Process for handling acetylene safely and employing it with safety in chemical reactions, especially in the production of vinyl ethers

摘要

PICT:0641436/IV (b)/1 In processes involving the handling of acetylene at temperatures and pressures at which it is normally explosive, the danger of explosion is eliminated by contacting the acetylene, while still under non-explosive conditions, with a volatile normally-liquid organic compound which is non-explosive under the conditions of handling; the compound is maintained at a predetermined temperature in the liquid phase, so that the ratio of acetylene to vapour taken up is also predetermined and such a mixture is non-explosive when raised to the temperature and pressure at which it is to be handled; the mixture is then compressed at a temperature above that at which the vapours will be condensed and, if necessary, finally brought to the desired temperature at which it is to be handled. The process is normally applicable to chemical reactions involving acetylene, when the liquid organic compound may be the other reactant or the product of reaction, if these materials have a suitable vapour pressure. Otherwise, an inert diluent may be used, a wide range of suitable compounds being mentioned, consisting of hydrocarbons, esters, ethers, furfural and pyridine. Fig. 1 shows apparatus suitable for batch processes. Acetylene at a low pressure (about atmospheric) is led from the holder 1 to the carburetter 3, held at a predetermined temperature, where the desired amount of the vapour of the organic liquid is taken up. The compressor 5 brings the pressure up to that necessary for the reaction, the temperature of the compressor being sufficiently high to prevent condensation of the vapour therein. The gaseous mixture is brought to the reaction temperature in the pre-heater 7 and introduced into the autoclave 8 where the reaction takes place. If the diluent has a vapour pressure greater than the reaction pressure, it is continuously run off through line 9, condensed in the condenser 11 and returned to the carburetter 3. If the product of the reaction is used as diluent, only a portion thereof is so used, the remainder being retained in the autoclave. Fig. 2 shows the application to a continuous process. Acetylene from a holder 21 passes through carburetter 27, compressor 29 and pre-heater 31 as before, and enters the reaction tower 32. The liquid products are separated from acetylene in the degasser 37 and are separated into diluent and reaction product in the still 40. If the reaction product is used as diluent, the still 40 serves to withdraw a certain portion thereof to the tank 49 for re-use. In each case, the unreacted acetylene is withdrawn from the reaction zone and recycled, the pressure being reduced to the safe value for acetylene alone before it is separated from the vapour of the organic liquid. Suitable types of carburetter for both types of process are illustrated. The process of the invention may be applied to any chemical reaction involving acetylene, e.g. production of mono-vinyl-acetylene, of vinyl chloride, and of acetaldehyde by the mercury process, but the reactions with secondary amines to give N-vinyl compounds and with carboxylic acids to give esters are excluded, these forming the subjects of Specifications 641,437 and 641,438 respectively. The Specification is particularly concerned with the reaction of acetylene with hydroxy compounds (especially lower aliphatic alcohols) to yield vinyl ethers. The hydroxy-compounds may be represented by the formula X.R.OH, R being an aliphatic, hydroaromatic or aromatic, preferably hydrocarbon radical or an aralkyl radical, X being -H, -NY2 or -(OR)n-OY, Y being -H, -R or -R.OH and n being zero or an integer. Hydroxy-acids are, however, excluded, since they yield esters, not ethers. Detailed examples are given of the production of methyl vinyl ether, ethyl vinyl ether and n-butyl vinyl ether using the apparatus shown in Fig. 2, and of n-octadecyl vinyl ether using that shown in Fig. 1. Suitable hydroxy compounds are mentioned, including aliphatic alcohols, glycols, polyhydroxy compounds and their alkyl and aryl ethers, amino-alcohols and phenols. Specification 427,036 is referred to. The Specification as open to inspection under Sect. 91 shows further types of carburetters where the acetylene is contacted with the diluent in the vapour phase instead of the liquid phase. The reaction between acetylene and hydroxy acids and their salts (e.g. alkali metal glycollates) is also mentioned, and the subject-matter of Specifications 641,437 and 641,438 as open to inspection under Sect. 91 is included. This subject-matter does not appear in the Specification as accepted.