Direct synthesis of a SAPO material with AFX structure comprising copper and use of this material

Abstract

The invention concerns a process for preparing a copper-comprising SAPO 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, at least one phosphorus source, a TETA complexing agent and a TMHD structuring agent, in order to obtain a gel, and hydrothermal treatment of said gel with a shear rate of less than 50 s.sup.−1 in order to obtain crystallization of said copper-comprising SAPO material with AFX structure.

Claims

1. A process for preparing a copper-containing SAPO material with an AFX structure, comprising at least the following: a) mixing, in an aqueous medium, of at least one aluminum source, at least one silicon source, at least one copper source, at least one phosphorus source, a complexing agent, TETA, and a structuring agent, TMHD, in order to obtain a gel of formula:
aSiO.sub.2:bAl.sub.2O.sub.3:cP.sub.2O.sub.5:dTMHD:eCuSO.sub.4:fTETA:gH.sub.2O a/c being 0.1 to 1, b/c being 0.1 to 1, g/c being 1 to 100, d/c being 0.5 to 4, e/c being 0.005 to 0.1 and f/e being 1 to 1.5; b) hydrothermal treatment of said gel at a temperature of 170 to 220° C., under an autogenous reaction pressure, for a period of 1 to 3 days with a shear rate of less than 50 s.sup.−1 in order to obtain the crystallization of said copper-containing SAPO material with an AFX structure.

2. The process as claimed in claim 1, wherein said b) is carried out at a temperature of 190 to 210° C.

3. The process as claimed in claim 1, wherein said step b) is carried out for a period of 1 to 2 days.

4. The process as claimed in claim 1, wherein said b) is carried out in the absence of stirring.

5. The process as claimed in claim 1, wherein said b) is carried out with a shear rate of 0.1 to 50 s.sup.−1.

6. The process as claimed in claim 1, comprising a heat treatment c) carried out at the end of b), comprising a treatment under dry inert gas, at a temperature of 400 to 600° C., for a period of 5 to 15 h, followed by a combustion treatment in dry air, at a temperature of 400 to 600° C., for a period of 5 to 15 h.

7. The process as claimed in claim 6, comprising an ion exchange which comprises bringing the solid obtained at the end of c) into contact with a solution comprising a species releasing copper in solution in reactive form with stirring at ambient temperature for a period of 1 h to 2 d.

8. The process as claimed in claim 6, wherein the dry air flow rate of said combustion treatment is 0.5 to 1.5 l/h/g of solid to be treated.

9. The process as claimed in claim 1, comprising an ion exchange which comprises bringing solid obtained at the end of b) into contact with a solution comprising a species releasing copper in solution in reactive form with stirring at ambient temperature for a period of 1 h to 2 d.

10. A process comprising preparing a copper-comprising SAPO material with an AFX structure by: a) mixing, in an aqueous medium, of at least one aluminum source, at least one silicon source, at least one copper source, at least one phosphorus source, a complexing agent, TETA, and a structuring agent, TMHD, in order to obtain a gel of formula:
aSiO.sub.2:bAl.sub.2O.sub.3:cP.sub.2O.sub.5:dTMHD:eCuSO.sub.4:fTETA:gH.sub.2O a/c being 0.1 to 1, b/c being 0.1 to 1, g/c being 1 to 100, d/c being 0.5 to 4, e/c being 0.005 to 0.1 and f/e being 1 to 1.5; b) hydrothermal treatment of said gel at a temperature of 170 to 220° C., under an autogenous reaction pressure, for a period of 1 to 3 days with a shear rate of less than 50 s.sup.−1 in order to obtain the crystallization of said copper-comprising SAPO material with AFX structure, and c) selectively reducing NO.sub.x by contacting NO.sub.X and a reducing agent in the presence of the copper-comprising copper-containing SAPO.

11. A process for the selective reduction of NO.sub.x by a reducing agent, comprising contacting NO.sub.X and the reducing agent in the presence of the copper-containing SAPO with an AFX structure as claimed in claim 10.

