A method for preparing styrene

Abstract

A method for preparing styrene comprises catalytically hydrogenating phenylacetylene in the presence of a hydrogen atmosphere and a single-atom platinum Y molecular sieve confined by a SOD cage to produce styrene. This method improves the selectivity of phenylacetylene hydrogenation to styrene, as well as the stability, anti-poisoning ability, and sustainability of the catalytic system.

Description

Technical Field

[0001] The present invention relates to a method for preparing styrene, and more particularly to a method for preparing styrene by catalytic phenylacetylene. Background Art

[0002] Styrene (ST) is an important monomer for the production of polystyrene, styrene-butadiene rubber, ABS resin, SAN resin and styrene-based thermoplastic elastomer (SBS). It is also an important material for the production of coatings, fuels and synthetic medicines.

[0003] Currently, the main methods for producing styrene include ethylbenzene dehydrogenation, extraction from the C8 fraction, a byproduct of ethylene cracking, methanol synthesis, and butadiene synthesis. While ethylbenzene dehydrogenation can produce styrene, this method is very expensive. Therefore, the advantages of extracting styrene from the C8 fraction, a byproduct of ethylene cracking, are gradually becoming apparent.

[0004] Pyrolysis gasoline accounts for about 60% to 70% of ethylene production capacity. The processing cost of extracting and recovering styrene from the C8 fraction is only half of that of producing styrene by dehydrogenating ethylbenzene. Therefore, the extraction method of producing styrene from the C8 fraction, a byproduct of pyrolysis gasoline, is the most competitive technology in the current styrene production technology with relatively low cost, low investment, and after reaching production scale. However, the C8 fraction of pyrolysis gasoline contains about 3000 to 7000 μg / g of phenylacetylene (PA) (Applied Chemical Industry, 2017, 46(3):448-452.). It is an unsaturated hydrocarbon with similar structure and similar physical and chemical properties as styrene, so it is difficult to separate the two by extraction. If phenylacetylene is not removed, it will be enriched during the styrene extraction process. The presence of phenylacetylene will poison the catalyst in the anionic polymerization process of styrene, thereby losing its activity. In addition, it will also cause styrene to deteriorate, such as taste change, color change, degradation, etc. Therefore, the best method is to selectively hydrogenate phenylacetylene to convert it into styrene to improve the purity of styrene.

[0005] Currently, the catalysts used for semi-hydrogenation of phenylacetylene to produce styrene are mainly loaded precious metal and non-precious metal catalysts.

[0006] Sonia et al. dissolved a Pd precursor in ethylene glycol, purified it with acetone, dissolved it in methanol, and finally loaded the Pd solution onto γAl2O3, MCM-41, and Al-MCM-41 zeolites to prepare supported catalysts. Furthermore, using an in-situ synthesis method, a certain amount of palladium nanomaterial was added to the silica solution used to synthesize MCM-4 and Al-MCM-41 precursors to obtain MCM-4-s and Al-MCM-41-s catalysts. Although the Pd / MCM-41 prepared by the impregnation method has a regular pore structure, Pd is distributed in a spherical shape on the surface, and the conversion rate and selectivity of semi-hydrogenation are excellent, the Pd on the surface of Pd / MCM-4-s exhibits irregular shapes and agglomeration (J Catal, 2008, 257(1):87-95).

[0007] Wang et al. prepared bimetallic catalysts Pd-Cu / Al2O3 and Pd-Zn / Al2O3 by colloid method. 0.6 / Al2O3 has better selectivity than Pd-Cu6 / Al2O3, and Pd-Zn 0.6 / Al2O3 selectivity is lower than that of Pd-Zn6 / Al2O3. The conversion rate and selectivity of Pd-Cu6 / Al2O3 and Pd-Zn6 / Al2O3 are 96% and 88.1%, 99.5% and 86.3%, respectively. (Catal Today, 2016, 264:37-43).

[0008] Leonid et al. prepared FeOx / SiO2 catalysts by impregnation method and applied them to the selective hydrogenation of phenylacetylene. First, SiO2 was impregnated into a saturated (NH4)3〔Fe(C2O4)3〕·3H2O solution and stirred. The impregnated catalyst was then dried at 60℃ and calcined in air at 250℃-600℃. Finally, FeOx / SiO2 catalysts with a certain loading were obtained. According to the different specific surface areas of silica, they were divided into high specific surface area catalysts (FeOx / HS) and low specific surface area catalysts (FeOx / LS). The catalysts were used in the liquid phase reaction of selective hydrogenation of phenylacetylene. When the two catalysts calcined at 350℃ were subjected to the reaction conditions of hydrogen pressure of 13 bar and reaction temperature of 110℃, phenylacetylene was completely converted and the selectivity of styrene was similar, 67% and 60%, respectively (Mendeleev Commun, 2017, 27(5):512-514).

