Catalysts for the condensation of methyl acetate and formaldehyde to prepare methyl acrylate and their preparation methods, as well as methods for preparing methyl acrylate.

Abstract

This invention relates to a catalyst for the condensation of methyl acetate and formaldehyde to prepare methyl acrylate, a method for preparing the same, and a method for preparing methyl acrylate. The catalyst disclosed comprises a zirconium-modified silica support and an active component; the active component includes basic active centers and acidic active centers. Applied to the method of condensing methyl acetate and formaldehyde to prepare methyl acrylate, by controlling the supply of formaldehyde monomer from the formaldehyde source and the ratio of methyl acetate to methanol, and simultaneously using a depolymerization reactor to depolymerize the formaldehyde source into formaldehyde monomers, a two-stage condensation reaction of methyl acetate and formaldehyde can be simultaneously catalyzed, effectively improving the yield of methyl acrylate.

Description

Technical Field

[0001] This invention relates to a catalyst for the condensation of methyl acetate and formaldehyde to prepare methyl acrylate, a method for preparing the same, and a method for preparing methyl acrylate. Background Technology

[0002] Methyl acrylate is an important fine chemical raw material with a wide range of applications. Currently, its preparation methods mainly include propylene oxidation, acrylonitrile hydrolysis, ketene method, propane oxidation, and methyl formate method. However, these methods have disadvantages such as serious pollution, high energy consumption, and low product yield.

[0003] CN101575290A discloses a method for synthesizing methyl acrylate using a segmented catalyst loading method. This method integrates two catalysts—vanadium phosphate catalyst and Cs-Sb2O5 / SiO2 catalyst—into a single catalyst loading process to catalyze the synthesis of methyl acrylate. The steps are as follows: (1) In a vanadium lactate solution, phosphoric acid is added to prepare an impregnation solution with a vanadium phosphate molar ratio of 2.0:1-3.5:1. This solution is then impregnated onto silica gel and dried and calcined to obtain the vanadium phosphate catalyst; (2) The prepared silica sol and Sb2O5 sol are mixed and stirred vigorously for 1-2 hours. The pH is adjusted to 8-10 to obtain a mixed sol. A 10% ammonium nitrate solution is added to dissolve the sol, and the temperature is raised to allow it to return to its original state. The reaction was carried out for 6-8 hours; the mixture was removed, dried, and calcined to obtain a white mixed gel. The mixed gel was ground to 20-40 mesh, impregnated with 5%-30% CsNO3 by mass, and calcined at 400-600℃ for 3 hours to obtain a Cs-Sb2O5 / SiO2 catalyst; (3) Methyl acrylate was synthesized in a fixed-bed micro-reaction chromatography device. The reaction tube was divided into 9 sections. The two catalysts, vanadium phosphate and Cs-Sb2O5 / SiO2, were packed from top to bottom. The vanadium phosphate catalyst was in sections 2-6, and the cesium alkali metal catalyst was in sections 2-9. Methyl acetate and methyl acetal were mixed and injected using a micro-pump. The molar ratio of methyl acetate / methyl acetal was 1:1-3:1, and the feed space velocity was 1-5 h. -1 The synthesis reaction was carried out at a furnace temperature of 350-420℃ to obtain methyl acrylate. Although this solved the problem of low reaction conversion, it required additional equipment and its selectivity was not high.

[0004] Therefore, developing new green and efficient production processes is of great significance. Summary of the Invention

[0005] The purpose of this invention is to overcome the problem of low yield of methyl acrylate in the prior art, and to provide a catalyst for the condensation of methyl acetate and formaldehyde to prepare methyl acrylate and its preparation method. This catalyst has high catalytic activity when applied to the condensation of methyl acetate and formaldehyde to prepare methyl acrylate.

[0006] To achieve the above objectives, the present invention provides a catalyst for the condensation of methyl acetate and formaldehyde to prepare methyl acrylate, the catalyst comprising a zirconium-modified silica support and an active component; the active component comprising basic active centers and acidic active centers.

[0007] The second aspect of the present invention provides a method for preparing the catalyst of the present invention, the method comprising: S1. preparing a zirconium-modified silica support by means of a sol-gel method; S2. subjecting an acidic active center source to a first contact with the zirconium-modified silica support, subjecting it to a first drying, calcining it, and then subjecting it to a second contact with an alkaline active center source in a solvent, and subjecting it to a second drying.

[0008] A third aspect of the present invention provides a method for preparing methyl acrylate by condensation of methyl acetate and formaldehyde, the method comprising: reacting a formaldehyde source, methanol, methyl acetate and a catalyst in a contact reaction; wherein the catalyst comprises the catalyst described in the present invention.

