Phthalic Anhydride


CONSER is in position to offer a well established and highly reliable phthalic anhydride (PA) technology based on the selective oxidation of o-xylene to PA, practiced in plants of the SISAS group The key features of the technology are:

  • - Reliability: since SISAS has been the largest PA producer in the world, the technology has been commercially proven to the maximum possible extent
  • - Easiness of operation: the technology is easy to operate, does not require highly sophisticated catalysts or equipment, does not entail extreme operating conditions.


Company Location Capacity T/y
SISAS  Italy 47000
PANTOCHIM   Belgium  110000
UCB/SISAS Belgium  95000




The phthalic anhydride technology offered by CONSER is based on the following major steps:
• Reaction
• Crude PA recovery
• Off-gas treatment
• Phthalic anhydride purification

O-xylene is preheated and injected into compressed air. The air/organic mixture is fed to a fixed bed oxidation reactor filled with catalyst.
The exothermic heat of reaction is removed by molten salts generating high pressure steam.
The reaction gases are cooled by preheating BFW and generating additional high pressure steam.

Crude PA recovery
The cooled reaction gases enter switch condensers where PA desublimation takes place by heat exchange with cold oil.
When the desired product hold up is reached, the gas flow is switched to another condenser and solid PA is then melted by means of hot oil.

Off-gas treatment
The off-gases from the switch condensers are treated in an incinerator.
Alternatively the off-gases may be treated in a scrubbing column to form a maleic acid aqueous solution, which can then be processed to fumaric acid or to maleic anhydride.
Phthalic anhydride purification

A heat treatment of the crude PA is required before the purification. The thermal treatment improves the quality of the crude PA and increases the efficiency of purification.
The latter consists of the continuous separation, by distillation, of light ends and of heavy ends yielding a product meeting high standards of quality

P.le Ezio Tarantelli, 100
00144 Rome - Italy

e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

Tel. (+39) 06 5262001
Fax (+39) 06 5205249

CF e n° reg. imp.: 00875210585
partita iva: 00938941002 
capitale sociale: € 130.800,00 i.v.
rea: 327729 trib. RM 318/70

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