Preparation method and device of isosorbide

Abstract

The invention relates to a method and device for preparing isosorbide, and the method comprises the following steps: (1) conveying raw materials of sorbitol and an acid catalyst to a first dehydration reactor for primary dehydration to obtain an intermediate material; (2) conveying the intermediate material to a rectifying tower, condensing rectified light components, and conveying the condensed light components to a second dehydration reactor; and (3) adding a solid catalyst into the second dehydration reactor, and carrying out secondary dehydration to obtain the product isosorbide. The method and the device provided by the invention can reduce the generation of by-products, improve the yield of isosorbide, and can keep good reaction activity and the service life of the catalyst in long-term operation.

Description

Technical Field

[0001] This invention belongs to the field of chemical preparation technology, specifically relating to a method and apparatus for preparing isosorbide. Background Technology

[0002] Isosorbide is widely used in pharmaceuticals, food, cosmetics, plastics, and polymers. In medicine, it is an effective osmotic oral diuretic. Industrially, it is an important intermediate in the preparation of Span and Tween surfactants. Due to its unique chirality, it can also be used as an intermediate in the synthesis of liquid crystal materials, finding wide application in electronics and defense. In materials science, isosorbide can be used to modify polymers such as polyethers, polyesters, polyurethanes, and polycarbonates, significantly improving the optical, thermal, and mechanical properties of polyurethanes. Therefore, isosorbide is considered a crucial future bio-based pharmaceutical and chemical raw material with broad market demand.

[0003] Currently, isosorbide is mainly prepared from sorbitol through two acid-catalyzed dehydration processes. The specific reaction formula is shown in the figure below. The first step of dehydration yields 1,4-dehydrated sorbitol, and the second step of dehydration of 1,4-dehydrated sorbitol yields the target product isosorbide.

[0004]

[0005] The byproducts obtained from the first dehydration step will condense in the second dehydration step to form high-polymer byproducts. These substances are collectively referred to as biomass humic substances and can adversely affect the reaction process. Generally, the stronger the acidity of the catalyst used, the better the degree of dehydration, the higher the product yield, and the easier it is to over-condense and generate more byproducts.

[0006] In traditional industry, sulfuric acid is used as a catalyst to prepare isosorbide through a one-pot dehydration reaction. This method causes significant damage to equipment due to the liquid acid, produces numerous byproducts, and involves many complex post-processing steps, resulting in high production costs for isosorbide.

[0007] At present, researchers are focusing on the development of solid acid catalysts. Although the catalyst and the reaction system can be separated, it is still impossible to avoid the byproducts generated by the two-step dehydration process from further condensing into high polymer byproducts. After a long period of reaction, these substances will block the internal pores of the solid acid catalyst, leading to catalyst deactivation and reducing its service life.

[0008] CN201611181594.6 discloses a method for preparing isosorbide. Using solid sorbitol as a raw material and solid acidic molecular sieve as a catalyst, the mass ratio of solid sorbitol to molecular sieve is 100:1.0–5.0. The reaction is carried out under catalytic conditions at a pressure of -0.02–-0.06 MPa and a temperature of 120–200 °C in the molten state for 2–6 hours to obtain isosorbide. After the reaction, the isosorbide content in the product is above 80%. This method uses β-molecular sieve as a solid acid catalyst. The two-step dehydration reaction can accumulate byproducts, and prolonged reaction can clog the catalyst's pore structure, leading to catalyst deactivation and reduced reactivity.

[0009] CN201710455008.0 discloses a highly efficient method for preparing isosorbide, using the biomass derivative 1,4-dehydrated sorbitol as a raw material. Under the presence of fatty ketone compounds, isosorbide is prepared via solid acid-catalyzed ketalization and intramolecular etherification, achieving a yield as high as 97%. This method features mild reaction conditions, simple operation, easy product separation, and recyclable catalyst. However, this method is a one-step reaction using 1,4-dehydrated sorbitol as a raw material, requiring an intermediate purification process for 1,4-dehydrated sorbitol; otherwise, the yield and purity of the target product will be affected.

