TW201240727A - Catalysts for use in ammonia oxidation processes - Google Patents

Abstract

A method is described for preparing a catalyst composition suitable for use in an ammonia oxidation process, comprising the steps of: (i) spraying a slurry containing a particulate mixed metal cobalt oxide on to the surface of a shaped support in a pan coater to form a coated support material, and (ii) drying and optionally calcining the coated support material to form the catalyst having the mixed metal cobalt oxide in a surface layer.

Description

201240727 VI. Description of the Invention: [Technical Field] The present invention relates to a method for preparing a supported catalyst suitable for the oxidation of ammonia, and in particular to an ammoxidation catalyst and an oxidation of a mixed metal cobalt oxide. Dinitrogen eliminates the catalyst. [Prior Art] In the industry, 'ammonia oxidation is produced by air to produce nitric oxide, which is used to produce nitric acid (Oswa method), or by air and decane to produce hydrogen cyanide (Andrewsov method) ). In both methods, the reaction gas/kun is combined through a reactor at a high temperature and a high pressure, and a set of platinum/ruthenium nets for catalytic oxidation reaction is placed in the reactor. The nets are generally circular and supported on a frame or basket that is oriented perpendicular to the flow of gas through the reactor. The catalyst group can also contain one or more palladium-rich nets, called "complement nets" for capturing volatile platinum. In recent years, it has been necessary to save the amount of platinum in the catalyst group and to test the catalyst configuration of the combined precious metal mesh and metal oxide catalyst particles. W〇 describes a crucible method in which a mixture of ammonia and air is fed at a high temperature to a catalyst comprising at least one of a noble metal in the form of an elemental filament, and the resulting gas mixture is passed through a layer of cobalt in the lower layer. Oxide catalyst particles. In addition, the nitrous oxide (ΝΑ) produced by the cyanide oxidation process has become a potential greenhouse gas under monitoring, and the nitrous oxide elimination catalyst has also been incorporated into the ammonia oxidation reactor as a noble metal ammoxidation catalyst. Lower level. SUMMARY OF THE INVENTION A preferred ammoxidation catalyst is based on a mixed metal #oxide. Such catalysts 162246.doc 201240727 are described in WO 98/28073. The disclosed catalyst preparation method comprises combining and calcining a metal oxide at a high temperature; coprecipitating; drying and calcining the mixed cobalt oxide; impregnating the oxidized support with a soluble cobalt compound, followed by drying and satin burning, or by containing a mixed metal cobalt The coating of the oxide catalyst is applied to a mesh, mesh or steel mat or ceramic wire; or a monolithic honeycomb construction or foam, followed by calcination. The latter preparation process can be complicated and expensive, and granular catalysts prepared from coprecipitated compositions are used today. However, the ammoxidation reaction occurs very quickly, and it has been recognized that short path lengths (available with coating catalysts) can improve catalyst selectivity and provide an effective catalyst for reducing cobalt loading. We have found an alternative way to overcome the problems encountered in previous preparation routes. Accordingly, the present invention provides a method for preparing a catalyst composition suitable for an ammoxidation process, the method comprising the steps of: (i) spraying a slurry containing mixed metal cobalt oxide particles in a flat plate coater The surface of the support is shaped to form a coated support material, and (ii) the coated support material is dried and optionally calcined to form a catalyst comprising a mixed metal cobalt oxide in the surface layer. [Embodiment] The method provides mixed oxidization in the outer layer of the molding (4). The present invention provides a catalyst which can be obtained by the above method and the catalyst is used for the ammoxidation method. The use of oxidizing two gases. Cobalt is locked in the structure and thus has an improved stability in the ammoxidation process. Suitable mixed metal compound filament oxide spinel _ oxide !62246*doc 201240727 I丐钦矿. The mixed metal cobalt oxide spinel which may be used may have the formula wherein Μ1 is selected from Co or, as the case may be, Cu, Ni, Mg, Ζ and Ca, and M2 is selected from A1 or Cr, and thus includes CuxC〇3 .x〇4(where πο"), C〇x.Mgl.x.Al204 (where χ' = (Μ), Co3.x,, Fex., 〇4 or Co3.x"aix"〇4 (where x&quot ; =0-2). The cerium oxide carrier sizing solution preferably comprises 〇.!