Process for the preparation of butadiene

Abstract

The present invention relates to a gas-phase process for the preparation of butadiene comprising (i) providing a gas stream G-1 comprising ethanol; (ii) contacting the gas stream G-1 comprising ethanol with a catalyst, thereby obtaining a gas stream G-2 comprising butadiene, wherein the catalyst comprises a zeolitic material having a framework structure comprising YO.sub.2, Y standing for one or more tetravalent elements, wherein at least a portion of Y comprised in the framework structure is isomorphously substituted by one or more elements X, as well as to a zeolitic material having a framework structure comprising YO.sub.2, Y standing for one or more tetravalent elements, wherein at least a portion of Y comprised in the framework structure is isomorphously substituted by one or more elements X, wherein the zeolitic material displays a specific X-ray powder diffraction pattern, and to its use.

Claims

1. A gas-phase process for the preparation of butadiene comprising: (i) providing a gas stream G-1 comprising ethanol; and (ii) contacting the gas stream G-1 comprising ethanol with a catalyst, thereby obtaining a gas stream G-2 comprising butadiene, wherein the catalyst comprises a zeolitic material having a MWW framework structure comprising YO.sub.2, and wherein at least a portion of Y comprised in the framework structure is isomorphously substituted by one or more elements X, wherein Y is selected from the group consisting of Si, Sn, Ti, Zr, Ge, and combinations of two or more thereof, and wherein X is selected from the group consisting of Zr, Ti, Sn, Ga, Nb, Ta, Sc, Ge, Al, B, Fe, and combinations of two or more thereof.

2. The process of claim 1, wherein the gas stream G-1 additionally comprises acetaldehyde.

3. The process of claim 2, wherein the molar ratio of ethanol to acetaldehyde in the gas stream G-1 is in the range of from 1:1 to 6:1.

4. The process of claim 2, wherein 80 vol.-% or more of the gas stream G-1 comprises ethanol or a mixture of ethanol and acetaldehyde.

5. The process of claim 1, wherein the molar ratio of Y:X in the framework structure ranges from 10:1 to 150:1.

6. The process of claim 1, wherein the molar ratio of Y:X in the framework structure ranges from 50:1 to 700:1.

7. The process of claim 1, wherein the catalyst comprises Sn-MWW and/or Ta-MWW.

8. The process of claim 1, wherein the zeolitic material comprised in the catalyst has an MWW framework structure, and wherein Y is Si and X is Ti.

9. The process of claim 8, wherein the zeolitic material further comprises Zn as a non-framework element.

10. The process of claim 1, wherein the catalyst comprises a zeolitic material having an X-ray powder diffraction pattern comprising at least the following reflections: TABLE-US-00007 Intensity (%) Diffraction angle 2/ [Cu K(alpha 1)] 67.0-87.0 15.16 0.3 79.8-99.8 15.82 0.3 45.3-65.3 22.47 0.3 100 23.88 0.3 52.3-72.3 27.06 0.3 75.0-95.0 27.21 0.3 wherein 100% relates to the intensity of the maximum peak in the X-ray powder diffraction pattern.

11. The process of claim 1, wherein contacting the gas stream G-1 with the catalyst is carried out at a temperature in the range of from 300 to 500 C.

12. The process of claim 1, wherein contacting the gas stream G-1 with the catalyst is carried out at a pressure in the range of from 1 to 5 bar.

13. The process of claim 1, wherein contacting gas stream G-1 with the catalyst is carried out in a continuous mode.

14. The process of claim 1, wherein contacting the gas stream G-1 with the catalyst is carried out in one or more reactors, and wherein the one or more reactors comprise the catalyst in the form of a fixed bed.

15. The process of claim 1, wherein prior to contacting the gas stream G-1 with the catalyst, the gas stream G-1 is heated.

16. The process of claim 1, wherein prior to contacting the gas stream G-1 with the catalyst, the catalyst is activated.

17. The process of claim 16, wherein the catalyst is activated by heating to a temperature in the range of from 300 to 450 C.

18. The process of claim 16, wherein the catalyst is heated with a temperature ramp in the range of from 0.5 to 10 K/min.

19. The process of claim 16, wherein the catalyst is activated in one or more reactors.

20. The process of claim 16, wherein during heating the catalyst is flushed with an inert gas.

21. The process of claim 1, wherein the gas stream G-2 comprises the butadiene in an amount of from 10 to 90 vol-%, based on the total volume of the gas stream G-2.

22. The process of claim 1, further comprising (iii) separating butadiene from the gas stream G-2, thereby obtaining a purified gas stream G-3 comprising butadiene.

23. The process of claim 1, wherein the gas stream G-2 further comprises diethyl ether, and wherein the diethyl ether is separated from the gas stream G-2 to be recycled in the gas-phase process for the preparation of butadiene.

24. The process of claim 23, wherein the gas stream G-2 comprises the diethyl ether in an amount of from 1 to 65 vol-% based on the total volume of the gas stream G-2.

25. The process of claim 23, further comprising hydrolyzing at least a portion of separated diethyl ether to ethanol prior to its recycling to the gas-phase process for the preparation of butadiene.

26. The process of claim 25, wherein the separated diethyl ether is hydrolyzed under acidic conditions.

27. The process of claim 1, wherein the gas stream G-2 further comprises crotonaldehyde.

28. The process of claim 27, wherein the gas stream G-2 comprises the crotonaldehyde in an amount of from 0.1 to 15 vol-%, based on the total volume of the gas stream G-2.

29. The process of claim 1, further comprising regenerating the catalyst.

30. The method of claim 1, wherein a selectivity of the process relative to butadiene is at least 10%.

Description

DESCRIPTION OF THE FIGURES

(1) FIG. 1: shows the X-ray diffraction (XRD) pattern (measured using Cu K alpha-1 radiation) of the crystalline zirconium-containing silicate (Zr-silicate) obtained from Example 3. In the figure, the diffraction angle 2 theta in is shown along the abscissa and the intensities are plotted along the ordinate.

(2) FIG. 2: shows the X-ray diffraction (XRD) pattern (measured using Cu K alpha-1 radiation) of the tin-containing zeolitic material (Sn-MWW) obtained from Example 5. In the figure, the diffraction angle 2 theta in is shown along the abscissa and the intensities are plotted along the ordinate

(3) FIG. 3: shows the UV-VIS spectra of Ta-MWW obtained according to Example 8. On the abscissa, the wavelength values (nanometer) are shown, and the Kubelka-Munk KM units are plotted along the ordinate.

(4) FIG. 4: shows the UV-VIS spectra of Ta-MWW obtained according to Example 9. On the abscissa, the wavelength values (nanometer) are shown, and the Kubelka-Munk KM units are plotted along the ordinate.

(5) FIG. 5: shows the X-ray diffraction (XRD) pattern (measured using Cu K alpha-1 radiation) of the tantalum-containing zeolitic material (Ta-MWW) obtained from Example 8. In the figure, the diffraction angle 2 theta in is shown along the abscissa and the intensities are plotted along the ordinate

(6) FIG. 6: shows the product formation and ethanol/acetaldehyde conversion as function of time by use of the Zr-silicate obtained from Example 3. On the x axis, the percent values are shown for the conversion of ethanol, as well as for the selectivity relative to ethylene, crotonaldehyde, ethylacetate, ethene, C1 to C3 compounds, C4-compounds, diethylether, C6 compounds, and other compounds, and on the y axis, the time in h is indicated.

EXAMPLES

Reference Example 1: Determination of the Crystallinity and of the Lattice Parameter c of Zeolitic Materials Having an MWW-Framework Structure

(7) The crystallinity and the lattice parameter c of the zeolitic materials according to the present invention were determined by XRD analysis. The data are collected using a standard Bragg-Brentano diffractometer with a Cu-X-ray source and an energy dispersive point detector. The angular range of 2 to 70 (2 theta) is scanned with a step size of 0.02, while the variable divergence slit is set to a constant illuminated sample length of 20 mm. The data are then analyzed using TOPAS V4 software, wherein the sharp diffraction peaks are modelled using a Pawley fit containing a unit cell with the following starting parameters: a=14.4 Angstrom and c=25.2 Angstrom in the space group P6/mmm. These are refined to fit the data. Independent peaks are inserted at the following positions. 8.4, 22.4, 28.2 and 43. These are used to describe the amorphous content. The crystalline content describes the intensity of the crystalline signal to the total scattered intensity. Included in the model are a linear background, Lorentz and polarization corrections, lattice parameters, space group and crystallite size.

Reference Example 2: Determination of the Crystallinity of Zeolitic Materials Having a BEA-Framework Structure

(8) 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 a single reflection 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 determination of the crystallinities was 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 areas of the reflections were determined by making use of the evaluation software EVA (from Bruker AXS). The ratios of the areas are given as percentage values.

Reference Example 3: Determination of Dv50

(9) 1. Sample Preparation

(10) 1.0 g of the micropowder is suspended in 100 g deionized water and stirred for 1 min.
2. Apparatus and Respective Parameters Used Mastersizer S long bed version 2.15, ser. No. 33544-325; supplier: Malvern Instruments GmbH, Herrenberg, Germany focal width: 300 RF mm beam length: 10.00 mm module: MS17 shadowing: 16.9 dispersion model: 3$$D analysis model: polydisperse correction: none

Reference Example 4: Conversion of a Mixture of Ethanol and Acetaldehyde to Butadiene

(11) Preparation of the Catalyst Samples:

(12) Before testing catalyst samples were compacted using pressure of 25 kN and sieved to particle size in the range of from 315 to 500 m.

(13) Set-Up:

(14) Experiments were conducted in a 16-fold Test-unit. For feed-dosage a mixture of acetaldehyde and ethanol was pumped to an evaporator in which it is heated to 125 C. within a gas stream of nitrogen. The trace-heated (170 C.) feed stream is then distributed to all 16 reactor tubes. Within each reactor tube (stainless steel; 400 mm long and 4 mm ID) the catalyst sieve fraction (1 cc) is guarded by an upper and a lower inert layer consisting of quartz (315-500 m, 2 cc). By means of a multiport-selection valve the trace-heated (200 C.) effluent of each reactor is led to the GC/MS for product analysis.

(15) Activation of the Catalyst

(16) For activation, samples are heated at 375 C. for 30 min under nitrogen.

(17) Performance

(18) A mixture of ethanol and acetaldehyde (molar ratio 2.75:1) was evaporated and mixed with nitrogen to obtain a feed composition of 90 vol.-% ethanol/acetaldehyde and 10 vol.-% nitrogen. The thus obtained feed stream was converted over the catalyst to butadiene at a temperature of 375 C. and under a pressure in the range of from 1 to 2 bar and with LHSV (liquid hourly space velocity) of 0.6 h.sup.1. The gaseous product mixture was analyzed by online gas chromatography.

(19) LHSV (liquid hourly space velocity): 0.6 h.sup.1

(20) Average conversions and selectivities over an operation time of 110 h were determined, wherein the conversions and selectivities were determined in 8 h interval.

Reference Example 5: Measurement of the UV-VIS Spectra

(21) The measurement of the UV-VIS spectra were performed using a Lambda 950 spectrophotomerter from PerkinElmer with 150 mm integrating spheres, wherein a spectralon white standard from the firm Labsphere was used as reference.

Example 1: Synthesis of Zirconium-Containing Zeolitic Material Having a BEA Frame Work Structure (Zr-BEA)

(22) In a round bottom flask 86.30 g of tetraethylorthosilicate (TEOS) was added together with 97.48 g of tetraethylammonium hydroxide (TEAOH). 1.33 g of ZrOCl.sub.2 and 3.31 g distilled water were added to the suspension. The alcohol was distilled under stirring at 95 C. After distillation the mixture was cooled to room temperature and transferred to a Teflon liner of a Berghof autoclave (250 mL). To the mixture 11.59 g of an aqueous hydrogen fluoride solution (40 weight-% in water) and 3.02 g of seeds of a dealuminated zeolitic material having a BEA framework structure were added. The autoclave was closed and the zeolite was hydrothermally synthesized in a static oven for 20 days at 140 C. After this period, the autoclave was cooled the room temperature and the solid was separated by filtration and washed with distilled water until the washing water had a pH of 7. The solid was dried in a static oven at 100 C. for 16 h, and calcined at 580 C. for 4 h.

(23) Characterization

(24) The obtained zeolitic material had a zirconium content of 0.75 weight-%, a silicon content of 45.0 weight-% and a crystallinity of 124%, determined by XRD. The BET specific surface area determined via nitrogen adsorption at 77 K according to DIN 66131 was 456 m.sup.2/g.

Example 2: Synthesis of Zirconium-Containing Zeolitic Material Having a BEA Frame Work Structure (Zr-BEA)

(25) In a round bottom flask 129.60 g of tetraethylorthosilicate (TEOS) was added together with 146.39 g or tetraethylammonium hydroxide (TEAOH). 1.00 g of ZrOCl.sub.2 and 5.59 g distilled water were added to the suspension. The alcohol was distilled under stirring at 95 C. After distillation the mixture was cooled to room temperature and transferred to a Teflon liner of a Berghof autoclave (250 mL). To the mixture 17.40 g of an aqueous hydrogen fluoride solution (40 wt.-% in water) and 4.54 g of seeds of dealuminated-Beta zeolite were added. The autoclave was closed and the zeolite was hydrothermally synthesized in a static oven for 20 days a 140 C. After this period, the autoclave was cooled the room temperature and the solid was separated by filtration and washed with distilled water until the washing water had a pH of 7. The solid was dried in a static oven at 100 C. for 16 h, and calcined at 580 C. for 4 h.

(26) Characterization

(27) The obtained zirconium-containing zeolitic material having a BEA framework structure had a zirconium content of 0.48 weight-%, a silicon content of 46.0 weight-% and a crystallinity of 124%, determined by XRD. The BET specific surface area determined via nitrogen adsorption at 77 K according to DIN 66131 was 472 m.sup.2/g.

Example 3: Synthesis of a Crystalline Zirconium-Containing Silicate (Zr-Silicate)

Example 3.1: Synthesis of a Boron-Containing Zeolitic Material Having an MWW Framework Structure (B-MWW)

(28) 15.75 kg de-ionized water and 6.08 kg piperidin were introduced in a stirring pressure vessel. Under stirring 3.63 kg boric acid were added and the suspension was stirred for additional 30 min. To the resulting solution, 3.5 kg Aerosil 200 were added in portions and the suspension was further stirred for 2 h. Finally, the crystallization vessel was heated to 170 C. within 2 h under autogenous pressure and stirred at 150 rpm. The temperature of 170 C. was kept essentially constant for 120 h. During these 120 h, the mixture was stirred at 150 rpm. Subsequently, the mixture was cooled to a temperature in the range of from 50 to 60 C. The aqueous suspension containing the boron-containing zeolitic material having an MWW framework structure (B-MWW) had a pH of 11.3 as determined via measurement with a pH electrode. From said suspension, the B-MWW was separated by filtration. The filter cake was washed with de-ionized water until the washing water had a conductivity of less than 700 microSiemens/cm. The filtercake was dried in a static oven at 100 C. for 16 h and the dried powder was calcined at 600 C. for 16 h.

(29) Characterization

(30) The obtained B-MWW had a boron content of 1.4 weight-%, a silicon content of 42 weight-% and a total organic carbon (TOC) content of 0.01 weight-%.

Example 3.2: Deboronation

(31) The B-MWW obtained according to Example 3.2 was deboronated following the below procedure:

(32) 122.5 kg of an aqueous HNO.sub.3 solution (30 weight-% in water) were introduced together with 4.08 kg of the B-MWW in a vessel equipped with a reflux condenser. The suspension was stirred and heated to 100 C. and kept for 20 h under reflux conditions. Afterwards the mixture was cooled down and the solid was recovered by filtration and washed with distilled water until the washing water had a pH of 7. The filtercake was afterwards dried in a static oven at 120 C. for 16 h.

(33) Characterization

(34) The obtained deboronated zeolitic material had a boron content of 0.07 weight-% and a silicon content of 41.0 weight-%

Example 3.3: Incorporation of Zirconium

(35) 540 g of water and 260.64 g of piperidine were introduced in a glass flask. The mixture was stirred at 200 rpm and 24.56 g of Zirconium-n-propoxide were added. The obtained mixture was further stirred for 20 min before drop-wise addition of 180 g of the deboronated zeolitic material having an MWW framework structure obtained according to Example 3.2. The suspension was further stirred for 2 h at 200 rpm until a gel was obtained. The formed gel was transferred to an autoclave. The autoclave was heated to 170 C. and kept at this temperature for 120 h under stirring at 150 rpm. Subsequently, the autoclave was cooled down and the solid was separated by filtration and washed until the washing water had a pH of 7. The filtercake was dried in a static oven at 120 C. for 16 h.

(36) Characterization

(37) The obtained zirconium-containing zeolitic material had a zirconium content of 3.2 weight-% and a silicon content of 38.5 weight-%.

Example 3.4: Acid Treatment of the Zirconium Containing Zeolitic Material

(38) 4200 g of an aqueous HNO.sub.3 solution (30 weight-% in water) was provided in a 10 L flask. To this solution the zirconium-containing silicate obtained according to Example 3.3 was added and the mixture was heated to 100 C. for 20 h under stirring with 170 rpm. Afterwards the suspension was filtered and washed until the washing water had a pH of 7. The filtercake was dried in a static oven for 16 h at 120 C. and calcined at 550 C. for 10 h.

(39) Characterization

(40) The obtained zeolitic material had a zirconium content of 0.27 weight-% and a silicon content of 43 weight-%. The BET specific surface area determined via nitrogen adsorption at 77 K according to DIN 66131 was 38 m.sup.2/g. The XRD of the obtained zeolitic material is shown in FIG. 1. The obtained zeolitic material has an XRD pattern having the following reflections:

(41) TABLE-US-00004 Diffraction angle 2 theta/ Intensity [Cu K(alpha 1)] [%] 7.2 0.1 2.3 0.1 7.9 0.1 3.6 0.1 12.9 0.1 22.6 0.1 14.5 0.1 4.3 0.1 15.2 0.1 77.0 0.1 15.9 0.1 98.6 0.1 18.1 0.1 25.0 0.1 18.3 0.1 47.0 0.1 19.9 0.1 44.4 0.1 22.4 0.1 35.7 0.1 22.5 0.1 55.3 0.1 23.7 0.1 49. 0.12 23.9 0.1 100 25.9 0.1 49.1 0.1 27.1 0.1 62.3 0.1 27.2 0.1 89.0 0.1 27.6 0.1 14. 0.16 28.9 0.1 13.0 0.1 29.2 0.1 21.6 0.1 30.2 0.1 16.6 0.1 32.9 0.1 9.9 0.1 33.1 0.1 9.0 0.1 33.4 0.1 8.4 0.1 34.6 0.1 7.6 0.1 35.5 0.1 16.0 0.1 35.6 0.1 19.1 0.1 36.7 0.1 5.0 0.1 37.8 0.1 10. 0.16 38.0 0.1 21. 0.13 39.1 0.1 10. 0.15 39.3 0.1 17.0 0.1 39.5 0.1 25.0 0.1 40.2 0.1 11.2 0.1 40.4 0.1 10.2 0.1 41.4 0.1 6.5 0.1 41,.7 0.1 9.2 0.1 42.5 0.1 5.6 0.1 42.8 0.1 4.4 0.1 44.7 0.1 6.7 0.1 45.6 0.1 5.6 0.1 45.9 0.1 7.1 0.1 46.5 0.1 10.5 0.1 46.7 0.1 9.5 0.1 47.9 0.1 11.0 0.1 48.4 0.1 12.0 0.1 48.6 0.1 12.4 0.1 48.8 0.1 15.3 0.1 48.9 0.1 15.8 0.1 50.2 0.1 8.2 0.1 50.5 0.1 13.5 0.1 51.3 0.1 9.1 0.1 51.8 0.1 11.9 0.1 52.3 0.1 6.1 0.1 54.2 0.1 10.9 0.1 55.2 0.1 10.1 0.1 55.4 0.1 9.1 0.1 56.0 0.1 8.7 0.1 56.9 0.1 9.7 0.1 57.2 0.1 12.9 0.1 57.8 0.1 11.9 0.1 58.4 0.1 9.2 0.1 58.9 0.1 16.3 0.1 59.4 0.1 11.9 0.1 61.4 0.1 7.7 0.1 62.9 0.1 10.6 0.1 63.8 0.1 7.7 0.1 64.3 0.1 9.1 0.1 64.4 0.1 10.6 0.1 65.3 0.1 10.1 0.1 65.5 0.1 9.1 0.1 66.1 0.1 12.7 0.1 66.3 0.1 8.1 0.1 66.8 0.1 14.7 0.1 67.0 0.1 10.9 0.1 67.6 0.1 8.9 0.1 68.2 0.1 14.8 0.1 68.5 0.1 13.2 0.1 68.7 0.1 13.0 0.1 69.2 0.1 10.7 0.1 69.4 0.1 9.1 0.1

Example 4: Synthesis of ZnTi-MWW

Example 4: 1 Preparation of Boron-Containing MWW

(42) 470.4 kg de-ionized water were provided in a vessel. Under stirring at 70, 162.5 kg boric acid were suspended in the water. The suspension was stirred for another 3 h. Subsequently, 272.5 kg piperidine were added, and the mixture was stirred for another hour. To the resulting solution, 392.0 kg Ludox AS-40 were added, and the resulting mixture was stirred at 70 rpm for another hour.

(43) 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. within 5 h. The aqueous suspension containing B-MWW had a pH of 11.3 as determined via measurement with a pH electrode.

(44) From said suspension, the B-MWW was separated by filtration. The filter cake was then washed with de-ionized water until the washing water had a conductivity of less than 700 microSiemens/cm

(45) The thus obtained filter cake was subjected to spray-drying in a spray-tower with the following spray-drying conditions:

(46) drying gas, nozzle gas: technical nitrogen

(47) temperature drying gas:

(48) temperature spray tower (in): 288-291 C. temperature spray tower (out): 157-167 C. temperature filter (in): 150-160 C. temperature scrubber (in): 40-48 C. temperature scrubber (out): 34-36 C.
pressure difference filter: 8.3-10.3 mbar
nozzle: two-component nozzle supplier Gerig; size 0 nozzle gas temperature: room temperature nozzle gas pressure: 2.5 bar
operation mode: nitrogen straight
apparatus used: spray tower with one nozzle
configuration: spray tower-filter-scrubber
gas flow: 1,900 kg/h
filter material: Nomex needle-felt 20 m.sup.2
dosage via flexible tube pump: SP VF 15 (supplier: Verder)

(49) 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. The spray-dried material was then subjected to calcination at 650 C. for 2 h.

(50) Characterization

(51) The calcined material had a boron content of 1.9 weight-%, a silicon content of 41 weight-%, and a total organic carbon content of 0.18 weight-%. The crystallinity determined by XRD was 74%, BET specific surface area determined via nitrogen adsorption at 77 K according to DIN 66131 was 448 m.sup.2/g, pore volume determined by HG porosimetry according to DIN 66133 was 5.9 mL/g, particle size distribution of the sprayed-dried particle determined by Malvern Dv50 was 26.9 m.

4.2 Preparation of Deborated MWW

(52) a) Deboration

(53) Based on the spray-dried material obtained according to section 4.1 above, 4 batches of deborated zeolite MWW were prepared. In each of the first 3 batches, 35 kg of the spray-dried material obtained according to section 4.1 and 525 kg water were employed. In the fourth batch, 32 kg of the spray-dried material obtained according to section 4.1 and 480 kg water were employed. In total, 137 kg of the spray-dried material obtained according to section 4.1 and 2025 kg water were employed. For each batch, the respective amount of water was passed into a vessel equipped with a reflux condenser. Under stirring at 40 r.p.m., the given amount of the spray-dried material was suspended into the water. Subsequently, the vessel was closed and the reflux condenser put into operation. The stirring rate was increased to 70 r.p.m. Under stirring at 70 r.p.m., the content of the vessel was heated to 100 C. within 10 h and kept at this temperature for 10 h. Then, the content of the vessel was cooled to a temperature of less than 50 C. The resulting deborated zeolitic material of structure type MWW was separated from the suspension by filtration under a nitrogen pressure of 2.5 bar and washed four times with deionized water. After the filtration, the filter cake was dried in a nitrogen stream for 6 h. The deborated zeolitic material obtained in 4 batches (625.1 kg nitrogen-dried filter cake in total) had a residual moisture content of 79%, as determined using an IR (infrared) scale at 160 C.
b) Spray-Drying of the Nitrogen-Dried Filter Cake From the nitrogen-dried filter cake having a residual moisture content of 79% obtained according to section a) above, an aqueous suspension was prepared with de-ionized water, the suspension having a solid content of 15 wt.-%. 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): 304 C. temperature spray tower (out): 147-150 C. temperature filter (in): 133-141 C. temperature scrubber (in): 106-114 C. temperature scrubber (out): 13-20 C. pressure difference filter: 1.3-2.3 mbar nozzle: two-component nozzle: supplier Niro, diameter 4 mm nozzle gas throughput: 23 kg/h nozzle gas pressure: 2.5 bar operation mode: nitrogen straight apparatus used: spray tower with one nozzle configuration: spray tower-filter-scrubber gas flow: 550 kg/h filter material: Nomex needle-felt 10 m.sup.2 dosage via flexible tube pump: VF 10 (supplier: Verder) 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.
Characterization

(54) The spray-dried boron-containing zeolitic material had a boron content of 0.08 weight-%, a silicon content of 42 weight-%, and a total organic carbon content of 0.23 weight-%. The BET specific surface area determined via nitrogen adsorption at 77 K according to DIN 66131 was 476 m.sup.2/g and the crystallinity, determined by XRD was 81%.

Example 4.3: Preparation of TiMWW

(55) Based on the deborated MWW material as obtained according to section 4.2, a zeolitic material of structure type MWW containing titanium was prepared, referred to in the following as TiMWW. The synthesis was performed in two experiments, described in the following as a) and b):

(56) a) First Experiment

(57) Starting materials: deionized water: 244.00 kg piperidine: 118.00 kg tetrabutylorthotitanate: 10.90 kg deborated zeolitic material: 54.16 kg 54.16 kg of the deborated zeolitic material of structure type MWW were transferred in to a first vessel A. In a second vessel B, 200.00 kg deionized water were transferred and stirred at 80 r.p.m. 118.00 kg piperidine were added under stirring, and during addition, the temperature of the mixture increased for about 15 C. Subsequently, 10.90 kg tetrabutylorthotitanate and 20.00 kg deionized water were added. Stirring was then continued for 60 min. The mixture of vessel B was then transferred into vessel A, and stirring in vessel A was started (70 r.p.m.). 24.00 kg deionized water were filled into vessel A and transferred to vessel B. The mixture in vessel B was then stirred for 60 min. at 70 r.p.m. At the beginning of the stirring, the pH of the mixture in vessel B was 12.6, as determined with a pH electrode. After said stirring at 70 r.p.m., the frequency was decreased to 50 r.p.m., and the mixture in vessel B was heated to a temperature of 170 C. within 5 h. At a constant stirring rate of 50 r.p.m., the temperature of the mixture in vessel B was kept at an essentially constant temperature of 170 C. for 120 h under autogenous pressure. During this crystallization of TiMWW, a pressure increase of up to 10.6 bar was observed. Subsequently, the obtained suspension containing TiMWW having a pH of 12.6 was cooled within 5 h. The cooled suspension was subjected to filtration, and the separated mother liquor was transferred to waste water discharge. The filter cake was washed four times with deionized water under a nitrogen pressure of 2.5 bar. After the last washing step, the filter cake was dried in a nitrogen stream for 6 h. From 246 kg of said filter cake, an aqueous suspension was prepared with deionized water, the 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): 304 C. temperature spray tower (out): 147-152 C. temperature filter (in): 133-144 C. temperature scrubber (in): 111-123 C. temperature scrubber (out): 12-18 C. pressure difference filter: 1.8-2.8 mbar nozzle: top-component nozzle: supplier Niro, diameter 4 mm nozzle gas throughput: 23 kg/h nozzle gas pressure: 2.5 bar operation mode: nitrogen straight apparatus used: spray tower with one nozzle configuration: spray tower-filter-scrubber gas flow: 550 kg/h filter material: Nomex needle-felt 10 m.sup.2 dosage via flexible tube pump: VF 10 (supplier: Verder) 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.

(58) Characterization The spray-dried TiMWW material obtained from the first experiment had a silicon content of 37 weight-%, a titanium content of 2.4 weight-%, and a total organic carbon content of 7.5 weight-%.
b) Second Experiment The second experiment was carried out in the same way as the first experiment described in section a) above. The spray-dried TiMWW material obtained from the second experiment had a silicon content of 36 weight-%, a titanium content of 2.4 weight-%, a total organic carbon content of 8.0 weight-%

Example 4.4: Add Treatment of TiMWW

(59) Each of the two spray-dried TiMWW materials as obtained in the first and the second experiment described in sections 4.3 a) and 4.3 b) above was subjected to acid treatment as described in the following in sections a) and b). In section c) hereinunder, it is described how a mixture of the materials obtained from a) and b) are spray-dried. In section d) hereinunder, it is described how the spray-dried material is calcined.

(60) a) Acid Treatment of the Spray-Dried Material Obtained According to Section 4.3.a)

(61) Starting materials: deionized water: 690.0 kg nitric acid: (53%): 900.0 kg spray-dried Ti-MWW 4.3. a): 53.0 kg 670.0 kg deionized water were filled in a vessel. 900 kg nitric acid were added, and 53.0 kg of the spray-dried TiMWW were added under stirring at 50 r.p.m. The resulting mixture was stirred for another 15 min. Subsequently, the stirring rate was increased to 70 r.p.m. Within 1 h, the mixture in the vessel was heated to 100 C. and kept at this temperature and under autogenous pressure for 20 h under stirring. The thus obtained mixture was then cooled within 2 h to a temperature of less than 50 C. The cooled mixture was subjected to filtration, and the filter cake was washed six times with deionized water under a nitrogen pressure of 2.5 bar. After the last washing step, the filter cake was dried in a nitrogen stream for 10 h. The washing water after the sixth washing step had a pH of about 2.7. 225.8 kg dried filter cake were obtained.
b) Acid Treatment of the Spray-Dried Material Obtained According to Section 4.3.b) Starting materials: deionized water: 690.0 kg nitric acid: (53%): 900.0 kg spray-dried Ti-MWW 4.3. b): 55.0 kg The acid treatment of the spray-dried material obtained according to section 4.3.b) was carried in the same way as the acid treatment of the spray-dried material obtained according to section 4.3.a) as described in section 4.4 a). The washing water after the sixth washing step had a pH of about 2.7. 206.3 kg dried filter cake were obtained.
c) Spray-Drying of the Mixture of the Materials Obtained from 4.4.a) and 4.4 b) From 462.1 kg of the mixture of the filter cakes obtained from 4.4.a) and 4.4 b), an aqueous suspension was prepared with deionized water, the 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): 304-305 C. temperature spray tower (out): 151 C. temperature filter (in): 141-143 C. temperature scrubber (in): 109-118 C. temperature scrubber (out): 14-15 C. pressure difference filter: 1.7-3.8 mbar nozzle: two-component nozzle: supplier Niro, diameter 4 mm nozzle gas throughput: 23 kg/h nozzle gas pressure: 2.5 bar operation mode: nitrogen straight apparatus used: spray tower with one nozzle configuration: spray tower-filter-scrubber gas flow: 550 kg/h filter material: Nomex needle-felt 10 m.sup.2 dosage via flexible tube pump: VF 10 (supplier: Verder) 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.

(62) Characterization The spray-dried acid-treated TiMWW material had a silicon content of 42 weight-%, a titanium content of 1.6 weight-%, and a total organic carbon content of 1.7 weight-%. The BET specific surface area determined via nitrogen adsorption at 77 K according to DIN 66131 was 435 m.sup.2/g and the crystallinity, determined by XRD was 80%.
d) Calcination of the Spray-Dried Material Obtained According to 4.4. c) The spray-dried material was then subjected to calcination at 650 C. in a rotary furnace for 2 h.
Characterization

(63) The calcined material had a silicon content of 42.5 weight-%, a titanium content of 1.6 weight-% and a total organic carbon content of 0.15 weight-%. The Langmuir surface are determined via nitrogen adsorption at 77 K according to DIN 66134 was 612 m.sup.2/g, the BET specific surface area determined via nitrogen adsorption at 77 K according to DIN 66131 was 442 m.sup.2/g. The total intrusion volume determined according to Hg porosimetry according to DIN 66133 was 4.9 ml/g (milliliter/gram), the respective total pore area 104.6 m.sup.2/g. The crystallinity, determined by XRD was 80% and the average crystallite size was 31 nm.

4.5 Impregnation of TiMWW with Zn

(64) a) Impregnation

(65) The acid-treated, spray-dried and calcined material as obtained according to 4.4 d) was then subjected to an impregnation stage. Starting materials: deionized water: 2610.0 kg zinc acetate dihydrate: 15.93 kg calcined Ti-MWW 4.4.d): 87.0 kg Impregnation was carried out in 3 batches a) to c) as follows: a) In a vessel equipped with a reflux condenser, a solution of 840 kg deionized water and 5.13 kg zinc acetate dihydrate was prepared within 30 min. Under stirring (40 r.p.m.), 28 kg of the calcined Ti-MWW material obtained according to 4.4.d) were suspended. Subsequently, the vessel was closed and the reflux condenser put into operation. The stirring rate was increased to 70 r.p.m. b) In a vessel equipped with a reflux condenser, a solution of 840 kg deionized water and 5.13 kg zinc acetate dihydrate was prepared within 30 min. Under stirring (40 r.p.m.), 28 kg of the calcined Ti-MWW material obtained according to 4.4.d) were suspended. Subsequently, the vessel was closed and the reflux condenser put into operation. The stirring rate was increased to 70 r.p.m. c) In a vessel equipped with a reflux condenser, a solution of 930 kg deionized water and 5.67 kg zinc acetate dihydrate was prepared within 30 min. Under stirring (40 r.p.m.), 31 kg of the calcined Ti-MWW material obtained according to 4.4.d) were suspended. Subsequently, the vessel was closed and the reflux condenser put into operation. The stirring rate was increased to 70 r.p.m.

(66) In all batches a) to c), the mixture in the vessel was heated to 100 C. within 1 h and kept under reflux for 4 h a t a stirring rate of 70 r.p.m. Then, the mixture was cooled within 2 h to a temperature of less than 50 C. For each batch a) to c), the cooled suspension was subjected to filtration, and the mother liquor was transferred to waste water discharge. The filter cake was washed five times with deionized water under a nitrogen pressure of 2.5 bar. After the last washing step, the filter cake was dried in a nitrogen stream for 10 h.

(67) For batch a), 106.5 kg nitrogen-dried filter cake were finally obtained. For batch b), 107.0 kg nitrogen-dried filter cake were finally obtained. For batch c), 133.6 kg nitrogen-dried filter cake were finally obtained.

(68) Characterization

(69) The thus dried Zn-impregnated TiMWW material (ZnTi-MWW), for each batch, had a silicon content of 42 weight-%, a titanium content of 1.6 weight-%, a zinc content of 1.4 weight-% and a total organic carbon content of 1.4 weight-%.

(70) b) Spray-Drying the Zn/Ti-MWW Powder

(71) From 347.1 kg of the mixture of the filter cakes obtained from Example 4.5, an aqueous suspension was prepared with deionized water, the 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: apparatus used: spray tower with one nozzle operation mode: nitrogen straight configuration: dehumidifier-filter-scrubber dosage: flexible-tube pump VF 10 (supplier: Verder) nozzle with a diameter of 4 mm (supplier: Niro) filter material: Nomex needle-felt 10 m.sup.2

(72) TABLE-US-00005 Runtime/h 0.5 1.5 2.5 3.5 4.5 Flow rate gas/(kg/h) 550 550 550 550 550 Temperature spray tower (in) 305 305 305 305 305 drying gas/ C. spray tower (out) 151 151 151 151 151 Filter (in) 140 137 130 127 126 Scrubber (in) 110 110 110 108 105 Scrubber (out) 14 14 15 15 15 Differential spray tower 3.1 3 3 2.8 2.9 pressure/ Filter 1.7 1.7 1.8 1.8 2.1 mbar Scrubber 3.8 4.1 4.2 4.2 4.2 Pressure/ spray tower 103 1.2 0.9 0.9 1.1 mbar Nozzle gas Flow rate kg/h 23 23 23 23 23 Temperature/ C. r.t.*.sup.) r.t.*.sup.) r.t.*.sup.) r.t.*.sup.) r.t.*.sup.) Pressure/bar 2.5 2.5 2.5 2.5 2.5 Spray-dried Temperature/ C. r.t.*.sup.) r.t.*.sup.) r.t.*.sup.) r.t.*.sup.) r.t.*.sup.) product *.sup.)Room temperature

(73) 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.

(74) Characterization

(75) The spray-dried material thus obtained had a zinc content of 1.4 weight-%, a titanium content of 1.7 weight-%, a silicon content of 40 weight-%, and a total organic carbon content of 0.27 weight-%

(76) c) Calcination

(77) The spray-dried product was then subjected to calcination for 2 h at 650 C. under air in a rotary furnace, yielding 76.3 kg of calcined spray-dried ZnTi-MWW.

(78) Characterization

(79) The calcined spray-dried material thus obtained had a zinc content of 1.4 weight-%, a titanium content of 1.7 weight-%, a silicon content of 42 weight-%, and a total organic carbon content of 0.14 weight-%.

(80) The bulk density of the calcined spray-dried ZnTi-MWW was 90 g/I (gram/liter). The micropores of the ZnTi-MWW contained in the micropowder had an average pore diameter of 1.13 nm as determined by nitrogen adsorption according to DIN 66134 (Horward-Kawazoe method). The Dv10 value of the particles of the micropowder as determined by Malvern 5.18 micrometers. The Dv50 value of the particles of the micropowder was 24.8 micrometers. The Dv90 value of the particles of the micropowder was 93.53 micrometers. The degree of crystallization determined via XRD was 86%, and the average crystallite size 38.5 nm. The Langmuir surface are determined via nitrogen adsorption at 77 K according to DIN 66134 was 586 m.sup.2/g, the BET specific surface area determined via nitrogen adsorption at 77 K according to DIN 66134 was 423 m.sup.2/g. The total intrusion volume determined according to Hg porosimetry according to DIN 66133 was 4.3 ml/g (milliliter/gram), the respective total pore area was 80.7 m.sup.2/g.

Example 5: Synthesis of a Tin-Containing Zeolitic Material Having an MWW Framework Structure (Sn-MWW)

Example 5.1: Preparation of a B-MWW

(81) 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 subjected to spray-drying in a spray-tower with the following spray-drying conditions:

(82) drying gas, nozzle gas: technical nitrogen

(83) temperature drying gas:

(84) temperature spray tower (in): 235 C. temperature spray tower (out): 140 C.
nozzle: two-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)

(85) 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.

(86) 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 0.06:1.

Example 5.2: Deboronation

(87) 9 kg of de-ionized water and 600 g of the calcined zeolitic material obtained according to Example 5.1 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 4 l deionized water at room temperature. After the filtration, the filter cake was dried at a temperature of 120 C. for 16 h.

(88) The dried zeolitic material having an MWW framework structure had a B.sub.2O.sub.3:SiO.sub.2 molar ratio of 0.0020:1.

Example 5.3: Incorporation of Sn

(89) 776.25 g deionized water were provided in a glass beaker and 280 g piperidine were added under stirring and further stirred for 20 minutes. Separately, in a glovebox 5 g tin(IV)-tertbutoxyde were dissolved in 95 g piperidine under nitrogen atmosphere. The mixture was added to the aqueous piperidine suspension and further stirred for 10 minutes. 172.4 g zeolitic material obtained according to Example 5.2 were added to the mixture and stirred for 1 h (200 r.p.m.) at room temperature. The obtained suspension was than filled in an autoclave. The mixture was treated for 120 h at a temperature of 170 C. under stirring (100 r.p.m.).

(90) Afterwards the autoclave was cooled down to room temperature and the resulting zeolitic material was separated from the suspension by filtration at room temperature and washed with deionized water until the washing water had a conductivity of less than 300 microSiemens/cm. After the filtration, the filter cake was dried at a temperature of 120 C. for 16 h.

(91) Characterization

(92) The dried zeolitic material had a silicon content of 37 weight-% and a tin content of 0.68 weight-%.

Example 5.4: Acid Treatment

(93) 170 g zeolitic material obtained according to Example 5.3 were provided in a round bottom flask and 5.1 kg of a 30 weight-% HNO.sub.3 aqueous solution, having a pH in the range from 0 to 1, were added. The mixture was stirred at a temperature of 100 C. for a period of 20 h (200 r.p.m.). The suspension was filtered and the filter cake was then washed with deionized water at room temperature until the washing water had a pH of approximately 7. The obtained zeolitic material was dried at 120 C. for 16 h and calcined by heating to 550 C. (2 C. per minute) and subsequent heating at 550 C. for 10 h.

(94) Characterization

(95) The dried and cacined zeolitic material had a silicon content of 43.5 weight-% and a tin content of 0.78 weight-% and a c parameter as determined via XRD of 27.069 Angstrom. Further, the zeolitic material had a BET surface area, determined according to DIN 66131 of 475 m.sup.2/g, a Langmuir surface, determined according to DIN 66135 of 657 m.sup.2/g and a total pore area of 189.42 m.sup.2/g. The XRD of the obtained zeolitic material is shown in FIG. 2.

Example 6: Synthesis of a Crystalline Zirconium-Containing Silicate (Zr-Silicate)

Example 6.1: Incorporation of Zirconium

(96) 540 g of water and 260.64 g of piperidine were introduced in a glass flask. The mixture was stirred at 200 rpm and 24.56 g of Zirconium-n-propoxide were added. The obtained mixture was further stirred for 20 min before drop-wise addition of 180 g of the deboronated zeolitic material having an MWW framework structure obtained according to Example 3.2. The suspension was further stirred for 2 h at 200 rpm until a gel was obtained. The formed gel was transferred to an autoclave. The autoclave was heated to 170 C. and kept at this temperature for 120 h under stirring at 150 rpm. Subsequently, the autoclave was cooled down and the solid was separated by filtration and washed until the washing water had a pH of 7. The filtercake was dried in a static oven at 120 C. for 16 h.

(97) Characterization

(98) The obtained zirconium-containing zeolitic material had a zirconium content of 0.73 weight-% and a silicon content of 38.5 weight-%. The XRD of the obtained zeolitic material is shown in FIG. 3.

Example 6.2: Acid Treatment of the Zirconium Containing Zeolitic Material

(99) 4200 g of an aqueous HNO.sub.3 solution (30 weight-% in water) was provided in a 10 L flask. To this solution the zirconium-containing silicate obtained according to Example 6.1 was added and the mixture was heated to 100 C. for 20 h under stirring with 170 rpm. Afterwards the suspension was filtered and washed until the washing water had a pH of 7. The filtercake was dried in a static oven for 16 h at 120 C. and calcined at 550 C. for 10 h.

(100) Characterization

(101) The obtained zeolitic material had a zirconium content of 0.73 weight-% and a silicon content of 43 weight-%. The BET specific surface area determined via nitrogen adsorption at 77 K according to DIN 66131 was 100 m.sup.2/g.

Example 7: Regeneration of the Zr-Silicate

(102) After the conversion of a mixture of ethanol and acetaldehyde according to Example 15, the catalyst was regenerated directly after the reaction inside the reactor. Therefore, the catalyst was heated with a heating ramp of 1 K/min to 500 C. under a 2 vol.-% 02 atmosphere. The temperature was kept at 550 C. for 7 h. Afterwards, the catalyst was cooled to 350 C. and subjected to the conversion of a mixture of ethanol and acetaldehyde according to Example 16.

Example 8: Synthesis of a Crystalline Tantalum-Containing MWW (Ta-MWW)

(103) 0.74 g tantalum oxalate-solution (25.7 g Ta/L (delivered from H.C. Starck, specification ID: D3067/02, order-Nr.: 1060010508)) was diluted with 7.4 mL distilled water and added to 5 g deborated MWW obtained from Example 4.2 and the suspension was allowed to stand for 2 h. Thereafter, the suspension was dried at a temperature of 120 C. for 2 h followed by drying at a temperature 500 C. for 4 h, using a heating ramp of 1.5 C./min.

(104) Characterization

(105) The obtained zeolitic material had a tantalum content of 1.5 weight-% and a silicon content of 41 weight-%. The BET specific surface area determined via nitrogen adsorption at 77 K according to DIN 66131 was 436 m.sup.2/g.

(106) The material was further characterized by UV-VIS measurements (see FIG. 3). As may be taken from the spectrum in FIG. 3, the maximum of the absorbtion is found in the range of from 205 to 220 nm indicating prevalent tetrahedrally coordinated Ta sites as these are found in the framework of the zeolite structure. Furthermore, no tantalum oxide would appear to be detected in the obtained material since there is no signal above 300 nm. Thus, it is apparent from the US-vis spectrum that the major portion of the tantalum contained in the material is isomorphously substituted in the framework structure. In this respect, reference is made to Catal Lett (2010) 135:169-174 with regard to the characterization of the tantalum sites in a zeolitic material via UV-vis measurements.

(107) The XRD of the obtained zeolitic material is shown in FIG. 5, indicating the material's MWW framework structure.

Example 9: Synthesis of a Crystalline Tantalum-Containing MWW (Ta-MWW)

(108) 2.12 g tantalum oxalate-solution (25.7 g Ta/L (delivered from H.C. Starck, specification ID: D3067/02, order-Nr.: 1060010508)) was diluted with 6.2 mL distilled water and added to 5 g deborated MWW obtained from Example 4.2 and the suspension was allowed to stand for 2 h. Thereafter, the suspension was dried at a temperature of 120 C. for 2 h followed by drying at a temperature 500 C. for 4 h, using a heating ramp of 1.5 C./min.

(109) Characterization

(110) The obtained zeolitic material had a tantalum content of 4.9 weight-% and a silicon content of 39 weight-%. The BET specific surface area determined via nitrogen adsorption at 77 K according to DIN 66131 was 416 m.sup.2/g. The material was further characterized by UV-VIS measurements (see FIG. 4). As may be taken from the spectrum in FIG. 4, the maximum of the absorbtion is found in the range of from 205 to 220 nm indicating prevalent tetrahedrally coordinated Ta sites as these are found in the framework of the zeolite structure. Furthermore, no tantalum oxide would appear to be detected in the obtained material since there is no signal above 300 nm. Thus, it is apparent from the US-vis spectrum that the major portion of the tantalum contained in the material is isomorphously substituted in the framework structure. In this respect, reference is made to Catal Lett (2010) 135:169-174 with regard to the characterization of the tantalum sites in a zeolitic material via UV-vis measurements.

Comparative Example 1: Synthesis of a Zeolitic Material Having an MWW Framework Structure (Si-MWW)

Comparative Example 1.1: Preparation of Boron-Containing MWW

(111) 480 kg de-ionized water were provided in a vessel. Under stirring at 70 r.p.m., 166 kg boric acid were suspended in the water. The suspension was stirred for another 3 h. 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.

(112) 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 r.p.m.). The temperature of 170 C. was kept essentially constant for 120 h; during these 120 h, the mixture was stirred at 50 r.p.m. Subsequently, the mixture was cooled to a temperature of from 50-60 C. within 5 h. The aqueous suspension containing B-MWW had a pH of 11.3 as determined via measurement with a pH electrode. After cooling the reactor a solution of 10 weight-% HNO.sub.3 was added to the suspension until the suspension had a pH in the range of from 7 to 8.

(113) From said suspension, the B-MWW was separated by filtration. The filter cake was then washed with de-ionized water until the washing water had a conductivity of less than 700 microSiemens/cm

(114) From the thus obtained filter cake, an aqueous suspension was prepared with deionized water, the 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:

(115) temperature drying gas:

(116) temperature spray tower (in): 206 C. temperature spray tower (out): 120 C.
nozzle: two-component nozzle supplier Gerig; size 0 nozzle gas pressure: 1 bar
apparatus used: spray tower with one nozzle
operation mode: nitrogen straight
configuration: dehumidifier-filter-scrubber
gas flow: 45 kg/h

(117) 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. The spray-dried material was then subjected to calcination at 650 C. in a rotary calcined with a throughput of 0.8-1.0 kg/h.

(118) Characterization

(119) The calcined material had a boron content of 1.3 weight-%, a silicon content of 44 weight-%, and a total organic carbon content of <0.1 wt. %. Crystallinity determined by XRD was 88%, BET specific surface area determined via nitrogen adsorption at 77 K according to DIN 66131 was 464 m.sup.2/g, pore volume determined by HG porosimetry according to DIN 66133 was 6.3 mL/g, particle size distribution of the sprayed-dried particle determined by Malvern Dv50 was 26.9 m.

Comparative Example 1.2: Preparation of Deborated MWW

(120) 1590 kg water were passed into a vessel equipped with a reflux condenser. Under stirring at 40 r.p.m., 106 kg of the spray-dried material obtained according to section 1.1 were suspended into the water. Subsequently, the vessel was closed and the reflux condenser put into operation. The stirring rate was increased to 70 r.p.m. Under stirring at 70 r.p.m., the content of the vessel was heated to 100 C. in 2 h and kept at this temperature for 10 h. Then, the content of the vessel was cooled to a temperature of less than 50 C.

(121) The resulting deboronated zeolitic material of structure type MWW was separated from the suspension by filtration and washed with 600 L deionized water. After the filtration, the filter cake was sprayed-dried.

(122) Characterization

(123) The dried MWW material obtained had a boron content of 0.04 weight-%, an silicon content of 42 weight-%, and a total organic carbon content of <0.1 wt. %. The BET specific surface area determined via nitrogen adsorption at 77 K according to DIN 66131 was 461 m.sup.2/g, the crystallinity, determined by XRD was 82%. The particle size distribution obtained from Malvern measurement was Dv50 11.1 m.

(124) Conversion of a Mixture of Ethanol and Acetaldehyde in the Presence of a Catalyst

(125) The process for the preparation of butadiene by the conversion of a mixture of ethanol and acetaldehyde in the presence of a catalyst according to Reference Example 4 was carried out by use of several catalysts:

Example 10

(126) Was carried out as described in reference Example 4 by use of the Zr-BEA obtained from Example 1, according to the present invention.

Example 11

(127) Was carried out as described in reference Example 4 by use of the Zr-BEA obtained from Example 2, according to the present invention.

Example 12

(128) Was carried out as described in reference Example 4 by use of the Zr-silicate obtained from Example 3, according to the present invention. The result of this experiment is shown in FIG. 6.

Example 13

(129) Was carried out as described in reference Example 4 by use of the ZnTi-MWW obtained from Example 4, according to the present invention.

Example 14

(130) Was carried out as described in reference Example 4 by use of the Sn-MWW obtained from Example 5, according to the present invention.

Example 15

(131) Was carried out as described in reference Example 4 by use of the Zr-silicate obtained from Example 6, according to the present invention.

Example 16

(132) Was carried out as described in reference Example 4 by use of the Zr-silicate obtained from Example 7, according to the present invention.

Example 17

(133) Was carried out as described in reference Example 4 by use of the Ta-MWW obtained from Example 8, according to the present invention.

Example 18

(134) Was carried out as described in reference Example 4 by use of the Ta-MWW obtained from Example 9, according to the present invention.

Comparative Example 2

(135) Was carried out as described in reference Example 4 by use of the Si-MWW obtained from Comparative Example 1.

Comparative Example 3

(136) Was carried out as described in reference Example 4 by use of ZrO.sub.2 (Commercial BASF sample (D9-89)).

(137) The obtained selectivities towards butadiene, ethyl ether and crotonaldehyde are shown in Table 1, wherein the selectivities are calculated based on the total amount of obtained products and given in percentage values.

(138) TABLE-US-00006 TABLE 1 Obtained selectivity's of Examples 10 to 16 and Comparative Examples 2 and Experiment Ex. 11 Ex. 13 Ex. 14 Ex. 16 Ex. 10 Zr- Ex. 12 ZnTi- Sn- Ex. 15 Zr-silicate Zr-BEA BEA Zr-silicate MWW MWW Zr-silicate regener. selectivity to 38 38 64 27 10 64 64 butadiene selectivity to 21 24 8 26 61 5 8 diethyl ether selectivity to 2 3 1 8 4 1 1 crotonaldehyde selectivity to 3 3 2 8 0 2 3 ethylacetate selectivity to 11 10 7 17 19 4 4 ethene selectivity to C.sub.1 9 6 7 8 2 9 8 to C.sub.4- compounds (olefins/parafins; excluding ethene) selectivity to 4 3 5 1 1 8 6 C.sub.6-compounds Selectivity to 12 13 5 6 2 6 6 other compounds Conversion of 20 13 36 32 24 47 43 ethanol/ acetaldehyde Experiment Ex. 17 Ex. 18 Comp. Comp. Ta- Ta- Ex. 2 Ex. 3 MWW MWW Si-MWW ZrO.sub.2 selectivity to 72 72 7 13 butadiene selectivity to 4 4 43 6 diethyl ether selectivity to 0 1 7 0 crotonaldehyde selectivity to 1 1 0 0 ethylacetate selectivity to 7 7 37 43 ethene selectivity to C.sub.1 4 5 2 6 to C.sub.4- compounds (olefins/parafins; excluding ethene) selectivity to 6 5 0 8 C.sub.6-compounds Selectivity to 6 5 2 20 other compounds Conversion of 39 42 26 93 ethanol/ acetaldehyde
Summary and Comparison of the Results of Examples 10 to 18 and Comparative Examples 2 and 3.

(139) Examples 10 to 18 are carried out according to the present invention, i.e. by a gas-phase process for the preparation of butadiene comprising providing a gas stream comprising ethanol and contacting the gas stream comprising ethanol with a catalyst, wherein the catalyst comprises a zeolitic material having a framework structure comprising one or more tetravalent elements, wherein at least a portion of the one or more tetravalent elements comprised in the framework structure is isomorphously substituted. In Examples 10 to 12 and 15 to 16 the framework structure comprises silicon, wherein a portion of silicon is isomorphously substituted by zirconium. In Example 13 the framework structure comprises silicon, wherein a portion of silicon is isomorphously substituted by titanium and in Example 14 the framework structure comprises silicon, wherein a portion of silicon is isomorphously substituted by tin. Further, in Examples 17 and 18 the framework structure comprises silicon, wherein a portion of silicon is isomorphously substituted by tantalum.

(140) Comparative Examples 2 and 3 are carried out according to a process for the preparation of butadiene comprising contacting a gas stream of ethanol and acetaldehyde with a catalyst comprising silicon (Comparative Example 2) or zirconium (Comparative Example 3), respectively, wherein the tetravalent element comprised in the catalyst is not isomorphously substituted by another element.

(141) In Examples 10, 11, 12, 15 and 16 which are carried out according to the invention by use of a catalyst comprising a zeolitic material having a framework structure comprising zirconium and silicon, unexpectedly high selectivities to butadiene in the range of from 38 to 64% are achieved, wherein the catalysts containing the zirconium-containing silicate (Zr-silicate) affords an astonishingly high selectivity of 64%, wherein at the same time unexpected high conversions of ethanol and acetaldehyde in the range of from 43 to 47% were achieved. Further, Example 13 is carried out according to the invention, wherein a catalyst comprising the ZnTi-MWW is used which leads to a selectivity of 27% to butadiene. Furthermore, in Examples 17 and 18 which are carried out according to the invention by use of a catalyst comprising a zeolitic material having an MWW framework structure comprising tantalum and silicon, unexpectedly high selectivities to butadiene of 72% were achieved and at the same time high conversions of ethanol and acetaldehyde in the range of from 39 to 42% were achieved. Thus, it was surprisingly found that by use of catalysts comprising a zeolitic material according to the present invention, very high selectivities to butadiene and at the same time high conversions of ethanol and acetaldehyde are achieved.

(142) In Example 14, which is carried out according to the invention by use of a catalyst comprising Sn-MWW, and in Comparative Examples 2 and 3, similar selectivities to butadiene are achieved. However, in Example 14 according to the invention, a selectivity to diethyl ether of 61% is achieved, wherein in the Comparative Examples 2 and 3 only a selectivity of 43% and 6%, respectively is achieved. Diethyl ether is a product of the present invention which can be hydrolyzed and recycled into the gas-phase process to obtain butadiene. Therefore, it was found that although the use of the Sn-MWW according to the present invention and the catalysts used in Comparative Examples 2 and 3 lead to similar selectivities to butadiene, the catalyst comprising the Sn-MWW according to the present invention has the advantage that diethyl ether is obtained in a high amount which can be hydrolyzed and recycled into the gas-phase process. Therefore, the use of the catalyst used in Example 14 leads to a far better yield compared to the catalysts used in Comparative Examples 2 and 3.

(143) In Examples 15 and 16 which are carried out according to the invention by use of a catalyst comprising a zeolitic material having a framework structure comprising zirconium and silicon, wherein the catalyst used in Example 15 is regenerated and used in Example 16, selectivities to butadiene of 64% and conversions of the starting material of 47% and 43%, respectively, were achieved. Therefore, it was surprisingly found the catalyst activity and selectivity of the catalyst according to the present invention remains constant after regeneration.

(144) Further, as may be taken from FIG. 6, which displays the results of Example 12, the conversion of ethanol and acetaldehyde as well as the selectivity to butadiene remain constant over the whole tested temporal range. Thus, besides displaying excellent selectivities, it has quite unexpectedly been found that the catalyst is further able to maintain these selectivities with not variation whatsoever over a very prolonged time on stream when considering the results of long term testing displayed in FIG. 6. In particular, it has surprisingly been found that a highly stable process may be provided by the present invention, wherein the product spectrum and the high yield in butadiene shows practically no changes over extended periods of time on stream.

(145) Accordingly, considering the detailed results in the foregoing and their discussion above, it was unexpectedly found that the use of a zeolitic material according to the invention leads to a considerable improvement of the process for the preparation of butadiene.

CITED PRIOR ART

(146) GB 331482 U.S. Pat. No. 2,421,361 WO 2012/015340 A1 Catal. Sci. Technol. 1 (2011), 267-272 Ind. Eng. Chem. 41 (1949), pages 1012-1017