WO2004030810A1 - Catalyst for the synthesis of ammonia - Google Patents

Catalyst for the synthesis of ammonia Download PDF

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WO2004030810A1
WO2004030810A1 PCT/NO2003/000330 NO0300330W WO2004030810A1 WO 2004030810 A1 WO2004030810 A1 WO 2004030810A1 NO 0300330 W NO0300330 W NO 0300330W WO 2004030810 A1 WO2004030810 A1 WO 2004030810A1
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catalyst
tio
content
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Per Thorbjørn SKAUGSET
Morten Schelver
Reidar Næss HANSEN
Tom Hallan
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Yara International Asa
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    • 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
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
    • B01J23/76—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/78—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with alkali- or alkaline earth metals
    • 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
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
    • B01J23/76—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/83—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with rare earths or actinides
    • 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
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/0081—Preparation by melting
    • 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
    • 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
    • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
    • B01J21/06—Silicon, titanium, zirconium or hafnium; Oxides or hydroxides thereof
    • B01J21/063—Titanium; Oxides or hydroxides thereof
    • 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
    • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
    • B01J21/06—Silicon, titanium, zirconium or hafnium; Oxides or hydroxides thereof
    • B01J21/066—Zirconium or hafnium; Oxides or hydroxides thereof
    • 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

