PROCESS FOR THE PREPARATION OF A ZEOLITIC MATERIAL HAVING A FAU-TYPE FRAMEWORK STRUCTURE AND USE THEREOF IN THE SELECTIVE CATALYTIC REDUCTION OF NOx

Abstract

The present invention relates to a process for the preparation of a zeolitic material having a FAU-type framework M structure comprising YO.sub.2 and X.sub.2O.sub.3, said process comprising: (a) preparing a mixture comprising one or more sources of YO.sub.2, one or more sources of X.sub.2O.sub.3, and one or more structure directing agents (SDA); (b) crystallizing the zeolitic material from the mixture obtained in (a); wherein Y is a tetravalent element and X is a trivalent element, and wherein the one or more structure directing agents comprise one or more isomers of diaminomethylcyclohexane as well as to a zeolitic material having an FAU-type framework structure obtainable and/or obtained according to the inventive process, to processes for preparing a coated substrate and a shaped body, respectively, from the zeolitic material having a FAU-type framework structure obtainable and/or obtained according to the inventive process, as well as to a method for selectively reducing nitrogen oxides NO.sub.x employing said zeolitic material.

Claims

1: A process for the preparation of a zeolitic material having a FAU-type framework structure comprising YO.sub.2 and X.sub.2O.sub.3, said process comprising: (a) preparing a mixture comprising a source of YO.sub.2, a source of X.sub.2O.sub.3, and a structure directing agent (SDA); and (b) crystallizing the zeolitic material from the mixture obtained in (a); wherein Y is a tetravalent element and X is a trivalent element, and wherein the structure directing agent comprises an isomer of diaminomethylcyclohexane.

2: The process of claim 1, wherein Y is at least one selected from the group consisting of Si, Sn, and Ge.

3: The process of claim 1, wherein X is at least one selected from the group consisting of Al, B, In, and Ga.

4: The process of claim 1, wherein the isomers of diaminomethylcyclohexane comprise 65 to 95 wt. % of 2,4-diaminomethylcyclohexane and 5 to 35 wt. % of 2,6-diaminomethylcyclohexane.

5: The process of claim 1, wherein the mixture prepared in (a) further comprises a solvent system comprising a solvent.

6: The process of claim 1, wherein a molar ratio YO.sub.2:diaminomethylcyclohexane of the mixture prepared in (a) is from 0.5 to 40.

7: The process of claim 1, wherein the process further comprises one or more of the following: (c) isolating the zeolitic material, and/or (d) washing the zeolitic material with a solvent; and/or (e) drying the zeolitic material obtained in (c), and/or (d); and/or (f) calcining the zeolitic material obtained in (c), (d), and/or (e).

8: The process of claim 7, wherein the process further comprises: (g) subjecting the zeolitic material obtained in (c), (d), (e), or (f) to an ion exchange procedure, wherein at least one ionic non-framework element or compound contained in the zeolitic material is ion-exchanged against a metal ion.

9: The process of claim 8, wherein the metal ion is at least one selected from the group consisting of ions of alkaline earth metal elements and/or transition metal elements.

10: A zeolitic material having a FAU-type framework structure comprising YO.sub.2 and X.sub.2O.sub.3 obtained by the process of claim 1, wherein Y is a tetravalent element and X is a trivalent element.

11: A process for preparing a coated substrate comprising: (1) preparing a mixture comprising a solvent system and a zeolitic material according to claim 10; (1.a) homogenizing the mixture obtained in (1); (1.b) providing a support substrate; (1.c) coating the support substrate provided in (1.b) with the homogenized mixture obtained in (1.a); (1.d) optionally drying the coated support substrate obtained in (1.c); and (2) calcining the coated support obtained in (1.c) or (1.d).

12: The process of claim 11, wherein the support substrate comprises at least one selected from the group consisting of ceramic substances and metallic substances.

13: A process for preparing a shaped body comprising: (1) preparing a mixture comprising a solvent system and a zeolitic material according to claim 10; (1.A) adding a refractory support material, and optionally adding a pasting agent to the mixture obtained in (1); (1.B) homogenizing the mixture obtained in (1.A); (1.C) shaping of the mixture obtained in (1.B); and (2) calcining the shaped mixture obtained in (1.C).

