Synthesis method for solution with high grade chloramine

Details Synthesis method for solution with high grade chloramine Synthesis method for solution with high grade chloramine

2000-03-29

2001-04-24

Richter, Johann (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Amino nitrogen containing

Reexamination Certificate

active

06222071

ABSTRACT:

The present application is a U.S. National Application filed under 35 USC 371 of PCT/FR98/02081, filed Sep. 29, 1998 based upon French application Serial No. 97.12109 filed Sep. 30, 1997.
The present invention relates to a process for the preparation of high-grade chloramine by the action of commercial eau de Javelle of 100 chlorometric degrees on a solution of ammonia in the presence of ammonium chloride. According to this process, the chloramine is obtained having a content greater than or equal to 2 mol L
−1
, that is to say greater than or equal to 10.3%. The process can be carried out continuously or discontinuously. Besides its applications as a bleaching, disinfecting and bactericidal agent, monochloramine is used in numerous reactions as a synthesis intermediate. In particular, it is the principal reagent in the synthesis of pharmaceutically valuable hydrazines by the Raschig process. For example, N-amino-2-methylindoline and N-amino-3-azabicyclo[3.3.0]octane are prepared by reacting NH
2
Cl with 2-methylindoline and 3-azabicyclo[3.3.0]octane according to the processes described in patent Specifications EP 462 016 and EP 277 267.
That method of preparation is currently attracting a great deal of interest in view of the fact that it causes little pollution compared with the prior methods of preparation, which make use of N-nitroso compounds. It does, however, have disadvantages associated with the low hydrazine content of the reaction liquors, which generally does not exceed 2 to 4%. That limitation is linked principally to the fact that the reagents, and especially sodium hypochlorite, are highly diluted, necessitating complicated and onerous extraction procedures. As a result, the momentary concentration of chloramine in the reactor does not, even in the best of cases, exceed 1 mol L
−1
(5.15%).
In view of the fact that NH
2
Cl is highly unstable in aqueous solution, synthesis in a more concentrated medium has not been attempted. Its instability is linked to competition between hydrolysis and autocatalytic dismutation reactions, which result in rapid acidification of the medium and in the preponderant formation of dichloramine and nitrogen chloride. In a non-buffered medium the degradation can rapidly result in the solution boiling. Obtaining a higher monochloramine titre requires the use of a new reagent of a high chlorometric degree and research into appropriate operating conditions.
The present invention makes it possible to double, at least, the NH
2
Cl titre by using solutions of eau de Javelle of the order of 100 chlorometric degrees and employing conditions compatible with obtaining high-grade (H.G.) chloramine. This new process makes it possible, starting from an identical unit volume of hypochlorite, to double the productivity in terms of hydrazine and to make savings in raw materials and energy in the synthesis, reagent recycling and distillation procedures.
Because oxidation of ammonia by sodium hypochlorite is an exothermic reaction, it must be carried out at low temperature in order to limit the degradation reactions. It is therefore necessary to cool the reagents beforehand, prior to their injection. For example, for a solution of eau de Javelle of 48 chlorometric degrees (crystallisation point=−21.4° C.), the temperature inside the reactor must not be higher than −5° C. That limit has to be lower for an NaOCl content that is twice as high. Unlike hypochlorite at 2.14 mol L
−1
(48° chl.), a solution of eau de Javelle of 100 chlorometric degrees crystallises in a stirred medium at 14° C. Crystallisation nevertheless remains difficult unless initiated. In a still medium, therefore, a very clear delay in crystallisation is observed and it is thus possible to maintain H.G. eau de Javelle solutions in a single-phase medium for several hours at −20° C. in glass vessels. However, in spite of the solution having little tendency to crystallise, it is necessary in the case of continuous industrial synthesis to use the H.G. eau de Javelle at approximately 14° C. in order to avoid possible caking in the pipework.
