Synthesis of superacid catalysts SO4 2-/ZrO2(Pt) and WOx/ZrO2(Pt) for isomerization of n-alkanes
Research has been conducted into the influence of the conditions of synthesis of SO42-/ZrO2 and WO3/ZrO2 systems and of doping of such systems with oxides of silicon and aluminium on their catalytic activity in n-hexane isomerization. An improved procedure for co-precipitation is used to synthezise...
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| Date: | 2001 |
|---|---|
| Main Authors: | , , , , |
| Format: | Article |
| Language: | English |
| Published: |
Chuiko Institute of Surface Chemistry National Academy of Sciences of Ukraine
2001
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| Online Access: | https://surfacezbir.com.ua/index.php/surface/article/view/51 |
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Surface| _version_ | 1869291134357864448 |
|---|---|
| author | Brei, V. V. Fraissard, J. Levchuk, N. N. Melezhyk, A. V. Patrylak, K. I. |
| author_facet | Brei, V. V. Fraissard, J. Levchuk, N. N. Melezhyk, A. V. Patrylak, K. I. |
| author_institution_txt_mv | [
{
"author": "V. V. Brei",
"institution": "Інститут хімії поверхні НАН України"
},
{
"author": "J. Fraissard",
"institution": "Universite Pierre et Marie Curie"
},
{
"author": "N. N. Levchuk",
"institution": "Institute of Bioorganic and Petroleum Chemistry of National Academy of Sciences"
},
{
"author": "A. V. Melezhyk",
"institution": "Інститут хімії поверхні НАН України"
},
{
"author": "K. I. Patrylak",
"institution": "Institute of Bioorganic and Petroleum Chemistry of National Academy of Sciences"
}
] |
| author_sort | Brei, V. V. |
| baseUrl_str | |
| collection | OJS |
| datestamp_date | 2018-11-27T09:42:39Z |
| description | Research has been conducted into the influence of the conditions of synthesis of SO42-/ZrO2 and WO3/ZrO2 systems and of doping of such systems with oxides of silicon and aluminium on their catalytic activity in n-hexane isomerization. An improved procedure for co-precipitation is used to synthezise superacid catalysts that exhibit high activity: the yield of branched isomers at 520 - 540 К is 65 - 70% with a selectivity for i-C6 of 70 - 94% and n-hexane conversion of the order of 80%; the content of the most valuable substance, namely 2,2-dimethylbutane, in the isomerization products is 17 - 21 wt.%. WOx/ZrO2(Pt) catalysts prove to be more stable than SO42-/ZrO2(Pt). Doping of WO3/ZrO2 systems with oxides of aluminium, silicon, and niobium decreases their isomerization activity. |
| first_indexed | 2025-09-24T17:25:23Z |
| format | Article |
| fulltext |
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-:.apman
sYNTIIЕsIs oF SUPЕ,RAC ID СATALYSTS So o2- /Zro,1P t1
AND'W О*/ZrО2Р0 FoR tsoРIЕRIZATIol{ oF и-ALKANЕS
V.V. Brei'' J. Frаissаrd2, N.N. Lеvсhuk3, A.V. Меlezhykl,
and К.I. Patrylak3
|^Insfinltе of Suфсе Сhеmistrу' Nаtionаl Аcаdеmу of Scienсеs, Kуiv' UKRАI]\Е.Lаborаtoirе dе Сhimiе dеs Suфces' Univеrsitе Piеrre еt l4аriе Curiе, Pаris, FRАNСЕ
з IпSti|t|tе of Bioorgаniс qnd Pеtroleum Сhеmistrу, Nаtioпаl Аcаdеmу of Sсiепcеs,
Kуiv' UKRАINЕ
Abstraсt
Rеsеaгсh has bеen сonduсtеd intо thе influеnсе of thе сonditions of synthеsis of
SОц2-/ZЮz andWОзlZтОz systеms and of dоping of suсh sуstеms with oхidеs of siliсon and
aluminium on thеiг сatalytiс aсtivity in rl-hехanе isomеrization. An impгovеd pгoсеdure foг со.
pгесipitation is usеd to synthеzisе supегaсid сatalysts that ехhibit high aсtivity: thе yiеld of
branсhеd isomеrs at 520 _ 540 K is 65 - 7Оo/o with a selесtivitу for i-С6 of 70 _ 94Ya and
л.hеxanе соnvеrsion of the oгdeг оf 80%; thе сontеnt of thе пlost valuаblе substanсе, namеiу
2,2-dimеthуlbutanе, in thе isomеrization pгoduсts is 17 - 21 \J"I.уo wo]ZЮz(Pt) сatalysts
рrovе to bе mоге stablе than Sol,_zZЮ:(Pt) Doping of Woз/ZЮ2 systеms with oхidеs of
aluminium, siliсon' and niobium dесгеasеs thеiг isomегization aсtivity'
l. Introduсtion
Isomеrization of linеar alkanes Сs _ Cс, is еmplоуеd for prоduсtion of mixturеs oi.
branсhеd isomers as high-oсtanе additives to motoг fuеls' Thе pгoсеss is еffесtеd iп thе
pгеsеnсе of bifunсtional aсid сatalysts basеd on thе aсidiс foгm оf mordеnitе [1] oг
сhloгinаtеd alumina t2] whiсh сontain platinum ог palladium as dehydrogenating-
hуdгogеnating componеnts. Сatalуsts basеd on moгdenitе сan funсtion at a tеmpегature сlf
520 _ 570 K, whiоh lowers thе уiеld of bгanсhеd isomeгs bесausе of thегmodynamiс faсtoгs.
Using сhlorinatеd alumina makеs it possiblе to сaгry out thе proсess аt relativelу low
tеmpегaturеs (400 _ 450 K) with high yields of isomеrs. Howеvеr, this сataiyst is rathег
sеnsitivе to thе prеsеnсе of watег and sulfur'
In гесеnt yеars m1ny rеsеarсh tеams havе сonduсtеd intеnsivе studiеs of promising
.еnvironmеntally bеnign' сatalуsts for isomегizаtion of n.alkanеs based on sulfate and
tungstatе.сontaining ziгсonia whiсh havе supегaсid sitеs [3.l9].
