Method for producing isosorbide

Abstract

The present invention relates to the field of isosorbide production, and discloses a method for producing isosorbide, the method including, in the presence of a first catalyst and a protective agent, performing a first dehydration treatment on sorbitol to obtain a first dehydrated product; in the presence of a second catalyst, performing a second dehydration treatment on the first dehydrated product to obtain isosorbide; wherein, the first catalyst is a sulfonic acid group ion exchange resin, and the second catalyst is different from the first catalyst. The present invention produces isosorbide by a two-step method, improves the selectivity of the intermediate key product 1,4-anhydrosorbitol (or 3,6-anhydrosorbitol), and also improves the yield of the final product isosorbide.

Description

Technical Field

[0001] The present invention relates to the field of isosorbide production, and in particular to a method for producing isosorbide. Background Art

[0002] Biomass, due to its renewable nature, abundant resources, high degree of functionalization, and environmental friendliness, has become a hot topic of research in the fields of fine chemicals and new materials. Isosorbide, a key biomass platform compound, possesses a unique chiral molecular structure and is a safe, non-toxic, green diol. It is widely used in pharmaceuticals, solvents, and plastic additives, and is also of great significance in the field of novel polymer materials. For example, isosorbide itself can be used as an excellent antihypertensive and diuretic agent; it can also be used to synthesize dimethyl isosorbide, a green solvent; and it can be used to synthesize new green plasticizers to replace phthalate plasticizers. Furthermore, isosorbide can be used to modify PET, significantly improving its high-temperature properties and impact resistance. In new carbonate material technology, it is also showing promise as a key raw material to replace bisphenol A, which has health risks, thereby improving the environmental friendliness of polycarbonate. Consequently, the synthesis technology and related applications of isosorbide have attracted considerable attention in recent years.

[0003] Currently reported isosorbide synthesis technologies primarily utilize sorbitol as the raw material, using solid or liquid acids as catalysts, via catalytic dehydration. Liquid acids typically include concentrated sulfuric acid, benzenesulfonic acid, hydrochloric acid, and methanesulfonic acid. While this homogeneous process is relatively mature, it suffers from severe equipment corrosion, complex product separation, and high production costs, hindering large-scale industrial application. Solid acids, including molecular sieves, ion exchange resins, metal phosphates, and heteropolyacids, have garnered attention due to their advantages, such as low material requirements for equipment, relatively simple product separation, and catalyst recyclability. Solid acid dehydration catalysts are expected to gradually replace liquid acid catalysts. However, solid acid catalyst technology remains immature, with issues regarding catalyst life and selectivity hindering industrialization.

[0004] Research has shown that isosorbide is produced through the continuous dehydration reaction of the raw material sorbitol, using an intramolecular SN2 mechanism. The first dehydration step produces the key intermediate product 1,4-anhydrosorbitol, which is then further dehydrated to produce isosorbide. Because the raw material sorbitol contains multiple functional groups, multiple byproducts can be produced during the reaction. Therefore, in addition to the desired 1,4-anhydrosorbitol and 3,6-anhydrosorbitol, byproducts such as 1,5-anhydro, 2,5-anhydro, and 2,6-anhydro may also be produced. Therefore, how to improve product selectivity and reduce the occurrence of byproducts has always been a hot topic and difficulty in research.

[0005]

[0006] CN202011201366 adopts a "one-pot" process, introducing L-acid centers through ion exchange resin modification to improve its electronic and hydrophobic properties, thereby increasing its reactivity and product selectivity and shortening the reaction time. This method not only avoids the problems of strong corrosiveness of liquid acids and difficulty in separating products, but also addresses the low catalytic selectivity of current solid acids, thereby reducing production costs and making it suitable for industrial applications. However, the key intermediate product 1,4-anhydrosorbitol and the final product isosorbide are simultaneously produced during the reaction, leaving room for further improvement in product yield.

[0007] US10759811 uses a liquid acid as a catalyst and a two-step dehydration process. The first step reaction temperature is controlled within the range of 100-150°C, and the second step reaction temperature is controlled within the range of 151-240°C. By improving the selectivity of the key intermediate 1,4-dehydration reaction product, the yield of the dehydrated sugar alcohol isosorbide is increased. However, this method uses the same catalyst for both steps, resulting in a low product yield.

