AU661970B2 - Self-gettering catalysts - Google Patents
Self-gettering catalysts Download PDFInfo
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- AU661970B2 AU661970B2 AU83248/91A AU8324891A AU661970B2 AU 661970 B2 AU661970 B2 AU 661970B2 AU 83248/91 A AU83248/91 A AU 83248/91A AU 8324891 A AU8324891 A AU 8324891A AU 661970 B2 AU661970 B2 AU 661970B2
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- catalytic material
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- 239000003054 catalyst Substances 0.000 title claims description 61
- 238000005247 gettering Methods 0.000 title claims description 11
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 claims description 104
- 239000000463 material Substances 0.000 claims description 92
- 230000003197 catalytic effect Effects 0.000 claims description 79
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 76
- 229910052763 palladium Inorganic materials 0.000 claims description 38
- 229910052697 platinum Inorganic materials 0.000 claims description 35
- 229910052751 metal Inorganic materials 0.000 claims description 13
- 239000002184 metal Substances 0.000 claims description 13
- 239000010948 rhodium Substances 0.000 claims description 9
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 claims description 7
- 229910052726 zirconium Inorganic materials 0.000 claims description 7
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 6
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 claims description 6
- 229910052737 gold Inorganic materials 0.000 claims description 6
- 239000010931 gold Substances 0.000 claims description 6
- 229910052703 rhodium Inorganic materials 0.000 claims description 6
- 229910017052 cobalt Inorganic materials 0.000 claims description 5
- 239000010941 cobalt Substances 0.000 claims description 5
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims description 5
- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 claims description 5
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 claims description 4
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 4
- KJTLSVCANCCWHF-UHFFFAOYSA-N Ruthenium Chemical compound [Ru] KJTLSVCANCCWHF-UHFFFAOYSA-N 0.000 claims description 4
- 229910052741 iridium Inorganic materials 0.000 claims description 4
- GKOZUEZYRPOHIO-UHFFFAOYSA-N iridium atom Chemical compound [Ir] GKOZUEZYRPOHIO-UHFFFAOYSA-N 0.000 claims description 4
- 238000000034 method Methods 0.000 claims description 4
- 229910052750 molybdenum Inorganic materials 0.000 claims description 4
- 239000011733 molybdenum Substances 0.000 claims description 4
- 229910052702 rhenium Inorganic materials 0.000 claims description 4
- WUAPFZMCVAUBPE-UHFFFAOYSA-N rhenium atom Chemical compound [Re] WUAPFZMCVAUBPE-UHFFFAOYSA-N 0.000 claims description 4
- 229910052707 ruthenium Inorganic materials 0.000 claims description 4
- 229910052742 iron Inorganic materials 0.000 claims description 3
- 229910052762 osmium Inorganic materials 0.000 claims description 3
- SYQBFIAQOQZEGI-UHFFFAOYSA-N osmium atom Chemical compound [Os] SYQBFIAQOQZEGI-UHFFFAOYSA-N 0.000 claims description 3
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 claims description 3
- 229910052721 tungsten Inorganic materials 0.000 claims description 3
- 239000010937 tungsten Substances 0.000 claims description 3
- ZSLUVFAKFWKJRC-IGMARMGPSA-N 232Th Chemical compound [232Th] ZSLUVFAKFWKJRC-IGMARMGPSA-N 0.000 claims description 2
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 2
- 229910052776 Thorium Inorganic materials 0.000 claims description 2
- 229910052804 chromium Inorganic materials 0.000 claims description 2
- 239000011651 chromium Substances 0.000 claims description 2
- 229910052802 copper Inorganic materials 0.000 claims description 2
- 239000010949 copper Substances 0.000 claims description 2
- 229910052759 nickel Inorganic materials 0.000 claims description 2
- 229910052727 yttrium Inorganic materials 0.000 claims description 2
- VWQVUPCCIRVNHF-UHFFFAOYSA-N yttrium atom Chemical compound [Y] VWQVUPCCIRVNHF-UHFFFAOYSA-N 0.000 claims description 2
- 229910001260 Pt alloy Inorganic materials 0.000 claims 1
- 239000000126 substance Substances 0.000 claims 1
- -1 tantalim Chemical compound 0.000 claims 1
- 229910018879 Pt—Pd Inorganic materials 0.000 description 28
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 10
- 230000008901 benefit Effects 0.000 description 10
- 229910045601 alloy Inorganic materials 0.000 description 9
- 239000000956 alloy Substances 0.000 description 9
- 238000002844 melting Methods 0.000 description 9
- 230000008018 melting Effects 0.000 description 9
