A catalyst for preparing 3,4-dihydro-2H-pyran and a method for preparing 3,4-dihydro-2H-pyran

Abstract

The application relates to a catalyst for preparing 3,4-dihydro-2H-pyran, a preparation method of the catalyst and a method for preparing 3,4-dihydro-2H-pyran by using the catalyst. The catalyst comprises a carrier, an active component and a promoter component, and is prepared by immersing the carrier in an active component precursor aqueous solution, stirring and uniformly standing, and then drying; calcining in an air atmosphere; reducing in a hydrogen atmosphere; immersing in a promoter component precursor aqueous solution, stirring and uniformly standing, and then drying; calcining in an air atmosphere; and reducing in a hydrogen atmosphere. The catalyst according to the application is applied to a process for preparing 3,4-dihydro-2H-pyran by taking tetrahydrofurfuryl alcohol as a raw material, the generation of a tetrahydropyran byproduct is reduced, the selectivity of 3,4-dihydro-2H-pyran is improved, and the difficulty of separation is reduced. The method for preparing 3,4-dihydro-2H-pyran provided by the application has the advantages of easy raw material, a more green route, simple process, high efficiency and continuous production.

Description

Technical Field

[0001] This application relates to the field of chemical synthesis, and more specifically, to a catalyst for the preparation of 3,4-dihydro-2H-pyran from tetrahydrofurfuryl alcohol dehydration rearrangement and a method for preparing 3,4-dihydro-2H-pyran using the catalyst. Background Technology

[0002]

[0003] 3,4-Dihydro-2H-pyran, CAS No.: 110-87-2, abbreviated as DHP, is a colorless liquid with a freezing point of -70℃, a boiling point of 86℃~87℃, a relative density of 0.9221 (19 / 15℃), a refractive index of 1.4402 (19℃), and a flash point of -15℃. It is widely used as a hydroxyl-protecting agent. Through polymerization, hydrogenation, and oxidation, it can be used to produce tetrahydropyran, pentanediol, glutaric acid, valerate, pentadiene, and resin products. It can also be used as a pharmaceutical intermediate, a solvent, and an organic synthesis intermediate. When used for hydroxyl protection, 3,4-dihydro-2H-pyran generally does not react with nucleophiles or organometallic reagents. It is resistant to strong bases but is prone to change under low pH or Lewis acid conditions.

[0004]

[0005] Numerous studies have reported on the dehydration rearrangement synthesis of 3,4-dihydro-2H-pyran from tetrahydrofurfuryl alcohol (as shown above). For instance, Schniepp and Geller (J. Am. Chem. Soc. 68 (1946) 1646–1648) reported in 1946 that 3,4-dihydro-2H-pyran could be synthesized from tetrahydrofurfuryl alcohol through dehydration rearrangement. Subsequently, Sato (Applied Catalysis A: General 453 (2013) 213-218) and Huber (Source: doi.org / 10.1016 / j.apcatb.2018.12.039) conducted detailed studies on the aforementioned dehydration rearrangement reaction and found that it was difficult to reduce the formation of the byproduct tetrahydropyran while maintaining high selectivity (>90%) for 3,4-dihydro-2H-pyran during the reaction. The standard quality for commercially available 3,4-dihydro-2H-pyran is typically a purity >98.5% and a tetrahydropyran content <1.5%. Because 3,4-dihydro-2H-pyran and tetrahydropyran have similar molecular structures and properties, with only a 2°C difference in boiling point (3,4-dihydro-2H-pyran 86°C, tetrahydropyran 88°C), separating them requires significant energy consumption, increasing production costs.

[0006] Currently, existing technologies often employ γ-Al₂O₃ or molecular sieves to directly catalyze the dehydration rearrangement of tetrahydrofurfuryl alcohol to synthesize 3,4-dihydro-2H-pyran. Huber et al. (doi.org / 10.1016 / j.apcatb.2018.12.039) compared the results of the dehydration rearrangement of tetrahydrofurfuryl alcohol to synthesize 3,4-dihydro-2H-pyran under the same conditions using γ-Al₂O₃ and various molecular sieve catalysts, finding that γ-Al₂O₃ exhibits higher reactivity and product selectivity compared to molecular sieves (HY, H-Beta, H-ZSM5). From a cost perspective, γ-Al₂O₃ is a more suitable catalyst support. The main problem with this reaction is the insufficient selectivity for 3,4-dihydro-2H-pyran in the product, while the content of the byproduct tetrahydropyran is difficult to reduce, which poses a significant drawback to the subsequent separation of the two products.

[0007] Therefore, while ensuring the yield of the target product 3,4-dihydro-2H-pyran, minimizing the content of the byproduct tetrahydropyran and significantly reducing the operational difficulty and energy consumption of the production process have become the key issues of this reaction. Summary of the Invention

[0008] Technical issues

[0009] One objective of this application is to provide a catalyst for the preparation of 3,4-dihydro-2H-pyran, which is used to prepare 3,4-dihydro-2H-pyran from tetrahydrofurfuryl alcohol via a continuous selective dehydration rearrangement reaction. The catalyst for the preparation of 3,4-dihydro-2H-pyran according to this application exhibits extremely excellent catalytic activity and target selectivity. It can catalyze the dehydration rearrangement of tetrahydrofurfuryl alcohol to prepare the target product 3,4-dihydro-2H-pyran with a selectivity of over 92%, while the selectivity of the byproduct tetrahydropyran is only about 0.2%. This ensures the yield of the target product while significantly reducing the difficulty of subsequent separation, eliminating the need for complex distillation operations to obtain high-purity 3,4-dihydro-2H-pyran.

