Process for producing gasoline having lower benzene content and distillation end point

• US 5,347,061 A
• Filed: 03/08/1993
• Issued: 09/13/1994
• Est. Priority Date: 03/08/1993
• Status: Expired due to Fees

• Current Assignee: Mobil Oil Corporation (Exxon Mobil Corporation)
• Original Assignee: Mobil Oil Corporation (Exxon Mobil Corporation)
• Inventors: Harandi, Mohsen N., Owen, Hartley, Schipper, Paul H.
• Primary Examiner(s): MCFARLANE, ANTHONY R
• Application Number:
  US08/028,057
• Time in Patent Office: 554 Days
• Field of Search: 585/804, 585/323, 585/322, 585/467, 585/800, 208/62, 208/92, 208/100
• US Class Current: 585/323
• CPC Class Codes: C10G 35/095 containing crystalline alumino-silicates, e.g. molecular sieves C10G35/065 takes precedence
• CPC Class Codes: C10G 45/64 containing crystalline alumino-silicates, e.g. molecular sieves
• CPC Class Codes: C10G 59/02 plural serial stages only

Abstract

A process is disclosed for upgrading reformate and/or light FCC gasoline by substantially reducing the amount of benzene in the gasoline product while simultaneously reducing the gasoline ASTM distillation End Point. The process comprises the fractionation of reformate to recover that fraction, C₇ -C₈ hydrocarbons, directly useful in gasoline without further conversion. A heavy bottom fraction comprising C₉ + aromatic and non-aromatic hydrocarbons is recovered and a C₆ fraction rich in benzene. The total C₆ fraction and a portion of the C₉ + fraction are converted by alkylation, transalkylation and cracking in contact with acidic metallosilicate catalyst particles to gasoline boiling range materials rich in alkylaromatics. Following debutanization or depentanization of the conversion product, the fraction containing unconverted benzene is recycled to the reformate fractionator.

Claims

1. A process for the production of gasoline having reduced benzene content and lower boiling end point, comprising:

a) introducing reformer effluent into a fractionation system for separation and recovery of an overhead stream comprising C₅ - hydrocarbons, a bottom stream comprising C₉ + alkylaromatic and non-aromatic hydrocarbons, a stream comprising benzene rich C₆ hydrocarbons, and a stream comprising C₇ -C₈ hydrocarbons;

b) passing said benzene rich C₆ stream and a portion of said C₉ + hydrocarbon stream to a hydrocarbon cracking and alkylation reactor containing acidic shape selective metallo-silicate catalyst particles under cracking, alkylation and transalkylation conversion conditions whereby a portion of said benzene is converted to C₇ + alkylaromatics and a portion of said C₉ + hydrocarbons is converted to lower molecular weight hydrocarbons;

c) recycling effluent from said reactor to said fractionation tower to separate and recycle unconverted benzene and unconverted C₉ + hydrocarbons whereby the production of C₇ -C₉ alkylaromatics is maximized.

2. The process of claim 1 including the further step of separating said effluent by first passing said effluent to a debutanizer or depentanizer and recycling said debutanizer or depentanizer C₅ + or C₆ + bottom stream to said fractionation tower.

3. The process of claim 1 wherein said conversion conditions comprise temperature between 300°

C. and 500°

C., pressure between 100 kPA and 1400 kPa and weight hourly space velocity between 0.1 and 10.

4. The process of claim 3 wherein said conversion conditions comprise temperature between 370°

C. and 455°

C., pressure between 350 kPa and 700 kPa and weight hourly space velocity between 1 and 5.

5. The process of claim 1 wherein said catalyst comprises crystalline aluminosilicate.

6. The process of claim 5 wherein said catalyst is selected from the group consisting of ZSM-5, ZSM-11 , ZSM-12, ZSM-22, ZSM-23, ZSM-35, ZSM-48, MCM-22, MCM-36, zeolite Beta and TEA mordenite.

7. The process of claim 1 wherein said reformer effluent is separated into an overhead stream comprising C₆ - hydrocarbons, a bottom stream comprising C₁₀ + alkylaromatic and non-aromatic hydrocarbons, and a stream comprising C₇ -C₉ hydrocarbons, whereby a portion of said C₁₀ + alkylaromatic and non-aromatic hydrocarbons is converted to lower molecular weight hydrocarbons.

