阅读说明：本技术 一种复合型固体酸催化剂及其制备方法与应用 (Composite solid acid catalyst and preparation method and application thereof ) 是由 李三保 韩宇卓 聂俊 朱晓群 于 2021-10-11 设计创作，主要内容包括：本发明的目的在于提供一种复合型固体酸催化剂及其制备方法与应用,所述复合型固体酸催化剂具有尖晶石型结构；所述复合型固体酸催化剂的结构式为SO-(4)～(2-)-AB-(2)O-(4)-M-TiO-(2)；其中,A为二价金属阳离子,B为三价金属阳离子,M为Zr～(4+)、Sn～(4+)、Cu～(2+)中的任意一种。本发明提供的复合型固体酸催化剂,用于酯化反应时,催化活性高,稳定性好；并且,在使用过程中,活性组分不易于流失,催化剂易于与产物进行分离；该复合型固体酸催化剂重复使用多次后,反应物仍有较高的转化率。(The invention aims to provide a composite solid acid catalyst, a preparation method and application thereof, wherein the composite solid acid catalyst has a spinel structure; the structural formula of the compound solid acid catalyst is SO 4 2‑ ‑AB 2 O 4 ‑M‑TiO 2 (ii) a Wherein A is a divalent metal cation, B is a trivalent metal cation, and M is Zr 4+ 、Sn 4+ 、Cu 2+ Any one of them. The composite solid acid catalyst provided by the invention is used for esterification reaction, and has high catalytic activity and good stability; in addition, in the using process, the active components are not easy to lose, and the catalyst is easy to separate from the product; the composite type fastenerAfter the body acid catalyst is repeatedly used for many times, reactants still have higher conversion rate.)

1. A composite solid acid catalyst is characterized by having a spinel structure; the structural formula of the compound solid acid catalyst is SO₄ ^2--AB₂O₄-M-TiO₂(ii) a Wherein A is a divalent metal cation, B is a trivalent metal cation, and M is Zr⁴⁺、Sn⁴⁺、Cu²⁺Any one of them.

2. Such as rightThe composite solid acid catalyst according to claim 1, wherein A is Zn²⁺B is Fe³⁺。

3. A method for preparing the composite solid acid catalyst according to claim 1 or 2, comprising the steps of:

s1: dissolving metal salt containing A, metal salt containing B and metal salt containing M in water to obtain a mixed solution; wherein A is a divalent metal cation, B is a trivalent metal cation, and M is Zr⁴⁺、Sn⁴⁺、Cu²⁺Any one of the above;

s2: preparing an alkaline solution;

s3: dropwise adding the alkaline solution into the mixed solution until the pH value of the system is 9.5, stirring in a water bath at 75-85 ℃, aging, and filtering to obtain a precipitate;

s4: drying and grinding the precipitate in sequence to obtain powder;

s5: calcining the powder at 800-900 ℃ to obtain AB₂O₄-an M precursor;

s6: the AB is₂O₄Adding the precursor M into an organic titanium salt hydrolysis solution, and stirring in a water bath at 70-80 ℃ to form gel; drying the gel at 90-100 ℃, and grinding to obtain AB₂O₄-M-TiO₂；

S7: the AB is₂O₄-M-TiO₂And (3) placing the catalyst in an ammonium sulfate solution for soaking, and then drying, grinding and calcining the catalyst in sequence to obtain the composite solid acid catalyst.

4. The method for producing a composite solid acid catalyst according to claim 3, wherein in step S1, the ratio of the total amount of the solid acid catalyst in terms of n (A): n (B): n (1.8-2.0) and (0.05-0.2) adding a metal salt containing A, a metal salt containing B and a metal salt containing M.

5. Preparation of the composite solid acid catalyst according to claim 3The method is characterized in that the metal salt containing A is selected from Zn (NO)₃)₂·6H₂O、ZnSO₄·7H₂O、ZnCl₂At least one of; the metal salt containing B is selected from Fe₂(SO₄)₃·9H₂O、FeCl₃At least one of; the metal salt containing M is selected from ZrCl₄、SnCl₄·5H₂O、Cu(NO₃)₂·3H₂At least one of O.

6. The method for preparing the composite solid acid catalyst according to any one of claims 3 to 5, wherein the alkaline solution is at least one selected from a sodium hydroxide solution, a sodium carbonate solution and a sodium bicarbonate solution.

7. The preparation method of the composite solid acid catalyst according to claim 6, wherein the total substance concentration of the alkaline solution is 3mol/L to 7.4 mol/L.

