A catalyst for preparing alkenyl ether by acetal cracking and preparation method thereof

Abstract

The present invention provides a catalyst for preparing alkenyl ethers by acetal cracking and a preparation method thereof, belonging to the technical field of catalyst preparation. The catalyst of the present invention comprises the following raw materials: phosphoric acid or a phosphate or sulfate, acid-washed diatomaceous earth, acid phosphate, a metal halide or an alkaline earth metal oxide, sesbania powder, silica sol, titanyl sulfate, and carbonamide. The present invention first prepares a catalyst precursor, then uses titanyl sulfate to prepare titanium dioxide, and then performs impregnation and doping, thereby obtaining ultrafine particles with uniform particle size and high purity. The carbonamide also provides alkalinity treatment on the catalyst surface, improving selectivity and further enhancing catalyst stability.

Description

Technical Field

[0001] The present invention relates to the technical field of catalyst preparation, and in particular to a catalyst for preparing alkenyl ether by cracking acetal and a preparation method thereof. Background Art

[0002] Vinyl ethers are a very important class of organic synthesis intermediates and monomers for polymers. Their homopolymers and copolymers are widely used in adhesives, coatings, lubricants, plasticizers, pesticides, and surface protection materials, among other applications. The active double bond properties of vinyl methyl ethers have led to their widespread application in organic synthesis, such as in the Diels-Alder reaction and the preparation of compounds such as glutaraldehyde, γ-pyran, and γ-pyridine. However, vinyl ethers cannot be synthesized using conventional ether preparation methods because halogenated alkenes exhibit little nucleophilic substitution activity, while enol compounds always exist as stable carbonyl tautomers. Therefore, the preparation of vinyl ethers has been a difficult problem in organic synthesis for many years.

[0003] Currently, the main methods for preparing alkenyl methyl ethers are the alkyne method and the acetal cleavage method. The alkyne method involves the synthesis of alkenyl ethers from alkynes and alcohols in the presence of a strong alkaline catalyst. This method suffers from a short catalyst life and poor safety. Acetal cleavage methods are available in two phases: gas-phase and liquid-phase. Liquid-phase cleavage requires the use of liquid acid, which places high demands on equipment. Furthermore, the high-boiling-point solvent presents difficulties in post-processing. Gas-phase cleavage offers the advantages of simple equipment, mild reaction conditions, and continuous production.

[0004] Early gas-phase cracking methods used metal catalysts such as silver. Gold, palladium, and platinum catalysts were difficult to prepare and expensive. Later improvements employed inorganic acidic catalysts, such as Brit. Patent 681.059.1952. Using BaO deposited on a silica gel surface as a catalyst, the reaction temperature was 290-305°C, and the reaction was carried out at a space velocity of 0.2-2.0°C through a catalyst bed to produce vinyl ether. The reaction conversion rate was 71% and the selectivity was 95%. US 4891451A reported the use of modified borosilicate to crack acetals to produce vinyl ether. The conversion rate was 100% and the selectivity was 88-95%. This method is difficult to prepare the catalyst and requires rare earth metal modification. US Pat. No. 4396782A uses CaO as a catalyst and a reaction temperature of 192-236°C to produce vinyl 2-chloroethyl ether from acetaldehyde dichloroethanol. The reaction conversion rate was 92.5%. U.S. Patent No. 4014941A describes a method using calcium phosphate as a cracking catalyst, achieving a conversion rate of 98.1% and a selectivity of 96.5%. German Patent No. DE3804162 uses borosilicate zeolite. The catalyst is synthesized by a hydrothermal method at a reaction temperature of 3000°C, achieving an acetal conversion rate of 100% and a selectivity of 95.6%. However, the catalyst is complex and difficult to prepare, requiring high-pressure reaction modification.

[0005] Related research in China has also been conducted by Liu Hong et al. from the Department of Chemical Engineering at East China University of Science and Technology (Journal of East China University of Science and Technology, 1995, 21(6): 305-310). They studied the activity and selectivity of the cracking reaction of diisobutyl acetal to vinyl isobutyl ether over calcium phosphate catalyst. The catalyst was calcined at 500°C for several hours. The reaction temperature was 300°C and the acetal space velocity was 1.0 h -1 When the reaction is carried out at 100% selectivity, the reaction conversion rate can reach 98.6%. Zhou Zhongshi et al. (Hangzhou Chemical Industry, 2000, 30(3): 6-8) from Zhejiang Light Industry School used calcium phosphate deposited on asbestos as a catalyst to produce vinyl isobutyl ether by cracking acetaldehyde diisobutyl acetal at 280°C. The reaction yield was 92.6%. Catalyst components and preparation methods reported domestically and internationally vary, and catalyst performance also varies. A common disadvantage is that the catalyst life is not long enough. Summary of the Invention

[0006] In view of this, the present invention provides a catalyst for preparing alkenyl ethers by acetal cracking and a preparation method thereof. The catalyst has a wide range of applications, high activity, a long stable period, and is suitable for industrialization.

