U.S. patent application number 12/956987 was filed with the patent office on 2011-03-24 for process for co-producing jet fuel and lpg from renewable sources.
Invention is credited to Ramin Abhari, Peter Havlik, Nathan Jannasch, Lynn Tomlinson.
Application Number | 20110071327 12/956987 |
Document ID | / |
Family ID | 39714198 |
Filed Date | 2011-03-24 |
United States Patent
Application |
20110071327 |
Kind Code |
A1 |
Abhari; Ramin ; et
al. |
March 24, 2011 |
PROCESS FOR CO-PRODUCING JET FUEL AND LPG FROM RENEWABLE
SOURCES
Abstract
The present invention generally relates to a method for
producing an isoparaffinic product useful as jet fuel from a
renewable feedstock. The method may also include co-producing a jet
fuel and a liquefied petroleum gas (LPG) fraction from a renewable
feedstock. The method includes hydrotreating the renewable
feedstock to produce a hydrotreating unit heavy fraction that
includes n-paraffins and hydroisomerizing the hydrotreating unit
heavy fraction to produce a hydroizomerizing unit heavy fraction
that includes isoparaffins. The method also includes recycling the
hydroisomerizing unit heavy fraction through the hydroisomerization
unit to produce an isoparaffinic product that may be fractionated
into a jet fuel and an LPG fraction. The present invention also
relates to a jet fuel produced from a renewable feedstock having
improved cold flow properties.
Inventors: |
Abhari; Ramin; (Bixby,
OK) ; Tomlinson; Lynn; (Tulsa, OK) ; Havlik;
Peter; (Tulsa, OK) ; Jannasch; Nathan; (Broken
Arrow, OK) |
Family ID: |
39714198 |
Appl. No.: |
12/956987 |
Filed: |
November 30, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12062970 |
Apr 4, 2008 |
7846323 |
|
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12956987 |
|
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60910573 |
Apr 6, 2007 |
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Current U.S.
Class: |
585/240 ;
585/310 |
Current CPC
Class: |
C10G 2300/1018 20130101;
C10G 2400/28 20130101; C10G 2400/08 20130101; C10G 3/46 20130101;
C10G 2300/1014 20130101; C10G 2300/301 20130101; C10L 1/04
20130101; C10G 3/50 20130101; C10G 2300/302 20130101; C10L 3/12
20130101; C10G 2400/02 20130101; Y02P 30/20 20151101 |
Class at
Publication: |
585/240 ;
585/310 |
International
Class: |
C07C 1/00 20060101
C07C001/00; C10L 1/16 20060101 C10L001/16 |
Claims
1. A method for producing from a renewable feedstock an
isoparaffinic product useful as jet fuel, the method comprising: a.
hydrotreating a renewable feedstock with a diluent to produce an
n-paraffinic fraction; b. hydroisomerizing n-paraffinic fraction to
produce an isoparaffinic fraction and a heavy fraction; c.
separating the heavy fraction from the isoparaffinic fraction; and
d. recycling the heavy fraction of step (c) to the hydroisomerizing
step of step (b) and wherein the diluent comprises C3-C18
n-paraffins and/or iso-paraffins produced by at least one of the
steps of the method.
2. The method of claim 1 further comprising the step of
fractionating the isoparaffin to produce jet fuel.
3. The method of claim 1, wherein the renewable feedstock comprises
triglycerides, free fatty acids, and combinations thereof.
4. The method of claim 1, wherein the renewable feedstock is
selected from the group comprising animal fats, animal oils,
vegetable fats, vegetable oils, rendered fats, restaurant grease,
waste industrial frying oils, fish oils, and combinations
thereof.
5. The method of claim 1, wherein the hydrotreating step operating
conditions comprise a reaction temperature of from about
300.degree. F. to about 850.degree. F. and a reaction pressure of
from about 250 psig to about 3000 psig.
6. The method of claim 1 wherein the liquid hourly space velocity
through the hydrotreating step is about 0.5 to about 5.0
h.sup.-1.
7. The method of claim 1, wherein the hydroisomerizing step
operating conditions comprise a reaction temperature of from about
300.degree. F. to about 850.degree. F. and a reaction pressure of
from about 250 psig to about 3000 psig.
8. The method of claim 1 wherein the hydrotreating step is carried
out in the presence of a sulfided bimetallic catalyst.
9. The method according to claim 8 wherein the catalyst is a
supported NiW, NiMo or a CoMo catalyst, the support being
alumina.
