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

“AN EFFICIENT PROCESS FOR THE PREPARATION OF HYDRAZINE HYDRATE”

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

The following specification particular describes 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 hydrazine hydrate.

BACKGROUND OF THE INVENTION
The hydrazine hydrate is an important intermediate in synthesis of agrochemical and pharmaceuticals. It is also used as laboratory reagent for synthesis of fine chemicals.
Hydrazine hydrate (N2H4.H2O), a colourless liquid having an ammonical odor, is the simplest diamine and unique in its class because of the N—N bond. It was first prepared in 1887 by Curtius from diazo acetic ester.
European Pat. No. 2123632 discloses a process for preparing hydrazine hydrate from ketazine intermediate wherein a solution containing the dialkyl ketone and aqueous ammonia is brought into contact with an oxidizing agent such as sodium hypochlorite or hydrogen peroxide in a tubular reactor to produce ketazine solution which is directly subjected to hydrolysis at elevated pressure and 150°C temperature to obtain hydrazine hydrate. However, it fails to provide the method for treatment of large aqueous effluent containing sodium chloride generated during ketazine preparation.
Chinese Pat. Pub. No. 110775950 discloses the separation of pure sodium chloride from aqueous effluent containing crude sodium chloride generated during hydrazine hydrate preparation. It involves the step of evaporation followed by cooling at room temperature and crystallization to separate hydrazine hydrate from crude sodium chloride solution. The crude sodium chloride solution is then treated with hydrochloric acid and hydrogen peroxide. It fails to disclose the treatment of aqueous effluent obtained directly after ketazine formation.
Chinese Pat. No. 100389893 discloses the tedious way for the recovery of acetone and ammonia from ketazine aqueous effluent containing sodium chloride, ammonia and acetone by bubble evaporation followed by flash vaporization.
U.S. Pat. No. 11225413 discloses a process for preparation of concentrated aqueous solutions of a hydrazine hydrate by reacting a hydrogen peroxide solution, ammonia, and methyl ethyl ketone in the presence of an activator such as acetamide and ammonium acetate, followed by separating the mixture into a ketazine layer and an aqueous solution layer. The ketazine layer is then concentrated and methyl ethyl ketone is removed by evaporation to obtain pure ketazine which is subjected to hydrolysis to obtain 80% concentrated hydrazine hydrate. The methyl ethyl ketone, acetamide were recovered and recycled back to produce ketazine. However, use of acetamide makes the process tedious and costlier at commercial scale.
Chinese Pat. No. CN114684798 also discloses a process for preparation of hydrazine hydrate from sodium hypo chlorite which is prepared in situ from sodium hydroxide and chlorine.
Thus, the conventional means of producing hydrazine hydrate through ketazine route using sodium hypochlorite results in large aqueous effluents which also needs treatment to recover and reuse various components like NaCl, ammonia and dialkyl ketone or required to minimize before its disposal to the environment.
While the attempts have been made to treat effluents for recovery of unreacted raw materials, solvents and other by-products but still there is a need to develop a cost effective and commercially viable process for preparation of hydrazine hydrate via ketazine route.
The present invention provides an alternative, environment friendly with minimum effluent generation, maximum recovery and reuse of components present in effluent and thus a cost-effective and industrially viable process for preparation of hydrazine hydrate.

OBJECT OF THE INVENTION
The object of the present invention is to provide an alternative, cost-effective and environment friendly process for preparation of hydrazine hydrate that involves minimum effluent generation.

SUMMARY OF THE INVENTION
The present invention provides a process for preparation of hydrazine hydrate, comprising the steps of:
a) reacting ketone, alkali hypochlorite and ammonia in presence of water to obtain a reaction mixture comprising alkali chloride, unreacted ketone, ammonia, water and ketazine;
b) separating substituted ketazine from step a) reaction mixture;
c) hydrolysing the ketazine to obtain hydrazine hydrate and ketone; and
d) isolating pure hydrazine hydrate,
wherein the ketone, ammonia, water and alkali chloride are recovered and reused.

