U.S. patent application number 09/859747 was filed with the patent office on 2002-02-21 for low molecular weight compression ignition fuel.
Invention is credited to Bailey, Brent K., Ohi, James M..
Application Number | 20020020107 09/859747 |
Document ID | / |
Family ID | 23362036 |
Filed Date | 2002-02-21 |
United States Patent
Application |
20020020107 |
Kind Code |
A1 |
Bailey, Brent K. ; et
al. |
February 21, 2002 |
Low molecular weight compression ignition fuel
Abstract
An improved hydrocarbon-based compression ignition fuel boils in
the naphtha boiling range and comprises hydrocarbons having from 5
to about 14 carbon atoms, preferably predominantly normal paraffins
having chain lengths from 6 to about 12 carbons. The fuel has an
average cetane number ranging from 40 to 80 and a Reid vapor
pressure of at least 2 psig to ensure safety in handling and
storage. Pentane and/or oxygenated hydrocarbons such as
dimethoxymethane can be added to reduce emissions and provide
sufficient vapor pressure for safe handling and storage.
Inventors: |
Bailey, Brent K.; (Rosewell,
GA) ; Ohi, James M.; (Denver, CO) |
Correspondence
Address: |
PAUL J WHITE, SENIOR COUNSEL
NATIONAL RENEWABLE ENERGY LABORATORY (NREL)
1617 COLE BOULEVARD
GOLDEN
CO
80401-3393
US
|
Family ID: |
23362036 |
Appl. No.: |
09/859747 |
Filed: |
May 17, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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09859747 |
May 17, 2001 |
|
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09347030 |
Jul 2, 1999 |
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Current U.S.
Class: |
44/447 ;
44/448 |
Current CPC
Class: |
C10L 10/02 20130101;
C10L 1/026 20130101; C10L 1/08 20130101 |
Class at
Publication: |
44/447 ;
44/448 |
International
Class: |
C10L 001/18 |
Goverment Interests
[0002] The United States Government has rights in this invention
under Contract No. DE-AC36-99GO-10337 between the U.S. Department
of Energy and the National Renewable Energy Laboratory (NREL,
operated for the U.S. Department of Energy by Midwest Research
Institute).
Claims
We claim: The embodiments of the invention in which an exclusive
property or privilege is claimed are defined as follows:
1. A hydrocarbon-based compression ignition fuel composition in the
naphtha boiling range comprising at least two hydrocarbon compounds
containing from 5 to about 14 carbon atoms, said composition having
a cetane number of at least 40, and said composition further having
a Reid vapor pressure of at least 2 psig.
2. The fuel composition of claim 1, wherein said composition has a
cetane number preferably in the range of about 50 to about 60.
3. The fuel composition of claim 1, wherein said hydrocarbon
compounds comprise predominantly normal paraffins having chain
lengths from about 6 to about 12 carbon atoms.
4. The fuel composition of claim 1, wherein one of said hydrocarbon
compounds is pentane.
5. The fuel composition of claim 1, said composition further
comprising an oxygenated hydrocarbon containing from 2 to about 4
carbon atoms and at least one oxygen atom, in a quantity effective
to reduce engine emissions when said fuel is employed in a
compression ignition engine.
6. The fuel composition of claim 5, wherein said oxygenated
hydrocarbon comprises dimethoxymethane.
7. The fuel composition of claim 5, wherein said oxygenated
hydrocarbon comprises diethyl ether.
8. The fuel composition of claim 1, said composition further
comprising light straight-run naphtha.
Description
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS
[0001] This patent application is a continuation-in-part of U.S.
patent application Ser. No. 09/347,030, filed on Jul. 2, 1999.
FIELD OF INVENTION
[0003] The present invention pertains generally to fuels for
compression ignition internal combustion engines, and particularly
to naphtha-type fuels which offer high cetane quality and safe
operations in storage and use.
