CA2222806A1 - Catalyst and process for preparing ammonia - Google Patents
Catalyst and process for preparing ammonia Download PDFInfo
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- CA2222806A1 CA2222806A1 CA002222806A CA2222806A CA2222806A1 CA 2222806 A1 CA2222806 A1 CA 2222806A1 CA 002222806 A CA002222806 A CA 002222806A CA 2222806 A CA2222806 A CA 2222806A CA 2222806 A1 CA2222806 A1 CA 2222806A1
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- Prior art keywords
- catalyst
- zeolite
- metal ions
- zeolite support
- divalent
- Prior art date
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- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 title claims abstract description 70
- 239000003054 catalyst Substances 0.000 title claims abstract description 55
- 229910021529 ammonia Inorganic materials 0.000 title claims abstract description 29
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 6
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 claims abstract description 61
- 239000010457 zeolite Substances 0.000 claims abstract description 61
- 229910021536 Zeolite Inorganic materials 0.000 claims abstract description 58
- 230000015572 biosynthetic process Effects 0.000 claims abstract description 19
- 229910052751 metal Inorganic materials 0.000 claims abstract description 19
- 239000002184 metal Substances 0.000 claims abstract description 19
- 238000000034 method Methods 0.000 claims abstract description 19
- 238000003786 synthesis reaction Methods 0.000 claims abstract description 19
- 229910001413 alkali metal ion Inorganic materials 0.000 claims abstract description 11
- 229910021645 metal ion Inorganic materials 0.000 claims description 17
- 238000006243 chemical reaction Methods 0.000 claims description 16
- 229910052723 transition metal Inorganic materials 0.000 claims description 12
- 150000003624 transition metals Chemical class 0.000 claims description 12
- 229910052783 alkali metal Inorganic materials 0.000 claims description 11
- 150000001340 alkali metals Chemical class 0.000 claims description 10
- 229910052700 potassium Inorganic materials 0.000 claims description 9
- 229910000069 nitrogen hydride Inorganic materials 0.000 claims description 6
- 229910052792 caesium Inorganic materials 0.000 claims description 5
- 239000007789 gas Substances 0.000 claims description 5
- 238000005470 impregnation Methods 0.000 claims description 5
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 claims description 4
- 229910001420 alkaline earth metal ion Inorganic materials 0.000 claims description 4
- 239000011591 potassium Substances 0.000 claims description 4
- 229910000323 aluminium silicate Inorganic materials 0.000 claims description 3
- TVFDJXOCXUVLDH-UHFFFAOYSA-N caesium atom Chemical compound [Cs] TVFDJXOCXUVLDH-UHFFFAOYSA-N 0.000 claims description 3
- 239000000203 mixture Substances 0.000 claims description 3
- 229910052701 rubidium Inorganic materials 0.000 claims description 3
- 229910001428 transition metal ion Inorganic materials 0.000 claims description 3
- -1 alkali metal alkoxides Chemical class 0.000 claims description 2
- 150000007514 bases Chemical class 0.000 claims description 2
- 230000003647 oxidation Effects 0.000 claims description 2
- 238000007254 oxidation reaction Methods 0.000 claims description 2
- 229910000000 metal hydroxide Inorganic materials 0.000 claims 2
- 150000004692 metal hydroxides Chemical class 0.000 claims 2
- IGLNJRXAVVLDKE-UHFFFAOYSA-N rubidium atom Chemical compound [Rb] IGLNJRXAVVLDKE-UHFFFAOYSA-N 0.000 claims 2
- 150000008044 alkali metal hydroxides Chemical class 0.000 claims 1
- 229910000272 alkali metal oxide Inorganic materials 0.000 claims 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 claims 1
- 230000008569 process Effects 0.000 abstract description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 10
- 239000007787 solid Substances 0.000 description 9
- 238000000921 elemental analysis Methods 0.000 description 7
- 150000001768 cations Chemical class 0.000 description 6
- 150000002500 ions Chemical group 0.000 description 6
- 229910052707 ruthenium Inorganic materials 0.000 description 6
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 5
- 239000001257 hydrogen Substances 0.000 description 5
- 229910052739 hydrogen Inorganic materials 0.000 description 5
- 229910052757 nitrogen Inorganic materials 0.000 description 5
- 229910052708 sodium Inorganic materials 0.000 description 5
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 4
- KJTLSVCANCCWHF-UHFFFAOYSA-N Ruthenium Chemical compound [Ru] KJTLSVCANCCWHF-UHFFFAOYSA-N 0.000 description 4
- 239000007864 aqueous solution Substances 0.000 description 4
- 238000005342 ion exchange Methods 0.000 description 4
- 238000012986 modification Methods 0.000 description 4
- 230000004048 modification Effects 0.000 description 4
- FGIUAXJPYTZDNR-UHFFFAOYSA-N potassium nitrate Chemical compound [K+].[O-][N+]([O-])=O FGIUAXJPYTZDNR-UHFFFAOYSA-N 0.000 description 4
- 150000003303 ruthenium Chemical class 0.000 description 4
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 3
- 229910052788 barium Inorganic materials 0.000 description 3
- 238000010348 incorporation Methods 0.000 description 3
- 239000000243 solution Substances 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- 239000003513 alkali Substances 0.000 description 2
- ITHZDDVSAWDQPZ-UHFFFAOYSA-L barium acetate Chemical compound [Ba+2].CC([O-])=O.CC([O-])=O ITHZDDVSAWDQPZ-UHFFFAOYSA-L 0.000 description 2
- 229910052742 iron Inorganic materials 0.000 description 2
- 150000002739 metals Chemical class 0.000 description 2
