Oxidation of Lubricating Oils Dialkyl Selenides as Inhibitors G . H. Denison and P. C.Condit CALIFORNIA RESEARCH CORPORATION, RICHMOND, CALIF,
A series of organic selenium compounds was prepared a n d investigated as antioxidants. Freedom from undesirable oxidation products, such as are obtained with thio ethers, was demonstrated i n laboratory a n d engine tests. As a class, the dialkyl seleno ethers were incomparably more effective oxidation inhibitors than the corresponding sulfur compounds; dicetyl seleno ether, for example, was more than tenfold as active an inhibitor as dicetyl thio ether. Like thio ethers, the seleno ethersin acting as antioxidants reduce organic peroxides, removing them from their active role in oxidation. In this process the seleno ethers are themselves converted to selenoxides b u t differ again from the sulfur compounds in not being converted to the hexavalent state. Dilauryl selenoxide rapidly decomposed thermally; it yielded among other products about 507, of the original seleno ether, explaining the absence of hexavalent selenium compounds and, i n part, accounting for the unpredictably powerful inhibitor action. T o the authors' knowledge this is the first established case of an even partially regenerated oxidation inhibitor.
E
VIDEKCE has been presented (9) to shov; that in function-
ing as a n inhibitor of oil oxidation a n alkyl sulfide reduced pcroxides and thus interrupted the chain reaction of oxidation, This does not preclude the possibility t h a t the active chainpropagating agent is some other material which is in rapid reversible equilibrium with the titrated peroxide. I n reducing the perouides, the alkyl sulfide is expended and, a t least in part, cnds up as a strong acid, presumably a sulfonic acid. Unpublished work indicates that sulfur-containing inhibitors are eventually in part converted through the sulfonic acid stage t o undesirable products which, although not negating the beneficial effect of the inhibitors, would detract from their value. Although selenides might be expected to react with peroxides in a manner analogous to sulfides, the data presented here show the selenides not only were freer of deleterious products, but, in addition, are unpredictably more effective inhibitors of oxidation, some ten- to fiftyfold more active, than the sulfides. The results werp made the
subject of several patents (3) An investigation of the mechanism of operation of the selenides shed some light on the reasons for superiority. ~
Testing of Selenides Several organic selenides were prepared for testing. Thew properties are given in Table I and their method of synthesis is indicated. It is anticipated t h a t another paper will give more detail on the synthesis and properties of various organic selenium compounds. Although many compounds of selenium are highly toxic, as yegarda ingestion and topical and intracutaneous application, test animals at least showed good iesistance t o the higher dialkyl selenides. Blends of dicetyl selenide in white oil as a base stock were rur a t 171 C. in the oxidizer used for previous work (2). The results of such a run using 0.1% dicetll selenide are shown in Figure 1 in comparison with a similar oxidation test obtained on the sanir base stock plus 0.5% dicetyl sulfide. I n spite of the fivefold difterence in concentration, the selenide is many times more active than the sulfide. In Figure 2 the results of oxidizer tests, under similar condition+ and tlith the same base stock, s h o the ~ relative inhibitory arti\?ity of various types of organic selenides. As in previous observations on sulfides @), the dialkyl selenides were the most active agents, while diphenyl selenide had almost negligible activity. I n addition to evaluation in ovggen absorption tests, a nuinbrr of bearing metal strip corrosion tests nere run a t 163" C. in a typical western paraffinic base stock, a i t h and xithout various dctergent-type compounding agents. The corrosion tests werp carried out in glass tubes 5 em. ( 2 inches) in diameter and 50 cm (20 Inches) long immersed in a thermostated oil bath. T h i e e hundred milliliters of oil were placed in the tube and air was bubbled through at a rate of 10 liters per hour. Weighed ctripq of copper-lead bearing metal n-ere suspended in the test oil. The results are presented in Table 11. Comparison of the figures shotl 5 that the selenide is approximatrlv ten times as activp in rediwing
1200
I CCG
8
603
o m z
s
600 L
r
3 iC3
203
c
I
2
t.om
3
1
>
2
1
4
HOURS
Figure 1. Relative Effect of Dialkyl Sulfide a n d Selenide at 17 1 O C.
