US2913394A - Butyrolactone solvent extraction process for removal of metal contaminants - Google Patents

Description

1959 c. N. KIMBERLIN, JR ET-AL 2,913,394

' BUTYROLACTONE SOLVENT EXTRACTION PROCESS v FOR REMOVAL OF METAL COIITAIVIINANTS Filed March 1, 1955 f Hi2 59km; T u

- sax wa r m SYSTEM 3 LIGHT GASES FRACTIONATION SYSTEM CRUDE LIGHT GAS on. s SOLVENT EXTRACTIONS 2 5 SYSTEM HEAVY GAS on! /SOLVENT STRIPPER I8 EXTRACT OIL Charles N. Kimberlin, Jr. I William J. Maflox mentors United Stte Charles Newton Kimberlin, Jr., and William Judson Mattox, Baton Rouge, La., assignors to Esso Research and Engineering Company, a corporation of Delaware Application March 1, 1955, Serial No. 491,322 9 Claims. (Cl. 208 -87) This invention concerns a novel solvent extraction process employing butyrolactone as a solvent for the upgrading of petroleum fractions. The invention is of particular application to the treatment of gas oil fractions derived from a crude petroleum oil so as to substantially improve the characteristics of the gas oil for processing by catalytic cracking. The extraction process of this invention is notable in providing a technique for the selective extraction of metal contaminants, normally present in high boiling petroleum oil fractions.

In recent times, a great deal of effort has been applied in the petroleum refining field to increase the recovery of catalytic cracking feed stock from residual fractions of petroleum oil. conventionally, the feed stock to a catalytic cracking operation constitutes a so-called gas oil fraction of crude oil which boils in the range of about 400 to 800 F. or somewhat higher. Portions of the petroleum crude oil boiling above the gas oil boiling range may be considered residual petroleum fractions. Such residual fractions may be used as sources of asphalt, fuel, and other products which are of relatively low economic value. It, therefore, becomes attractive to develop means for successfully utilizing portions of the residual fractions of crude oil as catalytic cracking feed stock. Attempts to employ heavier fractions of crude oil for catalytic cracking have been limited heretofore due to the presence of certain metal contaminants in such heavy fractions. Thus the highest boiling fractions of a crude oil contain substantial portions of metal contaminants, particularly including nickel, vanadium and iron compounds. The residual fractions of typical crude oils generally contain these metal contaminants in quantities of about 10 to 50 pounds per 1000 barrels of metal contaminants. When an attempt is made to segregate higher boiling distillate fractions of a crude oil, some portion of these metal contaminants is inherently and unavoidably carried over into the distillate products. For example, in a: vacuum distillation operation where a heavy boiling gas oil fraction is segregated from a crude oil, about 0.5 to 10 pounds per 1000 barrels of metal contaminants will be obtained in the gas oil distillate in a typical situation. In this example, the gas oil distillate referred to would have a boiling range of about 800 to 1100" F., or higher.

The problem of metal contaminant carry over in the segregation of heavy distillate fractions is apparently due to two phenomena. First of all, it appears that the metal contaminants occur or are converted during distillation to 2,913,394 Patented Nov. 17,, 1959 as mechanical entrainment. To generally indicate the mechanism of this effect, it can be considered that a small portion of high boiling liquid hydrocarbons from the residual fraction is normally entrained overhead in a distillation operation. Since such liquid hydrocarbons contain concentrated amounts of metal contaminants, such entrainment in distillate products accounts for a portion of the metal contamination of such distillates.

By virtue of the fact that catalytic cracking operations are adversely affected by the presence of such metal vcontarninants, it is apparent that the need exists for some means to recover high boiling fractions of a crude oil while eliminating contamination in the manner described. The presence of metal contaminants and particularly nickel and/or vanadium in a catalytic cracking operation results in direct contamination of the catalyst by the metal compound. Metal continues to accumulate on the catalyst during the life of the catalyst having the result of seriously altering the catalytic properties of the catalyst.

One of the effects of such catalyst poisoning is to cause excessive hydrogen to be produced during catalytic cracking as the result of the change in the cracking characteristics of the catalyst. In actual commercial operations hydrogen production has become so severe, due to catalyst poisoning, as to cause failure of gas compressors due to the change in the density of the gases, resulting in flooding of light end fractionation equipment and the like. It is to be understood, therefore, that the problem of catalyst contamination is a pressing problem at the present time.

