Phthalic anhydride was first produced by the oxidation of naphthalene in concentrated sulphuric acid in the presence of mercury sulphate. This route was later replaced by the catalytic vapour phase oxidation of naphthalene in air in the presence of a vanadium oxide catalyst.
Today, naphthalene feedstock has been generally superseded by the use of orthoxylene, with naphthalene now providing only 16% of feedstock requirements. In the US all production is now from orthoxylene with only Koppers having the facility to switch feedstocks. In Europe, more producers have the capability to use naphthalene.
In the orthoxylene-based process, an air-orthoxylene mixture in a weight ratio of 20:1 is fed to a reactor containing vanadium pentoxide with titanium dioxide-antimony trioxide catalyst. Alternative catalysts include molybdenum trioxide and calcium oxide, or manganese oxides. The reaction takes place at 375-425oC and below 1 bar pressure.
The effluent gases are cooled before entering switch condensers where the phthalic anhydride collects on the walls as a solid and is recovered by sublimation. Purification involves distillation under vacuum and the product is stored either in a molten state or bagged as flakes.
The process technology has changed little although catalysts have a longer life of three years and yields have improved. A development has been the lowering of the air to orthoxylene weight ratio to 9.5:1, allowing a reduction in capital costs and energy savings.
Phthalic anhydride
Price Reports
ICIS pricing gives you access on a weekly or real time basis to the latest price movements and critical market commentary on the Phthalic anhydride market. Click below to see a quarterly market overview.
More about Phthalic anhydride Price Reports
Phthalic anhydride
Uses and Outlook
The major outlet for phthalic anhydride (PA), accounting for just over half of production, is in the manufacture of phthalate plasticisers, the main product being dioctyl phthalate (DOP) which is used as a plasticiser in polyvinyl chloride (PVC). Hence, the consumption of PA is mainly dependent on the growth of flexible PVC, which is sensitive to general economic conditions as it consumed in the construction and automobile industries. Health and environmental issues that surround phthalates used in plasticisers for PVC could also hinder future growth prospects.
More about Phthalic anhydride Uses and Outlook
Search for
Phthalic anhydride
Suppliers
If you are sourcing
Phthalic anhydride
products and services, use ICIS search for fast and accurate results. ICIS search
is the search engine dedicated to the chemical industry – we show you only relevant
results -
search now.