10. The method of claim 1, wherein the isoparaffinic product has a
boiling point range of from about 150.degree. C. to about
300.degree. C.
11. A method of co-producing liquid petroleum gases, isoparaffinic
naphtha, and jet fuel, the method comprising: a. hydrotreating a
renewable feedstock with a diluent to produce a hydrotreated heavy
fraction and a light fraction. b. hydroisomerizing the hydrotreated
heavy fraction to produce a hydroisomerized heavy fraction and
isoparaffin. c. recycling the hydroisomerized heavy fraction to
step (b) and hydroisomerizing the hydroisomerized heavy fraction to
produce an isoparaffinic product; and, d. fractionating the
isoparaffinic product and the light fraction to produce liquid
petroleum gases, isoparaffinic naphtha, and jet fuel; and wherein
the diluent comprises C3-C18 n-paraffins and/or iso-paraffins
produced by at least one of the steps of the method.
12. The method of claim 11, wherein the liquid petroleum gases
comprise propane, iso-butane, and n-butane.
13. The method of claim 11 wherein the renewable feedstock
comprises triglycerides, free fatty acids and combinations
thereof.
14. The method of claim 11 wherein the renewable feedstock is
selected from the group comprising of animal fats, animal oils,
vegetable fats, vegetable oils, rendered fats, restaurant grease,
waste industrial frying oils, fish oils, and combinations
thereof.
15. The method of claim 11, wherein the hydrotreating step
operating conditions comprise a reaction temperature of from about
300.degree. F. to about 850.degree. F. and a reaction pressure of
from about 250 psig to about 3000 psig.
16. The method of claim 11 wherein the liquid hourly space velocity
through the hydrotreating step is about 0.5 to about 5.0
17. The method of claim 11, wherein the hydroisomerizing step
operating conditions comprise a reaction temperature of from about
300.degree. F. to about 850.degree. F. and a reaction pressure of
from about 250 psig to about 3000 psig.
18. The method of claim 11 wherein the hydrotreating step is
carried out in the presence of a sulfided bimetallic catalyst.
19. The method according to claim 18 wherein the catalyst is a
supported NiW, NiMo or a CoMo catalyst, the support being
alumina.
20. The method of claim 1, wherein the isoparaffinic product has a
boiling point range of from about 150.degree. C. to about
300.degree. C.
Description
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0001] Not applicable.
CROSS-REFERENCE TO RELATED APPLICATIONS
[0002] The present application is a continuation of U.S.
application Ser. No. 12/062,970, filed Apr. 4, 2008, which claims
benefit under 35 U.S.C. 119(e) of U.S. Provisional Application Ser.
No. 60/910,573, filed Apr. 6, 2007, both of which are hereby
expressly incorporated herein by reference in their entirety.
FIELD OF THE INVENTION
[0003] The present invention generally relates to a method for
producing from a renewable feedstock an isoparaffinic product
useful in producing jet fuel and/or jet fuel blendstock
(hereinafter referred to as "jet fuel") or an LPG product. The
present invention also relates to the resultant jet fuel, whereby
the jet fuel has improved cold flow properties.
BACKGROUND OF THE INVENTION
[0004] Due to concerns with limited resources of petroleum-based
fuels, the demand for using renewable feedstock, such as vegetable
oils and animal fats, to produce hydrocarbon fuels has increased.
There are a number of well-known methods for making diesel fuels or
diesel fuel additives from renewable feedstock. Such methods,
however, have limitations, including producing fuels that are not
always acceptable for commercial use.
[0005] Additives for diesel fuels whereby the additives have high
cetane numbers and serve as fuel ignition improvers are known to
have been made. One method for making such additives includes
subjecting a biomass feedstock, such as tall oil, wood oil, animal
fats, or blends of tall oil with plant or vegetable oil, to a
hydroprocessing method to produce a product mixture. The product
mixture is then separated and fractionated to obtain a hydrocarbon
product that has a diesel fuel boiling range commensurate with
known diesel fuel products. This method results in an additive
product that is characterized as performing poorly at low
temperatures. In particular, the additive has a high cloud point at
25.degree. C.
