A modified molecular sieve catalyst for the dehydration of sorbitol to produce isosorbide, and its preparation method and application

Abstract

The present invention belongs to the technical field of catalytic chemistry, and discloses a modified molecular sieve catalyst for the reaction of sorbitol dehydration to isosorbide, and a preparation method and application thereof. The modified molecular sieve catalyst uses a β molecular sieve as a carrier, and the β molecular sieve is loaded with a bimetallic ion and an ionic liquid, and the ratio of B acid to L acid of the modified molecular sieve catalyst is 0.02 to 1.0. The preparation method of the modified molecular sieve catalyst comprises the following steps: adding an ionic liquid to a bimetallic ion salt solution and stirring at 20 to 80° C. for 2 hours, loading it onto a β molecular sieve by an equal volume impregnation method, and calcining at 550° C. for 4 to 8 hours after drying to obtain a modified molecular sieve catalyst. The modified molecular sieve of the present invention is compositely modified by a metal salt solution and an ionic liquid, which improves the anti-coking performance of the catalyst while improving the catalytic activity, so that it has good repeatability.

Description

Technical Field

[0001] The invention belongs to the technical field of catalytic chemistry, and in particular relates to a modified molecular sieve catalyst for the reaction of dehydrating sorbitol to prepare isosorbide, and a preparation method and application thereof. Background Art

[0002] Sorbitol is a sustainable platform chemical, and its derivative isosorbide is widely used in pharmaceuticals, surfactants, polymer modification, etc. Isosorbide has unique chemical properties and significant environmental advantages, which meets the requirements of the dual carbon goals and the need for environmental protection, and will become one of the core bio-based components for the production of fine chemicals and biodegradable polymers.

[0003] The direct cyclodehydration of sorbitol to prepare isosorbide involves two steps. Under the action of an acid catalyst, sorbitol first undergoes a dehydration reaction to generate the main intermediate product 1,4-anhydrosorbitol. Subsequently, 1,4-anhydrosorbitol is further dehydrated and finally converted into the target product isosorbide. The reaction path is as follows:

[0004]

[0005] The difficulty of preparing isosorbide by dehydration of sorbitol lies in the uncertainty of the degree of dehydration, which results in low selectivity of isosorbide. The catalyst is the key to the reaction. The reaction is generally carried out under the action of a liquid acid catalyst, which has the disadvantages of being easy to corrode equipment, difficult to separate products, large amount of solid waste, and difficult to recycle.

[0006] Heterogeneous solid acid catalysts have many advantages over traditional liquid acid catalysts, including easy separation, recyclability, and environmental friendliness, which make solid acid catalysts more attractive in industrial applications. Existing solid catalysts for dehydration of sorbitol to isosorbide, such as metal phosphates and molecular sieves, are mostly used at higher reaction temperatures, which will produce a large amount of by-products, and the solid acid catalysts have poor activity and stability and severe coking. Therefore, the development of highly efficient, recyclable and excellent solid acid catalysts is the key. By continuously improving and optimizing the design of the catalyst, enhancing its catalytic activity and selectivity, the production efficiency of isosorbide can be further improved and its production cost can be reduced. Summary of the invention

[0007] In view of the problems in the prior art, the present invention discloses a modified molecular sieve catalyst for the reaction of dehydrating sorbitol to prepare isosorbide, and a preparation method and application thereof.

[0008] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0009] A modified molecular sieve catalyst for the reaction of dehydrating sorbitol to produce isosorbide, wherein the modified molecular sieve catalyst uses a β molecular sieve as a carrier, and the β molecular sieve is loaded with a bimetallic ion and an ionic liquid; the first metal ion in the bimetallic ion is Sn 4+ , the second metal ion is Nb 5+ 、 5+ , Fe 3+ 、Al 3+ , Ca 2+ Mg 2+ 、Ce 2+ The ionic liquid is one of imidazole, quaternary ammonium and pyridine, wherein the anion is one of chloride, bromide, tetrahydroborate and hexafluorophosphate; the ratio of B acid to L acid of the modified molecular sieve catalyst is 0.02 to 1.0.

