U.S. patent application number 11/149769 was filed with the patent office on 2006-12-14 for low foaming distillate fuel blend.
This patent application is currently assigned to Chevron U.S.A. Inc.. Invention is credited to Graham Nancekievill, Dennis J. O'Rear, Jeffrey J. Toman.
Application Number | 20060278565 11/149769 |
Document ID | / |
Family ID | 37523173 |
Filed Date | 2006-12-14 |
United States Patent
Application |
20060278565 |
Kind Code |
A1 |
Toman; Jeffrey J. ; et
al. |
December 14, 2006 |
Low foaming distillate fuel blend
Abstract
A distillate fuel composition having low foaming characteristics
and process for making the composition is described. The
composition and process uses Fischer Tropsch distillates to reduce
the foaming in distillate fuels. The use of Fischer Tropsch
distillates to control foaming in distillate fuels reduces or
eliminates the need to use silicon anti-foam agents. A preferred
composition comprises at least 20 vol. % of a petroleum derived
distillate having a foam vanishing time greater than 20 seconds;
and at least 5 vol. % of a Fischer-Tropsch derived distillate
having a foam vanishing time of less than 15 seconds; where the
resulting distillate fuel blend has a foam vanishing time of 15
seconds or less in the absence of an antifoam additive.
Inventors: |
Toman; Jeffrey J.; (Oakland,
CA) ; O'Rear; Dennis J.; (Petaluma, CA) ;
Nancekievill; Graham; (Felixstowe, GB) |
Correspondence
Address: |
CHEVRON TEXACO CORPORATION
P.O. BOX 6006
SAN RAMON
CA
94583-0806
US
|
Assignee: |
Chevron U.S.A. Inc.
|
Family ID: |
37523173 |
Appl. No.: |
11/149769 |
Filed: |
June 10, 2005 |
Current U.S.
Class: |
208/17 |
Current CPC
Class: |
C10L 1/04 20130101; C10L
1/08 20130101 |
Class at
Publication: |
208/017 |
International
Class: |
C10L 1/04 20060101
C10L001/04 |
Claims
1. A distillate fuel blend, comprising: at least 20 vol. % of a
petroleum derived distillate having a foam vanishing time greater
than 20 seconds; and at least 5 vol. % of a Fischer-Tropsch derived
distillate having a foam vanishing time of less than 15 seconds;
wherein the resultant distillate fuel blend has a foam vanishing
time of 15 seconds or less in the absence of an antifoam
additive.
2. A process for making a distillate fuel blend, comprising:
selecting a petroleum derived distillate having a foam vanishing
time greater than 20 seconds; and blending an amount of a
Fischer-Tropsch derived distillate having a foam vanishing time of
less than 15 seconds sufficient to achieve a distillate fuel blend
having a foam vanishing time of 15 second or less.
3. A distillate fuel blend according to claim 1 wherein the
petroleum derived distillate has a foam vanishing time in excess of
25 seconds.
4. A distillate fuel blend according to claim 1 wherein the
petroleum derived distillate has a foam vanishing time in excess of
30 seconds.
5. A distillate fuel blend according to claim 1 wherein the
petroleum derived distillate has a foam vanishing time in excess of
40 seconds.
6. A distillate fuel blend according to claim 1 wherein the
Fischer-Tropsch derived distillate has a foam vanishing time of
less than 12 seconds.
7. A distillate fuel blend according to claim 1 wherein the
Fischer-Tropsch derived distillate has a foam vanishing time of
less than 10 seconds.
8. A distillate fuel blend according to claim 1 wherein the
Fischer-Tropsch derived distillate has a foam vanishing time of
less than 8 seconds.
9. A distillate fuel blend according to claim 1 wherein the
petroleum derived distillate has a foam vanishing time in excess of
50 seconds.
10. A distillate fuel blend according to claim 1 wherein the
resultant distillate fuel blend is diesel fuel.
11. A distillate fuel blend according to claim 1 wherein the
resultant distillate fuel blend is jet fuel.
12. A distillate fuel blend according to claim 1 wherein the
Fischer Tropsch derived distillate contains less than 1 ppm
nitrogen, less than 1 ppm sulfur and less than 100 ppm oxygen as
oxygenates.
13. A distillate fuel blend according to claim 1 wherein the
Fischer Tropsch derived distillate fuel contains less than 25 ppm
oxygen as oxygenates.
14. A distillate fuel blend according to claim 1 comprising between
5 vol. % and 30 vol. % of a Fischer-Tropsch derived distillate.
15. A distillate fuel blend according to claim 1 comprising between
5 vol. % and 20 vol. % of a Fischer-Tropsch derived distillate.
16. The process of claim 2 wherein an antifoam additive is added to
the distillate fuel blend having a foam vanishing time of 15 second
or less.
17. A distillate fuel blend according to claim 1, further
comprising addition of an antifoam additive to the resultant
distillate fuel blend.
18. The process of claim 2 wherein the Fischer-Tropsch derived
distillate has a foam vanishing time of less than 12 seconds.
19. The process of claim 2 wherein the petroleum derived distillate
has a foam vanishing time in excess of 25 seconds.
20. A distillate fuel blend according to claim 1 wherein the
resultant distillate fuel blend is a dual use fuel.
Description
BACKGROUND OF THE INVENTION
[0001] Foam can form in distillate fuels during movement or
agitation of the fuels. Foam formation in distillate fuels can be a
particular problem during transfer of the fuel such as when filling
of tanks in vehicles, service stations, terminals and other
operations. When foam is generated during fueling of a vehicle, it
can cause the fill sensors on the fuel nozzle to shut off the flow
of fuel. When the foam breaks, fueling of the vehicle can continue.