As in the process for the preparation of NH
2
Cl starting from sodium hypochlorite of 48 chlorometric degrees, it is necessary to introduce into the ammonia-containing reagent an amount of an acceptor compound that is able to neutralise completely the hydroxyl ions formed in situ by the reaction:
ClO
−
+NH
3
→NH
2
Cl+HO
−
The acceptor may be an acid, a water-soluble acid salt or a water-soluble neutral salt. It is, however, preferable to use an ammonium salt of the type (NH
4
+
)H
+
&bgr;
A
(1+&bgr;)−
wherein &bgr; is 0 or 1 and A is Cl, CO
3
or NO
3
so as to buffer the reaction medium at approximately the pKa of NH
+
4
/NH
3
, to eliminate the HO
−
ions and to keep the concentration of free ammonia constant:
NH
4
+
+HO
−
→NH
3
+H
2
O
Furthermore, the combined ammoniacal mixture must be cooled to well below −10° C. so as to absorb the heat given off and to compensate for the heating associated with the injection of the hypochlorite at a temperature above its crystallisation temperature. Under those conditions, the cooling effect introduced principally by the ammoniacal solution avoids the use of eau de Javelle in a supercooled state and hence ensures synthesis in a homogeneous medium.
Those constraints require that new ammoniacal combinations having a low crystallisation point of from −20° C. to −30° C. be found. The composition of those mixtures is determined by the content of the hypochlorite solutions. The latter have a titre of about 100 chlorometric degrees, which means that, under normal conditions, one liter releases 100 liters of chlorine under the action of hydrogen chloride. The molar concentration of NaOCl is then 4.46 mol L
−1
. Unlike the extracts of 48 chlorometric degrees, the NaCl and NaOCl titres are not in equimolecular proportions.
To obtain quantitative yields, the conditions of synthesis must meet the following criteria:
The H.G. eau de Javelle can be used in the supercooled state but, in order to prevent any initiation of crystallisation, it is preferable to inject it at a temperature higher than or equal to 15° C. The H.G. eau de Javelle is relatively stable and loses, per 24 hours, approximately 1.3 degrees at 17° C. or 0.47 degree at 10° C.
The overall content of Lewis acid must be sufficient to neutralise at least 90% of the hydroxyl ions resulting from the NH
3
/NaOCl reaction.
The pH must be maintained at from 10 to 12, preferably at approximately 10.5.
The ratio [total ammonia]/[ClO
−
] must be from 2 to 5 (preferably 2.7) so as to stabilise the chloramine that is formed.
The crystallisation point of the (NH
4
+
)H
+
&bgr;
A
(1+&bgr;)−
/NH
3
/H
2
O wherein &bgr; is 0 or 1 and A is Cl, CO
3
or NO
3
ternary mixture must be from −20 to −30° C. so as to offset the frigorific deficit associated with the injection of the chlorinated reagent at T≧15° C. in the context of synthesis in a single-phase medium.
The temperature inside the reactor must be in the range from −5 to −20° C., preferably about −15° C.
A large number of acids (HCl, H
2
SO
4
, etc.), neutral salts (CaCl
2
, MgCl
2
, ZnSO
4
, etc.) and acid salts (NaH
2
PO
4
, NH
4
HCO
3
, NH
4
Cl, NH
4
NO
3
, etc.) may be used in the synthesis of chloramine. A priori, certain of those are extremely interesting because they possess more than one acid functionality in the same molecule. On the other hand, very few are soluble and precipitate below 0° C. At this stage, the ammonium salts are the most advantageous since they exhibit greater solubility, which increases as the ammonia content of the medium increases.
Under the conditions of synthesis defined above, use of polythermal diagrams involving the NH
+
4
ion shows that the ammoniacal combinations meeting the above criteria require the use of ammonium nitrate : NH
3
—NH

Affiliated with

Also associated with

Rating

Synthesis method for solution with high grade chloramine does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Synthesis method for solution with high grade chloramine, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Synthesis method for solution with high grade chloramine will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2487612