[0006] Another method of making a hydrocarbon suitable for use as
diesel fuel includes subjecting a renewable feedstock, comprising
C8-C24 fatty acids, derivatives of C8-C24 fatty acids, or
combinations thereof, to a decarboxylation/decarbonylation reaction
followed by an isomerization reaction. The product of the
isomerization reaction is a hydrocarbon suitable for use as a
diesel fuel additive. This process also produces a product having a
high cetane value but poor low temperature properties, such as a
high cloud point at around 25.degree. C. As such, both mentioned
resultant products are useful as diesel fuel additives but not
usable as diesel or jet fuel replacements. Note that jet fuel
requires significantly better low temperature properties than
diesel. The cloud point is the temperature at which a fuel becomes
hazy or cloudy because of the appearance of crystals within the
liquid fuel.
[0007] A separate process produces a middle distillate fuel useful
as diesel fuel having a cloud point of -12.degree. C. from
vegetable oil. The process includes hydrogenating the fatty acids
or triglycerides of the vegetable oil to produce n-paraffins and
then isomerizing the n-paraffins to obtain branched-chain
paraffins. This process still suffers from a cloud point at a
temperature that is comparatively too high.
[0008] To date, there appear to be no processes that produce a fuel
having lower cold flow requirements, i.e., a cloud point lower than
-12.degree. C. In particular, there are no known processes to
produce a stand-alone jet fuel from a renewable feedstock. To this
end, it is to such a process and jet fuel composition that the
present invention is directed.
SUMMARY OF THE INVENTION
[0009] The present invention relates to a method for producing from
a renewable feedstock an isoparaffinic product useful for producing
a jet fuel. The renewable feedstock includes animal fats, vegetable
oils, plant fats and oils, rendered fats, restaurant grease, waste
industrial frying oils, fish oils, and combinations thereof.
[0010] The method for producing an isoparaffinic product useful as
jet fuel typically includes hydrotreating a renewable feedstock to
produce a hydrotreated heavy fraction and a light fraction. This is
followed by hydroisomerizing the hydrotreated heavy fraction to
produce a hydroisomerized heavy fraction and a light fraction. The
hydroisomerized heavy fraction is passed into a separator to remove
the isoparaffin product with the remainder recycled back into the
hydroisomerizing unit to produce an isoparaffinic product.
[0011] The method may also include fractionating the isoparaffinic
product to produce a jet fuel, as well as naphtha and liquefied
petroleum gas (LPG), which includes primarily propane, iso-butane,
n-butane, as well as small quantities of methane and ethane.
[0012] The resultant jet fuel product has improved cold flow
properties. In particular, the jet fuel product has a viscosity of
less than 5 centistokes at about -20.degree. C., a boiling range of
about 150.degree. C. to about 300.degree. C. and a freezing point
of less than about -47.degree. C.
[0013] A blended jet fuel composition of the present invention
includes 0.1 to 99% by volume of a renewable jet fuel and a balance
of at least one non-renewable resource.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a schematic diagram of a method for co-producing
an isoparaffinic product that may be fractionated into jet fuel,
naphtha, and LPG from a renewable feedstock.
[0015] FIG. 2 is a gas chromatogram of hydrotreater effluent,
showing absence of unconverted feed component and cracked
products.
DETAILED DESCRIPTION OF THE INVENTION
[0016] The present invention relates to a method for producing from
a renewable feedstock an isoparaffinic product that can then be
fractionated into a jet fuel or a liquefied petroleum gas (LPG)
fraction. The process is illustrated by FIG. 1, with the method
including hydrotreating the renewable feedstock to produce a
hydrotreated heavy fraction that includes n-paraffins. Next, the
hydrotreated heavy fraction, in particular the n-paraffins, is
isomerized to produce among other products, isoparaffins. The
method includes recycling a hydroisomerized heavy fraction back
through the hydroisomerization unit to produce the isoparaffin
product. The isoparaffin is then fractionated into a jet fuel and
an LPG fraction. The LPG fraction includes primarily propane,
iso-butane, n-butane, as well as small quantities of methane and
ethane. A jet fuel is produced from a renewable feedstock whereby
the jet fuel has improved cold flow properties.
[0017] The present method for co-producing an isoparaffinic product
useful as a jet fuel and an LPG fraction includes three steps, a
hydrotreating step, a hydroisomerization step, and a fractionation
step having recycle of the heavy hydroisomerization products. As
shown on FIG. 1, a renewable feedstock is initially fed to the
processing system. The renewable feedstock can include animal fats,
animal oils, vegetable fats, vegetable oils, plant fats, plant
oils, rendered fats, restaurant grease, waste industrial frying
oils, fish oil, and combinations thereof. It should be understood
by one of ordinary skill in the art that other oils can be used so
long as they are of a sufficient structure to be ultimately
converted into the isoparaffinic product. In particular, the
renewable feedstock includes triglycerides and free fatty acids.
