368
INDUSTRIAL AND ENGINEERING CHEMISTRY
EFFECT O F AIR VELOCITY AND TEMPERATURE OY iM41,EIC ACID YIELDS
The catalyst used in these experiments was a fully developed catalyst 1lyith the iron molybdate formed in place; a nickel tube was used. As the air flow was varied from 2 to 8 liters per minute, the furfural feed as varied from 0.13 to 0.04 gram per hour, following the usual practice during this research of keeping the furfural excess below 5%. The curve in Figure 5 s h o w that the minimuni air flow necessary for optimum yields was 4 liters per minute and that an increase beyond this point had no effect on the yield. At an air f l o v of 4 liters per minute t,he t,ime of contact was 0.6 second: liters of effective catalyst volume per liters of gas mixture per second, 0.072/0.12 = 0.6. The linear velocity mts 0.48 meter per second: length of contact, mass in meters per contact time in seconds, 0.285/&6 = 0.48. I n these calculatiom, t,he expansion of the grtres from room temperature to 270" C. was taken into consideration. In estimating the catalyst volume, it was assumed that the first quarter of the catalyst bed served only as a preheater and was therefore not counted in as contact mass. I t v-as further assumed that the voids amounted t o 60%. With this catalyst batch, a series of runs also were made in which the conversion temperature v a s varied. The optimum temperature n-as 270" C., but the yields were high over a rather wide range (Figure G ) . In this series, the furfural feed was 0.25 t o 0.35 gram per hour and the air flow was 4 liters per minute. The conversion T T - ~ S959$ or better.
furnace x a s 260 cc. and catalyst 1 with iron molybdate formed in place was used. The results are shown in Figure 7. The grams of maleic acid produced per hour increased with an increase in the furfural fed, arid t,hc yield based on converted furfurill \?-as independent of the furfural fed. CONC1,IJSION
The present investigation has shomn that it is possible t o obtain high yields of maleic acid, when subjecting furfural to vapor phase oxidation over a mixed oxide catalyst. ACKNOWEEUGRIEST
Acknoi\-ledgnient is made to A4rleneLilly lor carrying out all the furfural and maleic acid determinations and l o A. P. Dunlop for the cited combustion analysis of maleic acid; both are on thc staff of the Quaker Oats Company. LITERATURE CITED (1)
(2) (3) (4) (5)
(6) (7)
CONVERSION CAPACITY
I n the experiments reported thus far, the furfural fced purposely was kept extremely low. Some capacity studies vr-ere made in a 5.1 X 15.2 em. aluminuiii furnace. The voluine of the
Vol. 41, No. 2
(8)
(9)
Downs, C. R., J . SOC.Chem. Iiad. (London), 4ST, 188-93, cspecially 190-1 (1926). Hughes. E. E., and Acree, S.F.,IKD.GWG.CHZM.,AKAI.. ED., 6, 123 (1934). Marek, L. P., and Hahn, D. A, "Catalytic Oxidation of Organic Compounds in Tapor Phase," -4.C.S. Monograph No. 61, p. 379, Ken, York, lteinhold Pub. Co., 1932. Milas, E.A., and Walsh, 7%'. L., J . Am. Chem. Soc., 57, 138993 (1935). Nielaen, E. R., U. S.Patent 2,421,425 (dune 3, 1947). Sessions, Wm. V., J . Am. Chem. Soc., 50, 1696-8 (1928). Zumstein, Fritz (C. €1. Bochringer c! Son), German Patent 478,726 (July 8, 1929). Zurnetein, Fritz, U. S. Patent 1,956,482, (April 24, l934!. Zunistein and Iioschara, private communication.
RLCEIVCD Julr 10, 1947.
J
R. T. SANDERSON' The Texas Company, Beacon, N. Y.
The
evaluation oi kinematic viscosity-temperature characteristics of liquids is based on a viscosity-temperature number (V.T.N.). Simple relationships among viscosities, V.T.N.'s, and nlolecular w-eights of hornologous compounds are presented. The effect o f structure on viscosity-telraperature of pure hydrocarbons is evaluated by V.T.N. JIethods of applying the same basic principle to calculating \ iscosities of multicomponent mixtures and of nil viscosity index improver blends are described.
HE iniportance of viscosity in lubrication is \\-ell known. 911 lubricating oils change in viscosity with temperature. This property becoines of particular interest in lubrication under spec.ia1 conditiolis involving unusually wide opcrating temperature ranges, n-here it is essential for the oil to maintain adequat,e fluidity a t lorn temperatures without becoming too thin a t higher temperatures. I n fundamental studios directed toward the development of such special purpose lubricants, methods of evaluating viscosity-temperature properties have been considered. The purpose of this paper is to present such a method, and to discuss some useful applications of the essential principle to some pure hydrocarbons and to lubricating oils. Present address, Universitv of Florida, Gctinesvillo, Fla.