[0010] Another objective of this application is to provide a method for preparing the aforementioned catalyst.

[0011] Another object of this application is to provide a method for preparing 3,4-dihydro-2H-pyran using the catalyst.

[0012] Technical solution

[0013] According to one aspect of this application, a catalyst for preparing 3,4-dihydro-2H-pyran is provided, said catalyst comprising a support, an active component, and a co-catalyst component, wherein:

[0014] The support includes one or more selected from γ-Al2O3, SiO2, ZrO2, TiO2, HZSM5, SAPO-34, HY, Hβ and HMOR;

[0015] The active component includes one or more metallic elements selected from platinum (Pt), palladium (Pd), ruthenium (Ru), and rhodium (Rh);

[0016] The co-catalyst component includes one or more metallic elements selected from potassium (K), sodium (Na), lithium (Li), magnesium (Mg), and calcium (Ca).

[0017] According to one embodiment of this application, in the catalyst, the mass ratio of the metal element in the active component to the support is (0.01-2):100. Below this range, the selectivity of the byproduct tetrahydropyran in the product increases, making the purification of the target product 3,4-dihydro-2H-pyran more difficult; while above this range, the reaction generates a large number of light component byproducts, resulting in a worse material balance of the reaction.

[0018] According to one embodiment of this application, in the catalyst, the mass ratio of the metal element in the co-catalyst component to the metal element in the active component is (0.05~2):1. Below this range, the reaction will generate a large number of light component byproducts, resulting in a poor material balance of the reaction; while above this range, the conversion rate of the target product 3,4-dihydro-2H-pyran in the reaction will be greatly reduced.

[0019] Preferably, the active component includes one or more metallic elements selected from platinum (Pt), palladium (Pd), and ruthenium (Ru).

[0020] Preferably, the co-catalyst component includes one or more metal elements selected from potassium (K), sodium (Na), and lithium (Li).

[0021] According to another aspect of this application, a method for preparing the catalyst is provided, the method comprising the following steps:

[0022] (1) Impregnate the carrier with an equal volume of the active component precursor aqueous solution, let it stand, and then dry it;

[0023] (2) The product obtained in step (1) is calcined in air at 250℃~300℃ for 2h~5h;

[0024] (3) Reduce the product obtained in step (2) in a hydrogen atmosphere at 250℃~350℃ for 2h~4h;

[0025] (4) Impregnate an equal volume of the product obtained in step (3) with an aqueous solution of the catalyst precursor, let stand, and then dry.

[0026] (5) The product obtained in step (4) is calcined in air at 250℃~300℃ for 2h~5h; and

[0027] (6) Reduce the product obtained in step (5) in a hydrogen atmosphere at 250℃~350℃ for 2h~4h.

[0028] According to one embodiment of this application, the active component precursor includes one or more of nitrates, chlorides (chloride coordination salts) and acetates selected from Pt, Pd, Ru and Rh.

[0029] According to one embodiment of this application, the cocatalyst component precursor includes one or more carbonates, sulfates and hydroxides selected from potassium, sodium, lithium, magnesium and calcium.

[0030] According to one embodiment of this application, in step (1), the concentration of the aqueous solution of the active component precursor is 0.005 mol / L to 0.05 mol / L.

[0031] According to one embodiment of this application, in step (1), the settling time is 2h to 5h.

[0032] According to one embodiment of this application, in step (1), the drying temperature is 110°C to 150°C and the drying time is 5h to 10h.

[0033] According to one embodiment of this application, in step (4), the concentration of the aqueous solution of the co-catalyst component precursor is 0.05 mol / L to 0.2 mol / L.

[0034] According to one embodiment of this application, in step (4), the settling time is 2h to 5h.

[0035] According to one embodiment of this application, in step (4), the drying temperature is 110°C to 150°C and the drying time is 5h to 10h.

[0036] According to one embodiment of this application, the method for preparing the catalyst further includes pretreatment of the support. Specifically, before step (1), the support is calcined in air at 200°C to 400°C for 2 to 5 hours.

[0037] According to another aspect of this application, a method for preparing 3,4-dihydro-2H-pyran using the above-described catalyst is provided, comprising:

[0038] In the presence of the catalyst, tetrahydrofurfuryl alcohol is subjected to a dehydration rearrangement reaction in a reactor at 200°C to 500°C.

[0039] According to one embodiment of this application, the reactor in the method for preparing 3,4-dihydro-2H-pyran is selected from any one of batch reactors, semi-batch reactors, continuous stirred tank reactors, plug flow reactors, stationary phase reactors, and fluidized bed reactors, or it can be a mixed reactor consisting of two or more of these reactors connected together. Preferably, it is a fixed bed reactor.

[0040] The catalyst can be in the form of strips, columns, or flakes.

[0041] According to one embodiment of this application, the dehydration rearrangement reaction temperature is preferably 250°C to 400°C.

[0042] According to one embodiment of this application, the dehydration rearrangement reaction can be carried out under one or more of a nitrogen atmosphere, a helium atmosphere, an argon atmosphere, and a hydrogen atmosphere.

[0043] According to one embodiment of this application, the method for preparing 3,4-dihydro-2H-pyran can be carried out at a reaction pressure of 0.1 MPa (or atmospheric pressure) to 4 MPa, preferably 0.1 MPa (or atmospheric pressure) to 2 MPa.

[0044] According to one embodiment of this application, the tetrahydrofurfuryl alcohol can be reacted in the presence of a solvent or in the presence of a solvent, wherein the solvent is one or more selected from tetrahydrofuran, acetonitrile and 1,4-dioxane, preferably tetrahydrofuran or acetonitrile.

