Title of Invention	PROCESS FOR PREPARING NICOTINIC ACID
Abstract	A process for preparing nicotinic acid from ammonium nicotinate characterized in that an aqueous solution of ammonium nicotinate is spray-dried at a drying gas temperature of from 160 to 250°C. 2. The process according to claim 1, wherein the spray drying is carried out in afluidized-bed spray-dryer. 3. The process according to any one of claims 1 or 2, wherein the nicotinic acid produced by the spray drying is subjected to a thermal post-treatment in a fluidized bed at a temperature of 100 to 200°C, preferably from 130 to 170°C.

Title of Invention

PROCESS FOR PREPARING NICOTINIC ACID

Abstract

A process for preparing nicotinic acid from ammonium nicotinate characterized in that an aqueous solution of ammonium nicotinate is spray-dried at a drying gas temperature of from 160 to 250°C. 2. The process according to claim 1, wherein the spray drying is carried out in afluidized-bed spray-dryer. 3. The process according to any one of claims 1 or 2, wherein the nicotinic acid produced by the spray drying is subjected to a thermal post-treatment in a fluidized bed at a temperature of 100 to 200°C, preferably from 130 to 170°C.

Full Text	The present invention relates to a process for preparing nicotinic acid from solutions of ammonium nicotinate. A known process for preparing nicotinic acid is based on the oxidation of 3-methylpyridine (P-picoline) with atmospheric oxygen in the presence of water with heterogeneous catalysis. However, this process has the disadvantage that, in a side reaction, some of the 3-methylpyridine is broken down in a sequence of oxidation and hydrolysis steps to form ammonia, which, together with the main product nicotinic acid, forms ammonium nicotinate. The latter, in contrast to the free nicotinic acid, is highly water soluble and thus makes the work-up of the product mixture more difficult, furthermore it represents a loss in yield, if it cannot be converted back to nicotinic acid. The latter is possible, for example, by adding a strong acid, but this forms the ammonium salt of this acid, which must be separated off and disposed of as waste. In addition, it must be noted here that nicotinic acid, as a pyridine derivative, can also react as a base and, with an excess of the strong acids, can form a salt. The object of the present invention was therefore to provide a process which permits the transformation of ammonium nicotinate to nicotinic acid without adding auxiliaries and without producing wastes. According to the invention this object is achieved by the process according to Patent Claim 1. It has surprisingly been found that an aqueous solution of ammonium nicotinate can be converted to nicotinic acid by spray-drying. In this process, the ammonia, together with the water, escapes in the exhaust gas of the spray-dryer. The spray-drying is preferably carried out at a drying gas temperature (at the inlet) of from 160 to 250°C. A suitable drying gas is air or an inert gas such as nitrogen or argon. The outlet temperature is advantageously kept below 110°C, in order to prevent sublimation of the product. Preferably, the spray-drying is carried out in a fluidized-bed spray-dryer. Fluidized-bed spray-dryers of this type are available under the name FSD™, for example, from Niro A/S in DK-2860 Saborg/Denmark. The nicotinic acid obtained after the spray-drying still contains small amounts of ammonium nicotinate, depending on the drying temperature. It has been found that this can be further decreased by a thermal post-treatment in a fluidized bed at from 100 to 200°C, preferably from 130 to 170°C. Any nicotinic acid dust produced in this treatment can be recirculated to the spray-dryer. As an alternative to this post-treatment in the fluidized bed, post-treatment under reduced pressure (partial vacuum or vacuum) at relatively low temperature can also be carried out. The pressure employed in this case is advantageously below 100 mbar, preferably below 50 mbar. The temperature in this case is expediently from 70 to 150°C, preferably from 80 to 120°C. Particularly good results have been achieved at from 10 to 15 mbar, from 80 to 90°C and a treatment time of from M to 1 h. At this low temperature, the losses due to sublimation are minimal and a product having excellent transparency, that is no discoloration, is obtained. Preferably, the process according to the invention is carried out using an ammonium nicotinate solution which was obtained by adding ammonia to the, possibly concentrated, aqueous crude solution from the catalytic oxidation of 3-methylpyridine. This can be achieved, for example, by metering gaseous or aqueous ammonia into an absorption column, to which is fed the gaseous reaction mixture from the oxidation reactor and from which the ammonium nicotinate solution is taken off as bottom product and the excess water is taken off overhead. The ammonia needed to prepare the ammonium nicotinate solution is in this case preferably wholly or partly withdrawn from the spray-drying exhaust gas. For this purpose, for example, the dryer exhaust gas can be cooled below the dew point and the condensing ammonia water can be separated off and recirculated to the nicotinic acid absorption. Since, as mentioned above, small amounts of ammonia are produced in any case as a by-product in the oxidation of 3-methylpyridine, overall an ammonia excess is produced, so that with sufficient efficiency of the ammonia recycling, in the continuous operation, feed of external