Catalysts and preparation methods for one-step CO2 preparation of cyclic carbonates from olefins

Abstract

A bifunctional catalyst and its preparation method for the one-step CO2 preparation of cyclic carbonates from olefins are disclosed. The catalyst is obtained through the preparation of a titanium-silicon molecular sieve and the loading of a metal component. The titanium-silicon molecular sieve contains 0.1-5 wt% titanium, and the metal component is one or more of K, Mg, Rb, Ca, Au, Ag, Fe, Cr, Mn, Ce, Zr, Rh, Ir, Ni, Co, and Cu, with a loading of 0.01-30 wt%. The promoter is one or more of tetrapropylammonium bromide, tetrabutylammonium bromide, tetrabutylammonium iodide, and potassium iodide. This catalyst utilizes the synergistic effect of the molecular sieve support and the metal to achieve effective coupling of epoxidation and cycloaddition functions, efficiently catalyzing the one-step oxidative carboxylation of olefins to cyclic carbonates under mild conditions.

Description

Technical Field

[0001] This application relates to a catalyst in the petrochemical field, specifically, to a catalyst for the one-step preparation of cyclic carbonates from olefins using CO2 and a method thereof. Background Technology

[0002] Ethylene carbonate, propylene carbonate, and butene carbonate are important cyclic organic carbonate products in the new energy field and crucial chemical products for the high-value recycling of CO2. They possess characteristics such as low toxicity, high boiling point, and good stability, and are widely used in key areas such as specialty environmentally friendly solvents and biodegradable materials, including lithium-ion battery electrolytes, polar solvents, biodegradable polymer monomers, pharmaceutical and fine chemical intermediates, and ingredients in cosmetics and personal care products.

[0003] The main synthetic methods for cyclic carbonates include CO2-epoxide cycloaddition, CO2-propylene glycol / glycerol, urea alcoholysis, CO2-haloalcohol, CO2-methanol, and one-step oxidative carboxylation of olefins using CO2. The cycloaddition of carbon dioxide and epoxides to prepare cyclic carbonates is the most widely studied method, but the high cost, toxicity, and difficulty in storing the reactant epoxides result in low economic efficiency in actual production. When glycerol or diols are used as raw materials, the presence of numerous byproducts and thermodynamic limitations lead to poor atom economy. The reaction of urea with diols can also produce cyclic carbonates, but its single-pass conversion rate is low and the operating conditions are demanding. The synthesis of cyclic carbonates from haloalcohols and carbon dioxide is also an important method, but it usually produces byproducts such as halide salts, which corrode equipment. Starting from propargyl alcohol, cyclic carbonates can also be produced under suitable catalysts, but this method is less economical and mainly used for laboratory synthesis. The CO2-methanol process is mainly used to produce dimethyl carbonate, with cyclic carbonates primarily produced as a co-product. This process suffers from drawbacks such as a long workflow, low product purity, and high energy consumption during separation. Therefore, the direct synthesis of cyclic carbonates from upstream olefins (the raw material for epoxides) via a one-step oxidative carboxylation reaction would have significant scientific importance and potential application value. The one-step oxidative carboxylation preparation of cyclic carbonates from upstream olefins offers advantages such as low-toxicity and low-cost raw materials, a simple reaction route, and high atom economy. It avoids the preparation and separation of intermediate products, greatly improving reaction economy and environmental friendliness.

[0004] Chinese Patent Application Publication No. CN113244954A discloses a bifunctional catalyst using mesoporous silica molecular sieve as a support and amino-functionalized imidazole ionic liquid as the active component. This catalyst can catalyze the one-step reaction of CO2 with olefins to prepare cyclic carbonates under solvent-free conditions. Chinese Patent Application Publications Nos. CN112480058A and CN112480059A disclose a method for the direct synthesis of cyclic carbonates from olefins via CO2 catalysis using metalloporphyrins; however, metalloporphyrins are expensive and difficult to produce on a large scale. Chinese Patent Application Publication No. CN104130236A discloses a one-pot, two-step method for preparing propylene carbonate, but this method has a long process flow and a demanding catalyst preparation process. Currently reported catalysts for the one-step oxidative carboxylation of olefins to prepare cyclic carbonates are mostly ionic liquids and metalloporphyrin catalysts, which are expensive and only applicable to aromatic olefins. There are few catalysts for aliphatic olefins, especially bulk low-carbon olefins (C2-C4). Summary of the Invention

[0005] This application provides a catalyst for preparing cyclic carbonates from olefins and CO2. This catalyst can prepare cyclic carbonates from low-carbon olefins and CO2 in one step, exhibiting good catalytic performance and improving the conversion rate of the reactant hydrogen peroxide.

[0006] A second aspect of this application provides a catalyst for the preparation of cyclic carbonates from olefins and CO2, wherein the catalyst, under mild reaction conditions, prepares cyclic carbonates from low-carbon olefins and CO2 in a one-step process.

[0007] A third aspect of this application provides a catalyst for the preparation of cyclic carbonates from olefins and CO2, which improves the selectivity of cyclic carbonates.

[0008] This application provides a final aspect: a method for preparing a catalyst for the production of cyclic carbonates from olefins and CO2, which is simple in process.

[0009] On the one hand, a catalyst for preparing cyclic carbonates from olefins and CO2 includes: a titanium-silicon molecular sieve support and a metal component, wherein the metal component includes one or a mixture of two or more of K, Mg, Ca, Rb, Au, Ag, Fe, Cr, Mn, Ce, Zr, Rh, Ir, Ni, Co, and Cu.

[0010] The metal components are uniformly dispersed on the surface of the titanium-silicon molecular sieve as metal nanoparticles, or form large metal clusters, exhibiting strong interactions with the support. Strong interactions exist between the metal components themselves, as well as between the metal components and the titanium-silicon molecular sieve, enabling them to jointly exert catalytic effects in the reaction system for preparing cyclic carbonates from olefins and CO2.

