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The Advantages of the Amoco Process in Producing Benzoic Acid

The Amoco process is applied to the purification of crude terephthalic acid, the product of which is suitable for polyester manufacturing. Benzoic acid, along with other derivatives, is collected as an impurity during this purification. Producing benzoic acid via the Amoco process is advantageous, as it generates a product of high purity at no extra economic or environmental cost.

  1. Amoco Process

    • The Amoco process is the most common purification technique used globally. It involves the air oxidation of p-xylene, using acetic acid and a cobalt acetate catalyst. The process is divided into the reactor unit, the separation and drying unit, and the recovery unit. The most predominant impurity is benzoic acid derivative 4-formylbenzoic acid, produced via the incomplete oxidation of p-xylene. Benzoic acid is also recovered in trace amounts.

    Benzoic Acid

    • The United States produces approximately 125,000 tons of benzoic acid annually. It is used as a preservative in the food industry, and has industrial uses as an intermediate product in fragrance and paint manufacturing. Benzoic acid is mainly produced via the liquid-phase oxidation of toluene, however, it is identified among the recovered impurities during the Amoco process, using capillary electrophoresis or high performance liquid chromatography.

    Economic Advantages

    • As benzoic acid is a by-product of the overall process, Amoco purification yields two commercially viable products. Although recovered in trace quantities, benzoic acid has a very high purity of up to 95 percent, thus requiring no further purification. Also, as the Amoco process is straightforward and involves only a single step, it requires little technical management.

    Environmental Advantages

    • Raw materials used in the Amoco process originate from the oil industry, and are recyclable. As a result, they are readily accessible and cause fewer pollution issues. The one step vapour phase reaction involved in the process also eliminates concerns over the high concentration build up of harmful materials such as bromine and various salts.

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