Title of Invention

AN IMPROVED PROCESS FOR THE ELECTRO-SYNTHESIS OF BENZYLCHLORIDE

Abstract The present invention describes a process for the electrosynthesis of benzyl chloride in aqueous acidic medium containing sodium chloride electrolyte with Metal -Metal Oxide (MMO) coated electrode for chlorine evolution as anode and graphite as cathode in two phase electrolysis, the top layer containing the aqueous sodium chloride solution as electrolyte and the bottom layer containing the organic solvent and toluene at a temperature ranging from 10 to 25 °C with stirring speed of 40-50 rpm. The conversion rate and yield is very high.
Full Text The present invention describes a process for the electrosynthesis of benzyl chloride in aqueous acidic medium containing sodium chloride electrolyte with Metal -Metal Oxide (MMO) coated electrode for chlorine evolution as anode and graphite as cathode in two phase electrolysis, the top layer containing the aqueous sodium chloride solution as electrolyte and the bottom layer containing the organic solvent and toluene at a temperature ranging from 10 to 25 °C with stirring speed of 40-50 rpm.
The electrochemical synthesis of benzyl chloride has industrial importance in pharmaceutical industry especially anti-infective area and occupies a central place in the context. Benzyl chloride is also used to synthesis of fine and specialty chemicals.
Hitherto preparation of benzyl chloride may be structurally the simplest side chain chlorinated derivatives of toluene, but industrially it is the most important. Benzyl chloride is the starting material for a large number of industrial products. The preparation of it involved the reaction of benzyl alcohol with hydrochloric acid.
Since, chlorine is used in halogenation reactions, the handling and storage of this noxious gas and the formation of halo substituted side or multi products are the difficulties involved in chemical halogenations.
The electrochemical method has been employed for the preparation of halo derivatives of many organic compounds. Toluene is electrolysed in aqueous electrolyte solution and the formation of chloro toluenes is in high percentages and benzyl chloride is very low percentage of yield. Therefore, electrolysis of a mixed solution (two phase) containing aqueous and non aqueous (organic) phase is preferred to electrolysis in homogenous non-aqueous solvents.
The main objective of this invention is a process for the electrosynthesis of benzyl chloride in aqueous acidic medium containing sodium chloride electrolyte with DSA-CI2 (Dimensionally Stable Anode) anode and graphite cathode in two phase electrolysis, the top layer containing the sodium chloride electrolyte and the bottom layer containing the
organic solvent and toluene at a temperature ranging from 10 to 25 °C with stirring speed of 40-50 rpm.
The main advantage of this process is the electrochemical generation of chlorine in aqueous medium in an undivided cell. The generated chlorine species which could be fully absorbed easily by the organic phase. In general the rate of conversion increases with mass transfer as the reaction moves from a predominantly mass transfer controlled region to a mixed control region. This could be achieved using this cell.
Accordingly the present invention provides a process for the electrosynthesis of
benzyl chloride in aqueous acidic medium containing sodium chloride electrolyte with
MMO-CI2 anode and graphite cathode in two phase electrolysis, the top layer containing
the sodium chloride electrolyte and the bottom layer containing the organic solvent and
toluene at a temperature ranging from 10 to 25 °C with stirring speed of 40-50 rpm.
In an embodiment of the invention wherein the anodes were unsists of platinum MMO-
Cl2.
In another embodiment of the invention wherein the cathodes are graphite and platinum
In yet another embodiment of the invention wherein the supporting electrolyte used is sulphuric acid.
In further embodiment of the invention wherein the anode and cathode height is equivalent to the aqueous layer height.
In yet another embodiment of the invention wherein the electrolysis was carried out at a current density range of 1-5 A/dm2.
In still another embodiment of the invention wherein the electrolysis was carried out at a temperature range of 10 to 25 °C
In an embodiment of the invention wherein the electrolysis was carried out at a stirring speed in the range of 40 - 50 rpm.
The two-phase electrolysis of toluene was carried out in an electrochemical cell under constant current electrolysis with a stirring speed of 50 rpm. In this two-phase electrolysis, the upper aqueous phase consists of 33% NaCl solution with catalytic amount of sulphuric acid, which acts as a chlorine evolution source. The lower phase consists of toluene dissolved in an organic solvent. The MMO-CI2 anode and graphite cathode were placed in the aqueous phase. During the electrolysis, the organic phase of the electrolyte should be stirred at a speed of 50 rpm and the organic phase should not contact the electrode surface to avoid multi chlorination. The anode and cathode inter-electrode distance is 2 cm.
