Preparation method of dipropylene glycol with low freezing point

Abstract

The invention discloses a preparation method of low-freezing-point dipropylene glycol, which comprises the following steps: carrying out condensation reaction on propylene oxide and propylene glycol by using a solid acid catalyst, and carrying out post-treatment to obtain the low-freezing-point dipropylene glycol. The sulfonic acid is loaded on the high-porosity inorganic nanoparticles, and the surface of the inorganic nanoparticles is modified with the crown ether in the form of a long cantilever, so that the preparation process of the dipropylene glycol is simplified, the dipropylene glycol with a low freezing point is obtained, the purity and the yield of the dipropylene glycol are improved, and the method is suitable for industrial production. And the solid acid catalyst still has good catalytic activity after being recycled for many times.

Description

Technical Field

[0001] The invention relates to the technical field of dipropylene glycol processing, and in particular to a method for preparing dipropylene glycol with a low freezing point. Background Art

[0002] Dipropylene glycol (DPG for short) is a colorless, odorless liquid at room temperature. It is non-corrosive and has very low toxicity. It is widely used in antifreeze, air fresheners, cosmetics, solvents, adhesives, lubricants, plastics, paints, coatings and printing inks.

[0003] Dipropylene glycol in the prior art has Among these three isomers, DPG-1 has a freezing point of 45-46.5℃ and is solid at room temperature, while DPG-2 and DPG-3 have lower freezing points and will not solidify even at a low temperature of -40℃. Traditional dipropylene glycol tends to crystallize and solidify in winter and can only be used in low-end fields such as unsaturated resins and industrial solvents, but is difficult to use in high-end fields such as flavors and fragrances, and cosmetics.

[0004] The prior art, an invention patent with publication number CN106831358A, discloses a method for preparing dipropylene glycol, which uses propylene oxide and propylene glycol as reaction raw materials, adopts a specific acidic ionic liquid as a catalyst, and synthesizes dipropylene glycol under certain temperature and pressure conditions. The ionic liquid catalyst used has high catalytic activity, so that the reaction conversion rate is high, and the freezing point of the obtained dipropylene glycol product is lowered, solving the problem of winter transportation and storage.

[0005] Although the above patent uses acidic ionic liquid as a catalyst to effectively reduce the freezing point of dipropylene glycol, the catalyst is a liquid. Even if the liquid catalyst can effectively improve the catalytic efficiency, its post-processing is complicated and the regeneration and recycling of the catalyst is difficult. For traditional solid acids as catalysts, in a liquid environment, the reactants need to diffuse to the catalyst surface to react with it. This diffusion process is affected by the interface barrier between the solid and liquid phases, which leads to the need for further improvement of the solid catalytic efficiency.

[0006] In view of the technical defects in this aspect, a solution is now proposed. Summary of the invention

[0007] The object of the present invention is to provide a method for preparing dipropylene glycol with a low freezing point, so as to solve the technical problems in the prior art that the freezing point of dipropylene glycol is high and the catalytic synthesis efficiency of dipropylene glycol and the regeneration and recycling performance of the catalyst need to be further improved.

[0008] The purpose of the present invention can be achieved by the following technical scheme: a method for preparing dipropylene glycol with a low freezing point, wherein the method for preparing dipropylene glycol with a low freezing point comprises: using a solid acid catalyst to carry out a condensation reaction of propylene oxide and propylene glycol, and post-treating to obtain dipropylene glycol with a low freezing point.

[0009] Furthermore, the dosage ratio of propylene oxide and propylene glycol is 1 mol:1.3-1.5 mol, the dosage of the solid acid catalyst is 4-6% of the total weight of propylene oxide and propylene glycol, the condensation reaction temperature is 80-100° C., the reaction pressure is 0.1-0.3 MPa, and the reaction time is 2-3 h. The post-treatment includes: after the reaction is completed, the temperature of the reaction system is lowered to room temperature, filtered, and the filtrate is transferred to a distillation tower with a temperature of 110-130° C. and a negative pressure of 0.1 MPa, and distilled to remove low-boiling impurities to obtain dipropylene glycol with a low freezing point.

[0010] Further, the solid acid catalyst is processed by the following steps:

[0011] A1. Add the composite polysiloxane microspheres to the activation solution, raise the temperature of the reaction system to reflux, keep the temperature for 90-120 minutes, and post-treat to obtain activated microspheres;

[0012] The synthetic reaction mechanism of activated microspheres is:

[0013] When the composite polysiloxane microspheres are in the activation solution, the zinc in the carbonized layer is dissolved and eluted, thereby increasing the porosity of the carbonized layer. At the same time, the activation solution composed of nitric acid and hydrogen peroxide can also etch the carbonized layer on the surface of the microspheres, while introducing oxygen-containing functional groups to prepare activated microspheres and improve the reaction activity of the activated microspheres.

[0014] A2. Under the protection of inert gas, activated microspheres and 1,3-propane sultone are added to tetrahydrofuran and stirred. The temperature of the reaction system is raised to reflux, and the reaction is kept warm for 8-10 hours. The solid acid catalyst precursor is obtained by post-treatment.

[0015] The synthetic reaction mechanism of the solid acid catalyst precursor is:

[0016] Stirring is used to promote full contact between 1,3-propane sultone and the activated microspheres. Under high temperature, 1,3-propane sultone begins to open its ring and undergoes esterification reaction with the hydroxyl groups on the surface of the microspheres, forming sulfonic acid group modification on the activated microsphere particles, thereby preparing a solid acid catalyst precursor.

