatebefore
beirg convertedinto benzene.By usingpuremethanefeed,it
was found that methaneconversionand iates of benzene
formaliondrasLically
decreaedto. a few hou-rsowing !o
107'.l
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27' - 2q Aug6t 2003. UniwBiti Malattit Sabah,Kota Kaabai
signjficantcokeformation.To reducecoke fo(nation, some
preliminaryeffortshavebeenmadetoadd sele€tedoxidative
reagentssuchasoxygenandcarbondioxide (10% or higher)
to the methanegasfeed, but the sromatic productfomation
was completely inhibiied on Mo/HZSM-5 catalyst as
previouslyIl2, l3l.
reported
On |he basisof the chemi€alsimilaritigs betweenMoO3and
WOr it seemsreasonableto expect a paralelism in their
cahlytic properties. Ding et al. Il4l reported the
non'oxidativemethanereaction over WHZSM-s Droduced
C:-C,: hydrocarbons.
Undermndirionof ?00oC,a;d a flow
rate of methane+ argon at 12.5 cmlmin, the Cr-CI,
hydrocarboDs
selectivitywas 70-80%.However,methane
conversion
wassmall,between2%znd3%.
Tungstenand Mo are under the samegoup in the periodic
table of the elements (VI B), and hence the chemicat
propertiesof oxides or ca$ides of W and Mo are similar.
Therefore,the structuraland catslytic resemblancebetween
W andMo-HZSM-5is expecte-d.
Xionget al. [5,16] studied
the incoryorationof metalsZn, Mg, Mn, La, andZr inio rhe
W IZSM-s caralysi.The WHZSM-s basedcatalysrwas
suitablefor reactiontemperaturesas high as 800oCto obtain
a much higher methaneconvercionand yields of arorDatic
hydrocarbon without loss of W component n5l. They
confimed that the intensity and concentrarionof Bdnsted
acid sites have affected the catalyst activity for ethylene
selectivity and the rat€ of aromatizationof ethylene [161.
The incorpomtion of Mg?* and Zn2* into the W IZSM-s
, resulted in the elimination of a large potion of strong
Brdnstedacid sites,but new mediumstrengthBrdnstedacid
sites emerged.The medium strength Brdnsted acid sites
enhancedthe benzene selertivity and suppressedcoke
formation,thusFolonging the lifetirne of the catalysr.
.Cu loadedZSM-5 catalyst via acidic ion exchangemethod
hasbeenidenlinedto be Lhepotenlialcaraiysrfor conversion
of methaneto liquid fireh [17,18]. However, rh€ infiared
study of meral loaded ZSM-5 catalysr indicated that the
catalysisarenot resistantto high temperatures.
At 800"Code
studyhasindi€atedthat metal loadedZSM-5 did not exhibir
vibrationbandsat 3610 cm' and 3660 cm-'. but ZSM-5
showeda weakvibradonband at 3666 cmr (ascribedto OH
groups on non-framework Al species) [18]. The result
suggestedthatthe frameworkandnon-frameworkaluminum
werc either exhactedto acidic solution or becamesilanol
defectform when calcinedat 800"C and madethe catalysts
ResponseSurface Methodology (RSM) is a method to
determinethe optimum condirion of a process. RSM has
similarity with regressionanalysis. In rcgressionanalysis,
empirical maihernatical model are derived from the
experim€ntaldata. RSM is a set of techdiquedesignedto
1078
find the optimum value of the r€sponseand the influencing
factors.
In this paper HZSM-s was modified with tungsten and
copp'ff and.the catalyst p€rformance was tested for the
oxidationofmethaneto liquid hydrocarbons(C5). The roles
of W and Cu, the Bronstedacid sites,and catalytic a€rivity
will be studiedby meansof hydrogen-TPR,anmonia-TPD,
FIIR, nitogen adsorption(NA) andmethaneoxidation.The
optimization of the direct conversion of merhaneusing
3.0Cu loaded WZSM-s catalyst was studied ro obtain
maximum methane convercion and C5+ selectivity by
utilizing experimentaldesigr andempiricatmodeling.
Exp€riment
Cstalyst Preparation
ZSM-5 zeolite with a Sior/Alrq mob ra{io of 30 was
supplied from Zeolyst Intemational Co. Lrd, Nethe ards.
