Description:FORM 2
THE PATENT ACT 1970
(39 of 1970)
&
THE PATENT RULES, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)

“PROCESS FOR PREPARATION OF
MONOMETHYLHYDRAZINE”

The present application is an improvement over the invention claimed in the complete specifications of the main granted patent IN295897 filed on 23/12/2011.

SRF LIMITED, AN INDIAN COMPANY,
SECTOR 45, BLOCK-C, UNICREST BUILDING,
GURGAON – 122003,
HARYANA (INDIA)

The following specification particular describe the invention and the manner in which it is to be performed.

FIELD OF THE INVENTION
The present invention provides a process for preparation of monomethylhydrazine. The monomethylhydrazine is used in a wide variety of applications.

BACKGROUND OF THE INVENTION
Monomethylhydrazine is used as an intermediate for complex organic molecules in the pharmaceutical and agricultural industries.
There are several methods known conventionally for producing monomethylhydrazine.
US 2954283 & US3102144 discloses a process for preparation of methylhydrazines by mixing anhydrous hydrazine with dimethyl sulphate at 115-125℃ to yield methyl hydrazine. The selectivity of monomethyl hydrazine in said process is 51.4%. Additionally, the process involves use of anhydrous hydrazine that is not easy to handle, which poses a greater safety hazard and is not conducive to industrial production.
CN101402586 discloses a process for preparation of monomethylhydrazine by reacting dimethyl sulfate with hydrazine hydrochloride in the presence of tetrabutylammonium bromide. The selectivity of monomethyl hydrazine in this process is 48%. The process involves the use of tetrabutylammonium bromide as a catalyst that increase the cost of production during commercial scaleups.
US7683217 discloses a process for preparation of monomethylhydrazine by methylating hydrazine or hydrazinium hydrochloride or hydrazinium dihydrochloride with methyl chloride and/or a methanol/HCl mixture. Here, the selectivity of the monomethylhydrazine achieved is upto 60%.
The above aforesaid methods provides less selectivity towards the desired product and generate large quantity of effluents and that require expensive and tedious effluent treatment for removal of catalyst and trapped solvent.
IN295897 granted to the present applicant discloses a process for preparation of monomethylhydrazine which comprises reacting under heating hydrazine hydrate with methanolic hydrochloric acid in the presence of excess hydrochloride gas; and recovering monomethylhydrazine from monomethylhydrazine hydrochloride. However, the process has high selectivity, however it has been observed that the use of excess acid in the process makes the process expensive and it obviously does not meet the requirements of industrial production.
Therefore, the process of the present invention involves an economical, safe and industrially doable process as compared to existing processes. The present invention provides a process for preparation of monomethylhydrazine using alkali metal methyl sulfate with high selectivity.

OBJECT OF THE INVENTION
The main object of the present invention is to provide a simple and safe process for preparation of monomethylhydrazine from alkali metal methyl sulfate and by circumventing the use of a catalyst thereby decreasing overall cost of the process at industrial scale.

SUMMARY OF THE INVENTION
The present invention provides a process for preparation of a monomethylhydrazine, comprising a step of methylating hydrazine using alkali metal methyl sulfate in the presence of a solvent.