- 238000011144 upstream manufacturing Methods 0.000 description 6
- 229910021529 ammonia Inorganic materials 0.000 description 5
- 238000007792 addition Methods 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 239000007789 gas Substances 0.000 description 3
- 230000003647 oxidation Effects 0.000 description 3
- 238000007254 oxidation reaction Methods 0.000 description 3
- 229910000990 Ni alloy Inorganic materials 0.000 description 2
- 238000005275 alloying Methods 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 239000011888 foil Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 229910052715 tantalum Inorganic materials 0.000 description 2
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 description 2
- 229910001020 Au alloy Inorganic materials 0.000 description 1
- 229910000846 In alloy Inorganic materials 0.000 description 1
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- 229910001252 Pd alloy Inorganic materials 0.000 description 1
- 229910001093 Zr alloy Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 229910000428 cobalt oxide Inorganic materials 0.000 description 1
- IVMYJDGYRUAWML-UHFFFAOYSA-N cobalt(ii) oxide Chemical compound [Co]=O IVMYJDGYRUAWML-UHFFFAOYSA-N 0.000 description 1
- 239000000356 contaminant Substances 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 239000003353 gold alloy Substances 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 239000011572 manganese Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
- 239000003921 oil Substances 0.000 description 1
- 239000002574 poison Substances 0.000 description 1
- 231100000614 poison Toxicity 0.000 description 1
- 239000010970 precious metal Substances 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 238000006467 substitution reaction Methods 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
- B01J35/00—Catalysts, in general, characterised by their form or physical properties
- B01J35/50—Catalysts, in general, characterised by their form or physical properties characterised by their shape or configuration
- B01J35/58—Fabrics or filaments
-
- 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
- B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
- B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group 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
- B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
- B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
- B01J23/44—Palladium
-
- 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
- B01J35/00—Catalysts, in general, characterised by their form or physical properties
- B01J35/19—Catalysts containing parts with different compositions
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B21/00—Nitrogen; Compounds thereof
- C01B21/20—Nitrogen oxides; Oxyacids of nitrogen; Salts thereof
- C01B21/24—Nitric oxide (NO)
- C01B21/26—Preparation by catalytic or non-catalytic oxidation of ammonia
- C01B21/267—Means for preventing deterioration or loss of catalyst or for recovering lost catalyst
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Inorganic Chemistry (AREA)
- Catalysts (AREA)
- Exhaust Gas Treatment By Means Of Catalyst (AREA)
Description
OPI DATE 02/03/92 AOJP DATE 09/04/92 APPLN. ID 83248 91 PCT NUMBER PCT/GR91/01292 INTERNATIONAL APPLICATION PU BiL1bitv ulINUIr inr rti cin i REATY (PCT) (51) International Patent Classification 5 (11) International Publication Number: WO 92/02300 B01J 35/06 Al (43) International Publication Date: 20 February 1992 (20.02.92) (21) International Application Number: PCT/GB91/01292 Published With international search report.
(22) International Filing Date: 30 July 1991 (30.07.91) Priority data: 6 6 9016788.3 31 July 1990 (31.07.90) GB 9 7 (71X72) Applicant and Inventor: HEYWOOD, Alan, Edward [GB/GB]; 209 Hugheiden Road, St. Albans, Hertfordshire AL4 9QP (GB).
(74) Agent: KELTIE, David, Arthur; David Keltie Associates, Buchanan House, 24-30 Holborn, London ECIN 2JB
(GB).
(81) Designated States: AT, AT (European patent), AU, BB, BE (European patent), BF (OAPI patent), BG, BJ (OAPI patent), BR, CA, CF (OAPI patent), CG (OAPI patent), CH, CH (European patent), CI (OAPI patent), CM (OA- PI patent), CS, DE, DE (European patent), DK, DK (European patent), ES, ES (European patent), FI, FR (European patent), GA (OAPI patent), GB, GB (European patent), GN (OAPI patent), GR (European patent), HU, IT (European patent), JP, KP, KR, LK, LU, LU (European patent), MC, MG, ML (OAPI patent), MN, MR (OAPI patent), MW, NL, NL (European patent), NO, PL, RO, SD, SE, SE (European patent), SN (OAPI patent), SU, TD (OAPI patent), TG (OAPI patent), US.
