EP1339676A1

EP1339676A1 - Method for photochemical sulphochlorination of gaseous alkanes

Info

Publication number: EP1339676A1
Application number: EP01978529A
Authority: EP
Inventors: Jean Ollivier
Original assignee: Atofina SA
Current assignee: Arkema SA
Priority date: 2000-11-27
Filing date: 2001-10-11
Publication date: 2003-09-03
Also published as: CA2429848A1; WO2002042260A1; US20040050683A1; CN1487918A; JP2004520281A; AU2002210635A1; KR20030062357A; FR2817258A1; FR2817258B1

Abstract

The invention concerns a method for making an alkanesulphonyl chloride by photochemical reaction of an alkane with chlorine and sulphur dioxide, which consists in using as light source an indium-doped medium-pressure mercury lamp.

Description

PROCESS FOR PHOTOCHEMIC SULFOCHLORINATION OF GASEOUS ALKANES

The present invention relates to the field of alkane sulfonyl chlorides and more particularly relates to the manufacture of these compounds by photochemical sulfochlorination of gaseous alkanes at ambient temperature.

Given the industrial utility of alkanesulfonyl chlorides, in particular methanesulfonyl chloride, the manufacture of these compounds has been the subject of several processes consisting in particular of the photochemical sulfochlorination of alkanes with chlorine and sulfur dioxide. Among these known processes, a particularly efficient process for the photochemical sulfochlorination of gaseous alkanes at room temperature such as methane is that described in patents FR 2,578,841 and FR 2,595,095.

This process which essentially consists in reacting a gaseous mixture of alkane, sulfur dioxide and chlorine in the presence of ultraviolet light supplied by a mercury lamp, is characterized in that the mixture contains a strong excess of sulfur dioxide by compared to the alkane and that liquid sulfur dioxide is injected into the reaction zone to keep the temperature thereof constant. An installation for implementing this method is also described in the aforementioned patents, the content of which is incorporated here by reference. Compared to the photochemical processes of the prior art, described in the work by F. ASINGER "Paraffins, Chemistry and Technology", Pergamon Press 1968, p.520 et seq. And in patent FR 2 246 520, the process of the patents FR 2 578 841 and FR 2 595 095 has the advantage of not requiring the introduction of any foreign product into the reaction medium and of forming the latter only with its compulsory constituents, namely the alkane, the dioxide of sulfur and chlorine. On the other hand, this process makes it possible to obtain good conversions and satisfactory yields both with respect to the alkane and with respect to the chlorine. In addition, contributing to a better absorption of photons by chlorine and to a very easy elimination of the heat of reaction, this process leads to excellent quantum yields and avoids any overheating of the reaction medium.

The performance of this process was then improved according to patent FR 2 777 565, using as a light source a mercury lamp doped with gallium. It has been shown that, compared to a mercury lamp of equal power, the use of such a light source makes it possible to obtain a significantly higher reactor productivity, as well as an improvement in the yield and the selectivity of the reaction.

It has now been found that this process can be further improved by using an indium-doped mercury lamp as the light source. Indeed, by compared to a mercury lamp doped with gallium, the use of a mercury lamp doped with indium allows, at equal power, to further improve the distribution of light energy in the reactor as well as the productivity, yield and selectivity.

In addition to their better light output, indium-doped lamps have a much longer life than gallium-doped lamps and, like the latter, are not subject to slow segregation of the dopant in the lower parts of the lamp.

The subject of the invention is therefore a process for the manufacture of alkanesulfonyl chlorides by the photochemical reaction of an alkane with chlorine and sulfur dioxide, optionally in the presence of hydrogen chloride, characterized in that use is made as light source a medium pressure mercury lamp doped with indium.

The process according to the invention relates more particularly to the sulfochlorination of methane which is the most difficult alkane to sulfochlorinate, but it also applies to all gaseous alkanes under the chosen temperature and pressure conditions.

Depending on the starting alkane, the proportions of the reactants in the gas mixture subjected to light radiation can vary between the following limits:

and are preferably chosen as follows:

It is preferably carried out under a pressure higher than atmospheric pressure. Generally, this pressure can range from 1 to 15 relative bars and is preferably between 8 and 12 relative bars.

The reaction temperature, generally between 10 and 90 ° C, depends on the working pressure chosen. It is for example around 60 ° C for 10 bar absolute and around 80 ° C for 15 bar absolute. As in the process described in patents FR 2 578 841, FR 2 595 095 and FR 2 777 565, the temperature is kept constant by injection of liquid SO ₂ into the reaction zone.

