CN116003350A - Preparation method of tetrahydrofuran - Google Patents
Preparation method of tetrahydrofuran Download PDFInfo
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- CN116003350A CN116003350A CN202211622811.6A CN202211622811A CN116003350A CN 116003350 A CN116003350 A CN 116003350A CN 202211622811 A CN202211622811 A CN 202211622811A CN 116003350 A CN116003350 A CN 116003350A
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- WYURNTSHIVDZCO-UHFFFAOYSA-N Tetrahydrofuran Chemical compound C1CCOC1 WYURNTSHIVDZCO-UHFFFAOYSA-N 0.000 title claims abstract description 102
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 title claims abstract description 51
- 238000002360 preparation method Methods 0.000 title claims abstract description 17
- 238000011084 recovery Methods 0.000 claims abstract description 29
- 239000003054 catalyst Substances 0.000 claims abstract description 25
- 239000000463 material Substances 0.000 claims abstract description 14
- 239000012808 vapor phase Substances 0.000 claims abstract description 11
- 230000015572 biosynthetic process Effects 0.000 claims abstract description 10
- 238000003786 synthesis reaction Methods 0.000 claims abstract description 10
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 claims description 27
- 238000000034 method Methods 0.000 claims description 26
- 239000002808 molecular sieve Substances 0.000 claims description 25
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 12
- 239000006200 vaporizer Substances 0.000 claims description 10
- 230000008569 process Effects 0.000 claims description 9
- 238000010992 reflux Methods 0.000 claims description 8
- CSDREXVUYHZDNP-UHFFFAOYSA-N alumanylidynesilicon Chemical compound [Al].[Si] CSDREXVUYHZDNP-UHFFFAOYSA-N 0.000 claims description 5
- 229910052755 nonmetal Inorganic materials 0.000 claims description 5
- 229910052723 transition metal Inorganic materials 0.000 claims description 5
- PAWQVTBBRAZDMG-UHFFFAOYSA-N 2-(3-bromo-2-fluorophenyl)acetic acid Chemical compound OC(=O)CC1=CC=CC(Br)=C1F PAWQVTBBRAZDMG-UHFFFAOYSA-N 0.000 claims description 4
- 238000001914 filtration Methods 0.000 claims description 4
- 238000011068 loading method Methods 0.000 claims description 4
- 150000003624 transition metals Chemical class 0.000 claims description 4
- 238000005406 washing Methods 0.000 claims description 4
- 239000002826 coolant Substances 0.000 claims description 3
- 229910002796 Si–Al Inorganic materials 0.000 claims description 2
- 238000001035 drying Methods 0.000 claims description 2
- 238000005470 impregnation Methods 0.000 claims description 2
- 230000004048 modification Effects 0.000 claims description 2
- 238000012986 modification Methods 0.000 claims description 2
- 229910052680 mordenite Inorganic materials 0.000 claims description 2
- 230000007935 neutral effect Effects 0.000 claims description 2
- 229910052698 phosphorus Inorganic materials 0.000 claims description 2
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims 2
- 238000004519 manufacturing process Methods 0.000 abstract description 8
- 238000003912 environmental pollution Methods 0.000 abstract description 2
- WERYXYBDKMZEQL-UHFFFAOYSA-N butane-1,4-diol Chemical compound OCCCCO WERYXYBDKMZEQL-UHFFFAOYSA-N 0.000 description 39
- 239000000047 product Substances 0.000 description 17
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 13
- 238000006243 chemical reaction Methods 0.000 description 9
- 239000002904 solvent Substances 0.000 description 8
- 238000007670 refining Methods 0.000 description 6
- 239000002253 acid Substances 0.000 description 4
- HYBBIBNJHNGZAN-UHFFFAOYSA-N furfural Chemical compound O=CC1=CC=CO1 HYBBIBNJHNGZAN-UHFFFAOYSA-N 0.000 description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical group [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 3
- 230000018044 dehydration Effects 0.000 description 3
- 238000006297 dehydration reaction Methods 0.000 description 3
- BSCHIACBONPEOB-UHFFFAOYSA-N oxolane;hydrate Chemical compound O.C1CCOC1 BSCHIACBONPEOB-UHFFFAOYSA-N 0.000 description 3
- 239000011555 saturated liquid Substances 0.000 description 3
- 239000010865 sewage Substances 0.000 description 3
