FI20196045A1

FI20196045A1 - METHOD OF PREPARATION OF THE CATALYST, CATALYST AND USE OF THE CATALYST

Info

Publication number: FI20196045A1
Application number: FI20196045A
Authority: FI
Inventors: Niko Heikkinen; Matti Reinikainen; Noora Kaisalo; Patrik Eskelinen; Matti Putkonen
Original assignee: Teknologian Tutkimuskeskus Vtt Oy
Priority date: 2019-12-02
Filing date: 2019-12-02
Publication date: 2021-06-03
Also published as: WO2021111034A1

Abstract

The invention relates to a method for preparing a catalyst, wherein a catalyst precursor is coated with an ALD-coating such that Al2O3-layer is arranged on the surface of the catalyst precursor to form the catalyst, the formed catalyst is treated by a thermal treatment in which temperature is increased in presence of nitrogen, and the catalyst is cooled after the thermal treatment in presence of nitrogen stream. Further, the invention relates to the catalyst and the use of the catalyst.

Description

METHOD FOR PREPARING A CATALYST, CATALYST AND USE OF CATALYST

FIELD The application relates to a method for pre- paring a catalyst defined in claim 1 and a catalyst defined in claim 13. Further, the application relates to a use of the catalyst defined in claim 17.

BACKGROUND In order to utilize challenging renewable re- sources efficiently, novel catalysts are required. Catalyst development should create robust and intrin- sically active catalyst for purpose. Three key perfor- mance indicators are activity, selectivity and re- sistance to deactivation.

OBJECTIVE The objective is to disclose a new type coat- ing method for enhancing catalyst performance. Fur- ther, the objective is to disclose a new type cata- lyst. Further, the objective is to disclose an im- proved highly-active catalyst. Further, the objective is to improve resistance to deactivation of the cata- lyst. Further, the objective is to improve a FT- process (Fischer-Tropsch process). >

S SUMMARY a The method and catalyst and use are charac- W 30 terized by what are presented in the claims. 9 In the method, a catalyst precursor is coated = with an atomic layer deposition (ALD) method and o treated by a thermal treatment for forming a catalyst.

O > S 35

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included to provide a further understanding of the invention and constitutes a part of this specification, illus- trate some embodiments of the invention and together with the description help to explain the principles of the invention. In the drawings: Fig. 1 - 4 show results from Fischer-Tropsch reaction experiments, and Fig. 5a and 5b show SEM-structures of the catalyst treated by a thermal annealing and the cata- lyst untreated by a thermal annealing.

DETAILED DESCRIPTION In a method for preparing a catalyst, a cata- lyst precursor is coated with an ALD-coating (atomic layer deposition -coating) such that Al,03-layer is ar- ranged on the surface of the catalyst precursor to form the catalyst, the formed catalyst is treated by a thermal treatment, such as a thermal annealing, in which temperature is increased in presence of nitro- gen, for example in a reactor, and the catalyst is cooled after the thermal treatment in presence of nitro- gen stream. In the present invention, the target is to increase the intrinsic activity, selectivity to de- o sired products and resistance towards deactivation > with nanometer scale top coating. With this conformal AN and thin coating, catalysts, regardless of preparation W 30 method, can be top coated for better performance. 7 In this context, the ALD-coating means any = atomic layer deposition (ALD) method which is suitable O to coat the catalyst precursor and to form the Al,03- 3 layer on the catalyst precursor. The atomic layer dep- DO 35 osition (ALD) is a technique for manufacturing nanome- N ter scale thin layers on various surfaces. The layer thickness can be altered digitally with high precision by amount of ALD cycles on the coated surface.

Multi- tude of chemical elements can be coated on the surface by ALD.

In the ALD-coating of the present method, de- sired agent, e.g. alumina, is deposited on the sup- port, e.g. catalyst precursor.

The atomic layer depo- sition technology provides a controlled way of adding minute alterations to a catalyst surface.