8. The method for preparing the composite solid acid catalyst according to claim 6, wherein the organic titanium salt is tetrabutyl titanate.

9. The method for preparing the composite solid acid catalyst according to claim 6, wherein the AB is added in step S7₂O₄-M-TiO₂Soaking in 5ml/g ammonium sulfate solution; the concentration of the ammonium sulfate solution is 0.5 mol/L-1.5 mol/L.

10. The use of the composite solid acid catalyst according to claim 1 or 2, wherein the composite solid acid catalyst is used as a catalyst for synthesizing acrylic ester by reacting acrylic acid with alcohol.

Technical Field

The invention relates to the technical field of catalysis, in particular to a composite solid catalyst and a preparation method and application thereof.

Background

The acrylic ester belongs to alpha, beta-unsaturated carboxylic ester compounds, is a common product in the chemical industry, and can be used for synthesizing a series of acrylic polymers; the self structure of the acrylate determines that the acrylate has various advantages of good transparency, toughness, color durability, chemical stability and the like.

The acrylate is used as a functional monomer, can prepare thousands of emulsion type, solvent type or plastic type copolymers through the self polymerization capability, and is widely used in the fields of cosmetics, medicaments, coating thickening agents, dispersing agents, adhesives and the like. In addition, these copolymers are useful as leather and textile finishes, paper strength agents, and the like. With the continuous expansion of the application, the market demand for acrylate is increasing.

At present, concentrated sulfuric acid is mostly used as a catalyst for preparing acrylic ester by esterification reaction of acrylic acid and alcohol in industry; sulfuric acid is used as a catalyst in the esterification reaction process, so that the method has the advantages of good catalytic effect, low production cost and the like, but has the problem that the catalyst is difficult to separate from a product.

Disclosure of Invention

The invention solves the problem that the catalyst is difficult to separate from the product in the esterification reaction process.

Therefore, the invention aims to provide a composite solid acid catalyst which has a spinel structure; the structural formula of the compound solid acid catalyst is SO₄ ^2--AB₂O₄-M-TiO₂(ii) a Wherein A is a divalent metal cation, B is a trivalent metal cation, and M is Zr⁴⁺、Sn⁴⁺、Cu²⁺Any one of them.

Alternatively, A is Zn²⁺B is Fe³⁺。

The invention also aims to provide a preparation method of the composite solid acid catalyst, which comprises the following steps:

s1: mixing metal salt containing A and metal salt containing BAnd dissolving a metal salt containing M in water to obtain a mixed solution; wherein A is a divalent metal cation, B is a trivalent metal cation, and M is Zr⁴⁺、Sn⁴⁺、Cu²⁺Any one of the above;

s2: preparing an alkaline solution;

s3: dropwise adding the alkaline solution into the mixed solution until the pH value of the system is 9.5, stirring in a water bath at 75-85 ℃, aging, and filtering to obtain a precipitate;

s4: drying and grinding the precipitate in sequence to obtain powder;

s5: calcining the powder at 800-900 ℃ to obtain AB₂O₄-an M precursor;

s6: the AB is₂O₄Adding the precursor M into an organic titanium salt hydrolysis solution, and stirring in a water bath at 70-80 ℃ to form gel; drying the gel at 90-100 ℃, and grinding to obtain AB₂O₄-M-TiO₂；

S7: the AB is₂O₄-M-TiO₂And (3) placing the catalyst in an ammonium sulfate solution for soaking, and then drying, grinding and calcining the catalyst in sequence to obtain the composite solid acid catalyst.

Alternatively, in step S1, according to n (a): n (B): n (1.8-2.0) and (0.05-0.2) adding a metal salt containing A, a metal salt containing B and a metal salt containing M.

Alternatively, the A-containing metal salt is selected from Zn (NO)₃)₂·6H₂O、ZnSO₄·7H₂O、ZnCl₂At least one of; the metal salt containing B is selected from Fe₂(SO₄)₃·9H₂O、FeCl₃At least one of; the metal salt containing M is selected from ZrCl₄、SnCl₄·5H₂O、Cu(NO₃)₂·3H₂At least one of O.

Optionally, the alkaline solution is selected from at least one of sodium hydroxide solution, sodium carbonate solution, sodium bicarbonate solution.

Optionally, the total substance concentration of the alkaline solution is 3 mol/L-7.4 mol/L.

Optionally, the organic titanium salt is tetrabutyl titanate.