[0045] According to one embodiment of this application, the method for preparing 3,4-dihydro-2H-pyran can be completed in 0.05 h. -1 ~5h -1 Preferably 0.03h -1 ~3h -1 The reaction proceeds at a reaction space velocity of [value missing].

[0046] According to one embodiment of this application, the method for preparing 3,4-dihydro-2H-pyran further includes activating the catalyst before the reaction. Specifically, before the reaction, the catalyst is heated to an activation temperature of 300°C to 500°C and maintained for 1 to 6 hours. Preferably, the activation temperature can be 300°C to 400°C.

[0047] According to one embodiment of this application, the method for preparing 3,4-dihydro-2H-pyran further includes post-reaction processing. Specifically, the reaction product is subjected to condensation and gas-liquid separation, followed by distillation. The condensation, gas-liquid separation, and distillation are conventional methods and conditions in the art for separating 3,4-dihydro-2H-pyran and byproducts including tetrahydropyran, and will not be described in detail here.

[0048] Beneficial effects

[0049] The catalyst provided in this application for the synthesis of 3,4-dihydro-2H-pyran can catalyze the reaction of tetrahydrofurfuryl alcohol with a high conversion rate and the reaction has very high 3,4-dihydro-2H-pyran selectivity (up to 92% or more) and extremely low byproduct tetrahydropyran selectivity (only about 0.2%). This can greatly reduce the amount of tetrahydropyran in the product, fundamentally solve the problem of separating tetrahydropyran from 3,4-dihydro-2H-pyran in the product, further reduce production energy consumption, reduce production costs, and facilitate industrial production. Attached Figure Description

[0050] Figure 1 This is a schematic diagram of a synthesis reaction apparatus for 3,4-dihydro-2H-pyran according to one embodiment of this application.

[0051] Figure 2 This is a transmission electron microscope (TEM) image of the catalyst prepared according to Preparation Example 1 of one embodiment of this application.

[0052] Figure 3 The results of the physical adsorption test are for the catalyst prepared according to Preparation Example 1 of one embodiment of this application.

[0053] Figure 4 The results of ammonia temperature-programmed desorption of the catalyst prepared according to Preparation Example 1 and Comparative Preparation Example 1 are shown.

[0054] Figure 5 This is a gas chromatogram of the reaction product of reaction example 1 according to one embodiment of this application.

[0055] Figure 6 This is a gas chromatogram of the reaction product of Comparative Reaction Example 1 according to one embodiment of this application. Detailed Implementation

[0056] Preferred embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. Before description, it should be understood that the terminology used in the specification and appended claims should not be construed as limited to its general and dictionary meaning, but rather should be interpreted based on the principle of allowing the inventors to appropriately define the terminology for the best interpretation, and based on its meaning and concept corresponding to the technical level of the invention. Therefore, the description herein is merely a preferred example for illustrative purposes and is not intended to limit the scope of the invention; thus, it should be understood that other equivalent implementations and modifications can be made without departing from the spirit and scope of the invention.

[0057] The following embodiments are merely examples of implementation schemes of this application and do not constitute any limitation on this application. Those skilled in the art will understand that any modifications that do not depart from the essence and concept of this application fall within the protection scope of this application.

[0058] Preparation of 3,4-dihydro-2H-pyran

[0059] In the method for preparing 3,4-dihydro-2H-pyran according to this application, tetrahydrofurfuryl alcohol is used as a raw material, and an enol is obtained through a dehydration rearrangement reaction. The product obtained after post-processing is filtered through a 0.22 μm filter membrane and analyzed by gas chromatography (GC). Qualitative analysis of the low-boiling-point product is performed by GC-MS and comparison with the GC retention time of the standard, confirming that the main reaction product is tetrahydrofurfuryl alcohol. Quantitative determination of the low-boiling-point substance is performed using a Shimadzu-GC 2020 gas chromatograph, and quantitative analysis is performed by comparing the retention time with the standard and the peak area. The relevant calculation formulas are as follows:

[0060]

[0061]

[0062]

[0063]

[0064]

[0065] The flow rate of tetrahydrofurfuryl alcohol is expressed in g / min, and the amount of catalyst is expressed in g.

[0066] like Figure 1 The diagram shows a schematic of a synthesis reaction apparatus for 3,4-dihydro-2H-pyran according to one embodiment of this application. The reaction tube is filled with a catalyst according to this application for the preparation of 3,4-dihydro-2H-pyran. First, a carrier gas is introduced into the reaction tube at a controlled flow rate using a mass flow meter to create a carrier gas atmosphere. Then, a furnace can be used to heat the reactor to activate the catalyst. Next, while maintaining the temperature of the reaction tube, tetrahydrofurfuryl alcohol is fed into the reaction tube via a feed pump. Under the carrier gas atmosphere and with the catalyst catalyzing the reaction, a product containing 3,4-dihydro-2H-pyran is generated. After condensation and gas-liquid separation, 3,4-dihydro-2H-pyran can be collected.

[0067] According to this application, the catalyst is applied to the process of preparing 3,4-dihydro-2H-pyran from tetrahydrofurfuryl alcohol. By reducing the formation of tetrahydropyran byproducts, the selectivity of 3,4-dihydro-2H-pyran is improved, and the separation difficulty is reduced. The method for preparing 3,4-dihydro-2H-pyran provided in this application uses readily available raw materials, has a more environmentally friendly route, a simple process, high efficiency, and can be used for continuous production.

