Solvent Extraction of Diesel Fuels

HE rapid increase in the use of high-speed Diesel engines for automotive and locomo-

tive as well as for stationary power has led to a large increase in the demand fur suitable fuels. Be- tween 1032 and 1936 the annual sale of Diesel horsepower increased from 130,000 to 1,830,000. There has also been a tendency toward Diesel engines of lower horsepower, for it has been estimated that 90 per cent of the installations in 1936 were engines of less than 100 horsepower (6).

These smaller high-speed engines will require approximately an additional 7,500,000 barrels of fuel on the basis of 4.5 barrels per horsepower per year. Most of this additional fuel will necessarily be of higher ignition quality than that used for the large slow-speed engines because the high-speed engines operate under widely varying conditions of load and speed. It is under such conditions that results accompanying the use of unsatisfactory fuels are most easily noticed. Under light load conditions, rough running, exhaust fumes, and increased fuel consumption are more easily observed. Less evident but more important effects following the use of unsatisfactory fuels are carbon deDosits on t h e sDrav

T Solvent Extraction of

Diesel Fuels C. G. DRYER, J. A. CHENICEK, GUSTAV EGLOFF.

AND J. c. MORRELL Universal Oil Products Company, Riverside, Ill.

Solvent extraction of cracked Diesel fuels with sulfur dioxide and furfural produced raffinates with improved ignition quality without materially affecting other physical properties. The improvement depended upon the solvent, the percentage removed, and the method of extraction. The rdffinates showed unchanged susceptibility to a pour-point depressant. The extracted portions had high-octane blending values and low pour points.

Extraction of straight-run fuels caused less improvement in ignition quality than solvent treatment of cracked fuels.

Acid treatment resulted in a negligible increase in ignition quality. Hydrogenation of fuels of low sulfur content produced fuels of high ignition quality.

nozzles, exhaust valve deposit;, an& piston-ring gum formations.

A survey of twenty-five manufacturers of high-speed Diesel engines showed that fuels with a minimum cetane number of 45 are recommended for high- speed engines (IS). Fuels of similar ignition quality are also recommended for use in Diesel electrolocomotives. The Army Air Corps and the Bureau of Aeronautics of the Navy specify fuels for aircraft purposes with a minimum Diesel index of 60 and a minimum aniline point of 150" F.

It is essential that large quantities of fuels of high ignition quality be available in order to ensure the continued develop- ment of the Diesel engine. Straight-run fuels produced from various crudes appear to have a sufficiently high cetane number to operate most high-speed engines. Cracked fuels, derived from crudes of various fieIds, however, have an average cetane number of 35 which is well below that recommended by the engine manufacturers (12). A fuel of sufficiently high ignition quality for most purposes probably can be made by blending straight-run and cracked fuels in the proper proportions. However, fuels for aircraft engines, besides having high ignition quality, must have other desirable properties such as low cloud and pour points. Straight-run fuels which have high ignition quality unfortu- nately have high pour points and consequently cannot be used a t low temperatures such as those accompanying use in aircraft. Cracked fuels, on the other hand, have low pour points but also low ignition quality. Woods (23) found that it is possible to prepare fuels of good ignition quality and lowered pour point by blending cracked and straight-run oils. However, it is necessary to use a straight-run fuel of very high ignition quality. The quantity of such fuels is limited, and therefore the possibility of producing fuels of

high ignition and low pour point by this method is limited. Woods' data follow:

Straight-run fuel, '% 0 20 40 60 80 100

Diesel index No. 43 48 53 58 66 71 Pour point, O F. -40 -25 -5 15 30 50

Cracked fuel, 100 80 60 40 20 0

As previously stated, the need for Diesel fuels of high ignition quality and low pour point necessitates the use of special refining processes. The following are possible methods of treatment : solvent extraction, hydrogenation, acid treatment, mild cracking, dewaxing, addition of dopes, addition of pour-point depressants, blending of straight-run and cracked fuels, and polymerization.

The work included here is concerned primarily with the first of these methods-namely, solvent extraction-which is considered most important. Results obtained by the use of some of the other methods are included for comparison.

Various other means of producing high-quality Diesel fuels are possible, but before discussing these methods it would be desirable to show the relation of physical properties and chemical composition to ignition quality.

Ignition Quality The ignition quality of a fuel is determined by the ignition

delay or the amount of time elapsing between injection and combustion of the fuel. Paraffins have the shortest and aromatics have the longest ignition delay; consequently, they have, respectively, the best and poorest ignition quality. Naphthenes, isoparaffins, and olefins fall between these two

813

814 INDUSTRIAL AND ENGINEERIKG CHEMISTRY VOL. 30, NO. 7

extremes. The effect of a paraffinic side chain on the ignition quality of a Diesel fuel is much less than it is on the antiknock properties of gasoline. The ignitibility of cetane is scarcely effected by.the introduction of a side chain, and no appreciable effect is apparent unless there is a large number of side chains (8). Kreulin (16) was able to show that the chemical composition of a Diesel fuel and its cetane number are closely related. He was able to calculate the cetane number to within five units by the use of the following expression:

cetane value = 0.2 A + 0.1 N + 0.85 P where A = aromatic ring content

N = naphthenic ring content P = paraffinic side-chain content as determined by the

The standard method of evaluating ignition quality is the determination of the cetane number in a standard test engine operated under specified conditions. By cetane number is meant the percentage of cetane in a reference fuel composed of that hydrocarbon and a-methylnaphthalene which has the same ignition characteristics as the fuel being investigated. This test is probably the best available method of evaluating Diesel fuels but involves considerable expensive equipment. For this reason numerous ignition quality expressions have been advanced which are based on readily determined physical properties of the fuel such as aniline point, specific gravity, etc. Certain Diesel engine manufacturers and fuel consumers prefer to specify ignition quality in terms of the Diesel index number proposed by Becker and Fischer (2) :

ring analysis method (21)

aniline point ( O F.) X gravity at 60' F. ( O A. P. I.) 100 Diesel index =

This expression is used more widely than any other since it is readily calculated and can be correlated with the cetane number as determined in an engine.

The viscosity-gravity number, which depends on the specific gravity and kinematic viscosity, has been suggested by Moore and Kaye (17). Their formula is a modification of one used by Hill and Coats in connection with lubricating oils (10) :

G = 1.082 A = 0.0887 + (0.776 - 0.72A) X loglog (KV - 4) where G = specific gravity a t 60" F.

A = viscosity-gravity constant KV = kinematic viscosity at 100' F., millistokes

The boiling point-gravity number was proposed by Jack- son (14):

G = A + (68 - 0.703A) log BP where G = gravity, O A. P. I.

A = boiling point-gravitz constant B P = 50% boiling point, 0.

