U.S. patent application number 17/250394 was filed with the patent office on 2021-09-02 for catalytic cracking of light naphtha over dual riser fcc reactor.
This patent application is currently assigned to SABIC Global Technologies B.V.. The applicant listed for this patent is SABIC Global Technologies B.V.. Invention is credited to Naif Ali AL-DALAAN, Khalid Ali AL-MAJNOUNI, Ahmad Mahdi AL-SHEHRI, Nabil AL-YASSER, Vidya Sagar GUGGILLA, Nandini PECHIMUTHU, Debdut S. ROY, Wojciech SUPRONOWICZ.
Application Number | 20210269725 17/250394 |
Document ID | / |
Family ID | 1000005627573 |
Filed Date | 2021-09-02 |
United States Patent
Application |
20210269725 |
Kind Code |
A1 |
PECHIMUTHU; Nandini ; et
al. |
September 2, 2021 |
CATALYTIC CRACKING OF LIGHT NAPHTHA OVER DUAL RISER FCC REACTOR
Abstract
Systems and methods for producing light olefins and aromatics
from light naphtha are disclosed. The light naphtha is fed to a
first catalyst riser to crack the C.sub.5 to C.sub.7 hydrocarbons
in the light naphtha stream. The cracked naphtha stream is
fractionated to produce a stream comprising primarily C.sub.4 to
C.sub.6 hydrocarbons or a stream comprising primarily C.sub.5 to
C.sub.12 hydrocarbons. When the stream comprising primarily C.sub.4
to C.sub.6 hydrocarbons is fed to the second catalyst riser, the
product stream from the second riser comprises light olefins as the
main product. When the stream comprising primarily C.sub.5 to
C.sub.12 hydrocarbons is fed to the second riser, the product
stream from the second riser comprises aromatics as the main
product.
Inventors: |
PECHIMUTHU; Nandini;
(Bangalore, IN) ; SUPRONOWICZ; Wojciech; (Riyadh,
SA) ; AL-MAJNOUNI; Khalid Ali; (Riyadh, SA) ;
AL-DALAAN; Naif Ali; (Riyadh, SA) ; AL-SHEHRI; Ahmad
Mahdi; (Riyadh, SA) ; AL-YASSER; Nabil;
(Riyadh, SA) ; ROY; Debdut S.; (Bangalore, IN)
; GUGGILLA; Vidya Sagar; (Bangalore, IN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SABIC Global Technologies B.V. |
Bergen op Zoom |
|
NL |
|
|
Assignee: |
SABIC Global Technologies
B.V.
Bergen op Zoom
NL
|
Family ID: |
1000005627573 |
Appl. No.: |
17/250394 |
Filed: |
July 26, 2019 |
PCT Filed: |
July 26, 2019 |
PCT NO: |
PCT/IB2019/056416 |
371 Date: |
January 15, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62711414 |
Jul 27, 2018 |
|
|
|
62777038 |
Dec 7, 2018 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C10G 2400/30 20130101;
C10G 51/026 20130101; C10G 2300/104 20130101; C10G 2400/22
20130101; C10G 11/182 20130101; C10G 2400/20 20130101 |
International
Class: |
C10G 51/02 20060101
C10G051/02; C10G 11/18 20060101 C10G011/18 |
Claims
1. A method of producing olefins and aromatics, the method
comprising: feeding a light naphtha stream to a first catalyst
riser of a fluid catalytic cracking (FCC) unit, the light naphtha
stream having an initial boiling point (IBP) in a range 15 to
40.degree. C. and a final boiling point (FBP) in a range 65 to
350.degree. C.; contacting the light naphtha stream with a first
catalyst in the first catalyst riser under reaction conditions
sufficient to crack C.sub.5 to C.sub.7 hydrocarbons of the light
naphtha stream and form a first cracked stream; fractionating the
first cracked stream to produce a plurality of streams that
comprises a first stream comprising primarily C.sub.4 to C.sub.6
hydrocarbons; flowing the first stream to a second catalyst riser
of the FCC unit; contacting the first stream with a second catalyst
in the second catalyst riser under reaction conditions sufficient
to crack C.sub.4 to C.sub.6 hydrocarbons of the first stream to
form a second cracked stream comprising C.sub.2 to C.sub.3 olefins,
wherein the first catalyst and the second catalyst are different
and wherein the reaction conditions in the first catalyst riser are
adapted such that yield of light olefins from C.sub.5 to C.sub.7
hydrocarbons is 20 to 60 wt. % and yield of aromatics from C.sub.5
to C.sub.7 hydrocarbons is 3 to 20 wt. %; and regenerating the
first catalyst and the second catalyst separately.
2. The method of claim 1, wherein the fractionating of the first
cracked stream further produces a second stream comprising
primarily C.sub.2 to C.sub.3 olefins; a third stream comprising
primarily benzene, toluene, and xylene, collectively; and a fourth
stream comprising dry gas.
3. The method of claim 2, wherein the fractionating further
produces a bottom stream comprising C.sub.12+ hydrocarbons.
4. The method of claim 3, wherein the bottom stream is recycled
back to the first catalyst riser.
5. The method of claim 2, wherein the dry gas is used as
fluidization medium in the first catalyst riser and/or the second
catalyst riser.
6. The method of claim 1, wherein the reaction conditions in the
second catalyst riser are adapted such that the yield of light
olefins from C.sub.4 to C.sub.6 hydrocarbons is 0 to 90 wt. %.
7. The method of claim 1, wherein the first catalyst and/or the
second catalyst comprises an acidic porous zeolite including
Mordenite Framework Inverted (MFI), Faujasite (FAU), Mordenite
(MOR), Beta, Omega structure type zeolites.
8. The method of claim 1, wherein the first catalyst and the second
catalyst are different in parameters comprising silicon to aluminum
ratio, pore size, surface area, promotor, or combinations
thereof.
9. The method of claim 1, wherein the reaction conditions in the
first catalyst riser include a reaction temperature of 600 to
720.degree. C., a steam to hydrocarbon ratio of 0 to 0.5, and dry
gas to hydrocarbon ratio of 0 to 0.5.
10. The method of claim 1, wherein the reaction conditions in the
second catalyst riser include a reaction temperature of 600 to
720.degree. C., a steam to hydrocarbon ratio of 0 to 0.5, and dry
gas to hydrocarbon ratio of 0 to 0.5.
11. A method of producing olefins and aromatics, the method
comprising: feeding a light naphtha stream to a first catalyst
riser of a fluid catalytic cracking (FCC) unit, the light naphtha
stream having an initial boiling point in a range 15 to 40.degree.
