Geometrical and chemical modification of silica matrices at high pressures of reagents
The effect of temperature and composition of modifying mixture, as well as mode of carrying out the process of hydrothermal (with water and with the mixture of water and some organic substances) modification of silica gels and silica in the form of hydrogel-xerogel, on the parameters of the pristine...
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| Дата: | 2001 |
|---|---|
| Автори: | , , , |
| Формат: | Стаття |
| Мова: | Англійська |
| Опубліковано: |
Chuiko Institute of Surface Chemistry National Academy of Sciences of Ukraine
2001
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| Онлайн доступ: | https://surfacezbir.com.ua/index.php/surface/article/view/53 |
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Репозитарії
Surface| _version_ | 1869291138737766400 |
|---|---|
| author | Tertykh, V. A. Sidorchuk, V. V. Leboda, R. Skubiszewska-Zieba, J. |
| author_facet | Tertykh, V. A. Sidorchuk, V. V. Leboda, R. Skubiszewska-Zieba, J. |
| author_institution_txt_mv | [
{
"author": "V. A. Tertykh",
"institution": "Інститут хімії поверхні НАН України"
},
{
"author": "V. V. Sidorchuk",
"institution": "Інститут хімії поверхні НАН України"
},
{
"author": "R. Leboda",
"institution": "Maria Curie-Sklodowska University"
},
{
"author": "J. Skubiszewska-Zieba",
"institution": "Maria Curie-Sklodowska University"
}
] |
| author_sort | Tertykh, V. A. |
| baseUrl_str | |
| collection | OJS |
| datestamp_date | 2018-11-27T09:42:39Z |
| description | The effect of temperature and composition of modifying mixture, as well as mode of carrying out the process of hydrothermal (with water and with the mixture of water and some organic substances) modification of silica gels and silica in the form of hydrogel-xerogel, on the parameters of the pristine adsorbents have been studied. The peculiarities of interaction between some organic substances and dispersed silica at high pressures and high temperatures were considered. These investigations were performed by IR spectroscopy, differential thermal analysis, and the porous structure characterization of the modified silicas. It was shown that depending on the nature of the compound used for modification such organic substances can promote the process of silica mass transfer. During this process, the possibility occurs of the occlusion of the modifying reagent inside silica globules, changes in the parameters of the porous structure, physical or chemical bonding of the modifier molecules with the silica surface. Possible mechanism of geometrical and chemical modification of silica adsorbents is discussed. |
| first_indexed | 2025-09-24T17:44:38Z |
| format | Article |
| fulltext |
GЕOMЕTRICAL AIчD сIIЕIиIсAL MODIFIсATION oF
SILICA N{ATRICЕS AТ I{IGII PRЕ,ssURЕ's oF RЕ.AGЕl{Ts
V.A. Tеrtykhl, v.v. Sidorсhukl, R. Leboda2, and J. Skubiszеwskа.Ziеba2
lIпstittttе of Suфcе Сhеmisф, Nationаl Асаdеmу of Sciencеs,
03680 Kуiv-161, Gen. Nаumoу str, I7, UKRАINE
e -mаi l : tе r tуkh@pub Ii c, u а, n e t
2l;асultу of Сhеmistry, Mqriа Сurie-Sklodows|сл Univеrsitу, 2003 ] Lublin, PОLАND
Abstraсt
Thе еffесt of tеmpегaturе and сomposition of modifуing mixtuге, as wеIl as modе of
сarrying out thе pгoсеss оf hydrothегmal (with watег and with thе miхtuге of watег and somе
organic substanсes) modifiсation of siliсa gеls and siliсa in thе foгm of hydrоgеl-хerogеl, on thе
pй'.,"., of thе pгistinе adsoгbеnts havе beеn studied. The peсuliaгitiеs of intеraсtion
Ь".*..n somе oгganiс substanсеs and dispегsеd siliсa at high pгеssures and high tеmpегaturеs
wеге сonsiderеd. Thеsе invеstigations wегe регГoгrnеd bу IR spесtrosсopy, differеntial thегmal
analуsis' and thе porous ,t..й,. сharaсtегization of thе modifiеd siliсas. It was shown that
dеpеnding on thе naturе оf the сompound цsеd for modifiсation suсh organiс substanсеs сan
p,on.,ot" ih. p,o..,, of siliсa mass tiansfеr. During this proсеss, the. possibility oссurs of the
Ьссlusion of thе modiфing rеagеnt insidе siliсa globulеs, сhanges in thе paramеtегs of thе
poгous struсtuге, pьуsl"ui oг ihеmiсal bоnding of thе modifi'ег molеоulеs with thе siliсa
su.Гaсе Possiblе mесhanism of gеomеtгiсal and сhеmiсal modifiсation of siliсa adsoгbеnts is
disсussеd'
Introduсtiоn
ovег a pегiod of sеvеral yеars thе Polish tеam from thе Chеmiсal Dеpaгtmеnt ot
Мaгia-Cuгiе Sklodowska Univеrsiiу in Lublin in сo-opеration with the Ukrainian tеam from
thе Institutе of SuгГaсe Chеmistry of National Aсadеmу of Sсiеncеs of Ukгainе havе madе
studiеs into thе еlaboration of mеthods of gеomеtriсal and сhеmiсal modifiсation of silica
*ut,i".,, inсluding siliсa modifiсation undеr high гeagenl prеssuгe tl-14] obtained data сan be
subdividеd into somе groups:
- гegulaгitiеs of сhеmiial and gеomеtriсal modifiсation of siliсas bу watеr.alсohol mixtuгеs;
. pйuliaгitiеs of intегaсtion oioгganiс substanсеs with siliсa at high pгеSsurе of rеagеnts;
- sуnthеsis and сharaсtеrization ofn.* typе сarbon.siliсa adsorbеnts - сaгboaeгosils.
