Spherical magnesium oxide with through pore channels as well as preparation method and application of spherical magnesium oxide

Abstract

The invention relates to the technical field of preparation of propylene carbonate, and discloses spherical magnesium oxide with through pores as well as a preparation method and application of the spherical magnesium oxide. The method comprises the following steps: (1) dropwise adding an aqueous solution containing a magnesium source into an aqueous solution containing an alkali source, and stirring and mixing to form a mixed solution; (2) standing and aging the mixed solution under the condition that the temperature is higher than 40 DEG C and lower than 100 DEG C; (3) carrying out solid-liquid separation on a mixture obtained after standing and aging to obtain a precursor; and (4) under the condition of 300 to 900 DEG C, roasting the precursor. The spherical magnesium oxide with the through pore channels prepared by the method disclosed by the invention has relatively strong capability of adsorbing and activating carbon dioxide, can effectively catalyze ring opening of epoxypropane, can obtain obviously relatively high propylene carbonate yield under mild conditions, does not inactivate after being used as a catalyst for multiple times, and has relatively strong stability.

Description

Technical Field

[0001] The present invention relates to the technical field of propylene carbonate preparation, and particularly relates to a spherical magnesium oxide with through channels, a preparation method thereof, and an application thereof. Background Art

[0002] Propylene carbonate is an important cyclic organic carbonate product in the new energy field and an important chemical product for the high-value recycling of CO2. Propylene carbonate has the characteristics of low toxicity, high boiling point, and good stability, and is widely used in key fields such as special environmental protection solvents and degradable materials, including lithium-ion battery electrolytes, polar solvents, degradable polymer monomers, drug and fine chemical intermediates, ingredients in cosmetics and personal care products, etc.

[0003] The synthesis methods of propylene carbonate mainly include phosgene method, CO2-propylene glycol / glycerol method, urea alcoholysis method, CO2-halohydrin method, CO2-methanol method, CO2-propylene oxide cycloaddition method, etc. The phosgene method seriously pollutes the environment and has been gradually phased out by the market. When glycerol or diol is used as the raw material, there are problems of more by-products and being restricted by thermodynamics, resulting in poor atom economy. The reaction of urea with diol can also produce propylene carbonate, but its single-pass conversion rate is not high and the operating conditions are relatively harsh. The synthesis of propylene carbonate from halohydrin and carbon dioxide is an important method, but it usually produces by-products such as halogenated salts, which corrode the equipment. Starting from propargyl alcohol, it can also react to form propylene carbonate under the action of a suitable catalyst, but the economic benefit is poor and it is mainly used for laboratory synthesis. The CO2-methanol method is mainly used for the production of dimethyl carbonate, and propylene carbonate is mainly produced as a by-product, with problems such as a long process, low product purity, and high separation energy consumption. The preparation of propylene carbonate by the cycloaddition of carbon dioxide and propylene oxide is the most widely studied method, with an atom economy of 100%, a high yield of propylene carbonate, and good economic value.

[0004] Currently, homogeneous catalysts such as organic small molecules and ionic liquids, and heterogeneous catalysts such as metal oxides, metal Schiff base complexes, and metal-organic framework materials are widely used in this system. For example, patent application CN116020568A discloses a heterogeneous catalyst for synthesizing propylene carbonate, which is composed of a metal Schiff base complex, a halogen anion, and a nanocage material, and the synthesis process of the catalyst is cumbersome and the structure is complex. Patent application CN115155656A discloses a homogeneous catalyst with a hydroxy quaternary phosphonium salt structure, and the preparation cost of the catalyst is high and the toxicity is strong. Patent application CN111393402A discloses a method for the acid / quaternary ammonium salt composite catalysis of the cycloaddition of CO2 and epoxide to prepare propylene carbonate, and the catalyst is a multi-component homogeneous catalyst, which is relatively difficult to separate.