·!〇m〇1% Co3-xMx04, wherein the lanthanide Fe or A1 and χ=0·2» can be used in the mixed metal cobalt oxidation The perovskite may have the formula ΑΒ〇3, wherein ruthenium may be selected from the group consisting of La, Nd, Sm and Pr, and the ruthenium may be selected from the group consisting of c, optionally containing Ni, Cr, Μη, Cu, Fe and Y. Partial substitutions (eg, up to 20 mol%) can be carried out by divalent or tetravalent cations (eg, Sr2+ or Ce4+). In addition, 'if needed' can be partially substituted for B-point elements by another element (eg Up to 50 mol%). Suitable perovskites include

LaCo03, LaNxSrxCo03, LahCexCoOW where xs〇.2) and LaCuyCc^C^ (where yS0.5). In a preferred embodiment, the mixed metal cobalt oxide is effective as a nitric oxide decomposing catalyst and is used for ammoxidation. Therefore, the most preferable mixed metal cobalt oxide is a composition fine particle containing an oxide of cobalt and other metals (specifically, rare earth), as described in EP-B-0946290, "The preferred catalyst contains the following oxides (a) And at least one element Vv selected from the group consisting of ruthenium and fins and at least one element Vn selected from the group consisting of immutable rare earths and lanthanum, and (b) cobalt, the cobalt and element Vv&VlUt examples (το V Vv and element Vn) The atomic ratio of cobalt is between 〇8 and 1 2, at least some of which are present as mixed oxide phases, and less than π% cobalt (in atomic juice) is present as free cobalt oxide. Preferably, the chain (by atom) of less than 25 〇/〇 162246.doc 201240727 is present as free cobalt oxide, more preferably less than 150/. The cobalt (in atomic number) is present as cobalt monoxide. The ratio of the different phases can be determined by X-ray diffraction (XRD) or thermogravimetric analysis (TGA), which utilizes the weight loss associated with the thermal decomposition of the characteristic properties performed in air at about 930 Torr. Preferably, ' less than 1% by weight, in particular less than 5% by weight, of the composition is free cobalt trioxide and less than 2% by weight is free cobalt monoxide. Therefore, a perovskite phase such as VnC〇〇3 or VvC〇〇3 may be mixed with other phases such as Vv2〇3, Vn2〇3, (ννχνηι χ)2〇3 or VvxVni-x〇2. The best mixed metal sulfoxide is _ do {〇〇3 (where XS0.2), such as La〇.8Ce〇.2Co〇3. Such materials can be prepared according to the examples of Ep B 〇 94629(R), which is incorporated herein by reference. The mixed metal cobalt oxide fine particles preferably have i_8 〇 μηη, preferably 丨_5 〇 μπι, more preferably 1-30 μηη, especially i_10 gmid 5 〇 average particle diameter. In order to form a slurry, the mixed metal cobalt oxide fine particles are dispersed in a liquid medium, and the liquid medium is preferably aqueous. The solid content of the slurry is preferably between 1 〇 6 〇 重量 %. (4) It should be formed by the grinding technology used in the preparation of the catalyst coating. Adhesive materials such as cerium oxide, titanium dioxide, oxidized or hydrated oxidized sol may be included and other conventional coating preparation techniques may be applied, such as grinding and mixing the dispersion to achieve the desired particle size prior to coating the carrier. In a preferred embodiment, the poly-liquid contains a polyethylene graft copolymer, such as the material that has been used for the coating of the coating to reduce the surface tension of the coating, which increases the wetting and droplets during spraying. Forming and imparting a degree of plasticization of the layer so that it is resistant to the appearance of the coating itself. For example, the extrudate pellet or the shaped carrier is in the form of a shaped unit. 162246.doc 201240727 granules The carrier material is prepared and: a binder. The extrudate and the pellet are preferably shaped carriers. The