Aссording to thе agrееd сlassifiсation, supеraсids arе сompounds whose aсid sites arе
сharaсteгizеd bу Hammеtt funсtion valuеs that arе lower than thosе for l00% sulfuгiс aсid
(нo < _l0) [20]' Тhеir numbеr oГ solid supеraсids is not laгge and inсludеs thе synthеtiс
polymег Nafion that сontains (CFz)SoзH groups (Hg х -12); hеteropolytungstatеs suсh as
Csr s}Iо.:PWrzОю (Ho = -l3); AlClз.CuClu and AlClз-CuSo+ (Ho * _13.5); sulfatеd oхides oГ
titanium (Hg x _14,5) and zirоonium (}16 l -16), and tungsten-сontaining ziгсonia WОJZrОz
(Hg * _|4.5) |з'4'20J'
Among thе familiar superaсids, sulfatеd ziгconia is outstanding in that it has thе
stгongest aсid sitеs and ехhibits a high aсtivity in thе isomеrization of paгaffins [5,l8]
Howеvег, it is known that Soq.-/ZЮ2 samplеs bесomе dеaсtivatеd duе to loss of sulfuг undеr
thе геduсtivе сonditions of thе isomегization pгoсеss' Nеveгthelеss, сatalysts basеd on
su|fatеd zirconia dopеd with iгon and manganеsе ions wеге tеstеd iп a pilоt plant foги-butane
rsomегization |21l. Zirconia with a suppoпсd tungstеn oхidе phasе WoJZrОz is lеss aсidiс
t)0
thanSoy'Zrozbutrtpгesеrvеsitsсatalytiсpгoреrtiеs.inrеduсingatmosphегеsathigh
tеmpеratuгеs. A fеw у"i., ugo Mobil.oil р,"nйo a numbеr оf сatalуsts basеd оn у1QJZrОz
rvhiсh сan Ье usеd гo.й" isЪmегization oг,-puiuйn', thе dесусlization of сусlohехanе, thе
h).drogеnation oг ь.n,.n",. thе alkуlation oГ.iolu.n. *itь mйanol, thе oligomerization of
оlеfins, thе alkylation "iЪ. 'Ь'.,iсs
with alkenеs, thе сatalytiстеd-uсtion of No,, as wеll as
fоr thе rеnroval оf sulfuг and nitrogen сompounds from сrudе ot]l |22],
Thеrе arе dеtailеd invеstigations on thе mеthods of So}-lzЮz aod WО'lZrОz
рrеparation whiсtr invoiiJ in.,p,.giutlon of zirсonium hуdгoхidе with solutions of sulfuriс
aсid (оr ammonlum surfatе) and ammоn,ium mеtatungstatЬ (oг со-prесioitation of ZгoClz and
ammonium mеtatungstatе using an aquеous.
'"i"ii""Ъг
amйonia).followеd bу сalсination of
satтplеs at 82o _ 1170?й;-;l,1з,i4'16,171..Тtre aсtivitу of thеsе сatalуsts is considеrablу
dеpеndеnt on thе сonortЪ'\''"гЪ."
j".,iЬ" Ьг iь.
'i"пйg
,,'"oni,m hуdгoxidе, of its sulfation
oriungstation, d?;Iж"'нlijlJil"i,o,
was to сompaге thе known proсеdurеs for synthеsis
of So12-/Zro2pt) and ф6jz,o,tгt) сatalysts and to work out a mеthod for thе pгеparation
r-ii an aсtivе сatalуst with rеproduсiblе pгopeпi., гo. tь. isomеrization of rl.hехanе, Thе studу
wаs aisо intеndеd .o *",iаЪ, ,hе avaiiablе d;;;;; thе рromoting. еffeсt of additivеs suсh as
irхiiеs оf siliсon, uru*iniu*, anсi niobium ;;
'h"
сat;lyst aсtivity in rеaсtions of сumеnе
сгaсking and lt.hехanе lsomегization,
2. ЕхреrimеntaI
i'l *ll#' f# ?!,,i" !i*o'е s \\lете р rе p aге d ]:' n*'*'j]:
::^ * i:l",1ll *:.
zirсonvl сhlorrdе -i.r., un аmnionia sоlution зЬ g..of ,,9,!]:
11l9.and
600 ml of Hzo wеrе
pr-rtintо aro..nd-bottйd flask еquippеd with a itirгеr Тhеn, undеr сonditions of сontinuous
miхing at З2О - 330.,;-ii.-.l "i'1'з'5 ^,t,*й""i"
and 30 пrl of watеr wеrе addеd. In
agrrrmentwith[6]tнернvaluеofthе.iooniun.,hуdгохidе.suspеnsionformеdwаs8.0.Thе
suspеnsiоn *u, .,,,,"i l'^зi.i? ror z ь, г"ii"*i"Ё whiсh.it.was{rlterеd using a Buсhnеr
iunnеl. Thе filterсak. *u, ,uu,ь"с with hot *aiеr (r T) and driеd at 370 K for 21Ь.
Samрlеs of thе Zгoz-Siou sуstеm *.,;;,;;;;,ьv gчtig thе ziгсonium hуdroхidе
driеd at l00.с i".n,o,tui*itь tь" addition of a.small amount of watеr and' subsеquently,
50Й'(,-kof Aеrosil;:;й. iй. p.,," "ь"i"J
*u..р.rr.ti,.d to foгm суlindrical pеllеts l
mm in diаmеt.. *ы";*l* j*а." 399 K.iй.ь-ЪЬ'inum and palladi'.tm wеге intгoduсed
l-lv imprеgnating thеl"*pi", *i,r., solutions "iйi;'сй
.nd Pd(Noз)з to 0.5 wt. % of Рt(Pd)'
Гollоrving whiсh thе;;;ъi;; *еi" d.i"а ";;6
i гoiz ь. Rеduоtion of paliadium ions was
сarriеd out in сo n";;;ъй к, onJ,"аu"'ion оf Pf- . in hуdrogеn at thе samе tеmpегatuге.
Тhе samplеs -",. ,"ri^i"о u..o,aing.io.thе follоwiлg pгoсеduге. Thе dгiеd samples
wеrе mixеd ,"itь sutfu.-J*iJ,orution, uьoй Ь" lJ
'n"r
of нu3oq pег molе of ZrОz. Тhе aсid
сonсеntгatlon was adjustеd so that. t].r" .:;;;;йng sotution соuld bе absoгbеd bу the
samp.lе (3'3 ml orz'Ji мъl,Soс and 6 g
"f
;i;;;;u*.iуаio"iа";^8.4 ml of О 5 М HzSoа and
7 g of Zroz-Siou) i"n" ,"-pr., opt1фа ;;;-;;;J ui no "С fo^r 2 h Finallу thе samples
ъ'еrе сalсinеd i"
^,,
ui.вйкЪr z h. в"ro* tiъ Ju'pr., *iri ье геfeпеd to аs Soq, /ZЮz.
Samplеs of zirсonium-tungstatе #;;;;.ovo-/z,o' *.'. pгеparеd both by
imprеgnation oг,i,.o-nй.ья.*iЬ:,''l un йmonium mеtatungstatе solution and bу co-
рrесiрitation fi","
';;;;;;;^o,г,ii.onyt
сhlоridе and ammonium mеtatungstatе,
2.|,I, Iпtprеgnation of zirconium ;;;;;;й; iо a solution of zйсonium oхychloгidе
an ammonia solutiБn was gradua.lly .dd;J;;.i" ,й s - rо Thе zirсonium hуdroxidе
prесipitatе fоrmеd *u, *u,ьЪа with watеrЪtiino сьto,ldе ion wаs dеtесtеd in thе washing
watегs. follow.rng ;;; i;;;dгiеd at зтo к^ijгв ыand tnеn at 410 K foг 1.5 h. Thе produсt
.lrilсj
llе i].:
2,7
Y,\-l
.slrtц Со }
. эiгtar2т]1г
T'\
:...-tгоnЬ.
- ....rрnго
t
-::] есtаnс е
1 ^:
,::icus tеГ
.- т>ffn..lэ
.:зlr.sет ]
j iРt]lnc.я
..:.].uсtS :
:.'.l rc еn tт е.
,.' зs htlоi.