The surfac€ area of the zeolite was 400 m%. Cu (3%
weight)-IzsM-5 catalysrwas preparedby impregnatinEa
certain amountof the HZSM-s zeolite carrier with €oDDer
nilraLe
solution. Thecoppernitratesolurion a" pr"pur"aby
"
dissolving coppff nitsate hyalrare (Cu(NOrr.3HrO)
in
deionized water and adding a small amounrof HZSO4to
rcgulatethe pH valueof the solution to 2-3. The sample(10
ml of solution per gram zeolite) was dried in an oven ar
120"C for two hours and then calcined at 50Ot for four
hou's.
The 3.0 wt.% ofcu loadedWAIZSM-s waspreparedby Ii$i
imprcgnatinga certainamountof the IIZSM-5 zeolitecanier
with a calculatedamount of tungstenhydmte in aqueous
solutions. The tungstenhydrate solurion nas preparedby
dissolving
ammonium
tungsten
hyalmre
((NH1)6.Wrr.Oao.HrO)
in deionizedwater andaddinga small
amountof H2SOaio rcgulatethe pH valueof the sotutionto
2-3, followed by drying at 120"Cfor two houls andcatcining
at 4O0.c for four houN,andsubsequentlyimpregnatingwith
a calculated amount of H2SOa acidified copper nitate
aqu€ous
solution(pH=2-3). Finally,rhesamplewasclriedaL
120'C for two houF. and calcined aL500"C in air for five
Characterizatlon and Cstalyst T€sting
The catalystswerc charactedzedby XRD, hydrogen"TpR,
ammonia-TPD, FTIR and nitrogen adsorption. The
peformance of the caralysrs was tested for methane
conv€mionto liquid hydrocarbons(LHC) via a single step
reaction in a fixed-bed micro reactor-Gc combination
systemund€rreaclioncondjlionat aunospherjc
pressure
and
800f. The fed g i wlrs composedol methane(99.9%
pu.ity) and oxygen, An on-line cas Ckomarogaphy
e.quippedwith TCD and Porapat-N column was utilized io
analyzefiegas.Theliquidproductswereanalyzed
usingGC
FID andEP-l capillarycolumn.
ISBNr983-2643-15-5
p
ol td.rnatio4ot CoiJ.anc? On Ch.akol aad 3iop44$ EnBk4nne
Prcc..dilss
' "27*
- 2a' Aulu"i 2o0J u^i!.Aii Malarsia sdbah Kota Kkobalu
*',
+1,"
bonsselectivitywere
andC5' hydrocarMeganeconversion
(2)' respeclivelv'
and
l)
t
basedon equaLions
aat-Julared.
l
moleofcHq {ir)- moleofcH4 (dr)
CJt4conv=-noteof CH4 ;;
mole of CH4(n) - mole of CH4lod)
00%
(l)
(2)
*tooso
From Figurc I (Pareto Chart)' the most significant
arecleartvthe% volofOr lXr) andils quadrahc
oarameLers
(X:xt.
ot loial tlow ot teedgasesfir)
The quadratic
;|fect
(Xr) are significant hrt less
W
quadratic
%
wt
of
of
aral
imponant. The % $l of W and loLalflow of fe€d gases
% wt of
u.tuully upp.* low, a" well as lhe interactions
W-totd flow (XrXr) and % wt of W-% vol of Oz (XrXJ'
The intemction of % vol of O?- total flow of feed (XrXr)
was insignificant
Optlmisation of C5+Selectivity by RegressionAnalysis
H']O'
wtrerei = CO, COz,CzHr.CrHa.CrH6,CrH6,Ci, and
Resultsand Discussions
Optimizallonot MerbaneConversionby Regressioo
AnelYsis
yielded$e
surfacemelhodology
ofresponse
TheaoDlication
lollowine regre.sionequalion. which is an empirical
relationshipbetweenCi selectivity and the test variable in
codedunit givenin Eq. (4).
Y = 67.0195+ 32.0514xr + 8 1699x, + 0 5304x3-0 0833
x,'?
xt'z
ri 4).4-s.1106
xrx3- o.oo
- o.s3s6
x,x - o.qoog
(4)
"
xr'?
o.oo12
The applicationof responsesurfaaemethodologyProduced
ttre foiiowing regressionequation, which is an empirical
relationship between methane conversion and the test
variablein codedunit givenin Fa (3).
x1- 0 0500
+ 9.5251xr + 4.4146x, + 0.1-549
Y = -28.5459'7
xlx,- 0.0042xrxr - 0.0003x.,xi- 1.275lxtz'O l7l3 x2''
(3)
o.odo3x3'?
