FR2499068A1 - PROCESS FOR THE PREPARATION OF TERT-ALKYL HYPOHALOGENITES - Google Patents

Abstract

PROCESS FOR PREPARING HYPOHALOGENITES OF TERT-ALKYL BY REACTION OF TERT-ALCANOL WITH A HALOGEN AND AN AQUEOUS SOLUTION OF A MINERAL BASE WHICH MAY BE HALOGENATED BEFORE. WE OPERATE AT A TEMPERATURE AND A PRESSURE AT WHICH THE HYPOHALOGENITE OF TERT-ALKYL FORM VAPORIZES DURING THE REACTION, THE HEAT EMITTED BY THE REACTION BEING EVACUATED IN THE FORM OF VAPORIZATION HEAT OF THE HYPOHALOGENITE VAPORIZED, WHICH ALLOWS THE TEMPERATURE OF CONTROL. OF REACTION; TERT-ALKYL HYPOHALOGENITE IS COLLECTED IN A VAPOR STATE.

Description

The present invention relates to a process for the preparation of

  tert-alkyl hypohalogenites and more particularly to a process for the preparation of

tert-alkyl hypochlorites.

  The reaction between a tert-alkanol, chlorine and an aqueous base leading to a tert-alkyl hypochlorite is generally known in the industry; cf. for example United States Patent Nos. 1,938,175 and 3,149,140. U.S. Patent No. 4,008,133 describes the preparation of tert-butyl hypochlorite in a general process of preparation

of olefinic oxides.

  The reaction between a halogen, a base

  and a tert-alkanol leading to the formation of a hypo-

  tert-alkyl halogenite is a strongly exothermic reaction, and there are difficulties when

  tries to dissipate the heat of reaction under conditions

  economic conditions and thereby ensure effective control

  of the temperature. Ineffective control of the temperature

  ture can lead to decomposition of o-tert-alkyl hypochlorite. naturally, a loss of performance

  and if necessary an uncontrollable reaction.

  The present invention relates to a novel method for preparing tert-alkyl hypohalogenite by reaction of a tert-alkanol, a halogen and an aqueous base. In accordance with the invention, a

  tert-alkyl hypohalogenite by reacting a tert-alkyl

  alkanol with a halogen and an aqueous mineral base and / or a pre-halogenated aqueous mineral base at a temperature up to 100 C and under a pressure under which the formed tert-alkyl hypohalogenite vaporizes

  and is collected in the vapor state. The reaction pressure

  The reaction is selected so that at the reaction temperature there is vaporization of the tert-alkyl hypohalogenite formed. The heat of reaction is removed in the form of latent heat (vaporization of the product) or automatic control of the reaction temperature. More specifically, the reaction is generally carried out under vacuum, the absolute pressure being generally in the range of 5 to 100 kPa, and more

  typically in the range of 20 to 60 kPa. The temperature

  The reaction temperature may range from the excluded freezing point up to 1000C, preferably up to 600C and in the

  better conditions it is of the order of 40 to 600C.

  As mentioned above, the pressure must be in relation to

  with the temperature so as to ensure the vaporisation

of the hypohalogenite formed.

  In a preferred embodiment, the

  The reaction is carried out continuously: the tert-alkanol, the

  logene and the aqueous solution of mineral base and / or tert-alkanol and the previously halogenated aqueous base

  are continuously introduced into a reactor and the hypohalo

  vaporized tert-alkyl genite, generally accompanied by a certain amount of water vapor, is discharged continuously from the reactor. The latter can be chosen from a wide variety of reactor types ensuring good contact between

  reagents, and in particular among the reactors which

  come for gas-liquid reactions. A reactor of the deep-tank type, into which the reagents are introduced

  in a mass of liquid constituted by the reagents themselves.

  and which is agitated by the bubbles of hypohalogenite which vaporizes, constitutes a particularly simple solution

and practical.

