2000
INDUSTRIAL AND ENGINEERING CHEMISTRY
( 5 ) Depev, H. A, IND.ESG. CHEM.,26, 1187 (1934). (6) Dietz, T. J., and Hansen, J. E., Rubber Age, 68, 699 (1951). (7) Fletcher, M. J., ArtificialLimbs, 15-24 (January 1954) : Advisory Committee on Artificial Limbs, Natl. Research Council, Advisory to Veterans Admin. and U. s. Army, O5ce of Surgeon General, Washington 25, D. C. (8) Guth, E., Proc. dnd Rubber Technol. Conf.,London, 1948,paper 20. (9) International Union of, Pure and Applied Chemistry, J . Polymer Sci., 8, 257 (1952). (10) Keilen, J. J., and associates, IND.ENG.CHEX, 44, 163 (1952). (11) Le Bras, J., and Piccini, I., Ihid., 43,381 (1951). (12) Leonard, F., Cort', I., and Blevins, T. B., Ibid., 43,2500 (1951). (13) Milton, C. L., and associates, Metal Finishing,45, 61 (1947). (14) blonsanto Chemical Co.. St. Louis, Mo., Tech. Bull. M-76-A, July 1947.
Properties Prooerties I
r
P
Vol. 46, No. 9
(15) Keverdeebm, G. van, and Houwink, R., Rec. g e m . caoutchouc, 18, 253 (1941). (16) Kuessle, -4.C., and Kine, €3. B., IXD,ENG.CHEM.,45, 1287 (1953). (17) Parkinson, D., Trans. Inst. Rubber Ind.,19, 1.31 (1943). (18) Rabbit, R. O., Rubber Age, 48,97 (1940). (19) Riddle, E. H., Chem. Eng. News, 31, 2854 (1953). (20) Schildknecht, C. E., "Vinyl and Related Polymers," p. 231, John Wiley, New York, 1952. (21) Schippel, H. F., IXD.ENG.CHEY.,12, 33 (1920). (22) Schmidt, E., Ibid.,43, 679 (1951). (23) Trommsdorff, E., Kunststofe. 29, 45 (1939). (24) R'iegand, W. B., IND. ENG.CHEM.,17, 939 (1925). (25) Wiley, I-from !he bulk oi solvent estracts of crude oil by an alcohol-ext'raction procedure. Therefore, portions of the PS and PI extracts were extracted ' extract with absolute ethyl a,lcohol. The solubilities of t,he 1s and PI est,ract in alcohol viere 83 aiicl 36%, respe spectra of the alcohol-soluble po~lioiisof the PS a n are sho1r.n in Figure 3 (concentrations as indicat,ed). The positione of the absorptioii peak at 330 nip acd the ri~x1~c.r peak a t 570 inp in the PS extract and the xcak absorption hantls a t 560 mp and 570 mp in the PI extract suggest th fair aniounts of the nickel-porphyrin complex aiid le of t,he vanadium-porphyrin complex. The major peak of 1hc synthetic nickel complex is a t 330 iiig ( I I ) , and the major pe;tli of the vanadium complex is a t 570 nip ( 1 5 ) . The alcohol extraction ac:conipliahrd some eonceiiwation of the porphyrin contents of the tmo portions of n-atei-spray extract. However, the separation x a s not as successful as tha;: observed with the alcohol extraction of solvent fractions of this crude oil (11). Accordingly, part of the PI extract vas w b divided by successive ext.raction with hexane, iso-ort:inc, cyclohexane, aiid benzene. The distribution of the PI extrart among these solvents was approximately 25, 10, 35, and SO%, respec-
.:
I
t
550 .LENGTH, m p
Figure 2.
600
4bsorption Spectra of \Iesoporph> rin IX Dirnethjl Ester Concn.. 6.15 X 10-3 If.
