Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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The present invention relates to a process for the
removal of acetylenic compounds from a hydrocarbon stream.
More particularly, the present invention relates to
a process which permits both organic or inorganic, hydrocarbon
streams to be purified, and the same acetylenic compounds to
be used for the simultaneous production of industrially inte-
resting products.
Even more particularly the present invention relates
to a method:
1. For the removal from a hydrocarbon stream comprising
ethylene, propylene and butylene, either alone or
in admixture with other saturated or unsaturated
hydrocarbons having the same number of carbon atoms t
of acetylene, propyne, l-butyne, 2-butyne, vinylacety-
lene an~ dia~etylene, with simultaneous production of vi-
nyl ethers and/or of the gem-diethers ofthesa~e compounds
2. For the removal from butadiene streams (either alone
or in admixture with saturated or unsaturated hydro-
carbons having the same number of carbon atoms, of
propyn~, l-butyne, 2-butyne, vinylacetylene and/or
diacetylene, with the simultaneous production of the
vinyl ethers andjor of the gem-diethers of the same
compounds.
3. For the removal from propylene streams (either alone
or in admixture with other saturated or unsaturated
hydrocarbons having the same number of carbon atoms),
of the propyne, with the simultaneous production of
corresponding vinyl ether and/or gem-diether.
4. For the removal from ethylene streams (either alone or
in admixture with ethane) or the acetylene with the
simultaneous production of corresponding vinyl ether
and/or gem-diether.
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It is known that in most uses the olefinic, saturated
hydrocarbons, and particularly the dienic hydrocarbons must be
free from acetylenic compounds; for instance their content in the
butadiene monomer must be ~ 50 ppm, owing to their poisoning action
on the polymerization catalysts.
A number of methods have been proposed and are actually
used for the removal of the acetylenic compounds; these methods
permit the desired content to be obtained, but require essentially
high operating costs and/or particular equipments and thus high
investment costs.
It has been found that the acetylenic compounds can be
totally removed without having recourse to the operations of
the prior art, considerable economic advantages being simultaneously
obtained both due to the simplicity of the operations proposed in
substitution for those actually used, and for the simultaneous use
of the acetylenic compounds (the streams rich in these compounds
being normally disposed by flame burning), through their conversion
into industrially interesting compounds.
The object of the present invention is a process for
the removal of acetylenic compounds from a hydrocarbon stream
which comprises the steps of :
(a) reacting an alcohol or glycol with the acetylenic
compounds in the hydrocarbon stream to produce vinyl ethers, gem-
diethers, or mixtures thereof, the reaction taking place in the
presence of an acid ion exchange resin catalyst wherein the
acid groups havè been totally replaced by mercuric ions (Hg~+ ions)
and ions of alkali-earth metals (Me n~ ions); and
(b) subjecting the reacted hydrocarbon stream from
step (a) to distillation to remove the vinyl ethers, gem-diethers,`
or mixtures thereof.
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The ion exchange resin which is used has, as
above indicated, acid property and preferably contains
sulphonic groups
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(-SO3H groups supported onto resins, for example polystyrene,
divinylbenzene or polyphenolic resins), but resins containing
-COOH groups, preferably supported onto acrylic resins,can also
be used.
Generally, the ions of the afore-mentioned metals can
be added to the resin in form of their salts, e.g. as mercuric
and sodium nitrate or acetate, but to this end hydroxides can
also be used (for instance sodium can be added in the hydroxide
form); the content of Hg+~ ions of the resin can also be higher
than that of the Men+ ions.
It is preferred that firstly the Men~ ions and then the
Hg~+ ions are added to the resins; it is also preferable that
during the operation aqueous solutions are employed and that the
resin, after the treatment, is dehydrated by washing with metha-
nol or, generally, with the alcohol used in the reaction.
The hydrocarbon streams which can be processed
according to the present invention are paraffinic, olefinic and
dienic streams (par~icularly streams rich in ethylene, propylene,
butadiene, acetylene, propyne, l-butyne, 2-butyne, vinylacetylene,
2Q and diacetylene). The hydrocarbon stream also comprises satura-
ted or unsaturated hydrocarbons having from 2 to 4 carbon atoms.
The addition can be carried out within a wide range of
temperatures and pressures; the treatment is advantageously
carried out between -20C and ~80C, and more suitably between
10C and 50C, under a pressure selected so as to maintain, at
- the operating temperature, the hydrocarbon streams under treat-
ment either in liquid ox in gaseous phase (depending on the
opportunity of treating these streams in vapour or liquid phase).
By operating in liquid phase, the spatial velocity (LHSV) of the
reaction is of between 0.1 and 100 (cu.cm/h.g). It is advisable
to carry out the treatment in the presence of a stoichiometric
excess of the alcohol or glycol with respect to the acetylenic
compounds: as a matter of fact a molar ratio (alcohol/total
acetylenic compounds) = 1.05 - 2.1 is suitably adopted, particu-
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larly depending on whether vinyl ethers or gcm-diethers are
desired.
It is o interest to point out that, by operating accor-
ding to the present invention, the resins totally exchanged
with mercuric ions as well as with ions of alkali and earth-
alkali metals maintain their activity for a period at least
three times higher than the resins without ions of alkali or
earth-alkali metals. This is probably also due to the fact
that in the case of the resins treated according to the in-
vention~ the secondary reactions normally occurring in the
presence of acid ion exchange resins are of minor importance.
Some examples having the purpose of better illustrating
the invention, without anyhow limiting it, shall be now provided.
EXAMPLE
98 g of acid resin of the Amberlyst 15 type (containing
acid groups such as those of the -S03H type) are treated with
2 lt of a 10% by weight aqueous solution of NaOH; the mixture
is stirred for one hour and then filtered~ and the resin is
washed with distilled water until a neutral reaction is obtain-
ed. The same resin is thereafter treated with 300 mls of an
aqueous solution~ made acid by acetic acid~ containing 2 g.ions
of Hg~ (as mercuric acetate); the mixture is kept under stirr~ng
for 24 hours and then filtered under vacuum and repeatedly washed
with anhydrous methanol.
- A part of the thus treated resin is charged in a 10 ml
volume reactor, maintained at 40C by means of a thermostatic
circuit. Under a pressure of 10 relative atmospheres~ 50 mls of
a C4 stream, rich in butadiene (about 55% ~, and containing
about ~300 ppm of vinylacetylene, about 1500 ppm of l-butyne~
and about 1000 ppm of propyne~ are continuously fed by a pump
together with methanol in an amount such as the alcohol/total
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acetylenic compounds is 2.1 moles/mole.
The content of all the three aforesaid acetylenic
compounds as determined in the samples of tne liquid effluent
from the reactor (the samples being taken every 5 hours) is
always ~ 10 ppm throughout the time of the test (120 hours ).
EXAMPLE 2
In the same reactor of the Example l~ by operating at
a temperature of 80C and under a pressure of a40ut 20 relative
atmospheres~ 50 mls/h of propylene~ containing 0.3% propy.ne are
fed by the pump together with methanol in an amount such as the
alcohol/acetylenic compound is 2.1 moles/mole The contents of
prop~ne and 2~2-dimethoxypropane~ as determined in the samples
of the liquid taken (every 5 hours~ from the reactor effluent
throughout the time of the test (300 hours ) are ~ lOppm
and o.78% by weight re6pectively.
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