Process for a continuous synthesis of zeolitic materials using seed crystals loaded with organotemplate

Abstract

Disclosed herein is a continuous process for preparing zeolitic material with a CHA-type framework structure comprising SiO.sub.2 and X.sub.2O.sub.3 and the zeolitic material so-obtained. The processes comprises (i) preparing a mixture comprising one or more sources of SiO.sub.2, one or more sources of X.sub.2O.sub.3, seed crystals, one or more tetraalkylammonium cation R.sup.5R.sup.6R.sup.7R.sup.8N.sub.+-containing compounds as structure directing agent, and a liquid solvent system; (ii) continuously feeding the mixture prepared in (i) into a continuous flow reactor at a liquid hourly space velocity; and (iii) crystallizing the zeolitic material with a CHA-type framework structure from the mixture in the continuous flow reactor.

Claims

1. A continuous process for preparing a zeolite material with a CHA-type framework structure comprising SiO.sub.2 and X.sub.2O.sub.3, the process comprising: (i) preparing a mixture comprising one or more sources of SiO.sub.2, one or more sources of X.sub.2O.sub.3, seed crystals, one or more tetraalkylammonium cation R.sup.5R.sup.6R.sup.7R.sup.8N.sup.+-containing compounds as a structure directing agent, and a liquid solvent; (ii) continuously feeding the mixture prepared in (i) into a continuous flow reactor at a liquid hourly space velocity ranging from 0.3 h.sup.−1 to 20 h.sup.−1 for a duration of at least 1 h; and (iii) crystallizing the zeolite material with the CHA-type framework structure from the mixture in the continuous flow reactor, wherein the mixture is heated to a temperature ranging from 100° C. to 300° C. and wherein the volume of the continuous flow reactor ranges from 50 cm.sup.3 to 75 m.sup.3; wherein the seed crystals comprise one or more zeolite materials with one or more cationic organotemplates as counter-ions at the ion exchange sites of the framework structure; wherein X is a trivalent element; wherein each of R.sup.5, R.sup.6, and R.sup.7 is independently chosen from one another and is an alkyl; and wherein R.sup.8 is a cycloalkyl; wherein (a) a surface of the inner wall of the continuous flow reactor is lined with an organic polymer material, and/or (b) wherein the mixture constituting the feed crystallized in (iii) consists of a first liquid phase, a second liquid phase, and a solid phase comprising the seed crystals, wherein the first liquid phase comprises the liquid solvent and the second liquid phase comprises a lubricating agent, wherein the lubricating agent comprises one or more fluorinated compounds.

2. The process of claim 1, wherein the continuous flow reactor is chosen from a tubular reactor, a ring reactor, and a continuously oscillating reactor.

3. The process of claim 1, wherein in (iii) the mixture is heated under autogenous pressure.

4. The process of claim 1, wherein the process further comprises one or more of the following: (iv) quenching a reaction product effluent continuously upon exiting the reactor in step (iii) with a liquid comprising one or more solvents, via expansion of the reaction product effluent, or combinations thereof; (v) isolating the zeolite material obtained in step (iii) or step (iv); (vi) washing the zeolite material obtained in step (iii), step (iv) or step (v); (vii) drying the zeolite material obtained in step (iii), step (iv), step (v), or step (vi); and (viii) calcining the zeolite material obtained in step (iii), step (iv), step (v), step (vi), or step (vii).

5. The process of claim 1, wherein the one or more cationic organotemplates are chosen from tetraalkylammonium cations and mixtures thereof.

6. The process of claim 1, wherein X is chosen from Al, B, In, Ga, and combinations of two or more thereof.

7. The process of claim 1, wherein the mixture prepared in (i) and crystallized in (iii) further comprises one or more tetraalkylammonium cation R.sup.1R.sup.2R.sup.3R.sup.4N.sup.+-containing compounds, wherein each of R.sup.1, R.sup.2, R.sup.3, and R.sup.4 is independently chosen from one another and is an alkyl.

8. The process of claim 4, wherein the process further comprises: (ix) subjecting the zeolite material obtained in (v), (vi), (vii), or (viii) to an ion-exchange procedure, wherein at least one ionic non-framework element or compound contained in the zeolite material is ion-exchanged against one or more metal ions.

