Double-acid-site heterogeneous catalyst, tert-butyl acrylate and preparation methods of double-acid-site heterogeneous catalyst and tert-butyl acrylate

Abstract

The invention discloses a double-acid-site heterogeneous catalyst, tert-butyl acrylate and a preparation method, and belongs to the technical field of petrochemical engineering. According to the method, isobutene and acrylic acid are used as reaction raw materials, tert-butyl acrylate is generated through an acid addition esterification reaction, a powdery catalyst Cex-HPW-F is added, the prepared catalyst has double acid sites, and due to the fact that the surface of the catalyst has rich acid sites, isobutene and acrylic acid can be effectively subjected to acid catalysis to be subjected to addition esterification to generate tert-butyl acrylate, and the catalyst has the advantages of being simple in preparation process and high in yield. The catalyst is in a solid state, so that the corrosion of liquid acid to reaction equipment is reduced in the reaction process; the catalyst is always in a solid phase in the catalysis process, so that a product solution generated by reaction is easily separated from the catalyst, and the product selectivity is high.

Description

Technical Field

[0001] This invention belongs to the field of petrochemical technology and relates to a heterogeneous catalyst with two acid sites, tert-butyl acrylate, and its preparation method. Background Technology

[0002] tert-butyl acrylate (TBBacrylate) is a very important basic chemical raw material and intermediate, and is a colorless and transparent liquid at room temperature. Due to its unsaturated bonds, carboxyl groups, and unique, highly reactive polar molecules, it can self-polymerize or polymerize with other vinyl monomers to derive many copolymers and polymers with excellent properties. These copolymers exhibit good light stability, weather resistance, water resistance, oil resistance, and chemical resistance, resulting in finished products with strong adhesion, good transparency, and high film clarity. Therefore, it is increasingly widely used in coating resins, high-grade automotive repair paints, and polymer paper setting agents.

[0003] Industrially, the production of organic esters mainly involves the esterification reaction of carboxylic acids and alcohols. However, tert-butanol molecules have significant steric hindrance, making acid-alcohol esterification difficult and resulting in low esterification yields. Therefore, in recent years, the technology of directly adding carboxylic acids to olefins to synthesize carboxylic esters has attracted widespread attention. Given the market demand for tert-butyl acrylate (TBMA), and the fact that isobutylene is an important substrate for its synthesis, as well as the existing technological limitations and bottlenecks in isobutylene synthesis, developing a method to produce high-purity isobutylene is of great significance.

[0004] In the process of acid-olefin addition reactions, reactions such as the oligomerization of olefins, the polymerization of acrylic acid or esters, and the decomposition of tert-butyl acrylate under reaction heat or trace amounts of strong acid all involve liquid acid catalysts. These liquid acid catalysts are prone to corroding equipment during use and are difficult to reuse. Therefore, it is of great significance to develop a new route for the synthesis of tert-butyl acrylate using a novel solid acid catalyst. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a heterogeneous catalyst with two acid sites, tert-butyl acrylate, and a preparation method thereof, in order to solve the problems that the existing acid-catalyzed esterification reaction of alcohols and esters is prone to equilibrium, resulting in low conversion rate, and that liquid acid catalysts are prone to corrosion of equipment during use.

[0006] To achieve the above objectives, the present invention employs the following technical solution: A heterogeneous catalyst with two acid sites, wherein the heterogeneous catalyst with two acid sites is Ce x -HPW-F is a solid; where HPW is phosphotungstic acid and F is fluorine; x is the molar ratio of Ce to phosphotungstic acid, 0 < x < 6.

[0007] A further improvement of the present invention is that: Preferably, x is 6, 3, 1 or 1 / 3.

[0008] A method for preparing a heterogeneous catalyst with two acid sites includes the following steps: S1, mix phosphotungstic acid and ethanol to obtain a phosphotungstic acid-ethanol solution, mix cerium nitrate hexahydrate and ethanol to obtain a cerium nitrate-ethanol solution; mix and stir the phosphotungstic acid-ethanol solution and the cerium nitrate-ethanol solution, add excess HF solution to obtain a mixed solution; the amounts of phosphotungstic acid and cerium nitrate hexahydrate are determined according to the molar ratio of the final product Ce to tungsten phosphate. S2, the mixed solution is obtained by rotary evaporation in a water bath and vacuum drying to obtain powder; S3, after calcining the powder, Ce is obtained. x -HPW-F; where HPW is phosphotungstic acid, F is fluorine, and x is the molar ratio of Ce to phosphotungstic acid, 0 < x < 6.

[0009] Preferably, in S3, the calcination temperature is 100-300℃ and the calcination time is 2-4h.

[0010] A method for preparing tert-butyl acrylate, comprising an addition esterification reaction of isobutylene and acrylic acid in the presence of a solid catalyst to obtain tert-butyl acrylate; wherein the solid catalyst is the dual-acid site heterogeneous catalyst Ce as described in claim 1. x -HPW-F.