Definitions

  • the invention concerns a catalyst for the synthesis of ammonia from hydrogen and nitrogen.
  • ammonia synthesis catalysts consist mainly of magnetite, Fe 3 O 4 , in the unreduced state. Additionally, the catalysts contain as promoters oxides of elements such as: Al, Ba, Ca, Ce, Cs, Cr, K, La, Mg, Ti, V, Zr and others, see, as example UUmanns's Encyclopedia of Industrial Chemistry. Additionally reducible oxides of metals, such as Co or Ni, may be present.
  • triply promoted catalysts which is magnetite with added Al 2 O 3 , K 2 O and CaO.
  • Other oxides such as SiO 2 , TiO , MnO 2 , V O 2 , MgO and Cr 2 O 3 may be present as impurities from the raw material magnetite.
  • oxides which are commonly used as support material for other catalysts have been considered as structural promoters, whereas the alkali metal oxides are considered as electronic promoters enhancing nitrogen adsorption and ammonia desorption by neutralising the acidic effects of the structural promoters.
  • the alkaline earth oxides have often been considered to have both effects.
  • WO 99/46038 relates to a catalyst for the synthesis of ammonia from hydrogen and nitrogen consisting of iron oxides and promoters where the promoters comprise oxides of both cobalt and titanium in addition to Al, K, Ca and Mg oxides, and where the concentration of cobalt is between 0.1 % and 3.0 % by weight of metal and the concentration of titanium is between 0.1 % and 1.0 % by weight of metal.
  • the promoters comprise oxides of both cobalt and titanium in addition to Al, K, Ca and Mg oxides, and where the concentration of cobalt is between 0.1 % and 3.0 % by weight of metal and the concentration of titanium is between 0.1 % and 1.0 % by weight of metal.
  • the main object of the invention was to provide a catalyst for the synthesis of ammonia from nitrogen and hydrogen having improved activity.
  • a usual ammonia synthesis catalyst comprising as the main component magnetite (Fe 3 O 4 ) or iron oxide with the atomic ratio Fe 2+ / Fe 3+ in the range 0.5 - 0.9, preferably in the range 0.5 to 0.65, and then adjust the amount of K 2 O.
  • Changing the content of one promoter in a catalyst is expected to change the effect of the other promoters.
  • the content of MgO should also be included in the optimisation, as a promoter with possibly both structural and electronic effect.
  • the first trials with ZrO 2 and TiO 2 showed positive effects with regard to activity.
  • the preferred ranges of the promoter concentrations were found by a total consideration of the results from a number of tests.
  • the present invention will in its widest scope comprise a catalyst for the synthesis of ammonia from hydrogen and nitrogen, comprising iron oxides and promoters of Al, K, Ca and Mg oxides, where the catalyst in addition comprises a promoter of TiO 2 in the amount of 0.3 - 2.5 weight % and a promoter of ZrO .
  • the content of ZrO 2 may be 0.05 - 2 weight %, preferably 0.05 - 1.0 weight %, and even 0.05 - 0.5 weight %.
  • the catalyst may also comprise a promoter of CeO 2 , which partly replaces ZrO 2 .
  • the content of CeO 2 may be 0.5 - 1 weight %, preferably 0.55 - 0.8 weight %.
  • the promoters are present in the following concentration range: 1.2 - 3.0 weight % Al 2 O 3 , 0.3 - 0.8 weight % K 2 O, 1.0 - 2.8 weight % CaO, 0.2 - 1.7 weight % MgO, 0.3 - 2.5 weight % TiO 2 and 0.05 - 2.0 weight % ZrO 2 .
  • the promoters can preferably be present in the following concentration range: 1.65 - 2.3 weight % Al O 3 , 0.4 - 0.7 weight % K 2 O, 1.5 - 2.3 weight % CaO, 1.25 - 1.65 weight % MgO, 1.3 - 2.2 weight % TiO 2 and 0.05 - 1.0 weight % ZrO 2