  In a particular embodiment

  of the invention, the reactor is kept in thermal equilibrium by controlling the pressure: the heat released by the chemical reaction is

  evacuated by vaporization of the hypohalogenite of tert-

  alkyl formed and in general also by the vaporization of small amounts of water and / or alkanol. So, he

  there is no need to cool the reaction medium

  from the outside to maintain the temperature of

  desired action. Therefore, in this preferred embodiment, the reaction is carried out in conditions

  essentially isothermal, that is, the temperature

  reaction does not vary by more than a few OCs in

all the reactor.

  The tert-alkanol used as reagent is

  preferably tert-butyl alcohol or tert-butyl alcohol

  amyl, and especially the first named. The aqueous mineral base can be selected from a wide variety of bases, including alkali metal and alkaline earth metal hydroxides; sodium hydroxide, potassium hydroxide and calcium hydroxide are preferred,

and especially sodium hydroxide.

  The reagents can be used in very varied relative proportions depending on the results sought in the reaction. Thus, for example, if it is desired to achieve substantially complete conversion of any reagent, an excess of the other reagents can be used. In general, it is preferred to use the reagents in approximately stoichiometric proportions,

  that is, in roughly equimolar amounts.

  Thus, to minimize the amount of halogen present in the formed hypohalite vapors, a halogen / base mole ratio of about 1.05: 1 will not be exceeded. The amount of halogen may be further decreased.

  present in the hypochlorite vapors formed in pre-

  see one or more additional process steps in which the vapors leaving the reactor come into contact with an aqueous base which absorbs halogen with

formation of hypohalogenite.

  Similarly, in order to avoid the presence of organic substances, for example tert-alkanol, in the aqueous phase leaving the reactor, it is necessary that the amount of tert-alkanol does not represent an excessive excess by

  basis of stoichiometric proportions

  In some cases, the amount of tert-alkanol must be less than the theoretical amount. Thus, for example, the tertalcanol / base ratio will generally be in the range of from 0.95: 1 to 1.3: 1 and more preferably

  in the range of 0.98: 1 to 1.05: 1. If it is often

  the tert-alkanol can be used in higher proportions: these higher proportions do not affect

the reaction.

  Although the process according to the invention is generally applicable to the preparation of hypochlorites or hypobromites and hypoiodites which are sufficiently stable under the reaction conditions, it is of particular interest in the preparation of hypochlorites and in particular in the preparation of tert-butyl hypochlorite. The invention will be described

  more fully hereinafter with reference to hypochlorite.

  The process according to the invention is of particular interest for the application in a general process for preparing olefinic oxides in which a tert-alkyl hypochlorite is used for the preparation of the chlorohydrin by reaction with the olefin and the water . Such

  The method is described, for example, in the US Pat.

  United States NI 4.008.133. So, and in such a way of realizing

  In a preferred embodiment, the product chlorine is introduced into an electrolysis cell and the electrolyte from the cathode compartment of the cell is an aqueous solution of sodium chloride and hydroxide.

  sodium, with a tert-alkanol, in the reactor of pre-

  paration of the hypochlorite which operates at the temperatures indicated above and at a pressure as specified above: the tert-alkyl hypochlorite is recovered in the vapor state by controlling the reaction temperature by evacuation of the heat reaction in the form of heat of vaporization of the tert-alkyl hypochlorite formed and a certain amount of water. The aqueous phase which consists of a brine is recycled after treatment

  appropriate when it is necessary for the electro-

  lysis. The tert-alkyl hypochlorite vapors are

  subsequently used in the reactor for preparing chlorohydrin as described in the US patent

  No. 4,008,133 for the preparation of olefin chlorohydrin.

  It is also possible to chlorinate all or part of the electrolyte beforehand and to react the chlorinated electrolyte beforehand with the tert-alkanol to form the tert-alkyl hypochlorite.

  collects in the vapor state as described above.

  The following example illustrates the invention without, however, limiting its scope. In this example, the indications of parts and percentages refer to

weight unless otherwise stated.

