FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. MONODISPERSE TRANSITION METAL NANO-CATALYST FOR
FISCHER-TROPSCH SYNTHESIS AND PREPARATION METHOD THEREFOR
AND APPLICATION THEREOF
2.
1. (A) WUHAN KAIDI ENGINEERING TECHNOLOGY RESEARCH
INSTITUTE CO., LTD.
(B) China
(C) T1 Jiangxia Avenue, Miaoshan Development Zone, Jiangxia District Wuhan,
Hubei 430212 China
The following specification particularly describes the invention and the manner in which it is to be
performed.
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FIELD OF THE INVENTION
[1] The invention relates to the field ofFischerTropsch synthesis catalyst, and more
particularly to a monodisperse transition metalnano catalyst for Fischer-Tropsch synthesis,
a preparation method and use thereof.
BACKGROUND OF THE INVENTION
[2] FischerTropsch synthesis (Fsynthesis) is a reaction that converts synthesis gas
prepared by gasifying carbon materials including coal, natural gas, and biomass to target
product mainly composed by alkane and olefin. The target product barely contains sulfur,
nitrogen,and aromatic compounds, thus the target product is processed to form
environmental-friendly clean fuels. The F-T synthesis is an ideal way to fully utilize the
carbon materials as a substitution for conventional fossil fuel. As the crude oil import in
China increases, and the environmental requirement is enhanced, the F-T synthesis
becomes increasingly important for energy security and environmental protection, and has
attracted attention from researchers.
[3] The performance of catalyst in the F-T synthesis is closely related to the chemical
element composition. Elements of group VIII, such as iron, cobalt, nickel, and ruthenium
have strong catalytic effect on the F-T synthesis, and are used as major metal components
of the catalyst. The catalyst for industrial F-T synthesis mainly uses iron or cobalt as the
major metal component and other metal elements as promotors so as to adjust and improve
the performance of the catalyst.
[4] Common methods for preparing the F-T synthesis catalyst are known to those skilled
in the art: cobalt-based catalyst for F-T synthesis is usually prepared by impregnation
method which loads the active metal components on a surface of oxide carrier; and
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iron-based catalyst for F-T synthesis is prepared by coprecipitation process or melting
method. Catalysts prepared using different methods have obviously different performance
in the F-T synthesis due to different microstructures of the catalysts. The pore structure
inside the catalyst particles and the size distribution of metal particles are both crucial for
the catalytic performance of the catalyst. Catalyst prepared using the impregnation method
and the coprecipitation process is rich in pore structure, therefore, the catalytic
performance of active metal in the pores is influenced by the concentration of raw materials
and the internal diffusion. In addition, when the active components of metal particles are
fitted in the carrier surface, the specific surface area of exposed active component is
relatively small, which limits the catalytic performance of the catalyst. Meanwhile,
researches indicate that when the particle size of the metal particles is controlled within a
specific range, the catalytic activity and the product selectively of the catalyst when used in
the F-T synthesis is the best, however, due to limitations of conventional preparation
methods, the particle size of metal particles at the catalyst surface is difficult to control.
[5] In view of the above problems, to improve the catalytic performance, researchers turn
to no-load nano-particle catalyst, however, the nano-particle catalyst has disadvantages as
low applicable temperature, low space time yield, and oversized active metal components.
For example, Chinese patent CN 200710099011 disclosed a method for performing F-T
synthesis and a special catalyst for the F-T synthesize. The patent mixed transition metal
salt (iron, cobalt, nickel, ruthenium, rhodium, or a mixture thereof) with high-molecular
stabilizer (polyvinylpyrrolidone or (BVIMPVP)Cl) to form a reaction mixture, and
dispersed the reaction mixture in a liquid medium. The reaction mixture was reduced using
hydrogen at a temperature between 100 and 200°C to yield a transition metal catalyst with
between 1 and 10 nm of nano particles. The transition metal catalyst is used for F-T
synthesis at a temperature between 100 and 200°C. However, the nano particle
concentration of the catalyst prepared by the method is relatively low, and the highest
concentration of transition metal salt in the liquid medium is only 0.014 mol/L. In addition,
the patent uses high-molecular compound as the stabilizer, and the catalyst can only be
applied to the F-T synthesis performed at a temperature lower than 200°C, moreover, the
space time yield is relatively low, all these limits the industrial application of the catalyst.