  • the promoters can also be present in the following concentration range: 1.65 - 2.3 weight % Al 2 O 3 , 0.4 - 0.7 weight % K 2 O, 1.5 - 2.3 weight % CaO, 1.25 - 1.65 weight % MgO, 1.3 - 2.2 weight % TiO 2 , 0.05 - 1.0 weight % ZrO 2 and 0.5 - 1.0 weight % CeO 2 .
  • the promoters can preferably be present in the following concentration range: 1.65 - 2.3 weight % Al 2 O 3 , 0.4 - 0.7 weight % K 2 O, 1.5 - 2.3 weight % CaO, 1.25 - 1.65 weight % MgO, 1.3 - 2.2 weight % TiO 2 , 0.05 - 0.5 weight % ZrO 2 and 0.55 - 0.8 weight % CeO 2 .
  • the mixtures were melted in a ceramic crucible; the temperature was kept at about 1600 °C to ensure complete melting, and then poured into an iron chill and cooled. Large- scale samples were made in principle in the same way, but then the batch size was about 800 kg.
  • Example 1 in Table 1 tests were carried out using a commercial sample (AS-4), which is included as a reference value.
  • the composition and activities were as given in Table 1.
  • Examples 2 - 17 are lab scale tests of samples where the amounts of the promoters were varied.
  • Example 2 tests were carried out with samples that had a composition, which was close to the reference sample. From Table 1 it is seen that the activities also were close to the reference sample of Example 1.
  • Example 3 The samples used in Example 3 had only 0.27 weight % ZrO 2 and a high TiO content, 2.20 weight . The activities were close to 1. This composition does not give any advantages compared to the reference catalyst.
  • Example 4 tests were carried out using samples where the TiO and MgO contents were lower than what was later found to be the preferred range, 0.46 weight % and 0.80 weight % respectively.
  • the activity at 420 °C was 1.04, and the activity at 350 °C was 1.21, which was better than the reference, but may be improved.
  • Example 5 the content of K 2 O in the samples used was close to the upper limit for what was later found to be the preferred range, 0.64 weight %, and the sample had low contents of MgO (0.81 weight %), Al 2 O 3 (1.30 weight %) and CaO (1.15 weight %).
  • the activities were 1.11 (420 °C) and 1.27 (350 °C), which means that the low temperature activity was good, but some high temperature activity was lost.
  • Example 6 the components in the samples were present in the following amounts: ZrO 2 : 0.68 weight , TiO 2 : 1.61 weight %, K 2 O: 0.51 weight %, MgO: 1.35 weight %, Al 2 O 3 : 1.70 weight % and CaO: 1.70 weight .
  • the activities were high, 1.3 at 420 °C and 1.43 at 350 °C.
  • Example 7 also gave high activities, 1.3 at 420 °C and 1.31 at 350 °C.
  • the contents of the promoters were: ZrO 2 : 0.69 weight , TiO 2 : 1.64 weight , K 2 O: 0.44 weight %, MgO: 1.36 weight %, Al 2 O 3 : 1.73 weight % and CaO: 1.73 weight %.
  • Example 8 The samples used in Example 8 had a low K 2 O content, 0.27 weight %.
  • the other promoters were within a range which after the good results of Example 6 and 7 should be expected to give good results, but the activities were low, 0.77 at 420 °C and 0.56 at 350 °C. This indicates that the K O content should not be too low.
  • Example 9 The samples used in Example 9 had a high K 2 O content, 0.68 weight %. The activities were 1.19 (420 °C) and 1.44 (350 °C). The low temperature activity was high, but some high temperature activity was lost.
  • Example 10 tests were carried out with samples resulting in high activities both at high temperature (1.24) and low temperature (1.34).
  • the contents of the promoters were ZrO 2 : 0.92 weight %, TiO 2 : 2.00 weight %, K 2 O: 0.56 weight %, MgO: 1.58 weight %, Al 2 O 3 : 1.91 weight % and CaO: 1.55 weight %.
  • Example 12 In the samples used in Example 12 there were no Al 2 O 3 and CaO. The contents of TiO 2 and K 2 O were high. The activities were only 0.38 and 0.32. This shows that Al 2 O 3 and CaO should not be omitted in the catalyst composition.