In thrs papег wе will summaгi," b.i"flу main rеsults сonсегning modifiсation of siliсas
bу watеr, *atеi-alсohol miхtuгеs and oгganiс сompounds under high геagепt pressuгe.
Gеоmеtriсаl and сhеmiсal modifiсаtion of siliсаs
bу watеr and watеr.alсоhol mixfurеs
Тhе foгmation pгoсеssеs of siliсa tехturе depеnd on many faсtors and thеrеforе thеy aге
diffrсult to bе сontгoilеd. Сonsеquently, хrrogеls arе oftеn modifiеd еithег thегmallу or
йус,o'ь"..ully in ordег to obtain siliсa gе!s of thе rеquirеd propепies.
Pесuliaritiеs of hydrotheгmal tr;atment of siliсa in thе foгm of hуdгogel-хerogеl wеrе
138
Е
Тs
еba2
studiеd in thе papeг [2]. Fтom
-an ana!уsis tlf thе obtainеd data thеrе emеrgеs a nе\L,hуdrothегmal siliсa trеatmеnt basеtl oп hуdгogеl-хеrogеi. This inсluJеs, fiгst, pгoсessеs spесifiсfoг hydгothегmal tгеatmеnt of both hydrоgеIs and- хегogеls, as weli as drying gеl in anautoсlavе and sесond, it сombinеs thе advantages of Ьoth treatmеnt foгms. Тhat is, thе newpгoсeduге allows onr to rеgulatе spесifiс
'uй.. aгеa (S), pоrе volumе (Vo) and аlso tоsynthesize vеry high-porositу samplеs сhагaсtегizеd by
.higЁ
Vo' and low S values, withsufiiciеntly laгge meсhaniсal strеngth. onе of thе tесhnolфiсal"dгawbaсks of this kind ofhydгothегmal treatmеnt is its low еffiсiеnсу (at lеast <з00 "ii bесausе thе levеl of autосlavеloading with siliса doеs not eхеееc 25 Yо Thus' thе trеatmеnt сan bе еffесtivе in thеtеmpеratuгe гaпgе 350-400 "С. It i-q also nесеssary to point out that hydгogеl.хегogеl
hydгotheгmal trеatmеnt is.moге еffесtlvе for pгеparation of фhегiсal and miсгЬsphiгiсаl sili"сagеls сharaсtегizеd by smallег pоrоsity and highеr mесhaniсa] siгеnsth.
The papег [l1] was dеvotеd to invеstigations on тhе йесhanism or high рrеssuгеhуdrothегmal trеatmеnt.of pугogеniс siliсas (aerosils) аs wеl! as titania. and alumiпi-сontaining
fцmеd siliсas. Thе aеrosils цеге modifiеc bv using diffегеnt,;..s oip.i,nury partiсlеs as wеll as
bу сontaining 8 and 9 Yo'wlvl оГ Al;o3 and Tio,iеsресtivеlу н,uаioiь..*ul tгеatmеnt ргoсеss''vаs регГогmеd in thе gas рhasе (ovеrhеаtесi stеam .,vith and with.,ut additiоn оf anmonia) in
thе tеmpегatulе гal.igr 100-з-sc oC' .rhе
сhangеs ог sttгfaсе рrоpегtiеs of thе adsoгbеnts tеstеd
сausеd bу h1'dгothегrnal modifiсation 'i'.'tге dеtеrminеd оn thс basis оi'adsоrptiоп isothегms оfwateг, mеthanol, сarbon tеtraсЫoгi.Jе. il-liех:enе and bелzеnе, an,J usiпg tilе data rеlating tcсhеmisогрtiоn of hехamеthyldisilazanе as y.е!l as оn thе basis of ipесifiс su,Гaсe i.еa
dеtеrminеd by thе mеthоd- of thепnal cеir;ipiiсп .]iГtгgОn It .'vаs siatеd tйat th'. hуdгothепnal
iгeatmеnt of fumеd siliсa lеads tо thе i;l'.;-еasе с,f h.;.,l:..-,х'',lа1iсltr dеirгее оt'lhеil suгfaсе' In thе
hycгоthеrmel trеatmеnt mесhanism iliе рiг.';g5ig5 оГ п-ass ll"а;lsfеrЪГ siliсa irr the gаs (stеam)
ph.asе play a vеry impoгtant гolе' Thе rntспsltv оf th.:sг i;lОi,g'S€S dеpеnds on lh. sizе oipгimary paгtiсlеs (globulеs) of modifiеd аdsогbеnt, оn lts Ьhеmiсal сomposition, aпd on thе
Dгrsеnсе of ammonia in stеem' Thе pоssibilitiеs оГ utiliziag thе prосеsses oссuггing in thе
vаpоur (stеam) phasе tо prеpaге рorоus сoveragеs (iayегs) lvеrе сlеmоnstгзtеd-
Thе еffесt of fumеd siliсas оn hydгоthегmal tгеаtmеnt сf i.laггorv and mesоpoгоus siliсagеls pоssеssing vaгious sizеs or ргimary globulеs r'vas studiеrj [ 12] Thе hуdгothегmal
tгeatmеnt was сaггiеd out in thе autoсlavе at 200 oС (6 h) in thе lrguld and gasеotis phasеs In
thе systеms studiеd, aегosil was in thе foгm оr mесhaniсаl miхtцге r*,ill siliсa gеl oг сЬnstitutес]
a sеpaгatе phasе in thе aquеоus suspеnsiоn fогm It wаs statec that thе рresеnсе of pyrogеniс
siliсa duгing thе hуdгothегmal modifiсatiоn оf s:liсa gеls аfIесts thе sizе сf thеiг ,pес;тiс ,й."
