Patent GB-798065-A (GB)
Title: Process for the production of carboxylic acids
IPC: C07C51/14
Filed: 1955-05-10
Abstract: Carboxylic acids are obtained by initially reacting an olefine with carbon monoxide in the liquid phase at elevated pressure and at a temperature below 100 DEG  C. without the addition of water and in the presence of a substantially anhydrous catalyst consisting of monohydroxy fluoboric acid or a complex compound thereof with phosphoric acid or sulphuric acid, and then adding water in not more than the stoichiometric amount required to form the acid, whereby the carboxylic acid separates out.  The catalyst which remains after separation of the carboxylic acid may be used again without further processing, in the reaction.  The reaction may be carried out under mild conditions, e.g. at or below room temperature and at pressures not higher than 100 atmospheres, e.g. between 50 and 100 atmospheres, but higher pressures up to 600 atmospheres may be used.  The olefine used may be an unbranched olefine but is preferably an olefine branched at the double bond. When the olefine is branched at the double bond it is desirable to use high carbon monoxide pressures so as to avoid dimerization of the olefine.  It is advantageous, particularly when an olefine branched at the double bond is used to react part of the olefine with carbon monoxide under pressure in the presence of the catalyst, then add water in less than the stoichiometric amount needed to form the acid, repeating these two stages at least once by adding more of the olefine and more water alternately, and then adding water to bring the total amount of water added to not more than the stoichiometric amount required to form the acid.  The monohydroxy fluoboric acid-phosphoric acid (or sulphuric acid) catalyst can be prepared by introducing boron trifluoride at elevated temperature, e.g. 100 DEG  C., into 50 per cent or 85 per cent phosphoric or sulphuric acid until no further increase in weight occurs.  The monohydroxy fluoboric acid [H(BF3OH)] may be obtained by the saturation of water with boron fluoride while cooling with ice. Examples are given for the production of (1) trimethyl acetic acid and minor amounts of C9 and higher acids from isobutene using a catalyst of the approximate composition 2(H3PO4BF3)+H(BF3OH) made from 85 per cent phosphoric acid and boron trifluoride; (2) and (3) a ,a -dimethyl valeric acid together with minor amounts of higher and lower molecular weight fatty acids from 2-methyl-pentene-1 using the same catalyst as in (1) and a catalyst of the composition H3PO4.-BF3+4H(BF3OH) made from BF3 and 50 per cent H3PO4; (4) and (5) a ,a -dimethyl valeric acid and minor amounts of higher and lower molecular weight fatty acids from 2-methylpentane-1 using monohydroxyfluoboric acid itself and a mixture thereof with sulphuric acid (made from boron trifluoride and 85 per cent sulphuric acid) respectively as catalysts; (6) C9 fatty acids together with some higher and lower molecular weight fatty acids from 2-ethyl-hexene-1 using a catalyst as in (1); and (7) a mixture of a ,a -dimethyl valeric acid and a C13 carboxylic acid together with small amounts of higher and lower fatty acids from an isododecene (obtained by dimerisation of 2-methyl pentene-1 using a catalyst as in (1).  In another example (8) 2-methyl-pentene-1 is reacted with carbon monoxide at pressures of 100 and 300 atmospheres in the presence of a catalyst as used in (1) and (5) respectively and the product reacted with water to form a ,a -dimethyl valeric acid and a C13 carboxylic acid, the latter product predominating at the lower pressure.  Other olefines specified are the unbranched pentene-2 which yields a mixture of a -methyl valeric acid, a -ethyl butyric acid, and a ,a -dimethyl butyric acid, and 2-methyl-butene-2 which yields a ,a -dimethyl butyric acid.  The isododecene used in (7) is obtained by dimerization of 2-methyl pentene-1 in the presence of a catalyst as in (1) and is a mixture of substantially three isomeric trimethyl nonenes.  Specification 743,597 is referred to.