1
100
t
!
b
E
E
obtainеd rvas impгеgnatеd lvith an аmmonium mеtatungstatе solution, dгied, and сalсined in а
mufТIе fuгnaсе at 1070 K for З h Thе Wo3 сontent in thе сalсinеd samplеs was l6-19 wt,%'
2'|.2. Sоmplеs of Wo,/Zroz with аddition of highlу clispеrsесI oхidеs of siliсon andаluminium. Тhе dгiеd ziгсоnium hydroхidе p..pu,.d Ьtto*ing pгoсеduге 2.1. I was
thoгoughly gгound in a mогtaг with highly dispегsеd pvгogеniс atumlna (140 m2 g-l) and
wateг [(Wo3lZrОz)'Д|zОз = 4.] w/w] Thе pastе foгmеd was ехtrudеd, and thе paпiсlеs
obtainеd wеrе at first dпеd at 370 K and thеn at 410 K foг l.5 h, following *ьiоь tьеyruеiе
impгеgnatеd with an ammonium mеtatrlngstatе solution, again dгiеd at з70 K and сalсinеd at
l070 К In a similaг waу, samрlеs with adcition of Aеrosil (30О m2 g-,, 1wo.izгoz).SiOz ==3:l w/r,v) wеrе sуnthеsizеd
2.|.3, Сo.precipitаtion in аt1uеous solutiоп. A solution of ziгсonium oхусhlогidе in
watег соntaining ainmonium mеtatungstatе lvas rеfluхеd simuhanеousi1, with slow
introduсtion of ammonia bу thе ''anреaring rеagеnt'' г-lеthоd' In oгdег to adjusi thе dеgгее оГ
hydrоlysis thе bоiling tiп-lе ivаs vаriеd fгt..;l.l 1 to 13 h and thе рH оГthе *olution during thе
сouгsе of samplеs agсlng ftоrn ] 0 tс 7 9 Тhе sclu;iоns obtainеd r,"'еге thеn сoоlеd and йadе
alkalinе by adding an an.:mоliia sоlution up to гH 92. gб, whrсh lеd to gеlation, Тhе
prесiрitatеs foпnеd v''еге thorou3hlv 'лashеd l'"'ith watег, fbllorving whiсi thеsе wеt
pгесipitatеs wеге eхtгtlcеd thгоugh a2 rnm ciamеtег oгifiсе Thе paпiсles obtainеd wеге dгied
in an ovеn and thеn hеatеd in a mrrt-flе fuгnaсе аt l070 K foг 3 h Тhe wеight сontеnt oГWo.
in thе sуnthеsizеd саtalуsts amountеd ta 19 o/ь' аnd thеir spесifiс suгfaсе a,.a *u,40 - 55 mi
g-j тhis rnodifiеd mеihоd gavе fоu; рlatinizеd samрlэs rvith a qraduallу inсrеasing dеgгее of
hydrolysis, Bеlorv thеу aге сjеn<-itеd аs WZгPI-l ,WZrPt-2' WZгРt.3, andWZrPt-4.
Sarnplеs with adrilrion of лiоbium oхidе (woJlzЮ2.Nbzos) wеге synthеsizеd
aссording to thе fоlltlw-iпg proсесir:ге То аn initiаi sоlutiоn oi ziгсonium oхyсhloгidе was
addеd a sоlutiоn of niobium pегoхidе сomplеx forrcеd by intегaсtiоn bеtwеeп prесipitatеd
niobium hуdгoхidе and hydгogеn peгоxidе in a nitгiс aсld soiution, Тhе mixturе wis hеitеd to
dесomposе pеroхidе groups. аnd a soiutlоn оiаnlmonium mеtatungstatе addеd' Тhе miхturе
was геfluхеd fог l h' nеutralizеd ll'iтh ammonia up to рН 9, аnd thеn thе rеsulting gеl trеatеd
to оbtain thе сaiсinеd fсrm as dеsсгibеd abovе. l-hе wеight сomposition оf thе сatalyst
obtainеdwasasfоllоws: ZгО2=,.14.8o^,Woз= 1.7.1 o^,NЪzoз =8,1 o/o.Immediatеlybеforе
tеsting thе Wo3/Zгo2(Рt) саtalуsts in tl.hехanе isоmеrization thе}' wеге rеduсеd in a
hуdrogеn flow at 62О _ 670 K foг 4 h,
2,2, |уIеthods fоr Сhоrасteri;ing thе Ссttаlуsts
Х.ray diflraсtion рatteгns оf samplеs lvеге rесoгdеd сn a DRON.UМ1 diffraсtomеter
using Co Kсr гadiatiоn Sресifiс suгГaсе arеa ц,егe mеаstiгеd bv thе standard method of low.
tеmpегatuгe dеsогption оf aгgоn
UV-Vis геflесtanсe sprсtгa of poв,сiегеd sаmpiеs wеrе гесогdеd on a Sресord М-40
spесtгophotomеtег. Тhe геlativе rеtlесtion соеffiсiеnt "R was mеasuгеd using Мgo as a
rеfегеnсе (Д = Л,un.рt.lЛlrр). Absогptiоn spесtгa of,samplеs wеrе сalсu!atеd frоm thеiг diffusе
rеflесtanсе sресtra with aссcrding tо Kubеrka.}lunk funсtiоn' F(R) = ( i -R)?/2R.
Aсid сhaгaсtеristiсs ъ,еге dеtеlп;lnеd in 1егins оf alnmоnia adsогрtion valuеs at
various tеmреratuгеs oГ samplеs pгеviоuslу aсtivatесi undег vaоuum as wеll as bу thе mеthod
of tеmpегatuге-pгogrammеd dеsогрtion of ammonia uslng an ]\41- 1201 mass sресtrometeг as
analуsег. Thе aсidity оf samplоs rvаs also tеstеd in сuinеnе dеalkуiatiоn' using the tесhniquе
of tеmpегatuге.pгogranlmеd rеaсt;оn (ТРR) and mas'j-sГесtroгпеtl iс mоnitoгing of геaсtion
produсts. Samрlеs (a-8 mg) wеге put in a quaгtz сuvеttе and еvaсuatеd at 52О - 620K (for
moгdеnitе, .720 K}, Сumеnе adsогрtion lvas еffесtеd at 300 K AJtеr еvасuation thе сuvеttе
was hookеd up to thе blееd.iл sуstеm oГ thе МI-1201 mass spесtгomеtеr to rеglstеr
ri
f-i
:
L-с
ше:
цсе
E1 .
E,
ЕЁc
B;r
il ls
G
r.еs
r: id
:hе
..А
I aiu
r:.еs
с:rdе
:хidе
s:.1n9
...1'rd
r0l
сonсurтently thе fragmеnt ion Сс}ls* (77 a.m.u) and molесula. b'"Y'.n. ion Colls* (78 a.m.u.1
with a linеar inсrеasе ";;;;;;;;.Iч*.riY ?j
a гatе of i0 K min .).
