Modified polystyrene particle, preparation method thereof and application of modified polystyrene particle in removal of aldehyde substance impurities in epoxypropane

Abstract

The invention discloses a modified polystyrene particle and a preparation method and application thereof in removal of aldehyde substance impurities in epoxypropane, main aldehyde substances contained in industrially produced epoxypropane are acetaldehyde and propionaldehyde, the boiling point of epoxypropane is between the boiling point of acetaldehyde and the boiling point of propionaldehyde, and the boiling points of acetaldehyde, propionaldehyde and epoxypropane are close to each other. In addition, epoxypropane can be subjected to ring-opening self-polymerization at a temperature higher than 30 DEG C, and can be subjected to ring-opening polymerization even have explosion risks under acidic and alkaline conditions, so that a conventional rectification method and adsorption under relatively extreme experimental conditions are not the optimal method for separating aldehydes from epoxypropane. Therefore, the loss of epoxypropane is caused, and even great potential safety hazards exist. By synthesizing the composite particle modified polystyrene resin, the limitation of temperature conditions is avoided, the danger in the experiment process is reduced, and aldehydes and epoxypropane can be safely separated under the low-temperature condition.

Description

Technical Field

[0001] The present invention belongs to the technical field of chemical separation, and specifically relates to a separation and purification method for removing aldehyde impurities from propylene oxide. More specifically, it relates to a method for synthesizing a composite particle by coupling, physical impregnation and electrostatic self-assembly of silica gel and activated carbon powder, and adding the composite particle to the preparation process of polystyrene particles to obtain a modified polystyrene particle with an outer layer coated with inorganic composite particles, which is used to remove aldehydes from propylene oxide solution. The present invention can achieve a removal rate of 99% for aldehydes in propylene oxide. Background Art

[0002] Propylene oxide (PO) is the second largest propylene derivative in industrial use after polypropylene. It is the raw material for the production of polyether polyols. Polyether polyols are important raw materials for the production of polyurethanes. In addition, they are also important organic chemical raw materials for the production of propylene glycol, propylene alcohol, isopropanolamine, etc. Polyether polyols are polymers containing ether bonds (ROR) in the molecule and OH groups at the end. Polyether polyols are often used to make general-purpose polyurethane foams, adhesives, and elastomers. Aldehydes in propylene oxide are inhibitors in the ring-opening polymerization process of polyethers, which prolong the reaction cycle, increase the reaction temperature, increase the number of unsaturated double bonds, and darken the product color. In addition, aldehydes in propylene oxide will directly affect the content of volatile components in polyether products, affect the product odor, and reduce the quality of polyethers. Since the boiling point of propylene oxide is between that of acetaldehyde and propionaldehyde, the boiling points of the three are close. In addition, due to the special chemical properties of propylene oxide itself, it will undergo ring-opening self-polymerization at temperatures above 30°C. Therefore, conventional distillation methods cannot separate aldehydes from propylene oxide and may even cause loss of propylene oxide.

[0003] At present, a large number of patent research directions are to adsorb aldehyde substances in propylene oxide by resin under low temperature conditions. There are also methods to adjust the production process to achieve the purpose of propylene oxide purification, but most of them still cannot reduce the aldehyde value in propylene oxide to below 100ppm. CN 03803981.8 uses C7~C20 to extract impurities in propylene oxide to achieve the purification of propylene oxide. However, although this method can remove a large number of impurities in propylene oxide by extraction, C7~C20 itself is also introduced into propylene oxide as an impurity, and aldehyde substances and other impurities may form new azeotropes with hydrocarbons, making subsequent impurity removal more difficult.

[0004] The following patents provide clearer ideas for removing formaldehyde by resin adsorption: CN201610115263.6 discloses a method of using a resin and desalted water containing ethanolamine / hydrazine hydrate to extract methanol, and then removing formaldehyde by resin adsorption. However, the disadvantage is that high-nitrogen wastewater containing hydrazone will be generated during the formaldehyde removal process. In addition, the resin adsorption will cause swelling, resulting in reduced strength or even rupture; CN201610473450.1 discloses a method for modifying molecular sieves. The modified molecular sieves have excellent mechanical strength and overcome the swelling effect of the resin. However, the molecular sieves prepared by the impregnation method have an extremely short adsorption life and need to be replaced frequently, and the regeneration procedure is frequent; CN201910342568.4 discloses a method for modifying cation exchange resins to achieve the purpose of removing formaldehyde. Mercapto groups and hydroxyl groups are introduced into the surface of the cation exchange resins to neutralize and modify them. However, the acidic sites of the cation exchange resins will cause the ring opening of propylene oxide, thereby causing the loss of propylene oxide. In addition, cation exchange resins need to be in an acidic environment to have more efficient adsorption performance, which runs counter to the most suitable storage conditions for propylene oxide; CN201910342544.9 discloses a method for modifying PMMA materials, and the modified PMMA materials have good swelling properties. In the process of removing impurities, the loss of propylene oxide is low, but the modification method of PMMA materials requires a large amount of diamines, the modification cost is higher, and the adsorption efficiency cannot reach a removal rate of more than 99%; the more special modified resin directly modifies the inorganic material for adsorption. CN110003137B discloses a modification method for modified inorganic materials. The modified glass beads and molecular sieves have a certain formaldehyde removal effect, but the formaldehyde removal ability is very low compared to the organic skeleton resin, and because the adhesion of silica is enhanced after coupling modification, the modified particles cannot be effectively dispersed in propylene oxide, resulting in a further reduction in the adsorption efficiency, and therefore is not suitable for industrial production.