[0017] A3. Add the acid catalyst precursor and the modified crown ether into the ethanol solution and stir. Raise the temperature of the reaction system to 50-60°C, keep the reaction warm for 60-80 minutes, and post-treat to obtain a solid acid catalyst.

[0018] The synthetic reaction mechanism of solid acid catalyst is:

[0019] During the reaction, the sulfonic acid groups on the acidic catalyst precursor particles provide an acidic environment to catalyze the scission of the siloxane bonds on the modified crown ether molecules and form crown ether grafting modifications with the acidic catalyst precursor molecules to prepare a solid acid catalyst.

[0020] Furthermore, in step A1, the amount ratio of the composite polysiloxane microspheres to the activation solution is 1g:10mL, the activation solution is composed of 28-32wt% nitric acid and 30wt% hydrogen peroxide in a volume ratio of 3:1, and the post-treatment includes: after the reaction is completed, the temperature of the reaction system is lowered to room temperature, filtered, the filter cake is washed 3 times with 3-5wt% nitric acid and then washed with deionized water until neutral, drained, and the filter cake is transferred to a drying oven at a temperature of 70-80°C, and vacuum dried to constant weight to obtain activated microspheres.

[0021] Further, in step A2, the amount ratio of the activated microspheres, 1,3-propane sultone and tetrahydrofuran is 3g:2g:15mL, and the post-treatment includes: after the reaction is completed, the temperature of the reaction system is lowered to room temperature, suction filtration, the filter cake is washed with tetrahydrofuran three times and then dried, the filter cake is transferred to a drying oven at a temperature of 60-70°C, and vacuum dried to constant weight to obtain a solid acid catalyst precursor; in step A3, the amount ratio of the solid acid catalyst precursor, modified crown ether and ethanol solution is 5g:1g:50mL, and the ethanol solution is composed of anhydrous ethanol and purified water in a volume ratio of 7:3, and the post-treatment includes: after the reaction is completed, the temperature of the reaction system is lowered to room temperature, suction filtration, the filter cake is washed with anhydrous ethanol three times and then dried, the filter cake is transferred to a drying oven at a temperature of 70-80°C, and vacuum dried to constant weight to obtain a solid acid catalyst.

[0022] Further, the composite polysiloxane microspheres are processed by the following steps:

[0023] B1, adding polysiloxane microspheres to the glucose solution and stirring, raising the temperature of the reaction system to 80-90°C, adding a catalyst to the reaction system, keeping the temperature for 5-7h, and post-treating to obtain a composite polysiloxane microsphere precursor;

[0024] B2. Immerse the composite polysiloxane microsphere precursor in a zinc chloride solution, raise the temperature of the reaction system to 65-75° C., keep warm and immerse for 6-7 hours, and post-treat to obtain composite polysiloxane microspheres.

[0025] The synthetic reaction mechanism of composite polysiloxane microspheres is:

[0026] Under the action of sodium hydroxide as a catalyst and high temperature, glucose molecules in the reaction system undergo a dehydration condensation reaction to form glycosidic bonds, while hydroxyl groups in the glucose molecules undergo a ring-opening reaction with epoxy groups on the surface of polysiloxane microspheres to form ether bonds, and glucose is loaded on polysiloxane microsphere particles to prepare a composite polysiloxane microsphere precursor; the composite polysiloxane microsphere precursor is introduced into a zinc chloride solution, and under acidic conditions, zinc ions in the zinc chloride solution react with functional groups such as hydroxyl groups and carboxyl groups on the surface or inside of the composite polysiloxane microsphere precursor to form coordination bonds or ionic bonds, and are fixed on the surface or inside of the microspheres; glucose is used as a carbonization base material and carbonized at high temperature in a nitrogen environment to prepare composite silicone microspheres.

[0027] Furthermore, in step B1, the dosage ratio of the polysiloxane microspheres, the glucose solution and the catalyst is 5g:30mL:1g, the glucose solution is composed of glucose and deionized water in a dosage ratio of 1g:8mL, the catalyst is sodium hydroxide, and the post-treatment includes: after the reaction is completed, the temperature of the reaction system is lowered to room temperature, filtered, the filter cake is washed with deionized water until it is neutral and then dried, the filter cake is transferred to a drying oven at a temperature of 70-80°C, and vacuum dried to constant weight to obtain a composite polysiloxane microsphere precursor.

[0028] Furthermore, in step B2, the amount ratio of the composite polysiloxane microsphere precursor and the zinc chloride solution is 1g:5mL, and the zinc chloride solution is composed of zinc chloride and 0.1-0.5mol / L hydrochloric acid at 1g:6mL. The post-treatment includes: after the reaction is completed, the temperature of the reaction system is reduced to room temperature, anhydrous ethanol is added to the reaction system, and the mixture is stirred for 20-30min, filtered, and the filter cake is transferred to a drying oven at a temperature of 70-80°C, vacuum dried for 4-6h, and the solid matter is transferred to a nitrogen-protected tubular furnace. The temperature of the tubular furnace is increased to 500-600°C, and the mixture is kept warm for 3-5h, and then naturally cooled to room temperature to obtain composite polysiloxane microspheres.

