U.S. patent application number 09/895621 was filed with the patent office on 2002-05-02 for skeletal iron catalyst having improved attrition resistance and product selectivity in slurry-phase synthesis processes.
This patent application is currently assigned to Hydrocarbon Technologies, Inc.. Invention is credited to Lee, Lap-Keung, Li, Guohui, Lu, Yijun, Zhou, Jinglai, Zhou, Peizheng.
Application Number | 20020052423 09/895621 |
Document ID | / |
Family ID | 23581233 |
Filed Date | 2002-05-02 |
United States Patent
Application |
20020052423 |
Kind Code |
A1 |
Zhou, Peizheng ; et
al. |
May 2, 2002 |
Skeletal iron catalyst having improved attrition resistance and
product selectivity in slurry-phase synthesis processes
Abstract
Particulate skeletal iron catalyst is provided which contain at
least about 50 wt. % iron with the remainder being a minor portion
of a suitable non-ferrous metal and having characteristics of
0.062-1.0 mm particle size (62-1000 micron), 20-100 m.sup.2/g
surface area, and 10-40 nm average pore diameter. Such skeletal
iron catalysts are prepared and utilized for producing synthetic
hydrocarbon products from CO and H.sub.2 feeds by Fischer-Tropsch
synthesis process. Iron powder is mixed with non-ferrous metal
powder selected from aluminum, antimony, silicon, tin or zinc
powder to provide 20-80 wt. % initial iron content and melted
together to form an iron alloy, then cooled to room temperature and
pulverized to provide 0.1-10 mm iron alloy catalyst precursor
particles. The iron alloy precursor particles are treated with NaOH
or KOH caustic solution at 30-95.degree. C. temperature to extract
and/or leach out most of the non-ferrous metal portion, and then
screened and treated by drying and reducing with hydrogen so as to
provide smaller sized skeletal iron catalyst material. Such
skeletal iron catalyst is utilized with CO+H.sub.2 feedstream for
Fischer-Tropsch reactions in either a fixed bed or slurry bed type
reactor at 180-500.degree. C. temperature, 0.5-5.0 mPa pressure,
and gas hourly space velocity of 0.5-3.0 L/g Fe/hr to produce
desired hydrocarbon products.
Inventors: |
Zhou, Peizheng;
(Lawrenceville, NJ) ; Lee, Lap-Keung; (West
Windsor, NJ) ; Zhou, Jinglai; (Taiyuan, CN) ;
Lu, Yijun; (Taiyuan, CN) ; Li, Guohui;
(Taiyuan, CN) |
Correspondence
Address: |
Fred A. Wilson
HYDROCARBON TECHNOLOGIES INC
1501 NEW YORK AVENUE
LAWRENCEVILLE
NJ
08648
US
|
Assignee: |
Hydrocarbon Technologies,
Inc.
|
Family ID: |
23581233 |
Appl. No.: |
09/895621 |
Filed: |
July 2, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09895621 |
Jul 2, 2001 |
|
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09399852 |
Sep 21, 1999 |
|
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6277895 |
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Current U.S.
Class: |
518/721 ;
502/338 |
Current CPC
Class: |
C22C 30/00 20130101;
B01J 25/00 20130101; C22C 38/16 20130101; C07C 1/0445 20130101;
B22F 9/16 20130101; C10G 2/332 20130101; B01J 37/0018 20130101;
C22C 38/06 20130101; C07C 2523/745 20130101; B01J 37/06 20130101;
B01J 23/745 20130101 |
Class at
Publication: |
518/721 ;
502/338 |
International
Class: |
C07C 027/06; B01J
023/74 |
Claims
1. A particulate skeletal iron catalyst comprising at least about
50 wt. % iron with the remainder being non-ferrous metal selected
from the group consisting of aluminum, antimony, nickel, tin and
zinc, and a non-ferrous promotor metal selected from the group
consisting of calcium, copper, chromium, magnesium and potassium,
which non-ferrous metals have been substantially removed from the
catalyst by a chemical extraction and/or leaching step and thereby
providing iron alloy particles having a skeletal type structure of
mainly iron, said catalyst having particle size smaller than 10 mm,
surface area of 20-100 m.sup.2/g, and average pore diameter of
10-40 nm.