The Universal Oil Products characterization factor was suggested by Watson and Xelson (26) :

Ta' '3 K = - S where Tb = molal av. boiling point, O Rankin

In the case of Diesel fuels the 50 per cent distillation point in degrees Rankin is used instead of the molal average boiling point. The use of the parachor, a function of the surface tension which was first suggested by Sugden (20) as a method of determining molecular constitution, was introduced by Heinoe and Marder (7) :

0.25 specific parachor = - sp. gr.

where CY = surface tension

The same authors recently used the Siedekennzifler (boiling characteristic) in conjunction with the parachor to determine ignition quality (9). They believe that, while the physical methods of determining ignition quality give an approximate value, the method ,would be more accurate and more useful if the chemical composition of the oil were taken into consideration. The ignitibility of a member of a series of hydrocarbons varies with the molecular weight. Therefore, if a property of the fuel which is related to the molecular weight is used in a formula for expressing ignition quality, the formula should become more accurate. Heinze and Marder at- tempted to do this by the use of the Siedekennzifler. This property is determined by distilling the fuel in an ordinary Engler-Ubbelohde apparatus and noting the temperature a t which 5, 15, 25, etc., up to 95 per cent of the fuel by volume distills over. The sum of these recorded temperatures is then divided by 10. The value thus obtained is roughly proportional to the average molecular weight of the oil. By the combined use of this value and the specific parachor Heinze and Marder claim to be able to calculate cetane numbers which do not vary more than 1.9-2.1 from values determined on an engine.

The ignition quality number (11) also attempts to take into account the nature of the molecules composing the oil by combining the 50 per cent distillation point of the fuel with the Diesel index number :

* G X A X B P = 100,000

where Q 5 ignition quality number A = aniline point, O F. G = gravity at 60" F., O A. P. I.

B P 5- 50 per cent distillation point, O F.

All of these expressions for ignition quality give results which can be correlated with cetane numbers %s determined in the standard engine. However, the usefulness of most of the formulas is limited since they cannot successfully be applied to doped fuels, fuels of origin other than petroleum, or the standard reference mixture of a-methylnaphthalene and cetane. They are sufficiently valuable, nevertheless, to war- rant their use as a means of following the efficiency of a solvent extraction. It will be shown later that the increase in ignition quality is a function of the amount of fuel extracted by a given solvent.

Previous Work Those constituents of a lubricating oil which impair its

value are the same as those that decrease the ignition quality of a Diesel fuel. It is reasonable to assume that the same types of solvents can be used to extract Diesel oils as are used t o treat lubricating oils. In both cases the object is to remove undesirable constituents-i. e., aromatics and olefins- and to increase the paraffinicity of the oil. However, the need for Diesel fuels of high ignition quality is relatively re- cent, and consequently little is available on this subject in the literature.

Edeleanu (4) has several patents for the production of fuels of high ignition quality by extraction with liquid sulfur dioxide. Two methods of obtaining such fuels are outlined: (a) an extraction of up to 75 per cent by volume of the constituents soluble in liquid sulfur dioxide or (b) an amount not exceeding 30 per cent of a raffinate produced by liquid sulfur dioxide extraction is added to a Diesel oil. Pyzel (18) discussed the use of sulfur dioxide to extract gas oils to yield raffinates suitable for compression ignition engines and extracts which give, on cracking, gasolines of high antiknock value. More recently Marder (16) improved brown-coal Diesel fuels by extraction with a sufficient quantity of a

JULY, 1938 INDUSTRIAL AND ENGINEERING CHEMISTRY 815

selective solvent. The raffinates thus produced were stable and could not be distinguished either by appearance or be- havior from the best petroleum Diesel oils. Glacial acetic acid was also suggested as a solvent for the extraction of the Diesel oil fraction of petroleum (1).

Feigin, Obleukhova, and Prorokov (5) treated a gas oil from Balakhany topped crude with furfural. They were able to increase the Diesel index by 12 units by extracting 38 per cent of the fuel a t 20" C.; this is not a very large increase, considering the amount removed, but the extract could be converted into aviation fuel by hydrogenation :

Volumes Raffinate, Sp. Gr. a t Diesel Furfural % 150 c . Index No.

0 1 2 3

0 ,898 6 2 . 4 73:O 0 .884 6 8 . 4 6 4 . 0 0.874 7 2 . 2 6 2 . 0 0.870 7 4 . 3

Woods (23) extracted several Diesel fuels a t 25" F. with liquid sulfur dioxide. Batch procedure was used, and the sulfur dioxide was allowed to boil off a t atmospheric pressure. Last traces were removed by caustic and steaming in an open vessel for several minutes. These experiments shorn that cracked fuels can be extracted to produce raffinates of substantially improved ignition quality but that treating losses are relatively large. I n order to make the solvent extraction of Diesel fuels commercially feasible, some use for the extracted portions must be found.

Solvent extraction has the advantage of increasing ignition quality without causing a large rise in the pour point of the fuel. A raffinate of 60 Diesel index was obtained with a pour point of -35" F., whereas a straight-run fuel with the same Diesel index has a pour point of about 15" F. The use of more than two volumes of solvent is questionable, for the results indicate that the increase in Diesel index is too small to compensatefor the treating loss and rise in pour point. Table I, taken from Woods, also shows that the low-grade straight-run f'uels do not respond to solvent treatment as well as the cracked fuels.

Steffen and Saegebarth (19) also recently investigated the action of liquid sulfur dioxide a t 30" F. on straight-run paraffinic, straight-run nonparaffinic, and cracked gas oils. They found that the cracked gas oils were especially sus- ceptible to treatment and that the straight-run paraffinic fuels were least improved. The results they obtained are as follows:

Son used, vol. % 0 50 100 300

Straight-run paraffinic oil:

Straight-run nonparaffinic oil:

Raffinate, weight % Diesel index No.

Ra-ffinate, weight % Diesel index No.

Raffinste, weight % Diesel index No.

Cracked gas oil:

100 68

100 47

92 73

82 48

90 75

77 61

84 79

55 67

100 65 56 49 40 62 73 81

Woods (23) also investigated the possibilities of other methods of producing fuels of high ignition quality and low pour point. Mild cracking carried out in an iron bomb a t 70G800" F. for 2, 4, or 8 hours caused a lowering of the pour point but there was a considerable cracking loss and decrease in ignition quality. In one case the pour point was lowered from 35" to -20" F., but there was a cracking loss of 19.1 per cent and the Diesel index number fell from 62 to 50.

Pour point depressants such as wool fat or Paraflow, when added in amounts of 0.1 and 0.3 per cent, were most effective on those fuels which already had low pour points so that their use is limited. Other workers (3) also found that fuels of high pour point are not greatly affected by the addition of Paraflow alone but that compounding is necessary to produce fuels of low pour point.

Woods (23) also determined the effect of solvent dewaxing on the ignition quality of Diesel fuels. Dewaxing losses were large but it was possible to obtain a fuel of low pour point from a straight-run oil of high ignition quality. A stock with an original Diesel index number of 73 and a pour point of 55 O F. had a Diesel index of 58 and a pour point of - 30 " F. after naphtha dewaxing treatment. Woods also carried out acid treatment of fuels with 98 per cent sulfuric acid a t room temperature. Treating losses were large and there was relatively small gain in ignition quality. Woods concluded that of all the methods used, solvent extraction offered the greatest possibilities.

Experimental Procedure The object of the present investigation was to determine

the effect of extracting various amounts of fuels with several solvents, on the properties of representative straight-run and cracked fuels. The relative efficiency of two solvents, furfural and liquid sulfur dioxide, was determined, and the results of extraction with these solvents were compared with results obtained by other methods. No attempt to recom- mend specifications for Diesel fuels to be used in high-speed engines was made.