[0011] On the other hand, the above-mentioned catalyst is used in the reaction of olefins and CO2 to prepare cyclic carbonates, wherein the reaction temperature is 80-150℃.

[0012] In this reaction system, the reactants olefin, CO2, and hydrogen peroxide react within the above temperature range to yield the product cyclic carbonate.

[0013] The reaction conditions are mild, and the conversion rate of hydrogen peroxide is high. Attached Figure Description

[0014] Figure 1 NH3-TPD diagrams of catalysts before and after metal loading

[0015] Figure 2 UV-vis images of catalysts before and after metal loading

[0016] Figure 3 TEM image of the Au-supported catalyst Detailed Implementation

[0017] The catalyst for preparing cyclic carbonates from olefins and CO2 according to this application is described in further detail below. This does not limit the scope of protection of this application, which is defined by the claims. Certain specific details disclosed provide a comprehensive understanding of the various disclosed embodiments. However, those skilled in the art will recognize that embodiments can be implemented using other materials, etc., without employing one or more of these specific details.

[0018] Unless the context requires otherwise, the terms "comprising" and "including" in the specification and claims shall be understood as open-ended and inclusive, meaning "including, but not limited to".

[0019] The terms "implementation," "an implementation," "another implementation," or "certain implementations" used in this specification refer to specific features, structures, or characteristics described in relation to the implementation, which are included in at least one implementation. Therefore, "implementation," "an implementation," "another implementation," or "certain implementations" do not necessarily all refer to the same implementation. Furthermore, specific features, structures, or characteristics can be combined in any way within one or more implementations. Each feature disclosed in this specification can be replaced by any alternative feature that provides the same, equivalent, or similar purpose. Therefore, unless otherwise specified, the disclosed features are merely general examples of equivalent or similar features.

[0020] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or as recommended by the manufacturer. Unless otherwise stated, all percentages, ratios, proportions, or parts are by weight.

[0021] The term "load" refers to the percentage of the mass of a metallic element relative to the mass of the carrier.

[0022] "Low-carbon olefins" refer to olefins with 2-4 carbon atoms. For example, monoolefins with C2-C4 atoms.

[0023] On the one hand, a catalyst for preparing cyclic carbonates from olefins and CO2 includes: a titanium silicate molecular sieve support and a metal component, wherein the metal component includes one or a mixture of two or more of K, Mg, Rb, Ca, Au, Ag, Fe, Cr, Mn, Ce, Zr, Rh, Ir, Ni, Co, and Cu.

[0024] In some embodiments, the mass of titanium in the titanium-silicon molecular sieve support is 0.1-5 wt% of the support mass.

[0025] In some embodiments, the mass of titanium in the titanium-silicon molecular sieve support is greater than 0.1% and less than or equal to 5% of the support mass.

[0026] In some embodiments, the mass of titanium in the titanium-silicon molecular sieve support is 0.1-2.5 wt% of the support mass.

[0027] In some embodiments, the mass of titanium in the titanium-silicon molecular sieve support is 1-2.5% of the support mass.

[0028] In this application, the mass ratio of titanium in the titanium-silicon molecular sieve carrier refers to the percentage of titanium element mass in the carrier mass.

[0029] In titanium-silicon molecular sieve supports, the presence of tetracoordinated titanium is beneficial for the effective conversion of hydrogen peroxide in the CO2-to-cyclic carbonate preparation from olefins. Excessive titanium content leads to the formation of non-framework titanium, which accelerates the ineffective decomposition of hydrogen peroxide and reduces the yield of cyclic carbonates. Furthermore, the presence of mesopores in the titanium-silicon molecular sieve allows for more effective anchoring of metal components and promotes the desorption of cyclic carbonates, reducing carbon deposition. Therefore, achieving both a high titanium content and high metal dispersion in the titanium-silicon molecular sieve support is crucial for the synergistic effect of the loaded metal components and the additives in the one-step CO2-to-cyclic carbonate preparation from olefins.

[0030] As an optional option, the specific surface area of ​​the titanium-silicon molecular sieve support is 200-500 cm².2 / g, pore size 0.5~10.0nm. Metal components can be effectively loaded onto titanium-silicon molecular sieve supports with the above structural characteristics.

[0031] In some embodiments, the pore volume of the titanium-silicon molecular sieve support is 0.20–0.85 cm³. 3 / g.

[0032] In some embodiments, the metal component includes one or a mixture of two or more of Au, Ag, Ce, Zr, Ni, and Co.

[0033] The alternative is a mixture of one or more of the following metal components: Au, Ag, Ce, Zr, and Ni.

[0034] Alternatively, the metal component may include a first metal and a second metal. The first metal may include one or a mixture of two or more of Au, Ce, Zr, and Ni, and the second metal may include one or a mixture of two or more of Fe, K, Rb, Mg, Ag, and Ca. For example, the metal component in the catalyst may include Au and K, or Au and Fe.

[0035] The molar ratio of the first metal to the second metal is (1-5):1.

[0036] Catalysts that support at least one metal element (K, Mg, Rb, Ca, Au, Ag, Fe, Cr, Mn, Ce, Zr, Rh, Ir, Ni, Co, or Cu) on a titanium-silicon molecular sieve support can convert olefin CO2 into cyclic carbonates via epoxidation and cycloaddition. In particular, supporting metal elements Au, Ag, Ce, Zr, Ni, or Co on a titanium-silicon molecular sieve support enhances the acidity of the support compared to a titanium-silicon molecular sieve. By adjusting the loading amount, the synergistic effect between the metal and the acidic sites can be enhanced, thereby improving the catalytic performance of one-step conversion of olefin CO2 into cyclic carbonates.

[0037] The loading of the metal component in the catalyst is 0.01 wt% to 3 wt%.

