Hydrogen Generation using Chemical Catalysts.

Martin Wills, David J. Morris, Tarn Johnson, Department of Chemistry, University of Warwick, Coventry, UK.

Joe Wood, Bushra Al-Duri, Suzanne Al-Samaq School of Chemical Engineering, University of Birmingham, UK.

Most attractive aspect of hydrogen generation from organic molecules is that up to half thehydrogen comes from water.

i.e. Organic molecules lever hydrogen out of water!

Potential energy content of hydrogen in organic molecules-

C6H12O6 + 6 H2O 12 H2 + 6 CO2

Glucose; 6 out of 12 hydrogen molecules are from water.

C3H8O3 + 3 H2O 7 H2 + 3 CO2

Glycerol; 3 out of 7 hydrogen molecules are from water.

Value of hydrogen produced:15,813 kJ per Kg of glucose

Value of hydrogen produced:18,050 kJ per Kg of glycerol

Comparisons:

Liquid hydrogen has an energy content of 118,600 kJ per Kg, but the volume is 14.2 Litres.

A typical hydrocarbon (hexane) has an energy content of 46,711 kJ per Kg (about 1.2 L).

A material containing 10% hydrogen (by mass) has ca. 11,860 kJ per Kg energy content.

Development of catalysts for hydrogen generation from alcohols at Warwick.

RuN Cl

HPh

Ph

N

TsRhN

Ph

Ph

N

TsH

H

Rhodium catalyst Ruthenium catalyst

Transfer hydrogenationcatalysts:

Ph Me

O 0.1 mol% rhodium orruthenium catalyst

O

HO

O

H

H

H Ph Me

O

or

H

H

The catalysts transfer hydrogenFrom an alcohol or formic acidTo a ketone substrate:

A. M. Hayes, D. J. Morris, G. J. Clarkson and M. Wills, J. Am. Chem. Soc. 2005, 127, 7318. J. Hannedouche, G. J. Clarkson and M. Wills, J. Am. Chem. Soc. 2004, 126, 986. D. S. Matharu, D. J. Morris, A. M. Kawamoto, G. J. Clarkson and M. Wills, Org. Lett. 2005, 7, 5489.

Application to hydrogen generation from formic acid.

Formic acid delivers relatively little energy per Kg, but benefits from a strong thermodynamicdriving force.

HCO2H H2 + CO2 5,156 kJ per Kg of formic acid

Hydrogen generation by decomposition of formic acid

H

OH

O

RhN

Ph

Ph

N

Ts

RhN

Ph

Ph

N

Ts

TS

HCO2H

RhN

Ph

Ph

N

TsH

H

-CO2

H2

16e -species

no substrate-hydrogen released

By removing the substrate, the catalysts take an alternative path and release hydrogen gas:

6.3 mg catalyst in 2,5 mL of a 5:2 azeotrope of formic acid: triethylamine (FA:TEA).

TON = turn over number = moles hydrogen per mole of catalyst.TOF = turn over frequency = moles hydrogen per mole of catalyst per hour.

0

100

200

300

400

500

600

700

800

900

0 50 100 150 200 250 300 350 400

T/min

tota

l g

as/T

ON

/TO

F

Total gas (50% is hydrogen)

TON (Mol H2/Mol cat)

TOF (TON/hr)

H2 + CO2HCO2H

0

2

4

6

8

10

12

14

16

0.00 20.00 40.00 60.00 80.00 100.00

Series1

Time/minutes

H2/L

Simple Ru(II) complexes are efficient at higher temperatures:10ml of 5:2 HCO2H/Et3N and 25µmol (ca 12.1 mg) [RuCl2(DMSO)4] at 120oC.

Boddien, A.; Loges, B.; Junge, H.; Beller, M. Angew. Chem. Int. Ed. 2008, 47, 3962-3965. Fellay, C.; Dyson, P. J.; Laurenczy, G. Angew. Chem. Int. Ed. 2008, 47, 3966-3968.

The formic acid sample is heated in the round-bottom flask fitted with a thermometer to monitor internal temperature.Two gas syringes are attached, allowing seamless monitoring of gas flow.In the picture above, the gas is being diverted into a small PEM fuel cell, which is running an electric fan.Reproduced with permission of Aman Dhir, Department of Chemical Engineering, Birmingham University.