ammonia can be dispensed with completely. Likewise, the water present in the spray-drying exhaust gas is preferably completely or partially recirculated to the oxidation reactor. Since, in the oxidation of 1 mol of 3-methylpyridine to nicotinic acid, in the ideal case, 1 mol of water is produced, a small excess of water is produced, which must be discharged from the plant in a suitable manner. Similarly, any unreacted 3-methylpyridine present is advantageously recycled to the oxidation reactor. Furthermore, it is possible to feed pure oxygen instead of air as oxidizing agent in the steady state to a continuous plant for carrying out the process according to the invention and to circulate the drying gas, so that a plant with minimum production of exhaust gas results. An advantage of the process according to the invention is also that the nicotinic acid thus obtainable is free-flowing without additional treatment and virtually has no tendency to clumping even at high temperature and relative humidity. Furthermore, by varying the spray-drying operating parameters, the particle size of the product can be set to the desired value. With reference to the accompanying drawings, in which, Figure 1 shows diagrammatically as an example a continuous plant suitable for carrying out the process according to the invention. Individually, the reference numbers denote the following: 1 fixed-bed reactor together with catalyst 2 absorption column for partial condensation of the reaction mixture 3 neutralization (addition of ammonia) 4 spray-dryer 5 drying gas feed (hot air or inert gas circulation) 6 spray-dryer exhaust gas 7 column for partial condensation of water and ammonia 8 gas recycle to the reactor 9 exhaust gas for exhaust gas treatment 10 exhaust gas treatment (combustion) 11 mixer/preheater 12 product take-off (nicotinic acid) 13 3-methylpyridine feed to the reactor 14 oxygen feed (air) to the reactor 15 water (steam) feed to the reactor 16 ammonia feed to the neutralization 17 ammonia (water) recycle. The following examples illustrate the procedure of the process according to the invention, without a restriction to be understood therefrom. Accordingly, the present invention therefore provides a process for preparing nicotinic acid from ammonium nicotinate characterized in that an aqueous solution of ammonium nicotinate is spray-dried at a drying gas temperature of from 160 to 250°C. Example 1 15 1/h of an aqueous ammonium nicotinate solution (40% by weight nicotinic acid, 6% by weight ammonia) were sprayed into a fluidized-bed spray-dryer (Niro FSD -4, diameter 1.2m, height 2.5m). The drying gas (nitrogen) inlet temperature was 220°C, and the outlet temperature 100°C. The internal fluidized-bed temperature was 70°C. This produced a free- flowing product comprising 89% by weight nicotinic acid and 11% by weight ammonium nicotinate having a residual moisture of 0.05%, a bulk density of 0.4 kg/1 and a mean particle size of 451 pm. Example 2 The spray-dried granules of nicotinic acid obtained in accordance with Example 1 were heated to a maximum of 170°C with air in the course of 45 min in a fluidized bed. The granules thus treated had a nicotinic acid content of 99.3% and a bulk density of 0.44 kg/1. It was still free-flowing even after storage of 48 h at 50°C and 100% relative humidity. Example 3 From the condensate of the reaction mixture of the gas-phase oxidation of 3-methylpyridine with air in the presence of water on a fixed-bed catalyst, with addition of ammonia, an approximately 3 0% strength solution of ammonium nicotinate was produced. This solution was sprayed in a laboratory spray-dryer (Buchi AG, Switzerland). At a drying gas inlet temperature of 250°C and an outlet temperature of 162°C, nicotinic acid having a content of from 99% to 100% was obtained at a nitrogen flow rate of 600 ml/min. At an inlet temperature of 200°C and an outlet temperature of 13 0°C, nicotinic acid having a content of 96.9% was obtained at a nitrogen flow rate of 600 ml/min. i WE CLAIM: 1. A process for preparing nicotinic acid from ammonium nicotinate characterized in that an aqueous solution of ammonium nicotinate is spray-dried at a drying gas temperature of from 160 to 250°C. 2. The process according to claim 1, wherein the spray drying is carried out in afluidized-bed spray-dryer. 3. The process according to any one of claims 1 or 2, wherein the nicotinic acid produced by the spray drying is subjected to a thermal post-treatment in a fluidized bed at a temperature of 100 to 200°C, preferably from 130 to 170°C. 4. The process according to any one of claims 1 and 2, wherein the nicotinic acid produced by the spray-drying is subjected to a thermal post-treatment under reduced pressure, preferably below 50 mbar, at a temperature of 70 to 150°C, preferably from 80 to 120°C. 5. The process according to any one of claims 1 to 4, wherein the aqueous solution of ammonium nicotinate used is the solution produced from the catalytic oxidation of 3-methylpyridine by adding ammonia to the possibly concentrated aqueous crude solution. 6. The process according to claim 5, wherein the ammonia for preparing the ammonium nicotinate solution is wholly or partially withdrawn from the spray-drying exhaust gas. 7. The process according to claim 5 or 6, wherein the water present in the spray-dried exhaust gas is wholly or partly recycled to the oxidation reactor. 8. A process for preparing nicotinic acid from ammonium nicotinate substantially as herein described and exemplified.