[0068] Unless otherwise specified, all raw materials used in this application are commercially available, and all methods and equipment used are conventional methods and equipment in the field.

[0069] In the following examples, tetrahydrofurfuryl alcohol, potassium carbonate, potassium sulfate, sodium carbonate, and magnesium nitrate were purchased from Sinopharm Chemical Reagent Co., Ltd.; chloroplatinic acid, palladium nitrate, and ruthenium chloride were purchased from Xi'an Kaili New Materials Co., Ltd.; and high-purity nitrogen, high-purity helium, and air were purchased from Qingdao Dehai Weiye Technology Co., Ltd.

[0070] Catalyst preparation

[0071] Preparation Example 1

[0072] A catalyst for the preparation of 3,4-dihydro-2H-pyran was prepared by a method including the following steps:

[0073] (i) Pretreatment of the support: 50g of γ-Al2O3 was calcined in air at 300℃ for 5h;

[0074] (ii) Impregnate the pretreated carrier obtained in step (i) with an equal volume of 0.01 mol / L chloroplatinic acid aqueous solution, let stand for 5 h, and then dry at 120 °C for 10 h.

[0075] (iii) The product obtained in step (ii) is calcined at 300°C in air for 5 hours;

[0076] (iv) The product obtained in step (iii) was reduced at 350 °C in a hydrogen atmosphere for 4 h, wherein the hydrogen flow rate was 50 mL / min;

[0077] (v) Impregnate an equal volume of the product obtained in step (iv) with a 0.03 mol / L potassium carbonate aqueous solution, let stand for 5 h, and then dry at 120 °C for 10 h;

[0078] (vi) The product obtained in step (v) is calcined at 300°C in air for 5 hours; and

[0079] (vii) The product obtained in step (vi) was reduced at 350 °C in a hydrogen atmosphere for 4 h, wherein the hydrogen flow rate was 50 mL / min, thereby obtaining catalyst 1.

[0080] Figure 2A transmission electron microscope (TEM) image of the catalyst prepared according to Example 1 of one embodiment of this application. From Figure 2 As can be seen, the active component metal Pt is uniformly distributed on the surface of the catalyst support with a particle size of about 3 nm to 4 nm.

[0081] Figure 3 The results of the physical adsorption test (specific surface area) of the catalyst prepared according to Example 1 of one embodiment of this application are shown. Specifically, the specific surface area and pore structure of the catalyst were determined using the Quantachrome Autosorb iQ fully automated rapid specific surface area and mesopore / micropore analyzer. The sample was first vacuum-treated at 150°C for 3 hours, then the sample weight was accurately measured. The amount of nitrogen adsorbed was then measured at liquid nitrogen temperature, and the specific surface area of ​​the sample was calculated based on the adsorption amount. The specific surface area of ​​the sample was calculated using the BET method, and the pore size distribution was calculated using the DFT method.

[0082] Figure 4 The results of ammonia temperature-programmed desorption (TPR) of the catalyst prepared according to Preparation Example 1 and Comparative Preparation Example 1 (shown below) according to one embodiment of this application are presented. Specifically, the NH3-TPR characterization of the catalyst was performed on a Micromeritics AutoChem 2920 chemisorption analyzer. The specific experimental steps are as follows: 0.1 g of sample was placed in a U-shaped quartz tube and purged at 150 °C for 2 h in an Ar atmosphere. Then, the temperature was lowered to 100 °C, and 5 wt% of the NH3 / Ar mixture was adsorbed at 100 °C for 2 h. Then, the physically adsorbed ammonia was purged under an Ar atmosphere for 1 h. After leveling the baseline, the temperature was increased to 800 °C at a rate of 10 °C / min. The NH3 signal was recorded using a TCD detector. The NH3-TPD comparison results show that both catalyst 1 and control catalyst 1 have acidic sites in the range of 130℃ to 220℃. The difference lies in the amount of these acidic sites in the two catalysts, with catalyst 1 showing a significantly lower amount than control catalyst 1 (the mass of catalyst added during testing was the same, so the peak area represents the amount of acidic sites). Therefore, the amount of acidic sites on the catalyst surface can be controlled by controlling the addition of the co-catalyst component.

[0083] Preparation Example 2

[0084] A catalyst for the preparation of 3,4-dihydro-2H-pyran was prepared by a method including the following steps:

[0085] (i) Pretreatment of the carrier: 50g of HY was calcined in air at 300°C for 5h;

[0086] (ii) Impregnate the pretreated carrier obtained in step (i) with an equal volume of 0.01 mol / L chloroplatinic acid aqueous solution, let stand for 5 h, and then dry at 120 °C for 10 h.

[0087] (iii) The product obtained in step (ii) is calcined at 300°C in air for 5 hours;

[0088] (iv) The product obtained in step (iii) was reduced at 350 °C in a hydrogen atmosphere for 4 h, wherein the hydrogen flow rate was 50 mL / min;

[0089] (v) Impregnate an equal volume of the product obtained in step (iv) with a potassium sulfate aqueous solution with a concentration of 0.03 mol / L, let stand for 5 h, and then dry at 110 °C for 10 h;

[0090] (vi) The product obtained in step (v) is calcined at 300°C in air for 5 hours; and

[0091] (vii) The product obtained in step (vi) was reduced at 350 °C in a hydrogen atmosphere for 4 h, wherein the hydrogen flow rate was 50 mL / min, thereby obtaining catalyst 2.

