Development of Pt/Zirconia Catalyst for
liquid phase HI Decomposition Reaction
in S-I Cycle
Deepak Tyagi, Alisha Gogia, Salil Varma, A. K. Tripathi, S. R.
Bhabha Atomic Research Centre, Mumbai
Hydrogen as future fuel
• Hydrogen as a future source of energy is a scenario of
high probability and necessity, considering the illeffects of fossil fuel based systems on the environment
and also the depleting natural resources.
• The fast development of hydrogen based power
sources like fuel cells will lead to more efficient and
cleaner energy supply.
• For this to be economically feasible, large scale
production of hydrogen has to be attained by
environment friendly route.
Production of Hydrogen:
Today hydrogen is mainly produced from fossil resources.
In the long term, because of
increasing energy demand,
lack of fossil resources
limitations on the release of green house gases
Water suitable raw materials for hydrogen production.
Production of Hydrogen from Water:
The two processes that have the greatest
likelihood of successful massive hydrogen
production from water are (i) steam electrolysis
(ii) thermochemical cycles.
This way hydrogen can be produced from water
at temperatures much lower than the direct
water decomposition at 3000 °C.
As heat can be directly used in thermochemical
cycles, they have the potential of better
efficiency than alkaline electrolysis.
The required thermal energy can be provided by
nuclear reactor (CHTR).
Sulfur - Iodine Cycle
Exothermic; T = 120 °C
Endothermic; T = 870 °C
9I2 + SO2 + 16 H2O
Endothermic; T = 450 °C
(2HI + 10H2O + 8I2) + (H2SO4+ 4H2O)
Hydriodic Acid Decomposition
Decomposition of hydriodic acid an integral part of Sulfur - Iodine
and Magnesium – Iodine thermochemical cycle.
Homogeneous azeotrope in HI-H2O binary system and
thermodynamically limited slow gaseous HI decomposition - highly
energy consuming step.
1.The General Atomic Co. proposed use of phosphoric acid
(Extractive Distillation) for concentration of the HI solution to obtain
99.7% molar HI vapour. But, concentration of recycled phosphoric
acid consumes large amount of heat and electricity.
2.Employment of electro-electrodialysis concentration method and
hydrogen permselective membrane reactor also reported by JAERI.
3.Reactive distillation - combining reaction and separation in a single
step leading to overall shift of equilibrium towards production of I 2
and H2. First reported by Roth et al in 1989.
Catalyst reported for HI decomposition
IJHE 34(2009) 1688-1695
IJHE 34(2009) 5637-5644
IJHE 34(2009) 4059-4056
IJHE 34(2009) 4057-4064
IJHE 33(2008) 602 – 607
IJHE 33(2008) 2211-2217
Chinese chemical letters 20 (2009) 102-105
IJHE 35(2010) 445-451
“ D. R. O’keefe et al, Catalysis Reviews 22(3), 325-369 (1980)”
Objective of the present
• Develop Pt catalysts over Zirconia support (with
different Pt loading)
• Demonstrate stability of the catalysts under the
• Evaluate activity of these catalysts for HI
development of future catalysts
Preparation of Catalyst
Zirconyl Nitrate solution
NH4OH solution added dropwise
with constant stirring
Zirconium Hydroxide Gel
Dried at 100°C for 6h
Calcined at 350°C for 3h
(i) Add Chloroplatinic acid Dropwise
With constant stirring
(ii) Reduction by Hydrazine at RT
(iii) Reduction by H2 flow at 300 °C
Platinum Zirconia Catalyst
Activity & Stability of Catalysts
50 ml of 27% HI + 250 mg of Catalyst
Heated for 2h at ~ 120oC
Filtrate analyzed for presence of Pt by ICP-OES
Used catalyst evaluated by XRD and SEM.
Activity & Stability of Catalysts
→ 1 I 2 + 1 H 2
For liquid phase decomposition reaction, dissolution of the I2 formed at
catalyst surface into the iodide solution as Ix- and continued intimate
contact between HI and catalyst maintains high reactivity levels even in
presence of I2.
Upto 50% conversion is reported by O’Keefe et al for 48h study at room
Using Glass electrode
Using Ag/AgCl electrode
Titration against NaOH
Titration against AgNO3
NaOH was standardized
AgNO3 was standardized
Activity and stability of the catalysts
Pt/Zirconia catalyst prepared was active for HI
The percentage conversion is dependent on noble
Catalyst prepared was found to be stable under liquid
phase HI decomposition conditions.
Catalytic activity of Pt/Titania catalyst was better as
compared to some of the Pt/C catalysts.