[0007] The catalyst for preparing alkenyl ether by acetal cracking of the present invention comprises the following raw materials in parts by weight:

[0008] 40-80 parts of phosphoric acid or phosphate or sulfate, 20-40 parts of pickled diatomaceous earth, 13-15 parts of acid phosphate, 6-10 parts of metal halide or alkaline earth metal oxide, 2-5 parts of sesbania powder, 8-15 parts of silica sol, 10-20 parts of titanyl sulfate, and 5-7 parts of carbonamide.

[0009] In the embodiment of the present application, the titanyl sulfate is titanyl sulfate with a purity of 99% that is commonly purchased on the market; and the silica sol is silica sol with a SiO2 content of 30%.

[0010] Preferably, the phosphoric acid is phosphoric acid with a mass concentration of 85%; the phosphate is any one of lithium phosphate, calcium phosphate, magnesium phosphate, aluminum phosphate or zinc phosphate; and the sulfate is any one of magnesium sulfate, calcium sulfate or copper sulfate.

[0011] Preferably, the acid phosphate is any one of calcium hydrogen phosphate or magnesium hydrogen phosphate.

[0012] Preferably, the metal halide is any one of calcium halide, iron halide, and vanadium halide; and the alkaline earth metal oxide is any one of magnesium oxide, calcium oxide, strontium oxide, and barium oxide.

[0013] Preferably, the acid-washed diatomaceous earth, metal halide, and alkaline earth metal oxide are powders with a particle size of less than 150 μm.

[0014] Another object of the present invention is to provide a method for preparing a catalyst for preparing alkenyl ethers by acetal cleavage, comprising the following steps:

[0015] (1) Mix the raw materials into a mass:

[0016] When adding phosphate or sulfate, the phosphate or sulfate, acid-washed diatomaceous earth, and acid phosphate are weighed in proportion and thoroughly mixed to obtain a mixture; metal halide or alkaline earth metal oxide and sesbania powder are added to the mixture in proportion, stirred evenly, and then distilled water and silica sol are added, blended, and extruded into a mass (the amount of water added is not critical, as long as it can play a blending role and be extruded into a mass);

[0017] When phosphoric acid is added, diatomaceous earth, acid phosphate, metal halide or alkaline earth metal oxide, and sesbania powder are mixed evenly in proportion, then impregnated with phosphoric acid, and then silica sol is added and kneaded into a mass;

[0018] (2) Extrusion molding, drying, shearing into 2-3 mm cylindrical particles, calcining, cooling and drying to obtain a granular catalyst precursor;

[0019] (3) Titanyl sulfate is weighed in proportion and prepared into an aqueous solution with a mass concentration of 10%, carbon amide is added, the temperature is raised to 60°C to 70°C, and the reaction is carried out for 30min to 40min, and the catalyst precursor prepared in step (2) is added thereto. The solution is kept warm and allowed to stand for 3 hours, then filtered, washed with cold water, vacuum-dried (to remove surface moisture), and dried and calcined to prepare a catalyst.

[0020] During the preparation process, carbonamide reacts with water to produce ammonia, which reacts with titanyl sulfate to form orthotitanic acid. The orthotitanic acid precipitate is impregnated into the catalyst precursor and calcined to form anatase titanium dioxide. This method is currently used to prepare titanium dioxide.

[0021] Preferably, the drying temperature in step (2) is 100° C. to 120° C., and the drying time is 2 h to 4 h.

[0022] Preferably, the calcination temperature in step (2) is 500° C. to 600° C., and the calcination time is 4 h to 5 h.

[0023] Preferably, the drying temperature in step (3) is 120° C., and the drying time is 3 to 7 hours.

[0024] Preferably, the calcination temperature in step (4) is 500° C. to 550° C., and the calcination time is 3 h to 4 h.

