A strongly hydrophobic basic ionic liquid and a preparation method and application thereof in tert-butyl hydroperoxide deacidification

Abstract

The application discloses a strong hydrophobic basic ionic liquid and a preparation method and application thereof in tert-butyl hydroperoxide deacidification, and particularly relates to a strong hydrophobic basic ionic liquid which is alkylamino functionalized and has a long-chain alkyl group. The ionic liquid can be used in PO / MTBE process and removal of organic acids such as formic acid and isobutyric acid in an oxidation reaction liquid containing tert-butyl hydroperoxide. The application can effectively remove acid impurities in TBHP, improve the selectivity of a downstream reaction, and thus improve the atomic utilization rate and production capacity of a device.

Description

Technical Field

[0001] This invention relates to a strongly hydrophobic alkaline ionic liquid and its preparation method, as well as a method for deacidifying tert-butyl hydrogen peroxide during the preparation of propylene oxide, specifically a method for deacidifying tert-butyl hydrogen peroxide (TBHP) in the process of preparing propylene oxide from isobutane, belonging to the field of organic chemical engineering. Background Technology

[0002] Propylene oxide (PO), also known as methyl ethylene oxide or propylene oxide, is a colorless, flammable liquid with an ether-like odor. It is an important organic chemical raw material, primarily used in the production of polyether polyols, propylene glycol, and dimethyl carbonate, and also in the manufacture of surfactants, pharmaceuticals, pesticides, and fragrances. Currently, there are three production processes for propylene oxide: the chlorohydrin process, the co-oxidation process, and the direct oxidation process. Due to environmental concerns, the chlorohydrin process is gradually being phased out; the direct oxidation process is also limited in its development due to hydrogen peroxide transportation issues; the co-oxidation process, also known as the indirect oxidation process, mainly involves the reaction of peroxides produced by the peroxidation reaction with propylene to generate PO. The co-oxidation process is further divided into isobutane co-oxidation (PO / TBA(MTBE)), ethylbenzene co-oxidation (PO / SM), and cumene co-oxidation (POCHP), which have received widespread attention due to their environmental friendliness and production flexibility.

[0003] Compared to the POCHP and PO / SM processes, the PO / MTBE process has lower carbon atom utilization and is less economical. One key factor is the high acid content in the TBHP produced by peroxidation, which leads to increased side reactions in the downstream epoxidation reaction and reduced PO selectivity. Although peroxidation reactions always produce organic acids as byproducts, the peroxides produced by the PO / SM and POCHP processes are hydrophobic. Therefore, the technical routes are designed with alkaline washing and water washing to remove the acid from the peroxides. However, the peroxide TBHP and impurity organic acids produced by the PO / MTBE process are hydrophilic, making the same treatment methods unsuitable. Patent CN 112375025 A points out that the acid in TBHP promotes the ring-opening reaction of epoxides, which is detrimental to reaction selectivity. Therefore, an azeotropic distillation method is designed to concentrate and purify the peroxidation reaction solution, followed by further deep acid removal using molecular sieves. However, this method has problems such as limited adsorption capacity of the adsorbent, large volume of adsorbent required for industrial application, and difficulties in regeneration and solid waste treatment.

[0004] Patent document US 5093506 discloses a method to reduce the acid value of a TBHP solution by adding a certain amount of calcium hydroxide to the solution. However, this method has a long reaction time, requiring tens of hours, and the solids in the product are difficult to separate.

[0005] Therefore, it is necessary to find an effective method for the deacidification of tert-butyl hydroperoxide to inhibit the formation of epoxidation byproducts and improve reaction selectivity, which is of great significance for improving the production capacity of the plant and reducing material consumption. Summary of the Invention

[0006] In view of this, one of the objectives of this invention is to provide a strongly hydrophobic basic ionic liquid and its preparation method, specifically a strongly hydrophobic basic ionic liquid functionalized with alkylamine and having a long-chain alkyl group. This ionic liquid can be used in the PO / MTBE process for the removal of organic acids such as formic acid and isobutyric acid from the peroxide reaction solution containing per-tert-butyl hydroperoxide (TBHP).

[0007] A second objective of this invention is to provide a method for removing tert-butyl hydroperoxide (TBHP) during the co-oxidation of isobutane to propylene oxide. This invention involves thoroughly mixing a strongly hydrophobic basic ionic liquid with a hydrophilic peroxide reaction solution containing TBHP. The ionic liquid reacts with organic acids such as formic acid and isobutyric acid in the reaction solution. Separation from the original system is achieved by grafting the organic acids onto the basic ionic liquid matrix. Simultaneously, the separated ionic liquid can be recycled. This effectively removes acidic impurities from TBHP, improves the selectivity of downstream reactions, and thus enhances the atom utilization and production capacity of the apparatus.

[0008] To achieve the above objectives, the technical solution of the present invention is as follows:

[0009] In a first aspect, the present invention provides a strongly hydrophobic alkaline ionic liquid, the preparation method of which includes the following steps:

[0010] (1) A short-chain alcohol, a haloalkylamino hydrohalide, and a long-chain alkyl-substituted imidazole were mixed and reacted under a nitrogen atmosphere. Then, an alkaline solution was added to the reaction solution to adjust the pH to 8-9. The mixture was cooled and crystallized. After filtration, 1-alkylamino-4-alkyl-imidazolium hydrohalide (abbreviated as [AmiAlk-IM]Br) was obtained.

[0011] (2) The 1-alkylamino-4-alkyl-imidazolium hydrohalate prepared in step (1) is mixed with sodium hexafluorophosphate (NaPF6) and an alcohol solvent to carry out an ion exchange reaction to obtain a strongly hydrophobic basic ionic liquid (containing the strongly hydrophobic anion PF6). - The ionic liquid [AmiAlk-IM]PF6).

