U.S. patent application number 12/227214 was filed with the patent office on 2009-04-30 for hydrogenation process.
This patent application is currently assigned to BP OIL INTERNATIONAL LIMITED. Invention is credited to Nicholas John Gudde, James Adam Townsend.
Application Number | 20090107033 12/227214 |
Document ID | / |
Family ID | 37416185 |
Filed Date | 2009-04-30 |
United States Patent
Application |
20090107033 |
Kind Code |
A1 |
Gudde; Nicholas John ; et
al. |
April 30, 2009 |
Hydrogenation Process
Abstract
A process for the production of a fuel composition comprising
hydrocarbons derived from carboxylic acids and/or carboxylic acid
esters, which process comprises feeding hydrogen and a
hydrocarbon-containing stream to a first reactor to reduce levels
of olefins and/or heteroatom-containing compounds in the
hydrocarbon-containing stream, and feeding the so-treated
hydrocarbon-containing stream to a second reactor together with
hydrogen and a carboxylic acid and/or ester to produce a second
hydrocarbon-containing stream in which at least some of the
hydrocarbons are derived from the carboxylic acid and/or ester.
Inventors: |
Gudde; Nicholas John;
(Surrey, GB) ; Townsend; James Adam; (Queensland,
AU) |
Correspondence
Address: |
NIXON & VANDERHYE, PC
901 NORTH GLEBE ROAD, 11TH FLOOR
ARLINGTON
VA
22203
US
|
Assignee: |
BP OIL INTERNATIONAL
LIMITED
Middlesex
GB
|
Family ID: |
37416185 |
Appl. No.: |
12/227214 |
Filed: |
May 18, 2007 |
PCT Filed: |
May 18, 2007 |
PCT NO: |
PCT/GB2007/001841 |
371 Date: |
November 12, 2008 |
Current U.S.
Class: |
44/308 |
Current CPC
Class: |
C10G 2300/202 20130101;
C10G 3/50 20130101; C10G 2400/04 20130101; C10G 3/46 20130101; C10G
2300/1018 20130101; Y02P 30/20 20151101; C10G 2300/1048 20130101;
C10G 2300/1014 20130101 |
Class at
Publication: |
44/308 |
International
Class: |
C10L 1/188 20060101
C10L001/188 |
Foreign Application Data
Date |
Code |
Application Number |
May 25, 2006 |
EP |
06252735.3 |
Claims
1. A process for the production of a fuel composition comprising
hydrocarbons derived from carboxylic acids and/or carboxylic acid
esters, which process comprises the steps of; (a) feeding hydrogen
and a first hydrocarbon-containing process stream to a first
reactor; (b) maintaining conditions within the first reactor
sufficient to produce a first hydrocarbon-containing product stream
with a reduced concentration of heteroatom-containing organic
compounds and/or olefins compared to the first
hydrocarbon-containing process stream; (c) removing the first
hydrocarbon-containing product stream from the first reactor;
characterised by the process additionally comprising the steps of;
(d) feeding hydrogen, a carboxylic acid and/or carboxylic acid
ester, and at least a 15 portion of the first
hydrocarbon-containing product stream to a second reactor; (e)
maintaining conditions within the second reactor sufficient to
convert at least some of the carboxylic acid and/or carboxylic acid
ester to one or more hydrocarbons; (f) removing a second
hydrocarbon-containing product stream from the second 20 reactor,
in which at least a portion of the hydrocarbons are derived from
the carboxylic acid and/or carboxylic acid ester.
2. A process as claimed in claim 1, in which the fuel composition
is a diesel fuel.
3. A process as claimed in claim 1, in which carboxylic acid and/or
carboxylic acid ester is a fatty acid and/or ester.
4. A process as claimed in claim 1, in which the carboxylic acid
and/or carboxylic acid ester is derived from plant or animal fat or
oil.
5. A process as claimed in claim 1, in which the first hydrocarbon
containing process stream comprises middle distillate hydrocarbons
from a crude oil refinery.
6. A process as claimed in claim 5, in which the hydrocarbons
comprise both straight-run middle distillate hydrocarbons, and
hydrocarbons derived from other refinery process with a similar
boiling range to that of the straight-run fraction.
7. A process as claimed in claim 1, in which the first
hydrocarbon-containing process stream has a sulphur concentration
of 200 ppm or more, expressed as elemental sulphur.
