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KINETICS OF HYDROLYSIS OF SODIUM BOROHYDRIDE USING COBALT CHLORIDE CATALYST

By Arshdeep Kaur

(Research scholar) Under guidance of

Dr. D. Gangacharyulu Pramod K. Bajpai

(Professor) (Distinguished Professor)

DEPARTMENT OF CHEMICAL ENGINEERINGTHAPAR UNIVERSITY

PATIALA-147004, INDIA. December 2013

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Outline of presentation Introduction

Literature Review

Experimental

Results and Discussions

Conclusion

Acknowledgements

References

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INTRODUCTION

3

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ENERGY FACTS

Fossil fuels are depleted at a rate

that is 100,000 times faster than

they are formed.

On average, 16 million tons of

carbon dioxide is emitted into the atmosphere every 24 hours by human use worldwide.

Coal is the single biggest air polluter and burning coal causes smog, soot, acid rain, global warming, and toxic air emission.

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Transition To Hydrogen Energy

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HYDROGEN FACTS

Hydrogen is considered as clean energy source and long term solution towards sustainable energy future.

1 kg of Hydrogen has same energy than 2.8 kg of gasoline, therefore hydrogen stores 2.8 times more energy than gasoline.

Effective storage of hydrogen is one of the key elements of hydrogen economy.

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LITERATURE REVIEW

7

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Lit. Rev....

Compressed Hydrogen Tanks Cyro-Compressed Hydrogen Storage

Storage in high pressurised tanks up to 700 bars.

Hydrogen cooled to 253oC and pressurised to 6 - 350 bars in insulated tanks.

High energy and cost requirements for pressurising gas in tanks .

Cost factors for cooling and pressurising hydrogen gas in tanks.

Physical storage in tanks

Compressed Gas Cryogenic Liquid

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Lit. Rev....

(A) Adsorption, hydrogen attaches to surface of molecules as hydrogen molecules.

(B) Absorption, hydrogen molecules dissociate into hydrogen atoms that are incorporated into the solid lattice framework .

Larger quantities of hydrogen in smaller volumes at low pressures and at temperature nearly equal to room temperature can be stored.

(C) & (D) Hydrogen is strongly bound within molecular structures, as chemical compounds containing hydrogen atoms.

Solid state hydrogen storage

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Storing hydrogen in chemical hydridesLit. Rev....

Source: M.Klanchar et al. [1]

Hydride reactions and hydrogen storage properties

Fraction H H2 Specific mass

(kg H / kg)

H2 Density

(kg H2 / liter)

LiH + H2O → LiOH + H2 0.126 0.25 0.122

NaH + H2O → NaOH + H2 0.042 0.083 0.106

CaH2 + 2H2 O → Ca(OH)2 + 2H2 0.048 0.095 0.121

MgH2 → Mg + H2 0.076 0.076 0.110

LiAlH 4 + H2 O → LiOH + Al + 2.5 H2 0.105 0.132 0.121

TiH2 → Ti + H2 0.040 0.040 0.152

LiBH 4 + H2O → LiOH + HBO2 + 4H2 0.184 0.367 0.235

NaBH4 + 2H2O→ NaBO2 + 4H2 0.105 0.211 0.226

Millennium Cell 35% Solution

NaBH4 + 4H2 O → NaBO2 + 4H2+ 2H2O 0.077 0.077

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Comparison of hydrogen storage properties

Lit. Rev....

Source: M. Klanchar et al. [1]

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Sodium borohydride hydrogen storage

Sodium borohydride reacting with water to produce hydrogen.

No side reactions or no volatile by products are formed.

Generated H2 is high purity (no traces of CO and S).

It is the least expensive metal hydride commercially available, and it is

safe to use, handle and store.

Hydrolysis Reaction

NaBH4 + 2H2O NaBO2 + 4H2

Lit. Rev....

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Comparison of chemical hydrides

Lit. Rev....

Source: Y. Wu et al. [2]

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Volumetric storage efficiency

Lit. Rev....

Source: Y. Wu et al. [2]

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Gravimetric storage efficiency

Lit. Rev....

Source: Y. Wu et al. [2]

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Cobalt chloride as a catalyst for hydrolysis reaction

CoCl2 + 2NaBH4 + 3H2O 25/4H2 + 1/2Co2B + 2NaCl

Cl- is neoclophilic in nature, Co2+ is electrophlic in nature, which increase its reactivity

toward BH- ions . Therefore this explains better reactivity of CoCl2 for NaBH4.