By adding atomic scale surface modification substance, e.g. alu- mina or platina, it is possible to create heterogenous catalyst with enhanced properties.

With heterogeneous catalyst ALD top coating, either catalyst active metal can be deposited on the surface, or protective inert layer can be added on top of the catalyst surface.

The present method described here uses ALD top coated Al,0; and thermal annealing of deposited Al203 surface for creating a protective porous layer on top of the cata- lyst.

The catalyst comprises a catalyst precursor and an Al,0z;-layer which is arranged by an ALD-coating on the surface of the catalyst precursor and which is treated by a thermal treatment, such as a thermal an- nealing, in which temperature is increased in presence of nitrogen and which is cooled after the thermal treatment in presence of nitrogen stream.

In this context, the catalyst precursor means o any catalyst precursor, initial catalyst, known cata- > lyst which is modified, or the like.

AN In one embodiment, the catalyst precursor com- W 30 prises catalyst material containing at least one cata- 7 lyst agent, e.g. suitable metal.

In one embodiment, a. the catalyst material is compound containing at least O one metal.

In one embodiment, the catalyst material 3 contains at least metal selected cobolt, nickel, plati- DO 35 num, iridium, other precious metals or other metals.

The N catalyst material is catalytically active.

In one embod-

iment, the catalyst precursor is a catalyst which is suitable for a Fischer-Tropsch process. Alternatively, any suitable catalyst precursor can be used as the catalyst precursor. In one embodiment, the catalyst precursor is a heterogeneous supported catalyst. The catalyst precursor can be in any form, for example, in the form of particles, plate or other suitable form. In one embodiment, the catalyst precursor can be in a form of powder, particulate, granulate or coated on a carrier surface. In one embodiment, the catalyst pre- cursor 1s formed from catalyst particles which are coated with the catalyst material or are formed from the catalyst material. In one embodiment, the catalyst precursor is formed from a plate or other element which is coated with the catalyst material. In one em- bodiment, the catalyst material is arranged as a coat- ing on a desired substrate, e.g. carrier material, metal substrate, ceramic substrate or other substrate, in order to form the catalyst precursor.

In one embodiment, the ALD-coating is per- formed in a reactor. In one embodiment, the ALD- coating is performed in an ALD-reactor. In this con- text, the ALD-reactor means any reactor which is suit- able for ALD-coating.

In the ALD-coating, the surface of the cata- lyst precursor is coated with the Al,03-layer, e.g.

o gamma alumina. Al,03-layer is arranged as a top-coating > material on the catalyst. In one embodiment, Al>03- AN layer is formed from an Al-based compound. In one em- W 30 bodiment, the Al,0s3-layer is formed by depositing an 7 alumina top coating onto the surface of the catalyst a. precursor by means of an atomic layer deposition (ALD) O method. Preferably, Al,0;-coating with specific thick- 3 ness can be added on top of the catalyst precursor in > 35 the ALD-coating.

In one embodiment, the Al,0:;-layer is formed from a selected Al-based compound. In one embodiment, the Al,03-layer is formed from Al (CH3;3)3s coating precur- sor. Alternatively, any suitable Al-based compound, 5 e.g. aluminum acetylacetonate, aluminum hexafluoroa- cetylacetonate, triethylaluminum, tris(2,2,6,6- tetramethyl-3,5-heptanedionato) aluminum, can be used to form the Al,0;-layer. In one embodiment, Al,03;-laver is arranged on the surface of the catalyst precursor during the AID- coating, for example in the ALD-reactor, by using the ALD coating for forming a desired thickness of the Al,03-layer on the surface of the catalyst precursor. In one embodiment, Al,03;-layer is formed as 0.1 - 8 nm, in one embodiment as 1 -— 6 nm thick layer, in one em- bodiment as 3 -— 5 nm thick layer, and in one embodi- ment as 3 — 4 nm thick layer, on the catalyst precur- sor. In one embodiment, a desired number of cycles of the ALD coating is used for forming a desired thick- ness of the Al,0;-layer on the surface of the catalyst precursor. In one embodiment, the thickness of Al,03- layer is increased 0.03 - 0.5 nm, in one embodiment

