FORM 2
THE PATENT ACT, 1970
(39 of 1970)
AND
THE PATENT RULES, 2003
COMPLETE SPECIFICATION
(See Section 10, Rule 13)


3. PREAMBLE TO THE DESCRIPTION :
COMPLETE SPECIFICATION
The following specification particularly describes the invention and the manner in which it is to be performed.
1. TITLE OF THE INVENTION
2. APPLICANT®

(a) Name:
(b) Nationality:
(c) Address:

A PROCESS FOR THE PRODUCTION OF CYCLOHEXYLAMINE AT LOW PRESSURE
M/S. HINDUSTAN ORGANIC CHEMICALS LIMITED
Indian
MR.A.S.DIDOLKAR,
Chairman and Managing Director,
81, Maharshi Karve Road, MUMBAI - 400 002,
Maharashtra, India.

PRIOR ART
Cyclohexylamine finds applications in the manufacture of insecticides, dyestuffs, emulsifying agents, metal corrosion inhibitors, plasticizers etc. It is commercially produced from cyclohexanone, cyclohexanol or phenol in presence of ammonia and hydrogen (Japanese Unexamined Patent Publication Nos. 45-19897, 45-19898, 51-41627). An alternative method for the production of cyclohexylamine consists of hydrogenating aniline with some base metal catalysts like nickel, and cobalt, and some noble metal catalysts viz. ruthenium, palladium, rhodium etc. (US Patent No. 4,914,239, Japanese Examined Patent Publication No.45-28368). It is generally seen that base metal catalysts are effective at elevated pressures and temperatures, where as noble metal catalysts require milder conditions (Paul N. Rylander, Hydrogenation Methods, pp 123-126). In a high, pressure process using ruthenium catalyst, cyclohexylamine has been produced at 50 tolOO bar pressure (Unpublished results at Hindustan Organic Chemicals Ltd.). In a low pressure process, this chemical has been produced nt a hydrogen pressure of about 2 bar using an alumina supported rhodium catalyst (Practical Catalytic Hydrogenation, Morris Freifelder, Wiley-hiterscience, pp 556-557, 1970). It can be produced even at 1 bar with a carbon supported palladium catalyst (J. Organ. Chem. USSR, Volume 1, pp769,1965).
It is usually experienced in the hydrogenation reactions that when catalytic reductions to produce primary amines are carried out to completion, very high levels of high boiling impurities: largely secondary amines are formed. Further, high pressure processes involve safety risks. In addition to above, achieving high pressures of hydrogen, a compressor is required which adds to the fixed cost in terms of equipments and instruments as well as variable cost in terms of power, and maintenance and repair costs. In order to reduce safety risks and the said costs, an economical process to produce cyclohexylamine from aniline and hydrogen at low pressure, as described in the present invention is developed.
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OBJECTIVE OF THE INVENTION
The objective of the present invention is to produce cyclohexylamine at lower pressure. More particularly, it is concerned with an economical process for making cyclohexylamine with considerably reduced safety risks.
SUMMARY OF THE INVENTION
This invention relates to a process for the production of cyclohexylamine from aniline and hydrogen at low pressure. More particularly, it is concerned with an economical process with considerably reduced safety risks. The process consists of hydrogenating aniline in liquid phase in a batch reactor in presence of an alumina supported group VIII metal catalyst, at a hydrogen pressure of about 5 kg/cm2 to 20 kg/cm2 with either continuous or intermittent venting of the reactor. Under the said process conditions, an aniline conversion of about 90 % to 100 % with a cyclohexylamine content of about 85 % to 95 % is achieved.
DESCRIPTION OF THE INVENTION
The present invention describes an economical process to produce cyclohexylamine at low pressure by the hydrogenation of aniline in liquid phase in a batch reactor made of stainless steel and equipped with stirrer, pressure gauge, thermo couple and safety disc. The reactor is heated electrically or by steam. An automatic temperature controller is used for controlling the reactor temperature. The reactor may be of laboratory scale (300 ml) or an industrial scale (5000 liters). The said hydrogenation is carried out in the said batch reactor in presence of an alumina supported group Vm metal catalyst which is a finely divided powder of 30 micron to 90 micron size with a metal content of about 2.5 to 7.5 % by weight Aniline and the said catalyst (0.10 % to 3.50 %, weight by volume) are charged in the said reactor. The reactor is first purged with nitrogen and then with hydrogen. The reactor is then pressurized with hydrogen to about 5 to 10 kgtem2 and heated to 190° to 225° C. Finally, the reactor pressure is adjusted to about 10 to 25 kg/cm2 for 5 to 15 hrs under constant stirring by maintaining the stirrer speed at about 100 to 1200 revolutions per minute. During the reaction, the vapors of the reactor
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are vented out either constantly at the rate of 1 to 20 liters/hr or intermittently by depressunzing the reactor. Under the said process conditions, the conversion of aniline is about 90 % to 100% weight with a cyclohexylamine content of about 85 % to 95 % weight.
The present invention is further described below by way of examples. However, these examples are illustrative and should not be construed as limiting the scope of mis invention.
EXAMPLE-I
Comparative Example
This experiment was carried out at high pressure for comparison. 300 ml of aniline and 0.75 g of an alumina supported ruthenium catalyst (ruthenium content, 5%) were charged in a 600 ml Parr reactor, model No- 4563, equipped with stirrer, internal cooling coil, thermocouple, pressure gauge, safety rupture disc, programmable temperature controller and solenoid valve with a water flow connection to the internal cooling coil. The reactor was purged first with nitrogen and then with hydrogen. The reactor was pressurized with hydrogen to 8 kg /cm2 and was heated to 220°C. The reactor pressure was men adjusted to 70 kg /cm2 and was maintained at this pressure and at the said temperature for 6 to 8 hrs under constant stirring at 1000 revolutions per minute. Through out the reaction, no venting of the reactor vapors was done. Under the said conditions, an aniline conversion of 97.01 % weight with a cyclohexylamine content of 89.27 % weight was achieved.