Chinese patent CN200810055122 disclosed a catalyst applicable in slurry bed reactor, a
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method for preparing the catalyst, and an application of the catalyst. The patent dissolved
nitrate of transition metal (iron, cobalt, or nickel) in a C6-C8straight chain alcohol solution
and heated to reflux the solution so as to yield transition metal catalyst with between 5 and
200 nm of nano particles. The transition metal catalyst is used for F-T synthesis in the
slurry bed reactor after being reduced and activated. However, due to the crystal water in
the nitrate, on the one hand, the hydrogen bond on the metal particle surface is increased
and the aggregation of crystal particles is enhanced (T. He, D. Chen, X. Jiao, Controlled
Synthesis of Co3O4 Nanoparticles through Oriented Aggregation, Chem. Mater., 16 (2004)
737-743), on the other hand, the decomposition temperature of the cobalt nitrate is
increased, resulting in fast formation and growth of metal crystal nucleus, both of which
lead to final large-size aggregated particles (Li Zezhuang, Chen Jiangang, Wang Yuelun,
Sun Yuhan, Preparation of Monodispersed Co/SiO2 Catalyst and Their Performance for
Fischer-Tropsch Synthesis (J), Industrial Catalysis 2009, Vol. 17(9), 43-47).
SUMMARY OF THE INVENTION
[6] In view of the above-described problems, it is one objective of the invention to provide
a monodisperse transition metalnano catalyst for Fischer-Tropsch synthesis, a preparation
method and use thereof. The catalyst has high catalyst activity and the grain size of the
active metal of the catalyst is controllable.
[7] To achieve the above objective, in accordance with one embodiment of the invention,
there is provided a monodisperse transition metalnano catalyst for Fischer-Tropsch
synthesis, comprising a transition metal and an organic solvent. The transition metal is
stably dispersed in the organic solvent in the form of monodisperse nanoparticles; the
transition metal has a grain size of between 1 and 100 nm; and the catalyst has a specific
surface area of 5 and 300 m2/g.
[8] In a class of this embodiment, the transition metal is manganese, iron, cobalt,
ruthenium, or a mixture thereof.
[9] In a class of this embodiment, the organic solvent is benzyl ether, aromatic alcohol,
pyrrolidone, or liquid paraffin.
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[10]In a class of this embodiment,the grain size of the transition metal is between 5 and 20
nm.
[11]In another aspect, the present disclosure also provides a method for preparing the
monodisperse transition metalnano catalyst for Fischer-Tropsch synthesis, the method
comprising:
[12]1) dissolving an organic salt of the transition metal into the organic solvent
comprising a polyhydric alcohol, to yield a mixture; and
[13]2) heating and stirring the mixturein the presence of air or inert gas, holding
the mixture at a temperature of between 150 and 250℃ for between 30 and 240
min, to yield the monodisperse transition metalnano catalyst for Fischer-Tropsch
synthesis.
[14]In a class of this embodiment, in 1), the transition metal is manganese, iron, cobalt,
ruthenium, or a mixture thereof, and the organic salt is oxalate, acetylacetonate, or carbonyl
metal salt.
[15]In a class of this embodiment, in 1), the polyhydric alcohol is C3-C18dihydric alcohol
or trihydric alcohol, and the organic solvent is benzyl ether, aromatic alcohol, pyrrolidone,
or liquid paraffin.
[16]In a class of this embodiment, in 1), a molar ratio of the polyhydric alcohol to the
organic salt of the transition metal is between 1-5: 1, and a molar ratio of the organic
solvent to the organic salt of the transition metal is between 30-500: 1.
[17]In a class of this embodiment, in 2), a heating rate of the mixture is between 1 and 10
℃/min, and a holding time of the temperature is between 60 and 120 min.
[18]The presentdisclosure further provides a method for Fischer-Tropsch synthesis
comprising applying the monodisperse transition metalnano catalyst of claim1, the method
comprising, without filtration, separation, cleaning, high temperature roasting and
activation reduction, directly employing the catalyst for the Fischer-Tropsch synthesis, and
controlling a reaction temperature of between 180 and 300℃, a reaction pressure of
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between 1 and 3 megapascal, a feed volume ratio of hydrogen to carbon monoxide of
between 1 and 2.5, and a total space velocity of between 0.5 and 15 L/h/g catalyst.
[19]Advantages of the monodisperse transition metalnano catalyst for Fischer-Tropsch
synthesis according to embodiments of the invention are summarized as follows:
[20]First, the catalyst of the invention is a non-loaded nano metal particle catalyst, the nano
metal particle can move freely in the reaction process, no need to attach to the surface of the
carrier, thus increasing the specific surface area and enhancing the catalytic properties of
the catalyst. In addition, the nano metal particles have high concentration.
[21]Second, the grain size of the active component particles is adjustable, so the size of the
metal nanoparticles is controllable.
[22]Third, the preparation method of the invention is simple and easy to operate,
environment friendly, can adjust the grain size of themetal nanoparticles, and the active
component is stably dispersed in the organic solvent in the form of monodisperse
nanoparticles, the disperse solvent is recyclable.
