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  • B01D53/9409—Nitrogen oxides
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  • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
  • B01J29/70—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65
  • B01J29/7015—CHA-type, e.g. Chabazite, LZ-218
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  • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
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  • B01J29/72—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65 containing iron group metals, noble metals or copper
  • B01J29/76—Iron group metals or copper
  • B01J29/763—CHA-type, e.g. Chabazite, LZ-218
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  • B01J29/82—Phosphates
  • B01J29/84—Aluminophosphates containing other elements, e.g. metals, boron
  • B01J29/85—Silicoaluminophosphates [SAPO compounds]
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  • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
  • B01J35/63—Pore volume
  • B01J35/633—Pore volume less than 0.5 ml/g
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  • C01B15/00—Peroxides; Peroxyhydrates; Peroxyacids or salts thereof; Superoxides; Ozonides
  • C01B15/055—Peroxyhydrates; Peroxyacids or salts thereof
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  • B01D2251/206—Ammonium compounds
  • B01D2251/2062—Ammonia
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  • B01D2255/20761—Copper
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  • B01J2229/00—Aspects of molecular sieve catalysts not covered by B01J29/00
  • B01J2229/10—After treatment, characterised by the effect to be obtained
  • B01J2229/18—After treatment, characterised by the effect to be obtained to introduce other elements into or onto the molecular sieve itself
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  • B01J2229/10—After treatment, characterised by the effect to be obtained
  • B01J2229/18—After treatment, characterised by the effect to be obtained to introduce other elements into or onto the molecular sieve itself
  • B01J2229/186—After treatment, characterised by the effect to be obtained to introduce other elements into or onto the molecular sieve itself not in framework positions
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  • B01J2235/15—X-ray diffraction
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  • B01J35/30—Catalysts, in general, characterised by their form or physical properties characterised by their physical properties

Definitions

• the present disclosure is related to hydrothermally stable microporous crystalline materials comprising a metal containing, high silica chabazite, that is able to retain a specific percentage of its surface area and micropore volume after treatment with heat and moisture.
• the present disclosure is also related to methods of using the disclosed high silica chabazite materials, such as in reducing contaminants in exhaust gases. Such methods include the selective catalytic reduction ("SCR") of exhaust gases contaminated with nitrogen oxides ("NO x ").
• Microporous crystalline materials and their uses as catalysts and molecular sieve adsorbents are known in the art.
• Microporous crystalline materials include crystalline aluminosilicate zeolites, metal organosilicates, and
• aluminophosphates among others.
• One catalytic use of the materials is in the SCR of NO x with ammonia in the presence of oxygen and in the conversion process of different feed stocks, such as an oxygenate to olefin reaction system.
• a class of silicon-substituted aluminophosphates which are both crystalline and microporous and exhibit properties characteristic of both
• SAPOs Silicoaluminophosphates
• the framework structure consists of P0 2 + , AI0 2 " , and Si0 2 tetrahedral units.
• the empirical chemical composition on an anhydrous basis is: mR:(Si x Al y P z )0 2
• R represents at least one organic templating agent present in the intracrystalline pore system
• m represents the moles of R present per mole of (Si x Al y P z )0 2 and has a value from zero to 0.3
• x, y, and z represent the mole fractions of silicon, aluminum, and phosphorous, respectively, present as tetrahedral oxides.
• U.S. Patent No. 4,961 ,917 discloses a method for the reduction of ⁇ with ammonia using a certain class of zeolite catalysts that are sulfur-tolerant, especially when the zeolites are promoted with a promoter such as iron or copper.
• the zeolites disclosed therein have pore diameters of at least 7 Angstroms and are selected from the groups including USY, Beta, and ZSM-20.
• the catalysts employed therein maintain good catalytic properties under high temperature conditions of use, from about 250-600 °C.
• U.S. Patent No. 5,451 ,387 discloses a method for improving the reduction activity of the zeolite catalyst at temperatures below 400 °C, without adversely affecting the reduction capacity above 400 °C, by introducing iron into an intermediate pore size zeolite, which are identified as ZSM-5 type zeolites.
