US2366490A - Production of diesel fuels - Google Patents

Description

Jan. 2, 1945. lG., H, CLOUD 2,366,490

PRODUCTION OF DIESEL FUELS 8mm/KM;

C5721 NE zvum Jan. 2; 1945.

G.. H.I CLOUD 2,366,490

PRDU-CTION 0F DIESEL FUELS Fired Feb. 18.11942 2 sheets-sheet 2 Patented Jan. 2, 1945 t UNITED STATES- PATENT OFFICE raonUc'noNoF DIESEL FUELS como n. cloud, Linden, N. J., menti te sumaard Catalytic Company, a corporation of Dela- Application February 18, 1942, Serial No. 431,365

4 Claims. (Cl. 196-13) 'I'his invention relates to a method for preparing high ignition quality Diesel fuels.

In order to insure continued development of Diesel engines, it is essential to havemethods for economically making available larger quantities of fuels having high ignition quality. Straight run gas oil distillates from highly parafilnic crudes meet the'requirements of modern Diesel engines, but it has become increasingly difficult to obtain the straight run distillatespf high ignition quality for it requires diversion of the paralnic' base gas oils from their use as superior cracking stocks in the preparation of high anti-knock gasolines.-

the requirements of ignition quality and at the.

same time have high heating values in terms of B. t. u. per gallon in order to put the operation of a Diesel engine at its best advantage in fuel economy.

The present invention is concerned with a vtreatment of petroleum gas oils to obtain emciently therefrom Diesel fuels of highly improved ignition quality, high heating value, and low pour points.

Although there has been a good deal of investigation of special rei'ining processes, such as solconsidering the cost of hydrogen and equipment used.

In accordance with the present invention, it has been found that certain selected fractional cuts of petroleum gas oils respond best to a solvent extractlon, others more advantageously to a hydrogenation, vwhile still -others practically require neither treatment in achieving the object of economically preparing the improved Diesel fuels.

The definition of the term gas oil as used hereinconforms with the authoritative A. S. T. M.

designations (D288-28T and D288-36T), and isk descriptive, of a liquid petroleum distillate having a viscosity and boiling range intermediate between kerosene and lubricating oil.

The procedure ofthe invention will be described with reference to the accompanying 'drawings which illustrate a dltic flow plan of a plant for .carrying out the desired steps, as shown inFlg. 1.

Referring to the drawings, a gas oil vdistillate -or fraction is represented as passing from feed inlet I into a fractionator 2. The gas oil fraction charge may be in the form of vapors directed past valve 3 thru line 'I into the fractionator, or the gas oil may be in the form of a distillate which maybe directed past valve 5 with valve 3 closed, then thru preheater 6 into the fractionator.

The fr'actlonator 2 is of any conventional type for -makinga fairly close fractionation of the gas oil fractioninto a number of cuts. The fractionvent extraction and hydrogenation for obtaining improved Diesel fuels, these processes have been Given only limited application commercially on account of their ,costlin'esa Solvent extraction,

as it hitherto has been recommended for application to Diesel fuels, in high treating losses. Most of the aroatic extract obtained in a selective solvent extraction of a total gas oil distillate has very little practical value in. commercial products, being usable only in low price products, such as bunker fuel oil. 'Hydrogenation, as it has beenprcposed, was found to be excessively expensive for theimprovement Gained ator may be equipped with a heating coil 'I or similar reboiling means-'at its base and with a cooling coil I or slmiler condensing means in the uppermost section. -In the interior of the fractionator are disposed baille plates Q and reflux condensate collecting pans Il or equivalent means for dephlegmation of the gas oil vapors ascending in the fractionator.- Also, there may be attached to the fractionator a side stream stripper Il to receive a side stream from line I2 and with a heat exchanger'` I 8 for making a closer fraction'- ation of an individual cut. The vapors separated in the stripper may be returned therefrom to the fractionator by valve control linel I 4 and the stripped condensate may be returned to another part of the fractionator as, for example,

5o thruline Il,orbewithdrawnthruline I6.