BRIEF DESCRIPTION OF DRAWINGS
Description of drawing 1
S1: aqueous ammonia solution; S2: Acetone; S3: aqueous sodium hypochlorite solution.
F1, F2: flow rectors.
M1: static mixer.
B1: back pressure regulator.
T1, T2: distillation tower.
1, 2: heat exchangers.
P1: ketazine solution; P2: aqueous NaCl.
Description of drawing 2
C1, C2: continuous stirred tank reactors.
S1: aqueous ammonia solution; S2: acetone; S3: aqueous sodium hypochlorite solution.
B1, B2: back pressure regulator.
V1: vessel.
P1: ketazine.

DETAILED DESCRIPTION OF THE INVENTION
As used herein, the ketone is a substituted ketone or acetone, wherein substituents on ketone are independently selected from C1-C6 straight or branched chain alkyl, provided at least one of substituent is not methyl.
As used herein, the alkali hypochlorite is selected from a group consisting of sodium hypochlorite, calcium hypochlorite and potassium hypochlorite.
As used herein, the term CSTR refers to continuous stirred tank reactor.
In a preferred embodiment, the substituted ketone is a dialkyl ketone selected from a group consisting of acetone, ethyl methyl ketone, methyl isobutyl ketone and diethyl ketone and the like.
As used herein, alkali chloride is selected from a group consisting of sodium chloride, calcium chloride and potassium chloride.
As used herein, the ammonia is in gaseous form with a concentration range of 98 to 100% or in aqueous solution form in a concentration range of 20 to 30%.
The ammonia is recovered from the ketazine reaction mixture by distilling the aqueous phase at a temperature selected in the range of 60-120°C.
In an embodiment, after separation of ammonia, substituted ketone and ketazine, a portion of the aqueous mixture is then treated with alkali hydroxide and chlorine to obtain alkali hypochlorite.
In another embodiment, remaining portion of aqueous mixture is used for ammonia scrubbing.
In another embodiment, pure alkali chloride gets precipitated out during the preparation of alkali hypochlorite and isolated thereafter with a purity greater than 99.5 and thus has commercial value.
In another embodiment, gaseous ammonia is used in ketazine synthesis which results in lesser aqueous effluents (20-25 kg aq. alkali chloride generated per kg of hydrazine hydrate) and thus makes the process more commercially viable.
In another embodiment, aqueous ammonia is used in ketazine synthesis which results in 30-35 kg aqueous alkali chloride per kg of hydrazine hydrate which is used in hypo generation and ammonia scrubbing and thus is fully utilized without disposal to environment.
In an embodiment, the present invention provides a process for preparation of hydrazine hydrate, comprising the steps of:
a) reacting acetone, alkali hypochlorite and gaseous ammonia in presence of water to obtain an aqueous reaction mixture;
b) distilling the aqueous reaction mixture to separate ammonia, acetone and dimethyl ketazine;
c) hydrolysing the dimethyl ketazine to obtain hydrazine hydrate and acetone; and
d) isolating pure hydrazine hydrate,
wherein the acetone and ammonia are recovered and reused.
In another embodiment, the present invention provides a process for preparation of hydrazine hydrate, comprising the steps of:
a) reacting acetone, alkali hypochlorite and ammonia in presence of water to obtain an aqueous reaction mixture;
b) distilling the aqueous mixture to separate ammonia, acetone and dimethyl ketazine;
c) a portion of the aqueous mixture is then treated with alkali hydroxide and chlorine to obtain alkali hypochlorite and precipitated alkali chloride;
d) recovering precipitated alkali chloride in pure form;
e) the remaining portion of aqueous phase is used for scrubbing excess ammonia;
f) hydrolysing the dimethyl ketazine to obtain hydrazine hydrate and acetone; and
g) isolating pure hydrazine hydrate,
wherein regenerated alkali hypochlorite, recovered excess ammonia and acetone are reused.
In another embodiment, the present invention provides a process for preparation of hydrazine hydrate, comprising the steps of:
a) reacting substituted ketone, alkali hypochlorite and ammonia in presence of water to obtain a biphasic reaction mixture comprising organic and aqueous phase;
b) separating the aqueous phase and distilling to recover ammonia and the substituted ketone;
