Direct Synthesis of a Microporous Aluminosilicate Material Having an AFX Structure and Comprising Copper, and Use of said Material

Abstract

The invention concerns a process for preparing a copper-comprising microporous aluminosilicate material with AFX structure, comprising at least the steps of mixing, in an aqueous medium, at least one aluminum source, at least one silicon source, at least one copper source, a TETA or TEPA organic complexing agent and a DABCO-C4 structuring agent, in order to obtain a gel, and hydrothermal treatment of said gel with stirring in order to obtain crystallization of said copper-comprising microporous aluminosilicate material with AFX structure.

Claims

1. A process for preparing a copper-containing microporous aluminosilicate material with AFX structure, comprising at least the following steps: a) mixing, in an aqueous medium, of at least one aluminum source, at least one silicon source, sodium hydroxide, at least one copper source, an organic complexing agent chosen from triethylenetetramine (TETA) or tetraethylenepentamine (TEPA) and a structuring agent 1,4-diazabicyclo[2.2.2]octane-C4-diquat dibromide (DABCO-C4), in order to obtain a gel of molar composition: a SiO.sub.2: b Al.sub.2O.sub.3: c Na.sub.2O: d DABCO-C4: e CuO: f OCPLX: g H.sub.2O a/b being between 100 and 40, c/b being between 25 and 50, d/b being between 3 and 10, e/b being between 0.05 and 0.1, f/e being between 1 and 1.5 and g/b being between 4000 and 1000; b) hydrothermal treatment of the gel at a temperature of between 130 and 180 C., under an autogenous reaction pressure, for a period of between 1 and 8 days with stirring in order to obtain the crystallization of the copper-comprising microporous aluminosilicate material with AFX structure; c) drying heat treatment of the solid obtained at the end of the preceding step at a temperature of between 80 and 120 C. under a stream of inert gas followed by calcining under dry air at a temperature of between 400 and 600 C.; d) ion exchange comprising bringing the solid obtained the end of the preceding step into contact with a solution comprising a species capable of releasing copper in solution in reactive form with stirring at ambient temperature for a period of between 1 h and 2 d; e) drying heat treatment of the solid obtained at the end of the preceding step at a temperature of between 80 and 120 C. followed by calcining under a stream of inert gas and then air at a temperature of between 400 and 600 C.; the total amount of copper contained in the material obtained at the end of the preparation process being between 1.5 and 5.75% by weight relative to the total weight of the material in its anhydrous form.

2. The process as claimed in claim 1, wherein steps c) and d) are inverted.

3. The process as claimed in claim 1, wherein the amount of copper introduced during step a) represents between 0.75 and 2%, the amount of copper introduced during step d) representing between 0.75 and 5%, the amount of copper contained in the material being ultimately between 1.5 and 5.75%, all the percentages being percentages by weight relative to the total weight of the material in its anhydrous form obtained at the end of the preparation process.

4. The process as claimed in claim 1, wherein a maturation step at ambient temperature is carried out at the end of step a) and before step b).

5. The process as claimed in claim 4, wherein the step b) is carried out at a temperature of between 140 and 170 C.

6. The process as claimed in claim 1, wherein the step b) is carried out for a period of between 3 and 6 days.

7. The process as claimed in claim 1, wherein the step b) is carried out with stirring with a rotation of the stirring shaft of between 100 and 4000 rotations per minute.

8. The process as claimed in claim 1, wherein the step b) is carried out with stirring with a rotation of the stirring shaft of between 200 and 2000 rotations per minute.

9. The process as claimed in claim 1, wherein the dry air flow rate of the calcination treatment in the course of the step c) is between 0.5 and 1.5 l/h/g of solid to be treated.

10. A copper-comprising microporous aluminosilicate material with AFX structure obtained by a process as claimed in claim 1.

