Post-treatment of deboronated MWW zeolite

Abstract

A process for the post-treatment of a zeolitic material having an MWW framework structure, the process comprising (i) providing a zeolitic material having an MWW framework structure, wherein the framework structure of the zeolitic material comprises X.sub.2O.sub.3 and YO.sub.2, wherein Y is a tetravalent element and X is a trivalent element and wherein the molar ratio X.sub.2O.sub.3:YO.sub.2 is greater than 0.02:1; (ii) treating the zeolitic material provided in (i) with a liquid solvent system thereby obtaining a zeolitic material having a molar ratio X.sub.2O.sub.3:YO.sub.2 of at most 0.02:1, and at least partially separating the zeolitic material from the liquid solvent system; (iii) treating the zeolitic material obtained from (ii) with a liquid aqueous system having a pH in the range of 5.5 to 8 and a temperature of at least 75? C.

Claims

1. A process for a post-treatment of a zeolitic material having an MWW framework structure, the process comprising (i) providing a zeolitic material (i) having an MWW framework structure, wherein the framework structure of the zeolitic material (i) comprises X.sub.2O.sub.3 and YO.sub.2, wherein Y is Si and X is B and wherein a molar ratio X.sub.2O.sub.3:YO.sub.2 is greater than 0.02:1; (ii) treating the zeolitic material (i) with a liquid solvent system thereby obtaining a zeolitic material having a molar ratio X.sub.2O.sub.3:YO.sub.2 of at most 0.02:1, and at least partially separating the zeolitic material from the liquid solvent system to obtain a zeolitic material (ii); (iii) treating the zeolitic material (ii) with a liquid aqueous system having a pH in a range of 5.5 to 8 and a temperature of at least 75? C. in a closed system under autogenous pressure to obtain a zeolitic material (iii), thereby obtaining the zeolitic material having a molar ratio X.sub.2O.sub.3:YO.sub.2 in the range of from 0.001:1 to 0.003:1, a crystallinity, as determined by XRD analysis, of at least 75% and a water uptake of at most 11 weight %; wherein the pH of the aqueous system used in (iii) is determined using a pH sensitive glass electrode, and wherein the treatment according to (ii) with the liquid solvent system reduces the molar ratio X.sub.2O.sub.3:YO.sub.2 of the zeolitic material framework by at least partially removing X from the MWW framework structure wherein the IR spectrum of the zeolitic material of (iii) exhibits a first absorption band with a maximum in the range of from 3710 to 3750 cm.sup.?1 and a second absorption band with a maximum in the range of from 3480 to 3540 cm.sup.?1, wherein the ratio of the intensity of the first absorption band relative to the intensity of the second absorption band is at least 1.0.

2. The process of claim 1, wherein in (i), at least 95 weight-% of the framework structure of the zeolitic material consists of X.sub.2O.sub.3 and YO.sub.2.

3. The process of claim 1, wherein in (i), the molar ratio X.sub.2O.sub.3: YO.sub.2 is at least 0.03:1.

4. The process of claim 1, wherein in (i), the zeolitic material having the MWW framework structure is provided by a process comprising (a) hydrothermally synthesizing the zeolitic material from a synthesis mixture comprising at least one silicon source, at least one boron source, and at least one template compound to obtain the zeolitic material in a mother liquor; (b) separating the zeolitic material from the mother liquor.

5. The process of claim 4, wherein (b) comprises drying the zeolitic material.

6. The process of claim 4, wherein after (b) and prior to (ii), the zeolitic material is subjected to calcination.

7. The process of claim 6, wherein the calcination is carried out at a temperature in a range of from 400 to 700? C.

8. The process of claim 1, wherein in (ii), the liquid solvent system is selected from the group consisting of water, methanol, ethanol, propanol, ethane-1,2-diol,propane-1,2-diol, propane-1,3-diol, propane-1,2,3-triol, and a mixture of two or more thereof.

9. The process of claim 8, wherein in (ii), the treating is carried out at a temperature in a range of from 50 to 125? C.