The solvent extractions with furfural were carried out in a continuous countercurrent extraction tower:

The tower consisted of a glass tube 120 cm. (47.2 inches) long and 4 cm. (1.6 inches) in diameter fitted with inlets and outlets for the fuel and solvent. The fuel was pumped into the tower through an inlet tube fitted with a sintered-glass disk which projected in 16 cm. (6.3 inches) from the bottom of the tower. The sintered-glass disk was made from 40-mesh ground glass and served to break the entering fuel into small droplets. The solvent was pumped into the top of the tower through a similar tube which projected in an equal distance from the top of the tower. The space between the inlet and the outlet tubes was filled with glass Raschig rings of uniform size. The treated fuel or raffinate was removed at the top of the tower, and spent solvent was removed at the base of the column. The spaces between the inlet

Treat, Yo TABLE I.

--loo- 7 - - z x loo-- --3 x 100- 7 4 x 100-7 -5 x loo--. 0 Raffinate Ext. Raffinate Ext. Raffinate Ext. Raffinate Ext. Raffinate Ext

EXTRACTION OF DIESEL FUELS WITH SULFUR DIOXIDE

Fuel cracked a t 395-650' F.: Yield, 70. 76 24 67 33 59 41 51 49 44 56

Aniline point, O F. 130 1.17 79 156 80 161 85 163 96 164 102 Diesel index No. 43 07 13 65 15 68 18 70 22 71 26 Pour point, O F. -40 -35 -50 -35 -50 -30 -50 -15 -50 -5 -50

Yield, % 75 25 65 35 57 43 50 50 41 59 Gravit.y, O,A. <. I. 3 i : 4 3 7 . 2 2 0 . 4 4 0 . 3 2 1 . 6 4 1 . 0 22 .9 4 1 . 8 23 .0 42 .2 2 5 . 6 Aniline point, F . 117 142 43 157 43 161 45 163 72 166 83 Diesel index No. 38 53 9 62 9 66 10 68 17 70 21

-15 -60 Pour point, F . - 50 -50 -50 -45 -55 -35 -55 -25 -55

Gravity, A. P. I. 3 0 . 0 3 1 . 4 . 3 3 . 5 . . 3 5 . 3 ' . . 37 .6 . 3 8 . 0 . . Aniline point F. 152 156 42 159 48 162 56 164 72 166 85 Diesel index No. 45 49 . . 53 . . 157 . . 60 . . 63 . .

Gravity, A. P. I. 33:2 3 8 . 7 161 4 1 . 6 1 8 . 0 4 2 . 3 2 1 . 2 4 3 . 0 23 .0 4 3 . 4 2 5 . 2

Fuel, cracked a t 600-640° F.:

Straight-run fuel (low-grade):

Pour point, F. -25 -25 .. -25 . . -20 .. -10 . . 0 . .

816 INDUSTRIAL AND ENGINEERING CHEMISTRY VOL. 30, NO. 7

TABLE 11. PROPERTIES OF RAFFINATES FROM CRACKED FUELS Furfural as S o l v e n i - - SOX as Solvent -

Pennsylvania Cracked Diesel Fuel Ratio, solvent/solute Raffinate, % Gravity A. P. I Aniline. boint, O F.' Diesel index No. Ignition quality No. Flash point, F. Pour point O F.: 0.5'7 Pdraflow 1.0% Paraflow

Cloud point O F.: 0.5 Par'aflow 1.02 Paraflow

Viscosity at 100' F., sc Total sulfur, % Conradspn cybon, Yo Distillation F.:

Initial b.'p. 10 over 50% over

0 100 30.1 131.7 39.6 21.3 180 5 0

-5 20 n

0.25 92

31.4 139.8 43.9 23.5 164 5

10 10 10

39.0 0.05 0.02

5 -0

0.5 84

33.5 149.5 50.1 27.1 212 5 10 -5 15 15 10

38.0 0.05 0.01

1.0 78

35.5 159.3 56.6 30.3 210 10 5 0 15 15 15

38.0 0.05 0.01

1.5 72

36.9 168.9 61.2 33.2 210 10 10 5 20 20 15

39.0 0.02 0.01

0.3 81

33.6 151.3 50.8 27.3 180 15 10

-15 20 20

5 38.0 0.04 0.01

0.6 75

36.2 162.3 58.8 31.6 185 10 10 -5 15 20 20

38.7 0.04 0.01

0.9 1.2 73 71

36.9 37.3 166.5 168.6 61.4 62.9 33.3 34.1 19(! 175

0 15 15 5 10 5 15 20 20 15 20 20

38.7 39.6 0.03 0.03 0.01 0.01

10 37.2 0.05 0.02

338 476 537 616 660 44

!C.

353 485 535

437 481 540 610 664 49

42 1 480 535 612 661 52

437 486 547 615 657 58

400 474 537 612 650 52

407 475 538 614 654 58

404 480 542 617 658 60

398 480 542 611 654 69

SO7 over E n 8 point

Cetane No. 613 668 47

Mid-continent Cracked Diesel Fuel

Ratio, solvent/solute Raffinate, '7 Gravity, 1. P. I . Aniline point a F. Diesel index No. Ignition guality No. Flash point, F. Pour point, F.:

Paraflow ::g Paraflow Cloud point ' F.: y : g~ Par'aflow

Paraflow Viscosity a t loOD F., I Total sulfur '% Conradson Garbon, '% Distillation, F.:

0 100

28.1 98.2 27.7 13.4 182 < -35

< -35 < -35

0.25 89

29.4 107.6 31.6 15.3 200 -30

< -35 < -35 0

-35 -35 35.7 0.23 0.10

0.54 81

30.9 122.7 37.9 18.2 200 -35

< -35 < -35 -5 -30 -30 35.6 0.16 0.08

0.86 70

32.3 125.6 40.6 19.5 204

1.2 62

35.2 137.3 48.3 23.0 182 -35

< -35 < -35 -25 -30 -30 35.0 0.10 0.04

0.25 89

28.7 102.0 29.3 14.2 185

< -30 < -35 < -35 -30 -35 -35 35.8 0.22 0.28

0.3 72

32.2 123.4 39.7 19.1 180 -30

< -35 < -35 -35 -30 -25 35.0 0.16 0.10

0.5 65

34.5 136.4 47.1 22.6 182 -25

< -35 < -35 -20 -25 -25 35.0 0.13 0.06

0.8 64

35.7 142.2 50.8 24.3 182 -25

< -35 < -35 -20 -25 -30 3.52 0.10 0.03

1.1 63

36.3 145.4 52.8 25.3 180 -30

< -35 < -35 -15 -20 -20 35.4 0.09 0.05

-25 < -35 < -3.5

-5 -25 -35 35.4 0.23 0.14

398 457 484 548 610 35 44

. .. -25 -m -- -30 35.3 0.15 0.07

iec.

425 418 42 1 400 456 454 454 440 485 481 480 476

407 411 404 450 450 445 484 481 480

403 400 444 442 479 478

Initial b. p.

$2 E:: 90% over End point

Cetane No. + 1 % acetone peroxide

554 554 544 543 609 598 607 603 39 41 43 44 47 52 58 63

~. .