-....-ih;"сtivitуandi"'.ffi
:iъ1.$''.;$::l;ж*ъl"ж,lТ:.}xlx.Tlу&Т,::
a flow rеaсtor. Samples
(0.8 - l.0 mm in o,"*,ji*'"o.,ni'in."Ьь,nЬl werе plaсеd into an isothermal zone of thе
iеaсtoг and aсtivatеd ,", o
^ti
";
;;Ь й in a floJ;;й;;l^Tn.чlт гeaсtor was brought to
stablе opегating.onoitin,^tp,.,,u,"
3.чu, l;й;;;500 -.540'K), following whiсh it
w as fеd w ith u . н,,,..'ii ;й; ; ;; ; ::*-: :tъ1fl,*:тl ;;,'; 1il l";i Ёl,; ;,"i:;;i
a:''"-liЩi:}#:Tj:#Т"T::;:t'};T' j*#,""'ж-1TТ;-;'Jж:ЕiTll
using a flamе-lontzattс
ol""""уr phthalatе as stationarу phasе'
3. Results and Disсussiоn
3,|. SuЧ:eed{:::;liЬ"o,o"
рattеrns ьr
1!rе
initia.l and sulfatеd
11;::'ъiii"Ч:"#:i#
}:. h
j;1iТ":l' ;;Т il} 1 * н*.;хщ:: :J.1 :.:l i"'"'""Ё
Ы Ъ o o ы в-]
.1
n' tь"
сasе of a sulfatеd ';;;i; ti"
.ut.ln.tion iЬ-*n, at thе.samе tеmpеraturе rеsultеd in
iоrmation ot u'..iii;;;'ff;;inuntrу l!il.й1 ;ffiтl";;:"тy:Ё};:i,Ь::
;;;;;. ;-l ч: i,уl*r ;rЪIг;:}Н'ff : :-"?'; -Т,T'.i'iН
-*i
ii.u. i n сгеased th е
arеa dесrеasеd ontу
spеcifiс suгfaсе a.еa Js'.'lfatеd sйplеs to 250 - 280 m. g ..
Intеnsitу (a.u.)
Fig. l. Х.raу diГfraсti"l^Y1l:T:J-T.?l otzюсэЪlz driеd at 370 K (1), So,2.lzЮz сalсinеd
l,'?';iаj];;;;;..i"inеd at s70 K (3)
;::]..ffi;;;;;;o{surгi1е]'i1:::1':::1.*Тi:,",iliT;T,T"l}'ilji"ilТ"iljB-sitеs (Bronstеd sitеs) of sulfatrd z'rсoп';;;;;ll;';;; l6 t3l When in сontaсt
tt'е rеs.iйlnjiiut. tьut lh".ф::l:l..3l:Р".j -lз 75) thе samplеs ь..um. уеllow. Thesе
ж.;,Нil,ж.:1'li lffжll:lJ.di:: :i.. ; 5j';; samplеs bесamе уеllow. Thesе
zo
102
:#tfi"{'."'цfi*1'f*oi:l';?",;:,,?H:}#!|in* *n,"n is one of thе most impoгtant
In thе ТPR spесtгa гесoгdеd in tье йuгsе of thе foгmation of benzеnе fгom сumеneadsoгbеd on So+2-/ZrО2.pгеviously vaсuum-trеatеd at 520 к, ,ь. ь.n,"ne pеak was obsеrvеdat.З70 _ a00 К (Fig zaj.ln thе сasе oil iеslaс.iсiс н.*o,с.nit"lьl
'u*i'um of bеnzenе
:жfi:'xx1,1}ж...1"т'11.,;.if3,xlii:;:},jl;;;;;;;ill"". oг paliadium in ihе
I,V
I1ftt.v
I-n
.iг
: - llr
;ln
3ю тla Ф ш{/o
470Ф
:аlсinеd
,.,lfS, and
. сontaсt
'.. Thesе
f,1i":d',}.
speсtгa foг formation of b;.}"е fгom сumеnе over Soa2./ZЮz (а) and
|- Soц"./ZЮ2 fгeslrJу сalсinеd at 87O K:
]- afteг eхposing SОцz.izЮzonе wееk in aiг'
Ехсeеding of thе 78 a.u' mass сuгvе ovег ,77
a'u-m, indiсates сraсking of сumenе.
Еxposuге of thеsе samрlеs to aiг Iеd to a high-tеmpегatuге shift of thе bеnzеnе peak(7', = 42О K) and to a dесrеasе in.its intеnsity (Fig 2) Aftег tеsting in rr-heхanе isomегizаtioпfoг 5 h the Soц2-/Zro2(Pt) samplе showеd almost no aсtivitу inЪumеnе сraсking, with thеsulfuг сontent in the sample bеiфdесгеas.a г'o' О 4 to 0.3 wt.Yo,
Soq2-/ZrОz(Pt; ana, so]2-zz.o,-sio,(Pt, Pd) systеms showеd high aсtivity inп-heхanе isomеrization . (Tab'e l)
-
Тh;
..
rеaсtion. p.oduJ,- *.,. predominantly2-methylpеntanе, 3.mеthylpentanе, z,i-аinetiуtьr-rtanе with.ad'i*i".., of сracking pгoduс!(CI _ Cs). The bгanсhеd isomег уiеld at 500 ( гangеd fi"' ;';;;; Yo at asеlесtivity withгеspесt to l-Cs of 80 _ 75 Yo and a п-hехanе сonvеrsion of 78 - 83 Yo. For palladizedH-moгdеnitе similar rеsults wеге aсhiеvеd оnly at 5з0 _ 550 K [1]. The abovе-mеntioned datafor Soq2-lZro2(Pt) at 5O0 K-aге vегy сloseto thе data in trz]'.rnсlusion of highly dispегsеdsiliсa into thе оomposition of thеsе сatalysts iеd to a,"сuЁtlon;.;;;;". сгaсking сompaгedto SОц,-lZro2(Pt) at 5oo _ 520 к anа to an' inсrea|r (up .o iт "п1 in thе yiеId of2,2-dimеthylbutanе whiсh is thе most valuablе produсt. i.n tЪ.., oг octane numbег.Сompaгison of thе dаta on thе уiеid and selесtivity^of ь,."n"ь.j-i.omегs and the data onhеxanе сгaсking for Soц2-/Zro:-Sio:(Pd) unа' s,o}:tzю";Ю;d;; samples shows (sееТablе l) that platinum is а morе еffесtivе dеhуdтщеnaйЪrh;;};;nating сomponеnt ofbifцnсtional сatalysts Гoг isomетization oГ r-аlkanеs thй
.patliaium,
supposing thatсоnсеntrations and strеngths of aсtivе B-sitеs in thе Pt- *а pa.l""tыning сatalysts aгe thе
l0з
i/
//'/
1?;
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- : a-
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tr1 7
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104
h-
l:t-
7:
3f,-
3.2, Tu ng stе n- c o ntai пi ng Zirc o n iа
As is sееn fгom.thе difГraсtion pattеrns (Fig 3), aftеr сalсination at l070 K ziгсoniumhydгoxide without addition of W or Nb is almost purely mono ciinic Zroz phasе (thе mostlntеnsе pеaks at 2@ =-32.9o and з6.8")' Addition of Wo3 lеads to fогmation of аprеdominantly tеtгagonal.phаsе of Zгo2 (the most intеnsе peak at 2@ = 35.3") Тhisobsегvation agгees with thе known data [li] aссoгding to whiсh thе addition of tungstategroups stabilizеs the
.tеtrаgonal ziгсonia pьasе tьai othегwisе is mеtastable at thеsеtеmpеraturеs' of notе also is thе faсt that thе dесгеasе in thе spесifiс surfaсe aгеa of ;"йi;;obsегved duгing thе сouгsе of thеiг thеrmal tгеatmеnt is substantially smaller than that foгzirсonium hуdгoхidе without suсh additivеs. on. thе diflтaсtion ;;;*' foг Nb.сontaiпing
samplеs theге aге no peaks that сould be attгibutеd to a monoсlйiсffise' Niobium pеntoхidе
sееms to staЬilize the tetгagonal phasе of ZrОz more е{fiсiеntlу than Wo3 does.