Lit. Rev....

Source:O.Akdim et al. [3]

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Lit. Rev......

S. No Hydrogen storage modes

Observations References

1. Hydrogen storage with chemical hydrides

Hydrogen fraction found best in LiBH4(0.184), LiH(0.126), LiAlH4 (0.105), NaBH 4 (0.105)

Klancher et al., 2003

2. Various modes of hydrogen storage

Energy density increases from compressed hydrogen storage <cryo- compressed hydrogen storage<adsorption <absorption<chemical hydrides

Cleveland, 2008

3. Hydrogen generation from chemical hydrides

Hydrogen storage system technologies , role of water in hydrolysis reaction are discussed

Marrero-Alfonso et al., 2009

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Lit. Rev....

S.No Catalyst Observations References

1. Carbon supported ruthenium catalyst

Rate kinetics studied, hydrolysis reaction with sodium borohydride was found to be is 1st order.

Shang , 2006

2.Co-B Hydrogen generation from NaBH4 using

Co- B catalyst.

Jeong et al., 2005

3. Co-BFirst order kinetics at low NaBH4 concentrations and zero order at high NaBH4 concentrations.

Dai et al.,2008

4. Cobalt (II) saltsCoCl2 showed best performance in hydrogen generation followed by Co(CH3OO)2>CoSO4>CoF2

Akdim et al., 2009

5.Acid treated CoCl2/Al2O3

Best performance was observed by HCl and CH3COOH followed by citric acid> oxalic acid>sulphuric acid.

Demirci, et al.,2009

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EXPERIMENTAL

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Chemicals

Sodium borohydride (NaBH4) powder with molecular weight of 37.8 g/mol and purity of 97%.

Cobalt chloride (CoCl2) salt powder in hexa-hydrate form, having molecular weight 237.93 g/mol with a purity of 98%.

NaOH pellets having molecular weight 39.9 g/mol and purity of 97% .

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Schematic diagram of experimental setup

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Experimental Setup

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RESULTS &

DISCUSSION

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Factors effecting the rate of hydrolysis reaction

1. Temperature

According to the hydrolysis reaction at concentration of NaBH4 equal to 0.55 g and CoCl2 concentration 0.06 g, rate of hydrogen generation increases with increase in temperature.

0 2 4 6 8 10 120

200

400

600

800

1000

1200

30◦C

35◦C

40◦C

45◦C

50◦C

Time(min)

rate

of

hydr

ogen

gen

erat

ion

(ml/m

in)

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Continued…

Rate constant with temperature can be expressed by Arrhenius equation

E is the apparent activation energy, A is the pre exponential factor ,R is the universal gas constant, and T is the reaction temperature, K.

The values of E and A were estimated by substituting the k values at 45 o

C and 63 °C, where E = 37.931 kJ/mol and A = 12.54 Χ 108 sec-1.

RT

E

Aek

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2. The Sodium Hydroxide (NaOH) Concentration

NaBH4 undergoes self hydrolysis and to suppress the self hydrolysis sodium hydroxide (NaOH)is added.

The excess amount of NaOH decreases the hydrogen yield.

Experimental results shows hydrogen generation rate decreases with increase NaOH concentration and temperature, at constant NaBH4 concentration and CoCl2 concentration.

Continued…

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3. The NaBH4 Concentration: The hydrogen generation rate increases with increase NaBH4 concentration with constant NaOH percentage.

Molality of NaBH4(mol/kg) CoCl2 (g) Temperature

(oC) NaOH (%)Hydrogen generation rate (ml/min)

1.19 0.05 45 0 300

1.45 0.06 45 0 480

1.71 0.07 45 0 520

1.98 0.08 45 0 600

1.19 0.05 55 0 320

1.45 0.06 55 0 420

1.71 0.07 55 0 480

1.98 0.08 55 0 560

1.19 0.05 63 0 340

1.45 0.06 63 0 480

1.71 0.07 63 0 560

1.98 0.08 63 0 620

Continued…

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Rate Kinetics

Rate increase with the increase of NaBH4 concentration at a fixed temperature and NaOH concentration.

where rH2 is the rate of hydrogen generation in milliliters per minute, mNaBH4 is the molality of NaBH4, and α is the apparent reaction order, k is proportionality constant.