10. The process of claim 9, wherein in (ii), the treating is carried out in an open system under reflux.

11. The process of claim 1, wherein in (ii), the zeolitic material (ii) is subjected to drying.

12. The process of claim 1, wherein in (ii), the zeolitic material (ii) is subjected to calcination.

13. The process of claim 1, wherein the zeolitic material (ii) has a molar ratio X.sub.2O.sub.3:YO.sub.2 of at most 0.01 1.

14. The process of claim 1, wherein the zeolitic material (ii) is in a form of a powder.

15. The process of claim 1, wherein in (iii), the zeolitic material is treated with the liquid aqueous system for a period in a range of from 0.5 to 24 h.

16. The process of claim 1, wherein in (iii), the zeolitic material is treated with the liquid aqueous system at a temperature in a range of from 75 to 200? C.

17. The process of claim 1, wherein the liquid aqueous system used in (iii) has a pH in a range of from 6 to 7.5.

18. The process of claim 1, wherein in (iii), a weight ratio of the liquid aqueous system relative to the zeolitic material is in a range of from 35:1 to 5:1.

19. The process of claim 1, wherein in (iii), the liquid aqueous system comprises at least 90 weight-% water.

20. The process of claim 1, wherein in (iii), the zeolitic material is treated with the liquid aqueous system in an autoclave.

21. The process of claim 1, wherein in (iii), the zeolitic material (iii) is subjected to drying.

22. The process of claim 1, wherein in (iii), the zeolitic material (iii) is subjected to calcination.

23. The process of claim 1, wherein neither prior to nor during nor after (iii), the zeolitic material is subjected to one or more of a steam treatment and a treatment with an aqueous solution having a pH of below 5.5 or above 8.

24. A zeolitic material having an MWW framework structure, wherein the framework structure comprises YO.sub.2 and X.sub.2O.sub.3, wherein Y is Si, and X is B, said zeolitic material having a molar ratio X.sub.2O.sub.3:YO.sub.2 in the range of from 0.001:1 to 0.003:1, a crystallinity, as determined by XRD analysis, of at least 75% and a water uptake of at most 11 weight %, wherein said zeolitic material is obtained by a process comprising: (i) providing a zeolitic material having an MWW framework structure, wherein the framework structure of the zeolitic material comprises X.sub.2O.sub.3 and YO.sub.2, wherein Y is a tetravalent element and X is a trivalent element and wherein a molar ratio X.sub.2O.sub.3: YO.sub.2 is greater than 0.02:1; (ii) treating the zeolitic material in (i) with a liquid solvent system thereby obtaining a zeolitic material having a molar ratio X.sub.2O.sub.3:YO.sub.2 of at most 0.02:1, and at least partially separating the zeolitic material from the liquid solvent system; (iii) treating the zeolitic material obtain from (ii) with a liquid aqueous system having a pH in a range of 5.5 to 8 and a temperature in the range of 75? C. to 200? C. in a closed system under autogenous pressure to obtain a zeolitic material (iii) and wherein the liquid aqueous system is in its liquid state; wherein the pH of the aqueous system in (iii) is determined using a pH sensitive glass electrode, wherein the treatment according to (ii) with the liquid solvent system reduced the molar ratio X.sub.2O.sub.3:YO.sub.2 of the zeolitic material framework by at least partially removing X from the MWW framework structure wherein the IR spectrum of the zeolitic material of (iii) exhibits a first absorption band with a maximum in the range of from 3710 to 3750 cm.sup.?and a second absorption band with a maximum in the range of from 3480 to 3540 cm.sup.31 1, wherein the ratio of the intensity of the first absorption band relative to the intensity of the second absorption band is at least 1.0.

25. The zeolitic material of claim 24, wherein the crystallinity of the zeolitic material is in a range of from 75 to 90%, and wherein the water uptake of the zeolitic material is in a range of from 4 to 11 weight-%.