[0005] At present, the application of propylene oxide requires that the content of aldehyde impurities in propylene oxide needs to be less than 50ppm. For a few production requirements, the aldehyde impurity content is even lower, requiring it to be reduced to less than 10ppm. Therefore, it is of great significance to develop a simple, convenient and efficient method for removing aldehyde impurities in propylene oxide. Summary of the invention

[0006] In order to solve the above problems, the present invention discloses a modified polystyrene microparticle and a preparation method thereof and an application thereof in removing aldehyde impurities from propylene oxide. A composite particle is synthesized by coupling, physical impregnation and electrostatic self-assembly of silica gel and activated carbon powder. The activated carbon powder and the modified silica gel particles can further reduce the adhesion of the coupled silica gel by electrostatic self-assembly, so that the composite particles present dispersed particles. The composite particles are added to the preparation process of polystyrene microparticles to obtain a modified polystyrene microparticle with an outer layer coated with inorganic composite particles. Silane coupling and electrostatic self-assembly modification can generate more solid surface active groups, thereby improving the frequent regeneration and low adsorption efficiency of inorganic skeleton resins. At the same time, the coating of the outer layer of composite particles gives protection to the organic skeleton resin, making it have stronger mechanical strength and anti-swelling ability, and can effectively remove aldehyde impurities in propylene oxide by physical adsorption and chemical adsorption. The aldehyde removal rate can reach more than 99%.

[0007] In order to achieve the above purpose, the present invention provides the following technical solutions: A method for preparing modified polystyrene particles for removing aldehyde substances from propylene oxide, the specific steps comprising the following: (1) After the inorganic material is activated by pickling with an inorganic acid, it is hydrated in a sealed device to obtain hydrated silica gel with an adsorption water content of 5wt% to 20wt%, and the hydrated silica gel is degassed using an organic solvent; (2) After the activated carbon is oxidized by strong acid or strong alkali, it is dehydrated in a nitrogen protection box; (3) mixing the hydrated silica gel treated in step (1) with the coupling agent organic solution, reacting for 16 to 24 hours at room temperature and under stirring, filtering the obtained solid product, washing it with deionized water and ethanol until it is neutral, and drying it to obtain modified silica gel powder; (4) dispersing the siloxane coupling agent and the activated carbon treated in step (2) in a solvent, stirring and mixing for 12 to 24 hours under a nitrogen atmosphere at a temperature of 50 to 70° C., to obtain a suspended organic solution of modified grafted activated carbon; (5) Pour the modified silica gel powder into the suspended organic solution of modified grafted activated carbon, keep it at 90°C to 100°C for 10 to 12 hours, and finally dry it in a vacuum oven at 60°C for 24 hours to obtain composite modified particles of activated carbon and silica gel; (6) dissolving the composite modified particles in anhydrous ethanol by ultrasonication; (7) In a constant temperature water bath and under stirring conditions, the polystyrene chloroform solution is uniformly added dropwise to the anhydrous ethanol solution containing the composite modified particles to obtain a suspension of polystyrene particles, which is filtered, washed, and dried to obtain polystyrene microparticles having an outer layer coated with the composite modified particles, namely the modified polystyrene microparticles.

[0008] Furthermore, the inorganic material used in step (1) is at least one of silicon dioxide nanoparticles and 40-400 mesh silica gel particles.

[0009] Furthermore, the inorganic acid in step (1) is one or more of hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid.

[0010] Furthermore, in step (2), the strong acid is one or more of hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid, and the strong base is one or more of sodium hydroxide and potassium hydroxide.

[0011] Furthermore, in step (3), the coupling agent is one or more of aminopropyltriethoxysilane, aminopropyltrimethoxysilane, APTES, diethylenetriaminopropyltrimethoxysilane, aminoethylaminopropylmethyldimethoxysilane, S17475, and ureidopropyltriethoxysilane.

[0012] Furthermore, the organic solvent in the coupling agent organic solution in step (3) is one of n-hexane, anhydrous methanol, and anhydrous ethanol, or a mixture of the two or more of the two in any proportion.

