Title of Invention	AN IMPROVED PROCESS FOR THE PREPARATION OF REDUCED NITRO AND DINITRO COMPOUNDS USING NOVEL TI/ CERAMIC TIO2 CATHODES.
Abstract	The present invention provides an improved process for the preparation of reduced nitro and dinitro compounds using novel Ti/ ceramic Tio2 cathodes which comprises electrolysing by known methods nitro / dinitro compound in an electrochemical cell having a novel Ti/ ceramic Tio2 cathode and lead anode, containing nitro / dinitro compound & sulphuric acid as catholyte and the said catholyte comprising of 8.5 to 11 gm of nitro or dinitro compound and 10% to 20% (v/v) sulphuric acid and sulphuric acid as anolyte at a concentration ranging 10% to 20% (v/v) at a current 1-10 amps, temperature of 40 - 90°C and recovering reduced nitro compounds by conventional methods.

Title of Invention

AN IMPROVED PROCESS FOR THE PREPARATION OF REDUCED NITRO AND DINITRO COMPOUNDS USING NOVEL TI/ CERAMIC TIO2 CATHODES.

Abstract

The present invention provides an improved process for the preparation of reduced nitro and dinitro compounds using novel Ti/ ceramic Tio2 cathodes which comprises electrolysing by known methods nitro / dinitro compound in an electrochemical cell having a novel Ti/ ceramic Tio2 cathode and lead anode, containing nitro / dinitro compound & sulphuric acid as catholyte and the said catholyte comprising of 8.5 to 11 gm of nitro or dinitro compound and 10% to 20% (v/v) sulphuric acid and sulphuric acid as anolyte at a concentration ranging 10% to 20% (v/v) at a current 1-10 amps, temperature of 40 - 90°C and recovering reduced nitro compounds by conventional methods.

