PROCESS FOR REDUCING THE LEVEL OF SULFUR IN A REFINERY PROCESS STREAM AND/OR CRUDE OIL

Abstract: This invention relates to a process for reducing the sulfur in a refinery process stream and/or crude oil, which comprises treating said refinery process stream and/or crude oil with an effective sulfur reducing amount of a reducing agent selected from the group consisting of hydrazine, oximes, hydroxylamines, carbohydrazide, erythorbic acid, and mixtures thereof wherein the reducing agent or the hydrocarbon treated has a temperature of at least 50 DEG C.

Description: P OCESS FOR REDUCING THE LEVEL OF SULFUR IN A REFINERY PROCESS STREAM AND/OR CRUDE OIL FIELD OF THE INVENTION This invention relates to a process for reducing the level of sulfur in a refinery process stream and/or crude oil, which comprises treating said refinery process stream and/or crude oil with an effective sulfur reducing amount of a reducing agent selected from the group consisting of hydrazine, oximes, hydroxylamines, carbohydrazide, erythorbic acid, and mixtures thereof wherein the reducing agent or the hydrocarbon treated has a temperature of at least 50° C. BACKGROUND OF THE INVENTION One of the major contaminants found in crude oil and refinery streams is sulfur. The amount of sulfur found in crude oil typically ranges from 0.001 weight percent to 5.0 weight percent based upon the total weight of the crude oil. Typically, the sulfur is in the form of dissolved free sulfur, hydrogen sulfide, and/or organic sulfur compounds such as thiophenes, sulfonic acids, mercaptans, sulfoxides, sulfones, disulfides, cyclic sulfides, alkyl sulfates and alkyl sulfides. Since the amount of sulfur permitted in gasoline and other fuels refined from crude oil is regulated by state and federal authorities, fuels produced from crude oil typically contain less than 1.0% to less than 0.05% by weight sulfur. The actual sulfur content of the fuel is primarily dependent upon the sulfur content of the crude oil being refined and the degree of additional processing, such as hydrotreating, that is performed on the refined product. Obviously, it is more expensive to reduce the sulfur content of higher sulfur containing crude oil, thus the production cost of fuels, particularly gasoline and diesel, will be higher for fuels produced from higher sulfur content crude oils. Typically sulfur from crude oil is eliminated during the refinery process by hydrotreating which requires expensive equipment and creates hydrogen sulfide (H 2 S) , a toxic gas that requires additional expense for its safe processing. As a consequence, the price differential between low sulfur and high sulfur crude oil reflects to some extent the capital cost of desulfurization, as well as the increasing demand for lower sulfur fuels. In view of this background, there obviously is a need for less expensive methods of desulfurizing crude oil and desulfurizing crude oil before it is processed in the refinery. This is particularly true for smaller refineries which cannot afford expensive hydrotreating equipment. SUMMARY OF THE INVENTION This invention relates to a process for reducing the level of sulfur in a refinery process stream comprising: treating said refinery process stream with an effective sulfur reducing amount of a reducing agent selected from the group consisting of hydrazine, oximes, hydroxylamines, carbohydrazide, erythorbic acid, and mixtures thereof wherein the reducing agent, the hydrocarbon treated, or both have a temperature of at least 50°C to thereby reduce the level of sulfur in said refinery process stream. The process can also be used to reduce the level of sulfur in crude oil or a process stream which contains crude oil and/or mixtures of other hydrocarbons. With respect to reducing the level of sulfur in crude oil, the reducing agent can be added to raw crude oil before refining or at any feedpoint in the refinery stream. The removal of sulfur prior to refining saves money by eliminating the need to remove sulfur during the refinery process. Since the process involves the chemical removal of sulfur, the cost of expensive equipment can be avoided. This is particularly advantageous to the smaller refinery operations. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of a simple refinery. DEFINITIONS AND ABBREVIATIONS CRUDE OIL — for purposes of this patent application, "crude oil" shall mean any unrefined or partially refined oil which contains sulfur in any significant amount, possibly in the presence of other contaminants, particularly heavy and light crudes which are refined to make petroleum products. DREWCOR — a registered trademark of Ashland Oil, Inc. DREWCOR 2130 is chemically defined as a blend of amines and MEKOR such that the amount of MEKOR is about 5% by weight. FEED POINT — place where reducing agent is injected into the sulfur containing hydrocarbon. LSCO — Louisiana sweet crude oil. MEKOR — MEKOR is a registered trademark of Ashland Oil, Inc. and is chemically defined as methyl ethyl ketoxime [H 3 C(C==NOH)CH2CH 3 ] . PETROLEUM PRODUCTS — products produced by refining crude oil including gasoline, diesel fuel, propane, jet fuel, kerosene, naphtha, benzene, gasoline, aniline, etc. REFINERY PROCESS STREAM — any refinery stream associated with the processing or transport of hydrocarbons in a refinery, including emulsions, water streams, condensate streams, stripping steam, particularly refinery process streams carrying crude oil and other hydrocarbons such as petroleum products, most particularly refinery process streams which carry three phases of material, namely a liquid hydrocarbon phase, a gaseous hydrocarbon phase, and an aqueous phase. The refinery process streams treated either contain sulfur as a contaminant or empty into a refinery process stream which contains sulfur as a contaminant. ppm — parts per million MEKOR. PSR — percent sulfur reduction. SAMPLE POINT — place where a sample of a treated crude oil or refinery process stream is taken to determine if there was a reduction in sulfur. SCBT — sulfur content before treatment. SCAT — sulfur content after treatment. DETAILED DESCRIPTION OF DRAWING FIG. 1 illustrates the flow chart of a simple refinery. It shows the sample points 1-12 for the refiner process streams tested, feedpoints for MEKOR 21-27, storage tanks 31-34, reformers 41-44, vessels 51-61, boiler 71, and hydrogen flare 72. Raw untreated crude oil 31 is fed to the desalter 54 where it is desalted and pumped into the crude tower 51. From the crude tower, a crude gasoline fraction is pumped into the raw gas accumulator 53 and then to the splitter tower 55. Fractions of the separated gasoline are pumped from the splitter tower to the depropanizer 57, the reformer 41-44, and to the hydrogen separator 59. The fraction from the hydrotreater is pumped to the stabilizer tower 60. MEKOR is fed into the process at feedpoints 21-27. Sample points include 1-12. The specific components in Fig. 1 are identified as follows: SAMPLE POINTS 1 RAW CRUDE 2 CRUDE OUT OF DESALTER 3 WATER OUT OF DESALTER 4 DIESEL TO STORAGE TANK 5 WATER OUT OF RAW GAS ACCUMULATOR 6 SPLITTER BOTTOMS 7 STABILIZER BOTTOMS 8 WATER OUT OF STABILIZER ACCUMULATOR 9 STABILIZER PROPANE 0 WATER OUT OF SPLITTER ACCUMULATOR 1 WATER OUT OF DEPROPANIZER ACCUMULATOR DEPROPANIZER PROPANE CHEMICAL FEED POINTS MEKOR INTO RAW CRUDE MEKOR INTO STRIPPING STEAM TO CRUDE TOWER MEKOR INTO CRUDE TOWER REFLUX DREWCOR 2130 INTO CRUDE TOWER REFLUX MEKOR INTO SPLITTER TOWER FEED 1,1,1 TRICHLOROETHANE INTO REFORMATE FEED MEKOR INTO REFORMERS STORAGE TANKS RAW CRUDE DIESEL GASOLINE PROPANE REFORMERS REFORMER #1 REFORMER #2 REFORMER #3 44 REFORMER #4 VESSELS 51 CRUDE TOWER 52 DIESEL DRIER 53 RAW GAS ACCUMULATOR 54 DESALTER 55 SPLITTER TOWER 56 SPLITTER ACCUMULATOR 57 DEPROPANIZER TOWER 58 DEPROPANIZER ACCUMULATOR 59 HYDROGEN SEPARATOR 60 STABILIZER TOWER 61 STABILIZER ACCUMULATOR OTHER 71 BOILER 72 HYDROGEN FLARE DETAILED DESCRIPTION OF THE INVENTION The reducing agents used in this process are selected from the group consisting of hydrazine, oximes, hydroxylamines (such as N,N-diethylhydroxylamine) erythorbic acid, and mixtures thereof. These reducing agents are described in U.S. Patents 5,213,678 and 4,350,606 which are hereby incorporated by reference. Preferably used as reducing agents are oximes such as the ones described in U.S. Patent 5,213,678 as having the formula: wherein Ri and R 2 are the same or different and are selected from hydrogen, lower alkyl groups of 1-8 carbon atoms and aryl groups, and mixtures thereof. Most preferably used as the oxime are aliphatic oximes, particularly methyl ethyl ketoxi e. The reducing agent, crude oil, and/or refinery process stream to be desulfurized must be heated to a temperature of at least 50°C in order to activate the reducing agent, preferably