WO2015020728A1

WO2015020728A1 - Integrated process for gasoline or aromatics production

Info

Publication number: WO2015020728A1
Application number: PCT/US2014/043580
Authority: WO
Inventors: Gregory A. Funk; Steven T. Arakawa
Original assignee: UOP LLC
Current assignee: Honeywell UOP LLC
Priority date: 2013-08-07
Filing date: 2014-06-23
Publication date: 2015-02-12
Anticipated expiration: 2016-02-07
Also published as: CN105612138B; US20150045597A1; EP3030539A4; TWI557220B; TW201522608A; EP3030539A1; KR20160040641A; CN105612138A

Abstract

A process for increasing the yields of hydrocarbon components to gasoline blending pools from a hydrocarbon feedstock is presented. The process includes separating a naphtha feedstock to components to a first stream that are more readily processed in a cracking unit and to components in a second stream that are more readily processed in a reforming unit. The process includes the ability to convert components from the cracking stream to the reforming stream.

Description

INTEGRATED PROCESS FOR GASOLINE OR AROMATICS PRODUCTION

STATEMENT OF PRIORITY

[0001] This application claims priority to U.S. Application No. 14/260,784 which was filed April 24, 2014, which claims benefit of U.S. Provisional Application No. 61/863,025 filed on August 7, 2013, the contents of which are hereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

[0002] The present invention relates to a process and system for the production of aromatics from a heavier hydrocarbon stream. In particular, this process provides for increasing yields and flexibility of the production of aromatics and light olefins from hydrocarbon feedstock.

BACKGROUND

[0003] The reforming of petroleum raw materials is an important process for producing useful products. One important process is the separation and upgrading of hydrocarbons for a motor fuel, such as producing a naphtha feedstream and upgrading the octane value of the naphtha in the production of gasoline. However, hydrocarbon feedstreams from a raw petroleum source include the production of useful chemical precursors for use in the production of plastics, detergents and other products.

[0004] The upgrading of gasoline is an important process, and improvements for the conversion of naphtha feedstreams to increase the octane number have been presented in US Patents 3,729,409; 3,753,891; 3,767,568; 4,839,024; 4,882,040; and 5,242,576. These processes involve a variety of means to enhance octane number, and particularly for enhancing the aromatic content of gasoline.

[0005] Processes include splitting feeds and operating several reformers using different catalysts, such as a monometallic catalyst or a non-acidic catalyst for lower boiling point hydrocarbons and bi-metallic catalysts for higher boiling point hydrocarbons. Other improvements include new catalysts, as presented in US Patents 4,677,094; 6,809,061; and

7,799,729. However, there are limits to the methods and catalysts presented in these patents, and which can entail significant increases in cost. [0006] Light olefins have traditionally been produced through the process of steam or catalytic cracking, and comprise ethylene and propylene. Light olefins are also derived from the same feedstocks as gasoline. Because of the limited availability and high cost of petroleum sources, the cost of producing light olefins from such petroleum sources has been steadily increasing. The ability to shift components in the feedstock for light olefins and gasoline pools enables producers to economically choose the most important product line and to shift some of the hydrocarbon components in an efficient manner.

