Catalyst composite and use thereof in the selective catalytic reduction of NO.SUB.x

Abstract

The present invention relates to a process for the preparation of a catalyst for selective catalytic reduction comprising • (i) preparing a mixture comprising a metal-organic framework material comprising an ion of a metal or metalloid selected from groups 2-5, groups 7-9, and groups 11-14 of the Periodic Table of the Elements, and at least one at least monodentate organic compound, a zeolitic material containing a metal as a non-framework element, optionally a solvent system, and optionally a pasting agent, • (ii) calcining of the mixture obtained in (i); and further relates to a catalyst per se comprising a composite material containing an amorphous mesoporous metal and/or metalloid oxide and a zeolitic material, wherein the zeolitic material contains a metal as non-framework element, as well as to the use of said catalyst.

Claims

1. A catalyst, comprising: a composite material comprising an amorphous mesoporous material and a zeolite material, wherein the amorphous mesoporous material is chosen from amorphous mesoporous magnesium oxide, amorphous mesoporous aluminum oxide, amorphous mesoporous gallium oxide, amorphous mesoporous indium oxide, amorphous mesoporous titanium oxide, amorphous mesoporous zirconium oxide, amorphous mesoporous hafnium oxide, amorphous mesoporous copper oxide, amorphous mesoporous zinc oxide, amorphous iron magnesium oxide, amorphous mesoporous manganese oxide, amorphous mesoporous vanadium oxide, amorphous mesoporous cobalt oxide, and combinations thereof, and the zeolite material comprises a metal as a non-framework element.

2. A process for preparing the catalyst of claim 1, the process comprising: (i) preparing a mixture comprising: a metal-organic framework material comprising an ion of a metal or metalloid selected from groups 2-5, groups 7-9, and groups 11-14 of the Periodic Table of the Elements, and at least one at least monodentate organic compound, the zeolite material, optionally a solvent system, and optionally a pasting agent, (ii) calcining of the mixture obtained in (i) wherein the catalyst is the catalyst of claim 1.

3. The catalyst of claim 1, wherein the amorphous mesoporous material has an average pore size in a range of 3 to 10 nm based on a porosity measured in a range of 2 to 50 nm, wherein the average pore size is determined according to ISO 15901-2:2006.

4. The catalyst of claim 1, further comprising: a support substrate onto which the composite material is provided.

5. The catalyst of claim 4, wherein the support substrate is selected from the group consisting of a granule, a pellet, a mesh, a ring, a sphere, a cylinder, a hollow cylinder, a monolith and mixtures and combinations of two or more thereof.

6. The catalyst of claim 4, wherein the support substrate comprises a ceramic substance, a metallic substance, or both.

7. The catalyst of claim 4, wherein the support substrate comprises SiC.

8. The catalyst of claim 1, wherein the metal in the zeolite material is selected from the group consisting of the elements of groups 3 to 12 of the Periodic Table of the Elements, and combinations of two or more thereof.

9. The catalyst of claim 1, wherein the metal in the zeolite material is selected from the group consisting of Cu and Fe.

10. The catalyst of claim 1, wherein the metal in the zeolite material is introduced into the zeolite material by ion-exchange.

11. The catalyst of claim 1, wherein a metal and/or metalloid in the amorphous mesoporous material is selected from the group consisting of Al and Zr.

12. The catalyst of claim 1, wherein the zeolite material has a framework structure of a type selected from the group consisting of CHA and AEI.

13. The catalyst of claim 1, wherein the amorphous mesoporous material has an average pore size in a range of 3.8 to 4.2 nm based on a porosity measured in a range of 2 to 50 nm, wherein the average pore size is determined according to ISO 15901-2:2006.

14. A process for preparing the catalyst of claim 1, the process comprising: (i) preparing a mixture comprising: a metal-organic framework material comprising an ion of a metal or metalloid selected from groups 2-5, groups 7-9, and groups 11-14 of the Periodic Table of the Elements, and at least one at least monodentate organic compound, the zeolite material, a solvent system, and optionally a pasting agent; (i.A) homogenizing the mixture obtained in (i), to obtain a homogenized mixture; (i.B) providing a support substrate; (i.C) coating the support substrate provided in (i.B) with the homogenized mixture obtained in (i.A), to obtain a coated support substrate; (i.D) optionally drying the coated support substrate obtained in (i.C), to obtain a dried coated support substrate; (i.E) calcining of the coated support substrate obtained in (i.C) or the dried coated support substrate obtained in (i.D), wherein the catalyst is the catalyst of claim 1.