[0008] To improve the reaction yield, US Pat. No. 10,221,187 uses a transition metal catalyst to synthesize isosorbide via a two-step dehydration process. The reaction temperature for the first step is controlled within the range of 240-285°C, and the temperature for the second step is controlled within the range of 286-340°C. The product yield can reach 57-62%. However, the reaction temperature is too high, making it difficult to promote industrially. Summary of the Invention

[0009] The present invention aims to overcome the problem of low product yield in the prior art of producing isosorbide by a two-step process from sorbitol, and to provide a method for producing isosorbide. The method uses different catalysts in the two-step reaction, thereby improving the selectivity of key intermediates and ultimately improving the yield of the product.

[0010] To achieve the above object, the present invention provides a method for producing isosorbide, which comprises performing a first dehydration treatment on sorbitol in the presence of a first catalyst and a protective agent to obtain a first dehydrated product; and performing a second dehydration treatment on the first dehydrated product in the presence of a second catalyst to obtain isosorbide.

[0011] Wherein, the first catalyst is a sulfonic acid ion exchange resin; and the second catalyst is different from the first catalyst.

[0012] Preferably, the protective agent is boric acid.

[0013] Preferably, the second catalyst is selected from at least one of phosphates or sulfates of Nb2O5, CuO and ZrO2.

[0014] The present invention uses solid sorbitol or a sorbitol solution as a raw material and adopts a two-step process to synthesize isosorbide. The first step is the synthesis of 1,4-anhydrosorbitol. A sulfonic acid ion exchange resin is used as a catalyst. A protective agent is added to form a chelate at the 1,4-position of sorbitol to reduce the formation of by-products. Analysis shows that the sorbitol conversion rate can reach over 95%, and the selectivity of 1,4-anhydrosorbitol can reach over 90%. In the second step, the 1,4-anhydrosorbitol product is used as a reactant and a second catalyst different from the first catalyst is used to catalyze the second dehydration step, further improving the product yield.

[0015] The product yield can be further improved with the preferred protecting agent, second catalyst and reaction conditions of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is an HPLC chart of the first dehydrated product in Example 1 of the present invention;

[0017] Figure 2 This is the HPLC chart of the second dehydrated product in Example 1 of the present invention. DETAILED DESCRIPTION

[0018] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0019] The present invention provides a method for producing isosorbide, which comprises performing a first dehydration treatment on sorbitol in the presence of a first catalyst and a protective agent to obtain a first dehydrated product; and performing a second dehydration treatment on the first dehydrated product in the presence of a second catalyst to obtain isosorbide.

[0020] Wherein, the first catalyst is a sulfonic acid ion exchange resin; and the second catalyst is different from the first catalyst.

[0021] In the present invention, the sulfonic acid ion exchange resin may be any sulfonic acid group-containing ion exchange resin in the art, such as Amberlyst 15, perfluorosulfonic acid ion resin, and sulfonic acid type ion exchange resin.

[0022] Preferably, the BET specific surface area of ​​the first catalyst is 20-100 m 2 / g, for example, 20, 30, 40, 50, 60, 70, 80, 90, 100m 2 / g and any range between any two values, more preferably 40-60m 2 / g.

[0023] The BET specific surface area can be measured by a low-temperature N2 adsorption method.

[0024] Preferably, the acidity of the first catalyst is 0.5-6 mmol / g, for example, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6 mmol / g and any range between any two values, more preferably 4-5.5 mmol / g.

[0025] The acidity can be measured by NH3-TPD.

[0026] Preferably, compared to 100 parts by weight of the sorbitol, the amount of the first catalyst is 0.1-10 parts by weight, for example, 0.1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 parts by weight and any range between any two values, more preferably 0.5-5 parts by weight.

[0027] Preferably, the protective agent is boric acid.

[0028] Preferably, compared to 1 mol of sorbitol, the amount of the protective agent is 0.01-5 mol, for example, 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 mol and any range between any two values, more preferably 0.05-0.5 mol.

[0029] The form of sorbitol is not particularly limited. Preferably, sorbitol is in the form of sorbitol solid or sorbitol solution (aqueous solution).

[0030] Preferably, the concentration of the sorbitol solution is 50% by weight or more.

[0031] Preferably, the conditions for the first dehydration treatment include: temperature of 115-135°C (for example, it can be 115, 120, 125, 130, 135°C and any range between any two values); vacuum degree of 0.01MPa to 0.03MPa (for example, it can be 0.01, 0.015, 0.02, 0.025, 0.03MPa and any range between any two values); time is 5-10h (for example, it can be 5, 6, 7, 8, 9, 10h and any range between any two values).

