Process for the production of alkylene carbonate
View Patent ↗The invention relates to a process for the production of an alkylene carbonate by the reaction of an alkylene oxide with carbon dioxide in the presence of a phosphonium catalyst in which process (a) the alkylene oxide, carbon dioxide and phosphonium catalyst are continuously introduced into a reaction zone from which a product stream containing alkylene carbonate and phosphonium catalyst is withdrawn; (b) alkylene carbonate and a stream containing phosphoniura catalyst are separated from the product stream; (c) the alkylene carbonate, separated in step (b), is recovered as product; and (d) the stream containing phosphoniura catalyst, separated in step (b), is recycled to the reaction zone, in which process a treatment of alkylene carbonate and/or catalyst with a sorption agent comprising carbon is carried out.
1. A process for the production of an alkylene carbonate by the reaction of an alkylene oxide with carbon dioxide in the presence of a phosphonium catalyst comprising:
(a) introducing the alkylene oxide, carbon dioxide and phosphonium catalyst continuously into a reaction zone from which a product stream containing alkylene carbonate and phosphonium catalyst is withdrawn;
(b) separating alkylene carbonate and a stream containing phosphonium catalyst from the product stream;
(c) recovering the alkylene carbonate, separated in step (b), as product; and
(d) recycling the stream containing phosphonium catalyst, separated in step (b), to the reaction zone,
wherein the phosphonium catalyst is treated with a sorption agent comprising activated carbon.
2. The process as claimed in claim 1 , wherein
(i) the treatment with the sorption agent is carried out during the production of alkylene carbonate in the reaction zone in step (a); or
(ii) the treatment with the sorption agent is carried out during the separation in step (b); or
(iii) the stream containing catalyst separated in step (b) is subjected to the treatment with the sorption agent before said stream is recycled to the reaction zone; or
(iv) the treatment is carried out in more than one of (i) to (iv).
3. The process as claimed in claim 2 , wherein the sorption agent is suspended in the stream containing catalyst separated in said step (b) before said stream is recycled.
4. The process as claimed in claim 3 , wherein the sorption agent is suspended in a vessel wherein the stream containing catalyst separated in said step (b) is stored before said stream is recycled.
5. The process as claimed in claim 2 , wherein the sorption agent is suspended in the reaction mixture that is present in the reaction zone in step (a).
6. The process as claimed in claim 1 , wherein the phosphonium catalyst is a phosphonium halide of formula (R) 4 PX, wherein the group R contains from 1 to 12 carbon atoms and X means halide.
7. The process as claimed in claim 6 , wherein the phosphonium catalyst is tetra(n-butyl) phosphonium bromide.
8. The process as claimed in claim 1 , wherein the alkylene oxide is selected from the group consisting of ethylene oxide, propylene oxide, and combinations thereof.
9. The process as claimed in claim 1 wherein
(e) the alkylene carbonate recovered as product in step (c) is contacted with an alkanol to obtain a reaction mixture containing an alkylene diol and a dialkylcarbonate; and
(f) alkylene diol and dialkylcarbonate are recovered.
10. The process as claimed in claim 9 , wherein the reaction in step (e) is performed in the presence of a heterogeneous transesterification catalyst.
11. The process as claimed in claim 9 wherein the alkanol is methanol, ethanol or isopropanol.
12. The process as claimed in claim 10 wherein the alkanol is methanol, ethanol or isopropanol.