11. Use of the copper-comprising microporous aluminosilicate with AFX structure as claimed in claim 10.

12. The use as claimed in claim 11, wherein the material is formed by deposition in the form of a coating on a honeycomb structure.

13. The use as claimed in claim 12, wherein the coating comprises the material in combination with a binder such as cerine, zirconium oxide, alumina, non-zeolite silica-alumina, titanium oxide, a cerin-zirconia mixed oxide, or a tungsten oxide.

14. The use as claimed in claim 11, wherein the coating is in combination with another coating having NO reducing capacities or capacities which promote the oxidation of pollutants.

15. The use as claimed in claim 11, wherein the structure coated by the material is integrated in an exhaust line of an internal combustion engine.

16. Use of the copper-comprising microporous aluminosilicate prepared as claimed in claim 1, for the selective reduction of NO by a reducing agent such as NH.sub.3 or H.sub.2.

Description

DESCRIPTION OF THE FIGURES

[0057] FIG. 1 shows an X-ray diffraction pattern of the Cu-aluminosilicate material prepared in example 4.

[0058] FIG. 2 shows the NOx conversion results, the Ex 1, Ex 2, Ex 3 and Ex 4 curves respectively corresponding to the tests carried out with the materials prepared according to example 1, example 2, example 3 and example 4. At the abscissa point 400 C., the curves correspond, respectively, from bottom to top to Ex 1, Ex 2, Ex 3 and Ex 4.

[0059] FIG. 3 shows the NOx conversion results, the Ex 1, Ex 4, Ex 5 and Ex 6 curves respectively corresponding to the tests carried out with the materials prepared according to example 1, example 4, example 5 and example 6. At the abscissa point 400 C., the curves correspond, respectively, from bottom to top to EX 6, Ex 5, Ex 1 and Ex 4.

EXAMPLES

Example 1 (not in Accordance with the Invention)

[0060] In this example, a Cu-exchanged SSZ-16 zeolite is synthesized according to the prior art. In this example, the copper is introduced by ion exchange.

[0061] Mixing Step

[0062] 17.32 g of sodium hydroxide are dissolved in 582.30 g of deionized water, with stirring (300 rpm) and at ambient temperature. 197.10 g of sodium silicate are added to this solution and the mixture is homogenized with stirring (300 rpm) at ambient temperature. Then, 9.95 g of NaY CBV100 zeolite are added with stirring (300 rpm) and this is thus continued until the zeolite has dissolved. 43.67 g of the DABCO-C4 structuring agent are dissolved in the solution obtained and it is thus homogenized with stirring (450 rpm) for 30 minutes, at ambient temperature.

[0063] The reaction mixture has the following molar composition: 100 SiO.sub.2: 1.67 Al.sub.2O.sub.3: 50 Na.sub.2O: 10 DABCO-C4: 4000 H.sub.2O

[0064] Maturation Step

[0065] The reaction mixture obtained in the mixing step is kept at ambient temperature with stirring for 24 hours.

[0066] Hydrothermal Treatment Step

[0067] The gel obtained is left in an autoclave at a temperature of 150 C. for 6 days with stirring (200 rpm). The crystals obtained are separated and washed with deionized water until a pH of the washing water of less than 8 is obtained. The washed material is dried.

[0068] An XRD analysis shows that the product obtained is a pure crude synthetic SSZ-16 zeolite with AFX structure (ICDD sheet, PDF 04-03-1370).

[0069] Heat Treatment Step

[0070] The crude synthetic SSZ-16 zeolite is treated under a stream of dry N.sub.2 at 550 C. for 8 h, then calcined under a stream of dry air at 550 C. for 8 h. The loss on ignition (LOI) is 18% by weight.