[0011] Preferably, the molar ratio of acrylic acid to isobutylene is 0.6-0.9.

[0012] Preferably, the addition esterification reaction temperature is 22-55℃ and the reaction time is 3-5h.

[0013] Preferably, the amount of catalyst added is 3%-5% of the total mass of isobutylene and acrylic acid.

[0014] Preferably, the specific steps are as follows: after stirring acrylic acid, polymerization inhibitor and catalyst evenly, freeze, mix the frozen product and isobutylene, heat and stir to react, and generate tert-butyl acrylate; The polymerization inhibitor is a mixture of two different types of polymerization inhibitors: Inhibitor 1 is tert-butanol, bisphenol A, 4-chlorobenzoquinone, or benzidine; Inhibitor 2 is hydroquinone, bisphenol A, 4-chlorobenzoquinone, or benzidine.

[0015] A tert-butyl acrylate synthesized by any one of the above methods.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention discloses a heterogeneous catalyst Ce with two acid sites. x-HPW-F, this catalyst is in solid form; when used in the esterification reaction of isobutylene and acrylic acid, the catalyst remains in a solid phase throughout, making it easy to separate the product solution from the catalyst and allowing for multiple recycling of the catalyst. Catalyst Ce x -HPW-F introduces Ce in different molar ratios into phosphotungstic acid. 3+ and the corresponding F - Prepared Ce x -HPW-F is a dual-acid (B and L acid) solid acid catalyst with a predominantly L acid site. Due to the abundant acidic sites on its surface, it can effectively catalyze the addition esterification of isobutylene with acrylic acid to produce tert-butyl acrylate. Using the catalyst of this invention, the addition esterification of isobutylene with acrylic acid is catalyzed to prepare tert-butyl acrylate. The resulting product exhibits high selectivity, the reaction process is simple and easy to operate, and it has excellent application prospects.

[0017] This invention also discloses a method for the synthesis of tert-butyl acrylate catalyzed by a heterogeneous catalyst with two acid sites, wherein the method involves adding a solid catalyst Ce x -HPW-F, with the addition of isobutylene and acrylic acid, reduces acid corrosion of the reaction equipment during the reaction process; at the same time, because the process involved in this method is simple and the products of each step are easy to separate, the selectivity of tert-butyl acrylate can reach 99%; during the catalytic process, the amount of catalyst used accounts for 3%-5% of the total mass of isobutylene and acrylic acid, which reduces corrosion of process pipelines and equipment while achieving low-cost and high-selectivity preparation of tert-butyl acrylate. Attached Figure Description

[0018] Figure 1 A schematic diagram of the synthetic route for the catalytic conversion of acrylic acid to tert-butyl acrylate provided by the present invention; Figure 2 The structure of the catalyst of this invention is shown in: (a) XRD pattern; (b) FT-IR pattern; Figure 3 The nitrogen adsorption-desorption isotherm of the Ce3 / 1-HPW-F catalyst prepared in this invention; Figure 4 The NH3-TPD curve of the Ce3 / 1-HPW-F catalyst prepared in this invention is shown. Detailed Implementation

[0019] The present invention will now be described in further detail with reference to the accompanying drawings: To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0020] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0021] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0022] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0023] As described in the background section, most existing technologies use homogeneous liquid catalysts to esterify acrylic acid with isobutylene to produce tert-butyl acrylate, or use homogeneous liquid acid catalysts to esterify acrylic acid with tert-butanol to produce tert-butyl acrylate. However, this process often involves strongly acidic homogeneous catalysts, which can easily corrode pipelines and equipment. Furthermore, this homogeneous reaction system makes subsequent product separation and catalyst separation difficult, resulting in significant equipment wear and high costs.

[0024] To address the aforementioned problems, the first aspect of this invention discloses a heterogeneous catalyst with two acid sites, wherein the heterogeneous catalyst with two acid sites is Ce. x -HPW-F is a solid; where HPW is phosphotungstic acid and F is fluorine; x is the molar ratio of Ce to phosphotungstic acid, 0 < x < 6.

[0025] Ce x-HPW-F is a dual-acid (B and L acid) solid acid catalyst with L acid sites as the main component. Due to the abundance of acidic sites on its surface, it can effectively catalyze the addition esterification of isobutylene with acrylic acid to produce tert-butyl acrylate.

[0026] To further improve the performance of the catalyst, Ce was introduced into phosphotungstic acid at different molar ratios. 3+ and the corresponding F - Prepared Ce x In the preferred scheme of -HPW-F, x = 6 / 1; 3 / 1; 1 / 1 or 1 / 3.

