matériaux avancés pour la catalyse et la santé

matériaux avancés pour la catalyse et la

santé

F. Di Renzo1*, A. Galarneau1, F. Quignard1, S. Valange2, Z. Gabelica3,

J.-P. Bellat4

[email protected] 1Institut Charles Gerhardt Montpellier, UMR 5253 CNRS-UM2-ENSCM-UM1,

Matériaux Avancés pour la Catalyse et la Santé, ENSCM, 8 rue Ecole Normale, 34296 Montpellier, France

2Laboratoire de Catalyse en Chimie Organique, Université de Poitiers, Poitiers, France

3LPI-GSEC, ENSCMu, Université de Haute Alsace, Mulhouse, France

4Institut Carnot de Bourgogne, UFR ST, Université de Bourgogne, Dijon, France

Adsorption and Intrusion Methods for the Characterization of

Mesoporous Materials

Nitrogen adsorption and mercury intrusion in mesoporous silicas with different pore connectivities

A. Galarneau1, B. Lefèvre1, H. Cambon1,S. Valange2, Z. Gabelica3, J .P. Bellat4, F. Di Renzo1

1Laboratoire de Matériaux Catalytiques et Catalyse en Chimie Organique, UMR 5618 ENSCM-CNRS-UM1 Institut Gerhardt FR 1878ENSCM, 8 rue de l'Ecole Normale, 34296 Montpellier Cedex 5, [email protected] de Catalyse en Chimie Organique, Université de Poitiers, France3Université de Haute Alsace, Mulhouse, France4Laboratoire de Recherches sur la Réactivité des Solides, Université de Bourgogne, Dijon, France
















matériaux avancés pour la catalyse et la

santé

Adsorption and Intrusion Methods for the Characterization of

Mesoporous Materials



















● an inventory of superposed phenomena

● surface tension, liquid-solid interfaces and capillarity

● new standard materials allow a new look at old models

● shape effects and the limits of capillarity

● non-wetting fluids and still more shape effects

N2 adsorption-desorption isotherms at 77 K for mesoporous silicas prepared by different methods

MCM-41 structured by CTMA swollen by TMBSBA-15 structured by PEO-PPO-PEO triblock copolymer Sylopol commercial precipitated silica

0

200

400

600

800

1000

1200

1400

0 0.2 0.4 0.6 0.8 1

p/p°

cm

3 g-1

ST

P

the relative pressure of the capillary condensation step

indicates the pore size

9.5 nm

10.3 nm

21 nm

2 cm3 g-1

1.5 cm3 g-1

1.2 cm3 g-1

adso

rbed

gas

vol

um

e

280 m2 g-1490 m2 g-1

840 m2 g-1

the amount adsorbed at the top of the first

adsorption step indicates the surface area

the amount of nitrogen adsorbed at the top of the condensation step

indicates the pore volume

N2 inside the pores is a dense phase and presents

nearly the density of liquid N2

for N2, ρliq/ρgas = 647

Isotherm interpretation : separation of superposed phenomena (which, happily, do not depend on pressure in the same way)

Contributions of capillary condensation and multilayer adsorption can be easily separated if mesopores present a narrow pore size distribution

Layer adsorption : spread over the whole pressure field according to a known law

pp

cpp

pp

c

n

n

m )1(11

BET equation (multilayer Langmuir)

n adsorbed amountnm monolayer capacityp/p° relative pressurec parameter related to the difference of adsorption heat between monolayer and following layers

Condensation : occurs at pressure values which depend on the pore size

RTr

V

p

p m2ln

0

Kelvin equation γ surface tension R gas constant T temperatureVm molar volume r mesopore core radius