c) separating organic phase from biphasic reaction mixture of step a) and distilling to recover pure substituted ketazine;
d) hydrolysing the substituted ketazine to obtain hydrazine hydrate and the substituted ketone; and
e) isolating pure hydrazine hydrate,
wherein the substituted ketone and ammonia are recovered and reused and wherein substituents are independently selected from C1-C6 straight or branched chain alkyl, provided at least one of substituent is not methyl.
In another embodiment, the present invention provides a process for preparation of hydrazine hydrate, comprising the steps of:
a) reacting substituted ketone, alkali hypochlorite and ammonia in presence of water to obtain a biphasic reaction mixture comprising organic and aqueous phase;
b) separating the aqueous phase and washing with water immiscible organic solvents;
c) distilling the washed aqueous layer for ammonia recovery;
d) separating organic phase from biphasic reaction mixture of step a) and distilling to recover pure substituted ketazine;
e) hydrolysing the substituted ketazine to obtain hydrazine hydrate and the substituted ketone; and
f) isolating pure hydrazine hydrate,
wherein the excess of the substituted ketone and ammonia are recovered and reused and wherein substituents are independently selected from C1-C6 straight or branched chain alkyl, provided at least one of substituent is not methyl.
In another embodiment, the present invention provides a process for preparation of hydrazine hydrate, comprising the steps of:
a) reacting substituted ketone, alkali hypochlorite and ammonia to obtain a biphasic reaction mixture comprising organic and aqueous phase;
b) recovering ammonia from the aqueous phase;
c) a portion of the aqueous phase is then treated with alkali hydroxide and chlorine to obtain alkali hypochlorite and precipitated alkali chloride;
d) recovering precipitated alkali chloride in pure form;
e) the remaining portion of aqueous phase is used for scrubbing excess ammonia;
f) separating organic phase from biphasic reaction mixture of step a) and distilling to recover pure substituted ketazine;
g) hydrolysing the substituted ketazine to obtain hydrazine hydrate and the substituted ketone; and
h) isolating pure hydrazine hydrate,
wherein regenerated alkali hypochlorite, recovered excess ammonia and the substituted ketone are reused and wherein substituents are independently selected from C1-C6 straight or branched chain alkyl, provided at least one of substituent is not methyl.
The washing of aqueous phase using water immiscible organic solvent helps in removal of various organic impurities, solvent and other by-products present in aqueous phase.
In an embodiment, the aqueous phase after washing is subjected to distillation for ammonia recovery and can directly be sent to effluent treatment plant for its disposal.
The water immiscible organic solvents are selected from a group consisting of methylene dichloride, chloroform, toluene, methyl ethyl ketone, methyl tetrahydrofuran, methyl tertiary butyl ether and ethyl acetate.
In an embodiment, the process of the present reaction is carried out in a batch mode.
In another embodiment, the process for preparation of hydrazine hydrate is carried out in continuous mode in a flow reactor or continuous stirred tank reactor wherein, product i.e., hydrazine hydrate is continuously isolated whereas, solvents and unreacted raw materials are continuously supplied back to the reactor along with fresh feed of reactant.
In an embodiment, the hydrolysis of ketazine is carried out by distilling in presence of water at a temperature selected in the range of 95-180°C at a pressure range selected from atmospheric to 9kg/cm2.
In an embodiment, the hydrazine hydrate is obtained with a purity greater than 80%, preferably greater than 95% and more preferably in the range of 98-100%.
In another embodiment, the recovered NaCl is obtained with an assay of greater than 95%, preferably greater than 98% and more preferably in the range of 98 to 99.5%.
In an embodiment more than 98% of ammonia and substituted ketone is recovered and reused for next batch.
In an embodiment, 2.5-4 kg of pure alkali chloride is obtained per Kg of hydrazine hydrate. during hypo generation.