- 235000010333 potassium nitrate Nutrition 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 150000004703 alkoxides Chemical class 0.000 description 1
- DSAJWYNOEDNPEQ-UHFFFAOYSA-N barium atom Chemical compound [Ba] DSAJWYNOEDNPEQ-UHFFFAOYSA-N 0.000 description 1
- ZOAIGCHJWKDIPJ-UHFFFAOYSA-M caesium acetate Chemical compound [Cs+].CC([O-])=O ZOAIGCHJWKDIPJ-UHFFFAOYSA-M 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 229910002090 carbon oxide Inorganic materials 0.000 description 1
- 239000000969 carrier Substances 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 239000008367 deionised water Substances 0.000 description 1
- 229910021641 deionized water Inorganic materials 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005984 hydrogenation reaction Methods 0.000 description 1
- 238000011065 in-situ storage Methods 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 1
- 239000000395 magnesium oxide Substances 0.000 description 1
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 150000002736 metal compounds Chemical class 0.000 description 1
- 239000002808 molecular sieve Substances 0.000 description 1
- 229910052762 osmium Inorganic materials 0.000 description 1
- 239000000376 reactant Substances 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 150000003304 ruthenium compounds Chemical class 0.000 description 1
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 description 1
- 229910001415 sodium ion Inorganic materials 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J29/00—Catalysts comprising molecular sieves
- B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
- B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
- B01J29/064—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof containing iron group metals, noble metals or copper
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01C—AMMONIA; CYANOGEN; COMPOUNDS THEREOF
- C01C1/00—Ammonia; Compounds thereof
- C01C1/02—Preparation, purification or separation of ammonia
- C01C1/04—Preparation of ammonia by synthesis in the gas phase
- C01C1/0405—Preparation of ammonia by synthesis in the gas phase from N2 and H2 in presence of a catalyst
- C01C1/0411—Preparation of ammonia by synthesis in the gas phase from N2 and H2 in presence of a catalyst characterised by the catalyst
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
- Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts
Abstract
A catalyst for synthesis of ammonia from N2 and H2, containing a basic zeolite support; Group VIII metal clusters supported on the basic zeolite support; and divalent and alkali metal ions incorporated into the zeolite support, and a process for the production of ammonia using such a catalyst.
Description
TITLE OF THE INVENTION
CATALYST AND PROCESS FOR PREPARING AMMONIA
The research leading to the invention described herein was supported in part by funds from Grant ~CTS-9257306 from the National Science Foundation. As such, the United States Government may have certain rights in the present invention.
BACXGROUND OF THE INVENTION
Field of the Invention The present invention relates to a novel supported catalyst comprising a Group VIII transition metal supported on a basic molecular sieve, for providing i~uved synthesis of ammonia from nitrogen and hydrogen gases and a process for using the same in preparing ammonia.
Discussion of the Backqround Conventional industrial ammonia synthesis processes use a triply promoted iron catalyst operating at temperatures of 400-700~C and pressures in excess of 300 atm. However, at such e~L ~- ? temperatures, the equilibrium reaction of N2 and H2 to give ~ on; a is not especially favored, hence the need for the extreme pressures.
In U.S. Patent No. 3,770,658, Ozaki et al disclosed a ~ transition metal based catalyst, preferably of ruthenium, which contained alkali metal, for the preparation of ammonia from nitrogen and hydrogen under temperatures less than 400~C.
In U.S. Patent No. 4,142,993, Elofson et al also disclose a Group VIII transition metal based catalyst cont~in;ng alkali metal, which is supported on an activated carbon support for synthesis of ammonia at temperatures of 375~C or higher and pressures of 27-67 atm.
Such traditional ruthenium-based ammonia synthesis catalysts consist of ruthenium clusters supported on carriers like carbon and magnesium oxide. In addition, as shown by Ozaki et al, alkali metal promotors such as potassium or cesium are often added to enhance the catalytic activity of the ruthenium.
In U.S. Patent 4,600,571, McCarroll et al disclose the use of ruthenium based ammonia synthesis catalyst which contain an alkali metal and barium, all supported on a carbon ~L.
R~ntly published work by Cicn~os and Lunsford [J.
Catal. 141 (1993) 191-205] and Wellenbuscher et al (Catal.
Letters 25(1994) 61-74) shows that ruthenium clusters supported on alkali-cont~; ni ng zeolites also catalyze the synthesis of ammonia from nitrogen and hydrogen at atmospheric pressure. From the results of Cisneros and Lunsford, ammonia synthesis at 650 K and atmospheric pressure over ruthenium clusters supported on potassium-loaded zeolite X occurs at a rate of 1.7 x 10-5 mol NH3/g Ru/sec.
However, each of the prior art catalysts still do not provide the desired level of activity and reaction rate.
Accordingly, an improved ammonia synthesis catalyst is desired.
SUMMARY OF THE INVENTION
Accordingly, one object of this invention is to provide a catalyst which provides improved ammonia synthesis rates under industrially useful conditions.
A further object of the present invention is to provide an i~ o~ed process for the preparation of ammonia from nitrogen and hydrogen gases.
