US2761815A - Preparation of specialty naphthas from high sulfur crudes - Google Patents

Description

Sept. 4, 1956 LE ROI E. HUTCHINGS 2,761,315

PREPARATION OF SPECIALTY NAPHTHAS FROM HIGH SULFUR CRUDES Filed June 17, 1953 2 Sheets-Sheet l GRUDE PETROLEUM FRAGT/OIVA T/OIV I VIRGIN IVA PH TI-IA FRACTION H Y DRODE 3 UL F UIPIZA TIO/V REGYCLE STABILIZATION CHEM/GAL TREATMENT FRAGT/O/VAT/O/V FIG.

INVEN TOR.

BY LEROI E. I-IUTGHI/VGS ATTOR/V Y P 4, 1956 LE ROI E. HUTCHINGS 2,761,815

PREPARATION OF SPECIALTY NAPHTHAS FROM HIGH SULFUR CRUDES Filed June 17, 1953 2 Sheets-Sheet 2 Q0 V 0 mt m1 ot 01 f a a Q V- O E t J 91 2 1 Q a Q N T i k Q .i Q 1 T W l x V 8 E RI INVENTOR.

LE ROI E. HUT OHM/65 ATTOR/V r United States Patent 'Office 2,761,815 Patented Sept. 4,1956

PREPARATION OF SPECIALTY NAPHTHAS FROM HIGH SULFUR Le Roi E. Hntchings, Crystal Lake, 111., assignor to The Pure Oil Company, Chicago, 111., a corporation of Ohio Application June 17, 1953, Serial No. 362,374

4 Claims. (Cl. 1962) The present invention relates to the preparation of rubber solvents, VM & P spirits, mineral spirits, and petroleurn naphthas which will pass themost severe corrosion tests and are low in sulfur content.

Crude petroleum is the source of a large number of products ranging from simple distillation products including pure hydrocarbons to high molecular weight natural and synthetic resins, elastomers, and polymers produced through physical and chemical transformations. Widely known petroleum derived products include' gasoline, kerosene, diesel fuels, lubricating oils, and heavy tars. in many instances, the products obtained from petroleum are employed as reactants in the synthesis of additional petroleum derivatives and chemicals and a large number of products of petroleum are used directly without extended treatment or modification. Petroleum naphthas comprise a wide variety of such latter products used extensively in the dyeing, rubber, extraction, protective coating, and allied industries. A large portion of the petroleum naphthas used is the straight run naphthas which are selected fractions of the lower boiling, more volatile constituents of crude petroleum The present invention is particularly directed to a'method of prepar-' ing such straight run naphthas and to naphtha compositions of this variety and, accordingly, the term naphthas as used herein shall mean straight run petroleum naphthas.

If the preparation of naphthas from petroleum is confined to physical means, the products inevitably contain other types of organic and inorganic compounds'dlle to the complex nature of petroleum which have been found to be deleterious as far as certain end uses of the naphthas are concerned and necessitate the application of additional refining steps. Even with such additional refining, it is exceedingly difiicult to prepare naphthas which meet. the exacting specificationsthat have been established 'by the industry. Of these deleterious non-hydrocarbon com pounds the sulfur and sulfur-containing constituents are generally the most bellicose and cling tenaciously to any environment in which they exist, imparting objectionable odor, corrosiveness, color, and 'otherphys'ical and chemical properties thereto. The odor of naphthasis important; however, no standard test'exists to cover this property and the odor of a well refined naphtha is generally de scribedassweet.