[0009] Through the above technical solution, the present invention has the following beneficial effects:

[0010] This invention provides a catalyst for the condensation of methyl acetate and formaldehyde to prepare methyl acrylate, comprising a zirconium-modified silica support and an active component; the active component includes basic active centers and acidic active centers; applied in the method of condensing methyl acetate and formaldehyde to prepare methyl acrylate, by controlling the supply of formaldehyde monomer from the formaldehyde source and the ratio of methyl acetate to methanol, and simultaneously using a depolymerization reactor to depolymerize the formaldehyde source into formaldehyde monomers, a two-stage condensation reaction of methyl acetate and formaldehyde can be simultaneously catalyzed, effectively improving the yield of methyl acrylate. Detailed Implementation

[0011] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0012] This invention provides a catalyst for the condensation of methyl acetate and formaldehyde to prepare methyl acrylate. The catalyst includes a zirconium-modified silica support and an active component; the active component contains basic active centers and acidic active centers.

[0013] The catalyst for the condensation of methyl acetate and formaldehyde to prepare methyl acrylate of the present invention has the advantage of simultaneously catalyzing methyl acetate and formaldehyde, and the catalyst of the present invention is beneficial to obtaining a higher yield of methyl acrylate product.

[0014] According to a particularly preferred embodiment of the present invention, the content of the active component is 1-25 wt%, preferably 5-20 wt%, based on the total mass of the catalyst. By adopting the aforementioned preferred embodiment, the yield of methyl acrylate can be further improved.

[0015] In this invention, there are no special requirements for the mass ratio of basic active centers to acidic active centers. According to a particularly preferred embodiment of the invention, the mass ratio of basic active centers to acidic active centers, calculated per 100 wt%, is 1-150, preferably 5-100. Examples of 5, 10, 6, and 100 are provided for illustrative purposes, but do not limit the scope of the invention. By employing the aforementioned preferred embodiment, catalytic activity can be further improved.

[0016] In this invention, there are no special requirements for the method of providing the basic active center; the description is illustrative but does not limit the scope of the invention. According to a preferred embodiment of the invention, the basic active center is provided by a potassium compound. By adopting the aforementioned preferred embodiment, the catalytic activity can be further improved.

[0017] In this invention, the method of providing the acidic active center is not particularly required; it is merely an illustrative example and does not limit the scope of the invention. According to a preferred embodiment of the invention, the acidic active center is provided by a phosphorus compound and / or a boron compound, preferably in the form of phosphorus oxides and / or boron oxides. By adopting the aforementioned preferred embodiment, the catalytic activity can be further improved.

[0018] In this invention, the content of the zirconium-modified silica support is not specifically required; this is merely an illustrative example and does not limit the scope of the invention. According to a preferred embodiment of the invention, the zirconium content is 0.5-10% by weight, preferably 1-5% by weight, based on the total mass of the zirconium-modified silica support. By adopting the aforementioned preferred embodiment, the catalytic activity can be further improved.

[0019] According to a preferred embodiment of the invention, the potassium compound content is 1-30% by weight, preferably 5-25% by weight, more preferably 5-20% by weight, based on the total mass of the catalyst. Examples are illustrated by 5% by weight, 10% by weight, and 18% by weight, but this does not limit the scope of the invention.

[0020] According to a preferred embodiment of the present invention, the content of the phosphorus oxide and / or boron oxide is 0.01-3% by weight, preferably 0.1-2% by weight, based on the total mass of the catalyst. Examples are exemplified by 0.1% by weight, 1% by weight, and 1.7% by weight, but this does not limit the scope of the invention.

[0021] By employing the aforementioned preferred embodiments, the catalytic activity can be further improved.

[0022] Catalysts for the condensation of methyl acetate and formaldehyde to prepare methyl acrylate with the aforementioned characteristics can all be used in this invention, and there are no special requirements for their preparation methods. For this invention, a method for preparing a catalyst for the condensation of methyl acetate and formaldehyde to prepare methyl acrylate is provided, the method comprising: S1. preparing a zirconium-modified silica support using a sol-gel method; S2. subjecting an acidic active center source to a first contact with the zirconium-modified silica support, performing a first drying, calcining, and then subjecting it to a second contact with a basic active center source in a solvent, followed by a second drying.

[0023] In this invention, step S1 uses the sol-gel method to prepare zirconium-modified silica support. The preparation method includes mixing silicon source and zirconium precursor in solution, adjusting pH, reacting under crystallization conditions, and then filtering, washing, drying, and calcining.