23. i As will be later shown, it is highly desirable to 25 separate gas oil cut withdrawn by pump ranging from v be conducted to the condensing coil I8 and from there be led thru-valve I9 into receiver 20. For the present purposes, the lowest boiling cut of the gas oil,4 such as collected in receiver 20, should boil predominantly below 550 F. It may be cut to have an end boiling point 450 F. to 550 F., and insome instances, somewhat higher.

The side stream stripper Il may be used to separate a stripped fractional condensate boiling in the range of about 450 F. to 550 F.

An intermediate reilux condensate boiling preferably in the range of about 550 F. to 650 F. may be withdrawn from the fractionator as a` side stream thru line 22.

thru line 2l to be passedthru a cooler 29 into a gas separator 3l. rator is recycled by line Il and booster pump I2. Make-up hydrogen gas is added thru line 33. The separated liquid products are withdrawn from the separator thru line I4 to be discharged into a rerun fractionator ll for removal of low boiling in the range of about 10 of the gas oil withdrawn The heaviest cut of the distillate boiling above about 600 F. and predominantly from about 600 F. or 650 F. to '750 F. may be withdrawn from the bottom section of the fractionator from the total gas oil distillate -the described heavy cut boiling above 600 F. for hy drogenation because this heavy'cut is the most responsive to the hydrogenation treatment for improvement.

The fraction of the `gas oil distillate boiling below 550 F. has relatively low ignition quality and does not respond satisfactorily to hydrogena- 'tion, but is the. most suitable part of the gas ou distillate for treatment by solvent extraction for a good increase in cetane'number by removal of aromatic compounds.

The heart cut or intermediate reux condensate boiling'in the range of 550 F. to 650 F. is given the least improvement by either solvent extraction or hydrogenation. y

To proceed with the treatment of the heavyfrom the base of fractionatorj`2 thru -line 23, this material is passed 24 thru heat exchanger 25 for regulating the temperatureV of the oil as it is conducted into the hydrogenation reactor 26. This reactor is made to contain .a suitable hydrogena-4 tion catalyst for con'tact with the oil in theV presence of hydrogen supplied by line 21.-

Suitable conditions for the hydrogenation are as follows: The reaction mixture is maintained at a temperature in the range of about '700 F. to 850 F. and under a superatmospheric lpressure drogen gas is supplied to the reactor at the rate. of about 4,000 to 15.000 cu. ft./bbl. of oil. The contact catalyst is of the type immune to sulfur poisoning and comprises an oxidev or sulfide of the 6th group metals, usuallychromium, denum, or tungsten, alone or mixed withoxidess or sulfides of other metals, such as nickel sulilde, zinc oxide, magnesium oxide, aluminum oxide, and the like. The space velocity is from products. At the base of fractionator 35 is a reboiling heat exchanger I5. led from the fractionator thru line I1 into the condenser coil 38. thence to receiver Il. A side stream may be removed from the fractionator thru line 4l. The high boiling hydrogenated product is withdrawn from the fractionator by line 4I to be sent therethru to storage tank 42.

The intermediate high ignition quality fraction as .a side stream from fractionator 2 is run by line 22 into cooling coil 43 and from there into the receiver 44. Any desired amount of this intermediate out may be passed by lines 45 and 45 to be combined with the hydrogenated heavy cut. Any remaining amount of the intermediate cut may be withdrawn for separate storage by line 41.