[0012] In some specific examples, the short-chain alcohol in step (1) has 1 to 4 carbon atoms, preferably ethanol, methanol, or propanol.

[0013] In some specific examples, the long-chain alkyl-substituted imidazole in step (1) is selected from alkyl-substituted imidazoles with a chain length of C6-C20, such as alkyl-substituted imidazoles with chain lengths of C6, C8, C10, C12, C14, C16, C18, and C20, preferably one or more of tetradecyl imidazole, hexadecyl imidazole, octadecyl imidazole, and eicosyl imidazole, more preferably one or more of hexadecyl imidazole and octadecyl imidazole.

[0014] In some specific examples, the haloalkylamino hydrohalate in step (1) is selected from halolinear alkylamino hydrohalates with a chain length of C2-C8, preferably brominated linear alkylamino hydrohalates with a chain length of C2-C8, such as halolinear alkylamino hydrohalates with a chain length of C2, C3, C4, C5, C6, C7, and C8, more preferably one or more of 2-bromoethylamine hydrobromide, 3-bromopropylamine hydrobromide, and 4-bromobutylamine hydrobromide, and even more preferably one or more of 3-bromopropylamine hydrobromide and 4-bromobutylamine hydrobromide.

[0015] In some specific examples, the mass ratio of the long-chain alkyl-substituted imidazole to the haloalkylamino hydrohalide in step (1) is 1:0.1 to 5, for example 1:(0.1, 0.2, 0.4, 0.6, 0.8, 1.0, 1.5, 2.0, 2.5, 3.0, 4.0, 5.0), preferably 1:0.4 to 2.

[0016] In some specific examples, the mass ratio of the long-chain alkyl-substituted imidazole to the short-chain alcohol in step (1) is 1:4 to 20, for example 1:(4, 6, 8, 10, 12, 14, 16, 18, 20), preferably 1:8 to 15.

[0017] In some specific examples, the reaction described in step (1) is carried out at a temperature of 20–70°C, for example, 20°C.

[0018] 30℃, 40℃, 50℃, 60℃, 70℃, preferably 50~70℃, for 8~24h, e.g., 8h.

[0019] 12h, 16h, 20h, 24h, with 12-20h being the preferred option.

[0020] In some specific examples, the alkaline solution in step (1) is one or more of sodium hydroxide solution, potassium hydroxide solution, and ammonia water, preferably one or more of sodium hydroxide solution and potassium hydroxide solution;

[0021] Preferably, the alkaline solution is selected from aqueous solutions of alkali, with a concentration of 0.01–1 mol / L, for example, 0.01 mol / L, 0.05 mol / L, 0.1 mol / L, 0.2 mol / L, 0.4 mol / L, 0.6 mol / L, etc.

[0022] 0.8 mol / L, 1.0 mol / L, preferably 0.04–0.08 mol / L.

[0023] In some specific examples, the cooling crystallization in step (1) is performed at a temperature of -2 to -20°C, for example, -2°C, -4°C, -8°C, -12°C, -16°C, or -20°C, preferably -8 to -15°C; and for a time of 8 to 30 hours, for example, 8 hours, 15 hours, 20 hours, 25 hours, or 30 hours, preferably 14 to 20 hours.

[0024] In some specific examples, the mass ratio of 1-alkylamino-4-alkyl-imidazolium hydrohalate to sodium hexafluorophosphate in step (2) is 1:0.1 to 2, for example 1:(0.1, 0.2, 0.4, 0.6, 0.8, 1.0, 1.5, 2.0), preferably 1:0.4 to 1.5.

[0025] In some specific examples, the alcohol solvent in step (2) is selected from C1 to C3 alcohols, preferably ethanol and methanol;

[0026] Preferably, the mass ratio of the 1-alkylamino-4-alkyl-imidazolium hydrohalate to the alcohol solvent is 1:6 to 30, for example, 1:(6, 10, 15, 20, 25), more preferably 1:12 to 25.

[0027] In some specific examples, the ion exchange reaction in step (2) is carried out at a temperature of 20 to 70°C, for example, 20°C, 30°C, 40°C, 50°C, 60°C, or 70°C, preferably 50 to 70°C, and for a time of 4 to 10 hours, for example, 4 hours, 6 hours, 8 hours, or 10 hours, preferably 5 to 8 hours.

[0028] In some specific examples, after the reaction in step (2) is completed, post-processing processes such as evaporation and water washing are also included. These are all conventional operations in the field and are not particularly required by the present invention. For example, in some specific examples, the reaction solution can be rotary evaporated to remove the solvent ethanol, and then NaPF6 can be removed by water washing to obtain the strongly hydrophobic alkaline ionic liquid [AmiAlk-IM]PF6.

[0029] Secondly, the present invention provides the application of the above-mentioned strongly hydrophobic alkaline ionic liquid in removing acidic impurities from materials, which is applicable to the removal of acidic impurities in the propylene oxide preparation process, and especially applicable to the removal of acidic impurities in the peroxide TBHP in the process of isobutane co-oxidation to prepare propylene oxide (PO / MTBE).

[0030] The acidic impurities include aliphatic organic mono- and poly-acids and aromatic organic mono- and poly-acids, such as formic acid, acetic acid, oxalic acid, isobutyric acid, benzoic acid, phenylacetic acid, isophthalic acid, etc.

[0031] In this invention, the above-mentioned strongly hydrophobic alkaline ionic liquid is mixed with the peroxide reaction solution in the PO / MTBE process. The acidic impurities such as formic acid and isobutyric acid contained in the material are coupled with the alkaline nitrogen on the parent ionic liquid, which further enhances the hydrophobicity of the ionic liquid. The two phases are obtained by phase separation: the deacidified peroxide reaction solution and the ionic liquid after coupling with acidic impurities. The former is sent to the TBHP concentration unit, and the latter is recycled after strong alkali treatment.

