WO1985002842A1

WO1985002842A1 - Process for the preparation of 1,2,4-triazole

Info

Publication number: WO1985002842A1
Application number: PCT/HU1984/000066
Authority: WO
Inventors: Ferenc KÓRÓDI; László LITKEI
Original assignee: Alkaloida Vegyészeti Gyár
Priority date: 1983-12-21
Filing date: 1984-12-21
Publication date: 1985-07-04
Also published as: HU195790B

Abstract

Process for the preparation of 1,2,4-triazole by the ring closure of diformyl hydrazine prepared by the formylation of hydrazine and ammonia which comprises reacting ammonium formiate with hydrazine hydrate by feeding continuously hydrazine or hydrazine hydrate at 120-160oC to the aqueous solution of ammonium formiate and removing continuously the formed water ammonia from the mixture and isolating, if desired, the cold precipitated triazole from the mixture.

Description

PROCESS FOR THE PREPARATION OF 1,2,4-TRIAZOLE

Technical FieId

The present invention is related to a process for the preparation of 1,2,4-triazole which is an important intermediate product for the preparation of pharmaceuticals, plant protecting agents, dyes and corrosion inhibitors.

Several methods are known for the preparation of 1,2,4-triazole and these methods can be divided into two big groups.

Background Art

It has been known since the end of the last century that 1,2,4-triazole can be prepared by heating an equimolar mixture of formyl hydrazine and formamide (Ber. 27, 1801 /1994/), by reacting hydrazinium salts with 2 moles of formamide (j. Am. Chem. Soc. 49, 1995 /1927/) or by the rapid distillation of hydrazine hydrate and 2 moles of formamide (J. Am. Ghem. Soc. 77., 621 /1955/). From this last reaction diformayl hydrazine is first formed which is then heated with excess of ammonia to 1,2,4-triazole in an autoclave at 200 °C for 24 hours.

This process has been improved by various technological methods (DOS 28 02491, DOS 29 43 265, USP 4 267 347 and EP 0044438).

A drawback of these processes is the necessity of working in an excess of formamide in most of the cases and the excess formamide can be separated from the product by extra operations (vacuum distillation, crystallization) and on the other hand the process is conducted at 160-260 °C and at this temperature dangerous decomposition products are formed in the formamide reaction mixture (CO, HCN) .

Disclosure of Invention

The present invention relates to a process for the preparation of 1,2,4-triazole by the ring closure of diformyl hydrazine prepared by the formylation of hydrazine and ammonia by reacting ammonium formiate with hydrazine hydrate and this is carried out by adding continuously hydrazine or hydrazine hydrate to an aqueous solution of ammonium formiate at 120-160 °C and by removing continuously the formed water and ammonia from the mixture and isolating if desired from the mixture the triazole which was precipitated in cold solution. According to our investigations it is preferred to feed hydrazine to the aqueous solution of ammonium formiate continuously and to ensure an excess of ammonium formiate even in the last phase of the feeding. Thus by keeping the hydrazine concentration constantly at a law level the possibility of the formation of

4-amino-triazole is reduced and during the whole reaction the ammonia releasing simultaneously with the feeding can be ensured. Considering the equilibrium states in the reaction mixture the removal of the formed water is important.

According to a preferred embodiment of the process of the invention hydrazine or hydrazine hydrate is continuously added for 4-20, preferably 8-12 hours to an aqueous solution of ammonium formiate which is immersed to a heating medium of 116-180 °C , preferably

130-160 °C .

In order to ensure the removal of continuously formed water and ammonia and in order to retain the components of higher boiling point than the boiling point of water a column of a head temperature of 95-100 °C is preferably used. The reactants are used at a molar ratio of 1 : 2.1-2.3 in order to ensure the excess of formulating agent even in the last phase of the hydrazine feeding. Upon cooling the product crystallizes from the reaction mixture. After isolating the product a mother lye is obtained which is a saturated solution related to triazole containing an excess of the formulating agent as well. The product can be isolated from the mother lye by vacuum distillation as well but it is preferred to add the mother lye to the ammonium formiate which can be used in the next reaction and the excess of the formulating agent can be ensured with the recycled mother lye.

The ammonia developed from the reaction mixture can preferably be used for the preparation of ammonium formiate by consuming the continuously formed ammonia from the reaction mixture in formic acid. Thus only a part of the ammonia which is necessary for the preparation of ammonium formiate has to be ensured from an outside source.

According to a preferred embodiment of the process of the invention the ammonium formiate which is necessary for the next reaction is prepared simultaneously with the preparation of the product by passing through the reaction mixture the necessary ammonia obtained from an outside source. To pass through the reaction mixture the ammonia which is necessary for the preparation of ammonium formiate is first of all advantageous because it promotes the removal of the formed water from the reaction mixture. In the process of the invention hydrazine, formic acid and ammonia are used for the preparation of 1,2,4-triazole.