C. and a final boiling point (FBP) in a range 65 to 350.degree. C.;
contacting the light naphtha stream with a first catalyst in the
first catalyst riser under reaction conditions sufficient to crack
C.sub.5 to C.sub.7 hydrocarbons of the light naphtha stream and
form a first cracked stream; fractionating the first cracked stream
to produce a plurality of streams that comprises a hydrocarbon
processing stream comprising primarily C.sub.5 to C.sub.12
hydrocarbons; flowing the hydrocarbon processing stream to a second
catalyst riser of the FCC unit; contacting the hydrocarbon
processing stream with a second catalyst in the second catalyst
riser under reaction conditions sufficient to crack C.sub.5 to
C.sub.12 hydrocarbons of the hydrocarbon processing stream to form
a second cracked processing stream comprising aromatics, wherein
the first catalyst and the second catalyst are different, and
wherein the reaction conditions in the first catalyst riser are
adapted such that yield of light olefins from C.sub.5 to C.sub.7
hydrocarbons is 5 to 35 wt. % and yield of aromatics from C.sub.5
to C.sub.7 hydrocarbons is 5 to 50 wt. % and wherein the reaction
conditions in the second catalyst riser are adapted such that yield
of aromatics from C.sub.5 to C.sub.12 nonaromatic hydrocarbons is 5
to 60 wt. %; and regenerating the first catalyst and the second
catalyst separately.
12. The method of claim 11, wherein the fractionating further
produces a light recycling stream comprising primarily C.sub.4 to
C.sub.6 hydrocarbons, a light olefin stream comprising primarily
C.sub.2 and C.sub.3 olefins, a dry gas stream comprising primarily
methane and hydrogen, collectively, an aromatic stream comprising
primarily benzene, toluene, and xylene, collectively.
13. The method of claim 12, wherein the light recycling stream is
recycled back to the first catalyst riser.
14. The method of claim 11, wherein the first catalyst and/or the
second catalyst comprises an acidic porous zeolite including
Mordenite Framework Inverted (MFI), Faujasite (FAU), Mordenite
(MOR), Beta, Omega structure type zeolites.
15. The method of claim 11, wherein the first catalyst and the
second catalyst are different in parameters comprising silicon to
aluminum ratio, pore size, surface area, promoter composition, or
combinations thereof.
16. The method of claim 12, wherein the first catalyst and the
second catalyst are different in parameters comprising silicon to
aluminum ratio, pore size, surface area, promoter composition, or
combinations thereof.
17. The method of claim 13, wherein the first catalyst and the
second catalyst are different in parameters comprising silicon to
aluminum ratio, pore size, surface area, promoter composition, or
combinations thereof.
18. The method of claim 14, wherein the first catalyst and the
second catalyst are different in parameters comprising silicon to
aluminum ratio, pore size, surface area, promoter composition, or
combinations thereof.
19. The method of claim 15, wherein the first catalyst and the
second catalyst are different in parameters comprising silicon to
aluminum ratio, pore size, surface area, promoter composition, or
combinations thereof.
20. The method of claim 2, wherein the reaction conditions in the
second catalyst riser include a reaction temperature of 600 to
720.degree. C., a steam to hydrocarbon ratio of 0 to 0.5, and dry
gas to hydrocarbon ratio of 0 to 0.5.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of priority to U.S.
Provisional Patent Application No. 62/711,414, filed Jul. 27, 2018,
and U.S. Provisional Patent Application No. 62/777,038, filed Dec.
7, 2018, the entire contents of each of which are hereby
incorporated by reference in their entirety.
FIELD OF INVENTION
[0002] The present invention generally relates to methods of
producing light olefins and aromatic hydrocarbons. More
specifically, the present invention relates to a method of
producing light olefins and aromatic hydrocarbons using two fluid
catalytic cracking units.
BACKGROUND OF THE INVENTION
[0003] Light olefins (C.sub.2 and C.sub.3 olefins) are building
blocks for many chemical processes. Light olefins are used to
produce polyethylene, polypropylene, ethylene oxide, ethylene
chloride, propylene oxide, and acrylic acid, which, in turn, are
used in a wide variety of industries such as the plastic
processing, construction, textile, and automotive industries.
Generally, light olefins are produced by steam cracking naphtha and
dehydrogenation of paraffin.
[0004] Aromatics, such as BTX (benzene, toluene, and xylene) are
used in many different areas of chemical industry, especially the
plastic and polymer sectors. For instance, benzene is a precursor
for producing polystyrene, phenolic resins, polycarbonate, and
nylon. Toluene is used for producing polyurethane and as a gasoline
component. Xylene is feedstock for producing polyester fibers and
phthalic anhydride. In the petrochemical industry, benzene,
toluene, and xylene are conventionally produced by catalytic
reforming of naphtha.
[0005] As the demand for light olefins and aromatics has increased
over the last few decades, other methods have been developed to
produce light olefins and/or aromatics. Fluid catalytic cracking of
light naphtha stream is capable of producing both light olefins and
BTX. In this process, light olefins are cracked in a fluidized bed
reactor under high reaction temperature (above 600.degree. C.) with
a relatively short residence time to overcome the endothermicity of
the reactions and oligomerization of light olefins. The effluent is
separated to recover light olefins and aromatics. However, the
overall selectivity from light naphtha to light olefins and
aromatics is limited. Undesired products from the reactor effluent
are merely recycled back to the same fluid catalytic cracking unit
with the same reaction conditions as the fresh feed. Therefore, the
recycling step in this process produces marginal improvement of the
light olefins and/or aromatics productivity while consuming a large
amount of energy during the endothermic process.
[0006] Overall, while methods of producing light olefins and BTX
exist, the need for improvements in this field persists in light of
at least the aforementioned drawbacks for the methods.
BRIEF SUMMARY OF THE INVENTION
[0007] A solution to at least some of the above-mentioned problems
associated with the production process for light olefins and
aromatics has been discovered. The solution resides in a method and
a system that involves processing light naphtha with two fluid
catalytic cracking units in series. The effluent from the first
fluid catalytic cracking unit can be fractionated to form a stream
comprising primarily C.sub.4 to C.sub.6 hydrocarbons and/or a
stream comprising primarily C.sub.5 to C.sub.12 hydrocarbons, which
can be fed to the second fluid catalytic cracking unit under
reaction conditions optimized for producing light olefins and/or
aromatics (e.g., BTX), respectively. This can be beneficial for at
least improving the overall conversion rate and productivity of
light olefins and/or aromatics. Notably, the reaction conditions in
the second fluid catalytic cracking unit can be optimized for
converting C.sub.4 to C.sub.6 hydrocarbons to light olefins and/or
converting C.sub.5 to C.sub.12 hydrocarbons to aromatics, resulting
in improved productivity of olefins and aromatics. Therefore, the
methods of the present invention provide a technical advantage over
at least some of the problems associated with the currently
available methods for producing light olefins and aromatics
mentioned above.