[0027] A second aspect of the present invention discloses a preparation process for a Cex-HPW-F catalyst, comprising the following steps: (1) Phosphotungstic acid H3PW 12 O 40 Dissolve it in ethanol and slowly add it dropwise to an ethanol solution containing Ce(NO3)3·6H2O, stirring at room temperature for 1 h. Then, add excess HF (0.2 mol / L) dropwise to the mixture and let it stand for 12 h; the molar ratio of phosphotungstic acid and cerium nitrate hexahydrate is x, 0 < x < 1.

[0028] (2) After rotary evaporation and drying in a water bath at 60 °C, a white solid was obtained. The solid was then vacuum dried at 60 °C overnight. Subsequently, the prepared product was ground to obtain a white powder. (3) Ce is obtained by calcining the above white powder at 100-300 ℃ for 2-4 h. X -HPW-F catalyst.

[0029] To obtain a Cex-HPW-F catalyst with better performance, in a typical embodiment, its synthesis is carried out by the following steps: (1) 1.92 g of phosphotungstic acid H3PW 12 O 40 Dissolved in 20 mL of ethanol, it was slowly added dropwise to 10 mL of ethanol solution containing 0.868 g Ce(NO3)3·6H2O, and stirred at room temperature for 1 h. Then, excess HF (0.2 mol / L) was added dropwise to the mixture and allowed to stand for 12 h; (2) After rotary evaporation and drying in a water bath at 60 ℃, a white solid was obtained, which was then vacuum dried overnight at 60 ℃. Subsequently, the prepared product was ground; (3) The above white powder was calcined at 200 ℃ for 3 h to obtain Ce 3 / 1 -HPW-F catalyst. The catalyst used in this invention is prepared through simple static settling and calcination. The preparation method is simple, the conditions are mild, and the cost is low. It exhibits high selectivity when used in the synthesis of tert-butyl acrylate.

[0030] A third aspect of the present invention discloses a method for preparing tert-butyl acrylate, such as... Figure 1 As shown, the process includes the following steps: using isobutylene and acrylic acid as raw materials, tert-butyl acrylate is prepared by catalytic addition esterification with a catalyst.

[0031] Acrylic acid is a polymerizable unsaturated acid and a key substance in the synthesis of tert-butyl acrylate. Its molecular formula is CH2CHCOOH. The unsaturated carbon-carbon double bond structure in its structure can be transformed into a single bond through monomer polymerization to generate polyacrylic acid. The hydroxyl functional group in the molecular structure can react with different kinds of compounds to generate compounds containing C=O double bonds, such as esters, acid anhydrides, and amides.

[0032] Isobutylene, also known as 2-methylpropene, is an olefin with the molecular formula C4H8 and has important industrial applications. It is one of the four isomers of butene and is a colorless, odorless, flammable, and easily liquefied gas at room temperature, typically stored as a pressurized liquefied gas in gas cylinders. Isobutylene is a key substance in the synthesis of tert-butyl acrylate. Common methods for synthesizing isobutylene include C4 fractionation, ion exchange, methyl tert-butyl ether method, and isobutane dehydrogenation method.

[0033] The method for preparing tert-butyl acrylate by the addition esterification of acrylic acid catalyzed by a heterogeneous catalyst with two acid sites provided by this invention utilizes a solid heterogeneous catalyst with two acid sites, Ce. x -HPW-F technology enables the low-cost, highly selective preparation of tert-butyl acrylate while reducing corrosion in process pipelines and equipment. The entire preparation process is simple, and the products of each step are easily separated. Specifically, isobutylene and acrylic acid undergo addition esterification catalyzed by a catalyst to prepare tert-butyl acrylate, with a selectivity of up to 99%.

[0034] The specific preparation process is as follows: The specific steps are: after stirring acrylic acid, polymerization inhibitor one, polymerization inhibitor two and catalyst evenly, freeze overnight, take it out and add isobutylene, heat and stir to react, and tert-butyl acrylate is generated.

[0035] Furthermore, the polymerization inhibitor can be tert-butanol, bisphenol A, 4-chlorobenzoquinone, or benzidine.

[0036] Furthermore, the polymerization inhibitor can be hydroquinone, bisphenol A, 4-chlorobenzoquinone, or benzidine.

[0037] Furthermore, in the reaction of acrylic acid addition esterification to synthesize tert-butyl acrylate, the molar ratio of acrylic acid to isobutylene is 0.6-0.9; for example, the molar ratio of acrylic acid to isobutylene can be 0.6, 0.7, 0.8 and 0.9.

[0038] Furthermore, during the catalytic process, the amount of catalyst used accounts for 3%-5% of the total mass of isobutylene and acrylic acid.

[0039] Furthermore, the reaction temperature is 25-55℃, preferably 35-45℃, and the reaction time is 3-5h, preferably 4h.

[0040] In several typical implementations, the conversion rate of acrylic acid is >99%, the selectivity of tert-butyl acrylate is >99%, and almost no polymerization byproducts are generated, thus achieving high conversion rate and high selectivity of tert-butyl acrylate.