[0009] In summary, the existing technologies have problems such as difficult synthesis, environmental pollution caused by template agents, low selectivity, poor resistance to sulfide poisoning, and poor stability, which make these catalysts difficult to use in industrial production. Summary of the Invention

[0010] The purpose of the present invention is to provide a method for preparing styrene that is different from the prior art, thereby improving the selectivity of hydrogenating phenylacetylene to produce styrene and the stability, anti-poisoning ability and sustainability of the catalytic system, so as to solve the above-mentioned technical problems.

[0011] To achieve the above object, the present invention provides a method for preparing styrene, characterized in that the method comprises catalytically hydrogenating phenylacetylene to obtain styrene in the presence of a hydrogen atmosphere and a single-atom platinum Y molecular sieve confined by a SOD cage.

[0012] Preferably, the SOD cage-confined single-atom platinum Y-type molecular sieve is prepared by a method comprising the following steps: adding choline chloride to a Y molecular sieve synthesis system comprising a silicon source, an aluminum source, and an alkali source and stirring uniformly, then adding a platinum precursor coordinated by ethylenediamine, aging, and then subjecting the crystallized product to in-situ static hydrothermal crystallization, and calcining and hydrogen reduction.

[0013] One implementation method for preparing the SOD cage-confined single-atom platinum Y molecular sieve is to add sodium aluminate, sodium hydroxide and choline chloride into water, add silica sol and continue stirring after the solution is dispersed, add platinum precursor solution coordinated by ethylenediamine and continue stirring after the sol is formed, place in a hydrothermal kettle after aging to perform crystallization synthesis, filter, wash, roast and reduce the crystallized product under hydrogen atmosphere.

[0014] In this embodiment, the molar ratio of the silica sol, sodium aluminate and alkali source is (9.0-11.0):1:(4.0-6.0), preferably (9.5-10.6):1:(4.0-5.4); the molar ratio of choline chloride to silica sol is 0.19-0.21:1; the ratio of the mass of platinum to the sum of the masses of sodium aluminate and silica sol is 0.01-0.25:100, the platinum precursor is calculated as platinum element, the sodium aluminate is calculated as Al2O3, and the silica sol is calculated as SiO2.

[0015] The ethylenediamine-coordinated platinum precursor is obtained by mixing an aqueous solution of a platinum salt with ethylenediamine. The molar ratio of platinum to ethylenediamine in the platinum salt is preferably 1:15-20. The platinum salt is preferably chloroplatinic acid. The ethylenediamine-coordinated platinum precursor is preferably added dropwise slowly at room temperature.

[0016] In the preparation method of the present invention, the aging conditions are preferably stirring at 25-30° C. for 8-12 hours; and the in-situ static hydrothermal crystallization has a crystallization temperature of 100-150° C. and a crystallization time of 8-15 days.

[0017] The process of recovering the crystallized product is well known to those skilled in the art, and generally includes filtering, washing and drying the crystallized product.

[0018] The calcination temperature is 300-350°C, and the hydrogen reduction temperature is 200-250°C. To avoid Pt atom agglomeration caused by excessively high temperatures, the heating rates during the calcination and hydrogen reduction treatments are preferably controlled. Preferably, the calcination heating rate is 0.2-0.6°C / min, and the hydrogen reduction heating rate is 0.1-0.5°C / min.

[0019] The Y molecular sieve prepared by the preparation method provided by the present invention has a silicon-aluminum molar ratio of 5-7.

[0020] The Y molecular sieve loaded with a single platinum atom obtained by the preparation method of the present invention is a Y molecular sieve loaded with a single platinum atom confined by a SOD cage, and the mass content of platinum is 0.01-0.2%.

[0021] In the present invention, the preparation method of the Y molecular sieve loaded with platinum single atoms, on the one hand, utilizes the characteristic that choline chloride will occupy a supercage during the synthesis process of the Y molecular sieve to ensure that the platinum precursor coordinated by ethylenediamine will not appear in the supercage, but can only occupy the SOD cage, thereby avoiding the aggregation of the platinum precursor in the supercage (one supercage of the Y molecular sieve can accommodate multiple platinum precursors); on the other hand, utilizes the characteristic that one SOD cage can only accommodate one platinum precursor to ensure that only platinum single atoms can be formed after calcination and reduction treatment, thereby obtaining a Y molecular sieve with platinum single atoms confined by the SOD cage.

[0022] Through observation and analysis under spherical aberration electron microscope, the Y molecular sieve loaded with platinum obtained by the preparation method provided by the present invention has a platinum atom size at the single-atom level, such as Figure 2 As shown, single-atom platinum is uniformly dispersed in the Y molecular sieve crystal and the size of platinum just matches the size of single-atom platinum. Figure 3 The typical structure example of the single-atom platinum Y molecular sieve loaded with SOD cage confinement obtained by DFT theoretical calculation is shown. It can be seen that the relative energy of 0 kcal / mol indicates that the system is the most stable, which further illustrates that the SOD cage-confined platinum single atom is obtained.

