Use of a solid hydrotalcite structure incorporating fluorides for basic catalysis of michael or knoevenagel reactions

Abstract

The invention concerns the use of a solid basic catalyst comprising a hydrotalcite structure wherein part at least of the compensating anions are fluoride anions F for producing Knoevenagel or Michael condensation reactions. The invention also concerns novel solid basic catalysts comprising a hydrotalcite structure characterised by a Mg/Al molar ratio ranging between 2.5 and 3.8 wherein at least part of the compensating anions are fluoride anions F, and methods for preparing said novel catalysts.

1 . Using a solid basic catalyst with a hydrotalcite structure wherein at least some compensation anions are fluoride anions F, for the basic catalysis of Knoevenagel and Michael's condensation reactions.  
     
     
         2 . Using the solid basic catalyst as per  claim 1  wherein the Mg/Al molar ratio of the catalyst's hydrotalcite structure is between 1.6 and 3.8.  
     
     
         3 . Using a solid basic catalyst as per  claim 1  or  claim 2  wherein the catalyst contains at least 0.5% of fluoride ion mass.  
     
     
         4 . Using a solid basic catalyst according to any of the  claims 1  to  3  mentioned above wherein at least 95% of fluoride ions present in the catalyst are integrated to the state of compensation anions within the hydrotalcite like structure.  
     
     
         5 . Using a solid basic catalyst according to any of the  claims 1  to  4  wherein the catalyst is a porous solid and the pore distribution radius is such that at least 50% have a mean diametre more than 2 nm  
     
     
         6 . Using a solid basic catalyst according to any of the claims  1 . to  6  wherein the catalyst is used in the range of 0.01 g to 0.10 g per substrata millimole.  
     
     
         7 . A solid basic catalyst with a hydrotalcite structure wherein the Mg/Al molar ratio is between 2.5 and 3.8 wherein a part of the compensation anions are fluoride anions F.  
     
     
         8 . A solid basic catalyst according to  claim 7 , wherein it contains at least 0.5% of fluoride ion masse.  
     
     
         9 . A solid basic catalyst according to  claim 7  or  8 , wherein at least 95% of fluoride ions present in the catalyst are integrated to the state of compensation anions within the hydrotalcite like structure.  
     
     
         10 . A solid basic catalyst according to any of the  claims 7  to  9  wherein the said catalyst is a porous solid and the pore distribution radius is such that at least 50% have a mean diameter more than 2 nm.  
     
     
         11 . A preparation method of a solid basic catalyst according to any of the  claims 6  to  10 , wherein the following stages are: 
 (1.1) Prepare a hydrotalcite structure solid wherein the Mg/Al molar ratio ranges between 2.5 and 3.8; and  
 (1.2) Subject the solid obtained at the end of stage (1.1) to an exchange reaction by fluoride ions.  
 
     
     
         12 . A preparation method of a solid basic catalyst according to  claim 11 , wherein the hydrotalcite structure solid at stage (1.1) is prepared from a solution containing magnesium nitrate and alumina nitrate by coprecipitating to a pH value between 8 to 10.  
     
     
         13 . A preparation method of a solid basic catalyst according to  claim 11  or  12 , wherein the exchange by fluoride anions at stage (1.2) is achieved by dispersion of the solid obtained at the end of stage (1.1) in an aqueous solution containing fluoride ions with a concentration ranging between 0.05 and 0.5 mol/l.  
     
     
         14 . A preparation method of a solid basic catalyst according to any of the claims from  6  to  10 , wherein the following stages are: 
 (11.1) Prepare mixed magnesium and aluminium oxide by hot-process carbonate removal of a carbonatised hydrotalcite structure solid wherein the Mg/Al molar ratio is between 2.5 and 3.8.  
 (11.2) Hydrate the mixed oxide of stage (11.1) in the presence of fluoride ions.  
 
     
     
         15 . A preparation method of a solid basic catalyst according to  claim 14 , wherein the removal of carbonates by hot process is carried out at temperatures ranging from 400° C. to 600° C.  
     
     
         16 . A preparation method of a solid basic catalyst according to claims  14  or  15 , wherein stage (11.2) is carried out by dispersion of the mixed oxide obtained at the end of stage (11.1) in an aqueous solution containing fluoride ions with a concentration ranging between 0.05 and 0.5 mol/l.