15. The process of claim 14, wherein the support substrate is selected from the group consisting of a granule, a pellet, a mesh, a ring, a sphere, a cylinder, a hollow cylinder, a monolith and mixtures and combinations of two or more thereof.

16. The process of claim 14, wherein the ion comprised in the metal-organic framework material is an ion of a metal selected from the group consisting of Mg, Al, Ga, In, Ti, Zr, Hf, Cu, Zn, Fe, Mn, V, Co and combinations of two or more thereof.

17. The process of claim 14, wherein the metal comprised in the zeolite material as the non-framework element is selected from the group consisting of the elements of groups 3 to 12 of the Periodic Table of the Elements, and combinations of two or more thereof.

18. A method for the selective catalytic reduction of NOx, the method comprising (1) providing a gas stream comprising NOx; (2) contacting the gas stream provided in (1) with the catalyst of claim 1.

19. A method for treating an exhaust gas, the method comprising contacting the exhaust gas with the catalyst of claim 1.

Description

DESCRIPTION OF THE FIGURES

(1) 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.

(2) FIG. 1a shows the X-ray diffraction pattern of the amorphous mesoporous aluminum oxide obtained from Reference Example 1.

(3) FIG. 1b shows the results from nitrogen sorption analysis at 77K (BJH analysis) of the amorphous mesoporous aluminum oxide obtained from Reference Example 1 wherein the pore diameter in nm is depicted in a logarithmic manner along the abscissa and the pore volume in cm.sup.3/g is plotted along the ordinate.

(4) FIG. 2 displays the X-ray diffractogram of the crystalline chabazite product obtained from hydrothermal synthesis after calcination in the Reference Example 2, wherein the line patter of the CHA-type framework structure has been included in the diffractogram as a reference.

(5) FIG. 3 shows results from comparative testing performed on coated filter substrates according to the core tests of Example 6, wherein the NO.sub.x conversion level in % is plotted along the ordinate and the testing temperature is shown along the abscissa.

EXAMPLES

Reference Example 1

Preparation of Al-Fumarate Metal Organic Framework (MOF) Powder

(6) Al-fumarate MOF powder was prepared as described in Example 6 of US 2012/0082864 A1. The resulting powder was then calcined by heating thereof in air (200 NI/h) in 7 h (1° C./min) to 540° C. and holding the powder at that temperature for 5 h.

(7) As may be taken from the X-ray diffraction pattern of the resulting powder shown in FIG. 1a, the material is completely amorphous.

(8) Results from nitrogen sorption analysis at 77K (BJH analysis) are displayed in FIG. 1b and show a well defined mesoporosity with an average pore size of around 4 nm in the range of from 3 to 50 nm. The material displays a BET surface area of 376 m.sup.2/g.

Reference Example 2

Preparation of Copper Chabazite

(9) 515.8 g (20.17 wt.-% in H.sub.2O; 0.49 moles) of adamantyltrimethylammonium hydroxide were dissolved in 196.5 g (10.92 moles) of distilled water, to which 224.3 g of an aqueous solution of tetramethylammonium hydroxide (25 wt.-% in H.sub.2O; 0.62 moles) were added. 93.5 g (0.46 moles) of aluminum triisopropylate were added thereto under stirring at ambient temperature. 19.0 g of chabazite seed crystals (5 wt.-% based on SiO.sub.2) were then added to the mixture, which was subsequently stirred for 5 min. Finally 950.8 g of colloidal silica (Ludox AS 40: 40 wt.-% in H.sub.2O; 6.34 moles) were added thereto and the mixture then stirred for 20 min. The pH of the resulting mixture was 13.6. The mixture was then placed in a stirred 2.5 L autoclave (430 rpm) and incrementally heated during 8 hours to a temperature of 175° C. at which it was held for 24 h. The resulting solid was filtered of and washed with 10 l distilled water to a conductivity of less than 250 μS/cm.sup.3. The powder was then dried over night at 120° C. and subsequently calcined by incremental heating at a rate of 2° C./min to 600° C. and held at that temperature for 6 h to afford 384 g of a white powder.