[0023] In the method for preparing styrene provided by the present invention, the phenylacetylene is subjected to catalytic hydrogenation at a temperature of 120-150° C., a hydrogen pressure of 0.6-1.0 MPa, and a time of 15-90 minutes. The molar ratio of the phenylacetylene to the platinum in the molecular sieve is 30-70:1.

[0024] The Y molecular sieve SOD cage (pore size 0.63nm, pore opening diameter 0.25nm) can accommodate just one single platinum atom. Confining the platinum atom into the SOD cage not only achieves 100% utilization of the precious metal atom, but also leverages the confinement effect of the SOD cage to enhance the catalytic performance of the Y molecular sieve as a catalyst, particularly improving its resistance to sulfur poisoning. The described method for preparing styrene is particularly suitable for phenylacetylene feedstocks containing sulfur impurities, such as phenylacetylene feedstocks containing 0.5-2% thiophene by mass of the phenylacetylene.

[0025] The preparation method of styrene provided by the invention uses methanol as solvent, and the mass of methanol is 100 to 300 times that of phenylacetylene.

[0026] The present invention uses single-atom platinum confined by the SOD cage of a Y-type molecular sieve synthesized with choline chloride to catalyze the hydrogenation of phenylacetylene. The confinement effect of the SOD cage weakens the interaction between sulfur impurities such as thiophene and Pt atoms, thereby achieving high selectivity and high resistance to sulfur poisoning in the selective hydrogenation of phenylacetylene to prepare styrene. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is the XRD pattern of the sample in Example 1.

[0028] Figure 2 This is the spherical aberration electron microscope image of the sample in Example 1.

[0029] Figure 3 This is an example diagram of DFT theoretical calculation of a single platinum atom in the SOD cage of Y molecular sieve.

[0030] Figure 4 This is the TEM image of the sample in Comparative Example 1. DETAILED DESCRIPTION

[0031] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that, unless there is a conflict, the embodiments and features in the embodiments of the present application can be combined with each other.

[0032] The following detailed description is an exemplary description, which is intended to provide further detailed description of the present invention. Unless otherwise indicated, all technical terms used in the present invention have the same meaning as those generally understood by those skilled in the art. The terms used in the present invention are only for describing specific embodiments, and are not intended to limit the exemplary embodiments according to the present invention.

[0033] Examples 1-9 illustrate the preparation of the SOD cage-confined single-atom platinum Y-type molecular sieve used in the present invention.

[0034] Example 1

[0035] 2.0g of sodium metaaluminate (NaAlO2) was dissolved in 24.2g of H2O, followed by 2.68g of NaOH and mixing. 3.45g of choline chloride was then added and ultrasonically mixed. Under vigorous stirring, 24.6g of 30% silica sol was added dropwise to the mixture to form the system for synthesizing Y molecular sieve. 0.042g of chloroplatinic acid hexahydrate and 0.11ml of ethylenediamine were dissolved in 16ml of deionized water. Under vigorous stirring, the ethylenediamine-coordinated platinum precursor solution was slowly added dropwise to the above system for synthesizing Y molecular sieve and mixed thoroughly.

[0036] In the system for synthesizing Y molecular sieve:

[0037] The molar ratio of SiO2, Al2O3 and NaOH is 10:1:5.4;

[0038] The molar ratio of choline chloride to silica sol is 0.2:1, and the silica sol is calculated as SiO2;

[0039] The ratio of the mass of platinum to the sum of the mass of alumina and silica is 0.2:100

[0040] The molar ratio of chloroplatinic acid to ethylenediamine is 1:20

[0041] The mixed liquid was then placed in a polytetrafluoroethylene-lined crystallization reactor for static crystallization at 110°C for 10 days. After crystallization, the sample was filtered, washed, and dried. The resulting sample was calcined in a tube furnace at 350°C for 2 hours (heating rate 0.3°C / min) in air, followed by reduction at 200°C for 1 hour (heating rate 0.3°C / min) in a hydrogen atmosphere to obtain molecular sieve sample A1.

[0042] Figure 1 The XRD spectrum of sample A1 shows that the prepared molecular sieve is Y molecular sieve. Figure 1 It can also be seen that no obvious Pt element characteristic peak is observed in the XRD spectrum data of the Pt-loaded molecular sieve, which indirectly indicates that the Pt loaded on the molecular sieve has no obvious agglomeration and the structure of the Y molecular sieve itself is not significantly affected.