DETAILED DESCRIPTION OF THE INVENTION
In an embodiment, the present invention provides a process for preparation of a monomethylhydrazine, comprising a step of methylating hydrazine using alkali metal methyl sulfate in the presence of a solvent.
As used herein, the alkali metal methyl sulfate selected from the group consisting of lithium methyl sulfate, sodium methyl sulfate, cesium methyl sulfate and potassium methyl sulfate. The preferred alkali metal methyl sulfate is sodium methyl sulfate.
In an embodiment, the mole ratio of alkali metal methyl sulfate and hydrazine is 0.1:1.5, preferably 0.6-1.0 moles.
In an embodiment of the present invention, the methylation of hydrazine is carried out in presence of solvent.
As used herein ‘solvent’ is selected from a group consisting of water, methanol, anisole, dimethylformamide, dimethyl acetamide, 1,4-dioxane, tetrahydrofuran, n-methyl pyrrolidone, sulfolane, acetonitrile and dimethyl or the like.
In an embodiment, the reaction of methylation is carried out at a temperature ranging from 100°C to 110°C.
In an embodiment, the reaction of methylation is carried out in the absence of catalyst.
After completion, reaction mixture is treated with base to adjust the pH of the solution.
As used herein ‘base’ is selected from a group consisting of alkali hydroxide may be selected from a group consisting of sodium hydroxide, potassium hydroxide, cesium hydroxide and magnesium hydroxide or the like.
In an embodiment, the mole equivalent of alkali metal methyl sulfate used is in the range of 0.3 to 0.7 molar equivalent.
The process of the present invention for preparation of monomethylhydrazine has following advantages over the known methods:
1. The process prevents effluent and improves yield significantly.
2. The process of present invention is simple, cost-effective and safe at commercial scale.
3. The present invention prevents the formation of impurities such as di, tri and tetra methylhydrazine and thereby increases the selectivity towards the desired product significantly.
4. The process of the present invention uses no hazardous or difficult to handle materials.
In an embodiment, the present invention involve use of hydrazine hydrate. The purest form of hydrazine is not safe to use. The present invention involves use of 64% of hydrazine hydrate which is environment friendly and convenient to use.
The reagents used in the present invention may be prepared or obtained commercially.
The compound of Formula 1 is isolated by using techniques known in the art for example distillation, evaporation, column chromatography and layer separation or combination thereof.
In an embodiment, the present invention provides a process for preparation of methylhydrazine, having yield greater than 80%, preferably, greater than 90%.
The completion of the reaction may be monitored by any one of chromatographic techniques such as Gas chromatography (GC) and potentiometric titration.
Unless stated to the contrary, any of the words “comprising”, “comprises” mean “including without limitation” and shall not be construed to limit any general statement that it follows to the specific or similar items or matters immediately following it.
Embodiments of the invention are not mutually exclusive, but may be implemented in various combinations. The described embodiments of the invention and the disclosed examples are given for the purpose of illustration rather than limitation of the invention as set forth in the appended claims.
The following examples are given by way of illustration and therefore should not be construed to limit the scope of the present invention.
EXAMPLES
Example 1: Preparation of monomethylhydrazine
Hydrazine hydrate (50g), sodium methyl sulfate (100g) and water (120g) were charged into the reactor at a room temperature. The reaction mass was heated to 104°C for 4 hours and then cooled the mass to room temperature. After the completion of reaction, the resulting mass was treated with sodium hydroxide solution (40%) to adjust the pH of the solution to 12 and then cooled the solution to 10°C, followed by filtration, washing and then distilled to obtain the titled compound. Selectivity of 99%; Yield: 90 %
Example 2: Preparation of monomethylhydrazine
Hydrazine hydrate (50g), sodium methyl sulfate (100g) and anisole (150g) were charged into a reactor at a room temperature. The reaction mass was heated to 100°C for 4 hours and then cooled the mass to room temperature. After the reaction completion, the resulting mass was treated with sodium hydroxide solution (40%) to adjust the pH of the solution to 12 and then cooled the solution to 10°C, followed by filtration, washing and then distilled to obtain the titled compound.
Purity: Selectivity of 99%; Yield: 88 %
, C , Claims:WE CLAIM:
1. A process for preparation of a monomethylhydrazine, comprising a step of methylating hydrazine using alkali metal methyl sulfate in the presence of solvent.
2. The process as claimed in claim 1, wherein the alkali metal methyl sulfate is selected from the group consisting of lithium methyl sulfate, sodium methyl sulfate, cesium methyl sulfate and potassium methyl sulfate.
3. The process as claimed in claim 1, wherein the mole ratio of alkali metal methyl sulfate and hydrazine is 0.1:1.5.
4. The process as claimed in claim 1, wherein the solvent is selected from a group consisting of water, methanol, anisole, dimethylformamide, dimethyl acetamide, 1,4-dioxane, tetrahydrofuran, n-methyl pyrrolidone, sulfolane, acetonitrile and dimethyl.
5. The process as claimed in claim 1, wherein the reaction of methylation is carried out at a temperature ranging from 100°C to 110°C.

Dated this 24th day of July 2023.