0

100

200

300

400

500

600

0 50 100 150 200 250

cm3 (STP) g-1 (aerosil reference)

cm3 (

ST

P)

g-10

100

200

300

400

500

600

0 0.2 0.4 0.6 0.8 1

p/p°

cm3 (S

TP

) g-1

monolayer adsorption

multilayer adsorption

mesopore filling

multilayer

mesopore emptying

slope proportional to the total surface area

slope proportional to the outer surface area

0

100

200

300

400

500

600

0 50 100 150 200 250


cm3 (

ST

P)

g-10

100

200

300

400

500

600

0 0.2 0.4 0.6 0.8 1

p/p°

cm3 (S

TP

) g-1



mesopore filling

multilayer

mesopore emptying



an isotherm of mesoporous solid and its comparison plot

N2 adsorption at 77 K on Lichrosphere 60 chromatographic silica

comparison plots are useful to evidence different mechanisms in

the adsorption isotherm

in a comparison plot, for each pressure value the adsorbed amount on the examined sample is compared with the adsorbed amount on the reference sample

reference adsorbent SBET 187 m2 g-1

slope of the comparison plot 3.9Scomparison plot = 187 x 3.9 = 730 m2 g-1

in good agreement with SBET 740 m2 g-1

0

100

200

300

400

500

600

0 50 100 150 200 250

cm3 (

ST

P)

g-1

0

100

200

300

400

500

600

0 0.2 0.4 0.6 0.8 1

p/p°

cm3 (S

TP

) g-1



mesopore filling

multilayer

mesopore emptying



0

100

200

300

400

500

600

0 50 100 150 200 250

cm3 (

ST

P)

g-1

0

100

200

300

400

500

600

0 0.2 0.4 0.6 0.8 1

p/p°

cm3 (S

TP

) g-1



mesopore filling

multilayer

mesopore emptying



experimental isotherm

P

Y

0

100

200

300

400

500

0 0.2 0.4 0.6 0.8 1p/p°

cm3 (

ST

P)

g-1

reference isotherm

aerosil 200 fumed silica

PX

0

100

200

300

400

500

600

0 50 100 150 200 250


cm3 (

ST

P)

g-1

0

100

200

300

400

500

600

0 0.2 0.4 0.6 0.8 1



mesopore filling

multilayer

mesopore emptying



0

100

200

300

400

500

600

0 50 100 150 200 250


cm3 (

ST

P)

g-1

0

100

200

300

400

500

600

0 0.2 0.4 0.6 0.8 1



mesopore filling

multilayer

mesopore emptying



comparison plot

Y

X

t-plot and αS-plot: two types of comparison plots

0

100

200

300

400

500

600

0 1 2 3 4

alpha S (aerosil reference)cm

3 (S

TP

) g-1



0

100

200

300

400

500

600

0 5 10 15 20

t / Å (aerosil reference)

cm3 (

ST

P)

g-1



0

100

200

300

400

500

600

0 1 2 3 4

alpha S (aerosil reference)cm

3 (S

TP

) g-1



0

100

200

300

400

500

600

0 5 10 15 20

t / Å (aerosil reference)

cm3 (

ST

P)

g-1



a positive deviation of the comparison plot indicates that a more effective mechanism of adsorption is superposed to the growth of the adsorbed layer

t-plot: reference adsorbed amount expressed as average thickness of the monolayer (assumption of constant density of the condensed phase)

thickness t = 1Å = 0.345 µmol m-2 = 15.4 cm3 (STP) m-2

αS-plot: the unit of the abscissae is the reference adsorbed amount at p/p° 0.4, an isotherm region expected to be often rid of condensation phenomena

http://citt.ufl.edu/Marcela/Sepulveda/html

If cohesive forces of the liquid are stronger than the adhesive forces at the interface, the sum of forces at the surface is directed towards the interior of the liquid.

This induces a pressure rise inside the liquid. The force balance inside a liquid droplet allows to correlate this pressure to the droplet size through the surface tension.

0

0.01

0.02

0.03

0 0.5 1 1.5 2droplet size (mm)

pre

ssu

re (

atm

)

water surface tension at 20 °C = 0.0728 N m-1

Young-Laplace law

Өcontact angle

in the presence of a solid, the contact angle depends on the sum of the surface tensions at the triple point

σvapour-liquid cos Ө + σliquid-solid = σvapour-solid

wetting non-wetting

liquid solid contact angle

waterglass 0°

silver 90°

wax 107°

mercury glass 135°

2σcos(Ө)

capillary rise

Surface tension around the perimeter of the tube results in a force with a vertical component that drives water upwards.