Optionally, the AB is used in step S7₂O₄-M-TiO₂Soaking in 5ml/g ammonium sulfate solution; the concentration of the ammonium sulfate solution is 0.5 mol/L-1.5 mol/L.

The invention further aims to provide application of the composite solid acid catalyst, which is used for synthesizing acrylic ester by reacting acrylic acid with alcohol.

Compared with the prior art, the composite solid acid catalyst provided by the invention has the following advantages:

the composite solid acid catalyst provided by the invention is used for esterification reaction, and has high catalytic activity and good stability; in addition, in the using process, the active components are not easy to lose, and the catalyst is easy to separate from the product; after the composite solid acid catalyst is repeatedly used for many times, reactants still have higher conversion rate.

Drawings

FIG. 1 shows ZnFe in the present invention₂O₄-XRD spectrum of M;

FIG. 2 shows ZnFe in the present invention₂O₄-IR spectrum of M;

FIG. 3 shows SO according to the present invention₄ ^2--ZnFe₂O₄-M-TiO₂XRD spectrum of (1).

Detailed Description

The following describes embodiments of the present invention in detail. The embodiments described below with reference to the drawings are exemplary and intended to be illustrative of the present invention and should not be construed as limiting the present invention, and all other embodiments that can be obtained by one skilled in the art based on the embodiments of the present invention without inventive efforts shall fall within the scope of protection of the present invention.

At present, sulfuric acid is used as a catalyst, and in the process of preparing acrylic ester through esterification reaction of acrylic acid and alcohol, since the sulfuric acid has an oxidation effect, side reaction is easy to occur in the reaction process, so that the problem that the catalyst is difficult to separate from a product is solved, the difficulties of rectification of a target product and recovery of alcohol are increased, and environmental pollution is caused; in addition, since sulfuric acid has strong corrosivity, even if corrosion-resistant equipment such as a stainless steel pipe, an enamel reactor and the like is adopted in the reaction process, the equipment still needs to be periodically updated, so that the production cost is increased.

In order to solve the problem that the catalyst is difficult to separate from the product in the existing esterification reaction process, the invention provides a composite solid acid catalyst, which has a spinel structure; specifically, the structural formula of the compound solid acid catalyst is SO₄ ^2--AB₂O₄-M-TiO₂(ii) a Wherein A is a divalent metal cation, B is a trivalent metal cation, and M is Zr⁴⁺、Sn⁴⁺、Cu²⁺Any one of them.

The application selects different divalent metal cations and trivalent metal cations respectively through A and B, so that AB is enabled to be₂O₄Constitute different kinds of spinels; the characteristic of stable spinel structure is utilized, so that the catalyst is convenient to recover while the catalytic capability is ensured; further through AB₂O₄Zr doping⁴⁺、Sn⁴⁺、Cu²⁺Form AB₂O₄-M; the AB is₂O₄-M unchanged AB₂O₄Such that the AB₂O₄M still has stronger structural stability, thereby being convenient for separating the catalyst from the product after the reaction is finished, recovering the catalyst and leading the catalyst to have better reusability; meanwhile, the introduction of M can improve the reaction with SO₄ ^2-The capability of forming a chelating structure generates more active sites, so that the catalytic performance of the composite solid catalyst is greatly improved; furthermore, by AB₂O₄-M-with TiO₂Compounding to make AB₂O₄Better dispersion of-M in TiO₂In the case of a plate-like structure of (1), it is advantageous to maintain the respective structural featuresContact with the reactant at the active site, thereby improving the catalytic efficiency.

The composite solid acid catalyst provided by the application is used for replacing concentrated sulfuric acid in the synthesis reaction of acrylic ester, has high catalytic activity, does not generate byproducts, is easy to separate from a product, is beneficial to reducing the recovery difficulty of a target product and alcohol, reduces the pollution to the environment, and can be recovered and reused for multiple times; in addition, the corrosion to equipment is not easy to generate, and the production cost is reduced.

The composite solid acid catalyst provided by the invention is used for esterification reaction, and has high catalytic activity and good stability; in addition, in the using process, the active components are not easy to lose, and the catalyst is easy to separate from the product; after the composite solid acid catalyst is repeatedly used for many times, reactants still have higher conversion rate.

A in the present application may be Mg²⁺、Fe²⁺、Co²⁺、Ni²⁺、Mn²⁺、Zn²⁺、Cd²⁺B may be Al, any one of divalent metal cations³⁺、Fe³⁺、Co³⁺、Cr³⁺、Ga³⁺Any one of the trivalent metal cations; preferred A in this application is Zn²⁺B is Fe³⁺That is, the compound solid acid catalyst preferably has the structural formula of SO₄ ^2--ZnFe₂O₄-M-TiO₂M is Zr⁴⁺、Sn⁴⁺、Cu²⁺Any one of them.