Warwick research on Hydrogen From Formic Acid:

Dr David Morris, Professor Martin Wills and Professor Kevin Kendall.

EPSRC feasibility study grant EP/031168/01

What are the gases?

FTIR revealed CO2 at 2350 cm-1 but no CO at 2200 cm-1.

Formic acid

triethylamine 5:2120oC

H2 CO2+RuCl2DMSO4 CO+

Hydrogen PEM fuel cell poweringa fan with the hydrogen from the reaction.

The same sample was then spiked with CO, and it then clearly showed up.

A gas sample was captured at the point where the maximum TOF was reached. This was then analysed below.

The new peak ca. 2171 and 2119 cm-1 correspond to CO which is reported to be ca. 2170-2180 cm-1. (see Krebs reference above). An expansion of the overlaid spectra is shown below. There is actually ca. 250-350 ppm CO in the CO in the gases produced by FA decomposition under the conditions used.This has been measured by GC (thanks to Gerald Chapman and Colin Murrell in Biological Sciences).

CO2

CO

min1 2 3 4 5 6 7 8 9

pA

0

5000

10000

15000

20000

25000

30000

35000

FID1 A, (20080608\FID000531.D)

0.72

9

1.82

7

CO

CO2

Gas ChromatographyMethod (Biol. Sci.)

New Ru catalysts implicated during testing:

Ru Ru

O O

H

O O

H

OC OC OC

Ph3PRuRu

OO

H

OO

H

COCOCO

PPh3

OC

CO

Ru Ru

O O

H

O O

H

OC

PPh3

OC OC

Ph3P

CO

Ru Ru

O O

H

O O

H

OC OC OC CO

•Crooks, G. R.; Johnson, B. F. G.; Lewis, J.; Williams, I. G.; Gamien, G.• J. Chem. Soc. (A). 1969, 2761-2769

Known*

HCO2H2Ru Ru

O O

H

O O

H

Ru RuO O

HO

OH

OH

O

Et3NHmechanism may involve a dimeric complex

David J. Morris, G. J. Clarkson and Martin Wills, Organometallics, 2009, 28, 4133–4140

Larger scale set up which allows continuous formation of hydrogen from formic acid, with Artur Majewski.

D. J. Morris and M. Wills, Organometallics, 2009, 28, 4133-4140.

Medium scale hydrogen generation from formic acid:

Larger scale set up which allows continuous formation of hydrogen from formic acid, with Artur Majewski.

D. J. Morris and M. Wills, Organometallics, 2009, 28, 4133-4140.

FA:TEA 5:2 100mlRuCl2DMSO41st day

time [min]

0 100 200 300 400

ga

ses

flow

[L

/min

]

0.0

0.5

1.0

1.5

2.0

2.5

3.0

tem

pe

ratu

re [

oC

]

0

20

40

60

80

100

120

140

gases volumetemperaturegases flow

Medium scale hydrogen generation from formic acid –Example of continuous production:

462L H2

Studies are being extended to hydrogen generation from alcohols.

HO

HO OH

HO

O OH

Chemicalcatalyst

HO

O O

ChemicalcatalystChemical

catalyst

- H2

-CO2

HO

OOH2 CO2 + H2

HO

HO OH + 3 H2O3 CO2 + 7 H2Glycerol to hydrogen with combined catalyst system:

glycerol

+ H2O, - H2

HO

O O

OH

Pyruvatedecarboxylase(enzyme)

HO

OH

- H2

+H2O

OOH

O

Chemical catalyst

- H2

HHO

OOH

Ooxalatedecarboxylase

(enzyme)

Overall reaction: 7 moles H2per mole glycerol

- H2 +H2O - H2

Chemicalcatalyst

Chemicalcatalyst

Hydrogen from glucose – with help from enzymes:

The pentose phosphate cycle (up to Ru5P)and its interception in this project at the 5C sugar stage to give hydrogen from glucose:

O(O)3PO

HO

HO OH

OH

glucose-6-phosphate(G6P)*

2-

O(O)3PO

HO

HO OH

O

D-glucuno-d-lactone-6-phosphate

2-OH(O)3PO

HO

HO OH

O

phospho-D-gluconate

2-

OH

* From glucose or from starch with glycogen phosphorylase then phosphoglucomutase.** Hydrogen not formed directly: hydrogenase will be added to release H2 from the formed NADH,which is the initial enzyme product.*** In the pentose phosphonate cycle, a series of 8 enzymes converts 6 molecules of Ru5P to five molecules of G6P and the cycle repeats.