[0092] Preparation Example 3

[0093] A catalyst for the preparation of 3,4-dihydro-2H-pyran was prepared by a method including the following steps:

[0094] (i) Pretreatment of the carrier: 50 g of Hβ was calcined in air at 300 °C for 5 h; 50 g of Hβ was calcined in air at 300 °C for 5 h as a pretreatment.

[0095] (ii) Impregnate the pretreated carrier obtained in step (i) with an equal volume of 0.01 mol / L chloroplatinic acid aqueous solution, let stand for 5 h, and then dry at 120 °C for 10 h.

[0096] (iii) The product obtained in step (ii) is calcined at 300°C in air for 5 hours;

[0097] (iv) The product obtained in step (iii) was reduced at 350 °C in a hydrogen atmosphere for 4 h, wherein the hydrogen flow rate was 50 mL / min;

[0098] (v) Impregnate an equal volume of the product obtained in step (iv) with a potassium sulfate aqueous solution with a concentration of 0.03 mol / L, let stand for 5 h, and then dry at 110 °C for 10 h;

[0099] (vi) The product obtained in step (v) is calcined at 300°C in air for 5 hours; and

[0100] (vii) The product obtained in step (vi) was reduced at 350 °C in a hydrogen atmosphere for 4 h, wherein the hydrogen flow rate was 50 mL / min, thereby obtaining catalyst 3.

[0101] Preparation Example 4

[0102] A catalyst for the preparation of 3,4-dihydro-2H-pyran was prepared by a method including the following steps:

[0103] (i) Pretreatment of the support: 50g of γ-Al2O3 was calcined in air at 300℃ for 5h;

[0104] (ii) Impregnate the pretreated carrier obtained in step (i) with an equal volume of 0.01 mol / L palladium nitrate aqueous solution, let stand for 5 h, and then dry at 120 °C for 10 h.

[0105] (iii) The product obtained in step (ii) is calcined at 300°C in air for 5 hours;

[0106] (iv) The product obtained in step (iii) was reduced at 350 °C in a hydrogen atmosphere for 4 h, wherein the hydrogen flow rate was 50 mL / min;

[0107] (v) Impregnate an equal volume of the product obtained in step (iv) with a potassium sulfate aqueous solution with a concentration of 0.03 mol / L, let stand for 5 h, and then dry at 110 °C for 10 h;

[0108] (vi) The product obtained in step (v) is calcined at 300°C in air for 5 hours; and

[0109] (vii) The product obtained in step (vi) was reduced at 350 °C in a hydrogen atmosphere for 4 h, wherein the hydrogen flow rate was 50 mL / min, thereby obtaining catalyst 4.

[0110] Preparation Example 5

[0111] A catalyst for the preparation of 3,4-dihydro-2H-pyran was prepared by a method including the following steps:

[0112] (i) Pretreatment of the support: 50g of SiO2 was calcined in air at 300°C for 5h;

[0113] (ii) Impregnate the pretreated carrier obtained in step (i) with an equal volume of 0.01 mol / L chloroplatinic acid aqueous solution, let stand for 5 h, and then dry at 120 °C for 10 h.

[0114] (iii) The product obtained in step (ii) is calcined at 300°C in air for 5 hours;

[0115] (iv) The product obtained in step (iii) was reduced at 350 °C in a hydrogen atmosphere for 4 h, wherein the hydrogen flow rate was 50 mL / min;

[0116] (v) Impregnate an equal volume of the product obtained in step (iv) with a sodium carbonate aqueous solution with a concentration of 0.03 mol / L, let stand for 5 h, and then dry at 110 °C for 10 h;

[0117] (vi) The product obtained in step (v) is calcined at 300°C in air for 5 hours; and

[0118] (vii) The product obtained in step (vi) was reduced at 350 °C in a hydrogen atmosphere for 4 h, wherein the hydrogen flow rate was 50 mL / min, thereby obtaining catalyst 5.

[0119] Preparation Example 6

[0120] A catalyst for the preparation of 3,4-dihydro-2H-pyran was prepared by a method including the following steps:

[0121] (i) Pretreatment of the support: 50g of γ-Al2O3 was calcined in air at 300℃ for 5h;

[0122] (ii) Impregnate the pretreated carrier obtained in step (i) with an equal volume of ruthenium chloride aqueous solution with a concentration of 0.01 mol / L, let stand for 5 h, and then dry at 120 °C for 10 h.

[0123] (iii) The product obtained in step (ii) is calcined at 300°C in air for 5 hours;

[0124] (iv) The product obtained in step (iii) was reduced at 350 °C in a hydrogen atmosphere for 4 h, wherein the hydrogen flow rate was 50 mL / min;

[0125] (v) Impregnate an equal volume of the product obtained in step (iv) with an aqueous solution of lithium hydroxide with a concentration of 0.03 mol / L, let stand for 5 h, and then dry at 110 °C for 10 h;

[0126] (vi) The product obtained in step (v) is calcined at 300°C in air for 5 hours; and

[0127] (vii) The product obtained in step (vi) was reduced at 350 °C in a hydrogen atmosphere for 4 h, wherein the hydrogen flow rate was 50 mL / min, thereby obtaining catalyst 6.

[0128] Comparative Preparation Example 1

[0129] The catalyst is prepared by a method including the following steps:

[0130] (i) Pretreatment of the support: 50g of γ-Al2O3 was calcined in air at 300℃ for 5h;

[0131] (ii) Impregnate the pretreated carrier obtained in step (i) with an equal volume of 0.01 mol / L chloroplatinic acid aqueous solution, let stand for 5 h, and then dry at 120 °C for 10 h.