згеa' avrгagе рoгеs size and сuп,еs oГ pогеs vоlumе distribution bаsеd on thеiг гadii, Тhе
ехtеnt of оbsеrvеd сhangеs dеpеnds on thе рoгous stгuсtuге оГ rnitial adsoгbеnts' Тhе
:nvеstigations shоw that it is possiblе to transfег the siliсa mass thгоugh thе gasеous phasе
cuгing thе hydгotheгmal trеаtmеnt. It was alsо рointеd out that intеnsitу oГsiliоimass tгansfег
оbsеrvеd duгing thе hydrothегmal modifiсation in the gasеous phase joеs not diffег from thе
mass tгansfег in thе liquid phasе sуstеms. It was obsеn'еd that foг both siliсa gels studiеd
:еlativе еffiсiеnсiеs of thе hydгothеrmal tгеatmrnt aге similaг- This rnakеs it оossibГе tо ргediсt
lhе ехtеnt of struсtural сhangеs in thе siliсa mаlriх- foг siliсa gеls оldiffег."i po.ou, struсtuге,
:ndег thе simiiar hуdrotheгmal trеatmеnt соnditions
Possibilitу оf simultaneous geomеtгiсal and сhеmiсal mоdifiсation rvas shown on thе
ехamplе of tгеatrnеnt of siliсas by watеr-butanо! miхtuгеs at 250"C foг 5 hгs [1]. Тwo
'eboratory samplеs of siliсa gеls wеге mсcifiеd, namеly pure aеrosilogеl (\/" = 1з7,сm,/s)..l'hiсh wаs ргoduсed fгоm susрension оf fumеd siiiсa (aеrоsil, s:34з й,lg1 in *atег bу in an
:эdе of
:.: somе
l. оn thе
rе:aсtion
эе:atuгеs
[' ::,егmal
с.'in that
Е:еs сan
:. cf thе
r, of the
:..: siliсa
сr:еnts is
г-.-.еnt of
в:: from
г. е madе
r :: siliсa
E: сan bе
t.:еs;
Fгi.
: :: siliсas
E
}. ::rеy aге
Ь :elly or
l]с)
еxtrusion routе, and narтow.рorе siliсa gеl (s=244 mуg and' vP : 0.28 сm./g1 сharaсteгizеd
bу thе abilitу to foгm "roй
po,.' аuнnl tье hуdгotheгmaltrеatmеnt with puге watеr' Watеr-
butanol mixtures *.,. u,.J ismodifiеrs*and tйеsе mixturеs сontainеd thе following amounts
of watег (Yo wlw)',20.s фaturatеd solution of water in alсohol), з2,38 5' 42.5 (hеtеrogrnеous
azеotropе) and 91.0 (sйгated solution of r.butanol in watеr). Thе modifуing геagеnt was
introduсеd into an autoсйе eithеr in a foгm of thе miхturе оr in a foгm of individual
(sеparatе) сompounds. In both сasеs into the autoсlavе therе wеrе intгoduсеd suсh amounts of
watег and ;r-butanol whiсh arе nесеssary to obtain еquilibгium vapour pгessuге foг a given
tеmpeгatuге. Тhе tеmpеraturе of trеatmеnt was 150.i50oC and time of trеatmеnt l-6 hrs.
Somе from obtainеd rеsults are presеntеd in Тables 1-3 and Fig. 1,2.