It has been appreciated that one technique for preventing the problem of catalyst contamination could conceivably be a selective solvent treatment for the catalytic cracking feed stock in order to remove metal contaminants which are normally present. Heretofore, however, difficulties have been encountered in finding a solvent capable of selectively removing metal contaminants. A solvent such as phenol or furfural which exerts a strong solvent action for high molecular weight aromatic compounds will also remove metal contaminants to some extent. However, the problem with such solvents is that they exhibit poor selectivity, resulting in substantial removal of hydrocarbon constituents as Well as metal contaminants. As a result use of such solvents has heretofore been economically prohibitive due to the loss in catalytic cracking feed stock.

The present invention is based on the discovery that butylrolactone is uniquely effective in selectively remov ing metal contaminants from heavy petroleum feed stocks. As a result, use of butyrolactone makes possible a selective removal of metal contaminants permitting substantial elimination of such contaminants from catalytic cracking feed stocks with little loss in feed stock yields.

The precise mechanism by which butyrolactone exhibits these specific and unusual solvent properties is not known at the present time. It seems probable, however, that the particular molecular configuration of this compound combines a critical balance between hydrocarbon solubility and solvent power for the compounds enumerated which is particularly adapted for the purposes of this invention. It has been established, for example, that butyrolactone exerts solvent powers in the practice of this invention completely distinct from those of other solvents which have been used, such as furfural. It is to be understood, therefore, that in the practice of this invention butyrolactone specifically is to be employed as the selective solvent.

At the same time, however, it is possible to employ solvent modifiers with butyrolactone for particular applications. Such solvent modifiers are chosen so as not to substantially affect the selective solvent action of butyrolactone while changing somewhat the oil solubility char acteristics of butyrolactone. Solvent modifiers are particularly useful for permitting extraction with butyrolactone at higher temperatures than normally attractive. Included among solvent modifiers which may be employed are water, water-soluble aliphatic alcohols, acetic acid, and ethylene glycol. Such compounds can be employed by combination with butyrolactone in minor amounts providing a solvent composition in which the solvent modifiers are present in amounts less than about one third of the total solvent composition.

Solvent extractions employing butyrolactone in accordance with this invention may be conducted at temperatures in the broad range of about 80 to 500 F. However, the selectivity properties of butyrolactone are not critically affected by temperature so that it is generally preferred to operate at moderate temperatures selected to maintain the feed stock at a suitable viscosity for treatment. Thus, in general, a temperature of about 100 to 200 F. is particularly attractive. The extraction can be conducted at any pressure selected from the broad range of about to 750 psi. Again, however, pressure is not particularly critical in the conduct of this invention, making it possible to conduct the process at atmospheric pressure as is normally preferred.

The amount of solvent composition employed in the practice of this invention varies somewhat in accordance with the feed stock to be treated and the degree of change required in the properties of the feed stock. In general, however, the amount of solvent to be employed will be selected from the range of 0.5 to 3 volumes of solvent per volume of oil to be treated. For most applications it is particularly preferred to use about 1 volume of solvent per volume of oil to be treated.

The solvent treating process may be carried out by conventional solvent extraction techniques. Thus, if desired, batch mixing and settling may be employed or continuous and countercurrent treating operations may be employed. In this connection, for example, it is particularly preferred to carry out the process by introducing butyrolactone at an upper portion of a treating tower to flow downwardly countercurrent to the oil to be treated which is introduced near the bottom of the treating tower. Packing elements, perforated plates, or other contacting aids can be employed in such a system. A raffinate phase constituting the treated oil and minor portions of butyrolactone may be removed overhead from such a tower. An extract phase, principally constituting butyrolactone together with minor amounts of constituents removed from the treated oil, can be removed from the bottom of the treating tower.

Solvent may be recovered from the rafiinate and extract phases by conventional techniques. Thus, solvent can be stripped from the extract and rafiinate by a simple distillation procedure permitting removal of butyrolactone as an overhead product for recycle to the solvent treating system. Alternatively and as a particular feature of this invention, solvent may be recovered by cooling the extract and rafiinate phases substantially below the extraction temperature. Cooling in this manner results in a change in solvent properties sufiicient to liberate butyrolactone for recycle to the extraction system.

Alternatively, solvent may be recovered by adding water to the extract and raflinate phases. The addition of water causes the separation of an upper oil layer and a lower layer comprising an aqueous solution of butyrolactone solvent. The lower, aqueous solvent layer is withdrawn and may be dehydrated by distillation or other means for recycling to the extraction zone.