The movement continues until the force due to surface tension equals the weight of the water column. h capillary rise

σ surface tensionӨ contact angle

r capillary radiusρ liquid densityg gravity acceleration

mechanical equilibrium (Young-Laplace)

dpliq-dpvap = d(2σ/rm)

physicochemical equilibrium (Gibbs-Duhem at constant T)

dμliq = dμvap

Vliqdpliq = Vvapdpvap

d(2σ/rm) = dpvap (Vliq-Vvap) / Vliq

Vliq negligible compared to Vvap

vapour as perfect gas

d(2σ/rm) = - RTdpvap / (Vliq Pvap)

integrating between (rm, p) and (∞, p°)

ln (p/p°) = - 2σVliq / (RT rm)

Kelvin equation

the driving force of capillary condensation and drop coalescence is the decrease of the liquid-vapour

interface area

William ThomsonLord Kelvin (1824-1907)

Kelvin equation

surface = high energy state

RTr

V

p

p m2ln

0

2σVm

Schematic representation of adsorbed layer and capillary meniscus in cylindrical (lefthand) and slit-shaped (rigthhand) pores

ln (p/p°) = - 2 σ VL / (R T rm)

rp = rm + t

Kelvin equation

the correlation between curvature of the meniscus and pore size depends on the shape of the pore

wp = rm + 2t

Did the availability of new reference materials modify our understanding of the

adsorption phenomena?

MCM-41, J.S. Beck et al., JACS 114 (1992) 10834

MCM-48V. Alfredsson and M.W. Anderson, Chem. Mater. 8 (1996) 1141

SBA-15, Z. Liu et al., ChemPhysChem (2001) 229

t

t

t = 0.5 nm

t = 1.0 nm

t = 2.0 nm

0

200

400

600

800

1000

1200

1400

1600

1800

2000

0 2 4 6 8 10

a ( nm)

S g (

m2 .g

-1)

t = 0.5 nm

t = 1.0 nm

t = 2.0 nm

0

200

400

600

800

1000

1200

1400

1600

1800

2000

0 2 4 6 8 10

a ( nm)

S g (

m2 .g

-1)

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

0 2 4 6 8 10

a (nm)

v f (

cm3 .g

-1)

t = 2.0 nm

t = 1.0 nm

t = 0.5 nm

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

0 2 4 6 8 10

a (nm)

v f (

cm3 .g

-1)

t = 2.0 nm

t = 1.0 nm

t = 0.5 nm

Correlations between cell size, pore size, wall thickness, surface area and

mesoporous volume for MCM-41-like silicas

r = (a - t)/2

Deq = 1.05 (a - t)

radius of inscribed circle

diameter of circle with the same area as the hexagon

A. Galarneau et al., Micropor. Mesopor. Mater., 27 (1999) 297; Stud. Surface Sci. Catal., 142 (2002) 1057.

Correlations between cell size, pore size, wall thickness, surface area and

mesoporous volume for MCM-48 silicas

B. Coasne et al., Langmuir, 22 (2006) 11097

A. Galarneau et al., Microp. Mesop. Mater.,

83 (2005) 172

L. Jelinek, E.s. Kovats, Langmuir 10 (1994) 4225

Cross-sectional areas of nitrogen molecule:16.2 Å2 over silylated silica (value usually used in syrface area calculations)13.5 Å2 over rehydroxylated silica

0

100

200

300

400

500

0 0.2 0.4 0.6 0.8 1p/p°

cm3 (

ST

P)

g-1

0

100

200

300

0 1 2 3alpha S (aerosil reference)

cm3 (

ST

P)

g-1

Reference isotherm of N2 adsorption at 77 K on Aerosil fumed silica

some mesoporosity in a reference solid assumed as non-porous

αS-plot for a Ca-alginate aerogel

negative deviation of the αS-plot of a

solid with less mesopores than

the reference

Ca-alginate aerogelF. Quignard, M. Robitzer, F. Di Renzo

New J. Chem. 32 (2008) 1300

0

200

400

600

800

0 0.2 0.4 0.6 0.8 1

p/p°

cm3 (

ST

P)