- 238000007086 side reaction Methods 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- NWUYHJFMYQTDRP-UHFFFAOYSA-N 1,2-bis(ethenyl)benzene;1-ethenyl-2-ethylbenzene;styrene Chemical compound C=CC1=CC=CC=C1.CCC1=CC=CC=C1C=C.C=CC1=CC=CC=C1C=C NWUYHJFMYQTDRP-UHFFFAOYSA-N 0.000 description 2
- YEJRWHAVMIAJKC-UHFFFAOYSA-N 4-Butyrolactone Chemical compound O=C1CCCO1 YEJRWHAVMIAJKC-UHFFFAOYSA-N 0.000 description 2
- OZJPLYNZGCXSJM-UHFFFAOYSA-N 5-valerolactone Chemical compound O=C1CCCCO1 OZJPLYNZGCXSJM-UHFFFAOYSA-N 0.000 description 2
- 229920002334 Spandex Polymers 0.000 description 2
- KMWBBMXGHHLDKL-UHFFFAOYSA-N [AlH3].[Si] Chemical group [AlH3].[Si] KMWBBMXGHHLDKL-UHFFFAOYSA-N 0.000 description 2
- -1 alicyclic ether compound Chemical class 0.000 description 2
- 239000006227 byproduct Substances 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 239000008367 deionised water Substances 0.000 description 2
- 229910021641 deionized water Inorganic materials 0.000 description 2
- 230000008021 deposition Effects 0.000 description 2
- 238000011161 development Methods 0.000 description 2
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- 229920003303 ion-exchange polymer Polymers 0.000 description 2
- 239000007791 liquid phase Substances 0.000 description 2
- FPYJFEHAWHCUMM-UHFFFAOYSA-N maleic anhydride Chemical compound O=C1OC(=O)C=C1 FPYJFEHAWHCUMM-UHFFFAOYSA-N 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 229910000510 noble metal Inorganic materials 0.000 description 2
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- 239000004759 spandex Substances 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N sulfuric acid Substances OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- ZQHLMWUFVRLDRK-UHFFFAOYSA-N 2,3-dichlorooxolane Chemical compound ClC1CCOC1Cl ZQHLMWUFVRLDRK-UHFFFAOYSA-N 0.000 description 1
- 239000004952 Polyamide Substances 0.000 description 1
- 239000004721 Polyphenylene oxide Substances 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical group [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- HSFWRNGVRCDJHI-UHFFFAOYSA-N alpha-acetylene Natural products C#C HSFWRNGVRCDJHI-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
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- 229930188620 butyrolactone Natural products 0.000 description 1
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- 238000013461 design Methods 0.000 description 1
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- MTHSVFCYNBDYFN-UHFFFAOYSA-N diethylene glycol Chemical compound OCCOCCO MTHSVFCYNBDYFN-UHFFFAOYSA-N 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000007598 dipping method Methods 0.000 description 1
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- 230000002708 enhancing effect Effects 0.000 description 1
- RTZKZFJDLAIYFH-UHFFFAOYSA-N ether Substances CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 description 1
- 125000002534 ethynyl group Chemical group [H]C#C* 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
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- 229910052751 metal Inorganic materials 0.000 description 1
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- 150000002739 metals Chemical class 0.000 description 1
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- 239000000025 natural resin Substances 0.000 description 1
- 239000003921 oil Substances 0.000 description 1
- 125000004430 oxygen atom Chemical group O* 0.000 description 1
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- 229920000728 polyester Polymers 0.000 description 1
- 229920000570 polyether Polymers 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- HNJBEVLQSNELDL-UHFFFAOYSA-N pyrrolidin-2-one Chemical compound O=C1CCCN1 HNJBEVLQSNELDL-UHFFFAOYSA-N 0.000 description 1
- 239000000376 reactant Substances 0.000 description 1
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- 229920003002 synthetic resin Polymers 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- RAOIDOHSFRTOEL-UHFFFAOYSA-N tetrahydrothiophene Chemical compound C1CCSC1 RAOIDOHSFRTOEL-UHFFFAOYSA-N 0.000 description 1
- 229920001169 thermoplastic Polymers 0.000 description 1
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- 229910052725 zinc Inorganic materials 0.000 description 1
Images
Classifications
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/10—Process efficiency
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- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
