Heterogeneous catalysis: Efficient utilization of energy

Heterogeneous catalysis:

Efficient utilization of energy

Dr E. Erasmus

Department of Chemistry,

University of the Free State,

Bloemfontein 9300, South Africa,

E-mail: [email protected]

Sustainability:

Sensible and economic use of

the earth’s resources to meet

the needs of the present

generation without

compromising the needs of

future generations

“The chemical and

petrochemical sector is

by far the largest

industrial energy user,

accounting for roughly

10% of total worldwide

final energy demand

and 7% of global GHG

emissions.”

2013

“The chemical industry is

a large energy user; but

chemical products and

technologies also are

used in a wide array of

energy saving and/or

renewable energy

applications so the

industry has also an

energy saving role.”

2013

Sustainable Production

Creation of products using chemical

process that are:

- Conserving energy

- Non-polluting

- Economically efficient

- Safe and healthy for workers

GREEN

CHEMISTRY

P.T. Anastas, J.C. Warner, Green Chemistry: Theory and Practics, Oxford University Press, New York, 1998.

P.T. Anastas, J.C. Warner, Green Chemistry: Theory and Practics, Oxford University Press, New York, 1998.

P.T. Anastas, J.C. Warner, Green Chemistry: Theory and Practics, Oxford University Press, New York, 1998.

Catalysis

Catalyst – is a

substance that

speeds up a

reaction without

being consumed

during the

reaction

Catalytic Converter

Advantages of Catalytic processes

Carry out reaction under

mild conditions (e.g. low

temperature, pressure) -

low energy

consumption

Advantages of Catalytic processes

– Reducing wastes – unwanted side products

– Producing certain products that may not be possible without catalysts

– Having better control of process

(safety, flexible etc.)

Catalysis

Types of Catalysts

1) Homogeneous : Catalyst and Reactant in the same phase

2) Heterogeneous : Catalyst and Reactant in different phases

Separation

energy consuming

P.T. Anastas, J.C. Warner, Green Chemistry: Theory and Practics, Oxford University Press, New York, 1998.

The E factor and atom efficiency

• Atom efficiency is the theoretical amount of waste

formed during a process. It is calculated by dividing the molecular weight of the product by the

sum total of the molecular weights of all substances formed

• The E-factor is the actual amount of waste formed

during a process.

Everything but the desired product

E= [raw materials-product]/product

• A good way to quickly show the enormity of the

waste problem

R. Sheldon, Green Chemistry, 2007, 9, 1261.

The E factor and atom efficiency

The E factor and atom efficiency

oxidation

I. Arends, R. Sheldon, U. Hanefeld, Green Chemistry and Catalysis, WILEY-VCH, Weinheim, 2007

P.T. Anastas, J.C. Warner, Green Chemistry: Theory and Practics, Oxford University Press, New York, 1998.

Production of syngas

Syngas feedstock for the synthesis of:

- Methanol

- Ammonia

- Fischer-Tropsch –

liquid fuels, chemicals

Production of syngas

-Currently produced by steam reforming of methane of higher

hydrocarbons. Highly endothermic – highly energy intensive!

-Autothermal catalytic reforming of methane or natural gas with

air or oxygen.

-Very high temperature 900-1000oC at catalyst and 1900oC

combustion zone. Highly energy intensive!

B. Elvers, S. Hawkins, M. Ravenscroft, J.F. Rouniaville, G. Schulz, Gas production. In: Ulmann's encyclopaedia of industrial

chemistry, vol. A 12. Weinheim: VCH.

R.E Kirk, D.F. Othmer, In: Hydrogen encyclopaedia of chemical technology, vol. 12.. New York: Wiley-Interscience.

V.R. Choudhary, T.V. Choudary, Angew. Chem. 47 (2008) 1828.

Production of syngas

NiO/MgO - oxidative conversion of methane to syngas

-oxy-steam reforming processes, exothermic

-oxy-CO2 reforming of methane, endothermic

reforming reactions are coupled, making the process

highly energy efficient!

V.R. Choudhary, A.S. Mamman, Applied Energy, 66 (2000) 161.

Catalysis to produce

renewable energy source Plant biomass including cellulose, hemicellulose, and lignin

could prove to be important renewable and abundant carbonneutral energy

sources in the post-fossil-fuel era

Catalyst:

Pd/C

Rh/C

Ru/C

Pt/C

N. Yan, C. Zhao, P.J. Dyson, C. Wang, L. Liu, Y. Kou, ChemSusChem, 1 (2008) 626.

Catalysis to produce Biodiesel

Diesel engines - energy efficiency

Higher fatty acid esters from plant materials

Produced by soluble alkali hydroxides – diesel needs to be washed –

large energy consumption

Supercritical water followed by esterfication

- high-temperature

Heterogeneous catalysts:

High temperature: TiO2/ZrO2, Al2O3/ZrO2,

Low temperature: H4PNbW11O40/WO3-Nb2O5

(heteropolyacid)

M. Hara, ChemSusChem, 2 (2009) 129

Catalysis to produce Biodiesel

Microwave-accelerated esterification of free fatty acid with a

heterogeneous Catalyst

Heterogeneous catalysts:

5 wt% sulfated zirconia

Temperature 60oC

Microwave Conventional oven

20min 130min

67% energy of calculated minimum energy needed.

M. Hara, ChemSusChem, 2 (2009) 129

Oxidation with gold

Addition of Au nano-particle significantly lowers the reaction temperature –

energy saving.

Oxidation of propane:

Pt/Al2O3 (~190oC), Au/TiO2 and Pt/Al2O3 (~150oC)

Oxidation of ammonia

Cu/Al2O3 (~380oC, ~650K),

AuCu/Al2O3 (~280oC, ~550K)

D.H. Kim, M.C. Kung, A. Kozlova, S.D. Yaun, H.H. Kung, Catalysis Letters, 98 (2004) 11.

S.D. Lin, A.C. Gluhoi, B.E. Niewenhuys, Catalysis Today, 90 (2004) 3.

Pt/Al2O3

Au/TiO2

Pt/Al2O3 + Au/TiO2 mixed

Pt/Al2O3 + Au/TiO2 2 reactors in

series

Summary:

Heterogeneous catalysis is essential

*energy production (biomass to useable energy, fuel cells, solar cells,)

*energy conservation (lower the activation energy and lower the reaction temperature)

Thank you for your

attention!