[0024] This is an illustrative example, but does not limit the scope of the invention. According to one embodiment of the invention, in step S1, the silicon source and the zirconium precursor need to be mixed evenly in a solution. The solution can be deionized water, and the amount used is not particularly required and is well known to those skilled in the art. It can be selected according to actual operation.

[0025] This is an illustrative example, but does not limit the scope of the invention. In one embodiment of the invention, the silicon source in step S1 is 40 wt% alkaline silica sol. This is an illustrative example, but does not limit the scope of the invention.

[0026] In this invention, there are no special requirements for the mixing conditions of the silicon source and the zirconium precursor in solution in step S1. As an example, the mixing is an immersion contact mixing, but this does not limit the scope of the invention.

[0027] In this embodiment of the invention, the solution used to adjust the pH in step S1 is 35wt% nitric acid as an example, but this does not limit the scope of the invention.

[0028] In this invention, the pH value in step S1 can be selected from a wide range. According to a preferred embodiment of the invention, the adjusted pH value is 0-7, preferably 1-5. The example uses pH 4 as an illustrative example, but this does not limit the scope of the invention. By adopting the aforementioned preferred embodiment, the catalytic activity can be further improved.

[0029] In this invention, the crystallization conditions in step S1 have no special requirements. According to a preferred embodiment of this invention, the crystallization conditions include: a temperature of 10-100°C, preferably 75-90°C. In the examples, 80°C is used as an example, but this does not limit the scope of the invention.

[0030] In this invention, the crystallization time can be adjusted as needed, as illustrated in the example, but this does not limit the scope of the invention. For example, the crystallization time is 1-30 hours, preferably 5-6 hours. The example uses 6 hours as an example, but this does not limit the scope of the invention. By adopting the aforementioned preferred embodiments, the catalytic activity can be further improved.

[0031] In this invention, there are no special requirements for the drying conditions described in step S1.

[0032] According to a preferred embodiment of the present invention, the drying temperature is 10-200°C, preferably 100-110°C. In the examples, 100°C is used as an example, but this does not limit the scope of the present invention.

[0033] According to a preferred embodiment of the present invention, the drying time is 1-20 hours, with 6 hours used as an example in the embodiment, but this does not limit the scope of the present invention.

[0034] By employing the aforementioned preferred embodiments, the catalytic activity can be further improved.

[0035] In this invention, there are no special requirements for the roasting conditions in step S1. According to a preferred embodiment of this invention, the roasting temperature is 300-1000℃, preferably 800-900℃. In the example, 800℃ is used as an example, but this does not limit the scope of the invention.

[0036] In this invention, the roasting time in step S1 can be adjusted as needed, generally 1-25 hours. In the example, 4 hours is used as an example, but this does not limit the scope of the invention.

[0037] In this invention, the solvent used for washing is deionized water. There are no special requirements for the number of washing cycles or the amount of deionized water used; it is sufficient to meet the actual experimental needs.

[0038] In this invention, there are no special requirements for the first drying and the second drying conditions in step S2.

[0039] This is an illustrative example, but does not limit the scope of the invention. According to one embodiment of the invention, the first drying temperature and the second drying temperature are each 10-200°C, preferably 110-120°C. In the example, 110°C is used as an illustrative example, but does not limit the scope of the invention.

[0040] According to one embodiment of the present invention, the drying time of the first drying and the second drying are adjusted as needed, generally 1-20 hours. In the example, 6 hours is used as an example, but this does not limit the scope of the present invention.

[0041] In this invention, the second drying process is carried out in a reactor, which is well known to those skilled in the art and can be carried out with reference to existing technology. The invention will not be described in detail here.

[0042] By employing the aforementioned preferred embodiments, the dispersion of active centers can be further improved.

[0043] In this invention, the calcination conditions in step S2 can be selected with reference to existing technologies.

[0044] According to a preferred embodiment of the present invention, the calcination temperature is 100-1000℃, preferably 400-800℃.

[0045] According to a preferred embodiment of the present invention, the roasting time is 1-16 hours.

[0046] In this invention, the first contact condition in step S2 has no special requirements. It is illustrative, for example, to impregnate contact mixing, but this does not limit the scope of the invention.

[0047] In this invention, in step S2, there are no special requirements for the second contact condition. As an example, the contact is an immersion contact, but this does not limit the scope of the invention.

[0048] This is an illustrative description, but does not limit the scope of the invention. According to a preferred embodiment of the invention, after the second contact and before the second drying, the conditions include: azeotropically dehydrating the solid obtained from the contact using at least one of toluene, xylene, and trimethylbenzene as a solvent; preferably, the dehydration temperature is 80-110°C and the dehydration time is 3-8 hours. In the examples, a dehydration temperature of 100°C and a dehydration time of 5 hours are used as illustrative examples, but this does not limit the scope of the invention. By employing the aforementioned preferred embodiment, the dispersion effect of the active centers can be further improved.