The preparation method of tetrahydrofuran adopts a synthesis device and comprises the following steps: 1) BDO is gasified and then enters a tubular fixed bed reactor, the inside of a tubular of the tubular fixed bed reactor is filled with a catalyst, the temperature of the gasified BDO is 233-245 ℃, and the airspeed is 20-40h ‑1 The bed temperature of the shell and tube fixed bed reactor is 233-245 ℃, and the outlet pressure is 5-10KPaG; 2) The materials discharged from the tubular fixed bed reactor enter a BDO recovery tower, the theoretical plate number is 14-17, the operating pressure is 1-5KPaG, and the operating temperature is 65-215 ℃; 3) Liquefying the top vapor phase of the BOD recovery tower, and then delivering the liquefied top vapor phase to a low-pressure rectifying tower, wherein the theoretical plate number is 15-20, the operating pressure is 5-10KPaG, and the operating temperature is 65-105 ℃; 4) Low pressure rectifying towerThe vapor phase at the top of the tower is liquefied and then sent to a high-pressure rectifying tower, the theoretical plate number is 25-30, the operating pressure is 500-900KPaG, the operating temperature is 130-145 ℃, and tetrahydrofuran products are produced at the bottom of the tower. The preparation method has the advantages of simple and convenient preparation process and high material utilization rate, can effectively reduce the manufacturing cost and avoid environmental pollution.
Description
Technical Field
The invention relates to the field of chemical industry, in particular to a preparation method of tetrahydrofuran.
Background
Tetrahydrofuran (THF) is mainly used as a solvent and as a chemical starting material. THF is an alicyclic ether compound, has excellent solubility to various natural and synthetic resins, has no steric hindrance to oxygen atoms in molecules, can form coordination complexes with various metals and salts thereof, and is widely applied to the solvent industry. For example: acetylene extraction solvent, special pigment treating agent, and solvents for pharmaceutical industry. The THF has low boiling point and good diffusivity, and can be widely used as a solvent for producing precise magnetic tapes. As an application in the aspect of chemical raw materials, THF mainly produces polytetramethylene glycol ether (PTMEG) and tetrahydrothiophene, 1, 4-dichloroethane, 2, 3-dichlorotetrahydrofuran, valerolactone, butyrolactone, pyrrolidone and the like, wherein PTMEG is widely used for manufacturing polyether type PU high resilience foam and PU rubber, spandex fiber, certain thermoplastic polyesters, polyamide elastomers and the like due to long carbon chain and low hydroxyl content, and is a basic raw material for producing high-elasticity Spandex. Over a decade of development, PTMEG has become a direction of development for high performance synthetic materials.
Currently, the current industrial methods for preparing tetrahydrofuran mainly include a furfural method, a 1, 4-butanediol method (BDO method) and a maleic anhydride method. The furfural method and the maleic anhydride method have the advantages of complex process, simple process of the 1, 4-butanediol method, less byproducts, high yield and less equipment investment. The BDO liquid phase THF synthesis process generally adopts concentrated sulfuric acid, ion exchange resin, heteropolyacid, noble metal catalyst and the like, the concentrated sulfuric acid severely corrodes equipment and pollutes the environment, the treatment difficulty of downstream waste acid is increased, the heteropolyacid catalyst is easily dissolved in a solvent, and the ion exchange resin has poor temperature resistance; the noble metal catalyst has high manufacturing cost; and the liquid phase dehydration process produces a lot of coke in the product.
Therefore, how to design a preparation method of tetrahydrofuran with high environmental friendliness and low manufacturing cost is a problem to be solved by the technicians in the field.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, and provides a preparation method of tetrahydrofuran, which has the advantages of simple and convenient preparation process, high material utilization rate, effective reduction of manufacturing cost and environmental pollution avoidance.