of thefitringof the modelcanbe checkedby
Theeoodness
Table I showslhe Analysir of Variance
."u"ot
";r..lu.
to mehane
model that corresPonds
for
$e
{ANOVAJ
convenion. The valu€ol coeffrcienlR'= 0940 indicares
thatonly 6% of total vanationis not explainedby tbe model'
The vahe of F is comparedto the tabie value &pr.N.Fa)'
which is the upper 100o PercentPoint of the F distribution,
with p.l and N-p degreesof freedom.respectively The
o[ lhe fined modelfrom Eq. (3) is lelled using
adeouacv
stad; F.- SinceF value at 10.4633exceededthe table vatue
a high
F€0.0r,= 7 9761. lhe FisherF test demonsEared
model.
regtessions
significance
for thefired
Tablet.ANOVAIoTft? methMcconv?tsion
Sun of
D€gree Mean
Squlre
s.s.
4J0.508
S.S-Enor
27.430
S.S.Tolal 457.918
9
F
F0.0r
Rl
Erld Earimab1tu3.1@v'rua)
Figure1-Parctocha of stfuda izedeffectsofmethane
con|ersion
Table 2 showsthe Analysis of Variance(ANOVA) for the
model that exptainsthe responseof the C5+selectivity. The
Analysisof Variance(ANOVA) for the modelexPlainsthe
of lhe Ci seleclivity. The co€mcientR'= 0.95
response
indicat€sihat only 5% of total variation is not exPlainedby
ihe model. The value of F is comparedto the table value
Fer,N*d , which is the upper 100 d percentpoint of rlle F
diitribution, with p-l and N-p. degees of fteedom'
respectively.Sincethe valueF = I 1.5647exceededthe table
value Rr.6rr) = .9761,the FisherF testalsodemonsaaEdits
high significancefor rhefitted regressionsmodel
'7_9161 0.94
47.834 10.4632
4.572
l5
ISBNr983-2643-15-5
1079
Praceedias oI tat.natiatul ConJerctueOn Chenical and Biaprues Euinee.ihe
2f -2q Ausust2003 , U^ive6ni Molottio Sdban,Kota Kihdba\
Table4 - The RONand conposition of liq idfuels ot)et
3.OCuloaded3.2w ,zSM-5 catalyst
Table2- ANOVAfoT the Cs- selectilrit,
Degre€
Sumof
F
Sqllare
s.s.
4866.406
S.S.Enor 280.532
F0.01 R,
l l .5 6 4
540.7t2 '72 7.9761 0.95
9
6
46.755
S.S.Toral 5146.938 l 5
Composition of Liquid Fuels
Gasolinerange(Cs-ro)
82.8
cr i range
18.2
Compositlon of Gasollne range
Vo
n-Paraffins
9.0
Iso-Paraffins
22.O
Olefins
52.O
r'7.o
The resultsin Table 3 pertainto the catalytic reactiontestat
the oplimized reaction condition when comparedwith the
modelingresult. The experimentalvaluesarc 27Eoar]d69Eo
for Clla conversionand Cs* selectivity, respectively. The
rcsults in Table 3 ako indicatedthat to achievea high Cr+
selectivity tbe percentageof 02 in the feed gas is very
critical; otherwise the oligomerizatiod activity will be
suppressed.Me€nwhile the % error betweenthe predrcted
and experim€ntal results for CH4 conve$ion tuid Cr'
The djscrcpancies
selectiviry
are8% and2 %. respectively.
betweenthe predictedand experimentalrcsults are probably
dueto ihe characteristicof the catalysb which havenot been
takeninto accountby the statisticalmodel. Nevenheless,the
differences are within the acceptablelimit. ftom these
rcsults,it is verified that the statisticalmodelis usefulfor the
prediclionofCr+selecliviryandCHaconversion.
accurale
TabLe3 - Cowaison betweenpredictedand obsened
o,
dop€d
(%
( %)
CH4
Ci
3.2
3.2
12.3
7.6
Totd
flow of
feed
Pred.
Obs.
%
Ermr
RON
86.1
Characterization of 3.0Cu8.2WHZSM-5 Catalyst
The isothem adsor?tionof 3.0Cu,/3.2WZSM-5-Frcshand
3.0Cu,/3.2WlzSM-5-Used,as shown in Figur€ 2 as an
example,is a combinationof typesI andIV. The p.esenceof
hysteresisloop was associatedwiahcapillary condensation,
where in the caseof zeolite, it indicated the fornation of
mesoporcs. The profile for 3.0Cu/3.2WZSM-5-Us€d
indicatedenlargementof somemicroporesresultingin mol€
mesoporesbeing fomed.
