U.S. patent application number 12/264847 was filed with the patent office on 2009-03-05 for process for the manufacture of hydrocarbons.
Invention is credited to Juha Jakkula, Eija KOIVUSALMI.
Application Number | 20090062578 12/264847 |
Document ID | / |
Family ID | 49515074 |
Filed Date | 2009-03-05 |
United States Patent
Application |
20090062578 |
Kind Code |
A1 |
KOIVUSALMI; Eija ; et
al. |
March 5, 2009 |
PROCESS FOR THE MANUFACTURE OF HYDROCARBONS
Abstract
A feedstock originating from renewable sources is converted to
branched and saturated hydrocarbons without heteroatoms in the
diesel fuel distillation range by skeletal isomerisation and
deoxygenation carried out by hydrodeoxygenation or alternatively by
combined decarboxylation and decarbonylation reactions, whereby the
consumption of hydrogen is decreased.
Inventors: |
KOIVUSALMI; Eija;
(Kulloonkyla, FI) ; Jakkula; Juha; (Kerava,
FI) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Family ID: |
49515074 |
Appl. No.: |
12/264847 |
Filed: |
November 4, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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|
11637176 |
Dec 12, 2006 |
7459597 |
|
|
12264847 |
|
|
|
|
60749581 |
Dec 13, 2005 |
|
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Current U.S.
Class: |
585/14 |
Current CPC
Class: |
C07C 2523/882 20130101;
C10G 3/46 20130101; C07C 2523/42 20130101; Y10S 585/93 20130101;
C07C 2523/28 20130101; Y02E 50/13 20130101; Y10S 585/932 20130101;
C10G 2400/04 20130101; C10G 3/47 20130101; C07C 2523/883 20130101;
C07C 9/16 20130101; C07C 2523/44 20130101; C07C 2521/04 20130101;
C07C 9/22 20130101; C07C 2523/755 20130101; C07C 2521/08 20130101;
C07C 2523/75 20130101; C10G 3/50 20130101; C10G 2300/1011 20130101;
Y02E 50/10 20130101; C07C 1/2078 20130101; C11C 3/123 20130101;
C10G 2300/44 20130101; C07C 1/2078 20130101; C07C 9/16 20130101;
C07C 1/2078 20130101; C07C 9/22 20130101 |
Class at
Publication: |
585/14 |
International
Class: |
C10L 1/16 20060101
C10L001/16 |
Claims
1. Branched saturated hydrocarbons prepared in a process comprising
skeletally isomerizing a feedstock comprising unsaturated fatty
acids or fatty acid esters with C.sub.1-C.sub.5 alcohols, or
mixtures thereof, and deoxygenating the skeletally isomerized
feedstock.
2. The branched saturated hydrocarbons according to claim 1,
wherein the feedstock comprises at least 20% by weight of
unsaturated fatty acids or fatty acid esters with C.sub.1-C.sub.5
alcohols.
3. The branched saturated hydrocarbons according to claim 1,
wherein the unsaturated fatty acid or fatty acid esters with
C.sub.1-C.sub.5 alcohols used as the feedstock has a total carbon
number of 8 to 26.
4. The branched saturated hydrocarbons according to claim 1,
wherein the feedstock originates from biological raw materials.
5. The branched saturated hydrocarbons according to claim 1,
wherein the skeletal isomerization is carried out at a temperature
of 150-400.degree. C., under the pressure of 0-5 MPa.
6. The branched saturated hydrocarbons according to claim 1,
wherein the skeletal isomerization is carried out in the presence
of an acidic catalyst selected from silico alumino phosphates and
zeolites.
7. The branched saturated hydrocarbons according to claim 1,
wherein 0-8% by weight of water or C.sub.1-C.sub.5 alcohol, based
on the total reaction mixture, is added to the feedstock.
8. The branched saturated hydrocarbons according to claim 1,
wherein after the skeletal isomerization, prehydrogenation is
carried out.
9. The branched saturated hydrocarbons according to claim 8,
wherein the prehydrogenation is carried out in the presence of a
hydrogenation catalyst containing one or more Group VIII and/or VIA
metals, at a temperature 50-400.degree. C. under a hydrogen
pressure of 0.1-20 MPa.
10. The branched saturated hydrocarbons according to claim 8,
wherein when the feedstock comprises fatty acid esters, the
prehydrogenation is carried out in the presence of a metal catalyst
at 25-30 MPa hydrogen pressure and at temperature of
200-230.degree. C.
11. The branched saturated hydrocarbons according to claim 1,
wherein the skeletal isomerization and optional prehydrogenation
forms a product which is subjected to deoxygenation, wherein the
deoxygenation is carried out by decarboxylation/decarbonylation or
hydrodeoxygenation.
12. The branched saturated hydrocarbons according to claim 11,
wherein in the decarboxylation and/or decarbonylation, the product
and optionally a solvent or a mixture of solvents are brought into
contact with an heterogeneous decarboxylation/decarbonylation
catalyst selected from supported catalysts containing one or more
Group VIII and/or VIA metals of the Periodic System, at a
temperature of 100-400.degree. C. under a pressure from atmospheric
pressure to 20 MPa of inert gas/hydrogen-mixture.
13. The branched saturated hydrocarbons according to claim 12,
wherein the heterogeneous decarboxylation and/or decarbonylation
catalyst is Pd on carbon or sulphided NiMo on alumina.
14. The branched saturated hydrocarbons according to claim 11,
wherein in the hydrodeoxygenation, the product and optionally a
solvent or a mixture of solvents are brought into contact with a
hydrogenation catalyst containing metals from Group VIII and/or VIA
of the Periodic System under a pressure between 1 and 20 MPa and at
a temperature between 200 and 500.degree. C.
