Promotion of Pt Nanoparticles by Lattice Oxygen in Smfeo3 Perovskite Group for Carbon

Promotion of Pt nanoparticles by lattice oxygen in SmFeO3 perovskite group for carbon monoxide and ethylene oxidation

Rima J. Isaifana, William D. Penwellb, Joao O.C. Filizzolaa, Javier B. Giorgib,

Elena A. Baranovaa*

a Department of Chemical and Biological Engineering, Centre for Catalysis Research and Innovation,

b Department of Chemistry, Centre for Catalysis Research and Innovation,

University of Ottawa, 161 Louis-Pasteur Ottawa ON, Canada, K1N 6N5

Supporting information

Figure S1 shows CO and ethylene conversion as a function of temperature over bare supports for complete oxidation of 909 ppm (a) CO, (b) C2H4, 3.5% O2, balance He.

(a) /
(b) /

Figure S1. Conversion of CO (a) and C2H4 (b) as a function of temperature on various materials as indicated in the figure. F = 77 mL·min-1, [Reactant] = 909 ppm, He balance, Po2 = 3.5 kPa.

Figure S2 shows the conversion as a function of temperature of supported Pt nanoparticles for complete oxidation of 909 ppm (a) CO, (b) C2H4, 3.5% O2, balance He.

(a) /
(b) /

Figure S2. Conversion of CO (a) and C2H4 (b) as a function of temperature over Pt nanoparticles supported on various materials as indicated in the figure. Conditions idem.

Figure S3 shows CO and C2H4 oxidation over the bare perovskites: a) SCF-0, b) SCF-1 and c) SCF-5. Three cycles were repeated for each experiment to show catalyst stability and reproducibility.

Figure S3. Conversion of CO (left side) and C2H4 (right side) as a function of temperature over the bare perovskites (a) SCF-0, (b) SCF-1 and (c) SCF-5. Conditions idem.

Figure S4 shows the reaction rate of Pt/SCF catalysts towards CO and C2H4 oxidation as a function of temperature.

(a) /
(b) /

Figure S4. Oxidation reaction rate for (a) CO and (b) C2H4 on supported catalysts as indicated in the Figure. F = 77 mL·min-1, [Reactant] = 909 ppm, He balance, Po2 = 3.5 kPa.

Mass and Heat Transfer limitation calculations for carbon monoxide and ethylene oxidation over Pt/YSZ, Pt/SCF-0, Pt/SCF-1, Pt/SCF-5 and Pt/γ-Al2O3

Assume all nanoparticles are spherical, non porous and uniform in shape with the average particle sizes deduced from TEM images as per Table 1 in the manuscript.

All calculations are based on the maximum rate at the highest temperature in each run, at which high conversions were achieved within the temperature range of experiments

1- Weisz-Prater Criterion for Internal Mass Diffusion (Fogler, p839)

External mass and heat transfer limitations were evaluated for the highest catalytic reaction rate of each experiment using Weisz - Prater criterion for internal mass diffusion [38,39]:

(S-1)

where,

CWP is Weisz-Prater number, r’A(obs) = observed reaction rate (kmol · kg-cat-1·s-1) preferably at the highest temperature, ρc = solid catalyst density (kg · m-3), R = catalyst particle radius (m), De = effective gas-phase diffusivity (m2·s-1) and CAs is the gas concentration of CO or C2H4 (kmol · m-3).

The mass and heat interphase and intraparticle transport limitations were calculated using Weisz-Hicks criterion [40-42]:

<1 (S-2)

with,

and

where;

Ea: the apparent activation energy (J · mol-1), R: gas constant = 8.314 (J · m-1 · K-1), T is preferably the maximum temperature at which high reaction rates are observed (K), ΔHr: heat of reaction = -283x103 (J · mol-1) for CO combustion and -1411 x103 (J · mol-1) for ethylene combustion, k: catalyst thermal conductivity = 70 (W ·m-1·K-1) for platinum , CAs is the gas phase concentration, provided that external mass transfer limitations are negligible, De is the effective diffusivity is theaverageof thegrain boundary diffusion coefficientand thelattice diffusion coefficient.