1
IS, L i,4
\
.21, ,
4 50
,
,
500
PENTANE
,
,
,
,
,
,
,
- SOLUBLE
2.2 WT. %
,
550
,
,
600
,
6 0
WAVELENGTH, mp
Figure 3. Absorption Spectra of Alcohol-Soluble Portions of PI and PS Water-Spray Extrarts in Ethanol
INDUSTRIAL AND ENGINEERING CHEMISTRY
September 1954
tively. The absorption spectra of the pentane-, hexane-, isooctane-, and cyclohexane-soluhle portions of the water-spray extract are shown in Figure 4. The cyclohexane and benzene fractions shotved no evidence of selective absorption. However, the high content of light-absorbing niaterial in these fractions prevents the detection of weak absorption peaks. The spectra in Figure 4 resemble spectra obtained with alcohol-soluble portions of successive solvent extracts of this crude oil ( 1 2 ) The major peak a t 550 mp and
2 HEXANE 3 150-OCTANE
7c
I Wt % 2wt %
4CYCLOHEXANE 0 3 ~ 1 %
450
500
600
550
2003
other properties of water-spray fractions obt'ained in duplicate extraction seri2s are given in Table 11. The interfacial activity of the crude oil was lowered by the extraction process, but no appreciable change in film formation was observed. The interfacial activit'y and film formation of the total extract are slightly greater than in the original crude oil. This is evidence that the water-spray process removes some of the interfacially active and film-forming constituents from this crude oil. These results generally corroborate similar observat,ions of Rartell m d Kiederhauser (.h) but indicate that the water-spray ext,raction process was rather inefficient. The considerable degree of interfacial activity and film formation of the material forming a stable emulsion in the aqueous phase is of interest although the amount of material is small. The porphyrin and nitrogen contents of the crude oil also mere decreased by the extraction process. The tot'al extract had a slight,lyhigher content of these substances than the crude oil, but thedifferencewasnot large. The changesinporphyrin and nitrogen content result'ing from the extraction process are similar t o the changes in interfacial act'ivity discussed above. This correlation may be extended to the PS and PI extracts. The PI extract had very high contents of porphyrin and nitrogen and a correspondingly high degree of interfacial activity and film formation. The porphyrin and nit>rogencontents and the int,erfacial activity of the PS extract were slightly loiver than in t>he extracted crude oil.
650
WAVELENGTH. m i i
Figure 4. Absorption Spectra of Successive Fractions of Water-Spray Extract
weak absorption bands a t 510 nip and 570 mp are as observed previously. However, the absorbance a t 570 mp in the isooctane extract is strong enough to form an actual peak, whereas there was only a weak absorption band at this wave length with the alcohol-soluble portion of the iso-octane extract previously studied (11). Further, a weak absorption band a t 530 mp is observed in the hexane-soluble and iso-octane-soluble portions of the Rater-spray extract. This absorption band is attributed to the minor peak of the vanadium-porphyrin complex and had not been detected previously.
TABLE 11.
SOME PROPERTIES O F
TT'ATER-SPR4Y FRACTIONS
(Data obtained from duplicate extraction series with exception of nitrogen determinationa which were made with fractions from second e x h e t i o n series Interfacial Film Total Tension& Formahkiterial Porphyrin Nitro- Decrease, tion, Balance, Aggregate, gen, Dynes/ % Drop Fraction Grams P.P.M. Wt. Yo Cm. Length Whole crude oil 4%,2 185 0.76 7.4b GO Extracted crude oil (raffinate) 363.4 420 .68 6.9 GO PR extract 62.5 390 ,GO 6.7 20 PI extract 0.3 1,550 2 38 15.9 95 Tot,al rxtract 68.8C 495C 0.810 8.4 80 Emulsion in aqueous phase 2.3 0 9.0 GO a I n 0.12 a-eight ,% benzene solutions a t water interface. b Interfacial tension a t benzene-water interface = 33.7 dynes/cm. C Contents of total extract were calculated from data for PS and PI extracts.
..
For the first time it has been possible t o identify interfacially active and film-forming constituents of petroleum that were concentrated in a mater-spray extraction process. Porphyrin Aggregate Determinations. In an effort t o make the identification of metal-porphyrin complexes in the water-spray extract more positive, the metal nnd porphyrin contents of the Rater-spray fractions were determined. The nickel and vanadium contents of these fractions from the first extraction series are listed in Table I. Average values of porphyrin contents and
Figure 5 .
