Synthetic method of methyl p-tert-butylbenzoate

Abstract

The invention provides a synthetic method of methyl p-tert-butylbenzoate, and belongs to the technical field of chemical synthesis, the synthetic method comprises the following steps: mixing sulfonic acid resin in a molten state with calcium salt of nano powder, then rapidly solidifying to prepare mixed particles, and then sequentially carrying out pickling activation, cleaning and drying to prepare a modified sulfonic acid resin catalyst; the calcium salt is at least one of calcium sulfate and calcium silicate; the method comprises the following steps: adding p-tert-butylbenzoic acid and absolute methanol into reaction equipment, carrying out a step-by-step esterification reaction of heating and cooling at 90-150 DEG C under the catalysis of a modified sulfonic acid resin catalyst, and carrying out post-treatment after the reaction is finished, so as to obtain methyl p-tert-butylbenzoate, wherein the molar ratio of p-tert-butylbenzoic acid to absolute methanol is (1: 3)-(1: 5). According to the method, the modified sulfonic acid resin is used as the catalyst, and the stepped esterification reaction of heating and cooling is combined, so that the methyl p-tert-butylbenzoate with the purity being greater than or equal to 99.99% is prepared, and the conversion rate of p-tert-butylbenzoic acid exceeds 99%.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical synthesis, and particularly relates to a method for synthesizing methyl p-tert-butylbenzoate. Background Art

[0002] Methyl 4-tert-butylbenzoate (MPTBBA) is an important organic synthesis and pharmaceutical chemical intermediate, widely used in medicine, cosmetics, flavors and fragrances, chemical synthesis and other industries. MPTBBA is mainly used to produce avobenzone, which is widely used in the cosmetics industry because of its antioxidant and skin protection functions against light, heat, moisture and ultraviolet damage.

[0003] At present, the mainstream synthesis process of methyl p-tert-butylbenzoate is: using p-tert-butylbenzoic acid and methanol as raw materials, heating under acidic catalyst conditions to carry out esterification reaction to produce methyl p-tert-butylbenzoate. The catalyst is a key factor affecting the yield, efficiency and purity of the product. At present, concentrated sulfuric acid is commonly used as a catalyst, which has the advantages of high catalytic efficiency and high yield; however, the reaction process causes organic matter to lose water and carbonize, and there are also defects such as long reaction time and separation and post-processing. In addition, as a liquid phase strong acid, concentrated sulfuric acid has strong corrosiveness and serious pollution. Summary of the invention

[0004] In view of this, the object of the present invention is to provide a method for synthesizing methyl p-tert-butylbenzoate, aiming to solve at least one technical problem among the background technology.

[0005] The present invention is achieved in that:

[0006] A method for synthesizing methyl p-tert-butylbenzoate, comprising the following steps:

[0007] The molten sulfonic acid resin and the calcium salt of nano powder are mixed and then rapidly solidified to form mixed particles, and then acid-washed, activated, cleaned and dried in sequence to obtain a modified sulfonic acid resin catalyst; the calcium salt is at least one of calcium sulfate and calcium silicate;

[0008] Adding p-tert-butylbenzoic acid and anhydrous methanol into a reaction device, carrying out a stepwise esterification reaction of first heating and then cooling at 90° C. to 150° C. under the catalysis of a modified sulfonic acid resin catalyst, and then performing post-treatment to obtain methyl p-tert-butylbenzoate; wherein, according to the molar ratio, p-tert-butylbenzoic acid: anhydrous methanol = 1:3 to 1:5.

[0009] Furthermore, the preparation steps of the modified sulfonic acid resin catalyst include:

[0010] The calcium salt is subjected to high-energy ball milling to obtain nano powder; the sulfonic acid resin is heated and kept warm to obtain the molten sulfonic acid resin;

[0011] The nano powder is mixed evenly with the molten sulfonic acid resin, and the mixture is kept warm for at least 30 minutes to obtain a modified sulfonic acid resin precursor;

[0012] The modified sulfonic acid resin precursor is made into powder by gas atomization to obtain mixed particles of the modified sulfonic acid resin precursor;

[0013] The mixed particles of the modified sulfonic acid resin precursor are immersed in a dilute inorganic acid for activation;

[0014] After solid-liquid separation, the solid is cleaned and dried at low temperature to obtain a modified sulfonic acid resin catalyst;

[0015] Wherein, the inorganic dilute acid is dilute sulfuric acid or dilute hydrochloric acid.

[0016] Furthermore, the modified sulfonic acid resin catalyst comprises the following raw materials in weight percentage: 50% to 60% sulfonic acid resin; 40% to 50% calcium salt; the sulfonic acid resin is perfluorosulfonic acid resin.

[0017] Furthermore, the 40% to 50% calcium salt includes 20% to 25% calcium sulfate and 20% to 25% calcium silicate.