[0132] (iii) The product obtained in step (ii) is calcined at 300°C in air for 5 hours;

[0133] (iv) The product obtained in step (iii) was reduced at 350 °C in a hydrogen atmosphere for 4 h, wherein the hydrogen flow rate was 50 mL / min, thereby preparing comparative catalyst 1.

[0134] The ammonia desorption results of the comparative catalyst 1 are as follows: Figure 4 As shown.

[0135] Comparative Preparation Example 2

[0136] The catalyst is prepared by a method including the following steps:

[0137] (i) Pretreatment of the support: 50g of γ-Al2O3 was calcined in air at 300℃ for 5h;

[0138] (ii) Impregnate the pretreated carrier obtained in step (i) with an equal volume of 0.5 mol / L potassium hydroxide aqueous solution, let stand for 5 h, and then dry at 110 °C for 10 h.

[0139] (iii) The product obtained in step (v) is calcined at 300°C in air for 5 hours;

[0140] (iv) The product obtained in step (vi) was reduced at 350 °C in a hydrogen atmosphere for 4 h, wherein the hydrogen flow rate was 50 mL / min, thereby preparing comparative catalyst 2.

[0141] Reaction Example 1

[0142] 3,4-Dihydro-2H-pyran is prepared by the following steps:

[0143] (a) 2g of the shaped catalyst 1 from Preparation Example 1 was added to a fixed-bed reactor, and the reactor was heated to 400°C and held for 3h under a N2 atmosphere for activation, then cooled to 350°C; and

[0144] (b) At a reaction temperature of 350°C and atmospheric pressure, tetrahydrofurfuryl alcohol was added at a reaction rate of 0.6 h⁻¹. -1 The air velocity is introduced into the reactor to carry out the reaction.

[0145] After condensation and gas-liquid separation, the reaction products were analyzed by GC. The results showed that the conversion rate of tetrahydrofurfuryl alcohol was 99.3%, the selectivity of 3,4-dihydro-2H-pyran was 92.4%, the selectivity of tetrahydropyran was 0.2%, and the reactor material balance was 97%.

[0146] like Figure 5 The image shows a gas chromatogram of the reaction products from Reaction Example 1. Figure 5 As can be seen, the content of 3,4-dihydro-2H-pyran in the reactants is extremely high, while the content of tetrahydropyran is negligible, proving that the catalyst according to this application has high selectivity for 3,4-dihydro-2H-pyran and very low selectivity for tetrahydropyran.

[0147] Reaction Example 2

[0148] 3,4-Dihydro-2H-pyran is prepared by the following steps:

[0149] (a) 2g of the shaped catalyst 2 from Preparation Example 2 was added to a fixed-bed reactor, and the reactor was heated to 400°C and held for 3 hours under a N2 atmosphere for activation, then cooled to 300°C; and

[0150] (b) At a reaction temperature of 300°C and atmospheric pressure, tetrahydrofurfuryl alcohol was reacted at a rate of 1.0 h. -1 The air velocity is introduced into the reactor to carry out the reaction.

[0151] After condensation and gas-liquid separation, the reaction products were analyzed by GC. The results showed that the conversion rate of tetrahydrofurfuryl alcohol was 87.2%, the selectivity of 3,4-dihydro-2H-pyran was 95.2%, the selectivity of tetrahydropyran was 0.1%, and the reactor material balance was 98%.

[0152] Reaction Example 3

[0153] The method for preparing 3,4-dihydro-2H-pyran according to this application is carried out by the following steps:

[0154] (a) 2g of the shaped catalyst 3 from Preparation Example 3 was added to a fixed-bed reactor, and the reactor was heated to 400°C and held for 3 hours under a N2 atmosphere for activation, then cooled to 300°C; and

[0155] (b) At a reaction temperature of 300°C and atmospheric pressure, tetrahydrofurfuryl alcohol was reacted at a rate of 0.6 h⁻¹. -1 The air velocity is introduced into the reactor to carry out the reaction.

[0156] After condensation and gas-liquid separation, the reaction products were analyzed by GC. The results showed that the conversion rate of tetrahydrofurfuryl alcohol was 99.4%, the selectivity of 3,4-dihydro-2H-pyran was 94.6%, the selectivity of tetrahydropyran was 0.1%, and the reactor material balance was 95%.

[0157] Reaction Example 4

[0158] A method for preparing 3,4-dihydro-2H-pyran using the following steps:

[0159] (a) 2g of the shaped catalyst 4 from Preparation Example 4 was added to a fixed-bed reactor, and the reactor was heated to 400°C and held for 3 hours under a N2 atmosphere for activation, then cooled to 280°C; and

[0160] (b) At a reaction temperature of 280°C and atmospheric pressure, tetrahydrofurfuryl alcohol was added at a reaction rate of 0.6 h⁻¹. -1 The air velocity is introduced into the reactor to carry out the reaction.

[0161] After condensation and gas-liquid separation, the reaction products were analyzed by GC. The results showed that the conversion rate of tetrahydrofurfuryl alcohol was 99.3%, the selectivity of 3,4-dihydro-2H-pyran was 94.1%, the selectivity of tetrahydropyran was 0.1%, and the reactor material balance was 97%.

[0162] Reaction Example 5

[0163] A method for preparing 3,4-dihydro-2H-pyran using the following steps:

[0164] (a) 2g of the shaped catalyst 5 from Preparation Example 5 was added to a fixed-bed reactor, and the reactor was heated to 400°C and held for 3 hours under a N2 atmosphere for activation, then cooled to 300°C; and

[0165] (b) At a reaction temperature of 300°C and atmospheric pressure, tetrahydrofurfuryl alcohol was added at a reaction rate of 0.3 h. -1 The air velocity is introduced into the reactor to carry out the reaction.

