Nonuniformity of hybrid adsorbents
Several series of pyrocarbon-mineral adsorbents (carbosils) were studied using the nitrogen adsorption method to compute structural and energetic parameters within the scope of overall adsorption isotherm approximation applying regularization procedure with consideration for surface heterogeneity. A...
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| Дата: | 2001 |
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| Автори: | , , , |
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Chuiko Institute of Surface Chemistry National Academy of Sciences of Ukraine
2001
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Репозитарії
Surface| _version_ | 1869291130413121536 |
|---|---|
| author | Gun'ko, V. M. Leboda, R. Turov, V. V. Villieras, F. |
| author_facet | Gun'ko, V. M. Leboda, R. Turov, V. V. Villieras, F. |
| author_institution_txt_mv | [
{
"author": "V. M. Gun'ko",
"institution": "Інститут хімії поверхні НАН України"
},
{
"author": "R. Leboda",
"institution": "Maria Curie-Sklodowska University"
},
{
"author": "V. V. Turov",
"institution": "Інститут хімії поверхні НАН України"
},
{
"author": "F. Villieras",
"institution": "Laboratoire Environnement et Mineralurgie"
}
] |
| author_sort | Gun'ko, V. M. |
| baseUrl_str | |
| collection | OJS |
| datestamp_date | 2018-11-27T09:42:39Z |
| description | Several series of pyrocarbon-mineral adsorbents (carbosils) were studied using the nitrogen adsorption method to compute structural and energetic parameters within the scope of overall adsorption isotherm approximation applying regularization procedure with consideration for surface heterogeneity. A portion of pyrocarbon deposits (graphene clusters) fills mesopores of the oxide supports, but another portion represents relatively large nonporous pyrocarbon globules formed on the outer surfaces of the oxide matrices. Contributions of these two types of pyrocarbon deposits depend on the nature of oxide matrices and carbonized precursors. |
| first_indexed | 2025-09-24T17:44:38Z |
| format | Article |
| fulltext |
NONUNIFORMITY oF HYBRID ADsoRBЕNTs
V.М. Gun'kol, R. Leboda2, V.V. Turovr, and F. YiПiёras3
|Institute otSuфce Chemistry, 17 GеnеrаI Nаumov Strееt,03164 Kуiv, UKRАINЕ
:Dеpаrtmeпt of ChеmicаI Phуsics, M' Сurie-Sklodowslrа (Jniversitу, 2003] Lublin, P1LАND
'I,аborаtoirе Environnement et МinerаIurgie, INPL еt CNRS UNR 7569, ENSG'
BP40' 54501 Vаndoеuwe lеs Nаncу сеdеx, FRАNCE
Abstraсt
Sevегal seгiеs of pyгoсarbon-minеral adsoгbents (сarbosils) wеrе studied using thе
rutrogеn adsoгption mеthod to сomputе struоtural and еnergеtiс parameters within thе sсopе
of ovеrall adsorption isothеrm approximation applying rеgularization pгoсeduгe with
сonsidеration foг surfaсе hetеrogеnеity. A portion ofpyroсarbon deposits (gгaphеne сlusteгs)
fills mesopores of the oxidе supports, but anothеr portion rеpгеsents relatively large
nonpoгous pyroсarbon globulеs foгmеd on thе outеr suгfaсеs of thе oxidе matriсеs.
Contгibutions of thеsе two types of pyroсшbon dеposits depеnd on thе natuге of oxidе
matгiсеs and сarbonizеd prесuгsors.
lntroduсtion
Tеxnrral сharaсteristiсs of hуbгid pyroсarbon.minеral adsorbents dеpеnd on featurеs
of both oxide matriсеs and organiо prесursoгs as wеll as on pyrolysis сonditiоns [l-7].
Cieaгly, the pyroсarbon struсturе сan signifiсantly differ fгom that of an oхidе support;
r.hеrеforе appliсation of standard adsoгption isothеrm еquations tо such hybrid adsогbеnts
gir.еs avеrage сharaсteristiсs with markеd erгors duе to negleсt of thе mеntionеd
hсtегogеneity' Foг instanсe, pores of оaгbon dеposits сan bе paгtially slitlike (miсropoгеs),
'.rlindriсal (mesopoгеs) or сolтеspond to gaps betwеen dense nonpoгous sphеriсal partiсlеs,
but porеs оf oxide matriсеs сan be of othеr shapе, e'g., rеlativеly smooth сylindriсal
mеsoporеs in siliсa gеl partiсles. Мany of adsorption еquations inсludе some paгamеters
dеpепdеnt of thе porе shapе [8.l1]; thеrеforе thе porе size distribution (PSD) /(R,)
dеtегminеd foг сomplех adsorbеnts using one of suсh еquations сan be inadequatе for onе of
thе adsoгbеnt componеnts (if thе method dеpеnds on thе porе shape). Additionally, some
сquations сan bе applied tо mеsoporous adsorbents, but othегs arе used only for miсroporous
onеs. Horvеvег, сompleх adsorbеnts typiоally possеss broadеned PSDs inсluding porеs of
diffегеnt shapеs. Thеrеforе, many of adsoгption isothеrm еquations arе utilizеd foг rеstгiсtеd
Prеssuге rаnges' whiсh сorrеspond to filling ofporеs ofone oftypes, and сoггесtеd isothеrms
аrе usеd to dеterminе thе parametеrs for othеr pores (е.g., consideration for adsoгption in
mеsoporеs to сalсцlatе the paramеtегs of miсropores) [8-12]. Howеver, suсh an appгoaсh сan
intгoduсe additional poorly сontгollеd епors in thе dеtегminеd struсtural paгamеtеrs. Bеsidеs,
thе геlationship betwеdn thе РSD and thе adsоrption rnегgy distгibutionlЕ,/ is ambiguous foг
hybrid adsoгb эnts, as f@) depends not only оn the pore struсture but also on thе naturе of the
adsoгbеnt surfaсеs, that rеstгiсts thе appliсation of thе сorrеsponding еquations to сomputе
.frR) if thе сorrеsponding еquatiоns inсludе еnergеtiс paramеtеrs instеad of struсtural onеs.
Additionally, nеglесt of thе heterogeneity оf compleх adsorbеnts dеtегminiщf(Е) сan lrad to
фе distortion ofthef(Е) shape, as thе еquation сonstants сan depеnd on thе surfaсе nature [8-
: l ] and thef(Е) distributions for сomponеnts of hybrid matеrials сan bе differеnt. Clearly, the
appliсation of the adsorption isothеrm equations independent of thе adsorbеnt nature (e.g.,
Fowler-GuggеnhеimordeBoег-Hillеquations)forсomputationsoftheovera||f@)doеsnot
givе information aьout*iь-е n9 dеpindеnсе ;; il" iеxtural and сhеmiсal рroprrtirs of
adsorbеnt соmponrnts l".сЪiiiri. ThЪrеfore, th"
"й
of this work is сonsidеration for thе
hetегogеneity oгьр,iс
"a,ьonйneral
adsorbешs in details on the study of thе struсtural and
rnеrgetiс сharaсtеrtsttc' oniь" basis of adsorption.dеsorption data.
Еxoеrimеntal
(а)Mаterials.Si l iсagеlSi .60(SсhuсhшdtМiinсhеn,Germany)wasusedtoргrрare
D'roсarbon-siliсa gel '"*irЕ' 9v.n.,roiysis
of ён,Cl, in a siainlеss steеl autoсlave (0.3 L) at
Ьiзк яo, 0.5, 1, 2, з, 4, and 6 h :"gтP"Фi;fio
аiгг"."nt CS.j сarbosils with variоus
amounts of pyгoсarbo; с.ii.ы" ])-t6,7j. д.""?pйь"n" Crzнro (0.5' 2 or 3 g pег 5 g of
siliсa gel сorrespondinЬiJ дшr' дшz' i"Ь дшj.'Ь'pr"' a|-Сс = ).o, ts.в, and 22.1 wt.Yo
resDесtivеlу) .u,ьonиh.Ъ;;ii";Ъi JiЪо-йЩ ^'n^^th: autoсlavr at 11Зк. for 6 h.
AсЬtуlaсеtonе C,I{*o,'.L.;Фia iи thе amounts oio.oz, 0'03 and 0.04 М pугolyzеd on 5
s of Si-60 (Меrсk) ut ziзк Б, 6 h gavе tь."ы"' of сarЬosils Aсl, Aс2 and AC3. Gluсosе
Lutl,,ou оf 6 g pуroly,"J""-ioc ;si-60 щ;rсk) undеr thе same сonditions gave сarbosil
Gl. Hydrothe.mut trеaйJ"'
"isйo
щ.,ф (labеiеd HTT) was сaгried out in thе autoсlavе
(0.3 L) сontaining 20 'L;f ;; i itizзкгo'.ii *i"Ыi g of siliсa gel or сarbosil plaсеd in
aquarIzvеssеl [14].
773К for 6 l
in dеpоsitiс
aсеtylaссton
саrbоn-minс
mеtаl vа.lеп
rcеtylасaon
(Гablе 2) [a
(Сс) але sho
p1тolysis of
l.4' at С. :
for 6 h (ТФ
anloсlar.е at
вrs utilizсd
trpor dеposi
.nd 87]К (I
sr"mplеs в.еr
тsG (к2E2'
iФthсrmal сr
Тeblс
Corксr
sаmpTablе 1
Struсtural Paramеtеrs of 5-60 lritial a3d Hydrothermally Treatеd
Giт\зt цzзК, andвifferеnt C-зцbosils _-_ _- *-
Samplе
Гi-со (Мeгсt)
Si-60I{Tт
AN1/si-60
AI.{2/Si-60
AN3/si-60
Aс1
ЬС2
Aс3 r;
GI
si-60
(Sсhuсhardt Мiinсhеn)
Сc' Sввт'BETэ D,
J
уrI.уo сm
0.153
0.731
0.650
0.480
0.453
0.111
0.606
0.566
0.433
0.800
0.14
0.67
0.56
0.41
0.39
0.28
11 ' , l
4.8
3.9
з , 9
А .
Ч . L
4. r
4 . 1
5.0
4.з
4 .0
4.0
3 . 8
з .6
J . )
з .4
CSт,
CSс..:
CSс,.r
сsс.