VISCOSITY-TEIIIPER~~TURE KU11HER
It is customary in lubrication practice to evaluate the viscositytemperatmureproperties of oils on the basij of their viscosities ai. certain fixed temperatures (usually 100" and 210" F.). The significance of this procedure is shovc-n by Figure I, which gives viscosity us. temperature curves for tn-o typical liquids, A and 13, of which B is more viscous. As excnq~liiiedby t,he curves i n Figure 1, licpids, in gcncral, change viscosity slo~vlywith temperature a t lovi viscosities and rapidly a t high viscosities. Whcn compared between tine same temperature limits, Liquid A a p y e a l ~ t o change viscosity inore slou-ly with toniporaturc than tloci: liquid B. Howevcr, the same temperat,ure? represent diff(1rt:iit relative positions on the complete curvcs for the two liquids. When coinpared at similar tenqxratures, a less viscous oil d \ w y s appears t,o be changing viscosity with temperature more slmvly ihan a mort: viscous oil because of being in a flattcr part of ita viscosity-temperature curve. Thu5, while the customary p 1 ' 0 eedure is practical for most purposes, it is unsuit,ablc for evaluating complete viscosity-temperature properties. A method of more coinpletc evaluation is sornetimcs needed, as, for example, in studying the effect of changes in molecular structurc on viscositv-temperature. Change in structurc usurtlly
IND-USTRIAL A N D E N G I N E E R I N G CHEMISTRY
February 1949
369
TEMPERATURE
TEMPERATURE
Figure 1. Comparison of Viscosity-Temperature of Typical Hydrocarbons between Fixed Temperatures
Figure 2. Comparison of Viscosity-Temperature of Typical Hydrocarbons between Fixed Viscosities
involves change in viscosity, so that two isomers compared within the same temperature range are unlikely to be a t exactly comparable positions in their viscosit,y vs. temperature curves. This difficulty is removed by comparing the curves between the same viscosity limits instead of the same temperature limits. Figure 2 gives the same curves as Figure 1, except that in Figure 2, the curve for liquid B has been shifted along the temperature axis until the two curves intersect a t an arbitrarily chosen low viscosity. I t is obvious here that the complete curve of B shows flatter viscosity-temperature properties than those of A. Furthermore, comparison of the viscosity-temperature changes of the two liquids betveen any two viscosities shows the same relative curvature as do the complete curves. This suggests that the complete curves may be compared merely by comparing the temperature spans between t,he same t,wo fixed viscosities. A simple means of making such a comparison is by use of a kinematic viscosity-temperature number (V.T.N.). This is defined as a number equal to the temperature span (in F.) between two fixed viscosities, here arbitrarily chosen as 2 and 100 cs. :
100 cs. T o prove that the curves have the same shape, it is necessary to show that the curves are the same temperature difference apart at all viscosities as they are at 2 and 100 cs. I n other words, in the A.S.T.M. equation it should be possible to substitute log (5" K ) for log T,where K is a constant temperature difference, and the resultant equation, log log (k.v.-t c ) = A log (2' +K) B , should still represent a straight line. This K ) were a linear function of log T . would be true if log ( T Actually, the logarithm of the sum of a variable plus a constant is not a linear function of the logarithm of the variable. Fortunately, however, within the ranges of temperature and K encountered in ordinary lubrication experience, this relationship is linear for all practical purposes. Therefore the complete curve3 of oils having equal viscosity-temperature numbers are for practical purposes identical in shape and may differ only in their position along the temperature axis. I t is apparent from the above that the choice of viscosity limits (2 and 100 cs.) is not critical and that if two liquids have the same viscosity-temperature numbers as defined in Equation 1, they will have equal temperature spans between any t,wo viscosity limits. Thus, although 2 and 100 cs. were chosen as convenicnt for the data to be considered herein, there is no reason why other limits may not be assigned. For example, 5 and 500 cs. have been found suitable for more viscous oils, and 5 and 100 cs. are satisfactory when oils of widely different viscosities are to be comparcd. If the axerage rate of change of temperature n-ith viscosity over a fixed viscosity range is expressed as tz-t1/vz--u1, then when v2 and v1 are the chosen viscosity limits, tz-tl is the viscositytemperature number. Thus the viscosity-temperature number is a number which is directly proportional to the average rate of change of temperature with viscosity between the set limits, or it is inversely proportional t o the average rate of change of viscosity with temperature. The viscosity-temperature number is a number which designates the shape of the kinematic viscosity us. temperature curve, or, in other words, characterizes the changing rate of change of viscosity with temperature for any oil which conforms to the A.S.T.M. chart. This does not mean that the viscosity-temperature number is based on the A.S.T.M. equation or chart. It is not. The A.S.T.M. chart is the most, convenient means of det,ermining the viscosity-temperature number but any other method of determining the temperatures a t two fixed viscosities could be used. Obviously, the liquid which has tho greater
V.T.N.