Tests have been devised to dete tively and qualitatively the prfe'senc be e odious cornpounds in an attempt to control thejp op andciuality of naphthas from petroleum sources; Eorthis'purp'os'e, various copper strip corrosion tests andthej fnp'ctgrff test have been used. Procedures established by ,S, may be used to determine the content ariddistribution of these sulfur compounds. Perhaps the most critical 'and rigorous qualitative test for determining the presence 'of sulfur compounds in naphthas is the distillation-corro sion test, known also as the Philadelphia test, the Amsco corrosion test, or the full boiling range corrosion teSt by any name, a species of copper strip corrosionf-t'est'; 'The test, Widely applied by the manufacturers,"distributors,

' ,e b th, quan i aand users of specialty naphthas, is carried out by the addition of a small pure copper coupon to an ordinary A. S. T. M. distillation flask containing cc. of the naphtha to be tested. The copper strip is so positioned in theflask that one end of the strip contacts the residue at the end of the distillation, and the distillation is conducted according to A. 'S. T. M. D86-38 as described in A. S. T. M. Standards on Petroleum Products and Lubricants, published by the American Society for Testing Materials, Philadelphia, Pennsylvania.

' At the completion of the test, wherein the flask has been heated to dryness, the color of the copper strip is an indication of the relative amount of corrosive sulfur compounds present in the naphtha sample. A negative test is shown by the presence of a very slight or no tarnish on the strip and stamps the naphtha as satisfactory. If the copper strip becomes moderately tarnished or blackerred, the results are interpreted as positive or unsatisfactory. The production of a slightly tarnished or slightly colored or corroded strip, indicated by a dark orange with peacock colorations thereon, is termed borderline and as such denotes a naphtha which is not acceptable and must be further refined. The market is limited for off-specification naphthas and further refining is expensive since even then there is no assurance that the product will pass thesevere distillation-corrosion test.

- The subjection of high sulfur content naphthas to various'refining operations which may include copper oxide slurry treating, sweetening methods, or extraction methods, or the recycling of rejected off-specification naphthas back through such a process, does not produce acceptable naphthas because the content of sulfur compounds is not reduced sufiiciently. In addition to the corrosion test, a total sulfur content specification must be met. High sulfur content naphthas usually have a poor odor as Well as other undesirable properties. If straight run naphthas from high 'sulfur crudes are subjected to other more severe refining methods, the resulting products do not pass the distillation-corrosion test; Even subjecting these naphthas to the usual desulfurization treatments involving vapor or liquid phase contact with clay or catalytic materials having strong afiinity for effecting desulfur izat-ion does not produce a satisfactory product.

The present "invention is directed to the discovery of a method of producing low sulfur, sweet, non-corrosive naphthas'from high sulfur pet-roleums by applying a combination refining treatment to such products. It has been found that in "order to prepare satisfactory specialty naphthas which meet the rigorous corrosion tests, refining methods must be used which not only attack such sulfur compounds as hydrogen sulfide, mercaptans, free sulfur, and disulfides, but also attack efficiently the so-ca-lled thermally stable sulfur compounds including the higher molecular weight cyclic, heterocyclic, polymeric, and aromatic type sulfur compounds. The method of this invention comprises a combination treatment of the corrosive naphthas with first a catalytic hydrodesulfurization' treatment followed by a chemical treatment.

Accordingly, a fundamental object :of this invention is to provide a combination process for the production of naphthas which are free from corrosive sulfur compounds from crude petroleum containing sulfur compounds.

A second object of this invention is to provide a method of producing naphthas which pass the distillati ncorrosi-on test.

A third object of this invention is to produce naphtha products passing the distillation-corrosion test from high sulfur crudesl A fourth object is to provide a combination hydrodesulfurization and chemical treating process to produce acceptable sweet, odor-free specialty naphthas.

These and other objects will become apparent as the description thereof proceeds.

In the attached drawings,

Figure l is a schematic flow diagram illustrating the generic embodiments of the invention, the relationship of the catalytic and chemical processes to each other and to the products produced therefrom. V

Figure 2 is a flow diagram illustrating the application of the combination process to a naphtha feed. 7