[0013] Furthermore, in step (4), the siloxane coupling agent is one or more of octyltrimethoxysilane, perfluorodecyltrimethoxysilane, vinyltriisopropoxysilane, 3-glycidyloxypropyltriethoxysilane, acetyltriacetoxysilane, vinyltriisopropenyloxysilane, and 3-glycidyloxypropyltrimethoxysilane.

[0014] Furthermore, the solvent in step (4) is a mixed solvent of ethanol and deionized water in a volume ratio of 4:5.

[0015] The modified polystyrene microparticles are prepared by the method described above.

[0016] Application: The modified polystyrene particles are used in removing aldehyde impurities from propylene oxide.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1) Compared with traditional inorganic adsorption material resins, polystyrene as the resin skeleton has stronger mechanical strength and longer adsorption effect. The inorganic composite particles on the surface can effectively prevent propylene oxide from swelling polystyrene; 2) Composite resin mainly relies on surface composite particles to adsorb impurities, and the pore structure of polystyrene can also participate in adsorption. Chemical adsorption and physical adsorption work together to further improve the adsorption efficiency; 3) Compared with the modification of molecular sieves by physical impregnation, inorganic materials can make the modified active groups adhere more firmly through coupling and electrostatic self-assembly, and will not dissolve in propylene oxide, thus eliminating the introduction of new impurities. In addition, the composite particle coating provides protection for the polystyrene resin and reduces the swelling effect, making the service life of the composite particle modified resin longer than that of the molecular sieve, and no frequent modification is required; 4) The presence of acidic active sites in the molecular sieve leads to the loss of propylene oxide due to ring opening. The composite particle-modified polystyrene resin has weak alkalinity through modification, thereby reducing the loss of propylene oxide during the adsorption process; 5) Organic skeleton resin can reduce the aldehyde value, but it cannot further reduce trace substances to achieve a lower aldehyde value. The outer layer inorganic composite particles can achieve a further reduction in the low aldehyde value by virtue of their smaller pore structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 FTIR spectra of activated carbon powder GO, GPTMS and modified activated carbon GPTMS-GO samples in Example 1; Figure 2 is the XPS spectrum of the composite particles in Example 1; Figure 3 This is the infrared comparison spectrum of the composite particle modified polystyrene, APTES and silica gel in Example 1; Figure 4 The infrared comparison spectra of the composite particle modified polystyrene, s17475 and silica gel in Example 2; Figure 5 It is the silica surface group; Figure 6 It is the silica gel coupling mechanism; Figure 7 Designed for hydration devices. DETAILED DESCRIPTION

[0019] The following examples further illustrate the content of the present invention, but should not be construed as limiting the present invention. Without departing from the spirit and essence of the present invention, modifications and substitutions made to the method, steps or conditions of the present invention all belong to the scope of the present invention. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art.

[0020] A method for preparing modified polystyrene particles for removing aldehyde substances from propylene oxide comprises the following steps: A) After the inorganic material is activated by pickling with inorganic acid, it is hydrated in a sealed device to obtain hydrated silica gel with 5wt%~20wt% adsorbed water, and the hydrated silica gel is degassed with an organic solvent. After the activated carbon is oxidized by strong acid or strong base, it is dehydrated in a nitrogen protection box.

[0021] The volume ratio of the inorganic material to the inorganic acid is 1:2-1:10.

[0022] The inorganic material is at least one of silicon dioxide nanoparticles and silica gel particles (40 mesh-400 mesh), with a purity of ≥99.5wt%, single impurity content requirements of chloride ≤0.02%, iron ≤0.02%, pH (10% water suspension) range of 6.0-7.0, and heating weight loss ≤2.0%.

[0023] The activated carbon is at least one of powdered activated carbons, with a purity of ≥99wt%, a moisture content of ≤5%, and a mesh size of 300 meshes.

[0024] The inorganic acid is one or more of hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid, and its concentration is 1-5 mol / L. The strong base is one or more of sodium hydroxide and potassium hydroxide, and its concentration is 5-10 mol / L.

[0025] The hydration temperature is 30-60°C.

[0026] The organic solvent is one of n-hexane, methanol and ethanol or a mixture of several of them in any proportion, and the concentration thereof is 98% to 99.5%.

[0027] B) The coupling agent is rapidly stirred and mixed with the organic solvent under the protection of dry gas; The coupling agent used for silica gel modification is aminosilane (one or more of aminopropyltriethoxysilane, aminopropyltrimethoxysilane, APTES, diethylenetriaminopropyltrimethoxysilane, aminoethylaminopropylmethyldimethoxysilane) or urea silane (one or more of s17475, ureapropyltriethoxysilane).