[0032] Preferably, the present invention provides a method for deacidification of tert-butyl hydroperoxide (TBHP) during the co-oxidation of isobutane to prepare propylene oxide, comprising the following steps:

[0033] 1) The peroxide reaction solution from the process of preparing propylene oxide from isobutane co-oxidation is mixed with a strongly hydrophobic basic ionic liquid and reacted to attach the acidic impurities in the solution to the ionic liquid.

[0034] 2) Separate the reaction material obtained in step 1) to obtain a tert-butyl hydrogen peroxide solution after removing acid impurities from the upper layer, which will then enter the subsequent tert-butyl hydrogen peroxide concentration process. The lower layer will obtain an ionic liquid connected to the acid impurities.

[0035] In some preferred embodiments, the method further includes step 3), mixing the ionic liquid with acidic impurities obtained in step 2) with an alkaline solution, stirring to carry out the reaction, then separating the phases, taking off the lower layer of liquid, and obtaining a recovered strongly hydrophobic alkaline ionic liquid phase, which is then returned to step 1) for recycling.

[0036] In some specific examples, the peroxide reaction solution in step 1) comprises, by mass percentage, 40-60% tert-butanol, 40-60% tert-butyl hydroperoxide, 1-4% acetone, 0.4%-1.2% water, and 0.6-1.5% acidic impurities; wherein the acidic impurities include 0.3-0.8% isobutyric acid, 0.2-0.4% formic acid, and 0.1-0.3% acetic acid.

[0037] The peroxide reaction solution from the process of preparing propylene oxide by co-oxidation of isobutane described in this invention is prepared by reacting isobutane with oxygen. This process is existing technology, and this invention does not have specific requirements for it. It can be prepared by any isobutane co-oxidation method (PO / TBA(MTBE)).

[0038] In some specific examples, the mass ratio of the strongly hydrophobic alkaline ionic liquid to the peroxide reaction solution in step 1) is 1:2 to 20, for example 1:(2, 6, 10, 14, 18, 20), preferably 1:10 to 15.

[0039] In some specific examples, the reaction described in step 1) is carried out at a temperature of 60–90°C, for example, 60°C, 70°C, 80°C, or 90°C, preferably 75–85°C;

[0040] Preferably, the total volume hourly space velocity (VHSV) of the strongly hydrophobic alkaline ionic liquid and the peroxide reaction solution in the feed is 1–8 h⁻¹. -1 For example, 1h -1 3h -1 5h -1 8h -1 Preferably 2.0 to 4.0 hours -1 .

[0041] In some specific examples, the peroxide reaction solution described in step 1) is mixed with the strongly hydrophobic alkaline ionic liquid using a static mixer;

[0042] Preferably, the mixing unit of the static mixer is made of carbon steel, stainless steel, PVC, etc., with stainless steel and PVC being the most preferred.

[0043] In some specific examples, the post-reaction material described in step 2) enters a coalescer for phase separation;

[0044] Preferably, the coalescer is equipped with stainless steel corrugated plate coalescing packing, and the packing thickness is 20-120mm, for example, 20mm, 60mm, 100mm, 120mm, preferably 50-100mm; it can coalesce small droplets with a particle size >25μm in the material into large droplets, thereby achieving phase separation;

[0045] Preferably, the phase separation temperature is 30-60℃, for example 30℃, 40℃, 50℃, 60℃, more preferably 40-50℃; the time is 6-30min, for example 6min, 10min, 15min, 20min, 25min, 30min, more preferably 15-21min.

[0046] In some specific examples, the alkaline solution in step 3) is selected from one or more of sodium hydroxide solution, potassium hydroxide solution, and ammonia water, preferably one or more of sodium hydroxide solution and potassium hydroxide solution;

[0047] Preferably, the alkaline solution is selected from an aqueous solution of alkali, with a concentration of 0.01 to 1 mol / L, for example...

[0048] 0.01mol / L, 0.05mol / L, 0.1mol / L, 0.2mol / L, 0.4mol / L, 0.6mol / L,

[0049] 0.8 mol / L, 1.0 mol / L, preferably 0.04–0.08 mol / L;

[0050] Preferably, the amount of alkali solution added is such that the pH of the system is controlled between 8 and 9.

[0051] In some specific examples, the reaction described in step 3) is carried out at a temperature of 30–80°C, for example, 30°C, 40°C, 50°C, 60°C, 70°C, or 80°C, preferably 50–60°C; and for a time of 0.1–1 h, for example, 0.1 h, 0.3 h, 0.5 h, 0.7 h, or 1.0 h, preferably 0.3–0.5 h.

[0052] In some specific examples, the post-reaction material described in step 3) enters a coalescer for phase separation;

[0053] Preferably, the coalescer is provided with stainless steel corrugated plate coalescing packing, and the packing thickness is 20-120mm, for example 20mm, 60mm, 100mm, 120mm, preferably 50-100mm;

[0054] Preferably, the phase separation temperature is 30-80℃, for example 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, more preferably 50-60℃; and the time is 30-90min, for example 30min, 50min, 70min, 90min, more preferably 42-60min.

[0055] In step 3) of this invention, the acidic impurities attached to the ionic liquid can be dissociated by reacting with alkaline solution, and phase separation is performed. The upper layer is an aqueous phase containing organic acid salts, which is sent to wastewater treatment, and the lower layer is the treated and recovered ionic liquid phase. The recovered strongly hydrophobic alkaline ionic liquid is returned to the front end for recycling.

[0056] In some specific examples, in this invention, the total content of acid impurities in the tert-butyl hydroperoxide (TBHP) feed solution after removing acid impurities is less than 0.4 wt%, preferably 0.1 to 0.25 wt%; more preferably, among the acid impurities, the content of isobutyric acid is less than 0.06 wt%, the content of formic acid is less than 0.04 wt%, and the content of acetic acid is less than 0.02 wt%.