(10) Elemental analysis of the product afforded <0.1 wt.-% of carbon, 3.0 wt.-% of Al, 0.16 wt.-% of Na, and 40 wt.-% of Si.

(11) The product displayed a BET surface area of 638 m.sup.2/g.

(12) The X-ray diffraction patter of the crystalline product is displayed in FIG. 2 and displays the CHA framework structure, as may be taken from a comparison with the line patter of the CHA-type framework structure included in the diffractogram as a reference.

(13) 150 g of the chabazite powder were then subject to ion exchange with copper. To this effect, the chabazite powder was dispersed in a solution of 1.2 g of acetic acid in 975.0 g of distilled water and heated to 60° C. 31.2 g of copper acetate monohydrate were then added under stirring and the mixture heated anew to 60° C. and held at that temperature under stirring (250 rpm) for 3 h. The solid was then filtered off an washed with distilled water to a conductivity of less than 200 μS/cm.sup.3, after which it was dried at 120° C. for 16 h to afford 150.0 g of a blue powder.

(14) Elemental analysis of the product afforded 3.0 wt.-% of Al, 2.8 wt.-% of Cu, and 39 wt.-% of Si.

(15) The product displayed a BET surface area of 534 m.sup.2/g.

Comparative Example 1

Shaping of Copper Chabazite

(16) 30 g of copper chabazite from Reference Example 2 were admixed with 1.5 g of polyethylene oxide (Alkox E-160, Meisei Chemical Works, Ltd.) and 31 g of distilled water and the resulting mixture kneaded and subsequently extruded with approximately 10 bars of pressure to extrudate strings with a diameter of 1.5 mm. The extrudates were then incrementally heated to 120° C. over 1 h and then held at that temperature for 5 h, and subsequently incrementally heated (1° C./min) in 7 h to 540° C. and calcined at that temperature for 5 h under air (200 NI/h).

(17) After cooling to ambient temperature, the calcinated strings were then split to chips with a length ranging from 0.5 to 1 mm.

(18) The resulting extrudate material displayed an SiO.sub.2:Al.sub.2O.sub.3 molar ratio or 25 and a copper loading of 3.8 wt.-% calculated as CuO on calcined basis. Furthermore, the total intrusion volume was determined to be 0.91 ml/g and the total pore area 5.5 m.sup.2/g as respectively obtained from Hg-porosimetrie. The extrudate material displayed a BET surface area of 552 m.sup.2/g and a bulk density of 0.421 g/ml.

Example 1

Shaping of Copper Chabazite with 15 wt% Al-Fumarate MOF

(19) 25.5 g of copper chabazite from Reference Example 2 were admixed with 1.5 g of polyethylene oxide (Alkox E-160, Meisei Chemical Works, Ltd.), 4.5 g of Al-fumarate MOF powder from Reference Example 1, and 30 g of distilled water and the resulting mixture kneaded and subsequently extruded with approximately 10 bars of pressure to extrudate strings with a diameter of 1.5 mm. The extrudates were then incrementally heated to 120° C. over 1 h and then held at that temperature for 5 h, and subsequently incrementally heated (1° C./min) in 7 h to 540° C. and calcined at that temperature for 5 h under air (200 NI/h).

(20) After cooling to ambient temperature, the calcinated strings were then split to chips with a length ranging from 0.5 to 1 mm.

(21) The resulting extrudate material displayed an SiO.sub.2:Al.sub.2O.sub.3 molar ratio or 13 and a copper loading of 3.3 wt.-% calculated as CuO on calcined basis. Furthermore, the total intrusion volume was determined to be 1.17 ml/g and the total pore area 11 m.sup.2/g as respectively obtained from Hg-porosimetrie. The extrudate material displayed a BET surface area of 532 m.sup.2/g and a bulk density of 0.378 g/ml.