[0005] Compared with homogeneous catalysts, heterogeneous catalysts have the advantages of easy structural regulation and separation, which can greatly reduce the complexity of the reaction process and production costs in principle. However, at present, heterogeneous catalysts still have the problem of low catalyst activity due to insufficient active sites or loss of active sites during long-term use, resulting in decreased catalyst stability. In addition, the preparation process of metal Schiff base complexes and metal organic framework materials is complicated and expensive, and is not suitable for large-scale production. Therefore, the development of a heterogeneous catalyst with a simple preparation process, high activity, high stability and easy product separation is a technical problem that needs to be solved urgently. Summary of the invention

[0006] The purpose of the present invention is to overcome the problems in the prior art that the active sites of heterogeneous catalysts for synthesizing propylene carbonate are insufficient, resulting in low catalyst activity, and the active sites are lost during long-term use, resulting in decreased catalyst stability, and to provide a spherical magnesium oxide with through-holes and a preparation method and application thereof. The spherical magnesium oxide with through-holes prepared according to the method of the present invention has highly developed porosity and strong ability to adsorb and activate carbon dioxide; a propylene carbonate yield of >98% can be achieved under solvent-free and additive-free conditions, and the catalyst will not be deactivated after multiple uses, and has strong stability.

[0007] In order to achieve the above object, the first aspect of the present invention provides a method for preparing spherical magnesium oxide having through-holes, the method comprising the following steps:

[0008] (1) adding dropwise an aqueous solution containing a magnesium source into an aqueous solution containing an alkali source and stirring and mixing the mixture to form a mixed solution;

[0009] (2) subjecting the mixed solution to static aging at a temperature higher than 40° C. and lower than 100° C.;

[0010] (3) subjecting the mixture obtained after standing and aging to solid-liquid separation to obtain a precursor;

[0011] (4) calcining the precursor at 300-900°C.

[0012] Preferably, in step (1), the magnesium source is Mg 2+ The molar ratio of the alkali source is (0.5-5):1, preferably (0.5-2):1.

[0013] Preferably, in the aqueous solution containing the alkali source, the concentration of the alkali source is 0.1-10 mol / L, preferably 0.1-3 mol / L.

[0014] Preferably, in the aqueous solution containing a magnesium source, the concentration of the magnesium source is 0.01-5 mol / L, preferably 0.01-3 mol / L.

[0015] Preferably, the alkali source is at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, cesium carbonate, sodium bicarbonate, ammonium bicarbonate, urea, ammonia water, n-butylamine, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, tetrapropylammonium bromide, and tetrabutylammonium bromide.

[0016] Preferably, the magnesium source is at least one of magnesium nitrate, magnesium acetate, magnesium carbonate, and magnesium chloride.

[0017] Preferably, in step (1), the stirring and mixing time is 0.1 - 3 h, preferably 0.2 - 0.5 h.

[0018] Preferably, in step (2), the temperature for static aging is 50 - 70 °C, and the time for static aging is 1 - 24 h, preferably 1 - 3 h.

[0019] Preferably, in step (2), during the static aging process, the pH value of the mixed solution is controlled within the range of 6 - 11, preferably within the range of 7 - 9.

[0020] Preferably, in step (4), the calcination temperature is 400 - 600 °C, and the calcination time is 2 - 8 h, preferably 3 - 5 h.

[0021] The second aspect of the present invention provides spherical magnesium oxide with through - channels prepared by the above method.

[0022] The third aspect of the present invention provides a method for preparing propylene carbonate, which includes: reacting propylene oxide and carbon dioxide in the presence of a catalyst, wherein the catalyst is the spherical magnesium oxide with through - channels described above.

