US2717858A

US2717858A - Heating oil blends

Info

Publication number: US2717858A
Application number: US271558A
Authority: US
Inventors: Ii Stanley O Bronson; Robert C Morbeck; Sumner B Sweetser
Original assignee: Exxon Research and Engineering Co
Current assignee: ExxonMobil Technology and Engineering Co
Priority date: 1952-02-14
Filing date: 1952-02-14
Publication date: 1955-09-13
Anticipated expiration: 1972-09-13

Description

p 13 1955 s. o. BRONSON u ETAL 2,717,858

HEATING OIL 'BLENDS Filed Feb. 14, 1952 M20 6 GT wzv dv w w b m m a t a v m UIO MN. N m hm b wZZuQQQr Q N k H T T m& w k mm s mm: wiw 8 aw mrm a wzFflw 0v 9 NS vim A uzON M 5 U OF EFQ at a W A U O 9) cm. :(w. B m um. LL C u a T 5R5 3 qfi 2 w N Al F Jr A m1 T m1 T 5 T m\ 5 y MION & Q @IJHMWQF H A. oai w rwin wzo 20.2 1599 United States Patent HEATING 01L BLENDS Stanley 0. Bronson II, Mountainside, Robert C. Morbeck, Fanwood, and Sumner B. Sweetser, Cranford, N. 31., assignors to Esso Research and Engineering Company, a corporation of Dciaware Application February 14, 1952, Serial No. 271,558 8 Claims. (Cl. 196-35) The present invention is concerned with an improved process for the production of high quality heating oils. The invention is more particularly directed to a process whereby cracked heating oils may be effectively blended with sweet virgin heating oils to produce a satisfactory high quality blended heating oil product. In accordance with the present invention a virgin heating oil is blended with a cracked heating oil which has been subjected to a mild and controlled hydrofining step.

The present invention is broadly concerned with the production of improved hydrocarbon mixtures known as, heating oils, of the nature employed in various burner systems, as diesel fuels, or as domestic and industrial heating oils. Heating oils may be derived from petroleum by a variety of methods including straight distillation from crude petroleum oil, and thermal or catalytic cracking of various petroleum oil fractions. Heretofore, in the art, heating oil blends comprised a relatively large proportion of virgin heating oil as compared to cracked heating oils. However, due to the desirability of Virgin heating oils as feed stocks to various cracking operations, as for example, a fluid catalytic cracking operation, the blends comprise an increasing proportion of cracked heating oil fractions as compared to virgin stocks. Virgin heating oil fractions are also very desirable as diesel oil products which further decreases their availability for heating oil blends.

It is known in the art that heating oils consisting completely or in part of catalytic cracked stocks are characterized by an undesirable instability giving rise to the formation of sediment. It is also known that when cracked heating oils are blended with sweetened virgin heating oils certain undesirable characteristics are increased due to their incompatibility. As a result, such blended fuel oils tend to cause clogging of filters, orifices, or conduits associated with the burning systems in which they are employed.

It is also known in the art that when a virgin heating oil is blended with a cracked heating oil, the carbon residue of the blend in many cases exceeds the carbon residue of either the virgin heating oil or the cracked heating oil. This carbon residue is an indication of the extent the blended heating oil will carbonize the burners, particularly a rotary burner in actual use and to some extent determines the burning characteristics and desirability of the fuel.

In order to improve the quality of blended heating oils, various processes have been practiced in the art. It is known in the art to process a virgin heating oil by a caustic wash if the oil be relatively sweet. On the other hand, if the virgin heating oil has a relatively high mercaptan content so as to render it sour, the oil is processed by a doctor treat or an equivalent sweetening operation. On the other hand, light cracked heating oils in many operations merely require a caustic wash. However, the conventional procedure is to secure the cracked heating oil from a relatively severe cracking operation in which case it is necessary to acid treat the cracked heating oil followed by a caustic wash in order to control the carbon residue. This latter operation is not desirable since acid treatment polymerizes many desirable constituents resulting in a loss in yield. Furthermore, the sludge is expensive and diflicult to handle.