The hydrazine hydrate obtained by the process of present invention is recovered in a concentration range of 80-100%.
The residence time in continuous preparation of hydrazine hydrate using CSTR or flow reactor is selected in the range of 5-30 minutes.
The substituted ketone, ammonia and alkali hypochlorite which are used as starting material can be obtained commercially. The alkali hypochlorite, generated during treatment of aqueous phase is also used in ketazine synthesis.
Unless stated to the contrary, any of the words “comprising”, “comprises” and includes 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: A clean oven dried 1000 mL round bottomed flask fitted with mechanical stirrer and temperature sensor was charged with methyl ethyl ketone (MEK) (185g, 2.55 mol) and water (40g, 2.2 mol). To the above mixture cold 10-11% sodium hypochlorite (450g, 373 mL, 0.635 mol, 1 eq.) was added simultaneously using dosing pump at the rate of 75-80 mL/h and ammonia gas (33 g, 1.918 mol) was purged at the rate of 6-7 g/h for about 5-6 hours at 25-35°C (Exothermic) and after complete addition, the mass was heated to 55-60 °C for about 2-3 hours. After completion of reaction by GC analysis, the biphasic mass was taken for layer separation. The organic layer was taken for MEK recovery and product isolation by distillation. The aqueous layer was taken for ammonia and MEK recovery by distillation.
Yield: 72%; Purity: 95%.
Example 2: A clean oven dried 1000 mL round bottomed flask fitted with mechanical stirrer and temperature sensor was charged with methyl ethyl ketone (185g, 2.55 mol). To the above solvent, cold 10-11% sodium hypochlorite (450g, 0.635 mol) was simultaneously added using dosing pump at the rate of 75-80 mL/h and 25% aq. ammonia (430 g, 6.3 mol) at the rate of 130-145 g/h for about 3-4 hours at 25-35 °C (Exothermic) and after complete addition, the mass was heated to 50-55°C for about 2-3 hours. After completion of reaction by GC analysis, the biphasic mass was taken for layer separation. The organic layer was taken for MEK recovery and product isolation by distillation. The aqueous layer-1 was taken for MDC extraction for residual MEK and MEK-ketazine followed by ammonia recovery.
Yield: 82%; Purity: 98%
Example 3: A clean oven dried 1000 mL round bottomed flask fitted with mechanical stirrer and temperature sensor was charged with methyl ethyl ketone (185g, 2.55 mol). To the above solvent cold 10-11% sodium hypochlorite (450g, 0.635 mol) was added simultaneously using dosing pump at the rate of 75-80 mL/h and 25% aq. ammonia (430 g, 6.3 mol) at the rate of 130-145 g/h for about 3-4 hours at 25-35°C (Exothermic) and after complete addition, the mass was heated to 50-55°C for about 2-3 hours. After completion of reaction by GC analysis, NaCl (72g, 1.2 mol) was added to reaction mass before layer separation. The organic layer was taken for MEK recovery and product isolation by distillation. The aqueous layer-1 was taken directly for ammonia recovery. The aqueous layer-1 after ammonia recovery (700g bottom aq. NaCl (20%)) was divided into two equal parts. The part-1 used for hypo generation by adding NaOH and chlorine. The part-2 i.e., aq. NaCl solution used as ammonia scrubber will be reused for next batch. The saleable pure NaCl solid precipitated during hypo preparation.
Yield: 86%; Purity: 98 %, NaCl: 82g (Assay: 99.4%)
Example 4: A clean oven dried 1000 mL round bottomed flask fitted with magnetic stirrer and temperature sensor was charged with 95-98% ketazine (108g, 0.770 mol) followed by DM water (400g, 22.2 mol) at 25-35 °C (Exothermic). The biphasic mass was heated to 110-120 °C for about 24 hours. The reaction progress was monitored for ketazine absence in the bottom aqueous layer by GC analysis. The top MEK layer was taken for recycle. The bottom aqueous hydrazine hydrate was concentrated to 100% by distillation.
Yield: 98%, Assay: 98.5 (by titration)