2. The skeletal iron catalyst of claim 1, wherein said catalyst
contains 60-90 wt. % iron, has surface area of 25-80 m2/g., and
particle size of 0.02-5 mm (20-5000 microns).
3. A method for preparing a skeletal iron catalyst useful for
Fischer-Tropsch synthesis processes, comprising the steps of: a)
providing a catalyst precursor metal alloy by mixing iron powder
together with non-ferrous metal powder selected from aluminum,
antimony, silicon, tin and zinc sufficient to provide iron content
of 20-80 wt. % and 0.01-5.0 wt. % non-ferrous promotor metal powder
selected from calcium, chromium, copper, magnesium and potassium;
heating said mixed metal powders together under inert gas
protection, while stirring said metal powders uniformly and melting
the metal powders to form precursor iron alloy material, then
cooling the melted iron alloy to room temperature and pulverizing
the resulting iron alloy to provide skeletal iron catalyst
precursor particles having 0.1-10 mm particle size; b) contacting
said skeletal iron alloy catalyst precursor particles with NaOH or
KOH caustic solution having 10-50% concentration under inert argon,
helium or hydrogen atmosphere, and heating the mixture to
30-95.degree. C. temperature while maintaining reaction condition
for 2-150 minutes and extracting and/or leaching out a major
portion of the non-ferrous metal from the iron alloy precursor
particles so as to provide a skeletal iron structure, then washing
said particles with ion-free water until pH=7, displacing the water
with alcohol, and placing the resulting skeletal iron catalyst
particles in ethanol; and c) treating said skeletal iron catalyst
particles by drying and reducing with hydrogen at high space
velocity at 100-500.degree. C. temperature for 2-12 hours, then
transferring the treated skeletal iron catalyst into water-free
ethanol or liquid paraffin for storage.
4. The skeletal iron catalyst preparation method of claim 3,
wherein step (b) is treating said skeletal iron catalyst precursor
particles by adding sufficient said NaOH or KOH caustic solution
into a stirred container under hydrogen atmosphere and heating the
solution to 30-95.degree. C. temperature, then adding the iron
alloy precursor particles into the caustic solution at suitable
periodic time intervals, while maintaining the reaction condition
for 5-150 minutes for extracting and /or leaching out a major
portion of the non-ferrous metal from the iron alloy precursor
particles, then washing the iron alloy precursor particles with
deionized water until pH=7, displacing the water with alcohol, and
placing the resulting skeletal iron alloy catalyst particles in
ethanol.
5. The skeletal iron catalyst preparation method of claim 3,
wherein step (b) is mixing said iron alloy precursor particles with
solid sodium hydroxide (NaOH) powder at weight ratio of the sodium
hydroxide to the iron alloy particles of 5-10:1, then adding
deionized water dropwise to wet the mixture to provide a paste but
not a fluid state while stirring so that reaction proceeds under a
wet paste state; after the reaction has proceeded 5-30 minutes
while gas release gradually decreases, adding to said paste mixture
fresh NaOH or KOH 10-50% concentration solution and maintaining for
2-60 minutes at 50-95.degree. C. temperature; then washing the iron
alloy particles with deionized water to pH=7, displacing water with
water-free ethanol and storing in ethanol.
6. The skeletal iron catalyst preparation method of claim 3,
wherein step (b) includes placing said iron alloy precursor
particles in a stirred container, spraying the particles with a
40-60% concentration NaOH or KOH solution, maintaining reaction in
a wet but not fluid state for 5-30 minutes, adding NaOH or KOH
caustic solution of 10-50% concentration and maintaining for 2-60
minutes at 50-90.degree. C. temperature, then washing the iron
alloy particles with deionized water to pH=7, then displacing the
water with water-free ethanol and storing in ethanol.
7. The catalyst preparation method of claim 3, wherein said mixed
metal powders are iron, aluminum and copper having an initial
respective weight ratio of 33:66:1.
14. (Amended) The skeletal iron catalyst of claim 1, wherein the
catalyst particle size after Fischer-Tropsch synthesis reaction is
0.025-1.0 mm. (25-1000 microns).
15. The catalyst preparation method of claim 3, wherein the step
(b) catalyst precursor metal alloy extraction and/or leaching
temperature is 50-95.degree. C., and the treated skeletal iron
catalyst particle size is 0.062-3.0 mm. (62-3000 microns).