The current density applied for the reaction is in the range of 10 to 30 mA/cm at a temperature ranging from 10 to 25 °C. The charge required for the complete conversion of toluene varies from 3.5 to 5.5 F at different conditions. Analyse the product formed in the reaction mixture periodically to avoid the formation of undesirable other chlorinated products. After completion of electrolysis the organic phase was separated from the aqueous phase and washed with water.
The electrolysis is carried out:
• In a conventional electrolysis cell, well known to the man skilled in the art, comprising only a single compartment jacketed cell.
• At a temperature which is generally between 0°Cand+30°C. preferably between 10°C. and +25°C, advantageously in the region of 20°C.
• At an anode current density which preferably varies between 1 and 10 A/dm2. In general, and preferably, the operation is carried out at a constant current, but it is also possible to operate at a constant voltage, at a controlled potential or with variable current and potential.
• While the solution is being stirred, for example by means of a bar magnet, after the solution has been degassed by bubbling an inert gas, for example nitrogen or argon.
After the passage of a quantity of current corresponding to approximately 2 Faradays (2 x 96,500 C) per mole of organic compounds or, if appropriate, until the latter have been completely converted, the electrolysis is discontinued. The principle constituents of the mixture, namely the unreacted organic compound (toluene), the
required product (benzyl chloride) and certain reaction byproducts are then analysised from the reaction mixture, using High Pressure Liquid Chromatography (HPLC). The required products are isolated by extraction and purified in conventional manner.
The following examples are given by way of illustration of the present invention and should not be construed to limit the scope of the invention.
Example 1:
Anode : MMO-Cl2
Anode size : Mesh type ( 0.25 dm2)
Cathode : Graphite ( 0.25 dm2)
Electrolyte : 75 ml of Saturated NaCl solution ( 30%) containing
5 ml of toluene, Sulphuric acid and 10 ml of chloroform
Cell type Undivided Cell
Cell Height/Diameter (H/D) ratio: 1.2
Cell voltage : 4 V
Current density : 3 A/dm2
Current passed : 750 mA.
Temperature : 20 °C
Stirring speed :100rpm
Toluene taken : 4.0 gms
Benzyl Chloride obtained : 4. 4 gms
Yield (based on the HPLC analysis) : 80%
Current Efficiency : 80 %
Conversion : 94%
Example 2:
Anode : Platinum ( 0.25dm2)
Anode size : Plate type ( 0.25 dm2)
Cathode : Graphite (0.25 dm2)
Electrolyte : 75 ml of Saturated NaCl solution ( 30%) containing
5ml of toluene, Sulphuric acid and 10 ml chloroform
Cell type :Undivided Cell
Cell Height/Diameter ( H/D) ratio: 1.2
Cell voltage : 4.5 V
Current density : 3 A/dm
Current passed : 700 mA
Temperature : 20 °C
Stirring speed :100rpm
Toluene taken : 4.0 gms
Benzyl chloride obtained : 4.4 gms
Yield : 80%
Current Efficiency : 80 %
Conversion : 94%
Example 3:
Anode : Platinum ( 0.25 dm )
Anode size : plate type ( 0.25 dm )
Cathode : Graphite ( 0.25 dm2)
Electrolyte : 75 ml of Saturated NaCl solution ( 30%) containing
5 ml of toluene, Sulphuric acid and 10 ml of chloroform
Cell type :Undivided Cell
Cell Height/Diameter (H/D) ratio: 1.2
Cell voltage : 4 V
Current density : 3 A/dm2
Current passed : 700 mA
Temperature : 10 °C
Stirring speed :100rpm
Toluene taken : 4.0 gms
Benzyl chloride obtained : 4.2 gms 1
Yield : 76 %
Current Efficiency : 76 %
Conversion : 95 %
Example 4:
Anode : Platinum ( 0.25dm )
Cathode : Graphite ( 0.25dm2)
Electrolyte : 75 ml of saturated NaCl solution ( 33%) containing
5 ml of toluene, Sulphuric acid and 10 ml of chloroform
Cell type Undivided Cell
Cell Height/Diameter ( H/D) ratio: 1.2
Cell voltage : 4 V
Current density : 5A/dm2
Current passed : 1.25 amp.
Temperature : 20 °C
Stirring speed : 100 rpm
Toluene taken : 4.0 gms
Benzyl Chloride obtained : 3.8 gms
Yield : 69%
Current Efficiency : 70 %
Conversion : 92%
The main advantages of the present invention are
1. The cell design is very simple and easy for scaling up and choice of the anode was catalytic in nature and rate of chlorine evolution required for this reaction is maximum.
2. The rate of conversion and yield is high
3. High mass transfer can be achieved.
4. Low cell voltage
5. Low energy consumption
6. Can be operated at atmospheric pressure
7. Uniform mixed region
8. This design will lower the capital and running costs and may render the technology more attractive.
9. The temperature can be controlled easily by jacketed design.
10. The cell is integrated easily and directly into the overall process.
11. Uniform and controlled potential and current distribution
12. The current efficiency is high