[23]Fourth, the nano metal particles of the catalyst have high dispersity, in a slurry reactor,
without involving filtration, separation, cleaning, high temperature roasting and activation
reduction,the catalyst can be directly used for Fischer-Tropsch synthesis, and exhibits
excellent catalytic properties and product selectivity.
BRIEF DESCRIPTION OF THE DRAWINGS
[24]FIG. 1 is animage of amonodisperse transition metalnano catalyst for Fischer-Tropsch
synthesisunder transmission electron microscope in Example 1 of the invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[25]For further illustrating the invention, experiments detailing a monodisperse transition
metal nano catalyst for Fischer-Tropsch synthesis, a preparation method and use thereofare
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described hereinbelow combined with the drawings. It should be noted that the following
examples are intended to describe and not to limit the invention.
Example 1
[26]6 g of ferric acetylacetonate (III)was dissolved in 550 mL of 2-pyrrolidone solution
(with density of 1.116 g/mL), followed by addition of 3.5 g of 1,2-dihydroxydodecane, to
yield a mixture. Thereafter, in the presence of mechanical stirring and air, the solution was
heated to the temperature of 160℃ with a heating rate of 1℃/min. The solution was held
for 120 min at the temperature of 160℃, and then cooled to room temperature, to yield a
grey black nano iron colloid solution, which was sealed using 250 mL of liquid paraffin for
use.
[27]The prepared grey black nano iron colloid solution, together with the liquid paraffin,
was transferred to a slurry bed reactorfor Fischer-Tropsch synthesis immediately. The
reaction temperature was 260℃, the feedvolume ratio of hydrogen to carbon monoxide
was 1.2, the gasspace velocitywas 13.7L/h/g catalyst (the gas flow velocity was 13 L/h),
and the reaction pressure was 2 MPa. Under the conditions, the performance evaluation of
the catalyst is listed in Table 1, and the microstructure of the catalyst is shown in FIG. 1.
Example 2
[28]2.6 g of cobalt oxalate (II) and 0.01 g of ruthenium nitrosyl nitrate (III) was dissolved
in 250 mL of dibenzyl ether solution (with density of 1.04 g/mL), followed by addition of
10 g of 1,2-hexadecanediol, to yield a mixture. Thereafter, in the presence of mechanical
stirring and argon gas, the solution was heated to the temperature of 250°C with a heating
rate of 10°C /min. The solution was held for 80 min at the temperature of 250°C, and then
cooled to room temperature, to yield a dark purple nano cobalt colloid solution, which was
sealed using 250 mL of liquid paraffin for use.
[29]The prepared dark purple nano cobalt colloid solution, together with the liquid paraffin,
was transferred to a slurry bed reactor for Fischer-Tropsch synthesis immediately. The
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reaction temperature was 180°C, the feed volume ratio of hydrogen to carbon monoxide
was 2.4, the gas space velocity was 4.8 L/h/g catalyst (the gas flow velocity was 5 L/h), and
the reaction pressure was 3 MPa. Under the conditions, the performance evaluation of the
catalyst is listed in Table 1.
Example 3
[30]4 g of ferric acetylacetonate (III) and 2 g of cobalt acetylacetonate (II) was dissolved in
450 mL of benzyl alcohol solution (with density of 1.04 g/mL), followed by addition of 9 g
of 1,2,4-butanetriol, to yield a mixture. Thereafter, in the presence of mechanical stirring
and air, the solution was heated to the temperature of 200°C with a heating rate of 5°C /min.
The solution was held for 60 min at the temperature of 200°C, and then cooled to room
temperature, to yield a dark grey nano ferrocobalt colloid solution, which was sealed using
250 mL of liquid paraffin for use.
[31]The prepared dark grey nano ferrocobalt colloid solution, together with the liquid
paraffin, was transferred to a slurry bed reactor for Fischer-Tropsch synthesis immediately.
The reaction temperature was 200°C, the feed volume ratio of hydrogen to carbon
monoxide was 2, the gas space velocity was 7.3 L/h/g catalyst (the gas flow velocity was 8
L/h), and the reaction pressure was 1 MPa. Under the conditions, the performance
evaluation of the catalyst is listed in Table 1.
Example 4
[32] 3.1 g of pentacarbonyl iron and 2.6 g of decacarbonyldimanganese were dissolved in
250 mL of liquid paraffin (with density of 0.87 g/mL), followed by addition of 5 g of
1,2,8-octanetriol, to yield a mixture. Thereafter, in the presence of mechanical stirring and
nitrogen, the solution was heated to the temperature of 235°C with a heating rate of 8°C
/min. The solution was held for 100 min at the temperature of 235°C, and then cooled to
room temperature, to yield a grey black nano ferrimanganic colloid solution, which was
sealed for use.