from 80°C to 150°C in order for the process to work effectively. The reducing agent can be added directly to a refinery process stream containing sulfur contamination, particularly a hydrocarbon process stream, or to an uncontaminated refinery process stream which flows into a contaminated refinery process stream contaminated with sulfur. The amount of reducing agent needed in the process is an amount effective to reduce the sulfur content of the refinery process stream or the crude oil treated. Generally this amount is from 1 ppm to 100 ppm of reducing agent based upon the weight of the crude oil or the volume of the refinery stream to be treated, preferably 5 ppm to 70 ppm, and most preferably 10 ppm to 50 ppm. The following detailed operating examples illustrate the practice of the invention in its most preferred form, thereby permitting a person of ordinary skill in the art to practice the invention. The principles of this invention, its operating parameters and other obvious modifications thereof will be understood in view of the following detailed procedure. The crude oil and refinery process streams tested in the examples were from a small refinery which refines approximately 10,000 barrels of crude oil per day. The diagram of the refinery is shown in Figure 1. The sulfur content of the refinery process streams in the Examples is expressed as percent by weight based upon the total weight of the process stream treated. Sulfur analysis for the treated and untreated crude oil and the various unrefined and refined petroleum fractions was determined by X-Ray florescence using the Horiba SLFA 1800/100 Sulfur-in-Oil Analyzer in accordance with ASTM standard test method D 4294-83. EXAMPLES Table I shows the test results for Louisiana sweet crude oil (LSCO) . Table I compares the Control, LSCO which does not have MEKOR added, to LSCO after MEKOR was added. Note that there was some reduction of sulfur in the Control even though no MEKOR was added because some sulfur is removed during the refinery process as the crude oil moves from the feed point to the sample point. In the Examples of Table I, the MEKOR was heated to a temperature of about 50°C to about 120°C and injected directly into the crude oil 1 at feedpoint 21. The samples tested were collected at sample points 1-3. The examples in Table I illustrate that MEKOR reduces the sulfur content of LSCO. TABLE I EFFECT OF MEKOR ON SULFUR IN CRUDE OIL TEST ppm SCBT SCAT PSR Control 0.0 662 654 1.2 1 5.6 590 489 17.1 2 5.6 551 490 11.1 3 4.7 681 600 11.9 4 4.7 735 619 15.8 5 11.9 579 463 20.0 Table I shows that the sulfur content of the LSCO was reduced by about 10 to about 20 weight percent by the addition of the MEKOR. The results of treating diesel fuel with MEKOR are shown in Tables II (Control), III, IV, V, and VI. Note that there was some sulfur reduction in the Control even though no MEKOR was added. The reason for this is because some sulfur is removed during the refinery process as the raw crude is processed into diesel oil even if no MEKOR is added. In the examples of Tables II-VI, MEKOR was heated to a temperature of 93°C unless otherwise indicated before adding it to the feedpoint. In the examples of Table II, III, and IV, MEKOR was injected directly at feedpoint 22 into the stripping steam entering crude tower 51. In the examples of Table V, 4.75 ppm of MEKOR was injected into the raw crude 1 (93°C) and 4.75 ppm MEKOR was injected into the stripping steam 22 of the crude tower 51. In the examples of Table VI, 11.9 ppm of MEKOR was injected into the raw crude (93°C) 1 and 4.8 ppm MEKOR was injected into the stripping steam 22 of the crude tower 51. The samples of diesel oil tested were collected at sample point 4. TABLE II (CONTROL/UNTREATED DIESEL OIL) TEST ppm SCBT SCAT PSR 1 0 490 453 7.6 2 0 490 417 14.9 3 0 505 450 10.9 4 0 465 444 4.5 Avg. 0 390.0 352.8 7.6 TABLE III (TREATED DIESEL OIL) (MEKOR Feed Point: Stripping steam entering crude tower. ) TEST ppm SCBT SCAT PSR 1 7.9 610 462 24.3 2 7.9 557 400 28.2 3 7.9 489 385 21.3 4 7.9 472 353 25.2 Avg. 7.9 532.0 400.0 24.8 TABLE IV (TREATED DIESEL OIL) (MEKOR Feed Point: Stripping steam entering crude tower. ) TEST ppm SCBT SCAT PSR 1 19.8 613 388 36.7 2 19.8 638 415 35.0 3 19.8 566 415 26.7 4 19.8 565 399 29.4 Avg. 19.8 595.5 404.3 32.0 TABLE V (TREATED DIESEL OIL) (MEKOR Feed Points: 4.75 ppm Raw Crude (93°C) , 4.75 ppm Stripping Steam) TEST