[0008] Embodiments of the invention include a method of producing
olefins and aromatics. The method comprises feeding a light naphtha
stream to a first catalyst riser of a fluid catalytic cracking
(FCC) unit. The light naphtha stream has an initial boiling point
in a range 15 to 40.degree. C. and a final boiling point (FBP) in
the range 65 to 350.degree. C. The method further comprises
contacting the light naphtha stream with a first catalyst in the
first catalyst riser under reaction conditions sufficient to crack
C.sub.5 to C.sub.7 hydrocarbons of the light naphtha stream and
form a first cracked stream. The method further comprises
fractionating the first cracked stream to produce a plurality of
streams that comprise a first stream comprising primarily C.sub.4
to C.sub.6 hydrocarbons. The method further still comprises flowing
the first stream to a second riser of the FCC unit. The method
further comprises contacting the first stream with a second
catalyst in the second catalyst riser under reaction conditions
sufficient to crack C.sub.4 to C.sub.6 hydrocarbons of the first
stream to form a second cracked stream comprising C.sub.2 to
C.sub.3 olefins. The first catalyst and the second catalyst are
different and the reaction conditions in the first catalyst riser
are adapted such that the yield of light olefins from C.sub.5 to
C.sub.7 hydrocarbons is 20 to 60 wt. % and the yield of aromatics
from C.sub.5 to C.sub.7 hydrocarbons is 3 to 20 wt. %. The method
further still comprises regenerating the first catalyst and the
second catalyst separately.
[0009] Embodiments of the invention include a method of producing
olefins and aromatics. The method comprises feeding a light naphtha
stream to a first catalyst riser of a fluid catalytic cracking
(FCC) unit. The light naphtha stream has an initial boiling point
in a range 15 to 40.degree. C. and a final boiling point (FBP) in
the range 65 to 350.degree. C. The method further comprises
contacting the light naphtha stream with a first catalyst in the
first catalyst riser under reaction conditions sufficient to crack
C.sub.5 to C.sub.7 hydrocarbons of the light naphtha stream and
form a first cracked stream. The method further comprises
fractionating the first cracked stream to produce a first stream
comprising primarily C.sub.4 to C.sub.6 hydrocarbons, a second
stream comprising primarily C.sub.2 and C.sub.3 olefins, a third
stream comprising primarily benzene, toluene, and xylene,
collectively, and a fourth stream comprising dry gas. The method
further comprises flowing the first stream to a second catalyst
riser of the FCC unit. The method further still comprises
contacting the first stream with a second catalyst in the second
catalyst riser under reaction conditions sufficient to crack
C.sub.4 to C.sub.6 hydrocarbons of the first stream to form a
second cracked stream comprising C.sub.2 to C.sub.4 olefins. The
first catalyst and the second catalyst are different. The reaction
conditions in the first catalyst riser are adapted such that the
yield of light olefins from C.sub.5 to C.sub.7 hydrocarbons is 20
to 60 wt. % and the yield of aromatics from C.sub.5 to C.sub.7
hydrocarbons is 3 to 20 wt. %. The reaction conditions in the
second catalyst riser are adapted such that the yield of C.sub.2
and C.sub.3 hydrocarbons from C.sub.4 and C.sub.6 hydrocarbons is 0
to 70 wt. %. The method further comprises regenerating the first
catalyst and the second catalyst separately.
[0010] Embodiments of the invention include a method of producing
olefins and aromatics. The method comprises feeding a light naphtha
stream to a first catalyst riser of a fluid catalytic cracking
(FCC) unit. The light naphtha stream has an initial boiling point
in a range 15 to 40.degree. C. and a final boiling point (FBP) in
the range 65 to 350.degree. C. The method further comprises
contacting the light naphtha stream with a first catalyst in the
first catalyst riser under reaction conditions sufficient to crack
C.sub.5 to C.sub.7 hydrocarbons of the light naphtha stream and
form a first cracked stream. The method further comprises
fractionating the first cracked stream to produce a plurality of
streams that comprises a heavy processing stream comprising
primarily C.sub.5 to C.sub.12 hydrocarbons. The method further
still comprises flowing the heavy processing stream to a second
catalyst riser of the FCC unit. The method further comprises
contacting the heavy processing stream with a second catalyst in
the second catalyst riser under reaction conditions sufficient to
crack C.sub.5 to C.sub.12 hydrocarbons of the heavy processing
stream to form a second cracked stream comprising aromatics. The
first catalyst and the second catalyst are different. The reaction
conditions in the first catalyst riser are adapted such that yield
of light olefins from C.sub.5 to C.sub.7 hydrocarbons to olefins is
20 to 60 wt. % and yield of aromatics from the C.sub.5 to C.sub.7
hydrocarbons to aromatics is 3 to 20 wt. %. The reaction conditions
in the second catalyst riser are adapted such that yield of
aromatics from C.sub.5 to C.sub.12 nonaromatic hydrocarbons is 5 to
50 wt. %. The method further still comprises regenerating the first
catalyst and the second catalyst separately.
[0011] The following includes definitions of various terms and
phrases used throughout this specification.
[0012] The terms "about" or "approximately" are defined as being
close to as understood by one of ordinary skill in the art. In one
non-limiting embodiment the terms are defined to be within 10%,
preferably, within 5%, more preferably, within 1%, and most
preferably, within 0.5%.
[0013] The terms "wt. %", "vol. %" or "mol. %" refer to a weight,
volume, or molar percentage of a component, respectively, based on
the total weight, the total volume, or the total moles of material
that includes the component. In a non-limiting example, 10 moles of
component in 100 moles of the material is 10 mol. % of
component.
[0014] The term "substantially" and its variations are defined to
include ranges within 10%, within 5%, within 1%, or within
0.5%.
[0015] The terms "inhibiting" or "reducing" or "preventing" or
"avoiding" or any variation of these terms, when used in the claims
and/or the specification, includes any measurable decrease or
complete inhibition to achieve a desired result.
[0016] The term "effective," as that term is used in the
specification and/or claims, means adequate to accomplish a
desired, expected, or intended result.
[0017] The term "Cn+ hydrocarbon," wherein n is a positive integer,
e.g. 1, 2, 3, 4, or 5, as that term is used in the specification
and/or claims, means any hydrocarbon having at least n number of
carbon atom(s) per molecule.
[0018] The term "dry gas" as that term is used in the specification
and/or claims, means a gas stream comprising primarily methane and
hydrogen, collectively, and less than 5 wt. % of water.
[0019] The use of the words "a" or "an" when used in conjunction
with the term "comprising," "including," "containing," or "having"
in the claims or the specification may mean "one," but it is also
consistent with the meaning of "one or more," "at least one," and
"one or more than one."
[0020] The words "comprising" (and any form of comprising, such as
"comprise" and "comprises"), "having" (and any form of having, such
as "have" and "has"), "including" (and any form of including, such
as "includes" and "include") or "containing" (and any form of
containing, such as "contains" and "contain") are inclusive or
open-ended and do not exclude additional, unrecited elements or
method steps.
[0021] The process of the present invention can "comprise,"
"consist essentially of," or "consist of" particular ingredients,
components, compositions, etc., disclosed throughout the
specification.
[0022] The term "yield," as that term is used in the specification
and/or claims, means the percentage of actual amount of product
produced over theoretical amount of product that can be produced
based on stoichiometry.