The application leads different metal ions to be introduced into the zinc-iron spinel SO that the metal ions and SO₄ ^2-Forming a chelating structure to generate new active sites to improve the composite solid acid catalyst matrix and SO₄ ^2-The binding ability of the catalyst can promote the progress of the acrylic esterification reaction and improve the catalytic activity.

Another object of the present invention is to provide a method for preparing the composite solid acid catalyst, the method comprising the steps of:

s1: will contain ADissolving the metal salt containing B, the metal salt containing M in water to obtain a mixed solution; wherein A is a divalent metal cation, B is a trivalent metal cation, and M is Zr⁴⁺、Sn⁴⁺、Cu²⁺Any one of the above;

s2: preparing an alkaline solution;

s3: dropwise adding the alkaline solution into the mixed solution until the pH value of the system is 9.5, stirring in a water bath at 75-85 ℃, aging, and filtering to obtain a precipitate;

s4: drying and grinding the precipitate in sequence to obtain powder;

s5: calcining the powder at 700-800 ℃ to obtain AB₂O₄-an M precursor;

s6: will AB₂O₄Adding the precursor M into an organic titanium salt hydrolysis solution, and stirring in a water bath at 70-80 ℃ to form gel; drying the gel at 90-100 ℃, and grinding to obtain AB₂O₄-M-TiO₂；

S7: will AB₂O₄-M-TiO₂Soaking in ammonium sulfate solution, drying, grinding, and calcining to obtain composite solid acid catalyst with SO as structural formula₄ ^2--AB₂O₄-M-TiO₂。

Wherein, the metal salt containing A in step S1 can be selected from Mg as cation²⁺、Fe²⁺、Co²⁺、Ni²⁺、Mn²⁺、Zn²⁺、Cd²⁺Any one of the divalent metal cation metal salts, the metal salt containing B can be selected from the metal salts with Al as cation³⁺、Fe³⁺、Co³⁺、Cr³⁺、Ga³⁺Any one of the trivalent metal cation metal salts, specifically spinel AB₂O₄Depending on the type of the compound; the M-containing metal salt may be selected from the group consisting of Zr as the cation⁴⁺、Sn⁴⁺、Cu²⁺The metal salt of (2) is specifically determined according to the kind of metal ions introduced into the composite solid catalyst.

Specifically, in the present application, in step S1, it is preferable that: n (B): n (1.8-2.0) adding (0.05-0.2) a metal salt containing A, a metal salt containing B and a metal salt containing M; it is further preferred herein that the A-containing metal salt is selected from Zn (NO)₃)₂·6H₂O、ZnSO₄·7H₂O、ZnCl₂At least one of; the metal salt containing B is selected from Fe₂(SO₄)₃·9H₂O、FeCl₃At least one of; the metal salt containing M is selected from ZrCl₄、SnCl₄·5H₂O、Cu(NO₃)₂·3H₂And O is any one of the above.

It is preferable that the alkaline solution in step S2 is at least one selected from the group consisting of a sodium hydroxide solution, a sodium carbonate solution, and a sodium bicarbonate solution, and it is further preferable that the total concentration of the alkaline solution is 3mol/L to 7.4 mol/L.

Dropwise adding the prepared alkaline solution into the mixed solution obtained in the step S1, so that metal cations in the mixed solution react with the added alkaline solution in a water bath at the temperature of 75-85 ℃ to form a precipitate; in order to promote the growth of precipitated crystal particles and improve the purity of precipitates, the stirring time in the water bath condition of 75-85 ℃ in the step S3 is preferably 3-5 h so as to be convenient for sufficient aging; in order to ensure the catalytic activity of the composite solid acid catalyst, the method preferably comprises the step of suction filtration in step S3, and washing the obtained precipitate with high-purity water and absolute ethyl alcohol in sequence until the filtrate is neutral to obtain the precipitate.

In the preferable step S4, the precipitate is placed in a vacuum drying oven with the temperature range of 60-80 ℃, and is fully ground after being dried for 24 hours to obtain powder; placing the obtained powder in a muffle furnace, calcining for 3h at the temperature of 700-800 ℃ to obtain AB₂O₄-M precursor.