8. The process of claim 1 including introducing into said reactor an additional feedstream comprising C₅ -C₆ oleflnic gasoline containing less than 3 weight percent benzene whereby said benzene is converted to C₇ + aikylaromatics and olefin content of said gasoline is reduced.

9. A process for the combined upgrading of reformate and light C₅ + olefinic gasoline to provide low boiling end point gasoline having reduced benzene and olefins content, comprising:

a) introducing reformer effluent into a fractionation tower for separation and recovery of an overhead stream comprising C₆ - hydrocarbons, a bottom stream comprising C₉ + alkylaromatic and non-aromatic hydrocarbons , a stream comprising benzene rich C₆ hydrocarbons, and a stream comprising C₇ -C₈ hydrocarbons;

b) passing said benzene rich C₆ stream, a portion of said C₉ + hydrocarbon stream and a feedstream comprising C₅ + light olefinic gasoline to a hydrocarbon cracking and alkylation reactor containing acidic shape selective metallosilicate catalyst particles under cracking, alkylation and transalkylation conversion conditions whereby a portion of said benzene is converted to C₇ + alkylaromatics, a portion of said C₉ + hydrocarbons is converted to lower molecular weight hydrocarbons and olefins are lowered;

c) recycling effluent from said reactor to said fractionation tower to separate and recycle unconverned benzene and unconverted C₉ + hydrocarbons whereby the production of C₇ -C₉ alkylaromatics is maximized.

10. The process of claim 9 including the further step of separating said effluent by first passing said effluent into a debutanizer or depentanizer and recycling said debutanizer or depentanizer C₅ + or C₆ + bottom stream to said fractionation tower.

11. The process of claim 9 wherein said conversion conditions comprise temperature between 300°

C. and 500°

C., pressure between 100 kPA and 1400 kPa and weight hourly space velocity between 0.1 and 10.

12. The process of claim 11 wherein said conversion conditions comprise temperature between 370°

C. and 455°

C., pressure between 350 kPa and 700 kPa and weight hourly space velocity between 1 and 5.

13. The process of claim 9 wherein said catalyst comprises crystalline aluminosilicate.

14. The process of claim 13 wherein said catalyst is selected from the group consisting of ZSM-5, ZSM-11 , ZSM-12, ZSM-23, ZSM-35, ZSM-48, zeolite Beta and TEA mordenite.

15. A process for the production of C₅ + gasoline having reduced benzene content and lower boiling end point, comprising:

(a) introducing a feedstream comprising C₅ + gasoline boiling range olefinic hydrocarbons rich in benzene and C₉ + alkylaromatic hydrocarbons into a hydrocarbon cracking and alkylation reactor containing acidic shape selective metallosilicate catalyst particles under cracking, alkylation and transalkylation conversion conditions whereby a portion of said benzene is converted to C₇ + alkylaromatics and a portion of said C₉ + hydrocarbons is converted to lower molecular weight hydrocarbons;

(b) introducing effluent from said reactor into a fractionation system for separation and recovery of an overhead stream comprising C₄ - or C₅ - hydrocarbons, a bottom stream comprising C₉ + alkylaromatic rich hydrocarbons, a stream comprising benzene rich C₆ hydrocarbons, and a stream comprising C₇ -C₈ hydrocarbons;

c) recycling a portion of said bottom stream and a portion of said fractionator C₆ hydrocarbon stream to said reactor.

16. The process of claim 15 wherein said conversion conditions comprise temperature between 300°

C. and 500°

C., pressure between 100 kPA and 1400 kPa and weight hourly space velocity between 0.1 and 10.

17. The process of claim 16 wherein said conversion conditions comprise temperature between 370°

C. and 455°

C., pressure between 350 kPa and 700 kPa and weight hourly space velocity between 1 and 5.

18. The process of claim 15 wherein said catalyst comprises crystalline aluminosilicate.

19. The process of claim 18 wherein said catalyst is selected from the group consisting of ZSM-5, ZSM-11, ZSM-12, ZSM-22, ZSM-23, ZSM-35, ZSM-48, MCM-22, MCM-36, zeolite Beta and TEA mordenite.