SUMMARY

[0007] A process for improving gasoline yields is presented. A first embodiment of the invention is a process for converting a treated hydrocarbon feedstream, comprising passing the treated hydrocarbon feedstream to a separation unit to generate an extract stream enriched in normal paraffins, and a raffinate stream having a reduced normal hydrocarbon content; passing the extract stream to an extract separation system to generate an extract overhead stream comprising nC5 and nC6 compounds, an extract intermediate stream comprising nC7 to nCl 1 compounds, and an extract bottoms stream comprising desorbent; passing the raffinate stream to a raffinate separation system to generate a raffinate overhead stream comprising iC5 and iC6 compounds, an intermediate raffinate stream comprising aromatics and non-normal hydrocarbons in the C6 to CI 1 carbon range, and a raffinate bottoms stream comprising desorbent; and passing the intermediate raffinate stream to a reforming unit to generate an aromatics stream. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph further comprising passing a hydrocarbon feedstream to a fractionation unit to generate an overhead stream comprising C4 and lighter hydrocarbons, and a bottoms stream comprising C5+ hydrocarbons; hydrotreating the bottoms stream to generate the treated hydrogenated stream; passing the treated hydrogenated stream to the separation unit. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph further comprising passing a portion of the extract overhead stream to an isomerization unit to generate an isomerized stream comprising C5 and C6 compounds. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph further comprising passing the isomerized stream to the separation unit. [0008] A second embodiment of the invention is a process for converting a naphtha feedstream, comprising fractionating the naphtha feedstream to generate a naphtha overhead stream comprising C4 and lighter hydrocarbons, and a naphtha bottoms stream comprising C5+ hydrocarbons; hydrotreating the naphtha bottoms stream to generate a hydrogenated stream having a reduced acetylene, diolefms, sulfur and nitrogen content; passing the hydrogenated stream to a separation unit to generate an extract stream enriched in normal hydrocarbons and a raffinate stream; passing the extract stream to a extraction separation system to generate an extract overhead stream comprising nC5 and nC6 compounds, an extract intermediate stream comprising nC7 to nCl 1 compounds, and an extract bottoms stream comprising desorbent; passing the raffinate stream to a raffinate separation system to generate a raffinate overhead comprising iC5 and iC6 compounds, an intermediate raffinate stream comprising C6 to CI 1 aromatics and non-normal hydrocarbons, and a raffinate stream comprising desorbent; passing the intermediate extract stream and the naphtha overhead stream to a naphtha cracking unit to generate light olefins; and passing the intermediate raffinate stream to a reforming unit to generate an aromatics stream. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph further comprising passing a portion of the extract overhead stream to an isomerization unit to generate an isomerized stream comprising C5 and C6 compounds. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph further comprising passing the isomerized stream to the separation unit.

[0009] Other objects, advantages and applications of the present invention will become apparent to those skilled in the art from the following detailed description and drawings.

BRIEF DESCRIPTION OF THE DRAWING [0010] Figure 1 is a flow schematic of the process; and

[0011] Figure 2 is a specific embodiment of the present process.

DETAILED DESCRIPTION

[0012] The present embodiment provides an efficient use of hydrocarbon feedstocks . The production of useful higher value products from lower value hydrocarbon feedstocks is important for the economics of a petroleum processing plant. Flexibility in the production of higher- value products is desirable for responding to shifting demands in different product lines.

[0013] The present embodiment provides flexibility in the processing of a hydrocarbon feedstream for the production of light olefins and/or aromatics. The process, as shown in Figure 1, includes passing a treated hydrocarbon stream 8 to a separation unit 10. The separation unit 10 generates an extract stream 12 enriched in normal hydrocarbons, and a raffinate stream 14 having a reduced normal hydrocarbon content. The extract stream 12 is passed to an extract separation system 20 to generate an extract overhead stream 22. The extract separation system 20 can also generate an extract intermediate stream 24, and an extract bottoms stream 26.

[0014] Normal components in the hydrocarbon stream are more readily cracked to form light olefins than non-normal components. The normal components are also more difficult to reform to aromatics than non-normal components. The separation of normal and non-normal components, combined with passing the different stream to appropriate downstream processing units improves flexibility and the economics of cracking and reforming naphtha. The ability to convert normal components to non-normal components allows the shifting of hydrocarbon components from the stream fed to a cracking unit to a stream for generating gasoline components.

[0015] The extract overhead stream 22 can comprise normal C5 and C6 compounds, the extract intermediate stream 24 can comprise normal C7 and heavier compounds, and the extract bottoms stream 26 can comprise a recycle stream passed back to the separation unit 10. The extract intermediate stream 24 is passed to a cracking unit 40 to generate light olefins. In one embodiment, the cracking unit 40 is a naphtha steam cracking unit.

