Phthalic Anhydride (PAF)

Chemical formula: C8H4O3 CAS Nu: 85-44-9 Hazard Class: 8 Synonyms: 1,3-Isobenzofurandione Density: 1/53 g/cm3

Petrochemical: Esfehan, Farabi

This product has partial electrical properties, heat and freezing resistance, low volatility, and its softening performance is better than DOP and is suitable for polyvinyl chloride resins.

Description of the PAF Unit Process

The Phthalic Anhydride unit has a nominal annual capacity of 35,000 tons. The raw material for producing phthalic anhydride is ortho-xylene. Phthalic anhydride is produced by oxidizing ortho-xylene with air using the catalyst V2O5 (vanadium pentoxide).

The phthalic anhydride unit operations occur in three stages:

  1. Oxidation
  2. Desublimation
  3. Distillation

During the production process, after combining ortho-xylene with air in the catalyst bed, PAC is produced, which is then converted to PAL (liquid phthalic anhydride). Part of this serves as feedstock for the DOP unit. Ultimately, PAL is converted to PAF (solid phthalic anhydride).

Uses of Phthalic Anhydride:

One of the primary uses of phthalic anhydride is in the production of polyester resins, with other minor applications in the production of alkyd resins used in paints and varnishes, insect repellents, and polyester polyurethanes. Phthalic anhydrides are also used as a retarder for rubber and a delay agent. The largest outlet for PA is in unsaturated polyester resins (UPR), which are typically combined with fiberglass to produce fiberglass-reinforced plastics. Phthalic anhydride is a precursor for various useful reactants in organic compounds. Important derivatives include phthalimide and many others. Phthalic anhydride is extensively used in industries to produce specific colors. A recognized application of this reactive compound is the preparation of anthraquinone quinizarin dye by reacting with para-chlorophenol and then hydrolyzing the chloride. However, its use is not limited to wire and cable applications, including roof membranes and swimming pool liners. Alkyd resins based on PA are used in solvent-based coatings for architectural applications, machinery, furniture, and cosmetics. Smaller volumes of PA usage include the production of dyes and pigments, detergents, herbicides and insecticides, fire retardants, cross-linking agents for polysaccharide and polyester resins.

  • Plasticizers: The vast majority of PA is used to produce dioctyl phthalate (DOP) and other phthalate esters. These phthalate esters are used as plasticizers in PVC (polyvinyl chloride) and other polymers to make them flexible. This flexibility is vital for products like vinyl flooring, wall coverings, PVC piping, and various other flexible products.

  • Unsaturated Polyester Resins (UPRs): PA is used to produce resins which, when combined with reinforcing agents (often fiberglass), create fiber-reinforced plastics or non-reinforced filled materials. These are used in a variety of applications, including boat hulls, swimming pools, industrial tanks, and corrosion-resistant equipment.

  • Alkyd Resins: PA is a key ingredient in the production of alkyd resins, which are used in paints, lacquers, and varnishes. These resins give the paint its desired properties like gloss, hardness, and durability.

  • Dyes and Pigments: PA serves as a precursor in the synthesis of certain dyes and pigments.

  • Phthalimide: Derived from PA, phthalimide is an intermediate used in the synthesis of various other chemicals.

  • Saccharin: PA is also used in the production of the artificial sweetener saccharin.

  • Other Chemical Intermediates: PA can be used in the synthesis of various other chemicals, including perfumes, pharmaceuticals, and many other organic compounds.

  • Rubber Additives: Certain chemicals derived from PA are used as retarders in the rubber industry, helping control the vulcanization process.

Item SPECIFICATION Test Method result
Appearance White Flakes /Clear ASTM D-3366 OK
Color in molten state Max 20 APHA ASTM D-3366 20
Freezing Point (o C ) Min 130.9’C ASTM D-1493 131-1
Heat Stability Max 40 APHA ASTM D-3366 25
Maleic Anhydride Max0.05% Wt Analytical method 0.038
Phthalic Acid Max 0.1% Wt Analytical method 0.064
Phthalide Max 0.1% Wt GC-Analytical method 0.0157
Benzoic Acid Max 0.1% Wt GC-Analytical method 0.014
Balk density 0.5-0.7 kg/l ASTM D-1298 0.65
Ash content Max 0.05% wt Analytical method 0.009
Assay Min99.5% Wt Analytical method 99.86

Phthalic Anhydride MSDS



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