[0023] The term "primarily," as that term is used in the
specification and/or claims, means greater than any of 50 wt. %, 50
mol. %, and 50 vol. %. For example, "primarily" may include 50.1
wt. % to 100 wt. % and all values and ranges there between, 50.1
mol. % to 100 mol. % and all values and ranges there between, or
50.1 vol. % to 100 vol. % and all values and ranges there
between.
[0024] The term "riser," as that term is used in the specification
and/or claims, means a reactor or a reaction zone, in which fluid
and solids move upward substantially concurrently. The terms
"downflow reactor" and "downer," as the terms are used in the
specification and/or claims, mean a reactor or a reaction zone, in
which fluid and solids move downward substantially
concurrently.
[0025] Other objects, features and advantages of the present
invention will become apparent from the following figures, detailed
description, and examples. It should be understood, however, that
the figures, detailed description, and examples, while indicating
specific embodiments of the invention, are given by way of
illustration only and are not meant to be limiting. Additionally,
it is contemplated that changes and modifications within the spirit
and scope of the invention will become apparent to those skilled in
the art from this detailed description. In further embodiments,
features from specific embodiments may be combined with features
from other embodiments. For example, features from one embodiment
may be combined with features from any of the other embodiments. In
further embodiments, additional features may be added to the
specific embodiments described herein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] For a more complete understanding, reference is now made to
the following descriptions taken in conjunction with the
accompanying drawings, in which:
[0027] FIG. 1A shows a schematic diagram for a system of producing
light olefins and aromatics optimized for high light olefins
productivity, according to embodiments of the invention;
[0028] FIG. 1B shows a schematic diagram for a system of producing
light olefins and aromatics optimized for high aromatics
productivity, according to embodiments of the invention; and
[0029] FIG. 2 shows a schematic flowchart for a method of producing
light olefins and aromatics, according to embodiments of the
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0030] Currently, light naphtha can be processed to produce light
olefins and/or aromatics in a single catalyst riser of a fluid
catalytic cracking unit at a high reaction temperature and with a
short residence time. However, the overall selectivity and
productivity for the process is limited as the reaction conditions
and/or the catalyst in the single catalyst riser of the fluid
catalytic cracking unit cannot be optimized to convert all the
components in the light naphtha to light olefins and/or aromatics.
Furthermore, the recycling of all the undesirable fractions from
the single fluid catalytic cracking unit consumes a large amount of
energy while producing a limited additional amount of light olefins
and/or aromatics. The present invention provides a solution to at
least one of the problems. The solution is premised on a method
including using a second fluid catalytic cracking unit to further
crack the C.sub.4 to C.sub.6 and/or C.sub.5 to C.sub.12
hydrocarbons from the effluent of the first catalyst riser to form
additional light olefins and/or aromatics with high yields,
resulting in improved overall productivity and energy efficiency.
These and other non-limiting aspects of the present invention are
discussed in further detail in the following section.
A. System for Processing Crude Oil and Producing Olefins and
Aromatics
[0031] In embodiments of the invention, the system for producing
light olefins and aromatics can include a system comprising two
catalyst risers of a fluid catalytic cracking unit and a
fractionation unit shared by the two catalyst risers. With
reference to FIG. 1A, a schematic diagram is shown of system 100
that is capable of processing a light naphtha stream to produce
light olefins C.sub.2 and C.sub.3 olefins and aromatics with
improved overall selectivity and production efficiency compared to
conventional fluid catalytic cracking process. System 100 may be
optimized for light olefins production. According to embodiments of
the invention, system 100 includes first catalyst riser 101 of a
fluid catalytic cracking (FCC) unit configured to receive and
catalytically crack light naphtha stream 11 to produce first
cracked stream 12. In embodiments of the invention, first cracked
stream 12 may include light olefins, aromatics, dry gas, and
C.sub.4 to C.sub.12 hydrocarbons. First cracked stream 12 may
further include gasoline.
[0032] In embodiments of the invention, first catalyst riser 101
may include a first fluidized bed reactor. The first fluidized bed
reactor may contain a first catalyst configured to catalyze the
cracking reaction of light naphtha stream 11 to produce cracked
stream 12. The first catalyst may include a single phase catalyst
and/or multi-phase catalyst. According to embodiments of the
invention, the first catalyst includes at least one component of an
acidic porous zeolite. The first catalyst may be a medium pore or
large pore catalyst. Non-limiting examples of the first catalyst
may include Mordenite Framework Inverted (MFI), Faujasite (FAU),
Mordenite (MOR), Beta, Omega structure type zeolites and
combinations thereof. In embodiments of the invention, the first
catalyst may include a Si/Al ratio in a range of above 20. The
first catalyst may be a medium pore or large pore catalyst. The
first catalyst may have a surface area in a range of 50 to 500
m.sup.2/g and all ranges and values there between including ranges
of 50 to 75 m.sup.2/g, 75 to 100 m.sup.2/g, 100 to 125 m.sup.2/g,
125 to 150 m.sup.2/g, 150 to 175 m.sup.2/g, 175 to 200 m.sup.2/g,
200 to 225 m.sup.2/g, 225 to 250 m.sup.2/g, 250 to 275 m.sup.2/g,
275 to 300 m.sup.2/g, 300 to 325 m.sup.2/g, 325 to 350 m.sup.2/g,
350 to 375 m.sup.2/g, 375 to 400 m.sup.2/g, 400 to 425 m.sup.2/g,
425 to 450 m.sup.2/g, 450 to 475 m.sup.2/g, and 475 to 500
m.sup.2/g.
[0033] An outlet of first catalyst riser 101 may be in fluid
communication with fractionator 102 such that first cracked stream
12 flows from first catalyst riser 101 to fractionator 102. In
embodiments of the invention, fractionator 102 may include a
distillation column, an acid wash unit, a base wash unit, a solvent
extraction unit, or combinations thereof. According to embodiments
of the invention, fractionator 102 may be configured to separate
first cracked stream 12 to form first stream 15a comprising
primarily C.sub.4 to C.sub.6 hydrocarbons, light olefins stream 14
(a second stream), aromatic stream 16 comprising primarily BTX, and
dry gas stream 13 (the fourth stream) comprising primarily methane
and hydrogen, collectively and, in some embodiments, heavy stream
17 (bottom stream) comprising primarily C.sub.12+ hydrocarbons. In
embodiments of the invention, dry gas stream 13 may include less
than 5 wt. % water.
[0034] In embodiments of the invention, a first outlet of
fractionator 102 may be in fluid communication with second catalyst
riser 103 of a fluid catalytic cracking unit such that first stream
15a flows from fractionator 102 to second catalyst riser 103.
According to embodiments of the invention, second catalyst riser
103 may be configured to receive and catalytically crack first
stream 15a to produce second cracked stream 18a comprising light
olefins (C.sub.2 and C.sub.3 olefins) and/or aromatics. In
embodiments of the invention, second cracked stream 18a may include
5 to 50 wt. % light olefins and all ranges and values there between
including ranges of 5 to 10 wt. %, 10 to 15 wt. %, 15 to 20 wt. %,
20 to 25 wt. %, 25 to 30 wt. %, 30 to 35 wt. %, 35 to 40 wt. %, 40
to 45 wt. %, and 45 to 50 wt. %.