Example 5: A clean oven dried 1000 mL round bottomed flask fitted with mechanical stirrer and temperature sensor was charged with acetone (185g, 3.1 mol) and water (40g, 2.2 mol). To the above mixture cold 10.5% sodium hypochlorite (450g, 0.635 mol) was added simultaneously using dosing pump at the rate of 75-80 mL/h and (33g, 1.918 mol) ammonia gas was purged at the rate of 6-7 g/h for about 5-6 hours at 25-35 °C (Exothermic) and after complete addition, the mass was heated to 55-60°C for about 2-3 hours. After completion of reaction by GC analysis, the reaction mass was taken for ammonia and acetone recovery followed by product isolation by azeotropic distillation.
Yield: 74%; Purity: 95%
Example 6: A clean oven dried 3000 mL round bottomed flask fitted with mechanical stirrer and temperature sensor was charged with acetone (130 g, 5.0 mol) and 25% aqueous ammonia solution (850 g, 25 eq.) was slowly added in one lot (5-7mins) using dropping funnel. To the above mixture, cold 10-11% aq. sodium hypochlorite solution (300g, 0.5 mol) was added using PVDF dosing pump at the rate of 160-170 mL/h for about 2-3 hours at 25-30°C (Slight exothermic, ?T±3 °C at this flow rate). After hypo addition, the reaction mass was heated to 50-55 °C and was maintained for 2 hours at the same temperature. The clear mass was taken for azine isolation and acetone recovery.
Approx bottom aq. layer comprising aq.NaCl, w/w 20% (900g) was divided into two equal parts. The part-1 was used for hypo generation and part-2 was used as an ammonia scrubber. The saleable pure NaCl solid precipitated during hypo preparation was filtered and dried.
Yield: 95%; Purity: 95%; NaCl: 57g (Assay: 99.4%)
Example 7: A clean oven dried 1000 mL round bottomed flask fitted with magnetic stirrer and temperature sensor was charged with 20-25% aqueous acetone azine (500g, 0.910 mol) and the mass was heated to 110-120 °C for about 22-24 hours. The reaction progress was monitored for ketazine absence in the bottom aqueous layer by GC analysis. The top acetone cut was taken for recycle. The bottom aqueous hydrazine hydrate concentrated to 80-100% by distillation.
Yield: 98%, Assay: 98.9% (by titration)
Example 8: Preparation of ketazine using flow reactor
An aqueous ammonia solution S1 (10.0 eq.,), acetone S2 (3 eq.,) and 10-12% aqueous sodium hypochlorite solution S3(1eq) were dosed to flow rector F1 at 5-10°C through a static mixer M1. The residence time of reactor F1 was 4-6 mins. The outlet of F1 was fed to flow reactor F2 at 40-65 °C where the residence time was 25-30 mins. The pressure of flow reactors F1 and F2 was maintained around 1-2 kg/cm2 using back pressure regulator B1. The output (crude reaction mass) of F2 was sent to distillation tower T1 to recover unreacted ammonia S1 and acetone S2 where S1 and S2 were condensed using heat exchanger 1 at the top of the column and recycled back. The ketazine solution with NaCl collected from the bottom was entered into distillation tower T2 to separate aqueous ketazine and aqueous NaCl. The aqueous ketazine solution P1 was condensed using heat exchanger 2 leaves from the top of tower T2 and goes for step-2. The bottom aqueous NaCl P2 collected from the tower T2 was recycled.
Example 9: Preparation of ketazine using CSTR
CSTRs C1 and C2 in the setup shown in Figure 2 were set to their specific temperatures (5-55°C). Aqueous ammonia solution S1 (10.0 eq.,), acetone S2 (3 eq.,) and 10-12% aqueous sodium hypochlorite solution S3 (1eq) were dosed into the reactor C1 at 5-10 °C. The overflow of C1 was connected to C2 where the temperature was maintained between 40-55°C. The pressure of the reactors were maintained around 1-2 kg/cm2 using back pressure regulator B1 and B2. The overflow of C2 was collected in vessel V1 at 20-25 °C and was taken for distillation to recover ammonia, acetone followed by ketazine isolation. The product ketazine P1 was isolated.
Yield: 84-88%; Purity: 99.3%
Example 10: An aqueous ketazine solution (25-45%) was hydrolysed under pressure (4-6 kg/cm2) at high temperature (140-160°C) using 3-meter SS304 metal distillation set-up. Initially, the system was kept under total reflux using acetone and water at 140-160 °C with 4-6 kg/cm2 pressure. The preheated aqueous ketazine was fed into column by maintaining the pressure (4-6 kg/cm2) and top temperature (120-125°C). Both, acetone and hydrazine hydrate were collected continuously from the top and bottom respectively by maintaining the reboiler level. The dilute hydrazine hydrate was concentrated to 98-99% by distillation.
Yield : 95.9%; Purity: 98-99% (by titration)