[0071] NH.sub.4.sup.+ Ion Exchange on Calcined SSZ-16

[0072] The calcined SSZ-16 zeolite is brought into contact with a 3 molar NH.sub.4NO.sub.3 solution for 5 hours with stirring at ambient temperature. The ratio between the volume of NH.sub.4NO.sub.3 solution and the weight of solid is 10. The solid obtained is filtered off and washed and the exchange procedure is repeated once more under the same conditions. The final solid is separated, washed and dried. An XRD analysis shows that the product obtained is a pure crude synthetic SSZ-16 zeolite in ammoniacal form (NH4-SSZ-16) with AFX structure (ICDD sheet, PDF 04-03-1370).

[0073] Heat Treatment Step

[0074] The SSZ-16 zeolite in ammoniacal form (NH4-SSZ-16) is treated under a stream of dry air at 550 C. for 8 hours with a temperature increase ramp of 1 C./min The loss on ignition (LOI) is 4% by weight. The product obtained is an SSZ-16 zeolite in protonated form (H-SSZ-16).

[0075] Cu Ion Exchange on H-SSZ-16

[0076] The H-SSZ-16 zeolite is brought into contact with a [Cu(NH.sub.3).sub.4](NO.sub.3).sub.2 solution for 1 day with stirring at ambient temperature. The final solid is separated, washed and dried. An XRD analysis shows that the product obtained is a pure SSZ-16 zeolite with AFX structure (ICDD sheet, PDF 04-03-1370).

[0077] The X-ray fluorescence (XRF) chemical analysis gave an Si/Al molar ratio of 6.5 and a weight percentage of Cu of 3%.

Example 2 (not in Accordance with the Invention)

Synthesis of an SSZ-16 Zeolite with Direct Incorporation of Cu Using a Tetraethylenepentamine (TEPA) Complexing Agent

[0078] Mixing Step

[0079] 2.64 g of sodium hydroxide dissolved in 77.92 g of deionized water, with stirring (300 rpm) and at ambient temperature. 30.06 g of sodium silicate are added to this solution and the mixture is homogenized with stirring (300 rpm) at ambient temperature. Then, 1.52 g of NaY CBV100 zeolite are poured into the solution previously obtained with stirring at 300 rpm and this is thus continued until the zeolite has dissolved. This solution is referred to as solution 2-1.

[0080] 0.14 g of copper sulfate are dissolved in 10.94 g of deionized water with stirring for 10 minutes then 0.11 g of tetraethylenepentamine (TEPA) are dissolved in this copper solution. Then, the solution is poured into the solution 2-1 with stirring at 300 rpm. The mixture is homogenized for 10 min with stirring (300 rpm) and then 6.67 of the DABCO-C4 structuring agent are added and it is thus homogenized with stirring at 300 rpm for 10 minutes, at ambient temperature.

[0081] The reaction mixture has the following molar composition: 100 SiO.sub.2: 1.67 Al.sub.2O.sub.3: 50 Na.sub.2O: 10 DABCO-C4: 0.38 CuO: 0.38 TEPA: 4000 H.sub.2O

[0082] Maturation Step

[0083] The reaction mixture obtained in the mixing step is kept at ambient temperature with stirring for 24 hours.

[0084] Hydrothermal Treatment Step

[0085] The gel obtained is left in an autoclave at a temperature of 150 C. for 6 days with stirring at 200 rpm. The crystals obtained are separated and washed with deionized water until a pH of the washing water of less than 8 is obtained. The washed material is dried.

[0086] Heat Treatment (Calcination) Step

[0087] The crude synthetic SSZ-16 zeolite is treated under a stream of dry N.sub.2 at 550 C. for 8 h, then calcined under a stream of dry air at 550 C. for 8 h.

[0088] The XRD analyses of the calcined zeolite show that the product obtained is an SSZ-16 aluminosilicate zeolite (ICDD sheet, PDF 04-03-1370). The X-ray fluorescence (XRF) chemical analysis gave an Si/Al molar ratio of 6.5 and a weight percentage of Cu of 3%.

