Solidothermal synthesis of a boron-containing zeolite with an MWW framework structure

Abstract

Described herein is a process for producing a zeolitic material having an MWW framework structure containing YO.sub.2 and B.sub.2O.sub.3, in which Y stands for a tetravalent element. The process includes the steps of (i) preparing a mixture containing one or more sources for YO.sub.2, one or more sources for B.sub.2O.sub.3, one or more organotemplates, and seed crystals, (ii) crystallizing the mixture obtained in (i) for obtaining a layered precursor of the MWW framework structure, and (iii) calcining the layered precursor obtained in (ii) for obtaining the zeolitic material having an MWW framework structure. Also disclosed herein are synthetic boron-containing zeolites obtain by the process and uses thereof.

Claims

1. A process for producing a zeolitic material having an MWW framework structure comprising YO.sub.2 and B.sub.2O.sub.3, wherein Y is Si, the process comprising: (i) mixing one or more sources for YO.sub.2, one or more sources for B.sub.2O.sub.3, one or more organotemplates, and seed crystals, to obtain a mixture; (ii) crystallizing the mixture to obtain a layered precursor of the MWW framework structure; and (iii) calcining the layered precursor to obtain the zeolitic material having the MWW framework structure, wherein: the one or more organotemplates have the formula (I):
R.sup.1R.sup.2R.sup.3N  (I) R.sup.1 is cyclohexyl; R.sup.2 and R.sup.3 are independently from each other H; and the mixture and the layered precursor comprise 35 wt. % or less of H.sub.2O based on 100 wt. % of YO.sub.2 contained in the mixture and the layered precursor, wherein the mixture prepared in (i) and crystallized in (ii) contains 5 wt. % or less of fluoride calculated as the element and based on 100 wt. % of YO.sub.2.

2. The process of claim 1, wherein the mixture and the layered precursor comprise 3 wt. % or less of fluoride calculated as the element and based on 100 wt. % of YO.sub.2.

3. The process of claim 1, wherein the mixture and the layered precursor comprise 5 wt. % or less of P and/or Al calculated as the respective element and based on 100 wt. % of YO.sub.2.

4. The process of claim 1, wherein the layered is selected from the group consisting of B-MCM-22(P), B-ERB-1(P), B-ITQ-1(P), B-PSH-3(P), B-SSZ-25(P), and mixtures of two or more thereof.

5. The process of claim 1, wherein the zeolitic material having the MWW framework structure is selected from the group consisting of B-MCM-22, B-ERB-1, B-ITQ-1, B-PSH-3, B-SSZ-25, and mixtures of two or more thereof.

6. The process of claim 1, wherein apart from organotemplate optionally contained in the seed crystals, the mixture does not contain piperidine or hexamethyleneimine.

7. The process of claim 1, wherein the crystallization is conducted under autogenous pressure.

8. The process of claim 1, wherein, after the crystallizing and prior to the calcining, the process further comprises: (a) isolating the layered precursor, to obtain an isolated layered precursor; (b) optionally washing the isolated layered precursor, to obtain a washed layered precursor; (c) optionally drying the isolated layered precursor or the washed layered precursor, to obtain a dried layered precursor; (d) optionally subjecting the layered precursor, the isolated layered precursor, or the washed layered precursor, or the dried layered precursor to ion exchange, to obtain an ion exchanged layered precursor; and (e) optionally subjecting the isolated layered precursor, the washed layered precursor, the dried layered precursor, or the ion exchanged layered precursor, to isomorphous substitution.

9. The process of claim 8, wherein the isomorphous substitution is performed such that boron in the framework structure of the isolated layered precursor, the washed layered precursor, the dried layered precursor, or the ion exchanged layered precursor, is isomorphously substituted against one or more trivalent and/or tetravalent elements.

10. The process of claim 1, wherein the calcination is carried out at a temperature of from 300 to 900° C.

11. The process of claim 1, further comprising, after the calcining: (iv) deboronating the zeolitic material having an MWW framework structure with a liquid solvent system, thereby obtaining a deboronated zeolitic material having an MWW framework structure.

12. The process of claim 11, wherein the deboronation is carried out at a temperature of from 50 to 125° C.

13. A synthetic zeolitic material having an MWW framework structure obtained by the process of claim 1.

14. A composition, comprising the synthetic zeolitic material of claim 13, wherein the composition is selected from the group consisting of a molecular sieve, an adsorbent, a catalyst, a catalyst component, and a combination thereof.

