Process for the production of dialkyl carbonate and alkanediol

• US 7,763,745 B2
• Filed: 02/22/2007
• Issued: 07/27/2010
• Est. Priority Date: 02/22/2006
• Status: Expired due to Fees

• Current Assignee: Shell Oil Company (Shell Plc)
• Original Assignee: Shell Oil Company (Shell Plc)
• Inventors: Van Der Heide, Evert, Vaporciyan, Garo Garbis, Nisbet, Timothy Michael
• Primary Examiner(s): Wilson; James O
• Assistant Examiner(s): SACKEY, EBENEZER O
• Application Number:
  US11/678,008
• Publication Number:
  US 20070197816A1
• Time in Patent Office: 1,251 Days
• Field of Search: 558/277
• US Class Current: 558/277
• CPC Class Codes: C07C 29/128 by alcoholysis
• CPC Class Codes: C07C 31/205 1,3-Propanediol; 1,2-Propanediol
• CPC Class Codes: C07C 68/065 from alkylene carbonates
• CPC Class Codes: C07C 68/08 Purification; Separation; Stabilisation
• CPC Class Codes: C07C 69/96 Esters of carbonic or haloformic acids
• CPC Class Codes: Y02P 20/10 Process efficiency
• CPC Class Codes: Y02P 20/141 Feedstock

Abstract

An alkylene carbonate and an alkanol are subjected to transesterification to yield a dialkyl carbonate and alkanediol in a process comprising

• (a) introducing the alkylene carbonate and an alkanol feedstock into a reaction zone to react in the presence of a transesterification catalyst to yield an alkanediol-rich stream and a stream comprising dialkyl carbonate and alkanol, which streams are separated;
• (b) passing the stream comprising dialkyl carbonate and alkanol to an extractive distillation zone in which an extractant is added to the stream;
• (c) obtaining from the extractive distillation zone an alkanol-rich vapor stream and a bottom stream containing the extractant and the dialkyl carbonate;
• (d) separating the bottom stream from step (c) in a second non-extractive distillation zone to yield a dialkyl carbonate-rich top stream and a extractant-rich bottom stream; and
• (e) at least partly recycling the extractant-rich bottom stream to the extractive distillation zone,
  wherein the extractant-rich bottom stream is used as heat source for the alkanol feedstock.

Claims

1. A process for the production of dialkyl carbonate and alkanediol from the transesterification of alkylene carbonate and alkanol, comprising:

(a) introducing an alkylene carbonate and an alkanol feedstock into a reaction zone to react in the presence of a transesterification catalyst to yield an alkanediol-rich stream and a stream comprising dialkyl carbonate and alkanol which streams are separated;

(b) passing the stream comprising dialkyl carbonate and alkanol to an extractive distillation zone in which an extractant is added to the stream;

(c) obtaining from the extractive distillation zone an alkanol-rich vapor stream and a bottom stream containing the extractant and the dialkyl carbonate;

(d) separating the bottom stream from step (c) in a second non-extractive distillation zone to yield a dialkyl carbonate-rich top stream and a extractant-rich bottom stream; and

(e) at least partly recycling the extractant-rich bottom stream to the extractive distillation zone, wherein the extractant-rich bottom stream is used as a heat source for the alkanol feedstock.

2. A process according to claim 1, in which in step (a) the alkylene carbonate is introduced into the upper part of a reactive distillation zone and an alkanol feedstock is introduced at a lower part of the reactive distillation zone to react in the presence of a transesterification catalyst to yield an alkanediol-rich stream at the bottom and a top stream comprising dialkyl carbonate and alkanol.

3. A process according to claim 1, in which the extractant is selected from the group consisting of phenol, anisole and alkylene carbonate.

4. A process according to claim 3, in which the alkylene carbonate is propylene carbonate.

5. A process according to claim 1, in which the alkanol is heated by the extractant-rich bottom stream by heat exchange.

6. A process according to claim 5, in which the alkanol is heated to a temperature from 65 to 100°

C.

7. A process according to claim 5, in which the alkanol is heated to at least partial vaporization.

8. A process according to claim 1, in which the extractant-rich bottom stream leaves the second non-extractive distillation zone at a temperature of from 150 to 180°

C.

9. A process according to claim 1, in which the extractant-rich bottom stream is cooled by heat exchange with the alkanol to a temperature of from 120 to 80°

C.

10. A process according to claim 1, in which the pressure in the extractive distillation zone ranges from 60 to 120 kPa, and the pressure in the second non-extractive distillation zone ranges from 5 to 50 kPa.