=
"F.(2CS.) - ' F.(100CS.)
(1)
The viscosity-temperature number is most easily obtained from viscosities experimentally determined at any two temperatures, by use of the American Society for Testing Materials (A.S.T.M. D 341-43) viscosity-temperature chart. The A.S.T.M. chart is based on the equation, log log (k.0.
+ c)
= A log T
+B
(2)
where k.w. is the kinematic viscosity in cent'istokes; T is the absolute temperature; A and B are constants different for each liquid; and c is a constant which is 0.6 for all viscosities above 1.5 cs. but increases slowly for lower viscosities to 0.75 a t 0.4 cs. This equation has been found to represent viscosit,y-temperature data for hydrocarbon oils quite well. For all materials which conform bo this equation-that is, give a straight line on the A.S.T.M. chart-kinematic viscosity vs. temperature curves have practically the same shape if 'the viscosity-temperature numbers are equal and can be made to coincide merely by shifting the curves along the temperature axis. This can be demonstrated as follows: If the viscosity-temperature numbers of two liquids are equal, the temperature difference between the two oils a t 2 cs. will be equal to the temperature difference a t
+ +
+
370
INDUSTRIAL AND ENGINEERING CHEMISTRY TABLE I.
Compound
Literature Cited
C I7 (') (L')
CZI c 2 6
Ch
100" F., Cs. Calcd. Obad. (Ea. 1) 3.50Q 3.5 6.40a 6.5 11.W 12.3 12.3 19.Za 18.8
k.v. a t -
S'ISCOSITY-TE~~PERATUREPROPERTIES O F n-PARAFFINS
k . ~ a. t 210' F., Cs. Calcd. Obsd. (Eq. 2) 1.41a 1.41 2.10a 2.11 3.20a 3.16' 3.30 3.15 4.40a 4.45
Cas (9) Lquations (1) log (k. I. a t 100" F.) = 2.968 log A f , W t . -6.524 (2) log (k. w. a t 210' F.)= 0.6i9 log ( k . z . a t 100' F.) -0 (3) V.T.N. = 118 log (k. a . a t 100" F.) +138
222
V.T.N., Obsd. 205 231 268 278 286
V.T.N,,
V.T.N.,
(Eq. 3)
(Eq. 4)
202 233 264 263 289
203 233 265 267 289
Calcd.
Alkyl Group
Literature Cited
a t 210" F., Cs. Calcd. Obsd. (Eq. 2) 0.87 0.87 0.96 1.15 1.61 1.94 1.94 2.37 2.38 2.81 3.01 3.26 3.51
k.
8.
Equations (1) log ( k . u. a t 100' F.) = 2.718 log M . W t . -5.872 log (k. u . a t 210" F.) = 0.704 log ( k . w. a t 100' F.)- 0 . 2 3 3 3) V.T.N. = 112 log (k. I. a t 100" F. +146 (4) V.T.N. = 159 log ( k . 2 ) . a t 210° F.1 +183
y)
Calcd.
t°F.. 2 CY., Obsd. 159 216 278 285 320
F., 2 Ce., Calcd. (Eq. 5) 159 217 274 273 323
t
Mol, Wt. 240 296 366 366 422
hlol. Wt., Cdcd. (Gq. 1) 241 296 361 361 428
(4) V.T.N. = 174 log (k. L'.a t 210' F.) 1 1 7 7 ( 5 ) t ' F. (2 cs ) = 222 log ( k . 2 . . a t 100' F.j +38 a Extiapolated froin published d a t a .
TABLE11. VISCOSITY-TEMPERATVRE PROPERTIES k. v. a t 100' F., Ca. Calcd. (Eq. 1) Obsd. 1.78 1.7 1.7 1.765 2.1 2.01a 2.45 2.5 4.2 4.21 5.6 5.61 5.6 5.50a 7.4 7.30a 7.4 7.36b 9.3 9.28 9.3 10.26b 11.5 11.6 13.1 13.68
Vol. 41, No. 2
B.T.S., Obsd.
1.T.X.. Calcd. (Eq. 3)
O F >~OKO-n-A~LKYLBEKZEPiES
T.T.S., Calcd. (Eq. 4)
t
F, 2 CE., Obsd. 86
t OF., 2 Cs., Calcd.
(Eq. 5 )
Mol. Wt.