(54) Title: IMPROVEMENTS IN OR RELATING TO SELF-GETTERING CATALYSTS 16 (121 12 I I22 24 Rh-Pt-Pd GAUZES 3 Rh-Pt-Pd GAUZES AND 2 Pd GAUZES 4 12zil (121 (57) Abstract A catalyst unit in which a quantity of a relatively expensive material eseh s(platinum)is replaced by a greater quantity of a relatively inexpensive material sewa-as(palladiunm.Thus, material cost saved by "tailoring" a pack is used to pay for a large quantity of a cheaper material. Although the cheaper material is generally less intrinsically efficient than the expensive material, a sufficient additional amount of the cheaper material can be used to more than compensate for this lack of efficiency. Thus, a catalytic pack of high catalytic efficiency, low material cost, low metal loss and long run duration can be produced.
See back of page WO 92/02300 PCT/GB91/01292 IMPROVEMENTS IN OR RELATING TO SELF-GETTERING CATALYSTS This invention relates to self-getterin, catalysts.
In use, catalysts can suffer greatly from material losses 5 through volatilisation, especially during highly exothermic reactions such as the oxidation of ammonia. Where the catalyst is of precious metal, this loss can be extremely expensive, leading to greatly increased production costs. It is therefore common for getter systems to be employed, with the aim of recovering some of the material lost from the catalyst.
Getter systems typically comprise one or more catchment gauzes situated downstream of one or more catalytic gauzes to recover catalytic material present in the post-reaction gases.
Examples of getter system are discussed in UK Patent No.
2037606. That patent also discloses a catalyst unit in which a palladium/gold alloy catchment gauze is placed in close proximity with a platinum catalytic gauze. By virtue of its composition, the catchment gauze itself has some catalytic properties and therefore, by virtue of its placement, the catchment gauze promotes the reaction initiated by the catalytic gauze. This 'self-gettering' catalyst has two main benefits. Firstly, less platinum is required to attain a given catalytic efficiency. Secondly, less platinum is lost from the catalyst in use.
UK Patent Application No. 2062486 discloses a catalyst unit comprising a pack of woven metallic gauzes in which at least some of the gauzes disposed at or towards the front of the pack are made from wire having a cross-sectional area greater than the wire of at least some of the gauzes disposed at or towards the rear of the pack. This 'tailoring' of the wire sizes is intended to reflect the well-known metal loss characteristic in which more metal tends to be lost from the m -2gauzes at or towards the front of the pack than is lost from the gauzes at or towards the rear of the pack. Thus, the durability of each gauze is selected to suit the rate at which it is expected to erode. In this way, no more of the expensive catalytic material need be used than is necessary; in effect, the amount of catalytic material at the lightly-loaded downstream end of the pack is reduced to a minimum.
The tailored pack disclosed in UK Patent Application No.
2062486 does not, however, propose the use of catchment or getter layers to reduce metal loss from the pack. As a result, the life of the pack is undesirably limited, and metal loss is undesirably high.
It is against this background that the present invention has been made. The invention embodies a principle, namely that a quantity of a relatively expensive first material can be replaced by a relatively inexpensive second material in such a quantity as to outweigh, overcome or compensate for any intrinsic disadvantages of the second material in comrrison with the first material.
The first material is wholly or predominantly platinum and the second material is wholly or predominantly palladium. At the time of writing, platinum is approximately four times as expensive as palladium, per unit weight. Platinum is also 1.75 .:*..times denser than palladium. On the other hand however, platinum is (in some but not all cases) a more effective catalyst than palladium; it can be said that palladium is intrinsically disadvantaged in that respect with respect to platinum. Nevertheless, given the cost and density differences, approximately seven units of palladium correspond to one unit of platinum for the same overall cost. So, in a catalyst pack for example, one platinum gauze may be replaced by seven similar palladium gauzes without adding to the material cost of the pack. In many cases, such a quantity of .77 palladium is sufficient to outweigh the intrinsic N disadvantages of palladium in terms of catalytic WO 92/02300 3 P- CT/GB91/01292 effect, so that the catalytic eificiency of the pack is q actually increased.
It will be clear that an unexpected and beneficial synergy underlies the invention. At one extreme, for a given material cost, the catalytic efficiency of a catalyst pack can be increased. At the other extreme, a given catalytic efficiency can be maintained while reducing the material cost of the pack. Of course, variations between those extremes are also possible: indeed, it has been found that the invention allows a catalyst pack to combine improved catalytic efficiency with lower material cost, as will be demonstrated.
A further important point is that palladium acts as a getter for platinum in catalyst packs. Thus, the addition of palladium catchment elements also improves the platinum loss characteristics of the pack. This is a further example of the synergy that underlies the invention.