The technical scheme of the invention is as follows: a preparation method of tetrahydrofuran adopts a synthesis device to prepare the tetrahydrofuran, and comprises the following steps:
the synthesis device comprises a tubular fixed bed reactor, a BDO recovery tower, a low-pressure rectifying tower and a high-pressure rectifying tower,
the feed inlet of the tubular fixed bed reactor is provided with a vaporizer, the discharge outlet of the tubular fixed bed reactor feeds the BDO recovery tower through a first pipeline, the top of the BDO recovery tower feeds the low-pressure rectifying tower through a second pipeline, the top condenser of the low-pressure rectifying tower feeds the high-pressure rectifying tower through a third pipeline,
1) BDO is gasified and then enters a tubular fixed bed reactor, the inside of a tubular of the tubular fixed bed reactor is filled with a catalyst, the temperature of the gasified BDO is 233-245 ℃, and the airspeed is 20-40h -1 The bed temperature of the shell and tube fixed bed reactor is 233-245 ℃, and the outlet pressure is 5-10KPaG;
2) The materials discharged from the tubular fixed bed reactor enter a BDO recovery tower, the theoretical plate number is 14-17, the operating pressure is 1-5KPaG, and the operating temperature is 65-215 ℃;
3) Liquefying the top vapor phase of the BOD recovery tower, and then delivering the liquefied top vapor phase to a low-pressure rectifying tower, wherein the theoretical plate number is 15-20, the operating pressure is 5-10KPaG, and the operating temperature is 65-105 ℃;
4) The vapor phase at the top of the low pressure rectifying tower is liquefied and then sent to the high pressure rectifying tower, the theoretical plate number is 25-30, the operating pressure is 500-900KPaG, the operating temperature is 130-145 ℃, and tetrahydrofuran products are produced at the bottom of the tower.
Further, a first heat exchanger is arranged on the first pipeline, and the third pipeline passes through a cold medium channel of the first heat exchanger.
Further, the bottom of the BDO recovery tower is connected with the inlet of the vaporizer through a fourth pipeline.
Further, a second heat exchanger is arranged on the second pipeline, and the bottom of the high-pressure rectifying tower passes through a heat medium channel of the second heat exchanger through a fifth pipeline.
Further, the top of the high-pressure rectifying tower is connected with the reflux port of the low-pressure rectifying tower and the reflux port of the high-pressure rectifying tower through a sixth pipeline, and the sixth pipeline passes through a heat medium channel of a reboiler at the bottom of the low-pressure rectifying tower.
Further, the purity of BDO in the step 1) is more than or equal to 99.8wt%, the catalyst is a modified silicon-aluminum molecular sieve catalyst, and the modification comprises the following steps:
1) Adding a silicon-aluminum molecular sieve catalyst into 15-30% NaOH solution, desilicating at 70-85 ℃ for 3-5h, taking out and washing to be neutral;
2) Exchanging with ammonium nitrate solution at 75-85deg.C for 3-6 hr to obtain NH 4 A type molecular sieve;
3) Roasting for 5-8H at 500-600 ℃ to obtain an H-type molecular sieve;
4) Loading transition metal or nonmetal elements with a volume-integrated impregnation method, wherein the loading amount is 1-5wt%, standing and filtering;
5) Drying at 100-120 deg.c and roasting at 500 deg.c for 6-8 hr to obtain the modified Si-Al molecular sieve catalyst.
Further, the silicon-aluminum molecular sieve in the step 1) is any one or more of ZSM-5, beta, mordenite and NAY.
Further, the transition metal or nonmetal element in the step 4) is any one or more than one of Fe, co, cu, zn, P.
The technical scheme has the following beneficial effects:
1. the invention utilizes vapor phase BDO cyclodehydration technology, uses modified molecular sieve as catalyst, high-selectivity catalyzes and generates tetrahydrofuran, and then obtains tetrahydrofuran product with purity reaching more than 99.99wt% through BDO recovery and rectification separation. The whole production process does not need extra solvent, the used modified catalyst has low cost, the whole method can maximally recycle heat, the production cost of tetrahydrofuran can be greatly reduced, and the environmental friendliness is high.