Mol. w t . , Calcd. (Eq. 1)
86
(5) t O F. (2 cs,) = 240 log ( k . I. a t loOD F.) +28 Extrapolated frol,, publisl,ed data, b Converted from Saybolt Cniveraal viscosity.
a
-
TABLE111. Alkyl
Group
Literature Cited
VISCOSITY-TE&fE'ERATURE PROPERTIES O F bfONO-)2cLkLKYLCYCLOHEXAPiES
a t 100' F., Cs. Calcd. Obsd. (Eq. 1) 2.36a 5 . 52a 7 . 65Q 10.42b 10.4a 13.10b 13.24 16.5 19.80
k.
I.
k. 0. a t 210' F.J& Obsd.
Calcd.
(Eq. 2)
Equations 1) log ( k . u. a t 100' F.) = 2.840 log M. Wt. -6.059 2) log (k.u. a t 210' I?.) = 0.710 log ( k . u. a t 100' F.) -0.245 3) V.T.K. = 142 log ( k . U . a t 100' F.) $118 4) V.T.N. 200 log ( k . w. a t 210' F.) +167
-
Alkyl
Group
Cd
cI8
Literature Cited
V.T.N., Obsd.
v.rr.N.,
v.T.N.,
(Eq. 3)
(Eq. 4)
Calcd.
Calcd.
OF., 2 Cs
~QF.,zc~.,
Qbsd:
Mol. M't.
Mol. Wt., Calcd. (Eq. 1)
Calcd. 5) 168 324
M 01. Wt. 2 12 380
9101. Wt., Calcd. (l4q. 1) 214 375
368
434
439
Calcd. (Eq. 5)
O F. (2 os,) = 216 log ( k . 1). a t 100' F.) f 4 0 Extrapolated from published data,
(5) t a
Converted from Saybolt .Universal viscosities.
TABLE Iv. ~TISCOSITY-TEhfPERATUREPROPERTIES O F P-nIONO-n-BLKYLNAPHTHALENES looo F., Cs. k. u. a t 210' l?.,C8. V.T.N., V.T.S t'F., t°F..2Cs.,
k. u. a t
Obsd. 4.82 22.86
Calcd.
(Eq. 1) 4.7 23.6
Calcd.
Obsd. 1.41 4.63 (211O F.) 6.53
(Eq. 2) 1.41 4.65
ClZ (8) 35.48 34.1 6.54 Equations (1) log (12. Y. a t 100' F.) = 2.778 log M . Wt. -5.788 (2) log (k. o. a t 210' F.) = 0.770 log ( k . u. at 100' F.) -0.378
V.T.S., Obsd. 173 278
Calcd. (Eq. 3) 173 279
310
309
173 279
2 Cs., Obsd. 109 322
309
370
Calcd."
(Eq. 4)
(Eq
(3) V.T.N. = 157 log (k. I. a t 100' F.) ~ 6 6 (4) V.T.N. = 204 log (k. I. a t 210' F.) +143 ( 5 ) t F. (2 cs.) = 231 log ( k . v. a t 100' F.) +10
temperature span between two fixed viscosities change viscosity more slowly with temperature. However, the viscosity-temperature number does not designate the position of the viscositytemperature curve with respect to temperature. -4s will be explained presently, the viscosity-temperature number must be considered together with the viscosity a t some definite temperature in order to complete the evaluation of these properties.
plished by selecting equalion types Irom grapliic studies, and calculating the necessary constants from the available data. By this means, empirical equations of the f'o!lowing simple linear types have been devised for each of the series:
V.T.N. = A log ( k . ~ a. t t,)
+B
log (k.v.at tl) = C log (k.v.a t h) $. D
(3)
(4)
VISCOSITY-TEMPERATURE IN HOMOLOGOUS SERIES
Among the hydrocarbons for which data are available in the literature are four different homologous series: The n-paraffins, the mono-n-alkylbenzenes, the mono-n-alkylcyclohexanes, and the @-mono-n-alkylnaphthalenes. An attempt has been made to correlate the viscosity-temperature data and the molecular weights of compounds in these series, This has hoen accom-
The letters A-J, inclusive, represent constants characteristic of the series; L.v. is kinematic viscosity, tl and tz a,rc any arbitrarily eeleoted temperatures, and M . Wt. is molecular weight. Equation 7 was obtained from Equations 3 and 6.
ld0
210
Z!O
2!0
2!D
ZbD
3;
3iO
310
370
VISCOSITY-TEMPERATURE NUMBER
Figure
3.