[0010] CN201510068551.6 discloses a continuous preparation method for isosorbide. The preparation apparatus used in this method includes: a raw material premixing device (1), a primary dehydration reactor (2), an intermediate dehydration device (3), a secondary dehydration reactor (4), a neutralization and deacidification reactor (5), a distillation column (6), an isosorbide condenser (7), a desalting and impurity removal device (8), connecting pipelines between equipment, control instruments, and various accessories. The preparation process involves sorbitol and a dehydration catalyst being premixed in the raw material premixing device (1) and then reacted in the primary dehydration reactor (2). After reaction, the mixture is dehydrated in the intermediate dehydration device (3) and then further dehydrated in the secondary dehydration reactor (4). This patent uses an acid catalyst, which cannot avoid the generation of byproducts during the reaction process. Furthermore, after secondary dehydration, the catalyst needs to be neutralized and deacidified before further distillation separation. Summary of the Invention

[0011] To address the problems existing in the prior art, this invention provides a method and apparatus for preparing isosorbide. The method and apparatus of this invention can reduce the formation of byproducts, improve the yield of isosorbide, and maintain good reactivity and catalyst lifespan during long-term operation.

[0012] This invention provides a method for preparing isosorbide, comprising the following steps:

[0013] (1) The raw material sorbitol and acid catalyst are fed to the first dehydration reactor for primary dehydration to obtain intermediate material;

[0014] (2) The intermediate material is transported to the distillation column, and the light components after distillation are condensed and transported to the second dehydration reactor;

[0015] (3) A solid catalyst is added to the second dehydration reactor for secondary dehydration to obtain the product.

[0016] In this invention, the purity of the raw material sorbitol mentioned in step (1) is above 99%.

[0017] In this invention, the acid catalyst in step (1) is a Lewis acid catalyst, preferably one or more of CuCl2, Fe2(SO4)3, Al2(SO4)3, Zr(SO4)2, Ti(SO4)2, etc.

[0018] In this invention, the amount of acid catalyst used in step (1) is 3%-7% of the mass of sorbitol.

[0019] In this invention, the dehydration reaction in step (1) is carried out under vacuum heating conditions, with a vacuum degree of 1-10 kPa, preferably 1-5 kPa; a heating temperature of 120-180℃, preferably 130-145℃; and a reaction time of 3-12 h, preferably 6-9 h.

[0020] In this invention, the bottom temperature of the distillation column in step (2) is 220-260℃, and the vacuum degree at the top of the column is 100-1000Pa.

[0021] In this invention, step (2) involves separation via a distillation column, where a mixture of light components 1,4-dehydrated sorbitol and isosorbitol is obtained at the top of the column. After condensation at 120-150°C, the mixture enters the second dehydration reactor; the heavy components are returned to the first dehydration reactor.

[0022] In this invention, the solid catalyst in step (3) is a zeolite molecular sieve, a sulfonic acid resin catalyst, a WO3 / ZrO2 solid acid catalyst, an AlPO4 / BPO4 phosphate, or an H3PW catalyst. 12 O 40 / H4SiW 12 O 40 One or more of the following: heteropoly acids.

[0023] Further preferably, the solid catalyst in step (3) is a fluorine-modified solid catalyst prepared by the method described in this invention. The preparation of this catalyst specifically includes the following steps:

[0024] (a) Mix beta molecular sieve with a fluoride ion solution, heat to 60-100℃ to react, separate the solid after reaction, wash and dry to obtain solid product;

[0025] (b) The solid was mixed with SnF4 in a certain proportion, ball-milled under an inert atmosphere, and then calcined to obtain the catalyst.

[0026] In the above catalyst preparation method, the beta molecular sieve mentioned in step (a) is preferably an H-beta molecular sieve, and the silicon-to-aluminum ratio of the molecular sieve, calculated as SiO2 / Al2O3, is 20-80, preferably 20-40. The solute in the fluoride-containing solution is at least one of hydrofluoric acid, ammonium fluoride, etc., and the mass fraction of the solute in the solution is 5%-30%. The solid-liquid ratio of the beta molecular sieve to the fluoride-containing solution is 1g:15-30mL.

[0027] In the above catalyst preparation method, step (a) involves heating to 60-100℃, preferably 70-90℃, for a reaction time of 4-8 hours. Solid-liquid separation is performed by filtration, centrifugation, etc. The solid is washed with water until neutral and then dried at 100-120℃ for 10-24 hours.

[0028] In the above catalyst preparation method, SnF4 in step (b) is mixed with the solid from step (1) at a mass ratio of 1:8-15. The inert atmosphere is any one of nitrogen, helium, or argon. The ball milling speed is 35-45 r / min, and the milling time is 6-10 h. The calcination temperature is 500-600℃, and the calcination time is 6-12 h.

[0029] In this invention, the amount of solid catalyst used in step (3) is 5%-12% of the mass of the raw material sorbitol.