extrusion 2: the lubricant granules can be purchased or can be easily prepared by the skilled person. Suitable powders and = early elements can have a variety of shapes and particle sizes, depending on the manufacture or house mold. For example, the units may be spheres, pore units, or A1 or multiple extrudates iJ may have a leaf-shaped cross section. Although the material or pellet may be spherical or cylindrical, i.e., circular in cross section, it is preferably in the form of a shape or a trough to increase the geometric surface area without increasing the thickness of the layer formed by the unit (4). This has the advantage of minimizing the drop in the bed through the catalyst bed. The forming unit should preferably have a minimum unit size, preferably in the range of i to 5 〇. The smallest dimension can be a width 'e.g. diameter or length, such as height. The forming unit may have a length of from i to 50 Å, preferably from i 2 to 25 咖. The cross-sectional width or diameter of the forming unit may range between about 25 mils and preferably between 1.2 ft and 10 mm, especially between 丨2 _ and 5 _. The aspect ratio 'i.e., the ratio of the largest dimension to the smallest dimension, such as length/section' is preferably less than ten. The use of molding enamels of these dimensions facilitates catalyst recovery and recycling. The shaped oxidic support can be a high temperature resistant oxide comprising alumina, vermiculite, aluminosilicate, titanium dioxide, oxidizing, oxidation. One or more of magnesium, cerium oxide or antimony trioxide, including a layered structure, wherein the shaped support comprises two or more supported oxides in a layered configuration. Preferably, the oxidizing support comprises a high temperature stable oxide such as a metal aluminate cement or alpha _ I62246.doc 201240727 alumina. If desired, the porosity or other characteristics of the forming unit, such as the 表面τ surface area, wear resistance or compressive strength, can be varied by physical or chemical treatment. For example, the shaped unit can be calcined to a temperature > 900t or treated with an organic or inorganic compound. In particular, we have found that when the shaped carrier is coated with a thin layer of zirconia particles by the same flat disk coating method, and then the mixed metal cobalt oxide slurry is applied, the abrasion resistance of the coated catalyst is remarkably enhanced. The oxidized stagger layer is preferably present in the dry catalyst in an amount of 〇·5·15 wt%, preferably 2-8 wt%. The mixed metal cobalt oxide particles are present in the surface layer of the carrier. The layer coating of the molding unit can be applied to the molding unit particles by spraying the mixed metal-containing oxide particles onto the heated roll-formed carrier unit in a flat plate coater, the flat coating machine It may be of the type used in the pharmaceutical or food industry for the preparation of coated spin products. These devices are commercially available. Multiple sprays can be applied between drying and spraying. Preferably, the slurry is applied to the carrier at a temperature of 30, preferably 30 to 50 °C. In this way, the carrier is not too moist and avoids the possibility of spray drying the slurry. The resulting coated material is then dried. The drying step can be carried out at a temperature of preferably 20-120 ° C, preferably 95-11 ° C, in air or an inert gas such as nitrogen, or in a vacuum oven for up to 24 hours. . The thickness of the layer containing the mixed metal cobalt oxide in the dried material is preferably from 5 to 250, (micrometers) but more preferably from 5 to 15 micrometers, and most preferably from 1 to 10 micrometers. Thinner layers can be used more efficiently (10). The thickness of the cobalt-containing layer can be determined by the method of 162246.doc 201240727, which is familiar to those skilled in the art, and is also known by conventional methods. For example, in this case, the light (d) micromethod is used to measure the color of the colored oxide compound on the surface of the white oxide support. Another electron microscopic probe analysis can be used to determine the thickness of the cobalt-containing coating. The loading amount is preferably from 1 to 15 parts by weight of the mixed metal cobalt oxide