[0032] In the present invention, preferably, the method further comprises performing a first purification on the first dehydration product to obtain sorbitan. The catalyst and protective agent are removed by the first purification to obtain sorbitan mainly composed of 1,4-sorbitan and 3,6-sorbitan.

[0033] In the present invention, unless otherwise specified, 1,4-sorbitan and 3,6-sorbitan are not particularly distinguished, that is, 1,4-sorbitan includes 1,4-sorbitan and 3,6-sorbitan.

[0034] The first purification method may be a conventional method in the art and may be adjusted according to the form of the reactants.

[0035] For example, when sorbitol participates in the dehydration process in the form of a solution, an alkali can be used to adjust the pH of the first dehydration product to neutral, and then the first catalyst can be removed by solid-liquid separation to obtain a liquid phase containing 1,4-anhydrosorbitol. The 1,4-anhydrosorbitol is extracted using a first solvent to obtain a first organic phase containing 1,4-anhydrosorbitol. After removing the first solvent, 1,4-anhydrosorbitol is obtained.

[0036] The conditions for the first purification may be conventional conditions in the art, for example, it may be carried out at room temperature (for example, 15-40° C.) and normal pressure.

[0037] The first solvent may be an organic solvent commonly used in the art, such as ethyl acetate, acetone, or isopropyl alcohol, etc. Those skilled in the art may adjust the amount thereof as needed.

[0038] The alkali may be, for example, sodium hydroxide, potassium hydroxide, etc. The alkali may be in the form of a solution, and the concentration of the material in the alkali solution may be, for example, 0.1-5 mol / L.

[0039] For example, when sorbitol participates in the dehydration process in solid form, the second solvent can be directly used to dissolve the first dehydration product, and the first catalyst can be removed by solid-liquid separation to obtain a second organic phase containing 1,4-anhydrosorbitol. After removing the second solvent, 1,4-anhydrosorbitol is obtained.

[0040] The second solvent may be an organic solvent commonly used in the art, such as ethanol, ethyl acetate or isopropanol, etc. Those skilled in the art can adjust the amount of the second solvent as needed.

[0041] The solid-liquid separation method can be a conventional method in the art, such as filtration or centrifugation.

[0042] The method for removing the solvent may be a conventional method in the art, such as rotary evaporation, nitrogen blowing, or vacuum distillation.

[0043] It should be understood that after the first dehydration treatment is completed, the first dehydration product can be cooled and then purified.

[0044] In the present invention, the second catalyst can be a liquid acid catalyst or solid acid catalyst used in the art that can catalyze the dehydration of sorbitan to produce isosorbide, preferably a solid acid catalyst. More preferably, the second catalyst is a metal phosphate or a metal sulfate. The metal is preferably at least one of Nb, Cu, and Zr.

[0045] Preferably, the second catalyst is selected from at least one of phosphates or sulfates of Nb2O5, CuO and ZrO2; for example, it can be Nb2O5 / H3PO4, Nb2O5 / H2SO4, CuO / H3PO4, CuO / H2SO4, ZrO2 / H3PO4, ZrO2 / H2SO4, etc.

[0046] Preferably, calculated as metal element, the amount of the second catalyst is 0.1-10 parts by weight, preferably 2-6 parts by weight, relative to 100 parts by weight of sorbitan.

[0047] In the present invention, the preparation method of the second catalyst can be a conventional preparation method in the art, for example, the metal oxide can be contacted with a phosphoric acid solution or a sulfuric acid solution, and then calcined to obtain the second catalyst.

[0048] In the present invention, the usage ratio of the metal oxide and phosphoric acid or sulfuric acid can be selected within a wide range. Preferably, based on the molar amount of the metal element, the usage ratio of phosphoric acid molecules or sulfuric acid molecules is 0.5-3 mol, preferably 1-2 mol, compared to 1 mol of the metal oxide.

[0049] The metal oxide may be, for example, Nb2O5, CuO or ZrO2.

[0050] In a preferred embodiment of the present invention, the second catalyst is prepared by contacting at least one of Nb2O5, CuO and ZrO2 with phosphoric acid or sulfuric acid and then calcining the resulting mixture to obtain the second catalyst.