Example 2

Shaping of Copper Chabazite with 30 wt % Al-Fumarate MOF

(22) 21 g of copper chabazite from Reference Example 2 were admixed with 1.5 g of polyethylene oxide (Alkox E-160, Meisei Chemical Works, Ltd.), 9 g of Al-fumarate MOF powder from Reference Example 1, and 32 g of distilled water and the resulting mixture kneaded and subsequently extruded with approximately 10 bars of pressure to extrudate strings with a diameter of 1.5 mm. The extrudates were then incrementally heated to 120° C. over 1 h and then held at that temperature for 5 h, and subsequently incrementally heated (1° C./min) in 7 h to 540° C. and calcined at that temperature for 5 h under air (200 NI/h).

(23) After cooling to ambient temperature, the calcinated strings were then split to chips with a length ranging from 0.5 to 1 mm.

(24) The resulting extrudate material displayed an SiO.sub.2:Al.sub.2O.sub.3 molar ratio or 7 and a copper loading of 3.0 wt.-% calculated as CuO on calcined basis. Furthermore, the total intrusion volume was determined to be 1.13 ml/g and the total pore area 22 m.sup.2/g as respectively obtained from Hg-porosimetrie. The extrudate material displayed a BET surface area of 497 m.sup.2/g and a bulk density of 0.375 g/ml.

Example 3

Shaping of Copper Chabazite with 50 wt % Al-Fumarate MOF

(25) 13 g of copper chabazite from Reference Example 2 were admixed with 1.3 g of polyethylene oxide (Alkox E-160, Meisei Chemical Works, Ltd.), 13 g of Al-fumarate MOF powder from Reference Example 1, and 27 g of distilled water and the resulting mixture kneaded and subsequently extruded with approximately 10 bars of pressure to extrudate strings with a diameter of 1.5 mm. The extrudates were then incrementally heated to 120° C. over 1 h and then held at that temperature for 5 h, and subsequently incrementally heated (1° C./min) in 7 h to 540° C. and calcined at that temperature for 5 h under air (200 NI/h).

(26) After cooling to ambient temperature, the calcinated strings were then split to chips with a length ranging from 0.5 to 1 mm.

(27) The resulting extrudate material displayed an SiO.sub.2:Al.sub.2O.sub.3 molar ratio or 4 and a copper loading of 2.8 wt.-% calculated as CuO on calcined basis. Furthermore, the total intrusion volume was determined to be 1.35 ml/g and the total pore area 39 m.sup.2/g as respectively obtained from Hg-porosimetrie. The extrudate material displayed a BET surface area of 470 m.sup.2/g and a bulk density of 0.331 g/ml.

Comparative Example 2

Shaping of Copper Chabazite Synthesized According to WO 2015/185625 A2

(28) 30 g of copper chabazite as obtained according to Example 3 of WO 2015/185625 A1 was admixed with 1.5 g of polyethylene oxide (Alkox E-160, Meisei Chemical Works, Ltd.) and 29 g of distilled water and the resulting mixture kneaded and subsequently extruded with approximately 10 bars of pressure to extrudate strings with a diameter of 1.5 mm. The extrudates were then incrementally heated to 120° C. over 1 h and then held at that temperature for 5 h, and subsequently incrementally heated (1° C./min) in 7 h to 540° C. and calcined at that temperature for 5 h under air (200 NI/h).

(29) After cooling to ambient temperature, the calcinated strings were then split to chips with a length ranging from 0.5 to 1 mm.

(30) The resulting extrudate material displayed an SiO.sub.2:Al.sub.2O.sub.3 molar ratio or 24 and a copper loading of 3.1 wt.-% calculated as CuO on calcined basis. Furthermore, the total intrusion volume was determined to be 0.73 ml/g and the total pore area 12 m.sup.2/g as respectively obtained from Hg-porosimetrie. The extrudate material displayed a BET surface area of 586 m.sup.2/g and a bulk density of 0.450 g/ml.

Reference Example 3

Preparation of Zr-Fumarate Metal Organic Framework (MOF) Powder

(31) Zr-fumarate MOF was obtained according to the procedure described in WO 2015/127033 A, paragraph [00208] (MOF-801-P).