BACKGROUND OF THE INVENTION
[0004] Conventional internal combustion fuels fall into two general
categories: 1) a naphtha-type gasoline and 2) distillate type
diesel fuel. The two general categories have been established for
safety in handling and fuel storage. The naphtha-type fuel is
considered safe because it has sufficient vapor pressure to provide
a rich vapor mixture in the storage tank, which is depleted in
oxygen content and not combustible. The distillate-type fuel is
considered safe because it has a low vapor pressure which yields a
lean vapor mixture in the storage tank which is not combustible due
to a lack of fuel mixed with ambient oxygen. The petroleum industry
has developed refining processes to improve the octane number of
components in the naphtha boiling range to 85 or above required for
spark ignition engines with compression ratios near 8 or above.
[0005] Distillate components generally have natural cetane quality
of 40 or above required for compression ignition engines.
[0006] Standard Fischer-Tropsch diesel fuel is produced from
synthesis gas (hydrogen and carbon monoxide) using one of many
Fischer-Tropsch catalysts and processes to generate products
primarily composed of straight-chain paraffins which are
subsequently processed and distilled into a boiling range similar
to petroleum diesel fuel. Standard Fischer-Tropsch diesel fuel has
excellent ignition delay (cetane number) quality, but it also
creates some performance problems in cold climates because of
paraffin wax precipitation. The standard Fischer-Tropsch diesel
fuel is known to reduce emissions of particulate matter and other
toxic compounds. Standard Fischer-Tropsch diesel fuel may also have
beneficial effects for reducing emissions of oxides of nitrogen.
Fischer-Tropsch naphtha is generated as a by-product of the
Fischer-Tropsch process.
[0007] Petroleum-derived diesel fuel is produced from crude oil
that is distilled or processed and distilled into a distillate
boiling range of about 185.degree. C. to 345.degree. C.
Petroleum-derived gasoline is produced from crude oil which is
highly processed through cracking, reforming, alkylation,
isomerization, and other means to increase the aromatic content,
olefin content, and chain branching of paraffins to the improve
octane number in a final blend in the naphtha-boiling range
(typically from 36.degree. C. to 219.degree. C.). Straight-chain
paraffins present in the original crude oil are minimized as part
of the processing scheme. Octane number is also enhanced in
gasoline through the addition of certain oxygenated components
demonstrated to have high-octane quality.
[0008] U.S. Pat. No. 5,611,912 (assigned to Mobil Oil Corp.)
discloses a process for the production of diesel fuel with a high
cetane number at low cloud point, by hydrocracking highly aromatic
fractions obtained from catalytic cracking operations. The fraction
of hydrocracker effluent boiling between 400-1000 deg. F. is
catalytically dewaxed to obtain a cloud point of 41 deg. F. or
less. This work is directed at processing crude oil feed streams
that are rich in aromatic compounds to a product suitable for use
as a diesel fuel by treatment over a hydrocracking catalysts.
Unlike the present invention, it does not address the formulation
of compression ignition engine fuels from light alkane hydrocarbons
such as would be found in a Fischer-Tropsch synthesis product
stream. This work also does not address the benefits derived from
incorporation of alkoxy containing moieties in a diesel fuel
formulated from straight chain paraffins as does the present
invention.
[0009] U.S. Pat. No. 5,639,931 (assigned to Mobil Oil Corp.)
discloses a process for converting mixtures of olefins and
isoparaffins to diesel fuel blending components by contacting the
mixture with a zeolite catalyst (MCM-22, -36, -49, or -56) to
provide a product containing a diesel fuel.
[0010] U.S. Pat. No. 5,780,703 (assigned to Mobil Oil Corp.)
discloses a process for converting mixtures of olefins and
isoparaffins to diesel fuel blending components by contacting the
mixture with a catalyst comprising an acidic solid comprising a
Group IVB metal oxide modified with an oxyanion of a Group VIB
metal to provide a diesel fuel.
