CA1260460A - Sulfurized olefin process - Google Patents

Abstract

ABSTRACT
A sulfurized olefin of improved solubility in lubricating oil is made by reacting sulfur monochloride with a monoolefin (e.g. isobutylene) to form an adduct which is reacted with sodium sulfide, sodium hydrosulfide, sulfur and alkyl mercaptan (e.g.
tert-butyl mercaptan) in an aqueous alcohol reaction medium.

Description

SULFURIZED OLEFIN PROCESS

Sulfuri~ed olefins are well-known additives in lubricating oil, cutting oil and the like.
Kimball, U.S. Pat. ~o. 2,249,312, describes such a product. Eby, U.S. Pat. No. 2,708,199, describes a similar product in which a sulfur halide is reacted with an olefin using a lower alkanol promoter to obtain an intermediate which is reacted with an alkali or alkaline earth metal polysulfide. Myers, U.S. Pat.
No. 3,471,404, describes a product in which sulfur monochloride is reacted with olefin to obtain an intermediate which is reacted with sulfur and alkali metal sulfide at a critical ratio of 1.8-2.2 gram moles of metal sulfide per gram mole of sulfur. This material is then refluxed forll-24 hours with aqueous alkali metal hydroxide. In U.S. 4,204,969, an effec-tive sulfurized olefin is made by reacting sulfur monochloride with an olefin in the presence of a lower alkanol promoter to obtain an adduct which is reacted with sodium sulfide and sulfur in aqueous alkanol.
According to the present invention, a sulfur-zed olefin having improved solubility especially in alpha-olefin oligomer lubricating oil is made by re-~; acting a monoolefin with S2C12 or SC12 to obtain _, , - :~

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126046~

an adduct which is reacted with sodium sulfide, sulfur alkyl mercaptan and optionally sodium hydrosulfide in an aqueous alcohol reaction medium.
A preferred embodiment of this invention is a process for making a sulfurized olefin having improved solubility in lubricating oil said process comprising:
(a) reacting a sulfide halide selected from SC12, S2C12 and mixtures thereof with an aliphatic monoolefin containing 3-6 carbon atoms to produce an adduct:
(b) reacting said adduct with sulfur, Na2S, an alkyl mercaptan containing 1-12 carbon atoms and optionally NaSH
in an aqueous alcohol medium at a temperature of 50C up to reflux to form said sulfurized olefin;
(c) recovering said sulfurized olefin from the aqueous alcohol medium.
Although a useful product can be obtained using either SC12 or S2C12, superior results were obtained with S2C12 so this sulfur halide is most preferred.
Useful olefins are the monoethylenically unsaturated aliphatic hydrocarbons referred to as aliphatic monoolefin containing 3 to 6 carbon atoms.

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These include l-butene, 2-butene, isobutene, l-pentene, 2-pentene, 2-methyl-l-butene, 3-methyl-l-butene, 2-methyl-2-butene, l-hexene, 2-hexene, 3-hexene, 2-methyl-l-pentene, 2-methyl-2-pentene,