[0038] The optional scheme has a metal component loading of 0.01 wt% to 2 wt%.

[0039] On the other hand, the method for preparing the catalyst for the above-mentioned preparation of cyclic carbonates from olefins and CO2 includes:

[0040] (1) Mix the titanium-silicon molecular sieve support with the metal salt solution to obtain mixture II;

[0041] (2) Mixture II was dried and calcined to obtain M / titanium silicon molecular sieve catalyst.

[0042] M is a metallic component, including one or a mixture of two or more of the following: K, Mg, Rb, Ca, Au, Ag, Fe, Cr, Mn, Ce, Zr, Rh, Ir, Ni, Co, and Cu. In the catalyst, metal M exists as its most stable metal oxide, namely MO. x .

[0043] The M metal component can include a mixture of two or more metals. Generally, when a bimetal is supported, the molar ratio of the transition metal to the alkaline earth metal or alkali metal is (1-5):1.

[0044] For example, the Au / K bimetallic loading has a molar ratio of (1-5):1.

[0045] In some embodiments, the calcination temperature in step (2) is 500-800°C.

[0046] In some embodiments, in step (2), the calcination temperature is 500-800℃ and the calcination time is 3-6h.

[0047] Alternatively, in step (2), the roasting temperature is 500-700℃.

[0048] In some embodiments, the metal salt solution is typically an aqueous solution with a concentration of 0.05 mol / L to 1 mol / L. The volume of the metal solution used can be adjusted according to the concentration of the metal solution, depending on the specific metal element loading required for the catalyst.

[0049] For example, the metal salt is chloroauric acid, cerium nitrate, or zirconium nitrate. In step (1), the mass-to-volume ratio of the titanium silicate molecular sieve carrier to the metal salt solution is 1 g / (0.5-1) mL.

[0050] Metal salts can be water-soluble salt solutions, such as nitrates, acetates, citrates, chlorides, or sulfates.

[0051] In some embodiments, mixture II is dried at a temperature of 50–100°C.

[0052] During the calcination process after drying the carrier mixture II, the metal components gradually disperse on the surface of the titanium-silicon molecular sieve as the calcination temperature increases. At calcination temperatures of 500-800℃, there is a strong interaction between the surface metal components and the titanium-silicon molecular sieve, and the acidic sites exposed on the surface can exert a catalytic effect. In particular, calcination at temperatures of 500-700℃ exhibits better catalytic performance in the one-step conversion of olefin CO2 to cyclic carbonates.

[0053] In the catalyst, the particle size of the metal supported on the titanium-silicon molecular sieve is 2-50 nm.

[0054] In some embodiments, the mixture II of the titanium-silicon molecular sieve support and the metal salt solution is aged before drying.

[0055] The aging process refers to leaving the plant still for a period of time, such as 6-12 hours.

[0056] In the aforementioned titanium-silicon molecular sieve support, the mass percentage of titanium is 0.1-5 wt%, and the specific surface area of ​​the titanium-silicon molecular sieve support is 200-500 cm². 2 / g, pore size 0.5~10.0nm.

[0057] The pore volume of the titanium-silicon molecular sieve support is 0.20–0.85 cm³. 3 / g.

[0058] Alternatively, the titanium-silicon molecular sieve support can be prepared using the following method:

[0059] (i) The template agent, silicon source and titanium source are mixed to obtain mixed solution I;

[0060] (ii) The titanium-silicon molecular sieve carrier is obtained by removing alcohol from mixed solution I, crystallizing, separating solid and liquid, drying and calcining; or the titanium-silicon molecular sieve carrier is obtained by crystallizing, separating solid and liquid, drying and calcining mixed solution I.

[0061] In some embodiments, mixture I is subjected to alcohol removal at a temperature of 50–100°C.

[0062] In some embodiments, mixture I is crystallized at a temperature of 100-200°C.

[0063] In some implementations, the calcination temperature in step (ii) is greater than 400-800°C.

[0064] In some embodiments, the calcination temperature in step (ii) is 550-650°C.

[0065] The roasting time in step (ii) can be adjusted according to actual needs. Usually, the roasting time is 2h-6h.

[0066] Alternatively, in the synthesis of the supported titanium-silicon molecular sieve, the titanium source includes one or a mixture of at least two of tetrabutyl titanate, tetraethyl titanate, tetraisopropyl titanate, titanium trichloride, and titanium tetrachloride.

[0067] The template agent includes one or a mixture of at least two of the following: ethylenediamine, tetraethylammonium hydroxide, n-butylamine, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, tetrapropylammonium bromide, and tetrabutylammonium bromide.

[0068] The silicon source includes tetraethyl orthosilicate and / or silica sol.

[0069] In some embodiments, preferably, the drying time in steps (2) and (ii) is 8-12 hours.

[0070] Preferably, the molar ratio of template agent to silicon source is (0.2-1.5):1.

[0071] The molar ratio of silicon source to titanium source is (30-160):1.

[0072] The titanium-silicon molecular sieve prepared by the above method, used as a support, and the catalyst obtained by loading the aforementioned metal elements, exhibits better catalytic activity when applied to the one-step oxidative carboxylation of olefins to prepare cyclic carbonates from CO2. The cyclic carbonates also show higher selectivity.

[0073] On another front, a method for preparing cyclic carbonates from olefins using CO2 includes: reacting reactants olefins, CO2, and hydrogen peroxide in the presence of the aforementioned catalyst to obtain cyclic carbonates. The reaction temperature is between 80-150℃.

[0074] The olefins mentioned are low-carbon olefins, that is, C2-C4 olefins.

[0075] Preferably, the reaction temperature is 100-120℃. The ratio of CO2 to olefins is not particularly limited, as long as CO2 is in excess.

[0076] In some implementations, the molar ratio of CO2 to olefin is (1-4):1.