Example 4

Shaping of Copper Chabazite Synthesized According to WO 2015/185625 A2 with 30 wt % Zr-Fumarate MOF

(32) 21 g of copper chabazite as obtained according to Example 3 of WO 2015/185625 A1 was admixed with 1.5 g of polyethylene oxide (Alkox E-160, Meisei Chemical Works, Ltd.), 9 g of Zr-fumarate MOF obtained according to Reference Example 3, and 22 g of distilled water and the resulting mixture kneaded and subsequently extruded with approximately 10 bars of pressure to extrudate strings with a diameter of 1.5 mm. The extrudates were then incrementally heated to 120° C. over 1 h and then held at that temperature for 5 h, and subsequently incrementally heated (1° C./min) in 7 h to 540° C. and calcined at that temperature for 5 h under air (200 NI/h).

(33) After cooling to ambient temperature, the calcinated strings were then split to chips with a length ranging from 0.5 to 1 mm.

(34) The resulting extrudate material displayed an SiO.sub.2:Al.sub.2O.sub.3 molar ratio or 24, a copper loading of 2.6 wt.-% calculated as CuO on calcined basis, and a content of 20 wt.-% ZrO.sub.2 on calcined basis. Furthermore, the total intrusion volume was determined to be 0.82 ml/g and the total pore area 15 m.sup.2/g as respectively obtained from Hg-porosimetrie. The extrudate material displayed a BET surface area of 487 m.sup.2/g and a bulk density of 0.413 g/ml.

Example 6

Selective Catalytic Reduction (SCR) Testing

(35) Powder Tests

(36) Prior to catalytic testing, the catalyst samples were aged in an aging reactor composed of a 1 mm thick steel tube (grade 1.4841 from Buhlmann Group) with 500 mm of height and 18 mm of internal diameter. A tube metal mantle based furnace was used to heat the reactor to the target reaction temperature which was monitored by an internal thermocouple at the location of the sample. The gas flow was saturated with water by heating of controlled amounts of water via a saturator. Water saturated gas flow was passed through a reactor from the bottom to top. The extrudates formed as described in Examples 1-4 and Comparative Examples 1 and 2 were hydrothermally aged in a tube furnace in a gas flow containing 10 percent H.sub.2O, 10 percent O.sub.2, balance N.sub.2 at a space velocity of 12,500 h.sup.−1 for 6 hours at 850° C.

(37) The aged catalyst samples were then evaluated for selective catalytic reduction of NOx activity using the following reactor set up: the reactor is composed of a 1 mm thick quartz tube with 500 mm of height and 18 mm of internal diameter. An electric split tube furnaces was used to heat the reactor to the target reaction temperature which was monitored by an internal 4-point-thermocouple at the location of the sample. 2 g of the respectively aged samples from Examples 1-4 and Comparative Examples 1 and 2 were loaded into the reactor and secured with a plug of silica wool at each end of the sample. The sample weight is controlled by filling the empty reactor volume with an inert silica based material (Ceramtek AG—product # 1.080001.01.00.00; 0.5 to 1 mm—76 g at the bottom and 90 g at the top of the sample). An inlet gas mixture was formed containing 500 ppm NO, 500 ppm NH.sub.3, 10 percent O.sub.2, 5 percent H.sub.2O and balance He. The steam was prepared by heating of controlled amounts of water at 150 degrees centigrade through a steel presteamer (grade 1.4541 from Buhlmann, dimensions were 6 mm internal diameter and 900 mm length) before mixing with the remaining gases in a static mixer. This gas mixture then passed through a preheater set at 250 degrees centigrade and static mixer before entering the SCR reactor.

(38) The DeNOx activity was measured under steady state conditions by measuring the NOx, NH.sub.3 and N.sub.2O concentrations at the outlet using a FTIR spectrometer. Samples were tested at reaction temperatures of 200, 300, 450 and 600° C. and 400 L/h inlet gas flow. NO conversion (%) was then calculated as ([NO inlet concentration (ppm)—NO outlet concentration (ppm)]/NO inlet concentration (ppm))*100. N.sub.2O make was also recorded as concentration in ppm. The results from the catalytic testing experiments are displayed in Table 1 below.