[0057] The TBHP obtained after removing acidic impurities as described above can be used to prepare the final product propylene oxide with a conversion rate of over 99% and a selectivity of over 95%.

[0058] Compared with the prior art, the positive effects of the present invention are as follows:

[0059] This invention provides a strongly hydrophobic alkaline ionic liquid, which is prepared by loading long alkyl chains onto cations and by compounding hydrophobic groups with anions. This alkylamino functionalized strongly hydrophobic alkaline ionic liquid with high asymmetry can be used in the PO / MTBE process to remove acidic impurities such as formic acid and isobutyric acid from the oxidative reaction solution containing TBHP.

[0060] This invention develops a deacidification method for tert-butyl hydrogen peroxide (TBHP) in the process of isobutane co-oxidation to propylene oxide. Taking advantage of the hydrophilicity of both TBHP and organic acids, a strongly hydrophobic alkaline ionic liquid is prepared by loading long alkyl chains onto cations and combining hydrophobic groups with anions. This liquid reacts with acidic impurities such as formic acid and isobutyric acid in TBHP. The organic acids combine with Lewis bases on imidazole to form inner salts on the parent compound. The imidazole head groups and their anions have strong interactions in the crystal lattice, further increasing the hydrophobicity before phase separation. After phase separation, the TBHP-containing material is concentrated downstream, and the ionic liquid is recycled after strong alkali treatment, thereby reducing production costs and waste generation.

[0061] This invention not only effectively removes acidic impurities from the peroxide reaction solution, thereby improving the selectivity and atom utilization of the epoxidation reaction and enhancing economic benefits, but also provides a renewable ionic liquid, making the method more environmentally friendly. Detailed Implementation

[0062] The embodiments of the present invention will be further described in detail below with reference to the examples. All the examples are operated in accordance with the operating conditions of the above technical solutions, but are not limited to the protection of the examples.

[0063] The main raw material sources in the embodiments and comparative examples of this invention are as follows; unless otherwise specified, all other raw materials were obtained through ordinary commercial channels:

[0064] Ethanol: 99.7% purity, purchased from Macklin Reagents Ltd.;

[0065] Methanol: 99.5% purity, purchased from Macklin Reagents Ltd.;

[0066] Propanol: 99.0% purity, purchased from Macklin Reagents Ltd.;

[0067] 1-Hexadecylimidazol: purity 97.0%, purchased from Shanghai Yuanye Biotechnology Co., Ltd.;

[0068] 1-Tetradecylimidazole: purity 97.0%, purchased from Shanghai Yuanye Biotechnology Co., Ltd.;

[0069] 2-Heptadecanylimidazole: 98.0% purity, purchased from Shanghai Yuanye Biotechnology Co., Ltd.;

[0070] 3-Bromopropylamine hydrobromide: 99.0% purity, purchased from Aladdin Reagents Ltd.;

[0071] 2-Bromoethylamine hydrobromide: 99.0% purity, purchased from Aladdin Reagents Ltd.;

[0072] 4-Bromobutylamine hydrobromide: 99.0% purity, purchased from Aladdin Reagents Ltd.;

[0073] Sodium hydroxide: 95.0% purity, purchased from Macklin Reagents Ltd.;

[0074] Sodium hexafluorophosphate: 98.0% purity, purchased from Macklin Reagents Ltd.;

[0075] Sodium monofluorophosphate: purity 95.0%, purchased from Macklin Reagents Ltd.;

[0076] Imidazole: 99.0% purity, purchased from Aladdin Reagents Ltd.;

[0077] The peroxide reaction solution in the examples and comparative examples was prepared by isobutane co-oxidation, which is generated by the reaction of isobutane and oxygen in a bubble reactor at approximately 3.6 MPag and 150°C. Its main components are shown in Table 1.

[0078] Table 1 Composition information of the peroxide reaction solution

[0079] Components Content (wt%) tert-butyl hydroperoxide 49.71 tert-Butanol 45.96 Isobutanol 0.41 acetone 1.91 methanol 0.57 water 0.50 Isobutyric acid 0.46 Formic acid 0.33 Acetic acid 0.15

[0080] The main equipment models used in the embodiments and comparative examples of this invention are as follows:

[0081] Static mixer: made of straight condenser tubes filled with metal packing material. The straight condenser tubes were purchased from Sichuan Shubo Group Co., Ltd., with a specification of 40cm. The metal packing material was purchased from Shanghai Leigu Instrument Co., Ltd., with a specification of φ3.

[0082] Coalescer: Made of straight condenser tubes filled with coalescing packing material. The straight condenser tubes were purchased from Sichuan Shubo Group Co., Ltd., with a specification of 40cm. The coalescing packing material was purchased from Sulzer and is of the type of stainless steel corrugated plate.

[0083] The main analytical instruments used in the embodiments and comparative examples of this invention are as follows:

[0084] Nuclear magnetic resonance (NMR): Fully digital nuclear magnetic resonance spectrometer, model AVANCE III 500, purchased from Bruker GmbH, Switzerland.

[0085] Gas chromatograph: Model 7890B, purchased from Agilent Technologies.

[0086] Example 1

[0087] The steps for preparing a strongly hydrophobic basic ionic liquid are as follows:

[0088] (1) Add 4g of 1-hexadecylimidazolium, 5g of 3-bromopropylamine hydrobromide and 40g of ethanol to a three-necked flask in sequence. Stir the reaction at 65°C for 16h under a nitrogen atmosphere. Then add 0.05mol / L sodium hydroxide aqueous solution to the reaction solution to adjust the pH to 8-9. Then crystallize at -10°C for 16h. Filter to extract the crystallized product to obtain 1-propylamino-4-hexadecylimidazolium hydrobromide.

[0089] Characterization: The chemical shift data δ of the relevant peaks in the 1H NMR spectrum of 1-propylamino-4-hexadecyl-imidazolium hydrobromide are: 1.50 (t, 2H), 2.68 (m, 2H), 2.58 (m, 2H).

