Hydrogenation
of Organic Compounds
Introduction
Hydrogenation is a process of major industrial importance. Gaseous H2
has relatively low solubility in conventional organic solvents, placing
significant limitations on reactions such as hydrogenation, which involve
addition of H2 to substrates. By contrast, H2 is
completely miscible with supercritical fluids such as scCO2 (TC
= 31.1°C, PC = 73.8 bar) or scPropane (TC = 96.8°C,
PC = 42.6 bar). Our research group was one of the first to exploit
this miscibility to synthesise highly labile organometallic
dihydrogen compounds.
Continuous flow reactors provide a simple means of increasing the yield
from a supercritical reaction without increasing the overall size of the
apparatus. Our other web pages describe a miniature
flow reactor for synthesis and isolation of organometallic compounds.
In collaboration with Thomas Swan
& Co. Ltd, we have now built a reactor which can be used for continuous
catalytic hydrogenation of a wide range of organic compounds with high
efficiency.
Hydrogenation under supercritical fluid conditions has several advantages:-
-
the reaction is not limited by mass transfer effects;
-
the fluid has good thermal properties and, on a small scale at least,
-
the fluid provides a much greater degree of control than is usually possible
in non-supercritical hydrogenation.
-
reactions can be carried out with very high space time yields (see cyclohexane
below)
Most of the reaction parameters (temperature, pressure, flow rate, concentration
of H2, etc.) can be controlled independently. This allows conditions
to be optimised to give high selectivity for a particular product in reactions
where several products can be generated. A wide range of organic funtional
groups can be hydrogenated with very high conversion and selectivity.
The continuous flow reactor can also be used to investigate other continous
reactions, such as Friedel-Crafts
Alkylations, Etherifications
and Hydroformylations.
Further Information
For further information please contact M.
Poliakoff
Key Publications from Nottingham
-
Continuous Hydrogenation of Organic Compounds in Supercriical Fluids, M.
G. Hitzler and M. Poliakoff, Chem. Commun., 1997, 1667-8
-
The Selective Catalytic Hydrogenation of Organic Compounds in Supercritical
Fluids as a Continuous Process, M. G. Hitzler, F. R. Smail, S. K. Ross
and M. Poliakoff, Organic Process Research & Development, 1998,
2, 137-46
-
Continuous Hydrogenation in Supercritical Fluids, T. Tacke, C. Rehren,
S. Wieland, P. Panster, S. K. Ross, J. Toler, M. G. Hitzler, F. R. Smail
and M. Poliakoff in “Catalysis of Organic Reactions” (Ed. Herkes), Marcel
Dekker, New York, 1998.
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Page created by: Simon Poliakoff
Created: July 1997
Last Revised: January 2001