Process for preparing ethene oxide

Abstract

A process for preparing ethene oxide comprising providing a liquid feed stream comprising ethene, hydrogen peroxide, and a solvent; passing the liquid feed stream into an epoxidation zone comprising a catalyst comprising a titanium zeolite comprising zinc and having framework type MWW, and subjecting the liquid feed stream to epoxidation reaction conditions in the epoxidation zone, obtaining a reaction mixture comprising ethene oxide, water, and the solvent; removing an effluent stream from the epoxidation zone, the effluent stream comprising ethene oxide, water and the solvent.

Claims

1. A process for preparing ethene oxide, comprising: (i) providing a liquid feed stream comprising ethene, hydrogen peroxide, and a solvent; (ii) passing the liquid feed stream provided in (i) into an epoxidation zone comprising a catalyst comprising a titanium zeolite comprising zinc and having framework type MWW, subjecting the liquid feed stream to epoxidation reaction conditions in the epoxidation zone, and obtaining a reaction mixture comprising ethene oxide, water, and the solvent; (iii) removing an effluent stream from the epoxidation zone, the effluent stream comprising ethene oxide, water, and the solvent.

2. The process of claim 1, wherein (i), (ii), and (iii) are each performed continuously.

3. The process of claim 1, wherein in the liquid feed stream provided in (i), a molar ratio of ethene relative to hydrogen peroxide is in a range of from 1:1 to 5:1.

4. The process of claim 1, wherein the solvent comprises one or more organic solvents.

5. The process of claim 1, wherein the liquid feed stream provided in (i) further comprises a dissolved salt.

6. The process of claim 1, wherein in the epoxidation zone according to (ii), the reaction mixture is liquid under the epoxidation conditions.

7. The process of claim 1, wherein the epoxidation zone according to (ii) comprises a first epoxidation subzone consisting of one or more epoxidation reactors A, wherein, if the first epoxidation subzone comprises two or more epoxidation reactors A, the two or more epoxidation reactors A are arranged in parallel, and wherein in (ii), the liquid feed stream provided in (i) is passed into at least one of the epoxidation reactors A, wherein the epoxidation conditions according to (ii) comprise: an epoxidation temperature in the first epoxidation subzone in a range of from 20 to 60 C., wherein the epoxidation temperature is defined as the temperature of a heat transfer medium used for adjusting a temperature of the reaction mixture in the first epoxidation reaction subzone, and a first epoxidation reaction pressure in a range of from 18 to 60 bar(abs), wherein the first epoxidation reaction pressure is defined as an absolute pressure at an exit of the first epoxidation subzone.

8. The process of claim 7, wherein the epoxidation conditions according to (ii) comprise a catalyst loading in the first epoxidation subzone in a range of from 0.05 to 125 h.sup.1, wherein the catalyst loading is defined as a ratio of a mass flow rate in kg/h of hydrogen peroxide comprised in the liquid feed stream provided in (i) relative to an amount in kg of the catalyst comprising a titanium zeolite comprising zinc and having framework type MWW comprised in the first epoxidation subzone according to (ii).

9. The process of claim 1, wherein the titanium zeolite comprising zinc and having framework type MWW comprised in the catalyst according to (ii) comprises: titanium, calculated as elemental titanium, in an amount in a range of from 0.1 to 5 weight-%, based on a total weight of the titanium zeolite comprising zinc and having framework type MWW, and zinc, calculated as elemental zinc, in an amount in a range of from 0.1 to 5 weight-%, based on the total weight of the titanium zeolite comprising zinc and having framework type MWW, wherein at least 98 weight-% of the titanium zeolite comprising zinc and having framework type MWW consists of Zn, Ti, Si, O, and H.

10. The process of claim 1, wherein the catalyst comprising the titanium zeolite comprising zinc and having framework type MWW is in the form of a molding comprising: the titanium zeolite comprising zinc and having framework type MWW and a binder.

11. The process of claim 1, wherein the epoxidation conditions according to (ii) comprise a hydrogen peroxide conversion in a range of from 85 to 100%, wherein the hydrogen peroxide conversion is defined as 100(1y) %, wherein y is a molar amount of hydrogen peroxide comprised in the effluent stream removed in (iii) relative to a molar amount of hydrogen peroxide comprised in the liquid feed stream provided in (i).

12. The process of claim 1, wherein the effluent stream removed in (iii) comprises ethene oxide, water, the solvent, ethene, and oxygen, the process further comprising: (iv) separating ethene and oxygen from the effluent stream, and obtaining: a stream S1 which, relative to the effluent stream, is enriched in ethene oxide, the solvent, and water; and a stream which, relative to the effluent stream, is enriched in ethene and oxygen.

13. The process of claim 12, further comprising: (iv-2) reducing an oxygen content of the stream enriched in ethene and oxygen, and obtaining a stream comprising ethene and depleted in oxygen relative to the stream enriched in ethene and oxygen; wherein the stream comprising ethene and depleted in oxygen is recycled, optionally after one or more work-up stages, to (i).

14. The process of claim 12, further comprising: (v) separating ethene oxide from the stream S1, obtaining a stream S11 comprising ethene oxide and depleted of the solvent and water relative to the stream S1, and obtaining a stream S12 enriched in the solvent and water relative to the stream S1; wherein the stream S12 enriched in the solvent and water is recycled, optionally after one or more work-up stages, to (i).

15. The process of claim 14, further comprising: (v-2) subjecting the stream S11 comprising ethene oxide and depleted of the solvent and water to further purification with regard to ethene oxide.

Description

EXAMPLES

Reference Example 1: Determination of Catalyst Characteristics

Reference Example 1.1: Determination of the Tortuosity Parameter

(1) The tortuosity parameter was determined as described in the experimental section of US 20070099299 A1. In particular, the NMR analyses to this effect were conducted at 25 C. and 1 bar at 125 MHz .sup.1H resonance frequency with the FEGRIS NT NMR spectrometer (cf. Stallmach et al. in Annual Reports on NMR Spectroscopy 2007, Vol. 61, pp. 51-131) at the Faculty for Physics and Geological Sciences of the University of Leipzig. The pulse program used for the PFG NMR self-diffusion analyses was the stimulated spin echo with pulsed field gradients according to FIG. 1b of US 20070099299 A1. For each sample, the spin echo attenuation curves were measured at up to seven different diffusion times (/ms=7, 10, 12, 25, 50, 75, 100) by stepwise increase in the intensity of the field gradients (g.sub.max=10 T/m). From the spin echo attenuation curves, the time dependence of the self-diffusion coefficient of the pore water was determined by means of equations (5) and (6) of US 20070099299 A1.

(2) Calculation of the Tortuosity

(3) Equation (7) of US 20070099299 A1 was used to calculate the time dependency of the mean quadratic shift
z.sup.2()=r.sup.2()
from the self-diffusion coefficients D(A) thus determined. By way of example, in FIG. 2 of US 20070099299 A1, the data is plotted for exemplary catalyst supports of said document in double logarithmic form together with the corresponding results for free water. FIG. 2 of US 20070099299 A1 also shows in each case the best fit straight line from the linear fitting of
r.sup.2()
as a function of the diffusion time . According to equation (7) of US 2007/0099299 A1, its slope corresponds precisely to the value 6 D where D corresponds to the self-diffusion coefficient averaged over the diffusion time interval. According to equation (3) of US 20070099299 A1, the tortuosity is then obtained from the ratio of the mean self-diffusion coefficient of the free solvent (D.sub.0) thus determined to the corresponding value of the mean self-diffusion coefficient in the molding.

Reference Example 1.2: Determination of Dv10, Dv50, and Dv90 Values

(4) 1.0 g of the micropowder is suspended in 100 g deionized water and stirred for 1 min. The sample was subjected to the measurement in an apparatus using the following parameters: 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 1.3: Determination of the Silanol Concentration of the Moldings of the Present Invention

(5) For the determination of the silanol concentration, the .sup.29Si MAS NMR experiments were carried out at room temperature on a VARIAN Infinityplus-400 spectrometer using 5.0 mm ZrO.sub.2 rotors. The .sup.29Si MAS NMR spectra were collected at 79.5 MHz using a 1.9 s /4 (microsecond pi/4) pulse with 10 s recycle delay and 4000 scans. All .sup.29Si spectra were recorded on samples spun at 6 kHz, and chemical shifts were referenced to 4,4-dimethyl-4-silapentane sulfonate sodium (DSS). For the determination of the silanol group concentration, a given .sup.29Si MAS NMR spectrum is deconvolved by the proper Gaussian-Lorentzian line shapes. The concentration of the silanol groups with respect to the total number of Si atoms is obtained by integrating the deconvolved .sup.29Si MAS NMR spectra.

Reference Example 1.4: Determination of the Crush Strength of the Moldings

(6) The crush strength as referred to in the context of the present invention is to be understood as determined via a crush strength test machine Z2.5/TS1S, supplier Zwick GmbH & Co., D-89079 Ulm, Germany. As to fundamentals of this machine and its operation, reference is made to the respective instructions handbook Register 1: Betriebsanleitung/Sicherheitshandbuch fr die Material-Prfmaschine Z2.5/TS1S, version 1.5, December 2001 by Zwick GmbH & Co. Technische Dokumentation, August-Nagel-Strasse 11, D-89079 Ulm, Germany. With said machine, a given strand is subjected to an increasing force via a plunger having a diameter of 3 mm until the strand is crushed. The force at which the strand crushes is referred to as the crushing strength of the strand. The machine is equipped with a fixed horizontal table on which the strand is positioned. A plunger which is freely movable in vertical direction actuates the strand against the fixed table. The apparatus was operated with a preliminary force of 0.5 N, a shear rate under preliminary force of 10 mm/min and a subsequent testing rate of 1.6 mm/min. The vertically movable plunger was connected to a load cell for force pick-up and, during the measurement, moved toward the fixed turntable on which the molding (strand) to be investigated is positioned, thus actuating the strand against the table. The plunger was applied to the stands perpendicularly to their longitudinal axis. Controlling the experiment was carried out by means of a computer which registered and evaluated the results of the measurements. The values obtained are the mean value of the measurements for 10 strands in each case.

Reference Example 1.5: .SUP.29.Si Solid-State NMR Spectra Regarding Q.SUP.3 .and Q.SUP.4 .Structures

(7) The effect of the inventive water treatment on the molding related to Q.sup.3 and Q.sup.4 structures in the material was characterized by comparing the changes in .sup.29Si solid-state NMR spectra under comparable conditions. All .sup.29Si solid-state NMR experiments were performed using a Bruker Advance spectrometer with 300 MHz .sup.1H Larmor frequency (Bruker Biospin, Germany). Samples were packed in 7 mm ZrO.sub.2 rotors, and measured under 5 kHz Magic Angle Spinning at room temperature. .sup.29Si direct polarization spectra were obtained using (pi/2)-pulse excitation with 5 microsecond pulse width, 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 hours. Spectra were processed using Bruker Topspin with 30 Hz exponential line broadening, manual phasing, and manual baseline correction over the full spectrum width. Spectra were referenced with the polymer Q8M8 as an external secondary standard, setting the resonance of the trimethylsilyl M group to 12.5 ppm. The spectra were then fitted with a set of Gaussian line shapes, according to the number of discernable resonances. Relating to the presently assessed spectra, 6 lines in total were used, accounting for the five distinct peak maxima (at approximately 118, 115, 113, 110 and 104 ppm) plus the clearly visible shoulder at 98 ppm. 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 outcome was numerically stable, i.e., distortions in the initial fit setup as described above did lead to similar results. The fitted peak areas were further used normalized as done by DMFit. After the water treatment of the invention, a decrease of signal intensity at the left hand side of the spectrum was observed, a region that includes Q.sup.3 silanol structures (here especially: around and above 104 ppm, i.e. left of 104 ppm). Further, an increase of signal at the right hand side of the spectrum (here: below 110 ppm, i.e. right of 110 ppm) was observed, which region comprises Q.sup.4 structures exclusively. For the quantification of spectrum changes, a ratio was calculated that reflects changes in the peak areas left hand and right hand, as follows. The six peaks were labeled with 1, 2, 3, 4, 5, and 6, and the ratio Q was calculated with the formula 100*{[a.sub.1+a.sub.2]/[a.sub.4+a.sub.5+a.sub.6]}/a.sub.3. In this formula, a.sub.i, i=1 . . . 6 represents the area of the fitted peak to which this number was attributed.

Reference Example 1.6: Water Adsorption/DesorptionWater Uptake

(8) The water adsorption/desorption isotherms measurements 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 were started, the residual moisture of the sample was removed by heating the sample to 100 C. (heating ramp of 5 C./min) and holding it for 6 h under a N.sub.2 flow. After the drying program, the temperature in the cell was decreased to 25 C. and kept isothermal during the measurements. The microbalance was calibrated, and the weight of the dried sample was balanced (maximum mass deviation 0.01 weight-%). Water uptake by the sample was measured as the increase in weight over that of 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 samples was exposed and measuring the water uptake by the sample at equilibrium. The RH was increased with a step of 10 weight-% from 5 to 85% and at each step the system controlled the RH and monitored the sample weight until reaching the equilibrium conditions and recording the weight uptake. The total adsorbed water amount by 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 1.7: FT-IR Measurements

(9) The FT-IR (Fourier-Transformed-Infrared) measurements were performed on a Nicolet 6700 spectrometer. The molding was powdered and then pressed into a self-supporting pellet without the use of any additives. The pellet was introduced into a high vacuum (HV) cell placed into the FT-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 to 800 cm.sup.1 at a resolution of 2 cm.sup.1. The obtained spectra are represented in a plot having on the x axis the wavenumber (cm.sup.1) and on the y axis the absorbance (arbitrary units, a.u.). For the quantitative determination of the peak heights and the ratio between these peaks a baseline correction was carried out. Changes in the 3000-3900 cm.sup.1 region were analyzed and for comparing multiple samples, as reference the band at 18805 cm.sup.1 was taken.

Reference Example 1.8: Determination of Crystallinity Via XRD

(10) The crystallinity of the zeolitic materials according to the present invention were determined by XRD analysis. The data were 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) was scanned with a step size of 0.02, while the variable divergence slit was set to a constant illuminated sample length of 20 mm. The data were then analyzed using TOPAS V4 software, wherein the sharp diffraction peaks were modeled using a Pawley fit containing a unit cell with the following starting parameters: a=14.4 Angstrom (1 Angstrom=10.sup.10 m) and c=25.2 Angstrom in the space group P6/mmm. These were refined to fit the data. Independent peaks were inserted at the following positions. 8.4, 22.4, 28.2 and 43. These were 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 were also a linear background, Lorentz and polarization corrections, lattice parameters, space group and crystallite size.

Reference Example 2: Preparation of an Ethene Epoxidation Catalyst

(11) A catalyst comprising a titanium zeolite comprising zinc and having framework type MWW, was prepared according to example 3 of WO 2013/117536 A, page 76, line 1 to page 78, line 11. The tortuosity parameter of this catalyst relative to water, determined as described in Reference Example 1.1 above, was 2.2+/0.1.

Reference Example 3: Epoxidation Setup, and Analytics

(12) Epoxidation Setup

(13) The experimental setup consisted of continuous plant with a fixed bed reactor. Feeds and products were weighed and analyzed by gas-chromatography (GC). The microplant was installed in two steel-chambers. All feeds were kept constant and the hydrogen peroxide conversion was maintained at 905% by adjusting the temperature and/or the dosage of the potassium salt.

(14) Conversion and temperature were checked and corrected once a day. The experiments were run with excess ethene (1.3 mol/mol H.sub.2O.sub.2). Ethylene (technical grade, >99 weight-% of ethylene was supplied in a 400 L pressure vessel. It was fed via pipeline to 2 L buffer vessels. A constant pressure of about 30 bar(abs) in the lecture bottles was maintained by pressing N.sub.2 to ensure a steady operation of the feeding pumps and a steady supply of the plant. Solvent (acetonitrile) was supplied in a 200 L drum. Hydrogen peroxide (40 weight-% in water) was stored in pressure vessels (5 L, 5 bar(abs) N.sub.2 pressure) with temperature control. Additives such as potassium salt(s) could be added either to the acetonitrile or to the hydrogen peroxide in the buffer vessels. All feed streams were mixed and fed to the epoxidation reactor in an up-flow mode (pressure: 20 bar(abs), temperature: 30 to 80 C.).

(15) The reactor (material: stainless steel 1.4571) was a 1400 mm10 mm tube with an internal diameter of 7 mm, and a double-jacket for cooling or heating with water. The cooling medium (ethylene glycol/water mixture) was fed in cocurrent and the temperature difference between input and output was less than 1 C. 15 g of the catalyst according to Reference Example 2 above were freshly loaded to the epoxidation reactor (fixed-bed) before starting an experiment. Remaining space in the reactor was filled with inert material.

(16) After release of pressure the reactor effluent stream was fed to a gas-liquid separator from which the liquid phase was pumped into the sewer pipeline. The reactor effluent stream was split into a liquid phase and a gas phase at 15 C./1013 mbar.

(17) Sampling and Analytics

(18) The gas phase was fed to the flare or to an online-GC via a three-way valve. A gas meter and a gas chromatograph for the analysis of the gas phase was allocated to the unit. The composition of the gas phase was double-checked by offline measurements at GMA/C on a regular basis. The liquid phase was collected for mass balancing and further analytics. H2O2 conversion was determined by photometric measurements (titanyl sulfate method) of the H2O2 concentration in the feed stream and the reactor effluent stream. All other components were quantified by gas chromatography. The general accuracy of the selectivity measurement in the described setup was estimated to be around 2%.

Example 1

(19) The liquid feed stream fed to the epoxidation reactor had the following composition: ethene: 9.1 weight-% (11.1 g/h) hydrogen peroxide: 13.8 weight-% (16.7 g/h; 40 weight-% aq.) water: 20.8 weight-% (25.2 g/h) potassium salt (potassium formate): 130 micromol/mol hydrogen peroxide solvent (acetonitrile): 56.2 weight-% (68.0 g/h)

(20) The experiment according to Example 1 was carried out at a mean hydrogen peroxide conversion of 90%. The results are shown in FIG. 2. As can be seen in FIG. 2, the selectivities of ethene oxide remained constantly at around 94% (based on hydrogen peroxide) and 98% (based on ethene), even at temperatures of around 40 C. The main by-products were ethylene glycol (selectivity of around 1%), peroxyethanol (selectivity of around 1.5%) and oxygen (selectivity of around 2%). An offgas analysis showed that no CO2 was formed during the first 1100 hours time on stream.

Example 2

(21) The experiment according to Example 2 was carried out based on the same liquid feed stream as Example 1 (see above) and at a mean hydrogen peroxide conversion of at least 98%. In order to achieve the hydrogen peroxide conversion, the cooling water temperature was increased by around 4 C. in comparison with the experiment in Example 1. The results are shown in FIG. 3. As can be seen in FIG. 3, the selectivities of ethene oxide thereby remained at the constant high level as already observed in Example 1.

DESCRIPTION OF THE FIGURES

(22) FIG. 1 shows a process flow sheet of the inventive process including a conceivable solvent work-up sequence wherein the abbreviations have the following meanings: (1) ethene stream (2) hydrogen peroxide stream (3) (make-up) solvent stream (4) stream comprising potassium salt (5) hydrogen (H.sub.2) stream (6) ethene oxide (product) stream (7) light boilers stream (8) heavy boilers stream (9) waste water stream (10) offgas stream (a) epoxidation unit (first epoxidation subzone) (b) oxygen (O.sub.2) and ethene separation unit (c) hydrogenation unit (ethene recycling) (d) solvent separation unit (e) ethene oxide purification unit (f1)(f2) first solvent work-up unit (part-stream distillation unit) (g) second solvent work-up unit (phase separation water/solvent)

(23) (h) third solvent work-up unit (solvent distillation) (i) fourth solvent work-up unit (water separation)

(24) FIG. 2 shows the selectivities of ethene oxide during the first 1100 hours time on stream of the epoxidation reaction as described in Example 1. The left hand Y axis shows the conversion of hydrogen peroxide in % and the normalized selectivities of ethene oxide based on hydrogen peroxide and based on ethene, respectively, both in %. The right hand Y axis shows the temperature in C. Further reference is made to the legend in FIG. 2.

(25) FIG. 3 shows the selectivities of ethene oxide during the first 600 hours time on stream of the epoxidation reaction as described in Example 2. The left hand Y axis shows the conversion of hydrogen peroxide in % and the normalized selectivities of ethene oxide based on hydrogen peroxide and based on ethene, respectively, both in %. The right hand Y axis shows the temperature in C. Further reference is made to the legend in FIG. 3.

CITED LITERATURE

(26) US 20070099299 A1 Stallmach et al., in: Annual Reports on NMR Spectroscopy 2007, Vol. 61, pp. 51-131 X. Lu et al., Selective Synthesis of ethylene oxide through liquid-phase epoxidation of ethylene with titanosilicate/H.sub.2O.sub.2 catalytic systems, Applied Catalysis A: General, 515 (2016) 51-59 EP 1 122 249 A1 WO 2013/117536 A