[0010] The ionic liquid is preferably one of 1-butyl-3-methylimidazolium chloride and 1-ethyl-3-methylimidazolium chloride.

[0011] A method for preparing a modified molecular sieve catalyst for the reaction of dehydrating sorbitol to produce isosorbide comprises the following steps: adding an ionic liquid to a bimetallic ion salt solution and stirring at 20-80°C for 2h, loading the ionic liquid onto a beta molecular sieve by an equal volume impregnation method, and calcining at 550°C for 4-8h after drying to obtain the modified molecular sieve catalyst.

[0012] The concentration of the first metal ion in the double metal ion salt solution is 0.05-1 mol / L, and the concentration of the second metal ion is 0.05-1 mol / L.

[0013] The mass ratio of the molecular sieve to the ionic liquid is (20-200):1.

[0014] The temperature for equal volume immersion is 40°C and the time is 2 h.

[0015] The drying condition was 110°C overnight.

[0016] A method for preparing isosorbide by dehydrating sorbitol specifically comprises: under the action of a modified molecular sieve catalyst, sorbitol is subjected to an etherification reaction and dehydrated to prepare isosorbide.

[0017] The mass ratio of the modified molecular sieve catalyst to sorbitol is 1:(10-20).

[0018] Preferably, the mass ratio of the modified molecular sieve catalyst to sorbitol is 1:15.

[0019] The reaction temperature is 170-180°C and the reaction time is 5-6h.

[0020] Beneficial effects:

[0021] (1) The modified molecular sieve catalyst of the present invention has a good catalytic effect on the etherification reaction. In the process of dehydration ring formation within the sorbitol molecule, it has the advantages of good high temperature resistance, good selectivity and regeneration. The molecular sieve catalyst is modified by a metal salt solution, which can improve the acid properties of the catalyst surface. By modifying with an ionic liquid, the local microenvironment of the catalytic active center is further regulated, and more binding sites are provided during the diffusion process of the reactants, which plays a good catalytic role. Compared with the unmodified β molecular sieve, the modified molecular sieve has a relatively enhanced absorption peak of L acid after being compositely modified with a double metal ion and an ionic liquid, and the number of L acid sites on its surface increases. A higher concentration of L acid sites exists on the surface of the modified molecular sieve, which improves the catalytic performance.

[0022] (2) The use of ionic liquid modification achieves a high degree of dispersion of the metal active centers, allowing the metal active centers to be more evenly loaded on the catalyst surface. The presence of ionic liquids can achieve the hydrophilicity and hydrophobicity regulation of the local microenvironment of the catalyst active center, which is beneficial to the internal and external diffusion of reactants and products and improves the mass transfer efficiency.

[0023] (3) The composite modification of metal salt solution and ionic liquid not only improves the catalytic activity of the catalyst, but also improves the anti-coking performance of the catalyst, making it have good reproducibility. After five repeated tests, the conversion rate of sorbitol of the modified molecular sieve catalyst can still reach 100%. Although the yield of isosorbide has decreased slightly, overall, pyridine infrared spectroscopy analysis confirmed that the catalyst structure and surface acid sites remain stable after recovery, indicating that the catalyst has good reuse potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Pyridine infrared spectrum of NbSn / β-[BMIM] molecular sieve. DETAILED DESCRIPTION

[0025] The method of the present invention is described in detail below with reference to specific examples.

[0026] Example 1

[0027] A modified molecular sieve catalyst for catalyzing the dehydration of sorbitol to produce isosorbide, wherein the modified molecular sieve catalyst uses a β molecular sieve as a carrier, and the β molecular sieve is loaded with a first metal ion Sn 4+ , the second metal ion Nb 5+ and the ionic liquid 1-butyl-3-methylimidazolium chloride ([BMIM]Cl).