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

13. The process as claimed in claim 12, wherein said coating comprises said material in combination with a binder.

14. The process as claimed in claim 13, wherein the binder is cerine, zirconium oxide, alumina, non-zeolite silica-alumina, titanium oxide, a cerine-zerconia mixed oxide, or a tungsten oxide.

15. The process as claimed in claim 12, wherein said coating is in combination with another coating having NO.sub.x reducing capacities or capacities which promote the oxidation of pollutants.

16. The process as claimed in claim 12, wherein said structure coated by said material is integrated in an exhaust line of an internal combustion engine.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 shows an image obtained by scanning electron microscopy (SEM) of the Cu-SAPO material with AFX structure obtained by the process according to the invention.

(2) FIG. 2 shows the NOx conversion results, the Ex 1, Ex 4, Ex 7 and Ex 8 curves respectively corresponding to the tests carried out with the materials prepared according to example 1, example 4, example 7 and example 8. At the abscissa point 400° C., the curves correspond, respectively, from bottom to top to Ex 1, Ex 8, Ex 4 and Ex 7.

(3) FIG. 3 shows an X-ray diffraction pattern of the Cu-SAPO material obtained according to example 7.

EXAMPLES

Example 1 (not in Accordance with the Invention)

(4) In this example, a Cu-exchanged SAPO-56 zeolite is synthesized according to the prior art. In this example, the copper is introduced by ion exchange.

(5) Mixing Step

(6) 131.33 g of phosphoric acid and 62.30 g of alumina (pseudo-boehmite Pural SB3) are cold mixed in 213.80 g of water. This mixture is kept in an ice-cold water bath and dispersed with vigorous stirring. The mixture is made up with 125.80 g of deionized water with stirring until homogenization. 20.39 g of fumed silica, then 197.17 g of TMHD structuring agent are added with vigorous stirring at ambient temperature until homogenization of the suspension.

(7) The reaction mixture has the following molar composition: 0.6 SiO.sub.2:0.8 Al.sub.2O.sub.3:1.0 P.sub.2O.sub.5:2 TMHD:40 H.sub.2O

(8) Hydrothermal Treatment Step

(9) The gel obtained is left in an autoclave at a temperature of 200° C. for 4 days without stirring. 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.

(10) An XRD analysis shows that the product obtained is a pure crude synthetic SAPO-56 zeolite with AFX structure (ICDD sheet, PDF 04-03-1370).

(11) Heat Treatment Step

(12) The crude synthetic SAPO-56 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 21% by weight.

(13) Cu Ion Exchange on Calcined SAPO-56

(14) The calcined SAPO-56 zeolite is brought into contact with a solution of [Cu(NH.sub.3).sub.4](NO.sub.3).sub.2 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 crude synthetic SAPO-56 zeolite with AFX structure (ICDD sheet, PDF 04-03-1370).

(15) The X-ray fluorescence (XRF) chemical analysis gave an Si/Al and Cu/Al molar ratio of 0.21 and 0.10, respectively.

Example 2 (not in Accordance with the Invention)

(16) In this example, the aim is to synthesize a SAPO-56 zeolite with direct incorporation of Cu using a complexing agent, tetraethylenepentamine (TEPA), and low shear crystallization.

(17) Mixing Step

(18) 13.73 g of phosphoric acid and 6.54 g of alumina (pseudo-boehmite Pural SB3) are cold mixed in 30.33 g of water. This mixture is kept in an ice-cold water bath and dispersed with vigorous stirring. 2.14 g of fumed silica are added at ambient temperature. 0.89 g of copper sulfate are dissolved in 5.01 g of deionized water with stirring for 5 minutes, then 0.69 g of TEPA and 20.70 g of TMHD structuring agent are added with vigorous stirring at ambient temperature until the suspension is homogenized.

(19) The reaction mixture has the following molar composition: 0.6 SiO.sub.2:0.8 Al.sub.2O.sub.3:1.0 P.sub.2O.sub.5:2 TMHD:0.06 CuSO.sub.4:0.06 TEPA:40 H.sub.2O

(20) Hydrothermal Treatment Step

(21) The gel obtained is separated into 4 samples left in an autoclave at a temperature of 200° C. for 1, 2, 3 and 4 days, respectively, with stirring, with a shear rate of 40 s.sup.−1. 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.