371
INDUSTRIAL AND ENGINEERING CHEMISTRY
February 1949
Viscosity-Temperature in Series of Hydrocarbons
Homologous
0 = &n-alkylnaphthalenes; 0 = mono-n-alkylbenzenes; mono-n-alkylcyclohexanes; X = n-para5ns
0
-
Tables I to IV give equations oi the above types for the four homologous series of hydrocarbons and comparisons of calculated with observed data. It would be desirable to have more extensive data, including more compounds of the same series and also different series, to determine the limits of applicability of such relations and, if possible, to establish them on a fundamental basis. I t appears that such equations may prove useful in permitting the prediction of complete viscosity-temperature properties of individual hydrocarbons which are not' available. Such relationships also give important, and somewhat unexpected, information regarding comparative values for different structural types of hydrocarbons. They demonstrate that as different hydrocarbon types increase in molecular weight in their respective homologous series, they do not necessarily maintain their same relative positions witth respect to viscosity-temperature (when compared on a basis of equal viscosities a t a specified temperature). This is shown in Figure 3, which is a graphical representation of Equation 3. Below about 9 cs. (log of 9 = 0.95) a t 100" F., mono-n-alkylbenzenes have flatter viscosity vs, temperature curves than mono-n-alkylcyclohexanes, but beyond that point, the reverse appears t o be true. Data for the n-paraffins are included in Figure 3 as a matter of interest. Although these data are inadequate to establish precisely the location of the viscosity-temperature number vs. log k.u. line, apparently the higher viscosity n-alkylcyclohexanes also may have flatter viscosity vs. temperature curves than the n-paraffins of corresponding viscosities. Furthermore, although the P-n-alkylnaphthalenes of relatively low viscosities appear to change viscosity rapidly with temperature in comparison with the other three types of compounds, the more viscous members of the series may actually change viscosity more slowly than the other types of compounds (assuming that the higher molecular weight compounds are still liquid, and that the linear relationship persists). Evidently, generalizations regarding the relative viscosity-temperature properties of different structural types of hydrocarbons, over any considerable molecular weight range may not be justifiable.
Previous investigators @ , 5 , 6 ) have made observations generdlp similar to those given here, but their conclusions have been based on more empirical, less reliable methods of evaluation. Data available in the literature therefore have been carefully studied, making use of the viscosity-temperature number. As indicated above, however, the following observations should be reviewed with the reservation that more information concerning higher molecular weight hydrocarbons must be obtained before the limits of applicability can be known. Increasing Viscosity. It has been shown (Tables I t o IV) that in homologous series, the viscosity-temperature number increases with molecular weight and viscosity. This tendency for more viscous liquids to have higher viscosity-temperature numbers has been observed to be general, in studies of several hundred different liquids (IO). Thus, a compound may have a high viscosity-temperatare number merely because its structure promotes high viscosity, whereas other structures at the same viscosity level would make the viscosity-temperature number even higher. It is therefore important to recognize that, as previously pointed out, while the viscosity-temperature number denotes the shape of the entire viscosity vs. temperature curve, the viscosity a t a particular temperature must be considered also in completing the whole viscosity-temperature picture. This tendency toward higher viscosity-temperature numbers with higher viscosity at a specific temperature should be borne in mind in considering the following sections. Chain Branching. Examples of the effect of chain branching are given by the series of C26 hydrocarbons shown in Table V. The viscosity is not changed greatly but the viscosity-temperature number becomes lower with branching. This effect appears to be greater, the larger the side chain or the greater the degree of branching. Position of Side Group. The effect of the position of a side group in a chain molecule is demonstrated clearly in Table VI. Side groups appear to decrease the viscosity-temperature number least when nearest the end of the molecule. Cyclization. Table VI1 shows the effects of cyclization in the branched molecules, Q-n-octylheptadecane and 7-n-hexyleicosane. In every case, cyclization increases the viscosity a t 100' F.
TABLEV.
Literature
Compound
ON
VISCOSITY-
Xinematio __liiscosity, CS.
Cited
loOD F.
210° F.
V.T.N.
(6) (9)
11.5 11.6a
3.30 3.20"
278 268
(6)
11.48
3.03
255
C4-&-C*-&-C, CZ
(6)
12.18
2.85
232
c2--&- e21
(6)
11.66
3.29
275
(6)
11.48
3.03
255
(6)
10.69
2.86
248
(6)
10.08
2.73
243
(6) (6)
10.39 11.71
2.75 2.89
242 235
k-C28 c4
C4-4-C,, c4
c4
C4
c4-dl-cll c6
C e - L
CS
Clo--b-cl0
cz-c-c2
clo-L-cto clo-c-clo
4
EFFECT OF STRUCTURE ON VISCOSITY-TEMPERATURE PROPERTIES
The viscosity-temperature properties of hydrocarbons are profoundly affected by the arrangement of atoms within the molecules, and these structural effects are of considerable interest.
