Hydrofining process for tetrahydrofuran

Abstract

The application provides a hydrofining method of tetrahydrofuran, and specifically comprises the following steps: providing a raw material liquid and a nickel-based catalyst; the nickel-based catalyst comprises a Raney nickel catalyst and a supported nickel catalyst, the Raney nickel catalyst is arranged in a first fixed bed reactor to form a first catalyst bed layer; the supported nickel catalyst is arranged in a second fixed bed reactor to form a second catalyst bed layer; the raw material liquid and hydrogen are preheated and mixed in a preheating furnace to obtain a gas-liquid mixture; and the gas-liquid mixture is sequentially subjected to hydrogenation reaction in the first catalyst bed layer and the second catalyst bed layer to obtain a refined product. The application solves the problem that the by-product tetrahydrofuran generated in the PBAT process cannot meet the polyester grade requirement, so that the tetrahydrofuran cannot be directly applied to the PTMEG production.

Description

Technical Field

[0001] This invention relates to the field of catalytic hydrogenation technology, and more particularly to a method for the hydrogenation purification of tetrahydrofuran. Background Technology

[0002] Tetrahydrofuran (THF) is a heterocyclic organic compound, belonging to the fully hydrogenated product of furan, an aromatic ether compound. Polytetramethylene glycol (PTMEG), also known as polytetrahydrofuran, is a homopolymer obtained by cationic ring-opening polymerization of tetrahydrofuran (THF) monomer in the presence of a catalyst. It is a white, waxy solid at room temperature, readily soluble in alcohols, esters, ketones, aromatic hydrocarbons, and chlorinated hydrocarbons, but insoluble in aliphatic hydrocarbons and water.

[0003] Polybutylene terephthalate (PBAT), also known as poly(butylene terephthalate-co-butylene adipate), undergoes a side reaction during its synthesis to generate THF and other impurities. Currently, the tetrahydrofuran byproduct obtained during PBAT production does not meet polyester-grade requirements and cannot be directly used in PTMEG production.

[0004] The patent "A System and Method for Preparing Polymer-Grade Tetrahydrofuran (Application No.: 202311034585.4)" creatively describes a process where tetrahydrofuran produced during the synthesis of PBAT is distilled, hydrogenated, and then distilled again to meet polyester-grade requirements. However, the distillation process has strict requirements on the content of unsaturated components in the distillation product tetrahydrofuran. The high reaction temperature, high energy consumption, and low reaction space velocity are affected by the content of unsaturated components, thus impacting its industrial production capacity.

[0005] Therefore, it is necessary to develop a hydrogenation purification method for tetrahydrofuran to solve the aforementioned problems in the existing technology. Summary of the Invention

[0006] The purpose of this invention is to provide a method for hydrogenating and refining tetrahydrofuran, which solves the problem that tetrahydrofuran, a byproduct of the PBAT process, cannot meet the requirements for polyester grade, thus preventing its direct application in PTMEG production.

[0007] To achieve the above objectives, the present invention provides a method for the hydrogenation purification of tetrahydrofuran, specifically comprising the following steps:

[0008] S0: Provides a feed liquid and a nickel-based catalyst, wherein the feed liquid comprises distilled tetrahydrofuran and unsaturated components;

[0009] S1: The nickel-based catalyst includes a Raney nickel catalyst and a supported nickel catalyst. The Raney nickel catalyst is placed in a primary fixed-bed reactor to form a primary catalyst bed; the supported nickel catalyst is placed in a secondary fixed-bed reactor to form a secondary catalyst bed.

[0010] S2: The raw material liquid and hydrogen are preheated and mixed in a preheating furnace to obtain a gas-liquid mixture;

[0011] S3: The gas-liquid mixture is subjected to hydrogenation reaction in the primary catalyst bed and the secondary catalyst bed in sequence to obtain a purified product.

[0012] Optionally, the tetrahydrofuran is a byproduct generated during the synthesis of polybutylene terephthalate-butylene adipate.

[0013] Optionally, the tetrahydrofuran content is 99.94% or more, and the content of the unsaturated component is 50-400 ppm, based on the mass percentage of the raw material liquid.

[0014] Optionally, in step S3, the temperature of the hydrogenation reaction of the gas-liquid mixture in the primary catalyst bed is 50-100℃, the pressure is 0.2-1.5 MPa, and the space velocity of the gas-liquid mixture is 0.5-8 h⁻¹. -1 .

[0015] Optionally, in step S3, the temperature of the hydrogenation reaction of the gas-liquid mixture in the secondary catalyst bed is 40-80℃, the pressure is 0.2-1.5 MPa, and the space velocity of the gas-liquid mixture is 0.5-8 h⁻¹. -1 .

[0016] Optionally, the refined product includes the tetrahydrofuran and unsaturated compounds, wherein the content of the tetrahydrofuran is 99.95% or more and the content of the unsaturated compounds is less than 2 ppm, based on the mass percentage of the refined product.

[0017] Optionally, the Raney nickel catalyst comprises nickel, aluminum, molybdenum, and a metal additive, wherein the nickel content is 60-75% by mass percentage, the molybdenum content is 0.51-2%, the metal additive content is 1-3%, and the remainder is aluminum.

[0018] Optionally, the metal additive is at least one of iron and copper.

[0019] Optionally, the Raney nickel catalyst is in particulate form, with a particle size of 2-8 mm and a specific surface area of ​​10-60 square meters per gram.