A still further benefit of the invention is that it allows a useful increase in the average run length of a catalyst pack, without necessarily adding to material costs, detracting from catalytic efficiency, or worsening metal loss characteristics.
Increasing the run length reduces plant shutdowns and thus minimises expensive downtime. The run length is increased because the palladium elements 'underpin' (compensate for) the decay of the platinum elements as platinum is evaporated from the platinum elements, it is picked up by the palladium elements which then improve as catalysts by virtue of their increasing platinum content. In simple terms, the palladium getter always provides some catalytic effect, but becomes a better catalyst as it ages. Some platinum is inevitably lost from the unit, but the remainder simply moves from one position to another within the unit and continues to do useful catalytic work.
In addition, some studies suggest that the addition of I; A WO 92/02300 PCT/GB91/01292 44 palladium increases the resistance of a catalyst unit to degradation by organic contaminants, notably (but not exclusively) oils which may be introduced from the ammonia feed, compressor bearings etc.
The various potential benefits of the invention may be expressed in terms of four performance indicators, i.e. 1.
improved catalytic efficiency; 2. improved metal loss characteristics; 3. increased run time; and 4. increased resistance to organic contamination. A further potential benefit (not strictly a performance benefit) is, of course, reduced material costs. Naturally, benefit may be gained by improving one or more of the four performance indicators (not j necessarily all of them), and/or by reducing material costs.
In this specification, references to improved 'performance' are intended to indicate that one or more of the four performance indicators have been improved.
The invention may thus be expressed as a method of improving.
the performance and/or the cost of a catalyst unit, comprising removing a quantity of a first, relatively expensive catalytic material from a region of the unit, and replacing that quantity of the first catalytic material with a larger quantity of a second, relatively inexpensive catalytic material.
The invention may also be expressed as a catalyst unit comprising a quantity of a first catalytic material distributed non-uniformly through the unit, including a second catalytic material positioned to act as a getter for the first catalytic material and to enhance the catalytic effect of the unit.
The distribution of the first catalytic miterial is suitably 'tailored' such that less of the first catalytic material is situated in regions of low expected metal loss than in regions of high expected metal loss. Tailoring of the amount of the I 1 I t /.1 WO 92/02300 PCT/GB91/01292 first catalytic material may be accomplished by varying the number of catalytic elements around a given position within a catalyst unit or preferably, by varying the cross-sectional area of the catalytic elements themselves.
The distribution of the second catalytic material within the pack may also be tailored in similar fashion, so that the amount of the second catalytic material at a given position within the catalyst unit is matched to the amount of the first catalytic material expected to be present in the gas stream at that position. In this respect, it will be noted that upstream getter or catchment elements generally co."ect more volatilised material than downstream getter or itchment 1 elements. Thus, the downstream getter or catchment elements need not have the capacity of the upstream elements.
Elements of the second catalytic material may be separated from elements of the first catalytic material by support elements. The support elements can, for example, be stainless steel gauzes. Other types of support element include ceramic elements or Pt/Pd/Rh-coated inert elements.
Preferably, the first catalytic material is platinum or a platinum-based alloy, and the second catalytic material is palladium or a palladium-based alloy. For example, the first catalytic material is suitably a Rh-Pt-Pd alloy, with Rh present in an amount between 1 and 15 wt%, and with Pd present in an amount between 1 and 30 wt%, preferably with additions of iridium, ruthenium, molybdenum, cobalt, manganese or zirconium. A US alloy, 5%Rh-90%Pt-5%Pd, is a specific example.
The second catalytic material is suitably mainly Pd with additional elements as above.
At present, rhodium is approximately forty times as expensive as palladium, weight for weight. Thus, a reduction in the amount of rhodium by deleting a Rh-Pd-Pt gauze) involves a substantially greater cost saving than simply removing some f 'i *I
*N
WO 92/02300 PCT/GB91/01292 6 platinum. This saving can be used to pay for still more palladium, to the further benefit of the unit's performance.
It is preferred that elements of the second catalytic material alternate with at least some elements of the first catalytic material in the unit.
The elements of the first and second catalytic materials are preferably of wire woven or knitted to form a gauze screen.
Mesh sizes for the gauze of the first catalytic material can range from, say, 100 to 1500 meshes per cm 2 and preferably from 200 to 1200 meshes per cm 2 Mesh sizes for the gauze of the second catalytic material can range from, say, 30 to 1200 1 meshes per cm 2 and preferably from 50 to 1000 meshes per cm 2 The diameter of wires of the first catalytic material can range, for example, from approximately 0.05 mm to 0.3 mm, and preferably from 0.05 mm to 0.15 mm. Wires of the second catalytic material are suitably in the range 0.05 mm to 0.25 mm.
