High molecular weight aliphatic straight-chain monocarboxylic acids and derivatives thereof are used in various polish formulations for shoes, leather, furniture, floors and automobiles, in carbon paper, in paper sizing compositions and in coatings. They are also useful as dispersing additives, lubricating agents, mold release agents and the like. In the past high molecular weight acids were typically obtained by treatment of natural products such as carnauba wax, beeswax, candelilla wax and montan wax. Montan wax (obtained from lignite and other bitumin-enriched soft coals by extraction with organic solvents) has been a particularly useful source for high molecular weight aliphatic acids since about 70% of the crude extract is a wax component composed primarily of free acids (25%) and mixed esters of long-chain acids and alcohols (65%).
The monocarboxylic acids can be obtained from montan wax using saponification procedures, however, the chromic acid oxidation process developed in Germany is used for commercial production of montan wax acids. Montan wax acids are primarily mixed aliphatic monocarboxylic acids containing from about 8 to 40 carbon atoms. The bulk of the acids contain an even number of carbon atoms and fall within the C.sub.22-34 carbon content range with the C.sub.26, C.sub.28 and C.sub.30 acids generally comprising about 30-45% by weight of the total acids. The acid distribution can vary depending on the particular type or source of montan wax. The composition of German montan wax, for example, differs appreciably from that of American montan wax. In all cases, however, the predominant monocarboxylic acids obtained by the chromic acid oxidation of montan wax have an even number of carbon atoms.
It would be extremely useful to have a synthetic source available for the production of high molecular weight aliphatic straight-chain monocarboxylic acids in approximately the same carbon content range as montan wax acids. In the past there has been no completely satisfactory method for producing such acids. The various known processes all have shortcomings and are not acceptable for commercial operations. For example, oxidation of .alpha.-olefins or mixtures of .alpha.-olefins such as are available from the polymerization of ethylene produce monobasic acids, however, large amounts of undesirable low molecular weight acids, polymeric residue and other undesirable by-products are formed. Nitric acid oxidation of .alpha.-olefins produces undesirable nitro by-products in addition to giving poor yields of the desired acids. The carboxylation of .alpha.-olefins with carbon monoxide using acid catalysts followed by hydrolysis also gives low yields due to the poor selectivity of the reaction. Procedures such as those described in U.S. Pat. Nos. 2,293,649 and 3,842,106 can also be employed to produce high molecular weight acids, however, these are branched-chain acids.
It would be highly useful and advantageous if a process were available to produce high molecular weight aliphatic straight-chain acids in good yield and high purity, especially if the process were readily adaptable to commercial operations.