g-1

0

200

400

600

800

0 1 2 3alpha S (aerosil reference)

cm3 (

ST

P)

g-1

N2 adsorption-desorption isotherms at 77 K (lefthand) and corresponding αS-plot (righthand) for a non-microporous SBA-15 silica (filled symbols)

and a sample functionalized with C16 hydrocarbon chains (void symbols)

effect of the nature of the surface on the comparison plots

0

20

40

60

80

100

120

140

160

180

200

0.0 0.2 0.4 0.6 0.8 1.0

alpha-S (Aerosil)

cm3 (

ST

P)

g-1

0

20

40

60

80

100

120

140

160

180

200

0.0 0.2 0.4 0.6 0.8 1.0

alpha-S (Aerosil)

cm3 (

ST

P)

g-1

Comparison plots of the adsorption of N2 at 77 K on (filled triangles) chitosan and (void triangles) chitin aerogels. The lines represent best-fit linear correlations extrapolated to αS = 0.

Comparison plots of the adsorption of N2 at 77 K on (filled circles) ionotropic alginate, (void circles) alginic acid, and (void squares) carrageenan aerogels. The lines represent best-fit linear correlations extrapolated to αS = 0.

t-plots for the adsorption of N2 at 77 K on polysaccharide aerogels

0

20

40

60

80

100

120

140

-10 -5 0 5 10 15 20intercept at αS = 0 (cm3 STP g-1)

C (

BE

T)

Correlation between the energetical parameter C of the BET equation and the intercept of the αS plots of polysaccharide aerogels with different surface groups: acetylated amines (chitin, void triangles), amines (chitosan, filled triangles), hydroxyls (agar, void lozenges), sulphates (carrageenan, void squares), carboxylic groups (alginic acid, void circles), and salified carboxylates (alginate, filled circles). St. Andrews cross for the Aerosil fumed silica used as reference isotherm.

chitin

chitosan

agarose κ-carrageenan

alginic acid

energetical parameters of the adsorption of N2

at 77 K on polysaccharide

aerogels

0

1

2

3

4

0 0.5 1 1.5 2monolayer fraction V/Vm

kJ m

ol-1

Net molar energy of adsorption of argon on (filled circles) Ca-alginate and (void triangles) chitin aerogels and (St. Andrews' crosses) fumed silica.

isosteric heats of adsorption of Ar on polysaccharide aerogels

alginic acid

chitin

am

ou

nt

ad

sorb

ed

, n

= H1 = H3 = H2

am

ou

nt

ad

sorb

ed

, n

= H1 = H3 = H2

am

ou

nt

ad

sorb

ed

, n

= H1 = H3 = H2

Different shapes of hysteresis of type IV isotherms

H4H1 narrow mesopore size distribution

H2 ink-bottle pores

H3 broad pore size distribution with smaller pores accessible through the larger ones

H4 similar to H3 in the presence of microporosity

Schematic representation of the N2 adsorption-desorption isotherms at 77 K and corresponding pore size distributions for materials with 10 nm cavities and

entrance sizes between 2 and 10 nm

lower limit of the hysteresis loop: catastrophic desorption

adsorption isotherms of N2 at 77 K on (a) SBA-15, (b) TMB-swollen MCM-41, and (c) MCM-41 silicas

limit of reversible pore filling

-12

-10

-8

-6

-4

-2

0

1 1.5 2 2.5Tc/Trpf

ln(p

rpf/p

c)

reduced temperature and pressure of the limits of reversible pore filling for N2 (void squares), Ar (filled squares), Xe (filled triangles), O2 (void lozenges), CO2 (void

triangles), cyclopentane (void circles), benzene (St. Andrews crosses), 2,2-dimethylbutane (crosses). Tc and pc are the critical conditions.