8. A process as claimed in claim 1, in which the first hydrocarbon
containing product stream comprises less than 200 ppm sulphur
expressed as elemental sulphur.
9. A process as claimed in claim 1, in which the first reactor is
maintained at a temperature in the range of from 250 to 430.degree.
C. and a pressure in the range of from 20 to 200 bara (2 to 20
MPa).
10. A process as claimed in claim 1, in which the second reactor is
maintained at a temperature in the range of from 200 to 410.degree.
C. and a pressure in the range of from 20 to 200 bara (2 to 20
MPa).
11. A process as claimed in claim 1, in which additional
hydrocarbons are fed to the second reactor.
Description
[0001] This invention relates to the field of hydrogenation, more
specifically to the hydroprocessing of carboxylic acids and/or
carboxylic acid esters, for example biologically derived fatty
acids and/or fatty acid esters, to produce fuels.
[0002] Fuels such as gasoline, diesel and jet fuel, are generally
produced by the processing of crude oil. In a crude oil refinery,
fuel precursor compositions are typically produced by mixing
straight run fractions from the crude distillation unit with
refinery streams derived from the upgrading of heavier or lighter
fractions from the crude distillation unit. Often, these
compositions contain undesirable components, such as aromatics,
olefins or sulphurous compounds, and require further treatment in
order to render them suitable for use as fuels. One way in which
this is achieved is to subject them to hydrogenation processes such
as hydrotreatment or hydrocracking in order to reduce levels of
undesirable components. Typically, such processes entail contacting
the precursor fuel composition with hydrogen at elevated
temperature and pressure, optionally in the presence of a catalyst,
wherein olefins and aromatics are hydrogenated to paraffins, and
sulphur-containing compounds are converted to hydrogen sulphide,
which can be removed from the fuel using a flash or separator
vessel.
[0003] With increasing focus on fossil fuel-derived carbon dioxide
and its potential impact on climate change, there is increasing
demand for fuels which reduce the net quantity of carbon dioxide
released to the atmosphere. One way of achieving this is to use
biomass as the source of the fuel. Biomass, whether plant or
animal-derived, is ultimately produced by the fixation of
atmospheric carbon dioxide through photosynthesis and associated
biochemical processes. As the quantity of carbon dioxide released
on combustion of biomass is equivalent to the quantity of carbon
dioxide extracted from the atmosphere for its production, biomass
combustion is effectively a CO.sub.2-neutral process. However, as
the quantity of biologically-derived materials suitable for use as
fuels, such as diesel or gasoline, is not always sufficient to meet
demand, the blending of biologically derived materials with
existing mineral-derived fuels is increasingly being considered as
an attractive option for reducing a fuel's atmospheric
CO.sub.2-impact.
[0004] A problem associated with blending biologically derived
oils, such as fatty acids and/or fatty acid esters, with existing
fuel formulations is that combustion engines may need to be
modified in order to run efficiently on the modified fuel. One way
of avoiding the need for engine modification is to convert the
biological oils to hydrocarbons that can readily be blended with
existing fuel. Such a process is described, for example, in U.S.
Pat. No. 5,702,722, in which a biomass feedstock is reacted with
hydrogen to produce a mixture of hydrocarbons, the middle
distillate fraction of which is suitable for blending with
conventional diesel fuel.
[0005] Another process, described by Baldauf & Balfanz in VDE
Reports No 1126 (1994) pp 153-168, describes the co-hydrotreatment
of a refinery-derived middle distillate stream and
biologically-derived oil to produce a diesel fuel.
[0006] However, a problem associated with co-hydrotreatment of
biologically-derived oils, which comprise fatty acids and/or fatty
acid esters, with a refinery middle distillate stream is that
hydrotreating fatty acids and/or fatty acid esters is generally
more exothermic and consumes more hydrogen than hydrotreating a
middle distillate fuel. In addition, more gaseous by-products such
as carbon dioxide are typically produced, which can lead to higher
rates of corrosion of process equipment.
