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Development of Pt/Zirconia
Catalyst for liquid phase HI
Decomposition Reaction in S-I
CycleDeepak Tyagi, Alisha Gogia, Salil Varma, A. K. Tripathi, S. R. Bharadwaj
Chemistry DivisionBhabha Atomic Research Centre, Mumbai
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• Hydrogen as a future source of energy is a scenario of high probability and necessity, considering the ill-effects 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.
Hydrogen as future fuelHydrogen as future fuel
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Origin Percent
Natural gas 48
Oil 30
Coal 18
Electrolysis 4
Total 100
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Today hydrogen is mainly produced from fossil resources.
In the long term, because ofincreasing energy demand,lack of fossil resourceslimitations on the release of green house gases
Water suitable raw materials for hydrogen production.
Production of Hydrogen:Production of Hydrogen:
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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).
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Production of Hydrogen from WaterProduction of Hydrogen from Water::
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Sulfur - Iodine Sulfur - Iodine
CycleCycle
Endothermic; T = 450 °CEndothermic; T = 870 °C
Exothermic; T = 120 °C
9I2 + SO2 + 16 H2O → (2HI + 10H2O + 8I2) + (H2SO4+ 4H2O)
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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 I2 and H2. First reported by Roth et al in 1989.
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Hydriodic Acid Hydriodic Acid DecompositionDecomposition
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Catalyst reported for HI Catalyst reported for HI
decompositiondecompositionCeria IJHE 34(2009) 1688-
1695
Ni/Ceria IJHE 34(2009) 5637-5644
IJHE 34(2009)8792-8798
Ni/Alumina IJHE 34(2009) 4059-4056
Activated Carbon IJHE 34(2009) 4057-4064
Pt/Ceria IJHE 33(2008) 602 – 607
IJHE 33(2008) 2211-2217
Pt/Alumina Chinese chemical letters 20 (2009) 102-105
Pt/Ceria-Zirconia IJHE 35(2010) 445-451
“ D. R. O’keefe et al, Catalysis Reviews 22(3), 325-369 (1980)”
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Objective of the present Objective of the present
WorkWork
• Develop Pt catalysts over Zirconia support (with different Pt loading)
• Demonstrate stability of the catalysts under the reaction conditions
• Evaluate activity of these catalysts for HI decomposition reaction
• Derive structure activity correlation for development of future catalysts
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Zirconium Hydroxide Gel
Dried at 100°C for 6h
Calcined at 350°C for 3h
Zirconia
(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
Zirconyl Nitrate solution
NH4OH solution added dropwisewith constant stirring
Preparation of Preparation of CatalystCatalyst
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Characterization:Characterization:
• XRD
• SEM
• FEG-SEM
• N2 Adsorption
• ICP OES
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X-Ray Diffraction:X-Ray Diffraction:
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10 20 30 40 50 60 70
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0.5 % Pt/ZrO2
Inte
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10 20 30 40 50 60 70
020406080
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1 % Pt/ZrO2
10 20 30 40 50 60 70
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2 % Pt/ZrO2
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SEM & EDAX:SEM & EDAX:
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FEG-SEM:FEG-SEM:
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1% Pt/ZrO2 2% Pt/ZrO2
Adsorption and Desorption Adsorption and Desorption isotherms isotherms
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Pore Size Pore Size Distribution:Distribution:
1% Pt/ZrO2 2% Pt/ZrO2
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S. No
Sample Surafce Area
Pore Size
Pore Volume
1. ZrO2 108.64 3.62 0.1125
2. 1%Pt ZrO2 139.71 3.72 0.1573
3. 2%Pt ZrO2 133.47 3.72 0.1492
Surface Area:Surface Area:
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Activity & Stability of Activity & Stability of
CatalystsCatalysts50 ml of 27% HI + 250 mg of Catalyst
Heated for 2h at ~ 120oC
Filtered
Filtrate analyzed for presence of Pt by ICP-OES
&Used catalyst evaluated by XRD and
SEM.
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Activity & Stability of Activity & Stability of CatalystsCatalysts
221
221 HIHI
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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 temperature.
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Activity MeasurementActivity Measurement
H+ Titration I- Titration
Using Glass electrode Using Ag/AgCl electrode
Titration against NaOH Titration against AgNO3
NaOH was standardized using KHP
AgNO3 was standardized using NaCl
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Activity and stability of the Activity and stability of the
catalystscatalysts
S. No. Catalyst % Conversion
1. 0.5% Pt/ZrO2 13.9 %
2. 1% Pt/ZrO2 16.7 %
3. 2% Pt/ZrO2 18.5 %
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20 30 40 50 60 70
020406080
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Used 0.5% Pt/ZrO2
Inte
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Used 1% Pt/ZrO2
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Used 2% Pt/ZrO2
XRD Used Catalysts:XRD Used Catalysts:
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Comparison with Pt/Carbon Comparison with Pt/Carbon catalystscatalysts
S. No.
Catalyst% Conversion(H+ Titration)
1 Pt/Gr 17.5 %
2 Pt/SBA 15.0 %
3 Pt/MCM-C 17.0 %
4 Pt/Zirconia 16.7 %
5 Pt/AC 12.1 %
6 Pt/FS-C 7.2 %
7 Blank 2.8 %
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ConclusionsConclusionsPt/Zirconia catalyst prepared was active for HI decomposition.
The percentage conversion is dependent on noble metal loading.
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.
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