CSs
CSа,
CSa-,
ClSz,-:
nm
з69
t2l
з2,I
244
/-5 t
15 . 8
22.1
Тr
So
(lt
4
9 . 1
14 . 5
16 . 5
сs.1
сs.2
сs-3
сs-4
сs-5
сs-6
Addi t iona l ly ,S i .60(Merфwasut i l i zеdtoprepareсarbonДUsi l i сamater ia ls
(сarbosils CSх) bУ p;;й of suсh '.".i *.iyrui.to1ш91. (AсAo) as Zг(AсAс)а,
iio(д"д"),, шiiдсдсl] Ёiiсд.д.j,,ё'ii.A.i;й.Ь(додс)z (Aldriсh) in the autoсlave at
0.8
4.4
14.9
20,3
26;7
35.0
зз9
296
215
174
3',72
з66
3з9
299
259
223
|6з
з6
773K for 6 h. The utilization of thе samе amounts (0.0l M) оf mеtal aсеtylaсеtonates results
in deposition of equal amounts of metal molеs but diffеrent amounts of moles of
aсetylaсеtonatе groups' as thе n values in M(AсAс). сompounds arе diffеrеnt (r : 2-ul). Thеsе
сarbon.mineral adsoгbеnts wеге labeled as CSтi, CSс,.t, CSсo, CSшь CSzь, and CSz..r. The
mеtal valenсе in М(AсAс)n was takсn into сonsidеrаtion and 2/3x0.0l М of сhгomium
aсetylaсеtonatе (CSс'-z) and 2/4x0'0| М of zirсonium aсеtylaсеtonate (CSa.z) rvеrе utilized
(Table 2) |4J.Conсentrations of Х phasеs (graftеd mеtal сompounds, Cу) and pщoсarbon
(Cg) arе shown in Tablе 2. Siliсa gel Si.40 (Мerсk) was usеd to prеpare pyгoсarbon.siliсa by
pyгolysis of aсenaphthеnе (0.5, |,2 or 3 g pеr 5 g of siliсa gеl сorrеsponding to AnjlSi-4O, i =
1-4' at Cc: 5.6, 8.3, |9.2, and 2|.8 wt.% rеspeсtivеly) оarbonizеd in thе autoсlave at 77зK
for 6 h (Tablе 3) [l5]. Hydrotheгmal trеatment of Si40 (labeled HТT) was сarriеd out in thе
autoсlavе at 423K for 6 h similarly to that foг Si.60. Меsoporous silica gеl KsК-2 (Russia)
was utilizеd to prrpaге titania.siliсa gеl (CVD-TSG) adsorbents by mеans of thе сhеmiсal
vapor dеposition (CVD) tесhniquе [16] foг TiCla сhеmisorbеd and hydrolyzеd at 473K (к28)
and 873K (K68, Тablе 4) using еight сyсles of thе сhеmisorption.hydrolysis. Carbon-oхidе
sаmples wеre synthesizеd using pyгolysis of сyсlohеxenе at the siliсa gеl (K03) and CVD-
TsG (K282, K682) surfaсеs at a сonstant paпial pгеssurе 5l.3 mm Hg in a flow rеaсtor undеr
isothermal сonditions and gгavimеtгiс сontrоl at 9,73K for 5 h (Tablе 4) [2'17}.
Tаblе 2
Conсеntrations of Мetal Compounds and Graftеd Caгbon in CS Samples (Si-60)
Sample Х phasе Сx'уltYo Cс,
ууt'o%
";\,*
J,p,IlШl
Sддт,
m'/s,
CSтi
CSс..l
CSс*z
CSсo
CSrqi
CSz'
CSz"t
t l .37
11.26
8.28
8.42
9.42
10.98
17.t4
10 . 1 9
9.2
12.0
4.8
6 . 1
5 .9
6 .5
13 . 8
'1.4
t92
2',18
29з
187
26з
212
2з6
28rCSz'.z ZrОz
Tioz (aпatase)
Crzoз (amorph.)
Cr2O3 (amorph.)
Co
Ni, Nio
ZпzSiОq
ZrOz
0.419 4 ,З5
0.44з 3.19
0.622 4.24
0.524 5.56
0.566 4.27
0.5з6 5.05
0.415 3 .52
0.53,1 з,82
Тablе 3
Struсtural Paгametеrs of Si.40 Initial and Afteг Hydrothermal Trеatment
(HTT) at 423K, Caгbosils АIrti Pгeparеd by Pyrolysis of Aсenaphthene
Sample Сс, Sup,, Vl, |p,
wt,,уo m,lg cm"/g nm
ls
k ,
al
si-40
si40нTT
AI.п/Si-40
Alt2/si-40
AN3/Si-40
AN4/Si-40
5.6
8.3
19.2
21.8
.Iз2
309
313
2з |
t28
92
0.542
0.512
0'з75
0'з|1
0 .163
0.149
r . 48
з ' 31
2.40
2.74
2.5з
з.24
з1
с/A.30o samples (Тable 5) were synthesized by thе pyгolysis -of CHzClz at thе fumеd
siliсa substratе (A.300 *i.ь ,ь" sieсifiс surfaсe '." J,,.o 300 m2 g ') at 673-823K for 40.
l20 min. The teсhniqu. Ь?йpi" Preparat!9n was deJсribеd in dеtail еlsеwhеге [3]. othег
сarbosil samplеs *itь ti"j'iйiйi1iф91tq9 matriсes were synthеsized using the pyrolysis
of сyоlohexе ne at 97З к {.iiio 'й (тuьt" 5) [2]. Fumеd.silica, alumin4 titania' and mixed
)vsioz (l = Al2Q сдЪl, iio, 1тs), а,rzoЛio, (дsт)) @ilot Plant of thе Instiшte of
Suгfacе Chemistry, Kuй#, Ыйin").na ёдоsio, were jtudiеd at diffеrent сonсrntгations
(Cx) ofХ oxidе phase (Tablе 5) [l8,19a].
Tаblе 4
Struсtural Paramеters of Siliоa gеl KSK, сvD.Tio2/KsK (K28, K68) and Afteг
tхto/o
,# rPD
nm
5.2
4.8
5.4
4.8
4.0
4.8
KSK
K28
K68
K03
K282
K682
24.4
17.9
20.5
20.5
19.9
з7'|
228
281
289
152
204
0.98
0.54
0.76
0.66
0.31
0.49
(b)Nitrogеnаdsorption.Nitrogеnadsoгption.desoгptionisothermswегereсordеdat
77.4K using a Мiсromеritiсs A5AP zoio aсsoгption analyzег at pфo> 1o-3-l0{, wherep and
pо dеnotе thе еquilibriЫ;;й; ana tье saturation рressurе of nitrogen at 77дK,
ъй;;y. дсJitionatty, thчlow.pгеssurе-adsorption isothеrms were obtainеd for some
samplеs (CS-i, Table т'l.'i t.6-, ; o;o'10.1: using a te9hnjцl3jescribed еlsewhеre |7,2|7.
The spесifiс surfaсe u'6o-sй *o,...,i"utut"d usinf standara Ьвт mёthod. The pore volume
Vo wasdеtеrminеd ao' 'Т*Ь on at p/poo.o.gв-o.gs. Average value of pore radius ro was
estimatеd as follows ;.:;;;i;; if,i'ц91ь*ms for unmodified or modifiеd m.soporous
siliсa gеls (suсh as siоo,-si.+б-and KSK) сoпеspond to thе IV1ypе [8,9] йth markеd
hystеrеsis loops. Thе i.oiй",'s for fumed oxides arе сlosе to thе Ш tре but have narrow
hуstеrеsis |oops at ptpo, o ii rзl. In this papеr, thе nitгogеn adsorption-drsorption isotherms
arenotshown(sееRet.'[2.7])whilефeсo-rrespondingсsplotsч:-T"ly,.d.Toсhаraсterizе
thе adsorptive p,op".ti", of сarbosiЪ Cs-i, ihе adiorption potential distributions f(А) =
-dа/dА (whеre с dеnоtеs thr adsorbеd amount of nitrogen; l :
-АG : R'TIn(p/p) is the
аш.,.ntiur mora, wo*, ц is thе gas сo1stanp сan be also utilizеd'
(c) Сornputi";:,i;;;td.' tь. ь.йg.neity of h^yb.rid adsorbents [22l, the
сomputational tесhniquе Ъun ь" following:. (a) сiьыaiions of the pаJamеtегs (},ф of the
adsorption isоtheгm .й;; * -".,to,}й)i*t'o. T is the ternPe1lturе, j is a number of an
adsorbent сomponent, i is a P{ajnеtеr. n,i'nь.') using adsorprion data for individual
(synthеsized undeг the ,uй
"oi,aitions
that thе сЬrrеsponding phases in multiсomponent
adsorbеnts) unа .o*-pй..''i.'иr' with сonsidеration for- tЬir fеaturеs using diгeсt
minimization *"tьoс*;'(ii"o'p".й oгthe distribution funсtions {xo) of parameters xn (e.g.'
porе radius ч, uс,o,piion
"n"ф
Е)Ъr сomplеx adsorbents utilizing the sum
38
Carbonization o!
Sample Сrioz,
в thс kсrnсJ
jфG юhJtk
Tb эrлkn
r* сoщo
fu3сз ш/
lфdoш
тr!
Smr
сgt
&
T
с
с
с
с
с
с
c
A
A
A
A
A
т
A
т
с
т
с
т
с
т
с
т
т
т
т
с
Е
! r
а =zc p j(p,T,1',,х,)
l
as the keгnеl ofthе ovеrall adsorption isothеrm еquation
0(T,p)= i;с,@,( T,p,)",,,х)f (х)fu (2)
o i
whosе solution in respeсt to f(х) can bе obtained with the regularization pгoсedurе |2з,24l.
Thе so|ution of Еq. (2) is known to bе an ill-posеd pгoblеm due to a markеd influеnce of
noisе сompоnrnts on thе experimental data (small сhangеs in 0(T,p) оan гesult in large
сhangеs inf(x), and thеre arе many solutions of this еquation fitting thе еxpеrimеntal data),
whiсh do nЬt a[ow onе to usе еxaсt invеrsion formulas оr iteгativе algorithms [11,23]'
Tablе 5
Struсtural Paramеters of Fumеd Siliсa, AS, TS and AST Bеfoге and Aftеr
сarьonization
Sample Сх, Cc, Sддъ т/е, fp,
(1)
с/A-300.