[0023] In the method for preparing the spherical magnesium oxide with through - channels of the present invention, the alkali source and the magnesium source are mixed in a specific manner, and static aging is carried out at a certain temperature, while controlling the calcination temperature of the precursor, so that the prepared spherical magnesium oxide product has a through - channel structure and a highly developed porosity, thereby having a strong ability to adsorb and activate carbon dioxide, being able to effectively catalyze the ring - opening of propylene oxide, and remaining inactive even after being used as a catalyst multiple times, with strong stability; moreover, when used for synthesizing propylene carbonate, compared with traditional heterogeneous catalysts, in the reaction process using the spherical magnesium oxide with through - channels of the present invention as the catalyst, no additional solvent and cocatalyst need to be added, and a propylene carbonate yield of more than 98% can be achieved under mild conditions.

[0024] In addition, in the method for preparing the spherical magnesium oxide with through channels according to the present invention, the raw materials used are all commercially available, inexpensive and easily obtainable; and in the preparation process, there is no need to add halogenated hydrocarbons, acids and bases for reflux treatment under a harsh atmosphere, no need to add pore-expanding agents, and no need to introduce polymers to construct a core-shell structure, which greatly reduces the synthesis time and shortens the synthesis steps, has no waste gas emission, and the process is green and environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is the XRD pattern of the spherical magnesium oxide with through channels prepared in Example 1;

[0026] Figure 2 is the nitrogen physical adsorption and desorption drawing of the spherical magnesium oxide with through channels prepared in Example 1;

[0027] Figure 3 is the pore size distribution diagram of the spherical magnesium oxide with through channels prepared in Example 1;

[0028] Figure 4 is the overall SEM image of the spherical magnesium oxide with through channels prepared in Example 1;

[0029] Figure 5 is the sectional SEM image of the spherical magnesium oxide with through channels prepared in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0030] The following provides a detailed description of the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only for the purpose of illustrating and explaining the present invention, and are not intended to limit the present invention.

[0031] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values and individual point values of each range, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0032] The method for preparing the spherical magnesium oxide with through channels according to the present invention includes the following steps:

[0033] (1) Drop an aqueous solution containing a magnesium source into an aqueous solution containing an alkali source and stir to mix to form a mixed solution;

[0034] (2) Under the condition of higher than 40 °C and lower than 100 °C, allow the mixed solution to stand and age;

[0035] (3) Separate the solid and liquid of the mixture obtained after standing and aging to obtain a precursor;

[0036] (4) Calcinate the precursor under the condition of 300 - 900 °C.

[0037] In the method of the present invention, the alkali source and the magnesium source are mixed in a specific manner, and static aging is carried out at a certain temperature. Meanwhile, the calcination temperature of the precursor is controlled, so that the prepared spherical magnesium oxide product has a through-channel structure and a highly developed porosity, thereby having a strong ability to adsorb and activate carbon dioxide, being able to effectively catalyze the ring-opening of propylene oxide, and still not deactivating after being used as a catalyst multiple times, with strong stability.

[0038] In step (1), the molar ratio of the magnesium source calculated as Mg 2+ to the alkali source is (0.5 - 5):1, preferably (0.5 - 2):1.

[0039] In step (1), in the aqueous solution containing the alkali source, the concentration of the alkali source can be 0.1 - 10 mol / L, preferably 0.1 - 3 mol / L.

[0040] In step (1), in the aqueous solution containing the magnesium source, the concentration of the magnesium source can be 0.01 - 5 mol / L, preferably 0.01 - 3 mol / L.

[0041] In the present invention, the alkali source can be selected from water-soluble or alkaline compounds that can dissolve in water. Specifically, the alkali source can be selected from at least one of inorganic alkali sources and organic alkali sources. In a preferred case, the alkali source is at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, cesium carbonate, sodium bicarbonate, ammonium bicarbonate, urea, ammonia water, n-butylamine, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, tetrapropylammonium bromide, and tetrabutylammonium bromide. Most preferably, the alkali source is sodium carbonate and / or sodium hydroxide.

[0042] In the present invention, the alkali source is used in the form of an aqueous solution. In the aqueous solution of the alkali source, the concentration of the alkali source can be 0.5 - 5 mol / L, preferably 1 - 3 mol / L.