16. The skeletal iron catalyst preparation method of claim 3,
wherein said non-ferrous metal powder is aluminum and said promotor
metal powder is copper.
17. The skeletal iron catalyst preparation method of claim 3,
wherein said metal powder mixture is heated and melted in an
electric induction furnace during magnetic stirring.
18. The skeletal iron catalyst preparation method of claim 3,
wherein the iron alloy catalyst particle extracting/leaching
temperature is 65-95.degree. C., particle size is 30-50 microns,
and relative separation of the catalyst in F-T synthesis product
liquid slurry is 20-25 % of the initial height in the product
liquid slurry.
19. A method for preparing a skeletal iron catalyst particularly
useful for Fischer-Tropsch synthesis processes, comprising the
steps of: a) providing a catalyst precursor metal alloy by mixing
iron powder together with aluminum powder sufficient to provide
iron content of 20-80 wt. % and 0.01-5.0 wt. % copper powder,
heating said mixed metal powders together in an electric induction
furnace under inert gas protection, while mixing said metal powders
uniformly by magnetic stirring and melting the metal powders to
form precursor iron alloy material, then cooling the melted
precursor iron alloy to room temperature and pulverizing the
resulting iron alloy to provide skeletal iron catalyst precursor
particles having 0.1-10 mm particle size; b) contacting said
skeletal iron alloy catalyst precursor particles with NaOH or KOH
caustic solution having 10-50% concentration under inert hydrogen
atmosphere by adding sufficient NaOH or KOH caustic solution having
10-50% concentration into a stirred container under the hydrogen
atmosphere and heating the solution to 30-95.degree. C.
temperature, then adding the iron alloy precursor particles into
the caustic solution at suitable periodic time intervals, while
maintaining the reaction condition for 2-150 minutes and extracting
and/or leaching out a major portion of the non-ferrous metal from
the iron alloy precursor particles so as to provide a skeletal iron
structure having particle size smaller than 10 mm, then washing
said skeletal iron particles with ion-free water until pH=7,
displacing the water with alcohol, and placing the resulting
skeletal iron catalyst particles in ethanol; and c) treating the
skeletal iron catalyst particles by drying and reducing with
hydrogen at high space velocity at 200-500.degree. C. temperature
for 2-12 hours, then transferring the treated skeletal iron
catalyst into water-free ethanol or liquid paraffin for storage.
Description
BACKGROUND OF INVENTION
[0001] This invention pertains to skeletal iron catalyst and its
preparation and use in Fischer-Tropsch and similar slurry-phase
synthesis processes. More particularly, such skeletal iron catalyst
utilized in slurry phase synthesis processes for H.sub.2+CO
feedstreams has increased attrition resistance and improved
catalyst/product liquid separation, while providing increased
selectivity for producing C.sub.2-C.sub.5 light olefin
products.
[0002] Slurry phase Fischer-Tropsch (F-T) synthesis process
technology is an important known route for indirect coal
liquefaction for synthesis of liquid fuels from H.sub.2+CO
feedstreams. Precipitated iron is currently a commonly used
catalyst for such Fischer-Tropsch processes. However, precipitated
iron catalysts are undesirably fragile and break down easily under
reaction conditions into very fine particles, so that separation of
such fine catalyst particles from reaction product waxes is
difficult to accomplish and results in inferior product quality and
significant catalyst loss. Such catalyst problems hinders
commercial use of the process.
[0003] For overcoming this problem, improved skeletal iron
catalysts made according to this invention are provided by
utilizing caustic extraction and/or leaching non-ferrous metals
from specific iron metal alloy particles, and such skeletal iron
catalysts have good particle strength and attrition resistance.
Literature studies on such catalysts to date have focused on
improvement of catalyst activity in simple gas-solid hydrogenation
reaction systems. Utilization of such improved skeletal iron
catalyst in slurry-phase or three-phase gas-liquid-solid
Fischer-Tropsch reaction processes fully realizes the advantages of
such skeletal iron catalysts. By utilizing such improved skeletal
iron catalysts, commercial slurry-bed Fischer-Tropsch synthesis
processes to produce clean hydrocarbon liquid transportation fuels
from syngas feedstreams is greatly facilitated.