[0035] In embodiments of the invention, second catalyst riser 103
comprises a fluidized bed reactor containing a second catalyst. The
second catalyst may be different from the first catalyst.
Differences between the first catalyst and the second catalyst may
include but are not limited to Si to Al ratio, topology (i.e.,
medium pore size or large pore size), surface area, promoter, post
production treatment of the catalysts, and combinations
thereof.
[0036] According to embodiments of the invention, an outlet of
second catalyst riser 103 may be in fluid communication with an
inlet of fractionator 102 such that second cracked stream 18a flows
from second riser to fractionator 102. Fractionator 102 may be
further configured to separate second cracked stream 18a to produce
additional light olefins (C.sub.2 and C.sub.3 olefins) and/or
additional aromatics (primarily BTX). In embodiments of the
invention, an outlet of fractionator 102 may be in fluid
communication with first catalyst riser 101 and/or second catalyst
riser 103 such that heavy stream 17 (bottom stream) flows from
fractionator 102 to first catalyst riser 101 and/or second catalyst
riser 103.
[0037] Alternatively or additionally, as shown in FIG. 1B,
fractionator may be configured to separate first cracked stream 12
to form heavy processing stream 15b comprising primarily C.sub.5 to
C.sub.12 hydrocarbons, light olefins stream 14 (a second stream),
aromatic stream 16 comprising primarily BTX, and dry gas stream 13
(the fourth stream) comprising primarily methane and hydrogen,
collectively and optionally heavy stream 17 comprising primarily
C.sub.12+ hydrocarbons. As shown in FIG. 1B, fractionator 102 may
be configured to further produce light recycling stream 19
comprising primarily C.sub.4 to C.sub.6 hydrocarbons. An outlet of
fractionator 102 may be in fluid communication with an inlet of
first catalyst riser 101 such that light recycling stream 19 flows
from fractionator 102 to first catalyst riser 101. According to
embodiments of the invention, system 100' as shown in FIG. 1B may
be optimized for aromatics production. In system 100' of FIG. 1B,
second catalyst riser 103 may be adapted to catalytically crack
heavy processing stream 15b to produce second cracked heavy stream
18b (cracked processing stream) comprising primarily aromatics
and/or light olefins. In embodiments of the invention, second
cracked heavy stream 18b may include 5 to 60 wt. % aromatics and
all ranges and values there between including ranges of 5 to 10 wt.
%, 10 to 15 wt. %, 15 to 20 wt. %, 20 to 25 wt. %, 25 to 30 wt. %,
30 to 35 wt. %, 35 to 40 wt. %, 40 to 45 wt. %, 45 to 50 wt. %, 50
to 55 wt. %, and 55 to 60 wt. %. In embodiments of the invention,
first catalyst riser 101 and/or second catalyst riser 103 may be
replaced by a first downflow reactor and/or a second downflow
reactor, respectively. Overall, configuration of system 100' as
shown in FIG. 1B is the same as system 100 as shown in FIG. 1A
except the compositions of the streams (first stream 15a and heavy
stream 15b) from fractionator 102 to second riser 103, the
compositions of streams (second cracked stream 18a and second
cracked heavy stream 18b) flowing from second riser 103 to
fractionator 102, and light recycling stream 19 only in system
100'.
B. Methods of Processing Crude Oil and Producing Olefins and
Aromatics
[0038] Methods of producing light olefins and aromatics have been
discovered to improve the light olefins and/or aromatics yield and
productivity via fluid catalytic cracking. As shown in FIG. 2,
embodiments of the invention include method 200 for producing light
olefins and aromatics. Method 200 may be implemented by system 100
and/or system 100' as shown in FIG. 1A and FIG. 1B, respectively.
According to embodiments of the invention, as shown in block 201,
method 200 may include feeding light naphtha stream 11 to first
catalyst riser 101 of a fluid catalytic cracking (FCC) unit. In
embodiments of the invention, light naphtha stream has an initial
boiling point (IBP) in a range of 15 to 40.degree. C. and all
ranges and values there between including ranges of 15 to
20.degree. C., 20 to 25.degree. C., 25 to 30.degree. C., 30 to
35.degree. C., and 35 to 40.degree. C. Light naphtha stream 11 may
have a final boiling point (FBP) in a range of 65 to 350.degree. C.
and all ranges and values there between including ranges of 65 to
80.degree. C., 80 to 95.degree. C., 95 to 110.degree. C., 110 to
125.degree. C., 125 to 140.degree. C., 140 to 155.degree. C., 155
to 170.degree. C., 170 to 185.degree. C., 185 to 200.degree. C.,
200 to 215.degree. C., 215 to 230.degree. C., 230 to 245.degree.
C., 245 to 260.degree. C., 260 to 275.degree. C., 275 to
290.degree. C., 290 to 305.degree. C., 305 to 320.degree. C., 320
to 335.degree. C., and 335 to 350.degree. C.
[0039] According to embodiments of the invention, light naphtha
stream 11 contains C.sub.5 to C.sub.7 hydrocarbons. In embodiments
of the invention, method 200 further comprises contacting light
naphtha stream 11 with the first catalyst in first catalyst riser
101 under reaction conditions sufficient to crack C.sub.5 to
C.sub.7 hydrocarbons of light naphtha stream 11 and form first
cracked stream 12, as shown in block 202. According to embodiments
of the invention, the reaction conditions in first catalyst riser
101 at block 202 are adapted such that the yield of light olefins
from C.sub.5 to C.sub.7 hydrocarbons is 5 to 50 wt. % and the yield
of aromatics from C.sub.5 to C.sub.7 hydrocarbons is 5 to 30 wt. %.
In embodiments of the invention, reaction conditions in first
catalyst riser 101 may include a reaction temperature in a range of
600 to 720.degree. C. and all ranges and values there between
including ranges of 600 to 610.degree. C., 610 to 620.degree. C.,
620 to 630.degree. C., 630 to 640.degree. C., 640 to 650.degree.
C., 650 to 660.degree. C., 660 to 670.degree. C., 670 to
680.degree. C., 680 to 690.degree. C., 690 to 700.degree. C., 700
to 710.degree. C., and 710 to 720.degree. C. The reaction
conditions in first catalyst riser 101 may further include a
reaction pressure in a range of 14 to 73 psi and all ranges and
values there between including ranges of 14 to 16 psi, 16 to 19
psi, 19 to 22 psi, 22 to 25 psi, 25 to 28 psi, 28 to 31 psi, 31 to
34 psi, 34 to 37 psi, 37 to 40 psi, 40 to 43 psi, 43 to 46 psi, 46
to 49 psi, 49 to 52 psi, 52 to 55 psi, 55 to 58 psi, 58 to 61 psi,
61 to 64 psi, 64 to 67 psi, 67 to 70 psi, and 70 to 73 psi. The
weight hourly space velocity in first catalyst riser 101 may be in
a range 0.5 to 30 hr.sup.-1. The residence time in first catalyst
riser 101 may be in a range of 1 to 10 s and all ranges and values
there between including 2 s, 3 s, 4 s, 5 s, 6 s, 7 s, 8 s, and 9 s.