Example 3 (in Accordance with the Invention)

[0089] In this example, an SSZ-16 zeolite is synthesized with incorporation of the copper in two steps: first step in the synthesis of the zeolite using a Cu-Tetraethylenepentamine (TEPA) complex followed by a second step after the calcination of the zeolite by ion exchange with the [Cu(NH.sub.3).sub.4](NO.sub.3).sub.2 complex.

[0090] Mixing Step

[0091] 2.64 g of sodium hydroxide dissolved in 77.92 g of deionized water, with stirring (300 rpm) and at ambient temperature. 30.06 g of sodium silicate are added to this solution and the mixture is homogenized with stirring at 300 rpm at ambient temperature. Then, 1.52 g of NaY CBV100 zeolite are poured into the solution previously obtained with stirring at 300 rpm and this is thus continued until the zeolite has dissolved. This solution is referred to as solution 2-1.

[0092] 0.05 g of copper sulfate are dissolved in 10.94 g of deionized water with stirring for 10 minutes then 0.05 g of tetraethylenepentamine (TEPA) are dissolved in this copper solution. Then, the solution is poured into the solution 2-1 with stirring at 300 rpm. The mixture is homogenized for 10 min with stirring (300 rpm) and then 6.67 of the DABCO-C4 structuring agent are added and it is thus homogenized with stirring at 300 rpm for 10 minutes, at ambient temperature.

[0093] The reaction mixture has the following molar composition: 100 SiO.sub.2: 1.67 Al.sub.2O.sub.3: 50 Na.sub.2O: 10 DABCO-C4: 0.13 CuO: 0.13 TEPA: 4000 H.sub.2O

[0094] Maturation Step

[0095] The reaction mixture obtained in the mixing step is kept at ambient temperature with stirring for 24 hours.

[0096] Hydrothermal Treatment Step

[0097] The gel obtained is left in an autoclave at a temperature of 150 C. for 6 days with stirring at 200 rpm. The crystals obtained are separated and washed with deionized water until a pH of the washing water of less than 8 is obtained. The washed material is dried.

[0098] Heat Treatment (Calcination) Step

[0099] The crude synthetic Cu-SSZ-16 zeolite is treated under a stream of dry N.sub.2 at 550 C. for 8 h, then calcined under a stream of dry air at 550 C. for 8 h.

[0100] The XRD analyses show that the product obtained is an SSZ-16 aluminosilicate zeolite (ICDD sheet, PDF 04-03-1370). The X-ray fluorescence (XRF) chemical analysis gave an Si/A1 molar ratio of 6.5 and a weight percentage of Cu of 1%.

[0101] Cu Ion Exchange on Cu-SSZ-16

[0102] The calcined Cu-SSZ-16 zeolite is bought into contact with a [Cu(NH.sub.3).sub.4](NO.sub.3).sub.2 solution for 1 day with stirring at ambient temperature. The final solid is separated, washed and dried.

[0103] Heat Treatment (Calcination) Step

[0104] The Cu-SSZ-16 zeolite obtained after contact with the [Cu(NH.sub.3).sub.4](NO.sub.3).sub.2 solution is treated under a stream of dry N.sub.2 at 550 C. for 8 h, then calcined under a stream of dry air at 550 C. for 8 h.

[0105] An XRD analysis shows that the product obtained is a pure SSZ-16 zeolite with AFX structure (ICDD sheet, PDF 04-03-1370).

[0106] The X-ray fluorescence (XRF) chemical analysis gave an Si/Al molar ratio of 6.5 and a weight percentage of Cu of 3%.

Example 4 (in Accordance with the Invention)

[0107] In this example, an SSZ-16 zeolite is synthesized with incorporation of the copper in two steps: first step in the synthesis of the zeolite using a Cu-Triethylenetetramine (TETA) complex followed by a second step after the calcination of the zeolite by ion exchange with the [Cu(NH.sub.3).sub.4](NO.sub.3).sub.2 complex.