These and other objects of the present invention have been satisfied by the discovery of a catalyst for ammonia synthesis, comprising Group VIII transition metal clusters supported on a basic zeolite, which further comprises alkali metal ions and divalent metal ions, which provides markedly improved rates of reaction of N2 and H2 to give ammonia.
DETATT~n DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention relates to a Group VIII transition metal/basic zeolite catalyst for the synthesis of ammonia from N2 and H2. The catalyst of the present invention comprises Group VIII transition metal clusters supported on a basic zeolitic support. The Group VIII transition metal cluster is preferably made of Fe, Ru or Os, with Ru being most preferred.
W 096/38222 PCTrUS96/07948 The Group VIII transition metal cluster can be prepared using conventional methods (see "Catalyst Manufacture", 2nd Ed., A.B. Stiles and T.A. Xoch, Marcel Dekker, New York, 1995).
For example, ruthenium clusters can be formed from various ruthenium compounds, such as Ru (NH3 )6Cl3. In particular, the Group VIII metal compounds are ion exchanged or impregnated onto the zeolite, following which the resulting material is reduced,.for example, by hydrogenation, thus providing the resulting clusters in an oxidation state of the corresponding metal (such as Ru~).
The zeolite used in the present catalyst as a support for the Group VIII metal clusters is preferably a Faujasite-type zeolite (or Faujasitic zeolite), such as Zeolite X, Zeolite Y, EMT, ZSM-3, ZSM-20, Zincophosphate X or SAPO-37. Preferably the zeolite is a microporous cryst~ll;ne aluminosilicate, preferably having a Si:Al ratio of from 1:1 to 6:1, more preferably 1:1 to 2.5:1.
The catalyst of the present invention further contains Group I alkali cations and clivalent metal cations. The divalent metal cations can be alkAl;ne earth ions or divalent transition metal ions. Preferably the A 1 kA l; ne earth ions are used, with Ba~2 being most preferred. The divalent metal ions can be incorporated into the Group VIII metal/zeolite catalyst by conventional processes, such as ion exchange or impregnation.
W 096/38222 PCTrUS96/07948 C_ ~~cially available zeolites often already contain alkali metal ions, such as Na. For example, Zeolite X is available containing Na ions and is conventionally called NaX
zeolite. These zeolites can be used as supplied, or can first be subjected to modification, such as ion exchange or impregnation, to replace Na with another alkali metal, such as K, with the preferred alkali metals being K, Rb and Cs. The alkali metal con~; n ing zeolite is then subjected to modification with divalent cations, such as alkaline earth metal ions, by ion exchange or a combination of ion exchange and impregnation.
Prior to or after this divalent cation modification, the Group VIII metal can be incorporated into the zeolite using conventional t~chn;ques to form the metal clusters and provide the Group VIII/M~2/basic zeolite catalyst. While the above sequence of steps can be used to prepare the present catalyst, the steps can be performed in any order, to provide incorporation of the divalent metal ions and the Group VIII
metal clusters, to provide the catalyst of the present invention which is active for the production of ammonia from N2 and H2.
The Group VIII metal based catalyst of the present -~ invention provides its advantages in reaction rate upon incorporation of even minute quantities of Group VIII metal into the basic zeolite. However, it is preferred that the loading be in the range of 0.1 to 10%, most preferably in the range of 1-5% by weight, based on the amount of zeolite. In the case of the more expensive Group VIII metals, the preferred loading is in the range of 0.1 to 2.0%.
The divalent metal ions also provide their advantages even upon incorporation of very small quantities into the catalyst. Preferably, the molar ratio of divalent metal ions to alkali metal ions is in the range from 0.01 to 100, most pre~erably from 10 to 100.
Once the divalent ions and Group VIII metals have been incorporated into the zeolite, it is important to render the zeoiite basic in nature. This is preferably done by impregnating the composition with a basic compound such as divalent or alkali metal hyclroxides, A lk;~l; alkoxides, ~lk;~l;
oxides, alkali metals, etc.
In using the catalyst o~ the present invention, the catalyst is contacted with ~T2 and H2 gas in a N2:H2 molar ratio of ~rom 10:1 to 1:10, preferably from 1:3 to 1:6. The reaction is performed at a temperature and pressure su~icient to provide ~c~llent yield per unit time. Pre~erably the tr ~ature of ammonia synthesis is from 200-600~C and the pressure is from atmospheric to 400 atmospheres. These parameters can be adjusted to provide the optimum reaction rate, depending primarily on the conditions achievable in the reaction vessels used. The contact time, or weight hourly space velocity (g feed/g ca~alyst/hour), is adjusted to achieve the desired yield o~ ammonia (i.e., longer contact gives more ammonia and vice versa). Further, the reaction can be performed either batchwise or continuously.
By using the catalyst of the present invention, it is possible to obtain surprisingly improved rates of ammonia synthesis when compared to the catalysts of the prior art.
These improved rates of reaction allow the use of milder conditions, which can prove industrially advantageous financially, as well as in the area of industrial safety.
Having generally described this invention, a further understanding can be obtained by reference to certain specific examples which are provided herein for purposes of illustration only and are not intended to be limiting unless otherwise specified.