[0030] In this invention, the secondary dehydration in step (3) is carried out under vacuum heating conditions, with a vacuum degree of 100-1000 Pa, preferably 400-600 Pa, a heating temperature of 140-170℃, preferably 150-160℃, and a reaction time of 2-5 h.

[0031] In this invention, after the reaction in step (3) is completed, the solid catalyst is separated to obtain the product. The solid catalyst can be reused.

[0032] A second aspect of the present invention provides an apparatus for the above-described method for preparing isosorbide, mainly comprising a first dehydration reactor, a distillation column, a condenser, and a second dehydration reactor. The first dehydration reactor is used for a primary dehydration reaction of sorbitol to obtain an intermediate material. The distillation column is used to distill the intermediate material, and the light component produced by distillation is condensed by the condenser and then transported to the second dehydration reactor, while the heavy component is returned to the first dehydration reactor. The second dehydration reactor is used for a secondary dehydration of the condensed component to obtain the product.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] (1) The present invention selects a one-time dehydration-distillation-two-time dehydration process, and the two dehydration processes use different dehydration conditions, which can prevent the acid catalyst from causing excessive condensation of the raw material to generate by-products, ensure the yield of isosorbide, and have good catalytic activity and service life in long-term operation.

[0035] (2) The first step of dehydration uses Lewis acid catalyst, and the reaction conditions are relatively mild. After the reaction, sorbitol can complete the first step of dehydration. After distillation, the light component is added to the solid catalyst for secondary dehydration. The two work together to reduce the generation of by-products and increase the content of isosorbitol.

[0036] (3) The secondary dehydration of the present invention uses a fluorine-modified solid catalyst, which can further reduce the generation of by-products caused by excessive dehydration condensation while ensuring the yield of isosorbide, thus avoiding catalyst blockage and extending the service life of the catalyst. Attached Figure Description

[0037] Figure 1 This is a process flow diagram of the preparation method of the present invention. Detailed Implementation

[0038] The technical solution and its effects of the present invention will be described in detail below with reference to specific embodiments. The embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures; however, the scope of protection of the present invention is not limited to the following embodiments.

[0039] Unless otherwise specified, the experimental methods used in the following examples are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following examples were purchased from conventional biochemical reagent stores.

[0040] This invention uses an Agilent 1260 liquid chromatograph with a BIO-RAD HPX-87H column for quantitative analysis of sorbitol and isosorbide.

[0041] Sorbitol conversion rate = (1 - mass of sorbitol after reaction / initial mass of sorbitol) × 100%.

[0042] Isosorbide yield = (Isosorbide mass / Initial sorbitol mass) × 100%.

[0043] By-product yield = by-product mass / initial sorbitol mass × 100%.

[0044] Isosorbide content in the product = (Isosorbide mass / Product mass) × 100%.

[0045] Example 1

[0046] (1) Weigh 100g of sorbitol (purity 99.1%) and 5g of CuCl2 and send them to the first dehydration vessel. The heating temperature is 140℃ and the vacuum degree is set to 3kPa. Dehydration is carried out under reduced pressure. After 8 hours of reaction, the intermediate material is sent to the distillation column.

[0047] (2) The temperature of the bottom of the distillation column is 230℃ and the vacuum degree is 400Pa. The intermediate material is distilled under reduced pressure to obtain light components 1,4-dehydrated sorbitol and isosorbitol. After being condensed at 130℃, they enter the second dehydration kettle. The heavy components in the bottom of the column are returned to the first dehydration kettle for the next reaction.

[0048] (3) 7g of zeolite molecular sieve was added to the second dehydration reactor. The reaction temperature was 150℃, the vacuum degree was 500Pa, and the reaction time was 4h. After the reaction was completed, the solid catalyst was separated to obtain the product. The experimental results are shown in Table 1.

[0049] Example 2

[0050] (1) Weigh 100g of sorbitol (purity 99.1%) and 3g of Fe2(SO4)3 and send them to the first dehydration kettle. The heating temperature is 130℃ and the vacuum degree is set to 1kPa. Dehydration is carried out under reduced pressure. After 6 hours of reaction, the intermediate material is sent to the distillation column.

[0051] (2) The temperature of the bottom of the distillation column is 220℃ and the vacuum degree is 600Pa. The intermediate material is distilled under reduced pressure to obtain light components 1,4-dehydrated sorbitol and isosorbitol. After being condensed at 120℃, they enter the second dehydration kettle. The heavy components in the bottom of the column are returned to the first dehydration kettle for the next reaction.

