A method for flexible production of tetrahydrofuran and gamma-butyrolactone

Abstract

The present application uses 1,4-butanediol as raw material, and through the series of dehydration reaction and dehydrogenation reaction, tetrahydrofuran and gamma-butyrolactone are produced flexibly, the generation of heavy components such as TBA is less, and the yield of tetrahydrofuran and gamma-butyrolactone main products is high.

Description

Technical Field

[0001] This invention relates to a flexible method for producing tetrahydrofuran and γ-butyrolactone, belonging to the field of chemical technology. Background Technology

[0002] Tetrahydrofuran and γ-butyrolactone are widely used in organic synthesis and as solvents. In organic synthesis, the former can be used to prepare polytetrahydrofuran, tetrahydrothiophene, tetrahydrothiophenol, and pharmaceutical raw materials; the latter is an important raw material for pyrrolidone compounds, acetylbutyrolactone, cyclopropylamine, and vitamin B1. As solvents, the former is known as a "universal solvent," capable of dissolving most organic compounds except for polyethylene, polypropylene, and fluoropolymers; the latter is widely used as an extractant, absorbent, auxiliary agent, and electrolyte solution.

[0003] Currently, the mainstream production processes for γ-butyrolactone are the 1,4-butanediol dehydrogenation cyclization method and the tetrahydrofuran production process is the 1,4-butanediol dehydration cyclization method. Given the current large surplus of 1,4-butanediol and the significant price fluctuations of both tetrahydrofuran and γ-butyrolactone, if it were possible to use 1,4-butanediol as a raw material to simultaneously produce both tetrahydrofuran and γ-butyrolactone, and to achieve an adjustable production ratio, it is expected to enhance the risk resistance of production enterprises and give them a competitive advantage in the fierce market competition.

[0004] The conventional reaction conditions for the 1,4-butanediol dehydrogenation cyclization method are 200–260 °C, 0.05–1.0 MPa G, and WHSV = 0.1–1.0 h. -1 This reaction is often carried out under hydrogen-containing conditions to improve the selectivity of the main product γ-butyrolactone, reduce the content of high-boiling byproducts, and extend catalyst lifetime. The hydrogen-to-ethanol ratio is generally set to 5–30 (mol / mol). The main reaction network is as follows:

[0005]

[0006] The dehydrogenation of 1,4-butanediol to γ-butyrolactone typically requires a conversion rate >97%. When the conversion rate is too low, the intermediate 2-hydroxytetrahydrofuran readily undergoes a condensation reaction with the 1,4-butanediol feedstock, generating the high-boiling byproduct 2-(4-hydroxybutoxy)tetrahydrofuran (TBA). The large-scale formation of TBA not only reduces the yield of γ-butyrolactone but also severely impacts catalyst lifetime. This reaction also requires a catalyst with low acidity and strong 4-hydroxytetrahydrofuran dehydrogenation activity to avoid the large-scale formation of low-boiling byproducts such as tetrahydrofuran, dihydrofuran, and n-butanol.

[0007] Simultaneous dehydration and dehydrogenation of 1,4-butanediol is an easily conceivable method for the co-production of γ-butyrolactone and tetrahydrofuran. CN1286829C utilizes a Cu-Ti-Al-O catalyst at 170-300℃ and 0.1-1 MPa under hydrogen-exposed conditions to convert 1,4-butanediol to γ-butyrolactone and tetrahydrofuran. However, the catalyst limits the adjustable ratio of the two products, resulting in poor flexibility. Furthermore, under the conditions for γ-butyrolactone formation, adjusting the catalyst's acidity or basicity to increase the yield of tetrahydrofuran inevitably leads to an increase in the production of other low-boiling and high-boiling byproducts. Considering its poor economic viability, this is not a preferred strategy.

[0008] CN113277996B discloses a flexible method for producing tetrahydrofuran and γ-butyrolactone. This method involves passing 1,4-butanediol feedstock through a first bed loaded with a dehydrogenation catalyst and a second bed loaded with a catalyst possessing dehydration and specific hydrogenation properties under hydrogen-exposed conditions, thereby achieving co-production of both. The ratio of the two products can be adjusted by regulating the catalyst loading ratio of the two beds. From an industrial production perspective, on the one hand, the catalyst loading ratio of the beds is difficult to adjust quickly, often requiring plant shutdown and catalyst reloading, resulting in high costs, low efficiency, and an inability to adapt to rapid market changes. On the other hand, the reaction strategy of first dehydrogenating and then dehydrating leads to an excessively low degree of reaction of 1,4-butanediol in the first bed, resulting in a large amount of heavy components such as TBA, as analyzed above, poor atom economy, and frequent catalyst replacement. Furthermore, TBA generated in the first bed can decompose into 2-hydroxytetrahydrofuran and 1,4-butanediol under acidic conditions after entering the second bed. 2-hydroxytetrahydrofuran dehydrates to 2,3-dihydrofuran under acidic conditions; this species readily polymerizes, leading to the precipitation of solid byproducts on the reactor and piping walls, and even blockage, making long-term continuous production impossible. γ-Butyrolactone can also undergo hydrolysis under acidic conditions to produce 4-hydroxybutyric acid.