However, this can be a very frustrating experience for the
customer, can cause delays in fueling, and can result in only
partial filling of the vehicle fuel tank. Foaming can also lead to
spilled fuel which creates a potential safety concern from
potential fires, slipping on a fuel-wetted surface, as well as an
environmental hazard. In order to minimize foaming, silicon
antifoam agents are often used in distillate fuels, especially in
Europe where the problem of foaming is more common. Silicon
antifoam agents are typically used in the range of 0.1-20 ppm
(weight), most commonly 1-10 ppm. Despite their low concentration,
silicon antifoam agents can be one of the most expensive additives
in distillate fuels. Silicon antifoam agents have also been
associated with deposits on injector nozzles and potentially are a
concern for other engine problems.
[0002] The World Wide Fuel Charter of December 2002 describes an
emerging specification for diesel fuels. It defines various
categories with Number Three being for "Markets with advanced
requirements for emission controls or other market demands" and
Number four being for "Markets with further advanced requirements
for emission control, to enable sophisticated NOx and PM
after-treatment technologies." See pages 15 and 16. The proposed
requirements for foaming for Category 3 and 4 diesel fuel--a
maximum of 100 ml of foam and a foam vanishing time of 15 seconds
or less as determined by NF M 07-075--see page 9. Of the two
measurements of foam, the vanishing time is felt to be the most
appropriate indicator of performance. Further discussion of diesel
foaming is on pages 45-46. Page 46 states the goal of selection of
additives to control foaming: "it is important that the eventual
additive chosen should not pose any problems for the long-term
durability of the emission post-treatment control systems."
[0003] GE Silicons is a supplier of silicon antifoam additives. In
their brochure on their product SAS.RTM.TP-325 they state that this
additive is " . . . a major step towards minimizing the potential
risks of silica deposits in engine car injectors."
[0004] Thus while silicon antifoam agents are effective in
controlling foaming, they are expensive and have been indicated in
problems associated with both emission control systems and
injectors. Approaches to minimize or eliminate their use are
desirable.
[0005] Art that relates to the control of foaming in hydrocarbon
fuels includes U.S. Pat. No. 4,690,688 to Adams et al. which
relates to the use of certain siloxane polyoxyalkylene copolymers
as antifoaming agents in diesel and jet fuel. Another patent that
relates to silicone foam control agents is U.S. Pat. No. 5,620,485
(Fey). A patent that relates to Diesel Fuel and Lubricating oil
antifoams and methods of their use is U.S. Pat. No. 6,221,815
(Grabowski et al.). A patent that provides a method for reducing
foaming of lubricating oils is U.S. Pat. No. 6,090,758 (Pillion et
al.). A patent that provides antifoaming agents of lubricating oils
is U.S. Pat. No. 5,766,513 to Pillion et al. Another patent that
describes silicone antifoam compositions is U.S. Pat. No. 5,531,929
(Kobayashi). A patent that describes a device for the controlled
release of antifoaming agents in the diesel fuel tank filling
nozzle is U.S. Pat. No. 4,687,034, Graiff et al. The patents listed
above all provide background and some theory on the problem of
hydrocarbon foam formation and provide various solutions to the
problem. They all also use silicon based antifoams (in various
forms) and highlight some of the problems associated with the use
of silicon based antifoams. The present invention provides an
alternative to the use of high levels of silicon based antifoams or
the elimination of the use of silicon based antifoams entirely
hence minimizing the problems/costs associated with silicon based
antifoam use.
[0006] Art that relates to blends of Fischer-Tropsch and petroleum
distillate for fuels includes U.S. Pat. Nos. 6,663,767 and
6,822,131 (Berlowitz et al.). A European patent that relates to
diesel or turbine engine fuels consisting of a mixture of petroleum
refinery hydrocarbons and Fischer-Tropsch hydrocarbons is EP
1,365,007 (Pavoni) which is incorporated by reference herein in its
entirety. Another patent that provides teachings about distillate
fuel blends from Fischer Tropsch products is U.S. Pat. No.
6,890,423 (O'Rear) which is also incorporated herein by reference
in its entirety.
[0007] As mentioned above silicone-containing anti-foams ("silicon
based anti-foams") are an integral part of diesel packages in
Europe. However, there is a great demand for a non-silicon based
anti-foam product, or a reduced need to use silicon based
anti-foams since several problems are associated with silicon based
anti-foams. For example, silicone anti-foams can separate from the
diesel fuel package due to poor solubility. This causes
inconsistent fuel and anti-foam performance. Excess silicon
anti-foam may need to be added to consistently achieve the desired
low level of foaming. Furthermore, silicone anti-foams can
contribute to the dispersion of sediments (rust, water, etc.) into
the diesel fuel. This may increase emissions and cause damage to
the engine. Additionally, there is some concern that the silicone
anti-foams themselves contributes to engine deposits and emissions.
Lastly, silicones can lose their effectiveness as an anti-foam
after the treated diesel fuel package has been stored for just a
few days unless a high dosage is charged.
[0008] Thus there is a need to develop a fuel that either does not
require anti-foam additives (particularly silicon based anti-foams)
or requires only reduced amounts of antifoam additives. The present
invention provides such a fuel.