Hydrogen generation rate decreased with the increase of NaOH concentration at a fixed NaBH4 concentration and temperature.

where , w NaOH is the concentration of NaOH in weight percent and k1 is a proportional constant.

4NaBH2

kmrH

NaOH1H wk1

1r

2

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Rate law of hydrogen generation from a basic NaBH4 solution can be expressed using equation ,

The parameters k/ (1 + k1wNaOH) and α can then be determined by regressing the maximum hydrogen generation rate and the initial NaBH4 concentration.

Calculated order of the reaction (α) w.r.t NaBH4 concentration equals 1 with experimental error ± 0.2 and is shown in tabulated form on next slide.

NaOH1

NaBH

H wk1

kmr 4

2

Continued…

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Parameters calculated at various temperature and NaOH concentrations

Temperature (◦C)NaOH concentration

(%)k/ (1 + k1WNaOH) α (Reaction Order)

25 0 133.62 1.2

35 0 226.16 0.94

45 0 271.10 1.2

55 0 283.68 0.96

63 0 377.09 1

25 1 214.32 1

35 1 345.50 0.95

45 1 438.12 0.98

55 1 676.88 1

63 1 871.15 1

35 3 241.65 1.2

45 3 375.21 1.2

55 3 566.79 1.2

63 3 464.05 1

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Calculation of the rate constants k and k1

Plot of 1/rH2 versus w NaOH /mNaBH4 gives a straight-line graph.

The intercept on the y axis is 1/kmNaBH4 and the slope is k1/k, from which both k and k1 may be determined.

4

4

2 NaBH

NaOH1NaBH

H m

w

k

km

k

1

r

1

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Calculations of the rate constants k and k1

Regression at 63oC and 1.45g of NaBH4

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Parameters calculated at various temperatures and NaBH4 concentrations

Molality (mol/kg) Temperature (o C) k (min-1) k1 (min-1)

1.19 35 192.30 0.02

1.19 45 555.55 0.13

1.19 63 1666.66 0.7

1.45 45 555.55 0.14

1.45 63 2000 0.8

1.71 35 740.74 0.4

1.71 45 769.23 0.6

1.71 63 2500 0.9

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Hydrogen Gas Qualitative Analysis by Pop Test

Light a wooden splint and then hold it to area that contain hydrogen, a squeaky pop is observed if hydrogen is present.

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Hydrogen gas quantitative analysis by gas chromatography

The Test shows the Purity of 85% with rest being nitrogen from air as per recovery basis from the sample.

A quantitative analysis test was conducted for hydrogen gas by Gas Chromatography, from Sophisticated Analytical Instrument Laboratory, Thapar University Patiala.

AIMIL-NUCON Gas Chromatograph

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Residual analysis

1. Scanning Electron Microscope (SEM): SEM was performed for the residual substance from Sophisticated Analytical Instrument Laboratory, Thapar University Patiala.

Residue analysis by SEM

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Continued…

2. Energy Dispersive Electron Microscopy (EDAX): EDAX was performed in Sophisticated Analytical Instrument Laboratory, Thapar University Patiala. It shows the presence of Sodium (Na), Cobalt (Co), Chlorine (Cl), Oxygen (O).

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CONCLUSIONS

Hydrolysis reaction of sodium borohydride with cobalt chloride as catalyst is a first order reaction.

Hydrogen generation rate increases with increase in temperature, sodium borohydride (NaBH4) concentration and decreases with sodium hydroxide (NaOH) concentration.

The rate constant ‘k’ with respect to sodium borohydride increased significantly from 555.50 min-1 to 1666.40 min-1 when the temperature increased from 45 to 63°C. However, rate constant ‘k1’ with respect to sodium hydroxide did not change significantly with NaBH4 concentration and temperature.

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Continued…

The gas chromatography analysis indicates, the hydrogen gas purity is 85% and rest is nitrogen. The tendency of sodium borohydride to store and release hydrogen is more effective and favorable.

The hydrogen generation rates are observed to be higher from hydrolysis studies of alumina nanoparticles - NaBH4 - CoCl2 system as compared to NaBH4 - CoCl2 systems.

