Improved process for preparing propylene oxide

Abstract

The present invention relates in a first aspect to a process for preparing propylene oxide. A second aspect of the invention is directed to a mixture, preferably for preparation of propylene oxide. A third aspect of the invention relates to the use of the mixture according to the second aspect of the invention for preparation of propylene oxide, a fourth aspect of the invention is directed to a method for preparing propylene oxide, wherein the mixture of the second aspect of the invention is brought into contact with a heterogeneous catalyst under epoxidation conditions, and a fifth aspect of the invention is related to propylene oxide, obtained or obtainable from a process according to the first aspect of the invention or from the method of fourth aspect of the invention.

Description

[0001] 240389W001

[0002] Improved process for preparing propylene oxide

[0003] The present invention relates in a first aspect to a process for preparing propylene oxide, the process comprising (a) providing propene, water, hydrogen peroxide and acetonitrile to an epoxidation zone comprising a heterogeneous epoxidation catalyst, thereby obtaining a mixture comprising propene, water and acetonitrile; (b) contacting the mixture comprising propene, water and acetonitrile in the epoxidation zone with the heterogeneous epoxidation catalyst under epoxidation conditions, thereby obtaining a mixture comprising propylene oxide, propene, water and acetonitrile; wherein: (I) the hydrogen peroxide in a) is provided as an aqueous solution comprising hydrogen peroxide in a concentration (CH202) in the range of from 42 to 50 weight-% based on the total weight of the aqueous solution being 100 weight-%; and (ii) the acetonitrile (ACN) and the aqueous solution comprising hydrogen peroxide (H2O2aq.) are provided in a) to the epoxidation zone in a weight-based ratio ACN:H2C>2 in the range of from Xi to X2, wherein Xi is calculated based on equation 1 and X2 is calculated based on equation 2: Xi = 13.6 - (0.135 x CH202) [equation 1], X2= 14.8 - (0.135 x CH202) [equation 2], wherein CH202 is the concentration at which the aqueous solution comprising hydrogen peroxide is provided in weight-%.

[0004] A second aspect of the invention is directed to a mixture, preferably for preparation of propylene oxide, comprising propene, water, hydrogen peroxide and acetonitrile, wherein the acetonitrile (ACN) and the hydrogen peroxide (H2O2) are present in a weight-based ratio ACN:H2O2 in the range of from Xi to X2, wherein Xi is calculated based on equation 1 and X2 is calculated based on equation 2: Xi = 13.6 - (0.135 X CH202) [equation 1] X2 = 14.8 - (0.135 x CH202) [equation 2], wherein Cn202 is the concentration of hydrogen peroxide in weight-% in the mixture, wherein the total weight of the mixture are 100 weight-%. A third aspect of the invention relates to the use of the mixture according to the second aspect of the invention for preparation of propylene oxide, a fourth aspect of the invention is directed to a method for preparing propylene oxide, wherein the mixture of the second aspect of the invention is brought into contact with a heterogeneous catalyst under epoxidation conditions, and a fifth aspect of the invention is related to propylene oxide, obtained or obtainable from a process according to the first aspect of the invention or from the method of fourth aspect of the invention.

[0005] State of the art

[0006] The HPPO (Hydrogen Peroxide to Propylene Oxide) process is a method that is used to produce propylene oxide. It involves using an aqueous hydrogen peroxide solution to selectively epoxidize propylene to propylene oxide in the presence of a heterogeneous catalyst, which is a Ti-silicate based zeolite. There are several HPPO processes known in the industry and reported in literature. One class of processes uses methanol as a solvent and TS-1 (MFI) type zeolites as catalysts, while another class of processes uses acetonitrile as a solvent and Ti-MWW (MMW) type zeolites as catalysts (see, for example, WO 2022 / 268859 A1).

[0007] In the HPPO process using MeOH / TS-1 , several qualities of hydrogen peroxide solutions were reported. The hydrogen peroxide used is in most cases produced by an anthraquinone type technology (AO process) (see Ullmann's Encyclopedia of Industrial Chemistry, 5th edition, volume A 13 (1989) pages 443-466). Different concentrations of hydrogen peroxide were reported to be suitable in the MeOH / TS-1 HPPO processes, where the hydrogen peroxide concentration 240389W001

[0008] - 2 - can vary from 27.5 wt. % to 70 wt. % (see, for example, WO 2015 / 0493279 A1). It is generally preferable to use hydrogen peroxide concentrations above 40 wt. %, thereby reducing the water content in the feed, in order to avoid a detrimental impact on the performance of the TS-1 catalyst. Additionally, less water in the reaction feed helps with the mixing of the reactants (avoids multiphase formation) and reduces the amount of wastewater produced.

[0009] The hydrogen peroxide solutions produced by the anthraquinone process are obtained by extracting the so-called oxidized working solution with water, but to achieve concentrations of more than 50 wt.-% requires a supplementary work-up step, involving the concentration of the solution by a distillation step (see, for example, WO2023 / 117360 A1). This process step induces a change in the composition (by-product content) of the produced hydrogen peroxide and increases the overall energy consumption since energy is needed to remove the water.

[0010] Overall, HPPO processes are very cost and energy consuming. Therefore, there was a need to provide a new process for preparing propylene oxide, which is more efficient and cost-effective compared to existing processes.

[0011] A first aspect of the invention thus relates to a process for preparing propylene oxide, the process for preparing propylene oxide comprising a) providing propene, water, hydrogen peroxide and acetonitrile to an epoxidation zone comprising a heterogeneous epoxidation catalyst, thereby obtaining a mixture comprising propene, water and acetonitrile; b) contacting the mixture comprising propene, water and acetonitrile in the epoxidation zone with the heterogeneous epoxidation catalyst under epoxidation conditions, thereby obtaining a mixture comprising propylene oxide, propene, water and acetonitrile; wherein: i) the hydrogen peroxide in a) is provided as an aqueous solution comprising hydrogen peroxide in a concentration (CH202) in the range of from 42 to 50 weight-% based on the total weight of the aqueous solution being 100 weight-%; ii) the acetonitrile (ACN) and the aqueous solution comprising hydrogen peroxide (H2O2aq.) are provided in a) to the epoxidation zone in a weight-based ratio ACN:H2C>2 in the range of from Xi to X2, wherein Xi is calculated based on equation 1 and X2 is calculated based on equation 2:

[0012] Xi = 13.6 - (0.135 x CH202) equation 1

[0013] X2= 14.8 - (0.135 x CH202) equation 2, wherein CH202 is the concentration at which the aqueous solution comprising hydrogen peroxide is provided in weight-%.

[0014] As described in more detail herein below, hydrogen peroxide (H2O2) can be prepared by a process known as anthraquinone process. An aqueous hydrogen peroxide solution is obtained therefrom by aqueous extraction of an organic mixture which results from said anthraquinone process, wherein the concentration can be varied in the range of from > 0 to 50 weight-% based on the extraction conditions used. The concentration of an aqueous hydrogen peroxide solution in the range of from 42 to 50 weight-% can thus be adjusted by selecting suitable extraction conditions. Using an aqueous solution comprising hydrogen peroxide in a concentration (CH202) in the range of from 42 to 50 240389W001

[0015] - 3 - weight-% in combination with using a weight-based ratio ACN:H2C>2 in the range of from Xi to X2 surprisingly enables to carry out the complete process more efficiently in view of energy consumption, i.e. it enables saving of energy compared to, for example, using an aqueous hydrogen peroxide in a concentration of 40 weight-%. On the other hand, using higher concentrations than 50 weight-% requires further concentration of the aqueous hydrogen peroxide solution, which in turn increases the overall energy demand.

[0016] It is preferred that Xi is calculated based on equation 1.1 and X2 is calculated based on equation 2.1 :

[0017] Xi = 13.8 — (0.135 x CH202) equation 1 .1

[0018] X2= 14.6 - (0.135 x CH202) equation 2.1 , wherein CH202 is the concentration at which the aqueous solution comprising hydrogen peroxide is provided in weight- %.

[0019] Preferably, propene is provided in step a) in a weight-based ratio propene: H2O2 in the range of from 1 :2 to 2:1 , preferably in the range of from 1.2:1 to 2.2:1 , more preferably in the range of from 1.5:1 to 1.9:1.

[0020] According to step (a), propene, optionally propane, hydrogen peroxide, water, and acetonitrile are provided, wherein either a pre-mixed single stream comprising these components is fed to the epoxidation zone comprising a heterogeneous epoxidation catalyst or individual streams or one or more mixtures of individual streams are fed to the epoxidation zone comprising a heterogeneous epoxidation catalyst. Preferably, at least a partial mixing of individual streams takes place before entering the epoxidation zone. Individual streams comprise a first stream comprising hydrogen peroxide, a second stream comprising propene and optionally propane and a third stream comprising the acetonitrile and water. Preferably, at least within the epoxidation zone the mixture comprising hydrogen peroxide propene, water and acetonitrile is present as one liquid phase. Preferably, the mixture comprising hydrogen peroxide propene, water and acetonitrile is fed to the epoxidation zone already as one single feed stream, i.e. the mixing is done prior to entering the epoxidation zone. The single feed stream is preferably fed to the epoxidation zone having a temperature in the range of from 0 to 60°C, preferably in the range of from 10 to 55°C, more preferably in the range of from 25 to 50°C.

