Two-stage hydrotreating process employing mercaptanization and hydrodesulfurization

Abstract

A two-step process for treating a sulfur-containing refinery feedstock that includes olefin and diolefin constituents by reacting the feedstock with hydrogen sulfide over a catalyst to produce the corresponding mercaptans and/or thiophenes, which are then desulfurized in a second reactor containing hydrodesulfurization catalysts, thereby avoiding the need for prior selective hydrogenation of the olefin and diolefin constituents.

Claims

1. A process for treating a sulfur-containing refinery feedstock of unsaturated hydrocarbons comprising olefins that has a maleic anhydride diene test value that is less than 4 g/100 g oil, the process comprising: a. introducing the unsaturated hydrocarbon feedstock and hydrogen sulfide into an unsaturated hydrocarbon treatment zone containing a catalyst for reaction of the H.sub.2S with the olefins to produce a treated effluent stream, wherein the unsaturated hydrocarbon treatment zone comprises a mercaptanization unit; and b. passing the treated effluent stream to a hydrodesulfurization zone to produce a desulfurized hydrocarbon stream.

2. The process of claim 1, wherein the unsaturated hydrocarbon treatment zone comprises a thiophenization unit.

3. The process of claim 1, wherein the treated effluent stream of step (a) is passed to a hydrogen sulfide separation zone for the separation and recovery of a hydrogen sulfide recycle stream for use in step (a).

4. The process of claim 1, wherein an excess of hydrocarbon sulfide is introduced into the unsaturated hydrocarbon treatment zone and the desulfurized hydrocarbon stream is introduced into a gas-liquid separation zone for separation into an off-gas stream and a desulfurized product.

5. The process of claim 4, wherein the desulfurized product is recovered.

6. The process of claim 4, wherein the off-gas stream is recovered.

7. The process of claim 1, wherein the sulfur-containing feedstock comprising unsaturated hydrocarbons is selected from the group consisting of thermally cracked distillates, fluid catalytic cracking distillates, naphthas, straight run gas oil, and refinery intermediate streams containing olefins and/or diolefins, and combinations thereof.

8. The process of claim 1, wherein the treated effluent stream is substantially free of olefins and has a bromine number of less than 1 g/100 g oil.

9. The process of claim 1, wherein the sulfur-containing feedstock comprising unsaturated hydrocarbons has a boiling point in the range of from 36° C. to 450° C.

10. The process of claim 1, wherein the sulfur-containing feedstock comprising unsaturated hydrocarbons has a sulfur content in the range of from 0.1 W % to 3 W %.

11. The process of claim 1, wherein the desulfurized hydrocarbon stream has a sulfur content in the range of from 10-500 ppm.

12. The process of claim 1, wherein the unsaturated hydrocarbon treatment zone contains a catalyst that is an active phase metal catalyst where the metal is selected from Periodic Table Groups 4-11 and is carried by an alumina, silica, silica-alumina, titania, or zeolite support.

13. The process of claim 1, wherein the hydrodesulfurization zone contains a catalyst having one or more active metal components selected from Periodic Table Groups 6-10 and is carried by an alumina, silica alumina, silica, or zeolite support.

14. The process of claim 1, wherein the hydrodesulfurization zone operates at a temperature of 420° C. and below, a hydrogen partial pressure of 80 bars and below, and a hydrogen feed rate of or below 1000 liters per liter of oil.

15. A process for treating a sulfur-containing refinery feedstock of unsaturated hydrocarbons comprising olefins and diolefins that have a maleic anhydride diene test value that is greater than or equal to 4 g/100 g, the process comprising: a. introducing the unsaturated hydrocarbon feedstock and hydrogen sulfide into an unsaturated hydrocarbon treatment zone containing a catalyst for reaction of the H.sub.2S with the olefins and diolefins to produce a treated effluent stream, wherein the unsaturated hydrocarbon treatment zone comprises a mercaptanization unit; b. passing the treated effluent stream to a mercaptan oxidation unit treatment to produce a disulfide oil product stream and a treated raffinate stream; c. recovering the disulfide oil product stream; and d. passing the treated raffinate stream to a hydrodesulfurization zone to produce a desulfurized hydrocarbon stream.