15. The branched saturated hydrocarbons according to claim 14,
wherein the hydrogenation catalyst is a supported Pd, Pt, Ni, NiMo
or a CoMo catalyst and the support is alumina and/or silica.
16. The branched saturated hydrocarbons according claim 11, wherein
in the decarboxylation/decarbonylation and/or hydrodeoxygenation,
the solvent is selected from the group consisting of hydrocarbons
with the boiling range of 150-350.degree. C., and recycled process
streams containing hydrocarbons, and mixtures thereof.
17. The branched saturated hydrocarbons according to claim 2,
wherein the unsaturated fatty acid or fatty acid esters with
C.sub.1-C.sub.5 alcohols used as the feedstock has a total carbon
number of 8 to 26.
18. The branched saturated hydrocarbons according to claim 2,
wherein the feedstock originates from biological raw materials.
19. The branched saturated hydrocarbons according to claim 3,
wherein the feedstock originates from biological raw materials.
20. The branched saturated hydrocarbons according to claim 2,
wherein the feedstock comprises at least 50% by weight of
unsaturated fatty acids or fatty acid esters with C.sub.1-C.sub.5
alcohols.
Description
[0001] This application is a Divisional of co-pending application
Ser. No. 11/637,176 filed on Dec. 12, 2006, and for which priority
is claimed under 35 U.S.C. .sctn. 120; and this application claims
priority of Application No. 60/749,581 filed in United States of
America on Dec. 13, 2005 under 35 U.S.C. .sctn. 119; the entire
contents of all are hereby incorporated by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a process for the
manufacture of hydrocarbons, particularly branched hydrocarbons
from renewable sources and to a process for the manufacture of
hydrocarbons, suitable for diesel fuel pool. The process comprises
a skeletal isomerisation step and a deoxygenation step carried out
by decarboxylation/decarbonylation or hydrodeoxygenation.
BACKGROUND OF THE INVENTION
[0003] Fatty acids have been used as raw materials in various
applications in the chemical industry, typically in the manufacture
of products ranging from lubricants, polymers, fuels and solvents
to cosmetics. Fatty acids are generally obtained from wood pulping
processes or by hydrolysis of triglycerides of vegetable or animal
origin. Naturally occurring triglycerides are usually esters of
glycerol and straight chain, even numbered carboxylic acids having
10-26 carbon atoms. Most common fatty acids contain 16, 18, 20 or
22 carbon atoms. Fatty acids may either be saturated or they may
contain one or more unsaturated bonds. Unsaturated fatty acids are
often olefinic having carbon-carbon double bonds with cis
configuration. The unsaturated centres appear in preferred
positions in the carbon chain. The most common position is
.omega.9, like in oleic acid (C18:1) and erucic acid (C22:1).
Polyunsaturated acids generally have a methylene-interrupted
arrangement of cis-olefinic double bonds.
[0004] Saturated long straight chain fatty acids (C10:0 and higher)
are solid at room temperature, which makes their processing and use
difficult in a number of applications. Unsaturated long chain fatty
acids like e.g. oleic acid are easily processable liquids at room
temperature, but they are unstable because of double bond(s).
[0005] Branched fatty acids mimic the properties of straight chain
unsaturated fatty acids in many respects, but they are more stable.
For example branched C18:0 fatty acid, known as isostearic acid, is
liquid at room temperature, but it is not as unstable as C18:1
acid, since the unsaturated bonds are absent in branched C18:0.
Therefore, branched fatty acids are more desirable for many
applications than straight chain fatty acids.
[0006] Diesel fuels based on biological material are generally
referred to as biodiesel. A definition for "biodiesel" is provided
in Original Equipment Manufacturer (OEM) guidelines as follows:
Biodiesel is mono-alkyl esters of long chain fatty acids derived
from vegetable oils or animal fats, which conform to ASTM D6751 or
EN 14214 specification for use in diesel engines as described in
following Table 1. Biodiesel refers to pure fuel before blending
with diesel fuel (B100).
TABLE-US-00001 TABLE 1 Specification for Biodiesel (B100, 100%)
Property ASTM D6751 EN 14214 Units Density at 15.degree. C. 860-900
kg/m.sup.3 Flash point (closed cup) 130 .gtoreq.120 .degree. C.
Water and sediment .ltoreq.0.050 .ltoreq.0.050 % Kinematic
viscosity 40.degree. C. 1.9-6.0 3.5-5.0 mm.sup.2/s Sulfated ash
.ltoreq.0.020 .ltoreq.0.020 % mass Sulfur .ltoreq.0.05
.ltoreq.0.001 % mass Cetane number .gtoreq.47 .gtoreq.51 Carbon
residue .ltoreq.0.050 % mass Carbon residue 10% dist .ltoreq.0.3 %
mass bottom Acid number .ltoreq.0.80 .ltoreq.0.5 mg KOH/g Free
glycerol .ltoreq.0.020 .ltoreq.0.02 % mass Total glycerol
.ltoreq.0.240 .ltoreq.0.25 % mass Phosphorus content .ltoreq.0.001
.ltoreq.0.001 % mass
[0007] High cetane number, proper viscosity range and good
low-temperature properties are required for a good diesel fuel.
Cetane number (CN) has been established for describing the ignition
quality of diesel fuel or its components. Branching and chain
length influence CN, the CN decreasing with decreasing chain length
and increasing branching. Hexadecane C.sub.16H.sub.34 has a CN of
100, and 2,2,4,4,6,8,8-heptamethylnonane C.sub.16H.sub.34 has a CN
of 15. From structural features also double bonds decrease CN.
Further, compounds with unsaturation can cause gumming in
engines.