[0009] Furthermore, direct hydrogenation of maleic anhydride or hydrogenation via esterification of maleic anhydride can co-produce tetrahydrofuran and γ-butyrolactone. For example, CN1139563C describes the hydrogenation of maleic anhydride after esterification with hexanediol to obtain 85 mol% 1,4-butanediol, 2 mol% tetrahydrofuran, and 8 mol% γ-butyrolactone. It is worth noting that this process is mainly used for the production of 1,4-butanediol, with low yields of tetrahydrofuran and γ-butyrolactone, and poor adjustability in their proportions. The more moderate maleic anhydride methyl esterification-hydrogenation route also suffers from the problem of methanol-tetrahydrofuran azeotropy and excessively high separation energy consumption (CN217248853U). In addition, maleic anhydride hydrogenation can also selectively produce γ-butyrolactone (CN1046509C, CN108114727A, CN116273139A, etc.), but there are few reports of co-production of tetrahydrofuran.

[0010] Therefore, it is necessary to provide a flexible method for producing tetrahydrofuran and γ-butyrolactone. Summary of the Invention

[0011] This invention provides a flexible method for producing tetrahydrofuran and γ-butyrolactone, the method comprising the following steps: a stream containing 1,4-butanediol enters a dehydration unit, undergoes a dehydration reaction in the presence of a dehydration catalyst to obtain a liquid containing tetrahydrofuran and unreacted 1,4-butanediol, which then enters an intermediate tank; the intermediate tank liquid subsequently enters a dehydrogenation unit, reacts in a hydrogen atmosphere and in the presence of a dehydrogenation catalyst to obtain a reaction product containing tetrahydrofuran and γ-butyrolactone.

[0012] In this invention, the source of the 1,4-butanediol-containing stream is not limited. It can be crude 1,4-butanediol with a purity of ≥99.0%, qualified 1,4-butanediol with a purity of ≥99.5%, or superior 1,4-butanediol with a purity of ≥99.7%, obtained by purification using the acetylene distillation method, maleic anhydride method, propylene method, or fermentation method. Alternatively, it can be 1,4-butanediol recovery liquid with a purity of ≥98.0% obtained by further purification of the acetylene distillation residue. It can also be a mixed raw material of 1,4-butanediol, butanol, γ-butyrolactone, and tetrahydrofuran after removing heavy components with boiling points higher than 1,4-butanediol by the maleic anhydride method. Depending on the purification capacity, the 1,4-butanediol raw material usually contains varying amounts of 2-(4-hydroxybutoxy)tetrahydrofuran (TBA), which can azeotropically react with 1,4-butanediol and is difficult to separate. To avoid excessive polymerization of TBA in the dehydration reactor, the TBA content in the raw material is ≤0.5%.

[0013] In this invention, the dehydration and dehydrogenation reactions occur in two reactors connected in series.

[0014] In this invention, the dehydration unit uses a fixed-bed reactor, which can be a stacked-bed reactor filled with a solid catalyst or a catalytic distillation column partially filled with a solid catalyst, thereby achieving higher tetrahydrofuran yield and adjustable product ratio. Industrially common reactive distillation methods use batch reactors, which tend to accumulate intermolecular dehydrated polymers during long-term operation, requiring frequent removal of bottom liquid and introduction of large amounts of water. This patented solution does not pursue a high tetrahydrofuran conversion rate, effectively avoiding the large-scale generation, accumulation, and even precipitation of polymers that can clog pipelines, enabling stable operation over long periods. To further increase catalyst stability, the product after the dehydration reaction can also undergo a deweighting treatment before being mixed and fed into the dehydrogenation unit. For example, in one embodiment, qualified 1,4-butanediol enters from the top of the fixed-bed reactor via a liquid distributor, subsequently undergoing a liquid-solid phase reaction with a tetrahydrofuran yield of 28%. The resulting product, after cooling, does not require separation and then enters the dehydrogenation unit. In another embodiment, the 1,4-butanediol recovery liquid enters the upper part of the catalyst section of the reactive distillation column and undergoes a liquid-solid phase reaction, with a tetrahydrofuran yield of 74%. The product at the bottom of the distillation column is deweighted, mixed with the product at the top of the column, and then sent to the dehydrogenation unit for further processing.