0.08 — 0.2 nm, and in one embodiment 0.09 — 0.12 nm, in each ALD coating cycle. In one embodiment, Al>03- layer is formed by means of 15 — 40 cycles, and in one embodiment by means of 25 - 38 cycles. In one embodi- o ment, the thickness of Al,0; on the surface of the cat- > alyst precursor is 0.1 - 8 nm, in one embodiment 1 — 6 AN nm, in one embodiment 3 — 5 nm, in one embodiment 3 — W 30 4 nm, and in one embodiment 3.2 - 3.8 nm. In one em- 7 bodiment, the thickness of Al,0; on the surface of the a. catalyst precursor is dependent on top coating precur- O sor or catalyst precursor, which are used in the coat- 3 ing.

DO 35 In one embodiment, the catalyst precursor is N pretreated before the AID-coating for providing the cat-

alyst precursor suitable for the ALD-coating. In one em- bodiment, the catalyst precursor is calcined before the ALD-coating. In one embodiment, the catalyst is reduced before thermal treatment, such as thermal annealing. In one embodiment, temperature is increased 2 -—- 8 °C/min, in one embodiment 3 - 7 °C/min and in one em- bodiment about 4 - 6 °C/min, during the reduction. In one embodiment, the temperature of the catalyst is 250 — 400 °C, in one embodiment 300 - 400 °C and in one embodiment 350 — 400 °C, after the reduction. In one embodiment, the reduction is performed by means of re- ductive gas stream, such as hydrogen or carbon monox- ide under atmospheric pressure. In one embodiment, the catalyst is cooled after the reduction. In one embodi- ment, the catalyst is cooled to a room temperature.

In one embodiment, the thermal treatment is a thermal annealing. By means of the thermal treatment, such as thermal annealing, porosity can be increased on the top coated layer, such as on the Al,0;-top coat layer.

In one embodiment, the thermal treatment, such as thermal annealing, is carried out in the reac- tor, such as in a tubular reactor. In addition, any reactor capable for thermal annealing conditions for gas flow and temperature can be used. In one embodi- o ment, the thermal treatment is carried out under at- > mospheric pressure. N In one embodiment, temperature is increased 2 W 30 - 6 °C/min, in one embodiment 3 - 5 °C/min and in one 7 embodiment about 4 °C/min, during the thermal treat- a. ment, such as thermal annealing. Preferably the ther- O mal treatment, such as thermal annealing, is performed 3 in the presence of nitrogen, such as under nitrogen DO 35 stream. In one embodiment, the nitrogen is supplied to N the reactor during the thermal treatment. In one em-

bodiment, a feed gas-hourly-space-velocity of the ni- trogen is 2.4 — 4.1 ht, in one embodiment 2.9 —- 3.7 ht! and in one embodiment 3.0 — 3.5 h', during the thermal treatment.

In one embodiment, temperature is 375 - 475 °C, in one embodiment 400 —- 450 °C and in one embodi- ment 410 — 430 °C, after the thermal treatment, such as thermal annealing, e.g. in the reactor. In one em- bodiment, temperature is about 420 °C after the ther- mal treatment.