If , then internal mass transfer effects can be neglected.

r’A(obs) = observed reaction rate, kmol/kg-cat · s, where kg-cat corresponds to kg-Pt only.

R = catalyst particle radius, m

ρc = solid catalyst density, kg/m3; [ρc, for Pt = 21090 kg/m3]

De = effective gas-phase diffusivity, m2/s [Fogler, p 815]

= where

DAB = gas-phase diffusivity m2/s; DAB= 2.03x10-9 m2/s for CO and 1.87x10-9 m2/s for C2H4 [Cussler, E. L. (1997).Diffusion: Mass Transfer in Fluid Systems(2nd ed.). New York: Cambridge University Press]

= pellet porosity;=constriction factor; =tortuosity, all assumed to be unity for nonporous, uniform spherical nanoparticles.

CAs = gas concentration of A at the catalyst surface, = 0.00003 kmol CO/m3 and 0.00003 kmol C2H4/m3

Pt/YSZ, R = (2.9/2) nm =1.45 nm for CO oxidation at Tmax of full conversion (T=140oC and corresponding rate of 4.69x10-9 mol/s in fig. S-4 (a))

rA(obs)= (4.69x10-9 mol CO2/s x molCO/molCO2x 1 Kmol/1000 mol)/( 0.052 g total catalyst x0.011 g Pt/ g total catalyst x 1 Kg/1000 g)= 8.849x10-6 Kmol CO/Kg cat. s

= [8.849 ´ 10-6 kmol-CO/kg-cat . s]´[ 2.109´104 kg-cat/m3] ´ [ 1.45 x 10-9 m]2 / ([2.03 x 10-9 m2/s] ´ [0.00003 kmol-CO/m3]) = 6.5´ 10-6 < 1

Pt/YSZ, R =(2.9/2) nm =1.45nm for C2H4 oxidation at Tmax of full conversion (T=200oC and corresponding to rate of 4.69x10-9 mol/s in fig. S-4 (b))

rA(obs)= (4.69x10-9 mol CO2/s x molC2H4 /2molCO2x 1 Kmol/1000 mol)/( 0.052 g total catalyst x0.011 g Pt/ g total catalyst x 1 Kg/1000 g)= 4.5 x10-6 Kmol CO/Kg cat. s

=[4.5 ´ 10-6 kmol-C2H4/kg-cat . s]´[ 2.109´104 kg-cat/m3] ´ [ 1.45 x 10-9 m]2 / ([1.87 x 10-9 m2/s] ´ [0.00003 kmol-C2H4/m3]) = 3.5´ 10-6 < 1

Similar calculations were performed to the rest of the catalysts and summary of results are in the tables S1 – S3:

Table S1. Weisz-Prater criterion for internal mass diffusion for CO and C2H4 oxidation

Catalyst / R (nm) / CWP for CO oxidation / CWP for C2H4 oxidation
Pt/YSZ / 1.45 / 6.5´ 10-6 / 3.5´ 10-6
Pt/g-Al2O3 / 1.25 / 6.9´ 10-6 / 3.7´ 10-6
Pt/SCF-0 / 1.40 / 6.0´ 10-6 / 3.3´ 10-6
Pt/SCF-1 / 1.60 / 7.5´ 10-6 / 4.1´ 10-6
Pt/SCF-5 / 1.50 / 6.9´ 10-6 / 3.7´ 10-6

2- Weisz-Hicks Criterion for Intraparticle mass and heat transfer Diffusion [Weisz-Hicks 1962 and Mears 1971]

; ;

Ea: activation energy, J/mol

R: gas constant = 8.314 J/mol.K

T: preferably maximum temperature at which high reaction rates are observed, K

ΔHr : heat of reaction = -283x103 J/mol for CO combustion and -1411kJ/mol for ethylene combustion

k: catalyst thermal conductivity

Pt/YSZ for CO oxidation

Ea = 35.8 kJ/mol

Tmax =T100 =140oC = 413K

γ = 35.8x103 J/mol /[8.314 J/mol.K x 413 K] =10.4

β =[ -283x103 J/mol x 2.03 x10-9 m2/s x 0.03 mol/m3]/[70 J/m.s.K x 413K]= -6.0x10-10