[0007] According to the present invention, there is provided a
process for the production of a fuel composition comprising
hydrocarbons derived from carboxylic acids and/or carboxylic acid
esters, which process comprises the steps of; [0008] (a) feeding
hydrogen and a first hydrocarbon-containing process stream to a
first reactor; [0009] (b) maintaining conditions within the first
reactor sufficient to produce a first hydrocarbon-containing
product stream with a reduced concentration of
heteroatom-containing organic compounds and/or olefins compared to
the first hydrocarbon-containing process stream; [0010] (c)
removing the first hydrocarbon-containing product stream from the
first reactor; characterised by the process additionally comprising
the steps of; [0011] (d) feeding hydrogen, a carboxylic acid and/or
carboxylic acid ester, and at least a portion of the first
hydrocarbon-containing product stream to a second reactor; [0012]
(e) maintaining conditions within the second reactor sufficient to
convert at least some of the carboxylic acid and/or carboxylic acid
ester to one or more hydrocarbons; [0013] (f) removing a second
hydrocarbon-containing product stream from the second reactor, in
which at least a portion of the hydrocarbons are derived from the
carboxylic acid and/or carboxylic acid ester.
[0014] The present invention comprises two hydrogenation stages,
wherein the first stage involves contacting a first
hydrocarbon-containing process stream with hydrogen to reduce the
levels of olefin and/or heteroatom-containing organic compounds
contained therein to produce a first hydrocarbon-containing product
stream, and the second step involves hydrogenation of a carboxylic
acid and/or ester in combination with at least a portion of the
first hydrocarbon-containing product stream. Such a process enables
carboxylic acids and/or carboxylic acid esters to be hydrogenated
in a way that is readily retrofittable to existing hydrogenation
processes, as operated for example in a crude-oil refinery, which
minimises any disruption or down-time during installation and
start-up of the second reactor. In addition, conditions within the
second reactor can be maintained such that the hydrogenation of the
carboxylic acid and/or carboxylic acid ester to hydrocarbons is
optimised, which may be different from the conditions maintained in
the first reactor. The present invention is particularly suitable
for the production of fuel compositions in which components derived
from the carboxylic acid and/or ester are in the minority, such
that the separate hydrogenations enable optimum yields of the
desired fuel to be achieved for each feedstock. Preferably, the
fuel comprises in the range of from 0.1 to 49.9% by weight of
components derived from carboxylic acid and/or carboxylic acid
ester, such as in the range of 2 to 15% by weight.
[0015] A mixture of more than one carboxylic acid and/or carboxylic
acid ester can be used. The carboxylic acid and/or ester, or
mixtures of carboxylic acids and/or esters, is preferably chosen
such that the one or more hydrocarbons produced by the reaction in
the second reactor are in the same range as those in the target
fuel. For example, diesel fuels typically comprise hydrocarbons
having in the range of from 10 to 22 carbon atoms. Thus, carboxylic
acids which produce hydrocarbons with numbers of carbon atoms in
this range would be suitable, such as mono- or di-carboxylic acids
including n-hexadecanoic acid or 1,16-di hexadecanoic acid and/or
esters thereof. Fatty acids and/or their esters are also suitable,
with general formula R.sup.1C(O)OH and/or R.sup.1C(O)O--R.sup.2,
where R.sup.1 and R.sup.2 are typically hydrocarbon chains.
Examples of fatty acids and/or esters suitable for use in
accordance with the present invention in the production of a diesel
fuel include, for example, lauric, myristic, palmitic, stearic,
linoleic, linolenic, oleic, arachidic and erucic acids and/or
esters thereof, wherein R.sup.1 comprises 11, 13, 15, 17, 17, 17,
17, 19 and 21 carbon atoms respectively. The esters may be present
as mono-, di- or triglycerides, with general formula
[R.sup.1C(O)O].sub.nC.sub.3H.sub.5(OH).sub.3-n, where n=1, 2 or 3
for mono-, di- or tri-glycerides respectively. The fatty acids
and/or esters thereof may have saturated or unsaturated hydrocarbon
groups. Di- or tri-glycerides may comprise hydrocarbon chains
derived from the same or different fatty acids.
[0016] Preferably, the carboxylic acid and/or ester is derived from
biomass, being a component for example of plant or animal-derived
oil or fat. Use of biologically-derived carboxylic acids and/or
esters ensures that the resulting fuel composition has a lower net
emission of atmospheric carbon dioxide compared to an equivalent
fuel derived purely from mineral sources. Suitable biological
sources of carboxylic acids and/or esters include plant-derived
oils, such as rapeseed oil, peanut oil, canola oil, sunflower oil,
tall oil, corn oil, soybean oil. Animal oils or fats, such as
tallow fat or chicken fat, are also suitable sources of carboxylic
acids and/or esters, as are waste oils, such as used cooking
oils.