• U.S. Patent No. 6,914,026 discloses an iron-promoted aluminosilicate zeolite with improved hydrothermal stability and good catalytic activity under high temperatures, e.g., 400 °C and above, in the presence of sulfur compounds.
• 6,689,709 and 7,1 18,722 disclose stabilized iron and/or copper promoted zeolite catalysts for NO x reduction, wherein the zeolites include USY, Beta, and/or ZSM- 20, and have pore diameters of at least 7 Angstroms.
• U.S. Patent No. 6,890,501 discloses Beta-zeolites loaded with iron for the SCR of NO x and N 2 0 with ammonia, wherein the zeolite was prepared by ion-exchange or impregnation.
• U.S. Patent No. 5,516,497 discloses a metal-promoted zeolite catalyst and a method for the catalytic reduction of NO x with ammonia using the catalysts in stages.
• the first catalyst is promoted with not more than about 1 % by weight of iron and/or copper promoter
• the second catalyst is promoted with more than about 1 % by weight of iron and/or copper promoter.
• the selectivity of the catalyst, favoring either reduction of NO x or ammonia can be tailored by controlling the content of the promoting metal.
• suitable zeolite materials high temperature gaseous streams, up to about 600 °C, may be treated without seriously affecting the life or efficiency of the catalyst.
• the present disclosure generally provides a
• hydrothermally stable microporous crystalline material comprising a metal containing, high-silica chabazite having a large crystal size.
• a microporous crystalline material comprising a metal containing chabazite, such as a copper chabazite, having a crystal size greater than 0.5 microns and a silica-to-alumina ratio (SAR) greater than 15, such as from 15-60, or even 20-60.
• the metal containing chabazite retains at least 80% of its initial surface area and micropore volume after exposure to temperatures of up to 900 °C in the presence of up to 10 volume percent water vapor for up to 1 hour.
• Other aspects of the present disclosure include methods of SCR of NO x in exhaust gas.
• One such method comprises contacting, in the presence of ammonia or urea, exhaust gas with the metal containing, high-silica chabazite described herein.
• the method comprises first providing an article comprising a microporous crystalline material comprising a metal containing chabazite as described herein.
• Figure 1 is a SEM of the SAPO-34 material described in Example 1 , before aging or cation-exchange.
• Figure 2 is a SEM of the SAPO-34 material described in Example 2, before aging or cation-exchange.
• Figure 3 is a XRD of the SAPO-34 material described in Example 1 , before aging or cation-exchange.
• Figure 4 is a XRD of the SAPO-34 material described in Example 2, before aging or cation-exchange.
• Figure 5 is a XRD of the Cu-exchanged SAPO-34 material described in Example 1 after hydrothermal aging at 800 °C.
• Figure 6 is a XRD of the Cu-exchanged SAPO-34 material described in Example 2 after hydrothermal aging at 800 °C.
• Figure 7 is a SEM of the SAPO-34 material described in
• Figure 8 is an SEM of a large crystal, high-silica chabazite described in Inventive Example 3.
• Figure 9 is an SEM of a small crystal, high-silica chabazite, described in Comparative Example 3.
• Hydrothermally stable means having the ability to retain a certain percentage of initial surface area and/or microporous volume after exposure to elevated temperature and/or humidity conditions (compared to room temperature) for a certain period of time. For example, in one embodiment, it is intended to mean retaining at least 80%, such as at least 85%, at least 90%, or even at least 95%, of its surface area and micropore volume after exposure to conditions simulating those present in an automobile exhaust, such as temperatures ranging up to 900 °C in the presence of up to 10 volume percent (vol%) water vapor for times ranging from up to 1 hour, or even up to 16 hours, such as for a time ranging from 1 to 16 hours.
• Initial Surface Area means the surface area of the freshly made crystalline material before exposing it to any aging conditions.
• Initial Micropore Volume means the micropore volume of the freshly made crystalline material before exposing it to any aging conditions.
• Direct synthesis refers to a method that does not require a metal-doping process after the zeolite has been formed, such as a subsequent ion-exchange or impregnation method.
• SCR' Selective Catalytic Reduction or “SCR' refers to the reduction of ⁇ (typically with ammonia) in the presence of oxygen to form nitrogen and H 2 0.