Figure 2.
Relative Effect of Various Selenides 0.1%
944
by weight
at
171° C .
May 1949
Properties of Organic Selenides
Table I.
Melting Boiling Pt., C., Selenium, % Pt., at Indicated 0 c. Mm. H g Found Theory Di-n-decyl selenide Dilauryl selenide Dicetyl selenide Diphenyl selenide
12 25 51
..
182-185, 3 201-209, 3 126-i27, 5
Table 11.
B
1 . 0 % diqetyl sulfide. ? 3 5 % dicetyl selenide
C D D D
1 07' cetyl ethyl sulfide 0:1% dicetyl selenide Nil 1 . 0 % cetyl ethyl sulfide 0 . 1 Yo dicetyl selenide
llill
1Y 11
A. SAE 30 B; SAE 30 C SAE 30 d. SAE 30
western naraffinic
21.9 18.9 14.9 33.8
Water white liquid N ~ formed ~ s in ~ (liquid) White wax NazSe 4- RC1 in alcohol (3) Whitewax Pale yellow liquid Phenyl sulfone Se (6)
+
Strip Corrosion Tests at 163' C. hours
Nil 1.0% dicetyl sulfide 0 . 1 % dicetyl selenide 0,.:35% dicetyl selenide
e e
18:5 14.3 32.8
Method of Preparation
Appearance
Loss of Cu-Pb Strips, Mg. -Weight 24 48 72
Corrosion Inhibitor
Oil A A A A B
B
945
INDUSTRIAL AND ENGINEERING CHEMISTRY
28.9 9.3 11.2 6.2 30.4 37.1 13.7 34.1 7.9 8.1 11.0 4.7 0.1
hours 63.8 23.2 22.7 11.2 91.1 124.1 35.2 88.6 18.6 17.6 30.5 6.4 -2.5
hours 82.3 32.2 30.0 12.5 138.4 212.0 48.3 106.3 21.8 20.6 44.0 8.2 1.5
Used Oil Inspection ___ Viscosity Acid Naphthsincrease No. inqoluble 69 9.7 1.19 5 1.59 7.3 51 2.18 7.5 1 1.10 3.9 12 7.54 16.8 1 3.18 9.3 1 0.72 5.5 28 1.03 7.4 14 1.58 9.8 2.27 0 3.8 45 1.28 7.6 1.52 58 9.2 0.41 0 2.1
To determine whether the dialkyl selenide will rapidly reduce peroxides, essentially the same technique as that previously used with sulfides was employed ( 2 ) . A weighed sample of the inhibitor wasincubated at 66" C. with white oil which had been oxidized t o a relatively high peroxide c o n t e n t . Samples were withdrawn periodically and titrated for peroxides, and the peroxide numbers plotted against time. Peroxide content was determined by the method of Wheeler (8) and expressed as peroxide number defined a s total equivalent cubic centimeters of oxygen gas per 100 grams of sample.
4- 0 . 5 % calcium oetvl ohenate. western paraffinic 1.0% calcium cetj.1 bhenate. western paraffinic 0 5% calcium cetyl phenate 4- 0 . 2 5 % calcium cetyl phosphate. western paraffinic + 0'.5% sulfurized calcium cetyl phenate 0.25% calcium cetyl phosphate.
+ +
corrosion as the corresponding sulfide, a b judged by the concentrations necessary t o accomplish the same degree of corrosion reducLion. The high degree of antioxidant action of the selenides, in addition t o their cleanliness in regard to the formation of deposits, was borne out by Lauson engine tests using a western SAE 60 grade aviation oil containing a phenate and phosphate-type detergent additive. Engine jacket temperature was 240" C. and crankcase temperature 104" C. As shown in Figure 3 (left), the piston discoloration number as based on inspections after 30 and 60 hours' operation is effectively reduced by the addition of dilauryl selenide. The piston discoloration number is proportional t o extent and depth of deposit, 800 being all black, 0 being clean. As shown in Figure 3 (right), a n even more marked redurtion in the percentage of oil ring clogging results from the addition of dilauryl selenide, especially at concentrations above 1%. Moreover, the inspections on the used oils (Table 111),show the selenide-containing oil i o be in much better condition than the base oil.