[0017] Biological oils or fats comprise triglycerides with
hydrocarbon groups having numbers of carbon atoms commensurate with
hydrocarbons typically found in diesel fuel. Thus, the process of
the present invention is preferably used to produce diesel fuel, in
which the second reactor is maintained under hydrotreating
conditions, which consumes less hydrogen and requires less energy
than converting the biological oils or fats to lower boiling fuels
such as jet fuel, gasoline or LPG, which typically require harsher
hydrocracking conditions.
[0018] In the process of the present invention, a first
hydrocarbon-containing process stream is fed to a first reactor, in
which it is reacted with hydrogen. The first hydrocarbon-containing
process stream is suitably a liquid process stream. It may be
derived from gas or coal, wherein liquid hydrocarbons have been
produced therefrom through processes such as steam reforming and/or
partial oxidation coupled with Fischer Tropsch synthesis.
Alternatively, the first hydrocarbon-containing process stream can
be derived from crude oil. The present invention is particularly
suitable for crude oil-derived liquid hydrocarbon process streams,
as they are typically higher in heteroatom-containing organic
compounds compared to Fischer Tropsch-derived hydrocarbons.
[0019] Suitable process streams derived from the refining of crude
oil include naphtha, kerosene, or middle distillate fractions. The
process stream may be a straight-run fraction taken directly from a
crude oil distillation unit, or it may be derived from or comprise
hydrocarbons produced by other refinery processes, such as
cracking, reforming, coking, dearomatisation and/or alkylation.
Typically, crude oil-derived streams contain components such as
olefins and/or heteroatom-containing organic compounds, in
particular organosulphur compounds, and hence are suitably treated
with hydrogen by processes such as hydrocracking or
hydrotreating.
[0020] The first hydrocarbon-containing process stream preferably
comprises middle distillate hydrocarbons, which boil at
temperatures typically in the range of from 150 to 400.degree. C.,
and wherein the number of carbon atoms is typically in the range of
from 10 to 22 carbon atoms. This fraction is preferably used to
produce diesel fuel, although it can also be used to produce
heating oil and jet fuel. The straight-run fraction may be mixed
with hydrocarbons produced by other refinery processes, such as
steam cracking and/or hydrocracking of heavier crude fractions,
which produce hydrocarbons in a similar boiling range to that of
the straight-run fraction.
[0021] The first hydrocarbon-containing process stream comprises
alkanes, olefins and/or one or more heteroatom-containing
compounds. Typically, the heteroatom-containing compounds are
sulphur-containing compounds such as mercaptans or thiols. They are
typically present at concentrations greater than that allowed in
the desired fuel by State regulatory authorities. Thus, the sulphur
content of the first hydrocarbon-containing process stream is
typically 200 ppm or more, such as 0.1% by weight or more, for
example in the range of from 0.2 to 2% by weight, expressed as
elemental sulphur. Olefins may be present at concentrations up to
50% by weight, typically up to 20% by weight. Other possible
constituents of the first hydrogen-containing product stream
include aromatic compounds, such as naphthenes. Preferably, the
first hydrocarbon-containing product stream does not comprise
carboxylic acids and/or esters or biomass-derived constituents, as
these are preferably fed to the second reactor.
[0022] Conditions in the first reactor are maintained so as to
reduce the concentration of olefins and/or heteroatom-containing
organic compounds contained in the first hydrocarbon-containing
process stream. This can be achieved by employing conditions
typically used in refinery hydrocracking or hydrotreating
processes.
[0023] Hydrotreating or hydrocracking is typically carried out at
temperatures in the range of from 250 to 430.degree. C. and
pressures in the range of from 20 to 200 bara (2 to 20 MPa). The
severity of the conditions depends on the nature of the
hydrocarbon-containing process stream being fed to the reactor, and
the nature of the desired fuel product. For example, where removing
heteroatom-containing organic compounds from a stream suitable for
gasoline fuel is the main concern, low severity, hydrotreating
conditions employing temperatures in the range of from 250 to
350.degree. C. and pressures in the range of from 20 to 40 bara (2
to 4 MPa) are typically used. For removing heteroatom-containing
organic compounds from a process stream suitable for diesel fuel,
then moderate severity hydrotreating conditions may be employed,
with temperatures typically in the range of from 300 to 400.degree.
