Method for the production of stable binder-free high-purity moldings composed of metal oxides and their use

Abstract

Stable high strength porous metal oxide articles suitable, for example, for use as catalyst supports, are prepared by predisposing fine metal oxide particles in water followed by fine dispersion under high shear, and subjecting the dispersion to a change in pH to coagulate the metal oxide particles and form a moldable viscoelastic composition. The moldings are substantially free of impurity atoms.

1 - 18 . (canceled) 
   
   
       19 . A stable, high-purity molding comprising one or more metal oxides, having a compressive strength of at least 2 N/mm 2  and a proportion of spalling in the presence of liquids or gases of less than 5% by weight, the molding free of binder and decomposition products thereof. 
   
   
       20 . The stable, binder-free, high-purity molding of  claim 19 , wherein the molding has a sum of impurities of all metals other than the metal of the metal oxide(s) and also carbon, phosphorus, and sulfur, of less than 400 ppm. 
   
   
       21 . The stable, binder-free, high-purity molding of  claim 19 , wherein the metal oxide is a pyrogenic metal oxide. 
   
   
       22 . The stable, binder-free, high-purity molding of  claim 19 , wherein the metal oxide is pyrogenic silicon dioxide. 
   
   
       23 . The stable, binder-free, high-purity molding of  claim 19 , wherein the metal oxide has the form of a SiO 2 /Al 2 O 3  or SiO 2 /TiO 2  mixed oxide. 
   
   
       24 . The stable, binder-free, high-purity molding of  claim 19 , wherein the BET surface area of the molding is in the range from 30 m 2 /g to 500 m 2 /g. 
   
   
       25 . The stable, binder-free, high-purity molding of  claim 24 , wherein the BET surface area of the molding is in the range from 50 m 2 /g to 500 m 2 /g and the compressive strength is at least 2 N/mm 2 . 
   
   
       26 . The stable, binder-free, high-purity molding of  claim 24 , wherein the BET surface area of the molding is in the range from 30 m 2 /g to 400 m 2 /g and the compressive strength is at least 10 N/mm 2 . 
   
   
       27 . A process for producing a molding of  claim 19 , comprising predispersing at least one metal oxide, subsequently finely dispersing the metal oxide(s), and subjecting the resulting dispersion to a change in pH to form a viscoelastic composition, shaping the viscoelastic composition to form a molding, and subsequently drying the molding. 
   
   
       28 . The process of  claim 27 , wherein the pH of the dispersion is changed to a pH of from 5.0 to 10.0. 
   
   
       29 . The process of  claim 27 , wherein at least one metal oxide is a pyrogenic metal oxide. 
   
   
       30 . The process of  claim 27 , wherein at least one metal oxide is pyrogenic silicon dioxide. 
   
   
       31 . The process of  claim 30 , wherein the dispersion has a pH of from 5.5 to 10.0. 
   
   
       32 . The process of  claim 27 , wherein the metal oxide is present in the form of a SiO 2 /Al 2 O 3  or SiO 2 /TiO 2  mixed oxide. 
   
   
       33 . The process of  claim 27 , wherein the dispersion coagulates to a viscoelastic composition, and after coagulation the storage modulus G′ is greater than 10,000 Pa, the ratio of loss modulus G″/storage modulus G′ is less than 1, and the storage modulus after a storage time of 1 week is greater than 70% of the initial value. 
   
   
       34 . The process of  claim 27 , wherein calcination is carried out after drying. 
   
   
       35 . The process of  claim 27 , wherein the sum of all metals other than those of the metal oxide(s), carbon, phosphorus and sulfur in the molding is less than 400 ppm. 
   
   
       36 . The process of  claim 27 , wherein the viscoelastic composition is free of organic binders and optionally free of organic solvents. 
   
   
       37 . A catalyst support comprising a stable, binder-free, high-purity molding comprising a metal oxide of  claim 19 . 
   
   
       38 . A catalyst support comprising a stable, binder-free, high-purity molding comprising a metal oxide, produced by the process of  claim 27 .