Method for preparing 1, 4-dioxane by catalyzing dehydration etherification of diethylene glycol through phosphotungsten / molybdenum solid acid

Abstract

The invention provides a method for preparing 1, 4-dioxane by catalyzing dehydration etherification of diethylene glycol through phosphotungsten / molybdenum solid acid, and relates to the technical field of catalysts. The chemical formula of the phosphotungsten / molybdenum solid acid is AxH (3-x) PB12O40. YH2O, A is Cs or Rb, B is W or Mo, x is equal to 0.5-3, and y is a natural number; the 1, 4-dioxane is obtained by catalyzing intramolecular dehydration and etherification of diethylene glycol by utilizing abundant acid sites on the surface of the solid acid and excellent dehydration performance. The method for preparing the 1, 4-dioxane through catalysis of the phosphotungsten (molybdenum) solid acid has the advantages of being simple in catalyst preparation cost, high in diethylene glycol conversion rate, good in 1, 4-dioxane selectivity and capable of being recycled and reused, and in addition, the process further has the advantages of being free of corrosion to equipment and small in environmental pollution.

Description

Technical Field

[0001] The invention relates to the technical field of catalysts, and in particular to a method for preparing 1,4-dioxane by dehydration etherification of diethylene glycol catalyzed by phosphotungstic / molybdenum solid acid. Background Art

[0002] 1,4-dioxane is an important heterocyclic compound. Its structure contains two ether bonds and is miscible with most organic matter and water. Therefore, it is widely used in paints, dyes, pharmaceutical synthesis, electronic cleaning agents, cosmetics, polyurethane synthetic leather and other fields as an organic solvent, reaction medium, extraction solvent, etc. Among them, in the field of pharmaceutical synthesis, 1,4-dioxane accounts for more than 40%. At present, the main industrial synthesis method of 1,4-dioxane is to use concentrated sulfuric acid or phosphoric acid as a dehydrating agent to catalyze the dehydration and etherification of ethylene glycol / diethylene glycol. Although concentrated sulfuric acid or phosphoric acid has high catalytic activity as a dehydrating agent and low catalyst cost, concentrated sulfuric acid or phosphoric acid has defects such as high corrosiveness and difficulty in controlling the reaction temperature, which leads to side reactions such as carbonization, polymerization, and over-oxidation of materials. At the same time, the use of strong acid causes great environmental pressure on this route. In addition, the use of sulfuric acid or phosphoric acid will also cause the acid value in 1,4-dioxane to be too high, resulting in a decrease in product quality. Therefore, developing a greener and more sustainable new process for producing 1,4-dioxane and adopting more advanced technologies to reduce the emission of "three wastes" are important development directions for the 1,4-dioxane industry.

[0003] The development of heterogeneous catalysts for the dehydration and etherification of ethylene glycol to synthesize 1,4-dioxane is one of the research directions of this process. The raw material ethylene glycol is adsorbed, dehydrated, and cyclized on the surface of the solid catalyst to produce the target product before desorption, which reduces the separation cost and reduces the corrosion of the equipment. At present, macroporous strong acid cationic resins and activated carbon-loaded SO4 2- 、SO4 2- / MxOy, activated carbon-supported alkali metal solid superacid catalysts, etc. In this reaction, the ethylene glycol conversion rate is as high as 90%, and the 1,4-dioxane selectivity is as high as 90%. Although the above catalyst system shows high activity in this reaction, the resin catalyst has poor temperature resistance and the solid-supported SO4 2-Problems such as the easy loss of alkali metal active components and high reaction temperature limit its industrial application. Diethylene glycol is one of the important by-products of the ethylene oxide hydration to ethylene glycol industry, accounting for about 9% of the process capacity. In recent years, with the expansion of ethylene glycol production capacity, the price of diethylene glycol has continued to fall, and the product value has continued to weaken. Therefore, the development of high-value-added downstream chemicals using diethylene glycol as a raw material can effectively improve the efficiency of ethylene glycol plants. Among them, the dehydration and etherification of diethylene glycol to produce 1,4-dioxane is one of the potential routes. Compared with the route of ethylene glycol to 1,4-dioxane, this route has the characteristics of low raw material consumption, short reaction path, small cyclization energy barrier, and half reduction in wastewater generation. Therefore, the route of dehydration and etherification of diethylene glycol to produce 1,4-dioxane is one of the important research directions for the green and sustainable development of this product.