[0018] Furthermore, the esterification reaction adopts a temperature-raising reflux reaction, and a condenser and a water separator are installed on the reaction equipment. The methanol volatilized during the reaction is collected by the condenser and then dried and refluxed into the reaction equipment.

[0019] Furthermore, the stepwise esterification reaction specifically includes:

[0020] In the first stage, the temperature inside the reaction equipment is quickly raised to 140°C to 150°C and kept at this temperature for 20min to 30min;

[0021] In the second stage, the temperature is lowered to 120℃~130℃ and kept warm for 90min~120min;

[0022] In the third stage, the temperature is lowered to 90℃~110℃ and kept warm for 30min~60min.

[0023] Furthermore, in the process of uniformly mixing the nano powder and the molten sulfonic acid resin, the nano powder is added to the molten sulfonic acid resin in batches, and the number of batches is no less than three times.

[0024] Furthermore, in the process of uniformly mixing the nano powder and the molten sulfonic acid resin, ultrasonic and / or microwave treatment is performed as an auxiliary.

[0025] Furthermore, in the esterification reaction, the amount of the modified sulfonic acid resin catalyst used is 10% to 30% by weight of the p-tert-butylbenzoic acid.

[0026] Furthermore, the post-treatment is specifically as follows: adding water to the reaction product and stirring it to separate the solid and liquid, wherein the liquid is the crude product of methyl p-tert-butylbenzoate; repeatedly extracting the liquid, combining the ester layers; and finally performing reduced pressure distillation to obtain the refined methyl p-tert-butylbenzoate.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. The present invention uses modified sulfonic acid resin as a catalyst, combined with a step-wise esterification reaction of first heating and then cooling, to prepare methyl p-tert-butylbenzoate with a purity of ≧99.99%, and the conversion rate of p-tert-butylbenzoic acid exceeds 99%.

[0029] 2. The esterification reaction process of the present invention takes less time, consumes less energy, and has less methanol loss.

[0030] 3. The present invention modifies the sulfonic acid resin, uses the sulfonic acid resin as an acid medium, and uses a calcium salt as a carrier to form a modified sulfonic acid resin catalyst with a rich pore structure, which effectively increases the specific surface area and acid strength of the sulfonic acid resin. The increase in specific surface area can increase the number of active points on the catalyst surface, expose more acidic groups, and thus increase the catalytic performance.

[0031] 4. The present invention combines melting-dispersion-rapid solidification-acid washing activation to prepare modified sulfonic acid resin. Compared with the conventional modification method of sulfonic acid resin, the sulfonic acid resin prepared by the present invention is more uniform and has a better morphology, and at the same time has better catalytic performance.

[0032] 5. The modified sulfonic acid resin catalyst of the embodiment of the present invention has stable catalytic performance and still has strong catalytic performance after multiple cycles.

[0033] 6. Compared with common sulfonic acid resin, the present invention prepares a composite by combining nano calcium salt and perfluorosulfonic acid resin, so that the surface of the composite has a large number of free sulfonic acid groups, and the surface has both B acid and L acid, which form a synergistic effect. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific implementation cases described herein are only used to explain the present invention and are not used to limit the present invention.

[0035] The present invention relates to a method for synthesizing methyl p-tert-butylbenzoate, which comprises the following steps:

[0036] S1, preparing a modified sulfonic acid resin catalyst;

[0037] (1) weighing 50% to 60% of sulfonic acid resin and 40% to 50% of calcium salt as raw materials; high-energy ball milling the calcium salt to form nanopowder; heating the sulfonic acid resin and keeping it warm to obtain a molten sulfonic acid resin;

[0038] (2) mixing the nanopowder and the molten sulfonic acid resin uniformly and keeping the mixture warm for at least 30 minutes to obtain a modified sulfonic acid resin precursor; preferably, the nanopowder is added to the molten sulfonic acid resin in batches, and the number of batches is not less than three times, and ultrasonic and / or microwave treatment is performed during the addition process;

[0039] (3) forming particles of the modified sulfonic acid resin precursor by a gas atomization method to obtain mixed particles of the modified sulfonic acid resin precursor;

[0040] (4) immersing the mixed particles of the modified sulfonic acid resin precursor in dilute sulfuric acid or dilute hydrochloric acid for acid immersion activation, with the activation time being at least 1 hour;

[0041] (5) After solid-liquid separation, the solid is cleaned and dried at low temperature to obtain a modified sulfonic acid resin catalyst.