[0011] The above noted U.S. Pat. No. 5,639,931 (directed at the
critical structure of a catalyst) and U.S. Pat. No. 5,780,703
(directed at the active metal incorporated into a catalyst) address
the nature of catalysts suitable for converting a mixture
containing a branched paraffin and an olefin of low carbon number
into a product liquid in which the olefin is alkylated by the
paraffin, and which is suitable for use as a diesel fuel. It does
not address the production of diesel fuels from straight chain
paraffins nor does it address the improvements in the contents of
combustion gasses obtained by the addition of compounds containing
alkoxy or methoxy moieties to such diesel fuels, as does the
present invention.
[0012] U.S. Pat. No. 5,763,716 (assigned to Rentech, Inc.)
discloses a process of converting a feed of hydrocarbon-containing
gases into liquid hydrocarbon products including a first reaction
of converting the feed into 1-2.5 parts hydrogen to 1 part carbon
monoxide in the presence of carbon dioxide, then reacting the
hydrogen and carbon monoxide in a Fischer-Tropsch synthesis reactor
using a promoted iron oxide catalyst slurry to form liquid
hydrocarbon products. The carbon dioxide from the first and second
reactions is separated from the product streams, and at least a
portion is recycled into the first reaction feed. The hydrocarbon
products are separated by distillation, and a normally gaseous
portion of the separated products are further reacted in another
Fischer-Tropsch synthesis reactor to form additional liquid
hydrocarbon products. This work is directed at maximizing the yield
of high boiling hydrocarbons produced in a Fischer-Tropsch
reaction, but does not specifically address the advantages
disclosed in the present invention obtained by formulating
compression ignition engine fuel from primarily straight chain
paraffins. It also does not address the advantages of incorporating
oxygen containing moieties into such a fuel.
[0013] U.S. Pat. Nos. 5,766,274 and 5,689,031 (both assigned to
Exxon) disclose two processes for producing clean distillates
useful as jet fuels or blending stocks or as diesel fuel or
blending stocks, respectively. Fischer-Tropsch waxes are separated
into heavier and lighter fractions, then the lighter fraction is
separated and the heavier fraction is hydroisomerized with the
portions of the light fraction above about 475.degree. F. or below
about 500.degree. F., respectively. The isomerized products are
blended with the untreated portion of the lighter fraction to
produce jet fuels or diesel fuels, respectively. The work in these
two patents is directed toward the conversion of high boiling
compounds derived from Fischer-Tropsch synthesis into a product
which when blended with lower boiling products of Fischer-Tropsch
synthesis is suitable for use as jet and diesel fuel. This work
does not address blends containing exclusively low molecular weight
straight chain paraffins as diesel fuel.
[0014] U.S. Pat. No. 5,752,989 (assigned to Ethyl Corp.) discloses
a diesel fuel additive comprising a mixture of a dispersant and a
carrier. The dispersant comprises at least one of polyalkylene
succinimides and polyalkylene amines. The carrier comprises at
least one oxygenate selected from polyalkoxylated ethers,
polyalkoxylated phenols, polyox-alkylated esters and
polyoxalkylated amines. This work is directed specifically at one
benefit of adding the subject compounds to a conventional diesel
fuel, namely that the injectors of a compression ignition engine
are subject to lower amounts of carbon deposit during operation.
This work does not address the advantages in lower hydrocarbon
emissions in combustion gases achieved by incorporation of an
oxygen containing moiety as a significant component in diesel fuel,
as is done in the present work, nor does it address the use of a
mixture of straight chain paraffins as a diesel fuel.
[0015] U.S. Pat. No. 5,746,783 (assigned to Martin Marietta Energy
Systems) discloses methods and compositions for controlling
nitrogen oxides emissions from diesel engines. Small amounts of
urea or a triazine compound (methylol melamines) are added to the
diesel fuel. These materials, generally insoluble in diesel fuel,
are suspended therein as microemulsions. This work is not directed
at the use of straight chain paraffins as a diesel fuel. While it
does address the reduction of certain types of emissions in
combustion gasses (oxides of nitrogen) through the inclusion of
nitrogen containing compounds in diesel fuel, it does not address
reduction of hydrocarbon emissions through the inclusion of an
oxygen containing moiety in the fuel. Additionally, the compound
taught in this work is insoluble in diesel fuel, necessitating the
use of a complex microemulsion to incorporate the additive into the
fuel, unlike the present invention which teaches the use of soluble
additives to achieve improved emissions.