556 543 546 616 596 625 39 42 54 .. 50 55 64

546 544 628 611 52 53 65 68

,Mixed East and West Texas Cracked Diesel Fuel

0 100 30.3 118.8 36.0 18.6 165

0.3 88

31.5 128.8 40.6 20.8 175 5

-35 < -35

25 25 20

37.0 0.51 0.07

0.5 84

33.4 137.8 46.0 23.8 180 10

-30 < -35 25 20 20

37.0 0.37 0.06

1.0 75

35.3 152.4 53.8 27.8 180 15

-25 -35 25 30 20

38.0 0.30 0.05

2.0 67

37.4 155,8 58.3 29.8 175 20

-20 -30 25 25 20

37.0 0.20 0.02

0.25 85

31.8 127.2 40.4 20.7 170 10 < -35 < -35 20 15 15

37.0 0.45 0.03

0.5 77

35.0 142.2 49.8 25.4 170 15 < -35

< -35 25 15 20

37.0 0.35 0.05

0.75 66

36.0 148.6 53.5 26.8 170 15

< -35 < -35 25 25 25

38.0 0.28 0.02

0.9 64

36.8 151.7 55.8 29.0 170

10 -30 < -35 25 25 25

37.0 0.25 0.02

375 429 520 643 682 52

Ratio, aolven$/solute Raffinateb 7 Gravity 1. P. I. Aniline boint, O F. Diesel index No. Ignition puality No. Flash point, F. Pour point, ' F.:

Paraflow Paraflow

Cloud point O F.: 0.5 Pa&,flow 1 ,o$ Paraflow

Viscosity a t loOD F., aec. Total sulfur '7 Conradson c'argon, % Distillation, F.:

Initial b. p.

- ;:2 :E:

5 < -35 < -35 Too dark Too dark Too dark

36.0 0.60 0.10

350 423 516 639 687 39

377 394 383 382 432 434 435 424 513 518 516 513

355 424 512 650 674 42

368 418 510 636 676 47

377 424 513 640 672 52

907 over ~ n 8 point

Cetane No. 642 639 642 643 684 687 6 84 684 42 47 49 49

California Cracked Diesel Fuel

Ratio, solvent/solute Raffinateb7 Gravity, 1. P. I. Aniline. point, O F. Diesel index No. Ignition puality No. Flash point, O F. Pour point, O F.: 0.5'7 Paraflow 1.0% Paraflow

Cloud point F.: Par'aflow ?: :B o Paraflow

Viscosity a t 100" F., sec. Total sulfur, '7 Conradson cargon, % Distillation F.:

Initial b.'p.

907 over E n 8 point

3% :E Cetane No.

0 100

30.7 111.6 34.3 16.2 190 < -35 < -35 < -35 10

-25 -30 35.2 0.45 0.06

0.45 87

32.6 125.1 40.8 19.2 180 -35 < -35 < -35 -10 -15 -20 35.0 0.33 0.03

0.9 81

34.7 133.2 46.2 21.5 180 -25 < -35 < -35 -10 -10 -15 35.0 0.27 0.03

1.5 78

34.9 134.6 47.0 21.9 178 -30 < -35 < -35 -15 -15 -15 35.0 0.24 0.03

0.25 85

.32.6 122.4 39.7 18.7 180 < -35 < -35 < -35 25

-25 -25 35.0 0.34 0.02

0.5 78

34.6 135.7 47.0 22.3 175 -25 < -35 < -35 -15 -20 -25 35.0 0.25 0.02

1.0 75

36.0 143.6 51.7 24.5 180 -25 < -35 < -35 -15 -15 -20 35.0 0.20 0.01

409 435 471 561 633 33

395 402 393 433 430 427 471 466 467

412 437 472 565 631 37

41 1 438 475 568 638 44

410 436 474 566 640 48

560 559 562 644 628 639 37 42 42


and exit tubes at the two ends of the column served as settling zones for the separation of solvent and fuel. The level of the interface between the fuel and solvent was regulated by means of a stopcock which controlled the outflow of used solvent. In ac- tual practice the level of the interface was kept at a point near the solvent inlet. The relative rates at which solvent and fuels were pumped into the tower depended upon the amount of fuel to be extracted and upon the solvent used. All extractions with furfural were single stage and carried out a t room temperature. Extraction with liquid sulfur dioxide was carried out in a batch apparatus at -30' F. The solvent and fuels were agitated at this temperature for 30 minutes by means of a motor stirrer and were then allowed to separate into extracts and raffinate layers.

Four cracked fuels from the Pennsylvania, mid-continent, Texas, and California fields were extracted with each of the solvents. Several different percentages of each fuel were removed in order to determine the change in physical properties with the amount extracted. Various ratios of solvent to fuels were used to extract the different amounts of fuels. Four straight-run fuels from the same fields were also treated, but only one extraction with each of the solvents was performed since it was found that these fuels were not materially improved by solvent extraction.

After the fuels had been extracted, the further treatment of the raffinate and extract depended upon the solvent which had been used. Furfural was removed from both raffinates and extracts by vacuum distillation. It was found that, even though the boiling point of the furfural is considerably below the initial boiling points of the Diesel fuels studied, some of the fuels always distilled over with the furfural, as evidenced by the formation of two layers in the distillate. To reduce this loss of the lower boiling constituents of the Diesel fuels to a minimum, the oil layer of the distillate was separated and returned to the system, and distillation was continued until no more furfural remained. The extract portions from the furfural treatments were freed of solvent as indicated above and were then vacuum distilled. In this way the fuel was separated from any furfural-polymerization products produced by the heating.

Sulfur dioxide was partially removed by allowing the extracts and rafhates to come t o room temperature. The last portions were removed by heating on a water bath for a few minutes and then washing with caustic and finally with water. After this treatment the raffinates and extracts were freed of moisture by heating on a water bath under a pressure of 75-100 mm. mercury. It was necessary to remove traces of water because the cloud and aniline points of the fuels are influenced by the presence of moisture.

The cetane number, Diesel index number, ignition quality number, and physical properties were then determined to note the effect of extraction. Paraflow was added to the original fuels and t o their raffinates in concentrations of 0.5 and 1.0 per cent by weight in order to determine the response of the fuels to pour point depressants before and after solvent extraction.

The fuels were also acid-treated for comparison with solvent extraction. Treatment was carried out with 25 pounds per barrel of 98 per cent sulfuric acid at room temperature. The treated fuel was separated from the sludge by decantation.

Several fuels were also hydrogenated in order to compare this method of producing high-ignition-quality fuels with solvent extraction. It was found t h a t hydrogenation could be accom- plished only when the fuel had a relatively low sulfur content. Fuels with larger amounts of sulfur poisoned the nickel catalyst which was used, even after removal of poisoned catalyst and addition of fresh catalyst several times. The fuels of low sulfur content were hydrogenated at a pressure of 100 atmospheres and a temperature of 150" C. (302" F.) for about 20 hours. This treatment did not change the boiling point range of the fuels.

In order to evaluate the results of solvent extraction, it is necessary to consider several factors, such as the percentage of the fuel extracted and the resulting improvement in ignition quality as expressed by the cetane number and physical properties. These results depend upon the treating temperature, method of extraction, charging stock, and selectivity of the solvent used. The selectivity of the solvent and the type of fuel extracted are the most important, and therefore the discussion of results will be concerned primarily with these two factors.