Triglycerides are esters of fatty acids and have a formula of
CH.sub.2 (OOCR.sub.1) CH (OOCR.sub.2) CH.sub.2 (OOCR.sub.3), where
R.sub.1, R.sub.2, and R.sub.3 are typically of a different chain
length. Fatty acids have a formula of CH.sub.3 (CH.sub.2).sub.x
COOH and contain 4 to 22 carbon atoms.
[0018] Referring now to the process embodiment of FIG. 1, renewable
feedstock 101 is pressurized using pump 102 as stream 103 to a
hydrotreater 109 operating pressure of about 1,000 to about 2,000
psig (with pressures as low as about 500 psig and as high as about
2,500 psig also within the embodiment operating range). The
renewable feedstock liquid hourly space velocity through the
hydrotreater 109 is preferably in the about 0.5 to about 5 h.sup.-1
range. The hydrotreater 109 catalyst is preferably a sulfided
bimetallic catalyst such as NiW (nickel-tungsten), NiMo
(nickel-molybdenum), and CoMo (cobalt-molybdenum) on alumina
support. One suitable catalyst is sulfided NiMo on alumina.
However, it should be understood that any catalyst may be used so
long as the catalyst functions in accordance with the present
invention as described herein. The catalyst may be in the oxide
form and sulfided during startup, or pre-sulfided and active when
loaded into the hydrotreater 109. The liquid feedstock is then
heated through a hydrotreater feed-effluent exchanger 104. The
heated feed 105 is combined with hot product 106 from
hydroisomerizer reactor 148. The diluted renewable feedstock 107 is
then combined with hydrogen 108 before entering the hydrotreater
109. Due to the high oxygen content and unsaturation level of the
renewable feedstock, the exothermic hydrodeoxygenation and olefin
hydrogenation reactions may result in a higher than desired
adiabatic temperature rise. Quench hydrogen 110 may thus be used to
maintain the hydrotreater temperature between about 500.degree. F.
to about 700.degree. F. The gas to liquid ratio (renewable feed
basis) for the hydrotreating reaction is in the about 2,000 to
about 14,000 scf/bbl range.
[0019] The hydrotreater effluent 111 is subsequently cooled in
exchanger 104. A cooled stream 112 includes two phases. The vapor
phase includes hydrogen, propane, carbon oxides, and water. The
liquid phase is predominantly the middle distillate boiling range
paraffin product. The vapor and liquid phases are separated in
separator 113 as streams 114 and 128, respectively.
[0020] The vapor phase 114 is cooled in air cooler 115 to condense
the water. Wash water 114a may be introduced upstream to prevent
scale formation in the cooler. A cooler outlet stream 116 includes
liquid water, hydrogen/propane vapors, and condensed light
hydrocarbons (mainly C3-C9 paraffins). These three phases are
separated in drum 117. Hydrogen-rich vapors 119 are recycled, a
condensed hydrocarbon stream 129 is sent to the product recovery
unit, and a water stream 118 is sent off-site for treatment prior
to disposal or usage.
[0021] A liquid paraffin product 128 is combined with the condensed
light hydrocarbon stream 129 to form a fractionation feed 130. The
fractionation feed 130 includes a debutanizer tower 133, a naphtha
stripper 138, and a heavy paraffin recycle tower 141. The
fractionation feed 130 is preheated in exchanger 131. The heated
fractionation feed 132 is separated in the debutanizer tower 133
which is used to recover the LPG stream 136. The effluent 137 from
the debutanizer tower 133 is fed to the naptha stripper 138. The
naptha stripper 138 is used to separate naphtha as stream 139. The
high volatility, low flash point C5-C8 hydrocarbons are undesirable
in jet fuel. The effluent 140 of the naptha stripper 138 is fed to
the recycle tower 141. The recycle tower 141 is used to separate
the jet fuel 142 from the heavier paraffin stream 143. In a
preferred embodiment, the jet fuel 142 is mainly a C9-C15
isoparaffin composition, while the heavier stream 143 is a
C16.sup.+ n-paraffin composition. (For most renewable feedstocks
wherein C16 and C18 fatty acids predominate, the heavy paraffin
fraction is a C16-C18 composition; however, for renewable
feedstocks with significant C20 and C22 fatty acids, such as peanut
oil and rapeseed oil, respectively, the heavier paraffin stream may
be a C16-C20 and a C16-C22 composition.) The distillation columns
range in pressure from 200 psig (debutanizer tower 133) to
atmospheric or even vacuum (heavy paraffin recycle tower 141). The
corresponding operating temperatures are in the about 300.degree.