SUMMARY OF THE INVENTION
[0009] The present invention provides a distillate fuel composition
and a process for making a distillate fuel having improved foaming
properties. As discussed above in the Background foaming can be a
serious problem in distillate fuels particularly during transfer of
fuel such as but not limited to fueling of a vehicle. The present
invention seeks to provide a distillate fuel having low foaming
characteristics and a process for reliably and consistently making
low foaming distillate fuels with reduced need for anti-foaming
additives or preferably without any anti-foaming additives.
[0010] In a preferred embodiment of the present invention a
distillate fuel blend is provided, comprising: [0011] at least 20
vol. % of a petroleum derived distillate having a foam vanishing
time greater than 20 seconds; and [0012] at least 5 vol. % of a
Fischer-Tropsch derived distillate having a foam vanishing time of
less than 15 seconds; wherein the resultant distillate fuel blend
has a foam vanishing time of 15 seconds or less in the absence of
an antifoam additive.
[0013] The present invention also provides a process for making
distillate fuel having improved foaming characteristics,
comprising: combining a petroleum derived distillate fuel having a
foam vanishing time greater than 20 seconds with a Fischer-Tropsch
derived distillate having a foam vanishing time of less than 15
seconds to form a distillate fuel blend having a distillate fuel
blend having a foam vanishing time of 15 seconds or less in the
absence of an antifoam additive.
[0014] As mentioned above an antifoam may be used in the present
invention however following the teaching of the present invention
will allow the use of antifoam additives to be reduced if not
eliminated entirely. It is advantageous to reduce the amounts of
antifoam additives used in a distillate to avoid some or all of the
negative effects of antifoam additives (particularly silicon based
antifoams) that are discussed in the Background section of this
application. Another embodiment of the present invention comprises
an improved distillate fuel composition for the prevention of
foaming during fuel transfer, wherein the improvement comprises
blending an effective amount of a FT derived distillate, with a
petroleum derived distillate having a foam vanishing time of above
20 seconds, sufficient to achieve a blended distillate fuel having
a foam vanishing time of 15 seconds or less in the absence of an
antifoam additive.
[0015] We have discovered that Fischer Tropsch distillate can be
used to control foaming when used with petroleum distillate fuel
components which exhibit foam formation in excess of 15 seconds of
vanishing time. This technology is useful for petroleum derived
distillate fuels that have a foam vanishing time in excess of 15
seconds, preferably in excess of 20 seconds, more preferably in
excess of 25 seconds, still more preferably in excess of 30
seconds, and most preferably in excess of 50 seconds.
[0016] Optionally a silicon based antifoam agent can be added to
further reduce foam formation or provide a safety margin.
Preferably less silicon based antifoam agent can be used when
employing the teachings of the present invention.
[0017] In the present invention the volume fraction of Fischer
Tropsch distillate in the blend (x) is less than or equal to 0.7
(70 vol. %), preferably less than or equal to 0.5 (50 vol. %), more
preferably greater than or equal to 0.05 (5 vol. %) and less than
or equal to 0.4 (40 vol. %), still more preferably between about
0.05 (5 vol. %) and 0.3 (30 vol. %), even more preferably between
about 0.05 (5 vol. %) and 0.25 (25 vol. %),still more preferably
between about 0.05 (5 vol. %) and 0.20 (20 vol. %), and most
preferably between about 0.10 (10 vol. %) and 0.20 (20 vol. %).
[0018] Not to be limited by theory the improvement (decrease) of
foam vanishing time by blending of Fischer-Tropsch derived
distillate with a petroleum derived distillate appears to be
non-linear and not simply a dilution effect. Thus significant
improvements in foaming in a blend can be achieved by use of less
Fischer-Tropsch derived distillate than might be expected.
[0019] As mentioned above the response of foam vanishing time to
addition of Fischer Tropsch distillate has been found to be highly
non-linear. The reduction in vanishing time when adding a
Fischer-Tropsch distillate is greater than what one would calculate
from a linear blend.
[0020] With a target foam vanishing time (Y), a measured vanishing
time of the petroleum-derived distillate (A) and a measured
vanishing time of the Fischer Tropsch derived distillate of B, the
volume fraction of Fisher Tropsch derived distillate fuel required
to at least reach the target vanishing time is x<(Y-A)/(B-A)
According to an embodiment of the present invention a method to
decrease the foam vanishing time of a petroleum-derived distillate
product to a target vanishing time Y is by adding to the
petroleum-derived distillate product an amount of a Fischer-Tropsch
derived distillate product having a lower vanishing time, B, than
the vanishing time of the petroleum-derived distillate product, A,
wherein the amount of added Fischer-Tropsch derived distillate
product is less than the amount which would be added if linear
blending is assumed.
[0021] In this embodiment of the present invention one can
determine the maximum amount of Fischer-Tropsch distillate that is
required to be added to a petroleum distillate to at least meet a
desired foam vanishing time. The volume fraction of Fischer-Tropsch
distillate product that is required, to at least achieve the foam
vanishing time of the blend, is less than x', wherein x' is the
target volume fraction that would be added if linear blending
assumptions would have been made according to the following
equation: Y=A+x'(B-A).
[0022] Among other factors the present invention is based on the
surprising finding that a relatively small amount of
Fischer-Tropsch derived distillate added to a petroleum derived
distillate can have a substantial effect on the foam vanishing time
of the blend. The teachings of the present invention can be used to
make distillate fuel blend compositions having desired low foam
vanishing times. Surprisingly low foam distillate fuel can be made
by blending a Fischer-Tropsch distillate with a petroleum derived
distillate without the use of an antifoam additive or with minimal
use of an antifoam additive while still meeting foam vanishing time
requirements for a finished fuel.