26. The zeolitic material of claim 24, wherein a .sup.29SiNMR spectrum of the zeolitic material comprises a first peak at ?99.0 ppm +/?3.0 ppm, a second peak at ?104.9 ppm +/?0.9 ppm, a third peak at ?110.7 ppm +/?0.7 ppm, a fourth peak at ?112.5 ppm +/?1.5 ppm, a fifth peak at ?115.1 ppm +/?0.7 ppm, and a sixth peak at ?118.9 ppm +/?0.7 ppm, wherein an integral of the sixth peak is at least 5% of a total integral.

27. The zeolitic material of claim 24, which is in a form of a powder.

28. The zeolitic material of claim 24, wherein the process does not comprise a steam treatment of a zeolitic material or treatment of a zeolitic material with an aqueous solution having a pH below 5.5 or above 8.

29. A catalyst, a catalyst precursor, or a catalyst component, comprising the zeolitic material according to claim 24.

Description

EXAMPLES

Reference Example 1

Determination of the Water Uptake

(1) Water adsorption/desorption isotherms were performed on a VTI SA instrument from TA Instruments following a step-isotherm program. The experiment consisted of a run or a series of runs performed on a sample material that has been placed on the microbalance pan inside of the instrument. Before the measurement was started, the residual moisture of the sample was removed by heating the sample to 100? C. (heat-ing ramp of 5? C./min) and holding it for 6 h under a nitrogen flow. After the drying program, the temperature in the cell was decreased to 25? C. and kept constant during the measurement. The microbalance was calibrated, and the weight of the dried sample was balanced (maximum mass deviation 0.01 weight-%). Water uptake of a sample was measured as the increase in weight compared to the dry sample. First, an adsorption curve was measured by increasing the relative humidity (RH) (expressed as weight-% water in the atmosphere inside of the cell) to which the sample was exposed and measuring the water uptake by the sample as equilibrium. The RH was increased with a step of 10% from 5% to 85% and at each step the system controlled the RH and monitored the weight of the sample until reaching the equilibrium conditions after the sample and recording the weight uptake. The total adsorbed water of the sample was taken after the sample was exposed to the 85 weight-% RH. During the desorption measurement, the RH was decreased from 85 weight-% to 5 weight-% with a step of 10% and the change in the weight of the sample (water uptake) was monitored and recorded.

Reference Example 2

Determination of the Crystallinity

(2) The crystallinity of the zeolitic materials according to the present invention was determined by XRD analysis, wherein the crystallinity of a given material is expressed relative to a reference zeolitic material wherein the reflecting surfaces of the two zeolitic materials are compared. The reference zeolitic material was zeolite ammonium beta powder commercially available under the CAS registry number 1318-02-1. The determinations of the crystallinities were performed on a D8 Advance series 2 diffractometer from Bruker AXS. The diffractometer was configured with an opening of the divergence aperture of 0.1? and a Lynxeye detector. The samples as well as the reference zeolitic material were measured in the range from 19? to 25? (2 Theta). After baseline correction, the reflecting surfaces were determined by making use of the evaluation software EVA (from Bruker AXS). The ratios of the reflecting surfaces are given as percentage values.

Reference Example 3

29Si-NMR Measurements

(3) All .sup.29Si solid-state NMR experiments were performed using a Bruker Avance spectrometer with 300 MHz .sup.1H Larmor frequency (Bruker Biospin, Germany). Samples were packed in 7 mm ZrO.sub.2 rotors, and measured less than 5 kHz Magic Angle Spinning at room temperature. .sup.29Si direct polarization spectra were obtained using (pi/2)-pulse excitation with 5 microseconds pulse with a .sup.29Si carrier frequency corresponding to ?65 ppm in the spectrum, and a scan recycle delay of 120 s. Signal was acquired for 25 ms under 45 kHz high-power proton decoupling, and accumulated over 10 to 17 h. Spectra were processed using Bruker Topspin with 30 Hz exponential line broadening manual phasing and manual baseline correction over the entire spectrum. Spectra were referenced with the polymer Q8M8 as an external secondary standard, setting the resonance of the trimethylsilyl group to 12.5 ppm. The spectra were then fitted with a set of Gaussian line shapes, according to the number of discernable resonances. Fitting was performed using DMFit (Massiot et al., Magnetic Resonance in Chemistry, 40 (2002), pp 70-76). Peaks were manually set at the visible peak maxima or shoulder. Both peak position and line width were then left unrestrained, i.e., fit peaks were not fixed at a certain position. The fitting result was numerically stable, i.e., distortions in the initial fit setup as described above led to similar results. The fitted peak areas were further used normalized as performed by DMFit.