Referring back now to UK Patent No. 2037606, whilst the arrangement therein is laudable for its reduced platinum 4 content and consumption, this advantage is negated to some extent by the use of substantial amounts of gold (up to in the catchment gauzes. More seriously perhaps, gold is known to be a poison for platinum catalysts in the oxidation of ammonia. This can cause considerable difficulties, particularly bearing in mind that the gold-containing gauzes are in close proximity with, and in some cases upstream of, the platinum gauzes. A further problem is that whilst gold improves the strength of palladium, gold also significantly reduces palladium's gettering efficiency.
In view of the above problems, a further object of this invention is to develop a self-gettering catalyst arrangement which employs substantially gold-free getter materials.
1 WO 92/02300 7 PCT/GB91/01292 With this object in view, a second aspect of the invention may be expressed as a catalyst, a getter or a self-gettering catalyst of palladium or palladium alloyed with at least one element selected from the group rhenium, iron, molybdenum, zirconium, tantalum, tungsten, cobalt, yttrium, thorium, ruthenium, iridium, osmium, rhodium, nickel, copper and chromium.
In Pd-Zr alloys, it is preferred that zirconium content does not exceed 2 wt%. In alloys of palladium with any other element in the group, it is preferred that the content of that other element does not exceed 8 wt%.
In general, it is desirable for an alloying element to increase the melting point of palladium (or at least not to reduce its melting point unduly), thereby minimising self diffusion and grain growth, and resultant expansion effects, under high-temperature conditions in use, which can occur with ,n4'ae palladium. Also, as gettering depends upon diffusion of platinum into the lattice of the catchment material, gettering efficiency may be expected to increase as the lattice constant of palladium is increased. It is therefore also desirable that the alloying element acts to increase the lattice constant of palladium.
Of the elements in the specified group: rhenium causes little or no reduction in melting point and, in small quantities, increases hardness markedly. Also, platinum readily alloys with rhenium.
i~i (ii) iron increases the lattice constant, and is very cheap; (iii) molybdenum increases the melting point of the alloy.
(iv) addition of zirconium does not significantly reduce the melting point of palladium and increases its lattice constant.
n- n n i mn Il :i
I
WO 92/02300 PCT/GB91/01292 88 also, zirconium can be slagged off as the oxide on melting.
It is also envisaged that a degree of internal hardening may take place in use. Zirconium may even be partially or fully oxidised before use to produce a dispersion strengthened alloy with excellent high temperature characteristics.
tantalum increases the melting point of the alloy.
(vi) tungsten raises the melting point of palladium considerably whilst largely maintaining its lattice constant.
(vii) cobalt can become oxidised in use to form cobalt oxide, which is itself a catalyst in the oxidation of ammonia. Thus, it is envisaged that cobalt may enhance the catalytic properties of palladium when used for this reaction.
(viii) ruthenium, iridium, osmium and rhodium all raise the melting point of palladium.
The invention further includes a catalyst unit as defined in accordance with the first aspect of the invention, comprising catalyst, getter, or self-gettering catalyst elements as defined in accordance with the second aspect of the invention.
In order that this invention may be more readily understood, embodiments thereof will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a schematic partial cross-sectional view through a typical known catalyst pack; and Figures 2, 3 and 4 are schematic partial cross-sectional views through catalyst packs constructed in accordance with this invention.
Referring to Figure 1, a typical known catalyst pack comprises a plurality of catalytic gauzes 12. In the example L
A
11-- WO 92/02300 PCT/GB91/01292 9 shown, twenty-eight identical 5% Rh 90% Pt 5% Pd gauzes 12 lie one above another. The gauzes 12 are connected at their edges by a heat resistant alloy foil 14 such as nickel alloy which overlaps an edge portion of the top and bottom gauzes 12 (denoted 12' and 12" respectively).