[0041] A fourth aspect of the present invention discloses a tert-butyl acrylate synthesized by the above preparation method.

[0042] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0043] Comparative Example 1 4.0g acrylic acid, 0.2g tert-butanol, 0.2g hydroquinone and 0.3g catalyst Ce 3 / 1 HPW (the specific synthesis method is described in Example 1) was added to the reactor, stirred evenly, and then frozen overnight. After that, it was taken out, 3.7 g of isobutylene was added, the temperature was raised to 45°C, and the reaction was carried out for 4 h with a stirring rate of 800 rpm to synthesize tert-butyl acrylate by addition esterification.

[0044] Comparative Example 2 Preparation of heterogeneous solid acid catalyst Ce-F: 0.868 g of cerium nitrate was added dropwise to 10 ml of ethanol solution and stirred for one hour. Then, 35 ml of 0.2 mol / L HF aqueous solution was slowly added dropwise while stirring. The mixture was then allowed to stand for 12 hours. The solvent was removed by rotating the solution in a water bath at 60 °C. The solution was then dried under vacuum at 60 °C overnight to obtain a white powder. The white powder was calcined in a tube furnace under an Ar atmosphere at 200 °C to obtain the Ce-F catalyst.

[0045] 4.0g acrylic acid, 0.2g tert-butanol, 0.2g hydroquinone and 0.3g catalyst Ce-F were added to the reactor, stirred evenly, and then frozen overnight. After that, 3.7g isobutylene was added, the temperature was raised to 45℃, and the reaction was carried out at a stirring rate of 800rpm for 4h to synthesize tert-butyl acrylate by addition esterification.

[0046] Comparative Example 3 Preparation of heterogeneous solid acid catalyst HPW-F: 1.92 g of phosphotungstic acid was dissolved in 20 ml of ethanol and stirred for one hour. Then, 35 ml of 0.2 mol / L HF aqueous solution was slowly added dropwise while stirring. The mixture was then allowed to stand for 12 h. The solvent was removed by rotating the solution in a water bath at 60 °C. The solution was then dried under vacuum at 60 °C overnight to obtain a white powder. The white powder was calcined in a tube furnace under an Ar atmosphere at 200 °C to obtain the HPW-F catalyst.

[0047] Example 1 A method for synthesizing tert-butyl acrylate by addition esterification of acrylic acid catalyzed by a heterogeneous solid acid catalyst with two acid sites: Preparation of the heterogeneous solid acid catalyst Cex-HPW-F with two acid sites: 1.92 g of phosphotungstic acid was dissolved in 20 ml of ethanol, and then slowly added dropwise to 10 ml of ethanol solution containing 0.868 g of cerium nitrate while stirring. The mixture was stirred for one hour, followed by slow dropwise addition of 35 ml of 0.2 mol / L HF aqueous solution while stirring. The mixture was then allowed to stand for 12 hours. The solvent was removed by rotary evaporation in a 60 °C water bath, and the solution was dried under vacuum at 60 °C overnight to obtain a white powder. The white powder was then calcined in a tube furnace under an Ar atmosphere at 200 °C to obtain Ce. 3 / 1 -HPW-F catalyst.

[0048] Addition esterification reaction process: 4.0g acrylic acid, 0.2g tert-butanol, 0.2g hydroquinone and 0.3g catalyst Ce 3 / 1 HPW-F was added to the reactor, stirred evenly, and then frozen overnight. After that, it was taken out and 3.7g of isobutylene was added (the molar ratio of acrylic acid to isobutylene was 0.84:1). The temperature was raised to 45℃, and the reaction was carried out at a stirring rate of 800rpm for 4h to synthesize tert-butyl acrylate by addition esterification.

[0049] Example 2 4.0g acrylic acid, 0.2g tert-butanol, 0.2g hydroquinone and 0.3g catalyst Ce 1 / 1 HPW-F (the specific synthesis method is described in Example 1) was added to the reactor, stirred evenly, and then frozen overnight. After that, it was taken out, 3.7 g of isobutylene was added, the temperature was raised to 45°C, and the reaction was carried out for 4 h with a stirring rate of 800 rpm to synthesize tert-butyl acrylate by addition esterification.

[0050] Example 3 4.0g acrylic acid, 0.2g tert-butanol, 0.2g hydroquinone and 0.3g catalyst Ce 1 / 3HPW-F (the specific synthesis method is described in Example 1) was added to the reactor, stirred evenly, and then frozen overnight. After that, it was taken out, 3.7 g of isobutylene was added, the temperature was raised to 45°C, and the reaction was carried out for 4 h with a stirring rate of 800 rpm to synthesize tert-butyl acrylate by addition esterification.