Mechanism of Action The work on selenides showed that they were less prone t o form strong acids and deleterious demsits than the sulfides and that they were far more effective inhibitors of oxidation. To attempt t o clarify this difference in effectiveness, a study of the reactions of selenium compounds was carried out in a manner similar t o t h a t previously applied to the sulfur compounds ( 2 ) . Because the efficacy of a n oxidation inhibitor will in part depend adversely upon the rapidity with which it can be used up by direct oxidation, a n oxidator test was run on pure dilauryl selenide. After running 2.5 hours a t 171 O C. no measurable absorption of oxygen had ocourred and the compound had not changed in color or melting point during the test; this indicated t h a t under these conditions i t was practically unattacked by molecular oxygen. This is one point of superiority over the analogous sulfides which, although not rapidly adsorbing oxygen as compared with ordinary mineral oils, show in a similar 2.5-hour oxidizer test absorption of about 100 cc. of oxygen per 100 grams of sample.,
+
Figure 4 is such a peroxide reduction curve for dicetyl sulfide. The line marked "Theoretical for Sulfoxide" is the final calculated peroxide value, assuming that, only the following reaction took place:
RIS
+ AOz +RBO + AO
The actual curve breaks somewhat above the theoretical point, but this was proved t o be the result of a systematic inaccuracy in the peroxide titration. Isolation of the product demonstrated t h a t the break actually represented the point a t which complete conversion t o the sulfoxide had taken place. Isolation of the product obtained when the oxidation was allowed t o proceed for longer times showed t h a t the sulfoxide was very slowly further oxidized t o the sulfone.
Table 111. Inspections of Used Oils from Lauson Test
Base Base Base Rase a
+ + +
Viscosity Jncrease, S.S.U. at 210° F. 76 0.5 a inhibitor G8 LO@,inhibitor 34 1.5% inhibitor 31
Conradson Carbon 3.1 2.8 1.7 1.7
hoid No. 1.2 0.2 0.4 0.4
B y weight.
.5 PERCENT
Figure 3.
1.0
DILAURYL SELENIDE I N OIL
Effect of Selenide on Engine Performance
1.5
2.0
INDUSTRIAL A N D E N G I N E E R I N G CHEMISTRY
946
HOLRS
Figure 4.
Reduction of Peroxides by Dicetyl Sulfide
When the same technique was applied to dilauryl selenide, using mixtures of 2.17 grams of selenide in 47.9 grams of oxidized white oil having a peroxide number of about 560, the curves shown in Figure 5 were obtained for tests a t 93' and 66' C. Both curves show the peroxide number rapidly falls t o a point well below t h a t calculated for conversion of selenide to the selenoxide, actuallp approaching closely the value required for conversion of selenide to selenone. During these test,s the blends developed a reddish cast and a t,race of precipitated red selenium. 4 repeat of these experiments at 38" C. presented a n anomaly: although the peroxide titration end points became increasingly sluggish with time, there was no measurable decreasc in peroxide number. The selenium formed in these tests could not result from simple thermal decomposition of dilauryl selenide, as separate tests proved it to be completely stable a t the temperatures employed. The marked difference between these result,s and those obtained x i t h the sulfides made it necessary t o have data on the properties of the corresponding selenoxide and selenone. No literature references could be found on dialkyl selenoxides and selenones, although some of the aryl compounds have been made. Dilauryl selenoxide was synthesized by the oxidat,ion of dilauryl selenide m7it.h theoretical quantities of perphthalic acid in cold chloroform solution according to the method used by Bohme on sulfides ( 1 ) . The selenoxide formed a soluble salt with phthalic acid, from which it had to be liberated by saturating with anhydrous ammonia. The chloroform solution, filtered free of ammonium phthalat,e, was evaporated down under vacuum and the residual selenoxide repeatedly triturated with cold ethyl ct,her. The selenoxide was too heat-sensitive bo recrystallize. Dilauryl selenone was obtained by oxidizing the selenide with l O O ~ ,excess of perphthalic acid in ethyl ether, removing the solvent under vacuum, and extracting the selenone from the residue with chloroform. After removal of chloroform under vacuum the product was recryst.allized from alcohol. The properties of dilauryl selenoxide and selenone are given in Table 11'. Table IV.