C. and pressures in the range of from 30 to 70 bara (3 to 7 MPa).
For vacuum gas oil feedstocks more severe hydrotreating conditions
may be employed, such as temperatures in the range of from 350 to
410.degree. C. and pressures in the range of from 70 to 150 bara (7
to 15 MPa). Where cracking of feedstocks to produce, for example, a
mixture of hydrocarbons suitable for gasoline and/or diesel fuels
is required, then higher severity, hydrocracking conditions are
employed, such as temperatures in the range of from 350 to
430.degree. C., and pressures in the range of from 100 to 200 bara
(10 to 20 MPa).
[0024] The hydrogenation reaction in the first reactor may be
catalysed or uncatalysed, preferably catalysed. Suitable catalysts
include those comprising one or more of Ni, Co, Mo (others),
preferably Ni and Mo, or Co and Mo. The catalyst is typically
supported on a support such as zirconia, titania or gamma-alumina,
preferably gamma alumina. Such catalysts are suitable for both
hydrotreating and hydrocracking, depending on the reaction
conditions.
[0025] The reaction in the first reactor may be a hydrocracking
reaction in the presence of a hydrocracking catalyst, a
hydrotreating reaction in the presence of a hydrotreating catalyst,
or may be a combined hydrocracking and hydrotreating reaction,
optionally in the presence of two or more catalyst beds.
[0026] The product of the first reactor, the first
hydrocarbon-containing product stream, has lower concentrations of
olefins and/or heteroatom-containing organic compounds than the
first hydrocarbon-containing process stream fed to the first
reactor.
[0027] In a preferred embodiment of the invention the sulphur
concentrations in the first hydrocarbon-containing product stream
are typically less than 200 ppm expressed as elemental sulphur. At
least a portion of the first hydrocarbon-containing product stream
is fed to the second reactor, optionally and preferably with prior
removal of light end components such as hydrogen sulphide and
unreacted hydrogen using, for example, a flash separator. The
unreacted hydrogen may suitably be recycled back to the first
reactor, used as feed to the second reactor, or used elsewhere, for
example in a different refinery process.
[0028] Carboxylic acid and/or carboxylic acid ester is fed to the
second reactor with hydrogen and at least a portion of the product
stream from the first reactor. An advantage of diluting the
carboxylic acid and/or ester in the second reactor with the first
hydrocarbon-containing product stream that has already been reacted
with hydrogen, the exotherm generated in the second reactor is
reduced. This is particularly advantageous in improving the yield
of diesel, for example, as the production of lighter hydrocarbons
that are more suitable for gasoline or LPG (liquefied petroleum
gas) is reduced. It may also extend the active life of the catalyst
by minimising the temperatures to which it is exposed. Additionally
the diluting effect of the first hydrocarbon-containing product
stream can mitigate the extent of catalyst fouling that may occur
by reducing unwanted side reactions of the carboxylic acid and/or
ester. The diluting effect may also reduce hydrogen consumption
within the catalyst bed, leading to reduced catalyst coking. Yet
another advantage of combining the carboxylic acid and/or ester
with a portion of the first product stream for the second reactor
is that the concentrations of any residual olefins and/or
heteroatom-containing organic compounds that remain in the first
product stream from the first reactor can be further reduced.
[0029] The carboxylic acid and/or ester, the hydrogen and the
portion of the first hydrocarbon-containing product stream may be
fed to the second reactor separately. Alternatively, any or all of
the separate components can be pre-mixed before being fed to the
second reactor. Optionally, additional hydrocarbons, for example a
portion of the first hydrocarbon-containing process stream that has
not been fed to the first reactor, can be fed to the second reactor
in addition to the first hydrocarbon-containing product stream and
the carboxylic acid and/or ester. In this embodiment, the quantity
of any additional hydrocarbons fed to the second reactor is
sufficiently low so that the advantages of diluting the carboxylic
acid and/or ester with an already hydrogenated product stream (the
first hydrocarbon-containing product stream) can still be
realised.