[0016] In one embodiment, the separation unit 10 is an adsorption separation unit, and the recycle stream 26 is the desorbent recycle from the extract separation system 20 to the separation unit 10. The extract separation system 20 can comprise one or more fractionation columns for separating the extract stream from the desorbent. The extract separation system 20 can also separate the extract stream 12 into multiple streams. Options in the separation process include a divided wall column, or other means for separating hydrocarbon streams.

[0017] The raffinate stream 14 is passed to a raffinate separation system 30 to generate a raffinate overhead stream 32, an intermediate raffinate stream 34 and a raffinate bottoms stream 36. The raffinate overhead stream 32 will comprises isopentanes and isohexanes, the intermediate raffmate stream 34 comprises aromatics, naphthenes, and non-normal hydrocarbons in the C6 to CI 1 range, and the raffmate bottoms stream 36 comprises a recycle stream that is returned to the separation unit 10.

[0018] With an adsorption separation system 10, the raffmate recycle is the desorbent used in the adsorption separation process. The intermediate raffmate stream 34 is passed to a reforming unit 50 to generate a reformate stream 52, comprising aromatics.

[0019] In a specific embodiment, the process, as shown in Figure 2, processes a naphtha feedstream. A naphtha feedstream comprises many hydrocarbon components, and is often passed to a cracking unit for the production of light olefins. However, the composition of a naphtha stream includes components that do not crack well to light olefins and this leads to further processing. A naphtha feedstream also include useful hydrocarbons for converting to aromatics. The present embodiment seeks to separate a naphtha feedstream to increase the yields and efficiencies of naphtha cracking units and reforming units. A naphtha feedstream 76 is passed to a fractionation unit 70 to generate an overhead stream 72 comprising C4 and lighter hydrocarbons, and a bottoms stream 74 comprising C5 and higher hydrocarbons. The overhead stream 72 is passed to a cracking unit 40 to generate a light olefins product stream 42.

[0020] A naphtha feedstream will typically comprise hydrocarbons in the C4 to C 11 range. The adsorption separation unit 10 will therefore utilize an appropriate desorbent, which is normally outside this range. One desorbent that works for a light naphtha having components in the C4 to CI 1 range is n-C12.

[0021] The naphtha bottoms stream 74 is passed to a hydrotreating unit 80 to generate a treated hydrocarbon stream 8. The hydrotreating of the naphtha bottoms stream 74 removes sulfur impurities and nitrogen impurities. The hydrotreating can also perform some hydrogenation of reactive components, such as acetylenes and diolefms. The hydrotreated, or hydrogenated, stream 8 is passed to an adsorption separation unit 10 to generate an extract stream 12 and a raffmate stream 14. The adsorbent in the adsorption separation unit 10 is selected for separating normal hydrocarbons, and in particular normal paraffins, from non- normal hydrocarbons. The extract stream 12 comprises normal hydrocarbons and the raffmate stream 14 comprises non-normal and aromatic hydrocarbons.

[0022] The raffmate stream 14 is passed to a raffmate separation system 30. The raffmate separation system 30 generates a raffmate overhead stream 32, an intermediate raffmate stream 34 and a raffmate bottoms stream 36. The raffmate separation system 30 can comprise two fractionation columns, a divided wall column, or other means for separating a mixture into two or three streams. Fractionation is preferred, as the components in the raffmate stream are readily separated by their boiling point differences. The adsorption separation system 10 uses a desorbent, and the raffmate bottoms stream 36 comprises desorbent that is recycled to the adsorption separation system 10. The raffmate overhead stream comprises iC5 and iC6 compounds, and can be used for downstream processing, including adding to a gasoline blending pool. The intermediate raffmate stream 34, comprising aromatics and non-normal hydrocarbons that have higher boiling points than iC5 or iC6 compounds, is passed to a reforming unit 50 to generate a reformate 52 having an increased aromatics content.

