Process for preparing a corrosion inhibitor/metal passivator...

Details Process for preparing a corrosion inhibitor/metal passivator... Process for preparing a corrosion inhibitor/metal passivator...

2000-08-17

2002-03-26

McAvoy, Ellen M. (Department: 1764)

Solid anti-friction devices, materials therefor, lubricant or se

Lubricants or separants for moving solid surfaces and...

Heterocyclic ring compound; a heterocyclic ring is one...

C252S391000, C252S394000, C548S142000

Reexamination Certificate

active

06362137

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to a process for preparing a corrosion inhibitor/metal passivator additive for lubricant, grease and fuel applications from waste refinery streams.
BACKGROUND
It is well known that various derivatives of 2,5-dimercapto-1,3,4-thiadiazole are useful lubricant, grease and fuel additives for inhibition of copper activity, i.e., corrosion or staining. Many patents have been issued on various derivatives of 2,5-dimercapto-1,3,4-thiadiazole. Amongst various derivatives of 2,5-dimercapto-1,3,4-thiadiazole, the bisulfides are preferred as corrosion inhibitors/metal passivator additives for lubricants, greases and fuels. These disulfides react with large quantities of sulfur or active sulfur compounds to give compounds, which are non-corrosive to metals, especially copper and silver. Their capacity to react with sulfur is large, as 2,5-dimercaptothiadiazole-bis(n-dodecyl) disulfide is able to react with 16 gram atoms of sulphur and the resulting product is a non-corrosive in modified EMD silver strip test. Thus 2,5-dimarcapto thiadiazole disulfides have ability to act as “sulfur sink”.
DESCRIPTION OF RELATED ART
U.S. Pat. No. 3,087,932 discloses a method of making 2,5-bis(alkyldisulphide)-1,3,4-thiadiazole. This process involves the reaction of hydrogen peroxide with 2,5-dimercapto-1,3,4-thiadiazole or its alkyl metal salt and alkyl mercaptan.
U.S. Pat. No. 4,097,387 describes metal deactivators derived from 2,5-dimercapto-1,3,4-thiadiazole by reaction with sulfur halide and an olefin to form an intermediate, which is then treated with sodium or potassium salt of thiadiazole. More recently, U.S. Pat. No. 4,487,706 describes the preparation of metal deactivator by reacting olefin, sulfur dichloride and 2,5-dimercapto-1,3,4-thiadiazole in a single step.
Other method of making these disulphides of thiadiazole involves reaction of chloromercaptan with 2,5-dimercapto-1,3,4-thiadiazole or formation of 2,5-dimercapto thiadiazole dichloride and subsequent reaction with mercaptans. This latter reaction is specially preferred in view of the high temperature stability of the dichlorides than alkyl sulfenyl chlorides. These methods have been reviewed by Ellis K Fields in Industrial and Engineering Chemistry, Vol. 49, 1957, p. 1361 to 1364; which is incorporated herein as reference.
As can be seen from the above description of the prior-art, the metal deactivator/corrosive inhibiting additives from 2,5-dimercapto-1,3,4-thiadiazole have been prepared either by reaction of thiadiazole with alkyl mercaptans or by using olefins and sulfur dichloride.
The disadvantages of the above processes are:
Alkyl mercaptans are expensive material and the cost of corrosion inhibitor/metal deactivator additives produced by these procedures becomes very high.
In U.S. Pat. No. 4,487,706, during the reaction of thiadiazole with sulfur dichloride and olefin, hydrogen chloride vapours are evolved and the additives contain residual chlorine by introduction of the HCl gas into olefinic unsaturation. This process evolves corrosive HCl gas and the product contains higher amount of chlorine and hence is not advantageous.
SUMMARY OF THE INVENTION
The object of the present invention is to overcome the aforesaid disadvantages by providing one step reaction process at much reduced cost.
To achieve the said objective, this invention provides a process for preparing a corrosion inhibitor/metal passivator additive for lubricant, grease and fuel applications from waste refinery streams, comprising reacting 2,5-dimercapto-1,3,4-thiadiazole either in powder form or in solution form in polar organic solvent, with disulphide oil obtained from Merox extraction/caustic wash of the refinery streams.
The said reaction takes places in the presence of redox agent for better yield.