Any desired portion of the light fraction of the gasoil separated in fractionator 2 and collected in receiver 20, as described, may be passed thru line 4l by pump 49 thru a precooler 48 and by line into extractor 5I. A selective solvent is fed into the extractor byline 52. The extract phase is withdrawn from the extractor by line any desired portion thereof may be sentthru lines l 62 andl for blending with the intermediate lgas oil cut and with the heavy hydrogenated oil. If the high degree of improvement obtained thru Ithe solvent extraction of the light cut is unneces- 50 sary. and nevertheless ifit' is desired to lower ftheviscosity of the final Diesel fuel product. any

50 to about 250 atmospheres.- Hy- .55

molybabout 1 to 3 volumes of liquid oil per unit volume 65 of catalyst 'per hour. As the temperature is increased, the space velocity in general is proportionately increased.` The reaction is predominantly a hydrogenation but a small amount of conversion to lower boiling hydrocarbons may ocis preferred torestrain the splitting cur, but it that less than about 10% of lower reaction so boiling hydrocarbons are formed from the' heavy gas oil c`ut in the hydrogenation.

The `products are withdrawn from the reactor desired amount ofthe light cut may be sentfrom receiver 2l by way of lines 63, 45, and 4l, to be mixed with the hydrogenated heavy cut.

For the solvent extraction of the light gas oil cut. either a vapor-liquid or liquid-liquid extraction' may be employed, but it is generally more convenientto employ the latter, using liqueiled sulfur dioxide or similar selective solvents, such as furfural, glycol ethers, or the like. As an illustration of the solvent extraction procedure.

the light gas oil distillate is intimately contacted in an extraction vessel as, for example, in a countercurrent extractor tower illustrated in the drawing at a 'temperature sufficiently low vto maintain the solvent in liquid phase, for example, in treating with liquid SO2, the temperature 'was maintained at about 0 F. to 20 F. The extract mixture of the solvent and extract in solution gravitates tothe bottom of the extractor, and in the extract separator the solvent is expelled by vaporization. The separatedsolvent may then be recovered for recycling. The ramnate mixed with a relatively small amount of the solvent is ,freed of the solvent in the separator 58.

Hydrogen gas from the sepa-I Overhead vapors are thene base crude) Pertinent data on various ses oil distillates tion. .As a matter of fact, the improvement of and their fractionated cuts are in the lightest cuts by hydrogenation is too small the following table: be worth the expense.

A typical straight run paraliin base (Penna.) gas oil B typical straight run naphthenic base gas oil O typical cracked gas oil Boiling Aniline M P I. B tm. Conradson Sayboit eme Pour 'ii" p22*" wie' w 115223. erin i. numb" pgiif' 121 39.4 130,000 .0i 30.0 34 0 134 32.5 141,400 .04 300 44 0 13s 205 144.400 .0e 51.0 41 0 152 20s 143,300 .30 220.0 40 5 340-150 130 2&3 m,500 .03 43.0 40 0 35o-450 110 30.3 130,000 .01 31.0 '31 o 45o-550 120 n.3 142,500 .01 31.0 33 0 550-050 112 21.0 14s, 300 .01 51.0 31 0 050-150 120 14.3 151, .01 310.0 20 0 440100 115 23.2 146,500 .11 48.0 23 0 The foregoing inspection data illustrates how TABLE 3 in all common varieties of gas oils the heart cut boiling within the approximate limits of 550 F. Hlldryenated naphthene base gas Oil Cut-9 to 650 F. has been found superior to other por-v tions of the gas oil in ignition quality and to Boiling points? F.' compare favorably with the other portions on Hydmgenad out Slatll heating value and low carbon residue forma-k Initial Mid Final tion. Although the lheaviest cut .boiling above about 600 F. has the best heating value, in genovergmd g g2g over en eral it forms carbon residue to the greatest exummm 418 486 596 47 tent, has a relat1vely low. ignition quality, and is gygiynrhm; d t gg ggg g over ea Cll high in pour point. The lightest cut also has very M95 overhead 588 610 630 59 low 1gnition quality. 11u-05% overhead eut 504 542 052 1 59 The relationship between the boiling points oi.' Ttlhydfgenad gas 1 4'08 493 682 49 the various gas oil components and their ignition quality is brought out graphically in the chart of Fig. 2. In this chart are shown-the cetane numbers corresponding to the mid-boiling points .of separate cuts derived from the three typical gas oils on which inspection data is given in Table 1. Also, in this chart is shown the relationship of cetane number to boiling points of representative hydrogenated type B gas oil cuts and ofi raflinate fractions from an SO2 extraction of the B type crude gas oil.