[0028] The preparation method of the modified molecular sieve catalyst specifically comprises the following steps:

[0029] The prepared 30 mL 0.3 mol / L SnCl4 solution and 30 mL 0.3 mol / L niobium pentachloride solution were mixed, and then 0.5 g [BMIM]Cl was added and stirred at 40 °C for 2 h. Then, it was loaded on 10 g β molecular sieve by an equal volume impregnation method, and after drying, it was calcined at 550 °C for 4 h to obtain NbSn / β-[BMIM] catalyst.

[0030] The method of preparing isosorbide by dehydrating sorbitol using NbSn / β-[BMIM] catalyst comprises the following steps: adding 2 g of catalyst and 30 g of sorbitol into a reactor, reacting at 180° C. for 6 h to prepare isosorbide. The conversion rate of sorbitol was measured to be 100%, and the yield of isosorbide reached 88.2%.

[0031] The acidity information (B acid, L acid) of NbSn / β-[BMIM] catalyst was tested by pyridine infrared method. The pyridine infrared spectrum of molecular sieve is shown in Figure 1 ,Depend on Figure 1 It can be seen that at 1540cm -1 and 1450cm -1 The absorption peaks at the bottom are those of B acid and L acid, respectively. Compared with the unmodified β molecular sieve, the absorption peak of L acid is relatively enhanced after the NbSn / β-[BMIM] molecular sieve is modified with double metal ions and ionic liquids, and the number of L acid sites on its surface increases. At this time, the ratio of B acid to L acid is 0.71. There is a higher concentration of L acid sites on the surface of the modified molecular sieve, which has a positive effect on the catalytic performance, especially in reactions that require L acid catalytic activity.

[0032] Example 2

[0033] A modified molecular sieve catalyst for catalyzing the dehydration of sorbitol to produce isosorbide, wherein the modified molecular sieve catalyst uses a β molecular sieve as a carrier, and the β molecular sieve is loaded with a first metal ion Sn 4+ , the second metal ion Ta 5+ and ionic liquid [BMIM]Cl.

[0034] The preparation method of the modified molecular sieve catalyst specifically comprises the following steps:

[0035] The prepared 30 mL 0.3 mol / L SnCl4 solution and 30 mL 0.3 mol / L tantalum pentachloride solution were mixed, and then 0.5 g [BMIM]Cl was added and stirred at 40 °C for 2 h. Then, it was loaded on 10 g β molecular sieve by an equal volume impregnation method, and after drying, it was calcined at 550 °C for 4 h to obtain TaSn / β-[BMIM] catalyst.

[0036] The method of preparing isosorbide by dehydrating sorbitol using TaSn / β-[BMIM] catalyst comprises the following steps: adding 2 g of catalyst and 30 g of sorbitol into a reactor, and reacting at 170° C. for 5 h to prepare isosorbide. The conversion rate of sorbitol is measured to be 100%, and the yield of isosorbide reaches 78.5%.

[0037] Example 3

[0038] A modified molecular sieve catalyst for catalyzing the dehydration of sorbitol to produce isosorbide, wherein the modified molecular sieve catalyst uses a β molecular sieve as a carrier, and the β molecular sieve is loaded with a first metal ion Sn 4+ , the second metal ion Nb 5+ and the ionic liquid 1-ethyl-3-methylimidazolium chloride ([EMIM]Cl).

[0039] The preparation method of the modified molecular sieve catalyst specifically comprises the following steps:

[0040] The prepared 30 mL 0.3 mol / L SnCl4 solution and 30 mL 0.3 mol / L niobium oxalate solution were mixed, and then 0.5 g [EMIM]Cl was added and stirred at 40 °C for 2 h. Then, it was loaded on 10 g β molecular sieve by an equal volume impregnation method, and after drying, it was calcined at 550 °C for 4 h to obtain NbSn / β-[EMIM] catalyst.

[0041] The method of preparing isosorbide by dehydrating sorbitol using NbSn / β-[EMIM] catalyst comprises the following steps: adding 2 g of catalyst and 30 g of sorbitol into a reactor, reacting at 170° C. for 5 h to prepare isosorbide. The conversion rate of sorbitol is measured to be 100%, and the yield of isosorbide reaches 72.5%.