[0090] 4.04 (t, 2H), 7.38 (s, 1H), 7.05 (d, 1H), 7.05 (d, 1H), 4.04 (t, 2H), 1.95 (m, 2H), 1.29 (m, 2H), 1.26 (m, 24H), 0.88 (t, 2H). According to the relevant theory of nuclear magnetic resonance spectroscopy, the triplet at chemical shift 1.50 represents the two hydrogen atoms on the amino group; the two quintets and one triplet at 2.68, 2.58, and 4.04 represent the hydrogen atoms on the propylamino group, respectively; the singlet and two doublets at 7.38, 7.05, and 7.05 represent the hydrogen atoms at positions 2, 4, and 5 on the imidazole ring, respectively; and the remaining peaks represent the hydrogen atoms on the hexadecyl group of the imidazole ring. The above nuclear magnetic resonance spectroscopy results show that the shape and number of all peaks in the spectrum are consistent with the molecular structure of 1-propylamino-4-hexadecyl-imidazolium bromide, and no obvious impurities were found. Therefore, the target intermediate was prepared with high purity.

[0091] (2) Add 5g of 1-propylamino-4-hexadecyl-imidazolium hydrobromide, 2.5g of sodium hexafluorophosphate and 60g of ethanol to a three-necked flask and stir until homogeneous. React at 55°C for 7h. After the reaction is complete, remove the solvent ethanol by rotary evaporation and remove the sodium hexafluorophosphate by washing with water to obtain a strongly hydrophobic basic ionic liquid (1-propylamino-4-hexadecyl-imidazolium hexafluorophosphate). The 1H NMR spectrum shows that it has a main chain structure that is basically the same as that of 1-propylamino-4-hexadecyl-imidazolium bromide.

[0092] The deacidification of tert-butyl hydroperoxide (TBHP) during the co-oxidation of isobutane to prepare propylene oxide involves the following steps:

[0093] 1) The peroxide reaction solution from the isobutane co-oxidation process to propylene oxide and the strongly hydrophobic alkaline ionic liquid (1-propylamino-4-hexadecyl-imidazolium hexafluorophosphate) are fed into a static mixer, and the flow rate is adjusted to make the feed mass ratio of the two 13:1 and the total volume hourly space velocity 3h⁻¹. -1The temperature is raised to 80°C to carry out the reaction, causing the acidic impurities to attach to the ionic liquid, and the reacted material is obtained.

[0094] 2) The reacted material is sent to a coalescer for phase separation. The coalescer is equipped with stainless steel corrugated plate coalescing packing with a packing thickness of 75 mm. It is held at 45°C for 18 min. The upper layer is tert-butyl hydrogen peroxide solution after removing acid impurities (the content of each substance in its composition is shown in Table 3). It enters the subsequent tert-butyl hydrogen peroxide concentration process to obtain TBHP. The lower layer is ionic liquid connected to acid impurities.

[0095] 3) The ionic liquid with acidic impurities in the lower layer obtained from the phase separation above is mixed with a 0.06 mol / L sodium hydroxide aqueous solution in a stirred tank. The amount of alkali added is controlled to maintain the pH of the system at 8-9. The reaction is carried out at 55°C for 0.4 h. The reaction solution is then fed into a coalescer for phase separation. The coalescer is equipped with stainless steel corrugated plate coalescing packing with a packing thickness of 75 mm. The reaction is carried out at 55°C for 48 min. After phase separation, the upper layer is saline wastewater, and the lower layer is the recovered ionic liquid, which is returned to the reaction in step 1) for recycling. The content of each substance in the tert-butyl hydrogen peroxide solution obtained after phase separation and removal of acidic impurities during the ionic liquid recycling process is shown in Table 2.

[0096] Table 2 Data on deacidification effect and ionic liquid recycling effect in Example 1

[0097]

[0098] The TBHP obtained after 30 cycles of deacidification treatment with the ionic liquid described above in this invention was further used to prepare the final product propylene oxide. The preparation method was based on section 4.4.4 of the paper "Process for Preparing Propylene Oxide by Co-oxidation of Tert-Butyl Hydrogen Peroxide and Propylene", with a conversion rate of 99.75% and a selectivity of 95.42%.

[0099] Example 2

[0100] The steps for preparing a strongly hydrophobic basic ionic liquid are as follows:

[0101] (1) Add 4g of 1-tetradecylimidazolium, 0.5g of 2-bromoethylamine hydrobromide and 16g of methanol to a three-necked flask in sequence. Stir the reaction at 20°C for 24h under a nitrogen atmosphere. Then add 1mol / L potassium hydroxide aqueous solution to the reaction solution to adjust the pH to 8-9. Then crystallize at -15°C for 8h. Filter to extract the crystallized product to obtain 1-ethylamino-4-tetradecyl-imidazolium hydrobromide.

[0102] (2) Add 5g of 1-ethylamino-4-tetradecyl-imidazolium hydrobromide, 0.5g of sodium hexafluorophosphate and 30g of methanol to a three-necked flask and stir thoroughly. React at 20°C for 10h. After the reaction is complete, remove the solvent methanol by rotary evaporation and remove the sodium hexafluorophosphate by washing with water to obtain a strongly hydrophobic basic ionic liquid (1-ethylamino-4-tetradecyl-imidazolium hexafluorophosphate).

[0103] The deacidification of tert-butyl hydroperoxide (TBHP) during the co-oxidation of isobutane to prepare propylene oxide involves the following steps:

[0104] 1) The peroxide reaction solution from the isobutane co-oxidation process to propylene oxide and the strongly hydrophobic alkaline ionic liquid (1-ethylamino-4-tetradecyl-imidazolium hexafluorophosphate) are fed into a static mixer, and the flow rate is adjusted to make the feed mass ratio of the two 20:1 and the total volume hourly space velocity 1 h⁻¹. -1 The temperature is raised to 60°C to carry out the reaction, causing the acidic impurities to attach to the ionic liquid, and the reacted material is obtained.