The ammonia-TPDspectraof the catalystprovided useful
information aboutthe intensity and the concenaationof lhe
acid sites on the catalystssurfaceas tabulatedin Table 5.
The concentrationof tbe sudace acid siies (acidity) of the
ZSM-s and 3.0CuB.2WHZSM-5-Fresh zeolite were the
same. The acidity of 3.0Cu/3.2WIZSM-5-Used was
undetected(- 0) becausethe aluminium in the ftamework
was Fobably €xtracted.after reactionat 752t for a period
of five hours.
20.].9 29.4% 27.0% 8.O%
208.9
702%
69.0% 2.0%
NoterPred.= predicted;Obs.= observed
The composition of liquid fuels and RON over
3.0CuB.2WZSM-5 catalyst is shown in Table 4. The
ResearchOcIaneNumber (RON) was estimated[9] !o be
86.1. The gasolinecompositionhas a low n-paratrin and
high aromaticscontent,at 9% and 177,, rc,spertivelywhile
(hemajority is olefins at 527, asindicatedin Table 4.
Table5 - Total volure, pore dishbhtion and aciditJ ol the
catalysts
Catalysts
Av. PoreDiam.
(a)
Acidity
(moYkg)
HZSM-5
24.3
0.87
3.0Cu/3.2W,{ZSM-
26.1
0.87
45.2
0
5 - Fresh
3.0Cur3.2WIZSM5 - Used
1080
ISBN:981-2643-15.5
ProceeAkssof IntebatioBL Confercnc.Oi Chenical atu Biapruess Ensineenns
2l - 2y AtBBt 2003 , Unive6iti Malayia Sabah,Kota Kinobalu
250'C
3.0Cu/3.2WHZSM-5-Fresh
430.C
3.0W6.0Cu/HZSM-i
l.0Cu,3.2W/HZSM-5-Used
200
300
400
500
T/"C
Figure 3 - Antnonia TPD spectraof samples
Figure 2 - 'Ihe diaeramsisothcrmadsorptionof catalrsts
Figure 3 depictslbe ammonia-TPDspectraof the HZSM-s
and modified HZSM-s with loading ofw and Cu. For ihe
HZSM-s, the amnonia-TPD pealGappearedat - 23?'C and
- 430'C, wbich may be ascrib€dto the desorptionof two
kinds of ammoniaspeciesadsorbedon weit acid (mostly
Lewis acid) sites and strong acid (mostly Br6nsted acid)
sites.respectively
1201.
Theadditionof3.2% W and3.0%Cu to HZSM-sledto rhe
reducedintensiiy ofthe high temperarure(- 430'C) peakand
a srnall downshift of its position as revealedin Figure 3.
This is similar to the results found by previousresearchers
of Mg'?+andZn2"into the
i15,161,wherethe incorporation
WHZSM-s host catalyst resulted in the elimination of
strong surfaceBrdnstedacid si.es. For the 3.0%Cu/3.2W
HZSM-s-Used,
the ammonia-TPDpeaksdisappeared
at 237"C and - 430"C. This indicatedthat after rcacrion, the
acidsitesof the3.07,Cu6.2WrZSM-5hadweakened.
Cu and W ioadedHZSM-s samplesshowedihar in the OH
stretchingvibration thfee IR bandsat = 3610 cm_r,due to
bridgeSi-OH (Al) acidic goups, at = 3660 cm'r due to
non-framework
A1sites,or octahe&al,andar 3740cm'r,
a$ributedto terminalSi-OHnon-acidicgroups[21].
ISBN:981-2643-15-5
Futher reactionwilh methaneand oxygenal 753oCfor five
hoursresulledin the disappearance
of lhe bandar = J.6t0
cm' for 3.0cu./3.2w,fi2sM-5-used
sample. This is
Fobably due to the extracrionof aluminum in tle zeolitic
frameworkinto the non-fiameworkor due (r the deposition
of carbonaceous
rcsidues. The deposilionof the coke led ro
catalystdeactivationafter five hoursof reaction.