  • Example 13 the contents of ZrO 2 and Al O 3 in the samples were high, 1.83 weight % and 2.51 weight %, respectively, and the content of TiO 2 was low, 0.45 weight %.
  • the activities were 1.03 and 1.16. Even though the activities were better than the reference sample, some of the other catalyst compositions gave better activities. In the compositions with better activities, the content of TiO 2 was higher than the content of ZrO 2 .
  • Example 14 there were used samples where the ZrO 2 and K 2 O contents were high; Al 2 O 3 and CaO contents were low.
  • the TiO content was higher than in Example 13, but still lower than the ZrO 2 content. This resulted in activities of 1.01 and 1.22.
  • the high ZrO 2 content did not compensate for the low Al 2 O 3 and CaO contents.
  • the composition used in this Example is not the most optimal one.
  • Example 15 the contents of all the promoters were outside what was later found to be the desired range. No CaO was added and the Al O 3 content was high (2.68 weight %). No extra TiO 2 was added, so only the TiO 2 from magnetite (0.2 weight %) was present. The ZrO 2 content was 1.89 weight %. The K 2 O content was extra high, 1.16 weight % and the MgO content was low, 0.30 weight %. The activities were 1.01 and 1.14, which was slightly better than the reference, but significantly lower than when more TiO 2 was added, as for instance in Examples 6 and 7. To obtain better results, also the MgO content should be higher and CaO should not be omitted in the catalyst composition.
  • Example 16 Example 16
  • Example 16 a relatively large amount of ZrO 2 , 2.5 weight %, was added to a composition close to the reference sample. No extra TiO 2 was added, so only the TiO from magnetite (0.2 weight %) was present, as in Example 15. The resulting activities were higher than for the reference sample, 1.03 at 420 °C and 1.19 at 350 °C, but significantly lower than when more TiO 2 was added and the ZrO 2 content was lower than the TiO 2 content.
  • Example 18 In the samples used in Example 18 the content of CeO 2 was 0.73 weight % and the content of ZrO was 0.10 weight %. The other promoters were present in almost the same amounts as in Example 17. The activities obtained were very high, 1.31 and 1.56. From examples 17 and 18 it is seen that the addition of CeO 2 has a positive effect on the activities of the catalyst.
  • Examples 19 - 21 are large scale tests. The compositions of the samples tested in large scale were chosen within the range, which showed the best results in the lab scale tests.
  • Example 19 it was used samples where the contents of the promoters were: ZrO 2 : 0.64 weight %, TiO 2 : 1.52 weight %, K 2 O: 0.62 weight %, MgO: 1.57 weight %, Al 2 O 3 : 2.29 weight % and CaO: 2.23 weight %.
  • the activities were 1.24 and 1.36.
  • Example 20
  • Example 20 it was used samples where the contents of ZrO 2 and TiO 2 were a little higher than in Example 19, and the contents of K 2 O, MgO, Al 2 O 3 and CaO were a little lower. The activities were 1.33 and 1.41.
  • Examples 19 and 20 show that high activities were obtained with some variation of the promoter contents within the ranges, which gave good results in the lab scale tests.
  • Example 21 In the samples used in Example 21, 0.58 weight % CeO 2 was added and the ZrO 2 content was lowered to 0.30 weight % and the rest of the promoters were present in about the same amounts as in Example 20. The activities were 1.19 and 1.33. Also in the large scale test, the catalyst composition with CeO 2 present gave high activities.
  • Examples 17, 18 and 21 show that ZrO 2 may be partly replaced by CeO 2 .