SRF LIMITED NO. OF SHEETS: 02
APPLICATION NO. IN202311011283 SHEET NO. 01

Drawing 1: Continuous process for production of ketazine using flow reactor

SRF LIMITED NO. OF SHEETS: 02
APPLICATION NO.IN 202311011283 SHEET NO. 02

Drawing 2: Continuous process for production of ketazine using CSTR
,CLAIMS:WE CLAIM:
1. A process for preparation of hydrazine hydrate, comprising the steps of:
a) reacting a ketone, alkali hypochlorite and ammonia in presence of water to obtain a reaction mixture comprising alkali chloride, unreacted ketone, ammonia, water and ketazine;
b) separating ketazine from step a) reaction mixture;
c) hydrolysing the ketazine to obtain hydrazine hydrate and ketone; and
d) isolating pure hydrazine hydrate,
wherein the ketone, ammonia, water, and alkali chloride are recovered and reused.
2. The process as claimed in claim 1 wherein, the ketone is a substituted ketone or acetone.
3. The process as claimed in claim 1 for preparation of hydrazine hydrate, comprising the steps of:
a) reacting acetone, alkali hypochlorite and ammonia in presence of water to obtain an aqueous reaction mixture;
b) distilling the aqueous mixture to separate ammonia, acetone and dimethyl ketazine;
c) a portion of the aqueous mixture is then treated with alkali hydroxide and chlorine to obtain alkali hypochlorite and precipitated alkali chloride;
d) recovering precipitated alkali chloride in pure form;
e) the remaining portion of aqueous phase is used for scrubbing excess ammonia;
f) hydrolysing the dimethyl ketazine to obtain hydrazine hydrate and acetone; and
g) isolating pure hydrazine hydrate,
wherein regenerated alkali hypochlorite, recovered excess ammonia and acetone are reused.
4. The process as claimed in claim 1 for preparation of hydrazine hydrate, comprising the steps of:
a) reacting substituted ketone, alkali hypochlorite and ammonia in presence of water to obtain a biphasic reaction mixture comprising organic and aqueous phase;
b) separating the aqueous phase and distilling to recover ammonia and the substituted ketone;
c) separating organic phase from biphasic reaction mixture of step a) and distilling to recover pure substituted ketazine;
d) hydrolysing the substituted ketazine to obtain hydrazine hydrate and the substituted ketone; and
e) isolating pure hydrazine hydrate,
wherein the substituted ketone and ammonia are recovered and reused and wherein substituents are independently selected from C1-C6 straight or branched chain alkyl, provided at least one of substituent is not methyl.
5. The process as claimed in claim 6, wherein the aqueous phase is washed with a water immiscible organic solvent.
6. The process as claimed in claim 6, wherein a portion of the aqueous phase is treated with alkali hydroxide and chlorine to obtain alkali hypochlorite and precipitated alkali chloride and the remaining portion of aqueous phase is used for scrubbing excess ammonia.
7. The process as claimed in claim 1, wherein the regenerated alkali hypochlorite, recovered excess ammonia and the substituted ketone are reused.
8. The process as claimed in claim 1, wherein the alkali hypochlorite is selected from a group consisting of sodium hypochlorite, calcium hypochlorite and potassium hypochlorite.
9. The process as claimed in claim 1, wherein the ammonia is in gaseous form with a concentration range of 98 to 100% or in aqueous solution form in a concentration range of 20 to 30%.
10. The process as claimed in claim 1, wherein the ammonia is recovered from the ketazine reaction mixture by distilling the aqueous phase at a temperature selected in the range of 60-120°C.

Dated this 19th Day of February 2023.
.