[0004] At present, for the route of dehydration and etherification of diethylene glycol to produce 1,4-dioxane, a variety of catalyst systems have been developed, including concentrated sulfuric acid, liquid-solid composite catalysts, ionic liquids, solid superacid resins, zeolite molecular sieves, etc. For example, patent CN1473823A discloses a method for using a liquid-solid composite catalyst to dehydrate and etherify diethylene glycol to produce 1,4-dioxane, with a product yield of up to 77%, wherein the liquid-solid composite catalyst is mainly acids, zeolites, and ion exchange resins. Patent CN103193758B discloses a method for dehydration and etherification of diethylene glycol to produce 1,4-dioxane catalyzed by a solid superacid resin, which overcomes the deficiency of using sulfuric acid as a catalyst in the traditional process. Patent CN109721584B discloses a method for preparing 1,4-dioxane by dehydration etherification of diethylene glycol catalyzed by isoquinoline, quinoline and benzimidazole ionic liquids, with a diethylene glycol conversion rate of up to 97.6% and a 1,4-dioxane selectivity of up to 98.2%. Guo Shaojie et al. (Progress in Fine Petrochemicals, 2003, 4(10), 24-26) reported the application of modified β-zeolite molecular sieves in the preparation of 1,4-dioxane by dehydration etherification of diethylene glycol, wherein the diethylene glycol conversion rate was up to 89.69% and the 1,4-dioxane selectivity was up to 95.01%. Although the above catalysts have excellent activity in the preparation of 1,4-dioxane by dehydration etherification of diethylene glycol, they have the following problems: resin catalysts have poor temperature resistance and active centers are easy to lose; ionic liquid catalysts are complex to synthesize and have high separation cycle energy consumption; molecular sieve catalysts are easy to be blocked by carbon deposition.

[0005] In summary, it is urgent to find and develop new catalyst systems for the dehydration etherification of diethylene glycol to produce 1,4-dioxane. Summary of the invention

[0006] In view of the shortcomings of the prior art, the present invention provides a method for preparing 1,4-dioxane by dehydration etherification of diethylene glycol catalyzed by phosphotungsten / molybdenum solid acid. The entire catalytic production process has the characteristics of few by-products and excellent catalytic performance. Solid acid is used as a catalyst, which is easy to separate, recover and reuse, has low corrosion to equipment, and the catalyst is simple to prepare and low in cost.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0008] A method for preparing 1,4-dioxane by dehydration etherification of diethylene glycol catalyzed by phosphotungstic / molybdenum solid acid, the method comprising the following steps:

[0009] S1, prepare chemical formula A x H 3-x PB 12 O 40 ·yH2O solid acid catalyst, and the solid acid catalyst is placed in a high-pressure reactor, and then diethylene glycol raw material is added to the reactor, and then sealed, and replaced with nitrogen three times, wherein A x H 3- x PB 12 O 40 In yH2O, A is Cs or Rb, B is W or Mo, x = 0.5 to 3, and y is a natural number;

[0010] S2, heating the above reactor and stirring the reaction for 4-24h;

[0011] S3. After the reaction is completed, the mixture is cooled to room temperature, and then centrifuged to separate the catalyst to obtain a reaction solution containing 1,4-dioxane.

[0012] Preferably, the solid acid catalyst is prepared by a precipitation method, which specifically comprises the following steps:

[0013] S1-1, prepare the metal salt compound A and the phosphorus tungsten / molybdic acid compound into an aqueous solution, according to the solid acid A x H 3- x PB 12 O 40 ·The value of x in yH2O, slowly add the aqueous solution of metal salt compound A dropwise into the aqueous solution of phosphotungstic / molybdic acid compound under stirring, and obtain a suspension after the addition is complete;

[0014] S1-2, drying the above suspension to obtain a solid powder for standby use;

[0015] S1-3, calcining and activating the solid powder to obtain a solid acid catalyst.

[0016] Preferably, the suspension is dried in step S1-2 by first evaporating the water from the suspension at 40-70°C, and then drying at 120-180°C for 5-12h.