[0023] The extract stream 12 is passed to an extraction separation system 20 to generate an extract overhead stream 22, an extract intermediate stream 24, and an extract bottoms stream 26. The extract separation system 20 can comprise multiple fractionation columns, with a preferred system using a divided wall column. The extract bottoms stream 26 includes desorbent that is recycled to the separation unit 10. The extract intermediate stream 24 is passed to a cracking unit 40 to convert the normal paraffins to light olefins 42. A typical cracking unit is a naphtha steam cracking unit, but can also comprise a catalytic cracking unit. The extract overhead stream 22 can also be passed to the cracking unit 40, but in an alternative, the extract overhead stream can be passed to an isomerization unit 60.

[0024] The isomerization unit 60 converts the overhead stream 22 having normal C5 and C6 paraffins to a isomerized stream 62 having a mixture of normal and iso- C5 and C6 paraffins. The isomerized stream 62 is passed to the separation unit 10, where the non- normal components of the isomerized stream 62 are then removed in the raffmate stream 14. This provides for more hydrocarbons passed to either the reforming unit 50 to increase reformate 52, or to the raffmate overhead stream 32 for downstream processing, including passing to the reforming unit 50 as an option.

[0025] A preferred embodiment is for the integration of a separation system, an isomerization system, and a catalytic reforming process into an integrated refinery-petroleum operation. The process provides for shifting hydrocarbons between a cracking process to generate light olefins, and a reforming process for generating aromatics. Thus providing flexibility for a plant to generate a desired product stream. [0026] In a preferred embodiment, the extract separation system, or the raffinate separation system will utilize a divided wall column to produce three separate streams. This will save on capital and operating costs. This process will allow flexibility in the area of gasoline production, through shifting of hydrocarbon components, and in particular C5 and C6 components in a naphtha feedstream, from a cracking stream to a reforming stream, or for directing to a gasoline blending pool.

[0027] While the invention has been described with what are presently considered the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but it is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims.

Claims

CLAIMS:

1. A process for converting a treated hydrocarbon feedstream, comprising:

passing the treated hydrocarbon feedstream to a separation unit to generate an extract stream enriched in normal paraffins, and a raffinate stream having a reduced normal hydrocarbon content;

passing the extract stream to an extract separation system to generate an extract overhead stream comprising nC5 and nC6 compounds, an extract intermediate stream comprising nC7 to nCl 1 compounds, and an extract bottoms stream comprising desorbent; passing the raffinate stream to a raffinate separation system to generate a raffinate overhead stream comprising iC5 and iC6 compounds, an intermediate raffinate stream comprising aromatics and non-normal hydrocarbons, and a raffinate bottoms stream comprising desorbent; and

passing the intermediate raffinate stream to a reforming unit to generate an aromatics stream.

2. The process of claim 1 further comprising:

passing a hydrocarbon feedstream to a fractionation unit to generate an overhead stream comprising C4 and lighter hydrocarbons, and a bottoms stream comprising C5+ hydrocarbons;

hydrotreating the bottoms stream to generate the treated hydrogenated stream;

passing the treated hydrogenated stream to the separation unit.

3. The process of claim 2 further comprising passing the overhead stream to a cracking unit.

4. The process of claim 1 further comprising passing the extract intermediate stream to a cracking unit.

5. The process of claim 1 further comprising passing a portion of the extract overhead stream to an isomerization unit to generate an isomerized stream comprising C5 and C6 compounds.

6. The process of claim 5 further comprising passing the isomerized stream to the separation unit.

7. The process of claim 1 further comprising passing a portion of the extract overhead stream to a cracking unit.

8. The process of claim 7 wherein the hydrocarbon feedstream is a naphtha feedstream.

9. The process of claim 7 wherein the cracking unit is a naphtha cracking unit.

10. The process of claim 1 further comprising passing the raffinate overhead stream to a gasoline blending pool.