F. to about 650.degree. F. range. All the distillation towers are
equipped with condensers (134a-c) and reboilers (135a-c). The
condensers may be water- or air-cooled. For the higher temperature
tower 141, super-heated steam injection may be used instead of a
reboiler exchanger. It should also be noted that any two
distillation columns with similar pressures may be combined and one
of the products separated as a side-draw. Further, it should be
understood that any such combination of columns may be utilized so
long as the combination functions in accordance with the present
invention described herein.
[0022] The heavy paraffins 143 are pumped using pump 144 as stream
145 to hydroisomerizer reactor pressure, preferably about 1,000 to
about 2,000 psig, and combined with hydrogen 146. The hydrogen
containing heavier recycle stream 147 is then heated in heater 149
to the desired hydroisomerizer inlet temperature of about
580.degree. F. to about 680.degree. F. Suitable catalysts for the
hydroisomerizer reactor 148 are bifunctional catalysts with
hydrogenation and acidic functionalities. Such catalysts include
Group VIII metals on amorphous (e.g., silica-alumina) or
crystalline (e.g., zeolite) supports. One preferred
hydroisomerization catalyst is platinum, palladium or combinations
of same on an amorphous silica-alumina support. However, it should
be understood that any catalyst may be used in accordance with the
present invention so long as it functions as described herein.
Preferred gas to liquid ratios are in the about 1,000 to about
10,000 scf/bbl range, and liquid hourly space velocity in the about
0.2 to about 5 h.sup.-1 range. The product of the mainly C15-C18
feed, stream 106, is a C3-C18 isoparaffinic composition. This
isoparaffinic product stream acts as a solvent/diluent for the
hydrotreater feed.
[0023] Part of the hydrogen-rich vapor recycle stream 119 is purged
as stream 120. In some embodiments, the purge stream 120 is
processed through a membrane separator to recover additional
propane. The recycle hydrogen is processed through a purification
unit 121 where ammonia, hydrogen sulfide, and carbon dioxide
byproducts of hydrotreating are removed. Unit 121 may be a scrubber
with an amine or caustic solvent. Clean hydrogen 122 is combined
with makeup hydrogen 123 (pressurized through compressor 124) to
form hydrogen stream 125. Recycle compressor 126 supplies
pressurized hydrogen 127 to both hydrotreater (stream 108) and
hydroisomerizer (stream 146), including quench service (110 for
hydrotreater and 146b for hydroisomerizer).
[0024] The resultant feedstock jet fuel meets aviation fuel cold
flow properties. The jet fuel of the present invention, unlike its
petroleum and synthetic jet fuel counterparts, such as Jet A-1,
JP-8, and Fischer-Tropsch IPK Jet Fuel, has a lower viscosity, for
example, a viscosity at about -20.degree. C. of less than about 5
centistokes, with a higher isomer/normal mass ratio, as is detailed
in Example 2. Table 1 summarizes the iso/normal ratio for each
carbon group in the jet fuel composition of the present invention.
The jet fuel composition of the present invention has an iso/normal
ratio of about 3.0 to about 25.0. Typically, a higher isomer/normal
mass ratio leads to a jet fuel product having a higher viscosity.
That is not the case with the jet fuel of the present invention. It
is believed that the lower viscosity of the jet fuel of the present
invention is due to the distribution of the isomers in the
isoparaffinic product as calculated by a nuclear magnetic resonance
(NMR) apparatus.
TABLE-US-00001 TABLE 1 Iso/Normal Group Ratio by Group C6 0.25-2.0
C7 2.0-3.0 C8 2.0-3.0 C9 2.0-3.5 C10 3.0-4.5 C11 4.0-5.0 C12
4.5-5.5 C13 4.5-6.0 C14 4.5-6.0 C15 5.0-6.5 C16 10.0-22.sup. C17
11.0-22.sup.
