Process for the preparation of stanol esters

Abstract

The invention relates to a process for the preparation of stanol esters by hydrogenating a sterol blend in a hydrogenation solvent and at an elevated temperature in the presence of a hydrogenation catalyst, by removing the hydrogenation catalyst from the obtained hot reaction solution, by transesterifying the intermediate stanol blend with a fatty acid methyl ester at an elevated temperature and in the presence of a transesterification catalyst, and by finally purifying the stanol ester blend thus obtained. According to the invention, the intermediate stanol blend is neither crystallized nor removed from the reaction solution but the hydrogenation solvent is replaced therein at least in part by a transesterification reagent. Alternatively, the hydrogenation solvent may also be used as the transesterification solvent, and preferably also as the transesterification reagent.

1 . A process for the preparation of stanol esters by hydrogenating at least one sterol in a solvent and at an elevated temperature in the presence of a hydrogenation catalyst, to form respectively at least one stanol, by removing the hydrogenation catalyst from the obtained reaction solution, by transesterifying the said at least one stanol with a lower alkyl ester at an elevated temperature and in the presence of a transesterification catalyst, and by purifying the stanol ester or stanol ester blend thus obtained, characterized in that the hydrogenation solvent is left in the reaction solution from which the hydrogenation catalyst has been removed, and the hydrogenation solvent 
 a) is replaced therein at least in part by a transesterification reagent and/or    b) is used as a solvent also in the transesterification and preferably at the same time as the transesterification reagent.    
     
     
         2 . A process according to  claim 1 , characterized in that a fatty acid methyl ester of vegetable oil origin is used as the transesterification reagent and possibly as the hydrogenation solvent.  
     
     
         3 . A process according to  claim 2 , characterized in that the hydrogenation solvent is lower boiling than the transesterification reagent and is removed by fractional distillation from the reaction solution, to which a transesterification reagent is added or has been added.  
     
     
         4 . A process according to  claim 3 , characterized in that a coconut fatty acid methyl ester is used as the hydrogenation solvent and a rapeseed oil fatty acid methyl ester as the transesterification reagent.  
     
     
         5 . A process according to  claim 1 , characterized in that an alcohol or a high boiling aliphatic hydrocarbon free of aromatic compounds is used as the hydrogenation solvent and at the same time as the transesterification solvent.  
     
     
         6 . A process according to any of the above claims, characterized in that a noble metal catalyst, preferably palladium on carbon or on an organic polymer compound, is used as the hydrogenation catalyst.  
     
     
         7 . A process according to  claim 6 , characterized in that the hydrogen catalyst is used in an amount of 0.1-2% active ingredient of the weight of the sterol to be hydrogenated.  
     
     
         8 . A process according to any of the above claims, characterized in that the hydrogenation is carried out at a temperature of at most about 120° C., and the hydrogenation catalyst is removed from the hot reaction solution, preferably by filtration.  
     
     
         9 . A process according to any of the above claims, characterized in that an alkali metal alcoholate, preferably sodium methylate or sodium ethylate, is used as the transesterification catalyst.  
     
     
         10 . A process according to  claim 9 , characterized in that the transesterification catalyst is used in an amount of 0.1-1% of the weight of the reaction solution.  
     
     
         11 . A process according to any of the above claims, characterized in that the transesterification is carried out at 100-130° C. and by using a stoichiometric excess of the transesterification catalyst relative to the stanol or the stanol blend.  
     
     
         12 . A process according to any of the above claims, characterized in that a sterol blend is hydrogenated which contains primarily sitosterol and additionally campesterol and possibly stigmasterol.  
     
     
         13 . A process according to  claim 12 , characterized in that a sterol blend based on tall oil or vegetable oil is hydrogenated.