METHODS FOR REPROCESSING USED CATALYSTS

Abstract

The following invention relates to methods for reprocessing SCR catalysts. In a first embodiment, the invention relates to a method for reprocessing SCR catalysts, wherein an oxygen-containing compound of titanium and tungsten or molybdenum is removed from the catalyst and is then reacted with a vanadium compound. In a second embodiment, the invention relates to a method for removing titanium oxide and vanadium, molybdenum, and tungsten compounds from SCR catalysts and to a method for reusing these compounds in such catalysts.

Claims

1.-30. (canceled)

31. A method for reprocessing a used catalyst including an oxygen- containing compound of titanium, vanadium, and at least one of the elements molybdenum or tungsten, comprising at least step (T4): (T4) heating of a solid fraction comprising an oxygen-containing compound of titanium and at least one of the elements tungsten or molybdenum in the presence of a vanadium compound at a temperature >200 C., and further comprising steps (T1) through (T3) prior to step (T4): (T1) bringing into contact of the used catalyst with an aqueous base, thus obtaining a water-containing mass, which comprises: a liquid fraction comprising a water-soluble material, and a solid fraction, which comprises a water-insoluble material; (T2) separation of the solid fraction from the liquid fraction of step (T1); (T3) bringing into contact of the separated solid fraction of step (T2) with a vanadium compound; wherein the aqueous base of step (T1) is selected from the group composed of an aqueous alkali hydroxide, an aqueous alkaline earth hydroxide, an aqueous alkali hydrogen carbonate, an aqueous alkali carbonate, an aqueous alkaline earth carbonate, an aqueous C1-C4 alkylamine, an aqueous amino alcohol, and a mixture of at least two of the aqueous bases thereof.

32. The method as claimed in claim 31, wherein the amino alcohol is selected from the group composed of: mono-, di- and triethanolamine, dimethylaminoethanol, diethylaminoethanol, N-methyldiethanolamine, mono-, di- and triisopropanolamine, or two or more thereof

33. The method as claimed in claim 31, wherein the amino alcohol is monoethanolamine (aminoethanol).

34. The method as claimed in claim 31, wherein the temperature in step (T1) is in the range of 30 to 100 C.

35. The method as claimed in claim 31, wherein the vanadium compound is an aqueous solution or suspension of an oxygen-containing vanadium compound.

36. The method as claimed in claim 31, wherein the vanadium compound is ammonium vanadate or comprises ammonium vanadate.

37. The method as claimed in claim 31, wherein the heating of step (T4) takes place in a temperature range of 200 to 1,000 C., 300 to 900 C., 400 to 800 C., or 500 to 700 C.

38. The method as claimed in claim 31, wherein the step (T1) comprises at least one of steps (R1) through (R7): (R1) mechanical cleaning of the used catalyst, preferably by ultrasound or pressurized gas, preferably compressed air; (R2) removal of the used catalyst from a catalyst device; (R3) crushing of the used catalyst, preferably to a grain size of 5 m to 10 mm, 5 m to 1 mm, or 5 m to 100 m; (R4) crushing of the used catalyst and separation from the crushed used catalyst of accompanying materials contained in the crushed used catalyst; (R5) bringing into contact of the used catalyst used in step (T1) or the crushed used catalyst obtained in step (R3) or the separated crushed used catalyst obtained in step (R4) with an acid; (R6) separation of the solid product obtained in step (R5); (R7) use of the product obtained in steps (R1) through (R6) in step (T1).

39. The method as claimed in claim 38, wherein the acid of step (R5) is selected from the group comprising hydrochloric acid, sulfurous acid, sulfuric acid, phosphoric acid, formic acid, acetic acid, chloroacetic acid, oxalic acid, malonic acid, citric acid, tartaric acid, methane sulfonic acid, benzene sulfonic acid, toluene sulfonic acid, sulfanilic acid, or at least two of the acids thereof.

40. The method as claimed in claim 37, wherein the temperature in step (R5) is in the range of 10 to 80 C.

41. The method as claimed in claim 31, wherein the step (T2) comprises at least step (R6): (R6) washing of the separated solid fraction.

42. The method as claimed in claim 31, wherein in the step (T1), the water-soluble material comprises a vanadium compound; and wherein the water-insoluble material comprises an oxygen-containing compound of titanium and at least one of the elements molybdenum and tungsten.

