Hydrodeoxygenation of guaiacol as model compound for pyrolysis oil on

noble metal catalysts

Andrea Gutierrez, Reetta Kaila, and Outi Krause

Laboratory of Industrial ChemistryHelsinki University of Technology

14th International Congress on CatalysisSeoul 2008

Biofuels

Biomass is the only renewable source that can meet the demand for carbon-based liquid fuels and

chemicals

Pyrolysis

Combustion of biomass in the absence of oxygen

Flash

pyrolysis

� Combustible gas (150 kg)

� Pyrolysis oil (700 kg)

� Char (150 kg)

1,000 kg wood

BTG - http://www.btgworld.com/2005/pdf/technologies/folder-pyrolysis.pdf

Pyrolysis oils…

� Higher energy density than biomass

� Complex mixture (volatile and non-

volatile compounds)

� High oxygen content (~ 40 wt-%)

� Water content (~ 20 wt-%)

� Typically less than 40 ppm sulfur

� Immiscible in mineral oil

� Not as stable as mineral oil

0

20

40

60

80

100

Pine Forest residue

Ma

ss %

Aldehydes, ketones

Acids

'Sugars'

Water

Extractives

LMM lignin

HMM lignin

Poor fuel properties

Pyrolysis - Upgrading

Wood-based bio-oils are complex mixtures

(Carboxilic acids, alcohols, ketones, carbohydrates, degraded lignin, water, etc.)

Difficult system to study

� Viscosity problems

� Large amount of side reactions

� Solubility problems

Model compounds to simulate the behavior of bio-oils

Pyrolysis - Upgrading

Catalytic total or partial removal of oxygenates

�Decarboxylation (CDO)

�Thermal cracking (CRA)

�Hydrodeoxygenation (HDO)

O4HHC4HOHC 2842486 +→+

S.R.A. Kersten, W.P.M. van Swaaij, L. Lefferts, K. Seshan, (2007) In: Catalysis for renewable: From feedstock to energy production, (Eds. Centi G., and van Santen R. A.), pp119-145, Wiley-VCH, Weinheim, Germany.

Existing knowledge in the refinery

• CoMoS/Al2O3 and NiMoS/Al2O3

• High H2 consumption

Upgrading - Experimental

� Wood base bio-oil

• Guaiacol (GUA)

� Catalysts

• Noble metals

- ZrO2–supported Rh, Pd and Pt

(0.5 wt-% total metal loading)

• Sulfided catalyst

- CoMo/Al2O3

� Experimental conditions

• Batch reactors

- T= 100 and 300 ºC, P= 8 MPa

- 5 h

Fresh ZrO2-supported Rh and Pd (T

calc.= 700 oC)

Assumptions…

� No H2 limitation

• Excess in the gas phase

• Long reaction time

• Vigorous agitation

ZrO2-supported noble metal catalysts

0

10

20

30

40

50

60

70

80

90

100

Non-

catalytic

ZrO2 Pt PdPt Pd RhPd RhPt Rh CoMo

GU

A c

on

vers

ion (

%)

T= 300 oC, 3 h

T= 100 oC, 5 h

Remarkable effect of temperature in catalyst performance• XGUA > 90 % at T= 300 oC (high risk of coke formation)

• XGUA ≈ 100 % with RhPt and Rh at T= 100 oC

CoMo

Non-catalyticZrO2

Rh

PtRhPt

GUA

Pd

RhPd

PdPt

0.00

0.05

0.10

0.15

0.20

0.25

0.30

1.0 1.2 1.4 1.6 1.8 2.0

H/C (mol/mol)

O/C

(m

ol/

mo

l)

Gasoline

and

diesel

ZrO2-supported noble metal catalysts

9.70.61.70.62.60.62.62.0300 ºC

6.71.81.01.00.60.40.60.5100 ºC

CoMoRhRhPtRhPdPdPdPtPtZrO2Carbon (wt-%)

Promising!

At 100 ºC

� Main product• Noble metals: cyclohexanediols

• CoMo: cyclohexanol and gaseous

sulfided compounds

� Limited deoxygenation

At 300 ºC

� Main product

• Noble metals: benzene

• CoMo: benzene, gaseous and liquid

sulfided compounds

� Deoxygenation predominates

300 ºC

ZrO2-supported noble metal catalysts

� HDO vs. hydrogenation (HYD)• Not limited by thermodynamics

- HYD favored at low T

- HDO favored at high T

� H2 coverage of catalyst surface• H2 equilibrium coverage decreases

with temperature

(more H2 on the surface at low T)

HYD at 100 oCHDO at 300 oC

Why different products at 100 and 300 oC?...

Reaction scheme - Experimental

Reaction intermediates

� Catalysts

• Noble metals

- Rh/ZrO2 and RhPd/ZrO2 catalysts

• Sulfided catalyst

- CoMo/Al2O3

� Experimental conditions

• Batch reactors

- T= 100 and 300 ºC, P= 8 MPa

OCH3

methoxyphenolCH3

toluene

OH

phenol

O

cyclohexanone

OH

cyclohexanol

Simplified reaction scheme

OCH3

GUA

OH

OH

OH

OH

OCH3

OCHOCH33

OCHOCH33

OCH3

OCH3

OHOH

H3C

OH

CH3

CH3

OH

CH3

CH3

O

OCH3

O

OH

OH

SH

Conclusion

� Rh and RhPd promising for the upgrading of the real pyrolysis oil

� RhPd cheaper catalysts than Rh

� Use of low operation temperatures in the upgrading prevent coke

formation

• Significant effect of temperature on activity and selectivity of the catalysts

- T = 100 oC � HYD

- T = 300 oC � HDO

� Upgrading of GUA

• Complicated network of reactions

- Differences in the reaction path catalyzed by the conventional sulfided CoMo

and the noble metal catalysts

Thank you!

Acknowledgements

Ms. Eeva-Maija Ryymin

Dr. Maija HonkelaDr. Tuula-Riitta Viljava

Technical Research

Centre of Finland

Financial support

EU-project BIOCOUP

Finnish Catalysis Society

Contact informationandrea.gutierrez@tkk.fi