[0077] The molar ratio of hydrogen peroxide to olefins is (0.5-2):1.

[0078] Additives are also added during the reaction process.

[0079] The additives include one or more of the following: tetrapropylammonium bromide, tetrabutylammonium bromide, tetrabutylammonium iodide, and potassium iodide.

[0080] In some embodiments, the mass ratio of catalyst to auxiliaries is (0.01-5):1.

[0081] An optional scheme is a catalyst to auxiliary agent mass ratio of (0.2-0.6):1.

[0082] This catalyst utilizes the synergistic effect of the supported metal and the auxiliary agent to achieve effective coupling of epoxidation and cycloaddition functions, promoting the one-step oxidative carboxylation of olefins to prepare cyclic carbonates.

[0083] Under the action of the aforementioned catalyst and additives, cyclic carbonates are prepared by one-step oxidative carboxylation of olefins with CO2 and hydrogen peroxide at temperatures of 80-150℃. The selectivity for cyclic olefins is over 90%, and the effective utilization rate of hydrogen peroxide can reach 99%.

[0084] The following is a detailed description of the reaction and calculation process for using the catalyst in the CO2 preparation of cyclic carbonates from olefins, as described in the embodiments of the present invention:

[0085] The substances used in the following examples are all chemically pure standards and are all commercially available products.

[0086] I. Catalysts Supported by Different Metals

[0087] Example 1

[0088] 18.28 g of tetrapropylammonium hydroxide (TPAOH, 25 wt%) was stirred with 8.12 g of deionized water for 30 min. Then, 10.5 g of tetraethyl orthosilicate (TEOS) was added and stirred until clear. This mixture is labeled A. 0.4 g of tetrabutyl titanate was dissolved in 15 mL of isopropanol (IPA) and stirred until clear. This mixture is labeled B. B was added dropwise to A and stirred until clear. The alcohol was removed using a water bath to maintain a constant volume of the mixture. The alcohol-free solution was placed in a crystallization vessel and crystallized in an oven at 170 °C for 72 h. After centrifugation, the solution was dried in an oven for 14 h and finally calcined at 550 °C for 6 h to obtain titanium-silicon molecular sieve powder (titanium element mass percentage approximately 1.46%). 0.5 g of titanium silicate molecular sieve powder was impregnated in 0.5 mL of 0.02 g / mL chloroauric acid solution and sonicated for 3 hours to ensure uniform dispersion of the salt solution between the TS-1 titanium silicate molecular sieves. The mixture was aged for 10 hours and then dried in an 80°C oven. The dried solid was then thoroughly ground in an agate mortar and calcined at 500°C at a rate of 2°C per minute for 4 hours to obtain a 2 wt% Au / TS-1 catalyst.

[0089] Example 2

[0090] 18.28 g of tetrapropylammonium hydroxide (TPAOH, 25 wt%) was stirred with 8.12 g of deionized water for 30 min. Then, 10.5 g of tetraethyl orthosilicate (TEOS) was added and stirred until clear. This mixture is labeled A. 0.4 g of tetrabutyl titanate was dissolved in 15 mL of isopropanol (IPA) and stirred until clear. This mixture is labeled B. B was added dropwise to A and stirred until clear. Alcohol was removed using a water bath to maintain a constant volume of the mixture. The alcohol-free solution was placed in a crystallization vessel and crystallized in an oven at 170 °C for 72 h. It was then centrifuged, dried in an oven for 12 h, and finally calcined at 550 °C for 6 h. 0.5 g of titanium silicate molecular sieve powder was impregnated in 0.5 mL of 0.02 g / mL cerium nitrate solution and sonicated for 3 hours to ensure uniform dispersion of the salt solution between the TS-1 titanium silicate molecular sieves. The mixture was aged for 10 hours and then dried in an 80°C oven. The dried solid was then thoroughly ground in an agate mortar and calcined at 500°C at a rate of 2°C per minute for 4 hours to obtain a Ce / TS-1 catalyst with a loading of 2 wt%.

[0091] II. Catalysts with Different Bimetallic Supports

[0092] Example 3

[0093] 18.28 g of tetrapropylammonium hydroxide (TPAOH, 25 wt%) was stirred with 8.12 g of deionized water for 30 min. Then, 10.5 g of tetraethyl orthosilicate (TEOS) was added and stirred until clear. This mixture is labeled A. 0.4 g of tetrabutyl titanate was dissolved in 15 mL of isopropanol (IPA) and stirred until clear. This mixture is labeled B. B was added dropwise to A and stirred until clear. Alcohol was removed using a water bath to maintain a constant volume of the mixture. The alcohol-free solution was placed in a crystallization vessel and crystallized in an oven at 170 °C for 72 h. It was then centrifuged, dried in an oven for 12 h, and finally calcined at 550 °C for 6 h. 0.5 g of titanium-silicon molecular sieve powder was impregnated in 0.5 mL of 0.02 g / mL chloroauric acid solution and sonicated for 3 hours to ensure uniform dispersion of the salt solution between the TS-1 titanium-silicon molecular sieves. After aging for 5 hours, it was dried in an 80°C oven. The dried solid was then thoroughly ground in an agate mortar and impregnated in 0.5 mL of 0.001 g / mL silver nitrate solution to ensure uniform dispersion of the salt solution between the TS-1 titanium-silicon molecular sieves. After aging for 5 hours, it was dried in an 80°C oven. The temperature was increased to 500°C at a rate of 2°C per minute and calcined for 4 hours to obtain a catalyst with a loading of (2 wt%) Au / (0.1 wt%) Ag-TS-1.

