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  • Hydrogen Use <br />

82 deepak tyagi 82 deepak tyagi Presentation Transcript

  • 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. Bharadwaj Chemistry Division 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. ICAER-2013, IITB
  • ICAER-2013, IITB
  • Production of Hydrogen: Today hydrogen is mainly produced from fossil resources. Origin Percent Natural gas 48 Oil 30 Coal 18 Electrolysis 4 Total 100 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. ICAER-2013, IITB
  • 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). ICAER-2013, IITB
  • Sulfur - Iodine Cycle Exothermic; T = 120 °C Endothermic; T = 870 °C 9I2 + SO2 + 16 H2O ICAER-2013, IITB → 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. ICAER-2013, IITB
  • Catalyst reported for HI decomposition Ceria 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)” ICAER-2013, IITB
  • Objective of the present Work • 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 ICAER-2013, IITB
  • 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 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
  • Characterization: • XRD • SEM • FEG-SEM • N2 Adsorption • ICP OES ICAER-2013, IITB
  • Intensity X-Ray Diffraction: 120 100 80 60 40 20 0 120 10 100 80 60 40 20 0 120 10 100 80 60 40 20 0 10 ICAER-2013, IITB 2 % Pt/ZrO2 20 30 40 50 60 70 1 % Pt/ZrO2 20 30 40 50 60 70 0.5 % Pt/ZrO2 20 30 40 2θ 50 60 70
  • SEM & EDAX: ICAER-2013, IITB
  • FEG-SEM: ICAER-2013, IITB
  • Adsorption and Desorption isotherms 1% Pt/ZrO2 ICAER-2013, IITB 2% Pt/ZrO2
  • Pore Size Distribution: 1% Pt/ZrO2 ICAER-2013, IITB 2% Pt/ZrO2
  • Surface Area: S. No 1. Sample Surafce Area Pore Size Pore Volume 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 ICAER-2013, IITB
  • Activity & Stability of Catalysts 50 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. ICAER-2013, IITB
  • Activity & Stability of Catalysts HI ← → 1 I 2 + 1 H 2 2 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 temperature. ICAER-2013, IITB
  • Activity 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 ICAER-2013, IITB
  • Activity and stability of the catalysts S. No. % Conversion 1. 0.5% Pt/ZrO2 13.9 % 2. 1% Pt/ZrO2 16.7 % 3. ICAER-2013, IITB Catalyst 2% Pt/ZrO2 18.5 %
  • XRD Used Catalysts: 100 80 Used 2% Pt/ZrO2 60 40 20 Intensity 0 120 20 100 80 60 40 20 0 120 20 100 80 60 40 20 0 20 30 40 50 70 Used 1% Pt/ZrO2 30 40 50 60 70 Used 0.5% Pt/ZrO2 30 40 50 2θ ICAER-2013, IITB 60 60 70
  • Comparison with Pt/Carbon catalysts S. No. % 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 ICAER-2013, IITB Catalyst Blank 2.8 %
  • Conclusions Pt/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. ICAER-2013, IITB
  • ICAER-2013, IITB