Absorption Spectrum of Desoxophylloer>-thrini n Pyridine (3)
The pentane extraction of the water-spray extract was much more effective in concentrating the interfacially active components and those containing nitrogen, nickel, vanadium, and porphyrin than \vas the water-spray extraction. A comparison of the properties of the PI extract arid of the pentane-insoluble portion of this crude oil 1s of interest. The pentane-inqoluble portion of the propane precipitate (11) of this crude oil had the following values for properties of the PI extract listed in Table 11: porphyrin aggregate, about 1500 p.p.m.; interfacial tension decrease of 0.12 weight % solution. 10.9 dynes pei em.; film formation, 90%; interfacial tension decrease of the porphyrin aggregate, 22.7 dynes per em.; amount of rrude oil remaining in precipitate, 10%. The asphaltic materials of this crude oil a e r e precipitated by slowly pouring the crude oil into a large volume of n-pentane with violent agitation. The precipitate thus formed was similar in appearance t o the pentane-insoluble portion of the propane precipitate, amounted t o 9.4% of the crude oil, contained 2.11 wt. % nitrogen, and exhibited an interfacial tension decrease of 11.3 dynes per em. in 0.12 weight % solution.
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
2004 CHj
C2H5
/
C
CH
L
m
PhYLLOFOPFLlYRlY
Figure 6.
;; 'co,r
H
X SESOXCF-~YL.OERVT~71lJ
Structural Formulas o f Some Hematin and Chlorophyll Derivatives
The PI extract resembles, in appearance, the aqhaltic material precipitated by t'he pent,ane-dilution method. Ilovever, the PI extract exhibits a greater degree of interfacial activity and film formation and appears l o be a slight,ly more refined extract than does the pentane-insoluble portion of the whole crude oil. This is further evidence that the water-spray extmction partly separates the interfacially active components of the crude oil. Absorption Spectra of Porphyrin Aggregate. The porphyrin aggregates isolated from the water-spray fractions were subjected to further study in an attempt to learn more of their origin and propert,ies. The absorption spectra of porphyrins in organic solvents generally are charact,erized by four major maxima in the visible region. Howevcr, t8hereare small differences in the relative intensit,ies of the maxima that may furnish a key t o the specific type of porphyrins involved. The four niaxima or
Vol. 46, No. 9
peaks comnionly are labeled I, IT, 111: and IF', proccedirig from longer to shorter wave length. Fisher ( 1 3 ) descrihes h r e e gericval types of spectra for various porphyrins. These are the rhodo, phyllo, and etio types. The &io and phyilo spectra are of the greatest interest in studying porphyrins from petroleum and there are two readily detectable differences between these til-o types of spectra. Thesc are: (lj The etio spectrum has a weak peak b e h e e n peaks I and 11, la~helcclIa and located at about' 590 mp> that is absent in the phyllo spectrum; and ( 2 ) in the et'io spectrum the peaks bocome progressively stronger proceeding from longer to short,er r a v e lengths. T h a t is, in relative intensity, the peaks of the etio spectrum are arranged IV > I11 > I1 > I. In thc 'pliyllo spectrum, peak I11 oftcn is no5 as strong as peak II ( 1 2 ) . The designation "etio" for a general type of spectrum is rather confusing since this type of spectrum is charaoterisbia not only of etioporphyrins (decarboxylated) but also of the majo porphyrins (2). This point is illustrated by reference to F in Khich it is observed t,hat the epectrum of mesoporphyrin IX dimethyi ester is of thc etio t,>-pe. The phyllo spectrum normally results from subetitut ioii 011 one of the four methene carbons that link the four pyrollc rings (3j. This subst,itution on a methene carbon atom ocoiii's in chlorophyll derivatives such as dejoxophylloerythrin and iiliylioporphyrin ( 6 ) . The spcctrum of dcsoxophyllocrvthrin (3) is reproduced in Figure 5. Treibs (18>f$) d a t e s that decal tion of desoxophylloervrhrin c a u m no change in its sp Further, decarboxylation of mcsoporphyrin I S 'LO form etioporphyrin results in no definite changes in the type of spectrum. The structural formulas of t,hesc compounds appear in Figure ti. The porphyrim prepared from chlorophyll commorily havc: spectra of the phyllo type and those prepared from henloglobin coinnionly have spect,ra of the et'io type. There arc: a fcw indi> 6 , 1934.