The H?-TPR profiles of
3.0W/3.0Cu/IIZSM-5,
3.0Cu/3.2WIIZSM-5 for ftesh and used samples are
depictedin Figure 4. As observed,all the curves conrain
severalpeaksin the temperaturerangeof 200-900"C. The
TPR pattemsof both catatystsexhibitedrwo peik with rhe
maximumat E800oCwhich could be due to rhereducrionof
W species.The reducibiliry of ihis type of catalystdecreased
as the strength of the intemction bet$,eenthe merat oxide
speciesandthe suface of ihe supportincreased
The observed hy&ogen-TPR peak at
for
3.0Cu./3.2w/HZSM-5-fteshcould be due to the-400"C
reducrionof
Cu'?*species. The spectrademonstrateal
the existenceof a
single reduction peak of Cu'+ ro Cuo at 420"C. However,
allerreactional800"Clhep€akdisappeared.
Oncrrrrrrcstmg
feature of Figure 4 is lhe HxTpR specra of
3.0CuB.2WHZSM-5-usedwhich indicaleda peakar 340'C
Gigure 4). This small pea-kmay be attributedto lhe
reduclionof Cu'* ro Cur'. Nevertheless,
lhe peakof W' ' did
not changebeforeandafter thereaction. TheTPRprofile for
tungstenrevealedthat the additionof rungstenhadincreased
1 08 1
Prcrc.dkss of tnkrnat;aaoJaohJp@c. On I h?nical aut sibpta pt: Lnpn..rino
27' - 29' Aus& 2@J , Uniec^ri Matdvia satah Ko@kifubal:u
the thermalstabiliry of the catalyst,as theW componenrwas
notlostby sublimation
afterreactionat 753oC.
3.0Cu/3.2W^IZSM-5-Used
3.0Cu/3.2WlzsM-s-Fresh
liquid fuets. rhe advantases of
y1i9l
l.*
- !9 HZSM-s
3.0CuB.2W
included higher crystalliniry, highe;
amounrof Brttnsredacid sites and medium strength of
Brdnsted acid sites. T?R analysis indicated that ii;
resjsLance
of HZSM-5 rowardstempemture
wasenhanced
bv
loadjngW andthehighreacLion
(?sJoC)did noi
remperarure
Iead to lhe loss of W componentby subtimarjon.
3.0Cu6.2WHZSM-5 catatysi is a potential catalysq
becauseunderoptimum conditionshigh methaneconversion
(2?%)andC5*selecriviry
(69%)wereobrained.
Acknowledgement
(D.D.Argrarelultyacknowledges
OneofrheauLhors
rle
^.
rnanclat
supportreceivedin the form o[ a researchgranl
(Project Nor 02-02-06-0101) and (project No:
09-02-06-005?-SR005/09-07)
fiom rheMinistry of Science,
Techrology andEnvironment,Malaysia.
References
370'C
S. Emst,J, Weirkamp,Inc.Inarisio, M. Frias,J.M.
Benrgen (Ed.), HydrocarbonsSourceof Energy,
craham& Trotman,London,1989,p.461.
[2] S, Han,D.J. Mafienak,R.E. patermo,J.A. pearson,D.E.
walsh,JournatofCatalysis148(1994)134.
lll
3.0w/3.0Cu7HZSM-5
300
't00
500
900
T/'C
,
Figurc 4 - Htbogen-TpR spectraof samples
Conclusions
The direcr conversionof merhanewff optjmjzedover
Cu-wZSM-5 calatysL
using SLarsofl
Stadsli;a version6.0
soflwarc. The three independentvariabtesjnvolved in rhe
optimisationa.e %wt. of W doped, %vol. of Or, and total
flow of f€ed gases. The parelo chart indicaied thar the
variablewith $e largesteffect was % vol. of O, (X, andits
quadrariceffecL(XrXr. This ;s fo[owed by ftow tolal of
feedgases(X,). % wt. of W dopedtxr) and itl quadmlic
effects(X3& andXrXr). The interacrionsbetweenany rwo
of rhe independent
variablescan be neglecred.From the
RSM resulrs lhe opdmal melhane conversion, Cj.
selectivity, and Cr* yield of 29.4%, '70.2qo,and 20.6%,
respectivelywereobtained.The adequacyof this modelwas
confirmed by means of vadance analysis and additional
Frcm the chamcterizationsrudies,the 3.OCu/3.ZW,4IZSM_5
had more potenrial to catalyze the methane oxidarion
1082
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ISBN:983-2643-15-5
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oflntltl,atioial co'fe@ce On Cheniel a"d Eiopt@es E situcnnq
2T -2y Ausut 2N3,lJnteebtti Malatsiosal,att, Kota Kitubtlu
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tl8l N A S Amin,D D Anggoro.accepr€d
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1083