Organic compounds -- part of the class 532-570 series – Organic compounds – Sulfur containing
Reexamination Certificate
2000-03-31
2001-09-25
Richter, Johann (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Sulfur containing
C568S021000, C568S023000, C568S025000
Reexamination Certificate
active
06294699
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a process for producing organic disulfides by oxidation of mercaptans.
BACKGROUND OF THE INVENTION
Organic disulfides are useful as chemicals for pre-sulfiding catalysts and as chemical intermediates in the production of agricultural and pharmaceutical products. Organic disulfides are produced by oxidation of mercaptans according to the general reaction:
2R-SH+Oxidant→R-S-S-R+Reductant, (1)
wherein R is a hydrocarby radical.
The most common oxidants for consideration are sulfur, hydrogen peroxide, a reducible metal ion, oxygen and sulfur dioxide.
Examples of these are as follows:
2 R-SH + S → R-S-S-R + H
2
S
(2)
2 R-SH + H
2
O
2
→ R-S-S-R + 2 H
2
O
(3)
2 R-SH + 2 Fe
+3
→ R-S-S-R + 2 Fe
+2
+ 2H
+
(4)
4 R-SH + O
2
→ 2R-S-S-R + 2H
2
O
(5)
4 R-SH + SO
2
→ 2 R-S-S-R + 2 H
2
O + S
(6a)
2 R-SH + S → R-S-S-R + H
2
S
(6b)
6 R-SH + SO
2
→ 3 R-S-S-R + 2 H
2
O + H
2
S
(6a + 6b)
In order to minimize production of polysulfides, when molten sulfur is used as the oxidant, excess mercaptan is used, generally in at least 50-100% excess. The mercaptan then needs to be recovered from the by-product hydrogen sulfide for recycle. Also, the organic disulfide must be recovered from the polysulfides formed.
The use of hydrogen peroxide suffers from the production of 2 moles of water per mole of organic disulfide produced as well as the additional water present with the aqueous solution of hydrogen peroxide. Thus, the reactor volume productivity is low for this method.
The use of a stoichiometric amount of metal ion such as ferric ion (Fe
+3
) is a possibility (reaction 4). However, this process also suffers from low volume productivity of organic disulfide produced per reactor volume. The advantage is that the ferrous ion (Fe
+2
) can be regenerated with air to produce ferric ion (Fe
+3
):
2 Fe
+2
+O
2
+2H
+
→2Fe
+3
+H
2
O.
The use of oxygen as the oxidant (reaction 5) can achieve high conversions (>99.5%) with high organic disulfide selectivity (>98%). The reactions are done in the presence of a basic liquid oxidation catalyst, such as caustic, or triethylamine.
The use of oxygen does have a significant potential safety issue due to the potential for explosions under certain conditions. For instance, at concentrations higher than 10 volume % oxygen, there is a risk of explosion if there is an ignition source present.
The other alternative is to use sulfur dioxide as the oxidant (reaction 6a+6b) in the presence of a liquid catalyst. The reaction is typically carried out in the presence of a basic liquid oxidation catalyst, such as triethylamine (C
2
H
5
)
3
N or boron trifluoride etherate (C
2
H
5
)
2
O&Circlesolid;BF
3
. The use of sulfur dioxide as the oxidant offers the advantage of less explosion hazard as compared to the use of oxygen, and decreased handling difficulties compared to the use of molten sulfur. On the other hand, the use of a liquid basic catalyst in thin method has the disadvantage of lower reactor throughput, lower product yield and lower product selectivity as compared to the use of a solid catalyst in a continuous flow reactor. Also, there is the need to separate the liquid basic catalyst from the liquid product and unreacted liquid feedstock.
Therefore, there is a need to develop a process for oxidizing a mercaptan to an organic disulfide using sulfur dioxide in the presence of a solid catalyst, and, optionally, in the presence of an oxygenated hydrocarbon, and achieving the highest possible yield of organic disulfide.
SUMMARY OF THE INVENTION
It is an object of this invention to provide a process of improved efficiency and economy for producing organic disulfides.