Further preparing AB₂O₄Putting the-M precursor into a hydrolysis solution of organic titanium salt, and hydrolyzing the organic titanium salt to generate TiO by a coprecipitation method-sol-gel method₂Simultaneously with AB₂O₄-M chargingMixing; in the application, the stirring time in the water bath condition of 70-80 ℃ in the step S6 is preferably 2 hours, so that gel is formed; drying the obtained gel at 90-100 ℃, and grinding to obtain AB₂O₄-M-TiO₂。

The organic titanium salt in the present application is preferably tetrabutyl titanate in step S6, and more preferably AB₂O₄-M-TiO₂In (AB)₂O₄-M-with TiO₂The mass ratio of (2-7): the amount of tetrabutyltitanate added depends on this ratio.

In order to ensure the catalytic activity of the composite solid acid catalyst, the application prefers that AB is used in step S7₂O₄-M-TiO₂Soaking in 5ml/g ammonium sulfate solution; and further preferably the concentration of the ammonium sulfate solution is 0.5mol/L to 1.5 mol/L.

Further, in the present application, it is preferable that the impregnation time in step S7 is 4 hours, and after the impregnation, drying is performed in a water bath environment at 80 ℃, and fully grinding the dried product; and placing the powder obtained after grinding into a muffle furnace, calcining for 3 hours at the temperature of 450-550 ℃, and naturally cooling to obtain the composite solid acid catalyst.

Referring to fig. 1 to 3, in the process of preparing the composite solid acid catalyst, the intermediate products and the products are sequentially detected; according to the detection results, as shown in fig. 1 and fig. 2, after the zinc-iron spinel is doped with different metal ions, the basic structure of the zinc-iron spinel is not changed, so that the composite solid acid catalyst has good structural stability; referring to FIG. 3, the composite solid acid catalyst, ZnFe, provided by the present application₂O₄-M-with TiO₂Compounding to form ZnFe₂O₄Better dispersion of-M in TiO₂The plate-shaped structure of (2) is beneficial to the contact of active sites and reactants under the condition of keeping respective structural characteristics, thereby improving the catalytic efficiency.

The composite solid acid catalyst is prepared by a coprecipitation-sol-gel method, the preparation method is simple, the cost is low, the preparation process is favorable for maintaining the basic structure of each component, so that the prepared composite solid acid catalyst has high catalytic activity and a stable structure, the composite solid acid catalyst is easy to recover in the use process, the active components are not easy to lose, and the composite solid acid catalyst can be repeatedly used.

Still another object of the present invention is to provide a use of the composite solid acid catalyst as described above for a catalyst for synthesizing acrylic ester by reacting (meth) acrylic acid with alcohol.

Specifically, the synthesis process of the composite solid acid catalyst for the reaction of acrylic acid and alcohol preferably comprises the following steps:

s1: adding alcohol and acrylic acid into a reactor in sequence according to the addition amount of the molar ratio of hydroxyl to acrylic acid (0.9-1.2) to 1; the alcohol in this step may be a mono-, di-or polyol;

s2: adding a composite solid acid catalyst into a reactor, wherein the adding amount of the composite solid acid catalyst is 3-8% of the total mass of reactants;

s3: heating the reactor until the water separator generates water separation, continuously heating for reaction for 4-8 h, naturally cooling to room temperature, filtering, washing, drying, recovering the catalyst, and determining the conversion rate of acrylic acid according to the method of GB 1668-81.

When the composite solid acid catalyst provided by the application is used for synthesizing acrylic ester by acrylic acid and alcohol, the catalytic activity is high, and the stability is good; experiments prove that the conversion rate of acrylic acid is still higher than 80% after the compound solid acid catalyst is repeatedly used for four times.

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.

Example 1

This example provides a composite solid acid catalyst, the structural formula of which is SO₄ ^2--ZnFe₂O₄-Cu²⁺-TiO₂。

S1: according to n (Zn)²⁺)：n(Fe³⁺)：n(Cu²⁺) Weighing Zn (NO) at a ratio of 1:1.8:0.2₃)₂·6H₂O、Fe₂(SO₄)₃·9H₂O、Cu(NO₃)₂·3H₂Dissolving O in high-purity water to obtain a mixed solution;

s2: preparing a sodium hydroxide solution with the total substance concentration of 5.2 mol/L;

s3: dropwise adding a sodium hydroxide solution into the mixed solution until the pH value of the system is 9.5, stirring for 3 hours in a water bath at 75 ℃, and filtering to obtain a precipitate;

s4: drying and grinding the precipitate in sequence to obtain powder;

s5: putting the powder into a muffle furnace, and calcining for 3 hours at 800 ℃ to obtain ZnFe₂O₄-Cu²⁺A precursor;

s6: according to ZnFe₂O₄-Cu²⁺With TiO₂The mass ratio is 5: 10 ratio of ZnFe₂O₄-Cu²⁺Adding the precursor into a hydrolysis solution of tetrabutyl titanate, and stirring for 2 hours at the temperature of 70 ℃ in a water bath to form gel; drying the gel at 90 ℃, and grinding to obtain ZnFe₂O₄-Cu²⁺-TiO₂；