16. The process of claim 15, wherein the conversion in step (a) comprises: introducing the unsaturated hydrocarbon feedstock and hydrogen sulfide into a thiophenization unit for conversion of diolefins into thiophenes to produce a thiophenized effluent stream; introducing the thiophenized effluent stream and hydrogen sulfide into the mercaptanization unit for conversion of olefins into mercaptans and recovering a mercaptanized and thiophenized effluent stream, wherein the mercaptanized and thiophenized effluent stream is the treated effluent stream of step (b).

17. The process of claim 16, wherein the thiophenized effluent stream is substantially free of diolefins and has a maleic anhydride diene value of less than 4 g/100 g oil.

18. The process of claim 16, wherein the mercaptanized and thiophenized effluent stream is substantially free of diolefins and olefins and has a maleic anhydride diene value of less than 4 g/100 g oil and a bromine number of less than 1 g/100 g oil.

19. The process of claim 15, wherein the unsaturated hydrocarbon treatment zone comprises a thiophenization unit.

20. The process of claim 15, wherein the treated effluent stream is substantially free of olefins and has a bromine number of less than 1 g/100 g oil.

21. The process of claim 15, wherein the treated effluent stream of step (a) is passed to a hydrogen sulfide separation zone for the separation and recovery of a hydrogen sulfide recycle stream for use in step (a).

22. The process of claim 15, wherein an excess of hydrocarbon sulfide is introduced into the unsaturated hydrocarbon treatment zone and the desulfurized hydrocarbon stream is introduced into a gas-liquid separation zone for separation into an off-gas stream and a desulfurized product.

23. The process of claim 22, wherein the desulfurized product is recovered.

24. The process of claim 22, wherein the off-gas stream is recovered.

25. The process of claim 15, wherein the sulfur-containing feedstock comprising unsaturated hydrocarbons is selected from the group consisting of thermally cracked distillates, fluid catalytic cracking distillates, naphthas, straight run gas oil, and refinery intermediate streams containing olefins and/or diolefins, and combinations thereof.

26. The process of claim 15, wherein the sulfur-containing feedstock comprising unsaturated hydrocarbons has a boiling point in the range of from 36° C. to 450° C.

27. The process of claim 15, wherein the sulfur-containing feedstock comprising unsaturated hydrocarbons has a sulfur content in the range of from 0.1 W % to 3 W %.

28. The process of claim 15, wherein the desulfurized hydrocarbon stream has a sulfur content in the range of from 10-500 ppm.

29. The process of claim 15, wherein the unsaturated hydrocarbon treatment zone contains a catalyst that is an active phase metal catalyst where the metal is selected from Periodic Table Groups 4-11 and is carried by an alumina, silica, silica-alumina, titania, or zeolite support.

30. The process of claim 15, wherein the hydrodesulfurization zone contains a catalyst having one or more active metal components selected from Periodic Table Groups 6-10 and is carried by an alumina, silica alumina, silica, or zeolite support.

31. The process of claim 15, wherein the hydrodesulfurization zone operates at a temperature of 420° C. and below, a hydrogen partial pressure of 80 bars and below, and a hydrogen feed rate of or below 1000 liters per liter of oil.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The process of the present disclosure will be described in more detail below and with reference to the attached drawings in which the same number is used for the same or similar elements, and where:

(2) FIG. 1 is a graph based on prior art data illustrating the relative reaction rates of certain sulfur compounds as a function of molecule size and difficulty of hydrodesulfurization;

(3) FIG. 2 is a simplified schematic diagram of a first embodiment of the process of the present disclosure;

(4) FIG. 3 is a simplified schematic diagram of a second embodiment of the process of the present disclosure;