[0105] 2) The reacted material is sent to a coalescer for phase separation. The coalescer is equipped with stainless steel corrugated plate coalescing packing with a packing thickness of 20 mm. It is held at 30°C for 30 min. The upper layer is tert-butyl hydrogen peroxide solution after removing acid impurities (the content of each substance in its composition is shown in Table 3). It enters the subsequent tert-butyl hydrogen peroxide concentration process to obtain TBHP. The lower layer is ionic liquid connected to acid impurities.

[0106] The deacidified TBHP was then used to prepare the final product propylene oxide, with a conversion rate of 99.51% and a selectivity of 95.12%.

[0107] Example 3

[0108] The steps for preparing a strongly hydrophobic basic ionic liquid are as follows:

[0109] (1) Add 4g of 2-heptadecylimidazolium, 20g of 4-bromobutylamine hydrobromide and 80g of propanol to a three-necked flask in sequence. Stir the reaction at 70°C for 8h under a nitrogen atmosphere. Then add 0.01mol / L potassium hydroxide aqueous solution to the reaction solution to adjust the pH to 8-9. Then crystallize at -8°C for 30h. Filter to extract the crystallized product to obtain 1-butylamino-4-octadecylimidazolium hydrobromide.

[0110] (2) Add 5g of 1-butylamino-4-octadecyl-imidazolium hydrobromide, 10g of sodium hexafluorophosphate and 150g of ethanol to a three-necked flask and stir thoroughly. React at 70°C for 4 hours. After the reaction is complete, remove the solvent ethanol by rotary evaporation and remove the sodium hexafluorophosphate by washing with water to obtain a strongly hydrophobic basic ionic liquid (1-butylamino-4-octadecyl-imidazolium hexafluorophosphate).

[0111] The deacidification of tert-butyl hydroperoxide (TBHP) during the co-oxidation of isobutane to prepare propylene oxide involves the following steps:

[0112] 1) The peroxide reaction solution from the isobutane co-oxidation process to propylene oxide and the strongly hydrophobic alkaline ionic liquid (1-butylamino-4-octadecyl-imidazolium hexafluorophosphate) are fed into a static mixer, and the flow rate is adjusted to make the feed mass ratio of the two 2:1 and the total volume hourly space velocity 8h. -1 The temperature is raised to 90°C to carry out the reaction, causing the acidic impurities to attach to the ionic liquid, and the reacted material is obtained.

[0113] 2) The reacted material is sent to a coalescer for phase separation. The coalescer is equipped with stainless steel corrugated plate coalescing packing with a packing thickness of 100 mm. It is held at 60°C for 6 min. The upper layer is tert-butyl hydrogen peroxide solution after removing acid impurities (the content of each substance in its composition is shown in Table 3). It enters the subsequent tert-butyl hydrogen peroxide concentration process to obtain TBHP. The lower layer is ionic liquid connected to acid impurities.

[0114] The deacidified TBHP was then used to prepare the final product propylene oxide, with a conversion rate of 99.71% and a selectivity of 95.25%.

[0115] Comparative Example 1

[0116] Ionic liquids were prepared according to the method in Example 1, except that in step (2), 1-hexadecylimidazole was replaced with hexadecylguanidine, while other operations and conditions remained unchanged, and ionic liquids were obtained.

[0117] Using the above-mentioned ionic liquid, the method of Example 1 was used for the deacidification of tert-butyl hydrogen peroxide in the process of co-oxidation of isobutane to prepare propylene oxide, and the tert-butyl hydrogen peroxide feed solution after the removal of acid impurities was obtained. The content of each substance in its composition is shown in Table 3.

[0118] The deacidified TBHP was then used to prepare the final product propylene oxide, with a conversion rate of 98.81% and a selectivity of 91.02%.

[0119] Comparative Example 2

[0120] Ionic liquids were prepared according to the method in Example 1, except that in step (2), hexadecylimidazole was replaced with butylimidazole, while other operations and conditions remained unchanged, and ionic liquids were obtained.

[0121] Using the above-mentioned ionic liquid, the method of Example 1 was used for the deacidification of tert-butyl hydrogen peroxide in the process of co-oxidation of isobutane to prepare propylene oxide, and the tert-butyl hydrogen peroxide feed solution after the removal of acid impurities was obtained. The content of each substance in its composition is shown in Table 3.

[0122] The deacidified TBHP was then used to prepare the final product propylene oxide, with a conversion rate of 97.75% and a selectivity of 91.56%.

[0123] Comparative Example 3

[0124] Ionic liquids were prepared according to the method in Example 1, except that in step (2), 3-bromopropylamine hydrobromide was replaced with bromopropanol, while other operations and conditions remained unchanged, and ionic liquids were obtained.

[0125] Using the above-mentioned ionic liquid, the method of Example 1 was used for the deacidification of tert-butyl hydrogen peroxide in the process of co-oxidation of isobutane to prepare propylene oxide, and the tert-butyl hydrogen peroxide feed solution after the removal of acid impurities was obtained. The content of each substance in its composition is shown in Table 3.

[0126] The deacidified TBHP was then used to prepare the final product propylene oxide, with a conversion rate of 98.52% and a selectivity of 90.47%.

[0127] Comparative Example 4

[0128] Ionic liquids were prepared according to the method in Example 1, except that sodium hexafluorophosphate was replaced with sodium monofluorophosphate in step (3), while other operations and conditions remained unchanged, and ionic liquids were obtained.

[0129] Using the above-mentioned ionic liquid, the method of Example 1 was used for the deacidification of tert-butyl hydrogen peroxide in the process of co-oxidation of isobutane to prepare propylene oxide, and the tert-butyl hydrogen peroxide feed solution after the removal of acid impurities was obtained. The content of each substance in its composition is shown in Table 3.