The relationship between ignition quality and volatility is strikingly changed when the cuts of the gas oil have been hydrogenated as is shown in the following tabulated data for a representative gas oil originally oi' type B (mixed naphcuts of a gas oil are given very little, if any, im-

provement in ignition quality by hydrogenation. These facts clearly `indicate that there isa considerable advantage Vto be gained in subjecting the heaviest fraction alone to hydrogenation and eliminating the expense of hydrogenating the lower boiling fractions of the gas oil. Moreover, by restricting the hydrogenation to the heaviest cuts of gas oils, one obtains gas oil fuel components of highest heatingovalue from the part of gas oil which in many instances is not adapted for use in a Diesel fuel on account of its high Hudrogenated aas oil cuts from mired-nephthene base crude (B) Y The data in Table 2 proves how the heaviest eut of a gas oil responds best to improvement by hydrogenation and how the lighter cuts, are not carbon residue formation and tendency to. foul the engine. Also, hydrogenation of vthe naphthenic heavy stock does not appreciably increase very susceptible to improvement by hydrogena- 76 its pour point.

ing oli.

Results on the solvent extraction of different cuts fractionated from gas oils are illustrated by the'following example:

EXAMPLE A type B gas oil was fractionated to obtain light and heavy cuts. Extractions of the total gas oil and of the cuts were carried out with liquefied SO2, phenol, and furfural solvents.

lRepresentative specic results: from an` SO2 extraction using 85% by volume of solvent at temperatures in the range of about 14 to 20 F. were obtained as shown in the following tabulated data:

TABLE 4 Solvent treated gas oil cuts from mired naphthene base crade (B) Rafilnate Cetane Diesel fuel tested pyirelgt number Initial untreated B gas oil 40 Ramnate o! total gas o 80. 49 Railinate of lowest boiling traction- 79. l 50 llainate oi highest boiling fraction. 77. 9 49 -gain is hardly significant, particularly in comparison to the improvement by hydrogenation;

and the particular inne4 of ou drained, so uns the initial and end boiling points of the gas oils` and of their fractions are variable to some degree.

In commercial distillation practice, it is to be expected that the honing range of one cut overlaps to some extent the boiling range of an adjacent cut. For instance. the heart cut of the gas oil in general has a mid-boiling point within the limits of about 550 F. to 600 F. but the initial :boiling point ofA this 'cut may be regarded `to be as low as 500 F. and its end point as high as 650 F. As a rule, the mid-boiling point of the heart cut tends to be closer to 600 F. for oils ot relatively low aniline point, whereas for oils of relatively high aniline point the heart cut of maximum cetane number has a mid boiling point closer toV 550 F.l The proportion of the heart cut varies and increases in quantity with increase in the aniline point. As already indicated, a point is reached at which less advantage is obtained ln separating out the heart cut and it is better to4 ,divide the gas oil into only two fractions for improvement, i. e., a light .fraction for solvent extraction and a heavy fraction boiling above 600 F. for hydrogenation. The isolation of the heart cut with separate treatments of the lighter and heavier cuts -is most advantageous when the gas oil has an aniline point in the range of about 130 F. to 175 F.

With the present procedure, less than about 30% of a typical gas oil requires improvement by and on the heart cut, the solvent treatment gives 1 no practical improvement.

By correlating the foregoing results, it becomes evident that with the procedure ofthe present invention, a gas oil is improved with considerable advantage if it is iirst divided into cuts so that the lightest cut of the gas oil may be subjected to the solvent extraction and the heaviest out maybe subjected to hydrogenation, while the middle cut, if desired, may be left untreated or be'subjected to any other suitable treatment.

