IES58442B2 - A method and apparatus for producing chlormequat - Google Patents

Description

The present invention relates to a method and apparatus for producing chlormequat (chlorcholine chloride) from ethylene dichloride and trimethylamine.

Chlormequat is used as a plant growth regulator which produces various effects with regard to stem growth, flowering, fruit set and tolerance of plants, particularly cereals. For example, it may reduce the amount of extra foliage produced by plants and increase crop yield.

UK Pat. No. 1 092 138 (BASF) teaches the use of mixtures of chlorocholine and choline salts resulting in a shortening of the growth length of plants, an increase in stem wall thickness and a subsequent lessening of lodging of certain types of grain.

At present chlorocholine chloride (CCC) or chlormequat is manufactured by reacting together ethylene dichloride (EDC) and trimethylamine (TMA), with both reactants in liquid form or with EDC in the liquid form and TMA in the gaseous state. In both cases the procedure, for example as outlined in UK 1 138 490 (UCB), is similar.

EDC is usually present in a large excess (although TMA may be used in excess) allowing easy separation of product and unreacted materials. TMA is introduced, in either liquid or gaseous form, to a reactor containing preheated EDC. After heating for a time sufficient to allow the reaction to take place the reaction mixture is cooled. 358442 - 2 Water added before, during or after the reactive step has the effect of transferring the product CCC from the organic or water-immiscible EDC phase, to the aqueous phase. Unreacted TMA remains in the organic phase, which is recycled and reused in the initial reaction step. Activated carbon may be added in a purification step. Any EDC in the aqueous phase is removed by distillation under vacuum and the volume of the product solution is reduced by further distillation. The solution is filtered to remove activated carbon and impurities and transferred to storage.

It is an object of the present invention to provide a method of producing chlormequat from ethylene dichloride and trimethylamine which combines both the reactants in a gaseous reaction rather than a reaction in the liquid state. This process allows for continuous production rather than batch production. The apparatus for carrying out the method also forms a part of the present invention.

The present invention provides a method of producing chlorcholine chloride from starting materials including trimethylamine and ethylene 20 dichloride, comprising the steps of: a) separately vapourising ethylene dichloride and trimethylamine to produce two continuous streams in a gaseous state, b) introducing the ethylene dichloride stream and the trimethylamine stream under pressure to a reactor vessel, c) accumulating the condensed reaction products, d) separating the condensed reaction products into organic and aqueous phases, and e) extracting substantially pure chlorcholine chloride solution from the aqueous phase.

Advantageously, the trimethylamine stream is introduced to the reactor vessel through a nitrogen-shielded injection nozzle to prevent a build-up of solid CCC on the nozzle. - 3 Recycled ethylene dichloride in the liquid phase is sprayed into the reactor vessel to wholly or partially absorb the heat of reaction between the gaseous reactants by itself vaporising in the reaction zone and absorbing its latent heat of vaporisation.

Preferably, the separation step d) is effected by a counter-current water scrubber, with or without recycling, and with or without chlorcholine chloride or any other agent dissolved in the water.

The gaseous reaction in the reaction vessel is maintained at a temperature of from 80° to 115°C, but more preferably from 100° to 115°C. Suitably, the reaction is effected at approximately atmospheric pressure.

However, the process is not limited to any particular reaction pressure or temperature.

The invention will now be described in further detail, with reference to the accompanying drawings, in which Figure 1 is a schematic diagram of apparatus for carrying out the process of the invention.

Referring to Figure 1 vapourisers (1) and (2) convert TMA and EDA 25 in their liquid states to the respective gases. Gaseous TMA is superheated, and introduced into the reactor vessel (4) by means of a nitrogen shrouded injection nozzle (3). Gaseous EDC is introduced by means of an injection nozzle (3a). Reaction between said gaseous reactants occurs in or around the vicinity of these nozzles within the 30 confines of the reactor vessel (4). The reactor (4) is thermally insulated and equipped with external heating and cooling means to allow for preheating the reactor before start-up and cooling the reaction during operation. Cooling is also achieved by injection (through nozzles (5)) of recycled EDC as a spray which vaporises in the reaction 35 zone absorbing its latent heat of vaporisation.

Condensed products settle and accumulate at the bottom of the gas/liquid separation area (6). Gaseous products proceed to the - 4 counter-current water scrubbing tower (7) where excess gaseous EDC is condensed and which dissolves CCC in water and any liquid droplets are removed. The nitrogen flow, which is essentially inert, carries gaseous reactants and products through to the scrubbing tower (7) and 5 is itself scrubbed and removed from the chamber by purge (8). The condensed products in the separation area (6) are thoroughly mixed to ensure that substantially all the CCC becomes dissolved in the aqueous phase, and are then separated into EDC and CCC solutions by a separator (9). The separation will happen easily due to a large difference in 10 density between the phases. A flame trap/demister may also be included because the reactants are flammable.

The reactor is also equipped with nozzle (12) which allow for purging of the apparatus with an inert gas before start-up or washing 15 of the reactor after shut-down.

According to the present invention the process proceeds as a continuous cycle rather than on a batchwise basis. This makes most efficient use of time and apparatus. It is also advantageous in that 20 the CCC product, in the form of an aqueous solution of a concentration of up to about 70% w/w, is likely to be of a high purity, containing substantially less of the by-products associated with the batch process since residence times in the reactor are in the order of minutes in the case of the continuous process, whereas for the batch process they are 25 in the order of hours. Since the product obtained is of high purity the purifying carbon treatment necessitated by the old process (of UK 1,138,490) is not now required. Additional plant can be facilitated to obtain a substantially pure crystaline product from the CCC solution produced.

Claims (5)

1. A method of producing chlorcholine chloride from starting materials including trimethylamine and ethylene dichloride, comprising the steps of: a) separately vapourising ethylene dichloride and trimethylamine to produce two continuous streams in a gaseous state, b) introducing the ethylene dichloride stream and the trimethylamine stream under pressure to a reactor vessel, c) accumulating the condensed reaction products, d) separating the condensed reaction products into organic and aqueous phases, and e) extracting substantially pure chlorcholine chloride solution from the aqueous phase.

2. A method according to claim 1, in which the trimethyl amine stream is introduced to the reactor vessel through a nitrogen-shielded injection nozzle.

3. A method according to claim 1 or claim 2, in which recycled ethylene dichoride in the liquid phase is sprayed into the reactor vessel to wholly or partially absorb the heat of reaction between the gaseous reactants.

4. A method according to any of claims 1 to 3, wherein the separation step d) is effected by a counter-current water scrubber, with or without recycling, and with or without chlorcholine chloride or any other agent dissolved in the water.

5. Apparatus for carrying out a process as claimed in any of the preceding claims, substantially as described herein with reference to, and as shown in the accompanying drawings.