[0017] Preferably, the calcination activation in step S1-3 is performed by placing the solid powder in a muffle furnace and calcining and activating the solid powder at 300-600° C. for 4-8 hours.

[0018] Preferably, the diethylene glycol raw material in step S1 is diethylene glycol or a diethylene glycol solution.

[0019] Preferably, the addition amount of the solid acid catalyst is 0.5%-20% of the total mass of the diethylene glycol raw material.

[0020] Preferably, the temperature of the reactor in step S2 is raised to 150-250°C.

[0021] The present invention provides a method for preparing 1,4-dioxane by dehydration etherification of diethylene glycol catalyzed by phosphotungstic / molybdenum solid acid, which has the advantages over the prior art in that:

[0022] (1) The core of the method of the present invention is to utilize the inherent stability of phosphotungstic / cesium molybdate solid acid and the abundant acid center sites on its surface to catalyze the intramolecular dehydration and etherification of diethylene glycol to produce 1,4-dioxane; and the method provided by the present invention has lower separation energy consumption, is non-corrosive to equipment, and is highly environmentally friendly.

[0023] (2) Compared with existing molecular sieve catalysts and resin catalysts, the solid acid catalyst used in the present invention has higher selectivity, stronger thermal stability, longer life, and no swelling phenomenon. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is the XRD spectrum of the solid acid catalyst in Examples 1-5 of the present invention;

[0025] Figure 2 This is an analysis diagram of the recycling results of the solid acid catalyst in Example 11 of the present invention; DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention is clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] Embodiment 1:

[0028] Cs 0.5 H2.5 PW 12 O 40 ·yH2O catalytic preparation of 1,4-dioxane:

[0029] (1) Cs 0.5 H 2.5 PW 12 O 40 ·yH2O solid acid preparation:

[0030] In a 250mL beaker, 50mL of 0.2mol / L cesium nitrate aqueous solution was slowly added dropwise to 100mL of 0.2mol / L phosphotungstic acid aqueous solution, and the mixture was stirred continuously for 30min before evaporating the water in a 60°C oven to obtain a solid powder. The solid powder was then dried at 120°C for 6 hours to obtain a catalyst precursor. The precursor was finally placed in a muffle furnace and calcined at 350°C for 5 hours to obtain Cs 0.5 H 2.5 PW 12 O 40 ·yH2O solid acid catalyst.

[0031] (2) Preparation of 1,4-dioxane:

[0032] Weigh 0.6 g Cs 0.5 H 2.5 PW 12 O 40 ·yH2O solid acid and 15 g of diethylene glycol were placed in a high-pressure reactor, sealed after a magnetic bar was placed in it, and replaced with nitrogen three times; then, the reaction was continued at 800 rpm and 180°C for 6 hours; after the reaction was completed, the reactor was cooled to room temperature, the catalyst and the reaction liquid were centrifuged to obtain a reaction liquid, which was analyzed and detected by an Agilent8860 gas chromatograph, and the diethylene glycol conversion rate was 97.79%, and the 1,4-dioxane selectivity was 91.70%.

[0033] Embodiment 2:

[0034] Cs 1.0 H 2.0 PW 12 O 40 ·yH2O catalytic preparation of 1,4-dioxane:

[0035] (1) Cs 1.0 H 2.0 PW 12 O 40 ·yH2O solid acid preparation:

[0036] In a 250mL beaker, 75mL of 0.2mol / L cesium nitrate aqueous solution was slowly added dropwise to 75mL of 0.2mol / L phosphotungstic acid aqueous solution, and the mixture was stirred continuously for 30min, and the water was evaporated in a 60℃ oven to obtain a solid powder; the solid powder was then dried at 120℃ for 6 hours to obtain a catalyst precursor; the precursor was finally placed in a muffle furnace and calcined at 350℃ for 5 hours to obtain Cs 1.0 H 2.0 PW 12 O 40 ·yH2O solid acid catalyst;

[0037] (2) Preparation of 1,4-dioxane:

[0038] Weigh 0.6 g Cs 0.5 H 2.5 PW 12 O 40 ·yH2O solid acid and 15 g of diethylene glycol were placed in a high-pressure reactor, sealed after a magnetic bar was placed in it, and replaced with nitrogen three times; then, the reaction was continued at 800 rpm and 180°C for 6 hours; after the reaction was completed, the reactor was cooled to room temperature, the catalyst and the reaction liquid were centrifuged to obtain a reaction liquid, which was analyzed and detected by an Agilent8860 gas chromatograph, and the diethylene glycol conversion rate was 94.43%, and the 1,4-dioxane selectivity was 89.74%.