Raffinates from Cracked Fuels The properties of raffinates obtained by the solvent ex-

The traction of four cracked fuels are given in Table 11.

fuels were representative of the Pennsylvania, mid-continent, Texas, and California fields. There was an appreciable increase in ignition quality of the fuels after solvent extraction with either of the solvents. The cetane numbers were raised 2 to 25 units, depending upon the fuel, solvent, and amount extracted. The A. P. I. gravity and the aniline point were increased, and consequently the Diesel index numbers of the fuels were substantially raised since they depend upon these two values. The Diesel index number and ignition quality number increased proportionately as percentage of fuel ex-

D/PSPL /#DPX NUUUER

FIGURE 1. EXTRACTION us. IGNITION QUALITY OF MID- CONTINENT CRACKED DIESEL FUEL

tracted. This is shown in Figure 1 which gives the relation between the Diesel index number and the percentage of mid- continent cracked Diesel fuel removed by each of the two solvents. The amount of fuel removed by a given volume of solvent is dependent upon the aromatic and olefinic content of the fuel. Treatment with a solvent causes a relatively large initial percentage extraction, but additional solvent removes less of the fuel since a large portion of the aromatic constituents is removed by the first treatment. Therefore, for any given fuel there is a certain amount which can readily be removed by extraction but, after this has been removed, i t is necessary to employ large volumes of solvent to cause any appreciable increase in percentage extraction and Diesel index number.

The pour points of these fuels were raised slightly by solvent extraction. The rise in pour point is greater, the larger the percentage of fuel removed by extraction. This is expected since the fuel becomes more paraffinic, and it is the paraffinic hydrocarbons that have the higher pour points. Extraction of 16 per cent of the mixed East and West Texas cracked Diesel fuel raised the pour point from 5" to 10" F.; removal of 33 per cent caused an elevation of the pour point to 20" F. However, the flash point, viscosity, and distillation range were practically unchanged, Total sulfur and Conradson carbon percentages of the raffinates were lower than for the original fuels.

Addition of Paraflow to the raffinates caused about the same decrease in pour point as on the original fuel. Evidently solvent treatment did not influence the response to the pour

VOL. 30, NO. 7 818 INDUSTRIAL AND ENGINEERING CHEMISTRY

TABLE 111. PROPERTIES OF EXTRACTS FROM CRACKED FUELS > Furfural as Solvent 7 SO2 as Solvent 7

Pennsylvania Cracked Diesel Fuel

Ratio solvent/solute Extrabtio?, % Gravity, A. P. I. Aniline. point, O F. Diesel index No. Blending val!e Flash point, F. Pour oint ".F. Viscosity a t 100' F., sec. Total sulfur, 70 Conradson carbon, % Distillation, F.:

Initial b. p. 107 over - 50% over

C!ou$poiLt, F.

0 0

30.1 131.7 39.6

180 5 20

37.2 0.05 0.02

338 476 537 616 660

. . .

0 0

28.1 98.2 27.7

< -35 -5

35.4 0.23 , 0.14

398 451 484 548 610

' i82

0 0

30.3 118.8 36.0

16:

Too dark 36.0 0.60 0.10

350 $423 516 639 687

. . . a

0 0

30.7 111.6 34.3

< -35 10

35.2 0.45 0.06

409 435 471 561 633

. . 190

0.25 8

14.0 -6

-0.8 79 . . . . . . . . . . . . ... ...

... . . . . . .

... . . .

0.25 11

17.2 -4

-0.7 78 . . . . . . ... . . . ... . . .

. . . . . . . . .

0.5 16

12.9 3

0.4 82 230 < -35 -20 42.0 0.15 0.02

1 .o 22

13.0 -1

-0.1 82

240 < -35 -20 38.0 0.12 0.05

1.5 28

13.3 3

0.4 80 240 < -35 -15 40.0 0.11 0.04

0.3 19

14.5 -20 -2.9

79 . . . . . . . . . . . . . . . ...

0.6 0.9 25 27

13.4 13.3 4 -36

0.5 -4.8 85 84 195 195 < -35 < -635

. . . . . . . . .Too dark. . . 38.4 38.2 0.12 0.10 0.18 0.12

1.2 29

13.2 -2

-0.3 86 190 < -35 38.0

0.12

. . . . . . . . .

. .

456 $60 474 501 000 516 533 530 542

... . . . ... 412 410 378 478 475 468 528 528 528

907 over E n 8 point

607 594 609 660 640 661

Mid-continent Cracked Diesel Fuel

~~. .. . 616 612 616 ... 664 664 644

Ratio solvent/solute Extrahtion, % Gravity, ' ,A. $. I. Aniline, point, F. Diesel index No. Blending val te Flash point, F. Pour oint, O F. ClouBpoint 0 F. Viscosity at'1000 F., sec. Total sulfur, % Conradson carbon, 70 Distillation ' F.:

In i t id b.'p. 107 over 50% over

455 364 414 . . . 420 410 413 410 474 467 473 . . . 458 459 459 458 499 498 498 . . . 494 494 495 495

90% over End point

545 543 545 . . . 582 583 576 579 588 589 593 . . . 622 624 628 637

Mixed East and West Texas Cracked Diesel Fuel

0.3 0.5 16

11.4 8

0.9 79 230 < -35 10

42.0 1.78 0.09

1.0 25

10.9 8

0.9 81 240

< -35

2.0 33

12.6 -2

-0.3 79 215

< -35 -15 43.0 1.60 0.07

0.25 0.5 0.75 15 23 34

17.4 16.1 15.2 10 -10 -17 17 -1.6 -2.6

0.9 36

14.4 -20 -2.9

12 11.6

8 0.9 80 . . . Blending value

Flash point, ' F. Pour point, ",F. Cloud point F. viscosity at'1000 F., sec. Total sulfur, % Conradson carbon, % Distillation, O F.:

Initial b. p. 107 over 5_0% over

66 . . . ... < -35 < -35 . . . .Too dark. . . . 38.0 39.0

. . . ' is0 180

. . . . . . . . . . . . . . . . . . 0:3i4 0:3i2

. . . 185 < -35

39.0

0:288

. . . . . . . . . . . . . . . . . . . . .

. ~~

- 10 44.0 1.70 0.15

. . . 445 436 407 . . . 377 366 375 ... 497 504 493 . . . 438 43 1 435 ... 554 559 ' 554 . . . 530 524 524

. . . 642 646 640 . . . 636 646 646 ... 676 683 676 ... 678 670 676 907 over E n 8 point

California Cracked Diesel Fuel

Ratio solven t/solute Extrabtion % Gravity ''A. P. I. Aniline boint, F. Diesel index No. Blending value Flash poinhOo F. Pour point, F. Cloud point O F. Viscosity at'10O0 F., sec. Total sulfur, % Conradson carbon, % Distillation, e F.:

Initrial b. p.

- i:g :E

0.45 13

15.5 -8

-1.2

0.9 1.5 19 22

15.6 15.5

0.25 15

18.7 -6

-1.1 75

0.5 22

17.5 -15 -2.6

80 190

< -35 Too dark 35.0

1.0 25

17.4 -30 -5.2

81

-23 -11 -3.6 -1.7

80 80 210 215

<-35 (-35 <-35 <-35 36.2 36.5 1.21 1.41 0.04 0.10

...

... . . . ... . . . . . . . . . ... . . . . . .

. . . 0:271

. . 396 439 . . 468 471 . . 498 502

408 438 475

. . . . . . ... . . 562 576 . . 626 647

... 574 . . . ... 620 . . . 907 over E n 8 point

point depressant. However, some of the fuels were more responsive to Paraflow than others. The pour point of the Pennsylvania cracked fuel was lowered from 5" to -5" F. by addition of 1 per cent of Paraflow (Table 11); the pour point of the mixed East and West Texas cracked oil was lowered from 5" to below -35" F. by the addition of an equal amount of depressant. Cloud points were practically unchanged by the addition of Paraflow.