Full Text

The present invention relates to a process for preparing nicotinic acid from solutions of ammonium nicotinate.
A known process for preparing nicotinic acid is based on the oxidation of 3-methylpyridine (P-picoline) with atmospheric oxygen in the presence of water with heterogeneous catalysis. However, this process has the disadvantage that, in a side reaction, some of the 3-methylpyridine is broken down in a sequence of oxidation and hydrolysis steps to form ammonia, which, together with the main product nicotinic acid, forms ammonium nicotinate. The latter, in contrast to the free nicotinic acid, is highly water soluble and thus makes the work-up of the product mixture more difficult, furthermore it represents a loss in yield, if it cannot be converted back to nicotinic acid. The latter is possible, for example, by adding a strong acid, but this forms the ammonium salt of this acid, which must be separated off and disposed of as waste. In addition, it must be noted here that nicotinic acid, as a pyridine derivative, can also react as a base and, with an excess of the strong acids, can form a salt.
The object of the present invention was therefore to provide a process which permits the transformation of ammonium nicotinate to nicotinic acid without adding auxiliaries and without producing wastes.
According to the invention this object is achieved by the process according to Patent Claim 1.
It has surprisingly been found that an aqueous solution of ammonium nicotinate can be converted to nicotinic acid by spray-drying. In this process, the ammonia, together with the water, escapes in the exhaust gas of the spray-dryer.
The spray-drying is preferably carried out at a drying gas temperature (at the inlet) of from 160 to