[0094] Example 4

[0095] 18.28 g of tetrapropylammonium hydroxide (TPAOH, 25 wt%) was stirred with 8.12 g of deionized water for 30 min. Then, 10.5 g of tetraethyl orthosilicate (TEOS) was added and stirred until clear. This mixture is labeled A. 0.4 g of tetrabutyl titanate was dissolved in 15 mL of isopropanol (IPA) and stirred until clear. This mixture is labeled B. B was added dropwise to A and stirred until clear. Alcohol was removed using a water bath to maintain a constant volume of the mixture. The alcohol-free solution was placed in a crystallization vessel and crystallized in an oven at 170 °C for 72 h. It was then centrifuged, dried in an oven for 14 h, and finally calcined at 550 °C for 6 h. 0.5 g of titanium-silicon molecular sieve powder was impregnated in 0.5 mL of 0.02 g / mL chloroauric acid solution and sonicated for 3 hours to ensure uniform dispersion of the salt solution between the TS-1 titanium-silicon molecular sieves. After aging for 5 hours, it was dried in an 80°C oven. The dried solid was then thoroughly ground in an agate mortar and impregnated in 0.5 mL of 0.001 g / mL potassium nitrate solution to ensure uniform dispersion of the salt solution between the TS-1 titanium-silicon molecular sieves. After aging for 5 hours, it was dried in an 80°C oven. The temperature was then increased to 500°C at a rate of 2°C per minute and calcined for 4 hours to obtain a catalyst with a loading of (2 wt%) Au / (0.1 wt%) K-TS-1.

[0096] Example 5

[0097] 18.28 g of tetrapropylammonium hydroxide (TPAOH, 25 wt%) was stirred with 8.12 g of deionized water for 30 min. Then, 10.5 g of tetraethyl orthosilicate (TEOS) was added and stirred until clear. This mixture is labeled A. 0.4 g of tetrabutyl titanate was dissolved in 15 mL of isopropanol (IPA) and stirred until clear. This mixture is labeled B. B was added dropwise to A and stirred until clear. Alcohol was removed using a water bath to maintain a constant volume of the mixture. The alcohol-free solution was placed in a crystallization vessel and crystallized in an oven at 170 °C for 72 h. It was then centrifuged, dried in an oven for 14 h, and finally calcined at 550 °C for 6 h. 0.5 g of titanium-silicon molecular sieve powder was impregnated in 0.5 mL of 0.02 g / mL cerium nitrate solution and sonicated for 3 hours to ensure uniform dispersion of the salt solution between the TS-1 titanium-silicon molecular sieves. The mixture was aged for 5 hours and then dried in an 80°C oven. The dried solid was then thoroughly ground in an agate mortar and impregnated in 0.5 mL of 0.001 g / mL potassium nitrate solution to ensure uniform dispersion of the salt solution between the TS-1 titanium-silicon molecular sieves. The mixture was aged for 5 hours and then dried in an 80°C oven. The temperature was increased to 500°C at a rate of 2°C per minute and calcined for 4 hours to obtain a catalyst with a loading of (2 wt%) Ce / (0.1 wt%) K-TS-1.

[0098] Example 6

[0099] 18.28 g of tetrapropylammonium hydroxide (TPAOH, 25 wt%) was stirred with 8.12 g of deionized water for 30 min. Then, 10.5 g of tetraethyl orthosilicate (TEOS) was added and stirred until clear. This mixture is labeled A. 0.4 g of tetrabutyl titanate was dissolved in 15 mL of isopropanol (IPA) and stirred until clear. This mixture is labeled B. B was added dropwise to A and stirred until clear. Alcohol was removed using a water bath to maintain a constant volume of the mixture. The alcohol-free solution was placed in a crystallization vessel and crystallized in an oven at 170 °C for 72 h. It was then centrifuged, dried in an oven for 12 h, and finally calcined at 550 °C for 6 h. 0.5 g of titanium silicate molecular sieve powder was impregnated in 0.5 mL of 0.02 g / mL zirconium nitrate solution and sonicated for 3 hours to ensure uniform dispersion of the salt solution between the TS-1 titanium silicate molecular sieves. After aging for 5 hours, it was dried in an 80°C oven. The dried solid was then thoroughly ground in an agate mortar and impregnated in 0.5 mL of 0.001 g / mL potassium nitrate solution to ensure uniform dispersion of the salt solution between the TS-1 titanium silicate molecular sieves. After aging for 5 hours, it was dried in an 80°C oven. The temperature was increased to 500°C at a rate of 2°C per minute and calcined for 4 hours to obtain a catalyst with a loading of (2 wt%) Zr / (0.1 wt%) K-TS-1.

[0100] III. Catalysts at Different Calcination Temperatures

[0101] Example 7

[0102] 18.28 g of tetrapropylammonium hydroxide (TPAOH, 25 wt%) was stirred with 8.12 g of deionized water for 30 min. Then, 10.5 g of tetraethyl orthosilicate (TEOS) was added and stirred until clear. This mixture is labeled A. 0.4 g of tetrabutyl titanate was dissolved in 15 mL of isopropanol (IPA) and stirred until clear. This mixture is labeled B. B was added dropwise to A and stirred until clear. Alcohol was removed using a water bath to maintain a constant volume of the mixture. The alcohol-free solution was placed in a crystallization vessel and crystallized in an oven at 170 °C for 72 h. It was then centrifuged, dried in an oven for 12 h, and finally calcined at 550 °C for 6 h. 0.5 g of titanium-silicon molecular sieve powder was impregnated in 0.5 mL of 0.02 g / mL chloroauric acid solution and sonicated for 3 hours to ensure uniform dispersion of the salt solution between the TS-1 titanium-silicon molecular sieves. After aging for 5 hours, it was dried in an 80°C oven. The dried solid was then thoroughly ground in an agate mortar and impregnated in 0.5 mL of 0.001 g / mL silver nitrate solution to ensure uniform dispersion of the salt solution between the TS-1 titanium-silicon molecular sieves. After aging for 5 hours, it was dried in an 80°C oven. The temperature was then increased to 400°C at a rate of 2°C per minute and calcined for 4 hours to obtain a catalyst with a loading of (2 wt%) Au / (0.1 wt%) Ag-TS-1.