S7: ZnFe is mixed with water₂O₄-Cu²⁺-TiO₂Soaking in 0.5mol/L ammonium sulfate solution at a ratio of 5ml/g for 4h, and oven drying in 80 deg.C water bath environment; drying, grinding, placing the powder obtained after grinding in a muffle furnace, calcining for 3h at 450 ℃, and naturally cooling to obtain the composite solid acid catalyst, wherein the structural formula of the composite solid acid catalyst is SO₄ ^2--ZnFe₂O₄-Cu²⁺-TiO₂。

The prepared composite solid acid catalyst is used for the esterification reaction of acrylic acid and n-octanol:

s1: weighing 14.4g of acrylic acid and 26.0g of n-octanol, adding the acrylic acid and the n-octanol into a 100ml three-neck flask, adding a toluene solvent accounting for 30% of the total mass of reactants as a water-carrying agent, and placing the mixture into an oil bath pan;

s2: adding a composite solid acid catalyst SO into an oil bath pan₄ ^2--ZnFe₂O₄-Cu²⁺-TiO₂And phenothiazine, a polymerization inhibitor; the adding amount of the composite solid acid catalyst is 6 wt% of the total mass of reactants; the adding amount of the polymerization inhibitor is 1 wt% of the total mass of the reactants;

s3: heating the oil bath pot until the water separator generates water separation, continuing heating for reaction for 5h, stopping heating, naturally cooling to room temperature, filtering, washing, drying, recovering the catalyst, calculating the recovery rate of the catalyst, detecting the product, and determining the conversion rate of acrylic acid according to the method of GB 1668-81.

Through calculation and detection, the recovery rate of the composite solid acid catalyst in the embodiment is 95.0%, no by-product is generated, and the conversion rate of acrylic acid is 86.8%.

Example 2

This example provides a composite solid acid catalyst, the structural formula of which is SO₄ ^2--ZnFe₂O₄-Zr⁴⁺-TiO₂。

S1: according to n (Zn)²⁺)：n(Fe³⁺)：n(Zr⁴⁺) Weighing Zn (NO) at a ratio of 1:2.0:0.05₃)₂·6H₂O、FeCl₃、ZrCl₄Dissolving in high-purity water to obtain a mixed solution;

s2: preparing sodium bicarbonate solution with the total substance concentration of 7.4 mol/L;

s3: dropwise adding a sodium bicarbonate solution into the mixed solution until the pH value of the system is 9.5, stirring for 4 hours in a water bath at 85 ℃, and filtering to obtain a precipitate;

s4: drying and grinding the precipitate in sequence to obtain powder;

s5: putting the powder into a muffle furnace, and calcining for 3 hours at 900 ℃ to obtain ZnFe₂O₄-Zr⁴⁺A precursor;

s6: according to ZnFe₂O₄-Zr⁴⁺With TiO₂The mass ratio is 6: 10 ratio of ZnFe₂O₄-Zr⁴⁺Adding the precursor into a hydrolysis solution of tetrabutyl titanate, and stirring for 2 hours at the temperature of 80 ℃ in a water bath to form gel; drying the gel at 100 ℃, and grinding to obtain ZnFe₂O₄-Zr⁴⁺-TiO₂；

S7: ZnFe is mixed with water₂O₄-Zr⁴⁺-TiO₂Soaking in 0.75mol/L ammonium sulfate solution at a ratio of 5ml/g for 4h, and oven drying in 80 deg.C water bath environment; drying, grinding, placing the powder obtained after grinding in a muffle furnace, calcining for 3h at 500 ℃, and naturally cooling to obtain the composite solid acid catalyst, wherein the structural formula of the composite solid acid catalyst is SO₄ ^2--ZnFe₂O₄-Zr⁴⁺-TiO₂。