In embodiments of the invention, the catalyst-to-oil ratio (C/O
ratio) in the fluidized bed of first catalyst riser 101 may be in a
range of 10 to 80 and all ranges and values there between including
ranges of 10 to 15, 15 to 20, 20 to 25, 25 to 30, 30 to 35, 35 to
40, 40 to 45, 45 to 50, 50 to 55, 55 to 60, 60 to 65, 65 to 70, 70
to 75, and 75 to 80.
[0040] According to embodiments of the invention, light naphtha
stream 11 may further include steam with a steam to hydrocarbon
ratio of 0 to 0.5 and all ranges and values there between including
ranges of 0 to 0.05, 0.05 to 0.10, 0.10 to 0.15, 0.15 to 0.20, 0.20
to 0.25, 0.25 to 0.30, 0.30 to 0.35, 0.35 to 0.40, 0.40 to 0.45,
and 0.45 to 0.50. Light naphtha stream 11 may further still include
dry gas comprising primarily methane and hydrogen, collectively.
The dry gas may be used as a fluidization medium in first catalyst
riser 101 and/or second catalyst riser 103. In embodiments of the
invention, the ratio of dry gas to hydrocarbon in light naphtha
stream 11 may be in a range of 0 to 0.5 and all ranges and values
there between including ranges of 0 to 0.05, 0.05 to 0.10, 0.10 to
0.15, 0.15 to 0.20, 0.20 to 0.25, 0.25 to 0.30, 0.30 to 0.35, 0.35
to 0.40, 0.40 to 0.45, and 0.45 to 0.50.
[0041] In embodiments of the invention, first cracked stream 12 may
include 5 to 50 wt. % light olefins and 5 to 35 wt. % aromatics
(BTX). In embodiments of the invention, as shown in block 203a,
method 200 further comprises, in fractionator 102, fractionating
first cracked stream 12 to produce a plurality of streams that
comprises first stream 15a comprising primarily C.sub.4 to C.sub.6
hydrocarbons. In embodiments of the invention, first stream 15a
comprises 50 to 100 wt. % C.sub.4 to C.sub.6 hydrocarbons.
Alternatively or additionally, as shown in block 203b, first
cracked stream 12 may be fractionated to produce a plurality of
streams including heavy processing stream 15b instead of first
stream 15a. Heavy processing stream 15b comprises primarily C.sub.5
to C.sub.12 hydrocarbons. Heavy processing stream 15b may comprise
50 to 100 wt. % C.sub.5 to C.sub.12 hydrocarbons and all ranges and
values there between.
[0042] According to embodiments of the invention, in both blocks
203a and 203b, the plurality of streams further comprises light
olefin stream 14 (the second stream) comprising primarily C.sub.2
to C.sub.4 olefins, aromatic stream 16 (the third stream)
comprising primarily BTX, and dry gas stream 13 (the fourth stream)
comprising primarily methane and hydrogen, collectively, and
optionally heavy stream 17 comprising primarily C.sub.12+
hydrocarbons. Alternatively or additionally, at block 203b,
fractionating the first cracked stream 12 further produces light
recycling stream 19 comprising primarily C.sub.4 to C.sub.6
hydrocarbons. Light recycling stream 19 may be flowed from
fractionator 102 back to first catalyst riser 101.
[0043] According to embodiments of the invention, as shown in block
204a, method 200 further comprises flowing first stream 15a to
second catalyst riser 103 of the FCC unit. As shown in block 205a,
method 200 may further still include contacting first stream 15a
with the second catalyst in second catalyst riser 103 under
reaction conditions sufficient to crack C.sub.4 to C.sub.6
hydrocarbons of first stream 15a to form second cracked stream 18a
comprising C.sub.2 to C.sub.4 olefins. In embodiments of the
invention, second cracked stream 18a may include 5 to 50 wt. %
light olefins and all ranges and values there between including 5
to 10 wt. %, 10 to 15 wt. %, 15 to 20 wt. %, 20 to 25 wt. %, 25 to
30 wt. %, 30 to 35 wt. %, 35 to 40 wt. %, 40 to 45 wt. %, and 45 to
50 wt. %. According to embodiments of the invention, second cracked
stream may further include aromatics.
[0044] According to embodiments of the invention, the reaction
conditions of second catalyst riser 103 in block 205a are adapted
such that the yield of light olefins from C.sub.4 to C.sub.6
hydrocarbons of first stream 15a is from 0 to 70% and the yield of
aromatics from C.sub.4 to C.sub.6 hydrocarbons of first stream 15a
is from 5 to 30%. In embodiments of the invention, the reaction
conditions at block 205a may include a reaction temperature in a
range of 500 to 700.degree. C. and all ranges and values there
between including ranges of 500 to 510.degree. C., 500 to
510.degree. C., 510 to 520.degree. C., 520 to 530.degree. C., 530
to 540.degree. C., 540 to 550.degree. C., 550 to 560.degree. C.,
560 to 570.degree. C., 570 to 580.degree. C., 580 to 590.degree.
C., 590 to 600.degree. C., 600 to 610.degree. C., 610 to
620.degree. C., 620 to 630.degree. C., 630 to 640.degree. C., 640
to 650.degree. C., 650 to 660.degree. C., 660 to 670.degree. C.,
670 to 680.degree. C., 680 to 690.degree. C., and 690 to
700.degree. C. The reaction conditions in block 204 may further
include reaction pressure in a range of 14 to 73 psi and all ranges
and values there between between including ranges of 14 to 16 psi,
16 to 19 psi, 19 to 22 psi, 22 to 25 psi, 25 to 28 psi, 28 to 31
psi, 31 to 34 psi, 34 to 37 psi, 37 to 40 psi, 40 to 43 psi, 43 to
46 psi, 46 to 49 psi, 49 to 52 psi, 52 to 55 psi, 55 to 58 psi, 58
to 61 psi, 61 to 64 psi, 64 to 67 psi, 67 to 70 psi, and 70 to 73
psi. A weight hourly space velocity in block 205a may be in a range
of 5 to 30 hr.sup.-1 and all ranges and values there between
including ranges of 5 to 9 hr.sup.-1, 9 to 12 hr.sup.-1, 12 to 15
hr.sup.-1, 15 to 18 hr.sup.-1, 18 to 21 hr.sup.-1, 21 to 24
hr.sup.-1, 24 to 27 hr.sup.-1, and 27 to 30 hr.sup.-1. A residence
time of second catalyst riser 103 in block 204a may be in a range
of 1 to 10 s and all ranges and values there between including 2 s,
3 s, 4 s, 5 s, 6 s, 7 s, 8 s, and 9 s. The catalyst-to-oil ratio of
the fluidized bed in second riser at block 205a may be in a range
of 10 to 80 and all ranges and values there between including
ranges of 10 to 15, 15 to 20, 20 to 25, 25 to 30, 30 to 35, 35 to
40, 40 to 45, 45 to 50, 50 to 55, 55 to 60, 60 to 65, 65 to 70, 70
to 75, and 75 to 80. In embodiments of the invention, the second
catalyst is different from the first catalyst. According to
embodiments of the invention, second cracked stream 18a is
fractionated in fractionator 102 to separate additional light
olefins and/or aromatics.
