Acetaldehyde oxygen requirements

The oxygen required for the one-step process is calculated based on the reaction stoichiometry and catalyst selectivity. For simplification, it is assumed that the ethylene that does not form acetaldehyde is oxidized to carbon dioxide and water. Actually, several hydrocarbon by-products are also formed but the quantities are small and this simplification does not introduce appreciable error. 

The ratios shown in Figure 11 are normalized based on 1.00 pound of actetaldehyde and can be used to calculate the approximate oxygen requirement per pound of acetaldehyde produced. The actual quantity of oxygen... 

Ethyl acetate is an oxygenated solvent widely used in the inks, pharmaceuticals and fragrance sectors. The current global capacity for ethyl acetate is 1.2 million tonnes per annum. BP Chemicals is the world s largest producer of ethyl acetate. Conventional methods for the production of ethyl acetate are either via the liquid phase esterification of acetic acid and ethanol or by the coupling of acetaldehyde also known as the Tischenko reaction. Both of these processes require environmentally unfriendly catalysts (e.g. p-toluenesulphonic acid for the esterification and metal chlorides and strong bases for the Tischenko route). In 1997 BP Chemicals disclosed a new route to produce ethyl acetate directly from the reaction of ethylene with acetic acid using supported heteropoly acids... 

Several processes based on air or oxygen have been developed.890-895 Oxidation with air (260-280°C) or oxygen (230°C) is carried out at about 15-25 atm at a limited conversion (about 10-15%) to achieve the highest selectivity.896-898 High-purity, sulfur-free ethylene is required to avoid poisoning of the catalyst. Ethylene concentration is about 20-30 vol% or 5 vol% when oxygen or air, respectively, is used as oxidants. The main byproducts are C02 and H20, and a very small amount of acetaldehyde is formed via isomerization of ethylene oxide. Selectivity to ethylene oxide is 65-75% (air process) or 70-80% (02 process).867... 

The reactions were conducted with monomer containing less than 50p.p.m. acetaldehyde at temperatures of 70°—110°C and required about two hours for completion. About half of this time was taken by an induction period which was due in part to water, oxygen and acetaldehyde present in the reaction mixtures but also to factors still unknown. The amount of catalyst was varied from 0.1 to 5% to give a suitable rate. The authors believe that the reaction occurs through an anionic type mechanism initiated by hydroxyl or bicarbonate ions. 

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