Patent GB-654471-A (GB)
Title: Improvements in or relating to preparation of esters of vinyl alcohol
Filed: 1948-03-05
Abstract: Vinyl esters are prepared by reacting acetylene with a saturated aliphatic or aromatic mono-carboxylic acid in the vapour phase at 200-400 DEG  C. in contact with a catalyst comprising a silicate of a metallic element having a maximum valence not greater than 2, mounted on a support such as pumice, starch, activated carbon or alumina. Preferred metal silicates are those of cadmium, zinc and mercury, but those of magnesium, calcium, strontium, barium, beryllium, copper, lithium, sodium, potassium and caesium may be used.  A mixture of silicates may be used in the catalyst.  Specified carboxylic acids are acetic, propionic, n-butyric, n-valeric, caproic, heptylic, caprylic, lauric, stearic, chloracetic, trichloracetic, phenylacetic, trimethylacetic, methoxyacetic, pyruvic, thioglycollic, benzoic, toluic, naphthoic, 1-anthroic and salicylic.  The reaction takes place at atmospheric pressure, preferably at 250-350 DEG  C.  The particles of catalyst should preferably be 4-6 mesh or larger to minimize the formation of by-products such as ethylidene esters. Examples show the production of vinyl acetate and vinyl benzoate, using as catalysts cadmium silicate on pumice and on starch and zinc silicate on pumice.  Specification 633,681 is referred to.  According to the Specification as open to inspection under Sect. 91, silicates of the above-mentioned metals may be used as catalysts, alone or supported on a carrier such as silica or one of the mountings quoted above, for the vapour-phase reactions of acetylene with carboxylic acids in general.  Additional acids specified are acrylic, methacrylic, crotonic, 3-butonoic, sorbic, propiolic, tetrolic, furoic, tetrahydrobenzoic, malonic, succinic, glutaric, adipic, pimelic, suberic, phthalic, trimellitic and pyridine carboxylic acids.  This subject-matter does not appear in the Specification as accepted.ALSO:Catalysts for the vapour-phase reaction of acetylene with carboxylic acids to give vinyl esters comprise a silicate of a metallic element having a maximum valence not greater than 2, supported on a carrier such as pumice, starch, activated carbon or alumina.  Preferred metal silicates are those of cadmium, zinc and mercury, but lithium, sodium, potassium, caesium, copper, beryllium, magnesium, calcium, strontium and barium may be used. A mixture of silicates may be used in the catalyst.  The particles should preferably be 4-6 mesh or larger to minimize the formation of byproducts.  The catalysts have a life of 100 hours or more and may be re-activated by steaming.  In the examples (1) pumice is boiled with cadmium chloride solution, sodium silicate solution added and the mixture filtered off, washed and dried at 125 DEG  C. for 2-3 hours.  Before using it is further dried at 300 DEG  C. in a stream of nitrogen; (2) solutions of cadmium nitrate and sodium silicate are mixed and the precipitate filtered off.  Without drying, it is mixed with starch paste and then dried at 125 DEG  C; (3) pumice is added to sodium silicate solution and stirred with zinc chloride solution. The water is evaporated and the residue dried at 165 DEG  C. Specification 633,681 is referred to.  According to the Specification as open to inspection under Sect. 91, silicates of the above-specified metals may be used as catalysts either alone or mounted on a support, silica being mentioned in addition to the carriers specified above.  This subject-matter does not appear in the Specification as accepted.