[0103] Example 8

[0104] 18.28 g of tetrapropylammonium hydroxide (TPAOH, 25 wt%) was stirred with 8.12 g of deionized water for 30 min. Then, 10.5 g of tetraethyl orthosilicate (TEOS) was added and stirred until clear. This mixture is labeled A. 0.4 g of tetrabutyl titanate was dissolved in 15 mL of isopropanol (IPA) and stirred until clear. This mixture is labeled B. B was added dropwise to A and stirred until clear. Alcohol was removed using a water bath to maintain a constant volume of the mixture. The alcohol-free solution was placed in a crystallization vessel and crystallized in an oven at 170 °C for 72 h. It was then centrifuged, dried in an oven for 12 h, and finally calcined at 550 °C for 6 h. 0.5 g of titanium-silicon molecular sieve powder was impregnated in 0.5 mL of 0.02 g / mL chloroauric acid solution and sonicated for 3 hours to ensure uniform dispersion of the salt solution between the TS-1 titanium-silicon molecular sieves. After aging for 5 hours, it was dried in an 80°C oven. The dried solid was then thoroughly ground in an agate mortar and impregnated in 0.5 mL of 0.001 g / mL silver nitrate solution to ensure uniform dispersion of the salt solution between the TS-1 titanium-silicon molecular sieves. After aging for 5 hours, it was dried in an 80°C oven. The temperature was then increased to 600°C at a rate of 2°C per minute and calcined for 4 hours to obtain a catalyst with a loading of (2 wt%) Au / (0.1 wt%) Ag-TS-1.

[0105] Example 9

[0106] 18.28 g of tetrapropylammonium hydroxide (TPAOH, 25 wt%) was stirred with 8.12 g of deionized water for 30 min. Then, 10.5 g of tetraethyl orthosilicate (TEOS) was added and stirred until clear. This mixture is labeled A. 0.4 g of tetrabutyl titanate was dissolved in 15 mL of isopropanol (IPA) and stirred until clear. This mixture is labeled B. B was added dropwise to A and stirred until clear. Alcohol was removed using a water bath to maintain a constant volume of the mixture. The alcohol-free solution was placed in a crystallization vessel and crystallized in an oven at 170 °C for 72 h. It was then centrifuged, dried in an oven for 12 h, and finally calcined at 550 °C for 6 h. 0.5 g of titanium-silicon molecular sieve powder was impregnated in 0.5 mL of 0.02 g / mL chloroauric acid solution and sonicated for 3 hours to ensure uniform dispersion of the salt solution between the TS-1 titanium-silicon molecular sieves. After aging for 5 hours, it was dried in an 80°C oven. The dried solid was then thoroughly ground in an agate mortar and impregnated again in 0.5 mL of 0.001 g / mL silver nitrate solution to ensure uniform dispersion of the salt solution between the TS-1 titanium-silicon molecular sieves. After aging for 5 hours, it was dried in an 80°C oven. The temperature was then increased to 800°C at a rate of 2°C per minute and calcined for 4 hours to obtain a catalyst with a loading of (2 wt%) Au / (0.1 wt%) Ag-TS-1. (See attached...) Figure 3 As shown, after high-temperature roasting, the metal forms large metal oxide particles.

[0107] Example 10

[0108] 18.28 g of tetrapropylammonium hydroxide (TPAOH, 25 wt%) was stirred with 8.12 g of deionized water for 30 min. Then, 10.5 g of tetraethyl orthosilicate (TEOS) was added and stirred until clear. This mixture is labeled A. 0.4 g of tetrabutyl titanate was dissolved in 15 mL of isopropanol (IPA) and stirred until clear. This mixture is labeled B. B was added dropwise to A and stirred until clear. Alcohol was removed using a water bath to maintain a constant volume of the mixture. The alcohol-free solution was placed in a crystallization vessel and crystallized in an oven at 170 °C for 72 h. It was then centrifuged, dried in an oven for 12 h, and finally calcined at 550 °C for 6 h. 0.5 g of titanium-silicon molecular sieve powder was impregnated in 0.5 mL of 0.02 g / mL zirconium nitrate solution and sonicated for 3 hours to ensure uniform dispersion of the salt solution between the TS-1 titanium-silicon molecular sieves. The mixture was aged for 5 hours and then dried in an 80°C oven. The dried solid was then thoroughly ground in an agate mortar and impregnated in 0.5 mL of 0.001 g / mL potassium nitrate solution to ensure uniform dispersion of the salt solution between the TS-1 titanium-silicon molecular sieves. The mixture was aged for 5 hours and then dried in an 80°C oven. The temperature was increased to 800°C at a rate of 2°C per minute and calcined for 4 hours to obtain a catalyst with a loading of (2 wt%) Zr / (0.1 wt%) K-TS-1.

[0109] Example 11

[0110] 18.28 g of tetrapropylammonium hydroxide (TPAOH, 25 wt%) was stirred with 8.12 g of deionized water for 30 min. Then, 10.5 g of tetraethyl orthosilicate (TEOS) was added and stirred until clear. This mixture is labeled A. 0.4 g of tetrabutyl titanate was dissolved in 15 mL of isopropanol (IPA) and stirred until clear. This mixture is labeled B. B was added dropwise to A and stirred until clear. Alcohol was removed using a water bath to maintain a constant volume of the mixture. The alcohol-free solution was placed in a crystallization vessel and crystallized in an oven at 170 °C for 72 h. It was then centrifuged, dried in an oven for 14 h, and finally calcined at 550 °C for 6 h. 0.5 g of titanium silicate molecular sieve powder was impregnated in 0.5 mL of 0.02 g / mL potassium nitrate solution and sonicated for 3 hours to ensure uniform dispersion of the salt solution between the TS-1 titanium silicate molecular sieves. The mixture was aged for 10 hours and then dried in an 80°C oven. The dried solid was then thoroughly ground in an agate mortar and calcined at 500°C at a rate of 2°C per minute for 4 hours to obtain a K / TS-1 catalyst with a loading of 2 wt%.