[0042] Example 4

[0043] A modified molecular sieve catalyst for catalyzing the dehydration of sorbitol to produce isosorbide, wherein the modified molecular sieve catalyst uses a β molecular sieve as a carrier, and the β molecular sieve is loaded with a first metal ion Sn 4+ , the second metal ion Ce 2+ and ionic liquid [BMIM]Cl.

[0044] The preparation method of the modified molecular sieve catalyst specifically comprises the following steps:

[0045] The prepared 0.3 mol / L SnCl4 solution and 0.3 mol / L cerium nitrate solution were mixed, and then 0.5 g of [BMIM]Cl was added and stirred at 40°C for 2 h. Then, it was loaded on 10 g of β molecular sieve by an equal volume impregnation method. After drying, it was calcined at 550°C for 4 h to obtain CeSn / β-[BMIM] catalyst.

[0046] The method of preparing isosorbide by dehydrating sorbitol using a CeSn / β-[BMIM] catalyst comprises the following steps: adding 2 g of the catalyst and 30 g of sorbitol into a reactor, and reacting at 180° C. for 6 h to prepare isosorbide. The conversion rate of sorbitol was measured to be 100%, and the yield of isosorbide reached 73.2%.

[0047] Example 5

[0048] A modified molecular sieve catalyst for catalyzing the dehydration of sorbitol to produce isosorbide, wherein the modified molecular sieve catalyst uses a β molecular sieve as a carrier, and the β molecular sieve is loaded with a first metal ion Sn 4+ 、Second metal ion Mg 2+ and the ionic liquid was [BMIM]Cl.

[0049] The preparation method of the modified molecular sieve catalyst specifically comprises the following steps:

[0050] The prepared 0.3 mol / L SnCl4 solution and 0.3 mol / L magnesium nitrate solution were mixed, and then 0.5 g of [BMIM]Cl was added and stirred at 40°C for 2 h. Then, it was loaded on 10 g of β molecular sieve by an equal volume impregnation method, and after drying, it was calcined at 550°C for 4 h to obtain MgSn / β-[BMIM] catalyst.

[0051] The method of preparing isosorbide by dehydrating sorbitol using a MgSn / β-[BMIM] catalyst comprises the following steps: adding 2 g of the catalyst and 30 g of sorbitol into a reactor, and reacting at 180° C. for 6 h to prepare isosorbide. The conversion rate of sorbitol is measured to be 100%, and the yield of isosorbide reaches 66.7%.

[0052] Example 6

[0053] The modified molecular sieve catalyst and its preparation method in this embodiment are the same as those in Example 1.

[0054] The difference is that the NbSn / β-[BMIM] catalyst is used to catalyze the dehydration of sorbitol to prepare isosorbide, which includes the following steps: 1g of the catalyst and 30g of sorbitol are added to a reactor, and the reaction is carried out at 180°C for 6h to prepare isosorbide. The measured sorbitol conversion rate is 98%, and the isosorbide yield reaches 83%.

[0055] By comparing Example 1 with Example 6, it can be seen that reducing the amount of catalyst used reduces the sorbitol conversion rate and the isosorbide yield.

[0056] Example 7

[0057] The catalyst of this example is the catalyst recovered in Example 1, and the reaction conditions remain the same. The conversion rate of sorbitol was measured 5 times and was 100%, and the yields of isosorbide were 88.2%, 87.5%, 87.1%, 86.9% and 86.5% respectively.

[0058] Comparative Example 1

[0059] A modified molecular sieve catalyst for catalyzing the dehydration of sorbitol to produce isosorbide, wherein the modified molecular sieve catalyst uses a β molecular sieve as a carrier, and the β molecular sieve is loaded with metal ions Sn 4+ and ionic liquid [BMIM]Cl.

[0060] The preparation method of the modified molecular sieve catalyst specifically comprises the following steps:

[0061] 0.5 g of [BMIM]Cl was added to the prepared 0.3 mol / L SnCl4 solution and stirred at 40°C for 2 h. It was then loaded onto 10 g of β molecular sieve by an equal volume impregnation method. After drying, the solution was calcined at 550°C for 4 h to obtain the Sn / β-[BMIM] catalyst.