с/A-300ь
сiA.300Ь
с/A-300b
с/A-300b
C/A-з00Ь
с/A-300b
ASr
ASз
AS23
AS30
A1zoз
TiOz
з85 0 '9б 4 .9
29',7 0.60 3.3
280 0.51 3.7
260 0.50 з,9
2з| 0.4з 3.'I
160 0.36 4.4
| | 2 0 . l 9 з . 4
20'7 0.42 4.1
188 0 .з9 4 . |
з53 0.80 4.5
2з9 0'57 4.8
159 0.42 5.3
60 0 .17 5 .1
з8 0.07 3' ,I
з 18 0 "7 l 4 , |
AST
'72
Tsz 1 .1"
C/TSz
TSs 5"
C/TSs
TSзз 3з.
C/TSзз
TSs 9'
C/TSя
TSr+
TSzo
TSzя
TSзс
l4 f
zof
zgf
36f
8 . 5
0.5
4
6.5
2A
40
o{
1 . 3
J .
J U
2A.r 286 0.'.71 4.6
. з 10 0 ' 1 | 4 , I
20'0 2,7з a.14 4'7
- 219 0.55 5.0
2з.| 169 0.47 5,6
- 238 0.5',7 4.8
26.з l88 0,4з 4'|
- 217 0.49 4.5
- 65 0 .13 4 .0
- 1з 0. l7 4. '7
- 1 l5 0 .25 4 ,з
C/TSзо = 29.7 84 0.22 5.2
Note i med Ts;
Х = Alzoз, Tioz, Alzoз/Tioz
The сonstants detегminrd using dirесt miniЦzшion mеthods for loсal еquations @, dеpеnd on
the nature of j-phase. iь. *Еreйi"J сoeffiсients с; detегminе thе aссessibility of./'.phase
(whiсh сan diffег ao' ii.Ъon.'.nt'йn in a сomplex adsorbent) for adsоrbatе. Foг еxamplе,
a graftеd phasе саn
"o,iiy
Ьio"r. porеs of sщpojpartiсles possеssing relativеly low exteгnal
suгfaсеs, and the '*';;";.;d ioгеs, the. йger the rеduсtion of thе porе volume due to
py.oсarbon grafting
";;й;ъ"il
Gig 1). Tie сl values сan be estimatrd usiпg different
adsorbatеs, whiсh adsй predБminaф onto Ъn.,of thе phases of hybrid adsorbents [l,7].
Additionallу, .ь" *"",Jiьiйй.й;;яа" 'u'г"""s of сarbon-oxidеs adsorbеnts сan bе
сomputed from thr i"i".""'y, t"p,iсJ а"n*i19 oi tье IR bands of freе surfacе hydroxyls
|з,25,267,
0,4
0,2
0.0
; ' - 0 , '
-0,4
-0,6
-0,8
з0 40
Cаrbon conсеntrаtion (wt'%)
Fig. r. Relative сhanges in the pore vo]umе foг сarbosils due to grafting of
;y?;й"" (preсuгsoгs шe showrr) on diffrrent silicas.
.Thе poге size distribut ь.nf(Rl
"-'b^ ..**?l*'уsinв
the ovегall adsorption isotheгm
equation iifil;й;й ;'; wriш"еn iы;.phase as
"'у:: (3)
4 i =
ц(p') ,ry w ''i'
I <*,>*, + I _frtr,R)f
(R)dRP
''tu'i. ,,l,rtrr'
ьеminimat.'#f, m:*..l1llry'9:n:.1:'.l?::,'"*T}'ffi fi
'#'Ii#i;
ltTlшil.ff'Т.li;ioi-oyrinа,i."r p*i',.iкpl i" dеiermined with modifiеd Kelvin
equation
ro(p\=9t+tg,,n;*ffi; (4)
aлd t(p,R) сan be сomputеd rvittr -11аiлe|Р"J
.T1':l
(s)cz $+(nb l2-n l
t(P,R)=t^f U
c|2)z ' . t f
t- -- аJSвм., b = eхp(Аa/R,i; ^сis'the:Y::,9:'}.,"I'11'":i;;-Hl 1;i"n:н lТТflЁ:;':,=,у':#flZ?!'{"^{it!,.!{";i'.Цfi;;i,:*:; jу,*-ж::.l:l"r;;;T*:Jl1i
, # .*,':ж #T""#ffi **-; l;.;" ", ":*iib,
_ Q,, I R 8n ; с, i s the BЕT сoeffrсi ent
+-сlIрц/A.з0{)
. t..снtсl/si.60
@ с.ttlo/(A300'As'тs)
v с.tt."(Ksк'тio/кsK)
A CS.(ХAсAс!Si.60
o (дffi,дсi,otysi.ьo
*_ANi/sЬuЮ
40
foг adsorption on flat surfaсе
",=1o#, Qtisthr liquеfaсtion hеat,.Е is the adsorption
еnегgy' 1 is a сonstaпt; Qв ?,d Q,-are the adsorption hrat on flat surfacе and in pores,
геspесtivеIy; z : p/po; ll is the number (nonintegег) of statistiсal monolayеrs of adsЬгbatе
moleсulеs and its maximal value foг a givеn 4 is еqual to Ep- o/2)/t';and о" is the сollision
diamеter of surfaсе atoT:'' Typiсally, dеsorption data weie utilized to сomрute rhe f(RP)distгibutions with Еq.. -(з) тd the rеgularization proсеdure |24] undеr non-negii*iiу
сondition for t(R) with unfixеd (automatiсally deteгmineс on tйе basis of F.tйt anа
соnfidenсe rеgions pa]) or fiхеd (сr = 0.0l-0'001) rеgu|arization parameter. Thе ry value in
Еqs. (з) and (a) is dеtегminеd by the dependence of dV/dS on Л,, whiсh' e.g.' сotтesponds to
R72 foг сylindriсal poгes [8]. It should be noted that Еqs. (3)-(5) сan be usеd notЪnly foг
mеsoporrs but also foг micropoгes|27,28] in сontrast to many of known adsorption isotЬегm
чuations, whiсh сan bе usеd only for mеsoporеs or only for miсropoгеs. Fоr fumed oХidеs'*.ith sphеriсal primary paгtiсles (or pyгoсaгbon with spheгiсal paгtiсles), Еq. (4) should be
rеplaсеd by following еquation [8]
г -
h!L=:Ъ|L- 1 ,= ! ru lp RrTlr ./1.R+r'+r1, -R, _r+.R+l,J \-' '
whеге.R is thе radirrq-of pгimary paгtiсles, and t' : t + o/2,Thеf(R) distributions
dеtегminеd with Еq. (3) and linkеd to thе funсtions dVу/dRP сan bе еasily transformed to thе
distгibutions;f5(Ro) w'lth respесt to dS/dRP using the сoпеsponding models of pores; е.g., foг
сvlindriсal porеs
1 t V
.f,(R,)=ftf,(R)-#- Q)
r I
Тo сomputе f(E), the modifiеd dеBorr-Hill-Toth (DHTh) equation for moЬilе
аdsoгption Il0] for7'-phase
K oo,,, p eхp(v oнт, i@ _
ffil0,(p,E) = (8)
1+ K on,,peхp(,,*'.,o - _Ч)
L*@ '
whегe K,*,, =Kf,,,',(T)eхp(ЕlkBT,, KЫ,,Уoнтiand7areсonstants; @=а/а,andp/po<
O. l, was usеd as thе kегnеl in Еq. (2). The valuеs of I{' ц and 7 inЕq. (s) сan bе determined
for individual mateгials using direсt minimization methods with the starting magnitudes 1 = 1
(соrгеsponding to the dеBoег.Нill (Dф equation), voн:5.622 and K$" : 7.3lx10-7 at
77.4K ш01.
Additionally, thе Fowler-Guggеnheim (FG) еquation (desсribing loсalizеd monolayer
adsогption with latегal intеraсtion)
0,(p, E) = FP.erp(ryo !k'..Т)
1+ Kp eхp(zw@ / kBT)
(9)
(whеге К=Кo(Z)ехp(Elk"T) is the Langmuir сonstant for adsoгption on monoenergеtiс
sitеs and the pre-еxponеntial factor Kg(T) is expгessеd in terms of the partition funсtions for
an isolatеd gas and suгfaсе phasеs, z is thе numbеr of nearest nеighbors of an adsorbate
molесulе (assuming z = 4), w is the intеraсtion enегgy bеtwееn a paiг of nеarеst neighboгs, й3
is the Boltzmann сonstant, zw/kg = 380K [29,30]) was used as a loсal isotheгm 4. A maхimal
p/pova|leforanisothегmport ionusеdwithЕq.(9)сorrеspondеdtoсovеrage.E-=dа,o
0.99.
@)]HNMR.ThеlнNNц'sprсtrawerеmeasuredusingahigh.геsolutionWP.100SY
(Brukеr) NMR spесtroЬ.*
"
100 lvfi{z *";1j* n."lyеnс{ a1!;уnsmission band of 50
k}lz. The tеmpегaшrе' й; ;;',ing
"ьj.iiu'
uiр*tJа with thе aссuraсy of *lK by
mеans of a VT.1000 (Brukег) tempеraturе ф"ii;,.
Ai еleсtroniс integrator гegistered the
intеnsity of NМR ,ig;;;;{ iй" u""u,u.y
"i;й';'
Thе lH NМR сhеmiсаl shifts for watеr
adsoгbеd on
"a,ьosits?Ъ.iь.
e", pьu"ё'(ц-zi iуо or in the aqueous suspensions (- 6
wt.% of solid,) oг
"с.o,й.
*й сЁ'.,*ined with respесt to-tetramеtфlsilane (TМS) as an
ехtегnal standard. rn o,о", to pгevеnt ou.,"*iing Ьiiь. ьurк *ut.', ih" сonоеntrations of
unfrozen watеr Werr Ьasured on ..,,p"n*iln
-.ьеаting
fтom 210K. This teсhniqur was
dеsсribed in dеtails "r,"*i.,.,"
rзr-ззt.
R"*"'t'yu'!-**"}:;iffOn thе oхidе surfaсes.by, th" ч{.у.:':^:|
a variety of рrесursors
rеduсes the total o;;;й"*i'ь-с. шrеrеntry"щie l) A.glTimal diminution of И, is
observеd foг Si.40 p*.o,ing mainly.n"o n"i'.# ;ъ;ъp;;": (тub]. 3, r,). For modifiеd Si-
60 with tu,g", *",opi;;;:;j' '"d.сtion is Ё;;й:'"
Cс.and dеoеnds only slightly on
the nature of organiсs (гi!. t,.тaьte, r *а ii. i small dесгеas. o, йn an inсгеasr inVois
sееn foг fumеd oxides afrеr thе
"y"loь"*"1l,p;;;y* 1iй:}-:..
a porosity typе of thеsе
oxidеs diffеrs from 1hat of mеsoporo* 'iii# g.i
""d.