After the thermal treatment, such as thermal annealing, the catalyst is cooled in presence of nitro- gen. In one embodiment, the nitrogen is supplied to the reactor during the cooling. In one embodiment, a feed gas-hourly-space-velocity of the nitrogen is 4.9 - 8.2 ht, in one embodiment 5.7 - 7.4 ht and in one embodiment 6.2 — 7.0 h', during the cooling. In one embodiment, temperature after the cooling is less than 200 °C, in one embodiment less than 180 °C, in one em- bodiment less than 160 °C and in one embodiment less than 150 °C, e.g. in the reactor. In one embodiment, temperature after the cooling is 100 — 200 °C, in one embodiment 130 - 180 °C and in one embodiment 140 - 160 °C. In one embodiment, the catalyst is reduced after the cooling and before the use of the catalyst. o In one embodiment, temperature is increased 2 — 8 > °C/min, in one embodiment 3 - 7 °C/min and in one em- AN bodiment about 4 - 6 °C/min, during the reduction. In W 30 one embodiment, the temperature of the catalyst is 350 7 — 450 °C, in one embodiment 380 - 430 °C and in 390 — 410 °C, after the reduction. In one 2 embodiment, the reduction is performed by means of re- O ductive gas, such as hydrogen or carbon monoxide > 35 stream under atmospheric pressure.

In one embodiment, the catalyst is cooled af- ter the reduction. In one embodiment, the catalyst is cooled to temperature of 150 - 200 °C, and in one em- bodiment to temperature of 170 — 190 °C. In one embod- iment, the catalyst is cooled to a room temperature.

In one embodiment, the catalyst can be used and utilized in a FT-synthesis, a production of hydro- carbons or other process, or in a FT-reactor, a micro- channel reactor or other reactor, or their combina- tions. In one embodiment, the catalyst is suitable for a FT-synthesis in which hydrocarbons are formed from synthesis gas. In one embodiment, the catalyst is suitable for a microchannel reactor.

Thanks to the method comprising ALD and ther- mal annealing process, an effective and highly active catalyst can be provided. The catalyst of the present invention has high intrinsic activity without compro- mising selectivity. The top coated and thermal an- nealed catalyst with high intrinsic activity increases the synthesis efficiency many times compared to tradi- onal catalysts. Further, the catalyst stability can be improved and performance enhanced. Furthermore, cata- lyst deactivation resistance is enhanced with the top coating layer. The catalyst is suitable for many reac- tor types, for example for microchannel reactors.

Further, any heterogeneous catalyst can be o modified for better activity and selectivity and pro- > tected against deactivation by the AID-coating and AN thermal annealing according to the present method. N 30

EXAMPLES i O Example 1 3 In this example, a catalyst is prepared. > 35 A catalyst precursor, e.g. Co-Pt -catalyst suitable for a Fischer-Tropsch -process, is coated with an ALD (atomic layer deposition)-top coating in a reactor such that Al,03-layer is arranged on the sur- face of the catalyst precursor to form a top coated catalyst.

The Al,0;-layer is formed by depositing ALD top coating precursors for forming a desired thickness of the Al,03-layer, in this example 1 -— 6 nm thickness.

In this example, the Al,03;3-layer is formed from tri- methylalumina (TMA) and water vapour.

The formed catalyst is treated by a thermal annealing, in which temperature is increased in pres- ence of nitrogen stream in the reactor.

The thermal annealing is performed under the atmospheric pressure in the reactor.

The temperature is increased 3 - 5 °C/min during the thermal annealing.

A feed velocity (GHSV) of the nitrogen is 3.0 - 3.5 ht during the thermal annealing.

The temperature is 410 — 430 °C af- ter the thermal annealing.

The catalyst is cooled after the thermal an- nealing in presence of nitrogen stream in which a feed velocity of the nitrogen is 6.2 - 7.0 h* during the cooling, and the temperature is 140 — 160 °C after the cooling in the reactor.

The catalyst is reduced after the cooling and before the use of the catalyst.

The reduction is per- formed by means of hydrogen stream under atmospheric pressure.

The temperature is increased 4 - 6 °C/min o during the reduction, and the temperature of the cata- > lyst is 390 — 410 °C after the reduction.

The catalyst AN is cooled after the reduction to temperature of 170 - W 30 190 °C.

Alternatively, the catalyst may be cooled to a 7 room temperature.

Ao a O Example 2 3 In this example, a cobalt-based Fischer- > 35 Tropsch catalyst was top coated with an atomic layer deposition (ALD) technology with different AID cycles.