[0166] After condensation and gas-liquid separation, the reaction products were subjected to GC analysis. The results showed that the conversion rate of tetrahydrofurfuryl alcohol was 99.0%, the selectivity of 3,4-dihydro-2H-pyran was 93.9%, the selectivity of tetrahydropyran was 0.3%, and the reactor material balance was 96%.

[0167] Reaction Example 6

[0168] A method for preparing 3,4-dihydro-2H-pyran using the following steps:

[0169] (a) 2g of the shaped catalyst 6 from Preparation Example 6 was added to a fixed-bed reactor, and the reactor was heated to 400°C and held for 3 hours under a N2 atmosphere for activation, then cooled to 300°C; and

[0170] (b) At a reaction temperature of 300°C and atmospheric pressure, tetrahydrofurfuryl alcohol was reacted at a rate of 0.6 h⁻¹. -1 The air velocity is introduced into the reactor to carry out the reaction.

[0171] After condensation and gas-liquid separation, the reaction products were analyzed by GC. The results showed that the conversion rate of tetrahydrofurfuryl alcohol was 99.0%, the selectivity of 3,4-dihydro-2H-pyran was 93.7%, the selectivity of tetrahydropyran was 0.1%, and the reactor material balance was 97%.

[0172] Comparative reaction example 1

[0173] A method for preparing 3,4-dihydro-2H-pyran using the following steps:

[0174] (a) 2 g of shaped comparative catalyst 1 was added to a fixed-bed reactor, and the reactor was heated to 400 °C and held for 3 h under a N2 atmosphere for activation, then cooled to 300 °C; and

[0175] (b) At a reaction temperature of 300°C and atmospheric pressure, tetrahydrofurfuryl alcohol was reacted at a rate of 0.6 h⁻¹. -1 The air velocity is introduced into the reactor to carry out the reaction.

[0176] After condensation and gas-liquid separation, the reaction products were analyzed by GC. The results showed that the conversion rate of tetrahydrofurfuryl alcohol was 99.7%, the selectivity of 3,4-dihydro-2H-pyran was 61.3%, the selectivity of tetrahydropyran was 0.1%, and the reactor material balance was 72%.

[0177] like Figure 6 The image shows a gas chromatogram of the reaction products from Comparative Reaction Example 1. Figure 6 As can be seen, there is a significant tetrahydropyran content peak in the reactants, proving that the proportion of tetrahydropyran relative to 3,4-dihydro-2H-pyran in the reaction products is extremely considerable.

[0178] Comparative reaction example 2

[0179] A method for preparing 3,4-dihydro-2H-pyran using the following steps:

[0180] (a) 2 g of shaped comparative catalyst 2 was added to a fixed-bed reactor, and the reactor was heated to 400 °C and held for 3 h under a N2 atmosphere for activation, then cooled to 300 °C; and

[0181] (b) At a reaction temperature of 300°C and atmospheric pressure, tetrahydrofurfuryl alcohol was reacted at a rate of 0.6 h⁻¹. -1 The air velocity is introduced into the reactor to carry out the reaction.

[0182] After condensation and gas-liquid separation, the reaction products were analyzed by GC. The results showed that the conversion rate of tetrahydrofurfuryl alcohol was 85.2%, the selectivity of 3,4-dihydro-2H-pyran was 80.2%, the selectivity of tetrahydropyran was 10.7%, and the reactor material balance was 96%.

[0183] Comparative reaction example 3

[0184] A method for preparing 3,4-dihydro-2H-pyran using the following steps:

[0185] (a) 2g of shaped γ-Al₂O₃ was added to a fixed-bed reactor, and the mixture was heated to 400°C and held for 3h under a N₂ atmosphere for activation, then cooled to 300°C; and

[0186] (b) At a reaction temperature of 300°C and atmospheric pressure, tetrahydrofurfuryl alcohol was reacted at a rate of 0.6 h⁻¹. -1 The air velocity is introduced into the reactor to carry out the reaction.

[0187] After condensation and gas-liquid separation, the reaction products were analyzed by GC. The results showed that the conversion rate of tetrahydrofurfuryl alcohol was 99.1%, the selectivity of 3,4-dihydro-2H-pyran was 83.9%, the selectivity of tetrahydropyran was 8.7%, and the reactor material balance was 96%.

[0188] Based on the reaction results of Examples 1-6 and Comparative Examples 1-3, it can be seen that in Comparative Example 1, the comparative catalyst 1 used only contained the active component and not the co-catalyst component, resulting in a significant reduction in the tetrahydropyran content of the obtained product, which was only 0.1%. This indicates that the addition of the active component in the catalyst can indeed greatly reduce the formation of tetrahydropyran. However, the absence of the co-catalyst component resulted in a significant decrease in the selectivity of the target product 3,4-dihydro-2H-pyran, which was only 61.3%. From the reaction material balance, it can be seen that when using comparative catalyst 1, the reaction produced more light component products that were difficult to condense. Figure 4The NH3-TPD characterization results show that the absence of the co-catalyst component may significantly increase the acidity of the catalyst surface, thereby reducing catalyst selectivity. In Comparative Example 2, the comparative catalyst 2 used only contained the co-catalyst component and did not contain the active component, resulting in a significant decrease in reaction conversion, and the selectivity of tetrahydropyran in the product reached over 10%. It is evident that in the case of containing only the co-catalyst component without the active component, only the acidity of the support is reduced, which only decreases the conversion of the feedstock but does not improve the product selectivity. In Comparative Example 3, when using the γ-Al2O3 catalyst, the selectivity of tetrahydropyran in the tetrahydrofurfuryl alcohol dehydration rearrangement reaction product reached as high as 8.7%. In contrast, when the catalyst prepared according to Examples 1-6 of this application is used, the generation of light component products can be significantly reduced while reducing the generation of tetrahydropyran. This increases the selectivity of the target product 3,4-dihydro-2H-pyran to over 92%, while the selectivity of tetrahydropyran in the reaction products is only about 0.2%. This greatly reduces the difficulty of subsequent separation while ensuring the yield of the target product, and high-purity 3,4-dihydro-2H-pyran can be obtained without complicated distillation operations.