EXAMPLES
CatalYst SYnthesis Exam~les Example 1. Ru/NaX
NaX zeolite (lS g) ~rom Union Carbide (elemental analysis: Si - 20.48%, Al - 16.55%, Na - 12.6%) was ion-~h~nged with 0.936 g o~ Ru(NH3)6C13 in 300 mL of distilled, deionized water. The resulting solids were filtered, dried and reduced in flowing H2 at 723 K. The final solid cont~;n~
1.8S% of Ru by weight.
ExamPle 2. Ru/KX
W O 96/38222 PCTrUS96107948 First, NaX zeolite ~rom Union Carbide (elemental analysis: Si -- 20.48~6, Al - 16.55%, Na -- 12.67%) was ion--exchanged three times with 1 molL~l aqueous KNO3 (7S, 230 and 350 mL, respectively) and dried to produce KX zeolite. 15 g of KX zeolite was ion o~r~h~rlged with 0.936 g of Ru(NH3)6Cl3 in l.Z L of water. The resulting solids were filtered, dried and reduced in ~lowing H2 at 723 K. The reduced solid was then impregnated with 310 mL oi~ a 0.2 molal aqueous solution o~ KOH
and dried. Elemental analysis: Ru -- 2.04%, Si -- 19.70%, Al 13.03%, Na -- 0.58%, K -- 16.08%.
Exam~le 3. Ru/CsX
1.24 g o~ sample in example 2 (before impregnation with KOH) were ion-exchanged three times with l molL~l aqueous cesium acetate solutions (12.5, 12.5 and 30 mL, respectively), ~iltered and dried. The resulting solids were impregnated with 0.2 molal aqueous solution o~ Cs(OH). Elemental analysis: Ru - 2.01%, Si - 13.88%, Al -- 7.9%, Na - 0.93%, K --
CATALYST AND PROCESS FOR PREPARING AMMONIA
The research leading to the invention described herein was supported in part by funds from Grant ~CTS-9257306 from the National Science Foundation. As such, the United States Government may have certain rights in the present invention.
BACXGROUND OF THE INVENTION
Field of the Invention The present invention relates to a novel supported catalyst comprising a Group VIII transition metal supported on a basic molecular sieve, for providing i~uved synthesis of ammonia from nitrogen and hydrogen gases and a process for using the same in preparing ammonia.
Discussion of the Backqround Conventional industrial ammonia synthesis processes use a triply promoted iron catalyst operating at temperatures of 400-700~C and pressures in excess of 300 atm. However, at such e~L ~- ? temperatures, the equilibrium reaction of N2 and H2 to give ~ on; a is not especially favored, hence the need for the extreme pressures.
In U.S. Patent No. 3,770,658, Ozaki et al disclosed a ~ transition metal based catalyst, preferably of ruthenium, which contained alkali metal, for the preparation of ammonia from nitrogen and hydrogen under temperatures less than 400~C.
In U.S. Patent No. 4,142,993, Elofson et al also disclose a Group VIII transition metal based catalyst cont~in;ng alkali metal, which is supported on an activated carbon support for synthesis of ammonia at temperatures of 375~C or higher and pressures of 27-67 atm.
Such traditional ruthenium-based ammonia synthesis catalysts consist of ruthenium clusters supported on carriers like carbon and magnesium oxide. In addition, as shown by Ozaki et al, alkali metal promotors such as potassium or cesium are often added to enhance the catalytic activity of the ruthenium.
In U.S. Patent 4,600,571, McCarroll et al disclose the use of ruthenium based ammonia synthesis catalyst which contain an alkali metal and barium, all supported on a carbon ~L.
R~ntly published work by Cicn~os and Lunsford [J.
Catal. 141 (1993) 191-205] and Wellenbuscher et al (Catal.
Letters 25(1994) 61-74) shows that ruthenium clusters supported on alkali-cont~; ni ng zeolites also catalyze the synthesis of ammonia from nitrogen and hydrogen at atmospheric pressure. From the results of Cisneros and Lunsford, ammonia synthesis at 650 K and atmospheric pressure over ruthenium clusters supported on potassium-loaded zeolite X occurs at a rate of 1.7 x 10-5 mol NH3/g Ru/sec.
However, each of the prior art catalysts still do not provide the desired level of activity and reaction rate.
Accordingly, an improved ammonia synthesis catalyst is desired.
SUMMARY OF THE INVENTION
Accordingly, one object of this invention is to provide a catalyst which provides improved ammonia synthesis rates under industrially useful conditions.
A further object of the present invention is to provide an i~ o~ed process for the preparation of ammonia from nitrogen and hydrogen gases.
These and other objects of the present invention have been satisfied by the discovery of a catalyst for ammonia synthesis, comprising Group VIII transition metal clusters supported on a basic zeolite, which further comprises alkali metal ions and divalent metal ions, which provides markedly improved rates of reaction of N2 and H2 to give ammonia.
DETATT~n DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention relates to a Group VIII transition metal/basic zeolite catalyst for the synthesis of ammonia from N2 and H2. The catalyst of the present invention comprises Group VIII transition metal clusters supported on a basic zeolitic support. The Group VIII transition metal cluster is preferably made of Fe, Ru or Os, with Ru being most preferred.
W 096/38222 PCTrUS96/07948 The Group VIII transition metal cluster can be prepared using conventional methods (see "Catalyst Manufacture", 2nd Ed., A.B. Stiles and T.A. Xoch, Marcel Dekker, New York, 1995).
