US3162597A

US3162597A - Process for color stabilization and hydrodesulfurization or cracked gas oils

Info

Publication number: US3162597A
Application number: US55263A
Authority: US
Inventors: Jr Joseph Hill Rogers Davis; Earl M Honcycutt
Original assignee: Sun Oil Co
Current assignee: Sunoco Inc
Priority date: 1960-09-12
Filing date: 1960-09-12
Publication date: 1964-12-22
Anticipated expiration: 1981-12-22

Description

J. H. R. DAVIS JR.. ETAL 3, PRQCESS FOR COLOR SI'ABILIZATIUN AND aynaoossuwuammu OR CRACKED GAS OILS Filed Sept. 12. 1960 m ms 0 v in F T. a ms... 7 WW2! 6 m .P M M 00 0| 7 I W lw 8 mm e 9 O p m. m e m M a I, 0 nl ow EL 0 h a O r. a s o b E n o t w B 0 G 0 f 0 .m m m m m R w r w Hm M m I o o c N F d w A [W o 6 o O o. o r. i 7 B. 5 4 4 0 m Ev n. 83 52 26 22 a m 28 53 m I 1m 2 8 II 6 0 IL n b M Ma! .Im a. o 6 map pl- 0 F mm a m r o M m% M 5 aw a O 0 4D 0 C I o h M 5 M LN & l on! G F E RIN C R QML +z l 76 L is w m 3 Q "a; o .1 ca A A .m 0 cu m 0 m 0 0 M o 3 2 .1 0g N w w 2 .385 B 5 m 55m J Dec. 22, 1964 E 2 0 2 m 0 zHmd ATTORNEY United States Patent l PROCESS FOR COLOR STABILIZATION AND HYDRODESULFURIZATION OR CRACKED GAS OILS Joseph Hill Rogers Davis, Jr., Rose Valley, and Earl M. Honeycutt, West Chester, Pa., assignors to Sun Oil Company, Philadelphia, Pa., a corporation of New Jersey Filed Sept. 12, 1960, Ser. No. 55,263 Claims. (Cl. 208-416) This invention relates to an improved process for upgrading petroleurn fractions. It especially relates to the catalytic desulfurization and color stabilization of cracked gas oils. More particularly, it relates to a liquid phase hydrogenation process which utilizes very mild conditions with no hydrogen recycle.

It is desirable to desulfurize catalytic gas oils in order that they can be used as home heating oils or furnace oils." It is further necessary that the furnace oils have a clear, light color which can be maintained over long periods of storage. These requisites and others have been demanded by the buying public and efforts to de sulfurize cracked gas oils are well known in the art.

One of the most widely used processes for desulfurization is one in which the petroleum fraction is contacted with concentrated sulfuric acid. Unfortunately. however, this acid treatment degrades a portion of the charge stock by forming sulfonates. polymers. and the like. These undesirable compounds are usually removed by subsequent. usually expensive, distillation of the acid treatel product. The heating of the refined petroleum oil in order to distill it has the further disadvantage of decreasing the color stability of the oil.

With the increasing use of high sulfur crudes such as Middle East and Venezuelan crudes, the cracked gas oils have become troublesome to desulturize due to their high sulfur content. The sulfur content of these cracked gas oils may be as high as 3% or higher, and the Sulfur should be reduced to around 1.0% or less, preferably around 0.3%, before they are salable as furnace oils. These gas oils may be desulfurized by another Widely used process-catalytic hydrorefining. However, temperatures in excess of 700 F. are required, together with pressures of from 650 p.s.i.g. and up. Even at these high temperatures and pressures, it is necessary to hold the liquid hourly space velocity to 2.5 vols/bulk volume of catalyst per hour or less in order to secure a satis factory degree of desulfurization.

Further. the hydrorefining of cracked gas oils, while reducing sulfur content, has an extremely undesirable tendency to destroy the light color of the oil and still further, to destroy the oils ability to maintain a pleasing, satisfactory color upon aging. In addition to a low sulfur content, a cracked gas oil in order to be salable as a furnace oil, should have an ASTM color, initially, of less than 1.0, preferably less than 0.5, and after storage, at 110 F. for six weeks, should have an ASTM color of less than 2.0.

it is an object of this invention to provide an improved method for reducing the sulfur content, improving the initial color, and increasing the color stability of cracked gas oils. It is a further object to provide a desulturization process that has increased eificiency for the removal of sulfur from such oils.