[0052] (3) 5g of zeolite molecular sieve was added to the second dehydration reactor. The reaction temperature was 140℃, the vacuum degree was 400Pa, and the reaction time was 2h. After the reaction was completed, the solid catalyst was separated to obtain the product. The experimental results are shown in Table 1.

[0053] Example 3

[0054] (1) Weigh 100g of sorbitol (purity 99.1%) and 7g of Ti(SO4)2 and deliver them to the first dehydration vessel. The heating temperature is 160℃ and the vacuum degree is set to 5kPa. Dehydration is carried out under reduced pressure. After 9 hours of reaction, the intermediate material is delivered to the distillation column.

[0055] (2) The temperature of the bottom of the distillation column is 260℃ and the vacuum degree is 200Pa. The intermediate material is distilled under reduced pressure to obtain light components 1,4-dehydrated sorbitol and isosorbitol. After being condensed at 150℃, they enter the second dehydration kettle. The heavy components in the bottom of the column are returned to the first dehydration kettle for the next reaction.

[0056] (3) 12g of zeolite molecular sieve was added to the second dehydration reactor. The reaction temperature was 170℃, the vacuum degree was 600Pa, and the reaction time was 6h. After the reaction was completed, the solid catalyst was separated to obtain the product. The experimental results are shown in Table 1.

[0057] Example 4

[0058] Similar to Example 1, except that: in step (1), the acid catalyst used was Al2(SO4)3, and in step (3), the solid catalyst used was Amberlyst-15 sulfonic acid resin catalyst (commercially available), and the final product was obtained. The test results are shown in Table 1.

[0059] Example 5

[0060] Similar to Example 1, except that: in step (1) the acid catalyst was Zr(SO4)2, and in step (3) the solid catalyst was WO3 / ZrO2 solid acid catalyst (commercially available), and the final product was obtained. The experimental results are shown in Table 1.

[0061] Example 6

[0062] Same as Example 1, except that: the solid catalyst in step (3) was prepared by the following method: (a) 6g of microporous H-Beta molecular sieve (SiO2 / Al2O3 ratio of 40) was added to the reaction vessel, 120mL of hydrofluoric acid solution (hydrofluoric acid mass content of 15%) was added, and the reaction was carried out at 80℃ for 6h. The solid was obtained by centrifugation, washed multiple times until neutral, and dried at 100℃ for 12h to obtain the solid product; (b) SnF4 powder and the solid product were mixed at a mass ratio of 1:10, and ball milled in a ball mill reactor under a nitrogen atmosphere at a speed of 40r / min for 6h. Then, the mixture was calcined at 550℃ for 8h to finally obtain the catalyst. The experimental results are shown in Table 1.

[0063] Example 7

[0064] Same as Example 1, except that: the solid catalyst in step (3) was prepared by the following method: (a) 6g of hierarchical H-Beta molecular sieve, of which the mesoporous ratio was 30% (SiO2 / Al2O3 was 40), was added to a reaction vessel, and 120mL of ammonium fluoride solution (ammonium fluoride mass content was 15%) was added. The reaction was carried out at 80℃ for 6h, and the solid was obtained by centrifugation. The solid was washed several times until neutral and dried at 100℃ for 12h to obtain the solid product; (b) SnF4 powder and the solid product were mixed at a mass ratio of 1:10 and ball-milled in a ball mill reactor under a nitrogen atmosphere at a speed of 40r / min for 6h. Then, the mixture was calcined at 550℃ for 8h to finally obtain the catalyst. The experimental results are shown in Table 1.

[0065] Comparative Example 1

[0066] Similar to Example 1, except that both dehydration reactions used the acid catalyst in step (1) to finally obtain the product. The experimental results are shown in Table 1.

[0067] Comparative Example 2

[0068] Same as Example 1, except that: both dehydration reactions used the solid catalyst in step (3) to finally obtain the product. The experimental results are shown in Table 1.

[0069] Comparative Example 3

[0070] Similar to Example 1, except that in step (1), the intermediate material is directly fed into the second dehydration reactor to finally obtain the product. The test results are shown in Table 1.

[0071] Table 1. Test results of each embodiment and comparative example.

[0072]

[0073] As shown in Table 1, the present invention ensures the yield of isosorbide while avoiding the generation of byproducts, and the isosorbide content in the product is relatively high; in particular, it can still maintain a good yield after long-term operation and the operation is more stable.

Claims

1. A method for preparing isosorbide, characterized in that... Includes the following steps: (1) The raw material sorbitol and acid catalyst are transported to the first dehydration reactor for primary dehydration to obtain intermediate material; (2) The intermediate material is transported to the distillation column, and the light components after distillation are condensed and transported to the second dehydration reactor; (3) A solid catalyst was added to the second dehydration reactor for secondary dehydration to obtain the product isosorbide.