For example, ruthenium clusters can be formed from various ruthenium compounds, such as Ru (NH3 )6Cl3. In particular, the Group VIII metal compounds are ion exchanged or impregnated onto the zeolite, following which the resulting material is reduced,.for example, by hydrogenation, thus providing the resulting clusters in an oxidation state of the corresponding metal (such as Ru~).
The zeolite used in the present catalyst as a support for the Group VIII metal clusters is preferably a Faujasite-type zeolite (or Faujasitic zeolite), such as Zeolite X, Zeolite Y, EMT, ZSM-3, ZSM-20, Zincophosphate X or SAPO-37. Preferably the zeolite is a microporous cryst~ll;ne aluminosilicate, preferably having a Si:Al ratio of from 1:1 to 6:1, more preferably 1:1 to 2.5:1.
The catalyst of the present invention further contains Group I alkali cations and clivalent metal cations. The divalent metal cations can be alkAl;ne earth ions or divalent transition metal ions. Preferably the A 1 kA l; ne earth ions are used, with Ba~2 being most preferred. The divalent metal ions can be incorporated into the Group VIII metal/zeolite catalyst by conventional processes, such as ion exchange or impregnation.
W 096/38222 PCTrUS96/07948 C_ ~~cially available zeolites often already contain alkali metal ions, such as Na. For example, Zeolite X is available containing Na ions and is conventionally called NaX
zeolite. These zeolites can be used as supplied, or can first be subjected to modification, such as ion exchange or impregnation, to replace Na with another alkali metal, such as K, with the preferred alkali metals being K, Rb and Cs. The alkali metal con~; n ing zeolite is then subjected to modification with divalent cations, such as alkaline earth metal ions, by ion exchange or a combination of ion exchange and impregnation.
Prior to or after this divalent cation modification, the Group VIII metal can be incorporated into the zeolite using conventional t~chn;ques to form the metal clusters and provide the Group VIII/M~2/basic zeolite catalyst. While the above sequence of steps can be used to prepare the present catalyst, the steps can be performed in any order, to provide incorporation of the divalent metal ions and the Group VIII
metal clusters, to provide the catalyst of the present invention which is active for the production of ammonia from N2 and H2.
The Group VIII metal based catalyst of the present -~ invention provides its advantages in reaction rate upon incorporation of even minute quantities of Group VIII metal into the basic zeolite. However, it is preferred that the loading be in the range of 0.1 to 10%, most preferably in the range of 1-5% by weight, based on the amount of zeolite. In the case of the more expensive Group VIII metals, the preferred loading is in the range of 0.1 to 2.0%.
The divalent metal ions also provide their advantages even upon incorporation of very small quantities into the catalyst. Preferably, the molar ratio of divalent metal ions to alkali metal ions is in the range from 0.01 to 100, most pre~erably from 10 to 100.
Once the divalent ions and Group VIII metals have been incorporated into the zeolite, it is important to render the zeoiite basic in nature. This is preferably done by impregnating the composition with a basic compound such as divalent or alkali metal hyclroxides, A lk;~l; alkoxides, ~lk;~l;
oxides, alkali metals, etc.
In using the catalyst o~ the present invention, the catalyst is contacted with ~T2 and H2 gas in a N2:H2 molar ratio of ~rom 10:1 to 1:10, preferably from 1:3 to 1:6. The reaction is performed at a temperature and pressure su~icient to provide ~c~llent yield per unit time. Pre~erably the tr ~ature of ammonia synthesis is from 200-600~C and the pressure is from atmospheric to 400 atmospheres. These parameters can be adjusted to provide the optimum reaction rate, depending primarily on the conditions achievable in the reaction vessels used. The contact time, or weight hourly space velocity (g feed/g ca~alyst/hour), is adjusted to achieve the desired yield o~ ammonia (i.e., longer contact gives more ammonia and vice versa). Further, the reaction can be performed either batchwise or continuously.
By using the catalyst of the present invention, it is possible to obtain surprisingly improved rates of ammonia synthesis when compared to the catalysts of the prior art.
These improved rates of reaction allow the use of milder conditions, which can prove industrially advantageous financially, as well as in the area of industrial safety.
Having generally described this invention, a further understanding can be obtained by reference to certain specific examples which are provided herein for purposes of illustration only and are not intended to be limiting unless otherwise specified.
EXAMPLES
CatalYst SYnthesis Exam~les Example 1. Ru/NaX
NaX zeolite (lS g) ~rom Union Carbide (elemental analysis: Si - 20.48%, Al - 16.55%, Na - 12.6%) was ion-~h~nged with 0.936 g o~ Ru(NH3)6C13 in 300 mL of distilled, deionized water. The resulting solids were filtered, dried and reduced in flowing H2 at 723 K. The final solid cont~;n~
1.8S% of Ru by weight.
ExamPle 2. Ru/KX
W O 96/38222 PCTrUS96107948 First, NaX zeolite ~rom Union Carbide (elemental analysis: Si -- 20.48~6, Al - 16.55%, Na -- 12.67%) was ion--exchanged three times with 1 molL~l aqueous KNO3 (7S, 230 and 350 mL, respectively) and dried to produce KX zeolite. 15 g of KX zeolite was ion o~r~h~rlged with 0.936 g of Ru(NH3)6Cl3 in l.Z L of water. The resulting solids were filtered, dried and reduced in ~lowing H2 at 723 K. The reduced solid was then impregnated with 310 mL oi~ a 0.2 molal aqueous solution o~ KOH
and dried. Elemental analysis: Ru -- 2.04%, Si -- 19.70%, Al 13.03%, Na -- 0.58%, K -- 16.08%.