[0042] Sulfonic acid resin (preferably perfluorosulfonic acid resin) is a solid strong acid and can be used as a heterogeneous catalyst to promote the esterification reaction. However, compared with liquid acid (such as concentrated sulfuric acid), its catalytic efficiency is low and the time required is longer, generally 6h to 12h, or even longer;

[0043] In order to solve this problem, the present invention modifies the sulfonic acid resin to increase the specific surface area and surface acid value of the sulfonic acid resin; uses the sulfonic acid resin as an acid medium and a calcium salt as a carrier to form a modified sulfonic acid resin catalyst with a rich pore structure and a large specific surface area; the calcium salt uses calcium sulfate and / or calcium silicate.

[0044] The reasons for using calcium sulfate and calcium silicate composite calcium salt are: (1) calcium sulfate and calcium silicate are stable and not easy to decompose when heated; (2) calcium sulfate and calcium silicate have a certain drying effect, which can promote the positive esterification reaction during subsequent catalysis; (3) after the esterification is completed, it is convenient to separate the catalyst from the reaction product; (4) increase the specific surface area and surface active sites of the sulfonic acid resin; in the specific implementation, since the sulfonic acid resin is the active component of the catalyst, its mass accounts for more than 50%, otherwise the catalytic effect is limited or an excessive amount of catalyst is required. Compared with ordinary sulfonic acid resin, the present invention prepares a composite of nano calcium salt and perfluorosulfonic acid resin, so that its surface has a large number of free sulfonic acid groups, and the surface has both B acid and L acid, and the two form a synergistic effect.

[0045] In order to compound the sulfonic acid resin with the calcium salt, a granulation method can also be used, such as the sulfonic acid resin + calcium salt is prepared by melt extrusion, water cooling and stretching granulation. However, since the melting point of the calcium salt is basically above 1000°C, and the melting point of the sulfonic acid resin is between 160°C and 300°C, the conventional (200°C to 300°C) screw extrusion method is used to prepare the sulfonic acid resin composite particles. In this process, the sulfonic acid resin cannot be evenly loaded on the calcium salt; or it can be prepared by a sol-gel method, but this process will cause the final catalyst product to contain crystal water, resulting in a decrease in acid strength.

[0046] The invention firstly forms uniform nano powder through high-energy ball milling on a calcium salt carrier, then heat-insulates and mixes the nano powder with a molten sulfonic acid resin, and combines a gas atomization method to prepare particles; in this process, the heating temperature of the sulfonic acid resin can be adjusted according to actual needs, and the sulfonic acid resin is kept warm for a period of time after being heated to be completely melted, and the process of adding powder is kept warm at the same time, so as to avoid the subsequent addition of nano powders causing the molten sulfonic acid resin to be locally cooled; adding powder in batches can make the powder and fluid mixed more uniformly and avoid agglomeration; assisting ultrasonic and / or microwave operation, using the vibration effect and thermal effect of the powder to promote rapid dispersion of the powder, so that the sulfonic acid resin and the calcium salt are combined more uniformly and efficiently, so that the sulfonic acid resin is uniformly loaded on the calcium salt, and the power of the ultrasonic and microwave treatment can be adjusted according to actual needs, generally set at 200W to 400W; the gas atomization method is to impact and break the molten fluid with the help of a high-speed airflow, so that the mixed material of the fluid can be quickly cooled to prepare composite particles with controllable particle size and spherical appearance; and then acid leaching activation, cleaning and drying are carried out in sequence to obtain a modified sulfonic acid resin catalyst with porous surface and multiple acid sites.

[0047] S2. Catalytic esterification reaction

[0048] (1) weighing raw materials, according to the molar ratio of p-tert-butylbenzoic acid (PTBBA): anhydrous methanol = 1:3 to 1:5, and a modified sulfonic acid resin catalyst containing 10% to 30% by weight of p-tert-butylbenzoic acid;

[0049] (2) Install a condenser and a water separator on the reaction equipment, mix p-tert-butylbenzoic acid and anhydrous methanol in the reaction equipment, so that p-tert-butylbenzoic acid is fully dissolved in the anhydrous methanol, then add a modified sulfonic acid resin catalyst, quickly heat up to 140° C. to 150° C. at a rate of more than 5° C. / min, and keep warm for 20 min to 30 min; then cool down to 120° C. to 130° C., and keep warm for 90 min to 120 min; finally cool down to 90° C. to 110° C., and keep warm for 30 min to 60 min; the methanol volatilized during the reaction is collected through the condenser and then dried and refluxed into the reaction equipment;

[0050] (3) adding water to the reaction product, stirring, and then performing solid-liquid separation, wherein the liquid is the crude methyl p-tert-butylbenzoate; repeatedly extracting the liquid, combining the ester layer, and finally performing reduced pressure distillation to obtain the refined methyl p-tert-butylbenzoate. This step is used to remove excess methanol, water, and residual reaction raw material methyl p-tert-butylbenzoate in the reaction system.