[0043] In the present invention, the magnesium source can be selected from water-soluble or magnesium-containing compounds that can dissolve in water. In a preferred case, the magnesium source is at least one of magnesium nitrate, magnesium acetate, magnesium carbonate, and magnesium chloride. Further preferably, the magnesium source is magnesium nitrate and / or magnesium acetate.

[0044] In step (1), by controlling the time of the stirring and mixing, it is beneficial to form spherical magnesium oxide with through channels. When the time of the stirring and mixing is too short or too long, spherical magnesium oxide with through channels cannot be formed. In a preferred case, the time of the stirring and mixing is 0.1 - 3 h, more preferably 0.2 - 0.5 h.

[0045] In step (1), in a preferred case, before dropping the aqueous solution containing the magnesium source into the aqueous solution containing the base source, the aqueous solution containing the magnesium source and the aqueous solution containing the base source are respectively heated to the operating temperature for static aging. Specifically, the aqueous solution containing the magnesium source and the aqueous solution containing the base source can be respectively heated to a temperature higher than 40°C and lower than 100°C, preferably heated to 50 - 70°C.

[0046] In step (2), the process of static aging needs to be carried out within a specific temperature range. When the temperature is too high or too low, spherical magnesium oxide with through channels cannot be formed. In the present invention, the temperature of the static aging is higher than 40°C and lower than 100°C. In a preferred case, the temperature of the static aging is 50 - 70°C.

[0047] In step (2), the time of the static aging can be 1 - 24 h, preferably 1 - 3 h.

[0048] In step (2), during the process of static aging, in order to more favorably adjust the pore structure and porosity of the prepared spherical magnesium oxide to further enhance the catalytic activity and stability of the spherical magnesium oxide product, in a preferred case, the pH value of the mixed solution is controlled within the range of 6 - 11, preferably within the range of 7 - 9.

[0049] In step (3), the process of solid-liquid separation of the mixture obtained after static aging may include: separating the solid phase from the mixture obtained after static aging, and then carrying out washing and drying. The operation mode of separating the solid phase can be centrifugal separation or suction filtration separation, preferably suction filtration separation. The process of the suction filtration separation can be carried out according to the conventional methods and conditions in the art. The process of the washing can be alternately washing with deionized water and ethanol for several times (such as 2 - 5 times). The drying temperature is preferably lower than the decomposition temperature of the precursor. Specifically, the drying temperature can be 40 - 120°C, preferably 70 - 90°C.

[0050] In step (3), in order to more favorably adjust the pore structure and porosity of the prepared spherical magnesium oxide to further enhance the catalytic activity and stability of the spherical magnesium oxide product, preferably, before separating the solid and liquid of the mixture obtained after standing and aging, the mixture obtained after standing and aging is first cooled to a lower temperature (such as room temperature). The cooling method can be water cooling or natural cooling, and natural cooling is preferred.

[0051] In step (4), the calcination process needs to be carried out within a specific temperature range. When the temperature is too high or too low, spherical magnesium oxide with through pores cannot be formed. In the present invention, the calcination temperature is 300 - 900 °C, preferably 400 - 600 °C.

[0052] In step (4), the calcination time can be 2 - 8 h, preferably 3 - 5 h.

[0053] The present invention also provides spherical magnesium oxide with through pores prepared by the above method. The spherical magnesium oxide with through pores has a through pore structure and highly developed porosity, thus having a strong ability to adsorb and activate carbon dioxide, being able to effectively catalyze the ring-opening of propylene oxide, and still not deactivating after being used as a catalyst multiple times, with strong stability.