[0004] Light olefins C.sub.2- to C.sub.5- are key component
materials in the petrochemical industry as important feedstocks and
building blocks for the synthesis of a variety of
chemical/petrochemical products. Conventionally, such light olefins
are produced by thermal cracking of hydrocarbons ranging from
ethane to vacuum gas oils, but not produced directly from natural
gas which is essentially methane (CH.sub.4). Such thermal cracking
is practiced under high temperatures (1,500-1,600.degree. F.), thus
requiring costly construction materials and consuming huge amounts
of energy for feedstream heating and reaction. A commercially
practiced technical route for making light olefins from natural gas
is to first convert natural gas via steam reforming into a mixture
of hydrogen and carbon monoxide, called synthesis gas or syngas.
The current technology of converting syngas into olefins is a
two-step catalytic conversion, the first step being catalytic
conversion of syngas to methanol, followed by conversion of
methanol into olefins. A unique catalyst/technology would be to
directly convert synthesis gas into light olefins, without the
necessity of an additional step for making methanol as an
intermediate material. The skeletal iron catalyst, promoted with
other metal ingredients and used in a fixed bed or in slurry-bed
reactor system with liquid paraffin as the liquid medium, can
advantageously convert syngas directly into light olefins
C.sub.2-C.sub.5 under mild conditions in a temperature range of
180-500.degree. C. and a pressure range of 0.5-5.0 mPa.
[0005] Thus, this invention provides a unique skeletal iron
catalyst having high activity for catalyzing the conversion of
syngas feeds to a broad range of hydrocarbon products, and has high
selectivity towards light olefins formation in a slurry-phase
catalytic reactor system under mild conditions conventionally used
in Fischer-Tropsch synthesis, so that the hydrocarbon product is
rich in olefins for production of clean liquid transportation fuels
and/or light olefins.
SUMMARY OF INVENTION
[0006] This invention provides a unique skeletal iron catalyst
material advantageously suitable for use in either fixed bed or
slurry-phase Fischer-Tropsch synthesis processes for H.sub.2+CO
feedstreams for producing clean liquid transportation fuels and
light olefin products. The particulate skeletal iron catalyst
contains at least 50 wt. % iron and preferably 60-90 wt. % iron,
with remainder being smaller percentages of non-ferrous metal
selected from the group including aluminum, antimony, nickel, tin
and zinc and a promotor metal selected from the group of calcium,
copper, chromium, magnesium, and potassium. The final skeletal iron
catalyst should have a surface area of 20-100 m.sup.2/g and average
pore diameter of about 10-40 nm.
[0007] The unique skeletal iron catalyst material of this invention
is made using a preparation method which includes providing an iron
powder mixed with suitable non-ferrous metal powder selected from
aluminum, antimony, silicon, tin, or zinc sufficient to initially
provide 20-80 wt % iron, together with 0.01-5 wt. % of a
non-ferrous promotor metal powder selected from calcium, copper,
chromium, magnesium, or potassium. The mixed metal powders are
heated and melted together to form an iron alloy precursor
material, which is then pulverized to 0.1-10 mm (100-10,000 micron)
particle size, followed by extracting and/or leaching the major
portion of the non-ferrous metal from the iron using a suitable
caustic solution of NaOH or KOH, and leaving mainly the iron
portion as the skeletal iron catalyst precursor material. The
resulting catalyst may be further pulverized and have smaller
particle size than 0.1-10 mm precursor particle, surface area of
20-100 m.sup.2/g and an average pore diameter of 10-40 nm. The
catalyst is next treated by drying and reducing with hydrogen at
high space velocity and at 100-500.degree. C. temperature for 2-12
hours, then transferred into water-free alcohol or liquid paraffin
for storage.
[0008] The preparation method and treatment procedures for this
skeletal iron catalyst are relatively simple and inexpensive. This
resulting skeletal iron catalyst has good particle strength and
attrition resistance, and activity equivalent to that of
precipitated iron catalyst because during reactions its skeletal
structure is easily accessible to H.sub.2 and produces larger
yields of gasoline-diesel fuel range hydrocarbons and variable
amounts of wax products. Also in F-T synthesis process it is easier
to separate the skeletal iron catalyst from the reactor liquid
medium and product, and thus achieves high recovery of the catalyst
and thereby provides light hydrocarbon liquid products containing
low concentrations of undesired catalyst fines.