=6.5´ 10-6 x (0.99) = 6.5x10-6<1

Table S2. Weisz-Hicks Criterion for Intraparticle mass and heat transfer Diffusion for CO oxidation

Catalyst / R (nm) / CWP / Tmax (K) / Ea
kJ/mol / γ / Β / 
Pt/YSZ / 1.45 / 6.5´ 10-6 / 413 / 35.8 / 10.4 / -6.0x10-10 / 6.5´ 10-6
Pt/g-Al2O3 / 1.25 / 6.9´ 10-6 / 398 / 57.1 / 17.3 / -6.2x10-10 / 6.9´ 10-6
Pt/SCF-0 / 1.40 / 6.0´ 10-6 / 403 / 42.4 / 12.7 / -6.1x10-10 / 6.0´ 10-6
Pt/SCF-1 / 1.60 / 7.5´ 10-6 / 403 / 33.2 / 9.9 / -6.1x10-10 / 7.5´ 10-6
Pt/SCF-5 / 1.50 / 6.9´ 10-6 / 383 / 25.7 / 8.1 / -6.4 x10-10 / 6.9´ 10-6

Pt/YSZ for C2H4 oxidation

Ea = 22 kJ/mol

Tmax =T100 =200oC = 473K

γ = 22x103 J/mol /[8.314 J/mol.K x 473 K] =5.59

β =[ -1411x103 J/mol x 1.87 x10-9 m2/s x 0.03 mol/m3]/[70 J/m.s.K x 473K]= -2.39x10-9

=3.5´ 10-6 x (0.99) = 7.5x10-6<1

Table S3. Weisz-Hicks Criterion for Intraparticle mass and heat transfer Diffusion for C2H4 oxidation

Catalyst / R (nm) / CWP / Tmax (K) / Ea
kJ/mol / γ / Β / 
Pt/YSZ / 1.45 / 3.5´ 10-6 / 473 / 22.0 / 5.59 / -2.4x10-9 / 3.5´ 10-6
Pt/g-Al2O3 / 1.25 / 3.7´ 10-6 / 433 / 32.0 / 8.88 / -2.6x10-9 / 3.7´ 10-6
Pt/SCF-0 / 1.40 / 3.3´ 10-6 / 473 / 34.1 / 8.67 / -2.4x10-9 / 3.3´ 10-6
Pt/SCF-1 / 1.60 / 4.1´ 10-6 / 453 / 18.3 / 4.85 / -2.5x10-9 / 4.1´ 10-6
Pt/SCF-5 / 1.50 / 3.7´ 10-6 / 443 / 20.5 / 5.56 / -2.6x10-10 / 3.7´ 10-6

All values obtained in Table S1- Table S3 are far less than unity, which indicates the absence of internal mass and heat-transfer resistances.

To insure that the catalyst temperature does not vary at the time of measurement, the thermocouple was attached to the vicinity of the catalyst bed as per the following illustration.

Figure S3. Illustration of the thermocouple position at the vicinity of the catalyst bed.

The temperature of the catalyst bed was left to stabilize for 30 minutes before taking measurements, each measurement was repeated for 3 times to check stability, the total time of the 3 measurement is about 12-15 another minutes.

Moreover, 2 thermocouples were used to measure the temperature difference at the top and the bottom of the catalyst bed; location (a) and (b) in Figure 3. No temperature difference was observed to the nearest 1oC when the temperature reached steady state.

Catalyst active surface area (CASA) calculations:

The following shows an example of the catalyst active surface area calculation considered in this manuscript.

The active surface area based on the dispersion values depicted from CO titration of each catalyst has been added to Table 1 as recommended.

*assuming all particles are identical in size and spherical, for example, let’s take Pt/SCF-5 which has a particle size of 3 nm.

1. Known Parameters:

Pt atomic surface area à 8.06 x 10-20

Dispersion à ex. 37.7%

Avogardo number à 6.023 x1023

Mass of Catalyst à ex. 0.053 g

Metal Loading à ex. 1%

CASA= moles Pt x dispersion x NAV x Pt atomic surface area

CASA= (0.053 g x 0.01 /195.08 g/mol) x 0.01 x (37.7/100) x 6.023x1023 atom/mol x 8.06x 10-20 m2/atom

= 0.0497 m2