Patent ID: 6153767
Filing Date: 2000-11-28
Classification: B01J,C07C

Abstract:
A process for producing pyromellitic dianhydride by feeding raw material mixed gas containing 1,2,4,5-tetraalkylbenzene and molecular oxygen to a fixed bed multitubular type reactor charged with a catalyst layer to carry out catalytic vapor phase oxidation, wherein the catalyst layer is divided into at least two layers of a layer at an outlet side of reaction gas and a layer at an inlet side of raw material mixed gas; and the layer at an outlet side of reaction gas is charged with a catalyst A represented by the following formula (1):V.sub.a (A).sub.b P.sub.c Ag.sub.d (B).sub.e O.sub.x ( 1)wherein V represents vanadium; P represents phosphorus; Ag represents silver; (A) represents at least one element selected from molybdenum and tungsten; (B) represents at least one element selected from alkaline metals and alkaline earth metals; O represents an oxygen element; a, b, c, d, e and x each represent an atomic number thereof, and when a is 1, 0<b.ltoreq.2, 0<c.ltoreq.1, d=0 to 0.2 and e=0 to 0.1, and x is a value determined by oxidation states of the respective elements other than an oxygen element, and the layer at an inlet side of raw material mixed gas is charged with a catalyst B represented by the following formula (2):V.sub.a Ti.sub.b (C).sub.c (D).sub.d Ce.sub.e O.sub.x ( 2)wherein V represents vanadium; Ti represents titanium; Ce represents cerium; (C) represents at least one element selected from rare earth elements (excluding cerium); (D) represents at least one element selected from phosphorus, antimony, hafnium, niobium, tantalum, boron and sulfur; O represents an oxygen element; a, b, c, d, e and x each represent an atomic number thereof, and when a is 1, 0<b.ltoreq.500, 0<c.ltoreq.0.5, d=0 to 1 and e=0 to 0.5, and x is a value determined by oxidation states of the respective elements other than an oxygen element.