EFFECTO F CHAIN BR.4NCHING TEMPERATURE
e-A-c e
Extrapolated from published data.
INDUSTRIAL A N D E N G I N E E R I N G CHEMISTRY
372
EFFECT OF SIDE-GROUP POSITION o s VISCOSITY-TU~IPCRATURC
TABLE VI. Literature Cited
1
Kinematic Viscosity, C s . 100' F. 210° F. 3.30 3 20a
V.T.N. 278
3.03
2s;
3
2 93
290
4
2.83
246
5
2.78
2 44
6
3.33
275
7
12.88
3.40
269
a
13.54
3.35
26 1
14.31
.
3 3x
284
3.38
2io
Cs-C-C11
13.90
3.20
244
16.5
4.13
280
17.29
4.13
285
15
15.96
3.85
27.5
16
lL94
3.80
263
17.44
3.70
2%
17.00
3.65
2.52
16,lQ
3 5%
217
13
14
0
C -C-Cis
c:--c-c,j
IR
10
246
3 28
Although some of the cyclized compounds show some increase in viscosity-temperature number, this increase secnis less than might be expected from the viscosity increase. Cyclopentyl cyclization seems to have greatest effect on viscosity-temperature number increase n-ith respect t o viscosity increase. The effect of cyclization to a condensed ring structure is shoa-n by conipa,risoii of the follovi.ing t,wo compounds: Literature Cited
(5)
14.v. a t 100" F. (cs.)
\-.T&
15.12
265
45.67
274
Cyclization causes a large viscosity increase, 1vit.h a relatively small increase in viscosity-temperature number. This is similar to the effect of simple cyclization in branched compounds. In contrast to cyclization of side chains, terminal cyclization appears to have only a slight effect on viscosit,y-temperaturc properties. This has been noted previously in comparing homologous series of mono-n-alkyclcyclohexanes and mono-n-alkylbenzenes wit,h n-paraffins. It is furt,her evidenced by the series of C26 hydrocarbons given in Table VIII. Hydrogenation of Aromatics. I n all cases studied, hydrogenation of aroma:ic groups, both single and condensed, increases
'vI A
10
I1
V.T.N.
/ 12
17 (6)
Kinematic Viscosity. Cs__ 100a F. 210' F.
Compound
268
2
9
Vol. 41, No. 2
'
Ca-C-CII
(' E x t i a p o l a t c d froin published
data
t,he viscosity-temperature number. Hydrogenation also increases the viscosity a t 100" F., and, particularly in hydrocarbons containing more than one ring; this viscosity increase appeals to be more than enough to account for the increase in viscositytrmpcrature number as shovm, for exannple, in Table SrII. VISCOSITIES OF 13YDROG.ARBON MIXTURES
Thc viscosity-temperature number has bceii found to bo approximately a linear function of the composition of binary hydrocarbon blends. Likewise, the temperature at which a binary mixture has any specified viscosity is usually a linoar function of the cornposition, as deinonstrat,ed in Figure 4. I t is thus possible to estimate the viscosity-temperature propertics of such a binary hydrocarbon blend from the viscosity-tcmpcrature properties of the components and the composition of the blend, by using the linear relationship to calculatx two viscosityteinperat,ure points. For example-lines 1 and 4 in Figure 4, rcpresent the temperatures corresponding to 5 and 50 cs., rcspectircly, for blends of SAE 60 oil in SAE 10 oil. For any given niirtu1.o composition, temperatures corresponding t o 5 and 50 cs. can be cltlculatjcd easily or read from the graph. From t'hcsc two viscosity-tcmpcrature points, viscosities of the inixturc a t any desired temperatures may be determincd by t,he use of t h o -4.S.T.M. viscosity chart. Conversely, it is possible to estimate the composition from the viscosity-t,emperat,ure propertics. A somewhat different method, based on the same principle of constant viscosity, has been described by Wright ( 1 1 ) . The above linaar relation has been generalized t o provide a
INDUSTRIAL AND ENGINEERING CHEMISTRY
February 1949
373
,
for the mixture are obtained; from these, viscosities at any desired temperatures can be estimated readily from the A.S.T.M. viscosity chart. The application of this method to multicomponent mixtures of lubricating oils is illustrated in Table IX. The same method was applied to two complex mixtures of hydrocarbons prepared under A.P.I. Project 42 ( F ) , with results suminarized in Table X.
COMPOSITION, VOLUME %
Figure 4.