EXAMPLE - n
This experiment was carried out in the same reactor and in a similar manner as described in example-I, except catalyst loading and at lower reaction pressure, which were 7.5 g and 17 kg /cm2 respectively. Through out the reaction, no venting of the reactor vapors was done. Under the said process conditions, conversion of aniline was 61.39 % weight with a cyclohexylamine content of 53.05% weight.
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EXAMPLE - HI
This experiment was carried out in the same reactor and in a similar manner as described in example-H However, in mis case, the reactor vapors were continuously vented out at a rate of 5 liters/hr during the hydrogenation reaction. Under the said process conditions, the conversion of aniline was complete with a cyclohexylamine content of 92.38 % weight.
EXAMPLE - IV
This experiment was carried out in the same reactor and in a similar manner as described in example-ID, except that the loading of the said alumina supported ruthenium catalyst was reduced to 2.25 g (0.75 %, w/v of aniline) and venting rate of the reactor vapors was increased to 7.5 liters/hr. Under the said conditions, the conversion of aniline was 99.68 % weight with a cyclohexylamine content of 86.85% weight.
EXAMPLE - V
This experiment was carried out in the same reactor and in a similar manner as described in example-IV, except mat venting rate of the reactor vapors was farther increased to 10.5 liters/hr. Under the said conditions, the conversion of aniline was 99.35 % weight with a cyclohexylamine content of 87.63 % weight
EXAMPLE - VI
This experiment was carried out in a 1000 liters stainless steel reactor equipped with steam jacket, internal cooling coil, stirrer, thermocouple, pressure gauge, safety valve and rupture disc. The reactor was made by M/s Zschokke Wartmann A.G., Switzerland. For venting of the reactor vapors, a stainless steel tube was connected at the top of the reactor. The other end of the said tube was connected through a control valve to a water trap with the help of another stainless steel tube.
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The reactor was charged with 550 liters aniline and 4 kg of the said ruthenium catalyst and was first purged with nitrogen and then with hydrogen. The reactor was then pressurized with hydrogen to 10 kg/cmz. The reactor contents were stirred at about 200 revolutions per minute and then heated to about 220° C by introducing steam in the jacket. As the reactor pressure started falling, it was controlled at the hydrogen pressure of 17 kg /cm . The reactor temperature was maintained at 220° C by circulating cooled oil through the internal cooling coil when ever required. The reaction was carried out at the said pressure and temperature for about 8 hrs with a constant venting of the reactor vapors at a rate of 8 -10 liters/hr. Under the said conditions, the conversion of aniline was found to be 99.63% weight with overall cyclohexylamine content of 93.28 % weight.
EXAMPLE - Vn
This experiment was carried out in the same stainless steel reactor and in the similar manner as described in example VI. The reaction was carried out at the said pressure and temperature for about 2 hrs and thereafter, the reactor was vented out (depressurized) up to 5 kg/cm and re-pressurized to 17 kg/cm . The reaction was carried out at the said pressure and temperature for another 3 hrs and again depressurized up to 5 kg/cm2 and re-pressurized to 17 kgfcm2. The reaction was carried out further at the said pressure and temperature for another 3 to 4 hrs. Under the said conditions, the conversion of aniline was found to be 75.93% weight with overall cyclohexylamine content of 80.68 % weight.
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We claim:
1. A process for the production of cyclohexylamine from aniline and hydrogen at low pressure in liquid phase, preferably in a batch reactor in presence of a supported group VDI metal catalyst either with a constant venting or intermittent venting of the reactor, without adversely affecting the activity and selectivity of the catalyst.
2. A process as claimed in claim 1, wherein the pressure of the hydrogenation reaction is about 5-25 kg /cm2.
3. A process as claimed in claim 1, wherein the group VIE metal is preferably ruthenium as an active ingredient.
4. A process as claimed in claims 1 and 3, wherein the amount of the ruthenium metal in the catalyst is about 2.5 to7.5% weight.
5. A process as claimed in claims 1, 3 and 4, wherein the support in the said catalyst is alumina powder.
6. A process as claimed in claim 1, wherein the catalyst loading for the batch is about 0.10% to 3.5 % weight / volume.
7. A process as claimed in claim 1, wherein the venting rate of the reactor vapors is 1 to 20 liters /hr.
8. A process as claimed in claim 1, wherein the intermittent venting is carried out first after 1 to 2 hrs and secondly after 2 to 5 hrs by de-pressurizing the reactor up to 5 kg/cm2 and there after, the reaction is carried out further for 2 to 5 hrs at the desired pressure of l7kg/cm2.
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9. A process as claimed in claims 1 to 8 for the production of
cyclohexylamine from aniline and hydrogen at low pressure as described herein with reference to the examples, I to VII.
Dated mis day of 2009.
For and on behalf of HINDUSTAN ORGANIC CHEMICALS LIMITED
(ARVIND SHRIRAM DIDOLKAR)
CHAIRMAN AND MANAGING DIRECTOR
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