In accordance with the present invention the instability of catalytically cracked heat g oils may be substantially overcome and its compatibility for blending with virgin heating oils increased by subjecting the cracked heating oil fraction to a hydrofining operation. Heating oil blends which may be processed by the hydrofining operation of the present invention are particularly hydrocarbon mixtures of which more than about 10%, preferably from about 15% to 60% by volume consist of stocks derived from cracking operations. More precisely still, the finished blends may be characterized as petroleum fractions containing a proportion of cracked stocks greater than 10%, preferably from about 15% to 60% by volume, and falling within A. S. T. M. specification D39648T for fuel oils (grades No. 1 or 2). Inspections of a typical heating oil blend are for example:

Gravity, API 34.5 Distillation, A. S. T. M.:

Initial, B. P., F 363 10% F 438 50% F 504 F 583 Final, B. B., F 640 Flash, F 158 Color, Tag Robinson 15 Viscosity, SSU/ F 34.7 Pour point, F 0 Sulfur, wt. percent .37 Suspended sediment, mgs./ 100 ml 1.0 Carbon residue on 10% residuum, percent .08 Corrosion, 1 hr. 212 F Pass Diesel index 48.2 Aniline point, F

The process of the present invention may be more fully understood by reference to the drawing illustrating one embodiment of the same. Referring specifically to the drawing, a crude oil feed stock is introduced into distillation zone 1 by means of line 2. Temperature and pressure conditions in zone 1 are adapted to remove overhead by means of line 3 normally gaseous hydrocarbons and to remove by means of line 4 hydrocarbon constituents boiling in the motor fuel and naphtha boiling ranges. A virgin heating oil fraction is removed from zone 1 by means of line 5 while a gas oil fraction is removed by means of line 6. comprising the higher boiling constituents is removed as a bottoms by means of line 7. The virgin heating oil fraction removed by means of line 5 may be treated by various processes in order to refine the same. Normally this fraction is treated with a mild caustic wash,

the spent caustic is removed by means of line 10.

The caustic treated virgin heating oil is removed by means of line 11 and sweetened if necessary by the removal of mercaptans in sweetening zone 12. The sweetening agent is introduced by means of line 13 while the spent sweetening agent is removed by means of line 14. Any suitable sweetening agent or process may be utilized as for example a doctor treat, a bauxite treat or by a Unisol process. The finished virgin heating oil is removed by means of line 15 and blended with cracked heating oil produced as hereinafter described.

It is to be understood that distillation zone 1, treating zone 8 and sweetening zone 12 may comprise any suitable number and arrangement of stages. The gas oil fraction removed by means of line 6 is passed to cracking zone 16 which may comprise any suitable cracking operation, as for example, a thermal or a catalytic cracking process. However, the present invention is particularly directed toward the production of a high quality virgin-cracked heating oil blend wherein the cracking process comprises a catalytic cracking operation, as for example a fluid catalytic cracking operation.

A fluid catalytic cracking plant is composed of three sections: cracking, regeneration, and fractionation. The cracking reaction takes place continuously in one reactor at a temperature in the range from about 800 F. to 1050 F. The spent catalyst is removed continuously for regeneration in a separate vessel, from which it is returned to the cracking vessel, which is at a pressure below about 200 lbs. usually below about 50 lbs. per sq. in. Continuity of flow of catalyst as well as of oil is thus accomplished, and the characteristic features of fixed-bed designs involving the intermittent shifting of reactors through cracking, purging, and regeneration cycles are eliminated.

Regenerated catalyst is withdrawn from the regenerator and flows by gravity down a standpipe, wherein a sufficiently high pressure head is built up on the catalyst to allow its injection into the fresh liquid oil stream. The resulting mixture of oil and catalyst flows into the reaction vessel, in which gas velocity is intentionally low, so that a high concentration of catalyst will result. The cracking that takes place results in carbon deposition on the catalyst, requiring regeneration of the catalyst. The cracked product oil vapors are withdrawn from the top of the reactor after passing through cyclone separators to free them of any entrained catalyst particles, while the spent catalyst is withdrawn from the bottom of the reactor and is injected into a stream of undiluted air which carries the catalyst into the regeneration vessel. The products of combustion resulting from the regeneration of the catalyst leave the top of this vessel and pass through a series of cyclones where the bulk of the entrained catalyst is recovered. The regenerated catalyst is withdrawn from the bottom of the vessel to complete its cycle.

The cracked products are removed from cracking zone 16 (overhead from the reactor) by means of line 28 and introduced into a distillation zone 29. Temperature and pressure conditions in zone 29 are adjusted to remove overhead by means of line 30 normally gaseous constituents and to remove by means of line 31 hydrocarbon constituents boiling in the motor fuel boiling range. A

fraction boiling above the heating oil boiling range is removed as a bottoms fraction by means of line 32. A fraction boiling in the heating oil boiling range is removed by means of line 33 and in accordance with the present invention may be caustic washed in zone 21. The fresh caustic or other treating agent is introduced by means of line 22. while the spent treating agent is removed by means of line 23. In accordance with the present invention the caustic washed, cracked heating oil fraction is hydrofined in zone 24. The hydrofined cracked heating oil is removed from hydrofining zone 24 by means of line 27 and blended as hereinbefore described with a virgin heating oil in line 15.