[0008] Besides CN, gross heat of combustion (HG) of a compound is
essential in providing the suitability of the compound to be used
as diesel fuel. For comparison the HGs of paraffinic and ester
biodiesels are as follows: HG of hexadecane is 2559 kg cal/mol at
20.degree. C. and of methyl palmitate (C16:0) 2550 kg cal/mol.
[0009] Cloud point presents the temperature where a petroleum
product shows just a cloud or haze of wax crystals when it is
cooled under standard test conditions, as described in standard
ASTM D2500. Cloud point measures the ability of the fuel to be used
in cold weather without plugging filters and supply lines.
[0010] Pour point is the lowest temperature at which a fuel will
just flow when tested under the conditions described in standard
ASTM D97. It is recommended by engine manufacturers that the cloud
point should be below the temperature of use and not more than
6.degree. C. above the pour point. Branching, saturation and chain
length influence also cloud and pour points and they decrease with
decreasing chain length, increasing unsaturation and increasing
branching.
[0011] The viscosity of vegetable oils is approximately one order
of magnitude greater than that of conventional diesel fuels. High
viscosity results in poor atomization in combustion chamber, thus
causing coking of nozzles and deposits.
[0012] Biodiesel is an alternative fuel, produced from renewable
sources and it contains no petroleum. It can be blended in minor
amounts with petroleum diesel to create a biodiesel blend, further
it is non-toxic and essentially free of sulfur and aromatics. It
can be used in compression-ignition (diesel) engines with little or
no modifications.
[0013] Diesel fuels based on biological material have been
demonstrated to have significant environmental benefits in terms of
decreased global warming impacts, reduced emissions, greater energy
independence and a positive impact on agriculture.
[0014] It has been demonstrated that the use of diesel fuels based
on biological material will result in a significant reduction in
carbon dioxide emissions. A biodiesel lifecycle study of 1998,
jointly sponsored by the US Department of Energy and the US
Department of Agriculture, concluded that biodiesel reduces net
CO.sub.2 emissions by 78 percent compared to petroleum diesel. This
is due to biodiesel's closed carbon cycle. CO.sub.2, released into
the atmosphere when burning biodiesel, is recycled by growing
plants, which are later processed into fuel. As such, the increased
use of diesel fuels based on biological material represents an
important step to meet the emission reduction target as agreed
under the Kyoto agreement. It is also believed that particulate
emissions and other harmful emissions, such as nitrogen oxides,
alleviating human health problems, are reduced.
[0015] Methyl esters of long-chain acids have higher cloud and pour
points than the corresponding triglycerides and conventional diesel
fuels. Cloud and pour points are important features when operating
engines in cooler environment.
[0016] Several approaches, as such transesterification, dilution,
micro-emulsification and co-solvent blending, as well as pyrolysis
have been suggested for obtaining diesel fuel from vegetable oils
and other triacylglycerol based feedstocks. The object of said
approaches is to reduce the high kinematic viscosity of neat
vegetable oils, which can cause severe operational problems and
improper atomization of the fuel.
[0017] In transesterification, triglycerides forming the main
component in vegetable oils are converted into the corresponding
esters with an alcohol in the presence of catalysts. Methanol is
the most commonly used alcohol due to its low cost and easy
separation from the resulting methyl ester and glycerol phases.
[0018] Diluting 0-34% of vegetable oils with conventional diesel
fuel leads to proper atomization but causes engine problems similar
to those with neat vegetable oils.
[0019] Micro-emulsion fuels are composed of conventional diesel
fuel and/or vegetable oil, a simple alcohol, an amphiphilic
compound such as a surfactant and a cetane improver. Trace
quantities of water are usually required for formation of the
microemulsion.
[0020] Pyrolytic methods, Kolbe electrolysis and thermal and
catalytic cracking of bio-materials like vegetable oils, their
methyl esters and animal fats result in a wide spectrum of
products, such as alkanes, alkenes, aromatics and carboxylic acids.
The reactions are generally unselective and less valuable
by-products are formed too.
[0021] Unsaturated and aromatic hydrocarbons present in the liquid
fraction make the products obtained by the above methods
unattractive for the diesel pool. Poor low-temperature properties
of the products limit their wider use as biodiesel in regions with
colder climatic conditions. In addition, the presence of oxygen in
esters results in undesirable higher nitrogen oxide (NO.sub.x)
emissions compared to conventional diesel fuels.
[0022] Sulphur free fuels are required in order to gain the full
effect of new and efficient anti-pollution technologies in modern
vehicles and to cut emissions of nitrogen oxides, volatile
hydrocarbons and particles, as well as to achieve direct reduction
of sulphur dioxide in exhaust gases. The European Union has decreed
that these products must be available to the market from 2005 and
must be the only form on sale from 2009. This new requirement will
reduce annual sulphur emissions from automotive fuels.
[0023] Branched fatty acids and fatty acid esters, mainly methyl
and ethyl esters, are obtained by isomerisation of straight chain,
unsaturated fatty acids and fatty acid esters having a
corresponding chain length, as described in U.S. Pat. No.
5,856,539. For example, branched C18:0 acids are pre-pared from
straight chain C18:1 acids or also C18:2 acids.
[0024] Decarboxylation of carboxylic acids to hydrocarbons by
contacting carboxylic acids with heterogeneous catalysts was
suggested by Maier, W. F. et al: Chemische Berichte (1982), 115(2),
808-12. Ni/Al.sub.2O.sub.3 and Pd/SiO.sub.2 catalysts were tested
for decarboxylation of several carboxylic acids. During the
reaction the vapours of the reactant passed through a catalytic bed
together with hydrogen at 180.degree. C. and 0.1 MPa. Hexane
represented the main product of the decarboxylation of heptanoic
acid. When nitrogen was used instead of hydrogen no decarboxylation
was observed.