[0029] Furthermore, the preparation method of polysiloxane microspheres is as follows: after evenly mixing tetraethyl orthosilicate and KH-560, slowly adding them into the emulsion, homogenizing and emulsifying, raising the temperature of the emulsification system to 40-50°C, homogenizing and emulsifying for 6-8h, raising the temperature of the emulsification system to 90-100°C, aging for 30-40h, and post-treating to obtain polysiloxane microspheres.

[0030] The synthetic reaction mechanism of polysiloxane microspheres is:

[0031] During the reaction, during the homogenization of the emulsion, the siloxane bonds on the ethyl orthosilicate and KH-560 molecules are hydrolyzed to form silanol groups, which then undergo a condensation reaction to form siloxane bonds. The mixture of hexadecyltrimethylammonium chloride and diacetyltartaric acid mono- and diglycerides constitutes the basis of the emulsion, forming a stable oil-water interface in the emulsion. Under the high-speed homogenization emulsification environment, a high-porosity structure is formed. Then, through aging treatment, the unreacted silanol groups are promoted to further condense to form a more stable and denser polysiloxane network structure, thereby preparing polysiloxane microspheres.

[0032] Furthermore, the dosage ratio of the tetraethyl orthosilicate, KH-560 and the emulsion is 3g:1g:50mL, the emulsion is composed of deionized water, 8-10mol / L hydrochloric acid, hexadecyltrimethylammonium chloride, and diacetyltartaric acid mono- and diglycerides in a dosage ratio of 50-60mL:40-50mL:4-5g:2-3g, and the post-treatment includes: after the reaction is completed, the temperature of the mixed system is lowered to room temperature, filtered, the filter cake is washed with deionized water until it is neutral and then dried, the filter cake is transferred to a drying oven at a temperature of 70-80°C, and vacuum dried to constant weight to obtain polysiloxane microspheres.

[0033] Furthermore, the preparation method of the modified crown ether is as follows: under the protection of inert gas, 10-isocyanatodecyltrimethoxysilane and 15-crown-5-methanol are added to tetrahydrofuran and stirred, the temperature of the reaction system is increased to 50-60° C., the reaction is kept warm for 2-3 hours, and the modified crown ether is obtained by post-treatment;

[0034] The mass spectrometry analysis data of modified crown ether are: m / z: 539.3126 (100.0%), 540.3159 (26.0%), 540.3121 (5.1%), 541.3094 (3.3%), 541.3193 (3.2%), 541.3168 (2.1%), 541.3155 (1.3%).

[0035] The synthetic reaction mechanism of modified crown ether is:

[0036] During the reaction, the isocyanate group on the 10-isocyanatodecyltrimethoxysilane molecule undergoes a condensation reaction with the hydroxyl group on the 15-crown-5-methanol molecule, and the crown ether molecule is modified with decyltrimethoxysilane to prepare a modified crown ether.

[0037] Furthermore, the dosage ratio of 10-isocyanatodecyltrimethoxysilane and 15-crown-5-methanol is 1 mol:1 mol, and the dosage ratio of 10-isocyanatodecyltrimethoxysilane and tetrahydrofuran is 1 g:6 mL. The post-treatment includes: after the reaction is completed, distilling off tetrahydrofuran under reduced pressure to obtain a modified crown ether.

[0038] The present invention has the following beneficial effects:

[0039] 1. The method for preparing dipropylene glycol with a low freezing point of the present invention increases the loading amount of sulfonic acid and the reaction efficiency by loading sulfonic acid onto solid microspheres. In the process of synthesizing dipropylene glycol, sulfonic acid activates propylene oxide to generate a carbon cation intermediate, wherein the secondary carbon cation is more stable than the primary carbon cation and is more likely to further react with propylene glycol to generate the isomer DPG-2, thereby increasing the content of the isomer DPG-2 in the dipropylene glycol, thereby reducing the freezing point of the dipropylene glycol product. Moreover, the sulfonic acid is loaded on solid particles, and the catalyst can be separated, recovered and reused by simple filtration separation, thereby significantly reducing the difficulty and cost of wastewater treatment and reducing environmental pollution.

[0040] 2. The method for preparing dipropylene glycol with a low freezing point of the present invention uses high-porosity polysiloxane microspheres as a matrix and coats the microspheres with a porous carbon layer to further improve the porosity of the activated microspheres. The rich porosity of the activated microspheres provides abundant attachment sites for 1,3-propane sultone loading, thereby increasing the loading amount of 1,3-propane sultone and the loading amount of sulfonic acid on the activated microspheres, thereby improving the catalytic performance of the catalyst. The sulfonic acid is loaded on the activated microspheres through an ester bond, and the sulfonic acid group has excellent acidity and thermal stability, and the ester bond also has good high temperature resistance, so that the solid acid catalyst exhibits good catalytic activity and regeneration performance.

[0041] 3. The method for preparing dipropylene glycol with a low freezing point of the present invention comprises the following steps: modifying the modified crown ether on the outside of a solid acid catalyst precursor through a siloxane bond; the crown ether, as a phase transfer agent, can complex with positive ions in the reaction system to form a complex, and make the complex soluble in an organic solvent, thereby increasing the contact area between the reactants and improving the reaction rate; and the crown ether is connected to the surface of the solid acid catalyst through a long alkane chain to form a long cantilever on the surface of the solid acid catalyst, further enhancing the contact between the solid acid catalyst and the reactants, reducing the influence of heterogeneous contact caused by the solid acid as a solid catalyst on the catalytic efficiency, and improving the catalytic efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0043] Figure 1 This is the analytical chromatogram of dipropylene glycol prepared in Example 4 of the present invention. DETAILED DESCRIPTION

[0044] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than 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 are within the scope of protection of the present invention.