(22) The XRD analyses show that the product obtained after 1, 2, 3 and 4 days of autoclaving is a SAPO-56 zeolite (ICDD sheet, PDF 04-03-1370) at approximately 85% by weight, mixed with the SAPO-34 zeolite (ICDD sheet, PDF 00-047-0429) at approximately 15% by weight.

(23) In this example, it is not possible to synthesize a pure copper-comprising SAPO material with AFX structure.

Example 3 (not in Accordance with the Invention)

(24) In this example, the aim is to synthesize a SAPO-56 zeolite with direct incorporation of Cu using a complexing agent, tetraethylenepentamine (TEPA), and high shear crystallization.

(25) The mixing step is carried out in the same manner as in example 2.

(26) Hydrothermal Treatment Step

(27) The gel obtained is left in an autoclave at a temperature of 200° C. for 4 days with stirring with a high shear (greater than 1000 s.sup.−1). 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.

(28) An XRD analysis indicates the presence of a mixture of SAPO-17 (ICDD sheet, PDF 00-047-0621) and SAPO-34 (ICDD sheet, PDF 00-047-0429). It is observed that SAPO-56 is not obtained under these synthesis conditions.

Example 4 (in Accordance with the Invention)

(29) In this example, a SAPO-56 zeolite is synthesized with direct incorporation of Cu using a complexing agent, triethylenetetramine (TETA), and low shear crystallization.

(30) Mixing Step

(31) 13.74 g of phosphoric acid and 6.55 g of alumina (pseudo-boehmite Pural SB3) are cold mixed in 30.38 g of water. This mixture is kept in an ice-cold water bath and dispersed with vigorous stirring. 2.15 g of fumed silica are added at ambient temperature. 0.90 g of copper sulfate are dissolved in 5.02 g of deionized water with stirring for 5 minutes, then 0.52 g of TETA and 20.74 g of TMHD structuring agent are added with vigorous stirring at ambient temperature until the suspension is homogenized.

(32) The reaction mixture has the following molar composition: 0.6 SiO.sub.2:0.8 Al.sub.2O.sub.3:1.0 P.sub.2O.sub.5:2 TMHD:0.06 CuSO.sub.4:0.06 TETA:40 H.sub.2O

(33) Hydrothermal Treatment Step

(34) The gel obtained is separated into 2 samples left in an autoclave at a temperature of 200° C. for 1 and 2 days, respectively, with stirring, with a shear rate of 40 s.sup.−1. 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.

(35) An XRD analysis shows that the product obtained is a pure Cu-SAPO-56 zeolite (ICDD sheet, PDF 04-03-1370) with AFX structure, and that the hydrothermal treatment step lasted one or two days.

(36) Heat Treatment Step

(37) A sample is treated under a stream of dry N.sub.2 at 550° C. for 8 h, and then calcined under a stream of dry air at 550° C. for 8 h.

(38) An XRD analysis shows that the product obtained is a pure zeolite with AFX structure. The X-ray fluorescence (XRF) chemical analysis gave an Si/Al and Cu/Al molar ratio of 0.21 and 0.11, respectively.

Example 5 (not in Accordance with the Invention)

(39) In this example, the aim is to synthesize a SAPO-56 zeolite with direct incorporation of Cu using a complexing agent, triethylenetetramine (TETA), and high shear crystallization.

(40) The mixing step is carried out in the same manner as in example 4.

(41) Hydrothermal Treatment Step

(42) The gel obtained is left in an autoclave at a temperature of 200° C. for 3 days with stirring with high shear (shear rate greater than 1000 s.sup.−1). 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.

(43) An XRD analysis shows that the product obtained is a mixture of SAPO-56 zeolite (ICDD sheet, PDF 04-03-1370) and SAPO-20 zeolite (ICDD sheet, PDF 00-045-0510).