Full Text	This invention relates to an improved process for the preparation of reduced nitro and dinitro compounds using novel Ti / ceramic TiO2 cathodes. Hitherto it has been the practice to reduce nitro compounds to the corresponding amines electrochemically at a copper cathode indirectly by using inorganic redox systems, such as Ti4+ / Ti3+, Ce 4+ / Ce 2+ in solution. These methods however, have the following drawbacks. 1. The choice of a minimum redox concentration is to be evaluated since below this concentration, there could be competition due to direct reduction. 2. If the free base is to be isolated from the electrolysis product by neutralisation (for reductions in acid medium), it is likely that the redox species gets precipitated as hydroxide, thereby making the separation difficult. 3. Tendency of the electrolysis products for complex formation is sometimes seen as is the case with several amines, thereby reducing the product yield. The object of the present invention is to provide an improved process for the electroreduction of nitro and dinitro compounds using novel Ti / ceramic TiC>2 cathode which obviates the disadvantages by immobilising the redox species Ti4+ / Ti3+ on the cathods surface itself. In our copending application no. 260/Del/92 we have described and claimed a Ti/ceramic/ TiO2 cathode and in our copending application no. 1121/DEL/98 we have described & claimed an electrochemical cell incorporating the said cathode. The titanium metal in the form of an expanded sheet is initially sand blasted and then etched in 50 % HC1 or 10 % oxalic acid at 90 ° C for one hour. It is then washed with distilled water and dried in an oven at 120 °C. A 0.05 solution of titanium acetyl acetonate is then prepared by dissolving 1.31 g of the compound in 4 - 8 ml of concentrated nitric acid, 2-5 ml water and then making up with isopropanol. The above solution is then applied onto the expanded titanium sheet treated as above, either by using a brush or a microsyringe. The sheet is then dried in an oven at 100 ° C. It is then fired in a muffle furnace at a temperature in the range 450 - 550 ° C for 5-10 minutes. It is then taken out and the above process of applying the solution, drying and firing is repeated 4-5 times. The cathode so prepared is Accordingly, the present invention provides an improved process for the preparation of reduced nitro and dinitro compounds using novel Til ceramic TiO2 which comprises electrolysing by known methods nitro / dinitro compound in an electrochemical cell having a novel Til ceramic TiO2 cathode and lead anode, containing nitro / dinitro compound & sulphuric acid as catholyte and the said catholyte comprising of 8.5 to 11 gm of nitro or dinitro compound and 10% to 20% (v/v) sulphuric acid and sulphuric acid is anolyte at a concentration ranging 10% to 20% (v/v) at a current 1-10 lamps, temperature of 40 - 90° C and recovering reduced nitro compounds by conventional methods According to further feature the amount of catholyte may ranges from 8.5 to 11 gm of nitro or dinitro compound & 10 to 20 % (v/v) sulphuric acid. The anolyte may be 10 to 20 % (v/v) sulphuric acid. The cell current may ranges from 1 to 10 A, corresponding to 6 or 12 faraday / gm mole of nitro / dinitro compound and current density may ranges from 3 to 9 A/dm2 is used. Typical uses of the Ti/ceramic TiO2 cathode in the reduction of a nitro and a dinitro compound and its efficiency during reuse of the electrolyte are given below. The following examples are given to illustrate the process of the present invention and should not be construed to limit the scope of the present invention. Example: 1 In a typical cell (a one litre glass beaker) consisting of 400 ml of 10% H2SO4 and 8.5 gm of nitro benzene (NB) as catholyte and 100 ml of 10 % H2SO4 as anolyte. Ti / ceramic TiO2 cathode of area 0.84 dm2 and lead anode, with ceramic porous pot as diaphram, with the catholyte being constantly agitated using a mechanical stirrer, passing a current of 4.2 A corresponding to 6 Faraday / g mole of NB with a current density of 5A / dm2, at a temperature of 40 - 50 'C with the cell voltage being 4-5 volts, the yield of aniline obtained upon neutralisation is 91.4% with a current efficiency of 91.8%. For electrolyte reuse, the same conditions as above were used except that 630 grams of NB were reduced by adding the compound in 5 instalments of 126 g each. The weight of aniline sulphate recovered was 620.8 g (124, 124.4, 124.4, 123.6 and 124.4 grams respectively) which accounts for 85.4% aniline. Example 2: In a typical cell (a one litre glass beaker) consisting of 400 ml of 20 % H2SO4 and 11 g of metadinitrobenzene (m - DNB) as catholyte and 100 ml of 20% H2SO4 as anolyte. Ti / ceramic TiO2 cathode of area 0.84 dm2 and lead anode, passing a current of 4.2 A corresponding to 12 Faraday / g mole of m-DNB with a current density of 5 A / dm2, at a temperature of 80 - 90 'C with a cell voltage of 3-4 V, the yield of m - phenylenediamine (m-PDA) estimated is 92.2 % with a current efficiency of 88.9 %. For electroyte reuse, the same conditions as above were used except that 225.5 grams of m-DNB were added in 5 instalments of 38.3, 46.8, 46.8, 46.8 and 46.8 grams respectively. The weight of m-PDA sulphate recovered is 337 grams ((58.7, 69.8, 69.0, 69.8 and 69.7 grams respectively) and the estimated amount of m-PDA is 116 g thereby accounting for 80 % yield of the diamine. The following are the main advantages of the invention: 1. In the use of Ti /ceramic TiO2 cathode, there is heterogeneous redox catalysis due to the Ti 4+ /Ti 3+ on the cathode surface and hence the reductioon efficiency is better than at copper or tin cathodes. 2. The reduction by this method involves no effluent problem. 3. This method affords the reuse of electrolyte possible and the electrode performance during reuse is extremely good. 4. During neutralisation of an electrolysis product, the problem of complex formation does not arise in this case in contrast to that observed during the use of redox systems in solution with a copper cathode. We claim : 1 . An improved process for the electrolytic preparation of aniline and m -phenylenediamine from the respective nitro compounds which comprises electrolysing by known methods nitro / dinitro compound in an electrochemical cell having a novel Ti/ ceramic TiO2 cathode and lead anode, containing nitro / dinitro compound & sulphuric acid as catholyte and sulphuric acid as anolyte at a current of 1 - 10 amps, temperature of 40 - 90 ° C and recovering reduced nitro compounds by conventional methods. 2. An improved process as claimed in claim 1 wherein the catholyte is 8.5 to 11 gm of nitro or dinitro compound and 10 % to 20 % (v/v) sulphuric acid. 3. An improved process as claimed in claims 1 and 2 wherein the anolyte is to 10 % to 20 % (v/v) sulphuric acid. 4. An improved process as claimed in claims 1-3 wherein the cell current is in the range of 1 to 10 A, corresponding to 6 or 12 Faraday / gram mole of nitro / dinitro compound and current density of 3 to 9 A/dm2. 5. An improved process as claimed in claims 1 - 4 wherein the diaphragm of the divided electrochemical cell is a ceramic porous pot. 6. An improved process for the preparation of reduced nitro and dinitro compounds using novel Ti / ceramic TiOi cathodes substantially as herein described with reference to the examples.