[0045] Example 1

[0046] This embodiment provides a method for preparing a solid acid catalyst for preparing dipropylene glycol with a low freezing point, comprising the following steps:

[0047] S1. Preparation of polysiloxane microspheres

[0048] Deionized water, 8 mol / L hydrochloric acid, hexadecyltrimethylammonium chloride, and diacetyltartaric acid mono- and diglycerides were mixed uniformly in a ratio of 50 mL: 40 mL: 4 g: 2 g to obtain an emulsion for later use;

[0049] Weigh: 1000 mL of emulsion is added to a homogenizer, the stirring speed is set to 900 r / min, 60 g of ethyl orthosilicate and 20 g of KH-560 are added to the homogenizer, the temperature of the homogenizer system is raised to 40°C, and homogenization is performed for 6 hours;

[0050] The homogeneous emulsified system was transferred to a hydrothermal reactor at a temperature of 90°C and aged for 30 hours. The temperature of the mixed system was lowered to room temperature and filtered. The filter cake was washed with deionized water until neutral and then dried. The filter cake was transferred to a drying oven at a temperature of 70°C and vacuum dried to constant weight to obtain polysiloxane microspheres.

[0051] S2. Preparation of composite polysiloxane microspheres

[0052] Mix glucose and deionized water in a ratio of 1 g:8 mL to obtain a glucose solution for later use;

[0053] Weigh: 50 g of polysiloxane microspheres and 300 mL of glucose solution are added to a three-necked flask and stirred. The temperature of the three-necked flask is raised to 80° C., 10 g of sodium hydroxide is added to the three-necked flask, and the reaction is kept warm for 5 hours. The temperature of the three-necked flask is lowered to room temperature, and the filter cake is filtered, and the filter cake is washed with deionized water until it is neutral and then dried. The filter cake is transferred to a drying oven at a temperature of 70° C. and vacuum dried to constant weight to obtain a composite polysiloxane microsphere precursor;

[0054] Mix zinc chloride and 0.1 mol / L hydrochloric acid at a ratio of 1 g:6 mL to obtain a zinc chloride solution for later use;

[0055] Weigh: 50 g of composite polysiloxane microsphere precursor and 250 mL of zinc chloride solution are added to a three-necked flask and stirred. The temperature of the three-necked flask is increased to 65°C, and the mixture is kept warm and stirred for 6 hours. The temperature of the three-necked flask is lowered to room temperature. 500 mL of anhydrous ethanol is added to the reaction system, and the mixture is kept warm and stirred for 20 minutes. The filter cake is transferred to a drying oven at 70°C and vacuum dried for 4 hours. The solid material is transferred to a nitrogen-protected tubular furnace, the temperature of the tubular furnace is increased to 500°C, and the mixture is kept warm for 3 hours. The mixture is naturally cooled to room temperature to obtain composite polysiloxane microspheres.

[0056] S3. Preparation of activated microspheres

[0057] 28 wt % nitric acid and 30 wt % hydrogen peroxide were mixed uniformly in a volume ratio of 3:1 to obtain an activation solution for later use;

[0058] Weigh: 50 g of composite polysiloxane microspheres and 500 mL of activation solution are added to a three-necked flask and stirred. The temperature of the three-necked flask is raised to reflux and kept warm for 90 minutes. The temperature of the three-necked flask is lowered to room temperature and filtered. The filter cake is washed three times with 3wt% nitric acid and then washed with deionized water until neutral. It is drained and the filter cake is transferred to a drying oven at 70°C and vacuum dried to constant weight to obtain activated microspheres.

[0059] S4. Preparation of solid acid catalyst

[0060] Weigh: 60 g of activated microspheres, 40 g of 1,3-propane sultone, and 300 mL of tetrahydrofuran are added to a three-necked flask protected by nitrogen and stirred. The temperature of the three-necked flask is raised to the reflux of the system, and the reaction is kept warm for 8 hours. The temperature of the three-necked flask is lowered to room temperature, and the filter cake is filtered by suction. The filter cake is washed with tetrahydrofuran for 3 times and then dried. The filter cake is transferred to a drying oven at a temperature of 60°C and vacuum dried to constant weight to obtain a solid acid catalyst precursor;

[0061] Weigh: 30.4 g of 10-isocyanatodecyltrimethoxysilane, 25.0 g of 15-crown ether-5-methanol, and 182.4 g of tetrahydrofuran, add into a three-necked flask protected by nitrogen and stir, raise the temperature of the three-necked flask to 50° C., keep the temperature for 2 h, and evaporate the tetrahydrofuran under reduced pressure to obtain a modified crown ether;

[0062] Mix anhydrous ethanol and purified water in a volume ratio of 7:3 to obtain an ethanol solution for later use;

[0063] Weigh: 50 g of acidic catalyst precursor, 10 g of modified crown ether and 500 mL of ethanol solution into a three-necked flask and stir. The temperature of the three-necked flask is raised to 50°C and the reaction is kept warm for 60 minutes. The temperature of the reaction system is lowered to room temperature and filtered. The filter cake is washed three times with anhydrous ethanol and then dried. The filter cake is transferred to a drying oven at a temperature of 70°C and vacuum dried to constant weight to obtain a solid acid catalyst.