Reference Example 4

IR Measurements

(4) The IR measurements were performed on a Nicolet 6700 spectrometer. The zeolitic materials were pressed into a self-supporting pellet without the use of any additives. The pellet was introduced into a high vacuum cell placed into the IR instrument. Prior to the measurement the sample was pretreated in high vacuum (10.sup.?5 mbar) for 3 h at 300? C. The spectra were collected after cooling the cell to 50? C. The spectra were recorded in the range of 4000 cm.sup.?1 to 800 cm.sup.?1 at a resolution of 2 cm.sup.?1. The obtained spectra were represented by a plot having on the x axis the wavenumber (cm.sup.?1) and on the y axis the absorbance (arbitrary units). For the quantitative determination of the peak heights and the ratio between the peaks a baseline correction was carried out. Changes in the 3000 to 3900 cm.sup.?1 region were analyzed and for comparing multiple samples, the band at 1800?5 cm.sup.?1 was taken as reference.

Example 1

Process According to the Invention

(5) (i) Providing a Starting Material (Zeolitic Material of Framework Structure MWW)

(6) 480 kg de-ionized water were provided in a vessel. Under stirring at 70 rpm (rounds per minute), 166 kg boric acid were suspended in the water at room temperature. The suspension was stirred for another 3 h at room temperature. Subsequently, 278 kg piperidine were added, and the mixture was stirred for another hour. To the resulting solution, 400 kg Ludox? AS-40 were added, and the resulting mixture was stirred at 70 rpm for another hour at room temperature. The finally obtained mixture was transferred to a crystallization vessel and heated to 170? C. within 5 h under autogenous pressure and under stirring (50 rpm). The temperature of 170? C. was kept essentially constant for 120 h. During these 120 h, the mixture was stirred at 50 rpm. Subsequently, the mixture was cooled to a temperature of from 50-60? C. The aqueous suspension containing B-MWW had a pH of 11.3 as determined via measurement with a pH-sensitive electrode. From said suspension, the B-MWW was separated by filtration. The filter cake was then washed with de-ionized water at room temperature until the washing water had a conductivity of less than 700 microSiemens/cm. The thus obtained filter cake was admixed with water to obtain a suspension having a solid content of 15 weight-%. This suspension was subjected to spray-drying in a spray-tower with the following spray-drying conditions: drying gas, nozzle gas: technical nitrogen temperature drying gas: temperature spray tower (in): 235? C. temperature spray tower (out): 140? C. nozzle: top-component nozzle supplier Gerig; size 0 nozzle gas temperature: room temperature nozzle gas pressure: 1 bar operation mode: nitrogen straight apparatus used: spray tower with one nozzle configuration: spray tower-filter-scrubber gas flow: 1,500 kg/h filter material: Nomex? needle-felt 20 m.sup.2 dosage via flexible tube pump: SP VF 15 (supplier: Verder)

(7) The spray tower was comprised of a vertically arranged cylinder having a length of 2,650 mm, a diameter of 1,200 mm, which cylinder was conically narrowed at the bottom. The length of the conus was 600 mm. At the head of the cylinder, the atomizing means (a two-component nozzle) were arranged. The spray-dried material was separated from the drying gas in a filter downstream of the spray tower, and the drying gas was then passed through a scrubber. The suspension was passed through the inner opening of the nozzle, and the nozzle gas was passed through the ring-shaped slit encircling the opening.

(8) The spray-dried material was then subjected to calcination at 600? C. for 10 h. The calcined material had a molar ratio B.sub.2O.sub.3:SiO.sub.2 molar ratio of 0.06 and a crystallinity of 74%, determined according to Reference Example 2.