Thе еxperimеntal obseгvations rvеге as follows: possibility oГ simultanеous gеometriсal
and сhеmiоal modifiсation of wide-porous aегosilogel is rеalizеd iГ watеr сontent in thе
rеaсtion miхtuге *u, r.,, 32 ok wlw; besidеs suгfaiе butохy gгoups theге is a fraсtion of
butanol mоlесulеs *ы.ь u." oссludеd in an inteгior of thе aеrosilogеl glоbulеs; as usually at
hуdrothегmal tгеatment siliсa mass transfеr takеs plaсе and-the. smallеst siliсa partiсlеs whiсh
possеss maхrmum *й.. .".'gу are thе first to bе dissoivеd' thеrеfoге as a гesult of this
;;;;;' ii.l" al,,"i".а.,iri.u i' йnsfеггеd and dеpositеа o1l9 bigg.еr paгtiсles whosе suгfaсе
еnегgyissmallег;wеobseгvеdthеdесrеasеinSofmodifiеdsiliсa,andinсrеasеofporе
diametеr from 1б up,o ubou,70 nm and dissolution and mass-transfеr pгoсesses arе intеnsifiеd
and aссеlеratеd wьеn шgh'p.",.u,.s and tempеratures are usеd; in thе majoгity of сasеs
alсohol mоlесulеs pгoйdе-thЁ inhibiting еffесt on the globulе gгo*th proсеss.
v. сm.'
Fis. 1. lR sресtra of aегosilogеl (с) aftег
,niаiп.u.ion at 250"с bу п.butanol (b) aлd its
il*iu,.' with 20.5 (с) and З8.5ok wlw watеr (ф
Fig.2. Dеrivаtogгams of thе siliсa gеl
'Jаiti.а
bу the mixtuге сontainеd
57.5% (w/ф of n.butanol and 42.5Yo of
water
140
tегizеd
Watег-
тounts
еnеous
nt was
lividual
unts of
r given
-6 hrs.
nеtгiсal
in thе
rion of
ually at
s rvhiсh
oГ this
suгГaсе
cf porе
еrsiГrеd
lf сases
Studies oГ modifiсation pгoсеss of two siliсa gеls rvhiсh arе сharaсtегizеd by diffегentporous structuгe with watег/butanol miхture in hydrothеrmal conditions havе shown that thеrееxists a possibility of simultaneous physiсal аnd сhеmiсal modifiсation of widе-poге aеrosilogel(vP:l.з7 сm./g, watег'":n':T^in modifoing miхturе <З2o/o Ww) and in a largeг dеgrеe ofnarтow.porе siliсa gеl (Vp=O zв сm,/g' watеr сontеnt in modiфing miхtuгe is 43.54 Й w/w)It is shown that a fгaсtion of butanol molесulеs is oссludеd in thJ intепoг of thе globulеs оfaerosilogel, wheгеas in thесasе of siliсa gеl thе сlosеd porous struсturеs сontaining-thе butoхуgгoups aге foгmеd. Тhеse butory-groups сan bе rеmovеd onlу at high tеmpеratuгеs, i.е. 485.
525 oС.
Tablе 1
Thе еffесt of watег/rz-butanol miхturе соmpоsition on thе paгameteгs of thе aегosilogеl poгous
struсturе aftег tгеatmеnt in an autооlavе 5 hгs at 250 .С
Мodifuing геagеnt Fогm of thе
N,IodiГrеr
Spесriiс
suгfaсе
arеa, S,
^2
lo...,D
Total porе Рcге
volume' diamеtеr,
Vo, сm]-/g d,' nm
I
I
oто l
I
i\lхL]
_ ___l
Initial siiiсa
ll-C+ЕlgoН
20. 5o^ L120+7 9. 5%'-C+ЕIsOH
32. 0уo Н20+ 68. 0% и-CЁIp0H
38 5уo Н20+61 5Yo n-СцНg}H
42.5oh H20+5.7 5Yo п-СцI1gОН
91 .0o^ 1120 + 9.0o^ll.ClHqOН
HzO
mlх1uге
sеparatеlу
miкtuге
sеpaгatеly
mlхtuге
sеparatеly
miхturе
sерaгatеly
miхtuге
sеpaгatеly
J+J
.1АL \A
188
186
159
l6б
144
1з9
127
132
r27
tt2
10з
1.3'7
t.2\
1.20
1.25
1.30
I 35
1'з1
lз8
|з7
| 'з7
139
t.J I
1.38
1б0
22.5
280
30.0
Jб )
t2.0
450
s00
52.О
51C
53 .5
б00
685
) i ,сa gеl
:.: rtainеd
:2 5o/o of
As known, undеr hуdгothегmal modifiсation thе globular stгuсtuге of siliсa gеls maу сhangе
into a spongy stгLlсturе, сrystallinе oг glassу statе dеpеncing on thе сonditions. Тhеsе
f ii
pгoсrssеs oссuг in thе wholе mass of modifiеd siliсa and thеrеforе its suгfaоe beсomes
h.t"l.og.n.ous. Thls hеtеrogеnеity dеpеnds on thе amount ofwatеr usеd for the modifiсation.