[0064] Example 2

[0065] This embodiment provides a method for preparing a solid acid catalyst for preparing dipropylene glycol with a low freezing point, comprising the following steps:

[0066] S1. Preparation of polysiloxane microspheres

[0067] Deionized water, 9 mol / L hydrochloric acid, hexadecyltrimethylammonium chloride, and diacetyltartaric acid mono- and diglycerides were mixed uniformly in a ratio of 55 mL: 45 mL: 4.5 g: 2.5 g to obtain an emulsion for later use;

[0068] Weigh: 1000 mL of emulsion is added to a homogenizer, the stirring speed is set to 950 r / min, 60 g of tetraethyl orthosilicate and 20 g of KH-560 are added to the homogenizer, the temperature of the homogenizer system is raised to 45°C, and homogenization is performed for 7 hours;

[0069] The homogeneous emulsified system was transferred to a hydrothermal reactor at a temperature of 95°C and aged for 35 hours. The temperature of the mixed system was lowered to room temperature and filtered. The filter cake was washed with deionized water until neutral and then dried. The filter cake was transferred to a drying oven at a temperature of 75°C and vacuum dried to constant weight to obtain polysiloxane microspheres.

[0070] S2. Preparation of composite polysiloxane microspheres

[0071] Mix glucose and deionized water in a ratio of 1 g:8 mL to obtain a glucose solution for later use;

[0072] Weigh: 50 g of polysiloxane microspheres and 300 mL of glucose solution are added to a three-necked flask and stirred. The temperature of the three-necked flask is raised to 85° C., 10 g of sodium hydroxide is added to the three-necked flask, and the reaction is kept warm for 6 hours. The temperature of the three-necked flask is lowered to room temperature, and the filter is filtered. The filter cake is washed with deionized water until it is neutral and then dried. The filter cake is transferred to a drying oven at a temperature of 75° C. and vacuum dried to constant weight to obtain a composite polysiloxane microsphere precursor;

[0073] Mix zinc chloride and 0.3 mol / L hydrochloric acid at a ratio of 1 g:6 mL to obtain a zinc chloride solution for later use;

[0074] Weigh: 50 g of composite polysiloxane microsphere precursor and 250 mL of zinc chloride solution are added to a three-necked flask and stirred. The temperature of the three-necked flask is increased to 70°C, and the mixture is kept warm and stirred for 6.5 hours. The temperature of the three-necked flask is lowered to room temperature, and 500 mL of anhydrous ethanol is added to the reaction system. The mixture is kept warm and stirred for 25 minutes. The filter cake is transferred to a drying oven at 75°C and vacuum dried for 5 hours. The solid material is transferred to a nitrogen-protected tubular furnace. The temperature of the tubular furnace is increased to 550°C, and the mixture is kept warm for 4 hours. The mixture is naturally cooled to room temperature to obtain composite polysiloxane microspheres.

[0075] S3. Preparation of activated microspheres

[0076] 30 wt % nitric acid and 30 wt % hydrogen peroxide were mixed uniformly in a volume ratio of 3:1 to obtain an activation solution for later use;

[0077] Weigh: 50 g of composite polysiloxane microspheres and 500 mL of activation solution are added to a three-necked flask and stirred. The temperature of the three-necked flask is raised to reflux and kept warm for 105 minutes. The temperature of the three-necked flask is lowered to room temperature and filtered. The filter cake is washed three times with 4 wt % nitric acid and then washed with deionized water until neutral. It is drained and the filter cake is transferred to a drying oven at 75° C. and vacuum dried to constant weight to obtain activated microspheres.

[0078] S4. Preparation of solid acid catalyst

[0079] Weigh: 60 g of activated microspheres, 40 g of 1,3-propane sultone, and 300 mL of tetrahydrofuran are added to a three-necked flask protected by nitrogen and stirred. The temperature of the three-necked flask is raised to reflux, and the reaction is kept warm for 9 hours. The temperature of the three-necked flask is lowered to room temperature, and the filter cake is filtered by suction. The filter cake is washed with tetrahydrofuran three times and then dried. The filter cake is transferred to a drying oven at a temperature of 65°C and vacuum dried to constant weight to obtain a solid acid catalyst precursor;

[0080] Weigh: 30.4 g of 10-isocyanatodecyltrimethoxysilane, 25.0 g of 15-crown ether-5-methanol, and 182.4 g of tetrahydrofuran, add into a three-necked flask protected by nitrogen and stir, raise the temperature of the three-necked flask to 55° C., keep the temperature for 2.5 h, and evaporate the tetrahydrofuran under reduced pressure to obtain a modified crown ether;

[0081] Mix anhydrous ethanol and purified water in a volume ratio of 7:3 to obtain an ethanol solution for later use;

[0082] Weigh: 50 g of acidic catalyst precursor, 10 g of modified crown ether and 500 mL of ethanol solution into a three-necked flask and stir. The temperature of the three-necked flask is raised to 55°C and the reaction is kept warm for 70 minutes. The temperature of the reaction system is lowered to room temperature and filtered. The filter cake is washed three times with anhydrous ethanol and then dried. The filter cake is transferred to a drying oven at a temperature of 75°C and vacuum dried to constant weight to obtain a solid acid catalyst.