[0009] Although the skeletal iron catalyst of this invention is
useful in either a fixed bed or slurry bed type (F-T) reactors, its
use in slurry bed reactors is preferred. For use in fixed bed
catalytic reactors, the catalyst particle size should be 1.0-10 mm,
and for use in slurry bed type reactors the catalyst particle size
should be 0.1-3.0 mm. For Fischer-Tropsch synthesis process
utilizing this skeletal iron catalyst, useful reaction conditions
are 0.3-3.0:1 H.sub.2/CO molar ratio, 180-500.degree. C.
temperature, and 0.5-5.0 mPa pressure.
DESCRIPTION OF INVENTION
[0010] The skeletal iron catalyst of this invention is made
utilizing the following basic steps:
[0011] 1. Catalyst Preparation. Mix iron powder and a non-ferrous
metal powder selected from aluminum, antimony, silicon, tin or zinc
in proportion of 20-80 wt. % iron and also add 0.01-5 wt. % of
promotor metal powder selected from calcium, copper, chromium,
magnesium or potassium into a suitable furnace such as an electric
induction furnace and mix together such as by magnetic stirring.
Then melt the mixed powders under inert gas protection to form an
iron alloy material, cool the iron alloy to room temperature and
pulverize it to provide 0.1-10 mm particle size precursor material.
Contact the iron alloy particles with 10-50% NaOH or KOH caustic
solution in a stirred container under inert gas protection of
argon, hydrogen or nitrogen, maintain reaction temperature
30-95.degree. C. for 2-150 minutes to provide a desired substantial
degree of extraction and/or leaching a major portion of the
non-ferrous metal, and leaving particles containg mainly
.infin.--Fe and some Fe.sub.3O.sub.4. Adding the iron alloy powder
to the caustic solution is usually preferred rather than the
reverse order, as it results in skeletal iron catalyst having
larger pore size. The skeletal iron catalyst is further pulverized
and screened to obtain a desired particle size for synthesis
reactions.
[0012] Alternatively, the iron alloy precursor particles can be
mixed with solid sodium hydroxide powder in a weight ratio to the
iron alloy powder of 5-10:1, add deionized water to from a paste
while stirring and allow the reaction to proceed for 5-30 minutes,
then add fresh NaOH or KOH solution (10-50% concentration) and
maintain for 2-60 minutes at 30-95.degree. C.
[0013] Another procedure for the catalyst preparation utilizes
spraying the iron alloy precursor particles with a high
concentration (40-60%) NaOH or KOH solution and maintaining the
reaction in wet state for 5-30 minutes, then add additional NaOH or
KOH 10-50% solution and maintain for 2-60 minutes at 30-95.degree.
C. temperature to effect the extraction and/or leaching step of
removing most of the non-ferrous metal from the iron alloy
particles. Then wash the iron particles with de-ionized water to
pH=7, displace water with water-free ethanol, and store the
resulting skeletal iron catalyst having 0.1-10 mm particle size in
ethanol. Use of moderate extraction temperature of 50-60.degree. C.
appears to facilitate more pores and increased surface area, while
longer extraction times cause undesirable partial oxidation of the
iron particles. Following such extraction or leaching step, the
catalyst can be further pulverized and screened as desired to
obtain appropriate particle size for the F-T synthesis reactions.
The catalyst is next treated by drying and reducing with hydrogen
at high space velocity and at 100-500.degree. C. temperature for
2-12 hours, then the treated skeletal iron catalyst is transferred
into water-free ethanol or liquid paraffin for storage before
further usage.