10 20 з0 40 50 60 70
z9
з1
hv, Еv
Fig.3. Fig. 4.
Х-ray diffгaсtion pattегns (сoK.) of ZrО2 (I), UV-Vis геflесtanсе sресtгa foг Woз/ZЮ: ( l )
WОз/ZЮz(2), aлd Woз-Nbzos/ZЮa (з) and Woз.NbzОslZЮz(2).
' Thе [hv(l-R)2/2R]l,2 funсtion fог Woз/Zro2 samplеs сalсulated from thеiг diffuse
геflесtanсе speсtra aге shown in Fig' 4 In thе case of sеmiсonduсtors oхides this funсtion is
aрproхimatеly Iinear on thе long.wavеlength еdgе ofthe abso1ption band, and the inteгсеpt of
the ехtгapolatеd linear portion of suсh a dеpеndеnсе makеs it possiblе to deteгminе foгbiddеn
gap values. For Wo3 сlustеrsthе.fo-гbiddеn gap dесreases with inсrеasing сlustег sizе [19]Aссording to [l9] for thе Woз/Zroz(Pt) sуstеm thе highеst сatalytiс aitivity in геaсiions
сatalysеd by supеraсidiс sitеs is obsеrvеd in thе сasе of samples with a сепain optimum sizе
of Woз сlustеrs whosе Дo valuеs arе appгoximately 3'1 _ З.i eУ. The [hv(1-R)2/iR1lД vs hv
plots for our samplеs arе similar to thosе prеsеntеd in [19] Thе infleсtion points inihe 1ong-
wavelength rеgion givе еvidеnсе foг thе prеsеnсe of Woз сrystallitеs.
Thе wеak pеaks in the 2@ intеrval from 27.О to 28.4" in thе diffгaсtion patterns
(Fig. 3) may be assigned to a monoсliniс Woз phase (t6 = 2,64 еV [19]) whose
'o,iint.n,.pеaks aгe a|2@=27 О,2,7.5,28.4' and 39.9o (rесаlсulatеd foг Сo Kсr гadiation). Тhus, high-
tеmpегatuге trеatmеnt of samplеs сausеs thе initially homogеnеous hydгoхidе struсtuгr of ihr
samplеs to bе dividеd into ZrО2 and Wo3 phasеs.
t05
Gгavimetгiс сuгvеs of ammonia thеrmal dеsогption fгom thе surfacе of samples allow
onе to еstimatе thе сonсеntration of aсid sitеs (Fig 5) Reduсtion of the Wo,/Zro2 samрlе
pгomotеd with platinum in a flow of hуdrоgen at 670 K foг 4 h lеads to a small inсгеasе in thе
lon'.n' of stгonglу геtainеd ammonia that undеrgoеs dеsoгption at temperaturеs abovе 420 K.
This сonсеntration makes up 0'16 mmol g.'in сomparison with 0'12 rnmol g-l Гoг an
unrеduсеd УlОзlZroz samplе. Thе сonсеntгation of aсid sitеs dеtегminеd for bоth samplеs by
baсk. titration of n-butуlaminе adsoгЬеd from toluеne solutions is 0.1З mrnol g-.' |f tеrь
butуlamine is usеd, thе aсid sitе сonсеntгations obtainеd Гoг all thе samplеs arе appгoximatеlу
20 % smallеr than thosе dеtегminеd with п-butуlaminе. This faсt is rеlated to thе diffеrеnt
aссеsibilitiеs of aсid sitеs to molесulеs of ammonia, ll-butуlamine , and tеrt-buIylaminе'
б
q)
- o'2с
т:Фz
Fig. 5. Gravimеtric сuгvеs foг thеrmal desoгption of ammonia foг WOз/ZгО2 (l) and
Wo/Zгo?(Рt) (2)
In thе сasе of a rеduсеd Wo^/ZrozРt) samplе thе сontеnt of sitеs that aге more aсidiс
than in H-mоrdеnitе (dеsoгption of ammonia at tempеraturеs aЪovе.600 K) is 0 035 mmol g-l
iгig ]i в""luation of the.aсiditу oltungstate.сoniaining Zro2 using llammеtt indiсatoгs is
impossiblе bесausе ut.,.ul"inution at toтo K thе samplеЪ bесomе уellow and aftег rеduсtion
theу bесomе blaсk.bluе. Wе havе еvaluatеd the соnсеntration of асid sitеs in tегms of
4-nitrotoluеnе (a-NТ) uJ,o.ption (PKo = -l1.3s) fгom tohtеnе solutions. Thе сonсеntration of
.l-NT was detеrminеd pi,oio*...i.uity ть. aЬount of 4.NT adsorbеd on the wОзlZтОz
samplе is 0'028 -*ol gj' wherеas thai adsorbеd on thе Wo,/Zroz(Pt) samplе is еqual to onlу
0.004 mmol g-. Тhе last valuе is сlosе to thе сontеnt of aсid sitеs (that are aсtivе in
isоmеrization oГ л.pеntanе) whiсh was сalсulatеd on thе basis of poisoning оГ thе Wo'/Zroz
сatalyst bу 2'6.dimеtьуtpцiаinе [14] It may be assumеd that thе еnhanссd adsoгption of
4-NT on thе Woз/Zroj
'."i"pr.
is duе to formation of сharge-tгansfеr suгfaсe сomplexes'
As distinсt г'o* ii. Ъo.,-lZЮz sыnp|es, the Wo,/Zro2 сatalysts рrеsе,r!.е thеiг aсtivitу
aftеr long-tегm storagr in aiг. As faг as сumеne сгaсking is conсегnеd' rеduсеd samplеs of
WО'lZrОz arе morе еffiсiеnt than WolZЮ, (Fig б). тhБ ьigьеst
'aсtivitу
is ехhibitеd by thе
ttinqstatе-сontatning zю, p1on",ot.d with Nbaol' ,{ааition oi highly disреrsеd alumina leads to a
106
l-
}tlц'
hщ'
!
f
!.
3:
]"
ш'.-
,, allow
.аmplе
.: in thе
.:10K
:oг an
эlеs by
I| tеrt-
:natеly
:l:Ъrеnt
.Jесreasе in thе сatа.Iytiс aфivitv.
Эеtwееn thе \NО'/ZЮz
sarnpie
,somегization as thеге was foг Soo
Нowevег, it should be noted
"aсtivity
in thе гeaсtions of.-/ZгОz.
that thеге is no dirесt согrеlation
cumеne сгaсking and rz-hехanе
з0o 35о 4io 'oio
50о a5о a.Ъ
тK
*--: (1) and
г= -.oге aсidiс
.,: nmol g-l
г .-jicatoгs is
r--.: геduсtion
s r tегms of
:. . зrtration of
.-:
= \ЧОз/ZrОz
; . .-al to onlу
::э aсtive in
.-. \\'lО,lZrОz
.:soгption oГ
'-: : ]ехеs.
