IE43609B1 - Process for the addition of alcohols to acetylenic compounds, and process for the removal of acetylenic compounds from mixtures - Google Patents

Abstract

The technical problem of purifying a hydrocarbon stream by removing alkyne type impurities, in particular of the acetylene type, is solved by carrying out an addition reaction with alcohol or glycol on these impurities with the aid of an acidic ion exchange resin, in which the acidic groups are totally exchanged either with mercuric ions or with alkali metal or alkaline earth metal ions, also producing vinyl ethers and geminal diethers, which are of industrial interest.

Description

The present invention relates to a process for the chemical addition of an alcohol to an acetylenic compound which may be present as a component of an organic mixture, preferably a hydrocarbon mixture, which mixture optionally contains at least one inorganic compound.

The present invention also relates to a process which permits such mixtures to be purified of the acetylenic compound which can be used for the concomitant production of industrially interesting products.

It is known that for many uses olefinic and saturated hydrocarbons, and particularly diolefinic hydrocarbons, must be free from acetylenic compounds; for instance, the content of acetylenic compounds in the butadiene monomer must be 50 ppm, owing to the poisoning action of the acetylenic compounds on polymerization catalysts.

According to the present invention, there is provided a process for adding an alcohol to an acetylenic compound, which process comprises reacting an alcohol and an acetylenic compound in the presence of an acidic ion-exchange resin, the acidic groups of which are substantially totally exchanged with both mercuric ions and ions of an alkali metal or alkaline earth metal.

The process can be effected when the acetylenic compound is part of a hydrocarbon mixture, without significantly affecting any olefinic compounds present.

In fact, it has been found that the acetylenic compounds can be substantially totally removed at a reasonable cost attributable to the simplicity of the -Z43609 operation and to the simultaneous conversion of the acetylenic compounds to industrially interesting compounds, instead of burning the separated acetylenic compounds as has happened previously.

The alcohol need not be a monohydric alcohol; it could be, for instance, a dihydric alcohol or a higher polyhydric alcohol. The alcohol could be methanol or a glycol, preferably ethylene glycol.

The resulting ethereal products can be subsequently removed and recovered through simple and economic distillation operations.

The ion exchange resin which is used has, as indicated above, an acidic nature and preferably contains sulphonic groups (-SOgH groups) preferahly supported on a polystyrene, di vinyl benzene or polyphenolic resin; another suitable resin is that containing -COOH groups, preferably supported on acrylic resins.' Generally, the ions of the aforementioned metals can be added to the resin in form of 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 be higher than that of the Hn+ ions, where M is the alkali metal or alkaline earth metal.

It is preferred that firstly the Mn+ 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 methanol or, generally, with the alcohol used in the reaction.

Hydrocarbon feeds which can be processed according to preferred embodiments of the present invention are paraffinic, olefinic and dienic feeds (particularly streams rich in ethylene, propylene and butadiene)..

More particularly, but not exclusively, the present invention also provides (i) the removal from a hydrocarbon stream comprising ethylene, prooylene and butadiene, either alone or in admixture with one or more other saturated or unsaturated hydrocarbons having 2 to 4 carbon atoms, of acetylene, propyne, 1-butyne, 2-butyne, vinyl acetylene and diacetylene, with the simultaneous production of vinyl ethers and/or of the gem-diethers of these compounds. (ii) the removal from butadiene streams, either alone or in admixture with one -3or more other saturated or unsaturated hydrocarbons having the same number of carbon atoms, of propyne, 1-butyne, 2-butyne, vinyl acetylene and/or diacetylene, with the simultaneous.production of the vinyl ethers and/or of the gem-diethers of these compounds; (iii) the removal from propylene streams, either alone or in admixture with one or more other saturated or unsaturated hydrocarbons having the same number of carbon atoms, of propyne, with the simultaneous production of the corresponding vinyl ether and/or gem-diether; and (iv) the removal from ethylene streams, either alone or in admixture with ethane, of the acetylene with the simultaneous production of the corresponding vinyl ether and/or gem-diether.

The vinyl ether(s) and/or gem-diether(s) produced in (i) to (iv) above can be separated by distillation.

The addition can be carried out within a wide range of temperatures and pressures; the treatment is advantageously carried out in the range from -20°C to +80°C, more preferably from 10°C to 50°C, at a pressure selected so as to maintain, at the operating temperature, the hydrocarbon stream under treatment either in the liquid or in the gaseous phase (depending on the wish to treat the stream in the vapour or the liquid phase). When operating in the liquid phase, the liquid hourly space velocity (LHSV) of the reaction is preferably in the range from 0.1 to 100 cc per hour per gram. It is advisable to carry out the treatment in the presence of a stoichiometric excess of the alcohol with respect to the acetylenic compound; as a matter of fact a molar ratio of alcohol:total acetylenic compounds in the range from 1.05:1-2.1:1 is suitably adopted, depending on whether vinyl ethers or gem-diethers are desired.

It is of interest to point out that, by operating according to the present invention, the resins totally exchanged with mercuric ions and ions of the alkali or alkaline earth metal maintain their activity for a period at least three times longer than similar resins without ions of alkali or alkaline metal. This is probably also due to the fact that, in the case of the resins treated according to the invention, the secondary reactions normally occurring in the presence of -443609 acidic ion exchange resins are of minor importance.

The following Examples illustrate the present invention.

EXAMPLE 1 Grams of acid resin of the Amberlyst 15 type (containing acid groups of the -S03H type) were treated with 2 litres of a 105« by weight aqueous solution of NaOH (the word Amberlyst being a Trade Mark); the mixture was stirred for one hour and then filtered, and the separated resin was washed with distilled water until a neutral reaction was obtained. The same resin was thereafter treated with 300 ml of an aqueous solution, which had been made acidic by the addition of acetic acid, containing 2 g. ions of Hg++ (as mercuric acetate); the mixture was kept stirred for 24 hours and then filtered under vacuum and repeatedly washed with anhydrous methanol.