In carrying out the present invention, thecrude oil, particularly a high'sulfur crude oil containing from 1.0 to 3.0 weight per cent of sulfur, is fractionated to remove a virgin or straight run naphtha fraction boiling from about 100 to 500 F. and preferably from about 110 to 450 F. The boiling range of the naphtha fraction removed for treatment in accordance with thisinvention may be varied somewhat from the 100 to 500 F. range if it is desired to obtain different amounts of rubber solvent, VM' & P naphtha, or specialty naphthas. By narrowing the boiling range of the virgin naphtha to within 100 to 250 F., for example, the process can be directed to obtaining rubber solvents almost exclusively. .On the other hand, by starting with a fraction boiling between 200 and 400 F., increased yields of VM & P solvents and specialty naphthas may be produced. One embodiment of the invention comprises the treatment of the entire first fraction boiling up to'500" F. to produce a wide variety of products ranging from rubber solvents up to higher boiling specialty naphthas, including, for example, petroleum ether 90140 F.', Special Textile Spirits l80-210 F., Light Mineral Spirits 290-330 F., Stoddard Solvent 3l0-385 F., and High Flash Dry Cleaning Solvent 360400 F., all of which are non-corrosive, odorless, and meet the rigorous requirements of the industry, from high sulfur crudes heretofore thought impossible of such treatment. Accordingly, the boiling range of the virgin naphtha may be:

varied considerably without departing from the spirit of the invention.

The virgin naphtha fraction selected from the crude is subjected to a catalytic hydrodesulfurization treatment carried out in accordance with well known techniques at elevated temperatures. In the treatment, the sulfur content of the charge stock is removed in the form of a gas virgin naphtha fraction subjected to hydrodesulfurization may contain from about 1 to 7 per centby weight of sulfur. The charge may be introduced to the catalyst catalyst per hour.

The products from the hydrodesulfurizatlon are subjected to stabilization wherein thehydrogen sulfide and any fixed gases are removed and the resulting stabilized products are subjected to chemical treatment wherein contact is had with a slurry of an active metal oxide or metal salt capable of chemical combination with the remaining small amount of corrosive sulfur compounds. Salts or metal oxides of metals in group I-B of the periodic table, particularly copper oxide or salts of copper, including copper suboxide (C1140), cuprous oxide of cuprite (CuzO),

. cupric oxide (CuO), and copper peroxide (CuOz-HzO) may be used in this chemical treatment. This second treatment may be carried out by employing the reducible oxide or metal oxide in finely divided form distributed 1 evenly throughout oriincorporatedwith a porous. supportv zone at from 0.5 to 10 liquid volumes per bulk volume of.

material, as, for example, the metal oxide may be. in finely divided form dispersed uniformly through a porous silica or alumina support] One particularly desirable method is to use the oxide in the form .of a slurry with a material capable of carrying the oxide in finely divided form. Such materials include slurry oils ranging from.

a light oil to heavier, high viscosity oils. In certain instances other organic solvents may be used as the slurry medium as long as they do not affect the process or enter into reaction with the sulfur. compounds in such way as to deleteriously affect the finished naphtha. The hydrodesulfurized products are mixed with the slurry of metal oxide and maintained in contact at temperatures from 400 to 650Fffor periods of time ranging from a few seconds to a minute. The preferred temperature is about 450 F. The charging rates for this chemical contacting may vary within wide limits and may be, for example, from 1 to 15 volumes-of hydrodesulfurized product (C311 culated in the liquid form) per hourper volume of contact mass.' The selection of the optimum rate or range of charging rates for any particular hydrodesulfurized product will depend largely upon the concentration of sulfur compounds present and the percentage of metal in the. contact mass. It is preferredto use lower rates of contact within the above range Where larger quantities of sulfur compounds are present or where smaller concentrations of the metal contact material are used.

T he chemical treatment may be carried out in any physical state, that is, with the hydrocarbons in liquid or vapor form and the well known suspensoid, fluid, fixed bed, or slurry type of treatments may be employed. At the end of the chemical treatment, portions of the refined virgin naphtha are removed and distilled to yield light hydrocarbons, rubber solvent, VM.& P solvent, mineral spirits, and heavy naphtha.