: :rеiг aсtivitу
:.: samplеs of
'..:эrtеd bу the
:. :,a lеads to a
Fig. 6. TPR speсtra foг. foгmation of beлzеnе from сumеnе over WolZгoz (a) and.]:yfJo,(o.)
(b). Ехсeеd;"g oiiь..iвlu'
'.,, сuгve ovег 77 a'ц,m.indiсatеs сraсkins ot
..- ,.,..Tin'I,];::,#.q
samples of Wo;ZrОzfoliоwing thе usual pгoсedurеs [22]. Whеn thеу
:з:alystso..pu.;;й1i'.'l?IiЁl]ff ;lTfiТ;iii,;Т:*r:"1*'3j**;*:ж.ж:'т;
.1a/o at 520 K. Тhе.еvaluЁs.;";;'li;;;n thosе с;t.o;nii'е
"oггеsр-onding patеnts [22]
=::"lxilfil.i,}l?.J Pr tь. .o-p..";l';;;;" mеthod ь. oьЫng Woз/ZrОz u." йo,"
::еaссеptedmеthodi{L'!'::liliH#fl ,ъ.,ж#:"",";E}lfl,Tlt:*;ж;:жlti;.:оvе (sесtion 2'l.3). тье wzгpi
'..й;;j3.ared following the above-desсгibеd modifiеd.'..pгeсipitation pгoсеduгe ехhibit ьigЁu.1i,uitу in zi.hеxanе Ьomегization (Table 2). As foг
..:.е SОц,-/Zro2@ф сat{y^sts, thе .й.'й.
Т:j":l'-T o,.i"'i".",ly 2-mеthуl pеntanс,-:-rrеthylpеntane, and ,z'z-аimыьуl;;;;; iui.ь .a*t*,uгеs of сгaсking (Cl * Cs) and:-lndеnsation (Cс*) produсts. rгwzrpt-j й wz,p,-+,.*pr., J...'p,.li'inarily aсtivated in, hydгogеn flow, at 52o-54o к .ь. Б*nJ"i i,o'.. yйi' оi,]dn, *u.ьa sеIесtivity foг.Сь of 70 _ 94% and n-heхane .on"".'ion ithe ordЬr otioй т#е resutts aге closе to thе:эпеspondin8 patent infoгmation tzzl risйrс also Ьe noi.liь.i.iь- WZгPtсatalysts allow
r; ;"#B:.:i:T.lТJi,llj.'"'tЬ. *o,i valuaЬlе p;й;;.nu,".ry 2,2-mеthylbutanе
Whеn the сatalyst сomposition inсludes highly dispегsеd siliсa and'.еspесially, highly::spеrsеd alumina, the' yiеld oг,.ь."un".lJi..::,g.:reаsеs sharply. rл тnls сasе thе main::oduсt is bеnzеnе with- admiхtu'*' oг oiьo uromаtiс hуdгoсаrbonЪ,,whiсh indiсatеs that thе\
.О'/ZrОz-Аlzoз(Sioz)(Pt) . systеms_- гй';nun.ly ;";.й"",;Ё o.n,o,o" уc|ization of:-зехane. Addition of niobium lе;ds ;; a- dесгеasе " in ,-ь.*un. сonvегsion аnd- J.dimеthуIbutane yield but thе
'"r."tшi! й1 .-сu геmains hish.
a b
107
It
(Wo3)'"(ц
suгfaсе [ l(
sizеs' nam
z1гсonium
е]есtгoniс
rr'hiсh wеа
sтrеngth о1
еfТесt dеhr
эalladium
:hе сatalуs
Sеr
'цtalvьL5 d
] аЬ '',4.^ ^.
:iatrnum с
so lnегizat ]
--lд nо.,ct.
:..' ldеnсе t.с
ln
; ( оnсlu
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ё- ФJO оо OФO OOO
о1 m nqq чq Фч.1 ч.1 тк9 экк Rк кR= э:9
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с\ч
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It is assumеd that supегaсid sitеs in thе iс,гm of H-tungstatе bгonzе сlustегs
(Woз).(ff 'oз)(n FГ) appеaг duгing rеduсtion оf thе Woз phasе ivith hydгogen on thе Zгoz
surfaсе [19j. of notе is thе faсt that сatalрiс aсtivit)/ is ехhibitеd оnlу b1z сlustегs of сегtaiп
sizes, namеlу bу сlustеrs whosе formation геquires trеatmеnt of samplеs of miхеd oxidеs ol
ziгconium and fungstеn at 97О _ 1l70 K' Тhе tungstatr bгonzеs aге kпown to havе high
еlесtгoniс сonduсtivitу' Thе tеtгagonal phasе of ZrОz aссеpts еlесtrons oГ Wo, сlustrгs,
whiсh wеakеns thе Coulombiс attraсtion bеtweеn plotons and сlustегs, and еnhanсеs thе aсid
strеn$h of B sitеs. It may bе suggеstеd that сonduсtivе сlustегs of Fi-tungstatе bгonzes соuld
effeсt dеhydгogеnation-hydгogеnation of alkanеs, i е. сorrld bеhal'е simi1aгly to platinum anri
palladium. Howеvег, our ехpеrimеntal rеsults show,(Tablе 2) that ехсlusion of platinum from
thе сatalyst сomposition lеads to a сonsidеrable dесrеasе in ri-hехanе сonvегsion.
Sеvегal meсhanisms foг п-alkanе isomегization on bifunсtional hеtегogеnеоus
сatalуsts arе disсussеd in thе litегatuге' Тhе most fгеquеntly оitеd mесhanism invоlvеs
dеhydrogеnation of a parafftn to olеfin as an intегmеdiatе and absoгption of hydrogеn bу
platinum oг рalladium, pгotonation оf thе olеfin thгough thе usе of B sitеs of thе сatalyst,
isomегization pгoрег of сaгbеnium iоns and hуdrogеnatiоn of thе isoolеfin to isoparafТin [6]
Thе nеgativе oгdеr of thе isomегization геaсtion lr,ith rеsресt tо hуdгogen givеs strong
еvidеnсе foг this mесhanism [7].
In anothеr mесhanism fог п-alkanе isomегrzatiоn, it is suggеstеd that thе pгoсеss
inсludеs following stagеs, 1) protonation of alkanе molесulеs bу thе stгonglу aсidiс B.sitеs,
2) foгmation of a сarbоnium ion with a 5-сooгdinatеd сaгbоn atom, з) abstraсtion oГ two
hydrogеn atoms fгom this ion with thе paгtiсiрatiОn of рlatinum, 4) isomеrization of thе
сaгbonium ion through thе tгansiеnt сусlоpгopanе statе, aild 5) addition oГa hydгidе ion to thе
isomег and that of a pгotоn to thе deрrotonаtеd B.sitе [5] Thе transpoгt of hуdгidе ions to
tsomегiс сaгbonium ions is assumеd to bе a rаtе-dеtегmining stеp оf the isomеrizatiоn ргосеss
[5]' It is еvident that this mесhanism dоеs not inr,Ol'",е fоrmation of an olеfin'
Aссording io |2з,24]' isomеrization of п.alkanеs on sulfatеd zirсonia proсееds with
oartiсipation of strong Lеwis sitеs (zirсоnium iоns) ..vhiсh abstгaсt hydгide ions from
Ьvdroсarbon molесulеs. Тhе сагbеnium ions foгmеd arе svnсhтonouslу attaсhеd to bridging
ьуdrogеn atoms and, as a Фnsequеnсе, undегgo isomеrizаtion' In thе finаl stagе thе sitеs arе
геgeneratеd with dеsoгption of isoparаfin molесules.
