METHOD FOR APPLYING A WASH COAT SUSPENSION TO A CARRIER STRUCTURE

• US 20100311573A1
• Filed: 06/02/2008
• Published: 12/09/2010
• Est. Priority Date: 05/31/2007
• Status: Active Grant

• Current Assignee: Clariant Produkte AG (Clariant AG)
• Original Assignee: Sud-Chemie AG (Clariant AG)
• Inventors: Estenfelder, Marvin, Gückel, Christian, Kading, Bastian, Mestl, Gerhard
• Granted Patent: US 8,722,565 B2
• Time in Patent Office: Days
• US Class Current: 502/170
• CPC Class Codes: B01J 2/16 by suspending the powder material in a gas, e.g. in fluidised beds or as a falling curtain
• CPC Class Codes: B01J 23/002 Mixed oxides other than spinels, e.g. perovskite
• CPC Class Codes: B01J 23/22 Vanadium
• CPC Class Codes: B01J 23/881 and iron
• CPC Class Codes: B01J 23/8885 containing also molybdenum
• CPC Class Codes: B01J 2523/00 Constitutive chemical elements of heterogeneous catalysts
• CPC Class Codes: B01J 2523/15 Caesium
• CPC Class Codes: B01J 2523/17 Copper
• CPC Class Codes: B01J 2523/47 Titanium
• CPC Class Codes: B01J 2523/51 Phosphorus
• CPC Class Codes: B01J 2523/53 Antimony
• CPC Class Codes: B01J 2523/55 Vanadium
• CPC Class Codes: B01J 2523/68 Molybdenum
• CPC Class Codes: B01J 2523/69 Tungsten
• CPC Class Codes: B01J 35/40 characterised by dimensions, e.g. grain size in a colloidal state B01J35/23; crystallite size B01J35/77
• CPC Class Codes: B01J 37/0232 by pulverisation
• CPC Class Codes: C07C 57/04 Acrylic acid; Methacrylic acid

Abstract

A method for applying a washcoat suspension to a support structure. To provide coatings with largely uniform thickness starting from washcoat suspensions, the method uses a device (10) set up to produce, by means of a process gas (40), a fluid bed of support structures in which the support structures circulate elliptically or toroidally, the method comprising the steps of:

• a) charging the device (10) with support structures and producing a support-structure fluid bed by means of a process gas (40), wherein the support structures circulate in the fluid bed elliptically or toroidally, preferably toroidally;
• b) impregnating the support structures with a washcoat suspension by spraying the support structures circulating elliptically or toroidally in the fluid bed with the washcoat suspension;
• c) drying the support structures sprayed with the washcoat suspension; and
• d) optionally calcining the support structures loaded with the solids contents of the washcoat suspension.

Claims

1-32. -32. (canceled)

33. A method for applying a washcoat suspension to a support structure, wherein the method is carried out using a device (10) which is set up to produce, by means of a process gas (40) a fluid bed of support structures in which the support structures circulate elliptically or toroidally, preferably toroi daily, said method comprising the steps of:

a) charging the device (10) with support structures and producing a support-structure fluid bed by means of a process gas (40), wherein the support structures circulate in the fluid bed elliptically or toroidally, preferably toroidally;

b) impregnating the support structures with a washcoat suspension by spraying the support structures circulating elliptically or toroidally in the fluid bed with the washcoat suspension;

c) drying the support structures sprayed with the washcoat suspension; and

d) optionally calcining the support structures loaded with the solids contents of the washcoat suspension.

34. The method according to claim 33, wherein the device (10) comprises a process chamber (15) with a bottom (16) in the centre of which bottom an annular gap nozzle (50) is arranged.

35. The method according to claim 34, wherein the process chamber (15) furthermore comprises a side wall (18), wherein the process gas (40) is fed, with a horizontal movement component aligned radially outwards, into the process chamber (15) through the bottom (16) of the process chamber (15), the bottom being preferably constructed of several overlapping annular guide plates laid one over the other (25, 26, 27, 29) between which annular slots (28) are formed, in order to produce the support-structure fluid bed.

36. The method according to claim 35, wherein the process gas (40) fed into the process chamber (15) is subjected to a circumferential flow component.

37. The method according to claim 36, wherein the process gas (40) fed into the process chamber (15) is subjected to the circumferential flow component by means of guide elements which are arranged between the annular guide plates (25, 26, 27, 29).

38. The method according to claim 36, wherein the process gas (40) fed into the process chamber (15) is subjected to the circumferential flow component by feeding additional process gas (61), with a movement component aligned diagonally upwards, through the bottom (16) of the process chamber (15) into the process chamber (15), preferably in the area of the side wall (18) of the process chamber (15).

39. The method according to claim 34, wherein the annular gap nozzle (50) atomizes a spray cloud (70) which runs parallel to the plane of the bottom (16).

40. The method according to claim 39, wherein the mouth (55) of the annular gap nozzle (50) is embedded into the fluid bed.