, Referring to Figure 2 for a specific embodiment of the invention, a naphtha charge boiling from about 110 to 450 F. obtained from a sour crude is passed through line 2 into heat exchanger 4 and thence into coil 6 of tube still 8. The preheated naphtha leaves tube still 8 via line 10. Hydrogen enters the system at line 12, passesthrough line 14 to coill6-of tube still 8 and thence into line 18. The preheated naphtha and hydrogen mix in line 20 and pass into either hydrodesulfurization reactors 22 or 24. More than one hydrodesulfurization reactor is used so that one reactor may be on stream while the other is regenerated. The hydrogen is heated to the maximum temperature in the hotter coil 16 of tube still 8 and the naphtha fraction is heated to a lower temperature in coil 6.

The mixture of naphtha and hydrogen enters reactor 22 or 24 at about 750 F. and 250 pounds per square inch gauge. The hydrodesulfuriz'ed naptha and excess hydrogen leave the reactor under substantially the same conditions through line 26, through heat exchanger 28 and heat exchanger. 4, through line 30 into stripper 32. In stripper 32 the products are at about 400 F. and

' 240 p. s. i. g.-and with theaid of added heat from reboilcr 34 the hydrogen and hydrogen sulfide are removed. The hydrogen and hydrogen sulfide pass through line 36 and heat exchangervSS'into thefirst stage of Girbitol unit 40 for countercurrent contact with an agent designed to dissolvev the hydrogen sulfide as an amine solution. Purified hydrogen passes through'iline 42,.heat exchanger 38, and

' line 44 for recycle in the system. Hydrogen sulfide. is removed fromthe amine solution by the second Girbitol unit 46 and recovered at line 48. Amine solution is recirculated between units 40 and 46 via lines 50 and 52 through heat exchanger 54.

The gas-free; naphtha passes through line 56, heat ex changer 28, and line 58,'to the slurry treater 60. Pump 62 serves to circulate the slurry of metal salt or metal oxide and naphtha through the treater 60. Spent slurry is redrawn at line 64 and fresh slurry introduced at line 66. The slurry: treating process is operated at about 450 F- ansiasub taatial iPQ ti W e i all h heat, is supplied by the vaporized naphtha entering the system. The treatment occurs mostly in the circulating system rather than in the treater 60, which acts more as a separator. Since very little treating or reaction occurs, the slurry does not need to be continuously regenerated.

The hydrogen added to the process may contain low boiling hydrocarbons up to about 30 per cent by volume and any build-up of such components in the process may be eliminated by absorption of same in oil or by discarding a portion of the recycle hydrogen.

The slurry-treated naphtha passes Via line 68 into distillation unit 70. Distillation unit 70 is operated to produce an overhead stream through line 72, two side streams at lines 74 and 76, and a heavy naphtha bottom stream at line 78. The side streams 74 and 76 are processed in strippers 80 and 82 to produce a VM & P naphtha at line 84 and a mineral spirits at line 86. Any vapors from these side stream products are returned via lines 88 and 90. The overhead stream passing through line 72 is similarly processed in stripper 92 to provide a rubber solvent at line 94. A reflux stream passes through line 96 and is proportioned back to distillation unit 70. Light petroleum gases pass off at line 98. Suitable heat exchangers like 100 serve to cool the products.

As an example of the invention, the following experiments were conducted: A virgin mineral spirits fraction was obtained from a Worland crude oil having 1.7 Weight per cent sulfur and an API gravity of 37.9. The fraction boiling between about 110 to 450 F. contained about 0.54 weight per cent of sulfur at an API gravity of 55.7 and contained about 15 volume per cent of aromatics, 35 volume per cent of naphthenes, and 50 volume per cent of parafiins. This fraction was hydrodesulfurized using a cobalt molybdate catalyst under reaction conditions of about 750 F. and 250 pounds per square inch under conditions of 3000 s. c. f. of hydrogen per barrel of charge. The hydrodesulfurized product so obtained after hydrogen sulfide removal contained 0.05 per cent total sulfur calculated as residual sulfur, including sulfide sulfur, and elemental sulfur, and, upon testing in the presence of copper under the distillationcorrosion test, was found to give a darkened strip and was positive and unsatisfactory. Test portions of this fraction were further treated with mercury to remove any elemental sulfur present but the test product still produced a borderline, unsatisfactory corrosion-distillation test. A test treatment of the product with sodium polysulfide did not improve the distillation-corrosion test. The main portion of this material was passed over a bed of cupric oxide precipitated on bauxite (2.5 per cent CuO) at 450 F. and the product gave a negative distillation-corrosion test, but the product so obtained had substantially the same total sulfur content as the hydrodesulfurized product. The odor was improved.