[0039] Embodiment 3:

[0040] Cs 1.5 H 1.5 PW 12 O 40 ·yH2O catalytic preparation of 1,4-dioxane:

[0041] (1) Cs 1.5 H 1.5 PW 12 O 40 ·yH2O solid acid preparation:

[0042] In a 250mL beaker, 90mL of 0.2mol / L cesium nitrate aqueous solution was slowly added dropwise to 60mL of 0.2mol / L phosphotungstic acid aqueous solution, and the mixture was stirred continuously for 30min, and the water was evaporated in a 60℃ oven to obtain a solid powder; the solid powder was then dried at 120℃ for 6 hours to obtain a catalyst precursor; the precursor was finally placed in a muffle furnace and calcined at 350℃ for 5 hours to obtain Cs 1.5 H 1.5 PW 12 O 40 ·yH2O solid acid catalyst.

[0043] (2) Preparation of 1,4-dioxane:

[0044] Weigh 0.6 g Cs 1.5 H 1.5 PW 12 O 40 ·yH2O solid acid and 15 g of diethylene glycol were placed in a high-pressure reactor, sealed after a magnetic bar was placed in it, and replaced with nitrogen three times; then, the reaction was continued at 800 rpm and 180°C for 6 hours; after the reaction was completed, the reactor was cooled to room temperature, the catalyst and the reaction liquid were centrifuged to obtain a reaction liquid, which was analyzed and detected by an Agilent8860 gas chromatograph, and the diethylene glycol conversion rate was 93.84%, and the 1,4-dioxane selectivity was 85.20%.

[0045] Embodiment 4:

[0046] Cs 2.0 H 1.0 PW 12 O 40 ·yH2O catalytic preparation of 1,4-dioxane:

[0047] (1) Cs 2.0 H 1.0 PW 12 O 40 ·yH2O solid acid preparation:

[0048] In a 250mL beaker, 100mL of 0.2mol / L cesium nitrate aqueous solution was slowly added dropwise to 50mL of 0.2mol / L phosphotungstic acid aqueous solution, and the mixture was stirred continuously for 30min and then evaporated in a 60°C oven to obtain a solid powder; the solid powder was then dried at 120°C for 6 hours to obtain a catalyst precursor; the precursor was finally placed in a muffle furnace and calcined at 350°C for 5 hours to obtain Cs 2.0 H 1.0 PW 12 O 40 ·yH2O solid acid catalyst.

[0049] (2) Preparation of 1,4-dioxane:

[0050] Weigh 0.6 g Cs 2.0 H 1.0 PW 12 O 40·yH2O solid acid and 15 g of diethylene glycol were placed in a high-pressure reactor, sealed after a magnetic bar was placed in it, and replaced with nitrogen three times; then, the reaction was continued at 800 rpm and 180°C for 6 hours; after the reaction was completed, the reactor was cooled to room temperature, the catalyst and the reaction liquid were centrifuged to obtain a reaction liquid, which was analyzed and detected by an Agilent8860 gas chromatograph, and the diethylene glycol conversion rate was 89.94%, and the 1,4-dioxane selectivity was 82.95%.

[0051] Embodiment 5:

[0052] Cs 2.5 H 0.5 PW 12 O 40 ·yH2O catalytic preparation of 1,4-dioxane:

[0053] (1) Cs 2.5 H 0.5 PW 12 O 40 ·yH2O solid acid preparation:

[0054] In a 250mL beaker, 100mL of 0.2mol / L cesium nitrate aqueous solution was slowly added dropwise to 40mL of 0.2mol / L phosphotungstic acid aqueous solution, and the mixture was stirred continuously for 30min and then evaporated in a 60°C oven to obtain a solid powder; the solid powder was then dried at 120°C for 6 hours to obtain a catalyst precursor; the precursor was finally placed in a muffle furnace and calcined at 350°C for 5 hours to obtain Cs 2.5 H 0.5 PW 12 O 40 ·yH2O solid acid catalyst.