O(O)3PO

HO

O OH

2-

OHO

2 H2O

Glucose-6-phosphatedehydrogenase. + H2

**

H2O

6-phospho-glucono-lactonase

1.1.1.49 3.1.1.17

OH(O)3PO

HO

O OH

D-ribulose-5-phosphate (Ru5P)***

2-

+ H2 **

Phosphono-gluconatedehydrogenase

1.1.1.44

retro-aldol

Previous slide

3 CO2 + 6 H23 H2O

hydrolysis2 CO2 + 4 H2

+ 6 H2O6 CO2 + 12 H2

Overall reaction: 7 moles H2per mole glycerol

GlucoseC6H12O6

Previousslide

Conclusions

Hydrogen is a clean fuel, at point of use.‘Clean’ hydrogen generation represents a significant challenge.

Acknowledgements:Funding: EPSRC (EP/031168/01)

Science: Dr David Morris

HDeliveryHDelivery

The Birmingham/Warwick Science Cities Hydrogen Energy Project.

A Collaborative Research Project that is part of the larger Energy Futures projects between:

The University of Warwick (Physics, Chemistry, Engineering, Biological Sciences, WHRI)

and

The University of Birmingham (Project leader Prof. Kevin Kendall, Chemical Engineering, Chemistry, Economics, Biological Sciences, Materials)

Part of Warwick strategy in energy research centred on WISER

Project started as an £8.3M project with AWM funding at £6.2M – in January 2007 and has already attracted another £1.5M of funding via Supply Chain Research Applied To Clean Hydrogen (SCRATCH) EPSRC project (Kendall PI)

Steam reforming is a long established process:(hydrogen generation for energy and synthesis)

In oil

CnH2n+2 + n H2O (2n+1) H2 + n CO requires very high temperatures and catalyst

or ‘syngas’ or ‘town gas’

If you have a lot of coal:

C + 2 H2O 2 H2 + CO CnH2n+2 + n H2O

Fischer–Tropsch Process (Co or Fe catalyst)

SASOL made extensiveuse of this process inSouth Africa

Comparison of Ruthenium Sources

-1000

1000

3000

5000

7000

9000

11000

13000

15000

17000

19000

0 2 4 6 8 10 12 14

Total gas volume/Litre

TO

F/h

r

RuCl2DMSO4

RuCl2(NH3)6

RuCl3 anhydrous

Ru2(O2CH)2(CO)4

Comparison of RuComplexes:

[RuCl2DMSO4]

(195 ppm CO)

[(NH3)6RuCl2]

(430 ppm CO)

[RuCl3]

(196 ppm CO)

[Ru2(HCO2)2(CO)4)](327 ppm CO)

Comparison of activity of four Ru catalysts.

Future work within the consortium Hydrogen from lignin components?:

HO OH

OHHO

MeO OMe

O O

OHHO

MeOOMe

+

component of lignin:

overall : C17H20O6 + 28 H2O ---> 38 H2 + 17 CO2

i) Chemicalcatalyst -H2

2) retro aldol A B

O

OH

OMe

B

O

OH

OMe

HO

i) +H2O

ii) Ru-catalystoxidation - H2

-CO2

Red = Hydrogen generation step.Blue = water addition step.Purple = carbon dioxide loss step.

OH

OMe

A

Moles

1 0

Running total (from starting material):

i) Chem. Cat.oxidn -H2

ii) +H2O

iii) Chem. Cat.oxidn -H2

4 2

O

HO

MeO

(two molecules fromeach starting material)

A

Moles MolesH2 H2O CO2formed used formed

0

1

O

HO

MeOi) +H2O

ii) Ru-catalystoxidation - H2

OH

O

HO

MeOOH

O

O

i) Intradiol oxidation(enzyme) -2H2

i) + 2 H2O

10 8 1

C

O

HO

HOOH

O

O

Ci) +H2O

MeOH +

i) +H2O 3 H2 + CO2

O

HO

HOOH

O

O

HO

OH

16 16 3

D

D

O

HO

HO

OH

O

O

O

O

+

+

i) +H2O

ii) Chem. Cat.oxidn -2H2

HO

OO

i) +H2O

ii) Chem. Cat.oxidn -H2

HO

OO

OH

H2 + 2 CO2

H2 + 2 CO2" """

