WO1999052866A1

WO1999052866A1 - A process for the production of 2-pyrrolidone in a continous fashion, starting from gamma butyrolactone and ammonia

Info

Publication number: WO1999052866A1
Application number: PCT/EP1999/002298
Authority: WO
Inventors: Aldo Bertola
Original assignee: Pantochim S.A.
Priority date: 1998-04-09
Filing date: 1999-04-02
Publication date: 1999-10-21
Also published as: AU3419999A; BE1011869A6

Abstract

A process for the production of 2-pyrrolidone (2-P) starting from gamma butyrolactone and ammonia in a continuous fashion, in three subsequent reaction stages, and in such operating conditions to allow production of a high purity 2-pyrrolidone in high yields.

Description

A process for the production of 2-pyrrolidone in a continuous fashion, starting from gamma butyrolactone and ammonia The present invention relates to a process for the production of 2-pyrrolidone (2-P) , in particular starting from gamma butyrolactone and ammonia in a continuous fashion, in three subsequent reaction stages, and in such operating conditions to allow the attainment of high purity and yields.

It is known from the prior art that there exist several processes for the synthesis of 2-pyrrolidone (2- P) , starting from gamma butyrolactone (GBL) and ammonia

(NH) .

In 1936 Spath and Lunder described in Berichte 69, page 2727 an analogous process for the first time. In this NH was allowed to react with GBL in a high molar ratio and a discontinuous process reactor for approx. 2 hours. A relatively low yield was obtained (64%).

In several patents, Mitsubishi Chemical

Industries Co. Ltd. described a number of processes for the continuous synthesis of 2-pyrrolidone starting from

GBL and NH.

The above processes involve a high ratio between water and GBL feedstock (typically varying between 2 and

4 mols of water for each mol of GBL) .

The processes designed by Mitsubishi result to be characterised by the high costs involved in the separation of unreacted NH and its recovery, and in the 2

separation of the water pumped into the reaction, to which the water produced in the reaction adds up (one mol of water for each mol of reacted GBL) .

To avoid the drawbacks associated with a discontinuous reaction, or with a continuous reaction in the presence of NH and excess water, several alternative methodologies have been proposed, and these are based on the employment of catalysts .

In EP 0 349 119, in the name of GAF CHEMICALS CORP, a synthesis with GBL, MH and steam as starting materials is described. This is carried out in the vapour phase, at a temperature ranging between 225° and 310°C, and pressure ranging between 3.5 and 21 ATE, on a magnesium silicate based catalyst.

The catalytic process described in the above patent does not seem to be industrially feasible, bearing in mind the enormous volumes of catalyst that are required which are in the range of about 100 m³ of catalyst for each m³ of reagents.

Analysis of the prior art therefore leads to the conclusion that yields in final product can still be remarkably improved, along with a minimisation of the by-products unwillingly obtained and bound to be separated. Costs in terms of catalyst used have to be minimised, too. 3

Aim of the present invention is to propose a process wherein the reaction occurs in a continuous fashion, without any catalysts and with a low ratio between NH and shot GBL, thus allowing the production of 2 -pyrrolidone at low costs, and moreover, minimal waste of starting materials and utilities.

The above aims have been accomplished by setting out a reaction of gammabutyrolactone with ammonia, characterised by the fact that the synthesis is carried out by a continuous, non catalytic liquid phase process, that consists of three distinct reaction stages which are connected in series.

These and other features will be more readily apparent from the following description of a preferred not limiting embodiment of the invention with reference to the accompanying drawing in which a scheme of the production process is shown.

According to the present invention, the synthesis of 2 -pyrrolidone from GBL and MH is carried out in the three following distinct reaction stages :

First Reaction stage Molar ratio between NH and GBL = from 1.05 to 1.4 Molar ratio between H₂0 and GBL = from 0.1 to 0.5 Temperature (reactor outlet) = from 130° to 200°C 4

Residence Time = from 5 to 30 minutes Second Reaction Stage Temperature = from 200° to 250°C

Residence Time = from 1 to 3 hours

Third Reaction Stage Temperature = from 250° to 320°C

Residence Time = from 0.5 to 2.0 hr

In all three reactors pressure ranges between 40 and 120 ATE, enough to keep all three reactants in the liquid phase.

The reactors in all the three reaction stages are of the adiabatic type, preferably tubular in shape. Suitable reactors are also vessels subdivided by separation sects that form compartments and prevent the mixture of the rection products from occurring as the reaction progresses .

In the first reactor an exothermal synthesis by reaction between GBL and NH takes place with formation of hydroxybutyramide (HBA) .

In the subsequent reactor, the HBA cyclisation reaction starts, with formation of 2-pyrrolidone (2-P) and water.