(39) TABLE-US-00001 TABLE 1 Catalytic performance of the aged samples from Examples 1-4 and Comparative Examples 1 and 2 in selective catalytic reduction (SCR) NO NO NO Conversion Conversion Conversion at 200° C. at 300° C. at 450° C. NO Conversion (%) (%) (%) at 600° C. (%) Comp. Ex. 1 91 95 86 37 Example 1 92 96 90 46 Example 2 96 99 95 54 Example 3 73 95 87 52 Comp. Ex. 2 96 100 91 45 Example 4 90 96 94 67

(40) Thus, as may be taken from the results displayed in Table 1, in some instances the catalysts according to the present invention display a somewhat lower NO.sub.x conversion activity than the comparative examples due to the presence of varying amounts of aluminum oxide or due to the presence of zirconium oxide therein, respectively, which accordingly dilute the catalyst activity to a given extent since the oxides themselves do not display any catalytic activity in this reaction. Quite surprisingly, however, strong synergestic effects are observed in the inventive samples between the metal oxide and zeolitic material. Thus, it has quite unexpectedly been found that the catalysts according to Examples 1 and 2 display a superior conversion activity at all tested temperatures compares to Comparative Example 1 which contains no metal oxide. Furthermore it has surprisingly been found that at higher conversion temperatures and in particular at 600° C., all of the inventive samples display clearly superior results in the selective catalytic reduction of NO.sub.x pared to the respective comparative examples containing the same zeolitic material yet no metal oxide.

(41) Core Tests

(42) For the core tests performed on a filter substrate coated with the inventive catalyst, a sample of the Cu-exchanged zeolite as obtained according to Comparative Example 2 was mixed with distilled water under continuous stirring until a homogeneous mixture was obtained, which was then milled. A slurry of Al-fumarate MOF from Reference Example 1 was then pre-milled to a D90 range of 4-6 μm, and subsequently blended with the the pre-milled zeolite slurry to obtain a final slurry containing 10 wt.-% Al-fumarate MOF, corresponding to an alumina loading of 3 wt.-%. The slurry was then coated on high porosity SiC filter (1.5″×5.54″) by dipping in two passes with a drying step in between both passes, followed by calcination of the coated substrate at 450° C. For comparative purposes, the procedure was repeated without the use of Al-fumarate MOF. Washcoat loading for the Cu-CHA containing core was obtained as 2 g/in.sup.3 and for the Cu-CHA/Al.sub.2O.sub.3 containing core was obtained as 1.9 g/in.sup.3.

(43) The coated filter samples were then aged in at 800° C. hydrothermally (20% O.sub.2 and 10% steam) for 16 hours an oven under prior to performance evaluation. The ramp up phase to target aging temperature lasted 4 hours.

(44) For light-off (steady state) DeNOx evaluation, coated cores were evaluated using an NO-only SCR test with a feed gas composition of NO (450 ppm) and NH.sub.3 (650 ppm) at flow rate of 100,000 h.sup.−1. The results from catalyst testing are shown in FIG. 3. Thus, as may be taken from the results, the testing performed on the core samples confirm the surprising effects observed for the powder samples, wherein the inventive composite material displays comparable results at low temperature and quite unexpectedly affords a substantially increased SCR performance at higher temperatures.

(45) Accordingly, it has quite unexpectedly been found according to the present invention that the combination of specific metal oxides with a zeolitic material, and in particular of mesoporous metal oxides which by themselves do not catalyze the selective catalytic reduction of NO with an SCR-active zeolitic material, leads to strong synergistic effects in view of the fact that the composite materials display improved conversion levels of NO.sub.x, an effect which is particularly pronounced at high temperatures. Furthermore, it has quite unexpectedly been found that said effects may be observed in the catalyst composites after have been subject to a severe aging regimen, such that a highly improved catalyst may be provided not only with respect to the activity in the selective catalytic reduction of NO.sub.x as such, but furthermore with respect to the aging resistance of the catalyst.