[0054] The present invention also provides a method for preparing propylene carbonate, which includes: reacting propylene oxide and carbon dioxide in the presence of a catalyst, wherein the catalyst is the above-mentioned spherical magnesium oxide with through pores. According to the method for preparing propylene carbonate of the present invention, the spherical magnesium oxide with through pores as a catalyst has a strong ability to adsorb and activate carbon dioxide, can effectively catalyze the ring-opening of propylene oxide, and still not deactivate after being used as a catalyst multiple times, with strong stability; moreover, compared with traditional heterogeneous catalysts, in the reaction process using the spherical magnesium oxide with through pores of the present invention as a catalyst, no additional solvent and cocatalyst need to be added, and a propylene carbonate yield of more than 98% can be achieved under mild conditions.

[0055] The following further illustrates the spherical magnesium oxide with through pores and its preparation method and application of the present invention through examples. The examples are implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific operation processes are given, but the protection scope of the present invention is not limited to the following examples.

[0056] The experimental methods in the following examples are all conventional methods in the art unless otherwise specified. The experimental materials used in the following examples can all be commercially obtained unless otherwise specified.

[0057] Example 1

[0058] (1) Dissolve 10.26 g of magnesium nitrate hexahydrate (0.04 mol) in 50 ml of deionized water to obtain solution A. Dissolve 4.24 g of anhydrous sodium carbonate (0.04 mol) in 100 ml of deionized water to obtain solution B. Heat solution A and solution B to 70 °C respectively, then quickly add solution B dropwise to solution A, stir and mix for 20 min to obtain mixed solution C.

[0059] (2) Adjust the pH value of the mixed solution C to 8, and then let it stand and age at 70 °C for 1 h.

[0060] (3) Naturally cool the aged mixture to room temperature, perform suction filtration, wash it alternately with ethanol and water 3 times, and dry it in an oven at 80 °C for 12 h to obtain the precursor.

[0061] (4) Calcinate the precursor at 550 °C for 3 h (heating rate: 2 °C / min) to obtain spherical magnesium oxide Cat-1 with through channels.

[0062] The XRD pattern of the spherical magnesium oxide Cat-1 with through channels is as shown in Figure 1 ; its nitrogen physical adsorption and desorption isotherm is as shown in Figure 2 ; its pore size distribution diagram is as shown in Figure 3 ; its overall SEM image is as shown in Figure 4 ; its sliced SEM image is as shown in Figure 5 ; As can be seen from Figure 1 , the spherical magnesium oxide has characteristic diffraction peaks of magnesium oxide and good crystallinity; as can be seen from Figure 2 and 3 , the adsorption isotherm of the spherical magnesium oxide is of type IV with an H3-type hysteresis loop, indicating that the spherical magnesium oxide is a mesoporous catalyst; as can be seen from the SEM images, the morphology of the spherical magnesium oxide is formed by the regular and close stacking of lamellae, and it can be clearly seen after slicing that the spherical magnesium oxide has through channels.

[0063] Example 2

[0064] (1) Dissolve 10.26 g of magnesium acetate (0.07 mol) in 50 ml of deionized water to obtain solution A. Dissolve 4.24 g of anhydrous sodium carbonate (0.04 mol) in 100 ml of deionized water to obtain solution B. Heat solution A and solution B to 60 °C respectively, then quickly add solution B dropwise to solution A, stir and mix for 30 min to obtain mixed solution C.

[0065] (2) Adjust the pH value of the mixed solution C to 7, and then let it stand and age at 60 °C for 2 h.

[0066] (3) The mixture after static aging is naturally cooled to room temperature, filtered by suction, washed alternately with ethanol and water three times, and dried in an oven at 80 °C for 12 h to obtain a precursor.

[0067] (4) The precursor is calcined at 450 °C for 5 h (heating rate: 2 °C / min) to obtain spherical magnesium oxide Cat-2 with through pores.