A largЪ amount of watег in rеlation to siliсa gеl pеrmits onе to pгеpaге moгe homogеnеous
gruini but it also makеs thе natuге oГ deсondеnsation and гесondеnsation proсessеs moге
iiol"nt u,hiсh, in tuгn, lеads to a сonsidеrablе rеduсtion of thе spесifiо suгГaсе of thе modifiеd
siliсa. Due to thе rnhibiting еffесt of alсohol molесulеs the proсеssеs of thе gloЬulе grоwth arr
lеss еvidеnt and thus .u,й. to сontгol, еvеn at laгgе watег amounts, homogеnеous grains of
modifiеd siliсa aге obtainеd in thrs routе
Tаblе 2
Thе еffесt of watег i л-trutar-rol mlхtiiге
struсtuгe aftег treetгnеnt in an autoсlar.е
сomposition on thе paralnetеrs of thе aегosilogеl pогous
5 hгs at diffегеnt tеmpеraturеs
Мodiфing rеagеnt Тemрегaturе, "С Spесifiс
suгГaсе
аrea, S'
m'lg
Total poге
Vo, сm3/g
Porе
diamеtеr'
do, nm
Initial siiiсa
ll.СoНpol{
2О, 59,ь |7 2О +7 9' 5
о,,ii ll-CцHq0Н
(mlхturе)
20 . 5o/o I12O+19. 5% r-C+Hg0H
(sepaгatеlу)
38 5% H20+61 5% rr-C+HsOH
(miхturе)
38,5% н20+6l '5oz,o rl.C+HqOH
(sеparatеlу;
HzO
2Оt)
l)u
30О
2О0
250
300
Ji+-)
21О
11А
.?-7 |
2\5
188
151
220
186
r66
15б
141
68
155
139
56
17'7
I {-rJ
60
| э! 160
18 5
225
220
240
280
з4'5
24.0
з0.0
35 s
380
45.0
805
360
450
980
31.0
68. s
91.5
25
zl
21
1.28
1.20
1.30
1.31
t.25
130
200
254
300
200
2s0
300
200
2s0
300
20О
25О
300
138
t37
l.J /
I,J I
I 38
I Ji
l.) |
l з8
\з7
1.12
Tаblе 3
Thе еffeсt oГ watеr/rl.butanol miхturе сomposition оn thе paгamеtегs of thе finеlу porous silica
gel struсturе aftеr trеatmеnt in an autoсlar;е for 5 hrs at dif;Гегеnt tеmpегatuгеs
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Ресuliaritiеs of siliсa modifiсation аt high рressurеs
of sоmе organiс and organosiliсоn сomрounds
In, thе paрег [5] an еffесt of thе Гollowing faоtors on thе сhеmiсal and gеomеtгiсal
modifiсation of aеrоsilogеl (prеpaгеd fгоm fumеd siliсa) was studiеd: thе phуsiсoсhеmiсal
сharaсtегistiсs of thе mоdiфing геagеnt prеssuгrs, thе prеpaгation сonditions for thе siliсa
suгfaсе, thе rеaсtion tеmрегaturе, thе rеagent prеssuгеs, thе duгation of tгеatmеnt and thе
mеthod еmploуеd for thе modifiсation proсеss' Thе сouгsе of thе surГaое геaсtion was
tЪllowed bу IR spесtгоsсoру' diffeгеntial thеrmal analysis and adsогption' It was dеmonstгatеd
lhat thе geomеtгiсal paramеtегs of thе рoгous siIiсa struсtuге may bе сhangеd duгing
high-prеssurе modifiсation, Fгom an analysis оf thе ехpеrimеntal data obtainеd [5]' thе
143
following сonсlusions wеге dгawn' Thе еffесt of thе substanсе usеd foг modiфing thе suгfaсе
prоpегtiеs of thе siliсa depеnds abovе all on thе mеthod whегеby thе proсеss is сonduсtеd
(liquid, vapouг or Solution, tеmpегatuге, prеssuге) and on thе mесhanism of its intегaсtion with
thе suгГaсе. An analуsis of thе kinеtiс data indiсates that 4.5 h aгe sufiiсiеnt for сomplеtion of
thе suгfaсе modifiсation ргoсеss. Bесausе the pressuге оГ thе modiГуing substanсe
сonsidеrablу ехсееds that of thе watег vapouг dеsoгЬеd from thе siliсa suгГaсе, an initial
theгmal tгеatment of thе adsorbеnt in a vaсuum (praсtiсally alwaуs indispensablе in noгmal
proсеssеs involving thе gasеous and liquid phases) is oftеn not nесеssary. Viгtually thе whole
ехtеnt of thе modifiсation pгoсеss (80.90%) can bе aсhiеved at рrеssuгеs whiсh arе onJу
o'2-o.з timеs thе еquilibгium valuе. All inоrеasе in tеmpегature favoгs a gгеatег extеnt oГ
modifiсation, tеmpегaturеs of thе oгdег of 200-300 oС are usually suffrсiеnt to attain a
maximum dеgrее of suгfaсе сovеragе with bound oгganiс гadiсals. For modifiсations
pгoсееding undег high rеagеnt pгеssurеs, сhеmiсal modifiсation is most likеly as well as
immobilization of thе organiс phasе on thе surfaсе by adsorption foгсеs. In ordеr to dеtегminе
thе typе of intеraсtions involvеd in suсh сasеs, aссulatе washing of thе siliсa with an
appropгiatе solvеnt is indispеnsablе foг rеmoving thе adsorbеd organiс phasе, follоwed bу
сhесking thе samplе using various tесhniquеs' Howеveг' whеn physiсal oг сhеmiсal
immobilization oссurs, gеоmеtгiсal modifiсation of thе adsorbent, i.е a сhange in thе
рaramеtегs ofits poгous stгuсtuге, takеs рlaсе.