*.T..ч::ds to the gaps bеtwren
sphеriсal primary йЬ; ,*аЬiшy n.aс}<ed й aggrеgates (whose apparеnt density is
approximatеl у Зo%;;; ii. i."'ltyl iiiri,з+i-д' diffеrеnt Cс valuеs, pyroсarDon
prЬduсеd by thе
"".ьiii,uiion
of CоHro
"-ffi;;-"iidеs
providеs a mшkеd inсreasе in thе
Ьoгe volumе unс.ь",Jp"if;.;й;; *i. tт"ЪТ" i,iil. rli howеvlr, after CHzClz pyrоlу.sis,
ieduсtion in И, for сli-iЬЫi.Ъь'"-"с *i'ь?" .Iii.i,iы"es fоr iЬmed oxides arе mainly
linkrd to thе сhannей in pгimaгy partiсlr щЬ*Ьй' ь.i,.ч. :1*,
spacе (V",,) in powdеrs,
whiсh is сonnесted ffi il;;d'* g;'i,JidЪ",i as follows !:,i-
l/p"o, is signifiсantly
iйt;.';r,*Ё;*1{*'ffi*il[.Ъt#;нъ"*цi*.*l*цk'ff ,"lll:il;
thе struсturе oI agl
(MсA)ofdryf-.;;, i i;;"*Ьi"..b;й;i l;;; i;g1;].|еnhanсethеe{fесtivеporе
volцmе (И, * l.10-iji^"*1Ё яr,"d by "g;;;
il/p' J,o,э21^ф aовroximatеly two times;
howevеr, мсд сurьe zii .Еj** 'й
"rг"ЪТJ"
po,е uotumе to 0.6i Ъmз/g сlose to V, (o..61
сm,/g1 for initial ,iiia;-";lъ; tюt. в-.-o"#;Ь;Ё(ASз шrd CVD-titaniа/fumеd siliсa
TSz, TSs, TSrz) atЁ;:"i;:;Ъ;y: (F1ч. i, iфlе s), appеaranсe of pуrосaгbon deposits
formеd on thе oй ,uЬ..s ofl aggrЬg"Ьч "г Р'ф".y e.щеs du'ing pyrolуsis of
сyсlohexеnе ,",'r,Jil u"l"i""""й.nй oЪ i\on oi V",o .aссessible
for adsorbеd nitrogеn at
p/po *0.99 due ,o'ioйuiion of tighteг
"#;;;;
,'йпu,ly to those aftеr MCA of silica
Ъowder. on thе *#ь*J' iь. гц".rv.rJЁ,г 'ii'iшЬiй9i;."1ё .c,ът,cl, сan ooсur to a lagеr
;1.*.,:;Tт:*eт**niшi:;нllhш1fl,."iЩ:l'g,й.}ЪН1#l1:
t's.z etcritr], *ьi],i. towеitьan tь" ыn,i.о йс., (ftom*2.2 g/cm3 for 5it|6n f9 х4.0
s/сmз for titania,..iiеЁг*. ,Ъи,i'. rooJ" Б'".й"" аеposits foгmЪd by the сyсlоhеxene
ivrolysis (in сontrast to othеr o,""u,,o,, ."uJьfi;;; JiЬ,"nt oxidе matгiсеs (Fig. 1)) сan
:H:JJ.i}*"g*тL".'""JJж'":',.1H1:::o"",:'$:''Tj]"" 1": of py.o:u,bol^lrеparеd by
thе mеthylеn. .n,iii" ,ц;*j#g:d;iЬ'.i [7], thе-speсiflri surfaсе arеa o| сarbon
dеpositsp",,.o.J,.J,.Jii"й А0mz|giа.":;;;йiisсio1tg(Сc=З5wt.%)buttotal
42
' - {
E-l
t-lrl
ar
;l
rl
a
D
g
f
I
a
I
ts
сiъ
э
o
- 100
ts
d 1 0
:
Б !
E
€
, . t
0.0 0'5 1,0 1'5 2,0 2,5 з'0 3.5
standаrd Reduсod Аdsorption с.
Sд;a deсгeases fтom з66 (Cs.l) to 163
mzlg (сs.6), rеspесtively. Howеver, in thс
сasr of pyroсaгbon.fumеd siliсa (prесuгsоl
СHzС|z), diminution of Sвдг (as well as И,,
Fig. l) is smallег (Tablе 5) than thosе tbг
pyrocarbon.siliсa gеls (Tablеs l.4).
Tуpiсally, pyroсarbon formеd on thе siliса
suгfaсеs (whiсh do not have a merkеd
сatalytiс aсtivity in thе pyrоlуsis) is
сomрosеd of гelativelу largе (еspесiaily at
Cс
paгtiоlеs [3-7] possessing low or nеgligiblе
own intеrnal (aссеssible) porosity [1]. In
thе сasе of miхеd oxidеs [ls,19] having a
signifiсant сatalytiс aсtivity in thе
pyгolysis, сarbon nuсlеi form nеaг suсh
aсtive surfaое sites as Bronstеd and Lеwis
aсid sitеs сatalyzing aсid-base rеaсtions оr
othеr sitеs (е.g.' on anatasе) aсtive in rеdox
геaсtions, whosе distribution impaсts suсh
structural сharaсtегistiсs of pyroсaгbon as
its partiсlе sizе distгibution and
aggrеgation fеatuгes of tiny сarbon
particles (l-3 nm) to larger globulеs up to
200 nm observеd in TЕМ miсгogгaphs
[3,7,14,15]. Thereforе сhanges in 56д7 and
И, for C/ТS (Tablе 5, Fig. 1) arе lоwег
than those for C/fumеd siliсa at сlosе
values of Cс; i.e., рyroсarbon in C/TS
(cусlohexеnе сarbonization) is morr
dispеrsed than that in C/fumed siliсa
(сн?сЬ pyrolysis). For C/siliсa gеl and
с/сvD.Tio2/siliсa gеl, thesе сhangеs are
larger due to thе intегnal porositу of thе
siliсa gel matriх, сrystalline and
morphologiсal fеaturеs of CVD-titania
b 10оo
o,01
зsд
o
Е 3
o
< 2
Ф
o
o
U
1Е-5 1Е..4 l Е . з 0,0't
stаndard Rэduсgd Adsorption o.
0 1 2 3 4 5 6 7
10
influenсing pyrolуsis [2,5,|6,|7J. For instanсе, sеgгеgatеd and dеnser CVD.Tio2 prepared on
thс siliсa gel surfaсes at 873 K (K68 sathplе with rutile + anatase on siliсa gеl KSK-2) [2]
сцlsеs lowеr сhangеs in ̂ Sвдт and I/e than less dеnse titania (K28 with grafted anatase more
rtivе iп гedoх reaсtions than rutilе) prеpared at a lower tеmperature (473K) (Tablе a)'
Yц.2. The сs plots in (a) lineaг sсale and (b) log-log sоale for сlsi-60 (CS.i, Tablе l), CiA.
30o at Cс : 8.5 (prесuгsor C6H19) and 64 wt'уo (С1f2Сl2) (Table 5), highly poгous aсtivatеd
сrrbons AJAх (Sff'r: 1345 m'/g) and ACF (519 m,lg) desсribed in detail elsewheгe [26]; (с)
impaсt of the type of rеfеrenсe matеrials (siliсa gel si-l000, сarbon blaсks Caгbopaсk F and
сsbоt BP 280) on thе сg plots foг some сarbosils.
П'еlativеly larger оhangеs in Vo and .9вgr агe obsеrved aftеr simultanеous CVD of сarbon and
titаnia on the pyrolysis of Tio(AсAс)l on Si60 (Table 2). It should bе notеd that pyrolysis of
^ a
+ J
aсetylaсetonatеs of Ti, Cг, Co' Ni' Zь and Zt on Si-60 results in formation of pyroсarbon-Х
(Х is the сorrespondingo*lde, ,iiiсate oг mrtal phase, see Tablе 2) deposits possessing the
Ьoгphology dеpЪndеnt onфe nafuге of Х [a]'
L
F
o
€ о
Е
a
а
э
(L
Й
.9
6
I
Ag
200
100
-6ГЪЭ_tio.t,s
zb z's з,0 з,5 4.0
strпderd Redrrced iМsoфioп ч
0
!-
a
€
o
.E
o
o
oъ
(L
ь
g
tt
6
Ёg
Fig. 3. Thе сs plots in (a) lineаr sсal9 an! Ii*.
n. The сs plots foг (a) KSK, K0з, K28,
фi log-log sсalе .fo}-, &si.oo (metal KЕв2'K68'ковz 1тaьtе 4), si-40, si4oIITT'
"*-*y_ч:^:.:T::?.*d;"й;;";;;;;;H:жl,'н*n?#:'ti#Ёi"й3i;*.prесursors, Labrc z).
н.::lн.*',1'*ly,';Yerof
fumеd
ThevaluеsofVp,Sвг. ,a ldrodеоге3sewithCсfoгthеmajo1rtУofthеstudiedhybr id
adsorbents (Tablеs r-оfdue to dtting of mеsopo,esЪv шгo9шч9.i (giaphenе сlustrгs) and duе
to reduсtion oсtье empti ioй;;;**' 'ili;;;"lЪ*tiсles (diamЪir > 0.01 mm) fillеd by
сarbon globulеs 1'o . ii] :ffi;;Ё;i;;;;Ё";'еr surfaсеs of thеse oaгtiсles (rеsulting
in the inсrеase in the ,p.Ъiг," сЬ".iiyЪгo",ьo.i6' d;йi"у..* of сS-; samplеs as well
as of othеr studiеd сarbosils baseil on rn.,opoiou' silica gеis is lowеr than that of pristinе
siliсa gеl (whosе,ni".poЬy i., ho'-"no, insignifiсant),*'..Ц:rРlots (siliсa gel Si.1000
шrd carbon blaсks с",ьЪЪ.Ji. {Ь' ш4x
"nj
[cо un6,сubot BP2ъ0 [35] wеre utilized as
the refeгеnсe uа,o.ь.nЫ-оitг.}. 'ig"iг*.ntly fтoй those for suсh aсtivated miсгoporous
$arrфrd Redrced АфоiЁion сts
stendа'd Redшed Adsoфon с" $andard Rеdюed Аdsorflim с.