Full Text

This invention relates to an improved process for the preparation of reduced nitro and dinitro compounds using novel Ti / ceramic TiO2 cathodes.
Hitherto it has been the practice to reduce nitro compounds to the corresponding amines electrochemically at a copper cathode indirectly by using inorganic redox systems, such as Ti4+ / Ti3+, Ce 4+ / Ce 2+ in solution. These methods however, have the following drawbacks. 1. The choice of a minimum redox concentration is to be evaluated since below this concentration, there could be competition due to direct reduction. 2. If the free base is to be isolated from the electrolysis product by neutralisation (for reductions in acid medium), it is likely that the redox species gets precipitated as hydroxide, thereby making the separation difficult. 3. Tendency of the electrolysis products for complex formation is sometimes seen as is the case with several amines, thereby reducing the product yield.
The object of the present invention is to provide an improved process for the electroreduction of nitro and dinitro compounds using novel Ti / ceramic TiC>2 cathode which obviates the disadvantages by immobilising the redox species Ti4+ / Ti3+ on the cathods surface itself.
In our copending application no. 260/Del/92 we have described and claimed a Ti/ceramic/ TiO2 cathode and in our copending application no. 1121/DEL/98 we have described & claimed an electrochemical cell incorporating the said cathode.

The titanium metal in the form of an expanded sheet is initially sand blasted and then etched in 50 % HC1 or 10 % oxalic acid at 90 ° C for one hour. It is then washed with distilled water and dried in an oven at 120 °C.
A 0.05 solution of titanium acetyl acetonate is then prepared by dissolving 1.31 g of the compound in 4 - 8 ml of concentrated nitric acid, 2-5 ml water and then making up with isopropanol. The above solution is then applied onto the expanded titanium sheet treated as above, either by using a brush or a microsyringe. The sheet is then dried in an oven at 100 ° C. It is then fired in a muffle furnace at a temperature in the range 450 - 550 ° C for 5-10 minutes. It is then taken out and the above process of applying the solution, drying and firing is repeated 4-5 times. The cathode so prepared is
Accordingly, the present invention provides an improved process for the preparation of reduced nitro and dinitro compounds using novel Til ceramic TiO2 which comprises electrolysing by known methods nitro / dinitro compound in an electrochemical cell having a novel Til ceramic TiO2 cathode and lead anode, containing nitro / dinitro compound & sulphuric acid as catholyte and the said catholyte comprising of 8.5 to 11 gm of nitro or dinitro compound and 10% to 20% (v/v) sulphuric acid and sulphuric acid is anolyte at a concentration ranging 10% to 20% (v/v) at a current 1-10 lamps, temperature of 40 - 90° C and recovering reduced nitro compounds by conventional methods
According to further feature the amount of catholyte may ranges from 8.5 to 11 gm of nitro or dinitro compound & 10 to 20 % (v/v) sulphuric acid.

The anolyte may be 10 to 20 % (v/v) sulphuric acid. The cell current may

ranges from 1 to 10 A, corresponding to 6 or 12 faraday / gm mole of nitro / dinitro compound and current density may ranges from 3 to 9 A/dm2 is used.
Typical uses of the Ti/ceramic TiO2 cathode in the reduction of a nitro and a dinitro compound and its efficiency during reuse of the electrolyte are given below.
The following examples are given to illustrate the process of the present invention and should not be construed to limit the scope of the present invention.
Example: 1
In a typical cell (a one litre glass beaker) consisting of 400 ml of 10% H2SO4 and 8.5 gm of nitro benzene (NB) as catholyte and 100 ml of 10 % H2SO4 as anolyte. Ti / ceramic TiO2 cathode of area 0.84 dm2 and lead anode, with ceramic porous pot as diaphram, with the catholyte being constantly agitated using a mechanical stirrer, passing a current of 4.2 A corresponding to 6 Faraday / g mole of NB with a current density of 5A / dm2, at a temperature of 40 - 50 'C with the cell voltage being 4-5 volts, the yield of aniline obtained upon neutralisation is 91.4% with a current efficiency of 91.8%.
For electrolyte reuse, the same conditions as above were used except that 630 grams of NB were reduced by adding the compound in 5 instalments of 126 g each. The weight of aniline sulphate recovered was 620.8 g (124, 124.4, 124.4, 123.6 and 124.4 grams respectively) which accounts for 85.4% aniline.