[0025] The feedstock jet fuel of the present invention also has a
higher flash point than that required for JP-8 and Jet A-1, a lower
viscosity and freezing point, and a higher smoke point. The jet
fuel is almost sulfur-free and produces a higher heat of combustion
than JP-8 and Jet A-1. In particular, the jet fuel of the present
invention has a flash point of greater than about 38.degree. C. and
greater than about 45.degree. C. One embodiment of the jet fuel of
the present invention has a boiling point range between about
150.degree. C. and about 300.degree. C., and a viscosity at about
-20.degree. C. of less than about 5 centistokes. The jet fuel of
the present invention also has a heat of combustion of greater than
about 42 MJ/kg and a smoke point of greater than about 25 mm. The
jet fuel has a freezing point of less than about -47.degree. C.,
less than about -50.degree. C., and less than about -55.degree. C.
The jet fuel also has a sulfur content of less than about 5 ppm,
preferably less than about 2 ppm.
[0026] Jet fuel is exposed to very low temperatures, both at
altitude--especially on polar routes in wintertime--and on the
ground at locations subject to cold weather extremes. Consequently,
the fuel must retain its fluidity at these low temperatures or fuel
flow to the engines will be reduced or even stop. Viscosity is a
measure of a liquid's resistance to flow under pressure, generated
either by gravity or a mechanical source.
[0027] As such, jet fuel must be able to flow freely from fuel
tanks in the wings to the engine through an aircraft's fuel system.
Fluidity is a general term that deals with the ability of a
substance to flow, but it is not a defined physical property.
Viscosity and freezing point are the physical properties used to
quantitatively characterize the fluidity of jet fuel.
[0028] Jet fuel at high pressure is injected into the combustion
section of the turbine engine through nozzles. This system is
designed to produce a fine spray of fuel droplets that evaporate
quickly as they mix with air. The spray pattern and droplet size
are influenced by fuel viscosity. If the viscosity is too high, an
engine can be difficult to relight in flight. For this reason, jet
fuel specifications place an upper limit on viscosity.
[0029] Despite conforming to jet fuel specifications, the renewable
isoparaffinic jet fuel of the present invention may need to be
blended with conventional petroleum jet fuel for use in existing
aircraft. Due to absence of aromatic components, the isoparaffinic
jet fuel does not swell the nitrile rubber closure gaskets of the
fuel tank. Without swelling of the closure gasket, a tight seal is
not achieved and fuel may leak out. Blending with petroleum fuel
addresses this issue. In the present invention, the blended jet
fuel composition is from about 0.01% to about 99% by volume and the
balance being from at least one non-renewable source.
[0030] In order to further illustrate the present invention, the
following examples are given. However, it is to be understood that
the examples are for illustrative purposes only and are not to be
construed as limiting the scope of the subject invention.
EXAMPLES
Example 1
Process of Making a Jet Fuel from Renewable Sources
[0031] The present example demonstrates how a jet fuel was made
from a renewable feedstock. A 100 cc isothermal tubular reactor was
filled with 80 cc of Criterion 424 Ni--Mo catalyst and +70-100 mesh
glass beads. The catalyst was sulfided with dimethyl disulfide at
two hold temperatures: 6 hours at 400.degree. F. and 12 hrs at
650.degree. F. Hydrogen sulfide break-through was confirmed before
the temperature was raised from 400.degree. F. to 650.degree. F. at
50.degree. F./hr. After sulfiding, the reactor was cooled to
400.degree. F.
[0032] Next a triglyceride/fatty acid feed was introduced to the
isothermal reactor. The reactor was slowly heated to 650.degree. F.
to achieve full conversion of the triglyceride/fatty acid feed to
n-paraffins. The reactor temperature was further increased to
700.degree. F. to maintain good catalyst activity at 80 cc/hr feed
rate (1 LHSV).
[0033] The total liquid hydrocarbon (TLH) from the hydrotreater was
then hydroisomerized to jet fuel using the conditions summarized in
the last column of Table 2 to produce an isoparaffinic product
useful as jet fuel. The hydrotreater performance with beef tallow
as the triglyceride/fatty acid feed is also summarized in Table
2.
