US2843529A - Upgrading of petroleum oils - Google Patents

Description

July 15, 1958 R. M. HILL ETAL UPGRADING OF PETROLEUM OILS Filed Aug. 17, 1954 All RALPH M. H|LL INVENTORS ARTHUR W. LANGER. JR.

ATTORNEY United States Patent UPGRADING 0F PETROLEUM OILS Ralph M. Hill, Mountainside, and Arthur W. Langer, Jr.,

Nixon, N. J., assignors to Esso Research and Engineering Company, a corporation of Delaware Application August 17, 1954, Serial No. 450,386

1 Claim. (Cl. 196-49) This invention relates to, the art of upgrading petroleum oils.. It is concerned with an integrated process wherein hydrocarbon oils are converted to lighter components by pyrolysis and hydrogenolysis. More particularly, this invention proposes to upgrade petroleum oils by coking the oils in contact with fluidized solids and then treating, substantially to extinction, the higher boiling constituents in the coker eflluent by hydrogen donor diluent cracking (HDDC).

Although the present invention is directed to the upgrading of heavy, low value, petroleum residual oils, in its broader aspects it may find application to the processing of oils comprising shale oils, tars and oils derived from coal, synthetic oils, asphalts, tars, extracts, cycle stocks, whole crudes, heavy distillate and residual fractions therefrom, or mixtures thereof.

It has been recently proposed to coke petroleum oils by injecting them into a coking vessel that contains a fluidized bed of high temperature, finely divided solids, e. g., sand, pumice, spent catalyst, etc. and especially coke produced by the process. Upon contact with the high temperature solids, the oil undergoes pyrolysis evolving lighter hydrocarbons and depositing carbonaceous residue on the solid particles. Usually the necessary heat for the pyrolysis is supplied by circulating a stream of the solids through an external heater, generally a combustion zone, and back to the coking vessel. This fluid coking process is more fully presented by copending application entitled, Fluid Coking of Heavy Hydrocarbons and Apparatus Therefor, S. N. 375,088, filed August 19, 1953, by Pfeiifer et a1.

There has also been introduced into the art a process termed hydrogen donor diluent cracking (HDDC). In this process a hydrogen deficient oil is upgraded by admixing it with a relatively inexpensive hydrogen donor diluent material, aromatic-naphthenic in nature, and thermally cracking the resulting mixture. The donor diluent is advantageously a normally surplusage refinery material, such as a thermal tar obtained from thermal cracking of catalytic cycle stock boiling in the range of 430 to 650 F., having the ability to take up hydrogen in a hydrogenation zone and readily release it to hydrogen deficient hydrocarbons in a thermal cracking zone. The selected donor material is partially hydrogenated by conventional methods using, preferably, a sulfur insensitive catalyst, such as molybdenum sulfide or nickel tungsten sulfide. In thismanner of hydrocracking oils, the oil being upgraded is not contacted directly with the hydrogenation catalyst and does not, therefore, impair its activity by contamination. This technique of HDDC is more fully depicted in co-pending and now abandoned 2,843,529 Patented July 15, 1958 application entitled, Upgrading of Heavy Hydrocarbon Oils, S. N. 365,335, filed July 1, 1953, by A. W. Langer, Ir., a co-inventor of the present application.

In the fluid coking process previously proposed, the amount of conversion per pass is usually limited to avoid undue thermal degradation of the oil. Also a low endpoint product may be desired in order to avoid the inclusion of catalyst contaminants, ash constituents, etc. in the product. To increase the yields, the higher boiling constituents in the coker eflluent normally are recycled for further treatment. This is undesirable as this recycled material is usually more volatile and refractory than the fresh feed introduced to the coker and will pass through the coker substantially unaltered. Consequently, there exists a high recycle rate unless special steps are taken to prevent it, such as operating under pressure, using a secondary high severity cracking zone, etc. Further, the higher boiling refractory constituents of the oils, such as aromatics, tend to concentrate in the recycle stream and upon cracking produce mostly light gases and coke. Thus this recycle operation, aside from increasing the cost of operation, also tends to disproportionately increase the amount of coke produced.

It is, therefore, desirable to process these high boiling constituents in the coker eflluent by an alternative method which would surmount these difliculties. The present invention proposes that the heavy ends in the coker eflluent can be subjected to hydrogen donor diluent cracking in such a manner as to substantially or completely eliminate the necessity of recycle operation in fluid coking processes.