[0083] Example 3

[0084] This embodiment provides a method for preparing a solid acid catalyst for preparing dipropylene glycol with a low freezing point, comprising the following steps:

[0085] S1. Preparation of polysiloxane microspheres

[0086] Deionized water, 10 mol / L hydrochloric acid, hexadecyltrimethylammonium chloride, and diacetyltartaric acid mono- and diglycerides were mixed uniformly in a ratio of 60 mL: 50 mL: 5 g: 3 g to obtain an emulsion for later use;

[0087] Weigh: 1000 mL of emulsion is added to a homogenizer, the stirring speed is set to 1000 r / min, 60 g of ethyl orthosilicate and 20 g of KH-560 are added to the homogenizer, the temperature of the homogenizer system is raised to 50°C, and homogenization is performed for 8 hours;

[0088] The homogeneous emulsified system was transferred to a hydrothermal reactor at a temperature of 100°C and aged for 40 hours. The temperature of the mixed system was lowered to room temperature and filtered. The filter cake was washed with deionized water until neutral and then dried. The filter cake was transferred to a drying oven at a temperature of 80°C and vacuum dried to constant weight to obtain polysiloxane microspheres.

[0089] S2. Preparation of composite polysiloxane microspheres

[0090] Mix glucose and deionized water in a ratio of 1 g:8 mL to obtain a glucose solution for later use;

[0091] Weigh: 50 g of polysiloxane microspheres and 300 mL of glucose solution are added to a three-necked flask and stirred. The temperature of the three-necked flask is raised to 90° C., 10 g of sodium hydroxide is added to the three-necked flask, and the reaction is kept warm for 7 hours. The temperature of the three-necked flask is lowered to room temperature, and the filter cake is filtered, and the filter cake is washed with deionized water until it is neutral and then dried. The filter cake is transferred to a drying oven at a temperature of 80° C. and vacuum dried to constant weight to obtain a composite polysiloxane microsphere precursor;

[0092] Mix zinc chloride and 0.5 mol / L hydrochloric acid at a ratio of 1 g:6 mL to obtain a zinc chloride solution for later use;

[0093] Weigh: 50 g of composite polysiloxane microsphere precursor and 250 mL of zinc chloride solution are added to a three-necked flask and stirred. The temperature of the three-necked flask is increased to 75°C, and the mixture is kept warm and stirred for 7 hours. The temperature of the three-necked flask is lowered to room temperature. 500 mL of anhydrous ethanol is added to the reaction system, and the mixture is kept warm and stirred for 30 minutes. The filter cake is transferred to a drying oven at 80°C and vacuum dried for 6 hours. The solid material is transferred to a nitrogen-protected tubular furnace. The temperature of the tubular furnace is increased to 5600°C, and the mixture is kept warm for 5 hours. The mixture is naturally cooled to room temperature to obtain composite polysiloxane microspheres.

[0094] S3. Preparation of activated microspheres

[0095] 32 wt % nitric acid and 30 wt % hydrogen peroxide were mixed uniformly in a volume ratio of 3:1 to obtain an activation solution for later use;

[0096] Weigh: 50 g of composite polysiloxane microspheres and 500 mL of activation solution are added to a three-necked flask and stirred. The temperature of the three-necked flask is raised to reflux and kept warm for 120 minutes. The temperature of the three-necked flask is lowered to room temperature and filtered. The filter cake is washed three times with 5wt% nitric acid and then washed with deionized water until neutral. It is drained and the filter cake is transferred to a drying oven at 80°C and vacuum dried to constant weight to obtain activated microspheres.

[0097] S4. Preparation of solid acid catalyst

[0098] Weigh: 60 g of activated microspheres, 40 g of 1,3-propane sultone, and 300 mL of tetrahydrofuran are added to a three-necked flask protected by nitrogen and stirred. The temperature of the three-necked flask is raised to reflux, and the reaction is kept warm for 10 hours. The temperature of the three-necked flask is lowered to room temperature, and the filter cake is filtered, and the filter cake is washed with tetrahydrofuran for 3 times and then dried. The filter cake is transferred to a drying oven at a temperature of 70°C and vacuum dried to constant weight to obtain a solid acid catalyst precursor;

[0099] Weigh: 30.4 g of 10-isocyanatodecyltrimethoxysilane, 25.0 g of 15-crown ether-5-methanol, and 182.4 g of tetrahydrofuran, add into a three-necked flask protected by nitrogen and stir, raise the temperature of the three-necked flask to 60° C., keep the temperature for 3 h, and evaporate the tetrahydrofuran under reduced pressure to obtain a modified crown ether;

[0100] Weigh: 50 g of acidic catalyst precursor, 10 g of modified crown ether and 500 mL of ethanol solution into a three-necked flask and stir. The temperature of the three-necked flask is raised to 60°C and the reaction is kept warm for 80 minutes. The temperature of the reaction system is lowered to room temperature and filtered. The filter cake is washed three times with anhydrous ethanol and then dried. The filter cake is transferred to a drying oven at 80°C and vacuum dried to constant weight to obtain a solid acid catalyst.

[0101] Example 4

[0102] This embodiment provides a method for preparing dipropylene glycol with a low freezing point, comprising:

[0103] 581 g of propylene oxide, 989.3 g of propylene glycol and 62.8 g of the solid acid catalyst prepared in Example 1 were added to a high-pressure reactor and stirred. The temperature of the high-pressure reactor was increased to 80° C., the pressure was increased to 0.1 MPa, and the reaction was maintained at this temperature and pressure for 3 hours.