We claim:
1. An improved process for the electrosynthesis of benzyl chloride which comprises; characterized in electrolyzing in an aqueous acidic medium containing sodium chloride electrolyte in undivided cell having MMO-Cl2 (Metal -Metal Oxide coated electrode for chlorine evolution) as anode and graphite as cathode in two phase electrolysis, the top layer containing the sodium chloride and sulphuric acid electrolyte and the bottom layer containing toluene dissolved in chloroform at a temperature ranging from 10 to 25°C with stirring speed of 40-50 rpm, separating the product by conventional method.
2. An process as claimed in claim 1,wherein the anodes are platinum and MMO-
Cl2.
3. An process as claimed in claims 1-2, wherein the cathodes are graphite and
platinum
4. An process as claimed in 1-4 wherein the anode and cathode height is equivalent
to the aqueous layer height.
5. An process as claimed in claims 1-5, wherein the electrolysis was carried out at a current density range of 1-5 A/dm2.
6. An improved process for the electro- synthesis of benzylchloride substantially as herein describe with reference to examples accompanying this specification.

Documents:

1655-del-2004-Abstract-(29-10-2010).pdf

1655-del-2004-abstract.pdf

1655-del-2004-Claims-(29-10-2010).pdf

1655-del-2004-claims.pdf

1655-del-2004-Correspondence-Others-(29-10-2010).pdf

1655-del-2004-correspondence-others.pdf

1655-del-2004-description (complete).pdf

1655-del-2004-form-1.pdf

1655-del-2004-form-18.pdf

1655-del-2004-form-2.pdf

1655-del-2004-Form-3-(29-10-2010).pdf

1655-del-2004-form-3.pdf

1655-del-2004-form-5.pdf


Patent Number 244507
Indian Patent Application Number 1655/DEL/2004
PG Journal Number 50/2010
Publication Date 10-Dec-2010
Grant Date 08-Dec-2010
Date of Filing 01-Sep-2004
Name of Patentee COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH
Applicant Address RAFI MARG, NEW DELHI-110 001,INDIA
Inventors:
# Inventor's Name Inventor's Address
1 THASAN RAJU CECRI INDIA
2 KUMARASAMY KULANGIAPPAR CECRI INDIA
3 MANICKAM ANBU KULANDAINATHAN CECRI INDIA
4 ARUNACHALAM MUTHUKUMARAN CECRI INDIA
PCT International Classification Number C07C 17/00
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA