U.S. patent application number 14/695328 was filed with the patent office on 2016-10-27 for process for the production of jet-range hydrocarbons.
The applicant listed for this patent is UOP LLC. Invention is credited to Geoffrey W. Fichtl, Stanley J. Frey, Charles P. Luebke, Christopher P. Nicholas, Dana K. Sullivan.
Application Number | 20160312134 14/695328 |
Document ID | / |
Family ID | 57147424 |
Filed Date | 2016-10-27 |
United States Patent
Application |
20160312134 |
Kind Code |
A1 |
Fichtl; Geoffrey W. ; et
al. |
October 27, 2016 |
PROCESS FOR THE PRODUCTION OF JET-RANGE HYDROCARBONS
Abstract
A method for producing jet-range hydrocarbons includes passing a
renewable olefin feedstock comprising C.sub.3 to C.sub.8 olefins to
an oligomerization reactor containing a zeolite catalyst to produce
an oligomerized effluent, separating the oligomerized effluent into
at least a light stream, and a heavy olefin stream. At least a
first portion of the heavy olefin stream is recycled to the
oligomerization reactor to dilute the renewable olefin feedstock.
portion of heavy olefin stream may be hydrogenated and separated to
provide a jet range hydrocarbon product.
Inventors: |
Fichtl; Geoffrey W.;
(Chicago, IL) ; Frey; Stanley J.; (Palatine,
IL) ; Luebke; Charles P.; (Mount Prospect, IL)
; Nicholas; Christopher P.; (Evanston, IL) ;
Sullivan; Dana K.; (Mount Prospect, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
UOP LLC |
Des Plaines |
IL |
US |
|
|
Family ID: |
57147424 |
Appl. No.: |
14/695328 |
Filed: |
April 24, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C10G 69/126 20130101;
C10G 2300/1088 20130101; C10G 2400/22 20130101; C10G 2400/08
20130101; C10G 50/00 20130101 |
International
Class: |
C10G 69/12 20060101
C10G069/12; C10L 1/04 20060101 C10L001/04; C10G 50/00 20060101
C10G050/00 |
Claims
1. process for producing hydrocarbons comprising: oligomerizing a
renewable olefin feedstock comprising C.sub.3 to C.sub.8 olefins in
an oligomerization reactor containing a catalyst comprising a MTT
zeolite that has not been selectivated and operating the
oligomerization reactor under conditions to produce an oligomerized
effluent; separating the oligomerized effluent to produce a light
hydrocarbon stream, a naphtha hydrocarbon stream and a heavy stream
comprising C.sub.8+ olefins; splitting the heavy stream into a
first portion and a second portion; and, diluting the renewable
olefin feedstock with the first portion of the heavy stream.
2. The process of claim 1 further comprising: controlling a flow
rate of the first portion of the heavy stream.
3. The process of claim 2 wherein the flow rate of the first
portion of the heavy stream is controlled to obtain a .DELTA.T from
an inlet to an outlet in the oligomerization reactor of at least
25.degree. C. and no more than 60.degree. C.
4. The process of claim 1 further comprising: hydrogenating the
second portion of the heavy stream in a hydrogenation zone having a
hydrogenation reactor to provide a hydrogenated stream.
5. The process of claim 4 further comprising: separating the
hydrogenated stream into a vent gas stream and a saturated
distillate stream.
6. The process of claim 5 further comprising: separating the
saturated distillate stream into a saturated jet range stream and a
saturated diesel range hydrocarbons stream.
7. The process of claim 5 further comprising: recycling at least a
portion of the saturated distillate stream to the hydrogenation
zone.
8. process for producing hydrocarbons comprising: passing a
renewable olefin feedstock comprising C.sub.3 to C.sub.8 olefins to
an oligomerization reaction zone comprising an oligomerization
reactor containing a catalyst comprising a non-selectivated MTT
zeolite and wherein said oligomerization reactor is operating under
conditions to produce an oligomerized effluent; passing the
oligomerized effluent to a first separation zone to provide at
least one stream comprising C.sub.7- hydrocarbons and a C.sub.8+
olefin stream; splitting the C.sub.8+ olefin stream into a first
portion and a second portion; and, recycling the first portion of
the C.sub.8+ olefin stream to the oligomerization reaction
zone.
9. The process of claim 8 further comprising: combining the first
portion of the C.sub.8+ olefin stream with the renewable olefin
feedstock to provide a combined stream; and, passing the combined
stream into the oligomerization reactor.
10. The process of claim 8 wherein the first separation zone
produces a light hydrocarbon stream and a naphtha hydrocarbon
stream.
11. The process of claim 8 further comprising: passing the second
portion of the C.sub.8+ olefin stream to a hydrogenation zone
having a hydrogenation reactor containing a catalyst and being
operated to provide a hydrogenated effluent.
12. The process of claim 11 further comprising: passing the
hydrogenated effluent to second separation zone to provide at least
a vent gas stream and a saturated jet range stream.
13. The process of claim 12 further comprising: recycling a portion
of the hydrogenated effluent to the hydrogenation zone as a recycle
stream.
14. The process of claim 13 further comprising: combining the
recycle stream and the second portion of the C.sub.8+ olefin stream
into a combined stream; and, passing the combined stream to the
hydrogenation reactor.
15. The process of claim 11 further comprising: passing the
hydrogenated effluent to a second separation zone having at least
two columns.
16. The process of claim 15 wherein a first column in the second
separation zone separates the hydrogenated effluent into a vent gas
stream and a saturated distillate stream.
17. The process of claim 16 wherein a second column in the second
separation zone separates the saturated distillate stream into a
saturated jet range stream and a saturated diesel stream.
18. The process of claim 17 further comprising: passing at least a
portion of the saturated distillate stream to the hydrogenation
reaction zone as a recycle stream.
19. The process of claim 8 further comprising: controlling a
temperature rise in the oligomerization reactor by adjusting a flow
rate of the first portion of the C.sub.8+ olefin stream.
20. The process of claim 8 further comprising: increasing a flow
rate of the first portion of the C.sub.8+ olefin stream to decrease
a temperature rise in the oligomerization reactor.
Description
FIELD OF THE INVENTION
[0001] The present disclosure generally relates to methods for
producing renewable fuels and chemicals from biorenewable sources
and the renewable fuels and chemicals produced thereby, and more
particularly relates to methods for producing jet-range
hydrocarbons from alkanols, including for example isobutanol, and
the jet-range hydrocarbons produced thereby.
BACKGROUND OF THE INVENTION
[0002] As the worldwide demand for fuel increases, interest in
sources other than crude oil from which to produce transportation
fuels, including aviation fuels, is ever increasing. For example,
due to the growing environmental concerns over fossil fuel
extraction and economic concerns over exhausting fossil fuel
deposits, there is a demand for using an alternate or "green" feed
source for producing hydrocarbons for use as transportation fuels
and for use in other industries. Such sources of interest include,
for example, biorenewable sources, such as vegetable and seed oils,
animal fats, and algae byproducts, among others as are well-known
to those skilled in the art. conventional catalytic
hydro-processing technique is known for converting a biorenewable
feedstock into green diesel fuel that may be used as a substitute
for the diesel fuel produced from crude oil. As used herein, the
terms "green diesel fuel" and "green jet fuel" refer to fuel
produced from biorenewable sources, in contrast to those produced
from crude oil. The process also supports the possible
co-production of propane and other light hydrocarbons, as well as
naphtha or green jet fuel.
[0003] Biomass fermentation products typically include lower
isoalkanols such as, for example, C.sub.3 to C.sub.8 isoalkanols
obtained by contacting biomass with biocatalysts that facilitate
conversion (by fermentation) of the biomass to isoalkanols of
interest. The biomass feedstock for such fermentation processes can
be any suitable fermentable feedstock known in the art, such as
fermentable sugars derived from agricultural crops including
sugarcane, corn, etc. Suitable fermentable biomass feedstock can
also be prepared by the hydrolysis of biomass, for example
lignocellulosic biomass (e.g. wood, corn stover, switchgrass,
herbiage plants, ocean biomass, etc.), to form fermentable
sugars.
[0004] Jet-range fuels are an important product for the aerospace
industry and the military. The specific characteristics of various
grades and types of jet-range fuels vary slightly according to the
particular application and environment in which they are used.
Generally, jet-range fuels comprise a mixture of primarily C.sub.8
to C.sub.16 hydrocarbons and typically have a freezing point of
about -40 or -47.degree. C. (-40 or -52.6.degree. F.). In order to
produce jet-range fuels from isoalkanols derived from fermented
biomass, in one example known in the art, isobutanol is first
dehydrated to form butenes. The butenes are then oligomerized, in
the presence of an oligomerization catalyst, in one or more
reactors to form heavier olefins, such as C.sub.5 to C.sub.20, or
even higher, olefinic oligomers. Finally, the resulting olefinic
oligomers are hydrogenated in a saturation reactor to form the
corresponding C.sub.5 to C.sub.20, or even higher, paraffins in a
mixture which can then be subjected to separation to obtain C.sub.9
to C.sub.20+ paraffins suitable for use as biorenewable jet
fuel.
[0005] Since the oligomerization reaction is highly exothermic, the
butene fed to the oligomerization reactors may be cooled before
entering the oligomerization reactors. Another measure taken to
control the temperature increase in the oligomerization reactors is
to limit the proportion of olefins contained in the feedstream
provided to each reactor to no more than about 15 percent by weight
(wt %). This is accomplished, at least in part, by adding
non-reactive diluent material to the reactors which also provides a
heat sink to control the temperature rise in the reactors.
[0006] Typically, this dilution may be done by recycling saturated
distillate product from a stripped effluent of a hydrogenation
section back to the oligomerization and hydrogenation reactors.
Hydrogen transfer from the saturated diluent to the light olefinic
feed to the oligomerization reactor can cause yield loss by
saturating the light olefin feeds into paraffins. Paraffins,
however, will not participate in the oligomerization reactions and
will be recovered as saturated liquefied petroleum gas, instead of
olefinic distillate range material. Since the desired product is a
distillate range material, conversion of the olefins into saturated
liquefied petroleum gas amounts to a loss of potential distillate
yield, and thus is considered undesirable. Therefore, it would be
desirable to have one or more processes in which the dilution of
the feedstock to the oligomerization reactor is less likely to
result in yield loss.
SUMMARY OF THE INVENTION
[0007] One or more processes have been invented in which a portion
of an olefin effluent from an oligomerization reaction is used to
dilute the feedstock to the oligomerization reaction.
[0008] In a first aspect of the invention, the present invention
may be broadly characterized as a providing a process for producing
jet range hydrocarbons by oligomerizing a renewable olefin
feedstock comprising C.sub.3 to C.sub.8 olefins in an
oligomerization reactor containing a catalyst and being operated
under conditions to produce an oligomerized effluent; separating
the oligomerized effluent to produce a light hydrocarbon stream, a
naphtha hydrocarbon stream, and a heavy stream comprising C.sub.8+
olefins; splitting the heavy stream into a first portion and a
second portion; and, diluting the renewable C.sub.4 olefin
feedstock with the first portion of the heavy stream.
[0009] In one or more embodiments of the present invention, the
process further comprises controlling a flow rate of the first
portion of the heavy stream. It is contemplated that the flow rate
of the first portion of the heavy stream is controlled to obtain a
desired .DELTA.T in the oligomerization reactor of at least
25.degree. C. and no more than 60.degree. C.
[0010] In various embodiments of the present invention, the process
further comprises hydrogenating the second portion of the heavy
stream in a hydrogenation zone having a hydrogenation reactor to
provide a hydrogenated effluent. It is contemplated that the
process includes separating the hydrogenated effluent into a vent
gas stream and a saturated hydrocarbons stream. It is further
contemplated that the process includes separating the saturated
hydrocarbons stream into a saturated jet range stream and a
saturated diesel range hydrocarbons stream. It is still further
contemplated that the process includes recycling at least a portion
of the saturated hydrocarbons stream to the hydrogenation zone.
[0011] In a second aspect of the present invention, the present
invention may be generally characterized as providing a process for
producing jet range hydrocarbons by: passing a renewable olefin
feedstock comprising C.sub.3 to C.sub.8 olefins to an
oligomerization reaction zone comprising an oligomerization reactor
containing a catalyst and being operated under conditions to
produce an oligomerized effluent; passing the oligomerized effluent
to a first separation zone to provide at least one stream
comprising C.sub.7- hydrocarbons and a C.sub.8+ olefin stream;
splitting the C.sub.8+ olefin stream into a first portion and a
second portion; and, recycling the first portion of the C.sub.8+
olefin stream to the oligomerization reaction zone.
[0012] In one or more embodiments of the present invention, the
process further comprises combining the first portion of the
C.sub.8+ olefin stream with the renewable C.sub.4 olefin feedstock
to provide a combined stream and passing the combined stream into
the oligomerization reactor.
[0013] In at least one embodiment of the present invention, the
first separation zone produces a light hydrocarbon stream and a
naphtha hydrocarbon stream.
[0014] In some of the embodiments of the present invention, the
process further comprises passing the second portion of the
C.sub.8+ olefin stream to a hydrogenation zone having a
hydrogenation reactor containing a catalyst and being operated to
provide a hydrogenated effluent. It is contemplated that the
process includes passing the hydrogenated effluent to second
separation zone to provide at least a vent gas stream and a
saturated jet range stream. It is also contemplated that the
process includes recycling a portion of the hydrogenated effluent
to the hydrogenation zone as a recycle stream. It is further
contemplated that the process includes combining the recycle stream
and the second portion of the C.sub.8+ olefin stream into a
combined stream and, passing the combined stream to the
hydrogenation reactor.
[0015] In one or more of the embodiments of the present invention,
the process further comprises passing the hydrogenated effluent to
a second separation zone having at least two columns. It is
contemplated that a first column in the second separation zone
separates the hydrogenated effluent into a vent gas stream and a
saturated hydrocarbon stream. It is also contemplated that a second
column in the second separation zone separates the saturated
hydrocarbon stream into a saturated jet range stream and a
saturated diesel stream. It is further contemplated that the
process includes passing at least a portion of the saturated
hydrocarbon stream to the hydrogenation reaction zone as a recycle
stream.
[0016] In at least one of the embodiments of the present invention,
the process further comprises controlling a temperature rise in the
oligomerization reactor by adjusting a flow rate of the first
portion of the C.sub.8+ olefin stream.
[0017] In some of the embodiments of the present invention, the
process further comprises increasing a flow rate of the first
portion of the C.sub.8+ olefin stream to decrease a temperature
rise in the oligomerization reactor.
[0018] Additional aspects, embodiments, and details of the
invention, which may be combined in any manner, are set forth in
the following detailed description of the invention.
DETAILED DESCRIPTION OF THE DRAWINGS
[0019] One or more exemplary embodiments of the present invention
will be described below in conjunction with the following drawing
FIGURE, in which:
[0020] the FIGURE shows a process flow diagram of one or more
processes according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0021] As used herein, the term "stream" can include various
hydrocarbon molecules and other substances. Moreover, the term
"stream comprising C.sub.x hydrocarbons" or "stream comprising
C.sub.x olefins" can include a stream comprising hydrocarbon or
olefin molecules, respectively, with "x" number of carbon atoms,
suitably a stream with a majority of hydrocarbons or olefins,
respectively, with "x" number of carbon atoms and preferably a
stream with at least 75 wt % hydrocarbons or olefin molecules,
respectively, with "x" number of carbon atoms. Moreover, the term
"stream comprising C.sub.x+ hydrocarbons" or "stream comprising
C.sub.x+ olefins" can include a stream comprising a majority of
hydrocarbon or olefin molecules, respectively, with more than or
equal to "x" carbon atoms and suitably less than 10 wt % and
preferably less than 1 wt % hydrocarbon or olefin molecules,
respectively, with x-1 carbon atoms. Lastly, the term "C.sub.x-
stream" can include a stream comprising a majority of hydrocarbon
or olefin molecules, respectively, with less than or equal to "x"
carbon atoms and suitably less than 10 wt % and preferably less
than 1 wt % hydrocarbon or olefin molecules, respectively, with x+1
carbon atoms.
[0022] As used herein, the term "zone" can refer to an area
including one or more equipment items and/or one or more sub-zones.
Equipment items can include one or more reactors or reactor
vessels, heaters, exchangers, pipes, pumps, compressors,
controllers and columns. Additionally, an equipment item, such as a
reactor, dryer, or vessel, can further include one or more zones or
sub-zones.
[0023] As used herein, the term "substantially" can mean an amount
of at least generally about 70%, preferably about 80%, and
optimally about 90%, by weight, of a compound or class of compounds
in a stream.
[0024] As used herein, the term "gasoline" can include hydrocarbons
having a boiling point temperature in the range of about 25 to
about 200.degree. C. (68 to 392.degree. F.) at atmospheric
pressure.
[0025] As used herein the term "naphtha" can mean C.sub.5
hydrocarbons up to hydrocarbons having a boiling point of
150.degree. C. (302.degree. F.) (i.e., hydrocarbons having a
boiling point in the range of 30 to 150.degree. C. (86 to
302.degree. F.)).
[0026] As used herein the term "diesel" can include hydrocarbons
having a boiling point temperature in the range of about 250 to
about 400.degree. C. (482 to 752.degree. F.) at atmospheric
pressure.
[0027] As used herein the term "jet-range hydrocarbons," "jet-range
paraffins," "jet-range fuels," or "jet fuels" can include
hydrocarbons having a boiling point temperature in the range of
about 130 to about 300.degree. C. (266 to 572.degree. F.),
preferably 150 to 260.degree. C. (302 to 500.degree. F.), at
atmospheric pressure. Additionally, as used herein, the terms
"jet-range hydrocarbons," "jet-range paraffins," "jet-range fuels,"
or "jet fuels" refer to a mixture of primarily C.sub.8 to C.sub.16
hydrocarbons with a freezing point of about -40.degree. C.
(-40.degree. F.) or about -47.degree. C. (-52.6.degree. F.).
[0028] As used herein, the term "distillate" comprises a mixture of
diesel and jet-range hydrocarbons and can include hydrocarbons
having a boiling point temperature in the range of about 150 to
about 400.degree. C. (302 to 752.degree. F.) at atmospheric
pressure.
[0029] As used herein, the phrase "a mixture of primarily . . . "
or "comprising primarily . . . " a specified range of
carbon-numbered hydrocarbons means that the group or category of
hydrocarbons being described may also contain very small amounts of
hydrocarbons outside the stated carbon number range, without
altering the general characteristics (e.g., boiling point) of the
group or category being described. For example, the description
that jet fuels are a mixture of primarily C.sub.8 to C.sub.16
hydrocarbons means that jet fuels contain at least 80 wt % of
hydrocarbon molecules each having from about 8 to about 16 carbon
atoms with, possibly, very small amounts of hydrocarbon molecules
each having less than about 8 carbon atoms, as well as very small
amounts of hydrocarbon molecules each having more than 16 carbon
atoms, such that the freezing point remains about -40.degree. C. to
about -47.degree. C. (-40 to 52.6.degree. F.). There are multiple
standards, established by various industries and governments, that
are useful for ensuring that particular types of jet fuels have
uniform characteristics that fall within expected ranges. For
example, one type of jet fuel, known as Aviation Turbine Fuel, Jet
A, or Jet A-1 fuel, is composition of hydrocarbons that boil in a
range such that the volatility characteristics of the hydrocarbon
(or paraffinic form of the hydrocarbon after hydrogenation)
substantially conform to the volatility standards of flash point
(typically minimum of 38.degree. C. (100.degree. F.), distillation
range (T10 boiling point maximum of 205.degree. C. (401.degree. F.)
and final boiling point (maximum of 300.degree. C. (572.degree.
F.), with all distillation valves measured by D86 or D2887 values
converted to D86) set forth in ASTM D7566-11a, "Standard
Specification for Aviation Turbine Fuel Containing Synthesized
Hydrocarbons," promulgated by ASTM International, Inc. of West
Conshohoken, Pa. Other standards that provide parameters useful for
characterizing and defining the jet fuels prepared using the
methods and apparatus contemplated and described herein include Jet
Propellant (JP)-5 and JP-8, which are set forth in the United
States military specifications found at MIL-DTL-83133, as well as
in British Defence Standard 91-87.
[0030] The term "column" means a distillation column or columns for
separating one or more components of different volatilities. Unless
otherwise indicated, each column includes a condenser on an
overhead of the column to condense and reflux a portion of an
overhead stream back to the top of the column and a reboiler at a
bottom of the column to vaporize and send a portion of a bottom
stream back to the bottom of the column. Feeds to the columns may
be preheated. The top pressure is the pressure of the overhead
vapor at the outlet of the column. The bottom temperature is the
liquid bottom outlet temperature. Overhead lines and bottom lines
refer to the net lines from the column downstream of the reflux or
reboil to the column.
[0031] As used herein, the term "boiling point temperature" means
atmospheric equivalent boiling point (AEBP) as calculated from the
observed boiling temperature and the distillation pressure, as
calculated using the equations furnished in ASTM D1160 appendix A7
entitled "Practice for Converting Observed Vapor Temperatures to
Atmospheric Equivalent Temperatures."
[0032] As used herein, "taking a stream from" means that some or
all of the original stream is taken.
[0033] Disclosed herein are methods and apparatus for producing
jet-range hydrocarbons from one or more biorenewable C.sub.3 to
C.sub.8 olefins via oligomerization. As mentioned above, the
oligomerization reaction is highly exothermic. In order to control
the temperature rise from the inlet to the outlet in the reactor
(i.e., the ".DELTA.T"), various processes utilize a diluent.
However, it has been discovered that by using a portion of the
heavy olefins produced in the oligomerization reactor, the
temperature rise can be controlled without using paraffin
hydrocarbons which can result in hydrogen transfer to the olefins
in the oligomerization reactor. The heavy olefins have been found
to resist further oligomerization, resulting in a diluent that can
minimize yield loss. While these methods find greatest utility in
converting feedstocks from alkanols, thereby allowing for
production of jet fuels from renewable sources, this is not
intended to limit the application of the methods of the present
invention.
[0034] With these general principles in mind, one or more
embodiments of the present invention will be described with the
understanding that the following description is not intended to be
limiting.
[0035] As shown in the FIGURE, one or more processes of the present
invention include a renewable olefin feedstock 10 being passed to
an oligomerization zone 12. As used herein, the term "renewable"
denotes that the carbon content of the olefin feedstock 10 is from
a "new carbon" source as measured by ASTM test method D6866-05,
"Determining the Bio-based Content of Natural Range Materials Using
Radiocarbon and Isotope Ratio Mass Spectrometry Analysis",
incorporated herein by reference in its entirety. This test method
measures the .sup.14C/.sup.12C isotope ratio in a sample and
compares it to the .sup.14C/.sup.12C isotope ratio in a standard
100% bio-based material to give percent bio-based content of the
sample. Additionally, "bio-based materials" are organic materials
in which the carbon comes from recently (on the order of centuries)
fixated carbon dioxide present in the atmosphere using sunlight
energy (photosynthesis). On land, this carbon dioxide is captured
or fixated by plant life (e.g., agricultural crops or forestry
materials). In the oceans, the carbon dioxide is captured or
fixated by photosynthesizing bacteria or phytoplankton. For
example, a bio-based material has a .sup.14C/.sup.12C isotope ratio
greater than zero. Contrarily, a fossil-based material has a
.sup.14C/.sup.12C isotope ratio of zero. The term "renewable" with
regard to compounds such as alcohols or hydrocarbons (olefins,
di-olefins, polymers, etc.) also refers to compounds prepared from
biomass using thermochemical methods (e.g., Fischer-Tropsch
catalysts), biocatalysts (e.g., fermentation), or other processes,
for example as described herein.
[0036] A small amount of the carbon atoms in the carbon dioxide in
the atmosphere is the radioactive isotope .sup.14C. This .sup.14C
carbon dioxide is created when atmospheric nitrogen is struck by a
cosmic ray generated neutron, causing the nitrogen to lose a proton
and form carbon of atomic mass 14 (.sup.14C), which is then
immediately oxidized, to carbon dioxide. small but measurable
fraction of atmospheric carbon is present in the form of
.sup.14C.
[0037] Atmospheric carbon dioxide is processed by green plants to
make organic molecules during the process known as photosynthesis.
Virtually all forms of life on Earth depend on this green plant
production of organic molecules to produce the chemical energy that
facilitates growth and reproduction. Therefore, the .sup.14C that
forms in the atmosphere eventually becomes part of all life forms
and their biological products, enriching biomass and organisms
which feed on biomass with .sup.14C. In contrast, carbon from
fossil fuels does not have the signature .sup.14C/.sup.12C ratio of
renewable organic molecules derived from atmospheric carbon
dioxide. Furthermore, renewable organic molecules that biodegrade
to carbon dioxide do not contribute to an increase in atmospheric
greenhouse gases as there is no net increase of carbon emitted to
the atmosphere. Assessment of the renewably based carbon content of
a material can be performed through standard test methods, e.g.,
using radiocarbon and isotope ratio mass spectrometry analysis.
ASTM International (formally known as the American Society for
Testing and Materials) has established a standard method for
assessing the bio-based content of materials. The ASTM method is
designated ASTM-D6866. The application of ASTM-D6866 to derive
"bio-based materials" is built on the same concepts as radiocarbon
dating, but without use of the age equations. The analysis is
performed by deriving a ratio of the amount of radiocarbon
(.sup.14C) in an unknown sample compared to that of a modern
reference standard. This ratio is reported as a percentage with the
units "pMC" (percent modern carbon). If the material being analyzed
is a mixture of present day radiocarbon and fossil carbon
(containing very low levels of radiocarbon), then the pMC value
obtained correlates directly to the amount of biomass material
present in the sample. In an aspect, renewable carbon substantially
comprises the renewable olefin feedstock 10. The percentage of
renewable carbon in the renewable olefin feedstock 10 may be
greater than 80% or greater than 90% or greater than 95% or greater
than 99% on a weight basis.
[0038] Returning to the FIGURE, the renewable olefin feedstock 10
includes at least C.sub.4 olefins, preferably comprising C.sub.3 to
C.sub.8 olefins. In an aspect, the renewable olefin stream may
comprise one or more carbon number olefins such as C.sub.3 to
C.sub.4 olefins or C.sub.3 to C.sub.5 olefins or C.sub.4 to C.sub.5
olefins or C.sub.3 to C.sub.6 olefins. The renewable olefins may be
derived from their corresponding alcohols (i.e., C.sub.4 alcohols,
especially including isobutanol), which are typically formed by
fermentation or by condensation reactions of synthesis gas. For
example, a feedstock for the fermentation process can be any
suitable fermentable feedstock known in the art, such as sugars
derived from agricultural crops including sugarcane, corn, etc.
Alternatively, the fermentable feedstock can be prepared by the
hydrolysis of biomass, for example lignocellulosic biomass (e.g.
wood, corn stover, switchgrass, herbiage plants, ocean biomass,
etc.). In another example, renewable alcohols, such as isobutanols,
can be prepared photosynthetically, for example using cyanobacteria
or algae engineered to produce isobutanol and/or other alcohols.
When produced photosynthetically, the feedstock for producing the
resulting renewable alcohols is light, water, and carbon dioxide,
which is provided to the photosynthetic organism (e.g.,
cyanobacteria or algae). Additionally, other known methods, whether
biorenewable or otherwise, for producing isobutanol are suitable
for supplying the C.sub.4 olefins; the methods described herein are
not intended to be limited by the use of any particular renewable
feed source. Typically, the renewable olefin feedstock 10 may
comprise greater than 50 wt % olefins such as greater than 70 wt %
or greater than 80 wt % or greater than 90 wt % olefins or greater
than 95 wt % or greater than 99 wt % olefins.
[0039] Olefin isomer types of the renewable olefin feedstock 10,
and of the oligomers produced by oligomerization, can be
denominated according to the degree of substitution of the double
bond, as follows:
TABLE-US-00001 TABLE 1 Olefin Type Structure Description I
R--HC.dbd.CH.sub.2 Monosubstituted II R--HC.dbd.CH--R Disubstituted
III RRC.dbd.CH.sub.2 Disubstituted IV RRC.dbd.CHR Trisubstituted V
RRC.dbd.CRR Tetrasubstituted
wherein R represents an alkyl group, each R being the same or
different. Type I compounds are sometimes described as .alpha.- or
vinyl olefins and Type III as vinylidene olefins. Type IV is
sometimes subdivided to provide a Type IVA, in which access to the
double bond is less hindered, and Type IVB where it is more
hindered. In an aspect, the renewable olefin feedstock 10 may
comprise high quantities of Type III olefins such as greater than
50 wt % or greater than 70 wt % or greater than 85 wt % or greater
than 90 wt % or greater than 95 wt % Type III olefins as a fraction
of the total olefins in the renewable olefins stream.
[0040] As shown in the FIGURE, the renewable olefins (possibly
derived and converted from the C.sub.4 alcohols, for example by
dehydration of the alcohol see, e.g., U.S. Pat. No. 4,423,251) are
mixed with a diluent stream 14 (discussed in more detail below)
prior to entering an oligomerization reactor 16 in the
oligomerization zone 12. Although depicted with a single
oligomerization reactor 16, the oligomerization zone 12 may contain
any number of reactors.
[0041] In the oligomerization reactor 16, at least a portion of the
renewable olefins are converted into a mixture of heavier boiling
hydrocarbons including jet range hydrocarbons via oligomerization
by reacting the olefins using a zeolitic oligomerization catalyst
under appropriate conditions. For example, the oligomerization zone
12 may, for example, without limitation, be operated at a
temperature from about 100 to about 300.degree. C. (212 to
572.degree. F.) and a pressure of from about 689 to about 6895 kPa
(100 to 1000 psig). For example, the operating temperature may be
from about 120 to about 280.degree. C. (248 to 536.degree. F.), or
even from about 160 to about 260.degree. C. (320 to 402.8.degree.
F.). The operating pressure may, for example, be from about 1034 to
about 5516 kPa (150 to 800 psi), or even from about 2068 to about
4964 kPa (300 to 720 psi).
[0042] The oligomerization catalyst in the oligomerization zone 12
is not limited to any particular catalyst and may comprise any
catalyst suitable for catalyzing conversion of the one or more
biorenewable C.sub.3 to C.sub.8 olefins in the olefin stream to
olefinic oligomers comprising heavier boiling C.sub.5+
hydrocarbons, including jet-range hydrocarbons. The oligomerization
catalyst may be any such catalyst known now or in the future.
[0043] Conventional oligomerization catalysts will generally
convert an olefin to a mixture of dimers, trimers, tetramers, and
sometimes pentamers, of the olefin. For example, where the C.sub.3
to C.sub.8 olefin is isobutylene, a C.sub.4 olefin, the products of
oligomerization in the presence of a conventional oligomerization
catalyst include C.sub.8, C.sub.12, C.sub.16, and sometimes
C.sub.20 olefins, together in a mixture. Conventional
oligomerization catalysts include, without limitation, solid
phosphoric acid ("SPA") and certain ion exchange resins such as
Amberlyst-36 (commercially available from The Dow Chemical Company
of Midland, Mich., U.S.A.). The olefinic oligomer mixture produced
using conventional oligomerization catalysts may be further
subjected to a separation process to produce a mixture of jet-range
hydrocarbons suitable for use as jet fuels. These jet fuels often
have a boiling point distribution that has well-defined boiling
point steps corresponding to only a few isomers of the
corresponding trimer, tetramer, and pentamer paraffins of the
starting olefin, which is different from petroleum-derived jet
fuels.
[0044] Alternative oligomerization catalysts comprising zeolite
materials, on the other hand, catalyze oligomerization conversion
of C.sub.3 to C.sub.8 olefins to dimers, trimers, tetramers, and
sometimes pentamers of the C.sub.3 to C.sub.8 olefins, but also
catalyze backcracking conversion of the resulting heavier olefinic
oligomers back into lighter and more random and varied sizes of
olefins including C.sub.5 to C.sub.20+ hydrocarbons. In other
words, under appropriate conditions, zeolitic catalysts such as,
without limitation, MTT, TON, MFI, and MTW, yield C.sub.5+
hydrocarbons, including jet-range hydrocarbons, with an increased
distribution and variety of carbon numbers than those made using
conventional non-zeolitic catalysts. This means that jet-range fuel
produced from biorenewable olefins via oligomerization in the
presence of zeolite catalysts has a boiling range and compositional
profile that is more similar to jet-range fuels produced from
petroleum refining processes.
[0045] Suitable zeolite catalysts may comprise between 5 and 95 wt
% of zeolite material. Suitable zeolite materials include zeolites
having a structure from one of the following classes: MFI, MEL,
ITH, IMF, TUN, FER, BEA, FAU, BPH, MEI, MSE, MWW, UZM-8, MOR, OFF,
MTW, TON, MTT, AFO, ATO, and AEL. 3-letter codes indicating a
zeotype are as defined by the Structure Commission of the
International Zeolite Association and are maintained at
http://www.iza-structure.org/databases/. UZM-8 is as described in
U.S. Pat. No. 6,756,030. In a preferred aspect, the zeolite
catalyst may comprise a zeolite with a framework having a ten-ring
pore structure. Examples of suitable zeolites having a ten-ring
pore structure include TON, MTT, MFI, MEL, AFO, AEL, EUO and FER.
The oligomerization catalyst comprising a zeolite having a ten-ring
pore structure may comprise a uni-dimensional pore structure.
uni-dimensional pore structure indicates zeolite materials
containing non-intersecting pores that are substantially parallel
to one of the axes of the crystal. The pores preferably extend
through the zeolite crystal. Suitable examples of zeolite materials
having a ten-ring uni-dimensional pore structure may include MTT.
In a further aspect, the oligomerization catalyst comprises an MTT
zeolite.
[0046] The zeolite catalyst may be formed by combining the zeolite
material with a binder, and then forming the catalyst into pellets.
The pellets may optionally be treated with a phosphorus reagent to
create a zeolite having a phosphorous component between 0.5 and 15
wt % of the treated catalyst. The binder is used to confer hardness
and strength on the catalyst. Binders include alumina, aluminum
phosphate, silica, silica-alumina, zirconia, titania and
combinations of these metal oxides, and other refractory oxides,
and clays such as montmorillonite, kaolin, palygorskite, smectite
and attapulgite. preferred binder is an aluminum-based binder, such
as alumina, aluminum phosphate, silica-alumina and clays.
[0047] One of the components of the zeolite catalyst binder
utilized herein is alumina. The alumina source may be any of the
various hydrous aluminum oxides or alumina gels such as
alpha-alumina monohydrate of the boehmite or pseudo-boehmite
structure, alpha-alumina trihydrate of the gibbsite structure,
beta-alumina trihydrate of the bayerite structure, and the like.
suitable alumina is available from UOP LLC under the trademark
Versal. preferred alumina is available from Sasol North America
Alumina Product Group under the trademark Catapal. This material is
an extremely high purity alpha-alumina monohydrate
(pseudo-boehmite) which after calcination at a high temperature has
been shown to yield a high purity gamma-alumina.
[0048] A suitable zeolite catalyst may be, for example, prepared by
mixing proportionate volumes of zeolite and alumina to achieve the
desired zeolite-to-alumina ratio. In an embodiment, the MTT content
may be about 5 to 85 wt %, for example about 20 to 82 wt % MTT
zeolite, and the balance alumina powder will provide a suitably
supported catalyst. silica support is also contemplated.
[0049] Monoprotic acid such as nitric acid or formic acid may be
added to the mixture in aqueous solution to peptize the alumina in
the binder. Additional water may be added to the mixture to provide
sufficient wetness to constitute a dough with sufficient
consistency to be extruded or spray dried. Extrusion aids such as
cellulose ether powders can also be added. preferred extrusion aid
is available from The Dow Chemical Company under the trademark
Methocel.
[0050] The paste or dough may be prepared in the form of shaped
particulates, with the preferred method being to extrude the dough
through a die having openings therein of desired size and shape,
after which the extruded matter is broken into extrudates of
desired length and dried. further step of calcination may be
employed to give added strength to the extrudate. Generally,
calcination is conducted in a stream of air at a temperature from
about 260 to about 815.degree. C. (500 to 1500.degree. F.). The MTT
catalyst is not selectivated to neutralize acid sites such as with
an amine.
[0051] The extruded particles may have any suitable cross-sectional
shape, i.e., symmetrical or asymmetrical, but most often have a
symmetrical cross-sectional shape, preferably a spherical,
cylindrical or polylobal shape. The cross-sectional diameter of the
particles may be as small as 40 .mu.m; however, it is usually about
0.635 mm (0.25 inch) to about 12.7 mm (0.5 inch), preferably about
0.79 mm ( 1/32 inch) to about 6.35 mm (0.25 inch), and most
preferably about 0.06 mm ( 1/24 inch) to about 4.23 mm (1/6
inch).
[0052] Returning to the FIGURE, An oligomerized effluent 18 from
the oligomerization zone 12 may be passed to a separation zone 20
including, for example, a distillation column 22. In the separation
zone 20, the oligomerized effluent 18 may be separated into a light
hydrocarbon stream 24 comprising C.sub.4- hydrocarbons, a naphtha
hydrocarbon stream 26 comprising C.sub.5 to C.sub.7 hydrocarbons,
and a heavy stream 28 comprising C.sub.8+ olefins. As will be
appreciated, there may be some overlap between the components of
the various streams. For example, the naphtha hydrocarbon stream 26
may include some C.sub.4 hydrocarbons or some heavier hydrocarbons
such as C.sub.8 or C.sub.9 hydrocarbons. It is preferred that such
streams include at least 50% of the intended components (i.e., the
naphtha hydrocarbon stream 26 comprises 80% C.sub.5 to C.sub.7
hydrocarbons).