[0104] After the reaction is completed, the temperature of the autoclave is lowered to room temperature, the filter is filtered, and the filter cake is washed three times with propylene glycol to obtain a regenerated solid acid catalyst. The washing liquid and the filtrate are combined and transferred to a distillation tower with a temperature of 110° C. and a negative pressure of 0.1 MPa. The distillation is carried out to remove low-boiling impurities and obtain dipropylene glycol with a low freezing point.

[0105] Example 5

[0106] This embodiment provides a method for preparing dipropylene glycol with a low freezing point, comprising:

[0107] 581 g of propylene oxide, 1065.4 g of propylene glycol and 82.3 g of the solid acid catalyst prepared in Example 2 were added to a high-pressure reactor and stirred. The temperature of the high-pressure reactor was increased to 90° C., the pressure was increased to 0.2 MPa, and the reaction was maintained at this temperature and pressure for 2.5 hours.

[0108] After the reaction is completed, the temperature of the autoclave is lowered to room temperature, the filter is filtered, and the filter cake is washed three times with propylene glycol to obtain a regenerated solid acid catalyst. The washing liquid and the filtrate are combined and transferred to a distillation tower with a temperature of 120° C. and a negative pressure of 0.1 MPa. The distillation is carried out to remove low-boiling impurities and obtain dipropylene glycol with a low freezing point.

[0109] Example 6

[0110] This embodiment provides a method for preparing dipropylene glycol with a low freezing point, comprising:

[0111] 581 g of propylene oxide, 1141.5 g of propylene glycol and 103.4 g of the solid acid catalyst prepared in Example 3 were added to a high-pressure reactor and stirred. The temperature of the high-pressure reactor was increased to 100° C., the pressure was increased to 0.3 MPa, and the reaction was carried out by maintaining the temperature and pressure for 2 hours.

[0112] After the reaction is completed, the temperature of the autoclave is lowered to room temperature, the filter is filtered, and the filter cake is washed three times with propylene glycol to obtain a regenerated solid acid catalyst. The washing liquid and the filtrate are combined and transferred to a distillation tower with a temperature of 130° C. and a negative pressure of 0.1 MPa. The distillation is carried out to remove low-boiling impurities to obtain dipropylene glycol with a low freezing point.

[0113] Comparative Example 1

[0114] The difference between this comparative example and Example 6 is that, when preparing the solid acid catalyst used, the composite polysiloxane microsphere precursor in step S2 is used to replace the composite polysiloxane microsphere in step S3.

[0115] Comparative Example 2

[0116] The difference between this comparative example and Example 6 is that when the solid acid catalyst used is prepared, the solid acid catalyst in step S4 is replaced by the solid acid catalyst precursor in step S4.

[0117] Comparative Example 3

[0118] The difference between this comparative example and Example 6 is that the solid acid catalyst used is composed of a mixture of a solid acid catalyst precursor and 15-crown ether-5-methanol in a weight ratio of 5:1.

[0119] Performance Testing:

[0120] The freezing point temperatures of the dipropylene glycol samples prepared in Examples 4-6 and Comparative Examples 1-3 were determined according to the standard GB / T 510-2018 "Determination of freezing point of petroleum products";

[0121] The purity of the dipropylene glycol samples prepared in Examples 4-6 and Comparative Examples 1-3 was determined according to standard HG / T 5799-2021 "Dipropylene glycol";

[0122] Reference formula Calculate the yield of dipropylene glycol prepared in Examples 4-6 and Comparative Examples 1-3, where m DGP is the mass of dipropylene glycol obtained, w DGP is the purity of dipropylene glycol, m 环氧丙烷 is the mass of propylene oxide, M 环氧丙烷 is the molecular weight of propylene oxide, M DGP is the molecular weight of dipropylene glycol;

[0123] The regenerated solid acid catalyst was reused, and the freezing point, purity and yield of the dipropylene glycol sample prepared when it was reused for the tenth time were measured. The specific test results are shown in Table 1 below.

[0124] Table 1-Performance test data of the sample

[0125]

[0126] Data Analysis:

[0127] Comparative analysis of the data in Table 1 above shows that the freezing point of the dipropylene glycol prepared by the present invention reaches -9.5°C, the purity reaches 99.78%, and the yield reaches 88.7%. After the prepared solid acid catalyst is reused 10 times, the freezing point of the prepared dipropylene glycol reaches -9.1°C, the purity reaches 99.75%, and the yield reaches 86.8%. All test data are better than those of the comparative example;

[0128] The present invention loads sulfonic acid onto high-porosity inorganic nanoparticles and modifies crown ether on the surface of the nanoparticles in the form of long cantilevers, which not only simplifies the preparation process of dipropylene glycol and obtains dipropylene glycol with a low freezing point, but also improves the purity and yield of dipropylene glycol. In addition, the solid acid catalyst is easy to regenerate and recycle, and still has good catalytic activity after multiple cycles of use.

[0129] The above are merely examples and explanations of the structure of the present invention. The technicians in this technical field may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the structure of the invention or exceed the scope defined by the claims, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing dipropylene glycol with a low freezing point, characterized in that: The method for preparing the dipropylene glycol with a low freezing point comprises: using a solid acid catalyst to carry out a condensation reaction on propylene oxide and propylene glycol, and then performing post-treatment to obtain the dipropylene glycol with a low freezing point.