2. The method according to claim 1, characterized in that: The purity of the raw material sorbitol mentioned in step (1) is above 99%.

3. The method according to claim 1, characterized in that: The acid catalyst mentioned in step (1) is a Lewis acid catalyst, preferably one or more of CuCl2, Fe2(SO4)3, Al2(SO4)3, Zr(SO4)2, and Ti(SO4)2.

4. The method according to claim 1 or 3, characterized in that: In step (1), the amount of acid catalyst used is 3%-7% of the mass of sorbitol.

5. The method according to claim 1, characterized in that: The dehydration reaction described in step (1) is carried out under vacuum heating conditions, with a vacuum degree of 1-10 kPa, preferably 1-5 kPa; a heating temperature of 120-180℃, preferably 130-145℃; and a reaction time of 3-12 h, preferably 6-9 h.

6. The method according to claim 1, characterized in that: The temperature of the bottom of the distillation column in step (2) is 220-260℃, and the vacuum at the top of the column is 100-1000Pa.

7. The method according to claim 1, characterized in that: Step (2) involves separation via a distillation column. The light components, a mixture of 1,4-dehydrated sorbitol and isosorbitol, are obtained at the top of the column. After condensation at 120-150°C, the mixture enters the second dehydration reactor. The heavy components are returned to the first dehydration reactor.

8. The method according to claim 1, characterized in that: The solid catalyst mentioned in step (3) is a zeolite molecular sieve, a sulfonic acid resin catalyst, a WO3 / ZrO2 solid acid catalyst, an AlPO4 / BPO4 phosphate, or an H3PW catalyst. 12 O 40 / H4SiW 12 O 40 One or more of the heteropolyacids.

9. The method according to claim 1, characterized in that: Step (3) The solid catalyst is prepared by the following method. The preparation of the catalyst specifically includes the following steps: (a) mixing beta molecular sieve with fluoride ion solution, heating to 60-100℃ for reaction, separating the solid after reaction, washing and drying to obtain solid product; (b) mixing the solid product with SnF4 in proportion, ball milling reaction under inert atmosphere, and then calcining to obtain the catalyst.

10. The method according to claim 9, characterized in that: The beta molecular sieve mentioned in step (a) is an H-beta molecular sieve, and the silicon-to-aluminum ratio of the molecular sieve, calculated as SiO2 / Al2O3, is 20-80, preferably 20-40.

11. The method according to claim 9, characterized in that: The solute in the fluoride-containing solution mentioned in step (a) is at least one of hydrofluoric acid and ammonium fluoride, and the mass fraction of the solute in the solution is 5%-30%.

12. The method according to claim 9, 10 or 11, characterized in that: The solid-liquid ratio of the beta molecular sieve to the fluoride ion solution in step (a) is 1g:15-30mL; the temperature is raised to 60-100℃, preferably 70-90℃, for a reaction time of 4-8h.

13. The method according to claim 9, characterized in that: In step (b), SnF4 is mixed with the solid from step (1) at a mass ratio of 1:8-15; the inert atmosphere is any one of nitrogen, helium, or argon; the ball milling speed is 35-45 r / min, and the ball milling time is 6-10 h; the calcination temperature is 500-600℃, and the calcination time is 6-12 h.

14. The method according to claim 1, characterized in that: The amount of solid catalyst used in step (3) is 5%-12% of the mass of the raw material sorbitol.

15. The method according to claim 1, characterized in that: The secondary dehydration in step (3) is carried out under vacuum heating conditions, with a vacuum degree of 100-1000 Pa, preferably 400-600 Pa, a heating temperature of 140-170℃, preferably 150-160℃, and a reaction time of 2-5 h.

16. The method according to claim 1, characterized in that: After the reaction in step (3) is completed, the solid catalyst is separated and reused.

17. An apparatus for the preparation method of isosorbide according to any one of claims 1-16, characterized in that: The system includes a first dehydration reactor, a distillation column, a condenser, and a second dehydration reactor. The first dehydration reactor is used for the primary dehydration reaction of sorbitol to obtain intermediate material. The distillation column is used to distill the intermediate material. The light component produced by distillation is condensed by the condenser and then sent to the second dehydration reactor, while the heavy component is returned to the first dehydration reactor. The second dehydration reactor is used for the secondary dehydration of the condensed component to obtain the product isosorbitol.

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