[0051] Example 4 4.0g acrylic acid, 0.2g tert-butanol, 0.2g hydroquinone and 0.3g catalyst Ce 6 / 1 HPW-F (the specific synthesis method is described in Example 1) was added to the reactor, stirred evenly, and then frozen overnight. After that, it was taken out, 3.7 g of isobutylene was added, the temperature was raised to 45°C, and the reaction was carried out for 4 h with a stirring rate of 800 rpm to synthesize tert-butyl acrylate by addition esterification.

[0052] 4.0g acrylic acid, 0.2g tert-butanol, 0.2g hydroquinone and 0.3g catalyst HPW-F were added to the reactor, stirred evenly, and then frozen overnight. After that, 3.7g isobutylene was added, the temperature was raised to 45℃, and the reaction was carried out at a stirring rate of 800rpm for 4h to synthesize tert-butyl acrylate by addition esterification.

[0053] Example 5 4.0g acrylic acid, 0.2g tert-butanol, 0.2g hydroquinone and 0.3g catalyst Ce 3 / 1 HPW-F was added to the reactor, stirred evenly, and then frozen overnight. After that, it was taken out, 3.7g of isobutylene was added, the temperature was raised to 35℃, and the reaction was carried out for 4 hours with a stirring rate of 800rpm to synthesize tert-butyl acrylate by addition esterification.

[0054] Example 6 4.0g acrylic acid, 0.2g tert-butanol, 0.2g hydroquinone and 0.3g catalyst Ce 3 / 1 HPW-F was added to the reactor, stirred evenly, and then frozen overnight. After that, it was taken out, 3.7g of isobutylene was added, the temperature was raised to 55℃, and the reaction was carried out for 4 hours with a stirring rate of 800rpm to synthesize tert-butyl acrylate by addition esterification.

[0055] Example 7 4.0g acrylic acid, 0.2g tert-butanol, 0.2g hydroquinone and 0.1g catalyst Ce 3 / 1 HPW-F was added to the reactor, stirred evenly, and then frozen overnight. After that, it was taken out, 3.7g of isobutylene was added, the temperature was raised to 45℃, and the reaction was carried out for 4 hours with a stirring rate of 800rpm to synthesize tert-butyl acrylate by addition esterification.

[0056] Example 8 4.0g acrylic acid, 0.2g tert-butanol, 0.2g hydroquinone and 0.2g catalyst Ce 3 / 1 HPW-F was added to the reactor, stirred evenly, and then frozen overnight. After that, it was taken out, 3.7g of isobutylene was added, the temperature was raised to 45℃, and the reaction was carried out for 4 hours with a stirring rate of 800rpm to synthesize tert-butyl acrylate by addition esterification.

[0057] Example 9 4.0g acrylic acid, 0.2g tert-butanol, 0.2g hydroquinone, and 0.05g catalyst Ce were added. 3 / 1 HPW-F was added to the reactor, stirred evenly, and then frozen overnight. After that, it was taken out, 3.7g of isobutylene was added, the temperature was raised to 45℃, and the reaction was carried out for 4 hours with a stirring rate of 800rpm to synthesize tert-butyl acrylate by addition esterification.

[0058] Example 10 4.0g acrylic acid, 0.2g tert-butanol, 0.2g bisphenol A and 0.3g catalyst Ce were added. 3 / 1 HPW-F was added to the reactor, stirred evenly, and then frozen overnight. After that, it was taken out, 3.7g of isobutylene was added, the temperature was raised to 45℃, and the reaction was carried out for 4 hours with a stirring rate of 800rpm to synthesize tert-butyl acrylate by addition esterification.

[0059] Example 11 4.0 g acrylic acid, 0.2 g tert-butanol, 0.2 g 4-chlorobenzoquinone and 0.3 g catalyst Ce were added. 3 / 1 HPW-F was added to the reactor, stirred evenly, and then frozen overnight. After that, it was taken out, 3.7g of isobutylene was added, the temperature was raised to 45℃, and the reaction was carried out for 4 hours with a stirring rate of 800rpm to synthesize tert-butyl acrylate by addition esterification.

[0060] Example 12 4.0g acrylic acid, 0.2g 4-chlorobenzoquinone, 0.2g hydroquinone and 0.3g catalyst Ce were added. 3 / 1 HPW-F was added to the reactor, stirred evenly, and then frozen overnight. After that, it was taken out, 3.7g of isobutylene was added, the temperature was raised to 45℃, and the reaction was carried out for 4 hours with a stirring rate of 800rpm to synthesize tert-butyl acrylate by addition esterification.

[0061] Example 13 4.0g acrylic acid, 0.2g tert-butanol, 0.2g hydroquinone, and 0.3g catalyst Ce were added. 3 / 1HPW-F was added to the reactor, stirred evenly, and then frozen overnight. After that, it was taken out and 3.0 g of isobutylene was added (the molar ratio of acrylic acid to isobutylene was 1.04:1). The temperature was raised to 45°C, and the reaction was carried out at a stirring rate of 800 rpm for 4 h to synthesize tert-butyl acrylate by addition esterification.