[0062] The Sn / β-[BMIM] catalyst is used to catalyze the dehydration of sorbitol to prepare isosorbide, comprising the following steps: 2 g of the catalyst and 30 g of sorbitol are added to a reactor, and the reaction is carried out at 180° C. for 6 h to prepare isosorbide. The measured sorbitol conversion rate is 99%, and the isosorbide yield reaches 71%.

[0063] Comparative Example 2

[0064] A modified molecular sieve catalyst for catalyzing the dehydration of sorbitol to produce isosorbide, wherein the modified molecular sieve catalyst uses a β molecular sieve as a carrier, and the β molecular sieve is loaded with a first metal ion Sn 4+ and the second metal ion Nb 5+ .

[0065] The preparation method of the modified molecular sieve catalyst specifically comprises the following steps:

[0066] The prepared 30 mL 0.3 mol / L SnCl4 solution and 30 mL 0.3 mol / L magnesium nitrate solution were mixed, stirred at 40°C for 2 h, and then loaded onto 10 g β molecular sieve by an equal volume impregnation method. After drying, the mixture was calcined at 550°C for 4 h to obtain a NbSn / β catalyst.

[0067] The method of using NbSn / β catalyst to catalyze the dehydration of sorbitol to prepare isosorbide comprises the following steps: adding 2g of catalyst and 30g of sorbitol into a reactor, reacting at 180°C for 6h to prepare isosorbide. The conversion rate of sorbitol was measured to be 99%, and the yield of isosorbide reached 71%.

Claims

1. A modified molecular sieve catalyst for the dehydration of sorbitol to isosorbide, characterized in that: The modified molecular sieve catalyst is prepared by calcining with β molecular sieve as a carrier, on which bimetallic ions and ionic liquid are loaded; The first metal ion in the double metal ion is Sn 4+ , the second metal ion is Nb 5+ 、 5+ , Fe 3+ 、Al 3+ , Ca 2+ Mg 2 + 、Ce 3+ One of; The ionic liquid is one of imidazole, quaternary ammonium and pyridine, wherein the anion is one of chloride, bromide, tetrahydroborate and hexafluorophosphate; The ratio of B acid to L acid of the modified molecular sieve catalyst is 0.02 to 1.0; The bimetallic ions are loaded onto the beta molecular sieve via a bimetallic ion salt solution; The concentration of the first metal ion in the double metal ion salt solution is 0.05-1 mol / L, and the concentration of the second metal ion is 0.05-1 mol / L; The calcination conditions are: calcination at 550℃ for 4~8 h.

2. A method for preparing the modified molecular sieve catalyst according to claim 1, characterized in that: The following steps are involved: The ionic liquid is added to the bimetallic ion salt solution and stirred at 20-80°C for 2 h, the bimetallic ions and the ionic liquid are loaded onto the β molecular sieve by an equal volume impregnation method, and after drying, the modified molecular sieve catalyst is calcined at 550°C for 4-8 h. The concentration of the first metal ion in the double metal ion salt solution is 0.05-1 mol / L, and the concentration of the second metal ion is 0.05-1 mol / L.

3. The method for preparing the modified molecular sieve catalyst according to claim 2, characterized in that: The mass ratio of the β molecular sieve to the ionic liquid is (20-200):

1.

4. A method for preparing isosorbide by dehydrating sorbitol, characterized in that: Specifically, under the action of the modified molecular sieve catalyst of claim 1, sorbitol undergoes an etherification reaction and dehydration to prepare isosorbide.

5. The method for preparing isosorbide by dehydrating sorbitol according to claim 4, wherein: The mass ratio of the modified molecular sieve catalyst to sorbitol is 1:(10~20).

6. The method for preparing isosorbide by dehydrating sorbitol according to claim 5, wherein: The mass ratio of the modified molecular sieve catalyst to sorbitol is 1:

15.

7. The method for preparing isosorbide by dehydrating sorbitol according to claim 4, wherein: The reaction temperature is 170-180°C and the reaction time is 5-6 h.

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