[0043] Figure 2 The spherical aberration electron microscope photo of sample A1 shows the bright spots of Pt single atoms. Figure 2 It can be seen that single-atom Pt is uniformly dispersed in the Y molecular sieve crystal, and the size of Pt just matches the size of single-atom Pt, indicating that the platinum loaded on the molecular sieve is at the atomic level.

[0044] Figure 3 The structure obtained by DFT calculation, the relative energy of 0kcal / mol indicates that the system is most stable when the platinum atom is confined by the SOD cage, which further shows that the Pt single atom confined by the SOD cage is obtained.

[0045] The molar ratio of silicon oxide to aluminum oxide in sample A1 was 6:1, and the platinum content in the molecular sieve was 0.1%. (Mass fraction calculation: the mass of the platinum nanoparticles in the loaded catalyst divided by the total weight of the catalyst).

[0046] Comparative Example 1

[0047] This comparative example illustrates the Pt / Y molecular sieve prepared by the impregnation method.

[0048] Weigh 173 μL of chloroplatinic acid and dissolve it in 300 ml of deionized water. Ultrasonic dispersion is performed. Once completely dissolved, add it dropwise to 100 mg of Y molecular sieve (silicon-aluminum ratio of 6) so that the molecular sieve is completely and evenly immersed in the sodium chloropalladate solution until it is wet. After standing overnight, place the sample in an oven and dry it in an air environment at 100°C for 4 hours. The heating and cooling time is 30 minutes each. After the sample cools, take the dried sample and place it in a muffle furnace. Roast it in an air environment at 200°C for 1 hour at a heating rate of 0.5°C / min. After calcination, the comparative sample Pt / Y prepared by the impregnation method is obtained, and the comparative sample is numbered D1.

[0049] The molar ratio of silicon oxide to aluminum oxide in comparative sample D1 is 6:1, and the content of platinum in the molecular sieve is 0.1%.

[0050] Example 2

[0051] Dissolve 2.0g of sodium metaaluminate (NaAlO2) in 24.2g of H2O, then add 2.68g of NaOH and mix thoroughly. Add 3.45g of choline chloride and mix thoroughly with ultrasound. Under vigorous stirring, add 24.6g of 30% silica sol dropwise to the mixture. This constitutes the system for synthesizing Y molecular sieve. Mix 0.042g of chloroplatinic acid hexahydrate with 0.083ml of ethylenediamine. Under vigorous stirring, slowly add the ethylenediamine-coordinated platinum precursor solution dropwise to the above system for synthesizing Y molecular sieve and mix thoroughly.

[0052] In the system for synthesizing Y molecular sieve:

[0053] The molar ratio of SiO2, Al2O3 and NaOH is 10:1:5.4;

[0054] The molar ratio of choline chloride to silica sol is 0.2:1, and the silica sol is calculated as SiO2;

[0055] The ratio of the mass of platinum to the sum of the masses of alumina and silica is 0.2:100;

[0056] The molar ratio of chloroplatinic acid to ethylenediamine is 1:15.

[0057] The mixed liquid was then placed in a polytetrafluoroethylene-lined crystallization reactor for static crystallization at 110°C for 10 days. After crystallization, the sample was washed and dried. The resulting sample was then calcined in a tube furnace at 350°C for 2 hours (heating rate 0.3°C / min) in air, followed by reduction at 200°C for 1 hour (heating rate 0.3°C / min) in a hydrogen atmosphere to obtain molecular sieve sample A2.

[0058] The XRD spectrum, electron microscope photos and DFT calculated structures of sample A2 are Figure 1 、 Figure 2 and Figure 3 characteristics.

[0059] The molar ratio of silicon oxide to aluminum oxide in sample A2 is 6:1, and the platinum content in the molecular sieve is 0.1%.

[0060] Example 3

[0061] Dissolve 2.0g of sodium metaaluminate (NaAlO2) in 24.2g of H2O, then add 2.68g of NaOH and mix thoroughly. Add 3.45g of choline chloride and mix thoroughly with ultrasound. Under vigorous stirring, add 24.6g of 30% silica sol dropwise to the mixture. This constitutes the system for synthesizing Y molecular sieve. Mix 0.042g of chloroplatinic acid hexahydrate with 0.096ml of ethylenediamine. Under vigorous stirring, slowly add the ethylenediamine-coordinated platinum precursor solution dropwise to the above system for synthesizing Y molecular sieve and mix thoroughly.

[0062] In the system for synthesizing Y molecular sieve:

[0063] The molar ratio of SiO2, Al2O3 and NaOH is 10:1:5.4;

[0064] The molar ratio of choline chloride to silica sol is 0.2:1, and the silica sol is calculated as SiO2;

[0065] The ratio of the mass of platinum to the sum of the masses of sodium metaaluminate and silica sol is 0.2:100;

[0066] The molar ratio of chloroplatinic acid to ethylenediamine is 1:17.5.

[0067] The mixed liquid was then placed in a polytetrafluoroethylene-lined crystallization reactor for static crystallization at 110°C for 10 days. After crystallization, the sample was washed and dried. The resulting sample was then calcined in a tube furnace at 350°C for 2 hours (heating rate 0.3°C / min) in air, followed by reduction at 200°C for 1 hour (heating rate 0.3°C / min) in a hydrogen atmosphere to obtain molecular sieve sample A3.

[0068] The XRD spectrum, electron microscope photos and DFT calculated structures of sample A3 are Figure 1 、 Figure 2 and Figure 3 characteristics.

[0069] The molar ratio of silicon oxide to aluminum oxide in sample A3 is 6:1, and the platinum content in the molecular sieve is 0.1 %.

[0070] Example 4

[0071] Take 2.0g of sodium metaaluminate (NaAlO2) and dissolve it in 24.2g of H2O. Then add 2.68g of NaOH and mix thoroughly. Then add 3.45g of choline chloride and mix thoroughly by ultrasonication. Under vigorous stirring, add 24.6g of 30% silica sol dropwise to the above mixed system to form the system for synthesizing Y molecular sieve. Then take 0.042g of chloroplatinic acid hexahydrate and 0.11ml of ethylenediamine and dissolve them in 16ml of deionized water. Under vigorous stirring, slowly add the ethylenediamine-coordinated platinum precursor solution dropwise to the above system for synthesizing Y molecular sieve and mix thoroughly.

[0072] In the system for synthesizing Y molecular sieve:

[0073] The molar ratio of SiO2, Al2O3 and NaOH is 10:1:5.4;

[0074] The molar ratio of choline chloride to silica sol is 0.2:1, and the silica sol is calculated as SiO2;

[0075] The ratio of the mass of platinum to the sum of the masses of sodium metaaluminate and silica sol is 0.2:100;

[0076] The molar ratio of chloroplatinic acid to ethylenediamine is 1:20.

[0077] The mixed liquid was then placed in a polytetrafluoroethylene-lined crystallization reactor for static crystallization at 110°C for 10 days. After crystallization, the sample was filtered, washed, and dried. The resulting sample was calcined in a tube furnace at 325°C for 2 hours (heating rate 0.3°C / min) in air, followed by reduction at 200°C for 1 hour (heating rate 0.3°C / min) in a hydrogen atmosphere to obtain molecular sieve sample A4.

[0078] The XRD spectrum, electron microscope photos and DFT calculated structures of sample A4 are Figure 1 、 Figure 2 and Figure 3 characteristics.

[0079] The molar ratio of silicon oxide to aluminum oxide in sample A4 is 6:1, and the platinum content in the molecular sieve is 0.1%.

[0080] Example 5

[0081] Dissolve 2.0g of sodium metaaluminate (NaAlO2) in 24.2g of H2O, then add 2.68g of NaOH and mix thoroughly. Add 3.45g of choline chloride and mix thoroughly with ultrasound. Under vigorous stirring, add 24.6g of 30% silica sol dropwise to the mixture. This constitutes the system for synthesizing Y molecular sieve. Mix 0.042g of chloroplatinic acid hexahydrate with 0.083ml of ethylenediamine. Under vigorous stirring, slowly add the ethylenediamine-coordinated platinum precursor solution dropwise to the above system for synthesizing Y molecular sieve and mix thoroughly.

[0082] In the system for synthesizing Y molecular sieve:

[0083] The molar ratio of SiO2, Al2O3 and NaOH is 10:1:5.4;

[0084] The molar ratio of choline chloride to silica sol is 0.2:1, and the silica sol is calculated as SiO2;

[0085] The ratio of the mass of platinum to the sum of the masses of sodium metaaluminate and silica sol is 0.2:100;

[0086] The molar ratio of chloroplatinic acid to ethylenediamine is 1:15.

[0087] The mixed liquid was then placed in a polytetrafluoroethylene-lined crystallization reactor for static crystallization at 110°C for 10 days. After crystallization, the sample was washed and dried. The resulting sample was then calcined in a tube furnace at 325°C for 2 hours (heating rate 0.3°C / min) in air, followed by reduction at 200°C for 1 hour (heating rate 0.3°C / min) in a hydrogen atmosphere to obtain molecular sieve sample A5.

[0088] The XRD spectrum, electron microscope photos and DFT calculated structures of sample A5 are Figure 1 、 Figure 2 and Figure 3 characteristics.

[0089] The molar ratio of silicon oxide to aluminum oxide in sample A5 is 6:1, and the platinum content in the molecular sieve is 0.1%.

[0090] Example 6

[0091] Dissolve 2.0g of sodium metaaluminate (NaAlO2) in 24.2g of H2O, then add 2.68g of NaOH and mix thoroughly. Add 3.45g of choline chloride and mix thoroughly with ultrasound. Under vigorous stirring, add 24.6g of 30% silica sol dropwise to the mixture. This constitutes the system for synthesizing Y molecular sieve. Mix 0.042g of chloroplatinic acid hexahydrate with 0.096ml of ethylenediamine. Under vigorous stirring, slowly add the ethylenediamine-coordinated platinum precursor solution dropwise to the above system for synthesizing Y molecular sieve and mix thoroughly.

[0092] In the system for synthesizing Y molecular sieve:

[0093] The molar ratio of SiO2, Al2O3 and NaOH is 10:1:5.4;

[0094] The molar ratio of choline chloride to silica sol is 0.2:1, and the silica sol is calculated as SiO2;

[0095] The ratio of the mass of platinum to the sum of the masses of sodium metaaluminate and silica sol is 0.2:100;

[0096] The molar ratio of chloroplatinic acid to ethylenediamine is 1:17.5.

[0097] The mixed liquid was then placed in a polytetrafluoroethylene-lined crystallization reactor for static crystallization at 110°C for 10 days. After crystallization, the sample was washed and dried. The resulting sample was then calcined in a tube furnace at 325°C for 2 hours (heating rate 0.3°C / min) in air, followed by reduction at 200°C for 1 hour (heating rate 0.3°C / min) in a hydrogen atmosphere to obtain molecular sieve sample A6.

[0098] The XRD spectrum, electron microscope photos and DFT calculated structures of sample A6 are Figure 1 、 Figure 2 and Figure 3 characteristics.

[0099] The molar ratio of silicon oxide to aluminum oxide in sample A6 is 6:1, and the platinum content in the molecular sieve is 0.1%.

[0100] Example 7

[0101] 2.0g of sodium metaaluminate (NaAlO2) was dissolved in 24.2g of H2O, followed by 2.68g of NaOH and mixing. 3.45g of choline chloride was then added and ultrasonically mixed. Under vigorous stirring, 24.6g of 30% silica sol was added dropwise to the mixture to form the system for synthesizing Y molecular sieve. 0.042g of chloroplatinic acid hexahydrate and 0.11ml of ethylenediamine were dissolved in 16ml of deionized water. Under vigorous stirring, the ethylenediamine-coordinated platinum precursor solution was slowly added dropwise to the above system for synthesizing Y molecular sieve and mixed thoroughly.

[0102] In the system for synthesizing Y molecular sieve:

[0103] The molar ratio of SiO2, Al2O3 and NaOH is 10:1:5.4;

[0104] The molar ratio of choline chloride to silica sol is 0.2:1, and the silica sol is calculated as SiO2;

[0105] The ratio of the mass of platinum to the sum of the masses of sodium metaaluminate and silica sol is 0.2:100;

[0106] The molar ratio of chloroplatinic acid to ethylenediamine is 1:20.

[0107] The mixed liquid was then placed in a polytetrafluoroethylene-lined crystallization reactor for static crystallization at 110°C for 10 days. After crystallization, the sample was filtered, washed, and dried. The resulting sample was calcined in a tube furnace at 300°C for 2 hours (heating rate 0.3°C / min) in air, followed by reduction at 200°C for 1 hour (heating rate 0.3°C / min) in a hydrogen atmosphere to obtain molecular sieve sample A7.

[0108] The XRD spectrum, electron microscope photos and DFT calculated structures of sample A7 are Figure 1 、 Figure 2 and Figure 3 characteristics.

[0109] The molar ratio of silicon oxide to aluminum oxide in sample A7 is 6:1, and the platinum content in the molecular sieve is 0.1%.

[0110] Example 8

[0111] Dissolve 2.0g of sodium metaaluminate (NaAlO2) in 24.2g of H2O, add 1.95g of NaOH, mix thoroughly, then add 3.45g of choline chloride and mix thoroughly under ultrasound. Under vigorous stirring, add 23.42g of 30% silica sol dropwise to the mixture. This constitutes the system for synthesizing Y molecular sieve. Mix 0.042g of chloroplatinic acid hexahydrate with 0.066ml of ethylenediamine. Under vigorous stirring, slowly add the ethylenediamine-coordinated platinum precursor solution dropwise to the above system for synthesizing Y molecular sieve and mix thoroughly.

[0112] In the system for synthesizing Y molecular sieve:

[0113] The molar ratio of SiO2, Al2O3 and NaOH is 9.52:1:4;

[0114] The molar ratio of choline chloride to silica sol is 0.2:1, and the silica sol is calculated as SiO2;

[0115] The ratio of the mass of platinum to the sum of the masses of sodium metaaluminate and silica sol is 0.21:100;

[0116] The molar ratio of chloroplatinic acid to ethylenediamine is 1:15.

[0117] The mixed liquid was then placed in a polytetrafluoroethylene-lined crystallization reactor for static crystallization at 110°C for 10 days. After crystallization, the sample was washed and dried. The resulting sample was then calcined in a tube furnace at 300°C for 2 hours (heating rate 0.3°C / min) in air, followed by reduction at 200°C for 1 hour (heating rate 0.3°C / min) in a hydrogen atmosphere to obtain molecular sieve sample A8.

[0118] The XRD spectrum, electron microscope photos and DFT calculated structures of sample A8 are Figure 1 、 Figure 2 and Figure 3 characteristics.

[0119] The molar ratio of silicon oxide to aluminum oxide in sample A8 is 6.2:1, and the platinum content in the molecular sieve is 0.11%.

[0120] Example 9

[0121] Dissolve 2.0g of sodium metaaluminate (NaAlO2) in 26.65g of H2O, add 1.95g of NaOH, mix thoroughly, then add 3.45g of choline chloride and mix thoroughly under ultrasound. Under vigorous stirring, add 24.6g of 30% silica sol dropwise to the mixture. This constitutes the system for synthesizing Y molecular sieve. Mix 0.042g of chloroplatinic acid hexahydrate with 0.11ml of ethylenediamine. Under vigorous stirring, slowly add the ethylenediamine-coordinated platinum precursor solution dropwise to the above system for synthesizing Y molecular sieve and mix thoroughly.

[0122] In the system for synthesizing Y molecular sieve:

[0123] The molar ratio of SiO2, Al2O3 and NaOH is 10:1:4;

[0124] The molar ratio of choline chloride to silica sol is 0.2:1, and the silica sol is calculated as SiO2;

[0125] The ratio of the mass of platinum to the sum of the masses of ammonium metaaluminate and silica sol is 0.2:100;

[0126] The molar ratio of chloroplatinic acid to ethylenediamine is 1:20.

[0127] The mixed liquid was then placed in a polytetrafluoroethylene-lined crystallization reactor for static crystallization at 110°C for 10 days. After crystallization, the sample was washed and dried. The resulting sample was then calcined in a tube furnace at 300°C for 2 hours (heating rate 0.3°C / min) in air, followed by reduction at 200°C for 1 hour (heating rate 0.3°C / min) in a hydrogen atmosphere to obtain molecular sieve sample A9.

[0128] The XRD spectrum, electron microscope photos and DFT calculated structures of sample A9 are Figure 1 、 Figure 2 and Figure 3 characteristics.

[0129] The molar ratio of silicon oxide to aluminum oxide in sample A9 is 6.4:1, and the platinum content in the molecular sieve is 0.1%.

[0130] The following examples illustrate the method for preparing styrene provided by the present invention.

[0131] Examples 10-14 are all methods for preparing styrene using the molecular sieve sample A1 of Example 1 as a catalyst.

[0132] Example 10

[0133] 0.1 mmol of phenylacetylene was added to the molecular sieve sample A1 prepared in Example 1 at a molar ratio of phenylacetylene to platinum in the catalyst of 50:1. 3 mL of methanol was then added, and the system was evenly dispersed by ultrasound. The system was placed in an autoclave and the air in the autoclave was replaced with hydrogen three times. The catalytic reaction was carried out at 150°C and 0.8 MPa of H2 for 30 minutes. The supernatant was centrifuged and diluted and then detected by GC-MS. The conversion rate and selectivity data are shown in Table 1.

[0134] Example 11

[0135] Same as Example 10, except that thiophene at a mass percentage of 0.5% of phenylacetylene was added to the system.

[0136] The conversion and selectivity data are shown in Table 1.

[0137] Example 12

[0138] Same as Example 10, except that thiophene at 1% of the mass of phenylacetylene was added to the system.

[0139] The conversion and selectivity data are shown in Table 1.

[0140] Example 13

[0141] Same as Example 10, except that 1% of the mass of thiophene by weight of phenylacetylene was added to the system and the reaction was carried out for 60 minutes.

[0142] The conversion and selectivity data are shown in Table 1.

[0143] Example 14

[0144] Same as Example 10, except that the reaction pressure was changed to 0.6 MPa.

[0145] The conversion and selectivity data are shown in Table 1.

[0146] Comparative Example 2

[0147] This comparative example illustrates a comparative method for preparing styrene using conventional platinum-loaded Y molecular sieve.

[0148] The same as Example 10, except that the catalyst used was Comparative Sample D1, prepared in Comparative Example 1, and the reaction temperature was adjusted to 40°C, 0.6 MPa, and 15 min. (Because Comparative Sample D1 is too active, over-hydrogenation would have resulted in decreased selectivity if the same reaction conditions as Example 10 had been used. Therefore, this comparative example compares selectivity at similar conversions.)

[0149] The conversion and selectivity data are shown in Table 1.

[0150] Comparative Example 3

[0151] This comparative example illustrates a comparative method for preparing styrene in the presence of thiophene using a conventional platinum-loaded Y molecular sieve.

[0152] The same as Example 10, except that 1% by weight of thiophene of phenylacetylene was added to the reaction raw materials, the catalyst was the comparative sample D1 prepared in Comparative Example 1, and the reaction temperature was 40° C., 0.6 MPa, and 15 min.

[0153] Table 1

[0154]

[0155] As can be seen from the data in Table 1, the present invention uses SOD cage-confined Pt single-atom Y molecular sieve as a catalyst. When the raw material phenylacetylene contains sulfur impurities, its selectivity for styrene is basically not weakened, reflecting good resistance to sulfur poisoning.

[0156] Examples 15-22

[0157] Examples 15-22 are methods for preparing styrene using samples A2-A9 prepared in Examples 2-9 as catalysts, respectively.

[0158] The specific reaction conditions, conversion rate and selectivity data are shown in Table 2.

[0159] Table 2

[0160]

Claims

1. A method for preparing styrene, characterized in that The method comprises the following steps: catalytically hydrogenating phenylacetylene in the presence of a hydrogen atmosphere and a single-atom platinum Y molecular sieve confined by a SOD cage to obtain styrene.

2. The preparation method according to claim 1, wherein The SOD cage-confined single-atom platinum Y-type molecular sieve is prepared by a method comprising the following steps: adding choline chloride to a Y molecular sieve synthesis system comprising a silicon source, an aluminum source, and an alkali source and stirring the mixture uniformly; then adding a platinum precursor coordinated by ethylenediamine; aging the mixture and subjecting it to in-situ static hydrothermal crystallization; and finally calcining and reducing the crystallized product with hydrogen.

3. The preparation method according to claim 2, wherein: Sodium aluminate, sodium hydroxide and choline chloride are added to water. After the solution is dispersed, silica sol is added and stirred continuously. After the sol is formed, platinum precursor solution coordinated by ethylenediamine is added and stirred continuously. After aging, the solution is placed in a hydrothermal autoclave for crystallization synthesis. The crystallized product is filtered, washed, calcined and then reduced under a hydrogen atmosphere.

4. The preparation method according to claim 3, wherein The molar ratio of the silica sol, sodium aluminate and alkali source is (9.0-11.0):1:(4.0-6.0); the molar ratio of the choline chloride to the silica sol is 0.19-0.21:1; the ratio of the mass of the platinum to the sum of the masses of the sodium aluminate and the silica sol is 0.01-0.25:100; the platinum precursor is calculated as platinum element, the sodium aluminate is calculated as Al2O3, and the silica sol is calculated as SiO2.

5. The preparation method according to claim 2, wherein The ethylenediamine coordinated platinum precursor is obtained by mixing an aqueous solution of a platinum salt with ethylenediamine.

6. The preparation method according to claim 5, wherein In the platinum salt, the molar ratio of platinum to ethylenediamine is 1:15-20.

7. The preparation method according to claim 5 or 6, wherein The platinum salt is chloroplatinic acid.

8. The preparation method according to claim 2, wherein The ethylenediamine coordinated platinum precursor is added by slow dropwise addition at room temperature.

9. The preparation method according to claim 2, wherein The aging condition is to stir at 25-30°C for 8-12 hours.

10. The preparation method according to claim 2, wherein The in-situ static hydrothermal crystallization has a crystallization temperature of 100 to 150° C. and a crystallization time of 8 to 15 days.

11. The preparation method according to claim 2, wherein The calcination temperature is 300-350°C, and the hydrogen reduction temperature is 200-250°C.

12. The preparation method according to claim 11, wherein The heating rate of the calcination is 0.2-0.6°C / min, and the heating rate of the hydrogen reduction is 0.1-0.5°C / min.

13. The preparation method according to claim 2, characterized in that The SOD cage-confined single-atom platinum Y-type molecular sieve has a silicon-aluminum molar ratio of 5-20.

14. The preparation method according to claim 1, wherein The phenylacetylene is subjected to catalytic hydrogenation at a temperature of 120 to 150° C., a hydrogen pressure of 0.6 to 1.0 MPa, and a time of 15 to 90 minutes.

15. The preparation method according to claim 1, wherein The molar ratio of the phenylacetylene to the platinum in the SOD cage-confined single-atom platinum Y molecular sieve is 30-70:

1.

16. The preparation method according to claim 1, wherein The phenylacetylene contains 0.5% to 2% of thiophene based on the mass of the phenylacetylene.

17. The preparation method according to claim 1, wherein The mass content of single-atom platinum in the SOD cage-confined single-atom platinum Y molecular sieve is 0.01-0.2 wt%.

18. The preparation method according to claim 4, wherein The molar ratio of the silica sol, sodium metaaluminate and alkali source is (9.5-10.6):1:(4.0-5.4).

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