Process for reducing the sulphur content of anatase titania and the so-obtained product

Abstract

The present invention relates to the field of heterogeneous catalysis. In more detail, it refers to a process for reducing the sulphur content of a stabilized titania, the so-obtained material and the use thereof for manufacturing of support materials for heterogeneous catalysts.

1 . Anatase titanium dioxide having a content of at least one compound selected from oxides of Si, Al, and Zr in an amount of 2-50% b.w., preferably 2-30% b.w., calculated as oxides, of the total weight of the oxides, and having a sulphur content of less than 150 ppm, preferably less than 100 ppm and more preferred of less than 80 ppm referred to the total weight of the oxides. 
     
     
         2 . Anatase titanium dioxide according to  claim 1  having a content of at least one compound selected from oxides of Si, Al, and Zr in an amount of 3-20% b.w., more preferably 4-12% b.w., calculated as oxides, of the total weight of the oxides and having a sulphur content of less than 150 ppm, preferably less than 100 ppm and more preferred of less than 80 ppm referred to the total weight of the oxides. 
     
     
         3 . Anatase titanium dioxide according to  claim 1  having a content of SiO 2  in an amount of 2-30% b.w., preferably 3-20% b.w., more preferably 4-12% b.w., calculated as oxide, of the total weight of the oxides, and having a sulphur content of less than 100 ppm, preferably less than 80 ppm referred to the total weight of the oxides. 
     
     
         4 . Process for preparing an anatase titanium dioxide having a content of at least one compound selected from oxides of Si, Al, and Zr in an amount of 2-30% b.w., preferably 3-20% b.w., more preferably 4-12% b.w., calculated as oxides, of the total weight of the oxides, and having a sulphur content of less than 150 ppm, preferably less than 100 ppm and more preferred less than 80 ppm, referred to the total weight of the oxides, of  claim 1  wherein:
 a titanium compound selected from metatitanic acid or titanylsulphate is mixed with at least one compound selected from oxides and/or hydroxides of Si, Al, and Zr or precursors thereof in an aqueous medium, 
 precipitating at least one compound selected from oxides and/or hydroxides of Si, Al, and Zr, 
 treating the obtained product to reduce the alkali content if the alkali content is above 200 ppm, to a level of at most 200 ppm, referred to the total weight of the oxides, 
 the product is optionally filtered, optionally washed with water, and optionally dried, 
 the product is then subjected to a calcination treatment at a temperature of more than 500° C., preferably in the range of 800° to 1200° C., over a time period sufficient to decompose the remaining sulphur containing compound such as sulphuric acid to a level below 150 ppm, preferably less than 100 ppm and more preferred less than 80 ppm referred to the total weight of the oxides, preferably over a time period of 0.5 to twelve hours. 
 
     
     
         5 . Process for preparing an anatase titanium dioxide according to  claim 3  wherein metatitanic acid is mixed with a SiO 2  precursor compound, precipitating at least one oxide and/or hydroxide of Si, treating the obtained product to reduce the alkali content if the alkali content is above 200 ppm, to a level of at most 200 ppm, referred to the total weight of the oxides, optionally filtering, optionally washing the obtained product and optionally drying the obtained product, then subjecting the product to a calcination treatment at a temperature of more than 500° C., preferably in the range of 800° to 1200° C., over a time period sufficient to decompose the remaining sulphur containing compound such as sulphuric acid to a level below 100 ppm, preferably less than 80 ppm referred to the total weight of the oxides, preferably over a time period of 0.5 to twelve hours, 
     
     
         6 . Process for preparing an anatase titanium dioxide according to  claim 3  wherein a titanium compound selected from a TiO 2  sol is mixed with an SiO 2  sol, adjusting the pH to obtain a precipitate, treating the obtained precipitate to reduce the alkali content if the alkali content is above 200 ppm referred to the total weight of the oxides, to a level of at most 200 ppm, referred to the total weight of the oxides, the obtained product is optionally filtered, optionally washed, optionally dried, and the obtained product is subjected to a calcination treatment at a temperature of more than 500° C., preferably in the range of 800° to 1200° C., over a time period sufficient to decompose the remaining sulphur containing compound such as sulphuric acid to a level below 150 ppm, preferably less than 100 ppm and more preferred less than 80 ppm referred to the total weight of the oxides, preferably in the range of 800° to 1200° C., preferably over a time period of 0.5 to twelve hours. 
     
     
         7 . Process for reducing the sulphur content of a stabilised anatase titania wherein an anatase titania having a content of a stabilizing agent is treated at a temperature more than 500° C., preferably in the range of 800° to 1200° C., over a time period sufficient to decompose a remaining sulphur containing compound such as sulphuric acid to a level below 150 ppm, preferably less than 100 ppm and more preferred less than 80 ppm referred to the total weight of the oxides, preferably for a time period of at least 30 min, wherein the stabilizing agent is selected from oxides of Si, Al, and Zr and wherein the content of the stabilizing agent is in the range of 2-50% b.w., preferably 2-30% b.w., calculated as oxides, of the total weight of the oxides. 
     
     
         8 . Use of a calcination treatment at a temperature more than 500° C. for reducing the sulphur content of a stabilised anatase titania to a level below 150 ppm, preferably less than 100 ppm and more preferred less than 80 ppm referred to the total weight of the oxides. 
     
     
         9 . Use of the anatase titanium dioxide according to  claim 1  or obtainable according to the process of  claim 4 , as a catalyst or catalyst support in catalysis reactions, gas to liquid reactions such as in particular Fischer-Tropsch catalysis, selective catalytic reduction (SCR), oxidation catalysis, photo catalysis, hydrotreating catalysis, Claus catalysis, phthalic acid catalysis. 
     
     
         10 . Catalyst or catalyst support, comprising the anatase titanium dioxide according to  claim 1  or obtainable according to the process of  claim 4 .