We have found that the foregoing objects may be attained by contacting, in an atmosphere of hydrogen, the sulfurcontaining cracked gas oil in liquid phase with a sulfur-resistant hydrogenation catalyst at a temperature which is controlled within relatively narrow limits. We further have found that the efficiency of sulfur removal can be improved by blending a relatively high sulfur content cracked gas oil with a relatively low sulfur content cracked gas oil and passing the blend over a sulfurresistant hydrogenation catalyst as mentioned hereinabove in the presence of hydrogen. According to the present invention, the relatively high sulfur content material must contain 0.5% to 50%, preferably 0.8% to 1.36%, more sulfur than the relatively low sulfur content" material.

The term cracked gas oil is defined herein as any petroleum fraction of gas oil boiling range derived from thermal or catalytic cracking of hydrocarbons. It includes those petroleum fractions so obtained which boil mainly between 425 F. and 700 F. and which contain at least 0.3% sulfur. By hydrogen is meant any hydrogen-containing gas which is 40-l00% free hydrogen, preferably, between 70100%. It can be mixed with inert diluents and can be derived from other refinery sources such as reforming units. Recycle hydrogen gas is not required for this process. The term atmosphere of hydrogen as used herein denotes that there is no net flow of hydrogen through the Contact zone other than the small amount which dissolves in the liquid effluent.

The process conditions require a temperature between 500 F. and 675 F., preferably between 550 F. and 650 F. The pressure may range from about 300 pounds per square inch gauge (p.s.i.g.) to about 1,000 p.s.i.g., preferably between 500 and 800 p.s.i.g. Liquid hourly space velocities of from about 0.5 to 10, preferably 1 to 6 are satisfactory. It should be noted that the choice of operating conditions will be determined by the charactcristics of the charge stock such as boiling range, sulfur content, degree of unsaturation, etc., the desired properties of the product such as sulfur content, initial color, color stability, sludge formation, etc., the purity of make-up hydrogen, and other well-known considerations.

According to the present invention, the cracked gas oil is heated to the desired reaction temperature, say, 600 F., and passed into a reactor in which it trickles downwardly over a sulfur-resistant catalyst. Hydrogen pressure of, say, 650 p.s.i.g., is maintained over a liquid level in the bottom of the reactor. and the hydrogen is admi tted in an amount sufficient to make up for the hydrogen consumed in the desulfurization of the feed. This amount may vary from 25 to 500 ftF/barrel of feed. The reaction products are removed from the reactor and are passed to a fractionator or separator where the hydrogen sulfide and dissolved hydrogen are removed. The resulting products which are recovered from the fractionator include high octane gasoline and a substantially desulfurized cracked gas-oil of improved color and increased color stability. Usually, the octane number of the gasoline produced is within the range of -95 Fl clear octane number.

Any suitable sulfur-resistant hydrogenation catalyst can be employed in the practice of this invention. Examples of suitable catalysts are metals such as copper, zinc, mercury, tin, vanadium, tungsten, chromium. molybdenum, manganese, cobalt, iron, nickel, platinum, ctc., oxides of such metals or combinations of such metals or oxides or sulfides thereof. Any suitable catalyst support can be employed, e.g., activated carbon, alumina, aluminum silicates, bauxite, charcoal, clay, kieselguhr, magnesium, pumice, silica, silica-alumina compositions, and the like. The preferred catalyst is cobalt molybdate supported on alumina. When the term cobalt molybdate" is used herein, it denotes a mixture of cobalt and molybdenum oxides which may or may not be in whole or in part chemically combined.

FIGURE 1 of the accompanying drawings illustrates the effect of reactor temperature on initial color. aged color, and sulfur content of a cracked gas oil obtained from Middle East crude. FIGURE 2 demonstrates the effect of reactor temperature on the color stability of cracked gas oil. FIGURE 3 illustrates the advantage: gained by blending a relatively high su!fur content cracked gas oil :md processing the blend as hereinabovc described.

The present imcntion is based on the discovery that color stabilization and substantial desulfurization oi? cracked gas oils is. possible only over a narrow range oi temperatures, i.e., the temperature is particularly critical .A temperature too low can impart a :zood initial color to the product oil bu the product oil will not be color stahl. and will not be nirterially dcsulfurized. As the temperature is increased, desulfurization is increased while initial color remains good and color stabilitv is increased. Be yond a certain temperature (which temperature depend. upon the other operating variables and charge stock prop crties) initial color gradually darkens with increase in tem perature, while desulfurization continues to increase.

is noted in FIGURE 2, that the color tability rating is maximum at 550 F. for the Middle East cracked gas oil. It is also noted that temperatures between 500 F. and 675 F. produce gas oils having acceptable color stability. While col r stability may also be satisfactory at temperatures below 500 F.. according to FIGURE 1, suifur removal would not be, e.g., product sulfur content is greater than 1.0%. Temperatures above 675 render the product unacceptable as a salable furnace oil even though the sulfur content may be reduced to 0.27% (at 700 F). At these higher temperatures, color and color stability are unsatisfactory. For examp e, at 700 F. the initial product is 1.50 and the aged color is 2.50 giving a color stability index of 5.5 compared to a color stability index of 6.75 at 550 F. reactor temperature.