[0049] In this invention, in the second contact step, after the catalyst undergoes azeotropic dehydration treatment and before the second drying, it is necessary to load the catalyst covered with organic solvent on its surface into the reactor and purge it with nitrogen gas during the reaction. This operation is well known to those skilled in the art and can be performed with reference to existing technology.

[0050] This invention provides a method for preparing methyl acrylate by condensation of methyl acetate and formaldehyde. The method includes: reacting formaldehyde source, methanol, methyl acetate and catalyst in a contact reaction; the catalyst includes the catalyst for preparing methyl acrylate by condensation of methyl acetate and formaldehyde as described in this invention.

[0051] In this invention, the formaldehyde source can be a conventional choice in the art. According to a preferred embodiment of the invention, the formaldehyde source is at least one of methylal, trioxymethylene, paraformaldehyde, and formaldehyde water, preferably paraformaldehyde, and more preferably paraformaldehyde is depolymerized in a depolymerization reactor to form monomeric formaldehyde. By employing the aforementioned preferred embodiment, the contact between methyl acetate and monomeric formaldehyde can be further improved.

[0052] In this invention, the conditions for depolymerization can be determined with reference to existing technologies.

[0053] According to a preferred embodiment of the present invention, the depolymerization temperature is 80-250°C, preferably 100-230°C. In the examples, 180°C is used as an example, but this does not limit the scope of the present invention.

[0054] According to a preferred embodiment of the present invention, the depolymerization time is 1-60s, preferably 2-35s. In the embodiment, 10s is used as an example, but this does not limit the scope of the present invention.

[0055] By employing the aforementioned preferred embodiments, the yield of methyl acrylate can be further improved.

[0056] In this invention, there are no special requirements for the conditions of the contact reaction.

[0057] This is an illustrative description, but does not limit the scope of the invention. According to a preferred embodiment of the invention, the contact reaction is carried out in the presence of an inert gas.

[0058] According to a preferred embodiment of the present invention, the contact reaction preferably includes a first contact and a second contact; the first contact and the second contact reactions are respectively carried out in a first reactor and a second reactor; after the reactants are fed into the first reactor for reaction, the reaction stream after the first contact is fed into the second reactor and a formaldehyde source methanol solution is introduced; the inert gas flow rates of the first contact and the second contact are selectable within a wide range, and those skilled in the art can adjust them according to actual needs. For example, the inert gas flow rate of the first contact is 20-400 mL / min, and the inert gas flow rate of the second contact is 50-650 mL / min. In the example, it is exemplarily illustrated that the inert gas flow rate of nitrogen in the first contact is 90 mL / min, and the inert gas flow rate of nitrogen in the second contact is 160 mL / min, but this does not limit the scope of the present invention.

[0059] This is an illustrative description, but does not limit the scope of the invention. According to a preferred embodiment of the invention, the reaction raw materials include methyl acetate, formaldehyde and methanol, wherein the molar ratio of methyl acetate to formaldehyde source is (1-15):1, preferably (3-12):1, and the methanol content is 1-40 wt%, preferably 10-35 wt%, based on the total weight of the liquid raw materials.

[0060] In this invention, the conditions for the first contact and the second contact can be selected from a wide range, as illustrated below, but this does not limit the scope of the invention.

[0061] This is an illustrative description, but does not limit the scope of the invention. According to a preferred embodiment of the invention, the reaction raw materials include methyl acetate, formaldehyde and methanol. The molar ratio of methyl acetate to formaldehyde source in the first contact is (5-15):1, preferably (7-12):1, and the methanol content is 1-40 wt%, preferably 10-35 wt%, based on the total weight of the liquid raw materials.

[0062] This is an illustrative example, but does not limit the scope of the invention. According to a preferred embodiment of the invention, the formaldehyde source methanol solution is introduced in the second contact; and the methanol content, calculated as formaldehyde, is 0.1-40 wt%, preferably 5-32 wt%. In the examples, the paraformaldehyde content is 30 wt% by mass, calculated as formaldehyde, as an example, but does not limit the scope of the invention.

[0063] According to a preferred embodiment of the present invention, the temperature of the first contact and the second contact is 280-400°C respectively. In the embodiment, 320°C is used as an example, but this does not limit the scope of the present invention.