The said corrosion inhibitor/metal passivator additive is 2,5-bis(alkylmercapto)-1,3,4-thiadiazole.
The disulphide oil used is obtained from Merox extraction/caustic wash of the cracked LPG or the vis-breaker naphtha of boiling range 30-150° C. or the mixture of sulfur containing refinery streams.
The composition of said disulphide oil consists of any number of components ranging from C
4
H
10
S
2
to C
12
H
26
S
2
.
The composition of said disulphide oil is:
S. No.
Component
Mol. Formula
1.
Ethylisopropyl disulphide
C
5
H
12
S
2
2.
Diisopropyl disulphide
C
6
H
14
S
2
3.
Isopropyl n-propyl disulphide
C
6
H
14
S
2
4.
Ethylisobutyl disulphide
C
6
H
14
S
2
5.
Di-n-propyl disulphide
C
6
H
14
S
2
6.
n-Butyl n-propyl disulphide
C
7
H
16
S
2
7.
2-Methylpropyl n-propyl disulphide
C
7
H
16
S
2
8.
2-Methylpropyl iso-propyl disulphide
C
7
H
16
S
2
9.
n-butyl isopropyl disulphide
C
7
H
16
S
2
10. 
Di n-butyl disulphide
C
8
H
18
S
2
11. 
C
5
/C
3
disulphide
C
8
H
18
S
2
12. 
1-cyclohexyl n-propyl disulphide
C
9
H
20
S
2
13. 
C
4
/C
5
disulphide
C
9
H
20
S
2
14. 
C
4
/C
6
disulphide
C
10
H
22
S
2
15. 
C
5
/C
5
disulphide
C
10
H
22
S
2
16. 
C
5
/C
6
disulphide
C
11
H
24
S
2
The redox agent used is hydrogen peroxide.
The instant process comprises dissolving 2,5,dimercapto-1,3,4-thiadiazole in a polar organic solvent, adding drop-wise hydrogen peroxide and the temperature of the mixture is maintained at 15-20° C. till a pale yellow precipitate is separated, the resulting slurry is stirred and disulphide oil, obtained from Merox extraction/caustic wash of the refinery streams, is added at room temperature and the reaction mixture is heated to 70-80° C. till reaction is complete, cooling the contents to room temperature and removing the organic solvent under reduced pressure, adding non-polar organic solvent in the residue, separating the said non-polar solvent soluble portion, and distilling off the said non-polar solvent under reduced pressure to obtain light yellow coloured liquid of 2,5-bis(alkyldisulphide)-1,3,4-thiadiazole.
The instant process comprises reacting 2,5-dimercapto-1,3,4-thiadiazole in powder form with disulphide oil obtained from Merox extraction/caustic wash of the refinery streams, heating the reaction mixture to 120-140° C., cooling the said reaction mixture to room temperature, extracting the reaction mixture with non-polar organic solvent and removing the said non-polar organic solvent under reduced pressure to get pale yellow product of 2,5-bis(alkyldisulphide)-1,3,4-thiadiazole.
The said polar solvent is alkyl alcohol and the alkyl alcohol is methyl alcohol, ethyl alcohol, isopropyl alcohol or mixtures thereof. However the preferred alcohol is ethyl alcohol.
The non-polar solvent used is hexane, petroleum ether, benzene, toluene or mixtures thereof.
The ratio of the reactants 2,5,dimercapto-1,3,4-thiadiazole and disulphide oil is in the ratio 1-4:4-1. The preferred ratio of the reactants 2,5,dimercapto-1,3,4-thiadiazole and disulphide oil is in the ratio 1:1.
0.5-1.2 mole of 30% hydrogen peroxide is added drop-wise and 1-3 moles of disulphide oil is added to the reaction mixture and stirred at room temperature for about 2 hours.
To complete the reaction, the reaction mixture is refluxed for 6 to 10 hours.
For separating the said non-polar organic solvent soluble portion, 800-1100 ml. of non-polar organic solvent is added. The non-polar solvent is preferably hexane.
The lubricating oil composition comprises 0.01 to 6% of 2,5-bis(alkylmercapto)-1,3,4-thiadiazole, as the corrosion inhibitor/metal passivator additive.
DETAILED DESCRIPTION OF THE INVENTION
One of the raw material i.e. 2,5-dimercapto-1,3,4-thiadiazole may be prepared by reacting one mole of hydrazine or hydrazine salt with two moles of carbon disulphide as described in British Patent No. 747,048.
Further modification for the synthesis of 2,5-dimercapto-1,3,4-thiadiazole have been carried out and described in U.S. Pat. No. 4,599,425.
The disulphided oil of the present invention is produced during the refining operation for production of low sulfur LPG, sulphur free low boiling naphtha and other hydrocarbons to be used as fuels. Various low boiling fractions undergo Merox extraction process, in the presence of an alk

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