Table I1 also shows that the raffinates were more suscep- tible to Diesel dopes than the untreated fuels. When one per cent of acetone peroxide was added to the mid-continent

cracked Diesel fuel the cetane number was raised 8 units; addition of the same amount to the raffinates showed increases up to 15 cetane numbers (Table 11). Fuels of high ignition quality, therefpre, can be prepared by extraction alone or by solvent extraction and doping, with or without the addition of a pour point depressant.

The above results are the general changes in physical properties after solvent extraction. The extent of these changes, however, is determined by the charging stock and the solvent used as the extracting agent. The more selective the solvent-i. e., the greater the difference in solubility of the de-


tG% over End point

Cetane No.

90.r over En3 point Cetane No.

TABLE IV. EXTRACTION OF STRAIUHT-RUN FUELS Furfural as Solvent SO2 as Solvent

Original Raffinate Extract Raffinate Extract

Pennsylvania S traight-Run Diesel Fuel

0 100

40.8 178.9 73.0 39.6

170 15 5 0

25 25 20

39.0 0.04 0.02

352 474 542 620 GSO

64

. . .

0 100

34. I 149.4 50.9 26.8

205 -20

< -35 < -35 -10 -10 -10 38.0 0.88 0.09

430 480 527 595 638

47

. . .

1 . 0 1 .0 0 . 5 91 9 96

41.4 19 .3 41.2 184.3 56.0 181.8 76.3 10 .8 74.9 41.4 . . . 40.7

56 . . . '205 . . . 175

20 . . . 15 5 ... 5 5 . . . 0

30 . . . 25 30 . . . 25 30 . . . 25

39.0 . . . 37.0 0.04 . . . 0.05 0.01 . . . 0.001

428 ... 366 487 . . . 474 543 ... 543 630 ... 630 668 . . . 668

88 . . . 67

West Texas Straight-Run Diesel Fuel

0.95 96

36.2 156.2 56.5 29.4

0.95 4

15.0 -1

-0.2 . . .

0 . 5 90

36 .0 160.0 59.4 31 . ? . . . 77

-15 . . . -20 < -35 . . . < -35 < -35 . . . < -35

205 . . . 205

15 . . . -5 -15 . . . - 10 -20 . . . -10

37.8 . . . 38.0 0 .58 . . . 0.60 0 .08 . . . 0.05

429 . . . 428 470 . . . 482 520 . . . 531 597 . . . 596 640 . . . 644 51 ... 54

0 . 5 4

17.8 0.0 0 .0 ... ... . . . . . . . . . . . . . . . . . . . . . ... ... ... . . . . . . . . . . . . . . . . . .

0.5 10

14.4 -26

-3.7 . . . . . . . . . . . I . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... . . . . . . . . .

Furfural as Solvent SOz as Solvent Original Raffinate Extract Raffinate Extract

Mid-continent Straight-Run Diesel Fuel

0 100

37.5 148.5 55.7 27.3

144 -15 -25

< -35 -10 -10 -5

35.7 0.19

0.004

364 43 1 490 580 627

52

. .

0 100

33.4 141.8 47.4 24.6

' i66 -15 < -35 < -35

5 0 5

39.0 0.71 0.03

3 89 452 519 612 677

41

1 .0 91

39.0 158.0 61.6 30.0

' i72 -15 -25

< -35 -5 -5

1.0 9

17.0 -8

-1.4

79 . . . ... ...

0.6 87

40.5 160.9 63.9 31.3

160 -10 -15 -20

-5 -5

...

-5 . . . -5 35.1 ... 35.1 0 . 1 1 ... 0.11

0.000 ... 0 t 002

365 . . . 432 . . . 487 ...

370 43 0 490

California Straight-Run Diesel Fuel

1 .0 1 . 0 0 . 5 93 7 88

35.7 14.8 35.4 150.6 0 152.2 53.8 0.0 53.9 27.2 . . 27.7

174 ... 175 -5 ... 0 < -35 . . . < -35 < -35 . . . < -35 10 . . . 10 0 . . . 0

. . . so . . .

0 , . . 0 37.0 . . . 37.0 0.53 , . . 0.03 . . . 0 : 005

388 440 505

378 438 514

613 . . . 614 662 . . . 662

43 . . . 47

0 . 5 13

17.6 - 24

-4.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

0 . 5 12

1 8 . 3 -4

- 0 . 7

77 . . . . . . , . . . . . . . I . . . . . . . . . I . . . . . . . . I . .

I , .

1 . .

. . . . . .

sirable and nondesirable components-the greater is the improvement in the properties of the resulting raffinates. The selectivity of a solvent is influenced by (a) the temperature, (b ) the ratio of solvent to solute, and (c ) the method of extraction. These factors will be discussed in greater detail later. Without consideration of the above factors, the relative selectivity of solvents can be estimated from the improvement in properties resulting from extraction of a given amount of fuel. Thus if two solvents are equally selective under the conditions used, they will yield raffinates with the same ignition quality when they extract the same amounts of the fuel.

From the results given in Table I1 it appears that sulfur dioxide is more selective than furfural. Extraction of approximately equal amounts of the mid-continent cracked Diesel fuel with sulfur dioxide and furfural yielded raffinates with Diesel indices of 52.8 and 48.3, respectively (Table 11). Treatment of other fuels also shows sulfur dioxide to be more selective, if the fuels are almost completely extracted. If, however, only part of the aromatics are removed, then sulfur dioxide does not seem to be more selective than furfural, as indicated by the properties of the resulting raffinates.

Extracts from Cracked Fuels The extracted portions of the fuel must also be considered,

both from the standpoint of possible usefulness and as an- other means of determining the selectivity of the solvents. Since the purpose of extracting these Diesel fuels was the improvement of ignition quality by removal of aromatic and

other undesirable constituents, the selectivity of a solvent can be determined qualitatively from the properties of its extracts. Aromatic hydrocarbons have a higher specific or lower A. P. I. gravity than paraffinic hydrocarbons. Consequently the solvent which best separates a fuel into its aromatic and paraffinic fractions should yield extracts with lower A. P. I. gravities. Table I11 shows that certain of the extracts from the sulfur dioxide treatments have lower A. P. I. gravities than those obtained by extraction of equivalent amounts with furfural.

The extracts have very low aniline points since they are composed largely of aromatic hydrocarbons. All of the aniline points below 0' F. are, however, necessarily inaccurate because the aniline solidifies a t these low temperatures, but they do indicate the essentially aromatic character of the extracts.

A more valuable property from the standpoint of possible usefulness is the blending value. Blending values of from 79 to 86 were obtained for extracts from cracked fuels, varying with the solvent, the fuel, and the amount extracted. High- est blending values were obtained for extracts from treatment with the most selective solvent, sulfur dioxide. The value did not vary as much with the fuel and amount extracted as did the Diesel index number and cetane number of the raffinates. Extracts with practically identical blending values were obtained by extracting from 8 to 28 per cent of the Pennsylvania cracked fuel with furfural (Table 111). The high blending values of the extracts suggest their use as a blending stock for tractor fuels or as cracking stock for the production of high- antiknock gasolines.

820 INDUSTRIAL AND ENGINEERING CHEMISTRY VOL. 30, NO. 7

The aromatic content of the extracts lowers the pour points below those of the original fuels. Pennsylvania cracked fuel extracts had pour points below -35" F.; the original fuel had a pour point of 5" F. (Table 111). The viscosity, distillation range, and flash points of the sulfur dioxide extracts are substantially the same as those of the original fuels. The flash point and distillation range of the furfural extracts are higher than those of the original fuels because some of the lighter ends are lost during the recovery of the furfural by vacuum distillation. The solvents also concentrate the sulfur-containing and carbon-residue-forming components of the fuels in the extracts.