[0016] U.S. Pat. No. 5,746,785 (assigned to Southwest Research
Inst.) discloses mixtures of alkoxy-terminated poly-oxymethylenes
useful as diesel fuel additives. The resulting fuels have improved
lubricity and reduced smoke formation, without degradation of the
cetane number of the base diesel fuel. This work is directed at
improving the combustion properties of conventionally formulated
diesel fuels by the addition of an oxygen containing polymer having
multiple ketonic functionality incorporated into its structure.
This work was not directed at the formulation of liquids suitable
for use as diesel fuel from straight chain paraffins.
[0017] U.S. Pat. No. 5,807,413 (assigned to Exxon) discloses
producing a diesel engine fuel through the separation of a light
density fraction from Fischer-Tropsch wax. This work is directed
toward C.sub.5-C.sub.15 hydrocarbons having at least 80 wt %
n-paraffins and limiting the alcohol content of the oxygen, the
olefins, the aromatics, and the sulfur and the nitrogen content.
This work does not identify a minimally acceptable cetane number,
nor does it exhibit a sufficient Reid vapor pressure to ensure a
safe rich mixture in storage as does applicants' claimed
invention.
[0018] U.S. Pat. No. 6,056,793 (assigned to University of Kansas
Center for Research) discloses a mixture of two components that
create a compression ignition fuel. The two components include a
light synthetic crude and a blendstock having an average molecular
weight less than that of the light synthetic crude. While this work
spans a very broad range from the heavy end of naphtha up to heavy
distillate fuels, it fails to provide a vapor pressure threshold as
does applicants' claimed invention, and it also does not disclose
an overall average molecular weight within the applicants'
range.
[0019] Jensen et al. describe in "Studies on Iron-Manganese Carbon
Monoxide Catalysts", Journal of Catalysis Vol. 92, pp. 98-108
(1985) certain bulk iron catalysts promoted with manganese oxide
which enhance the formation of low-molecular weight olefins when
used for carbon monoxide hydrogenation. This work was directed
toward characterization of a catalyst which selectively produces
low molecular weight, unsaturated hydrocarbons by Fischer-Tropsch
synthesis. It does not address the production of diesel fuels from
straight chain paraffins nor the advantages in combustion gas
composition obtained by the incorporation of an oxygen containing
moiety in such diesel fuels.
[0020] Maricq et al describe in "The Effect of Dimethoxy Methane
Additive on Diesel Vehicle Particulate Emissions," SAE Paper No.
982572 (San Francisco, October 1998) a 36.+-.8 percent reduction in
mass emissions of particulates with no change in NO.sub.xemissions
from a light-duty diesel engine when 16.6 percent of this additive
is mixed with a base European diesel fuel. This work is directed at
the improvement in combustion gas composition derived from adding
an oxygen containing moiety to conventional diesel fuel and does
not address formulation of diesel fuel from straight chain
paraffins.
[0021] Applicant Bailey et al. present in "Cetane Number Prediction
from Proton-Type Distribution and Relative Hydrogen Population,"
SAE Technical Paper No. 861521, presented at International Fuels
and Lubricants Meeting, Philadelphia, 1996, a theoretical model for
predicting cetane numbers of primary reference fuels from
parameters measurable by proton nuclear magnetic resonance. The
technique is extended to include secondary reference fuels, pure
hydrocarbons and commercial-type fuels.
[0022] Applicant Bailey's M.S. thesis, "Characterization of Alumina
Supported Cobalt Copper Catalysts for Fischer-Tropsch Synthesis of
Light Hydrocarbons," on file at the Department of Mining and Fuels
Engineering, University of Utah, describes the properties of such
catalysts which are suitable for the production of C.sub.2 to
C.sub.4 hydrocarbons.
SUMMARY OF THE INVENTION
[0023] The main aspect of the present invention is a compression
ignition fuel based upon hydrocarbons in the naphtha boiling
range.