[0051] The phosphoric acid may be in the form of a phosphoric acid solution, wherein the concentration of the phosphoric acid solution may be selected within a wide range, such as 50-85% by weight.

[0052] The sulfuric acid may be in the form of a sulfuric acid solution, wherein the concentration of the sulfuric acid solution may be selected within a wide range, such as 50-98 weight %.

[0053] The contact conditions can be selected from a wide range, for example, including: a temperature of 25-100° C., preferably 30-80° C.; a time of 5-24 hours, preferably 6-12 hours. The contact method can be, for example, immersion.

[0054] The calcination conditions can be selected within a wide range, for example, the calcination temperature is 200-600° C. and the calcination time is 3-8 hours.

[0055] Before calcination, the reactants may be dried. The drying conditions may include, for example, a temperature of 75-120° C. and a drying time of 5-24 hours.

[0056] Preferably, the conditions of the second dehydration treatment include: 130-150°C (for example, it can be 130, 135, 140, 145, 150°C and any range between any two values); the vacuum degree is 0.001MPa to 0.01MPa (for example, it can be 0.001, 0.003, 0.003, 0.007, 0.009, 0.01MPa and any range between any two values); the time is 3-7h (for example, it can be 3, 4, 5, 6, 7h and any range between any two values).

[0057] When the conditions of the first dehydration treatment and the conditions of the second dehydration treatment are within the corresponding preferred ranges, the yield of the product can be further improved.

[0058] Preferably, the method further comprises performing a second purification treatment on the product after the second dehydration treatment to obtain purified isosorbide.

[0059] The second purification method can be a conventional method in the art, for example, the product after the second dehydration treatment can be directly dissolved in a third solvent, and the second catalyst can be removed by solid-liquid separation to obtain a liquid phase containing isosorbide. After removing the third solvent, isosorbide is obtained.

[0060] The third solvent may be an organic solvent commonly used in the art, such as ethyl acetate, isopropanol or ethanol, etc. Those skilled in the art may adjust the amount thereof as needed.

[0061] The methods for solid-liquid separation and solvent removal are as described above and will not be repeated here.

[0062] It should be understood that after the second dehydration treatment is completed, the product after the second dehydration treatment can be cooled and then purified. The temperature after cooling can be adjusted according to the needs of purification, for example, it can be 60-80°C.

[0063] In order to obtain a product with higher purity, further purification can be performed, for example, the purified isosorbide can be purified by distillation, decolorization and recrystallization, etc. The methods and conditions can be conventional methods and conditions in the art and will not be repeated here.

[0064] The present invention will be described in detail below through examples.

[0065] Unless otherwise specified, operations were performed using conventional methods or means in the art.

[0066] In the following examples, the BET specific surface area was measured by nitrogen adsorption; the acidity was measured by acid-base titration;

[0067] Unless otherwise specified, 1,4-anhydrosorbitol includes 1,4-anhydrosorbitol and 3,6-anhydrosorbitol.

[0068] The calculation formulas for sorbitol conversion and isosorbide product yield are as follows:

[0069]

[0070]

[0071]

[0072] Where n refers to the corresponding molar amount, n sorbitol initial Refers to the amount of sorbitol raw material; n sorbitol in product Refers to the sorbitol in the product; n isosorbide refers to isosorbide; C refers to conversion; S refers to selectivity; Y sosorbide Refers to the yield of isosorbide.

[0073] Preparation Example 1

[0074] This preparation example is used to illustrate the preparation method of Nb2O5 / H3PO4.

[0075] Niobium pentoxide was added to a 10 mol / L phosphoric acid solution, immersed at 50°C for 8 hours, then calcined at 300°C for 5 hours and crushed to obtain the second catalyst 1. The amount of phosphoric acid molecules used was 2 mol per 1 mol of metal oxide, based on the molar amount of the metal element.

[0076] Preparation Example 2

[0077] This preparation example is used to illustrate the preparation method of CuO / H2SO4.

[0078] Copper oxide was added to a 10 mol / L H2SO4 solution, immersed at 60°C for 10 h, then calcined at 500°C for 6 h, and crushed to obtain the second catalyst-2.

[0079] Wherein, based on the molar amount of the metal element, the amount of sulfuric acid molecules used is 1 mol compared to 1 mol of the metal oxide.

[0080] Preparation Example 3

[0081] This preparation example is used to illustrate the preparation method of ZrO2 / H2SO4.