TABLE-US-00002 TABLE 2 Hydrotreater and Hydroisomerizer Operating
Conditions and Conversion Performance Hydrotreater Hydroisomerizer
Catalyst Active Metals Sulfided Ni/Mo Pt/Pd Support Alumina
Alumina/silica Reactor Conditions Feed Inedible tallow TLH from
inedible tallow hydrotreating Temperature (F.) 700 685 Pressure
(psig) 1,200 1,000 Gas/Oil Ratio (scf/bbl) 14,000 10,000 LHSV 1
0.75 Products (wt % feed basis) C1 + C2 1.5 0.13 LPG (C3 + C4) 6.1
8.6 Water 5.3 0 Total Liquid Hydrocarbons 88.2 91 (TLH)
Example 2
[0034] The hydrotreated effluent was analyzed using a gas
chromatogram. In particular, the total liquid hydrocarbon (TLH)
from the hydrotreater reaction of Example 1 was analyzed to confirm
triglyceride conversion, and quantify cracking to light ends.
[0035] The gas chromatogram utilized the following materials:
[0036] Materials:
[0037] Analytical Balance, capability to 0.1 mg
[0038] Carbon Disulfide, High Purity
[0039] Custom Alkane Standard--Restek Cat #54521
[0040] Pasteur Pipette with bulb
[0041] HP 5860 Gas Chromatograph--FID
[0042] GC Column, Restek--Rtx--1 MS, Cat #11624
[0043] Helium Gas--Alpha Gas
[0044] Hydrogen Gas--Alpha Gas
[0045] Zero Air Gas--Alpha Gas
[0046] Sharpie
[0047] GC Vials and Caps
[0048] The gas chromatogram was operated under the following
conditions:
[0049] Runtime 82 minutes
[0050] Injection Volume 1-pL
[0051] Inlet Temperature 320.degree. C.
[0052] Detector Temperature 350.degree.
[0053] Oven: [0054] Initial Temperature 35.degree. C. [0055] Rate
(.degree. C./min) 5.00 [0056] Equilibrate Time 0.20 min [0057]
Final Temperature 320.degree. C. [0058] Final Time (min) 25.0 As
observed in the chromatogram of FIG. 2, virtually no triglycerides
or cracked products were present in the TLH. Note the areas
circled.
Example 3
Jet Fuel from Renewable Sources
[0059] The resultant jet fuel and the isoparaffinic product from
Example 1 was analyzed and compared to similar products. The
feedstock jet fuel was found to have a cloud point of -53.degree.
C.
[0060] The composition of the isoparaffinic product was analyzed
via Gas Chromatograph and is summarized in Table 3. A key property
to observe is iso/normal ratio. The procedure employed to determine
iso/normal ratio is shown below. As indicated by Table 3 data, the
hydroisomerizer product may be fractionated to the desired jet fuel
boiling range. Such separation was performed using standard lab
distillation apparatus. The comparable properties of
Fischer-Tropsch IPK jet fuel distillate are summarized in Table 5.
As observed from Table 4, the renewable jet fuel of this invention
met or exceeded all key specifications of commercial jet fuel.
TABLE-US-00003 TABLE 3 Carbon Number Distribution and Iso/Normal
Ratio of Hydroisomerizer Product Iso/Normal Normal Isomer Normal
Ratio by Mass % Group MW Mass % Mass % Mass % Group by Group C6
86.2 0.8% 0.0% 0.8% 0.00 100.0 C7 100.2 3.9% 2.6% 1.3% 2.07 32.6 C8
114.2 6.6% 4.9% 1.7% 2.87 25.9 C9 128.3 9.3% 7.4% 1.9% 3.97 20.1
C10 142.3 11.5% 9.7% 1.7% 5.57 15.2 C11 156.3 12.5% 11.0% 1.5% 7.41
11.9 C12 170.3 12.1% 10.9% 1.3% 8.71 10.3 C13 184.4 10.4% 9.5% 0.9%
10.41 8.8 C14 198.4 8.5% 7.6% 0.9% 8.86 10.1 C15 212.4 9.5% 8.4%
1.1% 7.75 11.4 C16 226.5 8.5% 7.7% 0.7% 10.50 8.7 C17 240.5 5.3%
5.0% 0.3% 15.98 5.9 C18 254.5 1.1% 1.1% 0.0% 23.91 4.0 TOTAL 100.0%
85.9% 14.1% 6.12 Narrow Jet 73.8% 64.6% 9.2% 7.01 (C9-C15) Broad
Jet 88.9% 77.2% 11.7% 6.62 (C8-C16)
[0061] The iso/normal ratio is derived by processing GC data. Data
is first captured from the chromatogram, then it is compared to
standard libraries. Next, the amount of normal paraffin present for
each carbon number was calculated. Then, the amount of iso-paraffin
present for each carbon number was calculated. Finally, the ratio
for each carbon number was calculated.
