High-yield synthesis of nanozeolite Y crystals of controllable particle size at low temperature

Abstract

The present application relates to a method for synthesizing nanozeolite Y crystals, nanozeolite Y crystals obtainable by said method, and the use of the synthesized nanozeolite Y crystals in cracking hydrocarbons, as molecular sieves or as ion-exchangers.

Claims

1. A method for synthesizing nanozeolite Y crystals comprising the following steps: a) Preparing a first aqueous solution comprising a silicate source and quinuclidine; b) Preparing a second aqueous solution comprising an aluminate source and an alkali hydroxide; c) Combining the first and the second aqueous solution to obtain an aqueous reaction mixture; d) Incubating the aqueous reaction mixture to obtain nanozeolite Y crystals; e) Washing the obtained nanozeolite Y crystals with an aqueous washing buffer; f) Drying the washed nanozeolite Y crystals to remove residual crystalline water; and g) Calcining the washed nanozeolite Y crystals.

2. The method of claim 1, wherein the alkali hydroxide is sodium hydroxide and wherein the method comprises the additional steps: h) Mixing the calcined nanozeolite Y crystals with a third aqueous solution comprising ammonium ions to exchange the sodium ions of the calcined nanozeolite Y crystals against ammonium ions; i) Washing the ammonium containing nanozeolite Y crystals with an aqueous washing buffer; j) Drying the washed nanozeolite Y crystals to remove residual crystalline water; and k) Calcining the washed nanozeolite Y crystals.

3. The method of claim 2, wherein steps h) to k) are repeated to reduce the amount of Na.sup.+ ions in the calcined nanozeolite Y crystals to a) less than 5% Na.sup.+ ions, b) less than 3% Na.sup.+ ions, or c) less than 1% Na.sup.+ ions.

4. The method according to claim 1, wherein in the aqueous reaction mixture quinuclidine is contained in a fraction of a) between 0.0125 and 0.24 mol %, b) between 0.05 and 0.18 mol %, or c) between 0.09 and 0.11 mol %.

5. The method according to claim 1, wherein in the aqueous reaction mixture the silicate source ([SiO.sub.4].sup.4−) is contained in a fraction of a) between 0.8 and 4.9 mol %, b) between 1.0 and 3.0 mol %, or c) between 1.2 and 2.0 mol %.

6. The method according to claim 1, wherein in the aqueous reaction mixture the aluminate source ([Al(OH.sub.4)].sup.−) is contained in a fraction of a) between 0.48 and 1.06 mol %, b) between 0.60 and 1.0 mol %, or c) between 0.72 and 0.92 mol %.

7. The method according to claim 1, wherein in the aqueous reaction mixture sodium hydroxide is contained in a fraction of a) between 1.0 and 8.5 mol %, b) between 2.5 and 6.5 mol %, or c) between 4.5 and 5.5 mol %.

8. The method according to claim 1, wherein the first aqueous solution has a pH value of a) between 11 and 14, b) between 11.5 and 13.5, or c) between 12 and 13.

9. The method according to claim 1, wherein the second aqueous solution has a pH value of a) between 11 and 14, b) between 12.5 and 13.8, or c) between 13.2 and 13.6.

10. The method according to claim 1, wherein the aqueous reaction mixture has a pH value of a) between 11 and 14, b) between 11.5 and 13, or c) between 12 and 12.5.

11. The method according to claim 1, wherein the aqueous washing buffer has a conductivity a) smaller than 500 μS/cm, b) smaller than 50 μS/cm, or c) smaller than 15 μS/cm, and wherein the aqueous washing buffer has a pH of a) between 5.5 and 8.5, b) between 6 and 8, or c) between 6.5 and 7.5.

12. The method according to claim 1, wherein in the third aqueous solution the ammonium source is contained in a concentration of a) between 0.001 and 0.3 M, b) between 0.05 and 0.25 M, or c) between 0.1 and 0.2 M.

13. The method according to claim 1, wherein, after combining the first and the second solution, the aqueous reaction mixture is stirred for a time period of a) at least 1 h, b) at least 10 h, c) at least 25 h, or d) at least 40 h.

14. The method according to claim 1, wherein, after combining the first and the second solution or stirring the aqueous reaction mixture, the aqueous reaction mixture is incubated at a temperature of a) below 150° C. for a minimum time period of 5 h, b) between 20° C. and 75° C. for a time period between 60 h and 300 h, or c) between 75° C. and 100° C. for a time period between 20 h and 60 h.

15. The method according to claim 1, wherein the washing steps e) and/or i) is/are repeated, until the decanted washing buffer has a pH value of a) between 5.5 and 8.5, b) between 6 and 8, or c) between 6.5 and 7.5.

16. The method according to claim 1, wherein the nanozeolite Y crystals are calcined at a temperature of a) below 750° C. for a minimum time period of 2 h, b) between 650° C. and 750° C. for a time period between 2 and 10 h, or c) between 550° C. and 650° for a time period between 4 and 15 h.