140" to 150" C. and dilauryl selenoxide melted with dcconiposition a t 81" C. I n both cases the decomposition products consisted of water and an oily material containing traces of red selenium. No evidence could be obtained of the formation (if molecular oxygen during the decnmposit,ions. The large drop in peroxide number resulting from incubation ( 1 1 peroxide and dilauryl selenide a t 93" and 66" C. as shown in Figure 5 could not occur if selenoside or selenone were present, a: reaction products, because their ability to titrate as peroxide would compensate for any peroxide removal. This fact wa.: checked by showing that from a dilauryl selenide-peroxidized oil blend incubated at, 66" C . for 0.8 hour (Figure 5) neither selerioxide nor selenone could be isolated, although fresh dilauryl selenoxide or selenone added to the previously incubated mixtur(8 could be isolated in about, 907, yield. The method of isolat,iori was that used previously ( 2 ) for isolating sulfoxides and sulfones. The only product,s isolated from this 0.5-hour incubation w'zlw t,hose previously noted. water and traces of red selenium. Incubation of a similar blend a t 38" C. for 6 hours, alt.hough giving no drop in apparent peroxide numbers, was sho\vn to produce dilauryl selenoside. Selenone could not be found. There were two possible ways to account for the absence oi dilauryl selenone in the above reaction: Either it I n s not, formed at all, or else it was destroyed by thermal decomposition or COJIdensation with the peroxidized white oil. To test t8helat,ter possibilit>y,a 0.186-gram sample of the pure dilauryl selenonc was added t o 5 grams of t8hereaction mixture from the incubation experiment and heated t,o 93' C. for 0.5 hour. The result,ing solution was suhjected t o the same isolation procedure used before, and S570 of thr selenone was recovered. The only possible conclusion was t h a t t.he selenone had not been formed by the action of peroxides on dilauryl selenide, and some other reaction must account for t'hv reduction of the 2 moles of peroxide by 1 mole of selenide. By analogy to the proved case of the dialkyl sulfides arid lwcause the selenoxide was shown t o be produced in the 38" C. incubat'ion test, the primary reaction of the dialkyl selenides with oil peroxides must be as follows:
R2Se
+ A02
--d
BrBeO
+A0
I n the case of the sulfides, the sulfoxide is thermally stable ailti can survive in the reaction medium long enough t o undergo furthw oxidation changes. The selenoxide, on the other hand, decomposes rapidly a t 81" C. and it seemed reasonable to assume that although formed as the primary product,, its existence was transient and it did not last long enough t,o be oxidized to the selenontt. This conclusion is borne out by the occurrence of red selenium anc water in t,he incubation experiments, as both had been recognized
Properties of Dilauryl Selenoxide and Selenont Rlelting
Pt., C.
Dilauryl selenoxide Dilauryl aelenone
Vol. 41, No. 5
Decomposition
Pt.,
C.
81
81
103-106
140-150
General Basic, oxidizes iodide Neutral, oxidize. iodide
Analyses, L/o - ______ Found
66.09 C 11 . G O H 64.00 C
11.37 H
Theory 66.44 C 11.62 IT 64.08 C 11.20 H
Investigation of these compounds showed tn o stliking differences from the analogous sulfur compounds. First, both dilauryl selenoxide and dilauryl selenone n ere sufficiently strong oxidizing agents to titrate as peroxide in the chlornform-acetic acid-potassium iodide mixture used for peroxide analysis. This behavior wab noted by Gavthw-aite et al. in the cabe of diphenyl selenone ( 5 ) . Secondly, both compounds showed definite thermal rierompnsition. Dilauryl selenone decomposed reprodurihlv at
n l
I
I
I
2
I
3
1
4
HOURS
Figure 5 .