DETAILED DESCRIPTION OF THE INVENTION
[0023] In a preferred embodiment of the present invention a process
is provided for making a distillate fuel blend having improved
foaming characteristics, comprising: [0024] selecting a petroleum
derived distillate having a foam vanishing time greater than 20
seconds; and [0025] blending an amount of a Fischer-Tropsch derived
distillate having a foam vanishing time of less than 15 seconds
sufficient to achieve a distillate fuel blend having a foam
vanishing time of 15 second or less. Using the teachings of the
present invention it is possible to decrease or eliminate entirely
the use of anti foam additives such as silicon based antifoams.
Elimination or reduction of antifoam additives is quite desirable
for economic as well as performance reasons. These reasons are
discussed in detail in the background section of this application.
Surprisingly, the use of Fischer-Tropsch derived distillate having
a foam vanishing time of less than 15 seconds, blended with
petroleum derived distillate having a high foam vanishing time, can
result in a distillate fuel blend having greatly reduced foaming
characteristics as expressed in foam vanishing time.
[0026] In the present invention the Fischer-Tropsch derived
distillate should have a low foam vanishing time, preferably less
than 15 seconds, more preferably less than 12 seconds, still more
preferably less than 10 seconds, most preferably less than 8
seconds.
[0027] The terms "distillate fuel, distillate fuel fraction,
petroleum derived distillate, Fischer-Tropsch derived distillate"
means a hydrocarbon with boiling points between about 250 degrees
F. and 1100 degrees F., preferably 300 degrees F. and 700 degrees
F. The preferred method to measure boiling ranges is with ASTM
D2887 or for materials with Final Boiling Points greater than
1000.degree. F. ASTM D6352. The lower value of the boiling range is
the Initial Boiling Point (IBP) and the higher value of the boiling
range is the Final Boiling Point (FBP). While not preferred, ASTM
D-86 and ASTM D1160 can be used, but their results must be
converted to True Boiling Points (TBP) for comparison. The term
"distillate" means that typical conventional fuels of this type can
be generated from vapor overhead streams of petroleum crude
distillation or Fischer-Tropsch derived hydrocarbons. In contrast,
residual fuels cannot be generated from vapor overhead streams of
petroleum crude distillation, and are a non-vaporizable remaining
portion. Within the broad category of distillate fuels are specific
fuels that include: naphtha, jet fuel, diesel fuel, kerosene,
aviation gasoline, fuel oil, and blends thereof. Distillate fuel as
used herein may mean distillate fuels prepared by Fischer Tropsch
processes as well as distillate fuels generated from conventional
petroleum crude distillation as appropriate in the context.
[0028] A salable distillate fuel is a distillate fuel meeting the
specifications for one or more of naphtha, jet fuel, diesel fuel,
kerosene, aviation gas, fuel oil, and blends thereof.
[0029] The terms "Fischer-Tropsch derived distillate, petroleum
derived distillate and distillate fuel blend component" are
components which can be used with other components, to form a
salable distillate fuel meeting at least one of the specifications
for naphtha, jet fuel, diesel fuel, kerosene, aviation gas, fuel
oil, and blends thereof, especially diesel fuel or jet fuel, and
most especially diesel fuel. The component by itself does not need
to meet all specifications for the distillate fuel, only the
salable distillate fuel needs to meet the specifications.
[0030] In a preferred embodiment of the present invention the
Fischer Tropsch distillate is made in a Low Temperature Fischer
Tropsch (LTFT) process. Most preferably the Fischer Tropsch
distillate is made using a cobalt catalyst and operated in the
slurry bed mode.
[0031] For the purposes of the present invention the terms "foam
vanishing time, foam release time, and time of disappearance of
foam" are equivalent and are measured using the protocol described
in AFNOR NFMO7-075. The test method of the AFNOR French Standards
Organization can be obtained from AFNOR, 11 avenue Francis de
Pressense, 93571 Saint-Denis La Plaine Cedex (France). Their web
site is http://www.afnor.fr.
[0032] A diesel fuel is a material suitable for use in diesel
engines and conforming to at least one of the following
specifications: [0033] ASTM D 975-"Standard Specification for
Diesel Fuel Oils" [0034] European Norm EN590. [0035] Japanese Fuel
Standards JIS K 2204. [0036] The United States National Conference
on Weights and Measures (NCWM) 1997 guidelines for premium diesel
fuel. [0037] The United States Engine Manufacturers Association
recommended guidelines for premium diesel fuel (FQP-1A). A jet fuel
is a material suitable for use in turbine engines for aircraft or
other uses meeting at least one of the following specifications:
[0038] ASTM D1655. [0039] DEF STAN 91-91/3 (DERD 2494), TURBINE
FUEL, AVIATION, KEROSENE TYPE, JET A-1, NATO CODE: F-35. [0040]
International Air Transportation Association (IATA) Guidance
Materials for Aviation, 4.sup.th edition, March 2000.
[0041] The term "petroleum-derived diesel components", "petroleum
derived distillate" or "petroleum-derived distillate" means the
vapor overhead streams from distilling petroleum crude directly or
with intermediate refinery processing steps. A source of the
petroleum-derived crude can also be from a gas field condensate.
Other processing steps may also be employed in the refining of
petroleum crude such as but not limited to hydroprocessing,
hydrocracking, hydrotreating, alkylation, oligomerization,
catalytic reforming resulting in "petroleum-derived diesel
components", "petroleum derived distillate" or "petroleum-derived
distillate".