2. The method for preparing dipropylene glycol with a low freezing point according to claim 1, characterized in that: The dosage ratio of propylene oxide to propylene glycol is 1 mol:1.3-1.5 mol, the dosage of the solid acid catalyst is 4-6% of the total weight of propylene oxide and propylene glycol, the condensation reaction temperature is 80-100° C., the reaction pressure is 0.1-0.3 MPa, and the reaction time is 2-3 h.

3. The method for preparing dipropylene glycol with a low freezing point according to claim 1, characterized in that: The solid acid catalyst is processed by the following steps: A1. Add the composite polysiloxane microspheres to the activation solution, raise the temperature of the reaction system to reflux, keep the temperature for 90-120 minutes, and post-treat to obtain activated microspheres; A2. Under the protection of inert gas, activated microspheres and 1,3-propane sultone are added to tetrahydrofuran and stirred. The temperature of the reaction system is raised to reflux, and the reaction is kept warm for 8-10 hours. The solid acid catalyst precursor is obtained by post-treatment. A3. Add the acid catalyst precursor and the modified crown ether into the ethanol solution and stir. Raise the temperature of the reaction system to 50-60°C, keep the reaction warm for 60-80 minutes, and post-treat to obtain a solid acid catalyst.

4. The method for preparing dipropylene glycol with a low freezing point according to claim 3, characterized in that: In step A1, the amount ratio of the composite polysiloxane microspheres to the activation solution is 1g:10mL, and the activation solution is composed of 28-32wt% nitric acid and 30wt% hydrogen peroxide in a volume ratio of 3:1; in step A2, the amount ratio of the activated microspheres, 1,3-propane sultone and tetrahydrofuran is 3g:2g:15mL, and the post-treatment includes: after the reaction is completed, the temperature of the reaction system is lowered to room temperature, filtered, the filter cake is washed with tetrahydrofuran for 3 times and then dried, the filter cake is transferred to a drying oven at a temperature of 60-70°C, and vacuum dried to constant weight to obtain a solid acid catalyst precursor; in step A3, the amount ratio of the solid acid catalyst precursor, the modified crown ether and the ethanol solution is 5g:1g:50mL, and the ethanol solution is composed of anhydrous ethanol and purified water in a volume ratio of 7:

3.

5. The method for preparing dipropylene glycol with a low freezing point according to claim 3, characterized in that: The composite polysiloxane microspheres are processed by the following steps: B1, adding polysiloxane microspheres to the glucose solution and stirring, raising the temperature of the reaction system to 80-90°C, adding a catalyst to the reaction system, keeping the temperature for 5-7h, and post-treating to obtain a composite polysiloxane microsphere precursor; B2. Immerse the composite polysiloxane microsphere precursor in a zinc chloride solution, raise the temperature of the reaction system to 65-75° C., keep warm and immerse for 6-7 hours, and post-treat to obtain composite polysiloxane microspheres.

6. The method for preparing dipropylene glycol with a low freezing point according to claim 5, characterized in that: In step B1, the dosage ratio of the polysiloxane microspheres, the glucose solution and the catalyst is 5g:30mL:1g, the glucose solution is composed of glucose and deionized water in a dosage ratio of 1g:8mL, and the catalyst is sodium hydroxide; in step B2, the dosage ratio of the composite polysiloxane microsphere precursor and the zinc chloride solution is 1g:5mL, and the zinc chloride solution is composed of zinc chloride and 0.1-0.5mol / L hydrochloric acid in a dosage ratio of 1g:6mL.

7. The method for preparing dipropylene glycol with a low freezing point according to claim 5, characterized in that: The preparation method of polysiloxane microspheres is as follows: after uniformly mixing tetraethyl orthosilicate and KH-560, slowly adding the mixture into the emulsion, homogenizing and emulsifying, raising the temperature of the emulsification system to 40-50°C, homogenizing and emulsifying for 6-8h, raising the temperature of the emulsification system to 90-100°C, aging for 30-40h, and post-treating to obtain polysiloxane microspheres.

8. The method for preparing dipropylene glycol with a low freezing point according to claim 7, characterized in that: The dosage ratio of the tetraethyl orthosilicate, KH-560 and the emulsion is 3g:1g:50mL, and the emulsion is composed of deionized water, 8-10mol / L hydrochloric acid, hexadecyltrimethylammonium chloride, and diacetyltartaric acid mono- and diglycerides in a dosage ratio of 50-60mL:40-50mL:4-5g:2-3g.

9. The method for preparing dipropylene glycol with a low freezing point according to claim 3, characterized in that: The preparation method of the modified crown ether is as follows: under the protection of inert gas, 10-isocyanatodecyltrimethoxysilane and 15-crown-5-methanol are added to tetrahydrofuran and stirred, the temperature of the reaction system is increased to 50-60°C, the reaction is kept warm for 2-3 hours, and the modified crown ether is obtained by post-treatment.

10. The method for preparing dipropylene glycol with a low freezing point according to claim 9, characterized in that: The usage ratio of the 10-isocyanatodecyltrimethoxysilane and 15-crown-5-methanol is 1 mol:1 mol, and the usage ratio of the 10-isocyanatodecyltrimethoxysilane and tetrahydrofuran is 1 g:6 mL.

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