in the dry catalyst amount, more preferably from 2 to 10% by weight. Preferably, the dry catalyst precursor is calcined, i.e., heated at a temperature above 250 t (e.g., 250-1000 C) for 5-5 hours to prepare a catalyst that is stable under the operating conditions of the ammoxidation process. However, in the method of the present invention, it is not necessary to provide an active catalyst 'satin burning. The dried or consumed microparticles can be supplied to the audible container. This can be in the form of a fixed bed in a conventional catalyst carrier through which the reaction gas passes axially. S 'mixed metal oxide catalyst particles can be used in traditional Pt-based gold; | and / or Pd-based complement nets below ^ These particle bed thickness is generally UOOmm, preferably 3〇0mm, better $1〇 〇_. Or the 'particles can be supplied to the oxygen oxidizing vessel in a radial flow catalyst carrier structure' as described in the case of 2//75. With this configuration, in the case of the low-pressure ammonia oxidation method, the catalyst assembly comprises 15 g of 2 precious metal gas oxidation catalyst networks, and - or a plurality of palladium trapping nets and one of the oxidized dinitrogen oxides The radial flow bed of the forming unit of the medium. Also in a high pressure apparatus, there may be less than 15, for example 10, a noble metal ammoxidation catalyst network, and a capture network and a nitrite-decomposing catalyst bed 1 such as a 'catalyst assembly' It may contain 1 or less platinum or platinum alloy ammonia oxidation catalyst network '- or multiple (four) supplement network, a mixed metal rare earth chain contact catalyst 162246.doc 201240727 radial flow bed of the molding unit. In a preferred embodiment, the catalyst assembly comprises 10 or fewer # or surface alloy ammoxidation catalyst networks, and - or more comprising < 5 wt% _ replenishment nets and - mixed metal rare earths A radial flow bed of a titanium ore catalyst forming unit, which is prepared in accordance with the present invention. In the reaction of ammoxidation to -nitrogen oxide to prepare nitric acid, the oxidation method can be carried out at a temperature of 75 〇 1 () (for generations, specifically 95 generations, absolute pressure) to 15 (high pressure) bar. The concentration of ammonia in air is Μ vol% 'usually about 1 G volume. /. . In the Andrewsov method, in which the ammonia is oxidized with air in the presence of hydrazine to produce hydrogen cyanide, the preparation conditions are similar. Under the preparation conditions described so far, the ammonia gas passing through the noble metal catalyst network is usually sufficiently oxidized, and then, if necessary, the resulting nitrogen oxides are decomposed into the catalyst bed by nitrous oxide. In addition to reduced process efficiency, the operation otherwise exposes the operator to an undesired high risk of directing ammonia (i.e., "ammonia slip") to a nitrogen oxide absorber that can form explosive ammonium nitrate. # By decomposing the oxidized oxidizing gas into the catalyst and the human catalyst assembly, the controlled portion of the gas fed to the noble metal catalyst can be passed, and the nitrous oxide decomposition catalyst is also an effective ammonia oxidation catalyst. . This can reduce the amount of precious metal catalyst required or can increase the ammonia flow rate. In addition, conventional precious metal mesh catalysts, as previously mentioned, lose platinum usage, which is ultimately sufficient to cause conversion losses and increase the risk of ammonia slip. The combination of precious metal and mixed metal cobalt oxide catalyst under better conditions can increase the catalyst life or extend the "furnace period" before shutting down to replace the precious metal catalyst, because this preferred nitrous oxide decomposition catalyst can effectively catalyze Ammonia oxidation. The extended furnace life is critical and highly demanding for the operator of the plant. The method uses the catalyst prepared by the method described herein to convert the ammonia height to I62246.doc -10·201240727, and the aggregate concentration is less than 1600 ppm, preferably less than 6〇〇ppm, more preferably lower than 500 ppm and preferably less than 2 〇〇 ppm, for example 50-200 ppm when nitrous