[0108] Mixing Step

[0109] 17.37 g of sodium hydroxide are dissolved in 507 g of deionized water, with stirring (300 rpm) and at ambient temperature. 198 g of sodium silicate are added to this solution and the mixture is homogenized with stirring at 300 rpm at ambient temperature. Then, 9.95 g of NaY CBV100 zeolite are poured into the solution previously obtained with stirring at 300 rpm and this is thus continued until the zeolite has dissolved. This solution is referred to as solution 4-1.

[0110] 0.32 g of copper sulfate are dissolved in 73 g of deionized water with stirring for 10 minutes then 0.19 g of triethylenetetramine (TETA) are dissolved in this copper solution. Then, this solution is poured into the solution 4-1 with stirring at 300 rpm. The mixture is homogenized for 10 min with stirring (300 rpm) and then 43.7 of the DABCO-C4 structuring agent are added and it is thus homogenized with stirring at 300 rpm for 10 minutes, at ambient temperature.

[0111] The reaction mixture has the following molar composition: 100 SiO.sub.2: 1.67 Al.sub.2O.sub.3: 50 Na.sub.2O: 10 DABCO-C4: 0.13 CuO: 0.13 TETA: 4000 H.sub.2O

[0112] Maturation Step

[0113] The reaction mixture obtained in the mixing step is kept at ambient temperature with stirring for 24 hours.

[0114] Hydrothermal Treatment Step

[0115] The gel obtained is introduced into an autoclave and heated at a temperature of 150 C. for 6 days with stirring at 200 rpm. The crystals obtained are separated and washed with deionized water until a pH of the washing water of less than 8 is obtained. The washed material is dried.

[0116] Heat Treatment (Calcination) Step

[0117] The crude synthetic Cu-SSZ-16 zeolite is treated under a stream of dry N.sub.2 at 550 C. for 8 h, then calcined under a stream of dry air at 550 C. for 8 h.

[0118] The XRD analyses of the calcined zeolite show that the product obtained is an SSZ-16 aluminosilicate zeolite (ICDD sheet, PDF 04-03-1370). The X-ray fluorescence (XRF) chemical analysis gave an Si/Al molar ratio of 6.5 and a weight percentage of Cu of 1%.

[0119] Cu Ion Exchange on Cu-SSZ-16

[0120] The calcined Cu-SSZ-16 zeolite is bought into contact with a [Cu(NH.sub.3).sub.4](NO.sub.3).sub.2 solution for 1 day with stirring at ambient temperature. The final solid is separated, washed and dried.

[0121] Heat Treatment (Calcination) Step

[0122] The Cu-SSZ-16 zeolite obtained after contact with the [Cu(NH.sub.3).sub.4](NO.sub.3).sub.2 solution is treated under a stream of dry N.sub.2 at 550 C. for 8 h, then calcined under a stream of dry air at 550 C. for 8 h.

[0123] An XRD analysis shows that the product obtained is a pure SSZ-16 zeolite with AFX structure (ICDD sheet, PDF 04-03-1370).

[0124] The X-ray fluorescence (XRF) chemical analysis gave an Si/A1 molar ratio of 6.5 and a weight percentage of Cu of 3%.

Example 5 (not in Accordance with the Invention)

[0125] In this example, an SSZ-16 zeolite is synthesized with incorporation of the copper in two steps: first step in the synthesis of the zeolite using a Cu-Triethylenetetramine (TETA) complex followed by a second step after the calcination of the zeolite by ion exchange with the [Cu(NH.sub.3).sub.4](NO.sub.3).sub.2 complex. The final percentage of Cu in the calcined zeolite is greater than 6%.

[0126] Mixing Step

[0127] 17.37 g of sodium hydroxide are dissolved in 507 g of deionized water, with stirring (300 rpm) and at ambient temperature. 198 g of sodium silicate are added to this solution and the mixture is homogenized with stirring at 300 rpm at ambient temperature. Then, 9.95 g of NaY CBV100 zeolite are poured into the solution previously obtained with stirring at 300 rpm and this is thus continued until the zeolite has dissolved. This solution is referred to as solution 4-1.

