This invention relates to a process for the preparation of a vinyl
derivative of a Bronsted acid. "Vinyl" is defined here as a ethenyl radical optionally
substituted at the 1- and/or 2-positions, and the "Bronsted acid" is a compound
which can release protons. Typically, vinyl derivatives of Bronsted acids include
ethenyl esters of carboxylic acids and ethenyl ethers of hydroxy compounds, which
find extensive commercial use, e.g., as monomers in free radical initiated addition
Processes for the preparation of such vinyl derivatives by addition
of a Bronsted acid to an alkyne are known for a long time, and are typically catalyzed
by a Group 2b metal compound, for example a carboxylate of zinc, cadmium or mercury.
These known processes generally suffer from the disadvantage of loss of catalytically
active metal in the course of time. Whether using the Group 2b metal catalyst in
homogeneous or heterogeneous form, adequate measures are to be taken to prevent
a quick loss of catalyst activity, as shown, for example, by GB-A-1125055, DE-A-1233387
and US 3652659. Nevertheless, it has appeared to be difficult to effect high confinement
or recovery of the metallic catalyst component in practice. Moreover, the catalysis
by Group 2b metal compounds requires a relatively high load of catalytically active
metal, whilst for attractive reaction rates quite high reaction temperatures are
The present invention aims at providing an improved catalyst for
the above reaction avoiding or at least mitigating the described problems. More
particularly, the invention aims at providing an improved supported catalyst allowing
the reaction to be conducted in the gaseous phase.
It should be remarked, that a process for the preparation of a vinyl
derivative of a Bronsted acid is known from EP-A-351603, according to which a vinyl
derivative of a Bronsted acid is transvinylated with a different Bronsted acid
in the presence of a ruthenium compound. This process starts from different precursors,
and the separation of the several Bronsted acids and their derivatives may be
cumbersome. M. Rotem et al., Organometallics, 2, pp. 1689-91 (1983) disclose the
addition of carboxylic acids to substituted ethynes using unsupported ruthenium
compound catalysts. Despite the higher reactivity of substituted ethynes as compared
with unsubstituted ethyne, they observed acceptable conversions at reaction times
as high as 17 to 22 hours. Besides, the ruthenium complexes used are not suitable
for a continuous gas phase process over a contained catalyst bed.
An advantageous process for the preparation of vinyl derivatives
of Bronsted acids has now be found by the inventor, which process involves contacting
an acetylenically unsaturated compound and a Bronsted acid at elevated temperatures
in the presence of a heterogeneous catalyst comprising ruthenium supported on
an inert porous support.
It has been found that using the supported ruthenium catalyst high
conversion rates are achieved in the addition reaction of a Bronsted acid to an
acetylenically unsaturated compound, in particular to ethyne. Moreover, the catalysts
to be used according to the invention show no tendency of sublimation with consequent
loss of catalytic activity and problematic need of recovery of the lost metal.
The supported ruthenium catalysts are advantageously suitable for conducting the
present process in the gaseous phase. Finally, the process according to the invention
can be carried out at relatively mild temperature conditions.
Acetylenically unsaturated compounds typically used in the process
according to the invention include alkynes which may be unsubstituted or substituted
with one or more substituents not interfering with the addition reaction. Representative
substituents include alkyl, alkoxy, aryl, aryloxy and halo group. The alkynes
typically have from 2 to 10 carbon atoms. A preferred acetylenically unsaturated
compound is ethyne.
Bronsted acids typically used in the process according to the invention
include carboxylic acids such as acetic acid, propionic acid, butyric acid, pivalic
acid and other trialkylacetic acids, stearic acid, benzoic acid, the phthalic acids,
adipic acid, succinic acid, maleic acid, acrylic acid and methacrylic acid; alcohols
such as methanol, ethanol, isopropanol, phenol, hydroquinone and resorcinol; amino
compounds of sufficient acidity, such as secondary aromatic amines and primary
aliphatic amines; hydroxy esters such as hydroxy alkyl acrylates and hydroxy alkyl
alkanoates; and amides or imides such as 2-pyrrolidone, ε-caprolactam, succinimide
and toluenesulphonamide. Preferred Bronsted acids are selected from the group of
carboxylic acids, cyclic amides and aromatic hydroxy compounds, more preferably
from the group of aliphatic carboxylic acids having 1-30 carbon atoms. A most
preferred group of aliphatic carboxylic acids is constituted by the trialkylacetic
Representative addition product of the present process include vinyl
acetate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl neoheptanoate,
vinyl neodecanoate, vinyl benzoate, vinyl acrylate, vinyl methacrylate, divinyl
terephthalate, divinyl adipate, N-vinyl succinimide, N-vinyl 2-pyrrolidone, vinyl
phenyl ether, vinyl methyl ether, vinyl butyl amine, 2-vinyloxyethyl acetate and
The catalyst utilised in accordance with the present invention comprises
ruthenium supported on an inert porous support. Preferably the catalyst comprises
zerovalent ruthenium. The supported ruthenium catalyst is particularly advantageous
in the process of the instant invention as it is readily separated from the feed
and product. Suitable inert porous supports include refractory oxides and carbon.