[0025] U.S. Pat. No. 4,554,397 discloses a process for the
manufacture of linear olefins from saturated fatty acids or esters
by decarboxylation using a catalytic system, which consists of
nickel and at least one metal selected from the group consisting of
lead, tin and germanium. Additives may be included in the
above-mentioned catalysts and for example sulphur derivatives may
be added to decrease the hydrogenating power of nickel and make the
reaction more selective for olefin formation reaction. The presence
of hydrogen was necessary to maintain the activity of the catalyst.
The reaction was carried out at a temperature of 300-380.degree. C.
and the pressure was atmospheric pressure or higher.
[0026] Decarboxylation accompanied with hydrogenation of
oxo-compound is described in Laurent, E., Delmon, B.: Applied
Catalysis, A: General (1994), 109(1), 77-96 and 97-115, wherein
hydrodeoxygenation of biomass derived pyrolysis oils over sulphided
CoMo/Al.sub.2O.sub.3 and NiMo/Al.sub.2O.sub.3 catalysts was
studied. Hydrotreating conditions were 260-300.degree. C. and 7 MPa
in hydrogen. The presence of hydrogen sulphide promoted the
decarboxylation, particularly when a NiMo catalyst was used.
[0027] Unsaturated and aromatic hydrocarbons produced in the side
reactions in the above-mentioned processes make the obtained
products unattractive for the diesel pool. In addition, the
unbranched and highly saturated structures cause poor
low-temperature properties.
[0028] FI 100248 describes a two-step process for producing middle
distillate from vegetable oil by hydrogenating fatty acids or
triglycerides of vegetable oil using commercial sulphur removal
catalysts (NiMo and CoMo) to give n-paraffins and then by
isomerising said n-paraffins using metal containing molecule sieves
or zeolites to obtain branched-chain paraffins. The hydrotreating
was carried out at reaction temperatures of 330-450.degree. C.
[0029] Based on the above it can be seen that here is a need for a
new alternative process for the preparation of saturated and
branched hydrocarbons from renewable sources, suitable as biodiesel
of high quality.
OBJECT OF THE INVENTION
[0030] An object of the invention is a process for the manufacture
of branched saturated hydrocarbons from renewable sources.
[0031] A further object of the invention is a process for the
manufacture of branched saturated hydrocarbons suitable for the
diesel fuel pool.
[0032] Characteristic features of the process according to the
invention are provided in the claims.
DEFINITIONS
[0033] Skeletal isomerisation is understood to mean formation of
branches in the main carbon chain while the carbon number of the
compound is not altered.
[0034] Deoxygenation is understood to mean removal of carboxyl
oxygen, such as fatty acid or fatty acid ester oxygen.
Deoxygenation may be carried out by hydrodeoxygenation (HDO) or
decarboxylation/decarbonylation.
[0035] Decarboxylation/decarbonylation is understood to mean
removal of carboxyl oxygen through CO.sub.2 (decarboxylation)
and/or through CO (decarbonylation).
[0036] Hydrodeoxygenation (HDO) means removal of oxygen as water
using hydrogen.
[0037] The term "branched fatty acids" is herein to be understood
to comprise fatty acids containing one or more alkyl side groups,
which can be attached to the carbon chain at any position. Said
alkyl groups are generally C.sub.1-C.sub.4 alkyl chains.
[0038] Pressures are here understood to mean overpressures above
atmospheric pressure.
SUMMARY OF THE INVENTION
[0039] The present invention relates to a catalytic process for the
manufacture of branched saturated hydrocarbons, which are suitable
for diesel fuel pool, from renewable sources, such as plant,
vegetable, animal and fish fats and oils and fatty acids. The
invention concerns the transformation of a feedstock comprising
fatty acids or fatty acid esters with lower alcohols into branched
fatty acids or fatty acid esters with a acidic catalyst, followed
by converting the obtained branched fatty acids or fatty acid
esters into branched hydrocarbons either by contacting with a
heterogeneous decarboxylation/decarbonylation catalyst or with a
hydrodeoxygenation catalyst. The branched hydrocarbon product
formed via the decarboxylation/decarbonylation reaction has one
carbon atom less than the original fatty acid, and the branched
hydrocarbon product formed via the hydrodeoxygenation reaction has
an equal number of carbon atoms compared to the original fatty
acid.
[0040] A high quality hydrocarbon product with good low temperature
properties and high cetane number is obtained, employing minimum
amount of hydrogen in the process.
DETAILED DESCRIPTION OF THE INVENTION
[0041] It has now been surprisingly found that saturated and
branched hydrocarbon, suitable for biodiesel fuel, can be obtained
from oxygen containing feedstocks originating from renewable
sources by skeletal isomerisation followed by removal of oxygen
utilising deoxygenation carried out by
decarboxylation/decarbonylation or hydrodeoxygenation.
[0042] In the first process step a feedstock comprising unsaturated
fatty acids or fatty acid esters with lower alcohols, or mixtures
thereof are subjected to skeletal isomerisation wherein they are
isomerised to fatty acids or fatty acid alkyl esters containing
short alkyl branches in their carbon chain. In the subsequent
process step the branched products are deoxygenated. The
deoxygenation is carried out by decarboxylation/decarbonylation
wherein oxygen is removed in the form of CO and CO.sub.2, or
alternatively by hydrodeoxygenation wherein oxygen is removed in
the form of H.sub.2O from the isomerised fatty acids or fatty acid
alkyl esters. The process may also comprise an optional
prehydrogenation step before the deoxygenation step to remove
unsaturation after skeletal isomerisation and to liberate lower
alcohol in hydrodeoxygenation.
