Catalyst system for the preparation of an ester and processes employing this ester

1. A process for the preparation of an ester, at least based on

a. at least one alcohol component,

b. at least one carboxylic acid component,

c. optionally further additives,

d. at least two different catalysts, and

e. max 20 wt. % of a solvent;

as process components, comprising, in a reactor, the process steps:

i. provision of the process components,

ii. reaction of the process components to give an ester A,

iii. optionally after-treatment of the ester A,

wherein at least in each case one of the at least two different catalysts is an electron donor and a further catalyst of the at least two different catalysts is a sulphur-containing proton donor;

wherein

aa. sulphuric acid, or

bb. an aliphatic, cycloaliphatic or aromatic C 1 to C 10 -sulphuric acid, or a combination of two or more of these, is chosen as the sulphur-containing proton donor; and

wherein a metal, a metal compound, or a reducing acid, or a combination of two or more of these is employed as the electron donor.

2. The process according to claim 1 , wherein the carboxylic acid component contains non-metal atoms chosen from the group of carbon, oxygen, nitrogen or hydrogen.

3. The process according to claim 1 , wherein the carboxylic acid component comprises more than 5 carbon atoms.

4. The process according to claim 1 ,

wherein the amount of electron donor, based on the total amount of catalysts, is more than 12.5 wt. %.

5. The process according to claim 1 , wherein

aa) a metal chosen from the group consisting of: titanium, tin, zirconium, in particular tin, or

bb) a metal compound chosen from the group consisting of: tetralkyl titanate, organotitanium complex, titanium salt, tin alkanoate, tin tetraalcoholate, organotin complex, zirconium salt, organozirconium complex, in particular tin alkanoate and organotin complex, such as a tin octoate, tin oxalate or dibutyltin dilaurate, or

cc) a reducing acid chosen from the group consisting of: sulphurous acid, hypophosphorous acid, phosphorous acid,

or two or more of these, is chosen as the electron donor.

6. The process according to claim 1 , wherein the reaction is carried out at a temperature in a range of from 80 to 185° C., in particular from 100 to 185° C.

7. The process according to claim 1 , wherein the reaction is carried out under a pressure in a range of from 2 to 800 mbar.

8. The process according to claim 1 , wherein the weight content of catalyst is in a range of from 0.01 wt. % to 0.5 wt. %, based on the total amount of process components weighed out.

9. The process according to claim 1 , wherein a catalyst mixture of

5 to 50 wt. % of tin oxalate,

12.5 to 50 wt. % of hypophosphorous acid, and

30 to 90 wt. % of p-toluenesulphonic acid,

which can in each case be chosen independently of each other, is employed as the catalysts,

wherein

the sum of all the wt. % is 100.

10. The process according to claim 1 , wherein no steam distillation is carried out as an after-treatment step.

11. The process according to claim 1 , wherein an alcohol component with one or more hydroxyl groups is chosen as the alcohol component.

12. The process according to claim 1 , wherein a partial ester is prepared as the ester, wherein either

I. an alcohol component with two or more hydroxyl groups is reacted with a carboxylic group,

II. a carboxylic component with two or more carboxyl groups is reacted with an alcohol component with one hydroxyl group, or

III. a carboxylic acid component with two or more carboxyl groups is reacted with an alcohol component with two or more hydroxyl groups.

13. The process according to claim 1 , wherein the carboxylic acid component is chosen from the group consisting of octanoic acid, i-octanoic acid, nonanoic acid, i-nonanoic acid, decanoic acid, i-decanoic acid, sebacic acid, palmitic acid, stearic acid, oleic acid, azelaic acid, pelargonic acid, behenic acid, trimellitic acid, adipic acid, erucic acid, HOOC—C 36 H 72 —COOH, phthalic anhydride or a mixture of two or more of these.

14. The process according to claim 1 , wherein the alcohol component is chosen from the group consisting of glycerol, oligoglycerols, pentaerythritol, pentaerythritol dimer, n-butanol, i-butanol, n-propanol, i-propanol, 2,2-dimethylpropanol, 2-ethylhexanol, n-octanol, i-tridecanol, cetyl alcohol, stearyl alcohol, ethylene glycol, diethylene glycol, butyl glycol, dibutyl glycol, tributyl glycol, 2-propylheptanol, polyethylene glycol or a mixture of two or more of these.

15. The process according to claim 1 , wherein the ester has between 1 and 6 ester groups.