[0024] Another aspect of the present invention is a compression
ignition fuel which offers a relatively high average cetane number
and minimizes harmful emissions when used in compression ignition
engines.
[0025] Still another aspect of the present invention is a
compression ignition fuel which offers excellent fuel economy
combined with minimum harmful engine emissions.
[0026] Other aspects of this invention will appear from the
following description and appended claims.
[0027] This invention takes the novel approach of formulating a
safe naphtha-type fuel with high cetane quality for compression
ignition. Conventional petroleum-derived diesel fuel consists of
aromatic and paraffinic hydrocarbons which typically boil from
about 185.degree. C. to about 345.degree. C. Certain products of
diesel exhaust including particulates and some aromatic products
are considered toxic. Controlling the chemical composition of
diesel, or compression ignition fuel, to eliminate aromatic
compounds and reducing the boiling-point range or molecular weight
will yield significant reductions in mass emissions of toxic
components.
[0028] Improving the efficiency of the engine will reduce the
emissions of carbon dioxide, considered a greenhouse gas, which
contributes to global warming trends. The compression ignition
engine is approximately 30 percent more efficient than the spark
ignition engine and may be selected for ultra-high efficiency
engine systems required in the future for control of greenhouse gas
emissions.
[0029] The present invention includes compositions of
Fischer-Tropsch derived or petroleum crude oil-derived hydrocarbons
and oxygenates comprising low molecular weight paraffinic
hydrocarbons in the gasoline or naphtha boiling range (typically
from 26.degree. C. to 219.degree. C.). The compositions would be
primarily composed of straight-chain paraffins with an ideal
composition consisting essentially of the normal paraffins hexane,
heptane, octane, nonane, decane, undecane, and dodecane. The cetane
numbers of these components are about 45, 56, 64, 72, 77, 88, and
90 respectively. The fuel compositions may include various
combinations of single or individual compounds such as hexane,
heptane, octane, nonane, decane, undecane, and dodecane. The fuel
compositions may also contain varying percentage combinations of
two or more of these compounds. Pentane, diethyl ether (DEE),
dimethoxy-methane (DMM) or other high-vapor pressure oxygenates
with high-cetane numbers may be added to provide sufficient vapor
pressure in the final blend to yield a safe mixture with a Reid
vapor pressure of at least 2 psig or greater. The structural
formulas of these compounds are shown in Table 1 below.
[0030] In accordance with the invention, a hydrocarbon-based
compression ignition fuel is provided which has an average boiling
point in the naphtha boiling range (26.degree. C. to 219.degree.
C.), comprising blends of at least two hydrocarbons having from 5
to about 14 carbon atoms per molecule, each yielding cetane numbers
ranging from about 30 to about 90. Preferably, the hydrocarbons
have chain lengths of from about 6 to about 12 carbon atoms, plus
or minus one carbon atom, and are predominantly normal
hydrocarbons. The hydrocarbons are also preferably predominantly
saturated, or moderately unsaturated in structure. The blends
should have
1TABLE 1 Com- Carbon pound Atoms Structural Formula Pentane 5
H.sub.3C--CH.sub.2--CH.sub.2--CH- .sub.2--CH.sub.3 Hexane 6
H.sub.3C--CH.sub.2--CH.sub.2--CH.sub.2--C- H.sub.2--CH.sub.3
Heptane 7 H.sub.3C--CH.sub.2--CH.sub.2--CH.sub.2--
-CH.sub.2--CH.sub.2--CH.sub.3 Octane 8
H.sub.3C--CH.sub.2--CH.sub.2-
--CH.sub.2--CH.sub.2--CH.sub.2--CH.sub.2--CH.sub.3 Nonane 9
H.sub.3C (CH.sub.2).sub.7 CH.sub.3 Decane 10 H.sub.3C
(CH.sub.2).sub.8 CH.sub.3 Undecane 11 H.sub.3C (CH.sub.2).sub.9
CH.sub.3 Dodecane 12 H.sub.3C (CH.sub.2).sub.10 CH.sub.3 Diethyl- 4
H.sub.3C--CH.sub.2--O--CH.sub.2--CH.sub.3 ether Dimeth- 3
H.sub.3C--O--CH.sub.2--O--CH.sub.3 oxy- methane
[0031] an average cetane number of at least 40, preferably in the
range of from about 50 to about 60, plus or minus 3. Pentane and/or
oxygenated hydrocarbons containing from 2 to about 4 carbon atoms
and at least one oxygen atom can optionally be added to provide
improved combustion and fuel emissions properties and to provide a
Reid vapor pressure of at least 2 psig for safe handling and
storage. Additionally, light straight-run naphtha (LSRN, also known
as light petroleum naphtha and natural gasoline) having average
cetane numbers in the range of 30 to 45 can be used as blending
stock with the hydrocarbons described above to formulate fuel
compositions meeting the desired standards.