Consequently, it is an object of this invention to propound an integrated process for the upgrading of hydrocarbon oils. More specifically, it is an object of the present invention to convert hydrocarbon oils, particularly high boiling petroleum oils, to lighter compounds by a process comprising the steps of pyrolysis and HDDC. It is a further object of this invention to improve the operability of a fluid coking process by eliminating the need for recycle operation by application of the hydrogen donor diluent cracking process. By eliminating the coker recycle, it is readily apparent that for a given fluid coker a larger quantity of fresh feed can be handled.

Generally, the objects of this invention are attained by injecting an oil to be converted into a coking zone containing fluidized particulate high temperature solids. Preferably the solids used are coke produced in the process having a particle size in the range of 40 to 500 microns. The oil undergoes pyrolysis in the coking zone and the evolved vapors are separated into product hydrocarbons such as light gases, naphthas, heating oils, gas oils, etc., and bottoms or residuum. A preferred feature of the present invention is to subject this residuum to vacuum distillation to remove gas oil boiling up to about 1050 P. which is a suitable feed stock for catalytic cracking processes. The vacuum residuum is then admixed with a hydrogen donor diluent and subjected to thermal cracking such that the residuum is pyrolytically upgraded and concurrently hydrogenated by hydrogen transferring from the diluent. The thermally treated mixture is then separated into further product hydrocarbons, a diluent of intermediate boiling range and residue. The residue is recycled to the thermal cracking zone for further treatment. The diluent fraction is retional means and recycled to the thermal cracking stage..

A preferred embodiment of this invention is to make only a preliminary separation of the thermally cracked material and to send the material boiling below the diluent boiling range to the coker fractionator to be fractionated therein along with the coker products.

In brief compass, this invention proposes a hydrocarbon oil conversion process comprising, in combination, the steps of coking an oil by contact with high temperature fluidized particulate solids to obtain gasiform conversion products and carbonaceous residue which is deposited on said solids, separating from the conversion products relatively high boiling heavy ends, admixing the heavy ends with a hydrogen donor diluent in the proportion of 0.2 to 2 vols. diluent/vol. ends and thermally cracking the mixture under hydrogen donor diluent cracking conditions, reclaiming a major portion of the spent hydrogen donor diluent from the thermally cracked mixture, and regenerating the hydrogen donor diluent by partial hydrogenation.

This integration of the HDDC process with the fluid coking process has several salient advantages. By thermallycracking the bottoms from the coker in the presence of a hydrogen donor, instead of recycling them, there is a marked improvement in product distribution and the coke yield is drastically reduced. As the HDDC process consumes hydrogen, it is desirable to treat by this process only the difiicultly cracked components of an oil in order to reduce hydrogen consumption. This occurs in the process of the present invention as the coking operation effectively removes from the oil the easily cracked components. As will be noted in the following discussion, eflicient utilization is made by the present process of the heat created during the coking operation in that this heat is utilized in the HDDC unit and in the distillation towers.

The following discussion of the drawing, attached to and forming a part of the specification, will further elucidate this invention. The drawing diagrammatically portrays a process adapted to achieve the objects of this invention.

Referring to the drawing, the oil to be upgraded, such as a vacuum residuum, is injected into the coking vessel 1 via line 2. It is preferred to process by this invention heavy petroleum oils characterized by an API gravity of about to 20, a Conradson carbon of about 5 to 50 wt. percent, and a boiling point above about 850 to 1100 F. This oil may be suitably preheated to a temperature of, preferably, about 700 to 800 F. A bed of fluidized coke is maintained in the coking vessel at a temperature of about 950 F. Steam is admitted to the vessel by line 3 and serves first to strip the coke in the lower portion and then serves to fluidize the coke. Superficial fluidization gas velocities in the range of 0.1 to 5 ft./sec., e. g., 3 ft./sec. are used.

To maintain the coking temperature, a portion of the bed i continuously circulated by line 4 to a transfer line burner 5. A free oxygen-containing gas, e. g., air, is admitted to the base of the transfer line burner by line 6 and conveys the coke particles through the burner at a velocity above 20 ft./sec., e. g., 60 ft./sec., and supports a partial combustion of the coke particles, thereby raising their temperature 100 to 300 F. above the coking temperature. The heated solids are then separated by cyclone system 7 from the flue gas which is removed from the cyclone by line 8. The solids then are transferred to the coking vessel by line 9. The excess of coke produced by the process is removed by line 10.