44
сагbons as AJAX and AсF |27,2s] (Figs. 2-a). Notiсe that the геfеrenсе matеrial typе impaсtsthе shapes of thе сs plots at сrs > 2; howеvеr' this еffесt is rлleakег for рyгoсarboisiliсa sеt(е g.' CS-6) than that for pyгoсarboгr/fumеd siliсa (Fig. 2с)' Bеsidеs' й;i"'i';;tй;;;ii"
thе сg plots foг сabosilis depеnd on the гefегеnсеfiatеrials only slightly. The porosiiу typе offumеd oxidеs and сoггеsponding сarbosils @igs. 2-a aпd4b) diir;йonsiderably from that ofsiliсa gеIs' espeсially in rеspесt to mesopoгes (as the empty volume in fumed o*id", is йесto the gaps bеtwееn sphеriсal primary рartiсlеs randomiy Ъut not dеnse paгkеd in uggr.guiЬ,шd agglomеratеs [34];.theгеforе thе сapillaгy еffeсt in ihem is *.ut
"no
'"'ы лlйiЁ
"??"empty volumе by adsorbate сannot bе геaсhеd, as the plateau adsoщion is not obsегvЪо*u"n
u P'p0 -+ 1 [3] сoгresponding to the tr typе of the isothеrms [s,9]).
on thе basis оf thе с[s plots (Figs. 2-4), one сan assume that laгgеr сhangеs in thе poгeяruсturе сan be foг CSх. prеpат-ed using suсh pгесursors as mеtal aсetyйсetonй' 1сu>viil.io;or CьHto for C/CVD-TiOzКSK in сomparison with €/silica gеls' bhangе' l" 'i.1"
"'
pйi'rсlatеd to miсro- and mеsopoгеs arе grеatеr for сarbйils produсed using
-
йеtalrc$ylaсеtonatе prесuгsoгs than that foг purе pyroсarbon рrеpЬгed by aсetyЪсеtone
саrbonization. This еffесt is. сausеd by thе pyrolysis Ъitalysis by a nй Х phaЬe (oxiie, mеtal,or siliсate, Тablе 2) formеd during the сarboniiation' A simiйr еffeсt is observеd for othe.пiхеd oxidеs suсh as fumеd Tio2/sioz, сvD-Tiolfumеd Sioz, CVD-Tioz/sirlсa eer, еiс.(Fis +) Howеvег, сhаnges in the porosity of C/)?siliсa gels arе typiсalty laгgеr than йo'. ь'Ofumеd oхides (Fig. t) due to the diffеrеnсеs in botЁthе tе*iurе of 'йс". anа formес
ртoсaгbon.
Additional infoгmation illustrating fеatuгes of pyroсarbon deposits prеpaгed usingdiffеrеnt pгeсursors on a variеty.of oxidе supports сan boobtained on aпalysi' Ьгй" po'. ,i,ЪdЫгibutions/(R,/ сomputed with Еqs (l).(7) using thе regulaгizatioп pгoiеdure. To Ъalсulatе
.ftRJ' *e used modеIs of сylindriсal pores for siliсa gБl, po.., (gips) bеtweеn spheriсal
рпiсlеs foг fumеd and C-VD.oxides and pyroсarbon, and' at.last, 'йril" 'i..opo."*
"t
л, .?- using the sum of Е_q. (3) (i.е Еq. (2)) соrrеsponding to eaсhl-phasе in hybгid adsorbе"nts
[22] on solution of Еq. (3), one сan assumе iьat 7фo1 > o oveг thе total Л, гangе 1пon.сgativity сondition) and the regularization parameteг a сan be fiхed (0.01-0.o6t; or-unлхеd
- (altomatiсally determined on thе basis of F-tеst.and сonfidenсe геgions using the parsimony
фnсiplе [24] and shown in Figures). It should be noted that thJ герlariйion pu,u'.tй
vrlue соuld bе linkеd to.the quality of the expеrimеntal data, the nonrlnifoгmity oг"сso.ь"nt
шгfaсes and fitting (on thе геgulaгization) of a modеl adsoгption isotheгm to thЬ еxpeгimеntal
фta,
- Siliоa gеl-pугoсarbon samples CS-l (Table l) prepaгеd by thе pyгolysis of CHzClz onSi60 сan bе сonsidеrеd as simplе сarbosils, as siliоi gel Ъoеs ,й po''"'' tь" .ut"lyш" Ыпiy
iп thе pyгolysis and this prесursoг.рrov!flеs the simplеst nuсlеi for сarbon grains..тьe, j(R)
рpulation at R, < l nm is nеgligibly low @ig. 5) (utilized isotheгm poгtio-ns .o''..ponj iЬ
PPa> 0.00l; but the use of lowеr pressurеs atp/pо > l0-8lеads to appеaranсe of a naггow
fiR) peak at R, < l nm), whiсh сoгrеsponds to nеarly puгe mrsoporous typе of Si.бg and CS-j
сonfirmеd by thеir сg plot shapеs with a very small deviations from thе 6as plots for the
rcfеrеnсе matеrials at сg ( 1, as well as for other сarbosils (Figs. 2-a). The main f(R)
пахimцm shifts toward. smallеr ф with inсreasing Cс due to paпiil filling of '"'op;';;Ё;
;цrroсarbon dеposits @ig. 5a). own poгosity of pyroсaгbon paгtiсles is Tow ̂ "а iь" j1i)
hrеnsitу out of the PSD for pristinе Si.60 (e.g., nalTow peaks at Ro<2 nm foг сs.r anj bS-
J) саn bе linkеd to thе gaps Ъеtweеn tiny gгaphеnе paгtiсlеs and iorе rvalls in '",opo.", of
Si{o, thе gaps bеtween сarbon paпiсles peг se oг betweеn the Ьutег surfaсеs oг 'iti.u g.i
pertiсlеs and pyroсarbon dеposits. Notiсe that the Gs plot for CS-5 differs fгom others at lJw
45
adsorption (|ow p/po)Gig. 2b) and th1/flв|.pеak at R, аз l'1 nm for CS-5 (Fig. 5) сan be due
to its struФuгal fеatuгe. i-"' iь",едмйь1pu'"*Ь..' ais the smallеst (0.002s) for CS-5.
Diminution oгtье я*"jl';"" й.or гo' сj-?Ь'.* a sim||ar.f(R) pеak, espeсially with
rеspесt to fsв) : ds;d;,frц. iьl ry Jh: *ьoй, the Is(R) distгibutions possess grеatеr
intёnsity at smallеr щ t""o.*fi*iйn *.'lh/',r^J ;Ъ tЁdiff.'"n""Ъеtwееn thеm inсreasеs
for large porеs' e.g.' ,' йЪ",Ёorhydrothеimalfi йot"с siliсa gеl (Fig. 5b, si-60HTт).
b
A,
2 з 4 э
Porc Radius (шn)
Pore Radius (nm)
Fig. 5. Pоrе size distributions in rеspесt to (a)
)v)аn, (unfixеd rеgulaгizafion paratnstrг сl.
--i"lй*i'tш" figurе Геgеnd) ard ф) eф^o:
й)i*."Ы s,.io -а сs-i samples (с = 0.0l)
Ё{;Ёii]";а"i o-fсyrьаriсal porеs for siliсa
sоl and poгеs bеrwеrn sphсriсal partiсlеs for
i*"Ь'ьЬi' G) fв) сoЬputеd using Hill's
.appгo*imation and Еq. (a).
T&!ii",'. ffi -8,*ЁfiТ'flJ' iffig'1!
;;й *ш u,r'""а с value (shown.in
Ё#"Ё;;Ъoсuь of сylindriсal porеs. for
siliсa sеl and рrсs uоtwсon sphеriсalpartiсlеs
Ё' ;y"';й;gabelеd.,CSp.
solid lines) or
сvlindгiсal por€s tor sriiоa gзl аnd slitlikе
рЬi"' ь, сarЪоn (CSl' dashеd linеs).
Pсe Rаdt.в (nm)
Pore Rаdius (nm)
46
Fig. 7. Pore size distгibutioпs foг (a) ACi,
and (b, с) C/)0Si-60 сomputсd rvith with
unfixed с valuе (shown in Fiрre) using
modеls of сylindriсal pores for siliсa gel
and poгes bеtwеen spheriоal pаrtiсIеs for
pyroсaгbon (labeled CSp, solid lines) оr
сylindriсal porеs foг siliсa gеl and slitlike
pores (at & < 2t,)foг сarbon (CSI, dashed
linеs).
Fig. 8. Pоre sizе distributions for KSK,
K0з, К28, K68, K282, and K682 (unfixеd
с shown in Fiрф; two models (CSp and
CSl) were used foг hybrid adsoгbeпts and
thе CSl modеl (slitlikе poгеs at RP < 2to,)
was utilizеd for oхidеs.
aссording to pгеviously published results fз,6,,77 and thеsе invеstigations, pyroсarbоn
on thе pyrolysis of CHzClz on siliоa surfaсеs гepгrsents relatively dense and
t
j
lo
h
b
ls
с
Lc
47
Poгe нэlftv|dth (nm)
oraсtiсallynonporouspartiоlеsfromsmallgraphenеоlustеrs(1.5nm)inmоsoporesatR,<10
n* up to globulеs
"f
1й:;й iй g,afud Ъй Б;;;.; ,uj.u"". of siliсa partiсles. Changes
in thе naturе of thе prесir-so,, ., tй. oxidе matЬ, oun '.'utt in largе vaгiations in thе pore
struсture of сaгbosils Gйs. о-rol. In the сasе ;il"9йф o| aсiyг.1tьene (ANj сaгbosils),
teхtural сhangеs aгe laгg-еr for C/Si.40 (Fig. A*, T;йЬ +1 tьan thosе for с/si-60 (Fig. 6a'
Pоrе Hаlfwidth (nm)
Halfwidth (nm)
^ 0,06
Porr нalftvldth (nm)
Fis.9.Porеsizеdistributionsfoг(a}AJ00andC/A-300(Cс=!..5.wt."/"),(b)C/A-300atCс
= l and 6.5 wt.уo,(") ё;:Jй .i tc = 20*."z"'.Ьа1аi сJд-зoо a| Сc = 40 and 64 ,tlt."/o
сomputedwithunfixеd-r"рr",i,шi"np'"'.#tii';;й;шеshowninFigure)usingtwo
i"аЪr* of porеs (CSp and CSl)'
Tablеs2and3).AсеnaphtheneCroHrz^doеsnothavroxygelatomsinthеmolесules;
howevеr' its carbоnizati#Щ;; чч::т
ь
"iiiiЬ
iьat observed on hvdrothermal tгеatment
of Si-40 at 42ЗKсгie.Ы.ЪЪ. с/si-60, .