2. The synthesis device used in the invention comprises a tubular fixed bed reactor, a BDO recovery tower, a low-pressure rectifying tower and a high-pressure rectifying tower, wherein the tubular fixed bed reactor is used for catalyzing BDO to cyclize and dehydrate to obtain tetrahydrofuran, the BDO recovery tower is used for separating and recovering BDO, the low-pressure rectifying tower and the high-pressure rectifying tower are cooperatively matched, and a high-purity tetrahydrofuran product is obtained through separation and purification.
3. The modified silicon-aluminum molecular sieve used in the preparation method has rich pore canal structure and larger specific surface area, and provides a large number of acid sites for dehydration condensation or dehydration cyclization reaction. The mesoporous structure is formed in the molecular sieve by selectively removing framework silicon atoms by an alkali modification method, the purpose of enhancing molecular diffusion and reducing carbon deposition can be achieved under the condition that the acid position is not changed, and in addition, the acid quality of the molecular sieve is changed by introducing transition metal elements or nonmetal elements in a dipping or ion exchange mode, so that the selectivity of the product is improved.
4. The preparation method of the invention controls the bed temperature of the tubular fixed bed reactor to 233-245 ℃ which is the same as the temperature of the material at the inlet of the reactor, and suppresses the problem of increased side reaction caused by reaction temperature rise. The reaction is quickened at high temperature, the catalytic activity of reactants is improved, the conversion rate is improved, the carbon deposition speed is increased when the temperature is too high, the byproducts are increased due to the fact that the contact time is too long, the mass airspeed is high, the contact time with a catalyst is short, and the conversion rate is reduced. The materials discharged from the reactor are firstly separated from water and tetrahydrofuran in a BDO recovery tower from the top of the tower, and BDO at the bottom of the tower is returned to the reactor for recycling, so that the utilization rate of BDO is improved. The discharged tetrahydrofuran solution is preheated and then sent to a low-pressure rectifying tower, water is extracted from the bottom of the tower, an azeotrope of the water and the tetrahydrofuran is extracted from the top of the tower, preheated and then sent to a high-pressure rectifying tower, the azeotrope of the water and the tetrahydrofuran is extracted from the top of the tower and used as a heating medium for preheating materials, and the mixture is used as reflux liquid, and simultaneously meets the rectification requirements of the low-pressure rectifying tower and the high-pressure rectifying tower, and the tetrahydrofuran with the purity of more than 99.99 weight percent is extracted from the bottom of the tower. In the THF refining process, as the azeotrope is formed by THF and water in the reaction liquid, an extractant is usually added to obtain a qualified THF product, but the process is complicated, a recovery solvent unit needs to be added, and the equipment investment is increased. The invention breaks through the rectification limit by utilizing the difference of azeotrope compositions under different pressures.
5. According to the preparation method, the tetrahydrofuran-water azeotrope of the high-pressure rectifying tower is preheated by using high-heat materials discharged from the reactor, so that the feed of the high-pressure rectifying tower is in a saturated liquid state, the tetrahydrofuran solution of the low-pressure rectifying tower is preheated by using the tower kettle extract of the high-pressure rectifying tower, so that the feed of the low-pressure rectifying tower is in a saturated liquid state, and the energy consumption of the high-pressure rectifying tower and the low-pressure rectifying tower can be effectively reduced.
The applicant tests prove that the conversion rate of BDO reaches more than 91.2 percent, the selectivity of the catalyst to THF reaches more than 99.3 percent, and the purity of the extracted tetrahydrofuran product reaches more than 99.99 weight percent. Preheating a THF high-pressure refining tower feeding process by using a reactor outlet product, and saving heat by 103.3KW per ton of product; preheating THF low-pressure refining tower feeding by using a high-pressure refining tower kettle discharging product, and saving 32.2KW of heat per ton of product; the gas phase at the top of the THF high-pressure refining tower is used as a heat source of the THF low-pressure refining tower, so that 360.9KW of heat per ton of product is saved.
Further description is provided below with reference to the drawings and detailed description.
Drawings
Fig. 1 is a schematic connection diagram of embodiment 1 of the present invention.