As indicated, solvent extraction employing butyrolactone is particularly attractive for the upgrading of catalytic cracking feed stocks. Such feed stocks may be defined as the gas oil fraction of a petroleum crude oil boiling above the gasoline boiling range or boiling above about 450 F. The end point of such a gas oil fraction can be as high as desired, ranging upwardly to about 1050" to 1300 F. (equivalent atmospheric boiling point).

While, as indicated, the invention is broadly applicable to extraction of gas oil boiling in the range of about 450 to 1300 F., the invention is of particular application to the portion of such fractions boiling above about 900 to 950 F. Such high boiling gas oil fractions are those in which metal contaminants are particularly concentrated. For this reason, in preparing catalytic cracking feed stock it is particularly preferred to segregate the portion of the feed stock boiling above about 950 F. and then to subject this specific fraction to the process of this invention.

The accompanying drawing illustrates a specific and preferred embodiment of the present invention showing its application to the preparation of catalytic cracking feed stock.

Referring to the drawing, the number 1 is used to designate a fractionation system of the type conventionally used in segregating crude oil into fractions of different boiling range. Fractionation system 1 may constitute a combination of an atmospheric distillation unit and a vacuum distillation unit or may comprise other types of distillation equipment adapted to provide the separate fractions to be identified. The fractionation system is of the character permitting segregation of a crude oil introduced through line 2 into the products identified on the drawing. C and lighter gases may be removed overhead through line 3 and a naphtha fraction may be removed as a side stream product through line 4. Preferably a light gas oil stream boiling in the range of about 450 to 950 F. is removed as a higher boiling side steam product through line 5. Finally, the highest boiling side stream product, removed through line 6, is a heavy gas oil boiling in the range of about 950 to 1300 F. Heavy residual oil constituents are withdrawn from the fractionation system through bottom withdrawal line 7.

In accordance with this invention, the heavy gas oil fraction of line 6 containing substantial portions of metal contaminants is subjected to solvent extraction in tower 8. Butyrolactone is introduced to extraction system 8 through line 9 for countercurrent contact with the heavy gas oil in the tower. Extraction can be conducted for example at a temperature of about F., at atmospheric pressure and using about 1 volume of butyrolactone per volume of heavy gas oil.

The rafiinate phase constituting treated oil together with small amounts of butyrolactone, is removed overhead from extraction system 8 through line 10. Residual solvent can be removed overhead from the treated oil in stripping zone 11, permitting removal of segregated butyrolactone through line 12 for recycle to line 9. A treated oil freed of residual solvent is then passed through line 13 to the catalytic cracking system 14.

The extract phase removed from the solvent extraction system 8 through line 15 may similarly be passed to a solvent stripper 16 permitting removal of butyrolactone through overhead line 17. An extract oil will be withdrawn from the bottom of stripper 16 through line 18. This extract oil may be blended with fuel oil or can be employed as a source of chemicals or the like.

The treated oil of line 13 which is subjected to eatalytic cracking is of improved cracking characteristics by virtue of the substantial elimination of metal contami nants. This treated oil can be subjected to conventional catalytic cracking in zone 14. Thus, the cracking may be of the fixed-bed, suspensoid, moving bed or fluidized solids type. It is preferred, however, ,to employ a fluidized solids cracking process.

The fluidized solids technique for cracking hydrocarbons comprises a reaction zone and a regeneration zone, employed in conjunction with a fractionation zone. The reactor and the catalyst regenerator are or may be arranged at approximately an even level. The operation of the reaction zone and the regeneration zone is preferably as follows:

An overflow is provided in the regeneration zone at the desired catalyst level, The catalyst overflows into a withdrawal line which preferably has the form of a U- shaped seal leg connecting the regeneration zone with the reaction zone. The feed stream introduced is usually preheated to a temperature in the range from about 500 to 650 F., by heat exchange with regenerator flue gases which are removed overhead from the regeneration zone, or with cracked products. The heated feed stream is then introduced into the reactor. The seal leg is usually sufficiently below the point of feed oil injection to prevent oil vapors from hacking into the regenerator in case of normal surges. Since there is no restriction in the overflow line from the regenerator, satisfactory catalyst flow will occur as long as the catalyst level in the reactor is slightly below the catalyst level in the regenerator when the vessels are maintained at about the same pres-- sure. Spent catalyst from the reactor flows through a second U-shaped seal leg from the bottom of the reactor into the bottom of the regenerator. The rate of catalyst flow is controlled by injecting some of the air into the catalyst transfer line to the regenerator.