[0042] A highly paraffinic distillate fuel component is a
distillate fuel component that contains more than 70 wt. %
paraffins, preferably more than 80 wt. % paraffins, and most
preferably more than 90 wt % paraffins.
[0043] A distillate-boiling Fischer Tropsch product is a product
derived from a Fischer Tropsch process that boils within 60.degree.
F. and 11000.degree. F., preferably boiling between 250 and
700.degree. F. This stream is typically converted to a highly
paraffinic distillate fuel component by processes that may include
one or more additional step selected from the group consisting of
isomerization, hydroprocessing, hydrocracking, and
hydrotreating.
[0044] A heavy Fischer Tropsch product is a product derived from a
Fischer Tropsch process that can boil above the range of commonly
sold distillate fuels: naphtha, jet or diesel fuel. This means
greater than 400.degree. F., preferably greater than 550.degree.
F., and most preferably greater than 700.degree. F. This stream is
typically converted to a highly paraffinic distillate fuel
component by processes that include a hydrocracking step.
[0045] Syngas is a mixture that includes both hydrogen and carbon
monoxide. In addition to these species, water, carbon dioxide,
unconverted light hydrocarbon feedstock and various impurities may
also be present.
[0046] According to the present invention, a portion of the fuel
blend components of the present invention may be obtained from
Fischer Tropsch processes. In Fischer-Tropsch chemistry, syngas is
converted to liquid hydrocarbons by contact with a Fischer-Tropsch
catalyst under reactive conditions. Typically, methane and
optionally heavier hydrocarbons (ethane and heavier) can be sent
through a conventional syngas generator to provide synthesis gas.
Generally, synthesis gas contains hydrogen and carbon monoxide, and
may include minor amounts of carbon dioxide and/or water. The
presence of sulfur, nitrogen, halogen, selenium, phosphorus and
arsenic contaminants in the syngas is undesirable. For this reason
and depending on the quality of the syngas, it is preferred to
remove sulfur and other contaminants from the feed before
performing the Fischer Tropsch chemistry. Means for removing these
contaminants are well known to those of skill in the art. For
example, ZnO guardbeds are preferred for removing sulfur
impurities. Means for removing other contaminants are well known to
those of skill in the art. It also may be desirable to purify the
syngas prior to the Fischer Tropsch reactor to remove carbon
dioxide produced during the syngas reaction and any additional
sulfur compounds not already removed. This can be accomplished, for
example, by contacting the syngas with a mildly alkaline solution
(e.g., aqueous potassium carbonate) in a packed column.
[0047] In the Fischer Tropsch process, liquid and gaseous
hydrocarbons are formed by contacting a synthesis gas comprising a
mixture of H.sub.2 and CO with a Fischer Tropsch catalyst under
suitable temperature and pressure reactive conditions. The Fischer
Tropsch reaction is typically conducted at temperatures of about
300 to 700.degree. F. (149 to 371.degree. C.), preferably about
from 400 to 550.degree. F. (204 to 228.degree. C.); pressures of
about from 10 to 600 psia, (0.7 to 41 bars), preferably 30 to 300
psia, (2 to 21 bars) and catalyst space velocities of from about
100 to about 10,000 cc/g/hr., preferably 300 to 3,000 cc/g/hr.
[0048] Examples of conditions for performing Fischer-Tropsch type
reactions are well known to those of skill in the art. Suitable
conditions are described, for example, in U.S. Pat. Nos. 4,704,487,
4,507,517, 4,599,474, 4,704,493, 4,709,108, 4,734,537, 4,814,533,
4,814,534 and 4,814,538, the contents of each of which are hereby
incorporated by reference in their entirety.
[0049] The products of the Fischer Tropsch synthesis process may
range from C, to C.sub.200 + with a majority in the
C.sub.5-C.sub.100+ range. The reaction can be conducted in a
variety of reactor types; for example, fixed bed reactors
containing one or more catalyst beds, slurry reactors, fluidized
bed reactors, or a combination of different type reactors. Such
reaction processes and reactors are well known and documented in
the literature. Slurry Fischer Tropsch process are preferred for
the process of the invention.
[0050] In general, Fischer-Tropsch catalysts contain a Group VIII
transition metal on a metal oxide support. The catalysts may also
contain a noble metal promoter(s) and/or crystalline molecular
sieves. Certain catalysts are known to provide chain growth
probabilities that are relatively low to moderate, and the reaction
products include a relatively high proportion of low molecular
(C.sub.2-.sub.8) weight olefins and a relatively low proportion of
high molecular weight (C.sub.30+) waxes. Certain other catalysts
are known to provide relatively high chain growth probabilities,
and the reaction products include a relatively low proportion of
low molecular (C.sub.2-8) weight olefins and a relatively high
proportion of high molecular weight (C.sub.30+) waxes. Such
catalysts are well known to those of skill in the art and can be
readily obtained and/or prepared. The preferred catalysts of this
invention contain either Fe or Co, with Co especially
preferred.
[0051] The teachings of this invention may also be useful for
making a dual use or multi use fuel. An example of a dual use fuel
is one that can be used as both in Diesel and Jet engines. Jet fuel
specifications can have strict limitations on the use of additives.
The present invention provides a fuel that has desirable low
foaming characteristics without the use of additives. Such a fuel
can be used in both diesel and jet fuel applications. Dual use
fuels may become increasingly useful in the future. Dual use fuels
would be desirable to minimize infrastructure (such as tankage and
dedicated pipelines) or where infrastructure is limited. An example
of this is military uses where it would be very useful to have a
"flexible" fuel or "unifuel" that could be used as the fuel for two
or even several end uses. Alternatively a flexible fuel that
requires only a minimal addition of an additive package for
specific sues (such as diesel) would be useful.