j*ir.' Ъй.t ь observrd only on the gluсosе
оvгolYsis (Fig. 6a, Ф:.Ё{;;.u*l Ь.,..ьan.g;.in the pore. struсture of C/Si-60 duе to thе
ЬЬotvsis of aсеnaphthenе (Fig. 6a) шe. *iЁ;;, ;Р'ц:;; o}'s1rvеd aftеr the gцClz
Ъaфonization Gig. s). ЕIowеv.iru,eo *o*uГ.riung.s in CS аreobsеrved aftеr thе pyrolysis
of mеtаl aсеtylaсetonai;ъ;.'Цч t" th".й;#;;i;;; Х..phase on the pyгolysis of
subsеquеnt pornons 'iйii.Х.l.iтuьt". , *jji
""йe
availability of oxygen atoms in the
нa l fw id th (nm)
48
эleсules. Nevertheless, еven for last prесursoц thе main еffeсts are rеlated to filling of siliсa
3d mesopo.rеs by pyroсarbon and Х phases (Figs. 7 and 8), dеspite thе diffеrеnJes in thе
irrrсturе of pщoсaгbons, whiсh arе obsеrved in the TЕМ miсropйotographs of CS samplеs
[3'4'7] For еxample' morе nonuniform and dеnsеr сarbon deposiis are Ьbsеrvеd for CS1; and
oз oppositе rеsult is for CSz", whiсh сan be сaused by the diffегеnсе not only in the сataiytiс
Poгe Halfiruidth (nm) Adsoрtion Еneгgy (kJ/mo|)
6г
0,2 1 10 50
Pшe Ha|fraltlсlth (nm)
Fig. 10. Poгe sizе distгibutions Гor (а) А,.300, с/A.300
(сс = 8.5 wt.%) CVD.TS' and C/CVD-ТS, аnd (b) fumed
TS and C/fumеd тs (с6}110 pгесursoг) сomputеd йth
шfiхed regulаrizаtion pаrameteг (its valuеs ше shown in
Figuтe) using two moфls of рres (CSp and CSl).
6 8 1 0 1 2 1 4
Аdsorрtim Еnеrgy (kJ/md)
Fig. lr. Nitrogеn adsoгption спеrry distribufions
foг (а) CS., (Tablе l) сomputed using DHТh
(qymbols and solid linеs) and DHT (dаstrеd linеs)
equаtions йth fiхed с = 0.0l; arrd Ф f@ for siliса
gеl апd pyroсarbon in CS5 сomputеd with DI{Th.
49
impaсtoftheХphasеonthepyrolysisbu1фoinfеaturеsofpyroсarbondistributions.Notiсr
thatZnforms the ,iri"ui"Ъi#'-ьii py'щ'is oiтio(дсAс)i resu1ts in foгmation of ,anatasе
сrvstallitrs оf -l l .. iаБJф: in. CSсo as a mеtalliс phase (сrystallite size 2o-25
nm); niсkel in CSшi i, il;"th metalliс (сry.sиllй si ze -25 nm) and oxide phases (-l3 nm);
and CSz,.z inсludes ,{;;. dioxide ф ".l
[4]. These vшious Х partiсles саn affесt thе
DУroсarbon struсturе rn C/)USi-60 diffеrently.
For C/fumsd siliсa prepшed by the pyrolysis of CHzClz, orмn porositу of pyroсarbon is
connеоtеd mainly *i,ь-'i'..eup' 9..1ч:"
jй'. py'oЪ1фo1 гarticles (relativеly large
aссoгding to thе TЕМ.r"i"Ъйi. t3]). ThеrеБ,i"iйi,Ы*i,h theЪo''".ponding porе modеl
gives relatively small fryйi,:Р"..p:11T:j*
сr valuеi, lovrer' errors afi f(Rp) with shaгp
оeaks in сompaflson witlithе PSDs сomput"a u'йg th" йdеl of сylindriсal pores at Ro> 2t.
Ьа *tittiк" porеs at л, .)i. с"й{ сs]L}{;vеi, position of the f(R) peaks aге сlose
(Fig 9). A similar pf*'.-.Ьt'йn for CЛГS and TS samples (Fig. 10) whose poге s'zr
distributions *","
"o,npu,ed
with difreгent .oс.i' oi po'"'.o' th,-вaгs brtwren spheriсal
partiсlеs with сylindri'J"j.Ъ;;;;.iйьЬ.o ёsp) oi slitlikе mioropores (Rp < 2tn) and
Ьylindriсal mеsoporrs (labelеd с.sl). .
on thе basis oi.Ъьйo.с rЬsrrlts, onr. сan сonсlude that the porе modеl as thе gaps
bеtwееn sphеriсal pаrtiсles is moгe appropriatе for nonporous pyroсarbons than that йth
slitlike miсroporеs шrd сylindri."l ,o",opoБJ ;;j й; u"tфq саrbons U,8,9,21,281,
However, the f(R) pеak position, u," po.йry йо.p."a.т.P| lh.
appliеd porе models,
whiсh suggеst that thfiiir"й.j 'ЪJь"rqJ ;tth Еq'. ir)-.(z) anс the.сonstrained геgulaгization
рroсеdure ,o
"olnpu,J
ii" Ъ*" 'и. irъ''iьшion]' ;; d"lt" геliablе. The differеnсes in thе
naturе of thе surfaсе! }"'"й";й а"p**-*аЪiiе matriсеs.сausr distinсtions in thе
adsomtion оf polar and nonpolar oo*pouod-, й to variations in thе interaсtion energy
сompЬnents ts,91. тff;Ё;-й;.;''d;f ;;;йs ot f@) with сonsidеration foг the
hеteiogеnеity ".i'g
Ёq*..iii izl.-с^св) .;;;;;i" "с"q"й1or
hvbrid adsorbеnts than
those obtainеd with ,ii,ai_i'гЬ*ъ,.с.,ggr;.];.Gа. tnll Ь dеBoer.ilill щuations. Notiсe
that the absenсе of a strolg sPесifiс intегaltйi. Jiii,i"ri." molесules with solid surfaсes
provides thе possibiйy of {uite .*u.t .uutu-uiйi oг tь. 'Ь.t,"ы-parameteгs of adsorbеnts
Ьhaгaсterizеd ьy tьe,J{йrJi.Ь""jЬЫ*y oi,ь" *'r'."s [35]. Thеrеforе, onr с&n rxPeсt
only slight а"p.nс"iс"--ii jrrl on tь".ф"oi;";;Ji йеgrjl.eouation with or without
сonsideration г* tnЁ-uа,oЬ"nt non.,nidй;.;;; ьJ iЁ" аir"'еnсes in the сhemiсal
nature of hyb,lа *.t.йi,]Ь-.i'Ъ"йo";' *i,ьiь. йodifiеi DIIT equation foг heterogеneous
surfaсes (DI{тh) ,ьЫo .i,onЁ", {.ryо"й "q
jP)
"у9:,-*g..
fo' a peak at f, * |2,5
kJ/mol (Fig. 1l), tьйlь"t *Ji,шeс wц standard гс oг DII еquations (Fig. |2). ̂ maximal
intensity of thе last p"Ji* oЁ."*"а*' ;.itвъ. 11) having the uniquе сrs plot at low
Prеssufrs @ig. 2b) ;й; ,;uuд rв),Ы ;;.F' Ji t n*.свiв. 5a); i.е., thе maхimal
intеnsity of I@) utТ-*,i;j й,;"i fki 9Б is not in"iс.ntal;.also. a similar еffeсt (but
wеaker) is obse.uei ;;7;"@Г^u j*iй"rii'' Ыт *"х'Р
bе noted that the f@)
distгibutionsforsi l iсagelandprPybo1сomponеnts(e.g., i lCS-5)diffеrnotonlyforthе
hiяh-еnегgy pеaк ьut-йiь. iйы д ,-g.
"ЁЁ. ;ili. iьZ'.а,"'ptь" potential distгibцtions
гoi сs-i samples (Fig. 12с) dеpеnd.on
"'
. ',ui,*l u',!, o:oj.Yll"' сorresponding to p/po <
0.925. A IИ) r,гlinI7iir. ut ti,ь z{.va}дl iЁ шritеа to сompletion of sеoЪndary filling of
mesoporеs ***p""ii'e io ti" ."i'д.п,1;#Gt*.ъj iьr inлесtion of IИ) mгves at l
bеtwёеn 1 and 4 шJ"i?"'.sponds й tьЪ u:йi"diliТy of a sйall nortion of miсropores seеn
infъlin tь. .u,. oТ"ti'.-u.ii,Ьion 9r3 l.";:;;;щ.n"'t'1,', of thе isothеrms on thе PSD
сomputation. м,",й,o',-"*Б" дlдx ;;; 'i;;. minima at А > 0.9 kJ/mol as it possеssеs
bimodal .i".opo," ii,.-,Ь;Б" |27,281 ii-n' trel diffеrs stгongly fгom that for CS.i (Fig.