The pressure in the regenerator may be controlled at the desired level by a throttle valve in the overhead line from the regenerator. Thus, the pressure in the regenerator may be controlled at any desired level by a throttle valve which may be operated, if desired, by a differential pressure controller. If the pressure differential between the two vessels is maintained at a minimum, the seal legs will prevent gases from passing from one vessel into the other in the event that the catalyst flow in the legs should cease.

The reactor and the regenerator may be designed for high velocity operation involving linear superficial gas velocities of from about 2.5 to 4 feet per second. However, the superficial velocity of the upflowing gases may vary from about 1 to 5 feet per second and higher. Catalyst losses are minimized and substantially prevented in the reactor by the use of multiple stages of cyclone separators. The regeneration zone is also provided with cyclone separators. These cyclone separators usually include 2 to 3 or more stages.

Distributing grids may be employed in the reaction and regeneration zones. Operating temperatures and pressures may vary appreciably depending upon the feed stocks being processed and upon the products desired. Operating temperatures are, for example, in the range from about 800 to 1000 F., preferably about 850 to 950 F. in the reaction zone. Elevated pressures may be employed, but in general, pressures below 100 pounds per square inch gauge are utilized. Pressures generally in the range from 1 to 30 pounds per square inch gauge are preferred. Catalyst to oil ratios of about 3 to 10, preferably about 6 to 8 by weight, are used.

The catalytic material used in the fluidized catalyst cracking operation are conventional cracking catalysts. These catalysts are oxides of metals of groups II, III, IV and V of the periodic table. A preferred catalyst comprises silica-alumina wherein the weight percent of the alumina is in the range from about 5 to 20%. Another preferred catalyst comprises silica-magnesia where the weight percent of the magnesia is about 20 to 35%.

The size of the catalyst particles is usually below about 200 microns. Usually at least 50% of the catalyst has a micron size in the range from about 20 to 80. Under these conditions with the superficial velocities as given, a fluidized bed is maintained where, in the lower section of the reactor, a dense catalyst phase exists while in the upper area of the reactor a disperse phase exists.

Included in the catalytic cracking system is a product fractionator adapted to segregate gasoline and heavier boiling fractions of the cracked product.

In the particular embodiment of the invention illustrated in the drawing, the heavy gas oil fraction is subjected by itself to extraction with butyrolactone so as to improve the cracking characteristics of the; heavy gas oil. The light gas oil, withdrawn from fractionation system 1 through line 5, can be passed directly to catalytic cracking system 14. Alternatively, however, a part or all of this light gas oil can be extracted with the heavy gas oil in extraction zone 8. It is particularly preferred to employ a minor portion of light gas oil in admixture with heavy gas oil so as to reduce the viscosity of the gas oil to the extent desired.

The following examples illustrate the nature and utility of this invention:

Example 1 A heavy gas oil having a 50% boiling point of 950 F. and a final boiling point above 1100 F. derived from a South Louisiana crude oil was subjected to the process of this invention. This gas oil contained 2.3 p.p.m. of nickel and 0.2 p.p.m., of vanadium prior to treatment. The oil was treated in a batch extraction with butyrolactone in three treatments employing 1 volume of butyrolactone per volume of oil in each treatment at a temperature of 180 F. and at atmospheric pressure. Contacting by mechanical agitation for 5 minutes followed by settling for 5 to 10 minutes was adequate for this batch type of extraction. Solvent stripping from the raffinate product provided a treated oil yield of 87%. This oil had a nickel concentration of only 0.25 p.p.m. and 0.0 p.p.m. of vanadium. It will be seen from these data that the extraction process of this invention is particularly adapted for substantially eliminating metal contaminants from heavy gas oils while providing high yields of treated oil. For comparative purposes, it may be noted that in a similar extraction with phenol as solvent, and with minor amounts of water added to regulate oil solubility, substantially poorer results were obtained. In this case oil yields of only 72% were obtained when treated to the same nickel content. Extraction with furfural to 0.25 p.p.m. of nickel yielded only 77% of oil. It is to be seen, therefore, that butyrolactone was effective in reducing the nickel content of the treated oil to a very low concentration and that the treated oil yields were much higher than when the extraction was made with conventional solvents such as phenol or furfural.

