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!