• exhaust gas refers to any waste gas formed in an industrial process or operation and by internal combustion engines, such as from any form of motor vehicle.
• microporous crystalline materials comprising a molecular sieve or zeolite having an 8-ring pore opening structure of the present invention exhibit good hydrothermal properties, as evidenced by the stability of the surface area and micropore volume after exposure to high temperatures and humidity. For example, after being treated at up to 900 °C in the presence of up to 10 vol% water vapor for a time ranging from 1 to 16 hours, the microporous crystalline materials of the present invention maintain at least 80% of their initial surface area. Likewise, after the treatment, the microporous crystalline materials of the present invention maintain at least 80% of their initial micropore volume.
• a microporous crystalline material comprising a metal containing chabazite having a crystal size greater than 0.5 microns and a silica-to-alumina ratio (SAR) greater than 15, such as from 15-60, or even 20-60.
• the metal containing chabazite retains at least 80% of its initial surface area and micropore volume after exposure to temperatures of up to 900 °C in the presence of up to 10 volume percent water vapor for up to 1 hour.
• the metal portion of the chabazite comprises copper or iron, which can be introduced into the chabazite in various ways, such as by liquid-phase or solid ion-exchange or incorporated by direct-synthesis.
• the copper comprises at least 1.0 weight percent of the total weight of the material, such as a range from 1.0-4.0 weight percent of the total weight of the material.
• the metal portion of the chabazite may comprises iron instead of or in addition to copper.
• the iron comprises at least 0.2 weight percent of the total weight of the material, such as an amount ranging from 0.2-3.0 weight percent of the total weight of the material.
• metal containing chabazite material described herein has an initial surface area of at least 650 m 2 /g and an initial micropore volume of at least 0.25 cc/g.
• the crystal size of the metal containing chabazite may range from 0.5 to 5.0 microns.
• the microporous crystalline materials disclosed herein has an initial surface area of at least 650 m 2 /g, such as at least 700 m 2 /g, or even up to 800 m 2 /g.
• microporous crystalline materials disclosed herein may have an initial micropore volume of at least 0.25 cc/g, such as 0.30 cc/g.
• the method comprises contacting, typically in the presence of ammonia or urea, exhaust gas with a metal containing chabazite as described herein.
• the method comprises contacting exhaust gas with a metal containing chabazite having a crystal size greater than 0.5 microns and a silica-to-alumina ratio (SAR) greater than 15, such as from 15-60, or even 20-60.
• SCR selective catalytic reduction
• the metal containing chabazite typically retains at least 80% of its initial surface area and micropore volume after exposure to temperatures of up to 900 °C in the presence of up to 10 volume percent water vapor for up to 1 hour.
• SCR selective catalytic reduction
• an article comprising a microporous crystalline material comprising a metal containing chabazite described herein, such as one having a crystal size greater than 0.5 microns and a silica-to-alumina ratio
• This step may be performed in presence of ammonia or urea.
• the article described herein may be in the form of a channeled or honeycombed-shaped body; a packed bed; microspheres; or structural pieces.
• the packed bed comprises balls, pebbles, pellets, tablets, extrudates, other particles, or combinations thereof.
• the structural pieces described herein may be in the form of plates or tubes.
• the channeled or honeycombed-shaped body or structural piece is formed by extruding a mixture comprising the chabazite molecular sieve.
• the channeled or honeycombed-shaped body or structural piece is formed by coating or depositing a mixture comprising the chabazite molecular sieve on a preformed substrate.
• the microporous crystalline materials of the present invention comprise molecular sieves or zeolites, including SAPO-34, high- silica chabazite, or those having a structure defined by the Structure Commission of the International Zeolite Association as CHA.
• SAPO-34 structure described herein may contain Si0 2 in an amount ranging from 1-20% and may have a crystal size greater than 0.3 microns.
• the high-silica chabazite of the present invention may have a silica-to-alumina ratio ("SAR") greater than 15, such as ranging from 15-60.