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Abstract

The invention relates to a catalyst for the synthesis of ammonia from hydrogen and nitrogen, comprising iron oxides and promoters of Al, K, Ca and Mg oxides and where said catalyst in addition comprises a promoter of Ti02 in the amount of 0.3 - 2.5 weight % and a promoter of Zr02. The content of Zr02 is 0.05 - 2 weight %, preferably 0.05 - 1.0 weight %. The catalyst may also comprise a promoter of Ce02, which partly replaces Zr02.

Description

Catalyst for the synthesis of ammonia
The invention concerns a catalyst for the synthesis of ammonia from hydrogen and nitrogen.
Commonly used ammonia synthesis catalysts consist mainly of magnetite, Fe3O4, in the unreduced state. Additionally, the catalysts contain as promoters oxides of elements such as: Al, Ba, Ca, Ce, Cs, Cr, K, La, Mg, Ti, V, Zr and others, see, as example UUmanns's Encyclopedia of Industrial Chemistry. Additionally reducible oxides of metals, such as Co or Ni, may be present.
Most commonly used catalysts for the latest 30 years have been so called triply promoted catalysts, which is magnetite with added Al2O3, K2O and CaO. Other oxides such as SiO2, TiO , MnO2, V O2, MgO and Cr2O3 may be present as impurities from the raw material magnetite.
Traditionally oxides which are commonly used as support material for other catalysts (Al2O3, TiO2, SiO2, ZrO2) have been considered as structural promoters, whereas the alkali metal oxides are considered as electronic promoters enhancing nitrogen adsorption and ammonia desorption by neutralising the acidic effects of the structural promoters. The alkaline earth oxides have often been considered to have both effects.
In the literature listing the different promoters for the ammonia synthesis catalyst, sometimes just one promoter has been tried at a time, or usually one promoter with the addition of alkali. Surely there must be some combination effects. In some literature on supported catalysts (as example Wang & al. J. Catal. 83, 428 (1983)) special effects are reported on mixed oxides of Ti and Zr, which are markedly different from the pure oxides. They observed a marked increase of acidic and basic sites. Acidity or basic properties may be controlled by addition of alkali. WO 99/46038 relates to a catalyst for the synthesis of ammonia from hydrogen and nitrogen consisting of iron oxides and promoters where the promoters comprise oxides of both cobalt and titanium in addition to Al, K, Ca and Mg oxides, and where the concentration of cobalt is between 0.1 % and 3.0 % by weight of metal and the concentration of titanium is between 0.1 % and 1.0 % by weight of metal. For some applications, it could be desirable to have a catalyst without cobalt as one of the promoters.
The main object of the invention was to provide a catalyst for the synthesis of ammonia from nitrogen and hydrogen having improved activity.
It was another object to provide a catalyst being environmental friendly and cost effective.
It was a further object to provide a catalyst having improved activity especially in the low temperature range.
These and other objects of the invention were obtained by the product as described below. The invention is further defined and characterised by the patent claims.
The idea was to try a combination of TiO2 and ZrO2 as additional promoters to a usual ammonia synthesis catalyst comprising as the main component magnetite (Fe3O4) or iron oxide with the atomic ratio Fe2+ / Fe3+ in the range 0.5 - 0.9, preferably in the range 0.5 to 0.65, and then adjust the amount of K2O. Changing the content of one promoter in a catalyst is expected to change the effect of the other promoters. Thus a complete re- optimising of the promoter content had to be done. The content of MgO should also be included in the optimisation, as a promoter with possibly both structural and electronic effect. The first trials with ZrO2 and TiO2 showed positive effects with regard to activity. Thus a systematic work was started to find new ranges for the total promoter content. As TiO2 and ZrO2 are considered as structural promoters they could possibly replace used promoters such as Al2O3. This turned out not to be the case, as will be evident from the examples. It was also tried to replace some of the ZrO2 with CeO2. The amount of ZrO2 would typically be in the range 0.1 - 2 weight %, and if CeO2 is present the amount will be in the lower part of that range, 0.05 - 1 weight % ZrO2, or even lower, 0.05 - 0.5 weight %.
The preferred ranges of the promoter concentrations were found by a total consideration of the results from a number of tests.
The present invention will in its widest scope comprise a catalyst for the synthesis of ammonia from hydrogen and nitrogen, comprising iron oxides and promoters of Al, K, Ca and Mg oxides, where the catalyst in addition comprises a promoter of TiO2 in the amount of 0.3 - 2.5 weight % and a promoter of ZrO . The content of ZrO2 may be 0.05 - 2 weight %, preferably 0.05 - 1.0 weight %, and even 0.05 - 0.5 weight %. The catalyst may also comprise a promoter of CeO2, which partly replaces ZrO2. The content of CeO2 may be 0.5 - 1 weight %, preferably 0.55 - 0.8 weight %.