[0015] In this invention, the dehydration reaction is carried out at a temperature of 150-350°C and a pressure of 0.01-0.10 MPaG, with a mass hourly space velocity (WHSV) of 1,4-butanediol of 0.1-20 h⁻¹. -1 .

[0016] In this invention, the dehydration reaction feedstock may also contain a certain amount of hydrogen gas. The hydrogen gas is preheated to the dehydration reaction temperature before entering the dehydration unit. The molar ratio (hydrogen-to-ethanol ratio) of the hydrogen gas and 1,4-butanediol is 0~15:1. The hydrogen-rich conditions will help suppress the formation of unsaturated cyclic ethers such as 2,3-dihydrofuran.

[0017] In this invention, the dehydration catalyst is selected from one or more of acidic oxides, hydrogen-form molecular sieves, acidic ion exchange resins, and supported acidic solid catalysts. The solid catalysts are formed and then packed into a fixed bed or catalytic distillation column. The acidic oxides are selected from one or two of alumina and zirconium oxide; the hydrogen-form molecular sieves are selected from one or more of H-ZSM-5, H-beta, and HY; the acidic ion exchange resins are selected from one or two of Nafion-212 and Amberlyst-15; and the supported acidic solid catalysts are one or more of sulfuric acid-modified, grafted sulfonic acid, grafted carboxylic acid, and supported heteropolyacid immobilized catalysts.

[0018] In this invention, the dehydrogenation unit reactor adopts a tubular structure, with the catalyst packed in the tubes and the shell side heated by either heat transfer oil or heat transfer oil vapor. The dehydrogenation feedstock can be either top-in, bottom-out, or bottom-in, top-out, with no particular limitation. In one embodiment, the dehydrogenation feedstock, after vaporization and mixing with hydrogen, enters each tube in the upper part of the dehydrogenation reactor via a gas distributor, while the heat transfer oil vapor enters the shell side from the upper part of the reactor sidewall. The dehydrogenation reaction is concentrated in the upper part of the tubes, absorbing a large amount of latent heat released by the phase change of the heat transfer oil vapor, thus preventing the cooling point from becoming too low (~200°C).

[0019] In this invention, the dehydrogenation reaction is carried out at a temperature of 180-300°C, a pressure of 0.01-1.00 MPaG, and a mass hourly space velocity (WHSV) of 1,4-butanediol of 0.05-10 h⁻¹. -1 .

[0020] In this invention, the dehydrogenation reaction is a hydrogen-induced reaction, in which the dehydrogenation feedstock and hydrogen are mixed and preheated to the required reaction temperature. The molar ratio (hydrogen-to-ethanol ratio) of hydrogen to 1,4-butanediol is 5:1 to 30:1. Hydrogen-induced conditions can suppress the formation of high-boiling byproducts and extend catalyst lifetime.

[0021] In this invention, the dehydrogenation catalyst can be selected from one or more of the industrially commonly used copper-silicon, copper-zinc, copper-chromium, and copper-manganese systems. For example, in one embodiment, the dehydrogenation catalyst comprises 16 wt% copper oxide, 0.6% sodium oxide, and 83.4% silicon dioxide; in another embodiment, the dehydrogenation catalyst comprises approximately 25% copper oxide, 30% zinc oxide, 20% chromium oxide, and 25% zirconium oxide.

[0022] Optionally, this invention includes a step for removing moisture from the dehydrogenation feedstock between the dehydration unit and the dehydrogenation unit. This is because the presence of water can cause structural instability in some dehydrogenation catalysts, such as loss of metal components, reconstruction of the support pore structure, and changes in the catalyst's acidity or basicity. In one embodiment, the feedstock for the dehydrogenation unit is pre-treated with molecular sieve adsorption for dehydration, and multiple adsorption towers are set up to facilitate continuous regeneration operation.