Reduction of Peroxides by Dilauryl Selenide
M a y 1949
*
INDUSTRIAL AND ENGINEERING CHEMISTRY
qualitatively among the thermal decomposition products of dilauryl selenoxide. The theory advanced a t this point accounts for the absence of dilauryl selenone but does not explain how the selenides can consume twice as much peroxidic oxygen as is required for oxidation to the selenoxide and still not be oxidized beyond the tetravalent stage. A study of the deromposition of dilauryl selenoxide was undertaken and found to account for the additional reducing capacity. 4 30-gram sample of dilauryl selenoxide was thermally decomposed by destructive distillation under reduced pressure a t 175' C. Some selenium and a small amount of organic material were left as still bottoms. The overhead was fractionally distilled and the ruts were combined and refractionated several times. It was thus separated into three fairly distinct fractions as shown in Table V.
Table V. Decomposition of Dilauryl Selenoxide Cnt N o . I
I1
111
Boiling Range Corrected C. 52-71 92-96 207-213
t o 3 Mm.,
Percentage of Original Distillate 30-50 10-15 30-50
Color Water-white Faint yellow Orange solid at 0' C.
Water was also noted in the decomposition product but was not isolated in this particular experiment. The lowest boiling cut was further purified by treatment with mercuric chloride t o precipitate selenium compounds and was then analyzed. I t s constants were determined as shown under I-A in the following table in compariRon with the constants of 1-dodecene. Color %C 1-DodPcene Water-white 8 5 . 7 1 T- I Water-white 84.3R Cooling curve.
%H
Br No. 14.29 95 14.81 83
Melting Pt.Q, C. -34.4 -31.5
Boiling P t , 15 Mm., C. 96 91-96
These data make it fairly clrltr that, although not obtained completely pure, the product in the lightest fraction was principally 1-dodecene. It was contaminated with 10 or 15% of some more saturated component, but the quantities were too small to permit isolation. Analysis proved that cut I1 was a mixture of I-dodecene with a eelenium-containing material. The entire cut was treated with mercuric chloride and the resulting precipitate purified by recrystallization from benzene. The analysis of the precipitate, in comparison to mercuric laurylselenomercaptide, is: mercury found 29.0%, theory 28.78%. To make doubly sure of its identity, a sample of the mercuric salt was prepared from synthetic laurylselenomercaptan and found to be identical in solubility, analyses, and general appearance with that prepared from cut 11. Cut I11 was a n orange liquid which left a slight residue of selenium each time it was redistilled. I t s characteristics compared with those of dilauryl selenide are: Boiling Pt.,
c.
iC1gHzs)zSe c u t 111 Cooling curve.
201-210, 3 mm. 193-198, 2 mm.
n "D"
1 ,4700 1.4728
Melting
c.
25 22
To prove that the main part of cut 111 consisted of dilauryl selenide it was oxidized with a n excess of monoperphthalic acid and by titration was found t o require only slightly more active oxygen than theoretically expected. Isolation of the oxidation product yielded a material melting a t 105" C. and decomposing sharply a t 142 O C., which checked the properties previously determined for dilatmyl selenone. Thus cut I11 was principally
947
dilauryl selenide, probably containing Lome dilauryl diselenide which was known t o yield free selenium on distillation. Although a complete balance concerning the fate of the oxygen originally present in the selenoxide was not established, about half of the oxygen could be accounted for as water and a part of the remainder as carbon dioxide. No free oxygen was formed and it was indirectlv shown that selenium dioxide was not even transiently present in the decomposition mixture. This was accomplished by decomposing a sample in refluxing acetophenone which is very readily oxidized by selenium dioxide ( 7 ) . No phenylglyoxal was found among the products. Potentiometric titration of a whole unfractionated decomposition mixture showed no more than a trace of acidic material. The odor of hydrogen selenide was never noticeable. .4 rough balance of the materials formed in the decomposition of dilauryl selenoxide is given in Table VI. .Ilthough the reaction between a peroxide and dialkyl selenide rannot yet be expressed by simple balanced equations, the results of the incubation experiments along with the evidence on products of the thermal decomposition of dilauryl selenoxide will explain the anomalously large amount of peroxide reduced. The peroxide is reduced in the reaction RzSe
+ AOZ
----f
RzSeO
+A0
(1)
The resulting selenoxide then rapidly decomposes thermally to regenerate 30 t o 50% dialkyl selenide, as was shown above. Using the figure 50% for regeneration of the original inhibitor, the total capacity for reduction of peroxide by Reaction I is given by a 1/4 . . the sum of which is 2. Thus simple series 1 though the selenide is not converted to selenone, because of partial regeneration of the inhibitor the total peroxide reduced is twice that expected from simple conversion t o selenouide. This agrees with the results shown in Figure 5 .