Other methods of maintaining the coking temperature may, of course, be used, such as fluid bed burners, gravitating bed burners, shot heating systems, or other direct or indirect heating means.

The conversion products produced by the pyrolysis are removed overhead from the coker and transferred to a fractionator 12 by line 11 after having entrained solids removed. They are separated and removed from the fractionator as products, light gases by line 13, a naphtha fraction by line 14, a heating oil fraction by line 15, and a gas oil fraction by line 16. The product streams may be further processed as desired, as by reforming, desulfurization, catalytic cracking, stabilization, blending, etc. Preferably the bottoms from the fractionator are transferred by line 17 to a vacuum distillation zone 18 wherein a heavy gas oil, suitable for catalytic cracking, is separated and removed by line 19. This is not an essential feature, however, as the HDDC unit may process material having an initial boiling point as low as 430 F. As shown, the residuum boiling above about 1015 F. is transferred from the vacuum distillation tower to a furnace 21 by line 20. As this is a recycle operation, it is desirable to remove or bleed out about 0.2 to 2%, based upon feed, of the 1015 F. bottoms to prevent buildup of ash contaminants. This is accomplished through line 22.

The residuum transferred to the furnace is mixed with a hydrogen donor diluent supplied by line 23 and the resulting mixture is heated to a suitable cracking temperature. The heated mixture is then transferred to a soaking zone 24 which zone allows sufficient time for the cracking and hydrogen transfer reactions to occur. In some instances, this soaking drum may be eliminated or other means of thermal cracking may be used.

The cracked mixture is transferred to a fractionation zone 26 by line 25 wherein a rough separation is made. Products boiling below the diluent range, e. g., about 430 F are removed overhead and transferred by line 27 to the coker fractionator 12 wherein a complete separation is made. Thi reduces the amount of heat that must be supplied to the process. A fraction designated to be hydrogenated to form the hydrogen donor diluent is removed by line 28. The remainder, or bottoms from the separation zone 26, can be recycled to the thermal cracking unit by lines 29 and 39 for further treatment. When a lower boiling diluent is used, it is preferred to recycle this bottoms fraction by line 29 to the coker fractionation system in order that catalytic cracking gas oils can be removed from the bottoms before they are retreated.

Although the preferred diluent for use in the present invention boils in the range of 430 to 650 F., fractions having different boiling ranges may conveniently be used. The choice of the diluent boiling range depends upon such factors as the characteristics of the feed, operating conditions, product distributions desired, etc. Broadly, material boiling in the range of 430 to about 1050 F. may serve as a diluent. Thus diluent boiling ranges of 650 to 900 F. and 900 to 1050 F. can be used.

Because the cracking operation Will reduce or crack a part of the diluent to materials boiling below the boiling range of the diluent and because materials not suitable as hydrogen transfer media will be cracked into the diluent boiling range, the concentration of the materials suitable as hydrogen donors in the diluent may become too low to be effective. Depending upon the nature of the residuum and the operating conditions in the coker and HDDC units, it may be necessary to bleed up to about 5% of the spent diluent fraction prior to hydrogenation and add a suitable make-up oil, such as a thermal tar, in order to maintain a high level of aromaticity. Consequently a portion of the diluent fraction is bled from the process by line 28 and a make-up stock such as an aromatic extract, a thermal tar from thermal cracking of catalytic cracking cycle stock, etc., is added by line 36. The material selected to serve as make-up diluent is composed of a predominate proportion of condensed ring aromatic structures or aromatic-naphthenes. Of course, other means may be used to maintain the proper level of aromaticity in the donor diluent, such as solvent extraction to concentrate the aromatics, thermal cracking to form condensed ring structures and to crack out of the diluent paraiiins and alkyl groups, or the diluent stream may be catalytically aromaticized.

The material to be hydrogenated is transferred to a hydrogenator 31 by line 30. Line 32 supplies hydrogen to the hydrogenation vessel from any convenient source, such as from hydroforrning operations, gasification of the coke produced by the fluid coker, electrolysis, reformation of refinery tail gases, etc. The hydrogenator is operated under a pressure suflicient to secure the desired degree of hydrogenation, considering the hydrogen concentration available. It has been found that complete hydrogenation greatly reduces the eifectiveness of the aromatic diluent to transfer hydrogen. Generally the diluent should pick up enough easily removable hydrogen to be eifective as a donor, but not enough to approach saturation or to convert the aromatics to naphthenes. The spent gases from the hydrogenation zone are removed by line 33. A portion of these gases conveniently can be recycled by line 34. donor diluent is transferred from the hydrogenation vessel to the thermal treating furnace by line 23.