[0028] The coupling agent used for activated carbon modification is alkoxysilane (one or more of octyltrimethoxysilane, perfluorodecyltrimethoxysilane, vinyltriisopropoxysilane, 3-glycidyloxypropyltriethoxysilane, acetyltriacetoxysilane, vinyltriisopropenoxysilane, 3-glycidyloxypropyltrimethoxysilane).

[0029] The modified alkylation temperature is 90-100°C.

[0030] The organic solvent is one of n-hexane, anhydrous methanol and anhydrous ethanol or a mixture of the above in any proportion, and the concentration thereof is 98% to 99.5%.

[0031] The volume ratio of the coupling agent to the organic solvent used for stirring and mixing is 1:3-1:20.

[0032] C) Preparation of modified composite particles: the hydrated silica gel treated in step A) is mixed with the coupling agent organic solution, and reacted at room temperature and stirring conditions for 16 to 24 hours. The obtained solid product is filtered and washed with desalted water and ethanol until neutral, and then dried to obtain modified silica gel powder; the siloxane coupling agent and the activated carbon treated in step A) are dispersed in a solvent, and stirred and mixed for 12 to 24 hours in a nitrogen atmosphere at a temperature of 50 to 70°C to obtain a suspended organic solution of modified grafted activated carbon; the modified silica gel powder is poured into the suspended organic solution of modified grafted activated carbon, and maintained at a heating condition of 90°C to 100°C for 10 to 12 hours, and finally dried in a vacuum oven at 60°C for 24 hours to obtain composite modified particles of activated carbon and silica gel.

[0033] The temperature of the modified silica gel preparation reaction is 20°C-60°C, the preparation reaction time is 16-24 h, and the drying temperature is 60°C-90°C.

[0034] The modified activated carbon preparation temperature is 50-70°C, and the preparation reaction time is 12-24h.

[0035] The preparation temperature of the composite particles is 90°C to 100°C, and the preparation reaction time is 10 to 12 hours.

[0036] D) Preparation of modified polystyrene microparticles: the composite modified particles are dissolved in anhydrous ethanol by ultrasound; in a constant temperature water bath and under stirring conditions, the polystyrene chloroform solution is uniformly added dropwise to the anhydrous ethanol solution containing the composite modified particles to obtain a suspension of polystyrene particles, which is filtered, washed, and dried to obtain polystyrene microparticles with an outer layer covering the composite modified particles, namely the modified polystyrene microparticles.

[0037] The ultrasonic conditions are 500-1000 Hz, 30-60° C., and the ultrasonic time is 15-30 min.

[0038] The constant temperature water bath is 25° C., the volume ratio of polystyrene to chloroform is 10-20 g / L, and the uniform dropping speed is 2-10 ml / min.

[0039] Example 1 The present embodiment provides a method for removing acetaldehyde and propionaldehyde from propylene oxide. The removal method is divided into 10 steps in total, namely, silica gel activation, preparation of hydrated silica gel, silica gel modification experiment, activated carbon modification experiment, composite particle preparation and characterization, composite particle modified polystyrene preparation experiment, composite particle modified polystyrene microparticle characterization and analysis experiment, propylene oxide adsorption experiment and modified polystyrene regeneration experiment.

[0040] 1) Activation of silica gel: 40-60 mesh reagent grade chromatography silica gel was placed in a 500 ml three-necked volumetric flask, 5 wt% nitric acid was added, and the mixture was heated at 120°C for 8 hours. After the acid washing step, the reaction solution was immediately passed through a sand core funnel, and then the silica gel was washed with pure water and methanol to a pH of 7, and then dried in an oven at 100°C to constant weight.

[0041] 2) Preparation of hydrated silica gel: The activated silica gel obtained is placed in a container of a hydration device. Under experimental conditions of 120°C, the silica gel is activated by water vapor so that the silica gel adsorbs water to reach adsorption equilibrium. The silica gel is taken out and weighed to obtain hydrated silica gel with an adsorption water content of about 10 wt%.

[0042] 3) Silica gel modification experiment: ① Take 500 ml of n-hexane and add anhydrous sodium sulfate, and let it stand for 6 hours to remove water; ② Add 250 mL of dehydrated n-hexane to 20 g of hydrated silica gel prepared in step 2), stir, and degas under vacuum for 10 minutes. After degassing, maintain the nitrogen atmosphere in the reactor; ③ Accurate measurement. Add 90 mL of aminopropyltriethoxysilane (APTES) silane coupling agent into 250 mL of dehydrated n-hexane, and mix quickly under dry nitrogen protection to prepare a mixed solution; ④ Continuously introduce nitrogen into the reactor, and quickly pour the mixed solution prepared in step ③ into the reactor containing hydrated silica gel and n-hexane in step ②, and keep the experimental conditions at a speed of 1000r and room temperature for 16 hours. The obtained reaction product is immediately filtered using a sand core funnel, and washed with n-hexane and methanol in turn to obtain alkylated silica gel with aminosiloxane groups bonded to the surface; ⑤ Place the above alkylated silica gel in a vacuum drying oven or an oven and dry it at 100°C to constant weight to obtain alkylated silica gel.