250°C. A suitable drying gas is air or an inert gas such as nitrogen or argon. The outlet temperature is advantageously kept below 110°C, in order to prevent sublimation of the product.
Preferably, the spray-drying is carried out in a fluidized-bed spray-dryer. Fluidized-bed spray-dryers of this type are available under the name FSD™, for example, from Niro A/S in DK-2860 Saborg/Denmark.
The nicotinic acid obtained after the spray-drying still contains small amounts of ammonium nicotinate, depending on the drying temperature. It has been found that this can be further decreased by a thermal post-treatment in a fluidized bed at from 100 to 200°C, preferably from 130 to 170°C. Any nicotinic acid dust produced in this treatment can be recirculated to the spray-dryer.
As an alternative to this post-treatment in the fluidized bed, post-treatment under reduced pressure (partial vacuum or vacuum) at relatively low temperature can also be carried out. The pressure employed in this case is advantageously below 100 mbar, preferably below 50 mbar. The temperature in this case is expediently from 70 to 150°C, preferably from 80 to 120°C. Particularly good results have been achieved at from 10 to 15 mbar, from 80 to 90°C and a treatment time of from M to 1 h. At this low temperature, the losses due to sublimation are minimal and a product having excellent transparency, that is no discoloration, is obtained.
Preferably, the process according to the invention is carried out using an ammonium nicotinate solution which was obtained by adding ammonia to the, possibly concentrated, aqueous crude solution from the catalytic oxidation of 3-methylpyridine. This can be achieved, for example, by metering gaseous or aqueous ammonia into an absorption column, to which is fed the gaseous reaction mixture from the oxidation reactor and from which the ammonium nicotinate solution is taken

off as bottom product and the excess water is taken off overhead.
The ammonia needed to prepare the ammonium nicotinate solution is in this case preferably wholly or partly withdrawn from the spray-drying exhaust gas. For this purpose, for example, the dryer exhaust gas can be cooled below the dew point and the condensing ammonia water can be separated off and recirculated to the nicotinic acid absorption. Since, as mentioned above, small amounts of ammonia are produced in any case as a by-product in the oxidation of 3-methylpyridine, overall an ammonia excess is produced, so that with sufficient efficiency of the ammonia recycling, in the continuous operation, feed of external ammonia can be dispensed with completely.
Likewise, the water present in the spray-drying exhaust gas is preferably completely or partially recirculated to the oxidation reactor. Since, in the oxidation of 1 mol of 3-methylpyridine to nicotinic acid, in the ideal case, 1 mol of water is produced, a small excess of water is produced, which must be discharged from the plant in a suitable manner. Similarly, any unreacted 3-methylpyridine present is advantageously recycled to the oxidation reactor. Furthermore, it is possible to feed pure oxygen instead of air as oxidizing agent in the steady state to a continuous plant for carrying out the process according to the invention and to circulate the drying gas, so that a plant with minimum production of exhaust gas results.
An advantage of the process according to the invention is also that the nicotinic acid thus obtainable is free-flowing without additional treatment and virtually has no tendency to clumping even at high temperature and relative humidity. Furthermore, by varying the spray-drying operating parameters, the particle size of the product can be set to the desired value.

With reference to the accompanying drawings, in which,
Figure 1 shows diagrammatically as an example a continuous plant suitable for carrying out the process according to the invention. Individually, the reference numbers denote the following:
1 fixed-bed reactor together with catalyst
2 absorption column for partial condensation of the
reaction mixture
3 neutralization (addition of ammonia)
4 spray-dryer
5 drying gas feed (hot air or inert gas circulation)
6 spray-dryer exhaust gas
7 column for partial condensation of water and ammonia
8 gas recycle to the reactor
9 exhaust gas for exhaust gas treatment
10 exhaust gas treatment (combustion)
11 mixer/preheater
12 product take-off (nicotinic acid)
13 3-methylpyridine feed to the reactor
14 oxygen feed (air) to the reactor
15 water (steam) feed to the reactor
16 ammonia feed to the neutralization
17 ammonia (water) recycle.
The following examples illustrate the procedure of the process according to the invention, without a restriction to be understood therefrom.