[0023] In this invention, an acid removal step may optionally be included between the dehydration unit and the dehydrogenation unit. This is because some acidic species of the dehydration catalyst may be lost into the feedstock of the dehydrogenation unit, affecting the subsequent dehydrogenation effect. In one embodiment, the feedstock of the dehydrogenation unit is pre-treated with resin adsorption for acid removal, and multiple adsorption towers are set up to facilitate continuous regeneration operation.

[0024] In this invention, the ratio of tetrahydrofuran to γ-butyrolactone in the reaction products is adjusted by controlling the reaction temperatures of the dehydration reactor and the dehydrogenation reactor. In one embodiment, 1,4-butanediol is first dehydrated using acidic γ-alumina as a catalyst. When the reaction temperature is increased from 160°C to 200°C, the molar yield of tetrahydrofuran increases from 24% to 78%. The subsequent dehydrogenation reaction is controlled at a cooling point of 200-210°C, which can almost completely convert unreacted 1,4-butanediol into γ-butyrolactone, with a residual amount of 1,4-butanediol <0.5%.

[0025] Optionally, this invention also includes a dehydrogenation feedstock side stream for 1,4-butanediol feedstock directly connected to the dehydrogenation reactor, so as to achieve 100% feedstock use for the production of γ-butyrolactone.

[0026] Optionally, this invention also includes a dehydration product side stream that leads directly to the distillation unit, so as to achieve 100% raw material use for the production of tetrahydrofuran.

[0027] The beneficial effects of this invention are as follows:

[0028] (1) The dehydration and dehydrogenation reactions of 1,4-butanediol are combined to achieve the co-production of tetrahydrofuran and γ-butyrolactone using 1,4-butanediol as raw material, and the applicable raw material sources are wide.

[0029] (2) First, dehydrate part of the 1,4-butanediol, and then perform deep dehydrogenation on the remaining 1,4-butanediol. The heavy components such as TBA are generated in less, and the yields of tetrahydrofuran and γ-butyrolactone as the main products are high.

[0030] (3) The reaction depth of 1,4-butanediol is controlled by adjusting the dehydration reaction conditions (mainly the reaction temperature), and the unreacted 1,4-butanediol is converted into γ-butyrolactone by adjusting the dehydrogenation conditions (mainly the cold point), so as to realize the flexible production of tetrahydrofuran and γ-butyrolactone. Attached Figure Description

[0031] Figure 1 A simplified process flow diagram of the apparatus of the present invention;

[0032] Figure 2 Example 1: The gas chromatography-mass spectrometry (GC-MS) chromatogram of the product was obtained, in which THF: tetrahydrofuran, DMF: N,N-dimethylformamide needle washing solvent, GBL: γ-butyrolactone, BDO: 1,4-butanediol, and TBA: 2-(4-hydroxybutoxy)tetrahydrofuran. Detailed Implementation

[0033] The present patent will now be described in detail with reference to examples and accompanying drawings. The embodiments are merely exemplary and not restrictive.

[0034] The raw materials used in the examples were produced by Wanhua Chemical Plant and self-made samples in the laboratory. The acidic γ-alumina catalyst was from Jiangxi Kepaco Environmental Protection Chemical Co., Ltd., and the model was KA403-WH.

[0035] Preparation method of copper-zinc catalyst: Take 100 mL of water and add 26.1 g of copper nitrate, 29.8 g of zinc nitrate, 11.6 g of chromic anhydride and 13.4 g of zirconium nitrate, and stir evenly. Then prepare a 1 M sodium carbonate solution. The above two solutions are introduced into a 20℃ constant temperature water bath, stirred vigorously and controlled at pH 6±1 to obtain a precipitate. After filtration and washing, dry at 110℃ for 2 h, and then calcine at 450℃ for 24 h to obtain the catalyst. Then introduce lubricating graphite and press it into a φ5*5 mm cylindrical copper-zinc catalyst.

[0036] SO4 2- Preparation method of modified ZrO2 catalyst: Ammonia water was added dropwise to a 1M zirconium oxychloride solution until the pH was 9-10. The precipitate was aged at 60℃ for 2h, filtered and washed until neutral, dried at 120℃ for 10h, impregnated with an equal volume of 1M sulfuric acid, dried at 120℃ for 10h, calcined at 600℃ for 3h, and thoroughly ground to obtain catalyst powder. Lubricating graphite was then introduced and pressed into a φ5*5mm cylindrical copper-zinc catalyst.

