Heterogeneously catalyzed gas-phase partial oxidation of precursor compounds of (meth)acrylic acid

Abstract

In a process for the heterogeneously catalyzed gas-phase partial oxidation of precursor compounds of (meth)acrylic acid over a fixed catalyst bed which contains, as a catalyst, a mixed oxide active material shaped into a geometric body, the geometric body is a geometric base body into whose surface a cavity has been introduced.

1 - 15 . (canceled)  
   
   
       16 . A process for the heterogeneously catalyzed gas-phase partial oxidation of a precursor compound of (meth)acrylic acid to form at least one of (meth)acrolein and (meth)acrylic acid, comprising: 
 passing a reaction gas starting mixture comprising the precursor compound and molecular oxygen, at elevated temperatures, through a fixed catalyst bed which contains, as the catalyst, a mixed oxide active material shaped into a geometric body, this geometric body being a geometric base body into whose surface at least one cavity has been introduced, wherein the ratio of the volume of the geometric body V B  to the volume of the geometric base body V BA ≦0.63 and the ratio of the external surface area of the geometric body A B  to V B ≧22 cm −1 .    
   
   
       17 . The process as claimed in  claim 16 , wherein A B :V B ≧24 cm −1 .  
   
   
       18 . The process as claimed in  claim 16 , wherein V B :V BA ≦0.60.  
   
   
       19 . The process as claimed in  claim 16 , wherein the geometric base body is selected from the group consisting of a cylinder, a pyramid, a cone, a cube, a right paralleleped, a prism, a sphere, a truncated cone, and truncated pyramid.  
   
   
       20 . The process as claimed in  claim 16 , wherein the geometric body is a ring.  
   
   
       21 . The process as claimed in  claim 20 , wherein the ring geometry (external diameter×height×internal diameter) is at least one selected from the group consisting of 
 a) 5.5 mm×3mm×3.5 mm;    b) 6 mm×3 mm×4 mm;    c) 7 mm×3 mm×4.5 mm; and    d) 7 mm×3 mm×5 mm.    
   
   
       22 . The process as claimed in  claim 16 , wherein the empty volume of the fixed catalyst bed is ≧50% by volume.  
   
   
       23 . The process as claimed in  claim 16 , wherein the mixed oxide active material is at least one selected from the group consisting of 
 a) the elements Mo, Cu and P;    b) the elements Mo, Bi and Fe;    c) the elements Mo, V and W; and    d) the elements Mo, V, Te and Nb.    
   
   
       24 . The process as claimed in  claim 16 , wherein, in a single pass of the reaction gas mixture through the fixed catalyst bed, the conversion of the precursor compound of (meth)acrylic acid is ≧90 mol %.  
   
   
       25 . The process as claimed in  claim 24 , wherein the selectivity of the formation of (meth)acrolein and/or (meth)acrylic acid is ≧50 mol %.  
   
   
       26 . The process as claimed in  claim 16 , which is a process for the heterogeneously catalyzed gas-phase partial oxidation of propene to acrolein and wherein the mixed oxide active material is of formula I  
       Mo 12 Bi a Fe b X 1   c X 2   d X 3   e X 4   f O n   (I),  where    X 1  is nickel and/or cobalt,    X 2  is thallium, an alkali metal and/or an alkaline earth metal,    X 3  is zinc, phosphorus, arsenic, boron, antimony, tin, cerium, lead and/or tungsten,    X 4  is silicon, aluminum, titanium and/or zirconium,    a is from 0.5 to 5,    b is from 0.01 to 5,    c is from 0 to 10,    d is from 0 to 2,    e is from 0 to 8,    f is from 0 to 10 and    n is a number which is determined by the valency and frequency of the elements other than oxygen in I.    
   
   
       27 . The process as claimed in  claim 16 , which is a process for the heterogeneously catalyzed gas-phase partial oxidation of acrolein to acrylic acid and wherein the mixed oxide active material is of formula IV  
       Mo 12 V a X 1   b X 2   c X 3   d X 4   e X 5   f X 6   g O n   (IV),  where    X 1  is W, Nb, Ta, Cr and/or Ce,    X 2  is Cu, Ni, Co, Fe, Mn and/or Zn,    X 3  is Sb and/or Bi,    X 4  is one or more alkali metals,    X 5  is one or more alkaline earth metals,    X 6  is Si, Al, Ti and/or Zr,    a is from 1 to 6,    b is from 0.2 to 4,    c is from 0.5 to 18,    d is from 0 to 40,    e is from 0 to 2,    f is from 0 to 4,    g is from 0 to 40 and    n is a number which is determined by the valency and frequency of the elements other than oxygen in IV.    
   
   
       28 . The process as claimed in  claim 16 , which is carried out at from 200 to 450° C.  
   
   
       29 . A process for preparing esters of (meth)acrylic acid, comprising: 
 esterifying (meth)acrylic acid prepared by the process as claimed in  claim 16 .    
   
   
       30 . A process for preparing polymers of (meth)acrylic acid, comprising: 
 polymerizing (meth)acrylic acid prepared by the process as claimed in  claim 16 .    
   
   
       31 . The process as claimed in  claim 16 , wherein the starting mixture further comprises a gas which is inert with respect to the catalytic gas phase oxidation.