[0043] The process according to the invention provides a convenient
way for the manufacture of branched hydrocarbons from fatty acids
or fatty acid esters with lower alcohols. The fatty acid and fatty
acid esters originate from biological feedstock such as plant,
vegetable, animal and fish oils and fats.
Feedstock
[0044] The feedstock comprises fatty acids or fatty acid esters
with C.sub.1-C.sub.5, preferably C.sub.1-C.sub.3 alcohols, or
mixtures thereof. The feedstock preferably originates from
biological raw materials such as plant, vegetable, animal and fish
oils and fats. Biological raw materials my be treated using any
pre-treatment or purification method known in the art to obtain the
fatty acids or fatty acid esters useful as the feedstock, such as
hydrolysis etc. The feedstock comprises at least 20% by weight,
preferably at least 50% by weight and particularly preferably 80%
by weight of unsaturated fatty acids or fatty acid esters. The
feedstock may also comprise mixtures of fatty acids and fatty acid
esters, but it is preferable to use either fatty acids or fatty
acid esters.
[0045] The unsaturated fatty acid used as the feedstock is a fatty
acid having unsaturated bonds and a total carbon number of 8 to 26,
preferably 12 to 20 and particularly preferably 12 to 18. With
respect to the degree of unsaturation, i.e., the number of
unsaturated carbon-carbon bonds, any unsaturated fatty acids may be
used as long as one or more unsaturated carbon-carbon are pre-sent
in the molecule.
[0046] The feedstock may comprise C.sub.1-C.sub.5, preferably
C.sub.1-C.sub.3 alkyl esters of unsaturated fatty acids having a
total carbon number of 8-26, preferably 12-20 and particularly
preferably 12-18, corresponding to the above-mentioned unsaturated
fatty acids. Examples of suitable alkyl esters include methyl
esters, ethyl esters and propyl esters of said unsaturated fatty
acids, with preference given to methyl esters.
[0047] Typically, the number of unsaturated bonds in the feedstock
is 1 to 3. Preferably the feedstock comprises at least 40% by
weight of monounsaturated fatty acids or fatty acid esters, more
preferably at least 70% by weight. The feedstock may also comprise
polyunsaturated fatty acids or fatty acid esters. The presence of
an unsaturated bond in the molecule causes the formation of a
cation as an intermediate, thereby facilitating the skeletal
isomerisation reaction.
Skeletal Isomerisation
[0048] In the first step of the process according to the present
invention branched chain fatty acids or alkyl esters of fatty acids
are prepared. The earlier described feedstock is subjected to a
skeletal isomerisation step. The skeletal isomerisation is carried
out at a temperature of 150-400.degree. C., under the pressure of
0-5 MPa, preferably at 200-350.degree. C. and 0.1-5 MPa and
particularly preferably at 220-300.degree. C. and 0.1-2 MPa using
an acidic catalyst. Suitable acidic catalysts are silico alumino
phosphates and zeolites, preferably faujasite, offeretite,
montmorillonite and mordenite. Particularly preferably the catalyst
is mordenite.
[0049] Water or a lower alcohol may be added to the feedstock to
suppress acid anhydride formation due to dehydration or
dealcoholation. It is preferable to add water when the feedstock
comprises unsaturated fatty acids and alcohol when the feedstock
comprises esters of unsaturated fatty acids. Typically the amount
of added water or lower alcohol is 0-8%, and preferably 1-3% by
weight based on the total reaction mixture. The lower alcohol is
C.sub.1-C.sub.5 alcohol, and preferable alcohols are methanol,
ethanol and propanol, with a greater preference given to those
having the same alkyl group as that of the starting fatty acid
ester to be isomerised. Excess water (more than 10%) should be
avoided in order to prevent estolide formation. The skeletal
isomerisation step may also be carried out in the absence of water
or lower alcohol.
[0050] The skeletal isomerisation step may be carried out in a
closed batch reactor under the reaction pressure. This is to
prevent vaporization of water, alcohols and other low boiling
substances in the system, including those substances contained in a
catalyst. The reaction time is preferably less than 24 hours, more
preferably less than 12 hours and most preferably less than 30
minutes.
[0051] In general, the amount of catalyst employed in the process
is 0.01-30% by weight based on the total reaction mixture,
preferably the amount of catalyst used is 1-10% by weight.
[0052] When a continuous flow reactor is used the space velocity
WHSV is 0.1-100 l/h, more preferably 0.1-50 l/h and most preferably
1-10 l/h.
[0053] The product from the skeletal isomerisation step contains
both saturated as well as unsaturated branched chain fatty acids or
esters of fatty acids. Possible by-products are cyclic acids and
polymeric fatty acids, such as dimer acids and polymeric fatty acid
esters, when the feedstock comprises esters of unsaturated fatty
acids. The obtained branched chain compounds normally have short
alkyl side chains, the length being from 1 to 4 carbon atoms and
they are obtained as mixtures of many isomers with different
branching positions.
[0054] Preferably, the obtained branched chain fatty acids or fatty
acid esters are separated from dimer acids for example by
distillation, their unsaturated bonds are prehydrogenated and then
separated from linear, saturated alkyl fatty acids or their esters
by solvent fractionation. The order of distillation,
prehydrogenation and fractionation may be changed. Distillation and
solvent fractionation steps may also be at the end of the process
after deoxygenation.
[0055] The skeletal isomerisation product may optionally be
prehydrogenated in order to remove unsaturation, which may cause
formation of coke on the catalyst surface in the subsequent
catalytic steps. The prehydrogenation is carried out in the
presence of a hydrogenation catalyst at a temperature
50-400.degree. C. under a hydrogen pressure of 0.1-20 MPa,
preferably at 150-250.degree. C. and 1-10 MPa. The heterogeneous
hydrogenation catalyst contains one or more Group VIII and/or VIA
metals. Preferably the hydrogenation catalyst is Pd-, Pt-, Ni-,
NiMo- or CoMo-catalyst on aluminum and/or silicon oxide
support.