[0082] ZrO2 was added to a 10 mol / L H2SO4 solution, immersed at 60°C for 10 h, then calcined at 500°C for 6 h, and crushed to obtain the second catalyst-3.

[0083] Based on the molar amount of the metal element, the amount of sulfuric acid molecules used is 1.5 mol compared to 1 mol of metal oxide.

[0084] Example 1

[0085] This example is used to illustrate the production method of isosorbide.

[0086] 200 g of sorbitol solution with a concentration of 70 wt % was added to the reactor, 5 g of boric acid was added, and 3 g of the first catalyst (Amberlyst 15 purchased from Aladdin, with a BET specific surface area of ​​46 m 2 / g, acidity 5mmol / g), stirred, evacuated, vacuum controlled at about 0.02MPa, heated to 120°C, maintained for 7h, and then cooled to 30°C. Neutralized to neutrality with 2mol / L sodium hydroxide solution, filtered to remove the first catalyst, then extracted with ethyl acetate, collected the organic layer, and removed the solvent to obtain 125g of the first dehydrated product.

[0087] The first dehydrated product was added to the reactor, and 5 g of the second catalyst-1 prepared in Preparation Example 1 was added. The temperature was raised to 135°C and vacuumed. The vacuum degree was controlled at about 0.006 MPa. After maintaining for 5 hours, the temperature was lowered to 70°C, and the solvent ethyl acetate was added. The mixture was filtered and then vacuumed and distilled to obtain the second dehydrated product, i.e., isosorbide.

[0088] Figure 1 The HPLC chart of the first dehydration product is shown, wherein the peak time of 1,4-anhydrosorbitol is 10.665 min, and the peak time of isosorbide is 13.209 min.

[0089] Figure 2 The HPLC chart of the second dehydration product is shown, wherein the peak time of isosorbide is 12.936 min.

[0090] The yields of 1,4-anhydrosorbitol and isosorbide were calculated, and the conversion rate of sorbitol and the yield of isosorbide were calculated. The results are shown in Table 1.

[0091] Example 2

[0092] This example is used to illustrate the production method of isosorbide.

[0093] 140 g of solid sorbitol was added to the reactor, 2.4 g of boric acid was added, and 0.7 g of the first catalyst (perfluorosulfonic acid ion resin purchased from Aladdin, with a BET specific surface area of ​​40 m 2 / g, acidity is 4.5mmol / g). Then the operation was carried out according to the method described in Example 1 to obtain 124g of the first dehydrated product.

[0094] The first dehydrated product was added to the reactor, and 2.5 g of the second catalyst-1 prepared in Preparation Example 1 was added, and then the operation was carried out according to the method described in Example 1 to obtain the second dehydrated product, namely, isosorbide.

[0095] The yields of 1,4-anhydrosorbitol and isosorbide were calculated, and the conversion rate of sorbitol and the yield of isosorbide were calculated. The results are shown in Table 1.

[0096] Example 3

[0097] This example is used to illustrate the production method of isosorbide.

[0098] 200g of sorbitol solution with a concentration of 70% by weight was added to the reactor, 23.8g of boric acid was added, and 7g of the first catalyst (sulfonic acid type ion exchange resin purchased from Aladdin, with a BET specific surface area of ​​42m 2 / g, acidity is 4.7mmol / g). Then the operation was carried out according to the method described in Example 1 to obtain 123g of the first dehydrated product.

[0099] The first dehydrated product was added to the reactor, and 7.4 g of the second catalyst-1 prepared in Preparation Example 1 was added, and then the operation was carried out according to the method described in Example 1 to obtain the second dehydrated product, namely, isosorbide.

[0100] The yields of 1,4-anhydrosorbitol and isosorbide were calculated, and the conversion rate of sorbitol and the yield of isosorbide were calculated. The results are shown in Table 1.

[0101] Example 4

[0102] This example is used to illustrate the production method of isosorbide.

[0103] The operation was carried out according to the method of Example 1, except that the first catalyst was a sulfonic acid type ion exchange resin purchased from Sinopharm Reagent Co., Ltd., and its acidity was 3.5 mmol / g.

[0104] The yields of 1,4-anhydrosorbitol and isosorbide were calculated, and the conversion rate of sorbitol and the yield of isosorbide were calculated. The results are shown in Table 1.

[0105] Example 5

[0106] This example is used to illustrate the production method of isosorbide.