[0128] 0.32 g of copper sulfate are dissolved in 73 g of deionized water with stirring for 10 minutes then 0.19 g of triethylenetetramine (TETA) are dissolved in this copper solution. Then, this solution is poured into the solution 4-1 with stirring at 300 rpm. The mixture is homogenized for 10 min with stirring (300 rpm) and then 43.7 of the DABCO-C4 structuring agent are added and it is thus homogenized with stirring at 300 rpm for 10 minutes, at ambient temperature.

[0129] The reaction mixture has the following molar composition: 100 SiO.sub.2: 1.67 Al.sub.2O.sub.3: 50 Na.sub.2O: 10 DABCO-C4: 0.13 CuO: 0.13 TETA: 4000 H.sub.2O

[0130] Maturation Step

[0131] The reaction mixture obtained in the mixing step is kept at ambient temperature with stirring for 24 hours.

[0132] Hydrothermal Treatment Step

[0133] The gel obtained is introduced into an autoclave and heated at a temperature of 150 C. for 6 days with stirring at 200 rpm. The crystals obtained are separated and washed with deionized water until a pH of the washing water of less than 8 is obtained. The washed material is dried.

[0134] Heat Treatment (Calcination) Step

[0135] The crude synthetic Cu-SSZ-16 zeolite is treated under a stream of dry N.sub.2 at 550 C. for 8 h, then calcined under a stream of dry air at 550 C. for 8 h.

[0136] The XRD analyses show that the product obtained is an SSZ-16 aluminosilicate zeolite (ICDD sheet, PDF 04-03-1370). The X-ray fluorescence (XRF) chemical analysis gave an Si/Al molar ratio of 6.5 and a weight percentage of Cu of 1%.

[0137] Cu Ion Exchange on Cu-SSZ-16

[0138] The calcined Cu-SSZ-16 zeolite is bought into contact with a [Cu(NH.sub.3).sub.4](NO.sub.3).sub.2 solution for 1 day with stirring at ambient temperature. The final solid is separated and washed and the exchange operation is repeated once more.

[0139] Heat Treatment (Calcination) Step

[0140] The Cu-SSZ-16 zeolite obtained after contact with the [Cu(NH.sub.3).sub.4](NO.sub.3).sub.2 solution is treated under a stream of dry N.sub.2 at 550 C. for 8 h, then calcined under a stream of dry air at 550 C. for 8 h.

[0141] An XRD analysis shows that the product obtained is a pure SSZ-16 zeolite with AFX structure (ICDD sheet, PDF 04-03-1370).

[0142] The X-ray fluorescence (XRF) chemical analysis gave an Si/Al molar ratio of 6.5 and a weight percentage of Cu of 6.5%.

Example 6 (not in Accordance with the Invention)

[0143] In this example, an SSZ-16 zeolite is synthesized with incorporation of the copper in two steps: first step in the synthesis of the zeolite using a Cu-Triethylenetetramine (TETA) complex followed by a second step after the calcination of the zeolite by ion exchange with the [Cu(NH.sub.3).sub.4](NO.sub.3).sub.2 complex. The final percentage of Cu in the calcined zeolite is less than 1.5%.

[0144] Mixing Step

[0145] 17.37 g of sodium hydroxide are dissolved in 507 g of deionized water, with stirring (300 rpm) and at ambient temperature. 198 g of sodium silicate are added to this solution and the mixture is homogenized with stirring at 300 rpm at ambient temperature. Then, 9.95 g of NaY CBV100 zeolite are poured into the solution previously obtained with stirring at 300 rpm and this is thus continued until the zeolite has dissolved. This solution is referred to as solution 4-1.