9. The process of claim 8, wherein in (ix) the step of subjecting the zeolite material to an ion-exchange procedure comprises: (ix.a) subjecting the zeolite material obtained in (v), (vi), (vii), or (viii) to an ion-exchange procedure, wherein the at least one ionic non-framework element or compound contained in the zeolite material is ion-exchanged against NH.sub.4.sup.+; (ix.b) calcining the ion-exchanged zeolite material obtained in (ix.a) for obtaining the H-form of the zeolite material; and (ix.c) subjecting the zeolite material obtained in (ix.b) to the ion-exchange procedure, wherein H.sup.+ contained in the zeolite material as ionic non-framework element is ion-exchanged against one or more metal ions.

10. The process of claim 9, wherein the one or more metal ions are chosen from ions of alkaline earth metal elements, transition metal elements, and combinations thereof.

11. A zeolite material obtained according to the process of claim 1.

12. The zeolite material according to claim 11, wherein the zeolite material is as a molecular sieve, an adsorbent for ion-exchange, a catalyst, a catalyst precursor, a catalyst support, and a catalyst support precursor.

Description

DESCRIPTION OF THE FIGURES

(1) FIGS. 1, 2, 6, and 8 respectively show the X-ray diffraction pattern (measured using Cu K alpha-1 radiation) of the crystalline materials obtained according to Reference Example 1, Example 1, Example 5 and Example 6, respectively, wherein the line pattern of the CHA-type framework has been further included in the respective figures for comparison. In the figures, the angle 2 theta in ° is shown along the abscissa and the intensities are plotted along the ordinate.

(2) FIG. 3 displays two SEM images of a portion of a sample of the product obtained from Example 1 at different magnifications, wherein the scale in the images are indicated by the legend at the bottom right of the respective image.

(3) FIG. 4 displays two SEM images of a portion of the product obtained from Example 2 at different magnifications, wherein the scale in the images are indicated by the legend at the bottom right of the respective image.

(4) FIG. 5 displays results from SCR testing of Cu-CHA moldings from Example 3 according to Example 4, wherein the temperature in ° C. is shown along the abscissa, and the conversion rate of NOx in % is plotted along the ordinate. In the figure, the results for the samples aged at 650° C. for 50 h are indicated as “•”, and the results for the samples aged at 820° C. for 16 h are indicated as “.diamond-solid.”.

(5) FIG. 7 displays two SEM images of a portion of the product obtained from Example 5 at different magnifications, wherein the scale in the images are indicated by the legend at the bottom right of the respective image.

(6) FIG. 9 displays two SEM images of a portion of the product obtained from Example 7 at different magnifications, wherein the scale in the images are indicated by the legend at the bottom right of the respective image.

(7) FIG. 10 displays results from SCR testing of Cu-CHA moldings from Example 8 according to Example 9, wherein the temperature in ° C. is shown along the abscissa, and the conversion rate of NOx in % is plotted along the ordinate. In the figure, the results for the fresh samples are indicated as “•”, and the results for samples aged at 650° C. for 50 h are indicated as “.diamond-solid.”, and the results for the samples aged at 820° C. for 16 h are indicated as “.Math.”. Furthermore, the results from the SCR testing against a comparative sample are also shown.

(8) FIG. 11 displays as a bar chart the results from SCR testing of Cu-CHA moldings from Example 8 according to Example 9 against a comparative sample, showing the results for fresh, samples aged at 650° C. for 50 h, and samples aged at 820° C. for 16 h. As one can see, the bar chart indicates the results taken at 200° C. and 575° C. for each of the samples.

EXPERIMENTAL SECTION

Reference Example 1: Preparation of Seed Crystals Having a CHA-Type Framework Structure

(9) 194.5 g of deionized water and 943.1 g of a solution of 1-adamantyltrimethylammonium hydroxide (AdaTMAOH) (20.17 wt.-% aqueous solution obtained from BASF) were placed in a flask and treated with 86.4 g of a solution of sodium hydroxide (50 wt.-% aqueous solution) thus obtaining a clear solution. 28.1 g of aluminum hydroxide (obtained from Sigma Aldrich) were then added stepwise and the resulting mixture then stirred for 30 min at room temperature for obtaining a milky solution. 901.3 g of Ludox SM 30 (30 wt.-% SiO.sub.2 suspension in water obtained from Sigma Aldrich) were then added under stirring during which the viscosity of the mixture in-creased. The suspension displaying molar ratios of SiO.sub.2:Al(OH).sub.3:NaOH:AdaTMAOH of 1:0.04:0.24:0.20 was then stirred for a further 30 min at room temperature.