The prepared composite solid acid catalyst is used for esterification reaction of methacrylic acid and n-octanol:

s1: weighing 17.2g of methacrylic acid and 31.3g of n-octanol, adding the methacrylic acid and the n-octanol into a 250ml three-neck flask, adding a toluene solvent accounting for 30 percent of the total mass of reactants as a water-carrying agent, and placing the mixture into an oil bath pan;

s2: adding a composite solid acid catalyst SO into an oil bath pan₄ ^2--ZnFe₂O₄-Zr⁴⁺-TiO₂And phenothiazine, a polymerization inhibitor; the adding amount of the composite solid acid catalyst is 8 wt% of the total mass of reactants; the adding amount of the polymerization inhibitor is 1 wt% of the total mass of the reactants;

s3: heating the oil bath pan until the water separator generates water separation, continuing to heat for reaction for 6h, stopping heating, naturally cooling to room temperature, filtering, washing, drying, recovering the catalyst, calculating the recovery rate of the catalyst, detecting the product, and determining the conversion rate of the methacrylic acid according to the method of GB 1668-81.

Through calculation and detection, the recovery rate of the composite solid acid catalyst in the embodiment is 97.4%, no by-product is generated, and the conversion rate of methacrylic acid is 92.6%.

Example 3

This example provides a composite solid acid catalyst, the structural formula of which is SO₄ ^2--ZnFe₂O₄-Zr⁴⁺-TiO₂。

S1: according to n (Zn)²⁺)：n(Fe³⁺)：n(Zr⁴⁺) Weighing Zn (NO) at a ratio of 1:1.9:0.1₃)₂·6H₂O、Fe₂(SO₄)₃·9H₂O、ZrCl₄Dissolving in high-purity water to obtain a mixed solution;

s2: preparing a sodium carbonate solution with the total concentration of substances of 7.4 mol/L;

s3: dropwise adding a sodium carbonate solution into the mixed solution until the pH value of the system is 9.5, stirring for 4 hours in a water bath at 85 ℃, and filtering to obtain a precipitate;

s4: drying and grinding the precipitate in sequence to obtain powder;

s5: putting the powder into a muffle furnace, and calcining for 3 hours at 800 ℃ to obtain ZnFe₂O₄-Zr⁴⁺A precursor;

s6: according to ZnFe₂O₄-Zr⁴⁺With TiO₂The mass ratio is 4: 10 ratio of ZnFe₂O₄-Zr⁴⁺Adding the precursor into a hydrolysis solution of tetrabutyl titanate, and stirring for 2 hours at the temperature of 80 ℃ in a water bath to form gel; drying the gel at 90 ℃, and grinding to obtain ZnFe₂O₄-Zr⁴⁺-TiO₂；

S7: ZnFe is mixed with water₂O₄-Zr⁴⁺-TiO₂Soaking in 1.0mol/L ammonium sulfate solution at a ratio of 5ml/g for 4h, and oven drying in 80 deg.C water bath environment; drying, grinding, placing the powder obtained after grinding in a muffle furnace, calcining for 3h at 500 ℃, and naturally cooling to obtain the composite solid acid catalyst, wherein the structural formula of the composite solid acid catalyst is SO₄ ^2--ZnFe₂O₄-Zr⁴⁺-TiO₂。

The prepared composite solid acid catalyst is used for esterification reaction of acrylic acid and butanediol:

s1: weighing 48.0g of acrylic acid and 27.0g of 1, 4-butanediol, adding the acrylic acid and the 1, 4-butanediol into a 250ml three-neck flask, adding a toluene solvent accounting for 30 percent of the total mass of reactants as a water-carrying agent, and placing the mixture into an oil bath pan;

s2: adding a composite solid acid catalyst SO into an oil bath pan₄ ^2--ZnFe₂O₄-Zr⁴⁺-TiO₂And phenothiazine, a polymerization inhibitor; the adding amount of the composite solid acid catalyst is 6 wt% of the total mass of reactants; the adding amount of the polymerization inhibitor is 1 wt% of the total mass of the reactants;

s3: heating the oil bath pot until the water separator generates water separation, continuing heating for reaction for 5h, stopping heating, naturally cooling to room temperature, filtering, washing, drying, recovering the catalyst, calculating the recovery rate of the catalyst, detecting the product, and determining the conversion rate of acrylic acid according to the method of GB 1668-81.

Through calculation and detection, the recovery rate of the composite solid acid catalyst in the embodiment is 95.1%, the conversion rate of acrylic acid is 87.5%, and the ratio of diester compounds is 93.7%.