Further, the formed catalyst was tested in reaction conditions. A cobalt catalyst supported on gamma-alumina was used as a precursor catalyst, which comprised 21 w-% cobalt and 0.1 w-% Pt on y-Al;0:; and which has been prepared with an incipient wetness impregnation ac- cording to the known method. This cobalt precursor catalyst was used also as a comparative catalyst in the tests.

The catalyst precursor was coated by means of ALD-coating with Al,03;-coating in order to form the catalyst according to the present invention. The Al,0:- layers were formed on the surfaces of the catalyst precursors by using different ALD cycles for forming a desired thickness of the Al,0s;-layer on the catalyst precursors. In this example 15 cycles, 35 cycles and 40 cycles of the ALD coating were used, and the thick- ness of the Al,03;s-layver was increased 0.1 nm in each cycle.

A part of the formed catalysts was treated with a thermal annealing (TA). Around 0.6 g catalyst and 2 g SiC, i.e. 2 - 3 cc total, was packed in a tub- ular reactor after the ALD-top coating. The thermal annealing was performed under atmospheric pressure in presence of nitrogen stream which was 40 ml/min. The temperature was increased 4 °C/min to temperature of o 420 °C in the reactor. After that, the reactor was > cooled by nitrogen flow, which was 80 ml/min, to tem- AN perature of 150 °C.

W 30 The catalysts with the thermal annealing 7 treatment and the catalysts without the thermal an- a. nealing treatment were activated by hydrogen reduction O in the reactor. During the reduction, the temperature 3 was increased 5 °C/min from temperature of 150 °C to o 35 temperature of 400 °C. The reduction was carried out N under atmospheric pressure in presence of hydrogen flow, which was 100 ml/min. The residence of the re- duction was 12 hours. After the reduction, the reactor was cooled from 400 °C to 180 °C in presence of hydro- gen flow which was 100 ml/min.

The catalysts were tested in the reaction conditions in the reactor. The synthesis gas was sup- plied to the reactor in which temperature was 200 °C ja pressure was 20 bar.

Some test results are shown in Figs. 1 - 4.

Fig. 1 shows the ALD top coat thickness ef- fect on activity. From Fig. 1 can be observed that carbon monoxide (CO) conversion was 5 - 15 %. Further, CO conversion increased when Co-Pt catalyst precursor was ALD-coated with 35 cycles (35 c). In the Fig. 1, thermal annealing is signified with marking TA. The conversion level and space-time was adjusted with gas- hourly-space-velocity (GHSV).

Fig. 2 shows the effect of thermal annealing (TA) to activity. From Fig. 2 can be observed that carbon monoxide (CO) conversion was 5 - 15 %. Further, CO conversion increased when Co-Pt catalyst precursor was ALD-coated with 35 cycles (35 c) and treated by the thermal annealing (TA). Further, from Fig. 2 can be observed that the CO conversion can be improved when the catalyst precursor Co-PT was treated by the ALD-coating and/or thermal annealing.

o Fig. 3 shows the product formation (total hy- > drocarbons) for each ALD top coating thickness. From AN Fig. 3 can be observed that the total hydrocarbon pro- W 30 duction was increased notably by 35 ALD cycle cata- 7 lyst. As light hydrocarbons C1-C4 in Fischer-Tropsch a. are in most cases undesired products, Fig. 4 presents O the results for C5+ hydrocarbon production rate. The 3 catalyst activity can be increased by the preparation > 35 method of the present invention. By means of the pre-

sent preparation method, C5+ hydrocarbon production can be increased even about 80 %. Further, it was observed that the catalyst stability against deactivation can be improved by means of the invention. This present catalyst can be used in Fischer- Tropsch processes, for example in a microchannel reac- tor. Example 3 The catalyst according to example 3 was ALD top coated and treated by a thermal annealing. Fur- ther, the comparative catalyst to example 3 was pre- pared, however, without a thermal annealing. Fig. 5a shows SEM-structure of the catalyst treated by a ther- mal annealing before reduction of the catalyst. Fig. 5b shows SEM-structure of the catalyst untreated by a thermal annealing before reduction of the catalyst. From the SEM-structures it can be observed that the surface of the catalyst according to Fig. ba is more porous than the surface of the catalyst ac- cording to Fig. 5b. Therefore, it is apparent that thermal annealing is required to modify the surface for enhanced activity.

