Organic compounds -- part of the class 532-570 series – Organic compounds – Sulfur containing
Reexamination Certificate
2000-06-29
2002-06-04
Vollano, Jean F. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Sulfur containing
C568S025000
Reexamination Certificate
active
06399832
ABSTRACT:
The present invention relates to a process for selectively producing organic trisulfides.
BACKGROUND OF THE INVENTION
Organic polysulfides, especially organic trisulfides, are useful for many purposes such as additives for elastomers, antioxidants for lubricating oils, intermediates for the production of organic chemicals, insecticides, and germicides, and additives for diesel fuels to improve cetane number and ignition qualities. Organic polysulfides are also useful in the compounding of high pressure lubricants and in the acceleration of rubber treating processes.
It is known that organic polysulfides can be produced by reacting mercaptans with elemental sulfur in the presence of a catalyst. The product of such reaction typically comprises a distribution of individual organic polysulfide compositions, each containing a different number of sulfur atoms. In many commercial applications, especially for use in high pressure lubricants, organic trisulfides exhibit more desirable properties than other organic polysulfides. For example, organic polysulfides containing more than three sulfur atoms exhibit high copper-strip corrosivity (ASTM Copper Strip Corrosion Test D-130-56), rendering them unsatisfactory for many commercial applications. In addition, organic disulfides can be undesirable because they have a high flash point and exhibit poor lubrication properties.
If an organic polysulfide product contains a high quantity of organic polysulfides having more or less than three sulfur atoms, costly separation processes and equipment can be necessary to remove undesirable polysulfides and recover a more pure organic trisulfide product that is suitable for commercial purposes. Therefore, a reaction product having a distribution of organic polysulfides which maximizes the amount of organic trisulfides while minimizing the amount of other organic polysulfides is desired.
Conventional processes for making high-purity organic trisulfides typically require expensive catalysts and multiple reaction vessels, both of which contribute to the expense of the overall process.
In addition, conventional processes for making high-purity organic trisulfides typically require the mercaptan-sulfur reaction to be terminated before substantial completion in order to avoid the formation of undesirable organic polysulfides in the reaction product. Terminating the mercaptan/sulfur reaction before it goes to substantial completion causes the presence of unreacted mercaptan and/or sulfur in the reaction product. Such unreacted mercaptan and/or sulfur must be removed from the reaction product, thus requiring additional costly separation processes and equipment.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a process for selectively producing organic trisulfides.
Another object of the inventive process is to provide an organic polysulfide product having a higher concentration of organic trisulfides than products from conventional processes for making organic polysulfides.
A further object of the inventive process is to provide an organic polysulfide product having a lower concentration of organic tetrasulfides than products from conventional processes for making organic polysulfides.
A still further object of the inventive process is to provide an organic polysulfide product having a lower concentration of organic disulfides than products from conventional processes for making organic polysulfides.
An even further object of the present invention is to eliminate the need for expensive processes and equipment necessary to separate and recover a substantially pure organic trisulfide product.
A still further object of the inventive process is to eliminate the need for expensive catalysts which are required by conventional methods of selectively producing organic trisulfides.
Other objects and advantages of the present invention will become more apparent as the invention is more fully disclosed hereinbelow.
According to an embodiment of the present invention, a process for the selective production of organic trisulfides is provided. The process comprises contacting a mercaptan, a sulfur compound, and a catalyst in a reaction vessel under reaction conditions sufficient to produce a reaction product comprising an organic polysulfide product and subjecting the reaction product to trisulfide enhancing conditions which are effective to inhibit the formation of organic disulfides and promote the conversion of organic tetrasulfides to organic trisulfides.
In another embodiment of the present invention a process for selectively producing organic trisulfides is provided. The process comprises (a) contacting a mercaptan, a sulfur compound, and a catalyst in a reaction vessel under reaction conditions sufficient to produce a reaction product comprising an organic polysulfide product and hydrogen sulfide, thereby creating within the reaction vessel a liquid reaction solution comprising a mixture of liquid phase compounds, wherein a liquid hydrogen sulfide concentration is present in the liquid reaction solution; (b) increasing, for an initial reaction period, the liquid hydrogen sulfide concentration to a disulfide inhibiting hydrogen sulfide concentration that is effective to inhibit the formation of organic disulfides within the liquid reaction solution; (c) maintaining the disulfide inhibiting hydrogen sulfide concentration for a final reaction period; (d) lowering the temperature and pressure in the reaction vessel to trisulfide enhancing conditions that are effective to inhibit the formation of organic disulfides and promote the conversion of organic tetrasulfides to organic trisulfides; and (e) maintaining the trisulfide enhancing conditions within the reaction vessel for a trisulfide enhancing period.
DETAILED DESCRIPTION OF THE INVENTION
It has been discovered that, in a process for making organic polysulfides by reacting a mercaptan and a sulfur compound, the relative amount of organic trisulfides to other organic polysulfides in the reaction product can be increased by subjecting the product of the mercaptan/sulfuir reaction to trisulfide enhancing conditions.
The process of the present invention can be commenced by contacting a mercaptan, a sulfur compound, and a catalyst in a suitable reaction vessel to create a “liquid reaction solution” in the reaction vessel. The contacting of the mercaptan, sulfur compound and catalyst is generally accomplished by slowly adding one of the reactants to a mixture of the other reactant and the catalyst.
As used herein, the term “liquid reaction solution” means a mixture of all liquid phase compounds present in a reaction vessel. The composition of the liquid reaction solution of the present invention changes as the process progresses, however, during at least a portion of the process the liquid reaction solution can comprise unreacted mercaptan, the catalyst, organic polysulfides, and hydrogen sulfide.
The mercaptan suitable for use as a reactant in the process of the present invention can be any mercaptan having the formula of RSH, wherein R is a hydrocarbyl radical having 1 to about 30, preferably about 1 to about 20, and most preferably 2 to 15 carbon atoms. The hydrocarbyl radical can be linear or branched and can be alkyl, aryl, cycloalkyl, alkylaryl, aralkyl, alkenyl radicals, or combinations of two or more thereof. Preferably the hydrocarbyl radical is an alkyl radical. Presently preferred mercaptans are tertiary mercaptans. The presently most preferred mercaptan is t-butyl mercaptan.
The sulfur compound suitable for use as a reactant in the process of the present invention can be any sulfur containing compound capable of reacting with a mercaptan to produce an organic trisulfide and hydrogen sulfide. Preferably the sulfur compound is elemental sulfur.
The amount of sulfur compound contacted with the mercaptan depends on the desired sulfur content of the organic polysulfide product. For an average sulfur content of q sulfurs per polysulfide molecule, (q-1) moles of sulfur must be added per 2 moles of mercaptan and 1 mole of hydrogen sulfide wil
Phillips Petroleum Company
Stewart Charles W.
Vollano Jean F.
LandOfFree
Process for producing organic trisulfides 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 organic trisulfides, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for producing organic trisulfides will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2945945