Thus, it is еvidеnt that to еstablish thе truе mесhanism of r-alkanеs isomегization on
.эiflunсtional
aсid сatalуsts additional ехpегimental data arе геquiгеd'
4. Conсlusion
Тhe SОц2-lZЮzрt) and Wo*/ZЮ2@t) саtalуsts sуnthеsizеd ехhibit high aсtivitу in
tl-hexanе isomегization at 52О _ 540 K (ll-hехanе сonvегsiоn: 80_85%, isomегs yield 65 _
70%, sеleсtivitу foг l-Cь: 1О -g4%)' Wo^/Zгoz(Pt) сatalуsts рrove to Ьe thе moгe stablе. Тhе
сomparative studу of imprеgnation and сo.pгесipitation methоds for pгoduсing tungstatе-
сonйining zirсonia shows that сatalуsts сo-prесipitatеd following an improvеd pгoсedurе aге
гnoге aсtive in rl-hехane isomегization. Pгomotion of Soц2-lZrО? sуstеms with highly
dispersеd. siliсa lеads to an inсrеasе in thеir spесifiс suгfaсе arеa without loss of сatalуtiс
aсtivity, whеrеas pгomotion of WОзlZrОz systems with highlу dispеrsеd oxides of siliсon and
aluminium is aссompaniеd by a dесгеasе in сatahtiс aсti\'itу.
Rеfеrеnсеs
l. Patrylak K.I, BoЬonyсh FМ, Volоshуna Yu.G.' Lеvсhuk МN{., Il'in V.G', Yakovеnko
o.й ' Мanza I A, Tsupryk l.}vl Ukгainian moгdеnitе-сlinоptilo1itе гoсks as a basе for
linear hехanе isomегization сatalyst ll1ippl Сatal. A' . i998. -\|. \.I4' - P, l87-l98.
I
i1l-'l. Э]
I
1
: ^l
-l
I
l
.-l
- 1l-Эl
I
\ \с)
:'-
z
-
d
-
109
.l'}".{angnusP.J',JaсobsA..inB'ranKеrrlеn(Еd),A}izoCatalystsSуmpostum'
Hусiropгoсеssing, ,l,kzo Chепl. Div,, Amеrsfогt, Nеthегlands. - 1991. . P. 163.
j.}iinoN{''ArataK'SynthesisofSolidSщегасidСatalуstwith.AсirlStгеngthоfЦ<.1604
//J Сhеm soс, сnJ.. co,n'un, . 19s0. -N 18' . P 851-852
4. Hinо М., Arata к. sуnthЪsis of Solid Supеraсij of Tung,..n oхidе, Suoвoгtеd on Zirconia
аnd its Catal,,tiс i;.i;;f;; й"tions oiвut.n" un"а Pеntanе /ij chеm Soс,, Chеm.
Сo**un, - r-sвв -N 18..P'1259Jr260
э, lgiеsiaЕ, Solеd s r-..к'u*.' G'NI,.lll
^Catal.
- 1993-V l44 -P 2З8,
6' Тatsumi Т., Matsulrasil.к'-Ы"" к н sшdу ot'ь. в'.puгatiоn.Proсeduгe of Sulfatеd
ZirсaniaPгеpared г.o'n zii.onia Gеi Тhе iЕ..t oг tье pЁ of ttre т'tothег Solution on thе
jsоmеrization Aсtivitу of n-Pеntanеzв.,riсь.*. Soс Japar' - 1s96 - V.69 -N. 5. -
, .i;J-Зl.i,}]t"
'"un
J.W., Janсhеn J., Lеi G'D ' Sсhunеmа^rin V , van dе !е1 L.J.М,
Saсhtlеr W М Il , ;;n Jantеn R.A. A;iil Sitеs in Sulfаtеd arrd Меtal-Proтnotеo
Zirоoniunr Dioхidе сutыу'i' iд Сat{. - 1995 . V l51 -P з54-Зi2
8' lr,trэгtепa с, с".,utot-Ъ-,,pinnu г., s,gno.*tiо Ь{, Stnrkui G. on thе Aсid-Catalуzed
!sr.mеrization oГ Light Рaгraffrns o'.,- 11-ЫSoo'Sуstепl:
Тhе ЕiТесt of Нуdration //J
cutol 1994 - v. rqs. . rт 1 - P 1sl-18*
,сoniа.Strlfatе Aегogеls
'
-,,\,4rd D A '
Ko в r
.onе-itep
Svn1h^е1is and Сhaгaсtеrizatiоn оf Zi
аs Sоtid sup.,u.,оjii ё.i.л ] i994 . v 15сl -}i ] .P 1B.]3 f
:i) L.рe7,т.,шuuo,."i":,Gо'",R..Nol',aroo,Figuеras,Е,AгrnепdarizI{.Prеparattono
cОi-Gеl Su.ltЪtеd Zгoэ.Sioz and Charaсtе,iйtionЪгi:s SuгГaсе Aсiditу llЬppl Catal. A -
ir l.?]".:\i ],J"'T"ъ 'Ъ1li.?11. I^,TP:I"
J }v{ . Romеrо A A , L,Iaгinas J N,l Catal1tiс
Prоpеr.tiеs oг z.o,-iiЬ,,.^Ёгr..., oг sшtЬiion in thе Cvg!о}rехеnе Isomеrization Rеaсtion
,,з-'cшы - 1996. -v 161..P. 605.6lЗ
''2'iзoлza|ez мк, кoье JN{, Fogash.K.B, Durnеsiс JA Jгоmotion оf n-Butanе
1зоrnегization Aсtivitу bу Hydгatiоn oг s"йut.а 2i'.onl. lll Сatal' - 1996 . v 160 -
Р 290-298 fi-L...j^'.. ^Г Tlrnoqt2te оn Ziгсonia and tts
i3.iiоуsеRA,KoЕ.I.Crysta1iizationBеhaviouroГTungstatеonZiгсoniaandi
Rеlationship .o o.",ii. Р;;;;;'. l вгг".i.oгp'еpu,utiоn Piгаmеtегs lll' Сata.' -199.l. -
'*
;;"1l"';,;il"',Ё'
,il;l?''