Exam~le 3. Ru/CsX
1.24 g o~ sample in example 2 (before impregnation with KOH) were ion-exchanged three times with l molL~l aqueous cesium acetate solutions (12.5, 12.5 and 30 mL, respectively), ~iltered and dried. The resulting solids were impregnated with 0.2 molal aqueous solution o~ Cs(OH). Elemental analysis: Ru - 2.01%, Si - 13.88%, Al -- 7.9%, Na - 0.93%, K --
2.50%, Cs -- 24.S3%.
Example 4. Ru/BaX
1.22 g of sample in example 2 (be~ore; - ey-~ation with KOH) were ion--exchanged two times with 1 molL~1 aqueous barium acetate solutions (10 and 15 mL), ~iltered and dried. The resulting solids were impreynated with 50 mL o~ a 0.2 molal W 096/38222 PCTrUS96/07948 aqueous solution of Ba(OH) 2~ Elemental analysis: Ru -- 2.05%, Si -- 13.12%, Al -- 9.48%, K -- 1.32%, Ba -- 24.4%.
ExamPle 5. Ru/BaX(2) First, NaX zeolite from Union Carbide (elemental analysis: Si -- 20.48%, Al - 16.55%, Na -- 12.67%) was ion--exchanged three times with 1 molL~l of a~ueous KNO3 and dried to produce KX zeolite. 17.68 g of KX zeolite were ion exchanged with 1.1048 g of Ru(NH3)6C13 in water. The resulting solids were filtered, dried and reduced in flowing H2 at 723 K.
Example 4. Ru/BaX
1.22 g of sample in example 2 (be~ore; - ey-~ation with KOH) were ion--exchanged two times with 1 molL~1 aqueous barium acetate solutions (10 and 15 mL), ~iltered and dried. The resulting solids were impreynated with 50 mL o~ a 0.2 molal W 096/38222 PCTrUS96/07948 aqueous solution of Ba(OH) 2~ Elemental analysis: Ru -- 2.05%, Si -- 13.12%, Al -- 9.48%, K -- 1.32%, Ba -- 24.4%.
ExamPle 5. Ru/BaX(2) First, NaX zeolite from Union Carbide (elemental analysis: Si -- 20.48%, Al - 16.55%, Na -- 12.67%) was ion--exchanged three times with 1 molL~l of a~ueous KNO3 and dried to produce KX zeolite. 17.68 g of KX zeolite were ion exchanged with 1.1048 g of Ru(NH3)6C13 in water. The resulting solids were filtered, dried and reduced in flowing H2 at 723 K.
3.285 g of the solids were ion-~cch~nged two times with 1 molL~
aqueous barium acetate solutions (10 and 10 mL), filtered and dried. The resulting solids were impregnated with 30 mL of a 0.2 molal aqueous solution of Ba(OH) 2 ~ Elemental analysis: Ru -- 2.10%, Si - 14.38%, Al - 9.04%, K - 1.47%, Ba -- 21.6%.
CA 02222806 l997-ll-28 WO 96/3~222 PCT~US96/07948 Reactivity Examples All samples were sieved to 170 mesh (90 ~m) before reaction. Catalysts were loaded into a constant volume recirculation reactor and reduced in-situ at 723 K before reaction. A 3:1 molar ratio of H2:N2 reactant mixture at a total pressure of 1 atmosphere was introduced into the system.
The product ammonia was conclensed into a liquid nitrogen trap thus preventing the product from inhibiting the reaction.
Rates were calculated from the total pressure drop in the system as a function o~ time and are reported as moles of ammonia produced per gram of Ru per time. The fraction of Ru exposed to the surface (dispersion) was evaluated by a st~n~d hydrogen chemisorption measurement and results were used to calculate the specific rate of reaction per surface Ru atom.
Reaction Results~ Synthesis over ~--th~nium Catalysts Fraction of Temperature Reaction Rate 5pe~ific Rate ExampleSampleRu exposed /R(+5 R)/10-C molN~3 /10--s-~
(gRu)~ls~l 1 Ru/NaX 0.57 650 4.48 7.94 2a Ru/RX 0.93 650 2.84 3.09 20 2b Ru/XX 0.93 700 14.2 15.4 3a RutCsX 0.72 650 7.62 10.7 3b Ru~CsX 0.72 700 25.9 36.4 4a Ru/8aX 0.92 650 34.5 37.9 4b Ru/BaX 0.92 700 105 115 25 SaRu/BaX(2)0.79 650 33.6 43.0 5bRu/BaX(2)0.79 700 127 163 At a given temperature, the Ba-c~nt~i"ing Ru catalyst was more active for i~
synthesis than catalysts cont~in;ng alkali cations (Na, R, Cs) without Ba.
=. . . =
W 096/38222 PCTrUS96/07948 Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.
aqueous barium acetate solutions (10 and 10 mL), filtered and dried. The resulting solids were impregnated with 30 mL of a 0.2 molal aqueous solution of Ba(OH) 2 ~ Elemental analysis: Ru -- 2.10%, Si - 14.38%, Al - 9.04%, K - 1.47%, Ba -- 21.6%.