Example

  The reactor consists of a tube 50 mm in diameter and 90 cm in height. The lower part of the tube is empty and carries introduction tubes for chlorine gas, liquid tert-butanol and an aqueous solution containing 12% NaOH and 15% NaCl. This solution reproduces the composition of the cell liquor obtained

  by electrolysis of brine to about 25% NaCl.

é499068

  The top 15 cm of the tube are filled

  Raschig rings of 3 mm; this lining prevents the

  droplet formation. The outlet of the pro-

  The reaction vessel in the vapor state is located above the lining. In the middle of the packed region is an introducer tubing through which a stream of cell liquor can be introduced which contacts the vapors leaving the reactor and removes traces.

  unconverted chlorine from outgoing gases.

  An outlet located 45 cm above

  top of the reactor foot serves as an overflow conduit

  for brine; it is connected to a receiving container.

  The product vapors discharged from the top of the reactor are condensed in two cold traps arranged in series (water-ice and dry ice). The last cold trap

is connected to a vacuum pump.

  The column is equipped with an electric tracer -

  to heat it and the instruments needed to

  for a vacuum operation.

  An operation is started by introducing into the reactor 600 ml of 25% brine. The temperature is raised to 450C and a pressure of 37 kPa is established

(280 mmHg, absolute pressure).

  Using metering pumps, a stream of 1 ml / min (10.5 mmol / min) is introduced into the reactor.

  tert-butanol and 3.05 ml / min of cell liquor.

  Chlorine gas was bubbled into the reactor liquid in an amount of 270 ml / min (11 mmol / min). About 1% of the cell liquor is introduced at the bottom of the reactor, the remainder being pumped into the packed zone.

  The molar proportions between the reactions

  were maintained at 1.0 t-BuOCl / 1.04 NaOH / 1.05 C12. The contents of the reactor are mixed violently by the bubbles that form. When maintaining the pressure

  at the indicated value, it is easy to avoid

heating the reaction mixture.

  No phase presence is observed

  organic liquid in the reactor.

  At the end of the test, the contents of the traps are analyzed. The organic phase consists essentially

in pure t-BuOCl.

  The method according to the invention has a particular advantage in that it makes it possible to prepare a

  tert-alkyl hypochlorite by controlling

  Nomic the temperature and preventing a possible runaway. In addition, this result can be achieved without externally cooling the reagents and / or the reactor.

Claims (9)

  1. Process for preparing hypo-   tert-alkyl halogenites, wherein a tert-alkanol is reacted with a halogen and an aqueous solution of a mineral base or an aqueous solution of a previously halogenated mineral base, characterized in that the reaction is carried out at a temperature of temperature and pressure at which the tert-alkyl hypohalogenite formed vaporizes during the reaction, thereby controlling the reaction temperature, which can be up to 100 C, the formed tert-alkyl hypohalogenite being the state of vapor.   2. Method according to claim 1,   characterized in that the reaction pressure is lower than   below atmospheric pressure.   3. Method according to claim 2, characterized in that the halogen is chlorine and in this   that a tert-alkyl hypochlorite is prepared. -   4. Process according to claim 3,   characterized in that the reaction is carried out at a pressure of   sion to which the heat of reaction is removed by   porization, which allows to control the reaction temperature and maintain conditions essentially   isotherms in the absence of external cooling.   5. Method according to claim 4,   characterized in that the tert-alkanol is tert-butanol.   6. Process according to claim 5,   characterized in that the pressure is from 5 to 100 kPa.   7. Process according to Claim 6, characterized in that the reaction temperature ranges from 40 to 60 C.   8. Process according to claim 7,   characterized in that the reagents are introduced in   It is dissolved in a liquid consisting of the reagents and stirred by the bubbles of the hypochlorite which vaporizes, and in that the vapors containing the hypochlorite are continuously collected. 9. Process according to claim 1, characterized in that the base used is potassium hydroxide, sodium hydroxide or calcium hydroxide.