EXA MPLE 2 A catalytically cracked gas oil from Venezuelan crude was processed as in Example I with the following results:

Venezuelan Catalytic Gas Oil Hyrlrorcfining Conditions Further increase in temperature resul s in excessive dark-- ening of the initial and aged product color and a decrease in sulfur removal. Thus, there is a narrow range of tom-- peratures with which sulfur removal is substantial, initiai product color is light, and color stability is acceptable If the oil treated is relatively low in sulfur, and color improvement and stability are the chief goals. then I wider rang of temperatures may he sed. These advan tages are illustrated in the following examples \\hich ar. olfered in order that the invention may be more fully understood by those skilled in the art.

EXAMPLE I A catalytically cracked gas oil from Middle East crude. boiling between 435 F. and 675 F, was contacted with a cobalt molybdatc supported on alumina catalyst in the presence of hydrogen of 100% purity with the following l! addition of tie 1,000 bill.

NtllCO .50.; Ac inhibitor.

The. above data further demonstrate that temperatures above about 650 F. tend to destroy initial and aged color even though the sulfur content of the product is fu ther reduced. Further, temperatures between about 550 F. and about 6 F. must be adhered to if a product is to be obtained which has a better initial color than the charge stock and has a substantiallv reduced sulfur content.

Another product quality factor is itlustrated in the above examples, namely, filterable sludge. It is noted that the amount of filterable sludge, by which term is meant the sludge that can be removed by filtration, is also dependent upon reaction temperature and it is further noted that the sludge level is at a minimum between teriiperatures of about 550 F. and about 675 F. This is another factor in establishing these temperature limits as being critical in the operation of this invention. Clearly,

results: beyond a temperature of about 700 F.. further increase Middle East Catalytic Gas Oil Hyclroi'alfm'fmtion Conditions Temperature, F Charge 400 55 075 700 7125 Pressure, p.s.i .g 050 650 050 650 650 650 LHSV,v./hr./v 3 3 3 3 3 3 Wt. percent sulfur 1. 66 1. 0. 85 0. l0 0. 38 0. 27 0. 25 Percent S.rciu0val T T2 77 84 85 Initial Color, ASIM 0-1500 1.25 0.50 0.25 0.25 1.00 1.50 2.0 Aged ti wks. at110 F.21

ASTM 0-1500 Color a. 00+ 2.25 1.25 1.50 2.00 2.50 3.00

Filtcrable sludge, rue/100 ml ti. 5 2. 5 0. 0 0.7 0.5 0.5 1.0

1 With addition of Bit/1,000 bhl. laradyne Il0-4 inhibitor. These results are graphically illustrated in FIGURES 1 in temperature sharply increases the amount of filterable and 2. Note that the initial color of the product increases sludge in the product. sharply when a reactor temperature above about 625 F. Therefore, according to the present invention, operating is used. Aged color is similarly affected. Also. note that conditions must be as follows: the critical temperature range of 500 F. to 675 F. must be adhered to if the initial color of the product is to be 5 i below 1.0, aged color of product below 2.0, and sulfur tgffigg content less than 1.0%. For this charge stock. the preferred temperature is 625 F. whcrewith product initial 0 Sana-J5 5501650 color is 0.25, aged color 18 1.5, and sulfur content is 0.46. Pressure. 0 1s.. 5 0800 Using the above data, FIGURE 2 was plotted to illus- 5mm villi H) trate the effect of temperature on color stability. For T1115 mvemlon, Color slflblllly" Fm 000000 8 the Further, the benefits of this invention are only obtained aged color of the charge stock minus the aged color of the if th lf t t f h kd il Charge t k product. Thus, the higher the index number. the better is at least 0.3% sulfur, and the benefits are most if the the color stabillty compared to an untreated stock. It sulfur content is greater than [0%.

We have also discovered that the efficiency of sulfur removal for any given set of operating conditions can be markedly increased by blending a relatively high sulfur content cracked gas oil with a relatively low sulfur content cracked gas oil and processing as hereinabove described.