14: A method for selectively reducing nitrogen oxides NOx, the method comprising: contacting a gas stream comprising NOx with a zeolitic material according to claim 10, wherein at least one ionic non-framework element or compound contained in the zeolitic material is ion-exchanged against Cu and/or Fe.

15: A method, comprising employing a zeolitic material according to claim 10 as a molecular sieve, as an adsorbent, for ion exchange, or as a catalyst and/or catalyst support.

Description

DESCRIPTION OF THE FIGURES

[0152] The X-ray diffraction (XRD) patterns shown in the Figures were respectively measured using Cu K alpha-1 radiation. In the respective diffractograms, the diffraction angle 2 theta in is shown along the abscissa and the intensities are plotted along the ordinate.

[0153] FIG. 1 shows the X-ray diffraction pattern of a NaY zeolite product obtained from the process of the present invention and as described in Example 1.

[0154] FIG. 2 shows the X-ray diffraction pattern of a NaY zeolite product obtained not according to the present invention and as described comparative Example 2.

[0155] FIG. 3 shows the X-ray diffraction pattern of a NaY zeolite product obtained not according to the present invention and as described comparative Example 3.

[0156] FIG. 4 displays results from catalyst testing in NOx conversion and the N.sub.2O yield performed on the copper-exchanged zeolitic material according to Example 3 after forming to a shaped body as described in Example 4. The results are shown using fresh and aged catalyst samples of Example 3. In the figure, the temperature in C. is shown along the abscissa and the NOx conversion rate and the N.sub.2O yield in % are plotted along the ordinate.

EXAMPLES

Example 1: Preparation of NaY Zeolite with Diaminomethylcyclohexane as SDA

[0157] 4.9 g of NaOH-flakes were dissolved in 63 g of deionized water in a plastic beaker under stirring at room temperature. 10 g of sodium aluminate (30 wt.-% Na, 28.6 wt.-% Al) were added thereto and dissolved. 7.7 g of diaminomethylcyclohexane were subsequently added. Finally, 64.4 g of Ludox AS 40 were added thereto and the mixture was then stirred at room temperature for 1 h. The mixture was then left for 25 h at room temperature. The pH of the resulting mixture was 13. Batch composition: 3 Na.sub.2O:10 SiO.sub.2:1.23 Al.sub.2O.sub.3:1.4 diaminomethylcyclohexane:131 H.sub.2O.

[0158] 147.9 g of the resulting mixture were placed into a steel autoclave using a Teflon beaker. The autoclave was placed and heated in a dryer to a temperature of 110 C., during 1 h, and then left for 48 h (2 days) at 110 C. The pH of the resulting suspension was 12.5.

[0159] 147.6 g of the resulting solid were filtered off by using a porcelain suction filter and washed with 3 l of deionized water to a conductivity of less than 200 S/cm.sup.3.

[0160] The solid product was placed in a porcelain bowl and dried at 120 C. for 5 h and subsequently calcined by incremental heating rate of 2 C./min to 540 C. and held at that temperature for 6 h to afford 23.6 g of a white powder.

[0161] Elemental analysis of the product afforded <0.1 wt.-% of carbon, 9.8 wt.-% of Al, 7.8 wt.-% of Na and 26 wt.-% of Si.

[0162] The product displayed a BET surface area of 696 m.sup.2/g and a Langmuir surface area of 907 m.sup.2/g.

[0163] The X-ray diffraction patter of the crystalline product is displayed in FIG. 1 and displays the FAU-type framework structure.

Comparative Example 1: Preparation of NaY Zeolite with 15-Crown-5 as SDA According to H. Robson, Microporous Materials 22 (1998), 551-666

[0164] 6.1 g of 15-crown-5 template were dissolved in 48.2 g of deionized water in a Teflon-lined autoclave (Berghof). 4.5 g of NaOH-flakes were then added thereto under stirring and dissolved at room temperature. 9.9 g of sodium aluminate (30 wt.-% Na, 28.6 wt.-% Al) were subsequently added and dissolved in the solution. Finally, 81.4 g of Ludox AS 40 were added and stirred for 1 h at room temperature. Batch composition: 2.1 Na.sub.2O:10 SiO.sub.2:Al.sub.2O.sub.3:0.5 (15-crown-5):100 H.sub.2O. The mixture was stirred for 24 h at room temperature, the suspension starts to thicken. The pH of the resulting mixture was 13.2.