[0111] Example 12

[0112] 18.28 g of tetrapropylammonium hydroxide (TPAOH, 25 wt%) was stirred with 8.12 g of deionized water for 30 min. Then, 10.5 g of tetraethyl orthosilicate (TEOS) was added and stirred until clear. This mixture is labeled A. 0.4 g of tetrabutyl titanate was dissolved in 15 mL of isopropanol (IPA) and stirred until clear. This mixture is labeled B. B was added dropwise to A and stirred until clear. Alcohol was removed using a water bath to maintain a constant volume of the mixture. The alcohol-free solution was placed in a crystallization vessel and crystallized in an oven at 170 °C for 72 h. It was then centrifuged, dried in an oven for 14 h, and finally calcined at 550 °C for 6 h. 0.5 g of titanium silicate molecular sieve powder was impregnated in 0.5 mL of 0.02 g / mL ferric nitrate solution and sonicated for 3 hours to ensure uniform dispersion of the salt solution between the TS-1 titanium silicate molecular sieves. The mixture was aged for 10 hours and then dried in an 80°C oven. The dried solid was then thoroughly ground in an agate mortar and calcined at 500°C at a rate of 2°C per minute for 4 hours to obtain a 2 wt% Fe / TS-1 catalyst.

[0113] Example 13

[0114] 18.28 g of tetrapropylammonium hydroxide (TPAOH, 25 wt%) was stirred with 8.12 g of deionized water for 30 min. Then, 10.5 g of tetraethyl orthosilicate (TEOS) was added and stirred until clear. This mixture is labeled A. 0.1 g of tetrabutyl titanate was dissolved in 15 mL of isopropanol (IPA) and stirred until clear. This mixture is labeled B. B was added dropwise to A and stirred until clear. The alcohol was removed using a water bath to maintain a constant volume of the mixture. The alcohol-free solution was placed in a crystallization vessel and crystallized in an oven at 170 °C for 72 h. After centrifugation, the solution was dried in an oven for 14 h and finally calcined at 550 °C for 6 h to obtain titanium-silicon molecular sieve powder (titanium element mass percentage approximately 0.36%). 0.5 g of titanium silicate molecular sieve powder was impregnated in 0.5 mL of 0.02 g / mL ferric nitrate solution and sonicated for 3 hours to ensure uniform dispersion of the salt solution between the TS-1 titanium silicate molecular sieves. The mixture was aged for 10 hours and then dried in an 80°C oven. The dried solid was then thoroughly ground in an agate mortar and calcined at 500°C at a rate of 2°C per minute for 4 hours to obtain a Zr / TS-1 catalyst with a loading of 2 wt%.

[0115] Example 14

[0116] 18.28 g of tetrapropylammonium hydroxide (TPAOH, 25 wt%) was stirred with 8.12 g of deionized water for 30 min. Then, 10.5 g of tetraethyl orthosilicate (TEOS) was added and stirred until clear. This mixture is labeled A. 1.2 g of tetrabutyl titanate was dissolved in 15 mL of isopropanol (IPA) and stirred until clear. This mixture is labeled B. B was added dropwise to A and stirred until clear. The alcohol was removed using a water bath to maintain a constant volume of the mixture. The alcohol-free solution was placed in a crystallization vessel and crystallized in an oven at 170 °C for 72 h. After centrifugation, the solution was dried in an oven for 14 h and finally calcined at 550 °C for 6 h to obtain titanium-silicon molecular sieve powder (titanium element mass percentage approximately 4.38%). 0.5 g of titanium silicate molecular sieve powder was impregnated in 0.5 mL of 0.02 g / mL ferric nitrate solution and sonicated for 3 hours to ensure uniform dispersion of the salt solution between the TS-1 titanium silicate molecular sieves. The mixture was aged for 10 hours and then dried in an 80°C oven. The dried solid was then thoroughly ground in an agate mortar and calcined at 500°C at a rate of 2°C per minute for 4 hours to obtain a Zr / TS-1 catalyst with a loading of 2 wt%.

[0117] Comparative Example 1

[0118] 18.28 g of tetrapropylammonium hydroxide (TPAOH, 25 wt%) was stirred with 8.12 g of deionized water for 30 min. Then, 10.5 g of tetraethyl orthosilicate (TEOS) was added and stirred until clear. This mixture is labeled A. 0.4 g of tetrabutyl titanate was dissolved in 15 mL of isopropanol (IPA) and stirred until clear. This mixture is labeled B. B was added dropwise to A and stirred until clear. Alcohol was removed using a water bath to maintain a constant volume of the mixture. The alcohol-free solution was placed in a crystallization vessel and crystallized in an oven at 170 °C for 72 h. It was then centrifuged, dried in an oven for 14 h, and finally calcined at 550 °C for 6 h.

[0119] Experimental Example 1

[0120] Acidity analysis was performed on the catalysts prepared in Comparative Example 1, Example 1, Example 14, and Example 10. The NH3-TPD spectra of the catalysts from bottom to top are TS-1, Au / TS-1, Zr / TS-1, and K / TS-1. The loading of metals such as Au and Zr mainly enhances the acidity of the weak acid sites of the titanium silicate molecular sieve, while the loading of K will weaken the acidity of the support.