(5) FIG. 4 is a simplified schematic diagram of a third embodiment of the process of the present disclosure; and

(6) FIG. 5 is a simplified schematic diagram of a fourth embodiment of the process of the present disclosure.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(7) Referring now to FIG. 2, an embodiment, which will be referred to as “Embodiment 1”, of the process and system (200) of the present disclosure includes an unsaturated hydrocarbon treatment zone (290), and hydrodesulfurization zone (260), optionally a hydrogen sulfide separation zone (230) and optionally, a gas-liquid separation zone (270). Embodiment 1 is particularly useful for the treatment of feeds exhibiting a maleic anhydride test value that is less than a predetermined value, e.g., less than 4 mg/g indicating a relatively low concentration of diolefins. In Embodiment 1, unsaturated hydrocarbon treatment zone (290) comprises a mercaptanization unit (220).

(8) An unsaturated hydrocarbon feed (202) comprising olefins and hydrogen sulfide stream (204) are introduced into mercaptanization unit (220) to convert olefins present in the feed (202) into mercaptans and thereby produce a mercaptanized effluent stream (222) that is substantially free of olefins, e.g., having a bromine number of less than 1 g/100 g oil. The mercaptanized effluent stream (222) is mixed with hydrogen (244) and introduced into a hydrodesulfurization zone (260) as mixed stream (246) for desulfurization to produce a hydrodesulfurized effluent stream (262), which is recovered.

(9) In an alternative embodiment, hydrodesulfurized effluent stream (262) is optionally introduced into the gas-liquid separation zone (270) for separation and recovery of off-gas stream (274) and a desulfurized liquid product (272), which is recovered for downstream processing, e.g., for the production of ultra-low sulfur transportation fuels. Off gas stream (274) can include C1-C4, H.sub.2S and NH.sub.3. Desulfurized hydrocarbon product (272) comprises naphtha and diesel streams.

(10) In Embodiment 1, the mercaptanized effluent stream (222) can optionally be introduced via a three-way valve (225) into the hydrogen sulfide separation zone (230) for the separation and recovery of a hydrogen sulfide recycle stream (232) and a liquids effluent stream (234), discharged via a three-way valve (235), which is then mixed with hydrogen (244) and introduced into a hydrodesulfurization zone (260) as mixed stream (246). The hydrogen sulfide recovered can be optionally returned to the unsaturated hydrocarbon treatment zone (290) as recycle hydrogen sulfide stream (232) to supplement the hydrogen sulfide stream (204). The optional hydrogen sulfide separation zone (230) can include separation units such as flash units, gas-liquid separators, and the like.

(11) Referring now to FIG. 3, an embodiment, which will be referred to as “Embodiment 2”, of the process and system (300) of the present disclosure includes an unsaturated hydrocarbon treatment zone (390), and hydrodesulfurization zone (360), a mercaptan oxidation, or MEROX zone, (340), optionally a hydrogen sulfide separation zone (330) and optionally, a gas-liquid separation zone (370). Embodiment 2 is particularly useful for the treatment of feeds exhibiting a maleic anhydride test value that is less than a predetermined value, e.g., less than 4 mg/g indicating a relatively low concentration of diolefins and where sweetening is required. In Embodiment 2, unsaturated hydrocarbon treatment zone (390) comprises a mercaptanization unit (320).

(12) An unsaturated hydrocarbon feed (302) comprising olefins and hydrogen sulfide stream (304) are introduced into mercaptanization unit (320) to convert olefins present in the feed (302) into mercaptans and thereby produce a mercaptanized effluent stream (322) that is substantially free of olefins, e.g., having a bromine number of less than 1 g/100 g oil. The mercaptanized effluent stream (322) is introduced into the mercaptan oxidation zone (340) to convert mercaptans into disulfide oils, which are recovered as stream (348). The remaining stream comprising other sulfur containing compounds including sulfides, thiophenes, dibenzothiophenes and their alkylated forms (342) is mixed with hydrogen (344) and introduced into a hydrodesulfurization zone (360) as stream (346) for desulfurization to produce a hydrodesulfurized effluent stream (362).