(10) The reaction mixture was then placed in an autoclave with a volume of 2.5 L and then heated under stirring (200 rpm) in 45 min to 160° C., after which it was held at that temperature for 120 min. The maximum pressure measured in the autoclave during the reaction was 0.5 MPa (5 bar). After the synthesis, the suspension was filtered off and the solid product washed with distilled water. The filter cake (214.8 g) was then dried in a recirculating air oven at 120° C. over night for affording a crystalline product.

(11) As may be taken from the X-ray diffraction pattern of the product in FIG. 1, it displays a CHA-type framework structure. The crystallinity was calculated to be 52% based on the X-ray diffractogramm of the sample in question. The mean particle size D50 by volume as determined according to ISO 13320:2009 was 150 μm, and the particle size D10 and D90 was 12 μm and 504 μm respectively.

(12) Elemental analysis of the product afforded: C: 15.7%, Al: 2.3%, Na: 0.37%, Si: 34%.

Reference Example 2: Preparation of Synthesis Gel for the Continuous Synthesis of a Zeolitic Material Having a CHA-Type Framework Structure

(13) 423.3 g of an aqueous solution of cyclohexyltrimethylammonium hydroxide (CHTMAOH) (20 wt.-% aqueous solution from BASF) and 123.7 g of an aqueous solution of tetramethylammonium hydroxide (TMAOH) (25 wt.-% aqueous solution obtained from Sachem) were placed in a 2 L quadruple neck round bottom flask. 16.9 g of aluminum hydroxide (obtained from Wako) were then added stepwise and the resulting mixture then stirred for 45 min at room temperature for obtaining a white suspension. 450.0 g Ludox AS 40 (40 wt.-% SiO.sub.2 suspension in water obtained from Grace) were then added under stirring and the result mixture then stirred for additional 15 min. 18.0 g of the crystalline product obtained from Reference Example 1 were then added, and the resulting mixture displaying molar ratios of SiO.sub.2:Al(OH).sub.3:CHTMAOH:TMAOH:H.sub.2O=1:0.072:0.177:0.113:13 was then heated to 85° C. and stirred (270 rpm) at that temperature over night for affording an aged gel.

Reference Example 3: Determination of the BET Specific Surface Area

(14) The BET specific surface area was determined according to ISO 9277, second edition 2010, from the N.sub.2-isotherm obtained via nitrogen physisorption at 77 K.

Reference Example 4: Determination of the Micropore Volume

(15) The micropore volume was determined according to DIN 66134, from the N.sub.2-isotherm obtained via nitrogen physisorption at 77 K.

Example 1: Continuous Synthesis of a Zeolitic Material Having a CHA-Type Framework Structure

(16) The synthesis gel obtained from Reference Example 2 was continuously fed into a tubular reactor made of stainless steel having an inner diameter of 6 mm and a reactor volume of 150 ml and continuously crystallized in the reactor at a temperature of 230° C. and at a pressure of 50 bar wherein the retention time was set to 2 h. High pressure ball valves were installed after the outlet of the reactor connected by a short steel tube of 2.5 mL (d=6 mm). The reaction mixture was continuously guided through the reactor by introducing the synthesis gel under high pressure. Every 2 min the first high pressure ball valve was opened to allow synthesis gel to flow into the short steel tube and then closed again to maintain the pressure on the reactor. After closing of the first high pressure ball valve, the second opened immediately, allowing the reaction mixture to exit the tube. The suspension obtained at the exit of the reactor was continuously collected, washed with water, and then filtered off, wherein the filter cake was dried in a recirculating air oven at 105° C. over night and subsequently calcined at 550° C. for 6 h.

(17) A sample of the product was analyzed via X-ray diffraction, elemental analysis and scanning electron microscopy (SEM):

(18) As may be taken from the X-ray diffraction pattern of the sample of the product in FIG. 2, it displays a CHA-type framework structure. The crystallinity of the product was calculated to 91% based on the X-ray diffractogramm of the sample in question.

(19) Elemental analysis of the sample of the product afforded: Al: 2.9%, Na: 0.15%, Si: 41%.

(20) FIG. 3 displays two SEM images of a portion of the sample of the product at different magnifications.