J с'
' '
}Ia1 S., Bastian R-?. . сjTg С.D. Influеnсе оf thе
Рrерaгativе меtьoa Ь" ii" i.ii"ltу ot шЬь"йi.iai. lvо- tZrО-i ьnd thе Rеlativе Aсiditу
Сопlpaгеd *itь z."rit., ))l с"ы - 1gg1-. v t ьв. . P, 4з1-44 i'Bifun.tiunul
pathwaуs
.
li' lgiеsiaЕ' вuпon"Б'ё.Ъi,;.;; JA, Ginеsмl.r-, Sоlеd SL Bifunсtional pathwaуs tn
сataiуsis ьу so1id #ds;;;;;;;, ц.ч.у'i' ';ъ;;
: lssz.--v' 3s - N 3. . P 3з9-360.
iб, Baпon p с, sor;i ъ";.:];;ji 1 .s91j;.id
Catalуsts Basеd on Supportеd Tungstеn
. ; s*:;ilff t"жfr l'; }ъ lТ.!i-.o i'']};1?' 1. ^1^1 :
j u,., B С., Knё zi nP..:, н
Сhareсtегization oi^йЬ."z2,o, Ьу Vibтationai Spесtгosсopу and n-Pеntane Isomеrtzatton
'- ilTу.''.',g:тj,;l'Т; '"J:l"Т,l';i''L# o v . 111kоvskaуa-Sеrg!"]u
Е.G,
Kustov L ь,I , Zoiien P. Invеstigati"" ";,;i;;;elsomсгizaticn
in Preiеnсе of Supегaсid
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.i9
N 3 - P з96-406.
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,. :.J;i'."Т'Olno,guni" solld^}сid's'1no *.''.уj.^''-",Aсid.Сataiyzеd
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l./Сh;п-l, Rеv. . 1995 - v. 95. - N 3. - P . 559-614
:i 'l
(
:: -\
:_i
:.: Г
il0
,'
]:ff.oi1''#:Т]:ъ'Y:t iъtxТl'
Appliсation of Solid Aсid-Basе Catalуsts //Аppl
22.Мobil oil Coгp., US Patеnts 5,з45,026
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lП
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| id | oai:ojs.pkp.sfu.ca:article-51 |
| institution | Surface |
| keywords_txt_mv | keywords |
| language | English |
| last_indexed | 2025-09-24T17:44:38Z |
| publishDate | 2001 |
| publisher | Chuiko Institute of Surface Chemistry National Academy of Sciences of Ukraine |
| record_format | ojs |
| resource_txt_mv | surfacezbircomua/fd/3bb378f43b59f58415561b01efab7dfd.pdf |
| spelling | oai:ojs.pkp.sfu.ca:article-512018-11-27T09:42:39Z Synthesis of superacid catalysts SO4 2-/ZrO2(Pt) and WOx/ZrO2(Pt) for isomerization of n-alkanes Synthesis of superacid catalysts SO4 2-/ZrO2(Pt) and WOx/ZrO2(Pt) for isomerization of n-alkanes Synthesis of superacid catalysts SO4 2-/ZrO2(Pt) and WOx/ZrO2(Pt) for isomerization of n-alkanes Brei, V. V. Fraissard, J. Levchuk, N. N. Melezhyk, A. V. Patrylak, K. I. Research has been conducted into the influence of the conditions of synthesis of SO42-/ZrO2 and WO3/ZrO2 systems and of doping of such systems with oxides of silicon and aluminium on their catalytic activity in n-hexane isomerization. An improved procedure for co-precipitation is used to synthezise superacid catalysts that exhibit high activity: the yield of branched isomers at 520 - 540 К is 65 - 70% with a selectivity for i-C6 of 70 - 94% and n-hexane conversion of the order of 80%; the content of the most valuable substance, namely 2,2-dimethylbutane, in the isomerization products is 17 - 21 wt.%. WOx/ZrO2(Pt) catalysts prove to be more stable than SO42-/ZrO2(Pt). Doping of WO3/ZrO2 systems with oxides of aluminium, silicon, and niobium decreases their isomerization activity. Research has been conducted into the influence of the conditions of synthesis of SO42-/ZrO2 and WO3/ZrO2 systems and of doping of such systems with oxides of silicon and aluminium on their catalytic activity in n-hexane isomerization. An improved procedure for co-precipitation is used to synthezise superacid catalysts that exhibit high activity: the yield of branched isomers at 520 - 540 К is 65 - 70% with a selectivity for i-C6 of 70 - 94% and n-hexane conversion of the order of 80%; the content of the most valuable substance, namely 2,2-dimethylbutane, in the isomerization products is 17 - 21 wt.%. WOx/ZrO2(Pt) catalysts prove to be more stable than SO42-/ZrO2(Pt). Doping of WO3/ZrO2 systems with oxides of aluminium, silicon, and niobium decreases their isomerization activity. Research has been conducted into the influence of the conditions of synthesis of SO42-/ZrO2 and WO3/ZrO2 systems and of doping of such systems with oxides of silicon and aluminium on their catalytic activity in n-hexane isomerization. An improved procedure for co-precipitation is used to synthezise superacid catalysts that exhibit high activity: the yield of branched isomers at 520 - 540 К is 65 - 70% with a selectivity for i-C6 of 70 - 94% and n-hexane conversion of the order of 80%; the content of the most valuable substance, namely 2,2-dimethylbutane, in the isomerization products is 17 - 21 wt.%. WOx/ZrO2(Pt) catalysts prove to be more stable than SO42-/ZrO2(Pt). Doping of WO3/ZrO2 systems with oxides of aluminium, silicon, and niobium decreases their isomerization activity. Chuiko Institute of Surface Chemistry National Academy of Sciences of Ukraine 2001-06-10 Article Article application/pdf https://surfacezbir.com.ua/index.php/surface/article/view/51 Surface; No. 4-6 (2001): Chemistry, Physics and Technology of Surface; 99-111 Поверхность; № 4-6 (2001): Химия, физика и технология поверхности; 99-111 Поверхня; № 4-6 (2001): Хімія, фізика та технологія поверхні; 99-111 3154-8091 3154-8083 en https://surfacezbir.com.ua/index.php/surface/article/view/51/50 Авторське право (c) 2001 V.V. Brei, J. Fraissard, N.N. Levchuk, A.V. Melezhyk, and K.I. Patrylak |
| spellingShingle | Brei, V. V. Fraissard, J. Levchuk, N. N. Melezhyk, A. V. Patrylak, K. I. Synthesis of superacid catalysts SO4 2-/ZrO2(Pt) and WOx/ZrO2(Pt) for isomerization of n-alkanes |
| title | Synthesis of superacid catalysts SO4 2-/ZrO2(Pt) and WOx/ZrO2(Pt) for isomerization of n-alkanes |
| title_alt | Synthesis of superacid catalysts SO4 2-/ZrO2(Pt) and WOx/ZrO2(Pt) for isomerization of n-alkanes Synthesis of superacid catalysts SO4 2-/ZrO2(Pt) and WOx/ZrO2(Pt) for isomerization of n-alkanes |
| title_full | Synthesis of superacid catalysts SO4 2-/ZrO2(Pt) and WOx/ZrO2(Pt) for isomerization of n-alkanes |
| title_fullStr | Synthesis of superacid catalysts SO4 2-/ZrO2(Pt) and WOx/ZrO2(Pt) for isomerization of n-alkanes |
| title_full_unstemmed | Synthesis of superacid catalysts SO4 2-/ZrO2(Pt) and WOx/ZrO2(Pt) for isomerization of n-alkanes |
| title_short | Synthesis of superacid catalysts SO4 2-/ZrO2(Pt) and WOx/ZrO2(Pt) for isomerization of n-alkanes |
| title_sort | synthesis of superacid catalysts so4 2-/zro2(pt) and wox/zro2(pt) for isomerization of n-alkanes |
| url | https://surfacezbir.com.ua/index.php/surface/article/view/51 |
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