Example 6 (not in Accordance with the Invention)

(44) In this example, the intention is to synthesize a Cu-SAPO-56 zeolite with direct incorporation of Cu using a complexing agent, triethylenetetramine (TETA), high shear crystallization and a shorter crystallization time than in example 5.

(45) The mixing step is carried out in the same manner as in example 4.

(46) Hydrothermal Treatment Step

(47) The gel obtained is left in an autoclave at a temperature of 200° C. for 1 day with stirring with high shear (shear rate greater than 1000 s.sup.−1). 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.

(48) An XRD analysis shows that the product obtained with high shear crystallization is a mixture of SAPO-56 zeolite (ICDD sheet, PDF 04-03-1370) and SAPO-17 zeolite (ICDD sheet, PDF 00-047-0621).

Example 7 (in Accordance with the Invention)

(49) This example differs from example 4 by virtue of a different composition of the gel obtained at the end of the mixing step.

(50) Mixing Step

(51) 13.56 g of phosphoric acid and 6.47 g of alumina (pseudo-boehmite Pural SB3) are cold mixed in 29.14 g of water. This mixture is kept in an ice-cold water bath and dispersed with vigorous stirring. 2.82 g of fumed silica are added at ambient temperature. 1.17 g of copper sulfate are dissolved in 5.70 g of deionized water with stirring for 5 minutes, then 0.69 g of TETA and 20.47 g of TMHD structuring agent are added with vigorous stirring at ambient temperature until the suspension is homogenized.

(52) The reaction mixture has the following molar composition: 0.8 SiO.sub.2:0.8 Al.sub.2O.sub.3:1.0 P.sub.2O.sub.5:2 TMHD:0.08 CuSO.sub.4:0.08 TETA:40 H.sub.2O

(53) Hydrothermal Treatment Step

(54) The gel obtained is separated into several samples left in an autoclave at a temperature of 200° C. for a period of 1 to 2 days with stirring with low shear (shear rate of 40 s.sup.−1). 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.

(55) An XRD analysis shows that the product obtained is pure Cu-SAPO-56 zeolite (ICDD sheet, PDF 00-047-0621), for all the durations of the hydrothermal treatment step of between one and two days.

(56) Heat Treatment Step

(57) A sample is treated under a stream of dry N.sub.2 at 550° C. for 8 h, and then calcined under a stream of dry air at 550° C. for 8 h.

(58) An XRD analysis shows that the product obtained is a pure zeolite with AFX structure. The X-ray fluorescence (XRF) chemical analysis gave an Si/Al and Cu/Al ratio of 0.25 and 0.13, respectively.

Example 8 (in Accordance with the Invention)

(59) This example differs from example 4 by virtue of a different composition of the gel obtained at the end of the mixing step.

(60) Mixing Step

(61) 13.93 g of phosphoric acid and 6.64 g of alumina (pseudo-boehmite Pural SB3) are cold mixed in 30.08 g of water. This mixture is kept in an ice-cold water bath and dispersed with vigorous stirring. 1.45 g of fumed silica are added at ambient temperature. 0.60 g of copper sulfate are dissolved in 5.92 g of deionized water with stirring for 5 minutes, then 0.35 g of TETA and 21.03 g of TMHD structuring agent are added with vigorous stirring at ambient temperature until the suspension is homogenized.

(62) The reaction mixture has the following molar composition: 0.4 SiO.sub.2: 0.8 Al.sub.2O.sub.3:1.0 P.sub.2O.sub.5:2 TMHD:0.04 CuSO.sub.4:0.04 TETA:40 H.sub.2O

(63) Hydrothermal Treatment Step

(64) The gel obtained is separated into several samples left in an autoclave at a temperature of 200° C. for a period of 1 to 2 days with stirring with low shear (shear rate of 40 s.sup.−1). 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.

(65) An XRD analysis shows that the product obtained is a pure Cu-SAPO-56 zeolite (ICDD sheet, PDF 00-047-0621), for all the durations of the hydrothermal treatment step of between one and two days.

