Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Nitrogen compound containing
Reexamination Certificate
2000-03-13
2001-05-22
Wood, Elizabeth D. (Department: 1755)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Nitrogen compound containing
C423S406000, C423S409000
Reexamination Certificate
active
06235676
ABSTRACT:
FIELD OF INVENTION
The present invention relates to synthesis of ammonia from ammonia synthesis gas and in particular to a catalyst being highly active in the ammonia synthesis.
DISCUSSION OF THE RELATED ART
Industrial preparation of ammonia is most usually performed by contacting hydrogen and nitrogen containing synthesis gas with catalyst at a pressure in the range of 100-400 bar and temperatures between 300° C. and 600° C. Widely used catalysts contain iron, typically promoted with oxides of aluminum and magnesium, plus oxides of calcium and potassium to increase heat resistance and synthesis activity. Furthermore, ammonia synthesis catalysts containing other Group VIII metal compounds are known in the art.
WO 96/38222 discloses a catalyst for synthesis of ammonia in presence of a catalyst comprising Group VIII metal clusters supported on basic zeolite support.
Use of ruthenium containing catalysts in the synthesis of ammonia from synthesis gas is disclosed in U.S. Pat. No. 4,600,571, JP patent publication No. 9168739 and GB patent No. 2,033,776.
Furthermore, molybdenum oxycarbonitride as active catalyst in the ammonia synthesis is mentioned in U.S. Pat. Nos. 4,271,041 and 4,337,232.
Bimetallic ammonia synthesis catalysts consisting of nickel-molybdenum are described in Z. Elektrochem. Vol. 36, Pages 690-692, 1930.
It has now been found that bimetallic catalysts comprising a combination of a Group VIII metal and a Group VIB (CAS version) metal improve activity in the synthesis of ammonia from ammonia synthesis gas, when in the nitride form.
SUMMARY OF THE INVENTION
In accordance with the above observation, this invention provides a process for the preparation of ammonia from ammonia synthesis gas by contacting the synthesis gas with a bimetallic catalyst comprising ternary compounds of a Group VIII metal and a Group VIB metal at conditions being effective in the formation of ammonia, wherein the bimetallic catalyst is in its nitride form at contact with the synthesis gas.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
When operating the inventive process the catalyst will typically be arranged in a fixed bed in an ammonia converter. The catalyst may thereby be loaded in its oxidised form which, by contact with hydrogen and nitrogen and ammonia in the reacting synthesis gas, is converted to the active nitride form according to the following reaction:
M′xM″y Oz+H2
M′xM″y
M′xM″y+H2+NH3
M′xM″yN
In the above general formula of the catalyst, M′ represents a group VIB metal, M″ a group VIII metal and x and y are mixed numbers between 1 and 10.
Still improved catalytic activity has been observed when promoting the inventive catalyst with one or more metals selected from Group IA and IIA.
At present, preferred metals for use in the above process include iron, cobalt and nickel as Group VIII metals. Molybdenum is a preferred Group VIB metal. Caesium and barium are preferred as Group IA and Group IIA promoter metals, respectively.
Suitable promoters are additionally lanthanide metals. Furthermore, the invention provides a catalyst being active in the synthesis of ammonia from ammonia synthesis gas, which catalyst is a ternary nitride having the general formula
M′xM″yN,
wherein
M′ represents a group VIB metal,
M″ a group VIII metal and
x and y are mixed numbers between 1 and 10, the catalyst is optionally promoted with one or more metals selected from Group IA, IIA and the lanthanides.
Operation conditions of the catalyst and the above ammonia synthesis process are conventional and known to those skilled in the art.
REFERENCES:
patent: 4271041 (1981-06-01), Boudart et al.
patent: 4337232 (1982-06-01), McCandlish et al.
patent: 4342594 (1982-08-01), Ettmayer et al.
patent: 4600571 (1986-07-01), McCarroll et al.
patent: 4701381 (1987-10-01), Jack
patent: 5071813 (1991-12-01), Kugler et al.
patent: 5444173 (1995-08-01), Oyama et al.
patent: 2033776 (1980-05-01), None
patent: 9168739 (1997-06-01), None
patent: 9638222 (1996-12-01), None
E. Keunecke-Ludwigshafen, “Der Nickel-Molybdän-Mischkatalysator Bei Der Ammoniaksynthese”, vol. 36, Zeitschrift für Elektrochemie, 1930, pp. 690-692. Considered only to extent described in specification, no month.
Brorson Michael
Jacobsen Claus J. H.
Sehested Jens
Teunissen Herman
Törnqvist Eric O.
Haldor Topsoe A/S
Ostrolenk Faber Gerb & Soffen, LLP
Wood Elizabeth D.
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