Indium-doped medium-pressure mercury lamps to be used in accordance with the process according to the invention are well known and are described, for example, in the work by M. Déribéré entitled "Iodine Lamps - Lodide Lamps", Editions DUNOD, 1965, p.67, as well as in the book "Sources de Lumière" of the French Lighting Association (AFE) in LUX Editions, 1992, p.134, or finally in "Techniques d'Utilisation des Photons" "by JC André and A. Bernard Vannes, Editions ELECTRA / EDF, 1992, pp. 157-168. The content of these works is incorporated here by reference. Such lamps, sold by the companies SILITRO / SCAM or HERAEUS, re-emit more than 70% of their light energy in the form of radiation of wavelengths between 400 and 475 nm. Figures 1, 2 and 3 attached show respectively the emission spectrum of a 750 watt medium pressure mercury lamp, that of a gallium doped medium pressure mercury lamp of the same power and that of a mercury lamp medium pressure of the same power doped with indium. The light energy emitted by the medium-pressure mercury lamp (Figure 1) is distributed in the form of lines between 220 and 750 nm and that emitted by the gallium-doped lamp (Figure 2) between 400 and 430 nm while, for the indium doped lamp (figure 3), most of the energy emitted is concentrated in the 400 to 460 nm region. In addition to a gain in useful light energy efficiency (around 28% compared to gallium), the illumination of the reaction medium with a medium-pressure mercury lamp doped with indium is much more homogeneous than with a conventional mercury lamp . This contributes to a priming of the reaction better distributed in the reaction volume and, by favoring the heat transfers, makes it possible to attenuate the local overheating linked to the energy of the reaction; better selectivity is therefore observed. Compared to the gallium doped lamp, the productivity is improved by 23% and the selectivity with respect to chlorine is greater than 90%.

The method according to the invention can be implemented in an installation similar to that described in patent FR 2 578 841. Such an installation essentially comprising means for supplying the reagents, a photochemical reactor and means for separating the products from the reaction is represented by the diagrammatic drawing of attached FIG. 4.

In this drawing, the inputs 1, 2 and 3 are respectively those of the alkane, sulfur dioxide and chlorine which are introduced in the gaseous state into a mixer 4 provided with an agitator to homogenize the gas mixture. ; for safety reasons, a premixer of Cl ₂ and SO ₂ is preferably provided at 4 '. The gas mixture passes from the mixer 4 via the line 5 into the reactor 6 in which it is distributed uniformly by means of a 5 'ramp with orifices. Another similar ramp 7 is also placed along the height of the reactor to introduce the liquid SO ₂ intended for adjusting the temperature. A light source 8 passes through the reactor in a manner known per se. At the top of the reactor 6 there is a line 9 towards a pump 10, making it possible to recycle a fraction of the effluent from the reactor to line 5 with a view to prediluting the reagents coming from 4. A tube 11 carries the liquid product, formed in the reactor 6, to a separator 12 from which the liquid phase, that is to say the crude alkanesulfonyl chloride, descends into an intermediate storage 13, while the residual gases pass through a pipe 14 in a second separator 15. This separator is optionally provided with a cooler 15 'to bring the SO ₂ , arriving, to the liquid state; the liquid SO ₂ containing chlorine is recovered in an intermediate storage 16. A fraction of SO ₂ is recycled by the pipes 17 and 17 ′ via the pump 18 and the ramp 7 in the reactor 6. Another fraction of SO ₂ , coming from 16, goes through line 19 in the heater 20 and from there through 19 'to the supply of the mixer 4.

At the top of the separator 15, the HCI is evacuated via line 21 to treatment devices not shown. From the bottom of the intermediate storage 13 there is a pipe 22 to apparatuses for purifying the alkanesulfonyl chloride produced which, not forming the subject of the invention, are not shown here. The following examples illustrate the invention without limiting it.

EXAMPLE 1 (comparative)

In the device described above, methanesulfonyl chloride (CH3SO ₂ CI) was prepared using a medium pressure mercury lamp as the light source. This 750 watt lamp was placed axially in a 50 liter capacity reactor 6.

The gas mixture, prepared in 4, contained for one mole of methane, 6.25 moles of sulfur dioxide, 0.83 mole of chlorine and 0.417 mole of hydrogen chloride. This gas mixture was fed to the reactor at a rate of 5.75 Nm ^ / hour. The pressure in the reactor being fixed at 9 bars above the atmosphere, the temperature was adjusted to 65 ± 2 ° C by injection, by means of the ramp 7, of 5.1 kg / h of liquid SO ₂ .

The hourly quantity of crude methanesulfonyl chloride, collected after expansion in storage 13, was 2.5 kg. At atmospheric pressure and at room temperature, this crude product had the following composition by weight:

The gaseous effluent, arriving by 14 in the second separator 15 had the following volume composition:

The flow rate of this gaseous effluent was 6.57 Nm ³ / h and contained the gaseous SO ₂ resulting from the evaporation which served to cool the reaction. In order to collect the sulfur dioxide in the liquid state under 4 bars of relative pressure, the temperature in the separator 15 was kept below 32 ° C.