[0043] 4) Activated carbon modification experiment ① Take 300 mesh activated carbon black fine powder and place it in a 500ml three-necked volumetric flask, add 10wt% sodium hydroxide solution, and heat it at an experimental temperature of 120℃ for 8 hours. After the alkaline washing step, immediately pass the reaction solution through a sand core funnel, and then wash the activated carbon with pure water and methanol in turn to a pH value of 7, and then dry it in an oven at 100℃ to constant weight to obtain oxidized activated carbon powder.

[0044] ② Take 400 ml of ethanol and add deionized water to prepare 900 ml of mixed solution.

[0045] ③ Disperse 200 mg of oxidized activated carbon powder into 900 ml of ethanol / deionized water (4 / 5, v / v), add 0.4 ml of siloxane coupling agent GPTMS, and perform ultrasonic degradation for 15 minutes. Finally, react for 12 hours under continuous stirring, nitrogen atmosphere and 70°C reaction conditions to complete the alkylation reaction.

[0046] ④ Wash several times with a mixture of ethanol and deionized water to remove excess GPTMS. The obtained product was designated as GPTMS-GO.

[0047] 5) Activated carbon modification test experiment Figure 1 The FTIR spectra of oxidized activated carbon GO, GPTMS and modified oxidized activated carbon powder GPTMS-GO samples are shown in Figure 2. Figure 1 As shown in the figure, compared with the oxidized activated carbon powder, the spectrum of the modified oxidized activated carbon powder GPTMS-GO is at 1098 cm -1 -908cm -1 New characteristic peaks appeared at the locations corresponding to the stretching and contracting movements of Si-OC and epoxy groups, respectively. This phenomenon strongly proves that the surface modification of activated carbon powder is successful.

[0048] 6) Preparation and characterization of composite particles ① Take 200 mg of modified activated carbon GPTMS-GO, add 500 ml of anhydrous ethanol, and ultrasonicate for 5 minutes to prepare a suspended organic solution of modified grafted activated carbon.

[0049] ② Take 500 mg of modified silica gel powder and pour it into the suspended organic solution of modified grafted activated carbon obtained in the above step and keep it at 90°C for 10 hours.

[0050] ③ Dry in a vacuum oven at 60°C for 24 h to obtain composite modified particles of activated carbon and silica gel.

[0051] Using XPS, we can find: Figure 2 As shown in the figure, in addition to the -NH2 binding energy that the modified silica should have at 399.5 eV, the composite particles also have -NH3 at 401.6 eV. +- OOC represents a new binding energy. These results indicate that chemical reduction of carboxyl groups (-COO) on GPTMS-GO and APTES-SiO2 (-NH3 + ) are combined with each other by electrostatic attraction, and finally the composite particles are successfully synthesized.

[0052] 7) Experiment on preparation of modified polystyrene In a constant temperature water bath at 25°C, 500 ml of polystyrene-chloroform solution (the mass volume ratio of polystyrene and chloroform is 10 g / L) was uniformly added dropwise to a stirred anhydrous ethanol solution of composite modified particles (200 mg of composite modified particles, 500 ml of anhydrous ethanol) to obtain a suspension of polystyrene particles. After filtering, washing and drying, polystyrene microparticles with an outer layer coated with composite modified particles were obtained, which were labeled as APTES-GO-PS.

[0053] 8) Characterization and analysis experiment of composite particle modified polystyrene microparticles The composite particle modified polystyrene was tested by infrared spectroscopy and elemental analysis. The infrared spectrum of the composite particle modified polystyrene was different from that of the silica gel. Figure 3 Shown: at 2900-2800cm -1 Nearby (APTES: 2972.2cm -1 and 2885.4cm -1 ; Composite particle modified polystyrene: 2935.6cm -1 and 2877.7cm -1 ) Two characteristic peaks representing the antisymmetric stretching vibration and symmetric stretching vibration of the primary amine group appear, 1500cm -1 Nearby (APTES: 1593.2cm -1 ; Composite particle modified polystyrene: 1562cm -1 ) shows a characteristic peak representing the in-plane bending vibration of NH, 700 cm -1 Nearby (APTES: 680.9cm -1 ; Composite particle modified polystyrene: 690.4cm -1 ) shows a characteristic peak representing the NH out-of-plane bending vibration. In addition, at 1300 cm -1 (APTES:1388.7cm -1 ; Composite particle modified polystyrene: 1392.6cm -1 ) Characteristic peaks representing CN stretching vibration can also be seen near the surface of the composite particle-modified polystyrene and silica gel. By comparing the infrared spectra of the composite particle-modified polystyrene and silica gel, it can be observed that compared with silica gel, the composite particle-modified polystyrene has been grafted with CN and NH characteristic peaks representing primary amine groups; through elemental analysis, it was detected that the composite particle-modified polystyrene contains 4.72% nitrogen; in summary, these test results directly prove the success of the grafting experiment.