Extraction of Straight-Run Fuels Table IV gives results obtained by extraction of straight-

run fuels from Pennsylvania, mid-continent, Texas, and Cali- fornia fields. I n general, the results show the same trend as those for the cracked fuels; but since the straight-run fuels are more paraffinic, less of the fuel is extracted and consequently there is not so much improvement in properties. Since only a small fraction of the fuel was easily removed, only one extraction was made with each solvent. The cetane numbers and Diesel indices were improved a few units. Ex- traction of 9 per cent of the mid-continent straight-run fuel with furfural increased the Diesel index from 55.7 to 61.6 and the cetane number from 52 to 58 (Table IV). Proportional changes were made in each of the other fuels. As in the case of the cracked fuels, the raffinates had a lower sulfur and Con- radson carbon content but all of the other properties were substantially the same. The extracted portions of the straight- run fuels showed blending values that varied with the nature of the original fuel. The Pennsylvania fuel (the most paraffinic) gave extracts with high aniline points and low blending values; the California fuel (the least paraffinic) yielded extracts with low aniline points and relatively high blending values. The blending value of the extract varied with the solvent as well as with the nature of the fuel extracted.

These results indicate that liquid sulfur dioxide is the most selective solvent studied for the extraction of both cracked and straight-run fuels. It was previously pointed out that the selectivity of a solvent depended, among other things, upon the temperature and method of extraction. Since all of the sulfur dioxide extractions discussed were carried out by batch procedure, several fuels were extracted with furfural in the same apparatus to determine the effect of the method upon the selectivity of the solvents. It was known that a continuous countercurrent procedure is a more efficient way of solvent treatment but the exact difference was unknown. Table V gives a comparison of the batch and continuous methods of operation. It is apparent that the countercurrent

TABLE V. INFLUENCE OF EXTRACTION METHOD ON SELECTIVITY Furfural as Solvent

Fuel Original Countercurrent Batch Mid-continent cracked:

Extraotion 7% ... 19 18

Diesel index No. 27.7 3 7 . 9 35 .5

Gravity, O'A. P. I. 28 .1 30.9 30 .9 Aniline point, O F. 98 .2 122.7 115.0

Pennsylvania cracked: Extraction % ... 16 14 GrFvity, ''A. P. I. 30 .1 33 .5 3 2 . 5 Aniline. point, F. 131.7 149.5 143.4 Diesel index No. 39 .6 50.1 4 6 . 6

11 California cracked:

i i ) :7 32 .6 3 2 . 3 Extraction % Gravity ''A. P. I. Aniline boint, ' F. 111.6 125.1 122.4 Diesel index No. 3 4 . 3 4 0 . 8 3 9 . 4

7 3 8 . 3

Extraction % Gravity, ','A. P. I. 37 .5 3 9 . 0 Aniline point, ' F. 148.5 158.0 154.6 Diesel index No. 55 .7 61 .6 5 9 . 2

13

Mid-continent straight-run: ... 9

procedure gives the better results when the same temperature and ratio of solvent to solute are used., I n all cases the continuous method gave raffinates with Diesel indices about 2 units greater and also extracted a slightly larger amount of fuel per volume of solvent.

Table VI shows the influence of temperature on batch treatment with each of the two solvents. Extractions of the mid- continent cracked Diesel fuel with furfural a t 20", O", and -30" F. gave raffinates which had the sktme Diesel indices, within experimental error, as raffinates produced by extraction at room temperature. However, the percentage of fuel extracted a t lower temperatures was slightly less than at room temperature, and consequently the improvement in ignition quality for a given percentage extraction would be slightly greater if lower extraction temperatures were used. Extraction with liquid sulfur dioxide a t 10" F. produced a raffinate with a Diesel index 3 units lower than that resulting from treatment a t - 30 " F.

TABLE VI. INFLUENCE OF TEMPERATURE ON SELECTIVITY OF MID-CONTINENT CRACKED DIESEL FUEL

Ani!ine Diesel Treatment Extraction Point Gravity Index

% ' F . A . P . I . Untreated 0 9 8 . 2 28 .1 2 7 . 7 Furfural-treated:

Room temp. 18 115.0 3 0 . 9 3 5 . 5 20' F. 13 112.8 3 0 . 7 34 .6 O o F. 13 112.1 30 .3 3 4 . 0 -30' F. 12 113.2 3 0 . 5 3 4 . 5

10' F. 30 141.1 35 .4 49 .9 -30' F. 37' 145.4 3 6 . 3 52 .8

Sop-treated:

TABLE VII. ACID TREATMENT OF DIESEL FUELS Cracked Fuels Straight-Run Fuels

Mid-continent:

Acid- - ilcid- Original treated Original treated

Treating loss, To ... 5 . 5 3 . 2 Aniline point, F. 9 8 . 2 102.2 148:5 150.6 Gravity a t 60' F., A. P. I . 2 8 . 1 28 .3 37 .5 37 .5 Diesel index No. 2 7 . 7 28 .9 55 .7 56 .5

Pennsylvania: Treating loss, 3 1 . 7 1 . 4

Gravity at 6 0 ° F . , ' A . P. I. 30.1 3 0 . 3 4 0 . 8 40 .8 Diesel index No. 39 .6 40 .7 7 3 . 0 7 3 . 5

Aniline point, F. i i i : 7 134.2 i i S : 9 180.2

California: Treating loss, 3 3 . 5 2 . 4

Gravity at60' F., O A. P. I. 30.7 30.7 33 .4 34 .1 Diesel index No. 34 .2 3 5 . 2 47 .4 49 .4

Aniline point, F. i i i : 6 114 .8 i4i:s 144.8

Treating loss, 3 4.8 a 2 . 2 " Aniline point F. lis18 123.6 i49:4" 161.25

East and West Texas:

Gravity at 66' F., A . P. I. 3 0 . 3 30 .3 34.10 34.7" Diesel index No. 36 .0 3 7 . 4 50.9n 52.5"

0. West Texas straight-run fuel.

The results obtained by solvent extraction indicate that this method of improving ignition quality has d e h i t e possibilities, especially for cracked fuels. The fact that the raffinates show a greater response to Diesel dopes than do the untreated fuels suggests the possibility of a combination of solvent extraction and doping. Solvent treatment causes a large increase in ignition quality up to a certain percentage extraction, and then as more fuel is extracted the ignition quality as expressed by the Diesel index rises more slowly. Therefore, i t would perhaps be more economical to extract only a certain percentage of the fuel and then to raise the ignition quality further by the addition of a small quantity of a suitable dope. Solvent extraction also does not change the response of a fuel to Paraflow so that it is possible to obtain fuels of low pour point and high ignition quality by solvent extraction and addition of pour point depressants.