Foam Inhibitors
[0052] The present invention allows for the use of supplemental
amounts of an antifoam additive. Addition of a small amount of
antifoam additive can be used to guarantee low foaming properties
or to ensure very rapid foam vanishing times. Use of the teachings
of the present invention allows for significantly less antifoam
additives to be used to achieve a desired foam vanishing time.
Preferably a foam inhibitor, if used at all, is a silicone-based
foam inhibitor. Examples of silicone-based foam inhibitors include
siloxane-polyoxyalkylene copolymers, for example those described in
U.S. Pat. No. 3,233,986, the disclosure of which is incorporated by
reference herein, which comprise at least one siloxane block
containing at least two siloxane groups of the formula R2SiOO
5(4-b) wherein R represents a halogen atom or an optionally
halogenated hydrocarbon group and b represents from 1 to 3, and at
least one polyoxylalkylene block containing at least two
oxyalkylene groups.
[0053] Generally, the alkylene groups have 2 or 3 carbon atoms, and
usually both ethylenoxy and propyleneoxy groups are present.
Advantageously, the copolymer is a
polymethylsiloxane-polyoxylalkylene copolymer, preferably of the
general formula
(CH.sub.3).sub.3SiO[CH.sub.3(A)SiO].sub.m[(CH.sub.3).sub.2SiO]nSi(CH.sub.-
3).sub.3 in which A represents
-(CH.sub.2).sub.pO(C.sub.2H.sub.4O).sub.x(C.sub.3H.sub.6O).sub.yZ
in which Z represents hydrocarbyl, OC(hydrocarbyl) or, preferably,
hydrogen, and in which the absolute values of m and n, and their
ratios, and the values of p, x, and y, and their ratios, may vary
widely but total values advantageously give a weight average
molecular weight in the range of from 600 to 25000. The ratio of
m:n is advantageously in the range of from 10:1 to 1:20, or the
value of n may be zero, and the ratio of x:y is advantageously in
the range of from 1:100 to 100:1, preferably 20:80 to 100:1, or one
of x or y, but not both, may be zero.
[0054] Other anti-foams also useful in the present invention may be
non-silicon containing such as those made by acylating polyamines
as described in WO 94/06894.
[0055] This invention allows one to reduce the amount of foam
inhibitor used. Advantageously, the foam inhibitor is present in
the fuel at concentrations of less than 10 ppm, more preferably
less than 8 ppm, even more preferably less than 5 ppm by weight
relative to the total amount of fuel. Most preferably, the foam
inhibitor is not present at all.
EXAMPLES
The Examples that follow are intended to help illustrate aspects of
the present invention and are not meant to limit the scope of the
invention.
Example 1
Foam Measurements of Commercial Distillate Fuel Samples
[0056] Fourteen commercial diesel fuel samples not containing
antifoam additives were obtained from throughout Europe and
measured to determine foaming properties. The foam height and foam
vanishing time for the samples were determined using the AFNOR
(Association Francaise de Normalisation) NF M 07-075 test (dated
June 1997) which is incorporated by reference herein in its
entirety. The samples were also measured for other characteristics.
Results are shown in Table 1. TABLE-US-00001 TABLE 1 Foam Test
Results of Commercial Diesel Fuels Sample Test Method 1 2 3 4 5 6 7
8 9 10 11 12 13 14 Den. 15.degree. C. D4052 Kg/l 0.841 0.835 0.837
0.812 0.836 0.843 0.834 0.841 0.838 0.833 0.836 0.824 Viscosity
40.degree. C. D445 mm.sup.2/s 2.24 4.0 3.4 2.5 2.4 3.2 3.0 2.6 2.4
Sulfur XRF ppmw 346 37.0 52.0 1.0 8.0 416.0 3.4 33.5 24.5 <0.001
<0.038 Conductivity Ps/m 39 400.0 1.0 0.0 0.0 35.0 140.0 130.0
0.0 169.0 Cloud Point D445 .degree. C. -9 -15 -25 -25 -23 -16 -9 -8
-1 -15 Pour Point .degree. C. -36 <-30 -30 -12 -18 CFPP IP309
.degree. C. -13 -17 -23 -24 -24 -19 -12 -19 -5 -15 -20 Flash Point
D93A .degree. C. 64 110 70 64 69 67 Cetane Index D4737 54.4 61.3
58.2 48.4 50.8 54.4 51.7 53.9 50.6 Distill. PI D86 .degree. C. 195
246.4 227.9 192 173.1 196.4 178.4 155.2 153.8 160.9 0.05 D86
.degree. C. 228.4 259.4 242.2 206.1 197.7 225.8 202.6 190.2 199.8
181.3 0.1 D86 .degree. C. 239.2 264.1 248.8 210.8 205.9 237.2 211.1
205.2 213.6 190.2 0.3 D86 .degree. C. 260.2 276.7 265.8 235 234.7
259.6 240.6 246.4 241.2 219.6 0.5 D86 .degree. C. 277.4 289 280.3
270.9 259.7 277 270 273.7 259.9 256.3 0.7 D86 .degree. C. 299.4
302.2 296.5 292 282.5 298.8 299 299.8 277.7 295.2 0.9 D86 .degree.
