Synthesis method and application of catalyst stannous p-toluenesulfonate

Abstract

The invention provides a synthesis method and application of a catalyst stannous p-toluenesulfonate, firstly, p-toluenesulfonic acid and stannous oxide are added into water for reaction, and after the reaction is finished, standing is performed to layer reaction liquid; secondly, heating the supernate under a vacuum condition to evaporate moisture of the supernate to dryness; and finally, evaporating the supernate to dryness, and putting the supernate into a vacuum oven to obtain the stannous p-toluenesulfonate. And mixing the lactic acid oligomer with stannous p-toluenesulfonate, and carrying out condensation polymerization under a vacuum condition to obtain polylactic acid.

Description

Technical Field

[0001] The invention relates to the field of catalysts, and in particular to a synthesis method and application of a catalyst stannous p-toluenesulfonate. Background Art

[0002] The molecular formula of stannous p-toluenesulfonate is C 14 H 14 O6S2Sn, with a molecular weight of 461.11, is a white needle-shaped or powdery crystal with a pungent odor, is easily oxidized, is soluble in water, and reacts with water at low temperatures to produce a white precipitate that is insoluble in water. In the prior art, there are many types of tin catalysts, such as stannous chloride, stannous octoate, dibutyltin dilaurate, etc. For the polycondensation of lactic acid, stannous chloride, stannous octoate, etc. are commonly used polymerization catalysts, but stannous chloride contains chloride ions, which is highly corrosive and has high requirements on equipment materials, making it difficult to achieve in industry, and stannous octoate has poor polarity and poor compatibility with polar media such as lactic acid, which affects the catalytic activity. Summary of the invention

[0003] In view of the deficiencies in the prior art, the technical problem to be solved by the present invention is to provide a method for synthesizing and applying a catalyst stannous p-toluenesulfonate which has a simple preparation process and is easy to realize industrially. The catalyst has good catalytic effect and high efficiency in the polymerization process of lactic acid, the polymerization reaction takes a short time, and the prepolymer produced by polycondensation and the intermediate produced by cracking have high and stable optical purity.

[0004] To solve the above problems, the present invention provides the following technical solutions:

[0005] The synthesis method of catalyst stannous p-toluenesulfonate comprises the following steps:

[0006] (1) adding p-toluenesulfonic acid (TSA) and stannous oxide (SnO) to water for reaction, and after the reaction is completed, standing at 100-150° C. for 5-20 minutes to allow the reaction solution to separate into layers;

[0007] (2) After the reaction solution is separated into layers, the supernatant is poured into a flask at 100-150° C. and heated under vacuum to evaporate the water in the supernatant;

[0008] (3) After evaporating the water content of the supernatant, the supernatant is placed in a vacuum oven at a drying temperature of 100-150° C. for 3-8 h to obtain stannous p-toluenesulfonate.

[0009] Preferably, the technical solution of the present invention further comprises that the molar ratio of p-toluenesulfonic acid and stannous oxide added to the reaction is (0.5-1.5):1.

[0010] Preferably, the technical solution of the present invention further comprises that the molar ratio of p-toluenesulfonic acid and stannous oxide added to the reaction is (0.8-1.2):1.

[0011] The technical solution of the present invention also includes that the reaction temperature of p-toluenesulfonic acid and stannous oxide is 100-150° C. and the reaction time is 5-10 hours.

[0012] The technical solution of the present invention also includes purifying the stannous p-toluenesulfonate obtained in step (3) by a solvent crystallization method, wherein the solvent is a polar solvent.

[0013] Furthermore, the technical solution of the present invention also includes the step of purifying the stannous p-toluenesulfonate obtained in step (3) by a solvent crystallization method, wherein the solvent is water.

[0014] The second object of the present invention is to provide an application of stannous p-toluenesulfonate in lactic acid polymerization, comprising the steps of mixing lactic acid oligomer with stannous p-toluenesulfonate, and carrying out polycondensation reaction under vacuum conditions at a polymerization temperature of 150-200° C. and a stirring speed of 120-180 rpm / min to obtain polylactic acid. The lactic acid oligomer refers to a polymer with a low degree of polymerization obtained by dehydrating a lactic acid solution.

[0015] Furthermore, the technical solution of the present invention also includes that, in the application, the mass ratio of the lactic acid oligomer to stannous p-toluenesulfonate is 100:(0.01-0.5).

[0016] Furthermore, the technical solution of the present invention also includes that in the application, the mass ratio of the lactic acid oligomer and stannous p-toluenesulfonate is 100:(0.02-0.25).

[0017] The beneficial effects of the present invention are:

[0018] Compared with the prior art, the purpose of the present invention is to provide a method for synthesizing stannous toluenesulfonate, a catalyst with a simple preparation process, easy to implement in industry and good catalytic effect, and its application. The present invention adopts p-toluenesulfonic acid and stannous oxide to react, and utilizes the different solubility of stannous toluenesulfonate and stannous oxide in water to achieve simple separation. The synthesis method of the present invention has a simple process and is easy to implement in industry. In addition, the catalyst stannous toluenesulfonate of the present invention has good water solubility and better compatibility with the lactic acid system. Compared with the catalyst of the prior art, the catalyst of the present application makes the polymerization reaction of lactic acid take shorter time, and the optical purity of the prepolymer produced by polycondensation and the intermediate produced by cracking is more stable, the optical purity decreases less, and the cracking speed is faster. DETAILED DESCRIPTION

[0019] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0020] Synthesis of catalyst stannous p-toluenesulfonate:

[0021] 20 g TSA (purity: 99%), 15 g SnO, and 30 g pure water were added to a flask, and the reaction was carried out in an oil bath and stirring environment. The temperature of the oil bath was raised to 120° C. The stirring speed during the reaction was 60 rpm / min, and the reaction time was 7 hours.