[0165] 146.1 g of the resulting mixture were placed in a steel autoclave by using a Teflon beaker.

[0166] The autoclave was placed and heated in a dryer to a temperature of 110 C. during 1 h and then left for 192 h (8 days) at 110 C. The pH of the resulting suspension was 11.7.

[0167] 145.9 g the resulting solid were filtered off by using a porcelain suction filter and washed with 51 of deionized water to a conductivity of less than 200 S/cm.sup.3.

[0168] The solid product was placed in a porcelain bowl and dried at 120 C. for 4 days in a dryer and subsequently calcined by incremental heating rate of 2 C./min to 540 C. and held at that temperature for 6 h to afford 40.2 g of a white powder.

[0169] Elemental analysis of the product afforded <0.1 wt.-% of carbon, 8.3 wt.-% of Al, 6.8 wt.-% of Na and 31 wt.-% of Si.

[0170] The product displayed a BET surface area of 756 m.sup.2/g and a Langmuir surface area of 987 m.sup.2/g.

[0171] The X-ray diffraction patter of the crystalline product is displayed in FIG. 2 and displays the FAU-type framework structure.

Comparative Example 2: Preparation of NaY Zeolite without SDA

[0172] 63 g of deionized water was provided in plastic beaker. 4.9 g of NaOH-flakes were added under stirring and dissolved at room temperature. 10 g of sodium aluminate (30 wt % Na, 28.6 wt % Al) were subsequently added thereto and dissolved. Finally, 64.4 g of Ludox AS 40 was added and stirred for 1 h at room temperature. Batch composition: 3 Na.sub.2O:10 SiO.sub.2:1.23 Al.sub.2O.sub.3:131 H.sub.2O. The mixture was then left for 25 h at room temperature. The pH of the resulting mixture was 13.2.

[0173] 140.7 g of the resulting mixture were placed into a steel autoclave by using a Teflon beaker.

[0174] The autoclave is heated in a dryer up to 110 C. (within about 1 h) and hold for 48 h (2 days) at 110 C. The pH of the resulting suspension was 11.6

[0175] 140.6 g of the resulting solid were filtered off by using a porcelain suction filter and then washed with 5 l of deionized water to a conductivity of less than 200 S/cm.sup.3.

[0176] The solid product was placed in a porcelain bowl and dried at 120 C. overnight in a dryer and subsequently calcined by incremental heating rate of 2 C./min to 540 C. and held at that temperature for 6 h to afford 31.9 g of a white powder.

[0177] Elemental analysis of the product afforded 8.7 wt.-% of Al, 7.3 wt.-% of Na and 24.9 wt.-% of Si.

[0178] The product displayed a BET surface area of 305 m.sup.2/g and a Langmuir surface area of 400 m.sup.2/g.

[0179] The X-ray diffraction patter of the crystalline product is displayed in FIG. 3 and displays the FAU-type framework structure.

Example 2: NH.SUB.4.-Ion Exchange of Example 1

[0180] 225 g of deionized water (a portion) and 12.5 g of ammonium nitrate were provided in a 500 ml four-neck flask. The mixture was then heated up to 80 C. under stirring. After reaching that temperature, 25 g of NaY zeolite of Example 1 was added and rinsed with 25 g of deionized water (the rest). The resulting suspension was again heated up to 80 C. and then stirred for 30 min at that temperature (200 rpm).

[0181] The solids were filtered off by using a porcelain suction filter and washed with deionized water to an electrical conductivity of less than 200 S/cm.sup.3.

[0182] The solid product was placed in a porcelain bowl and dried at 120 C. overnight in a dryer.

[0183] The experiment was repeated to afford 26.0 g of a white powder.