[0037] Preparation method of copper-chromium catalyst: 315.6g of 20% silica-alumina sol (containing 19.5% silica and 0.5% alumina) was added to 500g of 5% ammonia water and stirred until homogeneous. Then, 17.9g of basic copper carbonate was added and stirred until dissolved and dispersed. The mixture was heated to 60℃ and stirred for 2h. Subsequently, the temperature was raised to 95℃ and stirred continuously to evaporate the dispersion to dryness. The mixture was dried at 120℃ for 10h and calcined at 00℃ for 4h to obtain the catalyst precursor. 14.2g of chromium oxalate was dissolved in water to prepare a solution. 100g of the above catalyst precursor was impregnated with an equal volume of this solution and then dried at 120℃ for 10h to obtain catalyst powder. 2% silica sol was added and thoroughly mixed. The powder was extruded into strips and calcined at 550℃ for 10h to obtain a strip-shaped copper-chromium catalyst with a diameter of 2-4mm and a length of 2-19mm.

[0038] The composition of raw materials and products was qualitatively determined by gas chromatography-mass spectrometry (Agilent 6890N-5973N), and the product distribution was quantitatively determined by gas chromatography (Agilent 7820A) using the internal standard method (γ-butyrolactone as the internal standard).

[0039] Example 1

[0040] Using qualified 1,4-butanediol (containing 99.5% 1,4-butanediol, 0.4% TBA, and 0.1% other impurities) as raw material, it was preheated to 185°C and then passed through a bed dehydration reactor packed with acidic γ-alumina catalyst. The reaction temperature was 180°C, the reaction pressure was 0.05 MPaG, and the mass hourly space velocity was 1.5 h⁻¹. -1 The outlet reaction product composition was 35.9% tetrahydrofuran, 55.0% 1,4-butanediol, 8.9% water, <0.1% TBA, and approximately 0.2% other components. The dehydration reaction product was preheated to 235°C and then passed through a tubular dehydrogenation reactor packed with a copper-zinc catalyst. The reaction temperature was 225°C, the reaction pressure was 0.05 MPaG, and the mass hourly space velocity (WHSV) was 1.5 h⁻¹. -1 (The mass hourly space velocity based on 1,4-butanediol is 0.83 h⁻¹) -1 The molar ratio of hydrogen to 1,4-butanediol was 20, and the reaction cooling point was 206℃. The mass composition of the liquid phase product at the outlet after the reaction was 37.3% tetrahydrofuran, 51.8% γ-butyrolactone, 9.4% water, 0.6% 1,4-butanediol, 0.5% n-butanol, 0.2% TBA, and approximately 0.2% other components.

[0041] Example 2

[0042] The purified product of the 1,4-butanediol distillation residue from the acetylacetonate method (containing 98.1% 1,4-butanediol, 0.8% γ-butyrolactone, 0.2% n-butanol, 0.5% TBA, 0.2% tetrahydrofuran, and 0.2% other impurities) was used as raw material. After preheating to 140℃, it was passed through a container filled with SO4. 2- In a reactive distillation column with modified ZrO2 catalyst, the reaction temperature was 150℃, the reaction pressure was 0.03 MPaG, and the mass hourly space velocity was 1.5 h⁻¹. -1 The tetrahydrofuran-rich gaseous phase from the top of the column and the 1,4-butanediol-rich liquid phase from the bottom of the column were cooled and then mixed in an intermediate tank. The product composition was 53.2% tetrahydrofuran, 32.4% 1,4-butanediol, 12.9% water, 0.8% γ-butyrolactone, 0.4% n-butanol, <0.1% TBA, and approximately 0.3% other components. The dehydration reaction product was preheated to 230°C and then fed into a tubular dehydrogenation reactor containing a copper-chromium catalyst. The reaction temperature was 220°C, the reaction pressure was 0.30 MPaG, and the mass hourly space velocity (WHSV) was 1.5 h⁻¹. -1 (The mass hourly space velocity based on 1,4-butanediol is 0.49 h⁻¹) -1 The molar ratio of hydrogen to 1,4-butanediol was 1:3, and the reaction cooling point was 202℃. The composition of the liquid phase product at the outlet after the reaction was 55.1% tetrahydrofuran, 29.9% γ-butyrolactone, 13.4% water, 0.5% n-butanol, 0.5% 1,4-butanediol, 0.2% TBA, and approximately 0.3% other components.