2-ethyl-2-butene and the like including mixtures thereof.
Preferably the olefins are branched-chain olefin such as isobutene, 2-methyl-l-butene, 2-methyl-2-butene, 2-methyl-2-pentene and the like. More preferably the ethylenic double bond adjoins a tertiary carbon atom such as isobutylene, the most preferred olefin.
The first stage reaction is preferably conducted by adding the olefin to sulfur mono-chloride. The olefin can be added as a gas or liquid. Preferably it is added beneath the surface of the sulfur monochloride as a liquid.
In practice the olefin is added until the reaction with the sulfur monochloride stops as 20 indicated by loss of exotherm. An amount of 0.75-3.0 gram moles of olefin for each 0.3-0.75 gram mole of sulfur monochloride usually suffices. A preferred amount is 1.5-2.0 gram moles of olefin per gram mole of sulfur monochloride.
The reaction between sulfur monochloride and olefin will proceed without adding an alcohol promoter, and since alcohol will tend to cause corrosion of metal equipment, it is not a highly preferred method of conducting the first stage. The use of an alcohol promoter, however, is included in one embodiment of the invention. Lower alcohol promoters which can be used in the first stage contains from 1 to 4 carbon atoms. Typical examples are methanol, ethanol, n-propanol, isopropanol r isobutanol, tert-butanol and the like. A preferred promoter is methanol. The amount of alcohol promoter is preferably 0.001 to 0.3 gram moles for each 0.3-0.75 gram mole of sulfur monochloride.
The first stage reaction can be conducted at any temperature high enough to cause the reaction to 15 proceed, but not so high as to cause decomposition of the reactants or products. A useful range is 30-100C. A more preferred range is 40-75C and a most preferred range is 50-60C.
The first stage reaction should be conducted for a time sufficient to complete the reaction between the sulfur chloride and olefin. This time is con-trolled by the rate at which heat can be removed.
Olefin feed rate is preferably controlled to hold the temperature within the desired range. When the sulfur chloride has been consumed the temperature will drop. External heat may be added to continue 1260~60 the reaction for a further time, but this does not appear to be necessary. The overall time required to complete the reaction depends upon the scale of the process and can vary from a few minutes up to 12 or more hours. The time is not critical.
During the first stage reaction HCl gas is evolved so means should be provided to scrub the vent gas from the reactor to remove HCl prior to releasing it to the atmosphere.
In the second stage reaction, adduct from the first stage is reacted with sodium sulfide, sulfur, alkyl mercaptan and optionally sodium hydrosulfide in an aqueous alcohol reaction medium. The second stage is preferably carried out by charging aqueous sodium 15 hydrosulfide, sodium hydroxide, water, alcohol and elemental sulfur flowers or powdered sulfur to a reactor and then adding the adduct and alkyl mercaptan to this at reaction temperature. The NaSH and NaOH
react toform sodium sulfide. Excess NaSH remains.
The sodium sulfide may be obtained from any of a number of sources. For example, it can be made by mixing approximately equal mole amounts of sodium hydrosulfide and sodium hydroxide. If hydrogen sulfide is available, it can be adsorbed in aqueous 25 NaOH to form a solution of sodium sulfide andtor sodium hydrosulfide depending upon the amount of ,, ~ , . . ' ~
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--126046~) hydrogen sulfide adsorbed. Whatever the source, the resulting solution should be adjusted with either NaOH, NaSH or H2S so that the resulting solution consists mainly of sodium sulfide and optionally sodium hydrosulfide with little or no free sodium hydroxide.
The amount of sodium sulfide can vary from 0.5-2.0 gram mole for each gram mole of sulfur monochloride used in the first reaction stage.
10 Preferably the amount of sodium sulfide is 0.5-1.0 gram mole per mole of sulfur monochloride and most preferably 0.6-0.0 gram mole per gram mole sulfur monochloride.
Presence of NaSH is optional. Use of up to 15 0.5 gram moles of NaSH per mole of S2Cl2 has given satisfactory results. A preferred amount is 0.1-0.3 gram moles and most preferably 0.25 moles per mole of S2Cl2.
The amount of water can vary widely without 20 detrimental effect. Good results can be obtained using 10-20 gram moles of water per gram mole of sodium sulfide. This includes water added as such, water in aqueous reactants and water which might be formed by reaction of hydrogen sulfide or sodium 25 hydrosulfide with sodium hydroxide in forming sodium sulfide solution.

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' Alcohol is required in the second stage reaction. Preferably, these are lower alcohols con-taining 1-4 carbon atoms such as methanol, ethanol, n-propanol, n-butanol, isobutanol, tert-butanol and the like, including mixtures thereof. The preferred alcohol is isopropanol either alone or mixed with other alkanols such as tert-butanol.
The amount of alcohol can likewise vary over a wide range. A useful range is 0.25-0.75 parts by weight per each part by weight of water. A more preferred range is 0.4-0.6 parts by weight alcohol per each part by weight water.
The alkyl mercaptan can be added separately to the aqueous alcohol reaction medium or it can be mixed with the first stage adduct and the mixture added to the aqueous alcohol containing the sodium sulfide and sulfur. When added separately it is preferred that it be added concurrently with the first stage adduct to the aqueous alcohol containing 20 the sodium sulfide and sulfur. Sequential addition can be used but it i8 not preferred.
Useful alkyl mercaptans include those in which the alkyl group contains 1 to 12 carbon atoms.
Representative example of these are methyl mercaptan, 25 ethyl mercaptan, n-propyl mercaptan, i-propyl mercaptan, n-butyl mercaptan, isobutyl mercaptan, .. ..