[0051] The reaction formula of the esterification reaction of tert-butylbenzoic acid and methanol is as follows:

[0052]

[0053] The theoretical molar amount of p-tert-butylbenzoic acid and methanol is 1:1. Since the esterification reaction needs to be heated, and the boiling point of methanol is only 64.7°C, methanol will volatilize during the esterification reaction. In actual industrial production, in order to ensure that the p-tert-butylbenzoic acid reacts completely, the actual amount of methanol needs to exceed the theoretical amount by several times. Generally, the actual molar amount of p-tert-butylbenzoic acid and methanol is 1:6-12. It is adjusted according to the time and temperature required for the reaction. In the present invention, a condenser and a water separator are added, and during reflux, methanol is dried by a desiccant or a distillation tower and then returned to the reaction system for recycling, thereby reducing the actual amount of methanol. The increase in water content in the reaction system caused by reflux can be reduced, which affects the forward progress of the reaction. The condenser and the water separator can discharge water generated by the reaction system in real time, thereby promoting the forward progress of the reaction.

[0054] The reason why the step-wise esterification reaction of first heating and then cooling is adopted in the present invention is that: it has been found through research that the esterification reaction between p-tert-butylbenzoic acid and methanol is difficult to occur or progresses slowly at room temperature, and heating can induce rapid start of esterification, and the esterification progresses faster as the temperature rises; however, if the temperature is too high, methanol evaporates too quickly, resulting in a decrease in reaction efficiency, and it is found that in the range of 120°C to 130°C, the reaction efficiency is the highest, and the reaction system can quickly reach equilibrium;

[0055] The step-by-step esterification reaction first heats up rapidly. At this stage, the amount of methanol is sufficient. Even if it evaporates, it will not affect the occurrence and advancement of esterification. First, the temperature is raised to 140℃~150℃, which can quickly induce the start of esterification, which is equivalent to causing a "qualitative change"; then the temperature is lowered to 120℃~130℃. At this stage, 4-tert-butylbenzoic acid can be effectively converted into methyl 4-tert-butylbenzoate, that is, a "quantitative change" occurs; finally, the temperature is lowered to 90℃~110℃, which can ensure that the residual or vapor state of 4-tert-butylbenzoic acid reacts with methanol.

[0056] Example 1

[0057] This embodiment prepares modified sulfonic acid resin catalysts of different components, specifically comprising the following steps:

[0058] (1) weighing raw material perfluorosulfonic acid resin and calcium salt according to the different components in Table 1 below; high-energy ball milling the calcium salt to prepare nano powder; heating and stirring the perfluorosulfonic acid resin and keeping the temperature to make it completely melt, thereby obtaining a molten perfluorosulfonic acid resin;

[0059] (2) adding the nanopowder to the molten perfluorosulfonic acid resin three or more times, and performing ultrasonic treatment with an auxiliary power of 240 W and / or microwave treatment with a power of 320 W during the adding process to fully mix the nanopowder, and keeping the mixture warm for 1 hour after mixing to obtain a modified sulfonic acid resin precursor in a fluid form;

[0060] (3) impacting the ejected modified sulfonic acid resin precursor with a high-speed inert gas flow, and then forming particles of the modified sulfonic acid resin precursor by a gas atomization method to obtain mixed particles of the modified sulfonic acid resin precursor;

[0061] (4) immersing the mixed particles of the modified sulfonic acid resin precursor in about 1 mol / L dilute sulfuric acid or dilute hydrochloric acid for acid leaching activation for about 2 hours;

[0062] (5) After the acid leaching is completed, the solid is separated from the liquid and the solid is cleaned, and then low-temperature drying is performed to obtain a modified sulfonic acid resin catalyst; the catalysts are numbered as modified sulfonic acid resin catalyst 1-1 to modified sulfonic acid resin catalyst 1-5.

[0063] The activated pure perfluorosulfonic acid resin (the activation step refers to the above steps (4) and (5)) was used as the comparative catalyst D1, and the pore structure and acid strength tests were performed on the modified sulfonic acid resin catalysts 1-1 to 1-5 and the comparative catalyst D1, wherein the pore structure related data were calculated by using a specific surface area instrument to perform N2 physical adsorption and desorption experimental measurements, and the acid strength was measured using the Hammett indicator method to measure the surface acid amount; the results are shown in Table 1.

[0064] Table 1

[0065]

[0066] The present invention mixes molten perfluorosulfonic acid resin and calcium salt of nano powder and then rapidly solidifies to form mixed particles, and then sequentially performs acid washing, activation, cleaning and drying to obtain a modified sulfonic acid resin catalyst. As shown in Table 1, the specific surface area and acid content of the modified sulfonic acid resin of the present invention are increased compared with those of conventional perfluorosulfonic acid resin after acid washing and activation. The increase in specific surface area can increase the number of active points on the catalyst surface, expose more acidic groups, and thus increase the catalytic performance.