The gauzes 12 are typically woven from wire 0.003" (0.0762 mm) in diameter, with 1024 meshes per cm 2 The gauze diameter is 434 inches. Such a configuration is suitable for a plant used to produce 450 tonnes/day of nitric acid (HNO,) from ammonia
(NH
3 Referring now to Figures 2, 3 and 4, catalyst packs 16, 18, and 20 constructed in accordance with the invention are similar in outward appearance to the typical pack 10 shown in Figure 1. That is to say, they have a top gauze 12', a bottom gauze 12", and a nickel alloy foil 14. The packs 16, 18 and differ from the typical pack 10 in their internal configurations, as follows: Pack 16 of Figure 2 contains a total of twenty-seven Rh-Pt-Pd gauzes 12 supplemented by two Pd gauzes 22. The Pd gauzes 22 are of 0.18 mm wire, with 140 meshes per cm 2 Moving downstream through the pack 16, there are twenty-four Rh-Pt-Pd gaues 12, one Pd gauze 22, one Rh-Pt-Pd gauze 12, one Pd gauze 22, and two Rh-Pt-Pd gauzes 12. As the Pd gauzes 22 replace one of the Rh-Pt-Pd gauzes 12 of the typical pack and are situated adjacent the downstream end of the pack 16, it can be said that the pack 16 is tailored, albeit simply, to suit the expected 'front-loaded' metal loss profile. That is to say, the amount of Rh-Pt-Pd catalytic material in the downstream region of the pack 16 is reduced with respect to the upstream region of the pack 16.
Pack 18 of Figure 3 contains a total of twenty-two Rh-Pt-Pd gauzes 12 plus a group of six lightweight Rh-Pt-Pd gauzes 24, supplemented by three Pd gauzes 22 adjacent the downstream end v i WO 92/02300 PCT/GB91/01292 10 of the pack. Moving downstream through the pack, there are seventeen Rh-Pt-Pd gauzes 12, six lightweight Rh-Pt-Pd gauzes 24, one Rh-Pt-Pd gauze 12, one Pd gauze 22, one Rh-Pt-Pd gauze 12, one Pd gauze 22, one Rh-Pt-Pd gauze 12, one Pd gauze 22 and two Rh-Pd-Pt gauzes 12. The lightweight Rh-Pt-Pd gauzes 24 are similar in mesh size to the ordinary Rh-Pt-Pd gauzes 12 and are of similar composition, but consist of wires 0.063 mm (nominally 0.060 mm) in diameter as opposed to 0.0762 mm in diameter. Thus, the pack 18 of Figure 3 contains a profile of catalytic Rh-Pt-Pd elements that is more finely 'tailored' in accordance with the expected metal loss profile.
Pack 20 of Figure 4 contains a total of twenty-two Rh-Pt-Pd gauzes 12 plus a group of seven lightweight Rh-Pt-Pd gauzes 24, supplemented by two Pd gauzes 22, one Pd gauze 26, and one Pd gauze 28. The Pd gauze 2C is of 0.19 mm diameter wire and has 100 meshes per cm 2 The Pd gauze 28 is of 0.15 mm diameter wire and has 150 meshes per cm 2 Thus, the Pd layers are also tailored in this example, in order to match them to the amount of platinum expected to be present in the gas stream at each location in the pack. It has been observed that upstream catchment gauzes tend to collect a greater quantity of platinum than downstream catchment gauzes; thus, the upstream catchment gauzes should, ideally, have a relatively greater resistance to saturation.
Moving downstream through the pack 20, there are sixteen Rh- Pt-Pd gauzes 12, seven lightweight Rh-Pt-Pd gauzes 24, one Rh- Pt-Pd gauze 12, one Pd gauze 26, one Rh-Pt-Pd gauze 12, one Pd gauze 22, one Rh-Pt-Pd gauze 12, one Pd gauze 22, one Rh- Pt-Pd gauze 12, one Pd gauze 28, and two Rh-Pt-Pd gauzes 12.
Whilst it is preferred that the Pd gauzes 22, 26, 28 are concealed within the pack so that the customer is presented with a unit of familiar appearance, it is also possible to arrange the pack such that one of the Pd gauzes 22, 26, 28 is exposed.
I 1 WO 92/02300 PCT/GB91/01292 11 A common feature of all of the above examples is that the Pd gauzes 22, 26, 28 in effect replace one or more of the Rh-Pd- Pt gauzes 12, 24 near the downstream end of each pack. Thus, the number of Rh-Pd-Pt gauzes in the downstream portion of each pack is tailored to some extent to suit the relatively low metal loss expected at that end of the pack. The material cost saved by removing or lightening the Rh-Pd-Pt gauzes 12 allows the substitution of more, cheaper Pd gauzes 22, 26, 28.
As will be shown below, this provides a highly desirable combination of lower total material cost, higher catalytic efficiency, lower platinum loss, and onger run length.
The following table, TABLE 1, sets out some advantages of the invention, based upon trials of the known pack illustrated in Figure 1 and the novel packs illustrated in Figures 2, 3 and 4. The table assumes the following material costs: Pt US$500/oz., Pd US$120/oz. and Rh US$5,000/oz.
