Novel catalysts and process for dehydrating glycerol

Abstract

A process for preparing acrolein from glycerol using an acidic solid-state catalyst which comprises tungsten compounds and further promoters.

1 . A solid-state catalyst which comprises at least one tungsten compound and having a Hammett acidity H o  of <+2 and which includes at least one promoter compound selected from the group consisting of compounds of gold, silver, copper, platinum, rhodium, palladium, ruthenium, samarium, cerium, yttrium, scandium, lanthanum, zinc, magnesium, iron, cobalt, nickel and mixtures thereof,
 and/or montmorillonite or an acidic zeolite.   
     
     
         2 . The catalyst according to  claim 1 , which has a Hammett acidity H o  of <+2 to −20. 
     
     
         3 . The catalyst according to  claim 1 , wherein the tungsten compound is selected from the group consisting of ammonium tungstate, tungstophosphoric acid, tungstic acid, tungstosilic acid, tungsten oxides, heteropolyacids with tungsten as a constituent and mixtures thereof. 
     
     
         4 . The catalyst according to  claim 1 , which further comprises natural or synthetic, silicatic or oxidic compounds. 
     
     
         5 . The catalyst according to  claim 1 , which further comprises a support material modified with a mono-, di- or polybasic inorganic acid or salt of an inorganic acid. 
     
     
         6 . The catalyst according to  claim 1 , which further comprises, as a support material, aluminium oxide, titanium dioxide, Nb 2 O 3 , silicon dioxide, zirconium oxide, activated carbon or mixtures or mixed oxides thereof. 
     
     
         7 . A process for preparing acrolein by dehydrating glycerol in the presence of a solid-state catalyst which comprises at least one tungsten compound and has a Hammett acidity H o  of <+2 and which includes at least one promoter compound selected from the group consisting of compounds of gold, silver, copper, vanadium, platinum, rhodium, palladium, ruthenium, samarium, cerium, yttrium, scandium, lanthanum, zinc, magnesium, cobalt, nickel and mixtures thereof,
 and optionally a compound of an element selected from the group consisting of lithium, sodium, potassium or cesium, and mixtures thereof,   and/or montmorillonite or an acidic zeolite.   
     
     
         8 . The process according to  claim 7 , in which the solid-state catalyst contains montmorillonite or acidic zeolites in an amount of 0.1 to 30% by weight. 
     
     
         9 . The process according to  claim 7 , in which the dehydrating effected in the absence of oxygen. 
     
     
         10 . A process for preparing acrolein by dehydrating glycerol in the presence of a catalyst according to  claim 1 . 
     
     
         11 . The process according to  claim 7 , in which the dehydrating is effected in the presence of hydrogen. 
     
     
         12 . The process according to  claim 7 , in which glycerol is used in an amount of 1 to 100% based on the total amount of a reaction mixture, containing glycerol, any remaining amount up to 100% consisting of compounds inert under reaction conditions. 
     
     
         13 . The process according to  claim 7 , in which an inert compound is present which is nitrogen and/or water. 
     
     
         14 . The process according to  claim 7 , in which pressures between 1 and 300 bar and temperatures between 150 and 450° C. are employed. 
     
     
         15 . The process according to  claim 7 , which is carried out at pressures between 1 and 100 bar and at temperatures between 180 and 350° C. 
     
     
         16 . The process according to  claim 7 , carried out in the gas phase. 
     
     
         17 . The process according to  claim 7 , in which dehydrating is performed in a fixed bed reactor, in a fluidized bed reactor, in a reactor with a circulating fluidized bed, in a moving bed reactor or in a reactor with regenerator-riser (-downer) design. 
     
     
         18 . The process according to  claim 7 , which produces a reaction mixture which is worked up with utilization of partial condensation, absorption, desorption and/or distillation. 
     
     
         19 . The process according to  claim 7 , in which a portion of water is circulated and is evaporated and condensed with utilization of thermal integration. 
     
     
         20 . The process according to  claim 7 , in which an inert gas or diluent is circulated. 
     
     
         21 . The process according to  claim 7 , in which unconverted glycerol is sent to an incineration or a distillation for crude glycerol. 
     
     
         22 . The process according to  claim 7 , in which the glycerol is obtained from hydrolysis of fats. 
     
     
         23 . The process according to  claim 7 , in which the glycerol is obtained from generation of fuels from natural raw materials. 
     
     
         24 . The process according to  claim 7 , in which the catalyst, after dehydrating, is regenerated under oxidizing conditions. 
     
     
         25 . The process according to  claim 7 , in which the catalyst, after dehydrating, is regenerated under reducing conditions. 
     
     
         26 . The process according to  claim 24 , in which a catalyst which comprises at least one promoter compound selected from the group consisting of compounds of gold, silver, copper, cerium, iron or platinum and mixtures thereof is used. 
     
     
         27 . The process according to  claim 25 , in which a catalyst is used which comprises a promoter compound selected from the group consisting of compounds of cobalt, nickel, palladium, platinum, ruthenium or rhodium and mixtures thereof. 
     
     
         28 . A process for preparing a compound of the formula 
       
         
           
           
               
               
           
         
         in which 
         R is H, or C 1  to C 3 -alkyl, 
         comprising reacting glycerol with a compound of the formula
   R—SH   (II) 
 
         in which 
         R is H or C 1  to C 3 -alkyl 
         in the presence of a catalyst according to  claim 1 .