43. The method as claimed in claim 1, wherein the catalyst used is an SCR catalyst.

44. A method for producing a catalyst or an SCR catalyst, comprising the method of claim 31, and further comprising at least one of steps (W1), (W2) or (W3): (W1) application of the product obtained as claimed in step (T4) to a carrier; (W2) extrusion of the product obtained as claimed in step (T4) into a beehive; (W3) mixing of the product obtained as claimed in step (T4) with starting products for producing a catalyst, wherein the starting products are selected at least from titanium dioxide or tungsten oxide or molybdenum oxide.

Description

DETAILED DESCRIPTION OF THE INVENTION

First Embodiment

[0088] In a first embodiment, the invention relates to a method for reprocessing a used catalyst, preferably an SCR catalyst, including an oxygen-containing compound of titanium, vanadium, and at least one of the elements molybdenum or tungsten.

[0089] The phrase oxygen-containing compound of titanium, vanadium, and at least one of the elements molybdenum or tungsten includes cases in which the oxides are adjacent to one another, but preferably in the form of mixed oxides. In particular, this phrase includes cases in which at least the oxides of titanium and vanadium are present in the form of mixed oxides, which means that vanadium can occupy lattice sites in the titanium oxide.

[0090] According to the invention, the method comprises step (T4), in which a solid fraction comprising an oxygen-containing compound of titanium and at least one of the elements tungsten or molybdenum is heated in the presence of a vanadium compound pound at a temperature200 C., wherein the solid fraction is preferably obtained by means of process steps (T1) through (T4) explained below.

[0091] Before carrying out step (T4), the used catalyst is preferably brought into contact with an aqueous base in step (T1). A water-containing mass is thus obtained which comprises a solid fraction and a liquid fraction.

[0092] The liquid fraction comprises a water-soluble material, said water-soluble material preferably comprising a compound of vanadium.

[0093] The solid fraction comprises a water-insolubles material, preferably wherein the water-insoluble material comprises an oxygen-containing compound of titanium and at least one of the elements molybdenum and tungsten.

[0094] Preferably, the base used in step (T1) is selected from the group composed of: an aqueous alkali hydroxide, an aqueous alkaline earth hydroxide, an aqueous alkali hydrogen carbonate, an aqueous alkali carbonate, an aqueous alkaline earth carbonate, an aqueous ammonium carbonate or ammonium acetate, aqueous ammonia, an aqueous C1-C4 alkylamine, or an aqueous amino alcohol, or a mixture of two or more thereof.

[0095] Preferably, the amino alcohol is selected from the group composed of: mono-, di- and triethanolamine, dimethylaminoethanol, diethylaminoethanol, N-methyldiethanolamine, mono-, di- and triisopropanolamine, or two or more thereof.

[0096] In a particularly preferred embodiment, the amino alcohol is monoethanolamine (aminoethanol).

[0097] Preferably, the temperature of step (T1) is in the range of 30 to 150 C., and more preferably 30 to 100 C. or 60 to 100 C. Step (T1) can optionally be carried out with or without pressurization.

[0098] According to the invention, in step (T2), the solid fraction is separated from the liquid fraction of step (T1).

[0099] Separation can be carried out according to known methods, preferably by filtration, centrifugation, sedimentation, and draining of the supernatant. The separated residue is washed with water as needed.

[0100] According to the invention, in step (T3), the separated solid fraction of step (T2) is brought into contact with a vanadium compound and then heated according to step (T4).

[0101] Preferably, in step (T3), the vanadium compound is brought into contact with an aqueous solution or suspension of an oxygen-containing vanadium compound.

[0102] Preferably, the vanadium compound is ammonium vanadate or comprises ammonium vanadate.

[0103] Preferably, in step (T3), contact is achieved by spraying the solid fraction with the vanadium compound, preferably in aqueous form, or by pouring or immersion.

[0104] According to the invention, in step (T4), the solid fraction comprising an oxygen-containing compound of titanium and at least one of the elements tungsten or molybdenum brought into contact in step (T3) with the vanadium compound is heated at a temperature 200 C.