D. Maldonado et al. J. Porous Mater. 14 (2007) 279

corresponding state graph for the limit of reversible pore filling

suction head

delivery head

piping head

the suction head of a pump is limited by the

evaporation of the liquid

TemperatureVapor Pressure

Maximal elevation

(oC) (oF) (kN/m2) (m)

0 32 0.6 10.3

10 50 1.2 10.2

20 68 2.3 10.1

30 86 4.3 9.9

40 104 7.7 9.5

50 122 12.5 9.1

60 140 20 8.3

70 158 32.1 7.1

80 176 47.5 5.5

90 194 70 3.2

100 212 101.33 0.0

Suction Head as Affected by Temperature

He = (Patm - Pv) / γ

maximum suction head

Clausius-Clapeyron calculations of the enthalpies of evaporation at the

limit of reversible pore filling

P. Trens et al., Langmuir 21 (2005) 8560

Adsorption/desorption isotherms of nitrogen at 77 K

MCM-41 3 nm (synthesis with CTAB)▲ MCM-41 4 nm (synthesis with CTAB, swelled with trimethylbenzene) MCM-41 5.5 nm (synthesis with CTAB, swelled with dodecylamine) MCM-41 10 nm (synthesis with CTAB, swelled with trimethylbenzene)

The pore size can be tuned by the

synthesis method

Enthalpies of adsorption of n-hexane as a function of coverage as calculated from (left hand) the adsorption data and (right hand) the desorption data on () MCM-41 3 nm, (▲) MCM-41 4 nm, (■) MCM-41 5.5 nm, (O) SBA-15 10 nm. Dashed line: condensation heat of hexane.

-40

-35

-30

0 0.5 1Fraction of pore filling

Ads

orpt

ion

enth

alpy

/ kJ

mol

-1-40

-35

-30

0 0.5 1

Fraction of pore filling

Ads

orpt

ion

enth

alpy

/ kJ

mol

-1

D. Maldonado et al. J. Porous Mater. 14 (2007) 279

30

32

34

36

38

40

42

0 2 4 6 8 10

D (nm)

-ΔH

(k

J m

ol-1

)

Condensation enthalpies of n-hexane as a function of the pore size. Isosteric data from adsorption () and desorption () results.

Continuous line: calculated condensation enthalpy.Dotted line: condensation enthalpy on a flat liquid surface.

inti hN

Nhh

cc

ntcondcc

When the meniscus advances, the interface between adsorbed layer and vapour disappears

In small mesopores, the energetical contribution of the interface affects

the enthalpy of capillary condensation

pore surface

adsorbed layer

core filled by capillary condensation

p

ccm N

NNN int

In the hypothesis of constant density of the adsorbed phase, the fraction of interface molecules can be evaluated from the adsorption isotherm

Nm = monolayer amount by BET equation

capillary rise and capillary depression

wetting fluidӨ < 90°

non-wetting fluidӨ > 90°

2σcos(Ө)

h capillary riseσ surface tensionӨ contact angler capillary radiusρ liquid densityg gravity acceleration

ΔP = (2γ/R) cosθ

Washburn-Laplace law for cylindrical pores

corelation pressure-pore size depending on contact angle

γ(Hg) 0.485 N m-1

if θ = 140°R = -743/ΔP

R = nm ΔP = MPa

180°

130°

110°

1.8

2

2.2

2.4

2.6

1.5 1.7 1.9 2.1 2.3

Log D (Angstrom)

Lo

g P

(M

Pa)

180°

130°

110°

1.8

2

2.2

2.4

2.6

1.5 1.7 1.9 2.1 2.3

Log D (Angstrom)

Lo

g P

(M

Pa)

rm

θrp

Hgrm

θrp

HgHg

intergranular porosity

grain packing

structural porosity

Mercury porosimetry on SBA-15 sample prepared at 130°C

0.7 µ 7.5 nm20 nm

1.0 ml/g

2.2 ml/g

Pore size calculated for θ = 140°

50 nm 3 nm

field of superposition with the data from nitrogen adsorption

0

1

2

3

4

5

6

7

0.0010.010.11101001000

Diameter (µm)

cum

ula

tive

vo

lum

e (m

l/g

)