[0121] Experiment Example 2

[0122] The catalysts prepared in Comparative Examples 1, 5, 4, and 3 were subjected to ultraviolet (UV) spectral analysis, as shown in the attached figures. Figure 2As shown, the diffraction peak at 210 nm is mainly attributed to the presence of four-coordinated titanium in the framework. The titanium-silicon molecular sieves loaded with AuAg and bimetals exhibit uniform dispersion and do not disrupt the framework structure of the molecular sieve. In contrast, the titanium-silicon molecular sieves loaded with AuK and CeK bimetals show obvious diffraction peaks at 330 nm and 600 nm, respectively, which is mainly attributed to the presence of large metal oxide particles.

[0123] Experimental Example 3

[0124] This experimental example demonstrates the performance of the catalysts prepared in Examples 1-11 and Comparative Examples 1-2 in the one-step CO2 preparation of cyclic carbonates from olefins. 10 mL of ethyl acetate solvent, 1.0 g of hydrogen peroxide (30 wt%), 0.05 g of metal-supported titanium silicate molecular sieve, and 0.23 g of tetrabutylammonium bromide auxiliary were weighed and mixed thoroughly in a high-pressure reactor. The amount of olefin added was 0.008 mol, and the CO2 pressure was 1 MPa. Under thorough stirring, the reaction was carried out at 100 °C for 240 min. The reaction results are shown in Table 1. The effective utilization rate of hydrogen peroxide = (amount of product) / amount of hydrogen peroxide converted.

[0125] Table 1. Results of reactions in each example and comparative example.

[0126]

[0127] It will be apparent to those skilled in the art that this application is not limited to the details of the exemplary embodiments described above, and that this application can be implemented in other specific forms without departing from the spirit or essential characteristics of this application. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of this application is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within this application.

Claims

1. A method for preparing cyclic carbonates from low-carbon olefins and CO2, comprising: The reactants, low-carbon olefins, CO2, and hydrogen peroxide, react under the action of a catalyst at a temperature of 80-150℃ to obtain cyclic carbonates. An auxiliary agent, tetrabutylammonium bromide, is added during the reaction. Low-carbon olefins are olefins with 2-4 carbon atoms; The catalyst comprises a titanium-silicon molecular sieve support and a metal component, wherein the loading of the metal component in the catalyst is 0.01 wt% to 3 wt%; and the mass of titanium in the titanium-silicon molecular sieve support is 1-2.5 wt% of the support mass. The preparation method of the catalyst includes: (1) mixing the titanium silicon molecular sieve support with a metal salt solution to obtain mixture II; (2) drying and calcining the mixture II at a temperature of 500-800℃ to obtain M / titanium silicon molecular sieve catalyst. The metallic component is Au or Ce; or The metal composition includes a first metal and a second metal, with a molar ratio of (1-5):1, wherein the first metal is Au and the second metal is Ag; or the first metal is Au and the second metal is K; or the first metal is Ce and the second metal is K; or the first metal is Zr and the second metal is K.

2. The method according to claim 1, characterized in that, The specific surface area of ​​the titanium-silicon molecular sieve support is 200-500 cm². 2 / g, pore size 0.5~10.0nm.

3. The method according to claim 1, characterized in that, The pore volume of the titanium-silicon molecular sieve support is 0.20–0.85 cm³. 3 / g.

4. The method according to claim 1, characterized in that, In the catalyst, the loading of the metal component is 0.01wt% to 2wt%.

5. The method according to any one of claims 1-4, characterized in that, In the catalyst, the particle size of the metal supported on the titanium-silicon molecular sieve is 2-50 nm.

6. The method according to any one of claims 1-4, characterized in that, In step (2), the roasting temperature is 500-800℃ and the roasting time is 3-6h.

7. The method according to any one of claims 1-4, characterized in that, In step (2), the roasting temperature is 500-700℃.

8. The method according to any one of claims 1-4, characterized in that, The metal salt solution is an aqueous solution with a concentration of 0.05 mol / L to 1 mol / L.

9. The method according to claim 8, characterized in that, Metal salts include nitrates, acetates, citrates, chlorides, or sulfates.

10. The method according to claim 8, characterized in that, In step (1), the mass-to-volume ratio of the titanium-silicon molecular sieve support to the metal salt solution is 1 g / (0.2~5) mL.

11. The method according to any one of claims 1-4, characterized in that, The preparation methods of titanium-silicon molecular sieve supports include: (i) The template agent, silicon source, and titanium source are mixed to obtain mixed solution I; (ii) The titanium-silicon molecular sieve carrier is obtained by removing alcohol, crystallizing, solid-liquid separation, drying and calcining the mixed solution I; or the titanium-silicon molecular sieve carrier is obtained by crystallizing, solid-liquid separation, drying and calcining the mixed solution I.

12. The method according to claim 11, characterized in that, Mixed solution I was subjected to alcohol removal at a temperature of 50~100℃.

13. The method according to claim 11, characterized in that, Mixed solution I was crystallized at a temperature of 100-200℃.

14. The method according to claim 11, characterized in that, The molar ratio of template agent to silicon source is (0.2-1.5):

1. The molar ratio of silicon source to titanium source is (30-160):

1.

15. The method according to claim 11, characterized in that, In step (ii), the calcination temperature is 400-800℃.

16. The method according to claim 11, characterized in that, In step (ii), the calcination temperature is 550-650℃.

17. The method according to any one of claims 1-4, characterized in that, The reaction temperature is 100-120℃.

18. The method according to claim 1, characterized in that, The mass ratio of catalyst to auxiliaries is (0.01-5):

1.

19. The method according to claim 1, characterized in that, The mass ratio of catalyst to auxiliaries is (0.2-0.6):

1.

20. The method according to any one of claims 1-4, characterized in that, The molar ratio of CO2 to low-carbon olefins is (1-4):

1.

21. The method according to any one of claims 1-4, characterized in that, The molar ratio of hydrogen peroxide to low-carbon olefins is (0.5-2):1.

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