The method for preparing the catalyst is o suitable in different embodiments for preparing new > types catalysts to different processes. Further, the AN catalyst is suitable in different embodiments for us- W 30 ing in different processes. 7 The invention is not limited merely to the = examples referred to above; instead many variations 2 are possible within the scope of the inventive idea O defined by the claims. > 35

Claims

1. A method for preparing a catalyst, characterized in that - a catalyst precursor is coated with an ALD- coating such that Al,03;3-layer is arranged on the surface of the catalyst precursor to form the catalyst, - the formed catalyst is treated by a thermal treatment in which temperature is increased in presence of nitrogen, and - the catalyst is cooled after the thermal treatment in presence of nitrogen stream.

2. The method according to claim 1, char - acterized in that Al,0s-layer is arranged on the surface of the catalyst precursor for forming a de- sired thickness of the Al,05;s-layer, in which the thick- ness of Al,03-layer is 1 — 6 nm.

3. The method according to claim 1 or 2, characterized in that the catalyst precursor comprises catalyst material which contains at least met- al selected from the group consisting of cobolt, nickel, platinum, iridium, other precious metals and other met- als.

4. The method according to any one of claims lto 3, characterized in that the catalyst precursor is calcined before the ALD-coating. o

5. The method according to any one of claims > lto4, characterized in that the Al,03;-layer AN is formed from Al (CH:;); compound. W 30

6. The method according to any one of claims 7 1 to 5, characterized in that the thermal = treatment is thermal annealing. 2

7. The method according to any one of claims O lto 6, characterized in that temperature is > 35 increased 2 — 6 °C/min during the thermal treatment.

8. The method according to any one of claims I to 7, characterized in that a feed velocity of the nitrogen is 2.4 - 4.1 ht during the thermal treatment.

9. The method according to any one of claims lto 8, characterized in that temperature is 375 - 475 °C after the thermal treatment.

10. The method according to any one of claims lto 9 characterized in that a feed velocity of the nitrogen is 4.9 — 8.2 h' during the cooling.

11. The method according to any one of claims I to 10, characterized in that temperature of the catalyst is increased 2 - 8 °C/min during the re- duction to temperature of 250 - 450 °C.

12. The method according to any one of claims lto 11, characterized in that the catalyst is cooled after the reduction to temperature of 150 - 200 °c.

13. A catalyst, characterized in that - the catalyst comprises a catalyst precursor and an Al,O03-layer which is arranged by an ALD-coating on the surface of the catalyst precursor, and - the catalyst is treated by a thermal treatment in which temperature is increased in presence of ni- trogen and is cooled after the thermal treatment o in presence of nitrogen stream. >

14. The catalyst according to claim 13, N characterized in that the thickness of the N 30 formed Al,03;-top coating is 0.1 - 8 nm. I

15. The catalyst according to claim 13 or 14, = characterized in that the catalyst precursor 2 comprises catalyst material which contains at least met- O al selected from the group consisting of cobolt, nickel, > 35 platinum, iridium, other precious metals and other met- als.

16. The catalyst according to any one of claims 13 to 15, characterized in that the catalyst precursor is a heterogeneous supported cata- lyst.

17. A use of the catalyst obtained by the method according to any one of claims 1 to 12, characterized in that the catalyst is used in a FT-synthesis, a production of hydrocarbons or other process, or in a FT-reactor, a microchannel reactor or other reactor, or their combinations.

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