[0056] In the case where fatty acid esters are used as feedstock in
the isomerisation step, the branched product from skeletal
isomerisation may optionally be prehydrogenated before the final
deoxygenation step to saturate the double bonds and to liberate the
lower alcohol used in esterification. Fatty acid alkylesters are
converted to fatty alcohols for hydrodeoxygenation. Liberated lower
alcohol may be recycled after distillation. Fatty acid alkylesters
are prehydrogenated with metal catalysts at 25-30 MPa hydrogen
pressure and at temperature of 200-230.degree. C. The metal
catalyst is preferably copper-chromite catalyst or chrome, ferrous
or rhodium activated nickel catalyst.
Deoxygenation
[0057] The branched product obtained from the skeletal
isomerisation step is then subjected to deoxygenation carried out
by decarboxylation/decarbonylation or hydrodeoxygenation.
[0058] In the first embodiment, the saturated and branched fatty
acids or esters of fatty acids and optionally a solvent or a
mixture of solvents are brought into contact with a heterogeneous
decarboxylation/decarbonylation catalyst selected from supported
catalysts containing one or more Group VIII and/or VIA metals of
the Periodic System. Preferably, the
decarboxylation/decarbonylation catalysts are supported Pd, Pt, Ni,
NiMo or a CoMo catalysts, the support being alumina and/or silica
and/or carbon. Particularly preferably Pd on carbon and sulphided
NiMo on alumina are used. Hydrogen may optionally be used. The
decarboxylation/decarbonylation reaction conditions may vary with
the feedstock used. The reaction is carried out in liquid phase.
The decarboxylation/decarbonylation reaction is carried out at a
temperature of 100-400.degree. C., preferably 250-350.degree. C.
The reaction may be conducted under atmospheric pressure. However,
in order to maintain the reactants in the liquid phase it is
preferable to use higher pressure than the saturation vapour
pressure of the feedstock at a given reaction temperature and thus
the reaction pressure ranges from atmospheric pressure to 20 MPa
and preferably from 0.1 to 5 MPa of inert gas/hydrogen mixture. The
product obtained from this embodiment is a mixture of hydrocarbons,
preferably branched paraffins boiling in the range of
180-350.degree. C., the diesel fuel range, and having one carbon
atom less than the original fatty acid chain.
[0059] In the second embodiment, in the hydrodeoxygenation step the
branched fatty acids or esters thereof obtained from the skeletal
isomerisation step, or the fatty alcohols obtained by the optional
prehydrogenation step, and optionally a solvent or a mixture of
solvents are brought into contact with an optionally pre-treated
heterogeneous hydrogenation catalysts containing metals from Group
VIII and/or VIA of the Periodic System, known in the art for
hydrodeoxygenation. Preferably, the hydrodeoxygenation catalysts
are supported Pd, Pt, Ni, NiMo or a CoMo catalysts, the support
being alumina and/or silica. Particularly preferably
NiMo/Al.sub.2O.sub.3 and CoMo/Al.sub.2O.sub.3 catalysts are used.
In the hydrodeoxygenation step, the pressure range can be varied
between 1 and 20 MPa, preferably 2-10 MPa, and the temperature
200-500.degree. C., preferably 250-350.degree. C.
[0060] The optional solvent in each deoxygenation embodiment can be
selected from the group consisting of hydrocarbons, such as
paraffins, isoparaffins, naphthenes and aromatic hydrocarbons in
the boiling range of 150-350.degree. C., and recycled process
streams containing hydrocarbons, and mixtures thereof, preferably
the recycled product streams obtained from the process according to
the invention are used.
Product
[0061] The process according to the invention yields a branched and
paraffinic hydrocarbon product suitable for diesel fuel pool. The
product contains typically some short carbon-carbon side branches,
resulting in an exceptionally low cloud point and cold filter
plugging point but still a good cetane number compared to the
products obtained by the known methods. In Table 2 properties of
the product produced with the process according to the invention
(1) are compared to those obtained by processes according to the
state of the art (2-6). All products are 100% (B100) diesel
components.
TABLE-US-00002 TABLE 2 Product Product Product Product Product
Product Property 1 2 3 4 5 6 kV40 2.4-4.4 2.9-3.5 4.5 3.2-4.5
2.0-4.5 1.2-4.0 mm.sup.2/s Cloud point -29--42 -5--30 -5 0--25
-10--34 .degree. C. Flash point 67-141 52-65 .gtoreq.55 PMcc,
.degree. C. Cold filter plug -31--45 -15--19 .ltoreq.+5--20
.ltoreq.-20--44 point, .degree. C. IQT cetane 60-93 84-99 51 73-81
.gtoreq.51 .gtoreq.51 number Sulfur <10 <10 <10 <10
<10 <10 ppm Density 15.degree. C. 799-811 775-785 885 770-785
820-845 800-840 kg/m.sup.3 Dist. 10% 195-286 260-270 340 260 180
90% 301-337 295-300 355 325-330 95% 312-443 360 340
[0062] The products of Table 2 are prepared as follows: [0063] (1)
is prepared by the method according to the invention, by skeletal
isomerisation and deoxygenation of fatty acids [0064] (2) is
prepared by hydrodeoxygenation and hydroisomerisation of
triglycerides [0065] (3) is fatty acid methyl ester prepared by
transesterification of rape seed oil [0066] (4) is natural gas
based diesel fuel prepared by gas to liquid and hydroisomerisation
processes [0067] (5) and (6) are mineral oil based diesel fuels
with different specifications for use in the arctic conditions
[0068] The structure of the branched, saturated hydrocarbon product
obtained using the process according to the invention is different
from the one obtained for example when hydroisomerising C16-C22
normal paraffins. In the present case the branches are mainly in
the middle of the long carbon chain, due to the common .omega.9
olefinic unsaturation positions responsible of branching. In the
hydroisomerised isoparaffins, the branches are mainly near the end
of the carbon main chain. The carbon number of the hydrocarbon
product of the invention is C13-C22, typically C15-C18 and the
carbon number in the product can be adjusted by changing the
hydrodeoxygenation and/or decarboxylation/decarbonylation reaction
conditions.
