Preparation of methane sulfonic acid

Details Preparation of methane sulfonic acid Preparation of methane sulfonic acid

1999-04-08

2001-03-27

Gorgos, Kathryn (Department: 1741)

Chemistry: electrical and wave energy

Processes and products

Processes of treating materials by wave energy

C204S157760

Reexamination Certificate

active

06207025

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an improved process for preparing methanesulfonic acid from a mixture comprising acetic acid, sulfur dioxide and oxygen by irradiation with light.
Methanesulfonic acid is the simplest representative of the class of alkanesulfonic acids and is of great use for a large number of industrial applications such as the production of metal coatings by electrodeposition or else as esterification catalyst.
2. Description of the Related Art
The most widely used processes for preparing methanesulfonic acid are the oxidation of methyl mercaptan or dimethyl disulfide with oxygen or with chlorine to give methanesulfonyl chloride, followed by hydrolysis. All these processes are associated with problems of toxicity and odor, because the starting materials are formed from hydrogen sulfide, which problems can be overcome only with great technical complexity.
DE 907 053 describes the irradiation of carboxylic acids in the presence of air and sulfur dioxide. The reaction products are the corresponding &bgr;-sulfo carboxylic acids.
By contrast, irradiation of acetic acid at room temperature in the presence of air and sulfur dioxide takes a different course, as described in Tetrahedron Lett. 1966, 3095. In the reaction, methanesulfonic acid and also 60%, based on the methanesulfonic acid formed, of sulfuric acid are obtained. However, an industrial process with formation of such a large amount of by-product is uneconomic.
BRIEF SUMMARY OF THE INVENTION
It is an object of the present invention to provide an economic process which affords methanesulfonic acid in good yield and in which not more than 50%, based on the methanesulfonic acid, of sulfuric acid is formed.
We have found that this object is achieved by a process for preparing methanesulfonic acid by irradiating a mixture comprising acetic acid, sulfur dioxide and oxygen with light, wherein the reaction mixture is irradiated with an average cumulative irradiance in the range from 240 to 320 nm of from 0.05 to 50 mmol quanta/cm
2
h at the light entry area.
DETAILED DESCRIPTION OF THE INVENTION
The lamps preferably employed are those emitting light in the range from 240 to 320 nm, such as low pressure mercury lamps, preferably high and medium pressure mercury lamps, either pure or doped, which are commercially available and whose radiated power is from 125 watts to 60 kW. Also suitable are excimer lamps, which are preferably used in the wavelength range from 240 to 320 nm in which sulfur dioxide shows strong absorption.
Further suitable light sources are halogen lamps, gas discharge lamps or fluorescent tubes.
The average cumulative irradiance in the range from 240 to 320 nm at the area where the light enters the reaction mixture is not more than 50 mmol quanta/cm
2
h, preferably not more than 10 mmol quanta/cm
2
h, and the effectiveness is optimal with irradiances of up to 5 mmol quanta/cm
2
h. Irradiances below 0.05 mmol quanta/cm
2
h slow down the reaction. In a preferred embodiment, irradiation is carried out with an irradiance of 0.1 mmol quanta/cm
2
h or above.
It is easily possible with knowledge of the quanta flux of the lamp, which is usually stated by the manufacturer, to select a reactor with a suitable irradiation area depending on the lamp output and the required amount to be converted.
Thus, a conventional 150 W high pressure mercury lamp has in the wavelength range of 240-320 nm a quanta flux of 0.128 mol quanta/h and a 700 W lamp has one of 0.6 mol quanta/h.
It is generally known to ensure thorough mixing in irradiation reactions, in particular at the zone of entry of the light into the reaction mixture.
Thorough mixing is achieved, for example, by producing turbulent flow near the wall or high velocities near the wall in the liquid. This can be achieved by reactor tubes which are curved in the region of irradiation, for example in the form of a loop or coil, when the reaction gases are bubbled through the liquid. Effective mixing can generally be achieved by passing the reaction gases as a stream of fine gas bubbles through the reaction mixture. This effect can furthermore be achieved or additionally assisted if the liquid in turn is transported through the reactor. It is also advantageous to use a gas back-mixing stirrer (hollow shaft stirrer).
Preferred types of reactor for the process are, for example, tubular reactors, tube bundle reactors, loop reactors or cocurrent packed columns, which are generally known to the skilled worker.
In a particularly preferred embodiment, the reaction mixture is circulated, for example by pumps or by stirrers, as is the case in the loop reactor. The reaction mixture advantageously flows through the reactor with flow rates of from 0.01 m/s to 1 m/s.
In principle, the various types of loop reactors decribed in “Chemische Reaktionstechnik, Lehrbuch der technischen Chemie”, Volume 1, Thieme Verlag, Stuttgart, New York 1992, pages 257-262, are suitable. The liquid can moreover be conveyed in an inner or outer circulation.
The process according to the invention can be carried out either continuously or batchwise.
It is is advantageous if the thickness of the layer of liquid to be irradiated is a multiple of the depth of penetration of the relevant radiation. The thickness of the layer of liquid to be irradiated is preferably at least 1 cm, particularly preferably at least 5 cm. It is likewise economically worthwhile, in order to reduce the holdup, if the thickness of the layer of liquid to be irradiated is chosen to be no larger than 150 cm, preferably no larger than 50 cm.
In industrial equipment, the light source is arranged in front of appropriately transparent windows, such as quartz glass, in the reaction vessels or, preferably as lamps immersed centrally or radially in the reaction chambers.
It is moreover perfectly possible to use more than one lamp if a larger amount of substance is to be reacted. It is also possible in principle to arrange a plurality of lamps in one reactor (Ullmann's encyclopedia of industrial Chemistry, Vol A 19, 5th edition, VCH, Weinheim, 1991, pages 573 to 586.)
In an advantageous embodiment, a loop reactor is chosen, in which case the reaction mixture is conveyed past a plurality of lamps in succession. For reasons of space, the lamps are advantageously arranged parallel to one another to result in a coil reactor. It is preferred in this case to use immersion lamps, but it is likewise possible by a suitable arrangement to convey the reaction mixture between the individual lamps. If a coiled reactor tube is used, the lamp is preferably located in the winding axis of the coil.
It is particularly advantageous to use a loop reactor with an immersion lamp arranged concentrically inside, or a tube bundle reactor where the individual tubes are arranged in the form of a circle around a light source, and the reaction mixture flows through each of them alternatively in parallel or in series. In the latter case, it is advantageous to design the individual tubes in the tube bundle to be flattened toward the light source in order to minimize radiation losses through diffraction or reflection.
To improve utilization of the radiation emitted by the radiation source, or else to promote or inhibit individual steps in the reactions taking place in the reaction mixture, and thus finally to increase the yield, it is possible to add auxiliaries to the reaction mixture.
In a preferred embodiment, sensitizers or photoinitiators are added to the mixture as auxiliaries which permit long wavelength radiation to be used exclusively or additionally. Examples of conventional photoinitiators are:
thermal initiator systems such as hydrogen peroxide, peroxides or azoisobutyronitrile,
ketones such as acetophenone, benzophenone or benzanthrone,
acyloins such as benzoin derivatives,
&agr;-diketones such as diacetyl, phenanthrenequinone or benzil,
quinones such as anthraquinone derivatives, sulfur compounds such as diphenyl disulfide or
tetramethylthiuram disulfide,
halogen compounds such as chlorine, bromotric

Affiliated with

Also associated with

Rating

Preparation of methane sulfonic acid does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Preparation of methane sulfonic acid, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Preparation of methane sulfonic acid will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2465250