The promoters are present in the following concentration range: 1.2 - 3.0 weight % Al2O3, 0.3 - 0.8 weight % K2O, 1.0 - 2.8 weight % CaO, 0.2 - 1.7 weight % MgO, 0.3 - 2.5 weight % TiO2 and 0.05 - 2.0 weight % ZrO2. The promoters can preferably be present in the following concentration range: 1.65 - 2.3 weight % Al O3, 0.4 - 0.7 weight % K2O, 1.5 - 2.3 weight % CaO, 1.25 - 1.65 weight % MgO, 1.3 - 2.2 weight % TiO2 and 0.05 - 1.0 weight % ZrO2
The promoters can also be present in the following concentration range: 1.65 - 2.3 weight % Al2O3, 0.4 - 0.7 weight % K2O, 1.5 - 2.3 weight % CaO, 1.25 - 1.65 weight % MgO, 1.3 - 2.2 weight % TiO2, 0.05 - 1.0 weight % ZrO2 and 0.5 - 1.0 weight % CeO2. The promoters can preferably be present in the following concentration range: 1.65 - 2.3 weight % Al2O3, 0.4 - 0.7 weight % K2O, 1.5 - 2.3 weight % CaO, 1.25 - 1.65 weight % MgO, 1.3 - 2.2 weight % TiO2, 0.05 - 0.5 weight % ZrO2 and 0.55 - 0.8 weight % CeO2.
The invention is further explained in the following examples. Preparation of samples
Experimental samples were made by mixing about 0.5 kg of the raw material magnetite with the appropriate amount of oxides of Al, Mg, Ti and Zr and carbonates of K and Ca to give the compositions shown in Table 1. After the melting, all components were present as oxides. The magnetite contained TiO2 at the level of 0.2 weight % and SiO2 at 0.1 weight %.
The mixtures were melted in a ceramic crucible; the temperature was kept at about 1600 °C to ensure complete melting, and then poured into an iron chill and cooled. Large- scale samples were made in principle in the same way, but then the batch size was about 800 kg.
Samples were tested in laboratory reactors as crushed and sieved to 0.4 to 0.63 mm particles. The sample size was about 10 g. The test conditions were as shown in Table 2:
Table 2. Test conditions.
Figure imgf000005_0001
The tests were done in parallel reactors where five samples at a time were compared to a reference sample. As the conditions were closely, but not exactly the same in all the reactors (individual gas flows and temperature profiles were measured), the comparison was done by comparing the calculated rate constants. The rate constants were calculated using a kinetic model, in which all the parameters except the rate constant were fitted to observations for the reference catalyst. As the experimental catalysts may have activation energies different from that of the reference catalyst, the comparisons were done at two temperatures. The results as relative rate constant compared to the reference sample in the same run and measured at the same time are given in Table 1. Table 1
Figure imgf000006_0001
Example 1
In Example 1 in Table 1 tests were carried out using a commercial sample (AS-4), which is included as a reference value. The composition and activities were as given in Table 1.
Examples 2 - 17 are lab scale tests of samples where the amounts of the promoters were varied.
Example 2
In Example 2 tests were carried out with samples that had a composition, which was close to the reference sample. From Table 1 it is seen that the activities also were close to the reference sample of Example 1.
Example 3
The samples used in Example 3 had only 0.27 weight % ZrO2 and a high TiO content, 2.20 weight . The activities were close to 1. This composition does not give any advantages compared to the reference catalyst.
Example 4
In Example 4, tests were carried out using samples where the TiO and MgO contents were lower than what was later found to be the preferred range, 0.46 weight % and 0.80 weight % respectively. The activity at 420 °C was 1.04, and the activity at 350 °C was 1.21, which was better than the reference, but may be improved.
Example 5
In Example 5 the content of K2O in the samples used was close to the upper limit for what was later found to be the preferred range, 0.64 weight %, and the sample had low contents of MgO (0.81 weight %), Al2O3 (1.30 weight %) and CaO (1.15 weight %). The activities were 1.11 (420 °C) and 1.27 (350 °C), which means that the low temperature activity was good, but some high temperature activity was lost. Example 6
In Example 6, the components in the samples were present in the following amounts: ZrO2: 0.68 weight , TiO2: 1.61 weight %, K2O: 0.51 weight %, MgO: 1.35 weight %, Al2O3: 1.70 weight % and CaO: 1.70 weight . The activities were high, 1.3 at 420 °C and 1.43 at 350 °C.
Example 7
The sample composition of Example 7 also gave high activities, 1.3 at 420 °C and 1.31 at 350 °C. The contents of the promoters were: ZrO2: 0.69 weight , TiO2: 1.64 weight , K2O: 0.44 weight %, MgO: 1.36 weight %, Al2O3: 1.73 weight % and CaO: 1.73 weight %.
Example 8
The samples used in Example 8 had a low K2O content, 0.27 weight %. The other promoters were within a range which after the good results of Example 6 and 7 should be expected to give good results, but the activities were low, 0.77 at 420 °C and 0.56 at 350 °C. This indicates that the K O content should not be too low.
Example 9
The samples used in Example 9 had a high K2O content, 0.68 weight %. The activities were 1.19 (420 °C) and 1.44 (350 °C). The low temperature activity was high, but some high temperature activity was lost.
Example 10
In Example 10 tests were carried out with samples resulting in high activities both at high temperature (1.24) and low temperature (1.34). The contents of the promoters were ZrO2: 0.92 weight %, TiO2: 2.00 weight %, K2O: 0.56 weight %, MgO: 1.58 weight %, Al2O3: 1.91 weight % and CaO: 1.55 weight %.