Тhе modеs of intеraсtion bеtwееn organiс substanсеs and аегоsilogеl at high prеssuгes
and high tеmpегatures lvеге соnsidеred in thе paрег [6] Тhе following tyреs of substanсеs
wеrе usеd as modifiегs oГ thе siliсa suгГaсе. (a) substanсеs w.hiсh did not intеraсt сhemiсally
with thе siliсa suгГaсе; (b) substenсеs сapablе оf pоlvmегization oг polусondеnsation; and (о)
suЬstanсes сapablе of сhеmiсal геaсtiоn with thе suгГaсе. Fгom an analуsis of data obtainеd foг
26 modifiеd adsorbents, it rеsults that dеpеnding on thе naturе of thе substanсе used for
modifiсation suсh substanсеs сan ргomоtе thе pгoсеss cl siliсa mass transfег. During this
proсеss, thе possibility oссurs оf thе oссlusiоn of thе substanсеs insidе siliсa globulеs, сhangеs
in thе paгamеtеrs of thе poгous struсturе, рhуsiсal сr сhеmiсal bonding of thе mоdifiег
molесulеs with thе aеrosilogеl suгf.aсе dеstг.-lсtiоn of thе rеaсtiоn pгoduсts, etс.
From an analуsis of thе ехpеrimenta! rеsults obtained [6], thе fоllor,r'ing obsеrvations wеrе
madе' Сompounds whiсh do not rеaсt сhеmiсaliу with a siliсa suгtaсe maу favoг siliсa mass
tгansfеr p.oЪ.,,., at hlghеr pгеssuгеs, altlrоugh this еffесt is maгkеdly ]еss than that bгought
about by hуdгothегmal tгеatmеnt In a numbеr of сasеs, it is possiblе to obsеrvе thе oссlusion
of thе organiс molесulеs insidе siliсa globules, Intеnsivе attaсhmеnt of polymеrs or oligоmегiс
.on1po,1й, onto thе siliсa suгfaсе is obsеrvеd foг сompоunds сapablе of polymегization
(1-oiеfins) oг polyсondеnsation (diphеnуlsilanеdio!) undеr high prеssurе сonditions and
еlеvatеd tеmpеraturеs. A signifiсant dесrеasе in thе suгГaсe arеa and tоtal poге volumе valuеs
fгom thosе ioг thе initial siliсa matriсеs is notеd undег thеsе соnditions. With сompounds
сapablе of сhеmiсal rеaсtion with suгfaсе silanol groups, mildеr сonditions for thеir
сhЬmisoгption aге obsегvеd at high ргessuгеs. In a numbег of сasеs (/-butanol'
monoсhloroaсеtiс aсid), it is possible to сaгry out rеaсtions that arе not obseгvеd in
сonvеntional gas- and liquid-phasе pгoсеssеs' It is quitе iikеlу that thе сhemisoгрtion
mесhanism is сhangеd in suсh сiгсumstanсеs. In addition to rеaсtions with thе silanol gгoups
of thе siliсa' diгесt addition rеaсtion involving suгfaсе siloхanе bоnds oссur quite widely with
manу nuсlеophiliс and еlесtrophiliс rеagеnts at inсrеasеd pгеssuгes' Тhе inflr-renсe of еvolved
gu,йu, геaition pгoduсts should bе takеn intо aссount in manу substitution pгoсessеs
ionduсtеd in сlosеd vеssеls at inсгеasеd prеssurеs. It is also neсеssary In takе into aссount thе
141
шl.::еssurеs
r -]'stanсеs
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t . and (с)
l:: ]]nеdfoг
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r - -rng this
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i .: . lodifiег
lil
F
!:'
possiblе dеstruсtion of thе initial rеagеnts,
Sуnthesis and сhaгaсtеrizаtion оf саrboаerosils
Synthеsis аnd somе soгptivе anrl еlесtгiс propегties of nеw typе сarbon-siliсa adsorbents .
сarboaеrosils pгеparеd frоm fumed siliсa and produсts of mейуlеnе сШoгidе pyгolуsis at500.С - wеrе fiгst studiеd in thе paреr [з] Highly-dispегsеd iarbon-siliсa pйoегЪ witь
spесifiс suгГaсе aгеa about 150 m,/g' paгtiсiе diamеtег 18.5 nm, and сaгbon сontеnts in a гangе
5-36 rи 9/o weГ€ prеpaгed. An еffесt оf thе amount of сaгbon dеposited on thе siliса suгfaсе Jn
lhе adsorption aпd еleсtriс propегtiеs and pоrе siruсtuге of the samplеs sуnthesizеd wеге
dеtегminеd' It rvas cеmоnstratеd that сaгbоaегosils arе сharaсtегizеd by inсгеaseа adsoгption
асiir,itу сompaгеd r.',ith pгistinе fumеd siliсa, and providе nеw еleсtгiс pгopегtiеs.
