US2902428A - Extraction of feedstock with polyethylene glycol solvent - Google Patents

Description

Sept. 1, 1959 EXTRACTION OF FEEDSTOCK WITH POLYETHYLENE GLYCOL SOLVENT Filed NOV. 1, 1955 CRUDE OIL -,SOLVENT SEPARATOR LIGHT CATALYTIC GASES CRACKING a SYSTEM l3 J FRACTIONATION SYSTEM iI NA HTHA ggl zgzwwvs i LIGHT \SOLVENT 6 EXTRACTION SYSTEM (HEAVY GAS on.

4' RESIDUAL I7 SOLVENT SEPARATOR Charle 'N. Kimberlin, Jr

I8 EXTRACT Invenfoi's William J. Maffox the form of metalcomplexes.

United States Patent EXTRACTION OF FEEDSTOCK WITH POLY:

ETHYLENE GLYCOL SOLVENT Application November 1, 1955, Serial No. 544,126

7 Claims. (Cl. 208-87) This invention concerns a novel solvent extraction process employing polyethylene glycols as solvents 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, condensed ring aromatic components, and nitrogen compounds 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. 7

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, vanadiumand 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 are 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. Firstof all, it appears that the metal contaminants occur or are converted during distillation to These complexes may generally be identificd as large condensed ring constitu'ents. Some of these metal complexes and particularly nickel and vanadium porphyrins are sufiiciently volatile so a as to be carried overhead at a temperature of about 1050 F. Consequently, when attempting to segregate high boiling gas oil fractions including components boiling ice 2 above about 900 F., volatile metal contaminants are unavoidably obtained in the distillate product. It appears that a second phenomenon is also involved which may be referred to 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 are 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 aflected by the presence of such metal contaminants, 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 eflfects 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 clue 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 actionfor 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 certain polyethylene glycols are uniquely efi'ective in selectively removing metal contaminants from heavy petroleum feed stocks. As a result, use of the glycols 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. Above and beyond these considerations, it has been found that they also exert a desirable selective solvent action toward other undesirable constituents normally present in the cracking feed stock. In particular polyethylene glycols serve to remove condensed ring aromatic compounds and nitrogen compounds concomitant with removal of metal contaminants so as to substantially improve the cracking characteristics of the feed stock treated.

The precise mechanism by which the polyethylene glycols exhibit these specific and unusual solvent properties is not known at the present time. It seems probable, however, that the particular molecular configuration of these compounds combines a critical balance bctween 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 the polyethylene glycols exert solvent powers in the practiceof this invention completely dis tinct from those of other solvents which have been used, such as furfural.

At the same time, it is possible to employ solvent modifiers with the glycols for particular applications. Such solvent modifiers are chosen so as not to substantially affect the selective solvent action of the polyglycols while changing somewhat the oil solubility characteristics thereof. Solvent modifiers are particularly useful for permitting extraction with the polyethylene glycols at higher temperatures than normally attractive. Included among solvent modifiers which may be employed are water, Water soluble aliphatic alcohols, and acetic acid, and even lower ethylene glycols. Such compounds can be employed by combination With the polyglycols 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.

In accordance with the present invention, polyethylene glycols having a molecular weight of from about 200 to 600, that is, tetraethylene glycol to the 13 unit compositions or their mixtures are employed as selective solvents for the purposes heretofore mentioned.

Solvent extractions employing these polyethylene glycols in accordance with this invention may be conducted at temperatures in the broad range of about 150 to 450 F. Thus, in general, a temperature of about 175 to 350 F. is particularly attractive. In general, with increasing number ethylene glycol units, a lower extraction temperature is preferred. Thus, with a polyethylene glycol of about 200 molecular weight, an extraction tem perature of about 250 to 350 F. is desirable. When a 600 molecular Weight polyethylene glycol extractant is employed, temperatures of 150 to 250 F. are more effective. The extraction can be conducted at any pressure selected from the broad range of about 15 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 compositionemployed 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, i.e., 50 to 300 volume percent, 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 the glycol at an upper portion of a treating tower to flow downwardly counterculrrent 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 polyethylene glycol may be removed overhead from such a tower. An extract phase, principally constituting the polyglycol together with minor. amounts of constituents removed from the treated oil, can be removed from the bottom of thetreating tower.

Solvent maybe recovered from the raftinate and extractphases by conventional techniques. Thus, a simple distillation procedure permits removal of the polyglycols for recycle to the solvent treatingsystem. Alternatively 4 and as a particular feature of this invention, solvent may be recovered by cooling the extract and raflinate phases substantially below the extraction temperature. Cooling in this manner results in a change in solvent properties sufficient to liberate the polyglycols 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 polyethylene 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 polyethylene glycols 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). It may be observed that solvent extraction of a lubricating oil distillate boiling within the gas oil boiling range as defined is also particularly attractive. Employing the process of this invention, such a solvent extraction serves to remove undesired aromatic compounds from a lubricating oil so as to provide high yields of high quality lubricating oil.

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,

Referringto 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 int-o the products identified on the drawing. C and lighter gases may be removed overhead through line 3 and a naphthafraction may be removed as a side stream product through line 4. Preferably a light gas on stream boiling in the range of about 450 to 950 F. is removed as a higher boiling side'stream 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. r r

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. A polyethylene glycol or glycol mixture 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 200 F., at atmospheric pressure and using about 2 volumes of the polyglycol per volume of heavy gas oil.