In the drawing, 1 is a tubular fixed bed reactor, 2 is a BDO recovery tower, 3 is a low-pressure rectifying tower, 4 is a high-pressure rectifying tower, 5 is a vaporizer, 6 is a first heat exchanger, 7 is a second heat exchanger, 101 is a first pipeline, 102 is a second pipeline, 103 is a third pipeline, 104 is a fourth pipeline, 105 is a fifth pipeline, and 106 is a sixth pipeline.
Detailed Description
In the present invention, the materials used are as follows:
example 1
The synthesis device for synthesizing the tetrahydrofuran comprises a tubular fixed bed reactor 1, a BDO recovery tower 2, a low-pressure rectifying tower 3 and a high-pressure rectifying tower 4, wherein the theoretical plate number of the BDO recovery tower is 15, the theoretical plate number of the low-pressure rectifying tower is 20, and the theoretical plate number of the high-pressure rectifying tower is 30. The feeding port of the tubular fixed bed reactor 1 is provided with a vaporizer 5, and the vaporizer adopts heat conduction oil as a heating medium. The feed outlet of the tubular fixed bed reactor 1 feeds the BDO recovery tower 2 through a first pipeline 101, specifically, the downstream end of the first pipeline is connected to the middle part of the BDO recovery tower, and a first heat exchanger 6 is arranged on the first pipeline 101. The top of BDO recovery tower 2 is fed to low pressure rectifying tower 3 through second pipeline 102, specifically, the downstream end of the second pipeline is located in the middle of the low pressure rectifying tower, second pipeline 102 is provided with second heat exchanger 7, the upstream end of the second pipeline is connected with the top condenser outlet of BDO recovery tower, and a buffer tank is arranged between the top condenser and the second heat exchanger, obviously, a return pipe is also required to be arranged to be connected with the reflux port of BDO recovery tower, and the bottom of BDO recovery tower is connected with the inlet of vaporizer 5 through fourth pipeline 104. The top condenser of the low pressure rectifying tower 3 feeds the high pressure rectifying tower 4 through a third pipeline 103, specifically, the downstream end of the third pipeline is located in the middle of the high pressure rectifying tower, a buffer tank is arranged between the top condenser and the third pipeline, and obviously, a return pipe is also required to be arranged to be connected with a return port of the low pressure rectifying tower, the third pipeline 103 passes through a cold medium channel of the first heat exchanger 6, the high temperature material flowing through the first pipeline is utilized as a preheating medium to preheat and raise the temperature, and the bottom of the low temperature rectifying tower discharges a small amount of wastewater to a sewage treatment station. The top of the high-pressure rectifying tower 4 is connected with the reflux port of the low-pressure rectifying tower and the reflux port of the high-pressure rectifying tower through a sixth pipeline 106, the sixth pipeline 106 passes through a heat medium channel of a reboiler at the bottom of the low-pressure rectifying tower, and the bottom of the high-pressure rectifying tower 4 passes through a heat medium channel of the second heat exchanger 7 through a fifth pipeline 105.
Example 2
Preparation of modified molecular sieve catalysts
NaOH solution of ZSM-5 molecular sieve with silicon-aluminum ratio of 50 at 15 percentThe molecular sieve is put into the solution according to the proportion of 20L of the solution per kilogram of the molecular sieve, and the desilication is carried out for 3 hours at 75 ℃. After desilication is completed, filtration is carried out, and deionized water is used for washing to neutrality. 1 mol.L for washed molecular sieve -1 The ammonium nitrate solution was exchanged three times, 3h each at 80℃to give NH4-ZSM-5. And roasting NH4-ZSM-5 at 550 ℃ for 5 hours to obtain the H-ZSM-5 sub-sieve. Impregnating 0.98L, 8wt% Zn (NO 3) per kg molecular sieve 2 The solution is placed for 12 hours, filtered, dried for 24 hours at 110 ℃, and baked for 6 hours at 500 ℃ to form the supported catalyst.