17. The method according to claim 1, wherein quinuclidine is used in the aqueous reaction mixture a) in a fraction of 0.04-0.10 mol % to obtain nanozeolite Y crystals of a diameter between 100-700 nm, b) in a fraction of 0.12-0.17 mol % to obtain nanozeolite Y crystals of a diameter between 50-300 nm, or c) in a fraction of 0.10-0.14 mol % to obtain nanozeolite Y crystals of a diameter between 30-200 nm.

Description

4. BRIEF DESCRIPTION OF THE DRAWINGS

(1) Possible embodiments of the present invention are further described in the following detailed description, with reference to the following figures:

(2) FIG. 1 X-Ray Diffractogram of synthesized Nanozeolite Y crystals of worked example 1

(3) FIG. 2 Scanning Electron Microscopy image of synthesized Nanozeolite Y crystals of worked example 1

(4) FIG. 3 X-Ray Diffractogram of synthesized Nanozeolite Y crystals of worked example 2

(5) FIG. 4 Scanning Electron Microscopy image of synthesized Nanozeolite Y crystals of worked example 2

(6) FIG. 5 X-Ray Diffractogram of synthesized Nanozeolite Y crystals of worked example 3

(7) FIG. 6 Scanning Electron Microscopy image of synthesized Nanozeolite Y crystals of worked example 3

(8) FIG. 7 DLS measurements from Na—Y (a) and H—Y (b) zeolites

(9) FIG. 8 DLS measurements from Na—Y (a) and H—Y (b) zeolites

5. DETAILED DESCRIPTION OF THE INVENTION

(10) Hereafter, worked examples of the present invention are described in detail.

Example 1

(11) A first aqueous solution was prepared by dissolving quinuclidine powder under strong mixing in de-ionized water, then adding colloidal silica to the solution, followed by mixing for 30 minutes. A second aqueous solution was prepared by dissolving sodium hydroxide in de-ionized water, then adding sodium aluminate to the solution, followed by mixing for 30 minutes.

(12) An aqueous reaction mixture was obtained by dropwise adding the first aqueous solution to the second aqueous solution, with the final mole to mole ratios: 0.11 quinuclidine, 3.84 SiO.sub.2, 1.00 Al.sub.2O.sub.3, 6.14 Na.sub.2O, 232.99 H.sub.2O.

(13) The aqueous reaction mixture was stirred at room temperature for 48 h, then incubated at 64° C. for 72 h to allow crystallization. The obtained crystals were collected by centrifugation and washed repeatedly until the decanted washing buffer exhibited a pH of 7.1. The crystals were dried at 80° C. for 5 h, and subsequently calcined at 550° C. for 10 h in air to remove any organic residue.

(14) Following the calcined nanozeolite Y crystals were ion-exchanged three times using a solution of ammonium chloride (0.1M) according to the subsequent procedure: mixing the calcined nanozeolite crystals with the ammonium chloride solution, washing of the crystals with pH neutral double distilled water, drying of washed crystals for 5 h at 80° C., calcinating for 10 h at 550° C. in air to remove any organic residue. This procedure was repeated three times such that more than 99% of the Na.sup.+ cations of the crystals were replaced with H.sup.+ cations, as determined by Inductively Coupled Plasma (ICP) analysis.

(15) The calcined crystals had a diameter ranging between 80 and 700 nm, a specific surface area of 650+/−65 m.sup.2/g and a Si:Al ratio of 3.84.

(16) A X-ray diffractometer was used to determine the framework type of the synthesized zeolites (CuKα radiation). The 2-theta angle was varied between 0° and 60°. Table 1, listing the peak positions versus the 2-theta angle, and FIG. 1 confirms that FAU type zeolites were synthesized.

(17) FIG. 2 shows a Scanning Electron Microscopy image of synthesized Nanozeolite Y as obtained in this example.

(18) TABLE-US-00001 TABLE 1 2-theta position ± 0.25 (°) Relative Intensity 6.3 100 10.2 29 11.8 21 15.6 39 18.6 13 20.3 25 23.6 55 26.9 49 29.4 15 30.5 27 31.2 61 33.8 24 34.5 13 37.6 14 41.1 10 41.6 8

Example 2

(19) A first aqueous solution was prepared by dissolving quinuclidine powder under strong mixing in de-ionized water, then adding colloidal silica to the solution, followed by mixing for 30 minutes. A second aqueous solution was prepared by dissolving sodium hydroxide in de-ionized water, then adding sodium aluminate to the solution, followed by mixing for 30 minutes.

(20) An aqueous reaction mixture was obtained by dropwise adding the first aqueous solution to the second aqueous solution, with the final mole to mole ratios: 0.23 quinuclidine, 3.84 SiO.sub.2, 1.00 Al.sub.2O.sub.3, 6.14 Na.sub.2O, 232.99 H.sub.2O.