+ + +
Table VI.
Decomposition Products of Dilauryl Selenoxide
Products Proved Present Dilauryl selenide Dilauryl diselenide Lauryl selenomercaptan I-Dodecene Water Carbon dioxide Selenium
Products Proved Absent Acid materials Molecular oxygen Selenium dioxide Hydrogen selenide
The following purely hypothetical scheme will serve to account For the products found and also for regeneration of inhibitor: RCHzCH&3eCH2CH2R -
+ &+ 0
11
+A0
(2)
+ RCHzCHO
(3)
+ RCHzCH2Se2CH&H2R
(4)
RCH2CH2SeCHzCH2R ___0
I/
RCH&H2SeCHzCH2R
+ RCHSCH2SeH
0
1
2RCH&H2SeCH2CHzR --+ Ha0 R C H = CHZ RCHZCHO
+
+
RCHzCHzSezCH2CHzR __
+Se + RCHaCHzSeCH&HzR
(5)
This scheme is pure conjecture and can be justified only because i t serves t o simplify summarizing the chemical compounds found, underscored in the above scheme. Reaction 3 might be justified by the work of Edwards et al. ( 4 ) , who showed that aryl alkyl selenoxides of low molecular weight decompose on heating t o yield the selenomercaptan and the aldehyde. If aldehyde is formed, i t must t o a great extent react further, as i t was not obvious in the decomposition products of dilauryl selenoxide. The reactions of a dialkyl selenide functioning as a n inhibitor of oxidation are thus seen to be markedly more effective than t,hase
948
INDUSTRIAL AND ENGINEERING CHEMISTRY
of the dialkyl sulhdes. h dialkyl mlfide, a s showii b j prrciou. work, is converted to sulfoxide and sulfone, both of which rapid11 autoxidize t o ineffective and in part deleterious products. The selenide, on the other hand, because of thermal instability of the selenoxide regenerates itself t o a degree that appreciably incwasrs its effectiveness.
Summary !arious dialkyl selenides have been prrpared and shovc-n to IIL markedly more effective inhibitors of oil oxidation than t h r corresponding sulfides. T h e dialkyl are far more active than tht. diary1 compounds. Strip corrosion and engine test data beai 0111 the inhibitory value of dialkyl selenides as determined by ouidation tests and, in addition, show t h a t the selenides are relativrl~ free from deleterious oxidation prodiicts w v h as are encountercatl with sulfur compounds. Dilauryl selenoxide and selenone IT eie prepared and 5hown T O be thermally unstable above 81 and 140" C., respectively. The\ are both capable of releasing iodine from the acetic acid-chlorotorm-iodide mixture used for titrating peroxides. The peroxide redurtion theory of oxidation inhibitor act ion haa been .;hewn t o br applieahle to dixlk\l ~rlvnidrq. In t l i t . case r i t
Vel. 41, Na 5
-elmides, however, the selenoxide tornled is decornpobed t to yield the original dialk, I selenide in appreciable perceii tagr Thus, in this case a partial regenerative mechanism is operating The observation t h a t selenide-inhibited oils form very little g u m or sludge is explained by the fact that the oxidation products ( i t the selenides arc thermallj clecompoaed t o non-gum-foirnirrg pioducts instead of heing further oxidized t o strongly acidic mfiterials which could, H S (10 *ulforiic w~ds,accentuate gun1 tormfi tion.