[0062] Example 14 4.0g acrylic acid, 0.2g tert-butanol, 0.2g hydroquinone, and 0.3g catalyst Ce were added. 3 / 1 HPW-F was added to the reactor, stirred evenly, and then frozen overnight. After that, it was taken out and 4.0 g of isobutylene was added (the molar ratio of acrylic acid to isobutylene was 0.78:1). The temperature was raised to 45°C, and the reaction was carried out at a stirring rate of 800 rpm for 4 h to synthesize tert-butyl acrylate by addition esterification.

[0063] Example 15 A method for synthesizing tert-butyl acrylate by addition esterification of acrylic acid catalyzed by a heterogeneous solid acid catalyst with two acid sites: Preparation of the heterogeneous solid acid catalyst Cex-HPW-F with two acid sites: 1.92 g of phosphotungstic acid was dissolved in 20 ml of ethanol, and then slowly added dropwise to 10 ml of ethanol solution containing 0.868 g of cerium nitrate while stirring. The mixture was stirred for one hour, followed by slow dropwise addition of 35 ml of 0.2 mol / L HF aqueous solution while stirring. The mixture was then allowed to stand for 12 hours. The solvent was removed by rotary evaporation in a 60 °C water bath, and the solution was then vacuum dried overnight at 60 °C to obtain a white powder. The white powder was calcined in a tube furnace under Ar atmosphere at 100 °C for 2 hours to obtain Ce. 3 / 1 -HPW-F catalyst.

[0064] Addition esterification reaction process: 4.0g acrylic acid, 0.2g tert-butanol, 0.2g hydroquinone and 0.3g catalyst Ce 3 / 1 HPW-F was added to the reactor, stirred evenly, and then frozen overnight. After that, it was taken out, 3.7g of isobutylene was added, the temperature was raised to 45℃, and the reaction was carried out for 4 hours with a stirring rate of 800rpm to synthesize tert-butyl acrylate by addition esterification.

[0065] Example 16 A method for synthesizing tert-butyl acrylate by addition esterification of acrylic acid catalyzed by a heterogeneous solid acid catalyst with two acid sites: Preparation of the heterogeneous solid acid catalyst Cex-HPW-F with two acid sites: 1.92 g of phosphotungstic acid was dissolved in 20 ml of ethanol, and then slowly added dropwise to 10 ml of ethanol solution containing 0.868 g of cerium nitrate while stirring. The mixture was stirred for one hour, followed by the slow addition of 35 ml of 0.2 mol / L HF aqueous solution while stirring. The mixture was then allowed to stand for 12 hours. The solvent was removed by rotary evaporation in a 60 °C water bath, and the solution was dried under vacuum at 60 °C overnight to obtain a white powder. The white powder was then calcined in a tube furnace under an Ar atmosphere at 300 °C for 4 hours to obtain Ce. 3 / 1 -HPW-F catalyst.

[0066] Addition esterification reaction process: 4.0g acrylic acid, 0.2g tert-butanol, 0.2g hydroquinone and 0.3g catalyst Ce 3 / 1 HPW-F was added to the reactor, stirred evenly, and then frozen overnight. After that, it was taken out, 3.7g of isobutylene was added, the temperature was raised to 45℃, and the reaction was carried out for 4 hours with a stirring rate of 800rpm to synthesize tert-butyl acrylate by addition esterification.

[0067] Example 17 4.0g acrylic acid, 0.2g tert-butanol, 0.2g hydroquinone and 0.3g catalyst Ce 3 / 1 HPW-F was added to the reactor, stirred evenly, and then frozen overnight. After that, it was taken out, 3.7g of isobutylene was added, the temperature was raised to 25℃, and the reaction was carried out for 5h with a stirring rate of 800rpm to synthesize tert-butyl acrylate by addition esterification.

[0068] Example 18 4.0g acrylic acid, 0.2g tert-butanol, 0.231g hydroquinone, and 0.3g catalyst Ce were added. 3 / 1 HPW-F was added to the reactor, stirred evenly, and then frozen overnight. After that, it was taken out, 3.7g of isobutylene was added, the temperature was raised to 45℃, and the reaction was carried out for 4 hours with a stirring rate of 800rpm to synthesize tert-butyl acrylate by addition esterification.

[0069] Example 19 4.0g acrylic acid, 0.2g tert-butanol, 0.2g hydroquinone and 0.385g catalyst Ce 3 / 1 HPW-F was added to the reactor, stirred evenly, and then frozen overnight. After that, it was taken out, 3.7g of isobutylene was added, the temperature was raised to 45℃, and the reaction was carried out for 4 hours with a stirring rate of 800rpm to synthesize tert-butyl acrylate by addition esterification.