[0045] Alternatively or additionally, as shown in block 204b, heavy
processing stream 15b instead of first stream 15a may be flowed to
second catalyst riser 103 of the FCC unit. As shown in block 205b,
method 200 may further include contacting heavy processing stream
15b with the second catalyst in second catalyst riser 103 under
reaction conditions sufficient to crack C.sub.5 to C.sub.12
hydrocarbons of the heavy processing stream to form second cracked
heavy stream 18b comprising aromatics. In embodiments of the
invention, second cracked heavy stream 18b may comprise 5 to 60 wt.
% aromatics. In embodiments of the invention, second cracked heavy
stream 18b may further include light olefins. In embodiments of the
invention, the reaction conditions in second catalyst riser 103 at
block 205b are adapted such that the yield of aromatics from
C.sub.5 to C.sub.12 nonaromatic hydrocarbons is 5 to 60 wt. % and
the yield of light olefins from C.sub.5 to C.sub.12 nonaromatic
hydrocarbons is 5 to 30 wt. %. In embodiments of the invention,
reaction conditions in second riser at block 205b may include a
reaction temperature in a range of 500 to 700.degree. C. and all
ranges and values there between. The reaction conditions in block
204 may further include reaction pressure in a range of 14 to 73
psi and all ranges and values there between. A weight hourly space
velocity in block 205b may be in a range of 0.5 to 30 hr.sup.-1 and
all ranges and values there between. The catalyst-to-oil ratio (C/O
ratio) of the fluidized bed in second catalyst riser 103 at block
205b may be in a range of 10 to 80 and all ranges and values there
between. A residence time of second catalyst riser 103 in block
205b may be in a range of 1 to 10 s and all ranges and values there
between. In embodiments of the invention, the second catalyst in
second catalyst riser 103 is different from the first catalyst in
first catalyst riser 101. According to embodiments of the
invention, second cracked heavy stream 18b is fractionated in
fractionator 102 to separate additional aromatics and/or light
olefins.
[0046] In embodiments of the invention, method 200 may further
still include regenerating the first catalyst and the second
catalyst separately, as shown in block 206. Alternatively or
additionally, the first catalyst and the second catalyst may be
regenerated in the same regenerator. According to embodiments of
the invention, the regenerating conditions may include a
regeneration temperature in a range of 650 to 900.degree. C. and
all ranges and values there between including ranges of 650 to
660.degree. C., 660 to 680.degree. C., 680 to 700.degree. C., 700
to 720.degree. C., 720 to 740.degree. C., 740 to 760.degree. C.,
760 to 780.degree. C., 780 to 800.degree. C., 800 to 820.degree.
C., 820 to 840.degree. C., 840 to 860.degree. C., 860 to
880.degree. C., and 880 to 900.degree. C. The regenerating at block
206 may include adding an additional stream of hydrocarbon (light
or/and heavy) to maintain heat balance. According to embodiments of
the invention, method 200 may include flowing a coke precursor in
first catalyst riser 101 and/or second catalyst riser 103 to form
coke on the first catalyst and/or second catalyst. In embodiments
of the invention, the formed coke may be burnt in the regenerating
at block 206 to provide heat to the first catalyst and/or second
catalyst.
[0047] Although embodiments of the present invention have been
described with reference to blocks of FIG. 2, it should be
appreciated that operation of the present invention is not limited
to the particular blocks and/or the particular order of the blocks
illustrated in FIG. 2. Accordingly, embodiments of the invention
may provide functionality as described herein using various blocks
in a sequence different than that of FIG. 2.
[0048] As part of the disclosure of the present invention, a
specific example is included below. The example is for illustrative
purposes only and is not intended to limit the invention. Those of
ordinary skill in the art will readily recognize parameters that
can be changed or modified to yield essentially the same
results.
EXAMPLE
Example 1
Production of Light Olefins and Aromatics Using Two Risers in
Series Via FCC
[0049] Light straight run naphtha (LSRN) was processed in a pilot
fluid catalytic cracking unit, which included two risers in series.
The catalyst in both risers included ZSM-5 based catalyst. The
reaction conditions in the first riser include a reaction
temperature of 675.degree. C., a reaction pressure of 38 psia, a
feed flow rate of 3.96 g/min, steam flow rate of 0.1 g/min, and a
catalyst-to-oil ratio (C/O ratio) of 60. The reaction conditions in
the second riser included substantially the same reaction
temperature, reaction pressure, feed flow rate, and steam flow rate
as the first riser. The catalyst-to-oil ratio in the second riser
was 61.86.
[0050] Light straight run naphtha containing primarily C.sub.5 and
C.sub.6 hydrocarbons was fed to the first riser. All liquid
products, including C.sub.5 to C.sub.12 hydrocarbons, from the
first riser were mixed with light straight run naphtha at a weight
ratio of 1:1. The mixture was fed to the second riser. The
compositions of the effluent stream from each riser were
analyzed.
TABLE-US-00001 TABLE 1 Compositions of the effluent streams from
the first and second risers Riser 1 Riser 2 Fresh-feed 50%
Fresh-Feed + 50% Recycle Temperature (C.) 675 675 Feed Rate
(gr/min) 3.96 3.95 Steam Rate (gr/min) 0.10 0.11 Riser Pressure
(PSIA) 38.50 38.70 C/O Ratio 60.00 61.86 Conversion 71.30 46.13 C2=
+ C3= 32.46 18.03 CH4 9.99 7.74 C2+ 10.37 6.89 C3+ 6.23 3.82 iC4+
0.94 0.49 nC4+ 1.03 0.45 C4= 7.82 3.12 Coke 1.60 4.69 LCO 0.61 4.11
DCO 0.11 0.50 Total Normal Paraffin 3.39 0.28 Total Iso Paraffin
2.98 0.44 Total Normal Olefin 5.60 3.52 Total Aromatic 14.62
43.41
[0051] The results are shown in Table 1. The results show that the
effluent stream from the first riser contained about 32.46 wt. %
light olefins and 14.62 wt. % aromatics. The effluent stream from
the second riser contained 18.03 wt. % light olefins and 43.41 wt.
% aromatics. Therefore, the use of two risers in series for
catalytically cracking light straight run naphtha was capable of
significantly increasing the productivity of light olefins and
aromatics.