TABLE 1 Sample Fig. 1 Fig. 2 Fig. 3 Fig. 4 Material costs 368,120 359,480 349,540 341,120 dollars) Platinum losses 0.29 0.25 0.23 0.2175 (gm/ton) Reduction in -14 20 platinum losses Av. run length 38 49 52 53 (weeks) As can be seen, the invention allows a marked reduction in material costs, a substantial reduction in platinum losses, and a substantial increase in the average run length. The 1 1 1 7 1 11 1 1 11 a WO 92/02300 PCT/GB91/01292 12 increased average run length is indicative of improved catalytic efficiency. This is because the end of a run is usually determined by the catalytic efficiency falling below a given threshold level. Thus, the higher the efficiency at the start of a run, and the shallower the gradient of the efficiency decay curve, the longer the run will be before the threshold level is crossed.
It is estimated that over the course of a year, the above examples will produce cost benefits of between US$80,000 and US$150,000.
i 1 p
Claims (14)
- 2. A catalyst unit comprising a quantity of a first catalytic material distributed non-uniformly through the unit, and a quantity of a second catalytic material positioned to act as a getter for the first catalytic material and to contribute towards the catalytic effectiveness of the unit.
- 3. A catalyst unit according to claim 1 or 2, wherein the second catalytic material is intrinsically less efficient as a catalyst than the first catalytic material, but is present in such a quantity as to outweigh, compensate for or overcome its relative inefficiency as a catalyst to produce a unit having greater performance than a unit of equal or greater material cost consisting entirely of the first catalytic material. wherein the second catalytic material is intrinsically less
- 4. A catalyst unit according to any one of claims 1 to 3, efficient as a catalyst than the first catalytic material, but is present in such a quantity as to outweigh, compenr.ate for or overcome its relative inefficiency as a catalyst to produce a unit having lower material cost than a unit of equal or) i lesser performance consisting entirely of the first catalytic material. A catalyst unit according to any preceding claim, wherein the second catalytic material is concentrated in a downstream region of the unit. C 2. I (57) Abstract A catalyst unit in which a quantity of a relatively expensive material uach.aii(platinum)is replaced by a greater quantity of a relatively inexpensive material s ck-aspalladiu4n.Thus, material cost saved by "tailoring" a pack is used to pay for a large quantity of a cheaper material. Although the cheaper material is generally less intrinsically efficient than the expensive material, a sufficient additional amount of the cheaper material can be used to more than compensate for this lack of efficiency. Thus, a ca- talytic pack of high catalytic efficiency, low material cost, low metal loss and long run duration can be produced. See back of page :I:1 14
- 6. A catalyst unit according to any preceding claim, wherein the quantity of the second catalytic material is distributed non-uniformly.
- 7. A catalyst unit according to elements of the second catalytic least some elements of the fir3t
- 8. A catalyst unit according to a pack of layers.
- 9. A catalyst unit according to a wire gauze. A catalyst unit according to gauze is knitted.
- 11. A catalyst unit according to the second catalytic material is unit.
- 12. A catalyst unit according to the second catalytic material is the first catalytic material or layer. any preceding claim, wherein material alternate with at catalytic material. any preceding claim, which is claim 8, wherein each layer is claim 9, wherein the wire any preceding claim, wherein situated internally of the any preceding claim, wherein incorporated into a layer of into a supporting or separating i: i i: 1
- 13. A catalyst unit as defined in any one of claims 1 to 12, including a catalyst, a getter or a self-gettering catalyst of palladium or palladium alloyed with at least one element selected from the group rhenium, iron, molybdenum, zirconium, tantalim, tungsten, cobalt, yttrium, thorium, ruthenium, iridium, osmium, rhodium, nickel, copper and chromium.
- 14.. A catalyst unit, substantially e. hereinbefore described with reference to any of Figures 2 to 4 of the accompanying drawings. The use of a catalyst unit as defined in any of claims 1 to 14. S Si S I a a S S SS S S. I I .V* 15
- 16. Any substance produced by use of a catalyst unit as defined in any of claims 1 to 14.
- 17. A method of improving the performance and/or the cost of a catalyst unit, comprising removing a quantity of a first catalytic material from a region of the unit, said first catalytic material being wholly or predominantly platinum but excluding tertiary platinum alloys containing more than thirty percent of palladium by weight, and replacing that quantity of r the first catalytic material with a greater quantity of a second catalytic material being wholly or predominantly palladium, characterised in that the remaining first catalytic material is distributed non-uniformly through the unit and in that the second catalytic material is substantially free of gold. I 18. A method according to claim 17, wherein the first catalytic material is removed from a downstream region of the ji pack.
