Preparation of glutaraldehyde
Provided is a process for the preparation of glutaraldehyde. The process comprises reacting an alkoxydihydropyran with water in the presence of an acidic catalyst. The alcohol by-product distilled from the reaction mixture is subjected to a heterogeneous catalyst that is located external to the distillation column used for distilling the alcohol, thereby increasing glutaraldehyde yield and decreasing the level of alkoxydihydropyran contamination in the alcohol.
1. A process for preparing glutaraldehyde, the process comprising:
(a) reacting in a vessel at from 80° C. to 120° C. a reaction mixture comprising an alkoxydihydropyran compound of formula I
wherein R is C 1 -C 20 alkyl, water, and an acidic catalyst to form glutaraldehyde and the alcohol corresponding to the alkoxydihydropyran compound's alkoxy group;
(b) removing from the reaction mixture a distillate comprising the alcohol and unreacted alkoxydihydropyran compound, wherein said removal is effected with a distillation column;
(c) contacting the distillate with a heterogeneous catalyst located externally to the distillation column such that at least a portion of the alkoxydihydropyran compound reacts therein; and
(d) returning at least a portion of the distillate of step (c) to the distillation column.
2. A process according to claim 1 wherein the distillation column is equipped with an overheads reflux system comprising a condenser, a condenser receiver, and a condensate reflux stream line, and the heterogeneous catalyst is located in the overheads reflux system.
3. A process according to claim 2 wherein the heterogeneous catalyst is located in the condensate reflux stream line.
4. A process according to claim 2 wherein the heterogeneous catalyst is located in the condenser receiver.
5. A process according to claim 1 wherein the alkoxydihydropyran compound is 2-methoxy-3,4-dihydro-2H-pyran.
6. A process according to claim 1 wherein the heterogeneous catalyst is an acid functionalized resin bead, zeolites or clay.
7. A process according to claim 1 wherein the heterogeneous catalyst is an acidic ion exchange resin.
8. A process according to claim 1 wherein R in formula I is methyl.