(9) (ii) Treatment with a Liquid Solvent SystemDeboronation

(10) 9 kg of de-ionized water and 600 g of the spay-dried material obtained according to Example 1 (i) were refluxed at 100? C. under stirring at 250 r.p.m. for 10 h. The resulting deboronated zeolitic material was separated from the suspension by filtration and washed with 8 l deionized water at room temperature. After the filtration, the filter cake was dried at a temperature of 120? C. for 16 h.

(11) The dried zeolitic material having an MWW framework structure had a B.sub.2O.sub.3:SiO.sub.2 molar ratio of 0.0022, a water uptake of 12%, determined according to Reference Example 1, and a crystallinity of 77%, determined according to Reference Example 2.

(12) (iii) Treatment with a Liquid Aqueous System

(13) 2 kg de-ionized water were provided in a vessel and 100 g of the deboronated zeolitic material obtained according to Example 1 (ii) having a crystallinity of 77% and a water uptake of 12 weight-% were added under stirring. The suspension was stirred for 10 min at room temperature. Thereafter, the suspension was heated at 140? C. under autogenous pressure for 12 h in an autoclave. The resulting zeolitic material was separated from the suspension by filtration and washed with deionized water. After the filtration, the filter cake was dried at a temperature of 120? C. for 16 h.

(14) The dried zeolitic material was then subjected to calcination. The zeolitic material was heated to 450? C. within 5.5 h and heated at this temperature for 2 h. The calcined material had a B.sub.2O.sub.3:SiO.sub.2 molar ratio of 0.0015, a crystallinity of 83% and a water uptake of 8.9 weight-%.

(15) Results of Example 1

(16) According to the present invention, a combination of a deboronation procedure using a liquid solvent system (water) with a treatment with a liquid aqueous system (water) was carried out. This combination, on the one hand, led to a zeolitic material having an MWW framework structure with a molar ratio B.sub.2O.sub.3:SiO.sub.2 which decreases from of 0.06:1 to 0.0015:1, and on the other hand, allowed to increase the crystallinity from 74% (or 77% after deboronation) to 83%.

(17) Moreover, the water uptake of the zeolitic material which characterizes the hydrophobicity of the zeolitic material and, thus, an important chemical parameter of the zeolitic material, did not change significantly (12 weight-% for starting material, 8.9 weight-% of the product).

Example 2

Process According to the Invention

(18) (iii) Treatment with a Liquid Aqueous System

(19) 1600 g de-ionized water were provided in a vessel and 80 g of the deboronated zeolitic material obtained according to Example 1 (ii) having a B.sub.2O.sub.3:SiO.sub.2 molar ratio of 0.002, crystallinity of 77% and a water uptake of 12 weight-% were added under stirring. The suspension was stirred for 10 min. Thereafter, the suspension was heated at 140? C. under autogenous pressure for 12 h in an autoclave.

(20) The resulting zeolitic material was separated from the suspension by filtration and washed with deionized water. After the filtration, the filter cake was dried at a temperature of 120? C. for 10 h.

(21) The dried zeolitic material was then subjected to calcination. For calcination, the zeolitic material was heated to 450? C. within 5.5 h and kept at this temperature for 2 h. The calcined material had a B.sub.2O.sub.3:SiO.sub.2 molar ratio of 0.0023:1, a crystallinity of 87% and a water uptake of 9.3 weight-%.

(22) Results of Example 2

(23) As Example 1, also Example 2 shows that the inventive process leads to a zeolitic material having an MWW framework structure with a molar ratio B.sub.2O.sub.3:SiO.sub.2 which decreases from of 0.06:1 to 0.0021:1, and simultaneously allows to increase the crystallinity from 74% (or 77% after deboronation) to 87%.

(24) Moreover, the water uptake of the zeolitic material which characterizes the hydrophobicity of the zeolitic material and, thus, an important chemical parameter of the zeolitic material, did not change significantly (12 weight-% for starting material, 9.3 weight-% of the product).