Example 3: Cu-Ion Exchange of Example 2

[0184] 146 g of deionized water (a portion) were provided in 250 ml four-neck flask and heated up to 60 C. 8.6 g of copper acetate monohydrate (Sigma Aldrich) were then added thereto under stirring and again heated up to 60 C. After reaching that temperature, 25.5 g of zeolite from Example 2 were added and rinsed with 20 g of deionized water. The suspension is heated up to 60 C. again, the pH of the suspension was 5.3 at 60 C., and then stirred for 1 h at this temperature (300 rpm). The pH of the suspension after 0.5 h was 5.2 at 60 C. and the pH of the resulting suspension after 1 h was 5.2 at 60 C.

[0185] The resulting suspension was filtered through a porcelain suction filter and washed with 5 l of deionized water to an electrical conductivity of less than 200 S/cm.sup.3.

[0186] The solid product was placed together with the porcelain suction filter in a dryer and dried at 120 C. for 16 h to afford 26.0 g of a blue powder.

[0187] Elemental analysis of the product afforded <0.1 wt.-% of carbon (high temperature), 9.8 wt.-% of Al, 5.7 wt.-% of Cu, 2.0 wt.-% of Na and 26.4 wt.-% of Si.

[0188] The product displayed a BET surface area of 666 m.sup.2/g and a Langmuir surface area of 868 m.sup.2/g.

Example 4: SCR (Selective Catalytic Reduction) Testing of Example 3

[0189] 1. Shaping Procedure:

[0190] For the test, the zeolite samples of Example 3 were mixed with a slurry of pre-milled gamma alumina (30 wt.-% Al.sub.2O.sub.3, 70 wt.-% zeolite). The slurry was dried under stirring on a magnetic stirring plate at 100 C. and calcined at 600 C., in air, for 1 h. The resulting cake was crushed and sieved to a target fraction of 250 to 500 m for testing. Fractions of the shaped powder were aged in a muffle oven at 750 C., in 10% steam/air, for 5 h.

[0191] 2. Test Procedure:

[0192] The SCR tests were performed on a 48-fold parallel testing unit equipped with ABB LIMAS NO.sub.x/NH.sub.3 and ABB URAS N.sub.2O analysers. For each fresh and aged catalyst samples of Example 3, 170 mg of powder diluted with corundum to a total volume of 1 mL were placed in each reactor.

[0193] Under isothermal conditions at temperatures of 200, 300, 450 and 575 C., a feed gas consisting of 500 ppm NO, 500 ppm NH.sub.3, 5% O.sub.2, 10% H.sub.2O balance N.sub.2 was passed at a GHSV of 80,000 h.sup.1 through the catalyst bed. In addition to 30 min equilibration time for thermal equilibration of the parallel reactor at each temperature, every position was equilibrated for 3.5 min followed by 30 sec sampling time. Data recorded by the analysers at a frequency of 1 Hz was averaged for the sampling interval and used to calculate NO conversions and N.sub.2O yield.

[0194] Thus, as may be taken from the results displayed in FIG. 4, it has unexpectedly been found that the fresh catalyst according to the present invention displays very high NOx conversion rates of around 99% at 300 C., of around 98% at 450 C. and of around 84% at 600 C., while maintaining a N.sub.2O yield under 20% at 600 C., and even under 10% at 300 and 450 C. Thus, even at high temperature, in particular at 600 C., the inventive sample comprising a Cu-containing zeolite having a FAU-type framework structure displays a great catalytic reduction of NOx, while maintaining a low yield of N.sub.2O. Further, it has surprisingly been found that the aged catalyst (5 h, at 750 C.) according to the present invention displays a somewhat lower NOx conversion at 300 C. but displays the same NOx conversion at 450 C. and even a greater one at 600 C. (high temperature) than the fresh catalyst, the N.sub.2O yield remaining low, i.e. under 10 at 300 C., under 20% at 450 C. and under 30% at 600 C. Thus, it has been surprisingly found that the improved zeolitic material having a FAU-type framework structure, i.e. with high catalytic activity and aging resistance, obtained and/or obtainable according to the present invention may be produced in a cost effective manner which is furthermore adapted to large-scale production while being environmental friendly.