TABLE-US-00004 TABLE 4 Jet Fuel Properties of Example Bio-jet
Product Compared to Other Synthetic Jet Fuels and Industry
Specifications ASTM D 1655 MIL-3133E Fischer-Tropsch Example Bio-
Property Units Jet A-1 JP-8 IPK Jet Fuel Jet Product Flash Point
.degree. C. 38 min. 38 min. 46 47 Distillation EP .degree. C. 300
max. 300 max. 280 275 Viscosity cSt 8.0 max. 8.0 max. 5.5 4.58 @
-20.degree. C. Freezing Point .degree. C. -47 max. -47 max. -48 -55
Density g/ml 0.775-0.840 0.775-0.840 0.76 0.76 Heat of MJ/kg 42.8
min. 42.8 min. 43.8 44.2 Combustion Smoke Point Mm 25 min. 25 min.
>50 33.4 Sulfur ppm 3,000 max. 3,000 max. <1 1.2 Hydrogen
Mass % none 13.4 min. 15.4 15.3 Color (Saybolt) -- none report +30
+30
TABLE-US-00005 TABLE 5 Carbon Number Distribution and Iso/Normal
Ratio of Fischer-Tropsch IPK Jet Fuel Iso/Normal Normal Isomer
Normal Ratio by Mass % Group MW Mass % Mass % Mass % Group by Group
C6 86.2 0.0% 0.0% 0.0% 0.59 62.9 C7 100.2 0.6% 0.4% 0.2% 2.16 31.7
C8 114.2 1.9% 1.3% 0.6% 2.13 32.0 C9 128.3 7.2% 4.8% 2.4% 2.02 33.2
C10 142.3 17.8% 13.9% 3.9% 3.57 21.9 C11 156.3 20.2% 16.4% 3.9%
4.25 19.1 C12 170.3 17.1% 14.2% 2.9% 4.88 17.0 C13 184.4 15.2%
12.8% 2.4% 5.46 15.5 C14 198.4 10.8% 9.0% 1.8% 4.89 17.0 C15 212.4
6.3% 5.3% 1.0% 5.41 15.6 C16 226.5 2.6% 2.4% 0.1% 21.33 4.5 C17
240.5 0.4% 0.4% 0.0% 11.77 7.8 C18 254.5 0.0% 0.0% 0.0%
[0062] Thus, there has been shown and described a method for
producing a jet fuel or LPG product from a renewable source and the
resultant product that fulfills all objectives and advantages
sought therefore.
[0063] The invention illustratively disclosed herein suitably may
be practiced in the absence of any element which is not
specifically disclosed herein. Further review of the two jet fuels
reveals that they are very similar in average carbon number (11.8
and 12.0 for the FT and renewable, respectively). Also, in the case
of the FT jet fuel, the hydroisomerization conditions were
703.degree. F. catalyst average temperature, LHSV of 0.83/hr (fresh
feed basis) and G/O ratio of 3,000 SCF/BBL with overall system
pressure of about 986 psig with the same catalyst (Pt/Pd on
alumina/silica). It is surprising that the processing conditions of
the present invention resulted in substantially different low
temperature property performance; that is, that the renewable jet
fuel would have had lower viscosity than the FT jet fuel product
based upon the difference in processing conditions.
[0064] From the above description, it is clear that the present
invention is well-adapted to carry out the objects and to attain
the advantages mentioned herein, as well as those inherent in the
invention. While presently preferred embodiments of the invention
have been described for purposes of this disclosure, it will be
understood that numerous changes may be made which will readily
suggest themselves to those skilled in the art and which are
accomplished within the spirit of the invention disclosed and
claimed.
[0065] Those skilled in the art will appreciate that variations
from the specific embodiments disclosed above are contemplated by
the present invention. Specifically, the improvement in cold-flow
performance of the renewable jet fuel was not anticipated based
upon extensive experience with Fischer-Tropsch feedstocks. The
typical Fischer-Tropsch feedstock to a hydroisomerization process
is about 85-99 wt % normal paraffin. The feedstock to the renewable
isomerization process is >95 wt % normal paraffin. The
distribution of isomers and the nature of the branching in those
isomers (as indicated by NMR) is different for the renewable
feedstock versus the Fischer-Tropsch feedstock. The invention
should not be restricted to the above embodiments, but should be
measured by the following claims.
* * * * *