RECYCLING OF POLYACETAL FOR THE PRODUCTION OF POLYOXYMETHYLENE DIALKYL ETHERS
The present invention relates to a process for recycling polyacetal containing from 8 to 100,000 carbon atoms for the production of a produced polyoxymethylene dialkyl ether of formula R—(OCH2)n-OR′, in which R and R′ independently represent a methyl group or an ethyl group and n is an integer greater than or equal to 1, the process comprising a step of reacting an acid catalyst with a mixture comprising a polyacetal containing from 8 to 100 000 carbon atoms, a reactive polyoxymethylene dialkyl ether of formula R—(OCH2)k-OR′ in which k is an integer greater than or equal to 1, and optionally a solvent.
1 . A process for recycling polyacetal containing from 8 to 100,000 carbon atoms for the production of a produced polyoxymethylene dialkyl ether of formula R—(OCH 2 ) n —OR′, in which R and R′ independently represent a methyl group or an ethyl group and n is an integer greater than or equal to 1, the process comprising a step of reacting an acid catalyst with a mixture comprising a polyacetal containing from 8 to 100,000 carbon atoms, a reactive polyoxymethylene dialkyl ether of formula R—(OCH 2 ) k —OR′ in which R and R′ are as defined above and k is an integer greater than or equal to 1, and optionally a solvent.
2 . The process as claimed in claim 1 , also comprising a step of filtering the polyacetal and/or the mixture.
3 . The process as claimed in claim 1 , also comprising an evaporation step to remove some or all light compounds of formula R—(OCH 2 ) n —OR′ with n=1 and optionally n=2.
4 . The process as claimed in claim 1 , also comprising a step of purification of recovering the produced polyoxymethylene dialkyl ether.
5 . The process as claimed in claim 4 , in which the recovery step allows for separation of the produced polyoxymethylene dialkyl ether from heavy compounds of formula R—(OCH 2 ) n —OR′ with n greater than the maximum n value of the produced polyoxymethylene dialkyl ether.
6 . The process as claimed in claim 4 , in which the recovery step is performed by distillation.
7 . The process as claimed in claim 1 , also comprising a recycling step to reintroduce a portion of the compounds of formula R—(OCH 2 ) n —OR′ with n greater than or equal to 1 into the reaction step as reactive polyoxymethylene dialkyl ether.
8 . The process as claimed in claim 7 , in which the recycling step reintroduces all or some light compounds removed in an evaporation step and/or all or some heavy compounds removed in a recovery step into the reaction step as reactive polyoxymethylene dialkyl ether.
9 . The process as claimed in claim 1 , also comprising a step of synthesizing (meth)acrylic acid or ester or (meth)acrolein or neopentyl glycol from the produced polyoxymethylene dialkyl ether.
10 . The process as claimed in claim 1 , in which the reactive polyoxymethylene dialkyl ether comprises methylal and/or ethylal.
11 . The process as claimed in claim 1 , in which the reactive polyoxymethylene dialkyl ether comprises methylal and/or ethylal and one or more compounds of formula R—(OCH 2 ) k —OR′ with a k number greater than or equal to 2.
12 . The process as claimed in claim 1 , in which the produced polyoxymethylene dialkyl ether is chosen from the group consisting of CH 3 —(OCH 2 )—OCH 3 , CH 3 —(OCH 2 ) 2 —OCH 3 , CH 3 —(OCH 2 ) 3 —OCH 3 , CH 3 —(OCH 2 ) 4 —OCH 3 , CH 3 —(OCH 2 ) 5 —OCH 3 , CH 3 —(OCH 2 ) 6 —OCH 3 , CH 3 —(OCH 2 ) 7 —OCH 3 , CH 3 —(OCH 2 ) 8 —OCH 3 , C 2 H 5 —(OCH 2 )—OC 2 H 5 , C 2 H 5 —(OCH 2 ) 2 —OC 2 H 5 , C 2 H 5 —(OCH 2 ) 3 —OC 2 H 5 , C 2 H 5 —(OCH 2 ) 4 —OC 2 H 5 , C 2 H 5 —(OCH 2 ) 5 —OC 2 H 5 , C 2 H 5 —(OCH 2 ) 6 —OC 2 H 5 , C 2 H 5 —(OCH 2 ) 7-0 C 2 H 5 , C 2 H 5 —(OCH 2 ) 8 —OC 2 H 5 and mixtures thereof.
13 . The process as claimed in claim 1 , in which the produced polyoxymethylene dialkyl ether is:
a mixture of compounds of formula CH 3 —(OCH 2 ) n —OCH 3 with n=2 to 8,
a mixture of compounds of formula CH 3 —(OCH 2 ) n —OCH 3 with n=2 to 4,
a mixture of compounds of formula CH 3 —(OCH 2 ) n —OCH 3 with n=3 to 4,
a mixture of compounds of formula CH 3 —(OCH 2 ) n —OCH 3 with n=3 to 5, or
a mixture of compounds of formula C 2 H 5 —(OCH 2 ) n —OC 2 H 5 with n=2 to 4.
14 . The process as claimed in claim 1 , in which the polyacetal is a homopolymer.
15 . The process as claimed in claim 1 , in which the ratio of mass of reactive polyoxymethylene dialkyl ether to mass of polyacetal is at least 2:1.
16 . The process as claimed in claim 1 , in which the acid catalyst is chosen from the group consisting of acidic resins, organic or mineral acids, trifluoromethanesulfonic acid, perchloric acid, methanesulfonic acid, para-toluenesulfonic acid, and sulfuric acid, Lewis acids, BF 3 , AsF 5 , acidic mixed oxides, WO 3 /TiO 2 , phosphate alumina, tungsten alumina, and zeolites; and mixtures thereof.
17 . The process as claimed in claim 1 , in which the solvent is chosen from the group consisting of sulfolane, methylsulfolane, ethylsulfolane, diethylsulfolane, propylsulfolane, dipropylsulfolane, butylsulfolane, dibutylsulfolane, pentylsulfolane, dipentylsulfolane, hexylsulfolane, octylsulfolane, DMSO and mixtures thereof.
18 . (canceled)
19 . (canceled)
20 . A process for synthesizing (meth)acrylic acid or ester or (meth)acrolein or neopentyl glycol, comprising a step of reacting a produced polyoxymethylene dialkyl ether obtained via the recycling process as claimed in claim 1 .