[0055] (2) Preparation of 1,4-dioxane:

[0056] Weigh 0.6 g Cs 2.5 H 0.5 PW 12 O 40 ·yH2O solid acid and 15 g of diethylene glycol were placed in a high-pressure reactor, sealed after a magnetic bar was placed in it, and replaced with nitrogen three times; then, the reaction was continued at 800 rpm and 180°C for 6 hours; after the reaction was completed, the reactor was cooled to room temperature, the catalyst and the reaction liquid were centrifuged to obtain a reaction liquid, which was analyzed and detected by an Agilent8860 gas chromatograph, and the diethylene glycol conversion rate was 83.90%, and the 1,4-dioxane selectivity was 79.25%.

[0057] Embodiment 6:

[0058] Cs0.5 H 2.5 PW 12 O 40 ·yH2O catalytic preparation of 1,4-dioxane:

[0059] Weigh 0.6 g Cs 0.5 H 2.5 PW 12 O 40 ·yH2O solid acid and 15 g of diethylene glycol were placed in a high-pressure reactor, sealed after a magnetic bar was placed in it, and replaced with nitrogen three times; then, the reaction was continued at 800 rpm and 170°C for 6 hours; after the reaction was completed, the reactor was cooled to room temperature, the catalyst and the reaction liquid were centrifuged to obtain a reaction liquid, which was analyzed and detected by an Agilent8860 gas chromatograph, and the diethylene glycol conversion rate was 77.65%, and the 1,4-dioxane selectivity was 90.55%.

[0060] Embodiment 7:

[0061] Weigh 0.6 g Cs 0.5 H 2.5 PW 12 O 40 ·yH2O solid acid and 15 g of diethylene glycol were placed in a high-pressure reactor, sealed after a magnetic bar was placed in it, and replaced with nitrogen three times; then, the reaction was continued at 800 rpm and 190°C for 6 hours; after the reaction was completed, the reactor was cooled to room temperature, the catalyst and the reaction liquid were centrifuged to obtain a reaction liquid, which was analyzed and detected by an Agilent8860 gas chromatograph, and the diethylene glycol conversion rate was 98.39%, and the 1,4-dioxane selectivity was 86.70%.

[0062] Embodiment 8:

[0063] Weigh 0.6 g Cs 0.5 H 2.5 PW 12 O 40 ·yH2O solid acid and 15 g of diethylene glycol were placed in a high-pressure reactor, sealed after a magnetic bar was placed in it, and replaced with nitrogen three times; then, the reaction was continued at 800 rpm and 200°C for 6 hours; after the reaction was completed, the reactor was cooled to room temperature, the catalyst and the reaction liquid were centrifuged to obtain a reaction liquid, which was analyzed and detected by an Agilent8860 gas chromatograph, and the diethylene glycol conversion rate was 97.04%, and the 1,4-dioxane selectivity was 83.72%.

[0064] Embodiment 9:

[0065] Weigh 0.6 g Cs 0.5 H 2.5 PW 12O 40 ·yH2O solid acid and 15 g of diethylene glycol were placed in a high-pressure reactor, sealed after a magnetic bar was placed in it, and replaced with nitrogen three times; then, the reaction was continued at 800 rpm and 180°C for 8 hours; after the reaction was completed, the reactor was cooled to room temperature, the catalyst and the reaction liquid were centrifuged to obtain a reaction liquid, which was analyzed and detected by an Agilent8860 gas chromatograph, and the diethylene glycol conversion rate was 93.79%, and the 1,4-dioxane selectivity was 88.21%.

[0066] Embodiment 10:

[0067] Weigh 0.6 g Cs 0.5 H 2.5 PW 12 O 40 ·yH2O solid acid and 15 g of diethylene glycol were placed in a high-pressure reactor, sealed after a magnetic bar was placed in it, and replaced with nitrogen three times; then, the reaction was continued at 800 rpm and 180°C for 10 hours; after the reaction was completed, the reactor was cooled to room temperature, the catalyst and the reaction liquid were centrifuged to obtain a reaction liquid, which was analyzed and detected by an Agilent8860 gas chromatograph, and the diethylene glycol conversion rate was 96.79%, and the 1,4-dioxane selectivity was 85.66%.