[0064] According to a preferred embodiment of the present invention, the pressure of the first contact and the second contact is 0.1-0.8 MPa respectively. In the embodiment, 0.2 MPa is used as an example, but this does not limit the scope of the present invention.

[0065] According to a preferred embodiment of the present invention, the liquid phase volume flow rate of the first contact is 0.01-0.2 mL / min. In the examples, the liquid phase volume flow rate of the first contact is 0.1 mL / min as an example, but this does not limit the scope of the present invention.

[0066] According to a preferred embodiment of the present invention, the liquid phase volume flow rate of the second contact is 0.005-0.1 mL / min. In the example, the liquid phase volume flow rate of the second contact is 0.03 mL / min as an example, but this does not limit the scope of the present invention.

[0067] According to a preferred embodiment of the present invention, the gas space velocity Q1 of the first contact reaction is 2 min.-1 -20min -1 The preferred time is 4 minutes. -1 -6min -1 In the example, 5 minutes -1 This is an illustrative example and is not intended to limit the scope of the invention.

[0068] According to a preferred embodiment of the present invention, the second contact gas space velocity Q1 is 5 min. -1 -16min -1 Preferably 8 minutes -1 -10min -1 .

[0069] According to a preferred embodiment of the present invention, the first contact gas space velocity Q1 is lower than the second contact gas space velocity Q2.

[0070] By employing the aforementioned preferred embodiments, the yield of methyl acrylate can be further improved.

[0071] In the following examples, the methyl acetate conversion rate and methyl acrylate selectivity are well known to those skilled in the art and can be performed with reference to the prior art. The present invention will not elaborate on them here.

[0072] In the following embodiments, the inert gas flow rate of nitrogen in the first contact of the first reactor is 90 ml / min, and the inert gas flow rate of nitrogen in the second contact of the second reactor is 160 ml / min.

[0073]

[0074]

[0075] Example 1

[0076] (1) Zirconium-modified silica support was prepared by sol-gel method. 40wt% alkaline silica sol was used as the silicon source, zirconium oxychloride was used as the zirconium precursor, and the target loading amount on the support was 3wt% zirconium element content. The pH was adjusted to 4 with 35wt% nitric acid, crystallized at 80℃ for 6h, filtered, washed 3 times with deionized water, dried at 100℃ for 6h, and calcined at 800℃ for 4h to obtain zirconium-modified silica support.

[0077] (2) Subsequently, ammonium phosphate solution was impregnated onto the aforementioned support by impregnation method, dried at 100°C for 7 hours, and calcined at 500°C for 4 hours. The P oxide loading content was 0.1% by weight. Then, potassium carbonate solution was impregnated by impregnation method to obtain a solid with a potassium carbonate loading of 10% by weight. The loaded solid was dehydrated by azeotropic dehydration with toluene as solvent at 100°C for 5 hours. Then, the catalyst with organic solvent covering the surface was loaded into the reactor, purged with nitrogen gas during the reaction, and dried at 110°C for 6 hours.

[0078] (3) The first contact and the second contact are respectively carried out in two reactors connected in series (16 mm inner diameter and 1500 mm long); wherein, the paraformaldehyde is first depolymerized in a depolymerization reactor to obtain formaldehyde, the depolymerization temperature is 180℃ and the depolymerization residence time is 10s.

[0079] Both the first and second reactors are loaded with 10g of the above-mentioned catalyst;

[0080] First reactor: temperature 320℃, pressure 0.2MPa, space velocity 5min -1 The reaction was carried out with the following feed rate (liquid phase volume flow rate): 0.1 ml / min. The molar ratio of methyl acetate to formaldehyde in the feed was 7:1, and the methanol content was 12 wt%.

[0081] Second reactor: temperature 320℃, pressure 0.2MPa, space velocity 10min -1 After the reaction in the first reactor is completed, the reactants are introduced into the second reactor, and a methanol-formaldehyde solution with a formaldehyde content of 30 wt% is introduced at the same time. The feed rate (liquid phase volume flow rate) is 0.03 ml / min, the methyl acetate conversion rate is 23%, the methyl acrylate selectivity is 90%, and the catalyst operates stably for 350 h.

[0082] Example 2

[0083] (1) Zirconium-modified silica support was prepared by sol-gel method. 40wt% alkaline silica sol was used as the silicon source, zirconium oxychloride was used as the zirconium precursor, and the target loading amount on the support was 1wt% zirconium element content. The pH was adjusted to 4 with 35wt% nitric acid, crystallized at 80℃ for 6h, filtered, washed 3 times with deionized water, dried at 100℃ for 6h, and calcined at 800℃ for 4h to obtain zirconium-modified silica support.