[0067] Example 2

[0068] In this example, the modified sulfonic acid resin catalyst 1-1 prepared in Example 1 was used to catalyze the esterification reaction, and the specific steps are as follows:

[0069] (1) In a reaction kettle equipped with a condenser and a water separator, 100 g of p-tert-butylbenzoic acid and 54 g of anhydrous methanol are added, and the mixture is stirred and mixed to make the p-tert-butylbenzoic acid fully dissolved in the anhydrous methanol, and then 10 g of a modified sulfonic acid resin catalyst is added, and the temperature is rapidly increased to 140° C. at a rate of 8° C. / min, and the temperature is kept for 30 min; then the temperature is decreased to 120° C. at a rate of 3° C. / min, and the temperature is kept for 120 min; finally, the temperature is decreased to 90° C. at a rate of 3° C. / min, and the temperature is kept for 60 min; the methanol volatilized during the reaction is collected through a condenser, dried, and refluxed into the reaction equipment;

[0070] (2) adding water to the reaction product and stirring it to separate the solid from the liquid, wherein the liquid is the crude product of methyl p-tert-butylbenzoate; repeatedly extracting the liquid, combining the ester layers; and finally performing reduced pressure distillation to obtain the refined product of methyl p-tert-butylbenzoate (MPTBBA) with a purity of ≧99.99%.

[0071] Example 3

[0072] In this example, the modified sulfonic acid resin catalyst 1-2 prepared in Example 1 is used to catalyze the esterification reaction. The specific steps are the same as those in Example 2 to obtain methyl p-tert-butylbenzoate with a purity of ≧99.99%.

[0073] Example 4

[0074] In this example, the modified sulfonic acid resin catalyst 1-3 prepared in Example 1 is used to catalyze the esterification reaction. The specific steps are the same as those in Example 2 to obtain methyl p-tert-butylbenzoate with a purity of ≧99.99%.

[0075] Example 5

[0076] In this example, the modified sulfonic acid resin catalyst 1-4 prepared in Example 1 is used to catalyze the esterification reaction. The specific steps are the same as those in Example 2 to obtain methyl p-tert-butylbenzoate with a purity of ≧99.99%.

[0077] Example 6

[0078] In this example, the modified sulfonic acid resin catalyst 1-5 prepared in Example 1 is used to catalyze the esterification reaction. The specific steps are the same as those in Example 2 to obtain methyl p-tert-butylbenzoate with a purity of ≧99.99%.

[0079] Example 7

[0080] The steps of Example 2 were repeated to obtain methyl p-tert-butylbenzoate with a purity of ≧99.99%. The difference was the stepwise esterification reaction, specifically:

[0081] Rapidly heat to 145°C at a rate of 8°C / min and keep warm for 25 min;

[0082] Then cool down to 125°C at a rate of 3°C / min and keep warm for 105min;

[0083] Finally, the temperature was lowered to 100°C at a rate of 3°C / min and kept at this temperature for 45 min.

[0084] Example 8

[0085] The steps of Example 2 were repeated to obtain methyl p-tert-butylbenzoate with a purity of ≧99.99%. The difference was the stepwise esterification reaction, specifically:

[0086] Rapidly heat to 150°C at a rate of 8°C / min and keep warm for 20 min;

[0087] Then cool down to 130℃ at a rate of 3℃ / min and keep warm for 90min;

[0088] Finally, the temperature was lowered to 110°C at a rate of 3°C / min and kept at this temperature for 30 min.

[0089] Example 9

[0090] In this example, the modified sulfonic acid resin catalyst 1-1 prepared in Example 1 was used to catalyze the esterification reaction, and the specific steps are as follows:

[0091] (1) In a reaction kettle equipped with a condenser and a water separator, 100 g of p-tert-butylbenzoic acid and 54 g of anhydrous methanol are added, and the mixture is stirred and mixed to make the p-tert-butylbenzoic acid fully dissolved in the anhydrous methanol, and then 20 g of a modified sulfonic acid resin catalyst is added, and the temperature is rapidly increased to 140° C. at a rate of 8° C. / min, and the temperature is kept for 20 min; then the temperature is decreased to 120° C. at a rate of 3° C. / min, and the temperature is kept for 100 min; finally, the temperature is decreased to 90° C. at a rate of 3° C. / min, and the temperature is kept for 50 min; the methanol volatilized during the reaction is collected through a condenser, dried, and refluxed into the reaction equipment;

[0092] (2) adding water to the reaction product, stirring and then performing solid-liquid separation, wherein the liquid is the crude product of methyl p-tert-butylbenzoate; repeatedly extracting the liquid, combining the ester layers; and finally performing reduced pressure distillation to obtain the refined product of methyl p-tert-butylbenzoate with a purity of ≧99.99%.