[0025] The catalyst prepared by the present invention can be used to prepare alkenyl ethers by cracking acetals, wherein the structure of the acetals is as shown in formula (1):

[0026]

[0027] Wherein R1 is hydrogen or a C1-C3 straight chain or branched chain alkyl group; R2 is a C1-C4 straight chain or branched chain alkyl group.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The present invention provides a catalyst for preparing alkenyl ethers by acetal cracking and a preparation method thereof. First, a catalyst precursor is prepared, and then titanium dioxide is prepared by using titanyl sulfate, and impregnation and doping are performed to obtain ultrafine particles with uniform particle size and high purity. At the same time, the addition of carbonamide can perform alkaline treatment on the catalyst surface, thereby improving selectivity and further improving catalyst stability.

[0030] The catalyst of the present invention has a simple preparation method, and the catalyst has the characteristics of high strength, good activity, strong selectivity, and long stable operation period. The catalyst prepared by the present invention has a crushing strength greater than 300N / cm 2 . DETAILED DESCRIPTION

[0031] The present invention will be further described below with reference to the embodiments.

[0032] Example 1

[0033] A catalyst for preparing alkenyl ethers by acetal cracking, comprising the following raw materials:

[0034] 75g magnesium phosphate, 30g acid-washed diatomaceous earth, 15g magnesium hydrogen phosphate, 8g barium oxide, 3g sesbania powder, 13g silica sol, 16g titanyl sulfate, 6.5g carbonamide. The acid-washed diatomaceous earth and barium oxide are powders with a particle size of less than 150μm.

[0035] The preparation method of the catalyst comprises the following steps:

[0036] (1) Weighing magnesium phosphate, acid-washed diatomaceous earth, and magnesium hydrogen phosphate in proportion, and thoroughly mixing them to obtain a mixture;

[0037] (2) Add barium oxide and sesbania powder to the mixture in proportion, stir evenly, then add appropriate amount of distilled water and silica sol, blend and extrude into a mass (the amount of water added is not critical, as long as it can play a blending role and extrude into a mass);

[0038] (3) Extrusion molding, drying at 120°C for 4 hours, then shearing into 2-3 mm cylindrical particles, calcining at 560°C for 5 hours, cooling and drying to obtain a granular catalyst precursor;

[0039] (4) Titanyl sulfate was weighed in proportion and prepared into a 10% aqueous solution by mass concentration. Carbon amide was added and the temperature was raised to 70°C. After the reaction for 30 minutes, the catalyst precursor prepared in step (3) was added thereto. The solution was kept at the temperature and allowed to stand for 3 hours. The solution was filtered, washed with cold water, dried under a negative pressure of 0.05 kPa, dried at 120°C for 4 hours, and then calcined at 550°C for 3 hours to prepare a catalyst. The crushing strength of the catalyst was 310 N / cm 2 .

[0040] Example 2

[0041] A catalyst for preparing alkenyl ethers by acetal cracking, comprising the following raw materials:

[0042] 60g calcium phosphate, 30g acid-washed diatomaceous earth, 13g calcium hydrogen phosphate, 7g calcium chloride, 3g sesbania powder, 11g silica sol, 14g titanyl sulfate, 6.0g carbamide. The acid-washed diatomaceous earth and calcium chloride are powders with a particle size of less than 150μm.

[0043] The preparation method of the catalyst comprises the following steps:

[0044] (1) weighing calcium phosphate, acid-washed diatomaceous earth, and calcium hydrogen phosphate in proportion, and mixing them thoroughly to obtain a mixture;

[0045] (2) adding calcium chloride and sesbania powder to the mixture in proportion, stirring evenly, then adding appropriate amounts of distilled water and silica sol, blending and extruding into a mass (the amount of water added is not required, as long as it can play a blending role and be extruded into a mass);

[0046] (3) Extrusion molding, drying at 120°C for 4 hours, then shearing into 2-3 mm cylindrical particles, calcining at 560°C for 5 hours, cooling and drying to obtain a granular catalyst precursor;

[0047] (4) Titanyl sulfate was weighed in proportion and prepared into an aqueous solution with a mass concentration of 10%, carbonamide was added, the temperature was raised to 70°C, and the reaction was carried out for 30 minutes. The catalyst precursor prepared in step (3) was added thereto, and the solution was kept at this temperature and allowed to stand for 3 hours. The solution was then filtered, washed with cold water, dried under a negative pressure of 0.05 kPa, dried at 120°C for 4 hours, and then calcined at 550°C for 3 hours to prepare a catalyst.