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[33]The prepared grey black nano ferrimanganic colloid solution was transferred to a
slurry bed reactor for Fischer-Tropsch synthesis immediately. The reaction temperature
was 240°C, the feed volume ratio of hydrogen to carbon monoxide was 1.8, the gas space
velocity was 0.8 L/h/g catalyst (the gas flow velocity was 1 L/h), and the reaction pressure
was 2 MPa. Under the conditions, the performance evaluation of the catalyst is listed in
Table 1.
Table 1
Catalysts of the invention
Parameters
Example 1 Example 2 Example 3 Example 4
Average grain size
of metal crystal (nm)
5.3 47.0 18.7 83.3
Physico-chemical
properties Specific surface area
of catalysts (m2/g)
288.3 17.4 54.1 8.6
Reaction
temperature (℃)
260 180 200 240
Reaction pressure
(MPa)
2 3 1 2
Feed volume ratio of
Hydrogen to carbon
monoxide
1.2 2.4 2 1.8
Evaluation index
Space velocity
(L/h/g catalyst)
13.7 4.8 7.3 0.8
CO conversion(%) 73.2 26.7 33.1 32.8
Methane
selectivity(mol%)
3.2 7.7 6.1 2.8
Catalytic
properties
Carbon dioxide 21.4 0.5 4.2 26.4
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selectivity(mol%)
C2-4hydrocarbon
selectivity(mol%)
23.6 16.3 19 22.9
C5+ hydrocarbon
selectivity(mol%)
51.8 75.5 70.7 47.9
The data in the table was obtained by statistical analysis of images from transmission
electron microscopy.
[34]Based on the physico-chemical properties and catalytic properties of the catalyst as
shown in Table 1, the preparation method of the present disclosure can quickly produce
high activity metal nanometer particle catalyst with different grain sizes. In general, the
smaller the grain size of the catalyst, the bigger the active specific surface area, and the
higher the catalytic activity. However, the stability of the catalyst will decrease. The
nano-metal catalyst having the grain size of 5-20 nm exhibits better comprehensive
properties. Compared with conventional industrial catalysts, the catalyst of the invention
exhibits better catalytic activity, lower methane selectivity, higher selectivity for
C2-4hydrocarbons, so the catalyst of the invention has better application prospect.
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We Claim:
1. Amonodispersetransition metalnano catalyst for Fischer-Tropsch synthesis,
comprising:
a transition metal; and
an organic solvent;
wherein
thetransition metal is stably dispersed in the organic solvent in the form of
monodisperse nanoparticles;
the transition metal has a grain size of between 1 and 100 nm; and
the catalyst has a specific surface area of 5 and 300 m2/g.
2. The catalyst of claim 1,wherein the transition metal is manganese, iron, cobalt,
ruthenium, or a mixture thereof.
3. The catalystof claim 1 or 2, wherein the organic solvent is benzyl ether, aromatic
alcohol, pyrrolidone, or liquid paraffin.
4. The catalystof claim 1 or 2, whereinthe grain size of the transition metal is between 5
and 20 nm.
5. Amethod for preparing the monodisperse transition metalnano catalyst for
Fischer-Tropsch synthesisof claim 1, comprising:
1) dissolving an organic salt ofthe transition metal into the organic solvent
comprising a polyhydric alcohol, to yield a mixture; and
2) heating and stirring the mixturein the presence of air or inert gas, holding
the mixture at a temperature of between 150 and 250℃ for between 30
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and 240 min, to yield the monodisperse transition metalnano catalyst for
Fischer-Tropsch synthesis.
6. The method of claim 5, whereinin 1), the transition metal is manganese, iron, cobalt,
ruthenium, or a mixture thereof, and the organic salt is oxalate, acetylacetonate, or
carbonyl metal salt.
7. The method of claim 5 or 6, whereinin 1), the polyhydric alcohol is C3-C18dihydric
alcohol or trihydric alcohol, and the organic solvent is benzyl ether, aromatic
alcohol, pyrrolidone, or liquid paraffin.
8. The method of claim 5 or 6, whereinin 1), a molar ratio of the polyhydric alcohol to the
organic salt of the transition metal is between 1-5: 1, and a molar ratio of the organic
solvent to the organic salt of the transition metal is between 30-500: 1.
9. The method of claim 5 or 6, wherein in 2), a heating rate of the mixture is between 1
and 10℃/min, and a holding time of the temperature is between 60 and 120 min.
10. Amethod for Fischer-Tropsch synthesis comprising applying the monodisperse
transition metalnano catalyst of claim 1, the method comprising, without filtration,
separation, cleaning, high temperature roasting and activation reduction, directly
employing the catalyst for the Fischer-Tropsch synthesis, and controlling a reaction
temperature of between 180 and 300℃, a reaction pressure of between 1 and 3
megapascal, a feed volume ratio of hydrogen to carbon monoxide of between 1 and
2.5, and a total space velocityof between 0.5 and 15 L/h/g catalyst.