[0146] 0.16 g of copper sulfate are dissolved in 73 g of deionized water with stirring for 10 minutes then 0.10 g of triethylenetetramine (TETA) are dissolved in this copper solution. Then, this solution is poured into the solution 4-1 with stirring at 300 rpm. The mixture is homogenized for 10 min with stirring (300 rpm) and then 43.7 of the DABCO-C4 structuring agent are added and it is thus homogenized with stirring at 300 rpm for 10 minutes, at ambient temperature.

[0147] The reaction mixture has the following molar composition: 100 SiO.sub.2: 1.67 Al.sub.2O.sub.3: 50 Na.sub.2O: 10 DABCO-C4: 0.06 CuO: 0.06 TETA: 4000 H.sub.2O

[0148] Maturation Step

[0149] The reaction mixture obtained in the mixing step is kept at ambient temperature with stirring for 24 hours.

[0150] Hydrothermal Treatment Step

[0151] The gel obtained is introduced into an autoclave and heated at a temperature of 150 C. for 6 days with stirring at 200 rpm. The crystals obtained are separated and washed with deionized water until a pH of the washing water of less than 8 is obtained. The washed material is dried.

[0152] Heat Treatment (Calcination) Step

[0153] The crude synthetic Cu-SSZ-16 zeolite is treated under a stream of dry N.sub.2 at 550 C. for 8 h, then calcined under a stream of dry air at 550 C. for 8 h.

[0154] The XRD analyses show that the product obtained is an SSZ-16 aluminosilicate zeolite (ICDD sheet, PDF 04-03-1370). The X-ray fluorescence (XRF) chemical analysis gave an Si/Al molar ratio of 6.5 and a weight percentage of Cu of 0.5%.

[0155] Cu Ion Exchange on Cu-SSZ-16

[0156] The calcined Cu-SSZ-16 zeolite is bought into contact with a [Cu(NH.sub.3).sub.4](NO.sub.3).sub.2 solution for 2 hours with stirring at ambient temperature. The solid obtained are separated, washed and dried.

[0157] Heat Treatment (Calcination) Step

[0158] The Cu-SSZ-16 zeolite obtained after contact with the [Cu(NH.sub.3).sub.4](NO.sub.3).sub.2 solution is treated under a stream of dry N.sub.2 at 550 C. for 8 h, then calcined under a stream of dry air at 550 C. for 8 h.

[0159] An XRD analysis shows that the product obtained is a pure SSZ-16 zeolite with AFX structure (ICDD sheet, PDF 04-03-1370).

[0160] The X-ray fluorescence (XRF) chemical analysis gave an Si/A1 molar ratio of 6.5 and a weight percentage of Cu of 1.2%.

Example 7

[0161] In order to evaluate the NO.sub.x conversion activity of the various materials prepared, a catalytic test is carried out for the reduction of nitrogen oxides (NO.sub.x) by ammonia (NH.sub.3) in the presence of oxygen (O.sub.2) at various operating temperatures. The materials not in accordance with the invention, prepared according to examples 1 and 2 are compared to the materials in accordance with the invention, prepared according to examples 3 and 4.

[0162] For each test, 200 mg of material in powder form is placed in a quartz reaction vessel. 145 l/h of a representative feedstock of a mixture of exhaust gas from a diesel engine are fed into the reaction vessel.

[0163] This feedstock has the following molar composition:

TABLE-US-00001 O.sub.2 8.5% CO.sub.2 9% NO 400 ppm NH.sub.3 400 ppm H.sub.2O 10% N.sub.2 qpc

[0164] The conversion results are shown in FIGS. 2 and 3, the Ex 1, Ex 2, Ex 3, Ex 4, Ex 5 and Ex 6 curves respectively corresponding to the tests carried out with the materials prepared according to example 1, example 2, example 3, example 4, example 5 and example 6.

[0165] It is observed that the materials prepared according to the invention have a better NO.sub.x conversion than the materials prepared according to example 1, example 2, example 5 or example 6, this being for all the temperatures tested.