• the microporous crystalline materials described herein may also comprise molecular sieves and aluminosilicate zeolites having an 8-ring pore opening structure defined by the Structure Commission of the International Zeolite Association chosen from: AEI, AFT, AFX, CHA, DDR, ERI, ITE, ITW, KFI, LEV, LTA, PAU, RHO, and UFI. These materials also exhibit the hydrothermal stability properties described herein, such as retaining at least 80% of their initial surface area and initial micropore volume after being treated at temperatures of up to 900 °C in the presence of up to 10 vol% water vapor for a time ranging from 1 to 16 hours. These materials may be an aluminosilicate having a SAR greater than 15, such as ranging from 20-60. Alternatively, these materials may also be SAPO molecular sieve structures containing Si0 2 in an amount ranging from 1-20%.
• the high silica chabazite compositions of the present invention exhibit good hydrothermal and thermal properties as identified herein. For example, after being treated at temperatures up to 900 °C in the presence of up to 10 vol% water vapor for 16 hours, the inventive compositions maintain at least 80% of their initial surface area, such as at least 85%, at least 90%, or even at least 95%. Likewise, after the treatment, the inventive compositions maintain at least 80% of their initial micropore volume, such as 85%, and even 90% of their initial micropore volume.
• the microporous crystalline materials of the present invention may comprise a metal, such as copper.
• the copper is introduced into the microporous crystalline material by liquid-phase or solid ion-exchange or incorporated by direct-synthesis.
• the present invention also is directed to hydrothermally stable microporous materials comprising a molecular sieve or zeolite having an 8-ring pore opening structure for SCR of NO x with urea or ammonia, wherein the microporous material comprises copper and retains at least 80% of its surface area and micropore volume after exposure to temperatures of up to 900 °C and up to 10% water for up to 1 hour.
• the copper may comprise at least 1.0 weight percent of the total weight of the material.
• iron oxide comprises at least 0.20 weight percent of the total weight of the composition, such as 0.25 weight percent, or even 0.30 weight percent.
• the resulting iron cation-exchanged SAPO-34 compositions have a surface area of at least 250 m 2 /g, such as at least 400 m /g, and even at least 600 m 2 /g.
• copper oxide comprises at least 1.90 weight percent of the total weight of the composition, such as 1.95 weight percent, and even 2.00 weight percent.
• the resulting copper cation-exchanged SAPO-34 compositions have a surface area of at least 550 m 2 /g, such as at least 600 m 2 /g, and even at least 650 m 2 /g.
• the resulting cation-exchanged SAPO-34 compositions also exhibit good hydrothermal and thermal properties, as evidenced by the stability of the surface area after exposure to high temperatures and humidity. For example, after being treated at temperatures up to 900 °C in the presence of up to 10 vol% water vapor for up to 1 hour, the iron cation-exchanged SAPO-34 compositions of the present invention maintain at least 20% of their initial surface area, such as at least 40%, and even at least 60%.
• microporous crystalline materials of the present invention are useful as exhaust catalysts, such as for reduction of NO x in automotive exhaust, in part because of their good thermal and hydrothermal stability. Under extreme conditions, automotive exhaust catalysts are exposed to heat up to and in excess of 900 °C. Therefore, some automotive exhaust catalysts are required to be stable at temperatures up to and in excess of 900 °C.
• exhaust gas refers to any waste gas formed in an industrial process or operation and by internal combustion engines, the composition of which varies.
• Non-limiting examples of the types of exhaust gases that may be treated with the disclosed materials include both automotive exhaust, as well as exhaust from stationary sources, such as power plants, stationary diesel engines, and coal-fired plants.
• the present invention is directed to a method for SCR of exhaust gases contaminated with NO x .
• the nitrogen oxides of exhaust gases are commonly NO and N0 2 ; however, the present invention is directed to reduction of the class of nitrogen oxides identified as NO x .
• Nitrogen oxides in exhaust are reduced with ammonia to form nitrogen and water.
• the reduction can be catalyzed to preferentially promote the reduction of the NO x over the oxidation of ammonia by the oxygen, hence "selective catalytic reduction.”