Accordingly, the present invention therefore provides a process for preparing nicotinic acid from ammonium nicotinate characterized in that an aqueous solution of ammonium nicotinate is spray-dried at a drying gas temperature of from 160 to 250°C.
Example 1
15 1/h of an aqueous ammonium nicotinate solution (40% by weight
nicotinic acid, 6% by weight ammonia) were sprayed into a fluidized-bed
spray-dryer (Niro FSD -4, diameter 1.2m, height 2.5m). The drying gas
(nitrogen) inlet temperature was 220°C, and the outlet temperature 100°C.
The internal fluidized-bed temperature was 70°C. This produced a free-
flowing product comprising 89% by weight nicotinic acid and 11% by
weight ammonium nicotinate having a residual

moisture of 0.05%, a bulk density of 0.4 kg/1 and a mean particle size of 451 pm.
Example 2
The spray-dried granules of nicotinic acid obtained in accordance with Example 1 were heated to a maximum of 170°C with air in the course of 45 min in a fluidized bed. The granules thus treated had a nicotinic acid content of 99.3% and a bulk density of 0.44 kg/1. It was still free-flowing even after storage of 48 h at 50°C and 100% relative humidity.
Example 3
From the condensate of the reaction mixture of the gas-phase oxidation of 3-methylpyridine with air in the presence of water on a fixed-bed catalyst, with addition of ammonia, an approximately 3 0% strength solution of ammonium nicotinate was produced. This solution was sprayed in a laboratory spray-dryer (Buchi AG, Switzerland). At a drying gas inlet temperature of 250°C and an outlet temperature of 162°C, nicotinic acid having a content of from 99% to 100% was obtained at a nitrogen flow rate of 600 ml/min.
At an inlet temperature of 200°C and an outlet
temperature of 13 0°C, nicotinic acid having a content
of 96.9% was obtained at a nitrogen flow rate of
600 ml/min. i

WE CLAIM:
1. A process for preparing nicotinic acid from ammonium nicotinate characterized in that an aqueous solution of ammonium nicotinate is spray-dried at a drying gas temperature of from 160 to 250°C.
2. The process according to claim 1, wherein the spray drying is carried out in afluidized-bed spray-dryer.
3. The process according to any one of claims 1 or 2, wherein the nicotinic acid produced by the spray drying is subjected to a thermal post-treatment in a fluidized bed at a temperature of 100 to 200°C, preferably from 130 to 170°C.
4. The process according to any one of claims 1 and 2, wherein the nicotinic acid produced by the spray-drying is subjected to a thermal post-treatment under reduced pressure, preferably below 50 mbar, at a temperature of 70 to 150°C, preferably from 80 to 120°C.
5. The process according to any one of claims 1 to 4, wherein the aqueous solution of ammonium nicotinate used is the solution produced from the catalytic oxidation of 3-methylpyridine by adding ammonia to the possibly concentrated aqueous crude solution.

6. The process according to claim 5, wherein the ammonia for preparing
the ammonium nicotinate solution is wholly or partially withdrawn
from the spray-drying exhaust gas.
7. The process according to claim 5 or 6, wherein the water present in
the spray-dried exhaust gas is wholly or partly recycled to the
oxidation reactor.
8. A process for preparing nicotinic acid from ammonium nicotinate
substantially as herein described and exemplified.

Documents:

2592-mas-1998 claims.pdf

2592-mas-1998 correspondence-others.pdf

2592-mas-1998 correspondence-po.pdf

2592-mas-1998 description(complete).pdf

2592-mas-1998 drawings.pdf

2592-mas-1998 form-2.pdf

2592-mas-1998 form-26.pdf

2592-mas-1998 form-4.pdf

2592-mas-1998 form-6.pdf

2592-mas-1998 petition.pdf

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Patent Number

187776

Indian Patent Application Number

2592/MAS/1998

PG Journal Number

30/2009

Publication Date

24-Jul-2009

Grant Date

27-Dec-2002

Date of Filing

17-Nov-1998

Name of Patentee

LONZA AG

Applicant Address

CH-3945 GAMPEL, WALLIS,

Inventors:

#	Inventor's Name	Inventor's Address
1	DR RODERICK JOHN CHUCK	JESUITENWEG 162, CH-3902 BIRG-GLIS,
2	DR. UWE ZACHER	SANDSTRASSE 37, CH-3904, NATERS

PCT International Classification Number

C07D213/79

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	2719/97	1997-11-25	Switzerland