[0054] 9) Propylene oxide adsorption experiment 0.2028g of composite particle modified polystyrene was placed in a 20ml glass bottle, and 20ml of propylene oxide solution was accurately taken into the glass bottle using a pipette, and the mass of propylene oxide was measured to be 15.6565g. The glass bottle was placed in a shaker at an experimental temperature of 10°C and a shaking speed of 200rpm for 8 hours. After the reaction, 2ml of adsorbed PO was taken out using a 0.22mm organic filter head, and gas chromatography was performed with raw material PO (99.8257% PO, 0.1085% acetaldehyde and 0.1085% propionaldehyde) at the same time. The results showed that the saturated adsorption of acetaldehyde by composite particle modified polystyrene was 0.0243g acetaldehyde / g composite particle modified polystyrene, and the saturated adsorption of propionaldehyde by composite particle modified polystyrene was 0.0155g propionaldehyde / g composite particle modified polystyrene. It is proved that composite particle modified polystyrene can well reduce aldehyde impurities in low aldehyde value PO.

[0055] Table 1 Experimental data of static adsorption of composite particles modified polystyrene Note: Silica gel-PS-1 represents polystyrene modified with silica gel alone. Except for not including steps 4-6, the rest of the preparation method is the same as Example 1. APTES-GO-PS-1 and APTES-GO-PS-2 in Table 3 are composite particle modified polystyrene APTES-GO-PS prepared from the same batch.

[0056] 10) Regeneration experiment of composite particle modified polystyrene The composite particle modified polystyrene after the adsorption experiment was washed with n-hexane and methanol in turn, and placed in an oven at 80°C for drying. The dried composite particle modified polystyrene was eluted with 5wt% sodium hydroxide solution at 2-4 times the volume for 30-60 minutes, then washed with pure water until neutral, and then washed with n-hexane and methanol, and placed in an oven at 100°C for drying to obtain the regenerated composite particle modified polystyrene (Re-APTES-GO-PS-1). The adsorption experiment was conducted again to detect the adsorption capacity of the composite particle modified polystyrene. After another static adsorption experiment, it was measured that the regenerated composite particle modified polystyrene still had the ability to remove formaldehyde, and its saturated adsorption capacity for acetaldehyde was 0.0137g acetaldehyde / g composite particle modified polystyrene.

[0057] Table 2 Experimental data of static adsorption of composite particle modified polystyrene regeneration Example 2 1) This embodiment provides a method for removing acetaldehyde and propionaldehyde from propylene oxide. The removal method is divided into 9 steps, namely, silica gel activation, preparation of hydrated silica gel, silica gel modification experiment, activated carbon modification experiment, composite particle preparation, composite particle modified polystyrene preparation experiment, composite particle modified polystyrene microparticle characterization analysis experiment and propylene oxide adsorption experiment.

[0058] 2) Activation of silica gel: 40-60 mesh reagent grade chromatography silica gel was placed in a 500 ml three-necked volumetric flask, 5 wt% nitric acid was added, and the mixture was heated at 120°C for 8 hours. After the acid washing step, the reaction solution was immediately passed through a sand core funnel, and then the silica gel was washed with pure water and methanol to a pH of 7, and then dried in an oven at 100°C to constant weight.

[0059] 3) Preparation of hydrated silica gel: The activated silica gel obtained is placed in a container of a hydration device. Under experimental conditions of 120°C, the silica gel is activated by water vapor so that the silica gel adsorbs water to reach adsorption equilibrium. The silica gel is taken out and weighed to obtain hydrated silica gel with an adsorption water content of about 10 wt%.

[0060] 4) Silica gel modification experiment: ① Take 500 ml of n-hexane and add anhydrous sodium sulfate, and let it stand for 6 hours to remove water; ② Add 250 mL of dehydrated n-hexane to 20 g of hydrated silica gel prepared in step 2), stir, and degas under vacuum for 10 minutes. After degassing, maintain the nitrogen atmosphere in the reactor; ③ Accurately measure 90 mL of ureapropyltrimethoxysilane (s17475) silane coupling agent, add it to 250 mL of dehydrated n-hexane, and quickly mix under the protection of dry nitrogen to prepare a mixed solution; ④ Continuously introduce nitrogen into the reactor, and quickly pour the mixed solution prepared in step ③ into the reactor containing hydrated silica gel and n-hexane in step ②, and keep the experimental conditions at a speed of 1000r and room temperature for 16 hours. The obtained reaction product is immediately filtered using a sand core funnel, and washed with n-hexane and methanol in turn to obtain alkylated silica gel with aminosiloxane groups bonded to the surface; ⑤ Place the above alkylated silica gel in a vacuum drying oven or an oven and dry it at 100°C to constant weight to obtain alkylated silica gel.