sec-butyl mercaptan, tert-butyl mercaptan, n-pentyl mercaptan, isopentyl mercaptan, tert-pentyl mercap-tan, 2-ethyl hexyl mercaptan, n-octyl mercaptan, l-methyl-heptyl mercaptan, l-ethyl-decyl mercaptan 5 and the like including mixtures thereof.
of the foregoing the more preferred mercap-tans are the tert-alkyl mercaptans. Of these the more preferred are the tert-alkyl mercaptans containing 4-8 carbon atoms. The most preferred 10 alkyl mercaptan is tert-butyl mercaptan.
The amount of alkyl mercaptan can vary over a wide range. A useful range in which to test is 0.05 to 0.8 moles for each mole of sulfur mono-chloride used in the first stage. A preferred range 15 is 0.08 to 0.5 moles of alkyl mercaptan per mole of sulfur monochloride and a more preferred range is 0.1 to 0.4 moles per mole of sulfur monochloride. The most preferred amount of alkyl mercaptan is 0.25 to 0.35 moles per mole of sulfur monochloride.
The preferred amount of sulfur added is 0-0.3 gram atom for each gram mole of S2C12.
More preferably, 0.05-0.15 gram atom of sulfur and most preferably 0.1-0.15 gram atom are used per gram mole of S2Cl2.
In a preferred mode of operation the mixture of sodium sulfide, sulfur and aqueous alkanol is ~ , ..

91260~60 stirred and heated to reaction temperature and then the adduct and alkyl mercaptan are added to it.
However, the reaction can be carried out in other ways such as by adding the sodium sulfide, sulfur, 5 alkyl mercaptan and aqueous alkanol mixture to the adduct or by mixing everything together and heating the mixture.
Preferred second stage reaction temperature is 50C up to reflux temperature. A more preferred 10 reaction temperature is 75-85C.
After the adduct and alkyl mercaptan have been added to the sodium sulfide/sulfur/aqueous alkanol mixture, which is usually completed in 1-8 hours, the mixture is preferably heated to reflux 15 just below for 2-8 hours to assure completion of the reaction.
A very convenient way in which to make an effective sulfurized isobutylene is to base the amount of Na2S and NaSH (or NaOH plus NaSH or NaOH
20 plus H2S), sulfur and tert-butyl mercaptan on the weight of S2C12 - isobutylene adduct. Following this procedure the Kg of Na2S, NaSH, sulfur and tert-butyl mercaptan per each 100 Kg of sulfurized isobutylene is preferably 15-45:0-12:0-7.5:3-20:100, 25 more preferably 20-35:2-10:1-6:4-18:100 and most preferably 25-30:4-8:2-5:5-15:100. After reaction of ~.~.................................................................. .

126046(3 the adduct with sodium sulfide, sodium hydrosulfide, alkyl mercaptan and sulfur the product is recovered by conventional methods such as removing alkanol, water washing and filtering.
The following example illustrates the manner of making the sulfurized olefin.

A sulfurized isobutylene adduct was made by adding isobutylene to sulfur monochloride at 50-65C
10 until reaction stopped. In a separate vessel was placed 177.9g aqueous alcohol (64.7 wt~ isopropanol, 13.8 wt% tert-butanol, 20.3 wt% water), 23.4g water, 240.4g 29.09% aqueous NaSH solution (0.9 moles), 76.2g 81.6g 50% aqueous NaOH solution (0.95 moles) 15 and 12.3g (0.38 moles) sulfur. This was stirred at 75C while 255.3g of the above adduct and 32.0g tert-butyl mercaptan (0.36 moles) were concurrently added dropwise over a two hour period. Heat was continued at reflux for three hours and then solvent 20 alcohol was distilled out up to 90C.
Vacuum was applied to remove more solvent. Heat was stopped and when the mixture cooled to 65C the mixture was washed with water. The aqueous brine layer was removed and the organic layer was stripped 25 of volatiles under vacuum at 100-110C for one hour . ,~
, ... .. . .. . .

lZ60460 and then filtered a second time giving a clear amber product which analyzed 47.7 weight percent sulfur.

