Split-feed two-stage parallel aromatization for maximum para-xylene yield

• US 6,051,128 A
• Filed: 06/06/1995
• Issued: 04/18/2000
• Est. Priority Date: 06/06/1995
• Status: Expired due to Term

• Current Assignee: Chevron Chemical Company (Chevron Corp.)
• Original Assignee: Chevron Chemical Company (Chevron Corp.)
• Inventors: Thom, Bruce J., Nacamuli, Gerald J.
• Primary Examiner(s): Caldarola, Glenn
• Assistant Examiner(s): Hailey, Patricia L.
• Application Number:
  US08/470,845
• Time in Patent Office: 1,778 Days
• Field of Search: 208/63, 208/65, 208/66, 208/78, 208/79, 208/133, 208/138, 585/412, 585/413, 585/418, 585/419
• US Class Current: 208/79
• CPC Class Codes: C10G 59/06 plural parallel stages only

Abstract

A full boiling hydrocarbon feed is reformed to enhance para-xylene and benzene yields. First, the hydrocarbon feed is separated into a C_5- cut, a C₆ -C₇ cut, and a C₈₊ cut. The C₆ -C₇ cut has less than 5 lv. % of C₈₊ hydrocarbon, and the C₈₊ cut has less than 10 lv. % of C_7- hydrocarbon. The C₆ -C₇ cut is subjected to catalytic aromatization at elevated temperatures in a first reformer in the presence of hydrogen and using a non-acidic catalyst comprising at least one Group VIII metal and a non-acidic zeolite support to produce a first reformate stream; and the C₈₊ cut is subjected to catalytic aromatization at elevated temperatures in a second reformer in the presence of hydrogen and using an acidic catalyst comprising at least one Group VIII metal and a metallic oxide support to produce a second reformate stream. Less than 20 wt. % of the total amount of C₈ aromatics produced in the first and second reformer is ethylbenzene, and more than 20 wt. % of the total amount of xylenes produced in the first and second reformer are para-xylenes.

Claims

1. A process for reforming a full boiling hydrocarbon feed to enhance para-xylene and benzene yields comprising:

(a) separating the hydrocarbon feed into a C_5- cut, a C₆ -C₇ cut, and a C₈₊ cut, wherein the C₆ -C₇ cut has less than 5 lv. % of C₈₊ hydrocarbon, and wherein the C₈₊ cut has less than 10 lv. % of C_7- hydrocarbon;

(b) subjecting the C₆ -C₇ cut to catalytic aromatization at elevated temperatures in a first reformer in the presence of hydrogen and using a non-acidic catalyst comprising at least one Group VIII metal and non-acidic zeolite support to produce a first reformate stream containing less than 5 lv % C₈ aromatics including xylenes; and

(c) subjecting the C₈₊ cut to catalytic aromatization at elevated temperatures in a second reformer in the presence of hydrogen and using an acidic catalyst comprising at least one Group VIII metal and a metallic oxide support to produce a second reformate stream containing C₈ aromatics including xylenes;

wherein less than 20 wt. % of the total amount of C₈ aromatics produced in the first and second reformer is ethylbenzene, and wherein more than 20 wt. % of the total amount of xylenes produced in the first and second reformer are para-xylenes.

2. A process for reforming according to claim 1 wherein the non-acidic catalyst comprises platinum on a non-acidic zeolite L.

3. A process for reforming according to claim 2 wherein the acidic catalyst is not presulfided.

4. A process for reforming according to claim 3 wherein the acidic catalyst comprises platinum and tin on an alumina support.

5. A process for reforming according to claim 3 wherein the process further comprises the steps of:

(d) combining the first reformate stream and the second reformate stream to form a combined reformate stream;

(e) separating the combined reformate stream into a light fraction and a heavy fraction;

(f) recycling at least part of the light fraction either to the hydrocarbon feed or to at least one of the reformers.