Table 1 summarizes the range of operating conditions pertinent to the present invention and presents a specific example of operating conditions. Table 11 presents an example of the products attainable, for the type of feed stock listed, when a process is operated in accordance with the example in Table I.

Table l The hydrogen Range Example Coking Conditions:

Temperature, F 850 to 1,200 950. Pressure, p. s.i 0 to 400 10. Oil injection rate, 1bs./hr./lb.

coke in coker 0.2 to 5.0 0.8. Steam, wt. percent on feed. 0 to 80 30. Coke particle size range,

microns to 1,000 to 500. l,0l5 F. Conversion, Percent to 60. Hydrogen Donor Diluent Cracking Conditions:

Diluent Boiling Range, F Airy rang%5\githin 430 to 650.

Diluent/residuum ratio, 0.2 to 2 0.5.

vol. vol. Temperature, F 750 to 1,000 900. Throughput, v./v./hr. 0.5 to 10..." 5. Pressure, p. s. i 450 to 2,000 500. 1,015 F. Conversion, Por- 30 to 90 h 60.

cent. Hydrogenation Conditions:

Catalyst, )is pills Nickel Tungsten Sulfide. Temperature, F 400 to 750 650. Pressure, p. s. i. a..." 1,000. Throughput, v./v./hr 1. Hydrogen consumption, cu. 200 to 1,000 400.

ltJbbl. diluent.

1,015 E. conversion is defined as: volume percent iced minus volume percent of products boiling above 1,015 F., excluding coke, on residuum.

2 Including bottoms from fluid coking and from the thermal treating units.

6 Table II HDDC Coker Feed Thermal Feed 1,015 F.+ Tar Coker Bottoms Feedstock Inspections:

Gravity, nPI 9. 0 s. 3 18.6 Conradson Carbon, Wt. Percent 18. 0 17.0 0. 003 11/0 Atomic ratio 1. so 1.43 1. 38 Sulfur, wt. Percent 4. O2 2. 63 1. 04 Boiling rang-e, F 1,000+ 1, 015+ 480/550 Equilibrium feed composition to HDDC: Wt. percent 1015 F. coker bottoms 40.3 1015 F. l-lDDC recycle bottoms 26.4 430/ 650 1 hydrogenated recycle diluent 27.3 430/ 650 F. hydrogenated thermal tar make-up 6.0

Product yields, percent on fresh feed C and lighter Wt. percent-.. 7.6 Q, vol. percent 2.7 (I /430 F 29.9 430/650 F -do 9.5 650/1,015 P do 50.8 1,015 F.+ bleed do 0.2 Coke ..Wt. perceuL- 10.4

3 Includes thermal tar make-up for HDDC.

Having described the invention What is sought to be protected by Letters Patent is succinctly set forth in the following claim.

What is claimed is:

A process for upgrading heavy petroleum oils, which comprises coking an oil by contact with fluidized solids maintained at a temperature in the range of 850 to 1100 F. in a coking zone, separating the emuent there from in a separation zone comprising atmospheric and vacuum units to obtain product fractions and a vacuum residuum boiling above 1015 F, admixing said residuum with 0.2 to 2 voL/vol. of a hydrogen donor diluent boiling Within the limits of 430 to 650 F., thermally cracking the admixture in liquid phase in the absence of catalyst, recovering a spent diluent fraction from the cracked admixture and returning the lighter portions thereof to said separation zone for further separation, partially hydrogenating said spent diluent fraction, and recycling the material so hydrogenated as said hydrogen donor diluent.

References Cited in the file of this patent UNITED STATES PATENTS 2,017,836 Angell Oct. 22, 1935 2,069,392 Seguy Feb. 2, 1937 2,312,445 Ruthrufi Mar. 2, 1943 2,426,929 Greensfelder Sept. 2, 194-7 2,467,920 Voge et al. Apr. 19, 1949 2,641,573 Weikart June 9, 1953 2,655,464 Brown et al. Oct. 13, 1953

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