[0048] Example 3

[0049] A catalyst for preparing alkenyl ethers by acetal cracking, comprising the following raw materials:

[0050] 50g aluminum phosphate, 20g acid-washed diatomaceous earth, 15g calcium hydrogen phosphate, 8g barium oxide, 2.5g sesbania powder, 9.5g silica sol, 12g titanyl sulfate, 5.0g carbonamide. The acid-washed diatomaceous earth and barium oxide are powders with a particle size of less than 150μm.

[0051] The preparation method of the catalyst comprises the following steps:

[0052] (1) weighing aluminum phosphate, acid-washed diatomaceous earth, and calcium hydrogen phosphate in proportion, and thoroughly mixing them to obtain a mixture;

[0053] (2) Add barium oxide and sesbania powder to the mixture in proportion, stir evenly, then add appropriate amount of distilled water and silica sol, blend and extrude into a mass (the amount of water added is not critical, as long as it can play a blending role and extrude into a mass);

[0054] (3) Extrusion molding, drying at 120°C for 4 hours, then shearing into 2-3 mm cylindrical particles, calcining at 560°C for 5 hours, cooling and drying to obtain a granular catalyst precursor;

[0055] (4) Titanyl sulfate was weighed in proportion and prepared into an aqueous solution with a mass concentration of 10%, carbonamide was added, the temperature was raised to 70°C, and the reaction was carried out for 30 minutes. The catalyst precursor prepared in step (3) was added thereto, and the solution was kept at this temperature and allowed to stand for 3 hours. The solution was then filtered, washed with cold water, dried under a negative pressure of 0.05 kPa, dried at 120°C for 4 hours, and then calcined at 550°C for 3 hours to prepare a catalyst.

[0056] Example 4

[0057] A catalyst for preparing alkenyl ethers by acetal cracking, comprising the following raw materials:

[0058] 75g copper sulfate, 35g acid-washed diatomaceous earth, 15g magnesium hydrogen phosphate, 8g calcium oxide, 3g sesbania powder, 13g silica sol, 17g titanyl sulfate, 6.8g carbamide. The acid-washed diatomaceous earth and calcium oxide are powders with a particle size of less than 150μm.

[0059] The preparation method of the catalyst comprises the following steps:

[0060] (1) copper sulfate, pickled diatomaceous earth and magnesium hydrogen phosphate are weighed in proportion and thoroughly mixed to obtain a mixture;

[0061] (2) adding calcium oxide and sesbania powder to the mixture in proportion, stirring evenly, then adding appropriate amounts of distilled water and silica sol, blending and extruding into a mass (the amount of water added is not required, as long as it can play a blending role and be extruded into a mass);

[0062] (3) Extrusion molding, drying at 120°C for 4 hours, then shearing into 2-3 mm cylindrical particles, calcining at 560°C for 5 hours, cooling and drying to obtain a granular catalyst precursor;

[0063] (4) Titanyl sulfate was weighed in proportion and prepared into an aqueous solution with a mass concentration of 10%, carbonamide was added, the temperature was raised to 70°C, and the reaction was carried out for 30 minutes. The catalyst precursor prepared in step (3) was added thereto, and the solution was kept at this temperature and allowed to stand for 3 hours. The solution was then filtered, washed with cold water, dried under a negative pressure of 0.05 kPa, dried at 120°C for 4 hours, and then calcined at 550°C for 3 hours to prepare a catalyst.

[0064] Example 5

[0065] A catalyst for preparing alkenyl ethers by acetal cracking, comprising the following raw materials:

[0066] 45g zinc phosphate, 25g acid-washed diatomaceous earth, 13g magnesium hydrogen phosphate, 9g barium oxide, 2g sesbania powder, 9g silica sol, 12g titanyl sulfate, 5g carbonamide. The acid-washed diatomaceous earth and barium oxide are powders with a particle size of less than 150μm.