[0070] Example 20 2.9g acrylic acid, 0.2g tert-butanol, 0.2g hydroquinone and 0.385g catalyst Ce3 / 1 HPW-F was added to the reactor, stirred evenly, and then frozen overnight. After that, it was taken out, 3.7g of isobutylene was added, the temperature was raised to 45℃, and the reaction was carried out for 4 hours with a stirring rate of 800rpm to synthesize tert-butyl acrylate by addition esterification.

[0071] Example 21 3.3g acrylic acid, 0.2g tert-butanol, 0.2g hydroquinone, and 0.385g catalyst Ce were added. 3 / 1 HPW-F was added to the reactor, stirred evenly, and then frozen overnight. After that, it was taken out, 3.7g of isobutylene was added, the temperature was raised to 45℃, and the reaction was carried out for 4 hours with a stirring rate of 800rpm to synthesize tert-butyl acrylate by addition esterification.

[0072] Example 22 3.8g acrylic acid, 0.2g tert-butanol, 0.2g hydroquinone, and 0.385g catalyst Ce were added. 3 / 1 HPW-F was added to the reactor, stirred evenly, and then frozen overnight. After that, it was taken out, 3.7g of isobutylene was added, the temperature was raised to 45℃, and the reaction was carried out for 4 hours with a stirring rate of 800rpm to synthesize tert-butyl acrylate by addition esterification.

[0073] Example 23 4.3g acrylic acid, 0.2g tert-butanol, 0.2g hydroquinone, and 0.385g catalyst Ce were added. 3 / 1 HPW-F was added to the reactor, stirred evenly, and then frozen overnight. After that, it was taken out, 3.7g of isobutylene was added, the temperature was raised to 45℃, and the reaction was carried out for 4 hours with a stirring rate of 800rpm to synthesize tert-butyl acrylate by addition esterification.

[0074] The reaction results in the above embodiments were analyzed using gas chromatography. The conversion rate of acrylic acid = the amount of acrylic acid reacted / the total amount of acrylic acid input, and the selectivity of tert-butyl acrylate = the amount of tert-butyl acrylate / the amount of acrylic acid reacted. The reaction results of some embodiments of the present invention are detailed in Table 1.

[0075] Table 1 Result Analysis Table of Example

[0076] As can be seen from the above, as the ratio of x increases from 0 to 6, the conversion rate of acrylic acid gradually increases and then decreases, with the best conversion rate observed when the ratio of x is 3. 3 / 1 The HPW-F catalyst exhibits optimal catalytic performance, enabling highly selective catalytic synthesis of tert-butyl acrylate.

[0077] like Figure 2As shown in Figure (a), Ce 1 / 3 -HPW-F, Ce 3 / 1 -HPW-F and Ce 1 / 1 -HPW-F exhibits similar diffraction peaks to HPW-F, displaying sharp characteristic diffraction peaks at 2θ of 10.3°, 20.7°, 23.1° and 25.3° and 29.4° and 34.6°, respectively, corresponding to the (110), (220), (310), (222) and (400) and (332) crystal plane diffraction peaks of HPW. With the addition of Ce to HPW... 3+ With increasing addition, the intensity of the characteristic diffraction peak of the Keggin structure of HPW decreased slightly, and a new characteristic diffraction peak appeared at 27.8°. The characteristic peaks of the Ce-HPW-F catalyst showed a shift towards lower 2θ values, which is due to the interaction between the protons and Ce in the HPW structure. 3+ Exchange leads to cell shrinkage.

[0078] Depend on Figure 2 As shown in Figure (b), the spectral characteristics of the Keggin anion can be clearly seen in the infrared spectrum of the Ce-HPW-F catalyst. (1080 cm⁻¹) -1 The peaks at 983, 891, and 799 cm⁻¹ are attributed to PO bonds. -1 The peaks are attributed to WO d WO C -W and WO d -W vibration absorption

[13] Weaker absorption occurs at approximately 589 cm⁻¹. -1 and 501 cm -1 The positions at these locations are due to the symmetric vibrations of OPO and WOW, respectively. All these Keggin characteristic bands appear in the spectra of all catalysts, and their positions remain unchanged relative to the HPW spectrum. This indicates that the introduction of F⁻ and the depletion of protons by Ce... 3+ When ionized, the structure of the Keggin anion in HPW remains unchanged.

