Integrated process for producing cyclic acetals and oxymethylene polymers
View Patent ↗A process for producing cyclic acetals is described. A formaldehyde source is contacted with an aprotic compound in the presence of a catalyst to produce the cyclic acetals. The aprotic compound can increase conversion rates and/or efficiency. In one embodiment, the formaldehyde source is obtained from methanol. In particular, methanol can be converted into formaldehyde which is then converted into a cyclic acetal. In one embodiment, the cyclic acetal can then be used to produce oxymethylene polymers.
1. A process for producing a cyclic acetal comprising:
converting methanol to a formaldehyde;
contacting the formaldehyde with a catalyst in the presence of an aprotic compound, the aprotic compound comprising a sulfur containing organic compound having a boiling point greater than 120° C. determined at 1 bar; and
at least partly converting the formaldehyde to a cyclic acetal.
2. A process according to claim 1 , wherein the methanol is dehydrogenated in order to form the formaldehyde.
3. A process according to claim 1 , wherein the formaldehyde is formed by nonoxidative dehydrogenation of methanol.
4. A process according to claim 1 , wherein the formaldehyde is formed by dehydrogenating methanol at a temperature of from about 300° C. to about 1100° C.
5. A process according to claim 1 , wherein the formaldehyde is formed in the presence of a catalyst comprising an alkali metal, an alkaline earth metal, copper, zinc, tin, compounds thereof, or mixtures thereof.
6. A process according to claim 1 , wherein the formaldehyde is formed by extractive distillation.
7. A process according to claim 1 , wherein the methanol is oxidized to form the formaldehyde.
8. A process according to claim 6 , wherein the extractive distillation is carried out by feeding crude formaldehyde containing water and methanol to a middle or lower part of a distillation column and feeding an extractant to an upper part of the distillation column, the extractant being inert to formaldehyde, and wherein formaldehyde gas is collected from a top of the distillation column.
9. A process according to claim 8 , wherein the extractant comprises diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, polyethylene glycol dimethyl ether having from about 5 ethylene oxide units to about 50 ethylene oxide units, corresponding diethylene ethers of the above or mixtures thereof.
10. A process according to claim 1 , wherein the formaldehyde is gaseous formaldehyde when contacted with the aprotic compound.
11. A process according to claim 1 , wherein the aprotic compound has a boiling point of greater than about 140° C. determined at one bar.
12. A process according to claim 1 , wherein the formaldehyde, the aprotic compound and the catalyst form a reaction mixture and wherein the reaction mixture comprises at least 60 wt.-%, of the aprotic compound, wherein the weight is based on the total weight of the reaction mixture.
13. A process according to claim 1 , wherein the aprotic compound comprises a dipolar nitro-group free compound.
14. A process according to claim 1 , wherein the aprotic compound is represented by formula (I):
wherein
n is an integer ranging from 1 to 6, and
wherein the ring carbon atoms may optionally be substituted by one or more substituents, selected from C 1 -C 8 -alkyl which may be branched or unbranched.
15. A process according to claim 1 wherein the aprotic compound is sulfolane.
16. A process according to claim 1 wherein the aprotic compound is represented by formula (II):
wherein R 1 and R 2 are independently selected from C 1 -C 8 -alkyl which may be branched or unbranched.
17. A process according to claim 1 wherein the aprotic compound is represented by formula (III):
wherein
n is an integer ranging from 1 to 6, and
wherein the ring carbon atoms may optionally be substituted by one or more substituents, selected from C 1 -C 8 -alkyl which may be branched or unbranched; or
the aprotic compound is represented by formula (IV):
wherein R 3 and R 4 are independently selected from C 1 -C 8 -alkyl which may be branched or unbranched.
18. A process according to claim 1 wherein the formaldehyde and the aprotic compound form a homogenous phase.
19. A process according to claim 1 wherein the conversion to the cyclic acetal is carried out at a temperature ranging from 20° C. to 150° C., and is carried out at a pressure of from 10 millibars to 10 bars.
20. A process according to claim 9 , wherein the extractant comprises sulfolane.