Porosity of SBA-15s from nitrogen adsorption at 77 K

pore size calculated by the method of Broekhoff and de Boer

# T (°C) synthèse

D (Å) adsorption

D (Å) désorption

3439 60 45 48

3440 100 73 75

3806 130 90 96

3441 130 100 105

pore size increases with the temperature of the second

step of the synthesis

0

100

200

300

400

500

600

700

800

900

0 0.2 0.4 0.6 0.8 1

P/P°

N2 m

l/g S

TP

3439C

3440C

3441C

3806C

A. Galarneau et al., Langmuir 17 (2001) 8328

structural porosity of SBA-15s from mercury intrusion

pore size calculated for contact angle θ = 140°

# T (°C) synthèse

D (Å) intrusion

D (Å) extrusion

3439 60 42 60

3440 100 52 100

3806 130 62 140

3441 130 76 200

hysteresis loop is wider for larger pores

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 0.02 0.04 0.06

diameter (micron)

volum

e (mL

/g)

-0,8 -0,4 0,0 0,4 0,8 1,2 1,6-4

-2

0

2

4

6

Intrusion

n = -1

Patm

MTS 10

0C8

MTS 50

C8

MTS

18 C8

MTS

16 C8

ln P

ln RP

-0,8 -0,4 0,0 0,4 0,8 1,2 1,6-4

-2

0

2

4

6

ln Rc1

Patm

(•)

ln P

ln RP

Pint RP-1

Pext RP-4

Retraction Propagation

Intrusion of water in MCM-41 grafted with octyldimethylsilane

Intrusion = Propagation

Extrusion depends on cavitation

(nucleation of the vapour phase)

B. Lefèvre et al., J. Colloid Surface A 2004, 241, 265.

p

471.122p4673.9168.366r

empyrical Kloubek-Rigby-Edler correlation for mercury retraction

Rigby and Edler, J. Colloid Interf. Sci. 2002, 250, 175

0

5

10

15

0 5 10 15

D(BdB) nm

D(W

ash

bu

rn)

nm

comparison of the pore size measured by mercury intrusion and N2 adsorption for MCM-41 (squares), SBA-15 (triangles)

and porous glass (circles) samples.

mercury porosimetry underevaluates the pore size for interconnected pore systems

Carbon replica of SBA-15 prepared at 100°C

Liu, Terasaki, Ohsuna, Hiraga, Shin, Ryoo, ChemPhysChem (2001) 229

The carbon rods formed inside the mesopores do not fall apart when the silica template is dissolved in HF

Carbon replica of SBA-15 prepared at 100°C

Liu, Terasaki, Ohsuna, Hiraga, Shin, Ryoo, ChemPhysChem (2001) 229

Disordered bridges connecting ordered parallel mesopores

Connections between pores depend on the conditions of synthesis

Galarneau, Cambon, Di Renzo, Ryoo, Choi, Fajula, New J. Chem. 27 (2003) 73

SBA-15 prepared at 60 °CThe platinum rods of the

replica do fall apart(same effect for MCM-41)

SBA-15 prepared at 100 °CInterconnected pores:

the platinum replica does not fall apart

50 nmPt-3532CPt-3522C

Pression of intrusion and retraction of mercury as a function of pore size from nitrogen adsorption

physical impossibility: contact angle higher than 180°

1.8

2

2.2

2.4

2.6

1.5 1.7 1.9 2.1 2.3

Log D(BDB) Angstrom

Lo

g P

/MP

a

intrusion

extrusion 110° 130°

180°

solids with pore interconnections

Evolution of the contact angle and the radius of the meniscus when mercury advances in a cylindrical pore with increasing diameter

Kloubek, Powder Technol. 1981, 29, 63; Galarneau et al., J. Phys. Chem. C 2008, 112,12921

Wenzel, J. Phys. Colloid Chem. 1949, 53, 1466

cos θrough = R* cos θflat

a higher pressure is needed to overcome the rim of a pore widening

surface roughness corresponds to an increase of contact angle

R* = ratio of the rough surface area to its projection on the average plane

Academic Press, 1982 Academic Press, 1999

Documents

matériaux avancés pour la catalyse et la santé