Example 4

The composite solid acid catalyst SO recovered in example 3₄ ^2--ZnFe₂O₄-Zr⁴⁺-TiO₂And then used for the esterification reaction of methacrylic acid and 1, 4-butanediol:

s1: weighing 38.7g of methacrylic acid and 22.5g of 1, 4-butanediol, adding the methacrylic acid and the 1, 4-butanediol into a 250ml three-neck flask, adding a toluene solvent accounting for 30 percent of the total mass of reactants as a water-carrying agent, and placing the mixture into an oil bath pan;

s2: adding a composite solid acid catalyst SO into an oil bath pan₄ ^2--ZnFe₂O₄-Zr⁴⁺-TiO₂And phenothiazine, a polymerization inhibitor; the adding amount of the composite solid acid catalyst is 6 wt% of the total mass of reactants; the adding amount of the polymerization inhibitor is 1 wt% of the total mass of the reactants;

s3: heating the oil bath pot until the water separator generates water separation, continuing heating for reaction for 5h, stopping heating, naturally cooling to room temperature, filtering, washing, drying, recovering the catalyst, calculating the recovery rate of the catalyst, detecting the product, and determining the conversion rate of the methacrylic acid according to the method of GB 1668-81.

Through calculation and detection, the recovery rate of the composite solid acid catalyst in the embodiment is 91.3%, the conversion rate of methacrylic acid is 90.2%, and the ratio of diester compounds is 94.8%.

Example 5

The composite solid acid catalyst SO recovered in example 4₄ ^2--ZnFe₂O₄-Zr⁴⁺-TiO₂And then the acrylic acid is used for esterification reaction with 1, 4-butanediol:

s1: weighing 45.6g of acrylic acid and 25.7g of 1, 4-butanediol, adding the acrylic acid and the 1, 4-butanediol into a 250ml three-neck flask, adding a toluene solvent accounting for 30 percent of the total mass of reactants as a water-carrying agent, and placing the mixture into an oil bath pan;

s2: adding a composite solid acid catalyst SO into an oil bath pan₄ ^2--ZnFe₂O₄-Zr⁴⁺-TiO₂And phenothiazine, a polymerization inhibitor; the adding amount of the composite solid acid catalyst is 6 wt% of the total mass of reactants; the adding amount of the polymerization inhibitor is 1 wt% of the total mass of the reactants;

s3: heating the oil bath pot until the water separator generates water separation, continuing heating for reaction for 5h, stopping heating, naturally cooling to room temperature, filtering, washing, drying, recovering the catalyst, calculating the recovery rate of the catalyst, detecting the product, and determining the conversion rate of acrylic acid according to the method of GB 1668-81.

Through calculation and detection, the recovery rate of the composite solid acid catalyst in the embodiment is 93.5%, the conversion rate of acrylic acid is 86.8%, and the ratio of diester compounds is 92.3%.

Example 6

The composite solid acid catalyst SO recovered in example 5₄ ^2--ZnFe₂O₄-Zr⁴⁺-TiO₂Is used again inThe acrylic acid and 1, 4-butanediol are subjected to esterification reaction, and the experimental process is the same as that of example 5; after the reaction is finished, the catalyst is recovered, the recovery rate of the catalyst is calculated, the product is detected, and the conversion rate of the acrylic acid is measured according to the method of GB 1668-81.

Through calculation and detection, the recovery rate of the composite solid acid catalyst in the embodiment is 91.3%, the conversion rate of acrylic acid is 75.1%, and the ratio of diester compounds is 79.9%.

From the data in the above embodiments, it can be known that the composite solid acid catalyst provided by the present invention has high catalytic activity and good stability when used for synthesizing acrylic ester from acrylic acid and alcohol; in addition, the compound solid acid catalyst is easy to separate from the product, and can be recycled and reused for multiple times; after the compound solid acid catalyst is repeatedly used for four times, the conversion rate of acrylic acid is still higher than 75%.

After the catalyst is recycled for multiple times, the catalytic activity of the catalyst can be improved by reactivating the recycled catalyst; the specific catalytic activation mode is as follows: SO after repeated use₄ ^2-/ZnFe₂O₄-Zr-TiO₂And placing the mixture in 0.75mol/L ammonium sulfate solution, stirring for 3h, filtering, drying, and calcining for 3h in an environment of 500 ℃ to complete the reactivation of the catalyst.

Although the present disclosure has been described above, the scope of the present disclosure is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present disclosure, and such changes and modifications will fall within the scope of the present invention.