[0084] (2) Subsequently, ammonium phosphate solution was impregnated onto the aforementioned support by impregnation method, dried at 100°C for 7 hours, and calcined at 400°C for 6 hours. The P oxide loading content was 1% by weight. Then, potassium carbonate solution was impregnated by impregnation method to obtain a solid with a potassium carbonate loading of 5% by weight. The loaded solid was dehydrated by azeotropic dehydration with toluene as solvent at 100°C for 5 hours. Then, the catalyst with organic solvent covering the surface was loaded into the reactor and purged with nitrogen during the reaction. It was dried at 110°C for 6 hours.

[0085] (3) The first contact and the second contact are respectively carried out in two reactors connected in series (16 mm inner diameter and 1500 mm long); wherein, the paraformaldehyde is first depolymerized in a depolymerization reactor to obtain formaldehyde, the depolymerization temperature is 180℃ and the depolymerization residence time is 10s.

[0086] Both the first and second reactors are loaded with 10g of the above-mentioned catalyst;

[0087] First reactor: temperature 320℃, pressure 0.2MPa, space velocity 5min -1 The reaction was carried out with the following feed rate (liquid phase volume flow rate): 0.1 ml / min. The molar ratio of methyl acetate to formaldehyde in the feed was 9:1, and the methanol content was 30 wt%.

[0088] Second reactor: temperature 320℃, pressure 0.2MPa, space velocity 8min -1 After the reaction in the first reactor is completed, the reactants are introduced into the second reactor, and a methanol-formaldehyde solution is introduced at the same time. The formaldehyde content is 30 wt%, the feed rate (liquid phase volume flow rate) is 0.03 ml / min, and the evaluation method in step (4) of Example 1 is adopted. The methyl acetate conversion rate is 22%, the selectivity is 91%, and the catalyst operates stably for 350 h.

[0089] Example 3

[0090] (1) Zirconium-modified silica support was prepared by sol-gel method. 40wt% alkaline silica sol was used as the silicon source, zirconium oxychloride was used as the zirconium precursor, and the target loading amount on the support was 5wt% zirconium element content. The pH was adjusted to 4 with 35wt% nitric acid, crystallized at 80℃ for 6h, filtered, washed 3 times with deionized water, dried at 100℃ for 6h, and calcined at 800℃ for 4h to obtain zirconium-modified silica support.

[0091] (2) Subsequently, ammonium phosphate solution was impregnated onto the aforementioned support by impregnation method, dried at 100°C for 7 h, and calcined at 750°C for 10 h. The P oxide loading content was 1.7% by weight. Then, potassium carbonate solution was impregnated by impregnation method to obtain a solid with a potassium carbonate loading of 18% by weight. The loaded solid was dehydrated by azeotropic dehydration with toluene as solvent at 100°C for 5 h. Then, the catalyst with organic solvent covering the surface was loaded into the reactor, purged with nitrogen gas during the reaction, and dried at 110°C for 6 h.

[0092] (3) The first contact and the second contact are respectively carried out in two reactors connected in series (16 mm inner diameter and 1500 mm long); wherein, the paraformaldehyde is first depolymerized in a depolymerization reactor to obtain formaldehyde, the depolymerization temperature is 180℃ and the depolymerization residence time is 10s.

[0093] Both the first and second reactors are loaded with 10g of the above-mentioned catalyst;

[0094] First reactor: temperature 320℃, pressure 0.2MPa, space velocity 5min -1 The reaction was carried out with the following feed rate (liquid phase volume flow rate): 0.1 ml / min. The molar ratio of methyl acetate to formaldehyde in the feed was 12:1, and the methanol content was 34 wt%.

[0095] Second reactor: temperature 320℃, pressure 0.2MPa, space velocity 8min -1 After the reaction in the first reactor is completed, the reactants are introduced into the second reactor, and a methanol-formaldehyde solution is introduced at the same time. The formaldehyde content is 30 wt%, the feed rate (liquid phase volume flow rate) is 0.03 ml / min, and the evaluation method in step (4) of Example 1 is adopted. The methyl acetate conversion rate is 21%, the selectivity is 88%, and the catalyst operates stably for 350 h.

[0096] Example 4

[0097] All conditions are the same as in Example 1, except that in step (3): the molar ratio of methyl acetate to formaldehyde in the reaction raw materials is 13:1.

[0098] Using the same evaluation method as step (4) in Example 1, the methyl acetate conversion rate was 17%, the selectivity was 92%, and the catalyst operated stably for 350 hours.