Example 2:
In a typical cell (a one litre glass beaker) consisting of 400 ml of 20 % H2SO4 and 11 g of metadinitrobenzene (m - DNB) as catholyte and 100 ml of 20% H2SO4 as anolyte. Ti / ceramic TiO2 cathode of area 0.84 dm2 and lead anode, passing a current of 4.2 A corresponding to 12 Faraday / g mole of m-DNB with a current density of 5 A / dm2, at a temperature of 80 - 90 'C with a cell voltage of 3-4 V, the yield of m - phenylenediamine (m-PDA) estimated is 92.2 % with a current efficiency of 88.9 %.
For electroyte reuse, the same conditions as above were used except that 225.5 grams of m-DNB were added in 5 instalments of 38.3, 46.8, 46.8, 46.8 and 46.8 grams respectively. The weight of m-PDA sulphate recovered is 337 grams ((58.7, 69.8, 69.0, 69.8 and 69.7 grams respectively) and the estimated amount of m-PDA is 116 g thereby accounting for 80 % yield of the diamine.
The following are the main advantages of the invention:
1. In the use of Ti /ceramic TiO2 cathode, there is heterogeneous redox
catalysis due to the Ti 4+ /Ti 3+ on the cathode surface and hence the
reductioon efficiency is better than at copper or tin cathodes.
2. The reduction by this method involves no effluent problem.

3. This method affords the reuse of electrolyte possible and the electrode
performance during reuse is extremely good.
4. During neutralisation of an electrolysis product, the problem of
complex formation does not arise in this case in contrast to that observed
during the use of redox systems in solution with a copper cathode.

We claim :
1 . An improved process for the electrolytic preparation of aniline and m -phenylenediamine from the respective nitro compounds which comprises electrolysing by known methods nitro / dinitro compound in an electrochemical cell having a novel Ti/ ceramic TiO2 cathode and lead anode, containing nitro / dinitro compound & sulphuric acid as catholyte and sulphuric acid as anolyte at a current of 1 - 10 amps, temperature of 40 - 90 ° C and recovering reduced nitro compounds by conventional methods.
2. An improved process as claimed in claim 1 wherein the catholyte is 8.5
to 11 gm of nitro or dinitro compound and 10 % to 20 % (v/v) sulphuric acid.
3. An improved process as claimed in claims 1 and 2 wherein the
anolyte is to 10 % to 20 % (v/v) sulphuric acid.
4. An improved process as claimed in claims 1-3 wherein the cell
current is in the range of 1 to 10 A, corresponding to 6 or 12 Faraday / gram
mole of nitro / dinitro compound and current density of 3 to 9 A/dm2.
5. An improved process as claimed in claims 1 - 4 wherein the
diaphragm of the divided electrochemical cell is a ceramic porous pot.
6. An improved process for the preparation of reduced nitro and dinitro
compounds using novel Ti / ceramic TiOi cathodes substantially as herein
described with reference to the examples.

Documents:

1124-del-1998-abstract.pdf

1124-del-1998-claims.pdf

1124-del-1998-correspondence-others.pdf

1124-del-1998-correspondence-po.pdf

1124-del-1998-description (complete).pdf

1124-del-1998-form-1.pdf

1124-del-1998-form-19.pdf

1124-del-1998-form-2.pdf

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Patent Number

216537

Indian Patent Application Number

1124/DEL/1998

PG Journal Number

13/2008

Publication Date

28-Mar-2008

Grant Date

14-Mar-2008

Date of Filing

27-Apr-1998

Name of Patentee

COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH,

Applicant Address

RAFI MARG, NEW DELHI-110001, INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	PAYYALLUR NARAYANAN ANANTHARAMAN	CENTRAL ELECTROCHEMICAL RESEARCH INSTITUTE, KARAIKUDI 630006, INDIA.
2	DEVANATH VASUDEVAN	CENTRAL ELECTROCHEMICAL RESEARCH INSTITUTE, KARAIKUDI 630006, INDIA.
3	CINGARAM RAVICHANDRAN	CENTRAL ELECTROCHEMICAL RESEARCH INSTITUTE, KARAIKUDI 630006, INDIA.

PCT International Classification Number

H01J 31/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA