Use of ssz-74 molecular sieve in adsorptive separation of benzene and cyclohexane
By utilizing the ordered silanol groups and multidimensional tortuous pore structure of SSZ-74 molecular sieve, combined with heat treatment and calcination processes, the stability and cost issues in the separation of benzene and cyclohexane were resolved, achieving efficient and low-cost industrial separation.
Patent Information
- Application Number
- CN202311102621.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-08-30
- Publication Date
- 2026-02-03
- Estimated Expiration
- 2043-08-30
AI Technical Summary
Existing technologies are insufficient for efficiently and cost-effectively separating benzene and cyclohexane. Traditional methods are energy-intensive and product purity is difficult to guarantee. The stability and cost issues of porous materials in the separation of benzene and cyclohexane have not been effectively resolved.
SSZ-74 molecular sieve was used as the adsorption and separation material. Its ordered silanol groups and multidimensional tortuous channels were utilized to achieve separation through π-bond interactions with benzene and cyclohexane. The stability and channel unobstructedness were improved by combining heat treatment and calcination processes.
This method achieves efficient separation of benzene and cyclohexane, reduces preparation costs, and improves the stability and regeneration performance of the material, making it suitable for industrial applications.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of adsorption separation technology, specifically relating to the use of SSZ-74 molecular sieve in the adsorption separation of benzene and cyclohexane. Background Technology
[0002] Cyclohexane is an important chemical raw material, widely used in the production of nylon, paints, and pharmaceutical intermediates. In recent years, my country's production capacity in related chemical fields has been gradually increasing. In actual chemical production, cyclohexane is generally produced by hydrogenation of benzene as a reactant. However, this reaction is generally difficult to achieve complete conversion, resulting in the product often containing both cyclohexane and unreacted benzene. Therefore, removing residual benzene to obtain high-purity cyclohexane is a crucial step in chemical production. However, benzene and cyclohexane have similar physical properties such as freezing point and density, as well as similar chemical properties such as molecular size and chemical structure. More importantly, their boiling points are almost identical, with benzene boiling at 80.1℃ and cyclohexane at 80.7℃. This makes it difficult to obtain high-purity cyclohexane in a single step using the commonly used industrial separation methods such as vacuum distillation, rectification, and extractive distillation, which rely on liquid-liquid azeotropic distillation. Using these traditional separation methods often requires multiple separations, leading to high purification costs and difficulty in guaranteeing product purity. Therefore, finding a highly efficient and simple way to separate and purify a mixture of benzene and cyclohexane is a significant challenge.
[0003] Against this backdrop, designing or finding a novel, efficient, and low-energy-consumption method for separating benzene and cyclohexane has become crucial for the industrial purification of cyclohexane. In recent years, with the rise of various novel crystalline and amorphous functional materials, many materials, due to their inherent advantages, have offered solutions to some classic industrial problems. Among them, the development of porous materials has provided many new options for the adsorption and separation of numerous important chemical raw materials.
[0004] Many porous materials, due to their high specific surface area, ordered pore distribution, and adjustable pore size, structure, and internal environment, are widely used to solve industrial problems such as hydrogen purification, alkyne separation, benzene and cyclohexane separation, and selective adsorption of xylene isomers. These include zeolite molecular sieves, carbon molecular sieves, metal-organic frameworks (MOFs), covalent organic frameworks (COFs), porous organic polymers (POPs), and porous organic cages. In the separation process of benzene and cyclohexane, the porous materials currently used are mainly metal-organic frameworks (MOFs) and porous organic cages. Adsorption separation is mainly achieved by matching the pore size with the size of benzene or cyclohexane, or by controlling the interaction between the ligands within the pores and benzene or cyclohexane to slow down the diffusion rate out of the pores. Although these porous materials exhibit excellent adsorption and separation performance, their structures often contain unstable dynamic chemical bonds, making them susceptible to structural damage under harsh conditions such as acidity, alkalinity, and high-temperature hydrothermal processes. This, in turn, affects the separation performance after recycling. Furthermore, the high synthesis costs significantly limit the industrial application of these porous materials in the adsorption and separation of benzene and cyclohexane.
[0005] Among many porous materials, zeolite molecular sieves have outstanding advantages in preparation cost and stability, and have already demonstrated excellent performance in hydrogen purification and olefin separation (Nature Materials, 2021, 20, 362–369; Science, 2020, 368, 1002-1006). However, there are very few studies on their application in the separation of benzene and cyclohexane. Only theoretical simulations and adsorption experiments involve some experimental assumptions. Therefore, selecting a zeolite molecular sieve suitable for the separation of benzene and cyclohexane may provide a new approach suitable for industrial production to solve this industrial problem. Summary of the Invention
[0006] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide the use of SSZ-74 molecular sieve in the adsorption and separation of benzene and cyclohexane, in order to solve the technical problems existing in the prior art.
[0007] To achieve the above objectives, the present invention specifically adopts the following technical solution.
[0008] The first aspect of this invention protects the use of SSZ-74 molecular sieve in the adsorption and separation of benzene and cyclohexane.
[0009] This invention selects SSZ-74 molecular sieve with a -SVR structure as the separation material. It utilizes the unique ordered silanol groups and its unique multidimensional tortuous channels to separate benzene and cyclohexane through the structure-selective adsorption of the multidimensional tortuous channels. At the same time, it separates benzene and cyclohexane through the interaction between the ordered silanol groups and the π bonds in benzene. The separation of benzene and cyclohexane is achieved by using the different penetration points of SSZ-74 molecular sieve for benzene and cyclohexane.
[0010] In the applications described in this invention, the SSZ-74 molecular sieve is selected from all-silicon SSZ-74 molecular sieves or heteroatom-doped SSZ-74 molecular sieves.
[0011] The all-silicon SSZ-74 molecular sieve is composed of silicon oxide (SiO2), and the heteroatom-doped SSZ-74 molecular sieve is composed of silicon dioxide and heteroatom oxides.
[0012] Preferably, the ratio of silicon to heteroatoms in the SSZ-74 molecular sieve is not less than 20, based on the molar ratio of silicon dioxide to heteroatom oxides. More preferably, it is 20 to 200.
[0013] Preferably, the heteroatom is selected from one or more of aluminum, titanium, boron and gallium.
[0014] More preferably, the heteroatom is aluminum, resulting in a silicon-aluminum SSZ-74 molecular sieve.
[0015] More preferably, based on the molar ratio of SiO2 to Al2O3, the silicon-to-aluminum ratio in the SSZ-74 silica-alumina molecular sieve is greater than 20, but can also be 20–200, 50–120, 20–60, 100–140, or 120–200, with 50–120 being more preferred. In some specific embodiments, it is 100 or 30.
[0016] More preferably, the heteroatom is titanium, resulting in titanium silicon SSZ-74 molecular sieve.
[0017] More preferably, the silicon-to-titanium ratio in the titanium-silicon SSZ-74 molecular sieve is greater than 50, or it can be 50-200, or 50-100, based on the molar ratio of SiO2 to TiO2. In some specific embodiments, it is 100.
[0018] In the application described in this invention, the SSZ-74 molecular sieve is obtained by heating SSZ-74 molecular sieve powder. Heating removes moisture from the SSZ-74 molecular sieve, thereby activating it.
[0019] Preferably, the heat treatment temperature is 30–400°C, or it can be 30–200°C, 80–350°C, or 220–400°C, with 80–450°C and 200–400°C being more preferred. In some specific embodiments, it is 200°C and 400°C.
[0020] Preferably, the heating treatment time is 0.1–24 h, or 0.1–5 h, or 4–15 h, or 12–24 h, with 1–6 h or 2–4 h being more preferred. In some specific embodiments, it is 2 h.
[0021] Preferably, the atmosphere for the heat treatment is selected from one or more of vacuum, air, nitrogen, helium, and argon.
[0022] Preferably, the heating treatment is performed by degassing or purging.
[0023] Preferably, the heat treatment further includes calcination to remove the template agent from the SSZ-74 molecular sieve powder. This application removes the template agent through calcination to ensure unobstructed pores, which is beneficial for subsequent benzene adsorption; then, activation through heat treatment removes the moisture adsorbed by the SSZ-74 molecular sieve, preventing it from competing with benzene and cyclohexane for adsorption.
[0024] More preferably, the roasting process further includes acid washing and silicon replenishment. The acid washing is performed by acid immersion treatment, and the silicon replenishment is performed by adding a silicon replenishing reagent. The acid can be an organic acid or an inorganic acid. For example, the organic acid can be citric acid, 2,4-dimethylbenzenesulfonic acid, or 2,4-dimethylbenzoic acid. The organic acid can be sulfuric acid, nitric acid, or hydrochloric acid. The silicon replenishing reagent can be selected from tetraethyl orthosilicate, ammonium hexafluorosilicate, or ethyl orthosilicate. For details, please refer to Crystal Growth & Design 2023, 23, 3681–3693.
[0025] More preferably, the calcination temperature is 200–800°C, or 200–550°C, or 450–650°C, or 600–800°C, with 400–800°C and 500–600°C being more preferred. In some specific embodiments, it is 550°C and 600°C.
[0026] More preferably, the calcination time is 0.5–24 h, or 0.5–3 h, or 2–10 h, or 6–15 h, or 12–24 h, with 2–8 h and 4–6 h being more preferred. In some specific embodiments, it is 4 h and 5 h.
[0027] More preferably, the calcination is carried out in a protective atmosphere. More preferably, the protective atmosphere is selected from one or more of nitrogen, argon, oxygen, air, and an oxygen-argon mixture, such as oxygen, air, or an oxygen-argon mixture.
[0028] More preferably, the preparation method of the SSZ-74 molecular sieve raw powder is as follows: 1) the silicon source, template agent and mineralizer react in an aqueous solution to obtain a gel mixture; 2) the gel mixture is crystallized to obtain the SSZ-74 molecular sieve raw powder.
[0029] More preferably, step 1) further includes the addition of a heteroatom source. The heteroatom is selected from one or more of aluminum, titanium, boron, and gallium. The heteroatom source originates from an oxide or sodium salt of the heteroatom. When the heteroatom is aluminum, it comes from sodium aluminate; when the heteroatom is titanium, it comes from tetrabutyl titanate; when the heteroatom is boron, it comes from boric acid; and when the heteroatom is gallium, it comes from gallium oxide.
[0030] More preferably, the silicon source is selected from one or more of silica, silica sol, tetramethyl orthosilicate, tetraethyl orthosilicate, and silica gel.
[0031] More preferably, the template agent is selected from one of hexamethylene-1,6-bis(N-methylpyrrolidone) divalent cation, hexamethylene-1-trimethylammonium-6-N-methylpyrrolidone divalent cation, and hexamethylene-1,6-bis(dimethylethyl) divalent cation. The template agent is one of the above-mentioned divalent cationic hydroxides or halides. Specifically, for example, the hexamethylene-1,6-bis(dimethylethyl) divalent cationic compound is hexamethylene-1,6-bis(dimethylethylammonium hydroxide).
[0032] The structural formula of the hexamethylene-1,6-bis(N-methylpyrrolidone) divalent cation is as follows:
[0033]
[0034] The structural formula of the hexamethylene-1-trimethylammonium-6-N-methylpyrrolidineonium divalent cation is as follows:
[0035]
[0036] The structural formula of the hexamethylene-1,6-bis(dimethylethyl) divalent cation is as follows:
[0037]
[0038] More preferably, the alkali metal source is selected from one or more of sodium hydroxide, potassium hydroxide, and cesium hydroxide.
[0039] More preferably, the fluorine source is selected from one or both of hydrofluoric acid and ammonium fluoride.
[0040] More preferably, the crystallization temperature can be 120–160°C, 140–180°C, 160–200°C, 180–220°C, or 200–240°C. In some embodiments, it is 160°C.
[0041] More preferably, the crystallization time can be 24–100 h, 96–168 h, 154–236 h, or 268–336 h. In some embodiments, it is 168 h.
[0042] A second aspect of the present invention protects an adsorption separation method for benzene and cyclohexane, which uses SSZ-74 molecular sieve to adsorb and separate a mixture of benzene and cyclohexane.
[0043] In the adsorption separation method of the present invention, the adsorption separation temperature is 20–100°C, or 20–45°C, or 30–65°C, or 55–100°C. In some specific embodiments, it is 25°C or room temperature.
[0044] In the adsorption separation method of the present invention, the volume ratio of benzene to cyclohexane is (1-99):(1-99). In some specific embodiments, it is 50:50 or 10:50.
[0045] In the adsorption separation method of the present invention, the conditions for adsorption separation are: the flow rate of the mixed gas is 0.1 to 100 sccm. Preferably, the flow rate is 1 to 50 sccm.
[0046] In the adsorption separation method of the present invention, the load gas is selected from one or more of nitrogen, helium, argon and air. Preferably, the load gas is helium.
[0047] Preferably, the flow rate ratio of benzene, cyclohexane, and load gas is 1:(0.5-5):(30-60). The flow rate ratio of load gas, cyclohexane, and benzene is 48:1:1 or 44:5:1.
[0048] In the adsorption separation method of the present invention, the SSZ-74 molecular sieve is selected from all-silicon SSZ-74 molecular sieve or heteroatom-doped SSZ-74 molecular sieve.
[0049] Preferably, the SSZ-74 molecular sieve is selected from either an all-silicon SSZ-74 molecular sieve or a heteroatom-doped SSZ-74 molecular sieve. The all-silicon SSZ-74 molecular sieve is composed of silicon oxide (SiO2), and the heteroatom-doped SSZ-74 molecular sieve is composed of silicon dioxide and heteroatom oxides.
[0050] Preferably, the ratio of silicon to heteroatoms in the SSZ-74 molecular sieve is not less than 20, based on the molar ratio of silicon dioxide to heteroatom oxides. More preferably, it is 20 to 200.
[0051] Preferably, the heteroatom is selected from one or more of aluminum, titanium, boron and gallium.
[0052] More preferably, the heteroatom is aluminum, resulting in a silicon-aluminum SSZ-74 molecular sieve. Even more preferably, the silicon-aluminum ratio in the silicon-aluminum SSZ-74 molecular sieve, based on the molar ratio of SiO2 to Al2O3, is greater than 20, but can also be 20–200, 50–120, 20–60, 100–140, or 120–200, with 50–120 being more preferred. In some specific embodiments, it is 100 or 30.
[0053] More preferably, the heteroatom is titanium, resulting in a titanium-silicon SSZ-74 molecular sieve. Even more preferably, the silicon-to-titanium ratio in the titanium-silicon SSZ-74 molecular sieve is greater than 50, or can be 50–200, or 50–100, based on the molar ratio of SiO2 to TiO2. In some specific embodiments, it is 100.
[0054] In the adsorption separation method of this invention, the SSZ-74 molecular sieve is obtained by heating SSZ-74 molecular sieve powder. Heating removes moisture from the SSZ-74 molecular sieve, thereby activating it.
[0055] Preferably, the heat treatment temperature is 30–400°C, or it can be 30–200°C, 80–350°C, or 220–400°C, with 80–450°C and 200–400°C being more preferred. In some specific embodiments, it is 200°C and 400°C.
[0056] Preferably, the heating treatment time is 0.1–24 h, or 0.1–5 h, or 4–15 h, or 12–24 h, with 1–6 h or 2–4 h being more preferred. In some specific embodiments, it is 2 h.
[0057] Preferably, the atmosphere for the heat treatment is selected from vacuum, air, nitrogen, helium, and argon. More preferably, it is air.
[0058] Preferably, the heating treatment is performed by degassing or purging.
[0059] Preferably, the heat treatment further includes calcination to remove the template agent from the SSZ-74 molecular sieve powder. This application removes the template agent through calcination to ensure unobstructed pores, which is beneficial for subsequent benzene adsorption; then, activation through heat treatment removes the moisture adsorbed by the SSZ-74 molecular sieve, preventing it from competing with benzene and cyclohexane for adsorption.
[0060] More preferably, the roasting process further includes acid washing and silicon replenishment. The acid washing is performed by acid immersion treatment, and the silicon replenishment is performed by adding a silicon replenishing reagent. The acid can be an organic acid or an inorganic acid. For example, the organic acid can be citric acid, 2,4-dimethylbenzenesulfonic acid, or 2,4-dimethylbenzoic acid. The organic acid can be sulfuric acid, nitric acid, or hydrochloric acid. The silicon replenishing reagent can be selected from tetraethyl orthosilicate, ammonium hexafluorosilicate, or ethyl orthosilicate. For details, please refer to Crystal Growth & Design 2023, 23, 3681–3693.
[0061] More preferably, the calcination temperature is 200–800°C, or 200–550°C, or 450–650°C, or 600–800°C, with 400–800°C and 500–600°C being more preferred. In some specific embodiments, it is 550°C and 600°C.
[0062] More preferably, the calcination time is 0.5–24 h, or 0.5–3 h, or 2–10 h, or 6–15 h, or 12–24 h, with 2–8 h and 4–6 h being more preferred. In some specific embodiments, it is 4 h and 5 h.
[0063] More preferably, the calcination is carried out in a protective atmosphere. More preferably, the protective atmosphere is selected from one or more of nitrogen, argon, oxygen, air, and an oxygen-argon mixture, such as oxygen, air, or an oxygen-argon mixture.
[0064] More preferably, the preparation method of the SSZ-74 molecular sieve raw powder is as follows: 1) the silicon source, template agent and mineralizer react in an aqueous solution to obtain a gel mixture; 2) the gel mixture is crystallized to obtain the SSZ-74 molecular sieve raw powder.
[0065] Further preferably, step 1) further includes the addition of a heteroatom source. The heteroatom is selected from one or more of aluminum, titanium, boron, and gallium. The heteroatom source originates from an oxide or sodium salt of the heteroatom. When the heteroatom is aluminum, it comes from sodium aluminate; when the heteroatom is titanium, it comes from tetrabutyl titanate; when the heteroatom is boron, it comes from boric acid; and when the heteroatom is gallium, it comes from gallium oxide.
[0066] More preferably, the silicon source is selected from one or more of silica, silica sol, tetramethyl orthosilicate, tetraethyl orthosilicate, and silica gel.
[0067] More preferably, the template agent is selected from one of hexamethylene-1,6-bis(N-methylpyrrolidone) divalent cation, hexamethylene-1-trimethylammonium-6-N-methylpyrrolidone divalent cation, and hexamethylene-1,6-bis(dimethylethyl) divalent cation. The template agent is one of the above-mentioned divalent cationic hydroxides or halides. Specifically, for example, the hexamethylene-1,6-bis(dimethylethyl) divalent cationic compound is hexamethylene-1,6-bis(dimethylethylammonium hydroxide).
[0068] More preferably, the mineralizing agent is selected from an alkali metal source or a fluorine source. The alkali metal source is selected from one or more of sodium hydroxide, potassium hydroxide, and cesium hydroxide. The fluorine source is selected from one or two of hydrofluoric acid and ammonium fluoride.
[0069] More preferably, the crystallization temperature can be 120–160°C, 140–180°C, 160–200°C, 180–220°C, or 200–240°C. In some embodiments, it is 160°C.
[0070] More preferably, the crystallization time can be 24–100 h, 96–168 h, 154–236 h, or 268–336 h. In some embodiments, it is 168 h.
[0071] The adsorption separation method for benzene and cyclohexane in this invention is a novel separation mechanism of SSZ-74 molecular sieve that integrates pore structure and microporous internal environment. It is different from the previous simple pore type-selective separation method. Compared with other porous materials, SSZ-74 molecular sieve has the advantages of low preparation cost and high stability, making it a more suitable material for the separation of benzene and cyclohexane in industrial applications.
[0072] Compared with the prior art, the present invention has the following beneficial effects:
[0073] 1) This invention uses SSZ-74 molecular sieve as an adsorption and separation material, which can achieve efficient breakthrough separation of benzene and cyclohexane, filling the gap in the field of molecular sieve materials for the adsorption and separation of benzene and cyclohexane. At the same time, compared with other existing porous materials separation methods, SSZ-74 molecular sieve itself has natural advantages such as low preparation cost and simple preparation method.
[0074] 2) The present invention utilizes SSZ-74 molecular sieve for the adsorption and separation of benzene and cyclohexane, which combines the advantages of the unique multidimensional tortuous channels of SSZ-74 for the type selectivity of benzene and cyclohexane, as well as the advantages of the abundant ordered silanol groups inside the pores of SSZ-74 molecular sieve interacting with the π bonds in benzene, thereby achieving the separation of benzene and cyclohexane in a synergistic manner.
[0075] 3) The adsorption separation method of the present invention can achieve efficient separation of benzene and cyclohexane at room temperature using SSZ-74 molecular sieve. At the same time, due to the high stability of SSZ-74 molecular sieve itself, it also has excellent regeneration performance as an adsorption separation material. It can be recycled 20 times and still has the ability to efficiently separate benzene and cyclohexane.
[0076] 4) When using SSZ-74 molecular sieve to adsorb and separate benzene and cyclohexane, the breakthrough point of benzene is at least 9 min / g later than that of cyclohexane, while when using other molecular sieves for adsorption and separation, the breakthrough point of benzene is less than 3.14 min / g later than that of cyclohexane. Attached Figure Description
[0077] Figure 1 The image shown is the PXRD pattern of the SSZ-74 molecular sieve after heat treatment in Example 1 of this invention.
[0078] Figure 2 The image shown is the PXRD pattern of the SSZ-74 molecular sieve after heat treatment in Example 2 of this invention.
[0079] Figure 3 The image shown is the PXRD pattern of the SSZ-74 molecular sieve after heat treatment in Example 3 of this invention.
[0080] Figure 4 The image shown is the PXRD pattern of the SSZ-74 molecular sieve after heat treatment in Example 4 of this invention.
[0081] Figure 5 The diagram shows the gas penetration adsorption of benzene and cyclohexane obtained using the SSZ-74 molecular sieve of Example 1 in Example 5 of this invention.
[0082] Figure 6 The diagram shows the gas penetration adsorption of benzene and cyclohexane obtained using the SSZ-74 molecular sieve of Example 2 in Example 7 of this invention.
[0083] Figure 7 The image shown is a gas transmission diagram of benzene and cyclohexane obtained using the SSZ-74 molecular sieve of Example 3 in Example 8 of this invention.
[0084] Figure 8 The diagram shows the gas penetration adsorption of benzene and cyclohexane obtained using the SSZ-74 molecular sieve of Example 4 in Example 9 of this invention.
[0085] Figure 9 The diagram shows the gas penetration adsorption of benzene and cyclohexane obtained after one regeneration of the SSZ-74 molecular sieve from Example 6 in Example 10 of this invention.
[0086] Figure 10 The diagram shows the gas penetration adsorption of benzene and cyclohexane obtained after regenerating the SSZ-74 molecular sieve of Example 5 20 times in Example 11 of this invention. Detailed Implementation
[0087] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.
[0088] Before further describing specific embodiments of the present invention, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments described below; it should also be understood that the terminology used in the embodiments of the present invention is for describing specific embodiments and not for limiting the scope of protection of the present invention. Test methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or as recommended by the respective manufacturers.
[0089] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. In addition to the specific methods, apparatus, and materials used in the embodiments, based on the knowledge of the prior art possessed by one of ordinary skill in the art and the description of this invention, any prior art methods, apparatus, and materials similar to or equivalent to those described, apparatus, and materials in the embodiments of this invention may be used to implement the present invention.
[0090] Through long-term experimental research, the inventors have discovered that SSZ-74 molecular sieves can achieve highly efficient separation of benzene and cyclohexane. Compared to previously disclosed porous separation materials, the SSZ-74 molecular sieve used in this invention has lower preparation costs, better stability, and is simpler to prepare, making it more suitable for industrial production.
[0091] In this invention, PXRD data were obtained using a Bruker D8 Advance X-ray diffractometer (Germany) to characterize the crystal structure of the molecular sieve; gas breakthrough curves were obtained using a Bestech Instruments BSD-MAB multi-component competitive adsorption breakthrough curve analyzer to characterize gas separation performance.
[0092] The technical solution of the present invention will be further described below through specific embodiments.
[0093] The structural formula of hexamethylene-1,6-bis(dimethylethylammonium hydroxide) used in the following embodiments of this application is as follows:
[0094]
[0095] Example 1
[0096] In this Example 1, SSZ-74 molecular sieve powder with a silicon-to-aluminum ratio of 100 is used as raw material for heat treatment, including the following steps:
[0097] The SSZ-74 molecular sieve powder was calcined at 550℃ for 4 hours, and then degassed under vacuum at 200℃ for 2 hours to obtain the SSZ-74 molecular sieve.
[0098] The preparation method of SSZ-74 molecular sieve raw powder with a silicon-to-aluminum ratio of 100 is as follows:
[0099] 1) Silica sol (40 wt% SiO2), sodium aluminate, sodium hydroxide solid powder, and hexamethylene-1,6-bis(dimethylethylammonium hydroxide) were used as the silicon source, aluminum source, mineralizer, and template agent (the template agent was named R), respectively. The mixture was stirred overnight at room temperature to obtain a gel mixture. The molar amount of SiO2 was calculated by converting the mass of the silicon source to the molar amount of silicon; the molar amount of Al2O3 was calculated by converting the mass of the aluminum source to the molar amount of Al. The molar ratio of silicon source, aluminum source, mineralizer, template agent, and water (SiO2:Al2O3:NaOH:R:H2O = 1.0:0.005:0.15:0.4:40) was 1.0:0.005:0.15:0.4:40.
[0100] 2) The product was then transferred to a reactor and crystallized at 160°C and 30 rpm for 168 h. After crystallization, the crystallized product was cooled, filtered, washed, and dried at 80°C to obtain SSZ-74 molecular sieve powder.
[0101] The heat-treated SSZ-74 molecular sieve was characterized by PXRD, and the results are shown in the figure. Figure 1 .
[0102] from Figure 1 As can be seen from the PXRD characterization results, the SSZ-74 molecular sieve obtained under these calcination and heat treatment conditions has the characteristic diffraction peaks of -SVR molecular sieves, and is a pure -SVR molecular sieve with a crystal micropore size distribution of 0.3 to 0.5 nm.
[0103] In summary, the activation method described in this application can maintain the high crystallinity of SSZ-74 molecular sieve.
[0104] Example 2
[0105] In this Example 2, the SSZ-74 molecular sieve powder with a silicon-to-aluminum ratio of 100 obtained in Example 1 is used as raw material. After calcination, it undergoes heat treatment, including the following steps:
[0106] The SSZ-74 molecular sieve powder was calcined at 600℃ for 5 hours and then degassed under vacuum at 400℃ for 2 hours to obtain the SSZ-74 molecular sieve.
[0107] The heat-treated SSZ-74 molecular sieve was characterized by PXRD, and the results are shown in the figure. Figure 2 .
[0108] from Figure 2 As can be seen from the PXRD characterization results, although the SSZ-74 molecular sieve obtained under these calcination and heat treatment conditions has the characteristic diffraction peaks of -SVR structure molecular sieves, the peak intensity is low. Although it is a pure -SVR structure molecular sieve, its crystallinity is poor. The micropore size of the SSZ-74 molecular sieve is distributed in the range of 0.3 to 0.5 nm.
[0109] In summary, the activation method described in this application can maintain the crystal structure of SSZ-74 molecular sieve.
[0110] Example 3
[0111] In this Example 3, all-silicon SSZ-74 molecular sieve powder is used as raw material. After calcination, it undergoes heat treatment, including the following steps:
[0112] The raw powder of all-silicon SSZ-74 molecular sieve was calcined at 550℃ for 4 hours and then degassed under vacuum at 200℃ for 2 hours to obtain SSZ-74 molecular sieve.
[0113] The preparation of the all-silica SSZ-74 molecular sieve raw powder is as follows:
[0114] 1) Silica sol (40 wt% SiO2), sodium hydroxide solid powder, and hexamethylene-1,6-bis(dimethylethylammonium hydroxide) were used as the silicon source, mineralizer, and template agent (the template agent was named R), respectively, and mixed and stirred overnight at room temperature to obtain a gel mixture. The molar number of SiO2 was obtained by converting the mass of the silicon source to the molar number of silicon elements. The molar ratio of silicon source, mineralizer, template agent, and water (SiO2:NaOH:R:H2O = 1.0:0.1:0.4:40) was 1.0:0.1:0.4:40.
[0115] 2) The gel mixture obtained in step 1) was transferred to a reaction vessel and crystallized at 160°C and 30 rpm for 168 h. After crystallization, the crystallized product was cooled, filtered, washed, and dried at 80°C to obtain SSZ-74 molecular sieve.
[0116] The heat-treated all-silica SSZ-74 molecular sieve was characterized by PXRD, and the results are shown in the figure. Figure 4 .
[0117] from Figure 3As can be seen from the PXRD characterization results, the SSZ-74 molecular sieve obtained under these calcination and heat treatment conditions has the characteristic diffraction peaks of -SVR structure molecular sieves, and is a pure -SVR structure molecular sieve with a crystal micropore size distribution of 0.3-0.5 nm.
[0118] In summary, the activation method described in this application can maintain the high crystallinity of SSZ-74 molecular sieve.
[0119] Example 4
[0120] In this Example 4, SSZ-74 molecular sieve powder with a silicon-to-aluminum ratio of 30 is used as raw material. After calcination, it undergoes heat treatment, including the following steps:
[0121] The SSZ-74 molecular sieve powder was calcined at 550℃ for 4 hours and then degassed under vacuum at 200℃ for 2 hours to obtain the SSZ-74 molecular sieve.
[0122] The preparation method of SSZ-74 molecular sieve raw powder with a silicon-to-aluminum ratio of 30 is as follows:
[0123] 1) Silica sol (40 wt% SiO2), sodium aluminate, sodium hydroxide solid powder, and hexamethylene-1,6-bis(dimethylethylammonium hydroxide) were mixed as the silicon source, aluminum source, mineralizer, and template agent (template agent named R), respectively, and stirred overnight at room temperature to obtain a gel mixture. The molar amount of SiO2 was calculated by converting the mass of the silicon source to the molar amount of silicon; the molar amount of Al2O3 was calculated by converting the mass of the aluminum source to the molar amount of Al; the molar ratio of silicon source, aluminum source, mineralizer, template agent, and water (SiO2:Al2O3:NaOH:R:H2O = 1.0:0.017:0.15:0.4:40) was 1.0:0.017:0.15:0.4:40.
[0124] 2) Add SSZ-74 molecular sieve seed crystals, then transfer to a reactor for crystallization at 160°C and 30 rpm for 168 hours. After crystallization, cool, filter, wash, and dry the crystallized product at 80°C to obtain SSZ-74 molecular sieve powder. The SSZ-74 molecular sieve seed crystals are the product of Example 3, and the amount of seed crystals added is 10% of the solid content of the gel mixture.
[0125] The heat-treated SSZ-74 molecular sieve was characterized by PXRD, and the results are shown in the figure. Figure 3 .
[0126] from Figure 4As can be seen from the PXRD characterization results, the SSZ-74 molecular sieve obtained under these calcination and heat treatment conditions has the characteristic diffraction peaks of -SVR structure molecular sieves, and is a pure -SVR structure molecular sieve with a crystal micropore size distribution of 0.3-0.5 nm.
[0127] In summary, the activation method described in this application can maintain the high crystallinity of SSZ-74 molecular sieve.
[0128] Example 5
[0129] In this Example 5, titanium-silicon SSZ-74 molecular sieve is used as raw material. After calcination, it undergoes heat treatment, including the following steps:
[0130] The titanium-silicon SSZ-74 molecular sieve raw powder was acid-washed and silicon-replenished, then calcined at 550℃ for 4 hours, and degassed under vacuum at 200℃ for 2 hours to obtain SSZ-74 molecular sieve. The acid washing and silicon replenishment were performed by mixing 1g of SSZ-74 molecular sieve raw powder with 0.1g of tetraethyl orthosilicate and 10g of 1M nitric acid aqueous solution, followed by hydrothermal treatment at 175℃ for 12 hours.
[0131] The preparation of SSZ-74 molecular sieve raw powder with a silicon-to-titanium ratio of 100 is as follows:
[0132] 1) Silica sol (40 wt% SiO2), tetrabutyl titanate, sodium hydroxide solid powder, and hexamethylene-1,6-bis(dimethylethylammonium hydroxide) were mixed as the silicon source, titanium source, mineralizer, and template agent, respectively, and stirred overnight at room temperature to obtain a gel mixture. The molar amount of SiO2 was calculated by converting the mass of the silicon source to the molar amount of silicon; the molar amount of TiO2 was calculated by converting the mass of the titanium source to the molar amount of titanium. The molar ratio of silicon source, titanium source, mineralizer, template agent, and water (SiO2:TiO2:NaOH:R:H2O = 1.0:0.01:0.1:0.4:40) was 1.0:0.01:0.1:0.4:40.
[0133] 2) The gel mixture obtained in step 1) was transferred to a reaction vessel and crystallized at 160°C and 30 rpm for 168 h. After crystallization, the crystallized product was cooled, filtered, washed, and dried at 80°C to obtain titanium silicon SSZ-74 molecular sieve.
[0134] Example 6
[0135] In this Example 6, the SSZ-74 molecular sieve after heat treatment in Example 1 was used as the adsorption and separation material, and its performance was tested using a multi-component competitive adsorption breakthrough curve analyzer.
[0136] The test conditions were as follows: the volume ratio of benzene to cyclohexane in the mixed gas was 50:50, the load gas was helium, the flow rate of benzene and cyclohexane was 1 sccm, the flow rate of helium was 48 sccm, the total test flow rate was 50 sccm, and the separation test temperature was 25℃.
[0137] The breakthrough column of the multi-component competitive adsorption breakthrough curve analyzer is filled with SSZ-74 molecular sieve. The mixed gas flows in through the inlet of the analyzer, is adsorbed by the SSZ-74 molecular sieve, and then flows out through the outlet of the analyzer. By measuring the changes in the concentrations of benzene and cyclohexane in the outlet gas over time, the breakthrough time of benzene and cyclohexane, as well as the selective adsorption capacity of each component of the mixed gas by the SSZ-74 molecular sieve, are determined.
[0138] Breakthrough curve analysis is a technique for analyzing the adsorption and separation of materials under dynamic flow conditions. Its principle involves a breakthrough column loaded with molecular sieves as the adsorption and separation material, stacked into a bed of a certain height. The bed remains stationary. A mixed gas flows in through the inlet of the adsorber, is adsorbed by the molecular sieve, and then flows out through the outlet. By measuring the change in the concentration of each component in the outlet gas over time—the breakthrough curve—the breakthrough time of components other than the carrier gas and the selective adsorption capacity of the molecular sieve for each component of the mixed gas can be determined. In a multi-component competitive adsorption breakthrough curve analyzer, the breakthrough adsorption curve is a curve showing the change in the concentrations of benzene and cyclohexane in the outflow gas over time as the gas flows through the molecular sieve.
[0139] The breakthrough adsorption diagram of SSZ-74 molecular sieve was obtained, and the results are shown in [the table below]. Figure 5 In the figure, the horizontal axis represents the ratio of time to adsorbed mass (t / g), and the vertical axis represents C / C0 at time t (i.e., the ratio of outlet concentration C to inlet concentration C0, i.e., relative concentration). When the adsorbate flows out of the molecular sieve in the penetration column, the corresponding point on the breakthrough curve when the outflow concentration C reaches 5% of the initial concentration C0 is called the breakthrough point.
[0140] from Figure 5 It can be seen that in the breakthrough adsorption separation, the breakthrough point of benzene appears at least 15 min / g later than that of cyclohexane, proving that it can achieve efficient separation of benzene and cyclohexane.
[0141] Example 7
[0142] In this Example 7, the SSZ-74 molecular sieve after heat treatment in Example 2 was used as the adsorption and separation material, and its performance was tested using a multi-component competitive adsorption breakthrough curve analyzer.
[0143] The test conditions were as follows: the volume ratio of benzene to cyclohexane was 50:50, the load gas was helium, the flow rate of benzene and cyclohexane was 1 sccm, the flow rate of helium was 48 sccm, the total test flow rate was 50 sccm, and the separation test temperature was 25℃.
[0144] The breakthrough adsorption diagram of SSZ-74 molecular sieve was obtained, and the results are shown in [the table below]. Figure 6 .
[0145] from Figure 6 It can be seen that in the breakthrough adsorption separation, the breakthrough point of benzene appears with a lag of about 9 min / g compared with cyclohexane, indicating that if the crystallinity of the sample is deviated after pretreatment, the separation performance will be low.
[0146] Example 8
[0147] In this Example 8, the SSZ-74 molecular sieve after heat treatment in Example 3 was used as the adsorption and separation material, and its performance was tested using a multi-component competitive adsorption breakthrough curve analyzer.
[0148] The test conditions were as follows: the volume ratio of benzene to cyclohexane was 50:50, the load gas was helium, the flow rate of benzene and cyclohexane was 1 sccm, the flow rate of helium was 48 sccm, the total test flow rate was 50 sccm, and the separation test temperature was 25℃.
[0149] The breakthrough adsorption chromatogram of the obtained SSZ-74 molecular sieve is shown in the figure below. Figure 7 .
[0150] from Figure 7 It can be seen that in the breakthrough adsorption separation, the breakthrough point of benzene appears at least 15 min / g later than that of cyclohexane, proving that it can achieve efficient separation.
[0151] Example 9
[0152] In this Example 9, the SSZ-74 molecular sieve after heat treatment in Example 4 was used as the adsorption and separation material, and its performance was tested using a multi-component competitive adsorption breakthrough curve analyzer.
[0153] The test conditions were as follows: the volume ratio of benzene to cyclohexane in the mixed gas was 50:50, the load gas was helium, the flow rates of benzene and cyclohexane were both 1 sccm, the flow rate of helium was 48 sccm, the total test flow rate was 50 sccm, and the separation test temperature was 25℃.
[0154] The breakthrough adsorption chromatogram of the obtained SSZ-74 molecular sieve is shown in the figure below. Figure 8 .
[0155] from Figure 8It can be seen that in the breakthrough adsorption separation, the breakthrough point of benzene appears at least 15 min / g later than that of cyclohexane, proving that it can achieve efficient separation.
[0156] Example 10
[0157] In this Example 10, the SSZ-74 molecular sieve after adsorption and separation of benzene and cyclohexane in Example 6 was used as the adsorption and separation material. After being heated in air at 400°C for 4 hours, the material was regenerated. Then, the performance was tested using a multi-component competitive adsorption breakthrough curve analyzer.
[0158] The test conditions were as follows: the volume ratio of benzene to cyclohexane in the mixed gas was 50:50, the load gas was helium, the flow rate of benzene and cyclohexane was 1 sccm, the flow rate of helium was 48 sccm, the total test flow rate was 50 sccm, and the separation test temperature was 25℃.
[0159] The breakthrough adsorption chromatogram of the obtained SSZ-74 molecular sieve is shown in the figure below. Figure 9 .
[0160] from Figure 9 It can be seen that in the breakthrough adsorption separation, the breakthrough point of benzene appears with a lag of about 15 min / g compared with cyclohexane, proving that it can achieve efficient separation after two regenerations.
[0161] Example 11
[0162] In Example 11, the SSZ-74 molecular sieve after adsorption and separation of benzene and cyclohexane in Example 5 was used as the adsorption and separation material. After heating at 400°C in air for 4 hours, regeneration was completed. After repeating the regeneration-adsorption-regeneration process 19 times, the performance was tested using a gas adsorption-penetration instrument.
[0163] The test conditions were as follows: the volume ratio of benzene to cyclohexane in the mixed gas was 50:50, the load gas was helium, the flow rate of benzene and cyclohexane was 1 sccm, the flow rate of helium was 48 sccm, the total test flow rate was 50 sccm, and the separation test temperature was 25℃.
[0164] The breakthrough adsorption chromatogram of the obtained SSZ-74 molecular sieve is shown in the figure below. Figure 10 .
[0165] from Figure 10 It can be seen that in the breakthrough adsorption separation, the breakthrough point of benzene appears with a lag of nearly 15 min / g compared with cyclohexane, proving that it can still achieve efficient separation after 20 minutes of regeneration.
[0166] Example 12
[0167] The difference between Example 12 and Example 6 is that the volume ratio of benzene to cyclohexane in the mixed gas is 10:50, the load gas is helium, the flow rates of benzene and cyclohexane are 1 sccm and 5 sccm respectively, the flow rate of helium is 44 sccm, the total test flow rate is 50 sccm, and the separation test temperature is 25°C.
[0168] In breakthrough adsorption separation, the breakthrough point of benzene appears with a lag of nearly 15 min / g compared to cyclohexane.
[0169] This application obtained LTA (4A) molecular sieve, BEA (Beta) molecular sieve, FER (ZSM-35) molecular sieve, and TON (ZSM-22) molecular sieve from commercially available channels. Performance tests were conducted using a gas adsorption breakthrough analyzer under the same conditions as in Example 6. The results showed that the breakthrough point of benzene lagged behind that of cyclohexane by 13 s / g, 18.7 s / g, 39.6 s / g, and 3.14 min / g, respectively, which is significantly lower than the 15 min / g of this application. This indicates that these sieves cannot separate benzene and cyclohexane, and the regeneration times of the other molecular sieves are lower than those of this application.
[0170] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.
Claims
1. Application of SSZ-74 molecular sieve in the adsorption and separation of benzene and cyclohexane.
2. The use as described in claim 1, characterized in that, The SSZ-74 molecular sieve is selected from all-silicon SSZ-74 molecular sieve or heteroatom-doped SSZ-74 molecular sieve; And / or, the SSZ-74 molecular sieve is obtained by heat treatment of SSZ-74 molecular sieve raw powder.
3. The use as described in claim 2, characterized in that, The heteroatoms are selected from one or more of aluminum, titanium, boron, and gallium; And / or, the heat treatment further includes calcination to remove the template agent from the SSZ-74 molecular sieve powder; And / or, the temperature of the heat treatment is 30–450°C; And / or, the heat treatment time is 0.1 to 24 hours; And / or, the atmosphere for the heat treatment is selected from one or more of vacuum, air, nitrogen, helium, and argon.
4. The use as described in claim 3, characterized in that, The proportion of silicon to heteroatom in the SSZ-74 molecular sieve is not less than 20, based on the molar ratio of silicon dioxide to heteroatom oxides. And / or, the calcination temperature is 200–800°C; And / or, the calcination time is 3 to 5 hours; And / or, the process before roasting also includes acid washing and silicon replenishment.
5. The use as described in claim 4, characterized in that, The ratio of silicon to heteroatom in the SSZ-74 molecular sieve is 20 to 200, based on the molar ratio of silicon dioxide to heteroatom oxides.
6. The use as described in claim 2, characterized in that, The preparation method of the SSZ-74 molecular sieve raw powder is as follows: 1) the silicon source, template agent and mineralizer react in an aqueous solution to obtain a gel mixture; 2) the gel mixture is crystallized to obtain the SSZ-74 molecular sieve raw powder.
7. The use as described in claim 6, characterized in that, In 1), the template agent is selected from one of hexamethylene-1,6-bis(N-methylpyrrolidone) divalent cation, hexamethylene-1-trimethylammonium-6-N-methylpyrrolidone divalent cation, and hexamethylene-1,6-bis(dimethylethyl) divalent cation; And / or, in 1), the reaction further includes the addition of a heteroatom source; In and / or, 1), the mineralizing agent is selected from an alkali metal source or a fluorine source.
8. The use as described in claim 7, characterized in that, The alkali metal source is selected from one or more of sodium hydroxide, potassium hydroxide, and cesium hydroxide; And / or, the fluorine source is selected from one or both of hydrofluoric acid and ammonium fluoride.
9. A method for adsorption separation of benzene and cyclohexane, characterized in that, The mixture of benzene and cyclohexane was separated by adsorption using SSZ-74 molecular sieve.
10. The adsorption separation method as described in claim 9, characterized in that, The adsorption separation temperature is 20–100℃; And / or, the volume ratio of benzene to cyclohexane is (1-99):(1-99); And / or, the conditions for adsorption separation are: the flow rate of the mixed gas is 0.1 to 100 sccm; And / or, the SSZ-74 molecular sieve is selected from all-silicon SSZ-74 molecular sieve or heteroatom-doped SSZ-74 molecular sieve; And / or, the SSZ-74 molecular sieve is obtained by heat treatment of SSZ-74 molecular sieve raw powder.
11. The adsorption separation method according to claim 10, characterized in that, The adsorption separation further includes a load gas, which is selected from one or more of nitrogen, helium, argon and air; And / or, the heteroatom is selected from one or more of aluminum, titanium, boron, and gallium; And / or, the heat treatment further includes calcination to remove the template agent from the SSZ-74 molecular sieve powder; And / or, the temperature of the heat treatment is 30–450°C; And / or, the heat treatment time is 0.1 to 24 hours; And / or, the atmosphere for the heat treatment is selected from one or more of vacuum, air, nitrogen, helium, and argon; And / or, the preparation method of the SSZ-74 molecular sieve raw powder is as follows: 1) the silicon source, template agent and mineralizer react in an aqueous solution to obtain a gel mixture; 2) the gel mixture is crystallized to obtain the SSZ-74 molecular sieve raw powder.
12. The adsorption separation method as described in claim 11, characterized in that, The flow rate ratio of benzene, cyclohexane, and load gas is 1:(0.5-5):(30-60). And / or, based on the molar ratio of silicon dioxide to heteroatom oxides, the proportion of silicon to heteroatoms in the SSZ-74 molecular sieve is not less than 20; And / or, the calcination temperature is 200–800°C; And / or, the calcination time is 3 to 5 hours.
13. The adsorption separation method according to claim 12, characterized in that, The ratio of silicon to heteroatom in the SSZ-74 molecular sieve is 20 to 200, based on the molar ratio of silicon dioxide to heteroatom oxides.