[0068] Embodiment 11:

[0069] Cs 0.5 H 2.5 PW 12 O 40 ·yH2O solid acid catalyst cycle experiment:

[0070] The Cs used in Example 1 0.5 H 2.5 PW 12 O 40 After the first reaction, the yH2O solid acid catalyst was centrifuged to obtain the used catalyst, washed with ethanol three times, and dried at 80°C for 4 hours. Then, the first cycle reaction was carried out according to the conditions of Example 1 to obtain the diethylene glycol conversion rate and 1,4-dioxane selectivity. Afterwards, it was recovered in a similar manner and recycled for a total of 6 times. The results are shown in FIG. Figure 2 .

[0071] Comparative Example 1:

[0072] Direct dehydration cyclization of diethylene glycol to prepare 1,4-dioxane:

[0073] 15 g of diethylene glycol was weighed and placed in a high-pressure reactor, which was sealed after a magnetic bar was placed in it and replaced with nitrogen three times; then, the reaction was continued at 800 rpm and 180° C. for 6 hours; after the reaction was completed, the reactor was cooled to room temperature, the catalyst and the reaction liquid were centrifuged to obtain the reaction liquid, which was analyzed and detected by an Agilent 8860 gas chromatograph, and the diethylene glycol conversion rate was 2.53%, and the 1,4-dioxane selectivity was 1.16%.

[0074] Statistics:

[0075] The reaction data of preparing 1,4-dioxane from diethylene glycol in the above Examples 1-10 and Comparative Example 1 are shown in the following table:

[0076]

[0077]

[0078] In the table, a: diethylene glycol conversion rate, b: 1,4-dioxane selectivity.

[0079] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing 1,4-dioxane by dehydration etherification of diethylene glycol catalyzed by phosphotungstic / molybdenum solid acid, characterized in that: The method comprises the following steps: S1. Prepare chemical formula A x H 3-x PB 12 O 40 ·yH2O solid acid catalyst, and the solid acid catalyst is placed in a high-pressure reactor, and then diethylene glycol raw material is added to the reactor, and then sealed, and replaced with nitrogen three times, wherein A x H 3- x PB 12 O 40 In yH2O, A is Cs or Rb, B is W or Mo, x = 0.5 to 3, and y is a natural number; S2, heating the above reactor and stirring the reaction for 4-24h; S3. After the reaction is completed, the mixture is cooled to room temperature, and then centrifuged to separate the catalyst to obtain a reaction solution containing 1,4-dioxane.

2. The method for preparing 1,4-dioxane according to claim 1, characterized in that: The solid acid catalyst is prepared by a precipitation method, which specifically comprises the following steps: S1-1, prepare the metal salt compound A and the phosphorus tungsten / molybdic acid compound into an aqueous solution, according to the solid acid A x H 3- x PB 12 O 40 ·The value of x in yH2O, slowly add the aqueous solution of metal salt compound A dropwise into the aqueous solution of phosphotungstic / molybdic acid compound under stirring, and obtain a suspension after the addition is complete; S1-2, drying the above suspension to obtain a solid powder for standby use; S1-3, calcining and activating the solid powder to obtain a solid acid catalyst.

3. The method for preparing 1,4-dioxane according to claim 2, characterized in that: The method of drying the suspension in step S1-2 is to first evaporate the water of the suspension at a temperature of 40-70°C, and then dry it at 120-180°C for 5-12 hours.

4. The method for preparing 1,4-dioxane according to claim 2, characterized in that: The method of calcination activation in step S1-3 is to place the solid powder in a muffle furnace and perform calcination activation at 300-600°C for 4-8 hours.

5. The method for preparing 1,4-dioxane according to claim 1, characterized in that: The diethylene glycol raw material in step S1 is diethylene glycol or a diethylene glycol solution.

6. The method for preparing 1,4-dioxane according to claim 1, characterized in that: The addition amount of the solid acid catalyst is 0.5%-20% of the total mass of the diethylene glycol raw material.

7. The method for preparing 1,4-dioxane according to claim 1, characterized in that: The temperature of the reactor in step S2 is raised to 150-250°C.

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