This additional embodiment of our invention is specifically illustrated in the following examples:

EXAMPLE 3 Two catalytically cracked gas oils, one from Middle East crude and the other from West Texas crude were processed over cobalt molybdate catalyst in the presence of hydrogen of 100% purity with the following unexpected results:

llY DROREFINTNG CONDITIONS Temperature, F Charge 475 550 550 625 Pressure, p.s.i.g Stock 350 350 650 500 LHSV, vjhrJv 0 6 6 6 IIYDRODESULFURTZING STOCK A Wt. Percent bult'ur 1.06 1.02 1. 29 1.15 0.74 Percent S. Removal 2 22 31 65 HYDRODESULFIRIZING STOCK B Wt. Port-cut ult'ur 0. 0. 21 0.17 0.19 0. 12 Percent S. Removal 30 43 37 62 CALCULATED RESULTS, FROM ABOVE DATA, OF A BLEND OF 1/3 A AND 2/3 B \\'t. Percent Hulfur 0. 75 0. 08 0. 54 O. 61 0. 33 Percent l e|noval ll 28 32 56 ACTUAL RESULTS FROM TIYDRODESVLFURIZING A BLEND OF 1/3 A AND 2].; B

Wt. lorcvut Sulfur 0.75 0. 0S 0. 52 0. 0. 25 Percent S. Removal 11 31 40 67 The above data show the remarkable benefit obtained by blending the two gas oils. For example, at 625 F., 500 p.s.i.g. and 6 LHSV, the relatively high sulfur content cracked gas oil was desulfurized and the relatively low sulfur content cracked gas oil was 62% desulfurized. Using these results, by calculation, a blend of 33% high sulfur stock with 67% low sulfur stock should give 56% sulfur removal. However, actual desulfurization reached 67% which was 5% higher than the best removal obtained on an individual charge stock. It is noted that the relatively high sulfur content gas oil contained 1.36% more sulfur than the relatively low sulfur content gas oil. It should also be noted that this remarkable benefit was similarly achieved at other randomly picked operating conditions. However, it should be further noted that the benefit of increased efficiency tends to disappear as the temperature drops below 500 F., e.g., at 475 F., there is no benefit from blending the feed stocks. On the other hand, as the temperature is increased, the difference between the expected result and the actual result also increases.

Thus. referring to FIGURE 1 and Example 3, it is seen again that the critical temperatures of this invention lie between 500 F. and 675 F. It is further noted in Example 3 that 33% by volume of relatively high sulfur content cracked gas oil can be blended with 67% relatively low sulfur content cracked gas oil to achieve an unexpected benefit.

EXAMPLE 4 Several commercially available catalytically cracked gas oils were treated over cobalt molybdate catalyst in the presence of hydrogen of 80% purity at a temperature 6 of 540 F., 750 p.s.i.g., and 5 LHSV with the following results:

Percent Re- Percent Re- Percent Re- Chg. Wt. Percent moval Premoval Premoval Pre- Percent; Sulfur dleted from dicted from dicted from Sulfur Removal 0.6% dz 1.8% 0.6% & 1.4% 1.0% dz 1.8%

S Data S Date. S Data 49.5 A A A NOTE; A =difference between removal experienced and removal calculated with a positive number indicating that the removal experienced. was greater than calculated.

The above results indicate, additionally, that the wider the difference in the sulfur contents of two charge stocks, the greater will be the synergistic effect on desulfurization when desulfurizing a blend of the charge stocks as opposed to desulfurizing the components individually. The amount of synergism which is obtained from any given blend is dependent upon the difference in sulfur contents of the two gas-oils which were blended. For example, it is seen from FIGURE 3, that the calculated blends comprising a mixture of 0.6% sulfur and 1.8%

sulfur (diflerence=l.2%) are further from the actual results than either the blend of 0.6% sulfur and 1.4% (dif ference=0.8%) or the blend of 1.0% sulfur and 1.8% sulfur (difference:0.8% Therefore, the benefits of the present invention may be obtained if the relatively high sulfur content cracked gas oil contains from 0.5% to 5 0% more sulfur than the relatively low sulfur content cracked gas'oil.

The data from Examples 3 and 4 also indicate that the amount of relatively high sulfur content material which can be blended with the relatively low sulfur content material can vary from 25% to In Examples 3 and 4, the minimum amount of high sulfur gas oil actually used successfully was 33% and in Example 4, the maximum amount used was 67%.

We claim:

1. Process for desulfurizing and increasing the color stability of sulfur-containing cracked gas oil boiling mainly within the range of 425 F. and 700 F. and containing at least 0.3% sulfur Which comprises contacting in liquid phase said gas oil with a sulfur-resistant hydrogenation catalyst in an atmosphere of hydrogen in a contact zone, said contacting being eflected at a temperature from 500 F. to 675 F., at a pressure from 300 p.s.i.g. to 1,000 p.s.i.g. and without any net flow of hydrogen vapor through said zone; and recovering a substantially desulfurized cracked gas oil of improved color and increased color stability.