It is another object of this invention to provide a process of improved efficiency and economy for producing organic disulfides by oxidizing mercaptans with sulfur dioxide in the presence of a solid catalyst comprising a solid-porous-basic material.
It is yet another object of this invention to provide a process of improved efficiency and economy for producing organic disulfides by oxidizing mercaptans with sulfur dioxide in the presence of a solid catalyst comprising a solid-porous-acidic material.
It is another object of this invention to provide a process of improved efficiency and economy for producing organic disulfides by oxidizing mercaptans with sulfur dioxide in the presence of an oxygenated hydrocarbon and in the presence of a solid catalyst comprising a solid-porous-basic material.
It is yet another object of this invention to provide a process of improved efficiency and economy for producing organic disulfides by oxidizing mercaptans with sulfur dioxide in the presence of an oxygenated hydrocarbon and in the presence of a solid catalyst comprising a solid-porous-acidic material.
In accordance with an embodiment of the invention, a process useful for producing an organic disulfide is provided. The process can comprise, consist essentially of, or consist of:
a) contacting a hydrocarbon feedstock comprising at least one mercaptan with a catalyst selected from the group consisting of a solid-porous-basic material and a solid-porous-acidic material in the presence of sulfur dioxide and in the substantial absence of a liquid oxidation catalyst to thereby form a hydrocarbon product comprising at least one organic disulfide; and
b) recovering said hydrocarbon product.
In accordance with another embodiment of the invention, a process useful for producing an organic disulfide is provided. The process can comprise, consist essentially of, or consist of:
a) contacting a hydrocarbon feedstock comprising at least one mercaptan with a catalyst selected from the group consisting of a solid-porous-basic material and a solid-porous-acidic material in the presence of sulfur dioxide and in the presence of an oxygenated hydrocarbon to thereby form a hydrocarbon product comprising at least one organic disulfide; and
b) recovering said hydrocarbon product.
Other objects and advantages will become apparent from the detailed description and the appended claims.
DETAILED DESCRIPTION OF THE INVENTION
The catalyst of the present invention can comprise, consist essentially of, or consist of a material selected from the group consisting of a solid-porous-basic material and a solid-porous-acidic material.
The solid-porous-basic material can be any such material which can catalyze the oxidation of a mercaptan. Suitable solid-porous-basic materials include, but are not limited to, Group IIA metal oxides, according to the CAS version of the Periodic Table of the Elements, (such as, but not limited to, magnesium oxide) and anion or basic ion exchange resins (such as, but not limited to, a polystyrene which contains amino groups).
Suitable anion or basic ion exchange resins include: Amberlite® IRA-67 ion-exchange resin;
Amberlite® IRA-400 ion-exchange resin;
Amberlite® IRA-400 (Cl) ion-exchange resin;
Amberlite® IRA-410 ion-exchange resin;
Amberlite® IRA-743 ion-exchange resin;
Amberlite® IRA-900 ion-exchange resin: and
Amberlyst® A-21 ion-exchange resin (tertiary amine substituted styrene divinyl benzene copolymer).
The solid-porous-acidic material can be any such material which can catalyze the oxidation of a mercaptan. Suitable solid-porous-acidic materials include, but are not limited to, alumina (preferably &ggr;-alumina); an alumina material consisting essentially of alumina; alumina impregnated with a metal selected from the group consisting of cobalt, molybdenum, tungsten, nickel, the oxides and sulfides of such metals, and combinations of any two or more thereof; and cation or acidic ion-exchange resins such as, but not limited to, carboxylic acid substituted styrene divinyl benzene copolymer or sulfonic acid substituted styrene divinyl benzene copolymer (Amberlyst® 15 ion-exchange resin). The metal impregnated alumina can be prepared by impregnating alum
Refvik Mitchell D.
Shaw James Edward
Anderson Jeffrey R.
Parsa J.
Richmond, Hitchcock, Fish & Dollar
Richter Johann
Stewart Charles W.
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