• the inventive method for SCR of NO x in exhaust gases comprises contacting, in the presence of ammonia or urea, exhaust gas with a hydrothermally stable microporous crystalline material comprising a molecular sieve or zeolite having an 8-ring pore opening structure, wherein the crystalline material retains at least 80% of its surface area and micropore volume after exposure to temperatures of up to 900 °C in the presence of up to 10 vol% water vapor for a time ranging from 1 to 16 hours.
• the molecular sieves and zeolites having an 8-ring pore opening structure comprising the microporous crystalline material may be chosen from those structures defined by the Structure Commission of the International Zeolite Association as AEI, AFT, AFX, CHA, DDR, ERI, ITE, ITW, KFI, LEV, LTA, PAU, RHO, and UFI.
• One inventive method of SCR of NO x in exhaust gas also comprises contacting, in the presence of ammonia or urea, exhaust gas with a hydrothermally stable microporous material comprising a molecular sieve or zeolite, such as a high silica chabazite or other material having an 8-ring pore opening structure, wherein the microporous material comprises metal and retains at least 80% of its surface area and micropore volume after exposure to temperatures of up to 900 °C in the presence of up to 10 vol% water vapor for up to 1 hour.
• a hydrothermally stable microporous material comprising a molecular sieve or zeolite, such as a high silica chabazite or other material having an 8-ring pore opening structure, wherein the microporous material comprises metal and retains at least 80% of its surface area and micropore volume after exposure to temperatures of up to 900 °C in the presence of up to 10 vol% water vapor for up to 1 hour.
• the inventive method for SCR of exhaust gases may comprise (1 ) adding ammonia or urea to the exhaust gas to form a gas mixture; and (2) contacting the gas mixture with a microporous crystalline composition comprising SAPO-34, having an initial surface area of at least 650 m 2 /g, wherein the surface area, after being treated at 700-900 °C in the presence of up to 10 vol% water vapor for a time ranging from 1 to 16 hours, is at least 80% of the initial surface area; such that the NO x and ammonia of the gas mixture is converted to nitrogen and water.
• the NO x of the exhaust gas are substantially converted.
• the inventive method may be performed using a microporous crystalline composition comprising SAPO-34 that has been cation exchanged with iron, wherein iron oxide is at least 0.20 weight percent of the total weight of the microporous crystalline composition, and wherein the SAPO-34 has an initial surface area of at least 250 m 2 /g, and wherein the surface area, after being treated at temperatures up to 900 °C in the presence of up to 10 vol% water vapor for up to 1 hour, is at least 10% of the initial surface area.
• the inventive method may also be performed using a microporous crystalline composition comprising SAPO-34 cation exchanged with copper, wherein copper oxide is at least 1.0 weight percent of the total weight of the microporous crystalline composition, and wherein the SAPO-34 has an initial surface area of at least 500 m 2 /g, and wherein the surface area, after being treated at temperatures of up to 900 °C in the presence of up to 10 vol% water vapor for up to 1 hour, is at least 80% of the initial surface area.
• microporous crystalline materials of the present invention show surprisingly high stability and high reduction of NO x activity over large pore zeolites.
• microporous crystalline materials of the present invention may also be useful in the conversion of oxygenate-containing feedstock into one or more olefins in a reactor system.
• SAPO-34 SAPO-34
• compositions may be used to convert methanol to olefins.
• a method of making the crystalline material according to the present invention includes mixing together an organic structural directing agent, such as a tetraethylammonium hydroxide solution (e.g., 35% TEAOH), a precursor of aluminum (e.g.,
• pseudoboehmite alumina pseudoboehmite alumina
• de-ionized water de-ionized water
• other known ingredients including a source of iron or copper, if desired, and silica sol can be added while stirring, to form a gel.
• Crystallization seeds such as a particular zeolite, may be added to the gel to form a desired molar composition.
• the gel can then be heated in an autoclave for a time and temperature to provide a substantially pure phase composition after cooling, washing, and filtering the product.
• the product can achieve a desired SAR and/or remove organic residue upon calcination.
• the present invention is also directed to a catalyst composition comprising the microporous crystalline material described herein.
• the catalyst composition may also be cation-exchanged, particularly with iron or copper.