24 20 7

32 24 11

i) +H2O

ii) Chem. Cat.oxidn -H2

O

OHO

OHO

i) +H2O2 H2 + 3 CO2 38 28 17

ii) +2 H2O

O

OHHO

OHO

HO

O

HO2C

CO2HO

muconolactone

Ir

N Cl

Cl

1

OH

2

Ph Me

OHH

Ph Me

O

+ H2

Ru

ClCl

Ru

Cl Cl

Development of some chemical catalysts for hydrogen generation.

Reported organometallic catalysts for hydrogen generation from alcohols:

Catalyst 1: K.-I. Fujita, N. Tanino and R. Yamaguchi, Org. Lett. 2007, 9, 109-111.Catalyst 2: G. R. A. Adair and J. M. J. Williams, Tetrahedron Lett. 2005, 46, 8233-8235.

with 1, 0.1 mol%, 20h reflux in toluene, 70% conversion.with 2, 5 mol%, 15 mol% LiOH, 48h in reflux in toluene, 100% conversion.

OHR +Ph NH2 Ph N

HR

O

+ 2 H2

N

P(tBu)2

NEt2

Ru

CO

H0.1 mol%

Toluene, reflux, 7-8h.

Reported organometallic catalysts for hydrogen generation from alcohols:

C. Gunanathan, Y. Ben-David and D. Milstein, Science, 2007, 317, 790-792.

OHR +Ph NH2 R O R

O

+ 2 H2

N

P(tBu)2

NEt2

Ru

CO

H0.1 mol%

Toluene, 115oC, 4h.

To form amides (thermodynamic drive):

To form esters (thermodynamic drive):

J. Zhang, G. Leitus, Y. Ben-David, and D. Milstein, J. Am Chem. Soc. 2005, 127, 10840 - 10841.

EPSRC funded ‘Delivery of Sustainable Hydrogen’ SUPERGEN project (14 partners, £5M, 48 months, start date 1st October 2008).

Partners:

John Irvine (StAndrews), Management coordinator and PI.

Ian Metcalfe (Newcastle), Finance coordinator.

Chris Whitehead (Manchester) Bartek Glowacki (Cambridge)

David Infield (Strathclyde) David Book (Birmingham)

Martin Wills (Warwick) Kang Li (Imperial)

Marcello Contestabile (Imperial) Shanwen Tao (Heriot-Watt)

Neil McKeown (Cardiff) Edman Tsang (Oxford)

Malcolm Eames (Brunel) Valerie Dupont (Leeds)

Equipment now available at Warwick and Birmingham

Solid state X-ray diffractometers, mass spectrometers, Solid state NMR.

FTIR, / RAMAN, Glove boxes, Confocal Microscopy.

High pressure reaction cells, pressure vessels,

Fuel cells, large scale bioreactors, biohydrogen pilot plant.

Extensive analytical equipment, Anaerobic growth reactors.

Scanning electrochemical microscope and associated equipment.

Full list available on request.

Useful contact: Robert HudsonScience City Project ManagerHydrogen Energy (Based at Birmingham).

Attempting to identify the active catalyst

Refluxing THF 5 hr2 eq. PPh3 relativeto the complex

Refluxing THF 30 min1 eq. PPh3 relative to the complex

Ruthenium carbonylrefluxing formic acid 6 hr

31P = 12.3 ppm 31P = 5.7 ppm

J. J. Lewis, J. Chem. Soc., 1969, 18, 2761-6

Many thanks to Guy Clarkson!

Formation of hydrogen gas from Biomass in a Biomass reactor:

Biomass at Warwick HRI is usedas fuel for enzymatic decomposition in the biomass reactor (purchased with science cities funds)

H2

Other valuable products can be formed in this reactor.

Hydrogen research: Examples of facilitiesBiological catalysis (Biological Sciences, Warwick HRI)

Recent icast:http://www2.warwick.ac.uk/newsandevents/icast/archive/s2week2/