(13) In an alternative embodiment, hydrodesulfurized effluent stream (362) is optionally introduced into the gas-liquid separation zone (370) for separation and recovery of off gases (374) and a desulfurized product (372), which is recovered for downstream processing, e.g., for the production of ultra-low sulfur transportation fuels. Off-gas stream (374) can include C1-C4, H.sub.2S and NH.sub.3. Desulfurized hydrocarbon product (372) comprises naphtha and diesel streams.

(14) The by-product disulfide oils (348) produced by the mercaptan oxidation unit can be processed and/or disposed of in other downstream refinery unit operations (not shown).

(15) In Embodiment 2, the mercaptanized effluent stream (322) can optionally be introduced via a three-way valve (325) into the hydrogen sulfide separation zone (330) for the separation and recovery of a hydrogen sulfide stream (332) and a liquids effluent stream (334), discharged via a three-way valve (335), which is then fed to the MEROX zone (340). The hydrogen sulfide recovered can be optionally returned to the unsaturated hydrocarbon treatment zone (390) as recycle hydrogen sulfide stream (332) to supplement the hydrogen sulfide stream (304). The optional hydrogen sulfide separation zone (330) can include separation units such as flash units, gas-liquid separators, and the like.

(16) Referring now to FIG. 4, an embodiment, which will be referred to as “Embodiment 3”, of the process and system (400) of the present disclosure includes an unsaturated hydrocarbon treatment zone (490), and hydrodesulfurization (HDS) zone (460), a gas-liquid separation zone (470) and optionally a hydrogen sulfide separation zone (430). The system of Embodiment 3 is preferably employed to treat feeds that exhibit a maleic anhydride test value that is greater than a predetermined value, e.g., equal to or greater than 4 mg/g, that indicates a concentration of dienes that will adversely affect the useful life of the catalyst(s) in the HDS zone. In Embodiment 3, unsaturated hydrocarbon treatment zone (490) comprises a thiophenization unit (410) and a mercaptanization unit (420).

(17) An unsaturated hydrocarbon feed (402) comprising predetermined proportions of a mixture of olefins and diolefins and a hydrogen sulfide stream (404) are introduced into thiophenization unit (410) to convert diolefins in the feed (402) into thiophenes and thereby produce a thiophenized effluent stream (412) that contains olefins that is substantially free of diolefins, e.g., having a maleic anhydride value of less than 4 g/100 g oil. The thiophenized effluent stream (412) that contains olefins and a hydrogen sulfide stream (404) are introduced into mercaptanization unit (420) to produce a mercaptanized and thiophenized effluent stream (422) that is substantially free of olefins and diolefins, e.g., having a bromine number of less than 1 g/100 g oil and a maleic anhydride value of less than 4 g/100 g oil. The mercaptanized and thiophenized effluent stream (422) is mixed with hydrogen (444) and introduced into a hydrodesulfurization zone (460) as mixed stream (446) for desulfurization to produce a hydrodesulfurized effluent stream (462).

(18) In some embodiments, hydrodesulfurized effluent stream (462) is optionally introduced into the gas-liquid separation zone (470) for the separation and recovery of off-gas stream (474), and a desulfurized hydrocarbon product (472), which is recovered for downstream processing, e.g., for the production of ultra-low sulfur transportation fuels. Off-gas stream (474) can include C1-C4, H.sub.2S and NH.sub.3. Desulfurized hydrocarbon product (472) comprises naphtha and diesel streams.