Examples of suitable refractory oxides include alumina, silica, silica-alumina,
titania, zirconia, magnesia and the like. Preferred inert porous supports for use
in the instant catalysts are alumina and carbon.
The catalysts which are utilised in the present invention can be
suitably prepared using any conventional technique such as, for example, impregnation,
coprecipitation, comilling, spray drying and the like; or any combination of these
The present reaction may be carried out batch-wise or continuously.
For example it may be carried out in a fixed bed reactor, the bed comprising the
catalyst, wherein the feed of acetylenically unsaturated compound and Bronsted
acid is passed over the bed. The feed may be passed in liquid or gaseous form over
the catalyst bed. Other continuous reactor configurations will be readily apparent
to one skilled in the art. In a batch mode, a gaseous feed of the acetylenically
unsaturated compound may be introduced into an agitated mixture of the Bronsted
acid and the supported catalyst. Any of the gaseous or liquid feeds or reaction
mixtures may be diluted with inert gases or solvents. Further batch reactor configurations
will be apparent to the skilled artisan.
The present reaction proceeds at a molar ratio between acetylenically
unsaturated compound and Bronsted acid of 1:1. However, the feed may comprise either
of the reactants in excess. For example, the excess of one of the reactants may
function as a carrier for the reaction product for ease of separation of the latter.
An excess of acetylenically unsaturated compound may be beneficial in suppressing
any undesired occurrence of a repeated addition of the Bronsted acid to the vinyl
derivative reaction product. The molar ratio between the acetylenically unsaturated
compound and the Bronsted acid may range from 100:1 to 1:100, more typically from
10:1 to 1:10.
The process of the invention is carried out at elevated temperatures.
The reaction temperature is typically in the range of 40-250 °C, preferably in
the range of 80-175 °C. Reaction pressures for the present process are not critical
and will typically be atmospheric. However, the reaction pressure may also be
subatmospheric, for example for volatilising high boiling reactants, or superatmospheric,
in so far as compatible with the safety requirements regarding acetylenically unsaturated
The invention will be further illustrated by the following examples.
After being flushed, a 250 ml autoclave was charged with 10 ml of
acetic acid, 40 ml of diglyme (2,5,8-trioxanonane), 1.4 bar of ethyne and 1 g of
a ruthenium (5 %wt) on carbon catalyst. For safety considerations, 20 bar of nitrogen
gas was added. Upon sealing, the agitated contents of the autoclave were heated
to 140 °C for 1.5 hour. Thereupon the autoclave was cooled and its content analysed
by means of standards gas liquid chromatography (GLC). It was found that 80 % of
the ethyne was converted. The selectivity into vinyl acetate was found to be 82%.
Example 1 was repeated using 10 ml of pivalic acid instead of 10
ml of acetic acid. Upon a reaction time of 2 hours, GLC analysis showed an ethyne
conversion of 80% with a selectivity to vinyl pivalate of 71%.
Example 1 was repeated using 1 g of rhodium (5 %wt) on carbon, platinum
(5 %wt) on carbon, and palladium (10 %wt) on carbon, respectively instead of the
ruthenium catalyst. Upon a reaction time of 8 hours, none of the experiments showed
a conversion of acetylene higher than 10%. These comparative experiments demonstrate
the unique suitability of supported ruthenium catalysts amongst the Group VIII
After being flushed, a 250 ml autoclave was charged with 10 ml of
2-pyrrolidone, 50 ml of diglyme (2,5,8-trioxanonane), 1.5 bar of ethyne and 1 g
of a ruthenium (5 %wt) on carbon catalyst. For safety considerations, 20 bar of
nitrogen gas was added. Upon sealing, the agitated contents of the autoclave were
heated to 170 °C for 7 hours. Thereupon the autoclave was cooled and its content
analysed by means of standards gas liquid chromatography (GLC). It was found that
90% of the ethyne was converted. The selectivity into N-vinyl 2-pyrrolidone was
found to be above 95%.