oxide is used to eliminate catalyst particles. The invention will now be further elucidated with reference to the following examples. Particle coating was performed using a Profile Automation Pilot XT bench top vented flat plate coater or a Capco Conical experimental mixer. The paint is applied by the spray pump feed, and the peristaltic pump (Wats〇n Mad〇w 101U/R) supplies the paint by a polysulfide tube (outer diameter 8 mm, inner diameter 5 mm). Flat Plate Coating Machine Pre-grinding the slurry with an Eiger Torrence Mini Motor Mill 250 and using 1 mm YSZ beads as the grinding media. The particle size distribution was measured using a Malvern Mastersizer laser diffraction particle size analyzer. The slurry pH was measured using a Jenway 370 pH meter and the slurry solids content was determined using Sartorius MA45 solids balance. Abrasion tests were carried out in a 135 mm diameter rotating steel flat plate with four 20 mm steel baffles. The sample (100 g) was rolled at 26 rpm for 5 minutes and the weight loss was recorded. This gives an indication of adhesion based on total weight loss, but the sample is also evaluated by ICP before and after wear to evaluate the actual paint loss percentage. • Example 1: Preparation of Catalyst 1 * a) Preparation of public liquor. La〇.8Ce〇.2Co03 material (200 g) was dispersed in demineralized water (400 g) at 2600 rpm using a Silverson mixer with a high shear head. Acetic acid was added to reduce the initial pH 9.5 to 7.3, and the slurry was ground at 350 rpm for 8 minutes. The particle size and d (50) were determined to be 2.1 μm. The solids content was 24.27% 〇 162246.doc 201240727 b) Coating. The α_Αΐ2〇3 cylinder (262 g, 3 mm x 3 mm) in a flat plate coater was heated to 55 °C. Kollicoat IR (2.36 g) was dissolved in demineralized water (200 ml) and added to the slurry (324 g) prepared in (a). The coating was applied using a flat plate coating apparatus. The pellet was kept at 40_5 Torr during coating. Hey. The product was dried in an oven at 105 ° C and calcined at 5001 for 2 hours. The catalyst 1 was found to have a La0.8Ce0.2CoO3 loading of 3.9% by ICP elemental analysis. Example 2: Preparation of Catalysts 2 and 3 a) Slurry preparation. La0.8Ce0.2CoO3 material (700 g) was dispersed in demineralized water (1 556 g) at 2600 rpm using a silverson mixer with a high shear head. The mixture was milled at 350 rpm for 1 minute. The particle size and d (50) were determined to be 4.7 μm. The pH was 9.8 and the solids content was 43.36%. Dispersible boehmite Dispera® 10/7 (61.5 g) (Sasol) was added to the slurry and mixed for 1 minute using a Silverson mixer. b) Coating - Catalyst 2. The α-Α1203 cylinder (1500 g '3 mm><3 mm) in a Pilot XT flat plate coater was heated to 50 °C. A 3 wt% oxidized base coating was applied to the pellets using NanoUse Zr40 BL colloidal oxidation (37.5 g) (Nissan Chemical, APS 6-8 nm), followed by catalyst coating immediately and coated in a flat plate Dry at 50 ° C in a cloth machine. Kollicoat IR (7.50 g) was dissolved in demineralized water (58 ml) and added to the coating (344 g) prepared in (a). Catalyst coating uses the same coating parameters as the substrate coating. The product was dried in a coater at 50 ° C in flowing air and calcined at 500 t for 2 hours. Catalyst 2 was found to have a 5.3% 2La0.8Ce0.2CoO3| loading by ICP elemental analysis. c) Coating-catalyst 3. Heat the α·Α12〇3 cylinder 162246.doc 201240727 (1500 g ′ 3 mmx3 mm) in the Pilot XT flatbed coater to 50 °C. Kollicoat IR (3.75 g) was dissolved in demineralized water (58 ml) and added to the coating (344 g) prepared in (a). The product was dried in a coater at 50 ° C in flowing air and calcined at 500 ° for 2 hours. Catalyst 3 was found to have a 4.3% La0.8Ce0 2CoO3 loading by 1 〇 elemental analysis. 3: Abrasion test The catalysts 2 and 3 were subjected to the abrasion test as described above. The results are as follows;