(19) In Embodiment 3, the mercaptanized and thiophenized effluent stream (422) can optionally be introduced via a three-way valve (425) into hydrogen sulfide separation zone (430) for the separation of a hydrogen sulfide stream (432) and a liquids effluents stream (434), discharged via three-way valve (435), which is then mixed with hydrogen (444) and introduced into a hydrodesulfurization zone (460) as mixed stream (446). The hydrogen sulfide can optionally be returned to the unsaturated hydrocarbon treatment zone (490) as hydrogen sulfide recycle stream (432) to supplement hydrogen sulfide stream (404). Optional hydrogen sulfide separation zone (430) can comprise separation units such as flash units, gas-liquid separators, and the like.

(20) Referring now to FIG. 5, an embodiment, which will be referred to as “Embodiment 4”, of the process and system (500) of the present disclosure includes an unsaturated hydrocarbon treatment zone (590), and a mercaptan oxidation or MEROX zone (540), a hydrodesulfurization zone (560), a gas-liquid separation zone (570) and, optionally, a hydrogen sulfide separation zone (530). Embodiment 4 can be used for feeds which exhibit a maleic anhydride test value that is greater than a predetermined value, e.g., equal to or greater than 4 mg/g. In Embodiment 4, unsaturated hydrocarbon treatment zone (590) comprises a thiophenization unit (510) and a mercaptanization unit (520).

(21) An unsaturated hydrocarbon feed (502) comprising diolefins and olefins, and hydrogen sulfide stream (504) are introduced into thiophenization unit (510) to convert diolefins in the feed (502) into thiophenes and thereby produce a thiophenized effluent stream (512) that is substantially free of diolefins, e.g., having a maleic anhydride value of less than 4 g/100 g oil. The thiophenized effluent stream (512) containing olefins and a hydrogen sulfide stream (504) are introduced into mercaptanization unit (520) to produce a mercaptanized and thiophenized effluent stream (522) that is substantially free of olefins and diolefins, e.g., having a bromine number of less than 1 g/100 g oil and a maleic anhydride value of less than 4 g/100 g oil. The mercaptanized and thiophenized effluent stream (522) is introduced into the mercaptan oxidation zone (540) to convert mercaptans into disulfide oils, which are recovered as stream (548). The remaining stream comprising other sulfur containing compounds including, sulfides, thiophenes, benzothiophenes, dibenzothiophenes (542) is mixed with hydrogen (544) and introduced into a hydrodesulfurization zone (560) as stream (546) for desulfurization to produce a hydrodesulfurized effluent stream (562).

(22) Hydrodesulfurized effluent stream (562) is introduced into the gas-liquid separation zone (570) for separation and recovery of off-gas stream (574) and a desulfurized product (572), which is recovered for downstream processing, e.g., for the production of ultra-low sulfur transportation fuels. Off-gas stream (574) includes C1-C4, H.sub.2S and NH.sub.3. Desulfurized hydrocarbon product (572) comprises naphtha and diesel streams.

(23) The by-product disulfide oils (548) produced by the mercaptan oxidation unit can be processed and/or disposed of in other downstream refinery unit operations (not shown).

(24) In Embodiment 4, the mercaptanized and thiophenized effluent stream (522) can optionally be introduced via a three-way valve (525) into hydrogen sulfide separation zone (530) for the separation of a hydrogen sulfide stream (532) and a liquids effluents stream (534), discharged via a three-way valve (535), which is then fed into mercaptan oxidation zone (540). The hydrogen sulfide can optionally be returned to the unsaturated hydrocarbon treatment zone (590) as hydrogen sulfide recycle stream (532) to supplement hydrogen sulfide stream (504).

(25) The optional hydrogen sulfide separation zone (530) can include separation units such as flash units, gas-liquid separators, and the like.

(26) As explained previously, Embodiments 1 and 2 are particularly useful for the treatment of feeds exhibiting a maleic anhydride test value that is less than 4 mg/g indicating a relatively low concentration of diolefins and Embodiments 3 and 4 are particularly useful for the treatment of feeds exhibiting a maleic anhydride test value that is equal to or greater than 4 mg/g. However, it will be understood that any of the Embodiments can be used with a feeds exhibiting any maleic anhydride test value. For example, Embodiments 1 and 2 can be used with feeds exhibiting a maleic anhydride test values that are equal to or greater than 4 mg/g, but the catalyst will deactivate faster resulting in fouling and a shorter unit cycle. Additionally, Embodiments 3 and 4 can be used with feeds exhibiting a maleic anhydride test value that is less than 4 mg/g, which would result in longer unit cycles.

