PREPARATION OF ACIDS AND ESTERS

Propylene and ethylene may be carbonylated to form carboxylic acid esters or carboxylic acids in the presence of a catalyst complex containing 1 mole of BF3 and 1 mole of a second complexing component. The carboxylic acid product or acid portion of the ester product has one more carbon atom than the olefin reacted. High yields of these products are obtained. In the case of the formation of the ester, the second complexing component is an alcohol, while in the case of the preparation of carboxylic acid, the second complexing component is water. Methyl isobutyrate and methyl propionate formed by the carbonylation of propylene and ethylene, respectively, in the presence of a BF3 CH3OH catalyst may be dehydrogenated to prepare methyl methacrylate and methyl acrylate, respectively. Similarly, the isobutyric acid and propionic acid formed from propylene and ethylene, respectively, in the presence of BF3 H2O catalyst may be dehydrogenated to prepare methacrylic acid and acrylic acid, respectively. In the case of the BF3 alcohol catalyst is used, it is readily recovered from the reaction product and recycled. After carbonylation is carried out and approximately one-half of the alcohol is consumed, a reaction mass containing the BF3, the alcohol, and the carboxylic acid ester in a 2:1:1 molar ratio is formed. In the first recovery step, the one mole of the free BF3 is vaporized from the reaction mass. The remaining admixture is a 1:1:1 mixture of the three aforesaid compounds. To this mixture additional alcohol is added and the mixture is subjected to distillation. A carboxylic acid ester/alcohol azeotrope and residual alcohol are removed by the distillation, to leave a residue containing a 1:2 BF3/alcohol complex. This complex is combined with an additional mole of BF3 to form the 1:1 catalyst complex used in the carbonylation. The additional mole of BF3 is preferably that initially separated from the reaction mass; however, it may be obtained from an external source. The carboxylic acid ester/ alcohol mixture may be separated by azeotropic distillation using an azeotroping agent, such as octane, to recover the alcohol-octane as overhead product and the carboxylic acid ester as bottoms product.