50
0 , 4
0 , 3
щ
0 , 1
tl,0
d
A d s о r р t i o n P o l o п t i a | ( k J / m o t ) A d s o r p t i o n Е л e r g y ( k J / m o l )
\.l:гоgen аdsoгрtion rnergy distributiоns foг СS-i (Тablе l) сomputеd using (a) FG;
еquаtiсlns; (с) adsoгption pot€ntial distributions and (d) f@) distпbutions-fоr СSх
1 able 2 сomputеd usiпg thе FG and DнTh еquations at fiхеd сr : 0.01
Е'r; С;:.sеquеntlу, onе сan assumе that pугoсarbon in CS.i doеs not havе rnarked оwn
*..с :liс;oрoгositу and thе gaps betwеen pyroсaгbon paгtiсlеs and thе pогe walls or thе
]в 'l::aсеs оf siliсa gel partiсlеs aге rеsponsiblе for low сontгibution of miсropores. An
b..зsе ir thе nonunifoтmity of C/)USioz (Тablе 2) in сomparison with CS-i (тablе i;
*с-с:.ts геsults in signifiсant сhanges inf@) for different CSa samples сomputеd using the
Е.J.-. ':: ЕG equations (Fig. 12d). It shоuld bе notеd that the differеnсes сaused by thе natuгe
d;L.: :nizеd prесuгsoгs arе laгgеr than thosе сausеd by using thе DHTh oг FG еquations foг
* rэт.е adsorbent. on thе othеr hand, thef@) distгibutions aге morе sеnsitivе to the pore
J*1-:i than to thе сhemiоal natuге of thе surfaсеs [35]. Consеquеntly, CSх сan be
*з..:с-rizеd by laгge diffеrеnсеs in thе structures of grafted phasеs oг mоdifiеd oxidе matгix,
lt..:- :: сonfiгmеd by TЕМ miсгogгaphs of thеsе matеrials (sеe Fig. 1 in Ref. 4). It should be
frэ:::аt thе use of Hill 's approximation foгЕq. (4) givеs only slight оhangеs inf(R) (Fig.
ft :rs:Jеs' thе PSDs for miсropoгous сarbons сomputеd using Еq. (3) arе simiiar to thosе
ф:.еl lvith DFT Мiсгorпeritiсs softwaге |27'28) that сonfiгms thе геliability of thе usеd
}.::. . J to саlсulatе the f(х) distributiоns' Utilization of the DHTh Еq. (s) and Еqs. (1) and
Е : ;..'lllputef(E) fоr fumеd oхidеs allows one tо оbtain dеtailеd piсturеs (Fig. l3) г.uitг"t
iсr :.:.r sis of сorrеlations bеtwеen thе struсtural (Figs. 1, 4b, l0) and еnегgеtiс (Fig. l3)
5 t
A d s o r р t i o п Е п о r g y ( k J / m o | ) A d s o r p t i o n Е n 6 r g y ( k J l m 0 t i
A d s o r p t i o n Е л e r g y ( k J i m o l )
цl
цl
6 6 l v
Adso rр t i on Еne rgy
1 2 1 ,
( k J /m o l )
Fig.13.Nitrogеnadsorption"n9.gy^distributionsforfumеdoxides(a)siliсa'
alumina, As ;nd ф) titania and TS i;;й;' ""mput1d]1тilc
DHTh (solid
linеs) and pйji'i,"ilii",)
"qu"tions
with fixed сr.:0.001.
anсe. titaniahas гelativеly loY.s{*
(largе рimary partiсlеs with thе
avегage diamеtеr oгzsЪ ""i."
-'""п vo фiьъ 5);ЪЫеvег, titania as a sепiсonduсtor
Dossesses a rеlativеlу ;#,- ;;;;i;;"p,Ё;.i .vj.м lшgе polшizabilitу, whiсh сausе
iisnif'сant dispeгsion ffi;;йЪitь uаs"йi nЬ,njoru' nТt,щ.n molесulеs. Theгеfoге
tйia has a |arge f@)ffi;i.ii йl^Py;;i .t,;t.а towф smallег Е in сompanson
with that fог fumеd titania-silica po.,..,ingffi;.i;; lsmattеr primary partiсlеs and
A d s o r p t i o n Е n e r g y ( k J / m o l )
52
thе
;1oг
цrsr
Гore
isоn
and
4 уtt,Yo
Ф 6 0 . 0 f t 0 . 2 0 . . o . Ф . Ф
сhзmiса| shift (рpft)
nalгowеr сhannеls in aggгegatеs сan
impaсt the pоsition of a high-еnеrgу
f@) peak) and aсidiс =Si-o(Ц-Ti=
groups strongly interaсting with Nu
molесulеs' Howeveг, thе numbeг оf
such aсtivе groups is relativеly small
and the high-еnеrgеtiс pеak is lоwег
for TS samplеs than that for titania
(Fig. 1зb). A similar pictuге is sееn iог
AS . samplеs (Fig 13a) pоssessing
signifiсant Bronstеd aсiditу t323зт'
Consequentlу, features of сaгbosil
samples rеsult in сoгrеlatеd сhansеs in
thе textural and еnфеtiс
сharaсteristiсs analyzed *itь
сonsideration for thе hеtеrogеnеitу of
hybrid adsoгbеnts. Thе structural and
еnergеtiс pгopеrties of thе suгfaсеs of
diffеrеnt phasеs in hеteгogеnеous
сaгbon-mineral adsoгbеnts сan
differently impaсt the adsorрtion оf
suсh polar сompounds as watеr.
4 vtt.Yo
24 wt.Yo
Fig. 14. Chеmiсal shifts (in respесt to TМS) for't{ Nпr,{R sprсtra of watrr adiorbed on si-oо,
Aс l and сДosi-60 (Table 2) at rоom
tеmpегatuге (adsorbed watеr conсentration is
shown in Figurе).
This hеtеrogеneity сould be analyzed using the 'н }.ПиR method with fтeezing-out of the bulk
wateг -[3l.3З]. Thе appliсation of this method to water adsorbеd on thJ most соmplеx
сагЪosils CSx prеparеd by thе pyгolysis of metal aсеtylaсеtonatеs, as wеll as for CS-i at
diffеrеnt Cc valuеs [6], shows substantial diffeгеnсеs in the lн NМR speсtra гесordеd at гoom
lеmpеratuгe (Fig. 14), amounts of unfrozrn watеr (С,,) and сhanges in thе Gibbs fгее еneгgy
iG of thе intеrfaсial watеr at T bеtweеn 210 and 2'7з K depеnding on thе nature of g.aгсеа
deposits and their сonоentгations (Fig. 15, Тablе 6). In Tablе 6, АG,o" сorrеsponds to ойangеs
in thе Gibbs frеe еneгgy of thе first mоnolayеr of the inteгfaсial water stгongly bouпd to 7hе
adsorbent surfaсеs; lGz .(in mJ pеr in2 of the adsoгbent suгfaсе) is thе overall сhangеs in G
duе to the water intеraсtion with thе surfaсеs distorting thе inteгfaсial watеr unfrozеn at T <
27з K, and Сu,,jn* dеnotеs thе total amounts of unfrozеn watег at T _> 2.7З K [3 l -33]. In thе
саsе of mesopoгous siliсa gеl Si-60 (Меrсk), the АG(C',) funсtion is neaгly linear (Fig. 15a);
iе.' thе amounts of thе unfrozеn water deсгеases nеarly linеarly with lowering tйpБ'atu.e.
Notiсе that АG(C',) for Si-60 (Мeгсk) differs fгom that for Si-60 (Sсhuсhaidt йrinсьеn;
(Figs. l5a and l5с), and thе PSDs for thеsе initial siliсa gels differ (Figs. 5.7). For caгbosils,
'tG(С*) has a сomplex shapе due to the hetеrogеneity of the surfaсes. A portion of thе
АG(С"") сuгves with a maximal inclinе (Figs. l5a and 15с) and large dеrivatives (Fig. l5b)
сoггеsponds to thе boundary betwееn stгongly and weakly bound
53
b
+s€0
. . . lс. l
.:Ф. сqт}
-?. cq}|)
.+.сqЙ)
. . t .сs}a
эЁ
з
dл
i 0,1
х
>
х
0,01
*Гъ-б-зш аш sm
с* (md9)
о
Е
( n
(.f
j
п
с*: (ms/s)
Fig. 15. Changes (a) and (с) in thе^Gibbs frее enеrgу (АG\.and (b)its dеrivative 4(AG)/dС""
foг thе intеrfaсial watеr'in the frozеn uqu.ou.-iu*p.n.ion, Q|o-z,.tз K) of (a, b) Si.60
(Мerсk), ACl and сл<lЪi-iЪ iiЫ" z); unа t"fii.й?s"ь"сharЬ Mtinсhеn) and CS-l (Тablе
1) еstimatеd fгom thе iЫ'Niй .p."t,u; taj iы"tь''hips between the total amounts of
unfrozеn water at T -+.213K (С";,r) and сhangеs in йe Gibbs free еnеrgy of the first
;;;;;й' AG,*andovеrall lGдvaluеs for CSх and CS-i samplеs.
waters ,assma l l сhangеs i r tCunresu l t in lшgevar ia t ions in .dG.onrсanassumеthat th i s
еffeсt is ul.o
"onn""t'J
;й"; *ш", luу...;"i;;;li"g with diffеrеnt phases (oxidе and
pуroсarbon) witь vaгьirl сiьБ, r,*. еnе,gi". but сlоsе tеmpeгatures of watеr freеzing at T <
2,7зK'In thе оasе
"'
;;.-;;;сa,bon on 'iri*.g.r.у{.:J: !ЧLln"
АG(С'") plot liеs to
thе left in сomparisoi1'i,t,lй"'" for CSх €ii, rsal duе to wеakеr intегaсtion bеtwеen
noщыu.o, slightly polar pyrocarbon partiсlеs and inteгfaсial water.
+slФ
. . -дс1
..}.cqт}
.?. сq,')
..&.сqar)
..L. сg.tzt
с* (mgs)
m 400 sоо оoо 7oo 800
с* (mgg)
54
d сs.
t b 1
of p1
i r r s C
iliсr rl
ч t с
crylrit
i Б l
Г )шс
flэ ш
ФЁ
п
d
F.itaт
b t h з с
-n'dу
lo
*iф с
-60
rblе
of
irst
this
and
Т <
:s to
Yееn
Tablе 6
Charaсtегistiсs of thе Inteгfaсial Water Layers in the Frozеn Aquеous
Susрensions of Carbosils
Adsorbent АG^*,
kJ/mol
АGь
mI/rrf
г m цvцw
ms/s
Si60 (Mеrсk)
Aсl
CSzn
CSтi
CSar
CSaz
Si-б0 (Sсhuсhardt Мtinсhеn)
сs.l
сs-2
сs.з
сs-4
сs-5
сs.6
3.3
3 . 8
з .2
3 . 2
2 .8
3 . 0
2 .8
3 .0
з ,2
4 .0
3 . 0
3 . 5
з . 7
160
26
204
208
88
118
115
110
1з2
109
72
139
240
700
250
535
424
200
250
850
550
530
400
275
450
400
Among CS-i samples thе most inоline is obsеrved for CS-5 (Fig. l5с)' whiсh also has a lшger
maхimum ot I@) at Е : 14 kJ/mol (Fig. l2a). However, CS-2 сan possrss a maхimal
nonuniformity, as its АG(C,") plot lies to thе right in сomparison with those for othеr CS-i
sаmples (Fig. 15с) in сontrast to CSx, whose АG(С"') graphs shift toward loweг C,' in
сompaгison with that for pгistinе Si60 (Fig. l5a). Thе observеd diffеrenсes tn АG(C'") for
CSх and CS.l samples сan Ье сaused by deposit distribution fеatures as thе Х phasе сan
catalУzе the pyгolysis dеpеnding on the nature of thе Х phasе (Table 2). Therefore nеw
Poгtions of pyroсarbon aге foгmеd around thе X grains. In thе casе of сarbonization of suсh
organiсs as CHzClz, CсHro, CtzHto, сaгbon grains are more aсtivе as the reaсtion pгomotегs
thал siliсa suгfaсes [2] that lеads to еnlaгgеmеnt of сarbon partiсles, and relatively large
рrtiсlеs up to 200 nm сan be foгmed on the outеr siliсa gel surfaсes at Cc > |0 wt'% |2-71.