[0043] Example 3

[0044] A mixed feedstock (containing 98.0% 1,4-butanediol, 0.4% γ-butyrolactone, 0.5% n-butanol, 0.9% tetrahydrofuran, and 0.2% other impurities) after removing heavy components by maleic anhydride method was used as raw material. This feedstock was preheated to 140°C and then passed through a container filled with SO4. 2- In a reactive distillation column with modified ZrO2 catalyst, the reaction temperature was 150℃, the reaction pressure was 0.03 MPaG, and the mass hourly space velocity was 1.5 h⁻¹. -1 The tetrahydrofuran-rich gaseous phase from the top of the column and the 1,4-butanediol-rich liquid phase from the bottom of the column were cooled and then mixed in an intermediate tank. The product composition was 53.7% tetrahydrofuran, 32.0% 1,4-butanediol, 13.2% water, 0.4% γ-butyrolactone, 0.5% n-butanol, <0.1% TBA, and approximately 0.2% other components. The dehydration reaction product was preheated to 230°C and then fed into a tubular dehydrogenation reactor containing a copper-chromium catalyst. The reaction temperature was 220°C, the reaction pressure was 0.30 MPaG, and the mass hourly space velocity (WHSV) was 1.5 h⁻¹. -1 (The mass hourly space velocity based on 1,4-butanediol is 0.48 h⁻¹) -1 The molar ratio of hydrogen to 1,4-butanediol was 1:3, and the reaction cooling point was 202℃. The composition of the liquid phase product at the outlet after the reaction was 55.5% tetrahydrofuran, 29.3% γ-butyrolactone, 13.7% water, 0.5% n-butanol, 0.5% 1,4-butanediol, 0.2% TBA, and approximately 0.3% other components.

[0045] Example 4

[0046] Using premium grade 1,4-butanediol (containing 99.7% 1,4-butanediol, 0.3% TBA, and <0.1% other impurities) as raw material, the product was preheated to 185°C and then passed through a bed dehydration reactor packed with acidic γ-alumina catalyst. The reaction temperature was 180°C, the reaction pressure was 0.05 MPaG, and the mass hourly space velocity was 1.5 h⁻¹. -1 The outlet reaction product composition was 35.7% tetrahydrofuran, 55.3% 1,4-butanediol, 8.8% water, <0.1% TBA, and approximately 0.1% other components. The dehydration reaction product was preheated to 235°C and then passed through a tubular dehydrogenation reactor packed with a copper-zinc catalyst. The reaction temperature was 225°C, the reaction pressure was 0.05 MPaG, and the mass hourly space velocity (WHSV) was 1.5 h⁻¹. -1 (mass hourly space velocity based on 1,4-butanediol: 0.83 h⁻¹) -1 The molar ratio of hydrogen to 1,4-butanediol was 20, and the reaction cooling point was 206℃. The mass composition of the liquid phase product at the outlet after the reaction was 37.0% tetrahydrofuran, 52.0% γ-butyrolactone, 9.3% water, 0.6% 1,4-butanediol, 0.6% n-butanol, 0.2% TBA, and approximately 0.2% other components.

[0047] Example 5

[0048] Using premium grade 1,4-butanediol (containing 99.7% 1,4-butanediol, 0.3% TBA, and <0.1% other impurities) as raw material, the product was preheated to 165°C and then passed through a bed dehydration reactor packed with acidic γ-alumina catalyst. The reaction temperature was 160°C, the reaction pressure was 0.05 MPaG, and the mass hourly space velocity was 1.5 h⁻¹. -1 The outlet reaction product composition was 19.2% tetrahydrofuran, 75.8% 1,4-butanediol, 4.8% water, <0.1% TBA, and approximately 0.2% other components. The dehydration reaction product was preheated to 241°C and then passed through a tubular dehydrogenation reactor containing a copper-zinc catalyst. The reaction temperature was 231°C, the reaction pressure was 0.05 MPaG, and the mass hourly space velocity (WHSV) was 1.5 h⁻¹. -1 (The mass hourly space velocity based on 1,4-butanediol is 1.14 h⁻¹) -1 The molar ratio of hydrogen to 1,4-butanediol was 20, and the reaction cooling point was 206℃. The mass composition of the liquid phase product at the outlet after the reaction was 20.5% tetrahydrofuran, 72.9% γ-butyrolactone, 5.3% water, 0.4% 1,4-butanediol, 0.6% n-butanol, 0.1% TBA, and approximately 0.2% other components.