Description

DESCRIPTION OF THE FIGURES

(1) FIG. 1 shows the XRD (X-Ray Diffraction) patterns of the layered precursor B-MWW(P) obtained from Example 1 (cf. lower diffraction pattern) as well as of the B-MWW material obtained from Example 2 after calcination of the layered precursor (cf. upper diffraction pattern). In the figure, the diffraction angle 2 theta in ° is shown along the abscissa and the relative intensities in arbitrary units are plotted along the ordinate.

(2) FIG. 2 shows the .sup.29Si MAS NMR of the layered precursor B-MWW(P) obtained from Example 1. In the figure, the chemical shift in ppm is plotted along the abscissa and the relative intensity is plotted in arbitrary units along the ordinate.

(3) FIG. 3 shows the .sup.11B 2D 3QMAS NMR of the layered precursor B-MWW(P) obtained from Example 1. In the figure, the isotropic chemical shift in ppm is plotted along the ordinate to the right of the figure whereas the ordinate opposite thereto displays the single dimensional isotropic spectrum. The figure further displays the second-order quadrupolar spectrum along the top of the figure, whereas the respective chemical shift in ppm is plotted along the abscissa opposite thereto. The relative intensities of the respective spectra are displayed in arbitrary units.

(4) FIG. 4 shows the .sup.29Si MAS NMR of the B-MWW zeolitic material obtained from Example 2. In the figure, the chemical shift in ppm is plotted along the abscissa and the relative intensity is plotted in arbitrary units along the ordinate.

(5) FIG. 5 shows the .sup.11B 2D 3QMAS NMR of the B-MWW zeolitic material obtained from Example 2. In the figure, the isotropic chemical shift in ppm is plotted along the ordinate to the right of the figure whereas the ordinate opposite thereto displays the single dimensional isotropic spectrum. The figure further displays the second-order quadrupolar spectrum along the top of the figure, whereas the respective chemical shift in ppm is plotted along the abscissa opposite thereto. The relative intensities of the respective spectra are displayed in arbitrary units.

(6) FIG. 6 shows the XRD (X-Ray Diffraction) patterns of the isomorphously substituted layered precursor [Al,B]-MCM-22(P) obtained from Example 3. In the figure, the diffraction angle 2 theta in ° is shown along the abscissa and the relative intensities in arbitrary units are plotted along the ordinate.

EXAMPLES

(7) The crystallinity and phase purity of the samples were determined by X-ray powder diffraction (XRD) with a Rigaku Ultimate VI X-ray diffractometer (40 kV, 40 mA) using CuKα (λ=1.5406 Å) radiation from 3° to 40° with 2θ.

(8) The argon sorption isotherm for determining the BET surface area was carried out with Micromeritics ASAP 2010M and Tristar system.

(9) Solid-state .sup.29Si MAS NMR spectra were recorded on Varian Infinity plus 400 spectrometer.

(10) .sup.11B 2D 3QMAS NMR experiments were recorded on a Bruker Infinity Plus 500 spectrometer.

(11) The elemental compositions of the samples were determined by inductively coupled plasma (ICP) with a Perkin-Elmer 3300 DV emission spectrometer.

Reference Example 1: Preparation of the Layered Precursor Al-MWW(P) Used as Seed Crystals

(12) 10.40 g of NaAlO.sub.2 (43 weight-% Na.sub.2O, 53 weight-% Al.sub.2O.sub.3) and 6.0 g of NaOH were dissolved in 1239.4 g of deionied water in a 2.5 L glass beaker. To this solution, 259 g of Ludox AS40 (40 weight-% SiO.sub.2) and 85.60 g of hexamethyleneimine were then added. The obtained gel has a molar composition of 40.28 SiO.sub.2:1.26 Al.sub.2O.sub.3:3.43 Na.sub.2O:1606H.sub.2O:20.13 hexamethyleneimine. Said gel was transferred into a 2.5 L autoclave, and heated up to 150° C. in 1 h under a rotating speed of 100 rpm. The crystallization was then carried out at 150° C. for 168 h.

(13) After the crystallization process, the white suspension obtained was adjusted with an HNO.sub.3 solution to reach a pH of about 6.0. Said suspension was then filtered, and washed with deionized water. The solid Al-MWW(P) product was dried at 120° C. for 16 h.