[0093] Example 10

[0094] In this example, the modified sulfonic acid resin catalyst 1-1 prepared in Example 1 was used to catalyze the esterification reaction, and the specific steps are as follows:

[0095] (1) In a reaction kettle equipped with a condenser and a water separator, 100 g of p-tert-butylbenzoic acid and 54 g of anhydrous methanol are added, and the mixture is stirred and mixed to make the p-tert-butylbenzoic acid fully dissolved in the anhydrous methanol, and then 30 g of a modified sulfonic acid resin catalyst is added, and the temperature is rapidly increased to 140° C. at a rate of 8° C. / min, and the temperature is kept for 20 min; then the temperature is decreased to 120° C. at a rate of 3° C. / min, and the temperature is kept for 90 min; finally, the temperature is decreased to 90° C. at a rate of 3° C. / min, and the temperature is kept for 30 min; the methanol volatilized during the reaction is collected through a condenser, and then dried and refluxed into the reaction equipment;

[0096] (2) adding water to the reaction product, stirring and then performing solid-liquid separation, wherein the liquid is the crude product of methyl p-tert-butylbenzoate; repeatedly extracting the liquid, combining the ester layers; and finally performing reduced pressure distillation to obtain the refined product of methyl p-tert-butylbenzoate with a purity of ≧99.99%.

[0097] Embodiment 11

[0098] In this example, the modified sulfonic acid resin catalyst 1-1 prepared in Example 1 was used to catalyze the esterification reaction, and the specific steps are as follows:

[0099] (1) In a reaction kettle equipped with a condenser and a water separator, 100 g of p-tert-butylbenzoic acid and 72 g of anhydrous methanol are added, and the mixture is stirred and mixed to make the p-tert-butylbenzoic acid fully dissolved in the anhydrous methanol, and then 10 g of a modified sulfonic acid resin catalyst is added, and the temperature is rapidly increased to 140° C. at a rate of 8° C. / min, and the temperature is kept for 20 min; then the temperature is decreased to 120° C. at a rate of 3° C. / min, and the temperature is kept for 100 min; finally, the temperature is decreased to 90° C. at a rate of 3° C. / min, and the temperature is kept for 50 min; the methanol volatilized during the reaction is collected through a condenser, dried, and refluxed into the reaction equipment;

[0100] (2) adding water to the reaction product, stirring and then performing solid-liquid separation, wherein the liquid is the crude product of methyl p-tert-butylbenzoate; repeatedly extracting the liquid, combining the ester layers; and finally performing reduced pressure distillation to obtain the refined product of methyl p-tert-butylbenzoate with a purity of ≧99.99%.

[0101] Example 12

[0102] In this example, the modified sulfonic acid resin catalyst 1-1 prepared in Example 1 was used to catalyze the esterification reaction, and the specific steps are as follows:

[0103] (1) In a reaction kettle equipped with a condenser and a water separator, 100 g of p-tert-butylbenzoic acid and 89 g of anhydrous methanol are added, and the mixture is stirred and mixed to make the p-tert-butylbenzoic acid fully dissolved in the anhydrous methanol, and then 10 g of a modified sulfonic acid resin catalyst is added, and the temperature is rapidly increased to 140° C. at a rate of 8° C. / min, and the temperature is kept for 20 min; then the temperature is decreased to 120° C. at a rate of 3° C. / min, and the temperature is kept for 90 min; finally, the temperature is decreased to 90° C. at a rate of 3° C. / min, and the temperature is kept for 30 min; the methanol volatilized during the reaction is collected through a condenser, dried, and refluxed into the reaction equipment;

[0104] (2) adding water to the reaction product, stirring and then performing solid-liquid separation, wherein the liquid is the crude product of methyl p-tert-butylbenzoate; repeatedly extracting the liquid, combining the ester layers; and finally performing reduced pressure distillation to obtain the refined product of methyl p-tert-butylbenzoate with a purity of ≧99.99%.

[0105] Comparative Example 1

[0106] In this comparative example, the sulfonic acid resin catalyst D1 prepared in Example 1 was used to catalyze the esterification reaction to obtain methyl p-tert-butylbenzoate with a purity of ≧99.99%. The specific steps were the same as those in Example 2.

[0107] Comparative Example 2

[0108] In this comparative example, the steps of Example 2 were repeated to obtain methyl p-tert-butylbenzoate with a purity of ≧99.99%. The difference was that the temperature of the esterification reaction was not stepped, but was rapidly heated to 140°C at a rate of 8°C / min and kept warm for 4 hours until the reaction system reached equilibrium.