(27) Both the mercaptanization and thiophenization units can be operates as fixed bed reactors.

(28) The mercaptanization unit can operate at temperatures in the range of from 80° C. to 300° C., 150° C. to 300° C., or 200° C. to 300° C.; at pressures in the range of from 10 bars to 50 bars, 10 bars to 30 bars, or 10 bars to 20 bars; at a liquid hourly space volume (LHSV) in the range of from 1 h.sup.−1 to 100 h.sup.−1, 2 h.sup.−1 to 40 h.sup.−1, or 5 h.sup.−1 to 30 h.sup.−1; and at hydrogen sulfide-to-olefin molar ratios in the range of from 1:1 to 100:1, 1:1 to 5:1, or 1:1 to 2:1.

(29) A suitable catalyst for use in the mercaptanization unit is an active phase metal catalyst where the metal is selected from Periodic Table IUPAC Groups 4-11 on an alumina, silica, silica-alumina, titania, or zeolite support.

(30) The thiophenization unit can operate at temperatures in the range of from 80° C. to 250° C., 150° C. to 225° C., or 150° C. to 200° C.; at pressures in the range of from 10 bars to 50 bars, 10 bars to 30 bars, or 10 bars to 20 bars; at an LHSV in the range of from 1 h.sup.−1 to 100 h.sup.−1, 2 h.sup.−1 to 40 h.sup.−1, or 5 h.sup.−1 to 30 h.sup.−1; and at a hydrogen sulfide-to-diolefin molar ratios in the range of from 1:1 to 100:1, 1:1 to 5:1, or 1:1 to 2:1.

(31) A suitable catalyst for use in the thiophenization unit is an active phase metal catalyst where the metal is selected from Periodic Table IUPAC Groups 4-11 on an alumina, silica, silica-alumina, titania, or zeolite support.

(32) The hydrodesulfurization zone utilizes hydrotreating catalyst(s) having one or more active metal components selected from the Periodic Table of the Elements Group 6-10. In certain embodiments the active metal component is one or more of cobalt, nickel, tungsten and molybdenum, typically deposited or otherwise incorporated on a support, e.g., alumina, silica alumina, silica, or zeolites. In certain embodiments, the hydrotreating catalyst used in the hydrodesulfurization zone includes a combination of cobalt and molybdenum, nickel and molybdenum or cobalt, nickel and molybdenum deposited on an alumina substrate.

(33) The operating conditions of the hydrodesulfurization zone will vary and the range of operating conditions are dependent on the characteristics of the feedstocks being processed and their determination is within the skill of the art.

(34) For most streams, operating conditions can be used that include an operating temperature of 420° C. and below, a hydrogen partial pressure of 80 bars and below, and a hydrogen feed rate of or below 1000 liters per liter of oil. In certain embodiments of the present process, the operating conditions are: a temperature in the range of from about 300° C. to about 400° C., and in certain embodiments about 320° C. to about 380° C.; a reaction pressure in the range of from about 10 bars to about 40 bars, in certain embodiments about 20 bars to about 40 bars and in further embodiments about 30 bars; a hydrogen partial pressure greater than about 35 bars in certain embodiments, and up to about 55 bars in other embodiments; a feedstock liquid hourly space velocity (LHSV) less than or equal to about 10 h.sup.−1, in certain embodiments in the range of from about 0.5 h.sup.−1 to about 10 h.sup.−1, and in certain embodiments about 1.0 h.sup.−1 to about 4.0 h.sup.−1; and a hydrogen feed rate in the range of from about 100 standard liters of hydrogen per liter of oil (SLt/Lt) to about 1000 SLt/Lt, and in certain embodiments about 100 SLt/Lt to about 300 SLt/Lt.

