Preparation of acrylic acid derivatives from alpha- or beta-hydroxy carboxylic acids

Abstract

The invention is directed to a process for the preparation of α,β-unsaturated acids, esters and amides from α- or β-hydroxycarboxylic acids or esters or precursors in high yields and high selectivity. The α,β-unsaturated acids or esters are optionally prepared in the presence of specific dehydration and/or esterification catalysts. The α,β-unsaturated amides or substituted amides are prepared optionally in the presence of a dehydration and/or amidation catalyst. The source of α- or β-hydroxycarboxylic acids or precusor is preferably from a renewable resource. The precursor is defined herein.

1 . A process for preparing α,β-unsaturated carboxylic acid esters comprising
 a) providing an aqueous solution comprising at least one of
 an α- or β-hydroxycarboxylic acid or salt thereof; 
 a polymer, oligomer, lactide or lactone formed from the α or β-hydroxycarboxylic acid; 
 or 
 an α- or β-hydroxycarboxylic acid derived from a microbial or plant cells that contains or produces α- or β-hydroxycarboxylic acids, polyesters of α- or β-hydroxycarboxylic acids or other derivatives capable of being converted into an α- or β-hydroxycarboxylic acid 
   and   b) heating the aqueous solution, optionally in the presence of a dehydration and/or esterification catalyst,   wherein step b) is carried out in the presence of an alcohol.   
   
   
       2 . A process according to  claim 1 , wherein the dehydration and/or esterification catalyst is γ-Al 2 O 3 , SiO 2 , TiO 2  or an aluminosilicate. 
   
   
       3 . A process according to  claim 1 , wherein the only catalyst is a heated surface and the heated surface is an aluminosilicate. 
   
   
       4 . A process according to  claim 2 , wherein the aluminosilicate is a zeolite. 
   
   
       5 . A process according to  claim 1 , wherein the reaction is run in the vapor phase. 
   
   
       6 . A process according to  claim 1 , wherein the reaction is run in the liquid phase. 
   
   
       7 . A process according to  claim 1 , wherein the aqueous solution of step b) is exposed to a heated surface to vaporize the solution and the heated surface is the dehydration catalyst and/or the esterification catalyst or an inert packing material. 
   
   
       8 . A process according to  claim 1 , wherein the β-hydroxycarboxylic acid is 3-hydroxy propionic acid, 3-hydroxybutyric acid or 3-hydroxy-2-methylpropionic acid. 
   
   
       9 . A process according to  claim 1 , wherein the α,β-unsaturated carboxylic ester is a C 1 -C 8  alkyl (meth)acrylic ester or a C 1 -C 8  alkyl crotonic ester. 
   
   
       10 . A process according to  claim 9 , wherein the C 1 -C 8  alkyl (meth)acrylic ester or C 1 -C 8  alkyl crotonic ester is selected from the group consisting of methyl (meth)acrylic ester, ethyl (meth)acrylic ester, n-propyl (meth)acrylic ester, isopropyl (meth)acrylic ester, n-butyl (meth)acrylic ester, isobutyl (meth)acrylic ester, sec-butyl (meth)acrylic ester, 2-ethylbutyl (meth)acrylic ester, isopentyl (meth)acrylic ester, 1-methylpentyl (meth)acrylic ester, 1,3-dimethylbutyl (meth)acrylic ester, n-hexyl (meth)acrylic ester, isoheptyl (meth)acrylic ester, 1-methylhexyl (meth)acrylic ester, tert-butyl (meth)acrylic ester, 2-ethylhexyl (meth)acrylic ester, n-pentyl (meth)acrylic ester, methyl crotonic ester, ethyl crotonic ester, n-propyl crotonic ester, isopropyl crotonic ester, n-butyl crotonic ester, isobutyl crotonic ester, sec-butyl crotonic ester, 2-ethylbutyl crotonic ester, isopentyl crotonic ester, 1-methylpentyl crotonic ester, 1,3-dimethylbutyl crotonic ester, n-hexyl crotonic ester, isoheptyl crotonic ester, 1-methylhexyl crotonic ester, tert-butyl crotonic ester, 2-ethylhexyl crotonic ester and n-pentyl crotonic ester. 
   
   
       11 . A process according to  claim 10 , wherein the C 1 -C 8  alkyl (meth)acrylic ester or C 1 -C 8  alkyl crotonic ester is selected from the group consisting of methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, methyl crotonic ester, n-butyl crotonate and ethyl crotonic ester. 
   
   
       12 . A process according to  claim 1  wherein the dehydration catalyst is a high surface area SiO 2  or a high surface area γ-Al 2 O 3 . 
   
   
       13 . A process according to  claim 1 , wherein the dehydration catalyst is a high surface area γ-Al 2 O 3  and the esterification catalyst is a zeolite. 
   
   
       14 . A process according to  claim 1 , wherein the process is continuous, fed-batch or batch. 
   
   
       15 . A process according to  claim 1 , wherein the only catalyst is a zeolite. 
   
   
       16 . A process according to  claim 15 , wherein the zeolite is a medium or large pore zeolite.