Composition us. Temperature of Hydrocarbon Mixtures at Constant Viscosity
SAE 60 oil in SAE 10 oil, 5 os.; (2) SAE 60 oil in light pale oil, OS.; (3) .9-cycloheryleioosane in 11-neopentylheneioosane, 3 os.; (4) SAE 60 oil in SAE 10 oil, 50 ca.; (5) SAE 60 oil in light pale oil, 50 os.; (6) 9-cyclohexyleicosane in 11-neopentylheneicoaane,30 CB. (1)
5
means of estimating the viscosities of multicomponent mixtures of hydrocarbons from the viscosities of the components, as follolvs:
t (mixture of n components)
=
rltl
+
+ . . . . . xntn
ZZ~Z
*.Lf
(9)
2.
IBO0
where t is the temperature corresponding t o any specified vi+ cosity; x is the volume fraction in the mixture; and subscripts (I ....n) denote the individual components. By calculating t (mixture) for two viscosities, t v o viscosity-temperature points
COMPOSITION, 70 V.I. IMPROVER
Figure 5 . Composition us. Temperature of Six Viscosity Index Improvers in Lubricating Oils at Constant Viscosity
TABLE VII. EFFECT O F CYCLIZATION I N BRANCHED HYDROCARBONS ON VISCOSITY-TEhfPER.4TURE Kinematic Viscosity, Cs. Literature Cited
Compound
(5)
8.93
2.49
250
2
cs-A-cs
(6)
9.38
2.53
232
3
c*-C-Cs
14.72
3.29
245
4
cB-&-C*
11.53
10.13
253
25 68
4 64
264
(6)
10.69
2.86
248
(6)
14.35
3.28
246
(6)
17.00
3.65
252
14
(6)
18.59
3 72
248
15
(6)
36.41
5 31
269
I -
*
O
Cz(r=. I/
170
2 91
210'
V.T.N.
C
C 6 - L
F.
F.
CS
1
100'
243 Cia
12.61
2.88
23 1
11 C6-A-C6 Cia 12 ~
CIS
13 6
C,-L-C2(3>
(6)
33.49
4.98
C e - k D
251 C1a
(6)
16.05
3.57
253
INDUSTRIAL AND ENGINEERING CHEMISTRY
374
EFFECT OF TERMINAL CYCLIZATION ON VISCOSITYTEMPERATURE
TABLE VIII.
1
Kinematic Viscosity, Cs. 100' F . 210' F. 11.5 3.30 11 .6a 3.20"
Literature Cited
Compound n-Cse
*
V.'I'.N 278 268
(6)
11.5
3.33
279
3
=czo
(5)
16.5
4,13
'290
4
)C I ?,
(5)
13.9
3 80
290
Q
Extrapolated from Published d a t a .
concentrations of improver in that oil and plotting viscosity index vs. concentration. This method may not be applicable to some types of improvers which have not been investigated, but where the linear relations hold, the method shows promise of having considerable practical utility. ACKNOWEEDG~~ENT
The assistance of L. C. Roess, E. C. Knowle3, C. C. Towne, H. D. Kluge, and F. C. Toettcher in many helpful discussions is apprecint'ively acknowledged. Other members of the Beacon Research Laboratory staff, including F. W. Morgan, oooperated by contributing the viscosity data for oil mixtures and oils containing viscosity iridex improver.
TABLEIX. ESTIMATION OF VIWOSITIE~ OF COMPLEX
LITERATURE CITED
LUBRICATING O I L X h X T C R E S Volume, Oil
%
.4 B
10
at
4.98 8.17 11.11 10 14.98 10 D 19.6 10 E 25.7 10 F 35.8 10 G 53.3 H 10 92.9 I 10 J 484.8 10 Mixture,ealcd. 2 4 . 0 obsd. 23.1
io
c
a
Viscosity a t 210' F.
k.0.
loOD F.
Cs.
S.U.S.a
1.63 2.12 2.52 2.89 3.34 3.87 4.60 5 ,75 8.54 17.53 3.8 3.68
33.3 34.7 35.9 37.4 39.0 41.3 45.0 54.2 87.9 38.8 38.4
e
F,, 2
Cs.
,..
284 279
Vol. 41, No. 2
Y.,Shen, G. and Wood, C. E., J . Inst. Petroleum, 26, 514- 31 (1940). (2) Larsen, R. G., Thorpe, R. E., and Armfield, F. A , , ISD. E N G . CHEM.,34,183-93 (1942). ( 3 ) Mikeska, L. A., I b i d . , 28, 970-84 (1936). (4) Otto, M., Miller, F. L., Blackwood, A . J., and Davis, G. H. B., Refiner iVutural Gasoline MJ'T,* 13, 411-22, 425 (1934), (5) Schiessler, R. W.,Clarke, D. G., Rowland, C. S., Sloatman, W.S., and Herr, C. H., Proc. Am. Petroleum Inst., 24 (ILI), 49-74 (1943). (6) Schiessler, R.Vi'., Cosby, J. N., Clarke, D. G., Rowland, C. S., Sloatman, W. S., and Herr, @. H., Petroleum Refiner, 21, 383400 (1942). (7) Schmidt, A. W., and Grosser, 9., Ber., 73, 930-3 (1940). ( 8 ) Schmidt, A. W., Hopp, G., and Schoeller, V., Ibid., 72, 18937 (1939). (9) Schmidt, A. W., Sohoeller, V., and Eberlein, K., Ibid., 74, 131324 (1941). (10) Texas Co., unpublished work. (11) Wright, W. A., presented before the Division of Petroleum Chemistry a t the 109th Meeting of the AXERICAN CHEMICAL SOCIETY, Atlantic City, N. J. (I.) Ju, T.