[0079] like Figure 3 As shown, the adsorption curves of the catalyst samples exhibit type IV adsorption isotherms based on the IUPAC classification, and a distinct H3-type hysteresis loop appears in the relative pressure range of P / P0 = 0.45 to 0.9. In the high-pressure region, capillary condensation of the adsorbate occurs, causing the isotherm to rise rapidly. This type of adsorption isotherm confirms that the material possesses mesoporous structural characteristics. Furthermore, a hysteresis loop appears at high relative pressures (P / P0 = 0.9-1.0), possibly due to macropores formed by catalyst particle accumulation. Additionally, calculations using the BJH model show that Ce... 3 / 1The average pore size of the -HPW-F catalyst is in the range of 5 to 50 nm, and the sharp peaks in the pore size distribution curve indicate that its pore size is relatively uniformly distributed in the mesoporous range.

[0080] NH3-TPD curve as shown Figure 4 As shown, Ce 3 / 1 The -HPW-F sample exhibits two large desorption peaks at 195.0 ℃ and 593.4 ℃, which are attributed to the chemisorption of NH3 at weak and strong acid sites, respectively. A sharp desorption characteristic peak appears at 593.4 ℃, indicating that Ce... 3 / 1 -HPW-F is a strong acidic solid acid. A broad desorption peak exists at 195.0 °C, indicating that it is present in Ce... 3 / 1 -HPW-F also contains weak acid sites and moderate acid sites, indicating that for HPW, Ce 3+ The introduction of F⁻ can alter the distribution of its acidic sites.

[0081] This invention discloses a method for the synthesis of tert-butyl acrylate using a heterogeneous catalyst with two acid sites. The method uses isobutylene and acrylic acid as reactants, and generates tert-butyl acrylate through an acid addition esterification reaction, by adding a powdered catalyst Ce. x The catalyst prepared by -HPW-F has two acid sites. Due to the abundance of acidic sites on its surface, it can effectively catalyze the addition esterification of isobutylene and acrylic acid to produce tert-butyl acrylate. Furthermore, because the catalyst is solid, it reduces the corrosion of the reaction equipment by liquid acid during the reaction. The catalyst remains in the solid phase throughout the catalytic process, making it easy to separate the product solution from the catalyst, resulting in high product selectivity and few by-products.

[0082] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A heterogeneous catalyst with two acid sites, characterized in that, The heterogeneous catalyst with dual acid sites is Ce. x -HPW-F is a solid; where HPW is phosphotungstic acid and F is fluorine; x is the molar ratio of Ce to phosphotungstic acid, 0 < x < 6.

2. The heterogeneous catalyst with two acid sites according to claim 1, characterized in that, x is 6, 3, 1 or 1 / 3.

3. A method for preparing a heterogeneous catalyst with two acid sites, characterized in that, Includes the following steps: S1, mix phosphotungstic acid and ethanol to obtain a phosphotungstic acid-ethanol solution, and mix cerium nitrate hexahydrate and ethanol to obtain a cerium nitrate-ethanol solution; The phosphotungstic acid-ethanol solution and the cerium nitrate-ethanol solution were mixed and stirred, and an excess of HF solution was added to obtain a mixed solution; the amounts of phosphotungstic acid and cerium nitrate hexahydrate were determined according to the molar ratio of the final product Ce to tungsten phosphate. S2, the mixed solution is obtained by rotary evaporation in a water bath and vacuum drying to obtain powder; S3, after calcining the powder, Ce is obtained. x -HPW-F; where HPW is phosphotungstic acid, F is fluorine, and x is the molar ratio of Ce to phosphotungstic acid, 0 < x < 6.

4. The method for preparing a heterogeneous catalyst with two acid sites according to claim 3, characterized in that, In S3, the calcination temperature is 100-300℃ and the calcination time is 2-4h.

5. A method for preparing tert-butyl acrylate, characterized in that, Isobutylene and acrylic acid undergo an addition esterification reaction in the presence of a solid catalyst to produce tert-butyl acrylate; the solid catalyst is the dual-acid heterogeneous catalyst Ce as described in claim 1. x -HPW-F.

6. The method for preparing tert-butyl acrylate according to claim 5, characterized in that, The molar ratio of acrylic acid to isobutylene is 0.6-0.

9.

7. The method for preparing tert-butyl acrylate according to claim 1, characterized in that, The addition esterification reaction temperature is 22-55℃, and the reaction time is 3-5h.

8. The method for preparing tert-butyl acrylate according to claim 1, characterized in that, The amount of catalyst added is 3%-5% of the total mass of isobutylene and acrylic acid.

9. The method for preparing tert-butyl acrylate according to claim 1, characterized in that, The specific steps are as follows: after stirring acrylic acid, polymerization inhibitor and catalyst evenly, freeze, mix the frozen product and isobutylene, heat and stir to react, and then generate tert-butyl acrylate; The polymerization inhibitor is a mixture of two different types of polymerization inhibitors: Inhibitor 1 is tert-butanol, bisphenol A, 4-chlorobenzoquinone, or benzidine; Inhibitor 2 is hydroquinone, bisphenol A, 4-chlorobenzoquinone, or benzidine.

10. A tert-butyl acrylate synthesized by any one of claims 5-9.

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