[0061] 5) Activated carbon modification experiment ① Take 200g of 300-mesh activated carbon black fine powder and place it in a 500ml three-necked volumetric flask, add 10wt% sodium hydroxide solution, and heat it at an experimental temperature of 120℃ for 8 hours. After the alkaline washing step, immediately pass the reaction solution through a sand core funnel, and then wash the activated carbon with pure water and methanol in turn to a pH value of 7, and then dry it in an oven at 100℃ to constant weight to obtain oxidized activated carbon powder.

[0062] ② Take 400 ml of ethanol and add deionized water to prepare 900 ml of mixed solution.

[0063] ③ Disperse 200 mg of oxidized activated carbon powder into 900 ml of ethanol / deionized water (4 / 5, v / v), add 0.4 ml of siloxane coupling agent GPTMS, and perform ultrasonic degradation for 15 minutes. Finally, react for 12 hours under continuous stirring, nitrogen atmosphere and 70°C reaction conditions to complete the alkylation reaction.

[0064] ④ Wash several times with a mixture of ethanol and deionized water to remove excess GPTMS. The obtained product was designated as GPTMS-GO.

[0065] 6) Preparation of composite particles ① Take 200 mg of modified activated carbon GPTMS-GO, add 500 ml of anhydrous ethanol, and ultrasonicate for 5 minutes to prepare a suspended organic solution of modified grafted activated carbon.

[0066] ② Take 500 mg of modified silica gel powder and pour it into the suspended organic solution of modified grafted activated carbon and keep it at 90°C for 10 hours.

[0067] ③ Dry in a vacuum oven at 60°C for 24 h to obtain composite modified particles of activated carbon and silica gel.

[0068] 7) Experiment on preparation of modified polystyrene In a constant temperature water bath at 25°C, 500 ml of polystyrene-chloroform solution (the mass volume ratio of polystyrene and chloroform is 10 g / L) was uniformly added dropwise to a stirred anhydrous ethanol solution of composite modified particles (200 mg of composite modified particles, 500 ml of anhydrous ethanol) to obtain a suspension of polystyrene particles. After filtering, washing and drying, polystyrene microparticles with an outer layer coated with composite modified particles were obtained, which were marked as s17475-GO-PS.

[0069] 8) Characterization and analysis experiment of composite particle modified polystyrene microparticles The composite particle modified polystyrene was tested by infrared spectroscopy and elemental analysis. The infrared spectrum of composite particle modified polystyrene is different from that of silica gel: Figure 4 Shown: at 2900-2800cm -1Nearby (s17475:2945.2cm -1 and 2839.1cm -1 ; Composite particle modified polystyrene: 2927.9cm -1 and 2850.7cm -1 ) Two characteristic peaks representing the antisymmetric stretching vibration and symmetric stretching vibration of the primary amine group appear, 1500cm -1 Nearby (s17475:1463.9cm -1 ; Composite particle modified polystyrene: 1475.5cm -1 ) shows a characteristic peak representing the NH in-plane bending vibration, with a wave number of 700 cm -1 Nearby (s17475:648.1cm -1 ; Composite particle modified polystyrene: 692.4cm -1 ) shows a characteristic peak representing the NH out-of-plane bending vibration. In addition, at 1300 cm -1 (s17475:1350.1cm -1 ; Composite particle modified polystyrene: 1386.8cm -1 ) Characteristic peaks representing CN stretching vibration can also be seen near the surface of the composite particle-modified polystyrene and silica gel. By comparing the infrared spectra of the composite particle-modified polystyrene and silica gel, it can be observed that compared with polystyrene, the composite particle-modified polystyrene has been grafted with CN and NH characteristic peaks representing primary amine groups; through elemental analysis, it was detected that the composite particle-modified polystyrene contains 3.12% nitrogen; in summary, these test results directly prove the success of the grafting experiment.

[0070] 9) Propylene oxide adsorption experiment Take 0.2167g of composite particle modified polystyrene (s17475-GO-PS) and place it in a 20ml glass bottle. Use a pipette to accurately take 20ml of propylene oxide solution and place it in the glass bottle. The mass of propylene oxide is measured to be 11.4875g. The glass bottle is placed in a shaker with an experimental temperature of 10°C and a shaking speed of 200rpm for 8 hours. After the reaction, use a 0.22mm organic filter to take out 2ml of adsorbed PO, and at the same time perform gas chromatography test with raw material PO (99.9602% PO, 0.0398% acetaldehyde). The results show that the saturated adsorption of acetaldehyde by composite particle modified polystyrene is 0.0154g acetaldehyde / g composite particle modified polystyrene. It is proved that this composite particle modified polystyrene can reduce aldehyde impurities in low aldehyde value PO.