The prepared catalyst was packed inside the column of the tubular fixed bed reactor of the synthesis apparatus of example 1. BDO with the purity of 99.8 weight percent is preheated to 150-160 ℃ (1.25 t/h), enters a vaporizer, is vaporized at 238 ℃, enters a tubular fixed bed reactor, and has the airspeed of 20h -1 The outlet pressure of the reactor is controlled to be 5KPaG, the cooling medium inlet of the tubular fixed bed reactor is hot water at 85 ℃, the outlet is hot water at 95 ℃, and the temperature of the reactor bed layer is controlled to be the same as the inlet temperature of the reactor, so that the problem of side reaction increase caused by reaction temperature rise is solved. The reactor outlet BDO conversion was 91.2 percent and the catalyst selectivity to THF was 99.3 percent as measured by sampling.
The materials at the outlet of the tubular fixed bed reactor enter a BDO recovery tower through a first pipeline, the operating pressure is 10KPaG, the operating temperature is 67 ℃ at the top, the temperature at the bottom is 210 ℃,99.9wt% of BDO and a small amount of heavy components return to the reactor from the bottom, 80wt% of THF solution is distilled out from the top of the tower, the materials enter a low-pressure rectifying tower, the operating pressure is 5KPaG, the operating temperature is 65 ℃ at the top of the tower, the temperature at the bottom of the tower is 100 ℃,99.9wt% of water is extracted from the bottom of the tower, sewage is sent to a sewage facility to treat or send into a system to be used as cooling hot water of the reactor for recycling, 94.5wt% of THF-water azeotrope enters a high-pressure rectifying tower, the operating pressure is 600KPaG, the operating temperature at the top of 130 ℃, the bottom of the tower is 141 ℃, 88.9wt% of THF-water azeotrope is extracted from the top of the tower, the THF product is refluxed to the low-pressure rectifying tower, and the flow rate of the THF product is 1.01t/h.
During the process, the first heat exchanger on the first pipeline is utilized to preheat the feed of the high-pressure rectifying tower, so that the feed of the high-pressure rectifying tower is in a saturated liquid state, and the heat is saved by 103.3KW per ton of product; preheating the feed of the low-pressure rectifying tower by using a second heat exchanger on a second pipeline to enable the feed of the low-pressure rectifying tower to be in a saturated state, and saving 32.2KW of heat per ton of product; and the vapor phase discharged by the sixth pipeline is used as a reboiler at the bottom of the low-pressure rectifying tower to obtain a heat source, so that the heat is saved by 360.9KW per ton of product.
Example 3
The ZSM-5 molecular sieve with the silicon-aluminum ratio of 50 is adopted for desilication treatment in a 30 percent NaOH solution. Molecular sieves were placed in solution at a rate of 20L of solution per kg of molecular sieve and desilicated for 3h at 75 ℃. After desilication is completed, filtration is carried out, and deionized water is used for washing to neutrality. 1 mol.L for washed molecular sieve -1 The ammonium nitrate solution was exchanged three times, 3h each at 80℃to give NH4-ZSM-5. And roasting NH4-ZSM-5 at 550 ℃ for 5 hours to obtain the H-ZSM-5 sub-sieve. Impregnating 0.98L, 12wt% (NH) per kg molecular sieve 4 ) 2 ·HPO 4 The solution is placed for 12 hours, filtered, dried for 24 hours at 110 ℃, and baked for 6 hours at 500 ℃ to form the supported catalyst.
The prepared catalyst was packed inside the column of the tubular fixed bed reactor of the synthesis apparatus of example 1.
BDO with the purity of 99.8 weight percent is preheated to 150-160 ℃ (1.25 t/h), enters a vaporizer, is vaporized at the temperature of 240 ℃, enters a tubular fixed bed reactor, and has the airspeed of 25h -1 The outlet pressure of the reactor is controlled to be 5KPaG, the cooling medium inlet of the tubular fixed bed reactor is hot water at 85 ℃, the outlet is hot water at 95 ℃, and the temperature of the reactor bed layer is controlled to be the same as the inlet temperature of the reactor, so that the problem of side reaction increase caused by reaction temperature rise is solved. The reactor outlet BDO conversion was 92.3 percent and the catalyst selectivity to THF was 99.5 percent as measured by sampling.
The material at the outlet of the tubular fixed bed reactor was purified according to the purification method of example 2.