Example 11
It was of interest to check whether TiO2 could replace Al2O3 as a structural promoter. Tests were therefore carried out with samples where the contents of TiO2 and K2O were high and no Al2O3 was present. This resulted in low activities, 0.62 and 0.69. Example 11 shows that Al2O3 should not be totally replaced by TiO2.
Example 12
In the samples used in Example 12 there were no Al2O3 and CaO. The contents of TiO2 and K2O were high. The activities were only 0.38 and 0.32. This shows that Al2O3 and CaO should not be omitted in the catalyst composition.
Example 13
In Example 13 the contents of ZrO2 and Al O3 in the samples were high, 1.83 weight % and 2.51 weight %, respectively, and the content of TiO2 was low, 0.45 weight %. The activities were 1.03 and 1.16. Even though the activities were better than the reference sample, some of the other catalyst compositions gave better activities. In the compositions with better activities, the content of TiO2 was higher than the content of ZrO2.
Example 14
In Example 14, there were used samples where the ZrO2 and K2O contents were high; Al2O3 and CaO contents were low. The TiO content was higher than in Example 13, but still lower than the ZrO2 content. This resulted in activities of 1.01 and 1.22. The high ZrO2 content did not compensate for the low Al2O3 and CaO contents. The composition used in this Example is not the most optimal one.
Example 15
In Example 15 the contents of all the promoters were outside what was later found to be the desired range. No CaO was added and the Al O3 content was high (2.68 weight %). No extra TiO2 was added, so only the TiO2 from magnetite (0.2 weight %) was present. The ZrO2 content was 1.89 weight %. The K2O content was extra high, 1.16 weight % and the MgO content was low, 0.30 weight %. The activities were 1.01 and 1.14, which was slightly better than the reference, but significantly lower than when more TiO2 was added, as for instance in Examples 6 and 7. To obtain better results, also the MgO content should be higher and CaO should not be omitted in the catalyst composition. Example 16
In Example 16 a relatively large amount of ZrO2, 2.5 weight %, was added to a composition close to the reference sample. No extra TiO2 was added, so only the TiO from magnetite (0.2 weight %) was present, as in Example 15. The resulting activities were higher than for the reference sample, 1.03 at 420 °C and 1.19 at 350 °C, but significantly lower than when more TiO2 was added and the ZrO2 content was lower than the TiO2 content.
Example 17
It was of interest to try to replace some of the ZrO2 with CeO2, and tests were carried out with samples where 0.63 weight % CeO2 was added. The content of ZrO2 was low, 0.18 weight %. The other promoters were present in the following amounts: K2O: 0.61 weight %, MgO: 1.36 weight %, Al2O3: 1.73 weight % and CaO: 1.73 weight %. The activities were high, 1.31 at 420 °C and 1.43 at 350 °C.
Example 18
In the samples used in Example 18 the content of CeO2 was 0.73 weight % and the content of ZrO was 0.10 weight %. The other promoters were present in almost the same amounts as in Example 17. The activities obtained were very high, 1.31 and 1.56. From examples 17 and 18 it is seen that the addition of CeO2 has a positive effect on the activities of the catalyst.
Examples 19 - 21 are large scale tests. The compositions of the samples tested in large scale were chosen within the range, which showed the best results in the lab scale tests.
Example 19
In Example 19 it was used samples where the contents of the promoters were: ZrO2: 0.64 weight %, TiO2: 1.52 weight %, K2O: 0.62 weight %, MgO: 1.57 weight %, Al2O3: 2.29 weight % and CaO: 2.23 weight %. The activities were 1.24 and 1.36. Example 20
In Example 20 it was used samples where the contents of ZrO2 and TiO2 were a little higher than in Example 19, and the contents of K2O, MgO, Al2O3 and CaO were a little lower. The activities were 1.33 and 1.41.
Examples 19 and 20 show that high activities were obtained with some variation of the promoter contents within the ranges, which gave good results in the lab scale tests.
Example 21
In the samples used in Example 21, 0.58 weight % CeO2 was added and the ZrO2 content was lowered to 0.30 weight % and the rest of the promoters were present in about the same amounts as in Example 20. The activities were 1.19 and 1.33. Also in the large scale test, the catalyst composition with CeO2 present gave high activities.
Examples 17, 18 and 21 show that ZrO2 may be partly replaced by CeO2.
From the examples it is clear that a catalyst combining regular promoters of Al, K, Ca and Mg oxides and ZrO2 and TiO2, and optionally also CeO , will increase the activity of the catalyst, especially in the low temperature range. The results show that a composition where the ZrO2 content is lower than the TiO2 content is favourable. Neither Al2O3 nor CaO should be omitted, but it is more critical to vary the Al2O3 content than the CaO content. K2O should also be present, a too low content results in low activities. The results also show that it is favourable for the catalyst activity to add extra MgO in addition to the MgO present as impurities. The new catalyst will not cause environmental or health problems during production, installation or disposal of used catalyst.