C. 332.7 322.2 323.7 318.2 310.7 33.8 338.4 336.1 308.8 334.4 0.95
D86 .degree. C. 352.3 341.8 343.6 340.2 324.8 351 355.5 351.4 328.9
347.7 PF D86 .degree. C. 362.8 353.5 359.8 359.2 341.6 361.2 365.3
356.3 336 357.2 Evaporated D86 ml 98.4 98.9 98 98.6 98.7 98 98.2
97.3 97.1 98.4 Residue D86 ml 1.6 1.1 1.8 1.4 1.3 1.9 1 2.6 2.9 1.6
Loss D86 ml 0 0 0.2 0 0 0.1 0.8 0.1 0 0 Foam ANFOR NF M ml 116 114
120 96 80 98 100 110 130 130 110 104 102 112 07-075 Foam ANFOR NF M
sec. 27.5 16.2 47.1 18 37.3 90.2 32.6 15.6 20.1 33.3 58.6 62.4 17.6
50.7 Vanishing Time 07-075''
Example 2
Preparation of a Fischer Tropsch Distillate
[0057] The preparation of the Fischer-Tropsch distillate sample is
described in Example 1 of U.S. Published Application 20040152930
which is incorporated by reference herein in its entirety and is
Fuel A of Table II of said reference. The Fischer Tropsch process
used to make this sample is a Low Temperature Fischer Tropsch
(LTFT) process using a cobalt catalyst and operated in the slurry
bed mode. It is important for this invention that the Fischer
Tropsch distillate not contain components which induce foaming or
give long foam retention times. The foam release time (foam
vanishing time) of the Fischer Tropsch distillate should be 15
seconds or less. Components to be minimized include heteroatoms,
such as sulfur, nitrogen and oxygen. Preferably the Fischer Tropsch
distillate will contain less than 1 ppm of sulfur and less than 1
ppm of nitrogen. Distillates directly from a Fischer Tropsch
process can contain oxygenates, such as primary linear alcohols.
These compounds are well known surfactants, and their composition
should be minimized by hydroprocessing (hydrocracking,
hydrotreating, hydroisomerization and combinations). The oxygenate
content of the Fischer Tropsch distillate should be less than 100
ppm of oxygen, preferably less than 25 ppm of oxygen, more
preferably less than 10 ppm oxygen, and very most preferably not
detectable. US20040152930 describes methods for measuring the
oxygen content of Fischer Tropsch distillates. The oxygenate
content of the Fischer Tropsch distillate in US20040152930 was
below the limit of detection, that is, less than 6 ppm. The oxygen
content is expressed on both a water-free and air-free basis.
Example 3
Properties of a Petroleum Derived Distillate with High Form
Formation
[0058] A petroleum-derived distillate fuel was obtained and tested.
It was a non-additized (without additives) diesel fuel from the
Belgium market and had the following properties shown in Table 2:
TABLE-US-00002 TABLE 2 Property Value Density, ASTM D4052 kg/l
0.8238 Sulfur, ISO 20884, ppm m/m 38.5 Kinematic Viscosity at
40.degree. C., ASTM D445-Aut., cSt 2.40 Lubricity at 60.degree. C.,
CEC F06A96microns 275 Electrical Conductivity, ASTM D2624 pS/m 169
Distillation, ASTM D-86 by LV %, .degree. C./.degree. F. IBP
160.9/322 5 LV % 181.3/358 10 LV % 190.2/374 30 LV % 219.6/427 50
LV % 256.3/493 70 LV % 295.2/563 90 LV % 334.4/634 95 LV %
347.7/658 FBP 357.2/675 Evaporated LV % 98.4 Residue LV % 1.6 Loss
LV % 0
This material is used in the later examples. Its foaming properties
are 5 described in Table 3 (Test A).
Example 4
Foam Formation Measurements
The foam height and vanishing time for various samples were
determined by the AFNOR (Association Frangaise de Normalisation) NF
M 07-075 test (dated June 1997).
[0059] To determine the effect of blending of Fischer Tropsch
derived distillate fuels, a blend was made of 70% volume petroleum
derived distillate fuel (from Example 3) and 30% volume Fischer
Tropsch derived distillate fuel (from Example 2). Duplicate
measurements on the Fischer Tropsch derived distillate were
obtained.
[0060] To determine the comparative effects of a commercial silicon
antifoam agent, blends were prepared with 250 volume ppm of a
multi-functional package containing a mixture of detergent,
demulsifier, corrosion inhibitor, solvents and 1.24 wt% silicon
antifoam additive. This is equivalent to 3 ppm weight silicon
antifoam additive in the diesel fuel. The silicon antifoam additive
is a commercial product supplied by Wacker. These results are shown
in tests H, I, and J shown below. TABLE-US-00003 TABLE 3 Vanishing
Vis at Foam, Time, 40.degree. C. Test Sample Description ml seconds
cSt A Example 3 - Petroleum Derived 112 50.7 2.40 Distillate Fuel B
Example 2 - Fischer Tropsch 94-98 7.5 - 6.2 1.97 Derived Distillate
Fuel C 90% Petroleum Derived Distillate 110 17.5 2.34 fuel with 10%
Fischer Tropsch Derived Distillate Fuel D 80% Petroleum Derived
Distillate 100 9.7 2.31 fuel with 20% Fischer Tropsch Derived
Distillate Fuel E 70% Petroleum Derived Distillate 110 10.8 2.26
fuel with 30% Fischer Tropsch Derived Distillate Fuel F 60%
Petroleum Derived Distillate 112 10.9 2.22 fuel with 40% Fischer
Tropsch Derived Distillate Fuel G 50% Petroleum Derived Distillate
100 9.2 2.20 fuel with 50% Fischer Tropsch Derived Distillate Fuel
H Petroleum Derived Distillate Fuel 70 5.0 with 3 ppm Silicon
Antifoam additive I Fischer Tropsch Derived Distillate 78 3.2 fuel
with 3 ppm Silicon Antifoam additive J 70% Petroleum Derived
Distillate 70 3.2 fuel with 30% Fischer Tropsch Derived Distillate
Fuel with 3 ppm Silicon Antifoam additive
Test A shows that the petroleum derived distillate fuel has foam
properties that do not comply with Category three or four diesel
fuels in the World Wide Fuel Charter. Both the vanishing time and
the amount of foam exceed the maximum values. In comparison the
Fischer Tropsch derived fuel meets both limits as shown by test B.