[0069] The branched, saturated hydrocarbon product contains
paraffins more than 80 vol-%, typically more than 99 vol-%.
[0070] The branched, saturated hydrocarbon product contains
n-paraffins less than 30 wt-%, typically less than 15 wt-%.
[0071] The branched, saturated hydrocarbon product contains
aromatics less than 20 vol-%, typically less than 10 vol-%
according to method IP-391.
[0072] Biodiesel components also contain .sup.14C-isotope, which
can be used as an evidence of the bio origin of the fuel. The
typical .sup.14C content of the branched, saturated hydrocarbon
product is at least 100% based on radiocarbon content compared to
radiocarbon content of air in the year 1950.
[0073] The process according to the invention has several
advantages. With the process, a branched, saturated hydrocarbon
product comprising branched chains and suitable for the diesel fuel
pool is obtained from renewable sources. Due to the absence of
unsaturation in the hydrocarbon product, the oxidation stability is
good and the tendency for polymerisation low compared to the
conventional fatty acid methyl ester based biodiesel compounds.
[0074] Branching in the paraffinic carbon chain enhances low
temperature properties, such as cloud point, pour point and
cold-filter plugging point. The extremely good low temperature
properties make it possible to use the branched, saturated
hydrocarbon product as diesel fuel or diesel fuel component also in
arctic fuels.
[0075] The branched, saturated hydrocarbon products manufactured
according to the invention are designed for use in
compression-ignition engines, where air is compressed until it is
heated above the auto-ignition temperature of diesel fuel and then
the fuel is injected as a high pressure spray, keeping the fuel-air
mix within the flammable limits of diesel. Because there is no
ignition source, the diesel fuel is required to have a high cetane
number and a low auto-ignition temperature.
[0076] Due to saturation and long paraffinic chain length, the
cetane number of the branched, saturated hydrocarbon product is
high, thus making the product suitable as cetane number improver.
The cetane number gauges the ease with which the diesel fuel will
auto-ignite when compressed. Higher cetane numbers indicate easier
self-ignition and better engine operation.
[0077] The high flash point of the branched, saturated hydrocarbon
product is important primarily from a fuel-handling standpoint. In
the ethanol/mineral oil diesel or ethanol/vegetable oil diesel
microemulsions, the flash point is remarkably lower. A too low
flash point will cause fuel to be a fire hazard, subject to
flashing, and possible continued ignition and explosion. In
addition, a low flash point may indicate contamination by more
volatile and explosive fuels, such as gasoline.
[0078] Because of the natural fatty acid based raw materials, the
branched, saturated hydrocarbon product contains no sulphur. Thus,
in the pretreatment of exhaust gas the catalysts and particulate
filters can easily be adjusted to the sulphur-free hydrocarbon
compound according to invention. Catalyst poisoning is reduced and
catalyst service lifetime is significantly prolonged.
[0079] Even though the branched, saturated hydrocarbon product is
produced from the natural fatty acid based raw materials it
contains no oxygen, thus the nitrogen oxide (NO.sub.x) emissions
are much lower than those of conventional biodiesel fuels.
[0080] The composition of the branched, saturated hydrocarbon
product produced according the invention resembles highly those of
conventional diesel fuels, thus it can be used in
compression-ignition (diesel) engines with no modifications, which
is not the case with fatty acid methyl ester based bio-diesel
compounds.
[0081] Further, due to the pure paraffinic composition without any
oxygen containing compounds, no gum is formatted in the fuel
delivery systems. Engine parts are not contaminated by carbon
deposits as with fatty acid methyl ester based bio-diesel
compounds.
[0082] The branched, saturated hydrocarbon product can be blended
at any level with petroleum diesel and with fatty acid methyl ester
based bio-diesel compounds. The latter may be advantageous if the
lubricity of the product needs to be enhanced.
[0083] Particularly, when the process is carried out using the
decarboxylation/decarbonylation route, consumption of hydrogen is
reduced significantly. Decarboxylation/decarbonylation reactions
decrease hydrogen consumption by 20-40%.
[0084] The invention is illustrated in the following examples
presenting some preferable embodiments of the invention. However,
it is evident to a person skilled in the art that the scope of the
invention is not meant to be limited to these examples only.
EXAMPLES
Example 1
Skeletal Isomerisation and Deoxygenation of Tall Oil Fatty Acid
[0085] Distilled tall oil fatty acids were isomerised in a Parr
high-pressure reactor with mordenite type zeolite. Tall oil fatty
acids, 5 wt-% of the catalyst and 3 wt-% of water, calculated of
total reaction mixture, were placed in a reactor and air was
removed from the autoclave with purging nitrogen. The mixture was
stirred with 300 rpm. The reactor was heated to 280.degree. C. and
kept under nitrogen atmosphere of 1.8 MPa for 6 hours. After
cooling, the reaction mixture obtained was taken from the
autoclave, and the zeolite was filtered off. The filtrate was
distilled under reduced pressure to yield monomeric acids.