Zr02 Substrate Coating Loss of Coating (%) Catalyst 2 ~ Yes 8 Catalyst 3 No 35 Oxidation recording base coating significantly improves the wear resistance of the catalyst. Example 4: Catalyst selectivity The lL oxidation test was carried out in a laboratory apparatus using a 5 Torr/〇nh 3 gas stream at a heating rate of 20 ° C / min and at 800 ° C for 30 minutes. Catalysts i and 2 were compared to commercially available ammonia oxidation catalysts under the same conditions. The results are as follows; Catalyst Γ" Cobalt content 詈% selectivity (%) NO N20 n2 Commercially available catalyst 24.0 95,4 0.82 3.8 Catalyst 1 0.9 95.3 0.49 4.2 Catalyst 2 1.3 95.2 0.78 4.0 The result shows 'three kinds of catalysts The high NO conversion rate, under the conditions produced under these conditions, the catalysts 1 and 2 are less than the commercial catalyst, and the Co content is significantly lower. 162246.doc

Claims (1)

201240727 VII. Patent application scope: 1. A method for preparing a catalyst composition for dropping an ammonia oxidation method, the method comprising the following steps: (i) containing right, and Japanese human heart metal oxide oxide particles The slurry is sprayed on a flat plate coating. The surface of the carrier is formed in a cloth machine to form a coated carrier material, and () dry = and, as the case may be, the coated carrier material is fired to form a surface layer containing the present Catalyst for metal oxides. 2. If the request item 丨古古 /Κ, 八八中 The slurry contains mixed metal uranium oxide 2 or mixed metal cobalt oxide perovskite. The method of claim 2, wherein the spinel has a core 2〇4, wherein two: is selected from the group consisting of ’1 or Cr. The method wherein the perovskite has the formula ab〇3, the straight/main is selected from the group consisting of La, Nd, P, &, S and 1^, and the B is selected from Co, optionally containing Ni, 5 n eu, Fe And Y, as the case may be replaced by a divalent or tetravalent cation moiety ^ A' with another _8 elemental moiety. The method of any one of the preceding claims wherein the mixed metal diamond oxidizes - nitrous oxide decomposes the catalyst and is used for ammoxidation. 6. If any of the requirements of items 1 to 4, the 土 古 . 土 土 勺 τ τ τ τ τ τ τ τ τ τ τ 其中 其中 其中 其中 其中 其中 其中 La La La La La La La La La La La La La La La La La La La La La La La An ancient soil method, wherein the shaped carrier is a "warm oxide" comprising a carrier selected from the group consisting of oxidized sulphate, (iv) acid, oxidized sharp, oxidized, oxidized, dioxin, and mixtures thereof. Extra-gas from P to oxidize mono-Oxide oxide, including layered structure, 162246.doc 201240727, Zhongcheng i carrier contains two or more carrier oxides in a layered configuration 0 8. As requested in item 1 A method according to any one of the preceding claims, wherein the carrier comprises a metal acid salt cement or an alpha-oxide. 9. If the method of claim 1 to 4 is in the form of a sigma*, +^, the method of the article And an oxidized outer layer on which the mixed cobalt oxide layer is applied. The shaped support comprises a product, pellet or granule of the method of any one of claims 1 to 4. The method of any one of claims 1 to 4, having a cross-sectional width or straightness of mm to 25 mm The length of mm to 50 mm, and the diameter of one. 12. The method of any of the above items, wherein the shaped carrier unit has a circular cross section of a leaf shape. Sub-tank porous pellet or extrudate. 13. The method according to any one of claims 1 to 4, wherein the carrier is coated at a temperature of 30 to 60 ° C. wherein the slurry is solid The method of any one of claims 1 to 4, wherein the method comprises a range of from 1 to 60% by weight, wherein the polyethylene graft copolymer comprises a dry supported type in which the dry material is mixed. The method of any one of claims 1 to 4 is carried out in the slurry. The method of any one of claims 1 to 4, wherein the cobalt compound is calcined. The thickness of the layer of cobalt oxide is 5-250 μη. 18. The catalyst can be obtained according to the method of request 丨 to 17 _ ^ χ ^ any term. I62246.doc 201240727 19. A request item 1 The catalyst of 8 or the use of the catalyst obtained by the method of any one of claims 1 to 7 for the ammoxidation Or used to reduce the oxidation of nitrogen dioxide by the ammonia oxidation method. 162246.doc 201240727 IV. Designated representative map: (1) The representative representative of the case is: (none) (2) The symbol of the representative figure is simple: If there is a chemical formula in this case, please reveal the chemical formula that best shows the characteristics of the invention: (none) 162246.doc