CA 02222806 l997-ll-28 WO 96/3~222 PCT~US96/07948 Reactivity Examples All samples were sieved to 170 mesh (90 ~m) before reaction. Catalysts were loaded into a constant volume recirculation reactor and reduced in-situ at 723 K before reaction. A 3:1 molar ratio of H2:N2 reactant mixture at a total pressure of 1 atmosphere was introduced into the system.
The product ammonia was conclensed into a liquid nitrogen trap thus preventing the product from inhibiting the reaction.
Rates were calculated from the total pressure drop in the system as a function o~ time and are reported as moles of ammonia produced per gram of Ru per time. The fraction of Ru exposed to the surface (dispersion) was evaluated by a st~n~d hydrogen chemisorption measurement and results were used to calculate the specific rate of reaction per surface Ru atom.
Reaction Results~ Synthesis over ~--th~nium Catalysts Fraction of Temperature Reaction Rate 5pe~ific Rate ExampleSampleRu exposed /R(+5 R)/10-C molN~3 /10--s-~
(gRu)~ls~l 1 Ru/NaX 0.57 650 4.48 7.94 2a Ru/RX 0.93 650 2.84 3.09 20 2b Ru/XX 0.93 700 14.2 15.4 3a RutCsX 0.72 650 7.62 10.7 3b Ru~CsX 0.72 700 25.9 36.4 4a Ru/8aX 0.92 650 34.5 37.9 4b Ru/BaX 0.92 700 105 115 25 SaRu/BaX(2)0.79 650 33.6 43.0 5bRu/BaX(2)0.79 700 127 163 At a given temperature, the Ba-c~nt~i"ing Ru catalyst was more active for i~
synthesis than catalysts cont~in;ng alkali cations (Na, R, Cs) without Ba.
=. . . =
W 096/38222 PCTrUS96/07948 Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.
Claims (32)
1. A catalyst for synthesis or ammonia from N1 and H2, consisting essentially of:
a basic zeolite support;
Group VIII transition metal clusters in which the metal is substantially in the zero oxidation state supported on said zeolite support; and divalent and monovalent metal ions incorporated into said zeolite support.
a basic zeolite support;
Group VIII transition metal clusters in which the metal is substantially in the zero oxidation state supported on said zeolite support; and divalent and monovalent metal ions incorporated into said zeolite support.
2. The catalyst of Claim 1, wherein said zeolite support is an aluminosilicate.
3. The catalyst of Claim 2, wherein said zeolite support has a Si:Al ratio of from 1:1 to 6:1.
4. The catalyst of Claim 2, wherein said zeolite support has a Si:Al ratio of 1:1 to 2:1.
5. The catalyst of Claim 1, wherein said zeolite support is a Faujasitic zeolite.
6. The catalyst of Claim 5, wherein said Faujasitic zeolite is a member selected from the group consisting of Zeolite X, Zeolite Y, EMT, ZSM-3, ZSM-20, SAPO-37 and Zincophosphate X.
7. The catalyst of Claim 1, wherein said Group VIII
transition metal clusters are Ru metal clusters.
transition metal clusters are Ru metal clusters.
8. The catalyst of Claim 1, wherein said divalent metal ions are alkaline earth metal ions.
9. The catalyst of claim 1, wherein said divalent metal ions are transition metal ions.
10. The catalyst of Claim 1, wherein said divalent metal ions are Bat+2.
11. The catalyst of Claim 1, further comprising alkali metal ions within said zeolite support.
12. The catalyst of Claim 11, wherein said alkali metal ions are selected from the group consisting of potassium, rubidium and cesium.
13. The catalyst of Claim 1, wherein said Group VIII
metal clusters are present in an amount of from 0.1 to 10 wt%, based on the weight of the zeolite.
metal clusters are present in an amount of from 0.1 to 10 wt%, based on the weight of the zeolite.
14. The catalyst of Claim 1, wherein said divalent metal ion to alkali metal ion molar ratio is from 0.1 to 100.
15. The catalyst of claim 14, wherein said divalent metal ion to alkali metal ion molar ratio is from 10 to 100.
16. The catalyst of Claim 1, wherein said catalyst is rendered basic by impregnation with a solution of a basic compound selected from the group consisting of divalent metal hydroxides, alkali metal hydroxides, alkali metal alkoxides, alkali metal oxides, and alkali metals.
17. The catalyst of Claim 16, wherein said divalent metal hydroxide is a hydroxide of a divalent metal which is identical to the divalent metal ion present in the catalyst.
18. A method for the production of ammonia comprising:
contacting a mixture of N2 and H2 gases with a catalyst comprising (i) a basic zeolite support (ii) Group VIII metal clusters supported on said zeolite support, (iii) divalent metal ions incorporated into said zeolite support and (iv) alkali metal ions incorporated into said zeolite support;
at a temperature and pressure sufficient to provide reaction of N2 and H2 gases to give NH3.
contacting a mixture of N2 and H2 gases with a catalyst comprising (i) a basic zeolite support (ii) Group VIII metal clusters supported on said zeolite support, (iii) divalent metal ions incorporated into said zeolite support and (iv) alkali metal ions incorporated into said zeolite support;
at a temperature and pressure sufficient to provide reaction of N2 and H2 gases to give NH3.