[0071] Table 3 Experimental data of static adsorption of composite particles modified polystyrene Note: Silica gel-PS-2 represents polystyrene modified with silica gel alone. The preparation method is the same as that of Example 2 except that steps 5 and 6 are not included.

[0072] The main aldehyde substances contained in the industrial production of propylene oxide are acetaldehyde and propionaldehyde. Since the boiling point of propylene oxide is between that of acetaldehyde and propionaldehyde, the three boiling points are close. In addition, due to the special chemical properties of propylene oxide itself, it will undergo ring-opening self-polymerization under a temperature condition higher than 30°C, and it will also undergo ring-opening polymerization under acidic and alkaline conditions and even have an explosion risk. Therefore, conventional distillation methods and adsorption using relatively extreme experimental conditions are not the best methods for achieving the separation of aldehydes in propylene oxide, which will not only cause the loss of propylene oxide, but also have great safety hazards. The present invention circumvents the limitation of temperature conditions by synthesizing a composite particle modified polystyrene resin, reduces the danger in the experimental process, and can safely achieve the separation of aldehyde substances and propylene oxide under low temperature conditions. The present invention has the characteristics of simple process, simple operation, and low material consumption.

[0073] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A method for preparing modified polystyrene particles for removing aldehyde substances from propylene oxide, characterized in that: The specific steps include the following: (1) After the inorganic material is activated by pickling with an inorganic acid, it is hydrated in a sealed device to obtain hydrated silica gel with an adsorption water content of 5wt% to 20wt%, and the hydrated silica gel is degassed using an organic solvent; (2) After the activated carbon is oxidized by strong acid or strong alkali, it is dehydrated in a nitrogen protection box; (3) mixing the hydrated silica gel treated in step (1) with the coupling agent organic solution, reacting for 16 to 24 hours at room temperature and under stirring, filtering the obtained solid product, washing it with deionized water and ethanol until it is neutral, and drying it to obtain modified silica gel powder; (4) dispersing the siloxane coupling agent and the activated carbon treated in step (2) in a solvent, stirring and mixing for 12 to 24 hours under a nitrogen atmosphere at a temperature of 50 to 70° C., to obtain a suspended organic solution of modified grafted activated carbon; (5) Pour the modified silica gel powder into the suspended organic solution of modified grafted activated carbon, keep it at 90°C to 100°C for 10 to 12 hours, and finally dry it in a vacuum oven at 60°C for 24 hours to obtain composite modified particles of activated carbon and silica gel; (6) dissolving the composite modified particles in anhydrous ethanol by ultrasonication; (7) In a constant temperature water bath and under stirring conditions, the polystyrene chloroform solution is uniformly added dropwise to the anhydrous ethanol solution containing the composite modified particles to obtain a suspension of polystyrene particles, which is filtered, washed, and dried to obtain polystyrene microparticles having an outer layer coated with the composite modified particles, namely the modified polystyrene microparticles.

2. The method according to claim 1, characterized in that: The inorganic material used in step (1) is at least one of silicon dioxide nanoparticles and 40-400 mesh silica gel particles.

3. The method according to claim 1, characterized in that: The inorganic acid in step (1) is one or more of hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid.

4. The method according to claim 1, characterized in that: In step (2), the strong acid is one or more of hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid, and the strong base is one or more of sodium hydroxide and potassium hydroxide.

5. The method according to claim 1, characterized in that: In step (3), the coupling agent is one or more of aminopropyltriethoxysilane, aminopropyltrimethoxysilane, APTES, diethylenetriaminopropyltrimethoxysilane, aminoethylaminopropylmethyldimethoxysilane, S17475, and ureidopropyltriethoxysilane.

6. The method according to claim 1, characterized in that: The organic solvent in the coupling agent organic solution in step (3) is one of n-hexane, anhydrous methanol, and anhydrous ethanol, or a mixture of the two or more of the two in any proportion.

7. The method according to claim 1, characterized in that: In step (4), the siloxane coupling agent is one or more of octyltrimethoxysilane, perfluorodecyltrimethoxysilane, vinyltriisopropoxysilane, 3-glycidyloxypropyltriethoxysilane, acetyltriacetoxysilane, vinyltriisopropenyloxysilane, and 3-glycidyloxypropyltrimethoxysilane.

8. The method according to claim 1, characterized in that: The solvent in step (4) is a mixed solvent of ethanol and deionized water in a volume ratio of 4:

5.

9. Modified polystyrene microparticles obtained by the method according to claim 1.

10. Use of the modified polystyrene particles according to claim 9 in removing aldehyde impurities from propylene oxide.

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