[0107] The operation was carried out according to the method of Example 1, except that the second catalyst was the second catalyst-2 prepared in Preparation Example 2.

[0108] The yields of 1,4-anhydrosorbitol and isosorbide were calculated, and the conversion rate of sorbitol and the yield of isosorbide were calculated. The results are shown in Table 1.

[0109] Example 6

[0110] This example is used to illustrate the production method of isosorbide.

[0111] The operation was carried out according to the method of Example 1, except that the second catalyst was the second catalyst-3 prepared in Preparation Example 3.

[0112] The yields of 1,4-anhydrosorbitol and isosorbide were calculated, and the conversion rate of sorbitol and the yield of isosorbide were calculated. The results are shown in Table 1.

[0113] Example 7

[0114] This example is used to illustrate the production method of isosorbide.

[0115] The operation was carried out according to the method of Example 1, except that the second catalyst was a copper oxide catalyst purchased from J&K Company.

[0116] The yields of 1,4-anhydrosorbitol and isosorbide were calculated, and the conversion rate of sorbitol and the yield of isosorbide were calculated. The results are shown in Table 1.

[0117] Comparative Example 1

[0118] This comparative example is used to illustrate the production method of isosorbide for reference.

[0119] 200g of a 70% by weight sorbitol solution was added to a reactor, followed by 7g of Amberlyst 15 ion exchange resin purchased from Aladdin. The reactor was evacuated and heated to 140°C. The reaction was maintained for 10 hours, then cooled, filtered, and added to a decolorization kettle. The decolorized product was collected and added to a distillation kettle. The solution was evacuated to a vacuum level of 0.02MPa and slowly heated to 180°C. The distilled product was condensed in a condenser and then transferred to a product receiving kettle. A solvent was then added to the kettle, heated and stirred to dissolve, and then cooled to allow the product to slowly crystallize. The product was then filtered and the resulting filter cake was dried to obtain pure isosorbide.

[0120] The yields of 1,4-anhydrosorbitol and isosorbide were calculated, and the conversion rate of sorbitol and the yield of isosorbide were calculated. The results are shown in Table 1.

[0121] Comparative Example 2

[0122] This comparative example is used to illustrate the production method of isosorbide for reference.

[0123] 200 g of a 70 wt% sorbitol solution was added to a reactor, followed by 3 g of the second catalyst-1 (Nb2O5 / H3PO4) prepared in Preparation Example 1. The reaction was evacuated and heated to 140°C. The reaction was maintained for 10 hours, then cooled. 0.1 mol / L sodium hydroxide solution was added for neutralization. The mixture was filtered and added to a decolorization kettle. The decolorized product was collected. The product was added to a distillation kettle, evacuated, and the vacuum was controlled at 0.02 MPa. The mixture was slowly heated to 240°C. The distilled product was condensed in a condenser and then placed in a product receiving kettle. A solvent was then added to the kettle, heated and stirred to dissolve, and then cooled to allow the product to slowly crystallize and precipitate. The mixture was then filtered and the resulting filter cake was dried to obtain pure isosorbide.

[0124] The yields of 1,4-anhydrosorbitol and isosorbide were calculated, and the conversion rate of sorbitol and the yield of isosorbide were calculated. The results are shown in Table 1.

[0125] Comparative Example 3

[0126] This comparative example is used to illustrate the production method of isosorbide for reference.

[0127] The operation was carried out according to the method of Example 1, except that the catalyst for the first dehydration and the catalyst for the second dehydration were used for the second dehydration and the first dehydration respectively.

[0128] The yields of 1,4-anhydrosorbitol and isosorbide were calculated, and the conversion rate of sorbitol and the yield of isosorbide were calculated. The results are shown in Table 1.

[0129] Comparative Example 4

[0130] This comparative example is used to illustrate the production method of isosorbide for reference.

[0131] The operation was carried out according to the method of Example 1, except that the catalyst for the first dehydration was concentrated sulfuric acid.

[0132] The yields of 1,4-anhydrosorbitol and isosorbide were calculated, and the conversion rate of sorbitol and the yield of isosorbide were calculated. The results are shown in Table 1.