[0067] The preparation method of the catalyst comprises the following steps:

[0068] (1) Weighing zinc phosphate, acid-washed diatomaceous earth, and magnesium hydrogen phosphate in proportion, and thoroughly mixing them to obtain a mixture;

[0069] (2) Add barium oxide and sesbania powder to the mixture in proportion, stir evenly, then add appropriate amount of distilled water and silica sol, blend and extrude into a mass (the amount of water added is not critical, as long as it can play a blending role and extrude into a mass);

[0070] (3) Extrusion molding, drying at 120°C for 4 hours, then shearing into 2-3 mm cylindrical particles, calcining at 560°C for 5 hours, cooling and drying to obtain a granular catalyst precursor;

[0071] (4) Titanyl sulfate was weighed in proportion and prepared into an aqueous solution with a mass concentration of 10%, carbonamide was added, the temperature was raised to 70°C, and the reaction was carried out for 30 minutes. The catalyst precursor prepared in step (3) was added thereto, and the solution was kept warm and allowed to stand for 3 hours, then filtered, washed with cold water, dried under a negative pressure of 0.05 kPa, dried at 120°C for 47 hours, and then calcined at 550°C for 3 hours to prepare a catalyst.

[0072] Example 6

[0073] A catalyst for preparing alkenyl ethers by acetal cracking, comprising the following raw materials:

[0074] 60g aluminum phosphate, 26g acid-washed diatomaceous earth, 13g calcium hydrogen phosphate, 8g magnesium oxide, 2g sesbania powder, 10g silica sol, 13g titanyl sulfate, 5.6g carbonamide. The acid-washed diatomaceous earth and magnesium oxide are powders with a particle size of less than 150μm.

[0075] The preparation method of the catalyst comprises the following steps:

[0076] (1) weighing aluminum phosphate, acid-washed diatomaceous earth, and calcium hydrogen phosphate in proportion, and thoroughly mixing them to obtain a mixture;

[0077] (2) adding magnesium oxide and sesbania powder to the mixture in proportion, stirring evenly, then adding appropriate amounts of distilled water and silica sol, blending and extruding into a mass (the amount of water added is not required, as long as it can play a blending role and be extruded into a mass);

[0078] (3) Extrusion molding, drying at 120°C for 4 hours, then shearing into 2-3 mm cylindrical particles, calcining at 560°C for 5 hours, cooling and drying to obtain a granular catalyst precursor;

[0079] (4) Titanyl sulfate was weighed in proportion and prepared into an aqueous solution with a mass concentration of 10%, carbonamide was added, the temperature was raised to 70°C, and the reaction was carried out for 30 minutes. The catalyst precursor prepared in step (3) was added thereto, and the solution was kept at this temperature and allowed to stand for 3 hours. The solution was then filtered, washed with cold water, dried under a negative pressure of 0.05 kPa, dried at 120°C for 4 hours, and then calcined at 550°C for 3 hours to prepare a catalyst.

[0080] The catalysts prepared in Examples 1-6 were used to prepare alkenyl ethers. The conversion and selectivity were calculated as shown in Formulas (2) and (3):

[0081]

[0082]

[0083] Where M is the molar fraction of acetal in the raw material; Ma is the molar fraction of aldehyde in the product; Me is the molar fraction of alkenyl ether in the product; f1 is the molecular weight of acetal; f2 is the molecular weight of alkenyl ether.

[0084] (1) 28 g of the catalyst prepared in Example 1-6 was added to a fixed bed continuous reactor to perform a dimethyl acetal cracking experiment to prepare vinyl methyl ether. The reaction temperature was 300°C, atmospheric pressure, and the dimethyl acetal liquid hourly space velocity was 1.2 h -1 The conversion rate of dimethyl acetal and the selectivity of vinyl methyl ether were calculated according to formula (2) and formula (3):

[0085] The conversion rate of dimethyl acetal and the selectivity of vinyl methyl ether are shown in Table 1:

[0086] Table 1

[0087] catalyst Acetal cracking conversion rate % Vinyl methyl ether selectivity% Example 1 95.3 96.5 Example 2 98.2 97.6 Example 3 99.0 98.5 Example 4 90.3 88.6 Example 5 94.8 97.2 Example 6 97.6 98.5

[0088] (2) 28 g of the catalyst prepared in Example 3 was loaded into a fixed-bed cracking reactor, and different raw materials were passed through the reactor for acetal cracking experiments. The reaction temperature was 310 ° C., the pressure was normal pressure, and the raw material liquid hourly space velocity was 1.1 h -1 , the test conversion rate and selectivity are shown in Table 2:

[0089] Table 2

[0090] raw material product Conversion Rate % Selectivity% 1.1-Diethoxyethane Ethyl vinyl ether 98.1 99.2 1.1-Diisopropoxyethane Isopropyl vinyl ether 97.5 98.5 1.1-Dimethoxypropane Propylene methyl ether 96.5 98.0 1.1-Diisopropoxybutane Isopropoxybutyl ether 95.5 96.7 1.1-Dimethoxyethane Vinyl methyl ether 98.7 98.5