Literature Cited Be?., 70,379 (1947). ( 2 ) Denison, G . H., and Contiit, P. C., I N DENG.C H ~ I37, IY(12 (1945) ( 3 ) Denison, G. H., and Condit, P C. ( t o California Research Coip U. 8.Patents 2,398,414, 2,398,415, 2,398,416(April 16, 1946 (4) IXwards, 0. K., Gaythwaite. v(T. R., Kenyon, J., and Phillip H., J. Chem. So(*.,1928,8293. ( 5 ) (iaythwaite, W E., Kenyon. J , and Philllps, H., 7 b ( I ) Rbhnle, H., a
2280. (6) Kiaft, F., and Lyo112, K. (7) Riley, H L , MorleJ J
. Rvr., 27, 1761 (1894)
1932,1875 (8) Wheeler, D. H.,Oil (XI S o n p 9, 8 Y
(1Y3fi)
Complex Thiophosphori as Lubricant Addi J. D. Bartleson and M. L. Sunday STANDARD 0x1, COMPANY (oms), CLEVELAND, OHIO
Some reactions of phosphorus pentasulfide with a secondary aliphatic amine of high molecular weight and the reaction of these products with metal hydroxides are described. The yields and reaction conditions involved are outlined. The structures of the reaction products are discussed. Chemical analyses showed the sulfide-amine products to be complex thiophosphoric amides. Neutralization of the amides gave a metal salt derivative. A typical product formed by these reactions was investigated as an addition agent for lubricating oils. It was very effective as a detergent, pour point depressor, and corrosion inhibitor and mildIy improved viscosity index.
D
URING the past 9 years over 100 patents covering the reac-
tion products of phosphorus sulfide with organic niaterialq have been granted (20). It is believed that some of these products have found considerable application as lubricating oil additives. -2 study in this laboratory has Ied t o the development of a reaction product of aliphatic amines with phosphorus pentasulfide of interest as multifunctional lubricating oil additives ( I d , 13). T h e work described here deals with the preparation of these materials and their properties as additives in lubricating oils. The effectiveness of the products as lubricant additives created interest in their chemistry. Some recent work concerning the structure of the additives is also presented.
Preparation number of both primary and secondary aliphatic amines were studied. T h e amine found most suitable from the standpoint of cost, availability, and perforniance was Armour & Company's AM-21 80-C, which consists largely of dioctaderglaminr
\ \ i t h miiior aniourite ( 5 t o 15yo\01 t,.i,,(.t,(tecylsmirie arid 5% ( I ' hydrocarbons (IO). The amine \Tas heated ~ i t phosphorus h pentasulfide €01Rev hours, either alone or 111 t h r presence of a diluent such a b iiiiri oil. Two reactions \yere ohirrved, depmding upon the 1rrriperatures employed.
4t temperatures be lo^ about 400" E'. the sulfide reacted ~ i t t the amine with a mild evolution of heat and dissolved complrtelj in a n amine-oil mixture This product deposlted waxy niateriall upon standing at room temprialurr, 01 upon dilution t o low r o n rentrations with lubricating oils. At reaction temperatures in the range of 400" to 500" F. ancl above there was a much more exothermic reaction which wa, accompanied by a vigorous evolution of hydrogen sulfide. Tht, product from the higher temperature reaction was liquid e v w a i room temperature, and was miscible with lubricating oils in any proportion. T h e use of the higher temperature was signihcarit i r ~ hat it permitted an optimum molar ratio of phosphorus pentaulfide to amine of 1.1. Unreacted phosphorus sulfide in the product was undesirable, as it decreased its effectiveness a b tin oil inhibitor and consumed basic reagents upon neutralization. The reaction of phosphorus pentasulfide with amines g a t ~ product yields of 95 weigh1 or higher, based on the totai weight of ingredients used. The loss lva? due to the evolution of hydrogen sulfide at the higher rraction temperature. The reaction products readily formed salts with inorgti~iic haves such as sodium, potassium, and barium hydroxides, arid zinr and calcium oxides. These salts were effective for use a.; oil additives. The barium salt i q discursed in detall below. I n preparing the barium derivative of the higher temperature sulfidc~-dioc*tadccylamine product, 1.1 bo 1.2 moles of barium hydroxide o d a hydrate per mole ofeulfide were heated a t 180" F. for 2 hou1- arid then blown with air at 250" F. for 2 hours to remove water. The reaction gave a product yield of 95 wcight yo based on the tolall charge of reactants and oil dilucnt. The by-products were hydiogen sulfide and inorganic compounds of barium. The product wac an oily liquid which was miscihlr wifh Iuhricating 011in all p r o ~ w tions
x,