Part of the thus treated resin was introduced into a 10 ml capacity reactor, maintained at 40°C by means of a thermostatic circuit. Under a pressure of 10 atmospheres gauge there were continuously fed to the reactor by a pump 50 ml (per hour) of a / stream, rich in butadiene (about 55%) and containing about 4300 ppm of vinyl acetylene, about 1500 ppm of 1-butyne, and about 1000 ppm of propyne, together with methanol in an amount such that the molar ratio of alcohol:total acetylenic compounds was 2.1:1.

The content of all the three acetylenic compounds, as determined in samples of liquid effluent from the reactor, where the samples were taken every 5 hours was always 1Θ ppm throughout the time of the test (120 hours).

EXAMPLE 2.

The same reactor as described in Example 1 filled with the same resin, was used. At a temperature of 80°C and at a pressure of 20 atmospheres gauge, 50 ml/hour of propylene, containing 0.3% propyne, were fed by a pump, as well as methanol in an amount such that the alcohol:acetylenic compound molar ratio was 1.1:1. The contents of propyne and 2,2-dimethoxypronane, determined in sambles of the liquid taken every 5 hours from the reactor effluent throughout the time of the test (300 hours), were 10 ppm and 0.78% by weight, respectively. -543609 Reference is made in accordance with Section 14 of the Patents Act 1964 to our Patents Nos. 41,363 and 41,364.

Claims (24)

1. A process for,adding an alcohol to an acetylenic compound, which process comprises reacting an alcohol and an acetylenic compound in the presence of an acidic ion-exchange resin, the acid groups of which are substantially totally exchanged with both mercuric ions and ions of an alkali metal or alkaline earth metal.

2. A process according to Claim 1, wherein the acetylenic compound is present in an organic mixture which optionally contains at least one inorganic compound.

3. A process according to Claim 1 or 2, wherein the organic mixture is a hydrocarbon mixture.

4. A process according to Claim 1, 2 or 3, wherein the alcohol is a monohydric or dihydric alcohol.

5. A process according to any preceding claim, wherein the acid ion-exchange resin contains sulphonic groups (-SO^H), the hydrogen ions of which have been exchanged by the metal ions.

6. A process according to Claim 5, wherein the sulphonic groups are supported on a polystyrene, polyphenolic or divinylbenzene resin, or a mixture of such resins.

7. A process according to any one of Claims 1 to 4, where the acid ion-exchange resin contains carboxylic groups (-COOH), the hydrogen ions of which have been exchanged by the metal ions.

8. A process according to Claim 7, wherein the carboxylic groups are supported on acrylic resins,

9. A process according to any preceding claim, wherein the mercuric ions have been previously added to the resin in the form of a mercuric salt.

10. A process according to Claim 9, wherein the mercuric salt is mercuric nitrate or acetate.

11. A process according to any preceding claim, wherein the ions of alkali metal or alkaline earth metal have previously been added to the resin in the form of a -7salt or hydroxide.

12. A process according to Claim 11, wherein the salt is the nitrate or acetate.

13. A process according to any preceding claim, wherein the alkali metal is sodium.

14. A process according to the preceding claims, wherein the reaction is carried out at a temperature in the range from -20°C to +80°C.

15. A process according to Claim 14, wherein the temperature is in the range from 10°C to 50°C.

16. A process according to any preceding claim, wherein the molar ratio of alcohol to total acetylenic compounds is in the range from 1.05:1 to 2.1:1.

17. A process according to any preceding claim, wherein, when operating in the liquid phase, the liquid hourly space velocity is in the range from 0.1 to 100 cc per hour per gram of resin.

18. A process for removing from butadiene, either alone or in admixture with one or more other saturated or unsaturated hydrocarbons having the same number of carbon atoms, any propyne, 1-butyne, 2-butyne, vinyl acetylene or diacetylene present, which process comprises adding an alcohol to the propyne, 1-butyne, 2-butyne, vinyl acetylene or diacetylene, according to the procedure claimed in any one of Claims 1 to 17, and separating the resulting vinyl ethers and/or gem-diethers by distillation.

19. A process for removing from a hydrocarbon mixture comprising ethylene, propylene and butadiene, either alone or in admixture with one or more other saturated Dr unsaturated hydrocarbons having from 2 to 4 carbon atoms, any acetylene, propyne, 1-butyne, 2-butyne, vinyl acetylene or diacetylene present, which process comprises adding an alcohol to the acetylene, propyne, 1-butyne, 2-butyne, vinyl acetylene, )r diacetylene, according to the procedure claimed in any one of Claims 1 to 17, ind separating the resulting vinyl ethers and/or gem-diethers by distillation. '.0. A process for removing propyne from propylene, either alone, or in admixture fith one or more other saturated or unsaturated hydrocarbons having the same number f carbon atoms, which process comprises adding an alcohol to the propyne according o the procedure claimed in any one of Claims 1 to 17, and separating the resulting inyl ether and/or gem-diether by distillation.

20. 21. A process for removing acetylene from ethylene, either alone or in admixture with ethane, which process comprises adding an alcohol to the acetylene according to the procedure claimed in any one of Claims 1 to 17, and separating the resulting vinyl ether and/or gem-diether by distillation.

21. 22. A process substantially as described in either of the foregoing Examples.

22. 23. A vinyl ether and/or gem-diether, whenever produced by a process according to any preceding claim.

23.

24. A hydrocarbon having a reduced content of acetylenic compound(s), whenever produced by a process according to any one of Claims 1 to 22.