[0053] The further processing of the light hydrocarbon stream 24
and the naphtha hydrocarbon stream 26 are not necessary for an
understanding or practicing of the present invention. However, the
naphtha hydrocarbon stream 26 may be recycled to the
oligomerization reactor 16 to further react these hydrocarbons into
the jet range. As shown in the FIGURE, in the various embodiments
of the present invention, the heavy stream 28 is split into a first
portion 28a and a second portion 28b. The first portion 28a of the
heavy stream 28 is used to dilute the renewable olefin feedstock 10
as the diluent stream 14. The further processing of the second
portion 28b of the heavy stream 28 is described below.
[0054] The heavy olefins in the first portion 28a of the heavy
stream 28 are relatively inert in the oligomerization reaction and
have a low tendency to further react with smaller olefins. Thus,
utilizing the first portion 28a of the heavy stream 28 to control
the temperature in the oligomerization reactor 16 is desirable
because the heavy olefins are less likely than similar saturated
diluents to transfer hydrogen to the smaller olefins resulting in
yield loss. Accordingly, it is contemplated that the relative
amounts of the first portion 28a and second portion 28b of the
heavy stream 28 are adjusted based upon the amount C.sub.8+ olefins
as well as the temperature and temperature rise in the
oligomerization reactor 16. If the temperature or temperature rise
is too high, the amount of the first portion 28a of the heavy
stream 28 may be increased. The C.sub.8+ olefins that are used as a
diluent will be separated out in the separation zone 20 and can be
utilized again as a diluent to the oligomerization zone 12 or the
C.sub.8+ olefins material can be processed further in the second
portion 28b of the heavy stream 28. Across a single bed of
oligomerization catalyst, the exothermic reaction will cause the
temperature to rise. Consequently, the oligomerization reactor 16
should be operated to allow the temperature at the outlet to be
over about 25.degree. C. greater but no more than 60.degree. C.
greater than the temperature at the inlet. In some embodiments,
this temperature difference between the outlet and the inlet of the
oligomerization reactor 16, the .DELTA.T, is at least 25.degree. C.
but no more than 40.degree. C. In still other embodiments, the
.DELTA.T is at least 25.degree. C. but no more than 35.degree.
C.
[0055] As shown in the FIGURE, the second portion 28b of the heavy
stream 28, along with a hydrogen containing gas 30 may be passed to
a hydrogenation zone 32 having a hydrogenation reactor 34.
Hydrogenation is typically performed using a conventional
hydrogenation or hydrotreating catalyst, which may include metallic
catalysts containing, e.g., palladium, rhodium, nickel, ruthenium,
platinum, rhenium, cobalt, molybdenum, or combinations thereof, and
the supported versions thereof. Catalyst supports can be any solid,
inert substance including, but not limited to, oxides such as
silica, alumina, titania, calcium carbonate, barium sulfate, and
carbons. The catalyst support can be in the form of powder,
granules, pellets, or the like. Hydrogenation suitably occurs at a
temperature of about 150.degree. C. (300.degree. F.) and at a
pressure of about 6895 kPa (1000 psig). Other process conditions
known by those of ordinary skill in the art may be utilized.
[0056] A hydrogenated effluent 36 from the hydrogenation zone 32
will substantially comprise saturated hydrocarbons (i.e.,
paraffins). The a stream of hydrogenated effluent 36 may be passed
to a separation zone 38 having one or more vessels or columns 40a,
40b configured to separate the saturated hydrocarbons into one or
more product streams 42a, 42b. Additionally, at least a portion of
the saturated hydrocarbons may be used as a recycle stream to the
hydrogenation zone.
[0057] For example, a first column 40a may separate the
hydrogenated effluent 36 into a vent gas stream 44 and a saturated
distillate stream 46. portion 46a of the saturated distillate
stream 46 may be used as a recycle stream to the hydrogenation zone
32. second column 40b may separate the saturated distillate stream
46 into a saturated jet range stream 42a and a saturated diesel
range stream 42b.
[0058] Thus, using the processes of the present invention,
jet-range hydrocarbons can be produced from a renewable olefin
feedstock with minimal yield loss due to hydrogen transfer to the
lighter olefins from heavy hydrocarbons in a diluent stream.
[0059] It should be appreciated and understood by those of ordinary
skill in the art that various other components such as valves,
pumps, filters, coolers, etc. were not shown in the drawings as it
is believed that the specifics of same are well within the
knowledge of those of ordinary skill in the art and a description
of same is not necessary for practicing or understating the
embodiments of the present invention.
[0060] While at least one exemplary embodiment has been presented
in the foregoing detailed description of the invention, it should
be appreciated that a vast number of variations exist. It should
also be appreciated that the exemplary embodiment or exemplary
embodiments are only examples, and are not intended to limit the
scope, applicability, or configuration of the invention in any way.
Rather, the foregoing detailed description will provide those
skilled in the art with a convenient road map for implementing an
exemplary embodiment of the invention, it being understood that
various changes may be made in the function and arrangement of
elements described in an exemplary embodiment without departing
from the scope of the invention as set forth in the appended claims
and their legal equivalents.
* * * * *
References