Organic compounds -- part of the class 532-570 series – Organic compounds – Sulfur containing
Reexamination Certificate
2000-01-28
2002-07-02
Vollano, Jean F. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Sulfur containing
Reexamination Certificate
active
06414193
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a process for producing dimethyl sulfoxide (hereinafter called DMSO) industrially widely used, for example, as a reaction solvent of medical and agricultural intermediate products, a synthetic reagent or as a special detergent for electronic materials, and the like. In more detail, the present invention relates to an improvement for the process of continuously oxidizing dimethyl sulfide (hereinafter called DMS) using NOx (a mixture of NO, N
2
O
3
, NO
2
or N
2
O
4
or mixture thereof) as a catalyst in a liquid phase for producing DMSO.
PRIOR ART
As a conventional process for producing DMSO, a process of continuously oxidizing DMS using NOx as a catalyst in a liquid phase is publicly known (U.S. Pat. No. 2,825,744 and Japanese Patent Publication (Kokoku) No. Sho 42-9771).
In the DMS oxidizing reaction, NOx gas to be used as a catalyst is supplied together with a gas mainly composed of oxygen to be used as an oxidizing agent to a DMS-containing liquid phase reaction system, and is released outside the reaction system as a reaction off gas, usually to be treated by an alkali for disposal. The amount of NOx gas used is as much as required as a catalyst for DMS. In the oxidation reaction, new NOx is kept supplied as a catalyst to the reaction system, and the used catalyst NOx is disposed of. So, since the conventional process requires a considerable amount of catalyst NOx, the disposal of used catalyst NOx is undesirable in view of cost and effective utilization of a resource.
Furthermore, the amount of oxygen gas used as an oxidizing agent in this process is generally an approximately theoretical amount for liquid phase DMS or slightly larger than it. However, the highly pure oxygen gas with an oxygen concentration of 99% or more used here is high in purchase price, and requires large equipment such as a receiving tank for use of oxygen.
OBJECTS OF THE INVENTION
An object of the present invention is to provide an efficient DMSO production process improved in the conversion from DMS to DMSO in the continuous oxidation reaction of DMS for producing DMSO by recycling NOx used as a catalyst, in order to improve the disadvantage of having to dispose of the used catalyst in the prior art. More specifically, it is an object to provide a DMSO production process improved in the recovery rate and/or absorption rate of NOx by recovering NOx from the reaction off gas and/or the gas removed from the reaction product solution, in the reaction to continuously oxidize DMS by a gas mainly composed of oxygen, using NOx as a catalyst in a liquid phase for producing DMSO.
Another object of the present invention is to provide a low-cost DMSO production process allowing the use of simpler production equipment, by using relatively low pure oxygen gas obtained by the pressure swing adsorption treatment of air.
Other objects of the present invention will be apparent from the following description.
BRIEF DESCRIPTION OF THE INVENTION
The inventors studied intensively to solve the above problems and, as a result, found that dimethyl sulfoxide (DMSO) can be produced very efficiently at a high yield, by supplying at least partially the reaction product solution containing dimethyl sulfoxide (DMSO) and NOx obtained by oxidation reaction of dimethyl sulfide (DMS) to said oxidation reaction for recycling.
The process for producing dimethyl sulfoxide of the present invention, in which dimethyl sulfide is continuously oxidized by a gas mainly composed of oxygen using NOx as a catalyst in a liquid phase, comprises the step of supplying at least partially the reaction product solution containing dimethyl sulfoxide and NOx obtained by said oxidation reaction, to the oxidation reaction for recycling. More specifically, the present invention relates to a process for producing dimethyl sulfoxide, in which dimethyl sulfide is continuously oxidized by a gas mainly composed of oxygen using NOx as a catalyst in a liquid phase using an oxidation reactor, comprising the steps of causing the dimethyl sulfoxide solution to absorb the NOx contained in the reaction off gas in an absorbing column, and supplying the NOx-containing solution to the oxidation reactor for recycling. It is preferable to use the oxygen gas obtained by the pressure swing adsorption treatment of air described later, as the gas mainly composed of oxygen.
The DMSO production process of the present invention also includes the following preferred embodiments.
(1) Nitrogen gas is blown into the reaction product solution at a temperature higher than the reaction temperature, for bringing nitrogen into contact with the reaction product solution, to remove NOx from the reaction product solution mainly composed of NOx and DMSO.
(2) Reaction off gas and/or the gas mainly composed of NOx removed from the reaction product solution is sent to a NOx absorbing column, for recovering NOx.
(3) The reaction product solution remaining after removing NOx is used as the NOx absorbable solution.
(4) NO in the reaction off gas and/or the gas removed from the reaction product solution is oxidized into NO
2
which is then sent to a NOx absorbing column, for recovering NOx.
(5) A gas with an oxygen concentration of about 80 to about 96% obtained by pressure swing adsorption treatment is used.
BRIEF DESCRIPTION OF THE DRAWING
The drawing show the outline of the recovering apparatus used for recovery of NOx in the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described below in more detail.
The present invention relates to an improvement of the process for continuously oxidizing DMS by a gas mainly composed of oxygen using NOx as a catalyst in a liquid phase for producing DMSO. The present invention includes several preferable conditions as described below for improving the conversion from DMS to DMSO in oxidation reaction, and for improving the recovery rate and/or absorption rate of NOx used as a catalyst, and also for allowing the use of a low pure oxygen gas as an oxidizing agent.
The oxidation reaction of DMS in the present invention is exothermic. So, though various types of oxidation reactors are available for the oxidation reaction of DMS, a highly effective mixing reactor and a multitubular reactor can be preferably used. Especially a highly effective mixing reactor can be preferably used.
In the present invention, it is preferable that the temperature in the oxidation reactor is about 10° C. to about 50° C. A more preferable range is about 20° C. to about 40° C. If the temperature is lower than about 10° C. the produced DMSO tends to be coagulated, thereby not allowing the reaction to continue. If higher than about 50° C. dimethyl sulfone (hereinafter called DMSO
2
) produced by further oxidizing DMSO is produced as a byproduct in a large amount.
It is preferable that the pressure in the reactor during the oxidation reaction is around atmospheric pressure, but the reaction can take place even at a higher pressure.
It is preferable that the catalyst NOx concentration used in the DMS oxidizing reaction in the present invention is about 0.01 to about 0.2 as NOx/DMS ratio by weight. A more preferable range is about 0.05 to about 0.12 as the NOx/DMS ratio by weight. If the reaction is effected at a NOx/DMS ratio by weight of lower than about 0.01, the conversion into DMSO declines disadvantageously. If the reaction is effected at a NOx/DMS ratio by weight of higher than about 0.2, DMSO
2
tends to be produced in a large amount.
Furthermore, in the present invention, it is preferable that the oxygen concentration of the gas mainly composed of oxygen (oxygen gas) used as an oxidizing agent is about 80 wt % or more. If a gas with an oxygen concentration of lower than about 80 wt % is used as an oxidizing agent, the conversion into DMSO tends to decline. To keep the conversion high, the reaction solution is retained for a period of time corresponding to more than twice that of an ordinary case.
As the oxygen gas, a highly pure oxygen gas with an oxygen concentration of about 99 wt % or
Aburai Kouji
Fukui Yoshiyuki
Sakamoto Kosuke
Schnader Harrison Segal & Lewis LLP
Toray Fine Chemicals Co., Ltd.
Vollano Jean F.
LandOfFree
Process for producing dimethyl sulfoxide does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for producing dimethyl sulfoxide, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for producing dimethyl sulfoxide will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2886970