[0105] Heating is preferably carried out in such a way that a solid-state reaction takes place between the solid fraction and the vanadium compound. In this solid-state reaction, vanadium ions are preferably incorporated into the lattice of the oxygen-containing titanium compound. This can be investigated by conventional x-ray tests.

[0106] Preferably, the heating of step (T4) takes place in a temperature range of 300 to 1,000 C. or 400 to 800 C. or 500 to 700 C.

[0107] Heating can preferably be carried out in conventional tunnel furnaces, rotary furnaces, or muffle furnaces.

[0108] The method of steps (T1) through (T4) can further include process steps.

[0109] Preferably, the method also comprises in step (T1) at least one of steps (R1) through (R7): [0110] (R1) mechanical cleaning of the used catalyst; [0111] (R2) removal of the used catalyst from a catalyst device; [0112] (R3) crushing of the used catalyst, preferably to a grain size of 5 m to 10 mm or 5 m to 1 mm or 5 m to 100 m; [0113] (R4) crushing of the used catalyst and separation from the crushed used catalyst of accompanying materials contained in the crushed used catalyst; [0114] (R5) bringing into contact of the used catalyst used in step (T1) or the crushed used catalyst obtained in step (R3) or the separated crushed used catalyst obtained in step (R4) with an acid; [0115] (R6) separation of the solid product obtained in step (R5); [0116] (R7) use of the product obtained in steps (R1) through (R6) in step (T1).

[0117] Before carrying out the actual method according to the invention, in step (R1), the used SCR catalysts can therefore, in a first step, be mechanically cleaned of adhering substances, preferably by ultrasound or pressurized gas, preferably compressed air.

[0118] In a second step, the catalysts can be removed from the metallic housings or holders that are ordinarily present [step (R2)].

[0119] In the case of plate catalysts, physical separation of the ceramic coating from the metallic carrier substrate can also take place.

[0120] After this, the SCR catalysts, or in the case of plate catalysts, the ceramic coating mass separated from the metallic carrier substrate, can be mechanically crushed into a powder or into small pieces [step (R3)].

[0121] Preferably, the crushing of step (R3) is carried out in a ball mill or a hammer mill.

[0122] Preferably, the used catalyst is crushed to a grain size in the range of 5 m to 10 mm, more preferably 5 m to 1 mm, and even more preferably 5 m to 100 m. In this case, the grain size distribution can be determined by means of common laser scattered-light methods.

[0123] Preferably, in step (R3), the used catalyst can also be crushed, and the crushed used catalyst can be separated from accompanying materials contained in said crushed used catalyst, wherein step (R4) is achieved.

[0124] In order to remove easily-soluble components or other adhering impurities, the crushed ceramic mass can be washed with water in a suspension, preferably an aqueous acid with a pH between 1 and 6.8 [step (R5)].

[0125] Preferably, the acid of step (R5) is selected from the group composed of: hydrochloric acid, sulfurous acid, sulfuric acid, nitric acid, phosphoric acid, formic acid, acetic acid, chloroacetic acid, oxalic acid, malonic acid, citric acid, tartaric acid, methane sulfonic acid, benzene sulfonic acid, toluene sulfonic acid, sulfanilic acid, or two or more thereof.

[0126] Preferably, the temperature in step (R5) is in the range of 10 to 60 C.

[0127] The crushed ceramic mass can also be treated with water in a suspension, preferably an aqueous acid with a pH between 1 and 6.8.

[0128] After this, the insoluble components of the suspension can be separated from the aqueous medium, preferably by filtration, centrifugation, sedimentation, and draining of the supernatant [step (R6)]. The separated residue is washed with water as needed.

[0129] The product obtained in one of steps (R1) through (R6) can be used as the starting product in step (T1).

[0130] Preferably, step (T2) comprises at least step (R8): [0131] (R8) washing of the separated solid fraction, preferably with water.

[0132] Further subject matter of the invention is also a composition comprising a solid fraction including an oxygen-containing titanium compound and at least one oxygen- containing compound of at least one of the elements molybdenum and tungsten and a liquid fraction comprising an aqueous base and a water-soluble compound of vanadium.

[0133] Further subject matter of the invention is also a method for producing a catalyst or an SCR catalyst comprising a method as defined above, and further comprising at least one of steps (W1), (W2) or (W3): [0134] (W1) application of the product obtained according to step (T4) to a carrier; [0135] (W2) extrusion of the product obtained according to step (T4) into a beehive; [0136] (W3) mixing of the product obtained according to step (T4) with starting products for producing a catalyst, wherein the starting products are selected at least from titanium dioxide or tungsten oxide or molybdenum oxide.