[0014] 2. Catalyst Treatment and Utilization. Before the skeletal
iron catalyst is evaluated or utilized in slurry-phase
Fischer-Tropsch reaction, the catalyst is treated by being dried
and reduced with hydrogen. Such treating is done by passing high
space velocity hydrogen stream over the ethanol-containing catalyst
at 100-500.degree. C. for 2-12 hours, which catalyst is converted
to mainly .infin.--Fe and is subsequently transferred into a liquid
paraffin medium. Reaction conditions for slurry-phase
Fischer-Tropsch synthesis process are 0.3-3.0:1 H.sub.2/CO molar
ratio, catalyst loading 5-20 wt. % relative to the liquid paraffin,
catalyst particle size 0.062-3.0 mm(62-3000 microns)
180-400.degree. C. temperature, 0.5-5 mPa pressure and reaction
duration 40-240 hours. After completion of such catalytic reaction,
the resulting catalyst/wax slurry material is removed, settled, and
filtered. After slurry settling, the extent of a catalyst/wax
separation is investigated. Also, the wax containing catalyst is
extracted with xylene and analyzed for change in particle size
distribution.
[0015] Compared with currently used fused iron and precipitated
iron catalyst in Fischer-Tropsch synthesis processes, the skeletal
iron catalyst of this invention provides the following
advantages:
[0016] 1. Catalyst preparation method is relatively simple and
inexpensive.
[0017] 2. For synthesis gas feed H.sub.2/CO molar ratio range of
0.5-3.0:1, the synthesis gas conversion is significantly higher
than that obtained by using fused iron catalyst, and conversion of
the feed is equivalent to that achieved by precipitated iron
catalyst.
[0018] 3. Product selectivity favors producing more lower molecular
weight hydrocarbons and less wax, resulting in lower slurry
viscosity which facilitates catalyst/wax separation.
[0019] 4. The skeletal iron catalyst particles has higher attrition
resistance, so that most of the skeletal iron catalyst can be
recovered after synthesis reactions, resulting in very low catalyst
loss and no significant effect on catalyst activity.
BRIEF DESCRIPTION OF DRAWINGS
[0020] The process of this invention for utilizing the skeletal
iron catalyst will be described with reference to the following
drawing, in which
[0021] FIG. 1 depicts a flowsheet for a typical Fischer-Tropsch
synthesis process utilizing a slurry phase reactor.
[0022] As shown by FIG. 1, separate feedstreams of pressurized CO
at 10 and H.sub.2 at 12 are provided having H.sub.2/CO molar ratio
range of 0.5-2.5:1, together with skeletal iron catalyst having
particle size of 10-300 micron provided at 13. The feeds and
catalyst are all introduced upwardly into a slurry type reactor 14
containing skeletal iron catalyst in a slurry bed 15. Reaction
condition in reactor 14 are maintained at 200-350.degree. C.
temperature, 1.0-5.0 mPa pressure, and gas hourly space velocity of
0.5-3.0 L/g Fe/h.
[0023] From the reactor 14, a gas product is removed at 16. Also, a
hydrocarbon liquid stream containing some catalyst particles is
withdrawn from internal cup 17 as stream 18 and passed to a
catalyst/liquid separator 20, which may be a settler vessel and/or
hydroclone separator or filter. From the separator 20, a clean
hydrocarbon liquid product containing minimal catalyst is removed
at 22, and used catalyst particles concentrated in a small portion
of hydrocarbon liquid are withdrawn at 24. If desired, a portion of
the used catalyst particles at 24 can be recycled at 25 back to the
reactor 14, as needed to reduce catalyst loss and improve process
economics. The remaining portion of the used catalyst at 26 is
discarded.
[0024] The skeletal iron catalyst preparation method and the
catalyst used in Fischer-Tropsch synthesis process will be
disclosed further by the following examples, which should not be
construed as limiting in their scope.
EXAMPLE 1
[0025] Mix powders iron, aluminum and a small amount of copper
promotor metal powder in a respective weight proportion of 33:66:1
in an electric induction furnace, heat and melt the metal powders
to form an iron metal alloy, then cool it to room temperature and
pulverize the resulting iron alloy to 0.1-1.0 mm size precursor
particles. Then provide a desired amount of 25% NaOH caustic
solution in a stirred container, add the iron alloy precursor
particles under hydrogen flow, into the caustic solution maintained
at 85.degree. C. temperature, and allow reaction to proceed for 30
minutes to extract and/or leach substantially the aluminum from the
iron alloy particles. Wash the particles with deionized water to
pH=7, displace water with water-free ethanol and store the
resulting skeletal iron catalyst particles in ethanol.