However, as previously noted, solvent extraction is only one of several methods of improving ignition quality. In order to compare solvent extraction with other methods, all


TABLE VIII. HYDROGENATION OF DIESEL FUELS ,--- Cracked Straigh t-Run --Pennsylvania--- -Mid-continent- -----California- --Pennsylvania- -Mid-continent-

Hydro- Hydro- Hydro- Hydro- Hydro- Original genated Original genated Original genated Original genated Original genated

Aniline point, F. 131.7 167.7 98.2 153.0 110.9 117.5 178.9 191.5 148.5 172.8 Gravity a t 60' F., A. P. I. 30.1 35.4 28.1 35.5 30.7 31.6 40.8 42.8 37.5 40.4 Diesel index No. 39.6 59.7 27.7 53.7 34.0 37.1 73.0 82.0 55.7 69.8

Flash point,o %. 180 172 182 175 190 172 170 154 144 142 Pour point F.: 5 5 <-35 <--35 <-35 <-35 15 15 -15 -15

Ignition ,qualit No. 21.3 31.3 13.4 25.2 16.2 17.4 39.6 44.3 27.3 33.9

0.57 Piraflow 0 -5 <-35 <-35 <-35 <-35 5 5 -25 . . . 1 .o& paraflow -5 -25 <-35 <-35 <-35 <-35 0 5 <-35 . . .

Cloud point O F.: 20 15 -5 -30 10 -25 25 25 -10 0 0.57 Par'aflow 0 15 - 25 . . . -25 -25 25 30 -10 , . .

35.4 36.0 35.2 35.8 39.0 38.9 35.7 35.4 0.19 0.01 0.45 0.26 0.04 0.00 0.19 0.01

1 .oJ Paraflow

Total sulfur % 0.05 0.01 Conradson o'arbon, % 0.02 0.02 0.14 0.02 0.06 0.03 0.02 0.01 0.004 0.01

Initial b.'p. 338 391 398 388 409 402 3 52 355 364 360 107 over 476 462 451 435 435 433 474 464 43 1 422 a% over 537 ' 525 484 469 471 470 542 54 1 490 486

616 606 548 534 561 564 620 626 580 574 En$ point 660 650 610 610 633 658 680 664 627 624 907 over

10 -35 . . . -30 -30 20 20 -5 . . . lo 38.5 37.2 Viscosity a t 100' F., sec.

Distillation ' F.:

of the fuels were acid-treated and several were hydrogenated. The results of treatment with 25 pounds per barrel of 98 per- cent sulfuric acid are given in Table VII. The average improvement in Diesel index after acid treatment was only 1 or 2 units. This negligible improvement could no doubt be increased by treatment a t higher temperatures or with more acid. Greater treating losses would result, and this would increase the cost of treatment.

Hydrogenation, on the other hand, produces fuels of high ignition quality without loss or change in physical properties, such as pour point, flash point, and distillation range. Hy- drogenation of the mid-continent cracked Diesel fuel yielded a product with a Diesel index higher than that produced by extraction of 37 per cent of the fuel with liquid sulfur dioxide. Hydrogenation of two straight-run fuels, mid-continent and Pennsylvania, raised the Diesel index above that obtained by solvent extraction. These results are given in Table VIII. However, the method of hydrogenation which was used can be applied only to fuels with low sulfur content since the nickel catalyst was poisoned by sulfur compounds. Even when the sulfur content was as low as 0.05 per cent, the catalyst was poisoned and had to be replaced by fresh catalyst before hydrogenation would proceed. The California cracked Diesel fuel was not hydrogenated to any great extent even after fresh catalyst had been added several times. For this reason i t appears that hydrogenation has but limited usefulness unless fuels of high sulfur content can be hydrogenated by some other method. Solvent extraction offers greater possibilities since i t can be adapted for use on a wide range of stocks, irrespective of their sulfur content.

Summary

Solvent ext>raction of cracked Diesel fuel from the Pennsyl- vania, mid-continent, Texas, and California fields produced raffinates of substantially improved ignition quality without appreciable change in physical properties of the fuels. Sulfur dioxide was more selective than furfural. The raffinates showed an improved response to a Diesel dope, acetone peroxide, over that of the original fuel. Addition of a pour point depressant to the raffinates caused the same lowering of pour points as addition to the untreated fuels. Thus it was possible to prepare fuels of high ignition quality from cracked stocks by solvent extraction, either alone or in conjunction with Diesel dopes, a pour point depressant, or both. Solvent extraction of straight-run fuels from the same four fields yielded raffinates with improved properties, but the increase in ignition quality was not as great as for the cracked fuels.

The extracted portions of the fuels had low aniline points

and high blending values, which indicated they were essentially aromatic in character. They probably could be used as blending stocks for tractor fuels, cracking stocks for high-antiknock gasoline, or as solvents.

Extractions with furfural a t lower temperatures indicate that these two solvents are only slightly more effective at lower temperatures than at room temperature.

Acid treatment of both cracked and straight-run fuels caused only a negligible increase in the Diesel index. Hy- drogenation caused a large increase in ignition quality without loss of fuel or change in such properties as pour point or distillation range. However, fuels with a high sulfur content could not be successfully hydrogenated even though poisoned catalyst was removed and fresh catalyst added several times.

Literature Cited (1) Batnager, S. S. (to Steel Bros. and Co.), British Patent 461,813

(Feb. 19, 1937). (2) Beoker, A. E., and Fisoher, H. G. M., S. A . E. Journal, 35, 376

(1934). (3) Doladugin, Solodovnik, and Englin, Neftyanoe Khoz. , 28, No. 4,

68 (1935). (4) Edeleanu, L., German Patent 573,211 (June 18, 1930); French

Patent 718,688 (June 15, 1931); and British Patent 381,941 (Oct. 10, 1932).

(5) Feigin, Obleukhova, and Prorokov, Neftyanoe Khoz., 1936, No. 3, 57.

( 6 ) Goodwin, R. T., Refiner Natural Gasoline Mfr., 16, No. 11, 514 (1937).

(7) Heinze and Merder, Brennstof-Chem., 16, 286 (1935) (8) Heinze and Marder, J. Ins t . Petroleum Tech., 23, 602 (1937). (9) Ibid.; Brennstoff-Chem., 17, 326 (1936). (10) Hill and Coats, IND. ENQ. CHEM.. 20, 641 (1928). (11) Hubner, W. H., S. A. E. Journal, 42, 27T (1938). (12) Hubner, W. H., and Murphy, G. B., Natl. Petroleum News, 28,

(13) Hubner, W. H., Murphy, G. B., and Egloff, Gustav, paper presented at 2nd World Petroleum Congress, Paris, June 14-19 (1937).

(14) Jackson, Oil Gas J. , 33, No. 44, 16 (1935). (15) Kreulin, D. J. C., J. Inst . Petroleum Tech., 23, 253 (1937). (16) Marder, M., Petroleum Z., 32, No. 32, 6 (1936). (17) Moore and Xaye, Oil Gas J., 33, No. 26, 108 (1934). (18) Pyrel, D., Petroleum 2.. 29, No. 11, 5 (1933). (19) Steffen, E., and Saegebarth, E., Refiner Natural Gasoline M j r . ,

(20) Sugden, J . Chem. SOC., 125, 1177 (1924). (21) Vlugter, Waterman, and van Westen, J . Inst . Petroleum Tech.,

(22) Watson and Nelson, IND. ENG. CHEM., 25, 88 (1933). (23) Woods, G. M., Petroleum Enor., 8, 58 (Dec., 1936).

NO. 4, 22, 24-6, 28; NO. 5, 25-8 (1936).

17, No. 1, 12 (1938).

21, 661 (1935).

RECEIVED rlpril 3, 1938. Presented before the Division of Petroleum Chemistry at the 95th Meeting of the American Chemical Society, Dallas, Texas, April 18 to 22, 1938.

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