[0021] Preferably, -as described already above- the stream comprising propene additionally comprises propane, wherein preferably at least 90 weight-%, more preferably at least 95 weight-%, more preferably at least 98 weight-%, more preferably at least 99 weight-%, more preferably at least 99.5 weight-%, more preferably at least 99.9 weight-% of the stream consist of propene and propane, based on the total weight of the stream being 100 weight-%. Preferably, the weight based ratio of propene relative to propane in the stream is at least 7:3, more preferably at least 95:5. Preferably, the stream comprising propene comprises, preferably consists of, chemical-grade propene or polymer-grade propene, wherein in case of chemical-grade propene, the stream comprising propene comprises at least 90 weight- %, preferably at least 95 weight-% of propene, and in case of polymer-grade propene, the stream comprising propene comprises at least 99.5 weight-% of propene, based on the total weight of the stream being 100 weight-%. 240389W001

[0022] - 4 -

[0023] The stream comprising hydrogen peroxide is an aqueous solution comprising hydrogen peroxide in a concentration (CH202) in the range of from 42 to 50 weight-% based on the total weight of the aqueous solution being 100 weight-% as indicated above, wherein further preferred embodiments are described herein below.

[0024] Preferably, the process further comprises c) removing an effluent stream S1 from the epoxidation zone, the effluent stream comprising propylene oxide, propene, water and acetonitrile.

[0025] According to (c), an effluent stream is removed from the epoxidation zone. Generally, there is no specific restriction with respect to the composition of the effluent stream, provided that it comprises propene, optionally propane, propylene oxide, water, and acetonitrile. Preferably, at least 95 weight-%, more preferably from 95 to 99.6 weight-%, more preferably from 98 to 99.7 weight-%, more preferably from 99 to 99.8 weight-%, of the effluent stream removed in (c) consist of propylene oxide, the organic solvent, water, propene, oxygen, and optionally propane. Further components that can be comprised in the effluent stream are acetone, acetaldehyde, formaldehyde, hydroxyacetone, propylene glycol, dipropylene glycol, tripropylene glycol, CO, CO2 and organic hydroperoxides. Preferably, the effluent stream removed in (c) comprises the propylene oxide in an amount of from 5 to 20 weight-%, preferably from 6 to 18 weight- %, more preferably from 7 to 14 weight-%, based on the total weight of the effluent stream; the acetonitrile in an amount of from 55 to 75 weight-%, preferably from 6 to 74 weight-%, based on the total weight of the effluent stream; the water in an amount of from 10 to 25 weight-%, preferably from 15 to 20 weight-%, based on the total weight of the effluent stream; the propene in an amount of from 1 to 5 weight-%, preferably from 3 to 4.5 weight-%, based on the total weight of the effluent stream; oxygen in an amount of from 0.05 to 1 weight-%, preferably from 0.1 to 0.5 weight-%, based on the total weight of the effluent stream; and the optional propane in an amount of from 0.1 to 2 weight-%, preferably from 0.2 to 1 weight-%, based on the total weight of the effluent stream.

[0026] Step d) (T1)

[0027] It is preferred that the propene provided in step a) comprises propene and propane, the mixture obtained in step b) and the effluent stream S1 removed in step c) comprising propane, the process comprising d) separating propene and propane from the effluent stream S1 removed in step c) by washing and distillation, thereby obtaining a stream S2 enriched in propylene oxide, water and acetonitrile compared to the effluent stream removed in step c); and a stream S3 enriched in propene and propane compared to the effluent stream removed in step c).

[0028] Step d) is preferably done in at least one distillation tower, wherein the stream S2 enriched in propylene oxide, water and acetonitrile compared to the effluent stream S1 removed in c) is preferably removed as a bottoms stream, more preferably as a liquid bottoms stream from said distillation tower. The stream S3 enriched in propene and propane 240389W001

[0029] - 5 - compared to the effluent stream S1 removed in c) obtained in d) is preferably obtained as top stream from said distillation tower. Preferably, the distillation tower has in the range of from 10 to 30 theoretical stages and is preferably operated at a top pressure in the range of from 0.5 to 1 .5 bar and / or, preferably and, a bottom temperature in the range of from 40 to 90°C, preferably in the range of from 50 to 90ooC, more preferably in the range of from 60 to 80°C. Either liquid acetonitrile or a mixture comprising acetonitrile and water is added in the upper part of the distillation tower as washing liquid, wherein the acetonitrile is preferably at least partially taken from a downstream process step. Preferably, the weight ratio of the amount of acetonitrile fed to the distillation tower relative to the weight of the effluent stream S1 removed in c) and fed to d) is in the range of from 1 :1 to 4:1 .Adding liquid acetonitrile or a liquid mixture of acetonitrile with water to the upper part of the distillation tower as washing liquid allows an external reflux, which serves as entraining agent, which, among others, prevents propylene oxide from being separated via the top of the distillation tower. The entraining agent is taken from a separate tank or at least partially taken from a downstream process step. The temperature of the external reflux is generally in the range of from 2 to 20 °C, preferably in the range of from 5 to 15 °C. Preferably, at least 90 volume-% of the stream S3 enriched in propene and propane obtained from d) consist of propene, propane and oxygen. Depending on the oxygen content of said stream, a work-up stage can be used after d) and before e.2), wherein the oxygen content is reduced preferably in the presence of a suitable catalyst with hydrogen, wherein prior to oxygen reduction, one or more optional workup-steps can be comprised such as compression and partial condensation, wherein a non-condensed part is then subjected to hydrogenation. Preferably, prior to (d), the effluent stream S1 is depressurized, preferably to a pressure of from 0.5 to 2.8 bar, more preferably of from 0.6 to 2.5 bar, more preferably of from 0.8 to 1 .5 bar. Generally, there is no specific restriction on how the effluent stream is depressurized. Preferably, the effluent stream is depressurized into a flash drum. Preferably, from depressurizing the effluent stream, a gaseous stream and a liquid stream are obtained, wherein the gaseous and liquid streams are preferably passed separately to the distillation unit employed according to (d), preferably to the same theoretical tray of the distillation tower employed according to (d).]

[0030] Distillation towers T4, T5 & (C1) T2, T3

[0031] Preferably, the process further comprises e.1 ) separating the stream S2 enriched in propylene oxide, water and acetonitrile obtained in step d) by one or more distillations, thereby obtaining a stream S4, which comprises more than 99 wt.-% of propylene oxide based on the total weight of the stream S4, a stream S5 comprising acetonitrile and water and a stream S6 comprising propene; and / or, preferably and, e.2) separating propane from the stream S3 enriched in propene and propane obtained in d) in a separation zone, comprising subjecting the stream enriched in propene and propane obtained in step d) to washing conditions in a scrubber, wherein a solvent mixture comprising acetonitrile and water is added as entraining agent, obtaining a liquid bottoms stream S7, which comprises acetonitrile, water and at least 70 weight-% of the propene comprised in the steam S3 enriched in propene and propane obtained in step d); and 240389W001

[0032] - 6 - a gaseous top stream S8, which comprises at least 5 weight-% of the propane comprised in the stream S3 enriched in propene and propane obtained in step d). distillation towers T4, T5

[0033] Preferably, e.1) comprises e.1. a) feeding the stream S2 enriched in propylene oxide, water and acetonitrile obtained in d) into a distillation tower, obtaining, preferably as bottom stream, a stream S5 comprising acetonitrile and water and being depleted of propylene oxide compared to the stream obtained in step d) and a stream, preferably a top stream, enriched in propylene oxide compared to the stream obtained in d); e.1.b) feeding the stream enriched in propylene oxide obtained in step e.1 a) into a further distillation tower, obtaining a stream S4 enriched in in propylene oxide compared to the stream obtained in step e.1 a), preferably as a side stream, said stream enriched in in propylene oxide comprising more than 99 wt.-%, preferably more than 99.9 wt.-%, more preferably more than 99.99 wt.-%, of propylene oxide based on the total weight of the stream S4.

[0034] Preferably, the distillation tower of step e.1 .a) has in the range of from 50 to 150, preferably in the range of from 80 to 120 theoretical stages, is preferably operated at a top pressure in the range of from 0.1 to 2 bar, preferably in the range of from 0.2 to 1 bar, a bottom temperature in the range of from 40 to 80°C, preferably in the range of from 50 to 70°C and / or at a reflux ratio in the range of from 0.5 to 1 .5, preferably in the range of from 0.6 to 1 .0. Preferably, the distillation tower of step e.1 .b) has in the range of from 10 to 100, preferably in the range of from 40 to 70 theoretical stages, is preferably operated at a top pressure in the range of from 1 to 5 bar, preferably in the range of from 2.5 to 3.5 bar, a bottom temperature in the range of from 50 to 90°C, preferably in the range of from 45 to 80°C. Preferably, the distillation tower of step e.1. a) is also called distillation tower T4 and the distillation tower of step e.1.b) is called distillation tower T5. Preferably, also a low boiler stream, a so-called stream LB, is taken from the top of T4.

[0035] Preferably, the distillation tower of step e.1.b) is operated with reflux, preferably with a reflux ratio in the range of from 0.5 : 1 to 1 : 1 , more preferably in the range of from 0.7 : 1 to 1 : 1 , more preferably in the range of from 0.9 : 1 to 1 : 1. When operated with reflux, the distillation tower of step e.1.b) is operated as a non-reboiled stripping unit. In step e.1 .a), preferably a further stream is removed from the distillation tower, preferably from a region at about half the height of the distillation tower, preferably in the range of from 35 to 55% of the height of the distillation tower, said further stream comprising propylene oxide, acetonitrile, water and one or more side products formed, preferably at least propionaldehyde. Said further stream is removed from the distillation tower in a ratio to the stream, preferably the top stream, enriched in propylene oxide obtained in step e.1. a), in the range of from 0.01 :100 to 0.05:100. Further details regarding step e.1. a) and the further stream are disclosed in WO 2018 / 015435 A1 , especially in the parts thereof related to side stream S1 b. Said further stream is also called stream IB.

[0036] Com pression unit C1 240389W001

[0037] - 7 -

[0038] It is preferred that step e.2) comprises e.2. a) feeding stream S3 enriched in propene and propane obtained in step d) and having a pressure ps3 into a compression unit, wherein the pressure is increased to ps3comPwith ps3comP> Ps3, followed by partial condensation, obtaining a condensed part stream S3COnd and a non-condensed part stream S3gase0Us of S3, condensed part stream S3COnd comprising propene and propane and the non-condensed part stream S3gase0Us comprising propene and propane.