(35) The feedstream to the process can include thermally cracked distillates, fluid catalytic cracking distillates, naphthas, straight run gas oil, and refinery intermediate streams containing olefins and/or diolefins, and combinations thereof. In some embodiments, the feedstream has a boiling point in the range of from about 36° C. to 450° C. Typical feeds include a sulfur content in the range of from 0.1 W % to 3 W %. The desulfurized product will typically have a reduced sulfur content in the range of from 10-500 ppm.

Example 1

(36) In accordance with Embodiment 4 described above, a feedstream that is a blend of coker naphtha and straight run naphtha, the composition and properties of which are identified in Table 3, was subjected to mercaptanization, and thiophenization and mercaptan oxidation processing steps in order to provide an intermediate stream that is substantially free of olefins and diolefins. The intermediate stream was then subjected to hydrodesulfurization processing. The coker naphtha was obtained from the delayed coking of a desulfurized vacuum residue.

(37) TABLE-US-00003 TABLE 3 Coker Straight run Property Unit naphtha naphtha Blend Volume % % 30 70 100 API Gravity ° 65.2 61.4   62.4 Density g/cc 0.7194 0.734     0.730 Sulfur ppmw 1126 960 1010  Nitrogen ppmw 24 3  9 Aromatics wt % 12.2 6.0    7.9 Olefins wt % 37.0 0.0   11.1 Diolefins wt % 5.5 0.0    1.7 Bromine number g/100 g 74 0.0   22.sup.1 Maleic Diene Value mg/g 7.6 0    2.28.sup.1 SIMDIST  0/5 ° C. −3 41  28 10 ° C. 40 49  46 50 ° C. 101 114 110 90 ° C. 144 180 169 95/100 ° C. 167 187 181 .sup.1calculated

(38) From Table 3, it is clear that the starting coker naphtha feed contains a relatively high concentration of diolefins (5.5 wt %) and olefins (37.0 wt %) with a maleic anhydride diene test value of 7.6 mg/g. When blended with the straight run naphtha, the maleic anhydride diene test value is lowered to a value of 2.28 mg/g. The blend was thiophenized and mercaptanized with hydrogen sulfide in a fixed-bed reactor, each at a temperature of 200° C., and a pressure of 15 bars. The hydrogen sulfide was generated in situ by the decomposition of DMDS with hydrogen over a catalyst bed in the same reactor.

(39) The material balance for the process of Example 1 is shown in Table 4. When 100 kg of the naphtha blend was processed according to Embodiment 3, 99.8 kg of desulfurized naphtha was recovered, indicating that the process is effective at desulfurizing olefin and diolefin containing feed streams.

(40) TABLE-US-00004 TABLE 4 Mass Flow Diolefins Olefins Thiophenes Mercaptans Sulfur Stream # Description Kg/h Kg/h Kg/h Kg/h Kg/h Kg/h 502 Unsaturated 100.0 1.7 11.1 0.101 hydrocarbon feed (Naphtha blend) 504 Hydrogen Disulfide 8.9 512 Thiophenized effluent 108.9 2.5 0.867 stream 522 Mercaptanized and 108.8 14.6 4.283 thiophenized effluent stream 532 Hydrogen sulfide 4.4 recycle 542 Mercaptanized and 104.3 4.283 thiophenized effluent stream 544 Hydrogen 2.7 574 Off gases 5.5 5.535 572 Desulfurized product 98.8 0.001 (desulfurized naphtha)

(41) It will be understood from the above description that the present disclosure provides a cost-effective process for pretreating feeds that contain olefins and diolefins prior to the catalytic hydrodesulfurization of the distillate streams.

(42) The process of the present invention has been described above and in the attached figures; process modifications and variations will be apparent to those of ordinary skill in the art from this description and the scope of protection is to be determined by the claims that follow.