(21) The aqueous reaction mixture was stirred at room temperature for 48 h, then incubated at 64° C. for 72 h to allow crystallization. The obtained crystals were collected by centrifugation and washed repeatedly until the decanted washing buffer exhibited a pH of 7.1. The crystals were dried at 80° C. for 5 h, and subsequently calcined at 550° C. for 10 h in air to remove any organic residue.

(22) Following the calcined nanozeolite Y crystals were ion-exchanged three times using a solution of ammonium chloride (0.1M) following the procedure described above for example 1.

(23) The calcined crystals had a diameter ranging between 50 and 450 nm, a specific surface area of 720+/−90 m2/g and a Si:Al ratio of 3.84.

(24) An X-Ray Diffractogram was acquired as described in Example 1. Table 2, listing the peak positions versus the 2-theta angle, and FIG. 3 confirms that FAU type zeolites were synthesized.

(25) FIG. 4 shows a Scanning Electron Microscopy image of synthesized Nanozeolite Y as obtained in this example.

(26) TABLE-US-00002 TABLE 2 2-theta position ± 0.25 (°) Relative Intensity 6.2 100 10.0 35 11.8 31 15.5 37 18.5 15 20.2 29 23.4 48 26.7 47 29.3 24 30.5 27 31.1 47 33.7 26 34.3 15 37.5 13 40.9 13 41.5 11 53.3 9

Example 3

(27) A first aqueous solution was prepared by dissolving quinuclidine powder under strong mixing in de-ionized water, then adding colloidal silica to the solution, followed by mixing for 30 minutes. A second aqueous solution was prepared by dissolving sodium hydroxide in de-ionized water, then adding sodium aluminate to the solution, followed by mixing for 30 minutes.

(28) An aqueous reaction mixture was obtained by dropwise adding the first aqueous solution to the second aqueous solution, with the final mole to mole ratios: 0.42 quinuclidine, 7.75 SiO.sub.2, 1.00 Al.sub.2O.sub.3, 6.14 Na.sub.2O, 252.55 H.sub.2O.

(29) The aqueous reaction mixture was stirred at room temperature for 96 h, then incubated at 80° C. for 24 h to allow crystallization. The obtained crystals were collected by centrifugation and washed repeatedly until the decanted washing buffer exhibited a pH of 7.1. The crystals were dried at 80° C. for 5 h, and subsequently calcined at 550° C. for 10 h in air to remove any organic residue.

(30) Following, the calcined nanozeolite Y crystals were ion-exchanged three times using a solution of ammonium chloride (0.1M) following the procedure described above for example 1.

(31) The calcined crystals had a diameter ranging between 40 and 200 nm, a specific surface area of 740+/−80 m.sup.2/g and a Si:Al ratio of 7.75.

(32) An X-Ray Diffractogram was acquired as described in Example 1. Table 3, listing the peak positions versus the 2-theta angle, and FIG. 5 confirms that FAU type zeolites were synthesized.

(33) FIG. 6 shows a Scanning Electron Microscopy image of synthesized Nanozeolite Y as obtained in this example.

(34) TABLE-US-00003 TABLE 3 2-theta position ± 0.15 (°) Relative Intensity 6.4 100 10.3 30 12.1 24 15.9 39 18.9 17 20.4 28 23.8 62 27.1 58 29.7 23 30.8 37 31.4 67 34.1 27 34.6 15 37.9 19 41.3 15 41.9 12 53.8 13

Example 4

(35) Zeolites were prepared according to example 1, except that the final mole to mole ratios were: 0.15 quinuclidine, 3.33 SiO.sub.2, 1.00 Al.sub.2O.sub.3, 5.17 Na.sub.2O, 205.83 H.sub.2O.

(36) Moreover, the aqueous reaction mixture was incubated at 80° C. for 48 h to allow crystallization.

(37) Dynamic light scattering (DLS) measurements were performed on the calcined nanozeolite Y crystals (Na—Y) (FIG. 7a) and on the ion-exchanged nanozeolite Y crystals (H—Y) (FIG. 7b). The mean hydrodynamic diameters for Na—Y is 380 nm and for H—Y is 392 nm.

Example 5

(38) Zeolites were prepared according to example 4, except that the final mole to mole ratios were: 0.21 quinuclidine, 3.33 SiO.sub.2, 1.00 Al.sub.2O.sub.3, 5.16 Na.sub.2O, 200.03 H.sub.2O.

(39) Dynamic light scattering (DLS) measurements were performed on the calcined nanozeolite Y crystals (Na—Y) (FIG. 8a) and on the ion-exchanged nanozeolite Y crystals (H—Y) (FIG. 8b). The mean hydrodynamic diameters for Na—Y is 332 nm and for H—Y is 370 nm.