This invention relates to the field of methods for catalytically oxidizing carbon monoxide to carbon dioxide, and more particularly, to methods for selectively catalytically oxidizing carbon monoxide present in a hydrocarbon stream using a specially prepared supported cobalt oxide catalyst.
Numerous synthetic routes to such products as acetic acid, acrylic acid, vinyl acetate and benzyl acetate, rely upon the catalytic oxidation of a hydrocarbon, for example, ethylene in the case of acetic acid and vinyl acetate, propylene in the case of acrylic acid, and toluene in the case of benzyl acetate. In addition to the principal reaction product, small quantities of carbon monoxide are also produced in these reactions. Following the recovery of the principal product, the reaction effluent is recycled so that any unreacted starting material can be fully utilized. It is known that carbon monoxide deactivates the catalysts, for example, palladium metal, which are commonly used for these syntheses. Accordingly, it is highly desirable that the carbon monoxide be converted to the dioxide prior to the recycling of the reaction effluent without, however, causing any significant oxidation of the unreacted hydrocarbon present in the effluent.
It is well known that cobalt oxide is a useful catalyst for the oxidation of carbon monoxide to carbon dioxide. Ismailov et al., Azerb. Khim. Zh., 1969, (4), 75-80 (Russian), describes the oxidation of carbon monoxide and gaseous hydrocarbon present in a simulated internal combustion engine exhaust using a supported cobalt oxide catalyst. The maximum level of carbon monoxide conversion was 50% and was achieved at 800.degree. C. Belgium Pat. No. 814,130 describes a cobalt aluminate catalyst useful in gas masks and as a component of cigarette filters. U.S. Pat. No. 3,839,545 describes the accelerated combustion of both carbon monoxide and hydrocarbons in exhaust gases using a catalyst containing a mixture of copper and manganese oxides and the oxides of other metals such as cobalt. The oxidation of hydrocarbons and CO is described in the article entitled "The Oxidation of Hydrocarbons and CO over Metal Oxides III. Co.sub.3 O.sub.4 " by Yung-Fan Yu Yao, Journal of Catalysis, 33, 108-122 (1974). In none of the foregoing is there a selective oxidation of carbon monoxide to the virtual exclusion of the hydrocarbon component which may be present. The catalytic oxidation of propylene is described in the article entitled "Regularities in Catalytic Properties of Metal Oxides in Propylene Oxidation" by U. Morooka and A. Ozaki, Journal of Catalysis, 5, 116-124 (1966). A series of experiments is discussed therein and shows that a cobalt oxide catalyst, prepared by calcining silicon carbide pellets impregnated with cobalt nitrate, readily oxidized propylene.