(66) Heat Treatment Step

(67) A sample is treated under a stream of dry N.sub.2 at 550° C. for 8 h, and then calcined under a stream of dry air at 550° C. for 8 h.

(68) An XRD analysis shows that the product obtained is a pure zeolite with AFX structure. The X-ray fluorescence (XRF) chemical analysis gave an Si/Al and Cu/Al ratio of 0.17 and 0.08, respectively.

Example 9 (in Accordance with the Invention)

(69) In this example, the aim is to synthesize a SAPO-56 zeolite with direct incorporation of Cu using a complexing agent, triethylenetetramine (TETA), and crystallization without stirring.

(70) All the steps are carried out in the same way as in example 4, but the hydrothermal treatment is carried out without stirring.

(71) An XRD analysis shows that the product obtained is a pure zeolite with AFX structure. The X-ray fluorescence (XRF) chemical analysis gave an Si/Al and Cu/Al molar ratio of 0.21 and 0.11, respectively.

Example 10 (in Accordance with the Invention)

(72) In this example, a SAPO-56 zeolite is synthesized with direct incorporation of Cu using a complexing agent, triethylenetetramine (TETA), and low shear crystallization. An additional amount of Cu is introduced by ion exchange.

(73) Mixing Step

(74) 13.74 g of phosphoric acid and 6.55 g of alumina (pseudo-boehmite Pural SB3) are cold mixed in 30.38 g of water. This mixture is kept in an ice-cold water bath and dispersed with vigorous stirring. 2.15 g of fumed silica are added at ambient temperature. 0.36 g of copper sulfate are dissolved in 5.02 g of deionized water with stirring for 5 minutes, then 0.21 g of TETA and 20.74 g of TMHD structuring agent are added with vigorous stirring at ambient temperature until the suspension is homogenized.

(75) The reaction mixture has the following molar composition: 0.6 SiO.sub.2:0.8 Al.sub.2O.sub.3:1.0 P.sub.2O.sub.5:2 TMHD:0.024 CuSO.sub.4:0.024 TETA:40 H.sub.2O

(76) Hydrothermal Treatment Step

(77) The gel obtained is separated into 2 samples left in an autoclave at a temperature of 200° C. for 1 and 2 days, respectively, with stirring, with a shear rate of 40 s.sup.−1. 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.

(78) An XRD analysis shows that the product obtained is a pure SAPO-56 zeolite (ICDD sheet, PDF 00-047-0621) with AFX structure, and that the hydrothermal treatment step lasted one or two days.

(79) Heat Treatment Step

(80) A sample is treated under a stream of dry N.sub.2 at 550° C. for 8 h, and then calcined under a stream of dry air at 550° C. for 8 h.

(81) An XRD analysis shows that the product obtained is a pure zeolite with AFX structure. The X-ray fluorescence (XRF) chemical analysis gave an Si/Al and Cu/Al molar ratio of 0.21 and 0.04, respectively.

(82) Cu Ion Exchange on Calcined Cu-SAPO-56

(83) The calcined Cu-SAPO-56 zeolite obtained in this example is brought into contact with a solution of [Cu(NH.sub.3).sub.4](NO.sub.3).sub.2 for 1 day with stirring at ambient temperature. The final solid is separated and dried.

(84) An XRD analysis shows that the product obtained is a pure SAPO-56 zeolite (ICDD sheet, PDF 00-047-0621).

(85) The X-ray fluorescence (XRF) chemical analysis gave an Si/Al and Cu/Al molar ratio of 0.21 and 0.11, respectively.

Example 11

(86) 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 material not in accordance with the invention, prepared according to example 1, is compared to the materials in accordance with the invention, prepared according to examples 4, 7 and 8.

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

(88) This load has the following molar composition:

(89) 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

(90) The conversion results are shown in FIG. 2, the Ex 1, Ex 4, Ex 7 and Ex 8 curves respectively corresponding to the tests carried out with the materials prepared according to example 1, example 4, example 7 and example 8.

(91) It is observed that the materials prepared according to the invention have a better NO.sub.x conversion than the material prepared according to example 1, this being for all the temperatures tested.