Patent ID: 6084109
Filing Date: 2000-07-04
Classification: B01J,C07C

Abstract:
A process for the preparation of pyromellitic dianhydride, comprising:(a) providing a feedstream containing a 1,2,4,5-tetraalkylbenzene of the formula ##STR1## where R.sub.1 is CH.sub.3, and R.sub.2, R.sub.3 and R.sub.4 are each independently C.sub.1 -C.sub.3 alkyl groups, and(b) subjecting the 1,2,4,5-tetraalkylbenzene in the feedstream to a selective oxidation at 300.about.450.degree. C. in the presence of a catalyst system comprising a catalyst support comprising rutile and at least one material selected from the group consisting of tungsten carbide, silicon carbide and a mixture thereof; a catalyst which is a mixture of vanadium and tungsten oxides; and a cocatalyst which is a combination of an oxide of an element of the I A and/or II A group of the periodic table, an oxide of manganese, antimony, bismuth, phosphorus, copper, aluminum, titanium or a mixture thereof, and an oxide of an element of the VIII B Group of the periodic table;wherein said catalyst and cocatalyst in combination has the formula:VM.sub.I.sbsb.a M.sub.II.sbsb.b M.sub.III.sbsb.c M.sub.IV.sbsb.d O.sub.Xwherein:V is vanadium;M.sub.I is tungsten;M.sub.II is manganese, antimony, bismuth, phosphorus, copper, aluminum, titanium or a mixture thereof;M.sub.III is an element of the VIIIB group of the periodic table;M.sub.IV is an alkali metal and/or an alkaline earth metal; andX is a value within the range of from 7 to 40.