Tests C to G show that blending a Fischer Tropsch derived
distillate fuel with a petroleum-derived distillate fuel
significantly improves the foaming tendency, especially the most
important foam vanishing time. A 20% blend of Fischer Tropsch
derived distillate fuel in 80% petroleum-derived distillate fuel
meets the foam vanishing time requirement of the Category three and
four fuels in the World Wide Charter, and just meets the maximum
amount of foam. The impact of blending the Fischer Tropsch
distillate fuel on foam is dramatic. Addition of Fischer Tropsch
distillate fuel reduces the vanishing time far more than what would
be expected from a linear blend or even from the drop in the
viscosity. Not wishing to be limited by theory it is speculated
that the polar functions in the petroleum derived distillate
contribute to foaming, and highly paraffinic nature of the Fischer
Tropsch product disrupts them. However, the reduction in foam is
highly non-linear and more than can be expected by a simple
dilution of the polar species in the conventional diesel fuel.
Blends with the antifoam additive show it to be highly effective in
reducing foaming, both in the vanishing time and the amount of
foam. But even here the blending of a Fischer Tropsch distillate
component leads to a lowering in the vanishing time for the
petroleum derived fuel indicating that less of the antifoam agent
would be needed to obtain a given foam value.
Example 5
Foam Formation with Low Sulfur Diesel
[0061] A diesel fuel containing less than 10 ppm by weight sulfur
and conforming to emerging diesel fuel specifications was obtained.
Properties are shown in Table 4. TABLE-US-00004 TABLE 4 Property
Test Value Units Density 15 C ASTM D4052 0.8333 kg/l Flash Point PM
ASTM D93 69 .degree. C. Cloud Point ASTM D2500 -0.5 .degree. C.
Pour Point ASTM D97 -12 .degree. C. Cold Filter IP309 -5.0 .degree.
C. Plugging Point Copper Corrosion ASTM D130 1A Rusting Test Proc
ASTM D665 100 % A Rusting Test Proc ASTM D665 100 % B BNPE Foam
Test NF M07-075 116/75.1 Ml - s Electrical ASTM D2624 130 pS/m
Conductivity Filter Blocking IP387 1.004 Tendency of Gasoils Diesel
Lubricity CEC F06A96 432 micron Test at 60 C Distillation ASTM D86
Initial Boiling ASTM D86 155.2 .degree. C. Point Distillation 5 ML
ASTM D86 190.2 .degree. C. Distillation 10 ML ASTM D86 205.2
.degree. C. Distillation 30 ML ASTM D86 246.4 .degree. C.
Distillation 50 ML ASTM D86 273.7 .degree. C. Distillation 70 ML
ASTM D86 299.8 .degree. C. Distillation 90 ML ASTM D86 336.1
.degree. C. Distillation 95 ML ASTM D86 351.4 .degree. C. Final
Boiling ASTM D86 356.3 .degree. C. Point Evaporated ML ASTM D86
97.3 ml Residue in ML ASTM D86 2.6 ml Loss in ML ASTM D86 0.1 ml
Oxidation Stability ASTM D2274 10.86 g/m3 on Gasoils Cetane Index
ASTM D4737 53.9 Kin. Viscosity 40 C ASTM D445-AUT 2.97
mm.sup.2/s
[0062] Blends of this diesel fuel with the Fischer Tropsch
distillate of Example 2 were 5 made and evaluated for foam
formation by the AFNOR NF M 07-075 test as shown in Table 5.
TABLE-US-00005 TABLE 5 Vanishing Foam, Time, Test Sample
Description ml seconds K Example 5 - Low Sulfur Petroleum Derived
116 75.1 Distillate Fuel B Example 2 - Fischer Tropsch Derived
94-98 7.5 - 6.2 Distillate Fuel L 90% Low Sulfur Petroleum Derived
112 18.7 Distillate fuel with 10% Fischer Tropsch Derived
Distillate Fuel M 70% Low Sulfur Petroleum Derived 114 13.6
Distillate fuel with 30% Fischer Tropsch Derived Distillate Fuel N
50% Low Sulfur Petroleum Derived 110 10.4 Distillate fuel with 50%
Fischer Tropsch Derived Distillate Fuel
The results on blend of the low sulfur petroleum derived diesel
with the Fischer Tropsch derived distillate fuel are very similar
to those obtained from Example 4. Specifically, the petroleum
derived distillate fuel has foam properties that do not comply with
Category three or four diesel fuels in the World Wide Fuel Charter.
Both the vanishing time and the amount of foam exceed the maximum
values. Blends that contain a Fischer Tropsch derived distillate
fuel show an improvement in the foam vanishing time, with blends
that contain 30% Fischer Tropsch derived distillate having a
vanishing time of less than 15 seconds.
* * * * *
References