Example 1: Preparation of the Layered Precursor B-MWW(P) Using Al-MWW(P) as Seed Crystals

(14) 0.12 g NaOH, 0.88 g orthoboric acid (H.sub.3BO.sub.3), 1.72 g solid silica gel (SiO.sub.2.Math.1.16H.sub.2O obtained from Qingdao Haiyang Chemical Reagent Co, Ltd.), and 0.065 g Al-MCM-22(P) seed crystals obtained from Reference Example 1 were mixed together. After grinding for 5 min, 0.72 g cyclohexylamine was added and the resulting mixture was ground for another 5 min to afford a gel having the molar composition 0.0665 Na.sub.2O:1 (SiO.sub.2.1.16H.sub.2):0.328 B.sub.2O.sub.3:0.335 cyclohexylamine including 5 wt. % of seed crystals based on 100 wt. % SiO.sub.2. Then the powder mixture was transferred to an autoclave and sealed. After heating for 10 days at 180° C., the crystallized product was filtered, washed with deionized water, and dried at 100° C. for 4 h for obtaining the layered precursor B-MWW(P).

(15) FIG. 1 shows the XRD of the resulting material (cf. lower diffractogram displayed in the figure), from which it is apparent that said product has the structure of a layered precursor of the MWW framework structure.

(16) The Si:B molar ratio of the obtained product is 6.7, as measured by ICP analysis.

(17) FIG. 2 shows the .sup.29Si MAS NMR of the layered precursor B-MWW(P). In the spectrum, the peaks of B-MCM-22(P) at −109˜−119 ppm are assigned to Si(4Si) species, whereas the peak at about −102.8 ppm is assigned to Si(3Si,1B) and/or Si(3Si,1OH).

(18) FIG. 3 shows the .sup.11B 2D 3QMAS NMR of the layered precursor B-MWW(P). The 2D 3QMAS spectrum was sheared so that the F1 axis is the isotropic chemical shift dimension and the F2 axis contains the second-order quadrupolar line shape. The 2D contours reveal that there exist two distinct B sites: B[4] species stemming from tetrahedral boron coordination in the framework, and B[3] species stemming from extra-framework boron in trigonal coordination.

Example 2: Preparation of B-MWW from the Layered Precursor

(19) 1 g of layered precursor B-MWW(P) as obtained from Example 1 was placed in 50 ml of 1 M NH.sub.4NO.sub.3 solution, and the solution was heated to 80° C. for 1 h, after which solid product was isolated. The procedure was repeated twice. The solid product was then calcined at 550° C. for 5 h for obtaining the B-MWW zeolitic material.

(20) FIG. 1 shows the XRD of the resulting material (cf. upper diffractogram displayed in the figure), from which it is apparent that said product has the MWW framework structure.

(21) The BET specific surface area of the B-MWW product was determined to be 391 m.sup.2/g.

(22) FIG. 4 shows the .sup.29Si MAS NMR of the B-MWW product, wherein the peaks are all assigned to Si(4Si) species. In particular, compared to the spectrum of the layered precursor, the peak at about −102.5 ppm assigned to Si(3Si,1B) and/or Si(3Si,1OH) for the layered precursor is shifted to −105.2 ppm after calcination, indicating that the Si(3Si,1OH) species between the layers of the precursor become Si(4Si) species in the B-MWW product due to the condensation of hydroxyl between the layers of the precursor material.

(23) FIG. 5 shows the .sup.11B 2D 3QMAS NMR of the B-MWW product. The 2D 3QMAS spectrum was again sheared so that the F1 axis is the isotropic chemical shift dimension and the F2 axis contains the second-order quadrupolar line shape. The ‘sheared’ 2D .sup.11B MQ-MAS spectrum of the B-MWW zeolite obtained upon calcination clearly shows the presence of three distinct boron signals assigned to boron in tedrahedral (B.sub.TET), distorted tetrahedral (B.sub.D.TET), and octahedrally coordinated (B.sub.OCT) environments, wherein the isotropic .sup.11B chemical shifts calculated for the resonances are around −4.4 (B.sub.OCT), 13.3 (B.sub.D.TET), and 19.0 (B.sub.TET) ppm. This result clearly indicates that deboronation has occurred to a certain extent upon calcination at 550° C.

Example 3: Isomorphous Substitution of the Layered Precursor of B-MWW with Al

(24) 0.2 g of layered precursor B-MWW(P) as obtained from Example 1 placed in 20 g of a 0.15 M Al(NO.sub.3).sub.3 solution which was then heated to 100° C. for 4 days for isomorphously substituting boron against aluminum. The solid was then isolated for obtaining an isomorphously substituted layered precursor [Al,B]-MCM-22(P). The Si:Al molar ratio of the obtained product is 10.3 and the Si:B molar ratio is 30.7, as respectively measured by ICP analysis.

(25) FIG. 6 shows the XRD of the resulting material, from which it is apparent that said product has the structure of a layered precursor of the MWW framework structure.

CITED LITERATURE

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