[0039] The compression unit used in step e.2. a) has at least one compression stage, preferably in the range of from 1 to 10 compression stage(s), more preferably in the range of from 3 to 5 compression stages. The compression unit used in step e.2. a) is also called compression unit C1

[0040] Towers T2, T3

[0041] It is preferred that step e.2) further comprises e.2.b) feeding the non-condensed part stream S3gase0Us obtained in step e.2. a) into a scrubber, optionally with addition of an inert gas, and subjecting S3gase0Us to washing conditions in the scrubber, wherein a solvent mixture comprising acetonitrile and water is introduced as entraining agent into the scrubber, preferably to the upper part of the scrubber; thereby obtaining a liquid bottoms stream S7, which comprises acetonitrile, water and propene; e.2.c) feeding the bottoms stream S7 comprising propene and acetonitrile obtained in step e.2.b) into a distillation tower, from which a gaseous top stream S8 and a liquid bottoms stream S9 are obtained, wherein liquid bottoms stream S9 comprises acetonitrile and gaseous top stream S8 comprises at least 5 weight-% of the propane comprised in the stream S3 enriched in propene and propane obtained in step d).

[0042] The scrubber of step e.2.b) is also called tower T2 and the distillation tower of step e.2.c) is also called tower T3.

[0043] It is preferred that the process comprises f) mixing the stream comprising acetonitrile and water obtained in step e.1) or in step e.1.a) and at least a stream comprising propene under phase separation conditions, thereby obtaining a liquid aqueous phase LAP comprising water and a liquid organic phase LOP comprising acetonitrile and propene, g) subjecting the liquid organic phase LOP comprising acetonitrile and propene obtained in step f) to distillation, thereby obtaining a liquid bottoms stream S10 comprising acetonitrile and propene and a gaseous top stream comprising propene; h) recycling the liquid bottoms stream S10 comprising acetonitrile and propene obtained in step g) into step a).

[0044] Preferably, the at least one stream comprising propene mixed to in step f) is selected from the group consisting of stream S3COnd ,part of stream S3COnd , stream comprising propene from a downstream process stage, fresh propene comprising stream and mixtures of two or more thereof. 240389W001

[0045] - 8 -

[0046] Step f) is preferably conducted in a separation unit, preferably a decanter, which is preferably operated at a temperature in the range of from 5 to 30°C, more preferably in the range of from 10 to 20°C and / or at a pressure in the range of from 5 to 30 bar, preferably in the range of from 10 to 25 bar. The separation unit, preferably the decanter, is also called D1 . The liquid aqueous phase LAP comprising water obtained in step f) preferably comprises water and acetonitrile, preferably in a weight-based ratio acetonitrile: water in the range of from 3:1 to 5:1, more preferably in the range of from 3.5: 1 to 4.5:1. Preferably, said LAP is further processed by distillation giving a stream being enriched in acetonitrile and depleted of water, preferably an azeotropic mixture of acetonitrile and water, wherein said azeotropic mixture is preferably returned to step f). The distillation of step f) is carried out in a distillation tower, which is also called T6. The distillation in g) is preferably carried out in a distillation tower, which has in the range of from 1 to 50, preferably in the range of from 2 to 10, more preferably in the range of from 3 to 8, theoretical stages, and / or is operated at a pressure in the range of from 10 to 30 bar, preferably in the range of from 15 to 25 bar and / or at a bottom temperature in the range of from 90 to 110°C, preferably in the range of from 95 to 105°C. A liquid bottoms stream S10 comprising acetonitrile and propene is obtained from said distillation tower. The distillation of step g) is carried out in a distillation tower, which is also called T7.

[0047] It is preferred that in step a), additionally an additive is provided to the epoxidation zone, wherein the additive comprises at least one potassium salt selected from the group consisting of at least one inorganic potassium salt, at least one organic potassium salt, and mixtures of at least one inorganic potassium salt and at least one organic potassium salt; preferably selected from the group consisting of at least one inorganic potassium salt selected from the group consisting of potassium hydroxide, potassium chloride, potassium nitrate, potassium hydrogen phosphate, potassium dihydrogen phosphate, at least one organic potassium salt selected from the group consisting of potassium formate, potassium acetate, potassium carbonate, and potassium hydrogen carbonate, and mixtures of at least one of the at least one inorganic potassium salts and at least one of the at least one organic potassium salts, more preferably, the additive is selected from the group consisting of potassium dihydrogen phosphate, dipotassium hydrogen phosphate potassium formate and mixtures of two or more thereof; more preferably the additive comprises at least potassium formate, more preferably the additive is potassium formate.

[0048] As indicated above, according to step (a), propene, optionally propane, hydrogen peroxide, water, and acetonitrile are provided, wherein either a pre-mixed single stream comprising these components is fed to the epoxidation zone comprising a heterogeneous epoxidation catalyst or individual streams or one or more mixtures of individual streams are fed to the epoxidation zone comprising a heterogeneous epoxidation catalyst. Preferably, at least a partial mixing of individual streams takes place before entering the epoxidation zone. Individual streams comprise a first stream comprising hydrogen peroxide, a second stream comprising propene and optionally propane and a third stream comprising the acetonitrile and water, and, if additive is provided to the epoxidation zone, also a fourth stream comprising the additive and water. Preferably, the aqueous fourth stream comprising additive is pre-mixed with the aqueous first stream comprising hydrogen peroxide, before the resulting pre-mixed steam is mixed with the remaining streams. 240389W001

[0049] - 9 -

[0050] Preferably, at least within the epoxidation zone the mixture comprising hydrogen peroxide propene, water, acetonitrile and additive is present as one liquid phase. Preferably, the mixture comprising hydrogen peroxide propene, water, acetonitrile and additive is fed to the epoxidation zone already as one single feed stream, i.e. the mixing is done prior to entering the epoxidation zone. Further details regarding the feeding to the epoxidation zone are as disclosed above. is preferred that: i.i) the hydrogen peroxide in a) is provided as an aqueous solution comprising hydrogen peroxide in a concentration (CH202) in the range of from 43 to 50 weight-%, preferably in the range of from 45 to 50 weight-%, based on the total weight of the aqueous solution being 100 weight-%.

[0051] According to the present invention, it is preferred to employ hydrogen peroxide (H2O2) which is obtained as crude hydrogen peroxide solution by extraction of a mixture which results from a process known as anthraquinone process by means of which virtually the entire world production of hydrogen peroxide is produced (see, e.g., Ullmann's Encyclopedia of Industrial Chemistry, 5thedition, volume A 13 (1989) pages 443-466) wherein a solution of an anthraquinone is used containing an alkyl group preferably having of from 2 to 10 carbon atoms, more preferably at least 5 carbon atoms such as 5 carbon atoms or 6 carbon atoms and where the solvent used usually consists of a mixture of two different solvents, whereby preferably none of the solvents is a nitrogen containing substance. This solution of the anthraquinone is usually referred to as the working solution. In this process, the hydrogen peroxide formed in the course of the anthraquinone process is generally separated by extraction from the respective working solution after a hydrogenation / re-oxidation cycle. Said extraction can be performed preferably with essentially pure water, and the crude aqueous hydrogen peroxide solution is obtained. While it is generally possible to further purify the thus obtained crude aqueous hydrogen peroxide solution by distillation, it is preferred, according to the present invention, to use such crude aqueous hydrogen peroxide solution which has not been subjected to purification by distillation. Further, it is generally possible to subject the crude aqueous hydrogen peroxide solution to a further extraction stage wherein a suitable extracting agent, preferably an organic solvent is used. More preferably, the organic solvent used for this further extraction stage is the same solvent, which is used in the anthraquinone process. Preferably the extraction is performed using just one of the solvents in the working solution and most preferably using just the most nonpolar solvent of the working solution. In case the crude aqueous hydrogen peroxide solution is subjected to such further extraction stage, a so-called crude washed hydrogen peroxide solution is obtained. The production of a crude solution is described, for example, in European patent application EP 1 122 249 A1 . As to the term "essentially pure water", reference is made to paragraph 10, page 3 of EP 1 122 249 A1 which is incorporated by reference. The hydrogen peroxide can also be treated to remove trace metals, for example, as described in the WO 2015 / 049327 A1 before use. Extraction without subsequent distillation of an aqueous hydrogen peroxide solution results in concentrations in the range of from 40 to 50 weight-% H2O2 based on the total weight of the aqueous solution being 100 weight-%. For achieving higher concentrations, distillation is required. 240389W001

[0052] - 10 -

[0053] Preferably, the process has an overall energy demand OED, wherein compared to a process, which does not fulfill requirements I) and 1.1) respectively and II), and has a comparative overall energy demand OEDCOmP, OED / OEDCOmPis <0.99, preferably <0.97, preferably 0.98 < OED / OEDCOmP< 0.99, more preferably 0.96 < OED / OEDCOmP< 0.97.

[0054] Epoxidation zone

[0055] Generally, there are no specific restrictions regarding the design of the epoxidation zone provided that it is suitable for carrying out a, preferably continuous, epoxidation reaction.

[0056] Preferably, the epoxidation zone according to (b) comprises a first epoxidation subzone consisting of one or more epoxidation reactors A. The term "first epoxidation subzone" as used in this context of the present invention relates to the epoxidation subzone into which the components provided in (a) are passed, wherein the epoxidation zone may comprise further epoxidation subzones which are arranged downstream of the first epoxidation subzone. If the first epoxidation subzone consisting of two or more epoxidation reactors A, it is preferred that the two or more epoxidation reactors A are arranged in parallel.

[0057] The epoxidation conditions according to (b) comprise an epoxidation temperature TN, wherein TNis the temperature of a heat transfer medium used for adjusting the temperature of the reaction mixture in the first epoxidation reaction subzone, wherein it is preferred that said temperature is adjusted by passing the heat transfer medium through a jacket of the one or more epoxidation reactors A, wherein TNis preferably the temperature of the heat transfer medium prior to adjusting the temperature of the reaction mixture, preferably the temperature of the heat transfer medium at the entrance of the jacket of the one or more epoxidation reactors A. If the first epoxidation subzone comprises two or more epoxidation reactors A, the epoxidation temperature TNrelates to the epoxidation temperature TNof a given reactor A in operation of first epoxidation subzone. Preferably, TNis a temperature in the range of from 10 to 80°C, more preferably in the range of from 20 to 70°C, more preferably in the range of from 25 to 55°C. The epoxidation reactor(s) of A are also called reactors R1 (preferably tube bundle reactors R1 a, R1 b, ,...R1x, with x being an integer and being at least 100, preferably at least 1 ,000, more preferably being selected from the range of from 1 ,000 to 100,000, more preferably from the range of from 10,000 to 50,000.

[0058] Preferably, the epoxidation conditions according to (b) comprise a first epoxidation reaction pressure in the range of from 14 to 100 bar, more preferably in the range of from 15 to 35 bar, more preferably in the range of from 15 to 30 bar. The first epoxidation reaction pressure is defined as the absolute pressure at the exit of the first epoxidation subzone. If the first epoxidation subzone comprises two or more epoxidation reactors A, the first epoxidation reaction pressure relates to the absolute pressures at the exit of a given reactor A in operation of first epoxidation subzone.

[0059] According to a first preferred embodiment of the present invention, the epoxidation zone according to (b) consists of the first epoxidation subzone. 240389W001

[0060] - 11 -

[0061] According to a second preferred embodiment of the present invention, the epoxidation zone according to (b) additionally comprises a second epoxidation subzone consisting of one or more epoxidation reactors B wherein, if the second epoxidation subzone comprises two or more epoxidation reactors B, the two or more epoxidation reactors B are arranged in parallel, wherein the second epoxidation subzone is arranged downstream of the first epoxidation subzone. In this case, it is preferred that in (b), the effluent stream obtained from the first epoxidation subzone, optionally after a suitable intermediate treatment, is passed into at least one of the epoxidation reactors B. The epoxidation reactors B are also called reactors R2. It is possible, for example, that, while the effluent stream obtained from the first epoxidation subzone, optionally after a suitable intermediate treatment, is passed into at least one of the epoxidation reactors B, at least one of the reactors B is taken out of operation, for example for maintenance purposes and / or for regenerating the catalyst comprised in the at least one of the reactors B. If the second epoxidation subzone comprises two or more epoxidation reactors B, the reactors in operation are operated essentially identically so that in every epoxidation reactor B in operation, a given epoxidation condition is in the same range in every reactor. Generally, it is conceivable that in addition to the first epoxidation subzone and the second epoxidation subzone, the epoxidation zone according to (b) comprises at least one further epoxidation subzone arranged downstream of the second epoxidation subzone. Preferably, according to the second preferred embodiment of the present invention, the epoxidation zone according to (b) consists of the first epoxidation subzone and the second epoxidation subzone.

[0062] Preferably, the epoxidation conditions according to (b) comprise a second epoxidation reaction pressure in the range of from 14 to 100 bar, preferably in the range of from 14.5 to 32 bar, more preferably in the range of from 15 to 25 bar. The second epoxidation reaction pressure is defined as the absolute pressure at the exit of the second epoxidation subzone. If the second epoxidation subzone comprises two or more epoxidation reactors B, the second epoxidation reaction pressure relates to the absolute pressures at the exit of a given reactor B in operation of second epoxidation subzone.

[0063] Preferably, the temperature of the reaction mixture in the second epoxidation reaction subzone is not adjusted by passing a heat transfer medium through a jacket of the one or more epoxidation reactors B. More preferably, the second epoxidation subzone is an essentially adiabatic epoxidation subzone. More preferably, the second epoxidation subzone is an adiabatic epoxidation subzone.

[0064] Epoxidation catalyst

[0065] According to (b), the mixture comprising propene, water and acetonitrile is contacted in the epoxidation zone with the heterogeneous epoxidation catalyst. The heterogeneous epoxidation catalyst comprising a titanium zeolite. Preferably, titanium zeolite comprised in the epoxidation catalyst is a titanium zeolite having ABW, AGO, AEI, AEL, AEN, AET, AFG, AFI, AFN, AFO, AFR, AFS, AFT, AFX, AFY, AHT, ANA, APC, APD, AST, ASV, ATN, ATO, ATS, ATT, ATV, AWO, AWW, BCT, BEA, BEG, BIK, BOG, BPH, BRE, CAN, CAS, CDO, CFI, CGF, CGS, CHA, CHI, CLO, CON, CZP, DAO, DDR, DFO, DFT, DOH, DON, EAB, EDI, EMT, EPI, ERI, ESV, ETR, EDO, FAU, FER, FRA, GIS, GIU, GME, GON, GOO, HEU, IFR, ISV, ITE, ITH, ITW, IWR, IWW, JBW, KFI, LAU, LEV, LIO, LOS, LOV, LTA, LTL, 240389W001

[0066] - 12 -

[0067] LTN, MAR, MAZ, MEI, MEL, MEP, MER, MMFI, MFS, MON, MOR, MSO, MTF, MTN, MTT, MTW, MWW, NAB, NAT, NEES, NON, NPO, OBW, OFF, OSI, OSO, PAR, PAU, PHI, PON, RHO, RON, RRO, RSN, RTE, RTH, RUT, RWR, RWY, SAO, SAS, SAT, SAV, SBE, SBS, SBT, SFE, SFF, SFG, SFH, SFN SFO, SGT, SOD, SSY, STF, STI, STT, TER, THO, TON, TSO, UEI, UFI, UOZ, USI, UTL, VET, VFI, VNI, VSV, WEI, WEN, YUG, ZON framework structure or a mixed structure of two or more of these framework structures, preferably a titanium zeolite having an MFI framework structure, an MEL framework structure, an MWW framework structure, an ITQ framework structure, a BEA framework structure, a MOR framework structure, or a mixed structure of two or more of these framework structures, preferably an MFI framework structure, or an MWW framework structure.

[0068] The epoxidation catalyst comprising a titanium zeolite can be employed in every conceivable form. Preferably, the catalyst comprising the titanium zeolite is employed as a molding comprising the titanium zeolite. More preferably, the catalyst comprising the titanium zeolite is present in the epoxidation zone as a molding, preferably as fluidized - bed catalyst or a fixed-bed catalyst, more preferably as a fixed-bed catalyst.

[0069] Preferably, the titanium zeolite comprised in the epoxidation catalyst is a titanium zeolite having MWW framework structure, which preferably comprises at least one of Al, B, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Zn, Ga, Ge, In, Sn, Pb, Pd, Pt, Au, preferably at least one of B, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Zn, Ga, Ge, In, Sn, Pb, Pd, Pt, Au, more preferably Zn.

[0070] Preferably, the titanium zeolite is an aluminum-free zeolitic material of MWW framework structure, containing titanium, preferably in an amount of from 0.5 to 5 weight-%, more preferably from 1 to 2 weight-%, calculated as elemental titanium and based on the total weight of the titanium containing zeolite, and containing zinc, preferably in an amount of from 0.5 to 5 weight-%, preferably from 1 to 2 weight-%, calculated as elemental zinc and based on the total weight of the titanium containing zeolite. The term "aluminum-free” in the context of the present invention refers to an embodiment according to which the aluminum content of the zeolitic material is 0.05 weight-ppm at most, preferably 0.03 weight-ppm at most, more preferably 0.02 weight-ppm at most, based on the total weight of zeolitic material. The weight-%-values refer to an embodiment according to which the zeolitic material is in dry state, preferably after drying for at least ten hours at 80 °C at a pressure of less than 1013.25 hPa.

[0071] More preferably, the titanium zeolite comprised in the epoxidation catalyst is a titanium zeolite of MWW framework structure, preferably being aluminum-free and comprising zinc.

[0072] 2ndaspect - mixture

[0073] A second aspect of the invention relates to a mixture, preferably for preparation of propylene oxide, comprising propene, water, hydrogen peroxide and acetonitrile, wherein the acetonitrile (ACN) and the hydrogen peroxide (H2O2) are present in a weight-based ratio ACN:H2O2 in the range of from Xi to X2, wherein Xi is calculated based on equation 1 and X2 is calculated based on equation 2: 240389W001

[0074] - 13 -

[0075] Xi = 13.6 — (0.135 x CH2O2) equation 1

[0076] X2 = 14.8 - (0.135 x CH202) equation 2, wherein CH202 is the concentration of hydrogen peroxide in weight-% in the mixture, wherein the total weight of the mixture is 100 weight-%.

[0077] The second aspect of the invention also relates to a mixture, preferably for preparation of propylene oxide, comprising propene, water, hydrogen peroxide and acetonitrile, wherein the acetonitrile (ACN) and the hydrogen peroxide (H2O2) are present in a weight-based ratio ACN:H2C>2 in the range of from Xi to X2, wherein Xi is calculated based on equation 1 and X2 is calculated based on equation 2:

[0078] Xi = 13.6 - (0.135 x CH202) equation 1

[0079] X2 = 14.8 - (0.135 x CH202) equation 2, wherein CH202 is the concentration at which the aqueous solution comprising hydrogen peroxide is provided in weight- %.

[0080] All details, embodiments and preferred embodiments described above in the section related to the first aspect of the invention apply also to the mixture of the second aspect of the invention.

[0081] It is preferred for the mixture that Xi is calculated based on equation 1.1 and X2 is calculated based on equation 2.1 : Xi = 13.8 - (0.135 x CH202) equation 1 .1

[0082] X2 = 14.6 - (0.135 x CH202) equation 2.1 , wherein CH202 is the concentration of hydrogen peroxide in weight-% in the mixture, wherein the total weight of the mixture is 100 weight-%.

[0083] It is also preferred for the mixture that Xi is calculated based on equation 1.1 and X2 is calculated based on equation 2.1 :

[0084] Xi = 13.8 - (0.135 x CH202) equation 1 .1

[0085] X2 = 14.6 - (0.135 x CH202) equation 2.1 , wherein CH202 is the concentration at which the aqueous solution comprising hydrogen peroxide is provided in weight- %.

[0086] The mixture preferably comprises propene and hydrogen peroxide in a weight-based ratio propene: H2O2 in the range of from 1 :2 to 2:1 , more preferably in the range of from 1.2:1 to 2.2:1 , more preferably in the range of from 1.5:1 to 1.9:1.

[0087] 3rdaspect - use

[0088] In a third aspect, the invention is directed to the use of the mixture according to the second aspect for preparation of propylene oxide, preferably by heterogeneous catalysis, more preferably in a process according to the first aspect of the invention as described herein above. 240389W001

[0089] - 14 -

[0090] All details, embodiments and preferred embodiments described above in the section related to the first aspect of the invention and in the section related to the second aspect of the invention apply also to the use of the third aspect of the invention.

[0091] 4thaspect - method

[0092] A fourth aspect of the invention is directed to a method for preparing propylene oxide, wherein the mixture of the second aspect of the invention as described herein above is brought into contact with a heterogeneous catalyst under epoxidation conditions.

[0093] All details, embodiments and preferred embodiments described above in the section related to the first aspect of the invention, in the section related to the second aspect of the invention, and in the in the section related to the third aspect of the invention apply also to the method of the fourth aspect of the invention.

[0094] 5thaspect - Propylene Oxide (product-by-process)

[0095] A fifth aspect of the invention relates to propylene oxide, obtained or obtainable from a process according to the first aspect of the invention as described herein above or from the method of the fourth aspect of the invention as described herein above.

[0096] All details, embodiments and preferred embodiments described above in the section related to the first aspect of the invention, in the section related to the second aspect of the invention, in the in the section related to the third aspect of the invention, and in the section related to the fourth aspect of the invention apply also to the propylene oxide of the fifth aspect of the invention.

[0097] The present invention is further illustrated by the following set of embodiments and combinations of embodiments resulting from the dependencies and back-references as indicated. In particular, it is noted that in each instance where a range of embodiments is mentioned, for example in the context of a term such as "The process of any one of embodiments 1 to 4", every embodiment in this range is meant to be explicitly disclosed for the skilled person, i.e. the wording of this term is to be understood by the skilled person as being synonymous to "The process of any one of embodiments 1, 2, 3 and 4". Further, it is explicitly noted that the following set of embodiments represents a suitably structured part of the general description directed to preferred aspects of the present invention, and, thus, suitably supports, but does not represent the claims of the present invention.

[0098] 1 . A process for preparing propylene oxide, the process for preparing propylene oxide comprising 240389W001

[0099] - 15 - a) providing propene, water, hydrogen peroxide and acetonitrile to an epoxidation zone comprising a heterogeneous epoxidation catalyst, thereby obtaining a mixture comprising propene, water and acetonitrile; b) contacting the mixture comprising propene, water and acetonitrile in the epoxidation zone with the heterogeneous epoxidation catalyst under epoxidation conditions, thereby obtaining a mixture comprising propylene oxide, propene, water and acetonitrile; wherein: i) the hydrogen peroxide in a) is provided as an aqueous solution comprising hydrogen peroxide in a concentration (CH202) in the range of from 42 to 50 weight-% based on the total weight of the aqueous solution being 100 weight-%; ii) the acetonitrile (ACN) and the aqueous solution comprising hydrogen peroxide (H2O2aq.) are provided in a) to the epoxidation zone in a weight-based ratio ACN:H2C>2 in the range of from Xi to X2, wherein Xi is calculated based on equation 1 and X2 is calculated based on equation 2:

[0100] Xi = 13.6 - (0.135 x CH202) equation 1 X2= 14.8 - (0.135 x CH202) equation 2, wherein CH202 is the concentration at which the aqueous solution comprising hydrogen peroxide is provided in weight-%.

[0101] 2. The process of embodiment 1 , wherein Xi is calculated based on equation 1.1 and X2 is calculated based on equation 2.1 :

[0102] Xi = 13.8 - (0.135 x CH202) equation 1 .1

[0103] X2= 14.6 - (0.135 x CH202) equation 2.1 , wherein CH202 is the concentration at which the aqueous solution comprising hydrogen peroxide is provided in weight-%

[0104] 3. The process of embodiment 1 or 2, wherein propene is provided in a) in a weight-based ratio propene: H2O2 in the range of from 1 :2 to 2:1 , preferably in the range of from 1.2:1 to 2.2:1 , more preferably in the range of from 1.5:1 to 1.9:1.

[0105] 4. The process of any one of embodiments 1 to 3 comprising c) removing an effluent stream S1 from the epoxidation zone, the effluent stream comprising propylene oxide, propene, water and acetonitrile.

[0106] 5. The process of any one of embodiments 1 to 4, wherein the propene provided in a) comprises propene and propane, the mixture obtained in b) and the effluent stream S1 removed in c) comprising propane, the process comprising d) separating propene and propane from the effluent stream S1 removed in c) by washing and distillation, thereby obtaining 240389W001

[0107] - 16 - a stream S2 enriched in propylene oxide, water and acetonitrile compared to the effluent stream removed in c); and a stream S3 enriched in propene and propane compared to the effluent stream removed in c).

[0108] 6. The process of any one of embodiments 1 to 5 comprising e.1 ) separating the stream S2 enriched in propylene oxide, water and acetonitrile obtained in d) by one or more distillations, thereby obtaining a stream S4, which comprises more than 99 wt.-% of propylene oxide based on the total weight of the stream S4, a streamS5 comprising acetonitrile and water and a stream S6 comprising propene; and / or, preferably and, e.2) separating propane from the stream S3 enriched in propene and propane obtained in d) in a separation zone, comprising subjecting the stream enriched in propene and propane obtained in d) to washing conditions in a scrubber, wherein a solvent mixture comprising acetonitrile and water is added as entraining agent, obtaining a liquid bottoms stream S7, which comprises acetonitrile, water and at least 70 weight-% of the propene comprised in the steam S3 enriched in propene and propane obtained in d); and a gaseous top stream S8, which comprises at least 5 weight-% of the propane comprised in the stream S3 enriched in propene and propane obtained in d).

[0109] 7. The process of embodiment 6, wherein e.1 ) comprises e.1.a) feeding the stream S2 enriched in propylene oxide, water and acetonitrile obtained in d) into a distillation tower, obtaining, preferably as bottom stream, a stream S5 comprising acetonitrile and water and being depleted of propylene oxide compared to the stream obtained in d) and a stream, preferably a top stream, enriched in propylene oxide compared to the stream obtained in d); e.1 b) feeding the stream enriched in propylene oxide obtained in e.1 a) into a further distillation tower, obtaining a stream S4 enriched in in propylene oxide compared to the stream obtained in e.1 a), preferably as a side stream, said stream enriched in in propylene oxide comprising more than 99 wt.-%, preferably more than 99.9 wt.-%, more preferably more than 99.99 wt.-%, of propylene oxide based on the total weight of the stream S4.

[0110] 8. The process of embodiment 6, wherein e.2) comprises e.2. a) feeding stream S3 enriched in propene and propane obtained in d) and having a pressure ps3 into a compression unit, wherein the pressure is increased to ps3comPwith ps3comP> Ps3, followed by partial condensation, obtaining a condensed part stream S3COnd and a non-condensed part stream S3gase0Us of S3, condensed part stream S3COnd comprising propene and propane and the non-condensed part stream S3gase0Us comprising propene and propane.

[0111] 9. The process of embodiment 8, wherein e.2) further comprises 240389W001

[0112] - 17 - e.2.b) feeding the non-condensed part stream S3gase0Us obtained in e.2.a) into a scrubber, optionally with addition of an inert gas, and subjecting S3gase0Us to washing conditions in the scrubber, wherein a solvent mixture comprising acetonitrile and water is introduced as entraining agent into the scrubber, preferably to the upper part of the scrubber; thereby obtaining a liquid bottoms stream S7, which comprises acetonitrile, water and propene; e.2.c) feeding the bottom stream comprising propene and acetonitrile into a distillation tower, from which a gaseous top stream S8 and a liquid bottoms stream S9 are obtained, wherein liquid bottoms stream S9 comprises acetonitrile and gaseous top stream S8 comprises at least 5 weight-% of the propane comprised in the stream S3 enriched in propene and propane obtained in d).

[0113] 10. The process of any one of embodiments 1 to 9 comprising f) mixing the stream comprising acetonitrile and water obtained in e.1) or in e.1.a) and at least a stream comprising propene under phase separation conditions, thereby obtaining a liquid aqueous phase LAP comprising water and a liquid organic phase LOP comprising acetonitrile and propene, g) subjecting the liquid organic phase LOP comprising acetonitrile and propene obtained in f) to distillation, thereby obtaining a liquid bottoms stream S10 comprising acetonitrile and propene and a gaseous top stream comprising propene; h) recycling the liquid bottoms stream S10 comprising acetonitrile and propene obtained in g) into a).

[0114] 11 . The process of embodiment 10, wherein the at least one stream comprising propene mixed to in f) is selected from the group consisting of stream S3COnd , part of stream S3cond„ stream comprising propene from a downstream process stage, fresh propene comprising stream and mixtures of two or more thereof.

[0115] 12. The process of any one of embodiments 1 to 11 , wherein in a), additionally an additive is provided to the epoxidation zone, wherein the additive comprises at least one potassium salt selected from the group consisting of at least one inorganic potassium salt, at least one organic potassium salt, and mixtures of at least one inorganic potassium salt and at least one organic potassium salt; preferably selected from the group consisting of at least one inorganic potassium salt selected from the group consisting of potassium hydroxide, potassium chloride, potassium nitrate, potassium hydrogen phosphate, potassium dihydrogen phosphate, at least one organic potassium salt selected from the group consisting of potassium formate, potassium acetate, potassium carbonate, and potassium hydrogen carbonate, and mixtures of at least one of the at least one inorganic potassium salts and at least one of the at least one organic potassium salts, more preferably, the additive is selected from the group consisting of potassium dihydrogen phosphate, dipotassium hydrogen phosphate potassium formate and mixtures of two or more thereof; more preferably the additive comprises at least potassium formate, more preferably the additive is potassium formate. . The process of any one of embodiments 1 to 12, wherein: 240389W001

[0116] - 18 - i.i) the hydrogen peroxide in a) is provided as an aqueous solution comprising hydrogen peroxide in a concentration (CH202) in the range of from 43 to 50 weight-%, preferably in the range of from 45 to 50 weight-%, based on the total weight of the aqueous solution being 100 weight-%.

[0117] 14. The process of any one of embodiments 1 to 13, having an overall energy demand OED, wherein compared to a process, which does not fulfill I) and i.i) respectively and ii), and has a comparative overall energy demand OEDcomp , OED / OEDcomp is <0.99, preferably <0.97, preferably 0.98 < OED / OEDCOmp < 0.99, more preferably 0.96 < OED / OEDcomp < 0.97.

[0118] 15. A mixture, preferably for preparation of propylene oxide, comprising propene, water, hydrogen peroxide and acetonitrile, wherein the acetonitrile (AON) and the hydrogen peroxide (H2O2) are present in a weight-based ratio ACN:H2O2 in the range of from Xi to X2, wherein Xi is calculated based on equation 1 and X2 is calculated based on equation 2:

[0119] Xi = 13.6 - (0.135 x CH202) equation 1

[0120] X2 = 14.8 - (0.135 x CH202) equation 2, wherein CH202 is the concentration of hydrogen peroxide in weight-% in the mixture, wherein the total weight of the mixture is 100 weight-%.

[0121] 16. The mixture of embodiment 15, wherein Xi is calculated based on equation 1.1 and X2 is calculated based on equation 2.1 :

[0122] Xi = 13.8 - (0.135 x CH202) equation 1 .1

[0123] X2 = 14.6 - (0.135 x CH202) equation 2.1 , wherein CH202 is the concentration of hydrogen peroxide in weight-% in the mixture, wherein the total weight of the mixture is 100 weight-%.

[0124] 17. A mixture, preferably for preparation of propylene oxide, comprising propene, water, hydrogen peroxide and acetonitrile, wherein the acetonitrile (ACN) and the hydrogen peroxide (H2O2) are present in a weight-based ratio ACN:H2C>2 in the range of from Xi to X2, wherein Xi is calculated based on equation 1 and X2 is calculated based on equation 2:

[0125] Xi = 13.6 - (0.135 x CH202) equation 1

[0126] X2 = 14.8 - (0.135 x CH202) equation 2, wherein CH202 is the concentration at which the aqueous solution comprising hydrogen peroxide is provided in weight-%. 240389W001

[0127] - 19 -

[0128] 18. The mixture of embodiment 17, wherein Xi is calculated based on equation 1.1 and X2 is calculated based on equation 2.1 :

[0129] Xi = 13.8 - (0.135 X CH2O2) equation 1.1

[0130] X2= 14.6 - (0.135 x CH2O2) equation 2.1, wherein CH202 is the concentration at which the aqueous solution comprising hydrogen peroxide is provided in weight-%.

[0131] 19. The mixture of embodiment 15 or 16 or of embodiment 17 or 18, comprising propene and hydrogen peroxide in a weight-based ratio propene:H2O2 in the range of from 1 :2 to 2:1, preferably in the range of from 1.2:1 to 2.2:1, more preferably in the range of from 1 .5: 1 to 1 .9: 1 .

[0132] 20. Use of a mixture according to any one of embodiments 15 to 19 for preparation of propylene oxide, preferably by heterogeneous catalysis, more preferably in a process according to any one pf embodiments 1 to 14.

[0133] 21. A method for preparing propylene oxide, wherein the mixture of any one of embodiments 15 to 19 is brought into contact with a heterogeneous catalyst under epoxidation conditions.

[0134] 22. Propylene oxide, obtained or obtainable from a process according to any one of embodiments 1 to 14 or from the method of embodiment 21 .

[0135] The present invention is further illustrated by the following reference examples, comparative examples, and examples.

[0136] Examples

[0137] For the purpose of illustrating the invention the different process options were simulated using the Aspen software suite, AspenONE, version V14 (company Aspentech) and physical data known in literature, taken from the Dort- munder Datenbank (DDB, version 2024). All the simulations were performed for production of 50 t / h of pure propylene oxide (PO, i.e. PO conforming to generally agreed specification for technically produced premium quality PO according to Chinese standard GB / T14491 -2015).

[0138] In all the cases the feed to the main reactor is identical. The state-of-the-art process is basically as described in WO 2017 / 140774A1 and WO2018 / 197234 A1. The conventional PP-splitter described sometimes in the state-of-the-art, while still perfectly possible, has been replaced by extractive distillation using acetonitrile as the entrained. Such PP- splitters are known from literature, and are known to be energetically advantageous, but are seldom used, because the pure propylene will always be contaminated to some extent with the extracting agent. But in this case, the extracting agent is identical with the solvent used in the process and thus the presence of traces of acetonitrile in the 240389W001

[0139] - 20 - recovered propylene are not a problem. For this reason, it was chosen to use the extractive distillation to separate propylene from propane.

[0140] The specific values of pressure, temperature, composition, etc. the values used in the simulation used to illustrate the invention are by no means to be understood as limiting the invention. Reference is made to the process scheme in Fig. 1. When giving the composition of feed streams only the main components were given.

[0141] Reference Example 1 : Process description

[0142] A pre-mixed feed containing mainly propylene, HP, water and additive (potassium formate, KFo) entered the main reactor R1. Reactor R1 was a tube bundle reactor (or several reactors R1a, R1 b, ... R1x), which was / were filled with a fixed bed of an epoxidation catalyst, which was a molding comprising a ZnTiMWW prepared as described in WO 2018 / 197234 A1, especially Reference Example 2. The composition of the liquid feed was chosen in such a way that the mixture under the conditions at which it was fed to the reactor was liquid and only one liquid phase was present. The feed preferably flowed in the reactor from bottom to top, to minimize the risk of gas-bubble entrapment in case of excessive HP decomposition.

[0143] A typical feed temperature was about 30°C and the pressure was chosen in such a way, that even if up to 4% of hydrogen peroxide (HP, H2O2) decomposed to O2 this would remain in solution. Usually, A pressure of 23 bar was used. The weight-based ratio of propylene to H2O2 in the feed stream to the main reactor was controlled. Since technical propylene always contains some propane, there was also some propane in this stream with a ratio of propylene to propane of 98:2. The composition of the feed stream was set.

[0144] The following selectivities based on H2O2 were used in all cases: PO (97.45 wt.-%), mono propylene glycol (MPG) (0.6 wt.-%), 02 (0.55 wt.-%), hydroperoxypropanols (0.58 wt.-%, sum of both isomers), acetaldehyde (0.38 wt.-%), propionaldehyde (0.017 wt.-%), acetone (0.008 wt.-%). The difference to 100 wt.-% were polar high boilers, which left the system with the wastewater stream. These minor by-products were not relevant to the present invention. The conversion of H2O2 was set to 95%, based on the amount of H2O2 fed to R1 being 100%. The output of all the main reactor(s) R1 were mixed and after a temperature adjustment to 42°C fed to the finishing reactor R2 (pressure 22 bar).

[0145] The finishing reactor R2 was an adiabatic fixed bed reactor which was filled with the same catalyst as the main reactor. The finishing reactor again converted 95% of the H2O2 contained in its feed. The total conversion of H2O2 after both reactors was thus 99.75%based on the amount of H2O2 fed to R1 being 100%.

[0146] This temperature of the stream S1 leaving the secondary reactor was adjusted to 47°C and the pressure was reduced to 1.3 bar. This stream S1 was then mixed with other streams (liquid from the interstage condensers of C1 (marked as (2) in Fig. 1), non-condensables at the top of T4 (marked as (3) in Fig. 1), non-condensables at the top of T7 (marked as (4) in Fig. 1) and non-condensables at the top of T6 (marked as (6) in Fig. 1)).

[0147] The mixed stream was then fed to the lower section of a combined washing / distillation tower T1, which was operated at a top pressure of 1 bar and a bottom temperature of 69°C. As a washing liquid, a stream taken downstream of the tower T4 was cooled to about 10°C and fed to the upper part of the tower. The composition of the stream, which was taken as a washing liquid, in wt.-% was: acetonitrile (76.4), hydrogen peroxide (0.02), water (22.2), propylene glycol 240389W001

[0148] - 21 -

[0149] (0.19). The gaseous product at the top of tower T 1 had the following composition in wt.-%: acetonitrile (4.7), propylene (88.2), water (0.4), propane (5.6), oxygen (0.6).

[0150] The gaseous product (stream S3) from the top of tower T 1 (marked as (2) in Fig. 1) was then fed to a multi-stage compressor C1 , where it was compressed to 16.7 bar. Any condensate collected in the intermediate cooling between stages was returned to the feed of tower T 1 . After the last compressor stage, the stream had a pressure of 16.7 bar and a temperature of 108°C. After cooling, the stream partly condensed. The condensed stream (stream S3COnd ), which contained in wt.-% propylene (87.9), propane (6.1), acetonitrile (5.0), was fed to the entrance of the decanter D1.

[0151] The condensation temperature was chosen in such a way that the non-condensed stream S3gase0Us, which contained propylene and O2 stayed well away from the explosible range. For the simulation, a condensation temperature of 38°C was set, leading to the following composition of the gas stream in wt.-%: propylene (89.7), propane (5.8), oxygen (2.0).

[0152] This stream S3gase0Us then went to the propene / propane separation section which used an extractive distillation setup (towers T2 and T3) with acetonitrile as solvent. The gas stream was first diluted with an inert gas, in this case a mixture of indicated in wt.-% N2 (80) and methane (20). The mixed stream was fed to the lower part of absorption tower T2, which was operated at 14 bar and a bottoms temperature of 80°C. To the top of the tower acetonitrile recycled from tower T2 was fed as extracting agent.

[0153] The bottoms of tower T2 contained the propylene dissolved in acetonitrile. The stream S7 was then fed to tower T3, which was operated at 12.5 bar and a bottoms temperature of 185°C to recover the propylene over top and the acetonitrile as the bottoms stream. The bottoms stream S9 contained acetonitrile and a trace of propylene. Before it was fed back to tower T2 make-up acetonitrile was added as required to compensate for the acetonitrile leaving the section with the overhead product.

[0154] The overhead product of tower T3 (stream S8) was then cooled down and condensed at 28°C. The uncondensable stream, which still contained in wt.-% mainly propylene (95.0), with some propane (2.7) and CO2 (1.5) was taken off and was disposed by incineration to avoid build-up of CO2. The condensed product separated into two liquid phases, of which the lower phase consisted in wt.-% mostly of water (99.0). This was disposed in the wastewater treatment system. The upper phase was partly returned to the tower as reflux (reflux ratio = 1 .3) and the remainder was fed to the entrance of the decanter D1 . The composition of this stream was as follows in wt.-%: propylene (96.0), propane (3.0), acetonitrile (0.5).

[0155] Going back to tower T1 , the bottoms product of this tower, stream S2, had the following composition in wt.-%: acetonitrile (69.0), water (20.0), propylene oxide (9.7), propylene glycol (0.2) and traces of other by-products like acetaldehyde, propionaldehyde, acetone, formaldehyde hydroperoxypropanols, and others in very small amounts (each was less than 0.1). This stream was mixed with the bottoms product of tower T5 (see below) and fed to tower T4. Tower T4 had 99 theoretical separation stages and was operated at a pressure of 0.5 bar and a bottom temperature of 61 °C and a reflux ratio of 0.8. Feeding point was at stage 55 counted from the top. At stage 43 (counted from the top) there was a side draw to remove a very small stream of intermediate boilers (shown as IB in Fig. 1). This stream had the following composition in wt.-%: propylene oxide (77.7), propionaldehyde (17.8), acetonitrile (3.3), water (1.2) and traces of acetone. This stream was discarded. 240389W001

[0156] - 22 -

[0157] The top stream of tower T4 was feed to a vapor recompression, which also provided most of the energy for the sump evaporator. The top product had the following composition in wt.-%: propylene oxide (99.79), acetaldehyde (0.15) and propylene (0.04).

[0158] This stream was fed to tower T5 with 54 theoretical separation stages, operated at 2.9 bar and a bottoms temperature of 68.5°C. Feed point was at stage 21 (counted from the top) and pure propylene oxide was taken as a side draw at stage 52. The obtained propylene oxide in stream S4 had a purity of 99.9985%. The bottoms product, which still contains mostly pure propylene oxide was fed back to tower T4. The top product of tower T5 (marked as LB for light boilers in Fig. 1), which consisted in wt.-% of propylene oxide (27.2), propylene (13.4), acetaldehyde (50.3) and formaldehyde (8.8) was disposed by incineration.

[0159] The bottoms product of tower T4, stream S5, had the following composition in wt.-%: acetonitrile (76.4), water (22.2), propylene glycol (0.2), hydroperoxypropanols (0.1), hydrogen peroxide (ca. 200 ppm) but essentially no propylene oxide. If required a part of this stream (usually less than 10%) can be detoured and passed to a purification tower to remove unpolar high boilers, like those usually contained as an impurity in technical hydrogen peroxide solutions and stemming from the working solution used in the H2O2 process. Examples of such compounds are for instance trioctyl phosphate, tetrabutyl urea, 2-methylcyclohexyl acetate, diisobutyl carbinol, C9-C10 aromatics hydrocarbons, or degradation and oxidation products therefrom. For this simulation, this tower was not included, and it is also not shown in Fig. 1 . Part of this stream was taken off and cooled to 10°C to be used as washing solvent in tower T 1 (marked as (1) in Fig. 1). The remainder was combined with the liquid stream at the top of tower T7 (marked as (5) in Fig. 1) and fed to the decanter D1 . The condensate stream after compressor C1 , the recovered propylene from the top of tower T3, the liquid top product of tower T6 and the fresh polymer grade propylene, all of which consisted mainly of propylene were mixed to obtain a stream with the following composition in wt.-%: propylene (74.1), propane (22.4), acetonitrile (1.2) and water (0.4). The stream was also fed to the decanter D1. Decanter D1 was operated at 15°C and 16 bar. The mixed feed of decanter D1 separated into two liquid phases which were removed separately from the decanted.

[0160] The lower liquid aqueous phase LAP taken from decanter D1 had the following composition in wt.-%: water (78.3), acetonitrile (19.9), propylene glycol (0.4), hydroperoxypropanols (0.25) and other polar by-products. This stream LAP was fed to tower T7, which was operated at 1 .5 bar and a sump temperature of 116°C. In this tower acetonitrile was recovered at the top as azeotrope with water with the following composition in wt.-%: acetonitrile (78.5), water (19.7) and returned to the decanter D1 (marked as (5) in Fig. 1). Uncondensable material at the top of the tower (marked as (4) in Fig. 1) is returned to the feed side of tower T 1 . The bottoms product of T7 contained in wt.-% water (98.7), propylene glycol (0.6), hydroperoxypropanol (0.3) and potassium formate (0.14), along with other polar by-products. This stream was cooled down and sent to the wastewater treatment station.

[0161] The upper liquid organic phase LOP from decanter D1 had the following composition: propylene (35.6), propane (10.7), acetonitrile (49.4), water (2.6). This was fed to tower T6, which had 5 theoretical separation stages, and was operated at 19 bar. The bottoms product of this tower, stream S10, was the recycled acetonitrile stream which was fed back to the reaction stage. The conditions in the tower (i.e. the energy input to the sump and associated sump temperature) were chosen in such a way that the amount of propylene required for the reaction remained dissolved 240389W001

[0162] - 23 - in the sump stream. When the sump temperature was set to 100.5°C the sump had the following composition in wt- %: acetonitrile (78.7), water (3.9), propylene (15.6) Enough fresh acetonitrile was added through the stream marked ACN in Fig. 1 to compensate for the losses of acetonitrile in streams leaving the process. This stream was then recycled back to the reactor, if necessary acetonitrile as solvent make-up was added and the stream was divided among the reactors R1 a,b,c, ...x and to each reactor feed 40% hydrogen peroxide solution and a 2.5% aqueous solution of potassium formate (w / w) were added to generate the reactor feed described at the beginning.

[0163] Comparative Example 1 : aqueous H2O2 solution having 40 weight-% of H2O2

[0164] A process for propylene oxide preparation was simulated as described in Reference Example 1 with an aqueous H2O2 solution having 40 weight-% of H2O2, wherein the pre-mixed feed stream had a composition as indicated in Table 1 . The weight-based ratio of propylene to H2O2 in the feed stream to the main reactor was controlled to be as indicated in Table 1. Further details including concentrations, ratios and energy required are also indicated in Table 1.

[0165] Example 1 : aqueous H2O2 solution having 50 weight-% of H2O2

[0166] A process for propylene oxide preparation was simulated as described in Reference Example 1 with an aqueous H2O2 solution having 50 weight-% of H2O2, wherein the pre-mixed feed stream had a composition as indicated in Table 1 . The weight-based ratio of propylene to H2O2 in the feed stream to the main reactor was controlled to be as indicated in Table 1. Further details including concentrations, ratios and energy required are also indicated in Table 1.

[0167] Example 2: aqueous H2O2 solution having 42 weight-% of H2O2

[0168] A process for propylene oxide preparation was simulated as described in Reference Example 1 with an aqueous H2O2 solution having 42 weight-% of H2O2, wherein the pre-mixed feed stream had a composition as indicated in Table 1 . The weight-based ratio of propylene to H2O2 in the feed stream to the main reactor was controlled to be as indicated in Table 1. Further details including concentrations, ratios and energy required are also indicated in Table 1.

[0169] Example 3: aqueous H2O2 solution having 45 weight-% of H2O2

[0170] A process for propylene oxide preparation was simulated as described in Reference Example 1 with an aqueous H2O2 solution having 45 weight-% of H2O2, wherein the pre-mixed feed stream had a composition as indicated in Table 1 . The weight-based ratio of propylene to H2O2 in the feed stream to the main reactor was controlled to be as indicated in Table 1. Further details including concentrations, ratios and energy required are also indicated in Table 1.

[0171] Comparative Example 2: aqueous H2O2 solution having 50 weight-% of H2O2 without adjustment of weight-based ratio ACN:H2O2 240389W001

[0172] - 24 -

[0173] A process for propylene oxide preparation was simulated as described in Reference Example 1 with an aqueous H2O2 solution having 50 weight-% of H2O2, wherein the pre-mixed feed stream had a composition as indicated in Table 1 . The weight-based ratio of propylene to H2O2 in the feed stream to the main reactor was controlled to be as indicated in Table 1. Further details including concentrations, ratios and energy required are also indicated in Table 1.

[0174] Table 1

[0175] * the residual amount from the sum of ACN, H2O2, water and propylene up to the value indicated for the total stream comprises additive, propane and side product(s) such as propionaldehyde.

[0176] The total power indicated in Table 1 represents the overall amount of energy required, including the required electricity and heating steam.

[0177] Using an aqueous solution comprising hydrogen peroxide in a concentration (CH202) in the range of from 42 to 50 weight-% in combination with using a weight-based ratio ACN:H2O2 in a specific range enabled to carry out the complete process more efficiently in view of energy consumption, i.e. it enables saving of energy compared to, for example, using an aqueous hydrogen peroxide in a concentration of 40 weight-%; reference is made to the total power values indicated in Table 1 above. On the other hand, using a concentration of H2O2 of 50 weight-% and not having regard to the weight-based ratio ACN:H2O2 increases the overall energy demand (see Comparative Example 2).

[0178] Short description of the Figure

[0179] Fig. 1 shows a scheme of the process described in Reference Example 1 .

[0180] Cited Literature 240389W001

[0181] - 25 -

[0182] - WO 2022 / 268859 A1

[0183] Ullmann's Encyclopedia of Industrial Chemistry, 5th edition, volume A 13 (1989) pages 443-466

[0184] - WO 2015 / 0493279 A1 - WO2023 / 117360 A1

[0185] - EP 1 122 249 A1

[0186] - WO 2015 / 049327 A1

Claims

240389W001- 26 -Claims1 . A process for preparing propylene oxide, the process for preparing propylene oxide comprising a) providing propene, propane, water, hydrogen peroxide and acetonitrile to an epoxidation zone comprising a heterogeneous epoxidation catalyst, thereby obtaining a mixture comprising propene, propane, water and acetonitrile; b) contacting the mixture comprising propene, water and acetonitrile in the epoxidation zone with the heterogeneous epoxidation catalyst under epoxidation conditions, thereby obtaining a mixture comprising propylene oxide, propene, propane, water and acetonitrile; wherein: i) the hydrogen peroxide in a) is provided as an aqueous solution comprising hydrogen peroxide in a concentration (CH202) in the range of from 42 to 50 weight-% based on the total weight of the aqueous solution being 100 weight-%; ii) the acetonitrile (ACN) and the aqueous solution comprising hydrogen peroxide (H2O2aq.) are provided in a) to the epoxidation zone in a weight-based ratio ACN:H2C>2 in the range of from Xi to X2, wherein Xi is calculated based on equation 1 and X2 is calculated based on equation 2:Xi = 13.6 - (0.135 x CH202) equation 1X2= 14.8 - (0.135 x CH202) equation 2, wherein CH202 is the concentration at which the aqueous solution comprising hydrogen peroxide is provided in weight-%; wherein the process further comprises: c) removing an effluent stream S1 from the epoxidation zone, the effluent stream comprising propylene oxide, propene, propane, water and acetonitrile; d) separating propene and propane from the effluent stream S1 removed in step c) by washing and distillation, thereby obtaining a stream S2 enriched in propylene oxide, water and acetonitrile compared to the effluent stream removed in step c); and a stream S3 enriched in propene and propane compared to the effluent stream removed in step c); wherein the process further comprises: e.1) separating the stream S2 enriched in propylene oxide, water and acetonitrile obtained in step d) by one or more distillations, thereby obtaining a stream S4, which comprises more than 99 wt.-% of propylene oxide based on the total weight of the stream S4, a stream S5 comprising acetonitrile and water and a stream S6 comprising propene; f) mixing the stream comprising acetonitrile and water obtained in step e.1) or in step e.

1. a) and at least a stream comprising propene under phase separation conditions, thereby obtaining a liquid aqueous phase LAP comprising water and a liquid organic phase LOP comprising acetonitrile and propene,240389W001- 27 - g) subjecting the liquid organic phase LOP comprising acetonitrile and propene obtained in step f) to distillation, thereby obtaining a liquid bottoms stream S10 comprising acetonitrile and propene and a gaseous top stream comprising propene; h) recycling the liquid bottoms stream S10 comprising acetonitrile and propene obtained in step g) into step a).

2. The process of claim 1 , wherein Xi is calculated based on equation 1.1 and X2 is calculated based on equation 2.1 :Xi = 13.8 — (0.135 x CH202) equation 1 .1X2= 14.6 - (0.135 x CH202) equation 2.1 , wherein CH202 is the concentration at which the aqueous solution comprising hydrogen peroxide is provided in weight-%3. The process of claim 1 or 2, wherein propene is provided in a) in a weight-based ratio propene: H2O2 in the range of from 1 :2 to 2:1 , preferably in the range of from 1.2:1 to 2.2:1 , more preferably in the range of from 1.5:1 to 1.9:1.

4. The process of any one of claims 1 to 3 comprising e.2) separating propane from the stream S3 enriched in propene and propane obtained in d) in a separation zone, comprising subjecting the stream enriched in propene and propane obtained in d) to washing conditions in a scrubber, wherein a solvent mixture comprising acetonitrile and water is added as entraining agent, obtaining a liquid bottoms stream S7, which comprises acetonitrile, water and at least 70 weight-% of the propene comprised in the steam S3 enriched in propene and propane obtained in d); and a gaseous top stream S8, which comprises at least 5 weight-% of the propane comprised in the stream S3 enriched in propene and propane obtained in d).

5. The process of any one of claims 1 to 4, wherein e.1) comprises e.1.a) feeding the stream S2 enriched in propylene oxide, water and acetonitrile obtained in d) into a distillation tower, obtaining, preferably as bottom stream, a stream S5 comprising acetonitrile and water and being depleted of propylene oxide compared to the stream obtained in d) and a stream, preferably a top stream, enriched in propylene oxide compared to the stream obtained in d); e.1 b) feeding the stream enriched in propylene oxide obtained in e.1 a) into a further distillation tower, obtaining a stream S4 enriched in in propylene oxide compared to the stream obtained in e.1 a), preferably as a side stream, said stream enriched in in propylene oxide comprising more than 99 wt.-%, preferably more than 99.9 wt.-%, more preferably more than 99.99 wt.-%, of propylene oxide based on the total weight of the stream S4.240389W001- 28 -6. The process of claim 4 or 5, wherein e.2) comprises e.

2. a) feeding stream S3 enriched in propene and propane obtained in d) and having a pressure ps3 into a compression unit, wherein the pressure is increased to ps3comPwith ps3comP> Ps3, followed by partial condensation, obtaining a condensed part stream S3COnd and a non-condensed part stream S3gase0Us of S3, condensed part stream S3COnd comprising propene and propane and the non-condensed part stream S3gase0Us comprising propene and propane.

7. The process of any one of claims 4, 5 or 6, wherein e.2) further comprises e.2.b) feeding the non-condensed part stream S3gase0Us obtained in e.

2. a) into a scrubber, optionally with addition of an inert gas, and subjecting S3gase0Us to washing conditions in the scrubber, wherein a solvent mixture comprising acetonitrile and water is introduced as entraining agent into the scrubber, preferably to the upper part of the scrubber; thereby obtaining a liquid bottoms stream S7, which comprises acetonitrile, water and propene; and e.2.c) feeding the bottom stream comprising propene and acetonitrile into a distillation tower, from which a gaseous top stream S8 and a liquid bottoms stream S9 are obtained, wherein liquid bottoms stream S9 comprises acetonitrile and gaseous top stream S8 comprises at least 5 weight-% of the propane comprised in the stream S3 enriched in propene and propane obtained In d).

8. The process of any one of claims 1 to 7, wherein in a), additionally an additive is provided to the epoxidation zone, wherein the additive comprises at least one potassium salt selected from the group consisting of at least one inorganic potassium salt, at least one organic potassium salt, and mixtures of at least one inorganic potassium salt and at least one organic potassium salt; preferably selected from the group consisting of at least one inorganic potassium salt selected from the group consisting of potassium hydroxide, potassium chloride, potassium nitrate, potassium hydrogen phosphate, potassium dihydrogen phosphate, at least one organic potassium salt selected from the group consisting of potassium formate, potassium acetate, potassium carbonate, and potassium hydrogen carbonate, and mixtures of at least one of the at least one inorganic potassium salts and at least one of the at least one organic potassium salts, more preferably, the additive is selected from the group consisting of potassium dihydrogen phosphate, dipotassium hydrogen phosphate potassium formate and mixtures of two or more thereof; more preferably the additive comprises at least potassium formate, more preferably the additive is potassium formate.

9. The process of any one of claims 1 to 8, wherein:1.1) the hydrogen peroxide in a) is provided as an aqueous solution comprising hydrogen peroxide in a concentration (CH202) in the range of from 43 to 50 weight-%, preferably in the range of from 45 to 50 weight-%, based on the total weight of the aqueous solution being 100 weight-%.240389W001- 29 -10. A mixture, preferably for preparation of propylene oxide, comprising propene, water, hydrogen peroxide and acetonitrile, wherein the acetonitrile (ACN) and the hydrogen peroxide (H2O2) are present in a weight-based ratio ACN:H2C>2 in the range of from Xi to X2, wherein Xi is calculated based on equation 1 and X2 is calculated based on equation 2:Xi = 13.6 - (0.135 x CH202) equation 1X2 = 14.8 - (0.135 x CH202) equation 2, wherein CH202 is the concentration at which the aqueous solution comprising hydrogen peroxide is provided in weight-%.11 . The mixture of claim 10, wherein Xi is calculated based on equation 1.1 and X2 is calculated based on equation 2.1 :Xi = 13.8 - (0.135 x CH202) equation 1 .1X2 = 14.6 - (0.135 x CH202) equation 2.1 , wherein CH202 is the concentration at which the aqueous solution comprising hydrogen peroxide is provided in weight-%.

12. Use of a mixture according to claim 10 or 11 for preparation of propylene oxide, preferably by heterogeneous catalysis, more preferably in a process according to any one pf claims 1 to 8.

13. A method for preparing propylene oxide, wherein the mixture of claim 10 or 11 is brought into contact with a heterogeneous catalyst under epoxidation conditions.

14. Propylene oxide, obtained or obtainable from a process according to any one of claims 1 to 8 or from the method of claim 13.

Images