CATALYTIC ETHANOL STEAM REFORMING

a

b

cO

CH2

CH3

O

CH2

CH3

O

CH2

CH3

a

b

cO

CH2

CH3

O

CH2

CH3

O

CH2

CH3

Am. Chem. Soc., Div. Pet. Chem. 2008, 51 p.1&2

M. Scott B.Sc. M.Sc.(hons)Department of ChemistryThe University of Auckland

Handbook of Green Chemistry, Wiley 2008

Topics in Catalysis, in press

Science, in press

H2 from ethanol

Traditional Energy non-sustainable

Renewable

Efficient

Renewable energy cycle

Photosynthesis 2807 kJ/mol

C6H12O6 Glucose

H2 combustion-286 kJ/mol

Fermentation 15 kJ/mol

Steam reforming 173 kJ/mol

6CO2 + 12H2

+ O2

+ H2O

2CH3CH2OH + 2CO2

Ethanol

+ hν

6CO2 + 12H2O

∆

The catalyst

• Cerium dioxide nanoparticles as the supporting material.

• Rhodium metal dissociates sp3 C-H bond• Rh/CeO2 dissociates C-C bond of ethanol

• Palladium excels in hydrogenation and oxidation

Bimetallic Rh,Pd/CeO2 displays ideal properties

Steam ReformingAn activated process

298K; Ethanol on reduced Rh/CeO2

J. Catal. 208, 393-403 (2002)

CH3CH2O Ce

H2C

CH2OCe Rh

H2C

CH2OCe Rh

CH4 + CO + H2

CH3CH2O CeCH3CH2OH

CO

Catalyst manufacture

Ce3+(NO3)3.6H2O Ce4+(OH)4.xH2O

Precipitation

Deposition

CeO2 nano-particles

pH 9

Ce4+(OH)4.xH2O CeO2

RhCl3(aq) Rh3+

PdCl2(aq) Pd2+

773 K

Catalytic testing• 6:1 water to ethanol ratio shows

higher CH4 conversion than 3:1 ratio => higher H2 vol. %

• Effects of varying reaction temperature

• Effects of varying weight percentage loading noble metal

• Varying throughput (2.5, 5, 6.5 and 11.5 mL/hour)

0

10

20

30

40

50

60

70

80

90

100

Mol

ar S

elec

tivity

493 540 596 643 697 737 789 843

Temperature (K)

Selectivity vs Temperature (6:1)

CH3CH2OH → CH4 + CO + H2 ΔH0 = 50 kJ/mol

CO + H2O → CO2 + H2

ΔH0 = -41 kJ/mol CH4 + 2H2O → CO2 + 4H2

ΔH0 = 164 kJ/mol

Temperature dependence

Temperature Programmed Desorption

Water

CH3CH2-

Acetaldehyde

Acetaldehyde

CH3

CH4

CO

CH3CH2-

CeO2

500K & 773K

1%Pd,1%Rh/CeO2

375K & 525K

CO2

CO2

Effect of metal loading11.5 mL/hour, 6:1 and 773K

wt.% on ceria

Vol.%

H2

Vol.%

CO2

Vol.%

CH4

Vol.%

CO

Χ % max.

H2 yield

1%Pd 74 22 2 2 0.24 24

1%Rh 59 23 15 3 0.77 61

½%Rh, ½%Pd 63 24 11 2 1 84

½%Rh, 1%Pd 69 17 9 5 0.56 51

½%Rh, 2%Pd 75 18 5 2 0.12 12

Transmission Electron Microscopy

Pd,Rh alloy

Used catalyst Used catalyst

•Alloying of Rh and Pd

•Reduction of Rh2O3

•Restructuring of Support

•Origins at interface

•Lowering CN of Cerium

• Rh/CeO2 based catalyst

• Bimetallic catalyst very active

• Low metal loadings show best activity

• Active sites at Rh-Ce and Pd-Ce interface

• High temperature required for CH4 oxidation

• CH4 reforming and CO oxidation inadequate

• Dramatic restructuring occurring

• Activation of catalyst occurring

• No signs of deactivation

CH3CH2OH + 3H2O → 6H2 + 2CO2∆H=173 kJ/mol

Future research

• In situ FTIR• TPD studies• Further XPS studies• Near Edge X-ray Absorption Fine Structure • Further PAS and TEM• Maximise outflow• Doping• ⅓wt.%Rh,⅓wt.%Pd,⅓wt.%Ni/Ce0.75Zr0.25O2

Inverse Opal Ceria

20000x

100000x

Scanning Electron MicroscopyTransmission Electron

Chem. Mater. 2008, 20, 1183–1190

Microscopy

•3D macroporous structure

•Resistant to sintering to 1073K

•Allow gas low through pores

•High surface to volume ratio

Acknowledgments:Associate Professor Hicham IdrissSupervisor

Dr Geoffrey Waterhouse,Dr William Chiu, Dr Maria GoeffreyUniversity of Auckland Graduates

Alister Gardiner and Simon Arnold Industrial Research Limited, Christchurch

Professor Jordi Llorca (HRTEM)Universitat Politècnica de Catalunya, Barcelona, Spain

Dr Steven J. Pas (PAS) Commonwealth Scientific and Industrial Research Organisation (CSIRO) Manufacturing and Materials Technology, Victoria, Australia

Mark Blackford (TEM)Australia’s Nuclear Science and Technology Organisation, Lucas Heights, Sydney, Australia

XPS 1%Rh,1%Pd/CeO2 and PAS1 Ethanol + 3 water at 773 K, 3 hours at ca. 100 Torr

880890900910920

Binding Energy (eV)

Co

un

ts p

er s

eco

nd

(arb.

Un

its)

vo

v

v’

v’’v’’’u

u’u’’u’’’

XPS Ce3d5/2,3/2 Rh-Pd/CeO2

Ce3+

Fresh

Used

EB = hν – (φ + EK)

Voids in the bulk

PAS 2%Rh,2%Pd/CeO2

•Oxidation of CeO2

•Reduction of metal

•Homogenization

•Growth of voids