[0099] Example 5

[0100] All conditions are the same as in Example 1, except that in step (3): the methanol content in the feedstock is 8 wt%;

[0101] The conversion rate of methyl acetate was 19%, the selectivity was 78%, and the catalyst operated stably for 150 hours.

[0102] Example 6

[0103] All conditions are the same as in Example 1, except that in step (3): paraformaldehyde is fed directly instead of formaldehyde without undergoing depolymerization in the depolymerization reactor;

[0104] The conversion rate of methyl acetate was 15%, the selectivity was 81%, and the catalyst operated stably for 150 hours.

[0105] Example 7

[0106] All conditions are the same as in Example 1, except that in step (3): the space velocity in the second reactor is 1 min. -1 ;

[0107] Using the same evaluation method as step (4) in Example 1, the methyl acetate conversion rate was 14%, the selectivity was 68%, and the catalyst operated stably for 70 hours.

[0108] Example 8

[0109] All conditions are the same as in Example 1, except that in step (2): ammonium phosphate solution is then impregnated onto the aforementioned carrier by impregnation (impregnation amount is the same as in Example 1), dried at 100°C for 7 hours, calcined at 900°C for 4 hours, and then potassium carbonate solution is impregnated by impregnation to obtain a solid (impregnation amount is the same as in Example 1). The loaded solid is then dehydrated by azeotropic dehydration with toluene as solvent at 100°C for 5 hours. The catalyst with organic solvent covering its surface is then loaded into the reactor and purged with nitrogen during the reaction. The solid is then dried at 110°C for 6 hours.

[0110] Using the same evaluation method as step (4) in Example 1, the methyl acetate conversion rate was 12%, the selectivity was 86%, and the catalyst operated stably for 150 hours.

[0111] Comparative Example 1

[0112] All conditions are the same as in Example 1, except that in step (2): only the potassium carbonate solution is immersed in the aforementioned carrier by the impregnation method (the impregnation amount is the same as in Example 1), and then azeotropic dehydration is carried out with toluene as solvent at a dehydration temperature of 100°C for 5 hours. Then the catalyst with organic solvent covering the surface is loaded into the reactor, and nitrogen is used to purge during the reaction. The catalyst is dried at 110°C for 6 hours.

[0113] Using the same evaluation method as step (4) in Example 1, the methyl acetate conversion rate was 10%, the selectivity was 78%, and the catalyst operated stably for 50 hours.

[0114] Methyl acetate conversion rate / % methyl acrylate selectivity / % Catalyst stable operation / h Example 1 23 90 350 Example 2 22 91 350 Example 3 21 88 350 Example 4 17 92 350 Example 5 19 78 150 Example 6 15 81 150 Example 7 14 68 70 Example 8 12 86 150 Comparative Example 1 10 78 50

[0115] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A catalyst for the condensation of methyl acetate and formaldehyde to prepare methyl acrylate, characterized in that, The catalyst comprises a zirconium-modified silica support and an active component; the active component includes basic active centers and acidic active centers. Based on the total mass of the catalyst, the content of the active component is 1-25 wt%; The mass content ratio of basic active centers to acidic active centers is 1-150, calculated at 100 wt%. The basic active center is provided by a potassium compound; The acidic active center is provided by a phosphorus compound and / or a boron compound; Based on the total mass of the catalyst, the potassium compound content is 1-30% by weight. The zirconium content is 0.5-10% by weight, based on the total mass of the carrier. The method for preparing the catalyst includes: S1. Zirconium-modified silica support was prepared by sol-gel method; S2. The acidic active center source is first contacted with the zirconium-modified silica support, then dried, calcined, and then contacted with the basic active center source in a solvent, followed by a second drying.

2. The catalyst according to claim 1, wherein, Based on the total mass of the catalyst, the content of the active component is 5-20 wt%; and / or The mass ratio of basic active sites to acidic active sites is 5-100 per 100 wt%; and / or The acidic active center exists in the form of boron oxide and / or phosphorus oxide; and / or The zirconium content is 1-5% by weight based on the total mass of the carrier.

3. The catalyst according to claim 2, wherein, Based on the total mass of the catalyst, the potassium compound content is 5-25% by weight; and / or The content of phosphorus oxide and / or boron oxide is 0.01-3% by weight.

4. The catalyst according to claim 3, wherein, Based on the total mass of the catalyst, the potassium compound content is 5-20% by weight; and / or The content of phosphorus oxide and / or boron oxide is 0.1-2% by weight.

5. The catalyst according to claim 1, wherein, In step S1, the sol-gel method preparation includes: mixing silicon source and zirconium precursor in solution, adjusting pH, reacting under crystallization conditions, and then filtering, washing, drying, and calcining.