[0052] In the context of the present invention, embodiments 1
through 14 are described. Embodiment 1 is a method of producing
olefins and aromatics. The method includes feeding a light naphtha
stream to a first catalyst riser of a fluid catalytic cracking
(FCC) unit, the light naphtha stream having an initial boiling
point (IBP) in a range 15 to 40.degree. C. and a final boiling
point (FBP) in a range 65 to 350.degree. C., then contacting the
light naphtha stream with a first catalyst in the first catalyst
riser under reaction conditions sufficient to crack C.sub.5 to
C.sub.7 hydrocarbons of the light naphtha stream and form a first
cracked stream. The method further includes fractionating the first
cracked stream to produce a plurality of streams that includes a
first stream containing primarily C.sub.4 to C.sub.6 hydrocarbons
and flowing the first stream to a second catalyst riser of the FCC
unit. The method also includes contacting the first stream with a
second catalyst in the second catalyst riser under reaction
conditions sufficient to crack C.sub.4 to C.sub.6 hydrocarbons of
the first stream to form a second cracked stream containing C.sub.2
to C.sub.3 olefins, wherein the first catalyst and the second
catalyst are different and wherein the reaction conditions in the
first catalyst riser are adapted such that yield of light olefins
from C.sub.5 to C.sub.7 hydrocarbons is 20 to 60 wt. % and yield of
aromatics from C.sub.5 to C.sub.7 hydrocarbons is 3 to 20 wt. %. In
addition, the method includes regenerating the first catalyst and
the second catalyst separately. Embodiment 2 is the method of
embodiment 1, wherein the fractionating of the first cracked stream
further produces a second stream containing primarily C.sub.2 to
C.sub.3 olefins, a third stream containing primarily benzene,
toluene, and xylene, collectively, and a fourth stream containing
dry gas. Embodiment 3 is the method of embodiment 2, wherein the
fractionating further produces a bottom stream containing C.sub.12+
hydrocarbons. Embodiment 4 is the method of embodiment 3, wherein
the bottom stream is recycled back to the first catalyst riser.
Embodiment 5 is the method of any of embodiments 2 to 4, wherein
the dry gas is used as fluidization medium in the first catalyst
riser and/or the second catalyst riser. Embodiment 6 is the method
of any of embodiments 1 to 5, wherein the reaction conditions in
the second catalyst riser are adapted such that the yield of light
olefins from C.sub.4 to C.sub.6 hydrocarbons is 0 to 90 wt. %.
Embodiment 7 is the method of any of embodiments 1 to 6, wherein
the first catalyst and/or the second catalyst contains an acidic
porous zeolite including Mordenite Framework Inverted (MFI),
Faujasite (FAU), Mordenite (MOR), Beta, Omega structure type
zeolites. Embodiment 8 is the method of any of embodiments 1 to 7,
wherein the first catalyst and the second catalyst are different in
parameters including silicon to aluminum ratio, pore size, surface
area, promotor, or combinations thereof. Embodiment 9 is the method
of any of embodiments 1 to 8, wherein the reaction conditions in
the first catalyst riser include a reaction temperature of 600 to
720.degree. C., a steam to hydrocarbon ratio of 0 to 0.5, and dry
gas to hydrocarbon ratio of 0 to 0.5. Embodiment 10 is the method
of any of embodiments 1 to 9, wherein the reaction conditions in
the second catalyst riser include a reaction temperature of 600 to
720.degree. C., a steam to hydrocarbon ratio of 0 to 0.5, and dry
gas to hydrocarbon ratio of 0 to 0.5.
[0053] Embodiment 11 is a method of producing olefins and
aromatics. The method includes feeding a light naphtha stream to a
first catalyst riser of a fluid catalytic cracking (FCC) unit, the
light naphtha stream having an initial boiling point in a range 15
to 40.degree. C. and a final boiling point (FBP) in a range 65 to
350.degree. C., then contacting the light naphtha stream with a
first catalyst in the first catalyst riser under reaction
conditions sufficient to crack C.sub.5 to C.sub.7 hydrocarbons of
the light naphtha stream and form a first cracked stream. The
method also includes fractionating the first cracked stream to
produce a plurality of streams that includes a hydrocarbon
processing stream containing primarily C.sub.5 to C.sub.12
hydrocarbons and flowing the hydrocarbon processing stream to a
second catalyst riser of the FCC unit. Further, the method includes
contacting the hydrocarbon processing stream with a second catalyst
in the second catalyst riser under reaction conditions sufficient
to crack C.sub.5 to C.sub.12 hydrocarbons of the hydrocarbon
processing stream to form a second cracked processing stream
containing aromatics, wherein the first catalyst and the second
catalyst are different and wherein the reaction conditions in the
first catalyst riser are adapted such that yield of light olefins
from C.sub.5 to C.sub.7 hydrocarbons is 5 to 35 wt. % and yield of
aromatics from C.sub.5 to C.sub.7 hydrocarbons is 5 to 50 wt. % and
wherein the reaction conditions in the second catalyst rise are
adapted such that yield of aromatics from C.sub.5 to C.sub.12
nonaromatic hydrocarbons is 5 to 60 wt. %, and regenerating the
first catalyst and the second catalyst separately. Embodiment 12 is
the method of embodiment 11, wherein the fractionating further
produces a light recycling stream containing primarily C.sub.4 to
C.sub.6 hydrocarbons, a light olefin stream containing primarily
C.sub.2 and C.sub.3 olefins, a dry gas stream containing primarily
methane and hydrogen, collectively, an aromatic stream containing
primarily benzene, toluene, and xylene, collectively. Embodiment 13
is the method of embodiment 12, wherein the light recycling stream
is recycled back to the first catalyst riser. Embodiment 14 is the
method of any of embodiments 11 to 13, wherein the first catalyst
and/or the second catalyst contains an acidic porous zeolite
including Mordenite Framework Inverted (MFI), Faujasite (FAU),
Mordenite (MOR), Beta, Omega structure type zeolites. Embodiment 15
is the method of any of embodiments 11 to 14, wherein the first
catalyst and the second catalyst are different in parameters
including silicon to aluminum ratio, pore size, surface area,
promoter composition, or combinations thereof.
[0054] Although embodiments of the present application and their
advantages have been described in detail, it should be understood
that various changes, substitutions and alterations can be made
herein without departing from the spirit and scope of the
embodiments as defined by the appended claims. Moreover, the scope
of the present application is not intended to be limited to the
particular embodiments of the process, machine, manufacture,
composition of matter, means, methods and steps described in the
specification. As one of ordinary skill in the art will readily
appreciate from the above disclosure, processes, machines,
manufacture, compositions of matter, means, methods, or steps,
presently existing or later to be developed that perform
substantially the same function or achieve substantially the same
result as the corresponding embodiments described herein may be
utilized. Accordingly, the appended claims are intended to include
within their scope such processes, machines, manufacture,
compositions of matter, means, methods, or steps.
* * * * *