[0068] Example 3

[0069] (1) Dissolve 10.26 g of magnesium acetate (0.07 mol) in 50 ml of deionized water to obtain solution A. Take 4.24 g of sodium hydroxide (0.11 mol) and dissolve it in 100 ml of deionized water to obtain solution B. Heat solution A and solution B to 50 °C respectively, then quickly add solution B dropwise to solution A, and stir and mix for 15 min to obtain mixed solution C.

[0070] (2) Adjust the pH value of mixed solution C to 9, and then statically age it at 50 °C for 3 h.

[0071] (3) The mixture after static aging is naturally cooled to room temperature, filtered by suction, washed alternately with ethanol and water three times, and dried in an oven at 80 °C for 12 h to obtain a precursor.

[0072] (4) The precursor is calcined at 600 °C for 3 h (heating rate: 2 °C / min) to obtain spherical magnesium oxide Cat-3 with through pores.

[0073] Example 4

[0074] (1) Dissolve 12 g of magnesium acetate (0.081 mol) in 50 ml of deionized water to obtain solution A. Take 5 g of anhydrous sodium carbonate (0.047 mol) and dissolve it in 100 ml of deionized water to obtain solution B. Heat solution A and solution B to 55 °C respectively, then quickly add solution B dropwise to solution A, and stir and mix for 25 min to obtain mixed solution C.

[0075] (2) Adjust the pH value of mixed solution C to 8, and then statically age it at 55 °C for 2.5 h.

[0076] (3) The mixture after static aging is naturally cooled to room temperature, filtered by suction, washed alternately with ethanol and water three times, and dried in an oven at 80 °C for 12 h to obtain a precursor.

[0077] (4) The precursor is calcined at 400 °C for 5 h (heating rate: 2 °C / min) to obtain spherical magnesium oxide Cat-4 with through pores.

[0078] Example 5

[0079] (1) Dissolve 12 g of magnesium nitrate hexahydrate (0.047 mol) in 50 ml of deionized water to obtain solution A. Take 4.24 g of anhydrous sodium carbonate (0.04 mol) and dissolve it in 100 ml of deionized water to obtain solution B. Heat solution A and solution B to 65 °C respectively, then quickly add solution B dropwise to solution A, stir and mix for 20 min to obtain mixed solution C.

[0080] (2) Adjust the pH value of the mixed solution C to 9, and then let it stand and age at 65 °C for 1.5 h.

[0081] (3) Naturally cool the aged mixture to room temperature, perform suction filtration, wash it alternately with ethanol and water 3 times, and dry it in an oven at 80 °C for 12 h to obtain the precursor.

[0082] (4) Calcinate the precursor at 500 °C for 4 h (heating rate: 2 °C / min) to obtain spherical magnesium oxide Cat-5 with through pores.

[0083] Example 6

[0084] (1) Dissolve 10.26 g of magnesium acetate (0.07 mol) in 50 ml of deionized water to obtain solution A. Take 5 g of sodium hydroxide (0.125 mol) and dissolve it in 100 ml of deionized water to obtain solution B. Heat solution A and solution B to 70 °C respectively, then quickly add solution B dropwise to solution A, stir and mix for 30 min to obtain mixed solution C.

[0085] (2) Adjust the pH value of the mixed solution C to 7, and then let it stand and age at 70 °C for 1 h.

[0086] (3) Naturally cool the aged mixture to room temperature, perform suction filtration, wash it alternately with ethanol and water 3 times, and dry it in an oven at 80 °C for 12 h to obtain the precursor.

[0087] (4) Calcinate the precursor at 550 °C for 3 h (heating rate: 2 °C / min) to obtain spherical magnesium oxide Cat-6 with through pores.

[0088] Example 7

[0089] (1) Dissolve 10.26 g of magnesium acetate (0.07 mol) in 50 ml of deionized water to obtain solution A. Take 5 g of anhydrous sodium carbonate (0.047 mol) and dissolve it in 100 ml of deionized water to obtain solution B. Heat solution A and solution B to 60 °C respectively, then quickly add solution B dropwise to solution A, stir and mix for 25 min to obtain mixed solution C.