6. The catalyst according to claim 5, wherein, In step S1, The adjusted pH value is 0-7; and / or The crystallization conditions include: a temperature of 10-100℃; and / or a time of 1-30h; and / or The drying conditions include: a temperature of 10-200℃; and / or a time of 1-20h; and / or The roasting conditions include: a temperature of 300-1000℃; and / or a time of 1-25h.

7. The catalyst according to claim 6, wherein, In step S1, The adjusted pH value is 1-5; and / or The crystallization conditions include: a temperature of 75-90℃; and / or a time of 5-6 h. and / or The drying conditions include a temperature of 100-110 ℃; and / or The roasting conditions include a temperature of 800-900℃.

8. The catalyst according to claim 1, wherein, In step S2, The roasting conditions include: The calcination temperature is 100-1000℃; and / or the time is 1-16h. and / or The first drying and the second drying conditions each include: Temperature: 10-200℃; and / or time: 1-20h; and / or After the second contact and before the second drying, the solid obtained from the contact is azeotropically dehydrated using at least one of toluene, xylene, and trimethylbenzene as a solvent.

9. The catalyst according to claim 8, wherein, In step S2, The roasting conditions include: The roasting temperature is 400-800℃; and / or The first drying and the second drying conditions each include: The temperature is 110-120℃; and / or The dehydration temperature is 80-110℃, and the dehydration time is 3-8 hours.

10. A method for preparing methyl acrylate by condensation of methyl acetate and formaldehyde, the method comprising: Formaldehyde source, methanol, methyl acetate and catalyst are reacted in contact; The catalyst includes the catalyst according to any one of claims 1-9.

11. The method according to claim 10, wherein, The formaldehyde source is at least one of methyl acetal, trioxymethylene, paraformaldehyde, and formaldehyde water.

12. The method according to claim 11, wherein, The formaldehyde source is paraformaldehyde.

13. The method according to claim 12, wherein, The formaldehyde source is paraformaldehyde, which is depolymerized in a depolymerization reactor to form monomeric formaldehyde.

14. The method according to claim 13, wherein, The conditions for depolymerization include: Temperatures of 80-250℃; and / or The time is 1-60 seconds.

15. The method according to claim 14, wherein, The conditions for depolymerization include: Temperature is 100-230℃; and / or The time is 2-35 seconds.

16. The method of claim 10, wherein, The conditions for the contact reaction include: The contact reaction is carried out in the presence of an inert gas; and / or The reaction raw materials include methyl acetate, formaldehyde, and methanol. The molar ratio of methyl acetate to formaldehyde source is (1-15):1 (based on formaldehyde). The methanol content is 1-40 wt% based on the total weight of the liquid raw materials. and / or The temperatures of the first and second contacts are each 280-400℃; and / or The pressures at the first and second contacts are each 0.1-0.8 MPa; and / or The liquid phase volumetric flow rate at the first contact is 0.01-0.2 mL / min; and / or The liquid phase volumetric flow rate in the second contact is 0.005-0.1 mL / min; and / or The initial contact gas space velocity Q1 is 2 min. -1 -20min -1 ; and / or The second contact gas space velocity Q2 is 5 min. -1 -25min -1 ; and / or The first contact gas space velocity Q1 is lower than the second contact gas space velocity Q2.

17. The method according to claim 16, wherein, The conditions for the contact reaction include: The contact reaction includes a first contact and a second contact; and / or the first contact and the second contact reaction are each carried out in a first reactor and a second reactor; after the reactants are fed into the first reactor for reaction, the reaction stream after the first contact is fed into the second reactor. and / or The molar ratio of methyl acetate to formaldehyde source (based on formaldehyde content) is (3-12):1, and the methanol content is 10-35 wt% based on the total weight of the liquid raw materials. and / or The initial contact gas space velocity Q1 is 4 min. -1 -6min -1 ; and / or The second contact gas space velocity Q2 is 8 min. -1 -10min -1 .

18. The method according to claim 17, wherein, The conditions for the contact reaction include: The first contact involves a molar ratio of methyl acetate to formaldehyde source (5-15):1, with a methanol content of 1-40 wt% based on the total weight of the liquid raw materials. The second contact introduces a formaldehyde source methanol solution, with a formaldehyde source content of 0.1-40 wt% based on the formaldehyde content.

19. The method according to claim 18, wherein, The conditions for the contact reaction include: In the first contact, the molar ratio of methyl acetate to formaldehyde source is (7-12):1, and the methanol content is 10-35 wt% based on the total weight of the liquid raw materials; in the second contact, the formaldehyde source content is 5-32 wt% based on formaldehyde.

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