41. The method according to claim 39, wherein a gas support cushion (72) is produced on the underside of the spray cloud (70).

42. The method according to claim 33, wherein the support structure is formed from a non-porous material or material mixture, preferably from steatite, quartz (SiO₂), porcelain, magnesium oxide, tin dioxide, silicon carbide, rutile, alumina (Al₂O₃), aluminium silicate, magnesium silicate, zirconium silicate or from cerium silicate or from mixtures of two or more of the above materials.

43. The method according to claim 33, wherein the support structure has a hardness greater than/equal to 20 N, preferably greater than/equal to 30 N, further preferably greater than/equal to 40 N and most preferably greater than/equal to 80 N.

44. The method according to claim 33, wherein the process gas (40) is selected from the group consisting of air, oxygen, nitrogen and the noble gases, preferably helium and argon.

45. The method according to claim 33, wherein the process gas (40) is heated, preferably to a temperature of more than/equal to 40°

C., by preference to a temperature of more than/equal to 60°

C., further preferably to a temperature of more than/equal to 70°

C. and most preferably to a temperature of 60 to 100°

C.

46. The method according to claim 33, wherein the process gas (40) is enriched, before being fed into the process chamber (15), with the suspending agent of the washcoat suspension, for example water, preferably in a range of 10 to 50% of the saturation vapour pressure.

47. The method according to claim 33, wherein the support structure is formed as sphere, cylinder, perforated cylinder, trilobe, tetralobe, ring, doughnut, star, cartwheel or as strand, preferably as ribbed strand or star strand.

48. The method according to claim 33, wherein the washcoat suspension contains TiO₂, V₂O₅ and Sb₂O₃ in particulate form.

49. The method according to claim 48, wherein the suspension furthermore comprises a phosphate compound, an alkali and/or alkaline earth compound, and an organic and/or inorganic binding agent.

50. The method according to claim 48, wherein the washcoat suspension is sprayed onto a ring as support structure.

51. The method according to claim 33, wherein the washcoat suspension contains iron molybdate.

52. The method according to claim 33, wherein the washcoat suspension contains a mixed oxide of Mo, V and W, or Mo, V and Nb, or Ta as well as optionally Te or Sb, which is preferably doped with Cu, Mn or Fe.

53. A shell catalyst produced according to the method of claim 33, comprising a shaped body to which a shell comprising a metal-oxide material is applied, wherein the shell catalyst is an element of a batch of a plurality of shell catalysts, wherein the ratio of the standard deviation of the shell thicknesses of the shell catalysts of the batch to the mean value of the shell thicknesses of the shell catalysts of the batch is smaller than/equal to 20%, preferably smaller than/equal to 15%, by preference smaller than/equal to 12% and more preferably smaller than/equal to 10% or 3 to 18%, preferably 3 to 15%.

54. The method of claim 33, wherein a device (10) produces, by means of a process gas (40), a fluid bed of support structures in which the support structures circulate elliptically or toroidally, preferably toroidally, for applying a washco at suspension to a support structure.

55. The method of claim 54, wherein the device (10) comprises a process chamber (15) with a bottom (16) in the centre of which bottom an annular gap nozzle (50) is arranged.

56. The method of claim 55, wherein the process chamber (15) furthermore comprises a side wall (18), wherein the bottom (16) is constructed of several overlapping annular guide plates laid one over another (25, 26, 27, 29) between which annular slots (28) are formed via which process gas (40) can be fed in with a horizontal movement component aligned radially outwards.

57. The method of claim 55, wherein the mouth (55) of the annular gap nozzle (50) is formed such that with the nozzle (50) a spray cloud (70) can be sprayed which runs parallel to the bottom plane.

58. The method of claim 57, wherein outlets (59) for support gas are provided between the mouth (55) of the annular gap nozzle (50) and the bottom (16) lying beneath it, in order to produce a support cushion on the underside of the spray cloud (70).

59. The method of claim 58, wherein the support gas can be provided by the annular gap nozzle (50) itself and/or by the process gas (40).

60. The method of claim 55, wherein the annular gap nozzle (50) has a conical head (57), and in that the mouth (55) runs along a circular circumferential line of a conical section.

61. The method of claim 55, wherein there is arranged in the area between the mouth (55) of the nozzle (50) and the bottom (16) lying beneath it a truncated-cone-shaped or hyperbolic wall (58) which preferably has passage openings (59) for support gas.

62. The method of claim 61, wherein an annular slot (60) for the passage of process gas (40) is formed between the underside of the truncated-cone-shaped or hyperbolic wall (58) and the bottom (16) lying beneath it.

63. The method of claim 55, wherein the position of the mouth (55) of the nozzle (50) is height-adjustable.

64. The method of claim 56, wherein guide elements which impose a circumferential flow component on the process gas passing through are arranged between the annular guide plates (25, 26, 27, 29).