Claims (8)
1. The preparation method of tetrahydrofuran is characterized by adopting a synthesis device for preparation, comprising the following steps:
the synthesis device comprises a tubular fixed bed reactor (1), a BDO recovery tower (2), a low-pressure rectifying tower (3) and a high-pressure rectifying tower (4),
the feed inlet of the shell and tube fixed bed reactor (1) is provided with a vaporizer (5), the feed outlet of the shell and tube fixed bed reactor (1) feeds BDO recovery tower (2) through a first pipeline (101), the top of BDO recovery tower (2) feeds low-pressure rectifying tower (3) through a second pipeline (102), the top condenser of the low-pressure rectifying tower (3) feeds high-pressure rectifying tower (4) through a third pipeline (103),
1) BDO is gasified and then enters a tubular fixed bed reactor, the inside of a tubular of the tubular fixed bed reactor is filled with a catalyst, the temperature of the gasified BDO is 233-245 ℃, and the airspeed is 20-40h -1 The bed temperature of the shell and tube fixed bed reactor is 233-245 ℃, and the outlet pressure is 5-10KPaG;
2) The materials discharged from the tubular fixed bed reactor enter a BDO recovery tower, the theoretical plate number is 14-17, the operating pressure is 1-5KPaG, and the operating temperature is 65-215 ℃;
3) Liquefying the top vapor phase of the BOD recovery tower, and then delivering the liquefied top vapor phase to a low-pressure rectifying tower, wherein the theoretical plate number is 15-20, the operating pressure is 5-10KPaG, and the operating temperature is 65-105 ℃;
4) The vapor phase at the top of the low pressure rectifying tower is liquefied and then sent to the high pressure rectifying tower, the theoretical plate number is 25-30, the operating pressure is 500-900KPaG, the operating temperature is 130-145 ℃, and tetrahydrofuran products are produced at the bottom of the tower.
2. The method for preparing tetrahydrofuran according to claim 1, wherein the first pipeline (101) is provided with a first heat exchanger (6), and the third pipeline (103) passes through a cooling medium channel of the first heat exchanger (6).
3. The process for the preparation of tetrahydrofuran according to claim 1, wherein the bottom of the BDO recovery column (2) is connected to the inlet of the vaporizer (5) via a fourth line (104).
4. The method for preparing tetrahydrofuran according to claim 1, wherein the second heat exchanger (7) is disposed on the second pipeline (102), and the bottom of the high-pressure rectifying tower (4) passes through the heat medium channel of the second heat exchanger (7) through the fifth pipeline (105).
5. The method for preparing tetrahydrofuran according to claim 1, wherein the top of the high pressure rectifying tower (4) is connected with the reflux port of the low pressure rectifying tower and the reflux port of the high pressure rectifying tower through a sixth pipeline (106), and the sixth pipeline (106) passes through a heat medium channel of a reboiler at the bottom of the low pressure rectifying tower.
6. The method for preparing tetrahydrofuran according to claim 1, wherein the purity of BDO in step 1) is not less than 99.8wt%, the catalyst is a modified silica-alumina molecular sieve catalyst, and the modification comprises the steps of:
1) Adding a silicon-aluminum molecular sieve catalyst into 15-30% NaOH solution, desilicating at 70-85 ℃ for 3-5h, taking out and washing to be neutral;
2) Exchanging with ammonium nitrate solution at 75-85deg.C for 3-6 hr to obtain NH 4 A type molecular sieve;
3) Roasting for 5-8H at 500-600 ℃ to obtain an H-type molecular sieve;
4) Loading transition metal or nonmetal elements with a volume-integrated impregnation method, wherein the loading amount is 1-5wt%, standing and filtering;
5) Drying at 100-120 deg.c and roasting at 500 deg.c for 6-8 hr to obtain the modified Si-Al molecular sieve catalyst.
7. The method for preparing tetrahydrofuran according to claim 6, wherein the silica-alumina molecular sieve in step 1) is one or more of ZSM-5, beta, mordenite and NAY.
8. The method according to claim 6, wherein the transition metal or nonmetal element in the step 4) is one or more of Fe, co, cu, zn, P.
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