There are several advantages of the process according to the invention as opposed to the processes known from the prior art. - the reaction temperature of 120-160 °C is lower than used in the known processes.

- The use of ammonium formiate as a formylating agent makes it possible to utilize the waste ammonia in the process. - The reaction partner of the highly explosive and inflammable hydrazine hydrate is an organic salt, i.e. its aqueous solution. This reduces the dangerous character of the process.

- The crystallization of the product from the reaction mixture and the recirculation of the mother lye to the next reaction reduces the losses.

- A product of good quality can be prepared by simple method and in excellent conversion by using cheaper raw materials. The process of the invention can be illustrated by the following example.

The equipment consists of two reaction vessels.

Reaction vessel No . 1 is a tubulated glass pear shaped bulb of a volume of 20 liters which can be heated with an oil bath and its temperature can be controlled.

To the ground necks of glass pear shaped bulb a stirrer, thermometer, an ammonia inlet tube a hydrazine feeder and a bulb condenser are attached and air is removed by suction through the jacket. To this condenser a descending cooler is attached which can be cooled with cold water connecting said cooler and the receiver by a vacuum pipe end.

The second reactor is also a tubulated glass pear shaped bulb of 20 liters equipped with a stirrer, thermometer, ammonia inlet tube and reflux cooled with cold water.

Best Mode of Carrying out the Invention

1. Cycle

To reactor 1 11.9 kg. (220 moles) 85 % formic acid are added and it is saturated with ammonia under stirring. After saturation the oil bath is heated to 160 °C and hydrazine hydrate is fed into the reactor while HΕL is let into the reactor at a rate of 10 mole per hour and 5.06 kg. (200 moles) 100 % hydrazine hydrate are added within 9 hours at an equal rate. The head temperature of the condenser attached to the reaction vessel is maintained at 95-100 ºC by removing the air through the jacket by suction. Water vapour and ammonia are leaving the reaction mixture from which the water vapour is condensed and the residual ammonia gas is consumed in 10.82 kg. (200 moles) 85 % formic acid in the reaction vessel 2. After adding the hydrazine hydrate the reaction is continued under similar conditions for one hour and at the temperature of the reaction the liquid product is removed by suction and allowed to cool to room temperature. The precipitated product is centrifuged and dried. Product: 3900 g. 96% 1,2,4-triazole (GLC) 56.5 % based on hydrazine

2. Cycle

The mother lye saturated related to triazole containing an excess of the formylating agent is recycled to reaction vessel 1 and ammonium formiate being in reaction vessel 2 is added. One may then proceed according to cycle 1.

Product: 7000 g. 96 % 1,2,4-triazole (GLC) 97.40 % based on hydrazine

3. Cycle

One may use the mother lye of cycle 2 and proceed according to the previous cycles-. Product: 6990 g. 96 % 1,2,4-triazole (GLC) 97.3 % based on hydrazine One may proceed as disclosed above and altogether 10 reaction cycles are carried out. The last cycle is performed as follows.

10. Cycle

By using the mother lye of the 9. cycle one may proceed as disclosed above. Product: 7050 g. 94 % 1,2,4-triazole (GLC) 96 % based on hydrazine When the mother lye is contaminated at an undesired extent the mother lye of a volume of 6 1. is distilled in vacuum and then 1.8 kg. 96 % 1,2,4-triazole are obtained at a pressure of 13 Hgmm and at a temperature of 125-135 °C. The total product of 10 subsequent reaction cycles as given above:

68970 g. 95.5 % 1,2,4-triazole (GLC)

95.4 % based on hydrazine

Claims

C l a i m s

1. Process for the preparation of 1, 2,4-triazole the ring closure of diformyl hydrazine prepared by the formylation of hydrazine and ammonia which comprises reacting ammonium formiate with hydrazine hydrate by feeding continuously hydrazine or hydrazine hydrate at 120-160 °C to the aqueous solution of ammonium formiate and removing continuously the formed water and ammonia from the mixture and isolating if desired, the cold precipitated triazole from the mixture.

2. A process according to claim 1 which comprises preparing the starting ammonium formiate in the reaction mixture from formic acid in the presence of water by adding ammonia.

3« A process according to claims 1 to 2 comprising continuously feeding ammonia gas into the reaction mixture during the whole reaction.

4. A process according to claims 1 to 3 which comprises applying the vapour substances leaving the reaction mixture onto a column of head temperature 95-100 °C in order to retain substances of higher boiling point than water.

5. A process according to claims 1 to 4 which comprises utilizing ammonia leaving the reaction mixture for the preparation of ammonium formiate necessary in the next reaction.

6. A process according to claims 1 to 5 which comprises recycling the obtained mother lye after isolating the product into the next reaction.