ppm SCBT SCAT PSR 1 9.5 681 422 38.0 2 9.5 735 442 39.9 3 9.5 675 439 35.0 4 9.5 807 398 50.7 Avg. 9.5 724.5 425.3 40.9 TABLE VI (TREATED DIESEL OIL) (MEKOR Feed Points 11.9 ppm Raw Crude (25°C) , 4.8 ppm Stripping Steam) TEST ppm SCBT SCAT PSR 1 16.7 471 424 10.0 2 16.7 503 435 13.5 3 16.7 510 415 18.6 4 16.7 477 383 19.7 Avg. 16.7 490.3 414.3 15.5 Tables II to VI show that the addition of MEKOR to the crude oil and/or stripping steam of the crude tower effectively reduces the amount of sulfur in the diesel oil produced by the refinery. The Examples of Tables VII and VIII illustrate the use of DREWCOR 2130 corrosion inhibitor and MEKOR in reducing sulfur in depropanizer propane and stabilizer propane. In the examples of Tables VII and VIII, MEKOR was not preheated, but was added at feedpoints 23-25. The samples of depropanizer propane were collected at sample point 12 and the samples of stabilizer propane were collected at sample point 9. TABLE VII (EFFECT OF MEKOR ON SULFUR - DEPROPANIZER PROPANE) (Test 1 used DREWCOR 2130 inhibitor. Test 2 used MEKOR) TEST ppm SCAT PSR Control 0 200.0 NA 1 1 70.0 65 2 30 2.5 98.8 TABLE VIII (EFFECT OF MEKOR ON SULFUR - STABILIZER PROPANE) (Test 1 used DREWCOR 2130 inhibitor. Test 2 used MEKOR) TEST ppm SCAT PSR Control 0 200.0 NA 1 1 6.5 96.5 2 30 2.5 99.8 The test data in Tables VII and VIII indicate that both DREWCOR 2130 corrosion inhibitor and MEKOR are effective at reducing the sulfur content in depropanizer propane and stabilizer propane. The data in Tables I to VIII show that MEKOR, at various concentrations, effectively reduces the sulfur content of the crude oil and petroleum products made from the crude oil. Furthermore, this effect is shown when the MEKOR is introduced in different feedpoints of the refinery.

Claims: CLAIMS We claim: 1. A process for reducing the sulfur in a refinery process stream comprising: treating said refinery process stream with an effective sulfur reducing amount of a reducing agent selected from the group consisting of hydrazine, oximes, hydroxylamines, carbohydrazide, erythorbic acid, and mixtures thereof wherein the reducing agent, the refinery stream treated, or both have a temperature of at least 50°C to thereby reduce the level of sulfur in said refinery process stream. 2. The process of claim 2 wherein the amount of reducing agent is from 1 ppm to 100 ppm, said ppm being based upon the volume amount of refinery stream treated. 3. The process of claim 1 wherein the reducing agent is methyl ethyl ketoxime. 4. The process of claim 3 wherein the reducing agent or the refinery process stream treated has a temperature of from 90°C to 150°C. 5. The process of claim 2 wherein the refinery process stream treated is a hydrocarbon stream and the amount of methyl ethyl ketoxime is from 20 ppm to 50 ppm based upon the volume amount of hydrocarbon in the refinery process stream treated. 6. The process of claim 5 wherein the methyl ethyl ketoxime is added to a refinery process stream by adding said methyl ethyl ketoxime to a chemical feed point selected from the group consisting of raw crude, the raw crude tower, stripping steam to crude tower, crude tower reflux, splitter tower feed, reformate feed, and reformer. 7. A process for reducing the sulfur in crude oil comprising: treating said crude oil with an effective sulfur reducing amount of a reducing agent selected from the group consisting of hydrazine, oximes, hydroxylamines, carbohydrazide, erythorbic acid, and mixtures thereof wherein the reducing agent, the crude oil treated, or both have a temperature of at least 50°C to thereby reduce the level of sulfur in said crude oil treated. 8. The process of claim 7 wherein the amount of reducing agent is from 1 ppm to 100 ppm based upon the weight of the crude to be treated. 9. The process of claim 8 wherein the reducing agent is methyl ethyl ketoxime. 10. The process of claim 9 wherein the reducing agent or the crude oil treated has a temperature of from 90°C to 150°C. 11. The process of claim 10 wherein the amount of methyl ethyl ketoxime is from 20 ppm to 50 ppm based upon the weight of the crude oil to be treated.

Inventors: FORET TODD L, MANSFIELD WILLIAM D, VIDRINE HUBERT P JR, FORET, TODD, L., MANSFIELD, WILLIAM, D., VIDRINE, HUBERT, P., JR.
Applicants: DREW CHEM CORP, DREW CHEMICAL CORPORATION
Application year: 1995
Main classification: C10G21
IPC codes: C10G21, C10G29