[0189] The specific embodiments described above are merely preferred embodiments for explaining this application and are not intended to limit this application. Those skilled in the art can make modifications without creative contribution as needed after reading this specification. However, any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A process for the preparation of 3,4-dihydro-2H-pyran, characterized in that, The method comprises: dehydration rearrangement of tetrahydrofurfuryl alcohol at 200℃~500℃ in the presence of a catalyst; The catalyst comprises a carrier, an active component and a promoter component, wherein: The carrier comprises one or more selected from γ-Al2O3, SiO2, ZrO2, TiO2, HZSM5, SAPO-34, HY, Hβ and HMOR; The active component comprises one or more metal elements selected from platinum, palladium, ruthenium and rhodium; The promoter component comprises one or more metal elements selected from potassium, sodium, lithium, magnesium and calcium; The mass ratio of the metal element in the active component to the carrier is (0.01~2):100; and / or The mass ratio of the metal element in the promoter component to the metal element in the active component is (0.05~2):

1.

2. The method according to claim 1, wherein: The active component comprises one or more metal elements selected from platinum, palladium and ruthenium; The promoter component comprises one or more metal elements selected from potassium, sodium and lithium.

3. The method according to claim 1 or 2, characterized in that, The preparation method of the catalyst comprises the following steps: (1) the carrier is immersed in an active component precursor aqueous solution in an equal volume, left to stand, and then dried; (2) the product obtained in step (1) is calcined in an air atmosphere at 250℃~300℃ for 2 h~5 h; (3) the product obtained in step (2) is reduced in a hydrogen atmosphere at 250℃~350℃ for 2 h~4 h; (4) the product obtained in step (3) is immersed in a promoter component precursor aqueous solution in an equal volume, left to stand, and then dried; (5) the product obtained in step (4) is calcined in an air atmosphere at 250℃~300℃ for 2 h~5 h; and (6) the product obtained in step (5) is reduced in a hydrogen atmosphere at 250℃~350℃ for 2 h~4 h.

4. The method according to claim 3, wherein: The active component precursor comprises one or more selected from nitrate, chloride and acetate of Pt, Pd, Ru and Rh; and / or The promoter component precursor comprises one or more selected from carbonate, sulfate and hydroxide of potassium, sodium, lithium, magnesium and calcium.

5. The method of claim 3, wherein, In step (1), The concentration of the active component precursor aqueous solution is 0.005 mol / L~0.05 mol / L; The standing time is 2 h~5 h; and The drying temperature is 110℃~150℃ and the drying time is 5 h~10 h.

6. The method of claim 3, wherein, In step (4), The concentration of the promoter component precursor aqueous solution is 0.05 mol / L~0.2 mol / L; The standing time is 2 h~5 h; and The drying temperature is 110℃~150℃ and the drying time is 5 h~10 h.

7. The method of claim 3, wherein, Further comprising pretreatment of the carrier: before step (1), the carrier is calcined in an air atmosphere at 200℃~400℃ for 2 h~5 h.

8. The method of claim 1, wherein, The method comprises at least one of the following features (a)~(g): (a) the reactor used in the method is selected from any one of a batch reactor, a semi-batch reactor, a continuous stirred tank reactor, a plug flow reactor, a fixed bed reactor and a fluidized bed reactor or is a combined reactor of two or more of these reactors; (b) the catalyst is in the form of a strip, a column or a sheet; (c) the temperature of the dehydration rearrangement reaction is 250°C to 400°C; (d) the dehydration rearrangement reaction is carried out under one or more of a nitrogen atmosphere, a helium atmosphere, an argon atmosphere and a hydrogen atmosphere; (e) the method for preparing 3,4-dihydro-2H-pyran is carried out under a reaction pressure of 0.1 MPa to 4 MPa; (f) the tetrahydrofurfuryl alcohol is reacted in the absence of a solvent or in the presence of a solvent, wherein the solvent is one or more selected from tetrahydrofuran, acetonitrile and 1,4-dioxane; (g) the process is carried out at a reaction space velocity of 0.05 h -1 5 h -1 0.05 h 9. The method of claim 8, wherein, In feature (a), the reactor is a fixed bed reactor.

10. The method of claim 8, wherein, In feature (f), the solvent is tetrahydrofuran or acetonitrile.

11. The method of claim 8, wherein, In feature (g), the process is carried out at a reaction space velocity of 0.03 h -1 ~3 h -1 .

12. The method of claim 1, wherein, The method comprises at least one of the following features (a) and (b): (a) the method further comprises activating the catalyst before the reaction: heating the catalyst to an activation temperature of 300°C to 500°C and maintaining for 1 h to 6 h; (b) the method further comprises a reaction post-treatment: after condensation and gas-liquid separation of the reaction product, performing rectification.

13. The method of claim 12, wherein, In feature (a), the activation temperature is 300°C to 400°C.

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