Consеquently, the siliсa patсhes in CS-j сan bе moге easily aссеssiblе than thosе in CSх,
whiсh ехplains the obsеrved differenсes in АG(C'") for thеsе carbosils (Fig. l5). The
rэlationships betweеn the total amounts of unfrozen water on CSх and CS-i at Т -+ 2,7ЗK
(c,,.:"*) and оhangеs in the Gibbs freе еnergy АG,* of thе first monolayег and overa|| АG2
vаluеs are nonlinеar (Fig. lsd) due to the influеnсe of thе naturе of the suгfaсеs, thеiг
шпunifoгmity, сharge distribution and PSDs, еtс.
.:l
Conсlusions
on the investigations of the struсtural and еnеrgetiс сhaгaсtегistiсs of hybrid
pуroсaгbon-minеral adsorbеnts inсluding tеxturally and сhemiсally difforеnt phasеs, thеiг
iruсtural and enеrgеtiс fеaturеs should bе analyzed using the ovегall isothегm approхimation
with сonsidегation for thе adsorbеnt hеtеrogеnеity.
In thе сase of C/Sioz, thв pyroсaгbon deposits rеprеsеnt mainly dеnse globulеs, whiсh
rс геlativеly largе and possеss low porosity, as сhangеs in the porе size distributions
ooпespond to геduсtion of mеsopoгes of the supports praсtiсally without appearanсr of nеw
рrеs, whiсh сan be assignеd to thе сarbon phasе per se.
55
Struсturalfeaturesoftitшria.siliсasprepшedusingsiliсagеlandfumedsiliсamatrices
and difrеrеnt .."r'niqu"]""lJ;;i;';;;;i' .Б сi*ьйion of pyroсarbon on the supports'
thе paгtiсlr sizе distributй anс othеr prщеrti; ffi;;;'t" ш.d adso'ьеnts as thе wholе. In
seniral, pyroсаrbon
",1i,"'."*""ф{1!.11severario
dozеns Prrсеnts oonsists mainly of
Iаrse individual dense jioьur., and possesse.;;;;'ь;osity.p.roviаed mainly by thе gaps
bйeen outеr surfaс"? ;;"*;":"i"9'. *i;;';йi" -*'яi:l.j.'JТ].J#iъ#."*'::ъ?
:H****н:;""*'*'т:нжнi,".fl":'i;}ТLЦf iТiяY;x}ШJJ#"'g1s;
;"'ж*,":;г;'";},жtl"fi -l!il1ЦцilЁ:i.i,*".l*тнн:{*1g'н;жжlн
CVD proсеsses for ь# pйЪ."ББ" *qфiii.i'* ""
'ь.-тio1liн"), pyrolysis. Similaг
but smallеr effесts #;Ы;Т9' -с.g1sй6.^;йй
by th1 pyгфsis of Zn ald Zт
aсetvlaсetonatr, o, ,,o-, ?ёw-тio/K9K ^йs'-iйе "ьoiЬe
of oxide matriсes, orgaшс
o,еiu,so,, anа teсьni{u",."fb;;]" ;;h;;ь 91"*i?'
Ьi .,ьon deposits allow onе to сhange
substantially tье struJЬ1!-"ьa,"сiе.ьti", "гТ'iЁ'ii;;;;i';й
adsoгbеnts in dеsirable
direсtion.
o.*"f,*l":#;Ji'.s supportedby.\}]Р @rantNo. т19^lя:,6890),
thе Polish State
Committeе for sсiеniiriiiЁ.iй.iйaмi"йй."iiigh Еduсation аnd Sсienсe of Ukrainе
Grant t'to. 2lvll3 03 -99)'
Rеfеrеnсеs r.. rт^.'^сiЬirсl. 1sg5 513 D
iт*нy*,ж"Ё"tъж#}riж-fl;i!r:,::'Jiфhеxenе/v.M..g:,ko,
R. Lеboda, W. G,;:*;';;й-i. рцчц#,d;;;.-M
.Mаrсinialq
A.A. Malygin,
it#**;.:t-"-lа:El,;.!lЖ;-',,''J?i1ni'?ffin'.^"hloride./v.щ.s{}l
J. Skubiszewska-ziй в. Lеboda, u.'. ,'iЗj7'."йilriooo. _ V. 16, No 2' -P.з74-
з82.
4.Si l iсaGеlModiГrеdDuetoЦ,,"1yчofAсеtylaсetoneorМеtal(Ti 'Cг,Co,Ni 'Zn,Zr)
Aсetvlaсеton".", l i]й*Ый;E..*ogil..i*й;ъ;;,;;'r.o.ziеЪ*
J. Rynkowski // J.
Fi{lx}l"'*Ч*':ъil,ъ1;.,,kJJ--'"''J'i*' зf ̂ .'т::T.Чon.Mineral Adsorbents. /
V.М. Gun,ko, R. Leboda" V.v..тч9n. '. v'ii.'.й, i. sк.iьi.,"*ska.Zi9bа' S. Chodorowski,
у*rн:*l',-тзffil"*g**Ц:н;n:hrеs^of
Carbo:t-SiliоaGеls/v.y.!un.ko,
R. Leboda, B. сharЬ, F. Villieras д с"i'ji."i"i]..-'000. _ v. 17з, N l.3. - P. l59.
}1hun*","lutionArgonPtчt':gч*:::Ч:"-o;i'Тff Ё"*ж:#.i"1ж:ff 7*
of Cйbosils r.. u,,i,Jй' ilъй;-" dii.йi'' ..;;ЫG. Gеrшd, W. Rudzinski //
Caгbon. _ 199s. _v;;'ill;--p. t3ot-tsto. sity. Mosсow: Мir, 19,
8.GrеggS.J.,SingK.s.W.Adsoгptioцju#"""fuеaandPoгosity.Мosсow:Mir,1970..
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с.it"i'j дj'o'p'i"" |l. Ьdv. Colloid Intегfaсe Sсi. -
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58
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|
| id | oai:ojs.pkp.sfu.ca:article-47 |
| 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/6e/afbb34ea8a81dda493e0a15b4387816e.pdf |
| spelling | oai:ojs.pkp.sfu.ca:article-472018-11-27T09:42:39Z Nonuniformity of hybrid adsorbents Nonuniformity of hybrid adsorbents Nonuniformity of hybrid adsorbents Gun'ko, V. M. Leboda, R. Turov, V. V. Villieras, F. Several series of pyrocarbon-mineral adsorbents (carbosils) were studied using the nitrogen adsorption method to compute structural and energetic parameters within the scope of overall adsorption isotherm approximation applying regularization procedure with consideration for surface heterogeneity. A portion of pyrocarbon deposits (graphene clusters) fills mesopores of the oxide supports, but another portion represents relatively large nonporous pyrocarbon globules formed on the outer surfaces of the oxide matrices. Contributions of these two types of pyrocarbon deposits depend on the nature of oxide matrices and carbonized precursors. Several series of pyrocarbon-mineral adsorbents (carbosils) were studied using the nitrogen adsorption method to compute structural and energetic parameters within the scope of overall adsorption isotherm approximation applying regularization procedure with consideration for surface heterogeneity. A portion of pyrocarbon deposits (graphene clusters) fills mesopores of the oxide supports, but another portion represents relatively large nonporous pyrocarbon globules formed on the outer surfaces of the oxide matrices. Contributions of these two types of pyrocarbon deposits depend on the nature of oxide matrices and carbonized precursors. Several series of pyrocarbon-mineral adsorbents (carbosils) were studied using the nitrogen adsorption method to compute structural and energetic parameters within the scope of overall adsorption isotherm approximation applying regularization procedure with consideration for surface heterogeneity. A portion of pyrocarbon deposits (graphene clusters) fills mesopores of the oxide supports, but another portion represents relatively large nonporous pyrocarbon globules formed on the outer surfaces of the oxide matrices. Contributions of these two types of pyrocarbon deposits depend on the nature of oxide matrices and carbonized precursors. 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/47 Surface; No. 4-6 (2001): Chemistry, Physics and Technology of Surface; 35-58 Поверхность; № 4-6 (2001): Химия, физика и технология поверхности; 35-58 Поверхня; № 4-6 (2001): Хімія, фізика та технологія поверхні; 35-58 3154-8091 3154-8083 en https://surfacezbir.com.ua/index.php/surface/article/view/47/46 Авторське право (c) 2001 V.M. Gun’ko, R. Leboda, V.V. Turov, F. Villieras |
| spellingShingle | Gun'ko, V. M. Leboda, R. Turov, V. V. Villieras, F. Nonuniformity of hybrid adsorbents |
| title | Nonuniformity of hybrid adsorbents |
| title_alt | Nonuniformity of hybrid adsorbents Nonuniformity of hybrid adsorbents |
| title_full | Nonuniformity of hybrid adsorbents |
| title_fullStr | Nonuniformity of hybrid adsorbents |
| title_full_unstemmed | Nonuniformity of hybrid adsorbents |
| title_short | Nonuniformity of hybrid adsorbents |
| title_sort | nonuniformity of hybrid adsorbents |
| url | https://surfacezbir.com.ua/index.php/surface/article/view/47 |
| work_keys_str_mv | AT gunkovm nonuniformityofhybridadsorbents AT lebodar nonuniformityofhybridadsorbents AT turovvv nonuniformityofhybridadsorbents AT villierasf nonuniformityofhybridadsorbents |