It is essential, in practicing the present invention that the hydrofining operation conducted on the cracked heating oil be a mild hydrofining operation. This is to be distinguished from conventional hydrofining operations heretofore practiced in the art. Such hydrofining operations have been employed at pressures from 200 to 500 lbs. per sq. in., at feed rates of .5 to 2.0 volumes of feed per volume of catalyst per hour. Relatively high rates of hydrogen recycle have been employed as for example, 2,000 to 4,000 standard cu. ft. per barrel in order to prevent carbonization of the catalyst. Likewise, very active catalysts have been used which are effective for desulfurization. Under these conditions hydrogen consumption has generally been in the range of 150 to 600 standard cu. ft. per barrel of feed. This relatively high consumption of hydrogen in the past has made the process expensive to operate, so that its application in the past has been limited to the treatment of relatively high sulfur stocks which could not be desulfurized by any other available treating operation. The catalyst heretofore employed has been a cobalt molybdate supported on a carrier, as for example alumina.

Due to the fact that the sulfur content of heating oils is relatively low, since the cracking operation desulfurizes to a great extent, conventional hydrofining operations have not been necessary in the processing of cracked heating oils. On the other hand, when conventional hydrofining operations, as described above, were employed in the processing of cracked heating oils for improving the carbon residue, these conventional operations were found entirely unsatisfactory, since they actually increased the carbon residue and further impaired the quality of the fuel. On the other hand, when employing the mild hydrofining process of the present invention, unexpected desirable results are secured with a higher quality blended fuel oil product.

The mild hydrofining conditions of the present invention may be secured by lowering the temperature, increasing the feed rate per volume of catalyst or by using a less active catalyst. In accordance with the pre ent invention the temperatures used are in the range from about 400 to 700 F, preferably in the range from about 500 to 650 F. Pressures employed are in the range from to 250 lbs. per sq. in., preferably in the range from about to 200 lbs. per sq. in. The feed rates, in accordance with the present process, are in the range from about 1l6 volumes of liquid per volume of catalyst per hour. Preferred feed rates are in the range from 4-12 v./v./hr. The hydrogen in the gas to the hydrofining unit may vary from 50 to 100%. This means that, for example dilute hydrogen from a hydroformer can be used in the hydrofining process. A particularly desirable method of hydrofining in accordance with the present process is to recycle appreciable quantities of hydrogen to the hydrofining unit in order to completely prevent carbonization of the catalyst.

The catalyst utilized in the present operation may comprise known hydrofining catalyst, as for example cobalt molybdate on a carrier as for example alumina, providing other operating conditions are adjusted to secure a mild hydrofining process. The preferred catalyst, however, of the present invention comprises molybdenum oxide on a carrier preferably alumina. The amount of molybdenum oxide employed is about 5 to 13% by weight based upon the weight of the alumina. The catalyst is prepared by known methods, such as by impregnation of the alumina with a Water-soluble molybdenum salt, followed by heating to convert this salt to molybdenum oxide, or by coprecipitation of aluminum and molybdenum hydroxides by addition of an ammoniacal solution of ammonium molybdate to an acid solution of an aluminum salt followed by water washing and by heating to convert to the oxides.

It is to be understood that the mild hydrofining conditions of the present invention are secured by the adjustment of the above named operating conditions. For instance, if a relatively high liquid feed rate is used as compared to the amount of catalyst present, the higher temperature range may be employed. On the other hand, if a very active catalyst is used, it is desirable to use a relatively high feed rate or to use a relatively low temperature. The mild hydrofining conditions of the present invention are measured by the amount of hydrogen consumption per barrel of oil feed. As pointed out heretofore in the art, conventional hydrofining operations utilized for the desulfurization of certain stocks are conducted under conditions whereby the hydrogen consumption ranges from to 600 standard cu. ft.

of hydrogen per barrel of oil. These operations used heretofore in the art secured a substantial sulfur reduction (50 to 90%). In accordance with the present process, operating conditions are adjusted so that the hydrogen consumption in standard cu. ft. per barrel does not exceed 60 and is preferably less than 40. Furthermore, the extent of the sulfur reduction when utilizing the mild hydrofining conditions of the present invention does not exceed about 35% and preferably does not exceed about 20%.