[0032] The hydrocarbon blends of the invention can be produced
through direct Fischer-Tropsch processing or by conversion of
Fischer-Tropsch products to create the desired ranges of
components. Alternatively, the fuel compositions can be produced
through petroleum crude oil distillation processing followed by
isolation or subsequent processing to create the desired ranges of
components.
[0033] The fuel compositions of the invention can be used as fuels
for conventional diesel engines, advanced compression ignition
engines and even fuel cells. The fuel compositions claimed under
this invention can be used in current technology diesel engines
which operate on a compression ignition principle. The fuel
compositions claimed can also be used in new generation direct
injection compression ignition engines including advanced control
systems designed to take advantage of the fuel composition to meet
current and future emission standards, or other compression
ignition engines without direct injection. The fuel compositions
claimed can also be used in fuel cell engines, provided an onboard
or stationary reformer is used to generate hydrogen for fuel cell
applications. Such engine-fuel combinations can be used to power a
variety of applications, including, but not limited to, highway or
off-road vehicles, aircraft, watercraft or stationary power plants.
When used to fuel such engines, the fuel compositions of the
invention can produce excellent fuel economy while reducing
emissions of particulate matter and other toxic products, nitrogen
oxides, carbon monoxide and other regulated gaseous emissions.
[0034] Before explaining the disclosed embodiment of the present
invention in detail, it is to be understood that the invention is
not limited in its application to the details of the particular
compositions and applications described, since the invention is
capable of other embodiments. Also, the terminology used herein is
for the purpose of description and not of limitation.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0035] As outlined above, the fuel compositions of the present
invention comprise blends of at least two hydrocarbons having from
5 to about 14 carbon atoms per molecule, each yielding cetane
numbers ranging from 30 to about 90. Light straight-run naphtha
(LSRN) can also be used as blending stock, and pentane or
oxygenates can be added for particular purposes. The claimed fuel
compositions encompass blends of the following components in the
proportions indicated by volume percent in Table 2:
2 TABLE 2 Component Volume Percent Pentane Zero to 15% Hexane Zero
to 50% Heptane Zero to 50% Octane Zero to 50% Nonane Zero to 40%
Decane Zero to 40% Undecane Zero to 40% Dodecane Zero to 40%
[0036] The components for these compositions can be obtained from
any suitable and economic source, including Fischer-Tropsch
syntheses and petroleum refining and distillation. Synthesis gas, a
mixture of carbon monoxide and hydrogen, is obtainable from a
variety of sources, including coal gasification and partial
combustion of natural gas or biomass feedstocks, and can readily be
subjected to Fischer-Tropsch synthesis reactions using suitable
catalysts and process conditions to produce products containing
suitable hydrocarbons for blending into compositions of the present
invention. Oxygenates such as diethyl ether and dimethoxymethane
are readily available from commercial sources. LSRN is obtained
from crude oil distillation, and has low octane numbers, and
therefore, reasonably adequate cetane numbers.