[0026] Before being evaluated in a reaction system, the
ethanol-containing skeletal iron catalyst is dried and reduced
under high space velocity hydrogen at 300.degree. C. for 2 hours,
then transferred into reaction medium (liquid paraffin) in a
stirred slurry autoclave reactor. Conditions for Fischer-Tropsch
synthesis reaction are feedstream H.sub.2/CO molar ratio 2.0:1,
catalyst loading 6 wt. %, particle size 0.100-0.125 mm, temperature
270.degree. C., pressure 1.6 mPa, space velocity 1.0 L/g Fe/h and
reaction time 40 hours. Test conditions and analytical results
compared with precipitated iron catalyst are shown in Table 1
below.
EXAMPLE 2
[0027] Mix powders iron and aluminum together with a small amount
of copper promoter metal powder in weight proportion 33:66:1 into
electric induction furnace, heat and melt the powders to form iron
metal alloy, then cool it to room temperature and pulverize the
iron alloy to 0.1-1.0 mm size precursor particles as for Example 1.
Then provide a desired amount of 25% concentration NaOH in a
stirred container under hydrogen stream, add the Fe-Al alloy
particles into the NaOH caustic solution maintained at 75.degree.
C. temperature, allow reaction for 30 minutes to extract and/or
leach substantially aluminum from the iron alloy particles. Then
wash the particles with de-ionized water to pH=7, displace water
with water-free ethanol and store skeletal iron catalyst particles
in ethanol.
[0028] Next dry and reduce the ethanol-containing skeletal iron
catalyst at 300.degree. C. under high space velocity hydrogen for 2
hours, and then transfer the catalyst into liquid reaction medium
(liquid paraffin) in a stirred slurry phase reactor. Conditions for
slurry phase Fischer-Tropsch synthesis reaction are: catalyst
loading 6 wt. %, particle size 0.100-0.125 mm, temperature
270.degree. C., and reaction time 40 hours. Test conditions and
analytical results are shown in Table 1.
EXAMPLE 3
[0029] Mix iron and aluminum powders together with a small amount
of copper promoter powder in weight ratio of 33:66:1 in an electric
induction furnace, heat and melt the metal powders to form an
iron-aluminum alloy, then cool to room temperature and pulverize to
0.1-1.0 mm precursor particle size same as for Example 1. Then add
desired amount of 25% concentration NaOH caustic solution to a
stirred container, add the Fe-Al alloy particles to the caustic
solution maintained at 65.degree. C. temperature, and allow
reaction for 30 minutes to extract and/or leach substantially the
aluminum from the iron alloy particles. Then wash the particles
with de-ionized water to pH=7, displace water with water-free
ethanol, and store the resulting skeletal iron catalyst in
ethanol.
[0030] Before the skeletal iron catalyst is evaluated in a reactor
system, the ethanol-containing catalyst is dried and reduced at
300.degree. C. under high space velocity H.sub.2 for 2 hours, and
is then transferred into slurry phase reaction medium (liquid
paraffin) in a stirred reactor. Conditions for Fischer-Tropsch
slurry phase reaction are: catalyst loading 6 wt. %, particle size
0.100-0.125 mm, temperature 270.degree. C. and reaction time 40
hours. The test conditions and analytical results are shown in
Table 1.
EXAMPLE 4
[0031] Mix iron and aluminum metal powders and small amount of
copper promoter powder in weight proportion of 33:66:1 in an
electric induction furnace, heat and melt the metal powder to form
an iron metal alloy, then cool it to room temperature and pulverize
the metal alloy to 0.1-1.0 mm precursor particles size same as for
Example I. Then provide a desired volume of NaOH caustic solution
25% concentration into a stirred container, add the Fe-Al alloy
particles into the caustic solution maintained at 95.degree. C.
temperature, and allow reaction for 30 minutes to extract and/or
leach substantially all the aluminum from the iron alloy particles.
Then wash the particles with de-ionized water until pH=7, displace
water with water-free ethanol, and store the skeletal iron catalyst
in ethanol.