19. The method of claim 18, wherein said zeolite support is an aluminosilicate.
20. The method of Claim 19, wherein said zeolite support has a Si:Al ratio of from 1:1 to 6:1.
21. The method of Claim 19, wherein said zeolite support has a Si:Al ratio of from 1:1 to 2:1.
Z2. The method of Claim 18, wherein said zeolite support is a Faujasitic zeolite.
23. The method of claim 22, wherein said Faujasitic zeolite is a member selected from the group consisting of Zeolite X, Zeolite Y, EMT, ZSM-3, ZSM-20, SAPO-37 and Zincophosphate X.
24. The method of Claim 18, wherein said Group VIII
transition metal clusters are Ru metal clusters.
transition metal clusters are Ru metal clusters.
25. The method of Claim 18, wherein said divalent metal ions are alkaline earth metal ions.
26. The method of claim 18, wherein said divalent metal ions are transition metal ions.
27. The method of Claim 18, wherein said divalent metal ions are Ba+2.
28. The method of Claim 18, further comprising alkali metal ions within said zeolite support.
29. The method of Claim 28, wherein said alkali metal ions are selected from the group consisting of potassium, rubidium and cesium.
30. The method of Claim 18, wherein the temperature is from 200 to 600°C.
31. The method of Claim 18, wherein the pressure is from 1 atm to 400 atm.
32. A catalyst for synthesis of ammonia from N2 and H2, comprising:
a basic zeolite support;
Group VIII transition metal cluster supported on said zeolite support; and alkaline earth metal ions and monovalent metal ions incorporated into said zeolite support.
a basic zeolite support;
Group VIII transition metal cluster supported on said zeolite support; and alkaline earth metal ions and monovalent metal ions incorporated into said zeolite support.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US44388595A | 1995-05-31 | 1995-05-31 | |
| US08/443,885 | 1995-05-31 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2222806A1 true CA2222806A1 (en) | 1996-12-05 |
Family
ID=23762565
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002222806A Abandoned CA2222806A1 (en) | 1995-05-31 | 1996-05-31 | Catalyst and process for preparing ammonia |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP0840646A1 (en) |
| CN (1) | CN1186452A (en) |
| AU (1) | AU5950396A (en) |
| BR (1) | BR9608749A (en) |
| CA (1) | CA2222806A1 (en) |
| WO (1) | WO1996038222A1 (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DK173814B1 (en) | 1999-03-15 | 2001-11-12 | Topsoe Haldor As | Process for the preparation of ammonia and catalyst for the synthesis of ammonia |
| DE60125103T2 (en) | 2000-07-06 | 2007-04-12 | Haldor Topsoe A/S | Recovery of the ammonia synthesis catalyst |
| RU2551383C2 (en) | 2010-12-07 | 2015-05-20 | Токио Инститьют Оф Текнолоджи | Ammonia synthesis catalyst and ammonia synthesis method |
| JP6344052B2 (en) * | 2014-05-20 | 2018-06-20 | 株式会社Ihi | Ammonia synthesis catalyst and ammonia synthesis method |
| CN110252376A (en) * | 2019-07-01 | 2019-09-20 | 吉林大学 | A kind of metal-semiconductor composite photo-catalyst, the preparation method and applications of photocatalysis nitrogen and hydrogen synthesis ammonia |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3253887A (en) * | 1962-08-03 | 1966-05-31 | Exxon Research Engineering Co | Ammonia synthesis catalyst and process |
| CA965766A (en) * | 1970-06-22 | 1975-04-08 | Akio Furuta | Ammonia synthesis catalyst and process |
| US4142993A (en) * | 1977-12-07 | 1979-03-06 | The Research Council Of Alberta | Transition metal catalyst |
| SE415173B (en) * | 1977-12-19 | 1980-09-15 | Atomenergi Ab | PROCEDURE FOR THE MANUFACTURING OF AMMONIA BY CATALYZED REACTION BETWEEN WHEAT AND NITROGEN |
| US4348370A (en) * | 1980-01-08 | 1982-09-07 | Phillips Petroleum Company | Ammonia synthesis with catalyst derived by heating on a support a salt selected from alkali metal, alkaline earth metal, iron and cobalt hexacyanocobaltates and hexacyanoruthenates |
| GB8307612D0 (en) * | 1983-03-18 | 1983-04-27 | British Petroleum Co Plc | Ammonia production and catalysts |
| FR2660578B1 (en) * | 1990-04-09 | 1994-09-23 | Elf Aquitaine | CATALYST BASED ON HIGH SYNTHESIS SI: AL FAUJASITE AND ITS APPLICATION TO ACID CATALYSIS REACTIONS CARRIED OUT ON HYDROCARBONIC LOADS. |
-
1996
- 1996-05-31 AU AU59503/96A patent/AU5950396A/en not_active Abandoned
- 1996-05-31 CN CN96194318A patent/CN1186452A/en active Pending
- 1996-05-31 EP EP96916741A patent/EP0840646A1/en not_active Withdrawn
- 1996-05-31 BR BR9608749-8A patent/BR9608749A/en unknown
- 1996-05-31 CA CA002222806A patent/CA2222806A1/en not_active Abandoned
- 1996-05-31 WO PCT/US1996/007948 patent/WO1996038222A1/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| EP0840646A1 (en) | 1998-05-13 |
| BR9608749A (en) | 1999-12-07 |
| CN1186452A (en) | 1998-07-01 |
| WO1996038222A1 (en) | 1996-12-05 |
| AU5950396A (en) | 1996-12-18 |
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