[0037] The fuel compositions claimed under this invention may be
produced through a variety of chemical processes including
separation processing in a conventional petroleum refinery used to
isolate hexane, heptane, octane, nonane, decane, undecane, or
dodecane, or any combination of these compounds. Processes used to
create fuel blends within the scope of the invention may also
include chemical reaction processes to thermally or catalytically
crack higher molecular weight hydrocarbons into paraffins from
about C.sub.6 to C.sub.12 carbon chain lengths, plus or minus one
carbon atom. Other processes may include thermal or catalytic
petroleum refinery processes which remove alkyl branches to
generate straight-chain paraffins. Conventional distillation or
adsorption separation processing may be used to isolate or
concentrate the desired products. Conventional cracking and
hydrotreating catalysts may also be used with appropriate
modifications to process conditions to obtain the desired
products.
[0038] The fuel compositions claimed under this invention may also
be produced through catalytic Fischer-Tropsch processes, that
directly generate low molecular weight normal paraffins ideally
from about C.sub.6 to C.sub.2 carbon chain lengths, plus or minus
one carbon atom, through control of process conditions, and/or
through catalyst formulation. Catalyst formulations including
binary or other combinations of active metals such as iron, cobalt,
copper, manganese, nickel, or other active Fischer-Tropsch metals
or chemicals as reaction modifiers may facilitate the production of
the desired products. The fuel compositions claimed under this
invention may also be produced through conventional Fischer Tropsch
processes and catalysts which create longer chain hydrocarbons
which are then thermally or catalytically cracked to yield products
in the C.sub.6 to C.sub.12 carbon number-size range, plus or minus
one carbon atom.
[0039] Since the fuel compositions of the present invention will
normally have lower viscosity than conventional diesel fuels,
lubricity additives are preferably included, in addition to other
conventional fuel additives. Commercial additives for enhancing the
lubricity of diesel fuels are readily available, and may improve
the final performance of the fuel compositions of the present
invention.
EXAMPLES
[0040] The invention will be further illustrated by the following
non-limiting examples (fuel compositions are composed of the
following ingredients in the volume percent proportions
indicated):
3TABLE 3 Blend Blend Cetane RVP Compound No. Index A B C D E F G H
I J LSRN 35 12.2 0 0 0 0 0 0 0 20 9 8 DMM 46 12.2 0 0 9 15 0 20 0 0
0 0 DEE 60 16 0 9 0 0 0 0 8 0 0 0 Pentane (C.sub.5) 35 14.7 9 0 0 0
10 0 0 0 0 0 Hexane (C.sub.6) 45 4.9 13 13 13 15 30 30 30 15 13 30
Heptane (C.sub.7) 56 1.0 13 13 13 15 25 25 25 13 13 25 Octane
(C.sub.8) 64 0.1 13 13 13 15 20 20 20 12 13 20 Nonane (C.sub.9) 72
0 13 13 13 10 10 5 12 10 13 12 Decane (C.sub.10) 77 0 13 13 13 10 5
0 5 10 13 5 Undecane (C.sub.11) 88 0 13 13 13 10 0 0 0 10 13 0
Dodecane (C.sub.12) 90 0 13 13 13 10 0 0 0 10 13 0 Volume % 100 100
100 100 100 100 100 100 100 100 Avg. Cetane No. 67.1 69.4 68.0 64.2
54.9 52.9 57.6 63.4 67.1 55.6 Blend RVP Index 3.7 4.0 3.2 4.7 5.4
7.0 5.0 5.8 3.2 4.3 Blend RVP psi 2.8 3.0 2.5 3.4 3.8 4.8 3.6 4.1
2.5 3.2
[0041] The examples above show several blend combinations that
produce calculated cetane numbers of 50 or better and have Reid
vapor pressure ratings greater than at least 2 psig.
[0042] For the hypothetical examples illustrated in Table 3, the
cetane numbers are estimated in a linear fashion as described by
the following equation:
Blend Cetane Number=.SIGMA.(Volume Fraction
Component).sub.ix(Cetane Number of Component).sub.i for i=1 to x,
and x=the number of blend components (1)
[0043] For example, Blend F, comprised of 5 components including:
DMM at 20% by volume with a cetane number of 45, hexane at 30% by
volume with a cetane number of 45, heptane at 25% by volume with a
cetane number of 56, octane at 20% by volume with a cetane number
of 64, and nonane at 5% by volume with a cetane number of 72 yields
a Blend Cetane number equal to
[(0.2)(45)+(0.3)(45)+(0.25)(56)+(0.2)(64)+(0.05)(72)], or 52.9.