- 19. A method of improving the performance and/or the cost of a catalyst unit, substantially as hereinbefore described with reference to any of Figures 2 to 4 of the accompanying drawings. Dated this fourteenth day of June, 1995 ALAN EDWARD HEYWARD 2 i By his Patent Attorney KERRY MOORE CHRYSILIOU i
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB909016788A GB9016788D0 (en) | 1990-07-31 | 1990-07-31 | Improvements in or relating to self-gettering catalysts |
GB9016788 | 1990-07-31 | ||
PCT/GB1991/001292 WO1992002300A1 (en) | 1990-07-31 | 1991-07-30 | Improvements in or relating to self-gettering catalysts |
Publications (2)
Publication Number | Publication Date |
---|---|
AU8324891A AU8324891A (en) | 1992-03-02 |
AU661970B2 true AU661970B2 (en) | 1995-08-17 |
Family
ID=10679936
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
AU83248/91A Ceased AU661970B2 (en) | 1990-07-31 | 1991-07-30 | Self-gettering catalysts |
Country Status (10)
Country | Link |
---|---|
EP (1) | EP0547071A1 (en) |
JP (1) | JPH06503743A (en) |
AU (1) | AU661970B2 (en) |
CA (1) | CA2088149A1 (en) |
FI (1) | FI930375A (en) |
GB (1) | GB9016788D0 (en) |
IE (1) | IE912689A1 (en) |
TW (1) | TW209181B (en) |
WO (1) | WO1992002300A1 (en) |
ZA (1) | ZA916029B (en) |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2274071A (en) * | 1993-01-06 | 1994-07-13 | Pgp Ind Inc | Catalyst pack |
US6073467A (en) * | 1994-04-06 | 2000-06-13 | Degussa Aktiengesellschaft | Catalyst gauzes for gaseous reactions |
DE4411774C1 (en) * | 1994-04-06 | 1995-08-17 | Degussa | Metal gauze catalyst for gas reaction, esp. ammonia oxidn. to nitric acid |
Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2445173A1 (en) * | 1978-12-27 | 1980-07-25 | Inst Nawozow Sztucznych | Catalyst contg. platinum and palladium based layers - used in oxidn. of ammonia to form nitric oxide |
Family Cites Families (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE3781629T2 (en) * | 1986-08-06 | 1993-02-18 | Engelhard Corp | PLATINUM-COATED PLATINUM AND RHODIUM CATALYST FIBERS, THEIR PRODUCTION AND USE FOR THE OXYDATION OF AMMONIA. |
GB8630728D0 (en) * | 1986-12-23 | 1987-02-04 | Johnson Matthey Plc | Ammonia oxidation catalyst pack |
-
1990
- 1990-07-31 GB GB909016788A patent/GB9016788D0/en active Pending
-
1991
- 1991-07-30 CA CA002088149A patent/CA2088149A1/en not_active Abandoned
- 1991-07-30 JP JP3513948A patent/JPH06503743A/en active Pending
- 1991-07-30 EP EP91914523A patent/EP0547071A1/en not_active Withdrawn
- 1991-07-30 AU AU83248/91A patent/AU661970B2/en not_active Ceased
- 1991-07-30 WO PCT/GB1991/001292 patent/WO1992002300A1/en not_active Application Discontinuation
- 1991-07-31 IE IE268991A patent/IE912689A1/en unknown
- 1991-07-31 ZA ZA916029A patent/ZA916029B/en unknown
- 1991-08-03 TW TW080106110A patent/TW209181B/zh active
-
1993
- 1993-01-29 FI FI930375A patent/FI930375A/en not_active Application Discontinuation
Patent Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2445173A1 (en) * | 1978-12-27 | 1980-07-25 | Inst Nawozow Sztucznych | Catalyst contg. platinum and palladium based layers - used in oxidn. of ammonia to form nitric oxide |
Also Published As
Publication number | Publication date |
---|---|
CA2088149A1 (en) | 1992-02-01 |
FI930375A0 (en) | 1993-01-29 |
TW209181B (en) | 1993-07-11 |
ZA916029B (en) | 1992-04-29 |
AU8324891A (en) | 1992-03-02 |
JPH06503743A (en) | 1994-04-28 |
IE912689A1 (en) | 1992-02-12 |
EP0547071A1 (en) | 1993-06-23 |
WO1992002300A1 (en) | 1992-02-20 |
GB9016788D0 (en) | 1990-09-12 |
FI930375A (en) | 1993-01-29 |
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