Process for the preparation of pyromellitic dianhydride
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United States of America Patent
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Jul 4, 2000
Grant Date -
N/A
app pub date -
Apr 16, 1999
filing date -
Jul 31, 1998
priority date (Note) -
Expired
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Abstract
The present invention relates to a process for preparing pyromellitic dianhydride via an oxidation in gas phase under normal pressure. The process is characterized in that a catalyst system is used, which catalyst system comprises a catalyst which is a mixture of vanadium and tungsten oxides; a catalyst support comprising rutile and at least one material selected from the group consisting of tungsten carbide, silicon carbide and a mixture thereof; and a cocatalyst comprising oxides of manganese, antimony, bismuth, phosphorus, copper, aluminum, titanium or a mixture thereof, an oxide of an element of the VIIIB group of the periodic table, and an oxide of an alkali metal and/or alkaline earth metal. In this process, pyromellitic dianhydride is produced from a feedstream containing 1,2,4,5-tetraalkylbenzene in a gas flow rate of 4,000.about.12,000 hr.sup.-1 via a selective oxidation at 300.about.450.degree. C. in the presence of air which acts as an oxidant.
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