[0022] After the reaction is completed, stand at 120°C for 10 minutes to allow the reaction liquid to separate, and quickly pour the supernatant into another flask at 120°C. Install a stirring device and a condensing device, and heat and evaporate to remove water in the supernatant under vacuum conditions. The heating temperature is 120°C, and the stirring speed of the stirring device is 60rpm / min.

[0023] After removing water for 1 hour, the flask was placed in a vacuum oven at 120° C. and dried for 5 hours to obtain the catalyst stannous p-toluenesulfonate.

[0024] The application of the above-mentioned stannous p-toluenesulfonate as a catalyst in the polymerization process of lactic acid:

[0025] 202.63g of lactic acid oligomer and 0.42g of stannous p-toluenesulfonate were added to the flask, and the polymerization reaction was carried out in an oil bath and stirring environment. The temperature of the oil bath pot was raised to 180°C, the stirring speed was set to 150rpm / min, and the polycondensation was carried out under a vacuum degree of 1.785mmHg. Samples were taken at 2h, 4h, and 5h of polycondensation to detect the molecular weight and optical purity of the oligomeric polylactic acid. The results are shown in Table 1.

[0026] Table 1 Polylactic acid test data using stannous p-toluenesulfonate as a catalyst in this embodiment

[0027] sample Number average molecular weight / g / mol Optical purity / % Oligomer 225 - Polycondensation 2h polylactic acid 767 99.56 Polycondensation 4h polylactic acid 1477 99.51 Polycondensation 5h polylactic acid 1669 99.52

[0028] It should be noted that the calculation formula for optical purity is: m L-乳酸 / (m L-乳酸 +m D-乳酸 )×100%.

[0029] Comparative Example:

[0030] 202.63g of oligomer and 0.42g of stannous octoate catalyst were added to the flask, the oil bath temperature was raised to 180°C, the stirring speed was 150rpm / min, and polycondensation was carried out under the condition of vacuum degree of 1.785mmHg. Samples were taken at 2h, 4h, and 5h of polycondensation to detect the molecular weight and optical purity of the oligomeric polylactic acid. The results are shown in Table 2.

[0031] Table 2 Polylactic acid test data using stannous octoate as catalyst

[0032] sample Number average molecular weight / g / mol Optical purity, %L / (L+D)×100 Oligomer 225 - Polycondensation 2h 657 99.43 Polycondensation 4h 1288 99.36 Polycondensation 5h 1628 99.28

[0033] From Table 1 and Table 2 of the above specific embodiments, it can be seen that the optical purity of the oligomer prepared by the catalyst of the present invention is 99.52%, which is greater than the optical purity of the oligomer prepared by using stannous octoate, which is 99.28%. Compared with the stannous octoate catalyst, the catalyst of the present invention has a shorter polymerization reaction time, and the optical purity of the prepolymer produced by polycondensation and the intermediate produced by cracking is more stable, the optical purity decreases very little, and the cracking speed is faster, thereby improving the yield of polylactic acid.

[0034] Although the present invention has been described in detail by way of preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, a person of ordinary skill in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and these modifications or substitutions shall be within the scope of the present invention. Any person of ordinary skill in the art who is familiar with the present invention may easily think of changes or substitutions within the technical scope disclosed by the present invention, and these shall be within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. A method for synthesizing catalyst stannous p-toluenesulfonate, characterized in that: The following steps are involved: Add p-toluenesulfonic acid and stannous oxide into water for reaction. After the reaction is completed, stand at 100-150° C. for 5-20 minutes to separate the reaction solution into layers. After the reaction solution is separated into layers, the supernatant is poured into a flask at 100-150°C and heated to evaporate the water in the supernatant under vacuum; After the water content of the supernatant is evaporated, the supernatant is placed in a vacuum oven at a drying temperature of 100-150° C. for 3-8 hours to obtain stannous p-toluenesulfonate.

2. The method for synthesizing the catalyst stannous toluenesulfonate as claimed in claim 1, characterized in that: The molar ratio of p-toluenesulfonic acid and stannous oxide added to the reaction is (0.5-1.5):

1.

3. The method for synthesizing the catalyst stannous toluenesulfonate as claimed in claim 2, characterized in that: The molar ratio of p-toluenesulfonic acid and stannous oxide added to the reaction is (0.8-1.2):

1.

4. The method for synthesizing the catalyst stannous toluenesulfonate as claimed in claim 1, characterized in that: The reaction temperature of p-toluenesulfonic acid and stannous oxide is 100-150° C., and the reaction time is 5-10 hours.

5. The method for synthesizing the catalyst stannous p-toluenesulfonate as claimed in claim 1, characterized in that: The stannous p-toluenesulfonate obtained in step (3) is purified by a solvent crystallization method, wherein the solvent is a polar solvent.

6. The method for synthesizing the catalyst stannous p-toluenesulfonate as claimed in claim 5, characterized in that: The solvent is water.

7. The use of stannous p-toluenesulfonate in lactic acid polymerization according to any one of claims 1 to 6, characterized in that: The lactic acid oligomer is mixed with stannous p-toluenesulfonate, and a polycondensation reaction is carried out under vacuum conditions at a polymerization temperature of 150-200° C. and a stirring speed of 120-180 rpm / min to obtain polylactic acid.

8. The use of stannous p-toluenesulfonate in lactic acid polymerization as claimed in claim 7, characterized in that: The mass ratio of the lactic acid oligomer to stannous p-toluenesulfonate is 100:(0.01-0.5).

9. The use of stannous p-toluenesulfonate in lactic acid polymerization as claimed in claim 8, characterized in that: The mass ratio of the lactic acid oligomer to stannous p-toluenesulfonate is 100:(0.02-0.25).