[0032] Before the skeletal iron catalyst is evaluated in a reactor
system, the ethanol-containing catalyst is dried and reduced with
high space velocity hydrogen at 300.degree. C. for 2 hours;
catalyst is subsequently transferred into a reaction medium (liquid
paraffin) in a stirred autoclave reactor. Conditions for
Fischer-Tropsch synthesis reaction are catalyst loading 6 wt. %,
particle size 0.100-0.125 mm, temperature 270.degree. C., and
reaction time 40 hours. Test conditions and analytical results
after reaction evaluation are listed below in Table 1.
1TABLE 1 Comparisons of Skeletal Iron Catalyst and Precipitated
Iron Catalyst in Fischer-Tropsch Slurry-Phase Synthesis Reaction
under Identical Conditions* Skeletal Iron Catalyst Precipitated
Example No. 1 2 3 4 Iron Catalyst Caustic Leaching 85 75 65 95 --
Temperature for Iron Alloy Precursor Particles, .degree. C.
Relative Separation of 20 20 25 25 100 Catalyst in Slurry, %**
Catalyst Particle Size .about.50 40-50 30-40 .about.30 1-10 After
Reaction, um CO Conversion Decline <5% <5% <5% <5%
>20% in 50 hours, % Catalyst Loss in 0.01 0.01 0.01 0.01 1.38 50
hours, % *Slurry-phase Fischer-Tropsch synthesis conditions:
H.sub.2/CO = 2.0:1 (molar), space velocity = 1.0 L/g Fe/h,
temperature = 270.degree. C., pressure = 1.6 mPa. **After a slurry
of catalyst and product liquid have settled for same length of
time, relative separation of catalyst in product liquid is
percentage of catalyst-containing wax relative to total volume of
slurry; 100% implies no catalyst settling separation in the
slurry.
[0033] Based on the above results, it is noted that the skeletal
iron catalyst examples of this invention retain larger particle
size, have improved attritiion resistance during F-T reaction, and
are much more easily separated from the reaction product liquid
than the known precipitated iron catalyst having smaller particle
size after the reaction. Also, the decline in CO conversion and
catalyst loss in product wax are substantially less for the
skeletal iron catalyst, thereby indicating its lower catalyst
consumption for the Fischer-Tropsch synthesis process.
EXAMPLE 5
[0034] Additional evaluations were made using this skeletal iron
catalyst in a liquid paraffin medium in a slurry bed autoclave
reactor. Reaction conditions for the H.sub.2+CO feedstream for
olefins production were: catalyst loading 5-20 wt. % relative to
the liquid paraffin, reaction duration 40-240 minutes. For a
specific series of catalyst evaluation tests, the following results
were obtained as listed below in Table 2.
2TABLE 2 Reaction Results With Skeletal Iron Catalyst for
H.sub.2/CO Feed Catalyst Parameters: Particle size, mm 0.062-0.30
(62-300 micron) Surface area, m.sup.2/g 22.5 Average pore size, nm
12.5 Reaction Conditions: System pressure, mPa 1.1-1.5 Reaction
temperature, .degree. C. 273-283.degree. C. Gas hourly space
velocity, L/g Fe/hr 1.0-2.0 Conversion (single-pass), % CO
82.7-94.5 H.sub.2 30.0-39.6 Yields (single-pass), g/Nm.sub.3
(H.sub.2 + CO) C.sub.1+ 65.7-132.0 C.sub.1-C.sub.4 43.8-78.3
Hydrocarbon Distribution, Vol. % C.sub.1 15.3-20.3 C.sub.2-C.sub.4
39.0-49.3 C.sub.2 - C.sub.4-/C.sub.2.sup.0 - C.sub.4.sup.0
1.2-2.4
[0035] Based on these results, it is noted that for slurry-bed
Fischer-Tropsch synthesis reaction at conditions of temperature
range 180-330.degree. C., pressure range 0.5-3.0 mPa, gas hourly
space velocity in the range of 0.5-3.0 L/gFe/h, and feed gas
H.sub.2/CO mole ratio of 0.5-2.0:1, single-pass CO conversion of
83-95%, single-pass syngas conversion of 48-57%, single-pass
hydrocarbon yield of 32-62 wt. % were achieved. About 1/5 to 1/3 of
the hydrocarbon products are C.sub.2-C4 olefins.
[0036] Although this invention has been disclosed broadly and also
identifies specific embodiments, it will be understood that
modifications and variations can be made within the scope of the
invention as defined by the following claims.
* * * * *