[0109] Comparative Example 3

[0110] In this comparative example, the steps of Example 2 were repeated to obtain methyl p-tert-butylbenzoate with a purity of ≧99.99%. The difference was that the temperature of the esterification reaction was not stepped, but was rapidly heated to 120°C at a rate of 8°C / min and kept warm for 5 hours until the reaction system reached equilibrium.

[0111] Comparative Example 4

[0112] In this comparative example, the steps of Example 2 were repeated to obtain methyl p-tert-butylbenzoate with a purity of ≧99.99%. The difference was that the temperature of the esterification reaction was not stepped, but was rapidly heated to 90°C at a rate of 8°C / min and kept warm for 7.5 hours until the reaction system reached equilibrium.

[0113] Comparative Example 5

[0114] This comparative example repeats the steps of Example 2 to obtain methyl p-tert-butylbenzoate with a purity of ≧99.99%. The difference is that the temperature of the esterification reaction is not stepwise, specifically:

[0115] The temperature was lowered to 90°C at a rate of 3°C / min and kept at this temperature for 60 min; then the temperature was lowered to 120°C at a rate of 3°C / min and kept at this temperature for 120 min; finally, the temperature was rapidly raised to 140°C at a rate of 8°C / min and kept at this temperature for 30 min; the methanol volatilized during the reaction was collected through a condenser and then dried and refluxed into the reaction equipment.

[0116] Comparative Example 6

[0117] In this comparative example, the steps of Example 2 were repeated to obtain a fine product of methyl p-tert-butylbenzoate with a purity of ≧99.99%. The difference was that the methanol volatilized during the esterification reaction was collected through a condenser and was not refluxed.

[0118] The weight of the methyl p-tert-butylbenzoate MPTBBA products obtained in Examples 2 to 12 and Comparative Examples 1 to 6 was measured, and the molar conversion rate of p-tert-butylbenzoic acid PTBBA was calculated. The results are shown in Table 2.

[0119] Table 2

[0120]

[0121]

[0122] From the data in Table 2, it can be seen that the modified sulfonic acid resin catalyst of the embodiment of the present invention and the stepwise esterification reaction of first heating and then cooling can produce methyl p-tert-butylbenzoate with a purity of ≧99.99%, and the conversion rate of p-tert-butylbenzoic acid exceeds 99%.

[0123] From the data of Examples 2 to 4, it can be seen that as the content of sulfonic acid resin in the modified sulfonic acid resin catalyst increases, its catalytic performance first increases and then decreases. The reason is that the increase of sulfonic acid resin will increase the acid value, but excessive increase leads to a decrease in its binding efficiency with calcium salt, resulting in a decrease in catalytic activity points.

[0124] It can be seen from the data of Examples 2 and 5 to 6 that the calcium salt using a composite calcium salt of calcium sulfate and calcium silicate has a higher catalytic conversion effect than single calcium sulfate or calcium silicate, and single calcium silicate is better than single calcium sulfate.

[0125] It can be seen from the data of Example 2, Example 7 and Example 8 that as the esterification reaction temperature increases, the conversion rate increases.

[0126] It can be seen from the data of Examples 2, 9 and 10 that as the amount of catalyst increases, even if the reaction time is reduced, the conversion rate does not decrease, but increases slightly.

[0127] It can be seen from the data of Example 2, Example 11 and Example 12 that as the amount of anhydrous methanol increases, the conversion rate still increases even if the reaction time is reduced.

[0128] It can be seen from the data of Example 2 and Comparative Example 1 that the catalytic effect of the modified sulfonic acid resin of the present invention is better than that of the unmodified perfluorosulfonic acid resin.

[0129] From the data of Example 2 and Comparative Examples 2 to 4, it can be seen that the conversion rate of the stepwise esterification reaction of first heating and then cooling of the present invention is better than that of a single temperature and takes less time.

[0130] It can be seen from the data of Example 2 and Comparative Example 5 that the conversion rate of the stepwise esterification reaction of first heating and then cooling of the present invention is better than the conversion rate of the stepwise esterification reaction of gradually heating and cooling.

[0131] It can be seen from the data of Example 2 and Comparative Example 6 that the reaction conversion rate of methanol reflux during the esterification reaction of the present invention is much better than that of methanol without reflux. The reason is that methanol volatilization leads to insufficient raw materials and incomplete reaction.

[0132] Embodiment 13

[0133] This example is used to test the cyclic stability of the catalyst, specifically: the modified sulfonic acid resin catalyst separated after the reaction in Example 2 is cleaned and dried, and then steps (4) and (5) of Example 1 are repeated to obtain a modified sulfonic acid resin; the modified sulfonic acid resin is recycled and used as a catalyst to repeat the reaction steps of Example 2.

[0134] Repeat the above steps, measure the weight of the refined methyl p-tert-butylbenzoate MPTBBA obtained at different cycle times, and calculate the conversion rate. The results are shown in Table 3.