Example 2: Ion Exchange of the Zeolitic Material Having a CHA-Type Framework Structure Obtained from Example 1

(21) An aqueous solution of ammonium nitrate (50 wt.-%) is prepared in a 500 ml quadruple neck round bottom flask and heated to 60° C. A portion of the product obtained from Example 1 was then added to the solution under heating, wherein the weight ratio of zeolite:ammonium nitrate:deionized water in the heated mixture were 1:1:100. The resulting mixture was then stirred for 1 h at 60° C. The suspension was then filtered off and washed with water. The filter cake was then dried at 120° C. for 4 h and the temperature then raised to 550° C. at which it was then held for 6 h for calcination.

(22) FIG. 4 displays two SEM images of a portion of the sample of the product at different magnifications.

Example 3: Preparation of a Cu-CHA Molded Material from the Ion-Exchanged Zeolitic Material from Example 2

(23) A sample of the product obtained from Example 2 was loaded with copper via incipient wetness impregnation of the zeolitic material with a copper nitrate solution. The impregnated material was then dried for 20 h at 50° C. and then calcined at 450° C. for 5 h for affording Cu-CHA with 3.3 wt.-% of copper calculated as CuO. The resulting Cu-CHA material was then slurried with alumina binder for affording a mixture with 70 wt.-% Cu-CHA and 30 wt.-% alumina. The slurry was then dried under stirring and then calcined at 550° C. for 1 h. The resulting solid was crushed and sieved to afford a 250-500 μm fraction of the molded material.

Example 4: SCR Testing of the Molded Cu-CHA Material from Example 3

(24) The molded material from Example 3 was tested in the selective catalytic reduction of NOx using a feed gas containing 500 ppm NO, 500 ppm NH.sub.3, 5 vol.-% H.sub.2O, 10 vol.-% O.sub.2, and balance N.sub.2, wherein the testing was conducted at a gas hourly space velocity of 80,000 h.sup.−1. The sample amount was adjusted by dilution with corundum to 120 mg Cu-CHA/reactor, wherein the reactor volume was about 1 mL volume. A first set of samples was then aged at 650° C. in air with 10 vol.-% steam for 50 h, and a second set of samples was aged at 820° C. in air with 10 vol.-% steam for 16 h.

(25) Prior to testing, a first run at 200° C., 400° C., and 575° C. was conducted for degreening of the respective samples. The SCR testing was then conducted with the aged samples, wherein the testing results are shown in FIG. 5. As may be taken from the results, the Cu-CHA molded material shows excellent SCR activity over a broad temperature range, even after severe aging at 820° C.

Example 5: Continuous Synthesis of a Zeolitic Material Having a CHA-Type Framework Structure Using a Lubricating Agent (Fomblin)

(26) A teflon-lined tubular reactor having an inner diameter of 6.4 mm and a reactor volume of 160 ml was filled with 250 ml of a perfluoropolyether (Fomblin). The synthesis gel obtained from Reference Example 2 was then fed into the reactor and continuously crystallized in the reactor which was heated to a temperature of 240° C. and at a pressure of 60 bar wherein the retention time was set to 1 h. High pressure ball valves were installed after the outlet of the reactor connected by a short steel tube of 2.5 mL (d=6 mm). The reaction mixture was continuously guided through the reactor by introducing the synthesis gel under high pressure. Every 2 min the first high pressure ball valve was opened to allow synthesis gel to flow into the short steel tube and then closed again to maintain the pressure on the reactor. After closing of the first high pressure ball valve, the second opened immediately, allowing the reaction mixture to exit the tube. The suspension obtained at the exit of the reactor was continuously collected, wherein the perfluoropolyether was removed from the reaction product via phase separation. The aqueous phase was then centrifuged, and the solid washed with water and dried at 80° C. over night. The product was then calcined at 550° C.

(27) A sample of the product was analyzed via X-ray diffraction, elemental analysis and scanning electron microscopy (SEM):

(28) As may be taken from the X-ray diffraction pattern of the sample of the product in FIG. 6, it displays a CHA-type framework structure. The crystallinity of the product was calculated to 87% based on the X-ray diffractogramm of the sample in question.

(29) Elemental analysis of the sample of the product afforded: C: <0.1%, Al: 3.0%, Na: 0.13%, Si: 38%.

(30) FIG. 7 displays two SEM images of a portion of the sample of the product at different magnifications.

Example 6: Continuous Synthesis of a Zeolitic Material Having a CHA-Type Framework Structure Using a Lubricating Agent (Perfluorinated Decalin)

(31) Example 5 was repeated, yet instead of employing Fomblin as the lubricating agent, perfluorinated decalin was employed.