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References

1. Shang, Y. and Chen, R., Semiempirical Hydrogen Generation Model Using Concentrated Sodium Borohydride Solution, J. Energy & Fuels, Vol. 20, No. 5, 2006, pp. 2149-2154.

2. Ying, W., Hydrogen Storage via Sodium Borohydride, Presented by Stanford University, 2003.

3. Liu, R.S.; Lai, H.C.; Bagkar, N.C.; Kuo, H.T.; Chen, H.N.; Lee, J.F.; Chung, H.J.; Chang, S.M.; and Weng, B.J., Investigation on Mechanism of Catalysis by Pt-LiCoO2 for Hydrolysis of Sodium Borohydride Using X-ray Absorption, J. Phys. Chem. B , Vol. 112, No. 16,2008 pp. 4870-4875.

4. Marrero-Alfonso, E.Y.; Beaird, A.M.; Davis, T.A.; Matthews, M.A., Hydrogen Generation from Chemical Hydrides, Ind. Eng. Chem. Res., Vol.48, No.8,2009 pp.3703-3712.

5. Shang, Y. and Chen, R., Hydrogen Storage via the Hydrolysis of NaBH4 Basic Solution, Optimization of NaBH4 Concentration, Energy & Fuels, Vol. 20, No. 5, 2006, pp.2142-2148.

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Continued...

6. Cleveland, C.J., Hydrogen storage, Encyclopaedia of Earth, 2008.

7. Klanchar, M.; Hughes, T.G.; Gruber, P., Attaining DOE Hydrogen storage Goals with Chemical Hydrides, Applied Research Laboratory, The Pennsylvania State University, 2003.

8. Klanchar, M.; Lloyd, C.L.; Compact Hydrogen Generating Systems Based on Chemical Sources for Low and High Power Applications, Proceedings of the 39 th

Power Sources Conference, 2000, pp. 188-191.

9. McClaine, A.W., Chemical Hydride Slurry for Hydrogen Production and Storage, New FY 2004 Project, U. S. Department of Energy, Office of Energy Efficiency and Renewable Energy, FY 2003 Progress Report for Hydrogen, Fuel Cells, and Infrastructure Technologies Program, October 2003.

10. Wu, Y., Process for the Regeneration of Sodium Borate to Sodium Borohydride for Use as a Hydrogen Storage Source, New FY 2004 Project, U. S. Department of Energy, Office of Energy Efficiency and Renewable Energy, FY 2003 Progress Report for Hydrogen, Fuel Cells, and Infrastructure Technologies Program, October 2003.  

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11. Hydrogen, Fuel Cells & Infrastructure Technologies Program Multi- Year Research, Development and Demonstration Plan, Department of Energy, Washington D.C., 2005.

12.  Zuttel, A., Hydrogen Storage Methods, Springer-Verlag, Vol. 91, No. 4, 2004, pp. 157–172.

13.  Aggrawal, R.; Offutt, M.R.; Ramage, M.P., Hydrogen Economy and Opportunity for Chemical Engineers, AIChE journal,Vol.51, No. 6, 2005, pp. 1582–1589.

14.  Kennedy, D., The Hydrogen Solution Science, Journal of American Chemical Society, Vol. 305, No.5686, 2004, pp.917.

15.  Ritter, J.; Ebner, A.; Wang, A.D.; Zidan, J., Implementing a Hydrogen Economy, Journal of Physical Chemistry, Vol.6, No. 9, 2003, pp.18–23. 

16. Othmer, K., Encyclopedia of Chemical Technology, 4th ed., Vol. 13, pp. 606-629, New York 1991.

17. James, B.D.; Wallbridge, G.H., Metal Tetrahydroborates, Prog. Inorg. Chem, Vol. 11, 1970, pp. 99–231.

18. Shang, Y. and Chen, R., Hydrogen Storage via the Hydrolysis of NaBH4 Basic Solution: Optimization of NaBH4 Concentration, Energy &Fuels, Vol.20, No.5, 2006, pp. 2142–2148.

19. www.eia.gov

Continued...

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Acknowledgements

The authors gratefully acknowledge the support provided by management of Thapar University, Patiala and Thapar Centre for Industrial Research and Development, Patiala, India, for providing the necessary facilities to carry out this research work.

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THANK YOU

44

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QUESTIONS ?