Linear, volume proportional weighting of cetane numbers of the
blend components is widely accepted in the petroleum industry as a
good method for estimating the cetane number of a final blend.
[0044] For the hypothetical examples illustrated in Table 3, the
Reid vapor pressures (RVP) are estimated by using a vapor
pressure-blending index, as shown by the following equation:
Blend RVP Index=.SIGMA.(Volume Fraction of Component).sub.ix(Reid
Vapor Pressure).sub.i.sup.125 for i=1 to x, and x=the number of
blend components (2)
[0045] where the RVP of each blend component, listed in the first
column of Table 3, is well known to persons skilled in the art. The
LSRN blend component may be composed of different light
hydrocarbons and thus its RVP value may vary. For this example, a
RVP of 12.2 is assumed as a typical value. For example, Blend F,
comprised of 5 components, including: DMM at 20% by volume with a
RVP of 12.2, hexane at 30% by volume with a RVP of 4.9, heptane at
25% by volume with a RVP of 1.0, octane at 20% by volume with a RVP
of 0.1, and nonane at 5% by volume with a RVP of 0.0 yields a Blend
RVP equal to [(0.2)(12.2).sup.1.25+(0.3)-
(4.9).sup.1.25+(0.25)(1.0).sup.1.25+(0.2)( 0.1).sup.1.25], or 7.01.
The Blend RVP Index is then converted to the Blend RVP by
performing the inverse function, e.g., raising the Blend RVP Index
to the 0.8 power. For example, Blend F would have a Blend RVP equal
to its Blend RVP Index, or 7.01, raised to the 0.8 power which
equals 4.75. The Blend RVP values for each of the ten formulated
blends, A through J, are disclosed in the last row of Table 3.
[0046] Upon testing, the blended fuels are found to have average
cetane numbers close to the values of 50-70 predicted by
calculations and Reid vapor pressures of at least about 2 psig. The
addition of about 5 to 20 percent of dimethoxymethane or diethyl
ether is found to further reduce emissions when used as a
compression ignition fuel without materially affecting engine
operation.
Examples 1 and 2
[0047] As actual examples, a bench-scale blend and a 30 gallon
blend containing 33 volume percent a hexane and 11 volume percent
each of heptane, octane, nonane, decane, undecane, and dodecane
were prepared and tested by an independent testing laboratory per
ASTM D975-97. The results are shown in Table 4. Average blend RVP
values were calculated independently for these two samples and were
found to be 2.1 psi.
4 TABLE 4 Test & Method Example 1 Example 2 Reid Vapor
Pressure, psi @ 2.3 (average 1.9 (average 100.degree. F. by mini
Herzog of 5 runs) of 4 runs) Flash Point, .degree. F. <68 <75
ASTM D93-97 Water & Sediment, vol % <0.05 <0.05 ASTM
D1796-83 Distillation, .degree. F. 390 390 ASTM D86-96 90% Volume
Recovered Viscosity, cSt @ 40.degree. C. 0.6918 0.7119 ASTM D445-94
Ash, weight % <0.001 <0.001 ASTM D482-95 Sulfur, weight%
0.003 0.004 ASTM D4294-98 Copper Corrosion 1B 1B 50.degree. C. for
3 hours ASTM D130-94 Cetane # (calculated) 65.0 66.6 ASTM D4737-90
Cloud Point, .degree. C. -52 -51 ASTM D2500-91 Rarnsbottom Carbon
<0.06 <0.06 Residue on 10% distillation residue per ASTM
D524-95
[0048] Although the present invention has been described with
reference to preferred embodiments, numerous modifications and
variations can be made and still the result will come within the
scope of the invention. No limitation with respect to the specific
embodiments disclosed herein is intended or should be inferred.
* * * * *