(32) As may be taken from the X-ray diffraction pattern of the sample of the product in FIG. 8, it displays a CHA-type framework structure. The crystallinity of the product was calculated to be 93% based on the X-ray diffractogramm of the sample in question.

(33) Elemental analysis of the sample of the product afforded: F<0.07 wt. %, C<0.1 wt. %, Al: 2.9 wt. %, Na: 0.10 wt. %, Si: 40 wt. %.

(34) N.sub.2 Isotherm of the sample of the product afforded: a BET specific surface area of 636.6 m.sup.2/g, determined as described in Reference Example 3; a t-plot micropore volume of 0.267 cm.sup.3/g, determined as described in Reference Example 4.

Example 7: Ion Exchange of the Zeolitic Material Having a CHA-Type Framework Structure Obtained from Example 6

(35) Example 2 was repeated, yet instead of employing the zeolitic material having a CHA-type framework structure obtained from Example 1, the material obtained from Example 6 was employed.

(36) Elemental analysis of the sample of the product afforded: F<0.03 wt. %, C<0.1 wt. %, Al: 2.7 wt. %, Na: <0.01 wt. %, Si: 38 wt. %.

(37) N.sub.2 Isotherm of the sample of the product afforded: a BET specific surface area of 620.6 m.sup.2/g, determined as described in Reference Example 3; a t-plot micropore volume of 0.257 cm.sup.3/g, determined as described in Reference Example 4.

(38) FIG. 9 displays two SEM images of a portion of the sample of the product at different magnifications.

Example 8: Preparation of a Cu-CHA Molded Material from the Ion-Exchanged Zeolitic Material from Example 7

(39) Example 3 was repeated, yet instead of employing the ion-exchanged zeolitic material from Example 2, the material from Example 7 was employed.

Example 9: SCR Testing of the Molded Cu-CHA Material from Example 8

(40) Example 4 was repeated, yet instead of employing the Cu-CHA material from Example 3, the material from Example 8 was employed.

(41) The SCR testing results are shown in FIGS. 10 and 11. As may be taken from the results for the inventive sample (Example 8), the Cu-CHA molded material shows excellent SCR activity over a broad temperature range, even after severe aging at 820° C.

(42) In this light, compared to a standard reference Cu-CHA sample (prepared according to Example 1 of WO2015/185625 A2), the molded Cu-CHA from example 8 as shown by the SCR testing gave significantly advantageous results at low temperatures, even after aging at 650° C. and 820° C.

Comparative Example 1: Continuous Synthesis of a Zeolitic Material Having a CHA-Type Framework Structure with Calcined Seed Crystals

(43) Reference Example 2 was repeated, yet instead of employing the seed material from Reference Example 1, calcined seeds of a zeolitic material having the CHA-type framework structure were employed. When attempting to repeat the procedure of Example 1 using such a synthesis gel, however, the continuous synthesis could not be performed as long as the synthesis as described in Example 1 above due to the eventual clogging of the reactor tube.

(44) Thus, it has surprisingly been found that by using a zeolitic material as seed crystals in the continuous synthesis of a zeolitic material, wherein the zeolitic material of the seed crystals contains cationic organotemplates at the ion exchange sites, the problem of clogging in the continuous synthesis may be effectively alleviated. As a result, continuous synthesis may be conducted for effectively longer periods of time before requiring interruption for maintenance of the apparatus used in the continuous synthesis.

(45) List of cited prior art: U.S. Pat. No. 5,989,518 US 2016/0115039 A1 Liu et al. in Angew. Chem. Int. Ed. 2015, 54, 5683-5687 Ju, J. et al. in Chemical Engineering Journal 2006, 116, 115-121 Vandermeersch, T. et al. in Microporous and Mesoporous Materials 2016, 226, 133-139 Liu, Z. et al. in Chemistry of Materials 2014, 26, 2327-2331 Slangen et al. “Continuous Synthesis of Zeolites using a Tubular Reactor”, 12th International Zeolite Conference, Materials Research Society 1999 Bonaccorsi, L. et al. in Microporous and Mesoporous Materials 2008, 112, 481-493 US 2001/0054549 A1 DE 39 19 400 A1 WO 2017/216236 A Hoang, P. H. et al. in J. Am. Chem. Soc. 2011, 133, 14765-14770 Nightingale, A. M. et al. in J. Mater. Chem. A, 2013, 1, 4067-4076 WO 2017/100384 A1 WO 2009/141324 A1