Thе adsorрtiоn рropегtiеs of h},drохуlatеd siliсa gel as wеll as сaгbon-siliсa adsoгbеnts
(Сaгbosils) сontaiлing 5 and ] 8 i\,t o,,о сarbon, both trеated hydгothегmally йth hydгogеn
hеrоxidе solutiоn' tolvaгds l\{еthуlеnе Bluе rvеге сompaгеd in thе papег tl4]. The "qйlь;i*ld:.iоrрtioп of l\,fеthуlеnе Bluе sоlutiоns сi6 5-7 0. l0.a mоlrl- сonсеntiation und ;t' dеpendenсе
оn рH wеrе studiеd At this сonсеntratiсn, сa ЗОok of thе adsorbеnt suгfacеs invеstisatеc
r.r';g1g g91.9;96! with ]v{еthr'lеnе Bluе mоlесules undег оptimal adsoгption соnditions' Thoulh an
lntrоduсtion оf a small amount оf сaгbоn dеposit on thе siliсa suгГaсе maу genегatе mosaiс
slruОtuге:-r, эuсh mоdifiсatiоn did not lrаd lо a dесrеаsе in thе adsorption сapaсity of Caгbоsils
.еlativе to that оf hуdгoхуlаtеd siliса But thе аdsoгрtiоn mесhanism of йеthуlеne Bluе аt
::iir:ilibгium in indi''.idual s},stеms оf thе adsorbent typе invеstigatеd сan diffеr signifiсantly on
thе оnе hand. this mесhanism is assосiаted lvith thе diffегing Ьеhaviour of siliсa ovеr a widе
гangе оГрH ге|зtii.е to trеatеd аnd ttnlгеatеd Caгbоsils and on thе cthеr hand with thе soесifiс
pгopегtiеs оf Меthу)еnе Blr':е nnоlесulе (its affinitу fоr both сaгbon and siliсa adsoгbеnts, its
oссurгеnсе in a сationiс fогm, thе possibilitу of vaгiоus fогms оf intеraсtion dеpеnding on the
рH valuе оf thе sоiution, еtс )' Нower'er. it was dеmonstгated that suсh modiфing сaгbon
cеpоsits inсгеasеd thе геsistanсе оf thе adsогbеnt towards the aсtion of alkalis oхiJation of
lhе сaгbon dеposit in thе hуdгоthегmal tгеatmеnt pгoсеss сausеd a fuгtheг inсrеasе in this
r.,.jsistanсе'
.{сknorvledgеment
Тhе rеsеarсh dеsсribеd in this publiсation was supрoгted in paп by NATO gгant
Nо. ЕST.CLG.976890 and by thе Foundatiоn of Fundamental Rеsearсh of thе Мinistry for
Еduсation and Sсiеnсе of Ukrainе'
Rеferenсеs
i Lеbоdа R, Меndуk Е , Sidoгсhuk V.v, and Tепykh V.A Мethods of simultanеous
physiсal and сhеmiсal mоdifiсation of siliсa gеlsi/ Мatег. Chеm. Phys.. 1994' - v.38. .
P. 146- I 56.
], SiсJorсhuk V V , Lеboda R ' lvIaydannik D'G, and Tегtykh V.A. Ресuliaгitiеs of
hуdгothеrmal tгеatrnеnt oГ siliсa in the foгm оf hуdrogеl-хеrogеV/ J. Сolloid Intегfaсе Sсi.-
\995' - \. 171. - Р.168-]72.
3, Leboda R., Skubiszеwska.Ziеba J, Sidorсhuk V.V., Tепуkh V.A., and Zarko У.|.
Prеpaгation and sоmе physiоoсhеmiсal propепiеs of сaгboaerosilУ/ J. Non-Cгyst Solids .
1995,V189.-P265-269
145
41
А1
4з
44
45
46
АQ
49
50
5i
i'l
5:
' Lеboda R, ]r,Iеndvk Е, aпd Теп:ikh V A Еf&сt оf thе h1drоtheгmal treatmеnt mеthod in
an autoсlave on thе siliсa gеl poгоus struсtuге// Мater. t]lrеrn .Рhуs.. t995. . v.42' Nl' -
P.7-11
. Sidorсhuk V.V , Tепуkh V.A ' Lеboda R', and Hubiсki Z. Some pесuliaгitiеs of siliсa
modifiсation undеr high геagеnt prеSsuге' 1 Меthodologiсal asресts// Ads. Sсi. Tесhnol. -
1995 . V 12, Nз -P 2з''.2з8.