F,, 100 CS. - 16 10 24 37 47 57 69 81 97 140 o
V.T.N. 199 207 214 215 221 226 231 241 270 210 229 226
55
53
Saybolt Universal seconds.
PREDICTING THE EFFECT O F VISCOSITY INDEX IMPROVERS
Various polymeric materials long have been known to raise the viscosity indexes of petroleum oils when present in small concentrations. By application of the principle of considering temperatures at fixed viscosities, a number of these mat'erials have RECEWED June 9 , 1947. Presented before the Division of Petroleum Chem.. been shown to behave normally in binary mixtures, as though SOCIETY, Atlantic i s t r y a t t h e 111th Meeting of the AMERICANCHBXICAL they were merely viscous oils of slow rates of change of viscosity C i t y , X~ J. with temperature, as would be expected of long chain polymers. By use of the linear relations discussed in the preceding section, it has been found possible to extrapolate to 1 0 0 ~ viscosity o index TABLEX. ESTIMATION OF VIscosIrrms OF Cobriucx improver, t o find blending temperatures corresponding to fixed IIYDROCARBON RIIXTURES viscosities. Whether or not these blending temperatures are Mixture S o . 1 2 identical with extrapolated values for the pure viscosity index 22 17 improver is unknown but it is immaterial as long as the linear 11 13 13 t o 52 17 t o 117 rclat,ions hold for all practically useful concentrat>ions of im13.6 16.8 13.49 prover. The blending temperatures appear to be charact'eristic 16.1 3.31 3.48 of the viscosity index improver and independent of the oil t o 3.50 3.30 256 242 which the improver is added. 255 248 From data of Otto, Miller, Blackwood, and Davis (4) on blends of Exanol, an olefin polyO F VISCOSITY I N D E X h P R O V E R I N LUBRICATIXC OILS TABLE XI. EFFECT mer, Exanol blending temperatures were found to k . u . a t 100' F., k.v. at 210' F., Visoosity be approximately 3075" F. a t 5 cs. and 805" F., Exanol, Cs. cs. Index at 500 cs. The use of these values is shown in % Calcd. 0bsd.a Calcd. Obsd.a Calcd. Obsd. Oil Table XI, nrhich shows fairly good agreement beCoastal distillate 0 77.5 ... 7.06 ... 26 358 S.U.S.b/lOO: F, 0.5 95 95.5 8.35 8.48 46 51 tween ohservcd and calculated viscosities for 49.2 S.U.S./210 F. 1.5 136 135.7 11.6 11.90 75 80 blends of Exanol in three different lubricating oils. 3.0 225 220.8 18.0 18.4 95 09 5.0 395 401 30.6 31.3 111 111 Similar results have been obtained for several 00 Viscosity index disother viscosity index improvers, as indicated by tillate 0 , ,. 64.1 . ., 7.71 ... 91 296 S U S 100' F. 0.5 77 74 2 8.9 8.89 97 100 Figure 5, vhich demonstrates the linearity of the 51.4 'S.b~'k./210° F. 1.0 91 90.6 10.6 10.40 103 106 relationship bet>Teen concentration of improver 125 121.4 13.7 2.0 13.76 112 114 287 123 125 5.0 286.2 28.8 28.7 and temperature corresponding to a fixed viscosity. Pennsylvania 0 ,,. 61.2 . .. 6.99 .._ 100 Sft,er the viscosity index improver blending 237 S.V.S./lOO" F . 0.5 00 :9.0 8.1 7.89 111 106 values have been obtained from viscosity data 49 s.U.S./210° F. 1.0 72 (1.9 9.3 9.76 113 119 9 3 . 5 1 2 . 3 120 120 2 . 0 98 1 2 . 6 0 for blends in one oil, the amount of improver re5.0 215 226.1 26.0 130 128 26.0 quired t,o bring any other oil to a desired viscosity a Converted from Saybolt Universal viscosities. b Saybolt Universal seconds. index may be estimated graphically by calculating viscosities at 100' and 210" F. for a number of ~~
,
,
I
