Published October 2000
Commercial liquid-phase oxidation of organic compounds based on pure or high-purity oxygen is a recent advancement in oxidation technology. This report reviews the technology and evaluates three potential areas of its applications-production of terephthalic acid, adipic acid and phenol on current commercial scales.
Conventionally, air is the source of oxygen gas for a number of liquid-phase oxidation reactions. The air is usually delivered into the reactors via axial flow impellers or gas spargers, which break up the gas into tiny bubbles providing a high interfacial area for mass transfer between the gas (oxygen) and the liquid reactants in the reaction vessel.
However, since air also contains the inert nitrogen gas, the reactor vent gas contains significant amounts of solvent and reactants entrained in the gas as vapor. The recovery of such organic chemicals from the gas requires an extensive chemical treatment. In general, solvent loss is higher than it would be when using an oxygen-enriched gas. Additionally, the lower concentration of oxygen in air depresses the oxidation rate necessitating higher reaction times and larger reactors.
Oxidation with pure or a high-purity oxygen gas reduces the amount of the vent gases from the reactor and results in a much lower loss of solvent and reactants. Means for oxygen distribution that keep the oxygen within the explosive limits in the reactor system are claimed to have been developed. Requirement of compression power for air compressors when using oxygen is completely eliminated. Reaction time is reduced, and smaller-sized or a fewer number of reactors are needed. This gives a net saving in terms of capital expenditure and operating costs.
Our report presents the economic benefits of the oxygen-based liquid-oxidation technology versus the conventional air-based technology and is of special interest to the current and potential producers of terephthalic acid, adipic acid, and phenol both for retrofitting and for grassroots plant construction.