The methane flow rate at the outlet 21 of the separator 15 was 0.278 Nm ³ / hour. The quantity introduced in 1 being 0.68 Nm ³ / h, the conversion of methane was therefore 59%. For chlorine, the conversion was 88%. The results led to the following yields and selectivity for methanesulfonyl chloride produced:

Reduced to the power of the medium pressure mercury lamp, the productivity of methanesulfonyl chloride was 2.55 kg / kW. EXAMPLE 2 (comparative)

In the same apparatus as in Example 1, methanesulfonyl chloride was prepared by replacing the conventional mercury lamp with a gallium doped lamp of the same electrical power (750 W).

In order to have the same chlorine conversion rate as in Example 1 (88%), the hourly flow rate of the feed gas mixture had to be brought to 6.86 Nm ³ / hour. The pressure in the reactor being fixed at 9 bars above the atmosphere, the temperature was adjusted to 65 ± 2 ° C by injection, by means of the ramp 7, of 7.5 kg / h of sulfur dioxide liquid.

The hourly quantity of crude methanesulfonyl chloride, collected after expansion in storage 13, was 3.54 kg. At atmospheric pressure and at room temperature, this crude product had the following composition by weight:

The flow rate of this gaseous effluent, containing the SO ₂ gas resulting from the evaporation which served to cool the reaction, was 8.3 Nm ³ / h. In order to collect the sulfur dioxide in the liquid state under 4 bars of relative pressure, the temperature in the separator 15 was kept below 32 ° C. The methane flow rate at outlet 21 of separator 15 was 0.26 Nm ³ / hour. The quantity introduced in 1 being 0.8 Nm ³ / h, the conversion of methane was therefore 67%. For chlorine, the conversion was 88%.

The results led to the following yields and selectivities of methanesulfonyl chloride produced:

Reduced to the power of the gallium lamp, the productivity of methanesulfonyl chloride was 3.58 kg / kW.

EXAMPLE 3

In the same apparatus as in Example 1, methanesulfonyl chloride was prepared by replacing the conventional mercury lamp with an indium doped lamp of the same electrical power (750 W).

In order to have the same chlorine conversion rate as in Example 1 (88%), the hourly flow rate of the feed gas mixture had to be brought to 8.82 Nm ³ / hour. The pressure in the reactor being fixed at 9 bars above the atmosphere, the temperature was adjusted to 65 ± 2 ° C by injection, by means of the ramp 7, of 9.64 kg / h of sulfur dioxide liquid.

The hourly quantity of crude methanesulfonyl chloride, collected after expansion in storage 13, was 4.55 kg. At atmospheric pressure and at room temperature, this crude product had the following composition by weight:

The flow rate of this gaseous effluent, containing the SO ₂ gas resulting from the evaporation which served to cool the reaction, was 7.49 Nm ³ / h. In order to collect the sulfur dioxide in the liquid state under 4 bars of relative pressure, the temperature in the separator 15 was kept below 32 ° C.

The methane flow rate at the outlet 21 of the separator 15 was 0.326 Nm ³ / hour. The quantity introduced in 1 being 1.038 Nm ³ / h, the conversion of methane was therefore 68.6%. For chlorine, the conversion was 88%.

Reduced to the power of the indium lamp, the productivity of methanesulfonyl chloride was 4.65 kg / kW. The following table summarizes the results of the previous examples:

Claims

1. Method for manufacturing alkanesulfonyl chlorides by photochemical reaction of an alkane with chlorine and sulfur dioxide, optionally in the presence of hydrogen chloride, characterized in that a lamp is used as the light source medium pressure mercury doped with indium.

2. Method according to claim 1 wherein one operates under a pressure ranging from 1 to 15 relative bars, preferably between 8 and 12 relative bars.

3. Method according to claim 1 or 2 wherein the reaction temperature is between 10 and 90 ° C and kept constant by injection of liquid SO ₂ into the reaction zone.

4. Method according to one of claims 1 to 3 wherein the alkane is methane, the gas mixture fed to the reactor comprising 1 to 12 moles of sulfur dioxide, 0.1 to 1 mole of chlorine and 0.1 to 0.6 moles of hydrogen chloride per mole of methane.

5. The method of claim 4 wherein the gas mixture contains 5 to 7 moles of sulfur dioxide, 0.7 to 0.9 mole of chlorine and 0.4 to 0.5 mole of hydrogen chloride per mole of methane .

6. Method according to one of claims 1 to 3 wherein the alkane contains at least 2 carbon atoms, the gas mixture supplied to the reactor comprising 7 to 14 moles of sulfur dioxide and 0.1 to 1 mole of chlorine per mole of alkane.

7. The method of claim 6 wherein the gas mixture contains

10 to 13 moles of sulfur dioxide and 0.7 to 0.9 mole of chlorine per mole of alkane.