• the present invention is directed to a catalyst composition
• a catalyst composition comprising a microporous crystalline composition comprising SAPO-34 having an initial surface area of at least 650 m 2 /g, wherein the surface area, after being treated at temperatures of up to 900 °C in the presence of up to 10 vol% water vapor for up to 16 hours, is at least 80% of the initial surface area and a matrix material.
• the catalyst composition may comprise a cation-exchanged SAPO-34 composition, particularly with iron or copper.
• Any suitable physical form of the catalyst may be utilized, including, but not limited to: a channeled or honeycombed-type body; a packed bed of balls, pebbles, pellets, tablets, extrudates or other particles; microspheres; and structural pieces, such as plates or tubes.
• High-silica chabazite (structure code CHA) was synthesized according to examples in U.S. Patent No. 4,544,538, which is herein incorporated by reference.
• NaOH, de-ionized water, ⁇ , ⁇ , ⁇ -Tri methyl- 1 - adamantammonium hydroxide (R) solution, and aluminum hydroxide (Reheis F- 2000) were mixed together to form a solution.
• Silica gel PQ Corporation was added to the solution to form a synthesis gel with the following molar composition:
• the synthesis gel was loaded in an autoclave and crystallization was conducted at 160°C for 96 hours with agitation. After filtering, washing, and drying, the product showed pure chabazite structure by XRD.
• the product was calcined at 550°C for 10 hours to remove residual organic. To remove residual sodium, the calcined product was slurried in 2 liters of 2 M NH 4 N0 3 solution and stirred at 80 °C for 2 hours. The NH 4 -form product was then ion-exchange with Cu(N0 3 ) 2 solution.
• Fig. 8 is an SEM showing the large crystal size associated with this Example.
• SAPO-18 Structure code AEI
• Pseudoboehmite alumina, phosphoric acid, silica sol, ⁇ , ⁇ -diisopropylethylamine (DIPEA), and deionized water were mixed to form a gel.
• DIPEA ⁇ , ⁇ -diisopropylethylamine
• deionized water was mixed to form a gel.
• the gel was stirred at room temperature for 120 min before being charged to an autoclave.
• the product was then dried and calcined at 550 °C to remove organic.
• Table 1 Table 1
• Low-silica chabazite (structure code CHA) was synthesized according to examples of U.S. Patent 5,026,532, which is herein incorporated by reference. After filtering, washing, and drying, the product was calcined at 550 °C. To remove residual sodium and potassium, the product was then washed in a solution containing 0.25 M HN0 3 and 4 M NH 4 N0 3 at 80 °C for 2 hours. The resulting properties are listed below in Table 1.
• Al isopropoxide, phosphoric acid, tetraethyl orthosilicate, TEAOH solution, and deionized water were mixed together to form a gel with the following composition: 0.33 Si0 2 : 1.0 Al 2 0 3 : 1.0 P 2 0 5 : 1.0 TEAOH: 51 H 2 0
• the gel was stirred at room temperature for about 30 min before charged to an autoclave.
• the autoclave was heated to 180 °C and maintained at the temperature for 12 hours.
• the product was recovered by filtration and washed with deionized water.
• the product was then dried and calcined to remove any organic.
• the resulting product was small crystals (less than 0.2 micron in size). The resulting properties are listed below in Table 1.
• Hvdrothermal Aging Tests [0077] The foregoing samples were hydrothermally aged at temperatures ranging from 700-900 °C in the presence of 10 vol% water vapor for between 1 and 16 hours to simulate automotive exhaust aging conditions. The activities of the hydrothermally aged materials for NO x conversion, using NH 3 as reductant, were tested with a flow-through type reactor. Powder zeolite samples were pressed and sieved to 35/70 mesh and loaded into a quartz tube reactor. The gas stream conditions are set forth in Table 2. Reactor temperature was ramped and NO x conversion was determined with an infrared analyzer at each temperature interval. The results are set forth in Table 2 below.
• Fig. 9 is an SEM showing the microstructure associated with this comparative sample.
• the hydrothermal stability properties of this comparative example were compared to the properties of inventive Example 3, as well as comparative Example 1. A summary of those results is provided in Table 3. NOx Conversion (%) at 38.5 16.9 150 °C***

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