[0086] The monomeric acids thus obtained were placed in an
autoclave, and double bonds were hydrogenated at 150.degree. C.
with a catalyst containing 5 wt-% Pd on carbon for 3 hours under
hydrogen atmosphere of 2 MPa until the reaction was complete.
Catalyst amount was 2 wt-% of monomeric acid. Then, the reaction
mixture was cooled, and the catalyst was filtered off.
[0087] The obtained crude branched chain fatty acids were subjected
to a conventional solvent fractionation procedure to yield
isomerised fatty acids. To the crude branched chain fatty acids,
about 2-fold amount by weight of hexane was added. After this
mixture was cooled to -15.degree. C., the resulting crystals were
filtered off. Then, the hexane was distilled off from the filtrate
to yield purified isomerised fatty acids.
[0088] In the subsequent deoxygenation step carried out by
hydrodeoxygenation the isomerised fatty acids were
hydrodeoxygenated in a Parr high-pressure reactor with dried and
presulphided NiMo/Al.sub.2O.sub.3 catalyst to the corresponding
paraffins at a hydrogen pressure of 3.3 MPa and 340.degree. C.
temperature. The amount of catalyst was 2.5 wt-% of fatty
acids.
[0089] The product was a branched, mainly paraffinic hydrocarbon
mixture with the properties shown in Table II. The color of the
product was lightly yellow and it contained<10 ppm of sulphur
originating from the HDO catalyst used in the batch
hydrodeoxygenation.
Example 2
Skeletal Isomerisation and Deoxygenation of Tall Oil Fatty Acids at
Lower Temperature
[0090] The distilled tall oil fatty acids were isomerised, the
double bonds hydrogenated and the branched, saturated fatty acids
hydrodeoxygenated otherwise as in example 1 except that the reactor
temperature in the hydrodeoxygenation was lower, 325.degree. C.
[0091] A crystal clear product with properties presented in Table 3
was obtained.
Example 3
Skeletal Isomerisation of Tall Oil Fatty Acids without Water,
Deoxygenation at Lower Temperature and Cold Filtration of the End
Product
[0092] In the skeletal isomerisation step tall oil fatty acids and
5 wt-% of the mordenite type zeolite catalyst were mixed and air
was removed from the Parr high-pressure autoclave with purging
nitrogen. The mixture was stirred with 300 rpm. The reactor was
heated to 275.degree. C. and kept in a nitrogen atmosphere 0.1 MPa
for 6 hours. After cooling, the reaction mixture obtained was taken
out from the autoclave, and the zeolite was filtered off. The
filtrate was distilled under reduced pressure to yield monomeric
acids.
[0093] The double bonds of the monomeric acids thus obtained were
hydrogenated as in example 1.
[0094] In the deoxygenation step the isomerised fatty acids were
hydrodeoxygenated in a Parr high-pressure reactor with dried and
presulphided NiMo/Al.sub.2O.sub.3 catalyst to paraffins at a
hydrogen pressure of 3.3 MPa and 325.degree. C. temperature. The
amount of catalyst was 2.5 wt-% of fatty acids. The mixture was
cooled to -15.degree. C. and the resulting crystals were filtered
off.
[0095] The product was a branched, mainly paraffinic hydrocarbon
mixture with the properties shown in Table 3. The color of the
product was crystal clear.
Example 4
Skeletal Isomerisation of Tall Oil Fatty Acids without Water and
Deoxygenation by Decarboxylation/Decarbonylation
[0096] Tall oil fatty acids were isomerised and prehydrogenated as
in example 3. In the deoxygenation step carried out by
decarboxylation/decarbonylation the isomerised fatty acids were
loaded in a Parr high-pressure reactor and the carboxyl groups were
removed with dried and presulphided NiMo/Al.sub.2O.sub.3
catalyst.
[0097] Isomerised fatty acids were decarboxylated/decarbonylated to
paraffins at a gas pressure of 0.3 MPa and 335.degree. C.
temperature. The amount of catalyst was 2.5 wt-% of fatty acids.
The gas consisted of 10% hydrogen in nitrogen.
[0098] The product was a branched, mainly paraffinic hydrocarbon
mixture with the carbon chain length typically one carbon atom less
than in the hydrodeoxygenation and with the properties shown in
Table 3. The color of the product was crystal clear.
TABLE-US-00003 TABLE 3 Properties of Hydrocarbon Products Example
Example Example Example Method Analysis 1 2 3 4 ASTM D4052 Density
15.degree. C., 811 809 799 800 kg/m.sup.3 ASTM D2887 Distillation
Start .degree. C. 245 219 225 117 5%, .degree. C. 277 281 270 170
10%, .degree. C. 283 286 280 195 30%, .degree. C. 294 293 294 262
50%, .degree. C. 300 296 300 271 70%, .degree. C. 309 310 309 283
90%, .degree. C. 326 337 323 301 95%, .degree. C. 362 443 357 312
End, .degree. C. 486 507 481 355 ASTM D445 kV40, 4.0 4.4 3.8 2.4
cSt n-Paraffins 6 15 7 11 GC wt-% Paraffinic C >70 >70 70 IR
wt-% Naphtenic C 24 IR wt-% Aromatic C 14 7 6 IR wt-% ASTM D3120 S,
mg/kg 9 <1 ASTM D4629 N, mg/kg <1 <1 EN 22719 Flash point
141 138 139 67 PMcc, .degree. C. IQT 93 78 93 60 cetane number EN
116 Cold Filter -39 -31 -35 -45 Plug Point .degree. C. ASTM D5773
Cloud Point, -32 -29 -29 -42 D5771 .degree. C. IP 391 Aromatics
16.1 7.8 5.8 % (mainly mono)
* * * * *