In the final stage, the 2-P formation reaction goes to completion at a higher temperature. The succession of the three reaction stages described in the present process allows a reduction in those byproducts which are present in the reaction effluents, particularly a 2 -pyrrolidone dimer, n- pyrrolidonil butyramide (PBA) , always present among the reaction products of the 2 -pyrrolidone synthetic processes .

The scheme associated with the process object of the present invention is shown in the enclosed drawing (Fig. 1) .

The NH feedstock (line 1) , together with recycle NH/H₂0 admixes with the GBL feedstock (line 3) , takes in static mixer 4, at a molar ratio between NH and GBL of 1.2:1.

The admixing activates the addition reaction, with HBA formation. The above reaction is very exothermal, and, once finished, it takes up the batch temperature to approximately 160°C.

The addition reaction goes to completion in reactor 5 within approximately 15 minutes . At the reactor outlet the liquid stream (line 6) undergoes further heating to 220 °C in exchanger 7, accomplished by hot oil.

After preheating, the liquid (line 8) feeds reactor 9 where the HBA cyclisation reaction gets 6

started with formation of water. Residence time in reactor 9 is approximately 2 hours.

The reactor is of the tubular type or, alternatively, it consists of a vessel subdivided into compartments by separation sects which aim at preventing the reaction products from remixing.

The effluent from reactor 9 (line 10) feeds heater 11 where temperature is taken up to 300°C by thermal exchange with hot oil .

After the second preheating, the liquid (line 12) feeds reactor 13 where conversion from 2-pyrrolidone goes to completion with a residence time of approximately 2 hours .

The effluent from reactor 13 (line 14) has the following typical molar composition:

2-P 42.1%

HBA traces

NH 9.9%

Light Byproducts 0.7% Heavy Byproducts 2.6% Water 44.7%

By dint of valve 15, effluent pressure is taken down to approximately 10 ATE, this yielding a liquid phase (line 17) in separator 16, and a vapour phase (line 18) which feed fractionation column 19, where an 7

aqueous ammonia solution with an equimolar H₂0:NH ratio

separates. This is then recycled to the reaction (line

2) .

The bottom product of column 19 feeds subsequent

column 21, where (line 22) water from the reaction and

as a side stream and (line 23) light organic byproducts

separate at the tops and bottoms respectively.

The bottom product of column 21 feeds (line 24) fractionation column 25 where heavy products separate

from purified 2-pyrrolidone at the bottom (line 26) and top (line 27) respectively.

GC analysis reveals that product 2-P is not any

less pure than 99% by weight, with a water content which

is lower than 0.1% by weight.

Claims

8CLAIMS

1. A process for the production of 2 -pyrrolidone, by

reaction of gammabutyrolactone with ammonia, characterised by the fact that the synthesis is carried

out by a continuous, non catalytic liquid phase process,

that consists of three distinct reaction stages which

are connected in series.

2. A process according to claim 1 characterised in

that : a) The first stage of the reaction operates at a temperature ranging between 130┬░ an 200 ┬░C, at the

reactor outlet, with a residence time ranging between 5

and 30 minutes. b) The second stage of the reaction operates at a

temperature ranging between 200┬░ and 250 ┬░C, at the

reactor inlet, with a residence time ranging between 1.0

and 3.0 hrs .

c) The third stage of the reaction operates at

a temperature ranging between 250┬░ and 320 ┬░C at the

reactor inlet, with a residence time ranging between 0.5

and 2.5 hrs .

3. A process according to claim 2, characterised in

that the first stage of the reaction operates at a

temperature ranging between 150┬░ and 180┬░C. 9

4. A process according to claim 2, characterised in that in the first stage of the reaction residence time is between 10 and 15 mins .

5. A process according to claim 2 characterised in that residence time in the second stage of the reaction is between 1.5 and 2.5 hrs

6. A process according to claim 2, characterised in that the third stage of the reaction operates at a temperature between 290┬░ and 310 ┬░C.

7. A process according to claim 2, characterised in that in the third stage of the reaction, the residence time is Between 1.5 and 2.0 hours.

8. A process according to the preceding claims characterised in that the molar ratio between ammonia and gammabutyrolactone at the reaction system feed ranges between 1.05 and 1.4.

9. A process according to claim 8, characterised in that the Ammonia : Gammabutyrolactone molar ratio at the reaction system feed ranges between 1.1 and 1.2.

10. A process according to the preceding claims characterised in that the reactants are kept in the liquid phase operating the three reaction stages at pressures ranging between 40 and 120 ATE. 10

11. A process according to claim 10, characterised in that the three reaction stages are operated at a pressure ranging between 60 and 100 ATE.

12. A process according to the preceding claims, where the reactors of each of the rection stages are made up of containers characterised by the presence of sects which have the aim of achieving a piston type reactant flow through separate reaction compartments, that prevent the products from remixing.

13. A process according to claims 1 to 11 where the reactors of each of the rection stages are of the tubular type .