Claims

Claims
1. A catalyst for the synthesis of ammonia from hydrogen and nitrogen, comprising iron oxides and promoters of Al, K, Ca and Mg oxides, characterized in that said catalyst in addition comprises a promoter of TiO in the amount of 0.3 - 2.5 weight % and a promoter of ZrO.
2. A catalyst according to claim 1, characterized in that the content of ZrO2 is 0.05 - 2 weight %, preferably 0.05 - 1.0 weight %.
3. A catalyst according to claim 1, characterized in that said catalyst may also comprise a promoter of CeO2 which partly replaces ZrO2.
4. A catalyst according to claim 3, characterized in that the content of CeO2 is 0.5 - 1 weight %, preferably 0.55 - 0.8 weight %.
5. A catalyst according to claims 3 and 4, characterized in that the content of CeO2 is 0.55 - 0.8 weight % and the content of ZrO2 is 0.05 - 0.5 weight %.
6. A catalyst according to claim 1, characterized in that the promoters are present in the concentration range: 1.2 - 3.0 weight % AlO3, 0.3 - 0.8 weight % K2O, 1.0 - 2.8 weight % CaO, 0.2 - 1.7 weight % MgO, 0.3 - 2.5 weight % TiO2 and 0.05 - 2.0 weight % ZrO2.
7. A catalyst according to claim 6, characterized in that the promoters preferably are present in the concentration range: 1.65 - 2.3 weight % Al2O3, 0.4 - 0.7 weight % K2O, 1.5 - 2.3 weight % CaO, 1.25 - 1.65 weight % MgO, 1.3 - 2.2 weight % TiO2 and 0.05 - 1.0 weight % ZrO2.
8. A catalyst according to claims 1 and 3, characterized in that the promoters preferably are present in the concentration range: 1.65 - 2.3 weight % Al2O3, 0.4 - 0.7 weight % K2O, 1.5 - 2.3 weight % CaO, 1.25 - 1.65 weight % MgO, 1.3 - 2.2 weight % TiO2, 0.05 - 1.0 weight % ZrO2 and 0.5 - 1.0 weight % CeO2.
9. A catalyst according to claim 8, characterized in that the promoters preferably are present in the concentration range: 1.65 - 2.3 weight % Al2O3, 0.4 - 0.7 weight % K2O, 1.5 - 2.3 weight % CaO, 1.25 - 1.65 weight % MgO, 1.3 - 2.2 weight % TiO2, 0.05 - 0.5 weight % ZrO2 and 0.55 - 0.8 weight % CeO2.
PCT/NO2003/000330 2002-10-02 2003-10-01 Catalyst for the synthesis of ammonia WO2004030810A1 (en)

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Cited By (1)

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Publication number Priority date Publication date Assignee Title
WO2010031247A1 (en) * 2008-09-18 2010-03-25 中国石油天然气股份有限公司 Iron-based ammonia synthesis catalyst and method for preparing the same

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US3653831A (en) * 1968-10-04 1972-04-04 Chevron Res Ammonia synthesis catalyst
US3839229A (en) * 1971-03-17 1974-10-01 Azote & Prod Chim Ammonia-synthesis catalyst
US4451578A (en) * 1982-04-26 1984-05-29 United Technologies Corporation Iron oxide catalyst for steam reforming
US4480051A (en) * 1983-08-03 1984-10-30 E. I. Du Pont De Nemours And Company Activated iron hydrogenation catalyst
WO1999046038A1 (en) * 1998-03-13 1999-09-16 Norsk Hydro Asa Catalyst for the synthesis of ammonia from hydrogen and nitrogen

Patent Citations (5)

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Publication number Priority date Publication date Assignee Title
US3653831A (en) * 1968-10-04 1972-04-04 Chevron Res Ammonia synthesis catalyst
US3839229A (en) * 1971-03-17 1974-10-01 Azote & Prod Chim Ammonia-synthesis catalyst
US4451578A (en) * 1982-04-26 1984-05-29 United Technologies Corporation Iron oxide catalyst for steam reforming
US4480051A (en) * 1983-08-03 1984-10-30 E. I. Du Pont De Nemours And Company Activated iron hydrogenation catalyst
WO1999046038A1 (en) * 1998-03-13 1999-09-16 Norsk Hydro Asa Catalyst for the synthesis of ammonia from hydrogen and nitrogen

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2010031247A1 (en) * 2008-09-18 2010-03-25 中国石油天然气股份有限公司 Iron-based ammonia synthesis catalyst and method for preparing the same

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