CORRESPONDENCE Editor’s Note: Both of E. G. Scheibel s communications concerning his paper, ”Physical Chemistry in Chemical Engineering,” published as part of the Fine Chemicals Symposium [IND. ENG. CHEM.,46, 1.569 (1954)], were referred to C. R. Wilke, who suggested that they be published without comment on his part at this time.
Liquid Diffusivities SIR: Liquid diffusivities are involved in the correlation and interpretation of the performance data on equipment that effects a transfer of a material to or from a liquid phase as in liquid-liquid extraction, absorption, distillation, and leaching. Xone of the theoretical approaches have yielded equations that can predict this diffusivity with satisfactory accuracy. Wilke ( 4 ) has expressed the liquid diffusivities in an equation of the form derived by Eyring ( I , 2 ) based on the theory of absolute reaction rates. This equation approaches the Stokes-Einstein equation for large molecules and requires the introduction of an empirical constant evaluated from a family of curves. The reference curve was developed for the wide range of data on water, and the other curves were arbitrarily constructed parallel to this curve a t one end and approaching it a t the other end. These curves were based on a limited range of data, and certain inconsistencies in the data can be noted. The parameter of the curves decreased to 0.7 as the molecular volume of the solvent increased to about 100. However, in order to handle the data on miscellaneous solvents available in the literature (most of which had this molecular volume or higher), Wilke recommended a parameter of 0.9 as giving the most probable value of the diffusivity. It is possible to express Wilke’s correlation by the empirical equation
F = 1.22
x
107 1
+
($y3
The value of F so determined is used to calculate the diffusivity according t o the equation
Equation 1 is in perfect agreement with Wilke’s curve for water over the entire range of the data, but the equation approaches the
theoretical slope required by the Stokes-Einstein equation a t a slower rate than M7ilke’sextrapolated curve, so the equation givee values about 10% higher a t solute volumes of 3000. No data are available in this region and the uncertainty of extrapolation was noted by Wilke in showing a clashed curve in this region. Equation 1 also shows perfect agreement with Wilhe’s curve for niethanol solvent over most of the range of the data and the calculated values for benzene as the solvent passes through the bulk of the data, but i t gives lower values than Wilke’s curve a t low solute volumes while all the observed data lie above his curve in this region. As the molecular volume of the solute approaches that of the solvent or becomes smaller, the mechanism for diffusion changes. I n the case of water, Equation 1 holds to V A = V B and thereafter, if the value of the denominator is retained constant a t this maximum value, the single point of data for hydrogen agrees Lvith the calculated diffusivity. I n the case of methanol, Equation l holds to VA = 1.5 V B without deviation. This represents the smallest value of VA for which data are available, and more data are required to establish the lower limit with this solvent. On the other hand, data for benzene solutions hold to BA = 2 8 8 , and then by maintaining the denominator constant a t this value, the points at the lower values of VA that lie above Kilke’s curve can be calculated correctly. The data on other miscellaneous solvents agree with the equation if tlie denominator is maintained a t some maximum value . an average value, the between V A = 2VB and V.4 = ~ V B As ~ then the equation may be assumed to hold to V A = 2.5 V B and denominator may be maintained constant a t this maximum value of 2.13 for the miscellaneous solvents. There is no theoretical reason for the denominator to remain constant at low values of VA; b u t since all the available data in this region consist of one or two scattered points, it is impossible to empirically develop any theory. The investigation of the diffusivities of small molecules in solvents of large molecules may lead to better understanding of the theory of the liquid state. The complete equation for liquid diffusivity from Equations 1 and 2 becomes 1
D
= 8.2 X 10-8-
Il
+ (3g)2’3 (3)
__-___
