Patent ID: 7157403
Filing Date: 2007-01-02
Classification: B01J,C07C

Abstract:
1. A process for preparing a vanadium, phosphorus, and oxygen catalyst precursor for preparing maleic anhydride by heterogeneously catalyzed gas-phase oxidation of a hydrocarbon having at least four carbon atoms, by reacting vanadium pentoxide (I) in the presence of a primary or secondary, noncyclic or cyclic, unbranched or branched, saturated alcohol having from 3 to 6 carbon atoms (II) with from 102 to 110% by weight of phosphoric acid (III) in a temperature range from 80 to 160° C. with stirring and subsequently filtering the resultant suspension, which comprises using the following measure: (a) adding the phosphoric acid (III) to the vanadium pentoxide (I), suspended in the alcohol (II) and heated to 60 to 160° C., the time of contact between the vanadium pentoxide (I) and the alcohol (II) prior to commencement of the addition of the phosphorus compound (III) at a temperature ≧50° C. being ≦1 hour; and at least one of the measures from the series (b) during the reaction of the vanadium pentoxide (I) in the presence of the alcohol (II) with the phosphoric acid (III), exposing the reaction mixture to a stirring power of from 0.01 to 0.6 W/kg suspension, the calculation of the stirring power being based on the physicochemical, properties of the mixed reactants prior to reaction and at 20° C.; and (c) filtering at a temperature of from 65°to 160° C.; to set a filtration resistance α H ·η of ≦25·10 13 mPa·s/m 2 .