[0137] Steps (W1) through (W3) in the method according to the invention are carried out analogously to known methods, and therefore do not need to be explained in further detail here.

Second Embodiment

[0138] Before carrying out the actual method according to the invention, the used SCR catalysts can be mechanically purified of adhering substances in a first step [step (S0.1)].

[0139] In a second step, the catalysts can be removed from the metallic housings or holders that are ordinarily present [step (S0.2)].

[0140] In the case of plate catalysts, physical separation of the ceramic coating from the metallic carrier substrate can also take place.

[0141] After this, the SCR catalysts, or in the case of plate catalysts, the ceramic coating mass separated from the metallic carrier substrate, can be mechanically crushed into a powder or into small pieces [step (S0.3)].

[0142] In order to remove easily-soluble components or other adhering impurities, the crushed ceramic mass can be washed with water in a suspension, preferably an aqueous acid with a pH between 1 and 6.8 [step (S0.4)].

[0143] The crushed ceramic mass can also be treated with water in a suspension, preferably an aqueous acid with a pH between 1 and 6.8. After this, the insoluble components of the suspension can be separated from the aqueous medium, preferably by filtration, centrifugation, sedimentation, and draining of the supernatant. The separated residue is washed with water as needed.

[0144] After this, the crushed mass according to the invention is preferably refluxed with an aqueous solution of ammonia or an amine-containing aqueous solution [step (S1)]. Primary, secondary, and tertiary amines can be used, preferably amines with 1 to 30 carbon atoms. In this case, Mo/V/W or compounds thereof are dissolved as amines in the aqueous solution of molybdate/vanadate/tungstate. TiO.sub.2 and SiO.sub.2 and/or Al.sub.2O.sub.3 remain as residue.

[0145] The suspension obtained can be cooled and the remaining residue can be separated from the liquid fraction [step (S2)]. This residue can again be washed with water.

[0146] The separated liquid fraction can then be concentrated by partial removal of the solvent. Further processing to obtain pure (NH.sub.4).sub.6Mo.sub.7O.sub.24 and (NH.sub.4).sub.10W.sub.12O.sub.41 is described in the patents EP 0555128 A1, WO 1999/058732, and EP 0477450 B1 for Mo/V separation in petrochemical catalysts or can be carried out analogously to this method [steps (S4), (S4.1), (S4.2)].

[0147] The residue of step (S2) is then heated in sulfuric acid and can be left therein for several hours while stirring. TiO.sub.2 is dissolved out from Ti(SO.sub.4).sub.2 and TiOSO.sub.4. SiO.sub.2 and/or Al.sub.2O.sub.3 remain(s) behind as an insoluble residue [step (S3)].

[0148] The residue is separated from the strongly acidic solution [step (S5)]. Optionally, the solution can first be slightly diluted with water.

[0149] The clear sulfuric acid solution is then diluted with water and optionally heated until an amorphous solid precipitates which comprises meta-titanic acid Ti(OH).sub.2O or consists of this acid [step (S6)].

[0150] This solid is isolated, preferably by common methods such as filtration or centrifugation [step (S7)]. The solid can be washed with water in order to remove acid residues, and can optionally be dried.

[0151] The BET area of this product is approx. 350 m.sup.2/g, which is relevant for low-SO.sub.2 conversion. This product can therefore be directly used in the production of catalysts, which is highly advantageous.

[0152] Alternatively, this obtained amorphous solid can be heated for further processing, preferably to temperatures <1,000 C., more preferably <650 C., and preferably in a rotary furnace. In this case, crystalline TiO2 of the anatase type forms [step (S8)].

[0153] The raw materials obtained according to the invention TiO.sub.2, (NR.sub.4).sub.6Mo.sub.7O.sub.24, and (NH.sub.4).sub.10W.sub.12O.sub.41 can be reused in the production of titanium oxide-based SCR catalysts. Separated vanadium compounds may also be reused.

[0154] Steps (M1) through (M12) of the method according to the invention are carried out analogously to known methods, and therefore do not need to be discussed here in further detail.