[0130] The deacidified TBHP was then used to prepare the final product propylene oxide, with a conversion rate of 97.69% and a selectivity of 91.76%.

[0131] Comparative Example 5

[0132] Referring to the deacidification method of tert-butyl hydrogen peroxide in Example 1, the only difference is that the ionic liquid is replaced with hexadecyl imidazole, while other operations and conditions remain unchanged, to obtain a tert-butyl hydrogen peroxide feed solution after removing acidic impurities. The content of each substance in its composition is shown in Table 3.

[0133] The deacidified TBHP was then used to prepare the final product propylene oxide, with a conversion rate of 98.01% and a selectivity of 90.24%.

[0134] Comparative Example 6

[0135] The deacidification method of tert-butyl hydrogen peroxide in Example 1 was followed, except that the ionic liquid was replaced with 1-propylamino-4-hexadecyl-imidazolium bromide prepared in Example 1, while other operations and conditions remained unchanged. The resulting tert-butyl hydrogen peroxide solution after the removal of acid impurities was shown in Table 3.

[0136] The deacidified TBHP was then used to prepare the final product propylene oxide, with a conversion rate of 98.09% and a selectivity of 90.28%.

[0137] Comparative Example 7

[0138] Referring to the deacidification method of tert-butyl hydrogen peroxide in Example 1, the only difference is that the ionic liquid is replaced with imidazole, while other operations and conditions remain unchanged, and the tert-butyl hydrogen peroxide feed solution after removing acidic impurities is obtained. The content of each substance in its composition is shown in Table 3.

[0139] The deacidified TBHP was then used to prepare the final product propylene oxide, with a conversion rate of 98.51% and a selectivity of 90.32%.

[0140] Table 3 Comparison of deacidification effects of different embodiments and comparative examples

[0141]

[0142] Based on the results of the above embodiments and comparative examples, it can be seen that the deacidification method of the peroxide reaction solution of the present invention has a good deacidification effect, significantly improves the selectivity of the downstream epoxidation reaction, increases atom utilization, and reduces production costs. Furthermore, the strongly hydrophobic alkaline ionic liquid of the present invention has good recyclability and is an environmentally friendly material with good industrial application value.

Claims

1. A method for removing tert-butyl hydroperoxide during the co-oxidation of isobutane to prepare propylene oxide, characterized in that, Includes the following steps: 1) The peroxide reaction solution from the process of preparing propylene oxide from isobutane co-oxidation is mixed with a strongly hydrophobic basic ionic liquid and reacted to attach the acidic impurities in the solution to the ionic liquid. 2) Separate the reaction material obtained in step 1) to obtain a tert-butyl hydrogen peroxide solution after removing acid impurities from the upper layer, which will then enter the subsequent tert-butyl hydrogen peroxide concentration process. The lower layer will obtain an ionic liquid connected to the acid impurities. The preparation method of the strongly hydrophobic basic ionic liquid includes the following steps: (1) A short-chain alcohol, a haloalkylamino hydrohalide, and a long-chain alkyl-substituted imidazole were mixed and reacted under a nitrogen atmosphere. Then, an alkaline solution was added to the reaction solution to adjust the pH to 8-9. The mixture was cooled and crystallized. After filtration, 1-alkylamino-4-alkyl-imidazolium hydrohalide was obtained. (2) The 1-alkylamino-4-alkyl-imidazolium hydrohalate prepared in step (1) is mixed with sodium hexafluorophosphate and an alcohol solvent to carry out an ion exchange reaction to obtain a strongly hydrophobic basic ionic liquid. The short-chain alcohol in step (1) has 1 to 4 carbon atoms, the long-chain alkyl-substituted imidazole is selected from alkyl-substituted imidazoles with a chain length of C6-C20, and the haloalkylamino hydrogen halide is selected from halolinear alkylamino hydrogen halide with a chain length of C2-C8.

2. The deacidification method according to claim 1, characterized in that, The short-chain alcohol mentioned in step (1) is ethanol, methanol, or propanol; The long-chain alkyl-substituted imidazole in step (1) is one or more of tetradecyl imidazole, hexadecyl imidazole, octadecyl imidazole, and eicosyl imidazole; In step (1), the mass ratio of the long-chain alkyl-substituted imidazole to the haloalkylamine hydrohalate is 1:0.1~5; In step (1), the mass ratio of the long-chain alkyl-substituted imidazole to the short-chain alcohol is 1:4~20; The reaction described in step (1) is carried out at a temperature of 20~70℃ for 8~24h. The alkaline solution mentioned in step (1) is one or more of sodium hydroxide solution, potassium hydroxide solution, and ammonia water; The cooling crystallization in step (1) is carried out at a temperature of -2 to -20°C for 8 to 30 hours.

3. The deacidification method according to claim 2, characterized in that, The haloalkylamine hydrohalate is selected from brominated straight-chain alkylamine hydrobromates with a chain length of C2-C8.

4. The deacidification method according to claim 3, characterized in that, The haloalkylamino hydrohalate is selected from one or more of 2-bromoethylamine hydrobromide, 3-bromopropylamine hydrobromide, and 4-bromobutylamine hydrobromide.

5. The deacidification method according to claim 2, characterized in that, The mass ratio of the long-chain alkyl-substituted imidazole to the haloalkylamino hydrohalate is 1:0.4~2.

6. The deacidification method according to claim 2, characterized in that, The mass ratio of the long-chain alkyl-substituted imidazole to the short-chain alcohol is 1:8~15.

7. The deacidification method according to claim 2, characterized in that, The reaction described in step (1) is carried out at a temperature of 50~70℃ for 12~20h.