The process of the present invention may be more fully understood by the following examples illustrating the same.

EXAMPLE I Cracked Virgin Heating Heating Blend Oil Oil Sulfur 1. 17 Carbon Residue, 1 Wt. Percent 10% Residuum) 09 25 1 Carbon residue (10% residuum) is obtained by subjecting the sample to an ASTM distillation, taking the 10% bottoms fraction from the distillation and subjecting it to a test for Conradson carbon.

From the above it is apparent that the virgin and cracked heating oil are incompatible since the carbon residue on the blend is about three-fold the carbon residue of the cracked heating oil.

oils are degraded with respect to carbon residue quality due to sweetening operations.

EXAMPLE III Cracked Sweetened gg gfi ea on Virgin Blend Hydrofined Hydrofined Heat. Oil

Carbon Residue .09 .13 .31 Do 05 .13 .07

From the above it is apparent that although sweetening of a sour virgin stock degrades the treated product by blending this product with a hydrofined cracked heating oil, an unexpected high quality blended product is secured. On the other hand, if the treated virgin heating oil is blended with a non-hydrofined cracked heating oil the carbon residue of the blended product is prohibitive.

In various operations the cracked heating oil was hydrofined using a cobalt molybdate on alumina catalyst wherein the concentration of the cobalt molybdate was about 10 to 15% by weight based upon the alumina. In other operations the catalyst comprised molybdenum oxide on alumina wherein the concentration of the molybdenum oxide by weight based upon the alumina was in the range of about 8 to 10%. The results of these operations are listed in the following table:

Hydrofi ning cracked heating oil Column A l B C D E F l G H Catalyst C0M004 on CoMoOi 0n CoMoOi on M003 on M00 on M003 on AAIzOa. A1203. Al O Feed 1 Temperature, F. Feed Rate, V./V./Hr Pressure, p. s. i. gm... Hz in Fresh Feed Excess Hz, 8. O. F./B 1,000... H2 Consumption, S. C. FJB 160 10 Product Inspections:

Sulfur, Wt. Percent 0.44 Sulfur Reduction, Percent 62 Carbon Residue (10% Res uum,

wt. percent 012 0.05 Blended Carbon Residue (10% Residuum), wt. percent 2 0 08 0.05

1 Feed "I Sulfur 1.17 1.54 Carbon Residue (10% Residuurn) Wt. Percent 0.09 0.13 Blended Carbon Residue (10% Residuum) Wt. Percent 0.25 0.21

2 Blended in vol. percent concentration in a 658 FE]? doctor sweetened virgin heating oil having a carbon residue of 0.05 wt. percent.

EXAMPLE II Carbon Copper Residue N 0.

Before sweetening 05 81 After sweetening 13 1 From the above it is apparent that certain virgin heating The first column in the table shows the results of hydrofining with cobalt molybdate catalyst at 600 F. and l v./v./hr. These are conditions for relatively severe hydrofining. At these conditions, sulfur was reduced from 1.17 to 0.44 wt. percent. It is to be noted that the hydrogen consumption was standard cu. ft. per barrel. On the other hand, carbon residue was increased from 0.09 to 0.12, showing that these conditions were not suitable for hydrofining cracked heating oil.

When conditions were made milder by increasing the feed rate from 1 to 7 v./v./hr., the sulfur content was reduced to only 0.95%, but the carbon residue was decreased from 0.09 to 0.05. Similar results were obtained when the temperature was decreased from 600 to 500 F. while maintaining a feed rate of 1 v./v./hr.

The catalyst comprising molybdenum oxide supported on alumina is a less active hydrogenation catalyst than cobalt molybdate. At 600 F. and 4 v./v./hr., this catalyst gave very little reduction in sulfur but a good im provement in carbon residue. A good reduction of carbon residue could also be obtained with this catalyst by operating at 500 F. and 1 v./v./hr.

At the severe conditions, where there was a good reduction in sulfur content, hydrogen consumption was relatively high, for example, about 150 to 200 cu. ft./bbl. On the other hand, when relatively mild hydrofining conditions were used with little reduction in sulfur but with good reduction in carbon residue, hydrogen consumption was less than 50 cu. ft./bbl.

The data presented above demonstrate the fact that a good improvement in carbon residue and carbon residue compatibility can be obtained under conditions giving very little, if any, reduction in sulfur content. While satisfactory results can be obtained with cobalt molybdate catalyst, operated at 600 F. and '8 to 16 v./v./hr., the preferred operating conditions include the use of the M003 on Al catalyst at 600 F. with a feed rate of 4 to 16 v./v./hr. Satisfactory operation can also be obtained at 500 F. with either catalyst at lower feed rates.