[0090] (2) Adjust the pH value of the mixed solution C to 8, and then let it stand and age at 60 °C for 2 h.

[0091] (3) The mixture after static aging is naturally cooled to room temperature, filtered by suction, washed alternately with ethanol and water three times, and dried in an oven at 80 °C for 12 h to obtain a precursor.

[0092] (4) The precursor is calcined at 600 °C for 3 h (heating rate: 2 °C / min) to obtain spherical magnesium oxide Cat-7 with through channels.

[0093] Example 8

[0094] (1) Dissolve 10.26 g of magnesium acetate (0.07 mol) in 50 ml of deionized water to obtain solution A. Take 4.23 g of anhydrous sodium carbonate (0.04 mol) and dissolve it in 100 ml of deionized water to obtain solution B. Heat solution A and solution B to 65 °C respectively, then quickly add solution B dropwise to solution A, and stir and mix for 15 min to obtain a mixed solution C.

[0095] (2) Adjust the pH value of the mixed solution C to 9, and then statically age it at 65 °C for 1.5 h.

[0096] (3) The mixture after static aging is naturally cooled to room temperature, filtered by suction, washed alternately with ethanol and water three times, and dried in an oven at 80 °C for 12 h to obtain a precursor.

[0097] (4) The precursor is calcined at 500 °C for 4 h (heating rate: 2 °C / min) to obtain spherical magnesium oxide Cat-8 with through channels.

[0098] Comparative Example 1

[0099] Spherical magnesium oxide is prepared according to the method of Example 1, except that the operation in step (1) is as follows: Take 10.26 g of magnesium nitrate hexahydrate and 4.24 g of anhydrous sodium carbonate and dissolve them in 150 ml of deionized water, stir and mix for 20 min, and then heat to 70 °C to obtain a mixed solution C. Finally, spherical magnesium oxide D1 is obtained.

[0100] Comparative Example 2

[0101] Spherical magnesium oxide is prepared according to the method of Example 1, except that in step (2), the pH value of the mixed solution C is adjusted to 12, and then static aging is carried out. Finally, spherical magnesium oxide D2 is obtained.

[0102] Comparative Example 3

[0103] Spherical magnesium oxide is prepared according to the method of Example 1, except that in step (2), the pH value of the mixed solution C is adjusted to 5, and then static aging is carried out. Finally, spherical magnesium oxide D3 is obtained.

[0104] Comparative Example 4

[0105] Spherical magnesium oxide was prepared according to the method of Example 1, except that in step (2), the temperature for static aging was 100 °C. Finally, spherical magnesium oxide D4 was obtained.

[0106] Comparative Example 5

[0107] Spherical magnesium oxide was prepared according to the method of Example 1, except that in step (2), the temperature for static aging was 40 °C. Finally, spherical magnesium oxide D5 was obtained.

[0108] Comparative Example 6

[0109] Spherical magnesium oxide was prepared according to the method of Example 1, except that in step (4), the calcination temperature was 950 °C. Finally, spherical magnesium oxide D6 was obtained.

[0110] Application Example 1

[0111] The spherical magnesium oxides prepared in Examples 1 - 8 and Comparative Examples 1 - 6 were used as catalysts in the reaction of propylene oxide cycloaddition to prepare propylene carbonate. The reaction conditions included: the catalyst dosage was 0.2 g, the propylene oxide (PO) dosage was 5 mmol, the reaction was carried out in a 10 ml batch reactor, and magnetic stirring was used to promote the uniform mixing of the reactants. The reaction was carried out at 100 °C and 2 MPa CO2 partial pressure for 12 hours. The solid - liquid mixture was separated by centrifugation, and then the liquid was passed through a liquid chromatograph for analysis. The results are shown in Table 1 below.