' Sidorсhuk V.V . Тепykh V A , Lеboda R', and Hubiсki Z. Sornе pесuliaritiеs of siliоa
modifiсation undеr high rеagеnt pfеssuге' 2. Influеnсе of сhemiсal natuгe of modiфing
rеagent/lAds. Sсi Tесhnоl, - l995 -У.|2'Nз. -P'239-246,
. Lеbodа R., lr,fеndуk Е,, Giеrak A., and Tегtуkh V'A. Hydгothегmal modifiсаtion of siliсa
gеls (хегogеls). l. Еffесt of trеatmеnt tеmpеrature on thеiг porous struсtuге// Colloids and
SuгГaсеs' A. - 1995. . V 105 - P.l81-189
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' Lеboda R., Меndyk Е., and Tегtykh V A. Еffeсt of mеdium pH оn hydгothегmaltrеatmеnt
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146
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| id | oai:ojs.pkp.sfu.ca:article-53 |
| 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/f5/a59c97a9689f1d9623ec8c4c5e4327f5.pdf |
| spelling | oai:ojs.pkp.sfu.ca:article-532018-11-27T09:42:39Z Geometrical and chemical modification of silica matrices at high pressures of reagents Geometrical and chemical modification of silica matrices at high pressures of reagents Geometrical and chemical modification of silica matrices at high pressures of reagents Tertykh, V. A. Sidorchuk, V. V. Leboda, R. Skubiszewska-Zieba, J. The effect of temperature and composition of modifying mixture, as well as mode of carrying out the process of hydrothermal (with water and with the mixture of water and some organic substances) modification of silica gels and silica in the form of hydrogel-xerogel, on the parameters of the pristine adsorbents have been studied. The peculiarities of interaction between some organic substances and dispersed silica at high pressures and high temperatures were considered. These investigations were performed by IR spectroscopy, differential thermal analysis, and the porous structure characterization of the modified silicas. It was shown that depending on the nature of the compound used for modification such organic substances can promote the process of silica mass transfer. During this process, the possibility occurs of the occlusion of the modifying reagent inside silica globules, changes in the parameters of the porous structure, physical or chemical bonding of the modifier molecules with the silica surface. Possible mechanism of geometrical and chemical modification of silica adsorbents is discussed. The effect of temperature and composition of modifying mixture, as well as mode of carrying out the process of hydrothermal (with water and with the mixture of water and some organic substances) modification of silica gels and silica in the form of hydrogel-xerogel, on the parameters of the pristine adsorbents have been studied. The peculiarities of interaction between some organic substances and dispersed silica at high pressures and high temperatures were considered. These investigations were performed by IR spectroscopy, differential thermal analysis, and the porous structure characterization of the modified silicas. It was shown that depending on the nature of the compound used for modification such organic substances can promote the process of silica mass transfer. During this process, the possibility occurs of the occlusion of the modifying reagent inside silica globules, changes in the parameters of the porous structure, physical or chemical bonding of the modifier molecules with the silica surface. Possible mechanism of geometrical and chemical modification of silica adsorbents is discussed. The effect of temperature and composition of modifying mixture, as well as mode of carrying out the process of hydrothermal (with water and with the mixture of water and some organic substances) modification of silica gels and silica in the form of hydrogel-xerogel, on the parameters of the pristine adsorbents have been studied. The peculiarities of interaction between some organic substances and dispersed silica at high pressures and high temperatures were considered. These investigations were performed by IR spectroscopy, differential thermal analysis, and the porous structure characterization of the modified silicas. It was shown that depending on the nature of the compound used for modification such organic substances can promote the process of silica mass transfer. During this process, the possibility occurs of the occlusion of the modifying reagent inside silica globules, changes in the parameters of the porous structure, physical or chemical bonding of the modifier molecules with the silica surface. Possible mechanism of geometrical and chemical modification of silica adsorbents is discussed. 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/53 Surface; No. 4-6 (2001): Chemistry, Physics and Technology of Surface; 138-146 Поверхность; № 4-6 (2001): Химия, физика и технология поверхности; 138-146 Поверхня; № 4-6 (2001): Хімія, фізика та технологія поверхні; 138-146 3154-8091 3154-8083 en https://surfacezbir.com.ua/index.php/surface/article/view/53/52 Авторське право (c) 2001 V.A. Tertykh, V.V. Sidorchuk, R. Leboda, and J. Skubiszewska-Zieba |
| spellingShingle | Tertykh, V. A. Sidorchuk, V. V. Leboda, R. Skubiszewska-Zieba, J. Geometrical and chemical modification of silica matrices at high pressures of reagents |
| title | Geometrical and chemical modification of silica matrices at high pressures of reagents |
| title_alt | Geometrical and chemical modification of silica matrices at high pressures of reagents Geometrical and chemical modification of silica matrices at high pressures of reagents |
| title_full | Geometrical and chemical modification of silica matrices at high pressures of reagents |
| title_fullStr | Geometrical and chemical modification of silica matrices at high pressures of reagents |
| title_full_unstemmed | Geometrical and chemical modification of silica matrices at high pressures of reagents |
| title_short | Geometrical and chemical modification of silica matrices at high pressures of reagents |
| title_sort | geometrical and chemical modification of silica matrices at high pressures of reagents |
| url | https://surfacezbir.com.ua/index.php/surface/article/view/53 |
| work_keys_str_mv | AT tertykhva geometricalandchemicalmodificationofsilicamatricesathighpressuresofreagents AT sidorchukvv geometricalandchemicalmodificationofsilicamatricesathighpressuresofreagents AT lebodar geometricalandchemicalmodificationofsilicamatricesathighpressuresofreagents AT skubiszewskaziebaj geometricalandchemicalmodificationofsilicamatricesathighpressuresofreagents |