This invention makes commercially feasible the preparation of superior Diesel fuels from all types of gas oil distillates which are petroleum fractions boiling intermediate kerosene and lubricat- In general, the gas oil distillates have boiling ranges of from about 350 F. to 750 F. The distillates to be processed may be procured from paraffin base, naphthene base, asphalt base, or mixedbase crudes. by straight distillation.

. They maybe obtained as reflux condensates from cracking processes provided the cracking isy not so severe as to excessively degrade the gas oil by making ,it extremely aromatic. From practicar considerations, the best results are obtained by treating gas oils having aniline points within the approximate limits of 100 to 175, which includes the usual run of gas oils derived from naphthene base crudes, mixed base crudes, some asphalt base crudes, and many recycle oils from cracking units. It isvto be understood that the gas oil cuts treated bythe method described to obtain an improved Diesel fuel may be derived from a number of gas oil distillates; for example, the paraffin base-intermediate gas oil cut may be combined with a hydrogenated heavy cut from a naphthene base gas oil. The distillation characteristics of gas oils may 'vary somewhat depending. upon the eaattype of. fractionating device solvent l extraction. Characteristically, from about 80% to 95% of the light gas oil fraction subjected .to the Asolvent extraction treatment boils within the range of 450 F. to 550 F., and this light fraction may be identied, also, as having a mid-boiling point within the limits of 450 F. to 550 F.. The heart cut fractions having peak cetane numbers which make them suitable for use without solvent extraction treatment often comprise from about 20% to 30% of the total gas y oil. Thus, the present procedure makes it possible to' obtain the desired high ignition quality Diesel fuels with greatly reduced expense of treatment. Furthermore, with the described operations, the resulting Diesel fuels have satisfactory high flash points and proper viscosities to meet all common specification requirements, such as a minimum ash point of 150 F. and BiLU. viscosity rangingirom about 32 to '15 seconds at Following the preparation of the Diesel fuel by the selective treatments described, there may be incorporated into the fuel various addition agents, such as ignition promoters, cold starting agents, pour point depressants, viscosity modiners, dyes, corrosion inhibitors. anti-oxidants, or other additives which serve to improve various qualities of the fuels.

It is not intended that the invention be limited to the speciiic examples given for the sake of illustration. Modifications which come within the spirit of the invention are intended to be included within its scope.

l. In a process of producing a Diesel dfuel of -high ignition quality, the steps comprising 4separating a petroleum glas oil into a light fraction, an intermediate fraction, and a heavy fraction. removing aromatic hydrocarbon components of the light fraction v"py selective solvent extraction,

hydrogenating the heavy fraction, and combining the light fraction separated from aromatic components with said intermediate traction and with the hydrogenated heavy fraction.L

g 2. In a process for preparing a Diesel fuel of ignition quality, high heating value, and low pour point, which comprises fractionating naphthene base petroleum gas oils which have aniline points in the range of about 130 F. to 175 F. into light fractions boiling below 550 F., intermediate fractions boiling in the range' of 500 F. to 650 F., and heavy' fractions boiling above 600 F., re

moving aromatic components of the light fracy 2o gas oil fraction with said raffinate to obtain the tions by selective solvent extraction, hydrogenating the heavy fractions, and combining a portion .of the light fractions, separated from extracted aromatic componentsthereof, with a portion of said intermediate fractions and a portion of the hydrogenated heavy fractions.

. 4. In a process for preparing a high quality Diesel fuel, the steps which comprise fractionating from petroleum gas oil having an aniline point in-the range of 100 F. to 175 F. and a midboiling point in the range of 550 F. to 650 F. a light fraction boiling below 550 F. and a heavy .fraction boiling above 600 F., treating said light fraction with a selective solvent for aromatic hydrocarbons to obtain a raffinate of increased cetane number, hydrogenating said heavy fraction to 'obtain a hydrogenated heavy gas oil frac- .tion boiling abnve 600 F. of increased cetane number, and combining said hydrogenated heavy Diesel fuel of high quality.

Gouin n .cLoun

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