As discussed, severe hydrofining for desulfurizing oil products is known in the art. The process has generally been used on high sulfur stocks. It has now been found, however, that mild hydrofining is useful for treating products which require no reduction in sulfur. The present invention is concerned with an application of hydrofining to this type of operation.

In accordance with the present process, hydrofining can be used in place of acid treating to improve the carbon residue and carbon residue compatibility of cracked heating oils. Furthermore, it has been found that the improvement obtained by hydrofining is considerably greater than can be obtained by acid treating. However, as pointed out, it has been found that severe hydrofining conditions are not effective in reducing carbon residue. As a matter of fact, severe hydrofiuing conditions actually increased carbon residue of the feed. On the other hand, by using relatively mild hydrofining conditions, a marked improvement in carbon residue and carbon residue compatibility is obtained.

In the hydroiining operation, hydrogen sulfide is formed. Small amounts of the hydrogen sulfide tend to remain in the treated product. These small amounts may be removed by any suitable method, as for example steam stripping, caustic washing or an equivalent operation.

What is claimed is:

1. A process for improving the quality of cracked heating oil which comprises subjecting cracked heating oil constituents to a temperature in the range of 400 to 700 F., and pressure in the range of 50 to 250 pounds per square inch in the presence of extraneously generated hydrogen and a hydrofining catalyst comprising molybdenum oxide on a carrier at feed rates in the range of 1 to 16 v./ v./ hr. so that there is a consumption of hydrogen not in excess of about 60 standard cubic feet per barrel antolf so that the sulfur reduction does not exceed about /0.

2. The process defined by claim 1 in which the said catalyst is cobalt molybdate on alumina.

3. The process defined by claim 1 in which the said catalyst is molybdenum oxide on alumina.

4. The process defined by claim 1 in which the said hydrogen consumption does not exceed about standard cubic feet of hydrogen per barrel, and the said sulfur reduction does not exceed about 20%.

5 A process for the preparation of a high quality heating oii blend comprising virgin fractions and cracked fractions, which comprises segregating virgin hydrocarbon constituents boiling in the heating oil boiling range and cracked hydrocarbon constituents boiling in the heating oil boiling range, subjecting said cracked constituents to a temperature in the range of 400 to 700 F., and pressure in the range of to 250 pounds per square inch in the presence of extraneously generated hydrogen and a hydroiining catalyst comprising molybdenum oxide on a carrier at feed rates in the range of 1 to 16 v./v./hr. so that there is a consumption of hydrogen not in excess of about standard cubic feet per barrel and so that the sulfur reduction does not exceed about 35%, and thereafter blending said treated cracked constituents With said virgin constituents to produce a high quality heating oil blend.

6. The process defined by claim 5 in which the said catalyst comprises cobalt molybdate on alumina.

7. The process defined by claim 5 in which the said catalyst comprises molybdenum oxide on alumina.

8. The process defined by claim 5 wherein said virgin hydrocarbon constituents are caustic treated prior to the said blending.

References Cited in the file of this patent UNITED STATES PATENTS 2,547,380 Fleck Apr. 3, 1951 2,574,447 Porter NOV. 6, 1951 2,574,448 Porter et al. Nov. 6, 1951 2,577,823 Stine Dec. 11, 1951 2,592,383 Blatz Apr. 8, 1952 FOREIGN PATENTS 456,764 Italy Apr. 21, 1950

Claims

1. A PROCESS FOR IMPROVING THE QUALITY OF CRACKED HEAT ING OIL WHICH COMPRISES SUBJECTING CRACKED HEATING OIL CONSTITUENTS TO A TEMPERATURE IN THE RANGE OF 400* TO 700* F., AND PRESSURE IN THE RANGE OF 50 TO 250 POUNDS PER SQUARE INCH IN THE PRESENCE OF EXTRANEOOUSLY GENERATED HYDROGEN AND A HYDROFINING CATALYST COMPRISING MOLYBDENUM OXIDE ON A CARRIER AT FEET RATES IN THE RANGE OF 1 TO 16V./V./HR. SO THAT THERE IS A COMSUMPTION OF HYDROGEN NOT IN EXCESS OF ABOUT 60 STANDARD CUBIC FEET PER BARREL AND SO THAT THE SULFUR REDUCTION DOES NOT EXCEED ABOUT 35%.