[0091] (III) 28 g of the catalyst of Example 6 was quantitatively loaded into a fixed-bed cracking reactor for continuous cracking of dimethylol acetal at a reaction temperature of 310° C., atmospheric pressure, and a liquid hourly space velocity of dimethylol acetal of 1.1 h -1 , the test conversion rate and selectivity are shown in Table 3:

[0092] Table 3

[0093] Reaction time Conversion rate of dimethyl acetal % Vinyl methyl ether selectivity% 100 98.2 99.2 500 98.2 99.0 1000 97.7 98.8 1500 96.8 98.2

[0094] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A catalyst for preparing alkenyl ethers by acetal cracking, characterized in that The invention comprises the following raw materials in parts by weight: 40-80 parts of phosphoric acid or phosphate or sulfate, 20-40 parts of pickled diatomaceous earth, 13-15 parts of acid phosphate, 6-10 parts of metal halide or alkaline earth metal oxide, 2-5 parts of sesbania powder, 8-15 parts of silica sol, 10-20 parts of titanyl sulfate, and 5-7 parts of carbonamide; The acid-washed diatomaceous earth, metal halide, and alkaline earth metal oxide are powders with a particle size of less than 150 μm; The method for preparing the catalyst for preparing alkenyl ether by acetal cracking comprises the following steps: (1) Mix the raw materials into a mass: When adding phosphate or sulfate, the phosphate or sulfate, acid-washed diatomaceous earth, and acid phosphate are weighed in proportion and thoroughly mixed to obtain a mixture; metal halide or alkaline earth metal oxide and sesbania powder are added to the mixture in proportion and stirred evenly; then distilled water and silica sol are added, and the mixture is blended and extruded into a mass; When phosphoric acid is added, diatomaceous earth, acid phosphate, metal halide or alkaline earth metal oxide, and sesbania powder are mixed evenly in proportion, then impregnated with phosphoric acid, and then silica sol is added and kneaded into a mass; (2) After extrusion and drying, the extrusion is cut into 2-3 mm cylindrical particles, calcined, cooled and dried to obtain a granular catalyst precursor; (3) Titanyl sulfate is weighed in proportion and prepared into an aqueous solution with a mass concentration of 10%. Carbon amide is added and the temperature is raised to 60°C to 70°C. After the reaction is carried out for 30 min to 40 min, the catalyst precursor prepared in step (2) is added thereto. The solution is kept at the temperature and allowed to stand for 3 hours. The solution is then filtered, washed with cold water, vacuum-drained, dried, and calcined to prepare a catalyst.

2. The catalyst for preparing alkenyl ether by acetal cracking according to claim 1, characterized in that The phosphoric acid is phosphoric acid with a mass concentration of 85%; the phosphate is any one of lithium phosphate, calcium phosphate, magnesium phosphate, aluminum phosphate or zinc phosphate; and the sulfate is any one of magnesium sulfate, calcium sulfate or copper sulfate.

3. The catalyst for preparing alkenyl ether by acetal cracking according to claim 1, characterized in that The acid phosphate is any one of calcium hydrogen phosphate or magnesium hydrogen phosphate.

4. The catalyst for preparing alkenyl ether by acetal cracking according to claim 1, characterized in that The metal halide is any one of calcium halide, iron halide, and vanadium halide; the alkaline earth metal oxide is any one of magnesium oxide, calcium oxide, strontium oxide, and barium oxide.

5. The catalyst for preparing alkenyl ether by acetal cracking according to claim 1, characterized in that The drying temperature in step (2) is 100° C. to 120° C., and the drying time is 2 h to 4 h.

6. The catalyst for preparing alkenyl ether by acetal cracking according to claim 1, characterized in that The calcination temperature in step (2) is 500° C. to 600° C., and the calcination time is 4 h to 5 h.

7. The catalyst for preparing alkenyl ether by acetal cracking according to claim 1, characterized in that The drying temperature in step (3) is 120° C., and the drying time is 3 to 7 hours.

8. The catalyst for preparing alkenyl ether by acetal cracking according to claim 1, characterized in that The calcination temperature in step (3) is 500° C. to 550° C., and the calcination time is 3 h to 4 h.

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