8. The deacidification method according to claim 2, characterized in that, The alkaline solution in step (1) is selected from an aqueous solution of alkali with a concentration of 0.01~1 mol / L.

9. The deacidification method according to claim 8, characterized in that, The alkaline solution in step (1) is selected from an aqueous solution of alkali with a concentration of 0.04~0.08 mol / L.

10. The deacidification method according to claim 2, characterized in that, The cooling crystallization process takes place at a temperature of -8 to -15°C for 14 to 20 hours.

11. The deacidification method according to claim 1, characterized in that, In step (2), the mass ratio of 1-alkylamino-4-alkyl-imidazolium hydrohalate to sodium hexafluorophosphate is 1:0.1~2; The alcohol solvent in step (2) is selected from C1-C3 alcohols; The ion exchange reaction in step (2) is carried out at a temperature of 20~70℃ for 4~10h.

12. The deacidification method according to claim 11, characterized in that, The mass ratio of the 1-alkylamino-4-alkyl-imidazolium hydrohalate to sodium hexafluorophosphate is 1:0.4~1.

5.

13. The deacidification method according to claim 11, characterized in that, The alcohol solvent is selected from ethanol and methanol.

14. The deacidification method according to claim 11, characterized in that, The ion exchange reaction is carried out at a temperature of 50-70℃ for 5-8 hours.

15. The deacidification method according to claim 1, characterized in that, The mass ratio of the 1-alkylamino-4-alkyl-imidazolium hydrohalate to the alcohol solvent in step (2) is 1:6~30.

16. The deacidification method according to claim 15, characterized in that, The mass ratio of the 1-alkylamino-4-alkyl-imidazolium hydrohalate to the alcohol solvent is 1:12~25.

17. The deacidification method according to claim 1, characterized in that, The method also includes step 3), which involves mixing the ionic liquid with acid impurities obtained in step 2) with an alkaline solution, stirring to carry out the reaction, then separating the phases, taking off the lower layer of liquid, and obtaining a recovered strongly hydrophobic alkaline ionic liquid phase, which is then returned to step 1) for recycling.

18. The deacidification method according to claim 1, characterized in that, Step 1) The peroxide reaction solution comprises, by mass percentage, 40-60% tert-butanol, 40-60% tert-butyl hydroperoxide, 1-4% acetone, 0.4-1.2% water, and 0.6-1.5% acidic impurities; wherein the acidic impurities include 0.3-0.8% isobutyric acid, 0.2-0.4% formic acid, and 0.1-0.3% acetic acid.

19. The deacidification method according to claim 1, characterized in that, Step 1) The mass ratio of the strongly hydrophobic alkaline ionic liquid to the peroxide reaction solution is 1:2~20.

20. The deacidification method according to claim 1, characterized in that, The reaction described in step 1) is carried out at a temperature of 60~90℃.

21. The deacidification method according to claim 1, characterized in that, Step 1) The peroxide reaction solution and the strongly hydrophobic alkaline ionic liquid are mixed using a static mixer.

22. The deacidification method according to claim 18, characterized in that, The mass ratio of the strongly hydrophobic alkaline ionic liquid to the peroxide reaction solution is 1:10~15.

23. The deacidification method according to claim 20, characterized in that, The reaction described in step 1) is carried out at a temperature of 75~85℃.

24. The deacidification method according to claim 21, characterized in that, The mixing unit of the static mixer is made of carbon steel, stainless steel, or PVC.

25. The deacidification method according to claim 1, characterized in that, Step 1) The total volumetric space velocity of the strongly hydrophobic alkaline ionic liquid and the peroxide reaction solution fed is 1~8h-1.

26. The deacidification method according to claim 25, characterized in that, The total volumetric space velocity of the feed of the strongly hydrophobic alkaline ionic liquid and the peroxide reaction solution is 2.0~4.0 h⁻¹.

27. The deacidification method according to claim 1, characterized in that, Step 2) The reacted material enters the agglomerator for phase separation.

28. The deacidification method according to claim 27, characterized in that, The coalescer is equipped with stainless steel corrugated plate coalescing packing with a thickness of 20~120mm.

29. The deacidification method according to claim 28, characterized in that, The thickness of the filler is 50~100mm.

30. The deacidification method according to claim 27, characterized in that, The phase separation in step 2) is carried out at a temperature of 30~60℃ for 6~30 minutes.

31. The deacidification method according to claim 30, characterized in that, Step 2) Phase separation is performed at a temperature of 40-50°C for 15-21 minutes.

32. The deacidification method according to claim 17, characterized in that, Step 3) The alkaline solution is selected from one or more of sodium hydroxide solution, potassium hydroxide solution, and ammonia water.

33. The deacidification method according to claim 17, characterized in that, The reaction described in step 3) is carried out at a temperature of 30~80℃ for a time of 0.1~1h.

34. The deacidification method according to claim 17, characterized in that, Step 3) The reacted material enters the agglomerator for phase separation.

35. The deacidification method according to claim 33, characterized in that, The reaction described in step 3) is carried out at a temperature of 50~60℃ for a time of 0.3~0.5h.

36. The deacidification method according to claim 34, characterized in that, The coalescer is equipped with stainless steel corrugated plate coalescing packing with a thickness of 20~120mm.

37. The deacidification method according to claim 36, characterized in that, The thickness of the filler is 50~100mm.

38. The deacidification method according to claim 34, characterized in that, Step 3) involves phase separation at a temperature of 50-60°C for 42-60 minutes.

39. The deacidification method according to claim 17, characterized in that, Step 3) The alkaline solution is selected from an aqueous solution of alkali with a concentration of 0.01~1 mol / L.

40. The deacidification method according to claim 39, characterized in that, Step 3) The concentration of the alkaline solution is 0.04~0.08 mol / L.

41. The deacidification method according to claim 17, characterized in that, Step 3) The amount of alkali solution added is to control the pH of the system at 8-9.

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