Example 2 The heavy South Louisiana gas oil employed in Example 1 was contacted with 90% butyrolactone-10% water solvent in a series of batch extractions at 180 F. Comparison of the oil yields at the same nickel content (0.25 to 1.0 p.p.m.) show the same selectivity as resulted from the use of butyrolactone as solvent.

Example 3 Butyrolactone extraction of South Louisiana gas oil was carried out at 100 F., by diluting the heavy oil with two volumes of a light hydrocarbon fraction (0;) Three batch extractions followed by flashing off the diluent yielded 94 weight percent of refined oil having a nickel content of 0.49 p.p.m. This yield is 13% higher than resulted from phenol extraction to the same nickel content.

It will be appreciated from the data presented that the process of this invention is a versatile and attractive process for upgrading petroleum fractions boiling in the gas oil boiling range.

What is claimed is:

l. A process for upgrading a hydrocarbon oil boiling within the range of about 450 to 1300" F. and containing metal contaminants, which comprises contacting said oil with about 0.5 to 3 volumes, per volume of oil, of butyrolactone at a temperature in the range of about 80 to 500 F., and segregating a treated oil of substantially reduced concentration of metal contaminants, said lactone being added as such to said oil to be treated.

2. The process defined by claim 1 in which the said oil to be treated constitutes the gas oil fraction of a crude oil including constituents boiling above about 950 F.

3. The process defined by claim 1 in which the said oil to be treated constitutes catalytic cycle oil.

4. The process defined by claim 1 in which the said butyrolactone includes solvent modifiers selected from the group consisting of water soluble aliphatic alcohols, acetic acid, and ethylene glycol.

5. The process defined by claim 1 wherein said metal contaminants comprise nickel and vanadium.

6. A process for providing a high-boiling, high-quality catalytic cracking feed stock comprising the steps of fractionating a petroleum crude oil to segregate a metalcontaminated fraction boiling within the range of about 450 to 1300 F., and including constituents boiling above 950 F., adding to said fraction about 0.5 to 3 volumes of butyrolactone per volume of said fraction, and segregating a treated oil product of substantially decreased concentration of metal contaminants.

7. The process defined by claim 6 wherein said metal contaminants in said crude oil comprise nickel and vanadium.

8, A combination process comprising the steps of fractionating a petroleum crude oil to obtain metal containing high boiling gas oil constituents including those within the range of about 950 to 1300 F., treating said high boiling fraction with added butyralactone and segre- 8 gating a treated oil product, and thereafter catalytically cracking said treated oil product. 9. The process defined by claim 8 in which the said high boiling gas oil is diluted with a minor portion of a lower boiling gas oil.

' References Cited in the file of this patent UNITED STATES PATENTS 2,217,429 Balcar Oct. 8, 1940 2,228,510 Dearborn et al. Ian. 14, 1941 2,246,297 Duncan et al. June 17, 1941 2,304,289 Tongberg Dec. 8, 1942 2,342,888 Nysewander et al. Feb. 29, 1944 2,374,102 Jahn et al. Apr. 17, 1945 2,383,057 Gross et al Aug. 21, 1945 2,396,299 Sweeney et al. Mar. 12, 1946 2,738,860 Lorenz et al. Mar. 20, 1956 2,771,494 Weedman Nov. 20, 1956 2,831,905 Nelson Apr. 22, 1958 2,846,358 Bieber et al. Aug. 5, 1958 OTHER REFERENCES Richter: Organic Chemistry, Third American Offset Reprint Ed., vol. I, pages 424, 425, 427, and 477; pub.

5 1944 by Elsevier Publishing 00., New York, NY.

Claims (1)

1. A PROCESS FOR UPGRADING A HYDROCARBON OIL BOILING WITHIN THE RANGE OF ABOUT 450* TO 1300* F. AND CONTAINING METAL CONTAMINANTS, WHICH COMPRISES CONTACTING SAID OIL WITH ABOUT 0.5 TO 3 VOLUMES, PER VOLUME OF OIL, OF BUTYROLACTONE AT A TEMPERATURE IN THE RANGE OF ABOUT 80* TO 500* F., AND SEGREGATING A TREATED OIL OF SUBSTANTIALLY REDUCED CONCENTRATION OF METAL CONTAMINANTS, SAID LACTONE BEING ADDED AS SUCH TO SAID OIL TO BE TREATED.

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