[0049] Example 6

[0050] Using premium grade 1,4-butanediol (containing 99.7% 1,4-butanediol, 0.3% TBA, and <0.1% other impurities) as raw material, the product was preheated to 205°C and then passed through a bed dehydration reactor packed with acidic γ-alumina catalyst. The reaction temperature was 200°C, the reaction pressure was 0.05 MPaG, and the mass hourly space velocity was 1.5 h⁻¹. -1 The outlet reaction product composition was 62.2% tetrahydrofuran, 22.2% 1,4-butanediol, 15.5% water, <0.1% TBA, and approximately 0.1% other components. The dehydration reaction product was preheated to 231°C and then passed through a tubular dehydrogenation reactor packed with a copper-zinc catalyst. The reaction temperature was 221°C, the reaction pressure was 0.05 MPaG, and the mass hourly space velocity (WHSV) was 1.5 h⁻¹. -1 (The mass hourly space velocity based on 1,4-butanediol is 0.33 h⁻¹) -1 The molar ratio of hydrogen to 1,4-butanediol was 20, and the reaction cooling point was 206℃. The mass composition of the liquid phase product at the outlet after the reaction was 63.0% tetrahydrofuran, 19.6% γ-butyrolactone, 15.8% water, 0.6% 1,4-butanediol, 0.4% n-butanol, 0.3% TBA, and approximately 0.2% other components.

[0051] Example 7

[0052] Using premium grade 1,4-butanediol (containing 99.7% 1,4-butanediol, 0.3% TBA, and <0.1% other impurities) as raw material, the product was preheated to 217°C and then passed through a bed dehydration reactor packed with acidic γ-alumina catalyst. The reaction temperature was 212°C, the reaction pressure was 0.05 MPaG, and the mass hourly space velocity was 1.5 h⁻¹. -1 The outlet reaction product composition is 79.5% tetrahydrofuran, 0.2% 1,4-butanediol, 19.9% ​​water, <0.1% TBA, and approximately 0.3% other components. The resulting product is directly sent to the distillation unit (without passing through the dehydrogenation reactor) via the dehydration product side pipeline.

[0053] Example 8

[0054] Using premium grade 1,4-butanediol (containing 99.7% 1,4-butanediol, 0.3% TBA, and other impurities <0.1%) as raw material, the product was preheated to 245℃ and then fed into a tubular dehydrogenation reactor containing a copper-chromium catalyst via a dehydrogenation feedstock side pipeline (without passing through a dehydration reactor). The reaction temperature was 235℃, the reaction pressure was 0.05 MPaG, and the mass hourly space velocity (WHSV) was 1.5 h⁻¹. -1 The molar ratio of hydrogen to 1,4-butanediol was 26, and the reaction cooling point was 206℃. The mass composition of the liquid phase product at the outlet after the reaction was 0.6% tetrahydrofuran, 97.6% γ-butyrolactone, 0.3% water, 0.3% 1,4-butanediol, 0.7% n-butanol, 0.1% TBA, and approximately 0.3% other components.

[0055] Comparative Example 1

[0056] Using premium grade 1,4-butanediol (containing 99.7% 1,4-butanediol, 0.3% TBA, and <0.1% other impurities) as raw material, the product was preheated to 235°C and then passed through a tubular dehydrogenation reactor packed with a copper-zinc catalyst. The reaction temperature was 225°C, the reaction pressure was 0.05 MPaG, and the mass hourly space velocity was 1.5 h⁻¹. -1 The molar ratio of hydrogen to 1,4-butanediol was 20, and the reaction cooling point was 206℃. The mass composition of the effluent liquid product after the reaction was: tetrahydrofuran 0.3%, γ-butyrolactone 60.1%, water 0.6%, 1,4-butanediol 32.5%, n-butanol 0.2%, TBA 4.1%, and approximately 2.2% other components. The dehydrogenation reaction product was preheated to 185℃ and then passed through a bed dehydration reactor packed with acidic γ-alumina catalyst. The reaction temperature was 174℃, the reaction pressure was 0.05 MPaG, and the mass hourly space velocity (WHSV) was 1.5 h⁻¹. -1 (mass hourly space velocity based on 1,4-butanediol: 0.49 h⁻¹) -1 The composition of the exit reaction products was 27.6% tetrahydrofuran, 59.1% γ-butyrolactone, 6.9% water, 0.1% 1,4-butanediol, 0.2% n-butanol, 1.3% TBA, and approximately 4.8% other components.