[0135] Table 3

[0136] Cycle times Conversion rate / % 1 99.40 3 99.56 6 99.63 8 99.40 10 99.30 12 98.53 14 97.36 15 94.11

[0137] It can be seen from the data in Table 3 that the modified sulfonic acid resin catalyst of the embodiment of the present invention has stable catalytic performance, and its activity will not be significantly reduced within 10 cycles. The reason is that part of the skeleton of the sulfonic acid resin is destroyed during the cycle, and more acid sites are exposed.

[0138] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for synthesizing methyl p-tert-butylbenzoate, characterized in that: The synthesis method comprises the following steps: The molten sulfonic acid resin and the calcium salt of nano powder are mixed and then rapidly solidified to form mixed particles, and then acid-washed, activated, cleaned and dried in sequence to obtain a modified sulfonic acid resin catalyst; the calcium salt is at least one of calcium sulfate and calcium silicate; Adding p-tert-butylbenzoic acid and anhydrous methanol into a reaction device, and carrying out a stepwise esterification reaction of first heating and then cooling at 90° C. to 150° C. under the catalysis of a modified sulfonic acid resin catalyst, and then carrying out post-treatment to obtain methyl p-tert-butylbenzoate; Among them, according to the molar ratio, p-tert-butylbenzoic acid: anhydrous methanol = 1:3 to 1:

5.

2. A method for synthesizing methyl p-tert-butylbenzoate according to claim 1, characterized in that: The preparation steps of the modified sulfonic acid resin catalyst include: The calcium salt is subjected to high-energy ball milling to obtain nano powder; the sulfonic acid resin is heated and kept warm to obtain the molten sulfonic acid resin; The nano powder is mixed evenly with the molten sulfonic acid resin, and the mixture is kept warm for at least 30 minutes to obtain a modified sulfonic acid resin precursor; The modified sulfonic acid resin precursor is made into powder by gas atomization to obtain mixed particles of the modified sulfonic acid resin precursor; soaking the mixed particles of the modified sulfonic acid resin precursor in a dilute inorganic acid for activation; After solid-liquid separation, the solid is cleaned and dried at low temperature to obtain a modified sulfonic acid resin catalyst; Wherein, the inorganic dilute acid is dilute sulfuric acid or dilute hydrochloric acid.

3. A method for synthesizing methyl p-tert-butylbenzoate according to claim 2, characterized in that: The modified sulfonic acid resin catalyst comprises the following raw materials in weight percentage: 50% to 60% sulfonic acid resin; 40% to 50% calcium salt; the sulfonic acid resin is perfluorosulfonic acid resin.

4. A method for synthesizing methyl p-tert-butylbenzoate according to claim 3, characterized in that: The 40% to 50% calcium salt includes 20% to 25% calcium sulfate and 20% to 25% calcium silicate.

5. A method for synthesizing methyl p-tert-butylbenzoate according to claim 1, characterized in that: The esterification reaction adopts a temperature-raising reflux reaction. A condenser and a water separator are installed on the reaction equipment. The methanol volatilized during the reaction is collected by the condenser and then dried and refluxed into the reaction equipment.

6. A method for synthesizing methyl p-tert-butylbenzoate according to claim 1, characterized in that: The stepwise esterification reaction specifically comprises: In the first stage, the temperature inside the reaction equipment is quickly raised to 140°C to 150°C and kept at this temperature for 20min to 30min; In the second stage, the temperature is lowered to 120℃~130℃ and kept warm for 90min~120min; In the third stage, the temperature is lowered to 90℃~110℃ and kept warm for 30min~60min.

7. A method for synthesizing methyl p-tert-butylbenzoate according to claim 2, characterized in that: In the process of uniformly mixing the nano powder and the molten sulfonic acid resin, the nano powder is added to the molten sulfonic acid resin in batches, and the number of batches is not less than three times.

8. A method for synthesizing methyl p-tert-butylbenzoate according to claim 2 or 7, characterized in that, In the process of uniformly mixing the nano powder and the molten sulfonic acid resin, ultrasonic and / or microwave treatment is performed.

9. A method for synthesizing methyl p-tert-butylbenzoate according to claim 1, characterized in that: In the esterification reaction, the amount of the modified sulfonic acid resin catalyst used is 10% to 30% by weight of p-tert-butylbenzoic acid.

10. The method for synthesizing methyl p-tert-butylbenzoate according to claim 1, characterized in that: The post-treatment is specifically as follows: adding water to the reaction product and stirring it to separate the solid from the liquid, wherein the liquid is the crude methyl p-tert-butylbenzoate; repeatedly extracting the liquid, combining the ester layers; and finally performing reduced pressure distillation to obtain the refined methyl p-tert-butylbenzoate.

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