2. Process according to claim 1 wherein said temperature is from 550 F. to 650 F. and said pressure is from 500 p.s.i.g. to 800 p.s.i.g.

3. Process according to claim 2 wherein said catalyst is cobalt molybdate supported on alumina.

4. Process according to claim 1 wherein said catalyst is cobalt molybdate supported on alumina.

5. Process according to claim 1 wherein said cracked gas oil contains between about 1% and 3% sulfur.

6. Process for desnlfurizing and increasing the color stability of sulfur-containing cracked gas oil boiling mainly within the range of 425 F. and 700 F. and containing from about 1% to 1.75% sulfur which comprises passing said gas oil in trickle manner in a contact zone over a sulfur-resistant hydrogenation catalyst comprising cobalt molybdate supported on alumina, in the presence of nonrecycle hydrogen added in an amount sufficient to make up for the hydrogen consumed, said contacting being effected at a temperature from 550 F. to 650 F., a pressure of from 500 p.s.i.g. to 800 p.s.i.g, a liquid hourly space velocity of from 0.5 to 10 and without any net flow of hydrogen vapor through said zone; and recovering a substantially desulfurized cracked gas oil of improved color and increased color stability.

7. Process for desulfurizing and increasing the color stability of sulfur-containing cracked gas oil boiling mainly within the range of 425 F. and 700 P. which cornprises blending a relatively high sulfur content cracked gas oil with a relatively low sulfur content cracked gas oil. the relatively high sulfur content gas oil containing from 0.5% to 5.0% more sulfur than the relatively low sulfur content gas oil; contacting the blend with a sulfurresistant hydrogenation catalyst in an atmosphere of hydrogen in a contact zone, said contacting being effected at a temperature of from 500 F. to 675 F., a pressure from 300 p.s.i.g. to 1,000 p.s .i.g., and without any net flow of hydrogen vapor through said zone; and recovering a substantially desulfurizcd cracked gas oil of improved color and increased color stability.

8. Process according to claim 7 wherein said catalyst is cobalt molybdate supported on alumina.

9. Process according to claim 7 wherein said relatively high sulfur content gas oil contains from 0.8% to 1.36% more sulfur than said relatively low sulfur content gas oil.

10. The process for desulfurizing and increasing the color stability of sulfur-containing cracked gas oil boiling mainly within the range of 425 F. and 700 F. which comprises blending from about 25% to 75% of relatively high sulfur content cracked gas oil with from about 75 7t:

to 25 relativelylow sulfur content cracked gas oil, the

relatively high sulfur content gas oil containing from 0.3% to 1.36% more sulfur than the relatively low sulfur content gas oil; passing the blend in trickle manner in a contact zone over .1; sulfur-resistant hydrogenation catalyst comprising cobalt molybdate supported on alumina, in the presence of non-recycle hydrogen added in an amount sufficient to make up for the hydrogen consumed, said contacting being effected at a temperature from 550 F. to 650" F., a pressure of from 500 p.s.i.g. to 800 p.s.i.g.. a liquid hourly space velocity of from 0.5 to 10 and without any net flow of hydrogen vapor through said zone and recovering a substantially desulfurized cracked gas oil of improved color and increased color stability.

References Cited by the Examiner UNITED STATES PATENTS 2,365,751 12/44 Drennan 208143 2,608,521 8/52 Hoog 208254 2.697,683 12/54 Engel et al. 208216 2.897.141 7/59 Honneycutt 20889 2.918.425 12/59 Berger et al zzz z 208108 2.022.759 1/60 Schlinger 208235 2.987,267 6/61 Keith et al. 208211 ALPHONSO D. SULLIVAN, Primary Examiner.

MILTON STERMAN, Examiner.

Claims

1. PROCESS FOR DESULFURIZING AND INCREASING THE COLOR STABILTY OF SULFUR-CONTAINING CRACKED GAS OIL BOILING MAINLY WITHIN THE RANGE OF 425*F. AND 700*F. AND CONTAINING AT LEAST 0.3% SULFUR WHICH COMPRISES CONTACTING IN LIQUID PHASE SAID GAS OIL WITH A SULFUR-RESISTANT HYDROGENATION CATALYST IN AN ATMOSPHERE OF HYDROGEN IN A CONTACT ZONE SAID CONTACTING BEING EFFECTED AT A TEMPERATURE FROM 500*