The hydrocarbon mixtures to be treated in accordance with this invention comprise any mixture of hydrocarbons regardless of source or chemical constitution which have a high content of sulfur or sulfur compounds. Such hydrocarbon mixtures generally have correspondingly high aromatic hydrocarbon contents and as such are extremely difficult to treat for the purpose of producing good fuels, naphthas, and kerosenes. The sulfur may be present as elemental sulfur but is generally present as sulfur compounds including hydrogen sulfide, organic sulfides, and disulfides of aromatic naphthenic and polycyclic origin. By high sulfur content is meant those hydrocarbon mixtures including crude oils having from 1.0 to 3.0 weight per cent of sulfur present. Also included are those mixtures or fractions having as high as 5.0 per cent of sulfur. Such crude oils or mixtures may have an API gravity ranging from about 20 to 40 or higher.

Those skilled in the art will immediately appreciate that the combination of treatments herein disclosed is capable of variation in its details without departure from the subject matter of the novel combination herein described. The invention is not to be strictly limited to the disclosure as set forth herein for illustrative purposes, but only as required by the appended claims.

What is claimed is:

l. The process for producing special solvent naphthas which pass the distillation-corrosion test from hydrocarbon mixtures containing deleterious sulfur compounds which comprises separating a virgin fraction having a boiling range of about to 450 F. from said hydrocarbon mixture, subjecting said virgin fraction to hydrosulfurization at about 500 to 800 F. in the presence of hydrogen and a catalyst comprising cobalt molybdate under conditions such that hydrogen sulfide is produced, separating the hydrogen sulfide so formed to produce a hydrodesulfurized product, subjecting said product to a chemical treatment in the presence of cupric oxide at about 400 to 650 F., separating a purified product and fractionating said purified product to produce fractions which pass the distillation-corrosion test.

2. The method in accordance with claim 1 in which said hydrocarbon mixture is a Worland crude oil having about 1.7 weight per cent sulfur and an API gravity of about 37.9.

3. The method in accordance with claim 1 in which said chemical treatment is carried out with said cupric oxide in slurry form.

4. The method in accordance with claim 1 in which said chemical treatment is conducted by contacting said hydrodesulfurized products with said cupric oxide distributed on silica.

References Cited in the file of this patent UNITED STATES PATENTS 1,837,963 Houdry Dec. 22, 1931 2,063,113 Morrell Dec. 8, 1936 2,151,721 Schulze Mar. 28, 1939 2,202,401 Rosen May 28, 1940 2,574,449 Lorne Nov. 6, 1951

Claims (1)

1. THE PROCESS FOR PRODUCING SPECIAL SOLVENT NAPHTHAS WHICH PASS THE DISTILLATION-CORROSION TEST FROM HYDROCARBON MIXTURES CONTAINING DELETERIOUS SULFUR COMPOUNDS WHICH COMPRISES SEPARATING A VIRGIN FRACTION HAVING A BOILING RANGE OF ABOUT 110* TO 450* F. FROM SAID HYDROCARBON MIXTURE, SUBJECTING SAID VIRGIN FRACTION TO HYDROSULFURIZATION AT ABOUT 500* TO 800* F. IN THE PRESENCE OF HYDROGEN AND A CATALYST COMPRISING COBALT MOLYBDATE UNDER CONDITIONS SUCH THAT HYDROGEN SULFIDE IS PRODUCED SEPARATING THE HYDROGEN SULFIDE SO FORMED TO PRODUCE A

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