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Sci Tech
New technology using fluorous catalyst
METHANOL IS a major feedstock for producing fuels and chemicals.
A decade ago, Horvath and others at the Exxon Research Laboratories, while searching without success for a better way to oxidise methane to methanol, landed instead in a spin-off that has created a new chemical technology.
Industrial process traditionally uses organic solvents such as ethers and amines for converting alkenes into useful materials.
They substituted fluorous solvents and their experiments showed that the fluorous solvents would not mix with the starting materials in the reactions.
Principle of the reaction
Whereas the standard solvents have C-H or C-Cl bonds, the new solvents have C-F bonds; though they readily dissolve small molecules like carbon monoxide and hydrogen, their affinity for electrons do not easily allow mixing with conventional solvents at room temperature.
Horvath saw immediately a practical application in the field of catalysis.
These are two kinds: homogenous catalysts, though highly efficient, are not easy for reclaiming, once the reaction is complete.
On the other hand, heterogeneous catalysts can be easily separated from the solution and reused.
But they require application of high temperatures and pressures, which add to the environmental problems.
Here fluorous catalysts come to the rescue and ensure the reactions are environment-friendly.
Poured into a solution of conventional reactants, the fluorous phase behaves like oil on water at temperature.
When warmed, the reagents react very effectively. On cooling, the catalyst drops out of solution and can be filtered.
While the industrial reactions are speeded up, they conserve catalysts and use less energy in the process.
Dennis Curran of the University of Pittsburgh describes, "During reaction, you have homogenous catalysts. During separation, it is heterogeneous. It is like having your cake and eating it too!"
He has floated a company Fluorous Technologies Inc. to supply fluorous reagents.
Laboratories around the world in France, Germany and Japan are offering variations to extend fluorous chemistry to workhorses of the chemical industry (`Green Chemistry' in Science, 27 June 2003)
R.Parthasarathy
R.Parthasarathy
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