The rafiinate phase constituting treated oil together with small amounts of solvent, is removed-overhead from separators. -cyclone separators.

regeneration zones.

extraction system 8 through line 10. Residual solvent can be removed overhead from the treated oil in separation zone 11, permitting removal of segregated polyglycol 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 separator 16 permitting removal of solvent 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 catalytic cracking is of improved cracking characteristics by virtue of the substantial elimination of metal contaminants. In addition, this oil is of better cracking characteristics because of the elimination of high molecular weight condensed ring aromatic compounds and nitrogen compounds. This treated oil can be subjected to con ventional 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 hydrocarlbons 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 sufiiciently below the point of feed oil injection to pre vent oil vapors from backing 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 pressure. 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 The regeneration zone is also provided with These cyclone separators usually include 2 to 3 or more stages.

Distributing grids may be employed in the reaction and 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 pounds per square inch gauge are utilized. Pressures generally in the range from 1 to 30 pounds per square inch gauge are preferred. Catalystto 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. Usuallyat 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 polyethylene glycols 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 eatalytic 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. j

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

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 about 2.3 parts per million (ppm) of nickel. The oil was treated in a batch extraction with polyethylene glycol mixtures having an average molecular weight of 200 and 600 respec tively, in three treatments employing 1 volume of the polyglycol per volume of oil in each treatment. Temperatures employed with each glycol were 180 F. and 300 F. at atmospheric pressure. Contacting was by mechanical agitation for 5 minutes, followed by settling for 15 minutes. The results obtained were as follows:

Table I Selectivity, Polyethylene Temp, Raffinate Nickel in Percent of Glycol, M.W. F. Yield, Wt. Raflinate, Phenol Yield Percent p.p.n1. At Same Nickel Content The above data show polyethylene glycols to be highly effective for the removal of metal containing components, especially with the 200 M.W. glycol at 300 F. and the 600 M.W. glycol at 180 F. It will be noted that efficiencies are superior to those of phenol. Thus, at 300 F. the selectivity of the 200 M.W. glycol was 109% of that of phenol when treated for the same nickel content.

The high thermal coefiicient of solubility character- Table II Solvent, M.W 106, 150 200 600 Raflinate Yield, Wt. Percent 91 96 94 91 i,p.p.m 2.50. 1.90 0.71 0.98 Percent Ni Removal 21 71 61 The above data show clearly that the polyethylene glycols of the present invention are superior to the lower molecular Weight diand triethylene glycols, for this service, and the 200 M.W. had the highest selectivities and highest nickel removal characteristics.

In a subsequent extraction of a South Louisiana high nickel gas oil with polyethylene glycol of 200 M.W. at 500 F., the nickel content was reduced from 2.3 ppm. to 0.6 ppm. On cooling the extract phase to 90 F. and removing the separated oil by solution in hexane, 94.9% of the extracted oil was removed from the solvent with only 5.1% remaining in the solvent. Of the extracted nickel, 87% was contained in the extracted oil separated from the solvent at 90 F., only 13% remaining in the solvent.

The process of the present invention may be subject to many modifications. It may be desirable to extract not only gas oil and catalytic cycle oil but lube oil fractions as well, thus raising the viscosity index of these oils by removal of undesirable aromatics.

What is claimed is:

1. A process for upgrading a hydrocarbon oil boiling within the range of about 450 to 1300 F. and including constituents boiling above about 950 F. and which contained metal comprising contaminants, which comprises contacting said oil with about 50 to 300 volume percent of polyethylene glycol having a molecular weight of about 200 to about 600 at a temperature in the range of about 150 to 450 F., and segregating a treated oil.

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 polyethylene glycol includes solvent modifiers selected from the group consisting of Water soluble aliphatic alcohols, acetic acid, and lower molecular weight ethylene glycol.

4. A process forproviding a, high-boiling, high-quality catalytic cracking feed stock comprising the steps of fractionating a petroleum crude oil to segregate a metal contaminated fraction boiling within the range of about 450 to 1300 F., and including constituents boiling above 950 F., thereafter contacting said metal contaminated fraction with about to.300 volume percent of a polyethylene glycol having a molecular weight of from about 200 to about 600 and segregating a treated oil product of improved cracking characteristics.

5. A combination process comprising the steps of fractionating a petroleum crude oil to obtain metal c0ntaminated high boiling gas oil constituents including those within the range of about 950 to 1300 F., treating said high boiling metal contaminated fraction with a polyethylene glycol having a molecular weight of about 200 to about 600 and segregating a treated oil product, and thereafter catalytically cracking said treated oil product.

6. The process defined by claim 5 in which the said high boiling gas oil is diluted with a minor portion of a lower boiling gas oil.

7. A process for producing high quality lubricating oil from a metal contaminated gas oil boiling within the range of about 700 to 1100 R, which comprises contacting said gas oil with about 100 to 300 volumes percent of a polyethylene glycol having a molecular weight of about 200 to about 600, segregating a raffinate oil product of improved 'viscosity index.

References Cited in the file of this patent UNITED STATES PATENTS Junk et al. July 23,

Claims (1)

1. A PROCESS FOR UPGRADING A HYDROCARBON OIL BOILING WITHIN THE RANGE OF ABOUT 450* TO 1300*F. AND INCLUDING CONSTITUENTS BOILING ABOVE ABOUT 950*F.AND WHICH CONTAINED METAL COMPRISING CONTAMINANTS, WHICH CONPRISES CONTACTING SAID OIL WITH ABOUT 50 TO 300 VOLUME PERCENT OF POLYETHYLENE GLYCOL HAVING A MOLECULAR WEIGHT

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