heterogeneous catalysis: efficient utilization of energy
TRANSCRIPT
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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]
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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
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“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
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“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
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Sustainable Production
Creation of products using chemical
process that are:
- Conserving energy
- Non-polluting
- Economically efficient
- Safe and healthy for workers
GREEN
CHEMISTRY
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P.T. Anastas, J.C. Warner, Green Chemistry: Theory and Practics, Oxford University Press, New York, 1998.
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P.T. Anastas, J.C. Warner, Green Chemistry: Theory and Practics, Oxford University Press, New York, 1998.
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P.T. Anastas, J.C. Warner, Green Chemistry: Theory and Practics, Oxford University Press, New York, 1998.
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Catalysis
Catalyst – is a
substance that
speeds up a
reaction without
being consumed
during the
reaction
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Catalytic Converter
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Advantages of Catalytic processes
Carry out reaction under
mild conditions (e.g. low
temperature, pressure) -
low energy
consumption
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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.)
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Catalysis
Types of Catalysts
1) Homogeneous : Catalyst and Reactant in the same phase
2) Heterogeneous : Catalyst and Reactant in different phases
Separation
energy consuming
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P.T. Anastas, J.C. Warner, Green Chemistry: Theory and Practics, Oxford University Press, New York, 1998.
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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
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R. Sheldon, Green Chemistry, 2007, 9, 1261.
The E factor and atom efficiency
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The E factor and atom efficiency
oxidation
I. Arends, R. Sheldon, U. Hanefeld, Green Chemistry and Catalysis, WILEY-VCH, Weinheim, 2007
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P.T. Anastas, J.C. Warner, Green Chemistry: Theory and Practics, Oxford University Press, New York, 1998.
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Production of syngas
Syngas feedstock for the synthesis of:
- Methanol
- Ammonia
- Fischer-Tropsch –
liquid fuels, chemicals
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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.
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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.
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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.
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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
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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
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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
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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)
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Thank you for your
attention!