Presentation slide

1. Kinetics of Glycerol Steam Reforming
Catalyzed by Bimetallic Co-Ni/Al2O3
Chin Kui Cheng Say Yei Foo and Adesoji A. Adesina
Cheng,
Reactor Engineering & Technology Group
School of Chemical Engineering
The University of New South Wales
Sydney, Australia
21st International Symposium on Chemical Reaction Engineering
Sunday June 13th - Wednesday June 16th, 2010
Loews Philadelphia Hotel, Philadelphia, PA, USA

2. Glycerol as potential feedstock
• Glycerol is produced in mass quantity as by-product of
biodiesel industry.
• Glycerol is inedible, thus poses no direct competition as
is the case with food derivatives.
• Glycerol has limited use; mainly in pharmaceuticals.
• Glycerol is a relatively non-volatile liquid and easily
transported.

3. Biodiesel industry

4. Glycerol – Reforming Source
Main Reaction:
C3H8O3 (g) + 3H2O (g) ↔ 3CO2 (g) + 7H2 (g) (1)
May be viewed as combination of:
(i) Glycerol decomposition
C3H8O3 (g) ↔ 3CO (g) + 4H2 (g) (2)
(i) Water-gas-shift reaction (WGS)
CO (g) + H2O (g) ↔ CO2 (g) + H2 (g) (3)

6. Advantages of Glycerol Steam
Reforming
• Simple set up with minimal control instruments.
• Higher operating temperatures (> 773 K) enable the use
of cheaper metals as catalysts, e.g. Ni, Co
• Reforming in vapour phase minimizes metal leaching
from catalysts - problem faced by aqueous phase
reforming technique.
• Thermodynamically, reaction is more favourable for H2
production, while at the same time coking is reduced
under low (atmospheric) pressure.

7. Experimental
Catalyst Preparation Co-Ni/Al2O3
+
Al2O3 support
Precursors
Drying/calcination
Titration
Sieving

8. EXPERIMENTAL SETUP
Reaction Study Description Value
Reactor Type Fixed-Bed (10mm ID)
Syringe Pump 50 mL
Pressure 1 atm
Reaction Temp. 773 – 823 K
Vaporizer STGR (3 – 12) : 1 ratio

9. Results – fresh catalyst
characterization

10. Temperature-programmed thermal studies
Calcination profiles XRD pattern
Co(NO3)2 → CoO + N2O5
Ni(NO3)2 → NiO + N2O5
i) Thermal decomposition of metal nitrates
3CoO + ½O2 → Co3O4
ii) Oxidation of metal oxide to mestable oxide Co3O4 + 2NiO + CoO + ½O2 → 2NiCo2O4
phase
iii) Formation of metal-aluminate phase NiO / CoO + Al2O3 → NiAl2O4 / CoAl2O4

11. Temperature-programmed thermal studies
Summary table of TPR studies
Peak Reduction Reduction process
temperature
(K)
(1) 620 NiO and Co3O4 Ni & CoO
(2) 670 - 790 NiCo2O4 Ni & CoO
CoO Co
(3) 973 NiAl2O4 & CoAl2O4 Ni & Co

12. Results – Kinetic studies
Glycerol consumption rate at 823 K

13. Yield as function of (a) Pglycerol and (b) Psteam at T = 823 K

14. Product ratio as function of (a) Pglycerol and (b) Psteam at T = 823 K

15. Arrhenius plot (Steam to Glycerol Ratio = 12)

16. Power-law Modelling
(ri ) = Ae − E /RT Pglycerol Psteam
A β γ

17. Mechanistic Modelling
• Mechanistic modelling was based on
i) Langmuir-Hinshelwood, and
ii) Eley-Rideal mechanism
• Bimolecular surface reaction was assumed as
r.d.s.
• Model discrimination based on
(i) Statistical regression result, and
(ii) Thermodynamic limitation (BMV criteria)

18. Langmuir-Hinshelwood

19. Eley-Rideal Mechanism

20. Langmuir-Hinshelwood (LH) Eley-Rideal (ER)
k rxn PG PW k rxn PG PW k rxn PG PW
(1 + K G PG + KW PW )2 (1 + ) 9 (1 + K P )
1 7 2
K G PG + K W PW G G
k rxn PG PW k rxn PG PW k rxn PG PW
2
(1 + K G PG )(1 + K W PW ) 8
(1 + )(
K G PG 1 + K W PW ) 10
(1 + K G PG )
k rxn PG PW k rxn PG PW
(1 + K )
11
3
GP +
G K W PW
2
(1 + KW PW )
k rxn PG PW k rxn PG PW
4
(1 + K G PG )(1 + K W PW )
12
(1 + K W PW )
k rxn PW PG
(1 + K )
5 2
WP +
W K G PG
Best model
k rxn PW PG with
6
(1 + K W PW )(1 + K G PG ) E = 69.4 kJ mol-1
krxn = 5.57 × 10-7 at 823 K
KG = 0.283 at 823 K
KW = 0.0369 at 823 K

21. Results – used Catalyst
characterization
TOC Analysis (823 K)
• At fixed Psteam, TOC
with Pglycerol
• At fixed Pglycerol, TOC
is nearly unchanged
with Psteam

22. BET/ pore volume of used catalysts

23. Regeneration of used catalysts
TPO-TPR-TPO-TPR TPR-TPO-TPR-TPO

24. conclusions
• H2 and CO2 were the main products of glycerol steam
reforming. CH4 was present in minimal concentration.
• Power-law modelling indicate that glycerol steam
reforming can be presented by (− rGSF ) = Ae −7.6×10 / T Pglycerol Psteam
3
0.25 0.36
• L-H model ; based on molecular adsorption
of both reactants on two different sites was the best
mechanistic model.
• Carbon deposition is a strong function of Pglycerol while
weakly inhibited by Psteam.
• Temperature-programmed gasification with H2 or O2
showed the presence of at least two types of carbon
species on used catalyst surface.

25. Question time