In a reaction vessel was placed 188.4g aqueous alcohol (same as in Example 1), 23 . 3g water, 246.0g 29.09 wt~ aqueous NaSH (1.27 moles), 78.0g 50%
aqueous NaOH (0.98 moles) and 6.1g sulfur (0.44 moles). This mixture was stirred and heated to 75C
and then 270.0g of the sulfurized isobutylene adduct described in Example 1 was fed to the reaction mixture together with 33.9g tert-butyl mercaptan over a two hour period at 75 to reflux. Reflux was continued for three hours and then solvent was distilled out up to liquid temperature of 90C. Vacuum was applied 15 and heating stopped. When the temperature dropped to 65C water was added to wash the organic phase. The lower aqueous brine layer was removed. The organic phase was stripped under vacuum at 100-110C for one hour and then filtered using a filter aid. Product 20 analyzed 43.6 weight percent sulfur.

In a reaction vessel was placed 100.41g of a 34.3 wt% aqueous solution of NaSH containing 1.03 wt%
Na2S, 37.27g of a 50 wt% aqueous NaOH solution, 4.0g 1260~6~

of sulfur, 43.64g water and 86.19g of a mixture of 67.17 wt~ isopropanol, 16.89 wt~ tertbutanol and the balance water. This was stirred and heated to 75C
at which time 133.47g of S2C12 - isobutylene adduct made by adding isobutylene to S2C12 at 60C
to the point where no further isobutylene would react was added concurrently with 6.66g tert-butyl mercaptan over a two hour period. Stirring was continued at reflux (about 80C) for three hours at which time alcohol-water was distilled out up to 90C. Vacuum was applied and distillation continued until 70C
liquid temperature at a vacuum of twenty-four inches Hg. The mixture was then water washed at 70C. Wash water was drained off and 1~ Dicalite filter aid added. The mixture was stirred at 100-105C at 28"
Hg vacuum for one hour and then filtered. Product analyzed 48.8 weight percent sulfur.

Another product was made following the same 20 procedure as Example 3 except using 98.27g 34.3 wt~
aqueous NaSH, 36.48g 50 wt~ aqueous NaOH, 2.95g sul-fur, 42.70g water, 84.66g of same aqueous isopropanol tert-butanol solution 16.33g tert-butyl mercaptan and 130.64g S2C12 - isobutylene adduct. The product analyzed 46.4 weight percent sulfur.

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ThiC example followed the same procedure as Example 3 except using 94.85g 35.04 wt% aqueous ~aSH, 35.96g 50 wt% aqueous NaOH, 6.22g sulfur, 29.77g 5 water, 99.83g 56.39 wt% isopropanol - 13.85 wt~ tert-butanol - water solution, 16.21g tert-butyl mercaptan and 129.70g S2C12 - isobutylene adduct. The product analyzed 4~ weight percent sulfur.

The sulfurized olefins are especially useful in lubricating oil formulations used in gear applica-tions. The base oil may be a mineral oil or a syn-thetic oil. Useful synthetic oils include olefin oligomers such as decene trimer, tetramer and pentamermade by oligomerizing l-decene using a BF3 catalyst.
Useful olefin oligomers can be made using other catalysts such as the aluminum alkyl Ziegler catalyst.
Likewise, other olefins can be used such as C6 14 l-olefins.
Synthetic alkylbenzenes can also be used such as di-dodecylbenzene and the like.
Synthetic ester lubricating oil can also be employed such as the alkyl esters of dicarboxylic acid (e.g. di-2-ethylhexylsebacate), fatty acid esters of polyols (e.g. trimethylolpropane, tripelargonate) or complex esters of alkanols, alkane, polyols and carboxylic or polycarboxylic acid.

In this use the sulfurized olefin is added in an amount sufficient to i~prove the EP property of the lubricant. An amount of O.l to 10.0 wt % is usually sufficient.
Fully formulated gear lubricants include other conventional additives which perform various functions. hxamples of such other additives are corrosion inhibitors for ferrous and non-ferrous metals such as tetrapropenyl succinic acid and bis-(2,5-alkyldithia)-1,3,4-thiadiazoles. Antiwear addi-tives such as alkyl or aryl phosphonates, phosphite, thiophosphates, dithiophosphates, and phosphoric acids. Also zinc dialkyl or diaryl dithiophosphate, chlorinated hydrocarbons, sulfurized fatty esters and 15 amines.
Tests have been conducted which demonstrate the EP effectiveness of the sulfurized olefin.
The tests were conducted in SAE 9O mineral oil. The first was a 4-ball weld test (ASTM D2783) 20 in which a steel ball is rotated in loaded contact with three fixed balls. The maximum load without weld is recorded as the pass load.
The test additive was blended in the base oil at a concentration which imparted l.O weight 25 percent sulfur to the oil. Results obtained were as follows:

,: . " ' lZ60460 Additive of Weld Load (Kg) Example 1 315 Example 2 315 Example 3 315 Example 4 315 Example 5 315 In another standard test the present additive was used as a componenet in a formulated gear oil.
The test was an L-42 High Speed Axle Test. Using the additives of Example 1 or 2 gave a gear oil which passed the test.
The mercaptan-capped sulfurized olefins of this inventicn have been found to be much more soluble in hydrogen-treated mineral oil and alpha-olefin 15 oligomer synthetic lubricating oil compared to the same sulfurized olefin made without mercaptans. In the first comparison blends were made at 4.0 weight percent sulfurized olefin in a hydrotreated base oil, a hydrocracked base oil an alpha-decene oligomer.
20 The blends were rated as clear or cloudy. The results were as follows:

Additive Hydrotreated Hydrocracked Alpha-Decene Base Oil Base OilOligomer Example 1 clear clear clear 25 Example 2 clear clear clear Example 3 clear clear cloudy Example 4 clear clear clear Example 5 clear clear clear Standardl cloudy cloudy cloudy 30 1 Sulfurized isobutylene made without alkyl mercaptan.

1260~60 Further solubility tests were conducted to determine the solubility limits of the different additives in a SAE 90W alpha-decene oligomer. The 5 following table gives the maximum concentration for a clear solution and concentration at cloudy mixture:

Concentration (wt%) Additive Clear Cloudy Example 3 3 4 10 Example 4 8 9 Example 5 5 6 Standard - 1 These results show the improvement in solubility in a synthetic alpha-olefin oligomer gear 15 oil base stock due to use of the alkyl mercaptan.

Claims (10)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS
FOLLOWS:

1. A process for making a sulfurized olefin having improved solubility in lubricating oil said process comprising:
(A) reacting a sulfur halide selected from S2Cl2 and SCl2 with an aliphatic monoolefin containing 3-6 carbon atoms to produce an adduct (B) reacting said adduct with sulfur, Na2S, an alkyl mercaptan containing 1-12 carbon atoms and from 0-0.5 grams NaSH per mol sulfur halide in an aqueous alcohol medium at a temperature of 50°C up to reflux to form said sulfurized olefin (C) recovering said sulfurized olefin from said aqueous alcohol medium.

2. A process as claimed in Claim 1 in which said sulfur halide is S2C12.

3. A process as claimed in Claim 2 in which said monoolefin is a branched chain monoolefin having 4 to 6 carbon atoms.

4. A process as claimed in Claim 3 in which said monoolefin is isobutylene.

5. A sulfurized olefin useful as an extreme pressure additive in lubricating oil having improved solubility, said sulfurized olefin being the product made by a process comprising:
(A) reacting a sulfur halide selected from S2C12 and SC12 with an aliphatic monoolefin containing 3-6 carbon atoms to produce an adduct (B) reacting said adduct with sulfur, Na2S, an alkyl mercaptan containing 1-12 carbon atoms and from 0-0.5 grams NaSH per mol sulfur halide in an aqueous alcohol medium at a temperature of 50°C
up to reflux to form said sulfurized olefin (C) recovering said sulfurized olefin from said aqueous alcohol medium.

6. A sulfurized olefin as claimed in Claim 5 in which said sulfur halide is S2C12.

7. A sulfurized olefin as claimed in Claim 6 in which said monoolefin is a branched chain mono-olefin having 4-6 carbon atoms.

8. A sulfurized olefin as claimed in Claim 7 in which said monoolefin is isobutylene.

9. A lubricating oil composition comprising a major amount of an oil of lubricating viscosity containing a minor extreme pressure improving amount of a sulfurized olefin as claimed in Claim 5.

10. A lubricating oil composition as claimed in Claim 9 in which said olefin is isobutylene, said sulfur halide is S2C12 and said alkyl mercaptan is tert-butyl mercaptan.