[0112] Table 1

[0113]

[0114]

[0115] Application Example 2

[0116] The spherical magnesium oxides prepared in Examples 1 - 8 and Comparative Examples 1 - 6 were used as catalysts in the reaction of propylene oxide cycloaddition to prepare propylene carbonate. The reaction conditions included: 5 mmol of PO and 0.2 g of the catalyst as reaction raw materials were added to a 25 ml micro - high - pressure reactor, filled with 2 Mpa CO2, the reaction parameters were set at 100 °C, the reaction was carried out for 12 h, and the rotation speed was 600 r. After the reaction, it was naturally cooled to room temperature. 25 ml of ethyl acetate was used to absorb the tail gas after the reaction. The tail gas absorption liquid was mixed evenly with the reaction liquid. The solid - liquid mixture was separated by centrifugation, and then the liquid was passed through a liquid chromatograph for analysis. Then the mixed solution was centrifuged, washed 4 times with ethanol, dried at 80 °C, and the above experimental operation was repeated until the catalytic effect of the catalyst decreased by 5 - 10%.

[0117] The results are shown in Table 2 below.

[0118] Table 2

[0119]

[0120]

[0121] From the results of Table 1 and Table 2, it can be seen that the spherical magnesium oxide with through channels prepared by the method according to the present invention can effectively catalyze the ring-opening of propylene oxide, and significantly higher yields of propylene carbonate can be obtained under mild conditions. Moreover, it will not deactivate even after being used as a catalyst multiple times, showing strong stability.

[0122] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A method for preparing spherical magnesium oxide with through channels, characterized in that, The method comprises the following steps: (1) Drop an aqueous solution containing a magnesium source into an aqueous solution containing an alkali source and stir to mix them to form a mixed solution; (2) Under the condition of higher than 40 °C and lower than 100 °C, leave the mixed solution to stand and age; (3) Separate the solid and liquid of the mixture obtained after standing and aging to obtain a precursor; (4) Calcinate the precursor under the condition of 300 - 900 °C.

2. The method according to claim 1, wherein In step (1), the molar ratio of the magnesium source calculated as Mg 2+ to the molar amount of the base source is (0.5 - 5):1, preferably (0.5 - 2):1; Preferably, in the aqueous solution containing the alkali source, the concentration of the alkali source is 0.1 - 10 mol / L, preferably 0.1 - 3 mol / L; Preferably, in the aqueous solution containing the magnesium source, the concentration of the magnesium source is 0.01 - 5 mol / L, preferably 0.01 - 3 mol / L.

3. The method according to claim 1 or 2, characterized in that, The alkali source is at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, cesium carbonate, sodium bicarbonate, ammonium bicarbonate, urea, ammonia water, n-butylamine, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, tetrapropylammonium bromide, and tetrabutylammonium bromide.

4. The method according to claim 1 or 2, characterized in that, The magnesium source is at least one of magnesium nitrate, magnesium acetate, magnesium acetate, magnesium carbonate, and magnesium chloride.

5. The method according to any one of claims 1 to 4, characterized in that, In step (1), the stirring and mixing time is 0.1 - 3 h, preferably 0.2 - 0.5 h.

6. The method according to claim 1, characterized in that In step (2), the temperature for standing and aging is 50 - 70 °C, and the time for standing and aging is 1 - 24 h, preferably 1 - 3 h.

7. The method according to claim 1 or 6, characterized in that, In step (2), during the standing and aging process, control the pH value of the mixed solution within the range of 6 - 11, preferably within the range of 7 - 9.

8. The method according to claim 1, characterized in that, In step (4), the calcination temperature is 400 - 600 °C, and the calcination time is 2 - 8 h, preferably 3 - 5 h.

9. Spherical magnesium oxide with through pores prepared by the method according to any one of claims 1 - 8.

10. A method for preparing propylene carbonate, the method comprising: React propylene oxide and carbon dioxide in the presence of a catalyst, wherein the catalyst is the spherical magnesium oxide with through pores according to claim 9.

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