Example 3

Process According to the Invention

(25) (iii) Treatment with a Liquid Aqueous System

(26) 1600 g de-ionized water were provided in a vessel and 80 g of the deboronated zeolitic material obtained according to Example 2 (ii) having a B.sub.2O.sub.3:SiO.sub.2 molar ratio of 0.002, crystallinity of 77% and a water uptake of 12 weight-% were added under stirring (200 rpm). The suspension was stirred for 10 min. Thereafter, the suspension was heated at 140? C. under autogenous pressure for 14 h in an autoclave.

(27) The resulting zeolitic material was separated from the suspension by filtration and washed with deionized water. After the filtration, the filter cake was dried at a temperature of 120? C. for 10 h.

(28) The dried zeolitic material was then subjected to calcination. The zeolitic material was heated to 450? C. within 5.5 h and heated at this temperature for 2 h. The calcined material had a B.sub.2O.sub.3:SiO.sub.2 molar ratio of 0.0008 a crystallinity of 85% and a water uptake of 10.7 weight-%.

(29) Results of Example 3

(30) As Examples 1 and 2, also Example 3, carried out for 14 h under autogenous pressure, shows that a combination of a deboronation procedure using a liquid solvent system (water) with a treatment with a liquid aqueous system (water) according to the invention, leads to a zeolitic material having an MWW framework structure with a molar ratio B.sub.2O.sub.3:SiO.sub.2 which decreases from of 0.06:1 to 0.0008:1, and simultaneously allows to increase the crystallinity from 74% (or 77% after deboronation) to 85%.

(31) Moreover, the water uptake of the zeolitic material which characterizes the hydrophobicity of the zeolitic material and, thus, an important chemical parameter of the zeolitic material, did not change significantly (12 weight-% for starting material, 10.7 weight-% of the product).

Comparative Example 1

Steam Treatment

(32) A shallow bed sample of 100 g deboronated zeolitic material obtained according to Example 2 (ii) having a B.sub.2O.sub.3:SiO.sub.2 molar ratio of 0.0022, a crystallinity of 77% and a water uptake of 12 weight-% was provided in a muffle oven and heated to 650? C. (temperature ramp 5 K/min). For the steam-treatment, a gas flow of 6 L/min (10% steam in air) was used, wherein the water dosing started at a temperature of 200? C. The steam-treatment was carried out for 1 h at 650? C.

(33) The obtained material had a B.sub.2O.sub.3:SiO.sub.2 molar ratio of 0.0026, a crystallinity of 74% and a water uptake of 9.7 weight-%. The multipoint BET specific surface area determined via nitrogen adsorption at 77 K according to DIN 66131 was 413 m.sup.2/g.

(34) Thus, steaming the deboronated zeolitic material according to the prior art carried out for decreasing the B.sub.2O.sub.3:SiO.sub.2 molar leads to a decrease in crystallinity, contrary to the process of the present invention which allows to keep the crystallinity constant of even increase the crystallinity.

Comparative Example 2

Steam Treatment

(35) A shallow bed sample of 100 g deboronated zeolitic material obtained according to Example 2 (ii) having a B.sub.2O.sub.3:SiO.sub.2 molar ratio of 0.0022, crystallinity of 77% and a water uptake of 12 weight-% was provided in a muffle oven and heated to 850? C. (temperature ramp 5? C./min). For the steam-treatment, a gas flow of 6 L/min (10% steam in air) was used, wherein the water dosing started at 200? C. The steam-treatment was carried out for 1 h at 850? C.

(36) The obtained material had a B.sub.2O.sub.3:SiO.sub.2 molar ratio of 0.0027, a crystallinity of 54 and a water uptake of 7.5 weight-%. The multipoint BET specific surface area determined via nitrogen adsorption at 77 K according to DIN 66131 was 397 m.sup.2/g.

(37) Thus, steaming the deboronated zeolitic material according to the prior art carried out for decreasing the B.sub.2O.sub.3:SiO.sub.2 molar leads to a decrease in crystallinity, contrary to the process of the present invention which allows to keep the crystallinity constant of even increase the crystallinity.

Cited Literature

(38) EP 0 013 433 A1 WO 02/057181 A2 WO 2009/016153 A2