[0030] Conditions in the second reactor are maintained such that
the carboxylic acid and/or ester is converted into one or more
hydrocarbons. Typically, other by-products such as carbon dioxide,
carbon monoxide, propane and water, are also produced during the
reaction. Conditions typically used in a hydrotreater or
hydrocracker, as described above, are maintained in the second
reactor, these being dependent on the nature of the carboxylic acid
and/or ester or the biomass material that is fed to the reactor.
Hydrogen consumption by the carboxylic acid and/or ester is
typically greater than that of the hydrocarbon-containing first
product stream that is also fed to the second reactor, hence
hydrotreating conditions are typically maintained so as to prevent
more hydrogen than necessary being utilised through processes such
as hydrocracking of any of the feed components. Temperatures in the
range of from 200 to 410.degree. C. are typically maintained,
preferably in the range of from 320.degree. C. to 410.degree. C.
Typically, pressures in the range of from 20 to 200 bara (2 to 20
MPa) are used, preferably in the range of from 50 to 200 bara (5 to
20 MPa). Conditions are preferably maintained in the reactor such
that almost complete conversion of the carboxylic acid and/or ester
is achieved, for example greater than 90 wt % conversion,
preferably greater than 95% conversion.
[0031] The second hydrocarbon-containing product stream removed
from the second reactor comprises one or more hydrocarbons derived
from the carboxylic acid and/or ester fed to the second reactor.
Optionally and preferably, the second hydrocarbon-containing
product stream is treated to remove light end impurities, such as
unreacted hydrogen or any hydrogen sulphide derived from further
desulphurisation of the first hydrocarbon-containing product
stream. This is suitably achieved by means of a flash separator for
example.
[0032] As the second reactor is preferably operated under
hydrotreating conditions, the catalyst in the second reactor is
preferably a hydrotreating catalyst as hitherto described. In
embodiments of the invention having a sulphided catalyst in the
second reactor, then hydrogen sulphide generated from
desulphurisation reactions in the first reactor can advantageously
assist in maintaining a sulphided active metal in the second
reactor.
[0033] Either or both of the first and second
hydrocarbon-containing product streams may comprise some
hydrocarbons that are too heavy or light to be used as a single
type of fuel. Thus, either or both of the product streams may
optionally be fractionated or distilled such that, for example, one
or more of a light hydrocarbon fraction, a gasoline fraction, a jet
fuel fraction and a diesel fraction can be produced. This minimises
waste from the process, and ensures that the final fuel blend
maintains the quality and consistency of analogous fuels produced
by means other than the present invention.
[0034] The process will now be illustrated by reference to FIG. 1,
which is a schematic overview of a process in accordance with the
present invention.
[0035] A straight-run middle distillate stream 1 with sulphur
content of 1 wt % is fed, together with hydrogen 2, to first
reactor 3, which contains a sulphided Co--Mo/Alumina catalyst.
Conditions in the first reactor are 370.degree. C. and 100 bara
pressure. The Liquid Hourly Space Velocity (LHSV) of the middle
distillate over the catalyst is 3 hr.sup.-1. The first
hydrocarbon-containing product stream 4 removed from the reactor,
having a sulphur content of 75 ppm is joined with a feed of tallow
oil 5 and fed into a second reactor 7 together with hydrogen 6. The
second reactor is maintained at 350.degree. C. and 99 bara
pressure, with a total LHSV (i.e. the combined LHSV of the product
from the first reactor and the biological oil) of 4 hr.sup.-1. The
second hydrocarbon-containing product stream 8 removed from the
second reactor is fed to a flash separator 9, wherein volatile
components 10, including H.sub.2S and unreacted hydrogen, are
separated from a liquid phase 11 comprising fuel hydrocarbons. The
liquid phase comprising fuel hydrocarbons is fed to a fractionation
and stripping column 12 operating at 2 bara with a temperature at
the base of the column of 380.degree. C. A light phase 13
comprising light hydrocarbons and hydrogen sulphide is removed from
the head of the column, a jet fuel stream 14 is removed from the
middle portion of the column, above the point at which the fuel
hydrocarbon stream 11 is fed, and a diesel fuel stream 15 is
removed from the base of the column. The diesel fuel has a sulphur
content of less than 50 ppm.
* * * * *