[0057] Comparative Example 2

[0058] The purified product of the 1,4-butanediol distillation residue from the acetylacetonate-aldehyde process (containing 98.1% 1,4-butanediol, 0.8% γ-butyrolactone, 0.2% n-butanol, 0.5% TBA, 0.2% tetrahydrofuran, and 0.2% other impurities) was used as raw material. After preheating to 230°C, it was fed into a tubular dehydrogenation reactor containing a copper-chromium catalyst. The reaction temperature was 220°C, the reaction pressure was 0.30 MPaG, and the mass hourly space velocity (WHSV) was 1.5 h⁻¹. -1 The molar ratio of hydrogen to 1,4-butanediol was 1:3, and the reaction cooling point was 202℃. The composition of the effluent liquid product after the reaction was: tetrahydrofuran 0.2%, γ-butyrolactone 38.8%, water 0.5%, n-butanol 0.2%, 1,4-butanediol 55.3%, TBA 3.2%, and approximately 1.8% other components. The dehydration reaction product was preheated to 140℃ and then passed through a container filled with SO42-. 2- In a reactive distillation column with modified ZrO2 catalyst, the reaction temperature was 146℃, the reaction pressure was 0.03 MPaG, and the mass hourly space velocity was 1.5 h⁻¹. -1 (The mass hourly space velocity based on 1,4-butanediol is 0.83 h⁻¹) -1 The tetrahydrofuran-rich gas phase at the top of the column and the 1,4-butanediol-rich liquid phase at the bottom of the column are cooled and then mixed in an intermediate tank. The product composition is 45.7% tetrahydrofuran, 37.0% γ-butyrolactone, 11.1% water, 0.2% n-butanol, 0.1% 1,4-butanediol, 0.5% TBA, and about 5.3% other components.

[0059] As can be seen from the examples and comparative examples, the method of the present invention for flexibly producing tetrahydrofuran and γ-butyrolactone has a high yield of main product, low yield of TBA and other by-products, and a wide range of adjustable products, which will bring good benefits to industrial production.

Claims

1. A method for the flexible production of tetrahydrofuran and γ-butyrolactone, the method comprising the following steps: a stream containing 1,4-butanediol enters a dehydration unit, undergoes a dehydration reaction in the presence of a dehydration catalyst to obtain a liquid containing tetrahydrofuran and unreacted 1,4-butanediol, which then enters an intermediate tank; the liquid in the intermediate tank subsequently enters a dehydrogenation unit, reacts in a hydrogen atmosphere and in the presence of a dehydrogenation catalyst to obtain a reaction product containing tetrahydrofuran and γ-butyrolactone, wherein the 1,4-butanediol contains ≤0.5% 2-(4-hydroxybutoxy)tetrahydrofuran, the dehydration reaction is carried out at a temperature of 150~350℃ and a pressure of 0.01~0.10 MPaG, the dehydrogenation reaction is carried out at a temperature of 180~300℃ and a pressure of 0.01~1.00 MPaG; the dehydration catalyst is selected from one or two of alumina and zirconium oxide; the dehydrogenation catalyst is selected from one or more of copper-zinc systems and copper-chromium systems.

2. The method as described in claim 1, characterized in that, The 1,4-butanediol-containing stream comprises one or more of the following: crude 1,4-butanediol with a purity ≥99.0%; qualified 1,4-butanediol with a purity ≥99.5%; superior 1,4-butanediol with a purity ≥99.7%; 1,4-butanediol recovery liquid with a purity ≥98.0% obtained by further purification of the residue from the acetylene distillation method; and a mixture of 1,4-butanediol, butanol, γ-butyrolactone, and tetrahydrofuran after removing heavy components with boiling points higher than 1,4-butanediol by the maleic anhydride method.

3. The method as described in claim 1, characterized in that, The mass hourly space velocity (HHSV) of 1,4-butanediol in the dehydration reaction is 0.1–20 h⁻¹. -1 .

4. The method according to any one of claims 1-3, characterized in that, The dehydration reaction may optionally include hydrogen in the 1,4-butanediol stream, wherein the molar ratio of hydrogen to 1,4-butanediol is 0 to 15:

1.

5. The method according to any one of claims 1-3, characterized in that, The mass hourly space velocity (WHSV) of 1,4-butanediol in the dehydrogenation reaction is 0.05–10 h⁻¹. -1 .

6. The method according to any one of claims 1-3, characterized in that, The dehydrogenation reaction is a hydrogen-dependent reaction, in which the dehydrogenation feedstock and hydrogen are mixed and preheated to the required reaction temperature. The molar ratio of hydrogen to 1,4-butanediol is 5:1 to 30:

1.

7. The method according to any one of claims 1-3, characterized in that, The dehydration unit and the dehydrogenation unit also include steps for removing moisture from the dehydrogenation feedstock and deacidifying it.

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