[0133] Table 1

[0134] serial number 1,4-Anhydrosorbitol yield g Isosorbide yield g Sorbitol conversion rate% Isosorbide yield% Example 1 125 91 99 81 Example 2 124 87 98 77 Example 3 123 85 97 75 Example 4 120 82 95 73 Example 5 125 86 99 76 Example 6 125 84 99 75 Example 7 125 71 99 63 Comparative Example 1 - 76 95 67 Comparative Example 2 - 71 95 63 Comparative Example 3 105 72 83 64 Comparative Example 4 110 58 90 51

[0135] It can be seen from the results in Table 1 that when the method of the present invention is used to produce isosorbide, especially in the case of a preferred catalyst, a higher isosorbide yield can be obtained, with significantly better results.

[0136] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A method for producing isosorbide, characterized in that, The method comprises the following steps: performing a first dehydration treatment on sorbitol in the presence of a first catalyst and a protective agent to obtain a first dehydration product; and performing a second dehydration treatment on the first dehydration product in the presence of a second catalyst to obtain isosorbide; wherein the first catalyst is a sulfonic acid ion exchange resin; the second catalyst is different from the first catalyst; The protective agent is boric acid; The preparation method of the second catalyst comprises: contacting a metal oxide with a phosphoric acid solution or a sulfuric acid solution, and then calcining to obtain the second catalyst; The metal oxide is at least one of Nb2O5, CuO and ZrO2.

2. The method according to claim 1, wherein The BET specific surface area of ​​the first catalyst is 20-100 m 2 / g; acidity is 0.5-6mmol / g.

3. The method according to claim 2, wherein: The BET specific surface area of ​​the first catalyst is 40-60 m 2 / g; acidity is 4-5.5mmol / g.

4. The method according to any one of claims 1 to 3, wherein: Compared to 100 parts by weight of the sorbitol, the amount of the first catalyst is 0.1-10 parts by weight.

5. The method according to claim 4, wherein Compared to 100 parts by weight of the sorbitol, the amount of the first catalyst is 0.5-5 parts by weight.

6. The method according to any one of claims 1 to 3 and 5, wherein: Compared to 1 mol of sorbitol, the amount of the protective agent used is 0.01-5 mol.

7. The method according to claim 6, wherein: Compared to 1 mol of sorbitol, the amount of the protective agent used is 0.05-0.5 mol.

8. The method according to any one of claims 1 to 3, 5 and 7, wherein: Sorbitol exists in the form of sorbitol solid or sorbitol solution.

9. The method according to claim 8, wherein The concentration of the sorbitol solution is 50% by weight or more.

10. The method according to any one of claims 1 to 3, 5, 7 and 9, wherein: The conditions of the first dehydration treatment include: temperature of 115-135°C; time of 5-10 hours; The first dehydration treatment is performed under a vacuum environment.

11. The method according to claim 10, wherein: The vacuum degree in the vacuum environment is 0.01 MPa to 0.03 MPa.

12. The method according to any one of claims 1 to 3, 5, 7, 9 and 11, wherein: The method further comprises performing a first purification on the first dehydration product to obtain dehydrated sorbitol.

13. The method according to any one of claims 1 to 3, 5, 7, 9 and 11, wherein: Calculated as metal element, the amount of the second catalyst is 0.1-10 parts by weight relative to 100 parts by weight of sorbitan.

14. The method according to claim 13, wherein Calculated as metal element, the amount of the second catalyst is 2-6 parts by weight relative to 100 parts by weight of sorbitan.

15. The method according to any one of claims 1 to 3, 5, 7, 9 and 11, wherein: The preparation method of the second catalyst is to contact at least one of Nb2O5, CuO and ZrO2 with phosphoric acid or sulfuric acid and then calcine to obtain the second catalyst.

16. The method according to claim 15, wherein The contacting method is immersion.

17. The method according to claim 15, wherein: The contact conditions include: temperature of 25-100° C.; time of 5-24 hours.

18. The method according to claim 15, wherein The calcination conditions include: temperature of 200-600° C.; time of 3-8 hours.

19. The method according to any one of claims 1 to 3, 5, 7, 9 and 11, wherein: The conditions of the second dehydration treatment include: temperature of 130-150°C; time of 3-7h; And / or, the second dehydration treatment is performed under a vacuum environment.

20. The method according to claim 19, wherein The vacuum degree in the vacuum environment is 0.001 MPa to 0.01 MPa.

21. The method according to any one of claims 1 to 3, 5, 7, 9 and 11, wherein: The method further comprises performing a second purification treatment on the product after the second dehydration treatment to obtain purified isosorbide.

Images