[0020] Optionally, the supported nickel catalyst includes an active component, a support, and an additive; the active component includes nickel oxide and molybdenum oxide, the support includes titanium oxide and aluminum oxide, and the additive includes one or two of alkali metals and alkaline earth metals.

[0021] The alkali metals include sodium oxide and potassium oxide, and the alkaline earth metals are calcium oxide.

[0022] The beneficial effects of this invention are as follows:

[0023] 1. The tetrahydrofuran of this invention is a byproduct generated during the synthesis of polybutylene terephthalate-butylene adipate. From the perspective of unsaturated component content, the secondary hydrogenation unit is obviously less difficult and energy-intensive than the primary unit. Most unsaturated components are removed during primary hydrogenation, and secondary hydrogenation can achieve hydrogenation depth at a lower temperature, thus reducing energy consumption.

[0024] 2. The present invention employs a two-stage hydrogenation process to reduce the content of unsaturated compounds in tetrahydrofuran after hydrogenation. At the same time, it achieves higher space velocity and greater production capacity. The two-stage hydrogenation process allows for secondary hydrogenation of high-content unsaturated compounds, further reducing the unsaturated compound content and resulting in higher precision of tetrahydrofuran.

[0025] 3. The material contains harmful impurities, so Raney nickel catalyst is used in the first stage to protect the second stage supported catalyst and extend the catalyst's service life.

[0026] 4. In the hydrorefining process of tetrahydrofuran, the Raney nickel catalyst and the supported nickel catalyst can achieve the best hydrogenation effect on the unsaturated products in tetrahydrofuran only within the range of temperature, pressure and space velocity specified in this application. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] To achieve the above objectives, the present invention provides a method for the hydrogenation purification of tetrahydrofuran, specifically comprising the following steps:

[0029] S0: Provides a feed liquid and a nickel-based catalyst, wherein the feed liquid comprises distilled tetrahydrofuran and unsaturated components;

[0030] S1: The nickel-based catalyst includes a Raney nickel catalyst and a supported nickel catalyst. The Raney nickel catalyst is placed in a primary fixed-bed reactor to form a primary catalyst bed; the supported nickel catalyst is placed in a secondary fixed-bed reactor to form a secondary catalyst bed.

[0031] S2: The raw material liquid and hydrogen are preheated and mixed in a preheating furnace to obtain a gas-liquid mixture;

[0032] S3: The gas-liquid mixture is subjected to hydrogenation reaction in the primary catalyst bed and the secondary catalyst bed in sequence to obtain a purified product.

[0033] In some embodiments of the present invention, the preheating and mixing process is carried out in a preheating furnace.

[0034] In some embodiments of the present invention, the tetrahydrofuran is a byproduct generated during the synthesis of polybutylene terephthalate-butylene adipate (PBAT).

[0035] In some embodiments of the present invention, the tetrahydrofuran content is 99.94% or more, and the content of the unsaturated component is 50-400 ppm, based on the mass percentage of the raw material liquid.

[0036] In some embodiments of the present invention, the method for hydrogenating and refining tetrahydrofuran specifically includes the following steps: placing the Raney nickel catalyst in a primary fixed-bed reactor to form a catalyst bed; placing the supported nickel catalyst in a secondary fixed-bed reactor to form a catalyst bed; then flowing the gas-liquid mixture through the bed packed with the Raney nickel catalyst, and then through the bed packed with the supported nickel catalyst, to carry out a secondary hydrogenation reaction to obtain the refined product.

[0037] In some embodiments of the present invention, in step S3, the temperature of the hydrogenation reaction of the gas-liquid mixture in the primary catalyst bed is 50-100°C, the pressure is 0.2-1.5 MPa, and the space velocity of the gas-liquid mixture is 0.5-8 h⁻¹. -1 .

[0038] In some embodiments of the present invention, in step S3, the temperature of the hydrogenation reaction of the gas-liquid mixture in the secondary catalyst bed is 40-80°C, the pressure is 0.2-1.5 MPa, and the space velocity of the gas-liquid mixture is 0.5-8 h⁻¹. -1 .

[0039] In some embodiments of the present invention, the refined product includes the tetrahydrofuran and unsaturated compounds, wherein the content of the tetrahydrofuran is 99.95% or more and the content of the unsaturated compounds is less than 2 ppm, based on the mass percentage of the refined product.

[0040] In some embodiments of the present invention, the Raney nickel catalyst comprises nickel, aluminum, molybdenum and a metal additive, wherein the nickel content is 60-75% by mass percentage of the Raney nickel catalyst, the molybdenum content is 0.51-2%, the metal additive content is 1-3%, and the remainder is aluminum.

[0041] In some embodiments of the present invention, the metal additive is iron or copper.

[0042] In some embodiments of the present invention, the Raney nickel catalyst is in particulate form, the particle size of the Raney nickel catalyst is 2-8 mm, and the specific surface area per gram of the Raney nickel catalyst is 10-60 square meters.

[0043] In some embodiments of the present invention, the supported nickel catalyst comprises an active component, a support, and an additive; the active component comprises nickel oxide and molybdenum oxide, the support comprises titanium oxide and aluminum oxide, and the additive comprises one or two of alkali metals and alkaline earth metals.

[0044] In some embodiments of the present invention, the alkali metal substance includes sodium oxide and potassium oxide, and the alkaline earth metal substance is calcium oxide.

[0045] The nickel-based catalyst provided by this invention is applied to the hydrogenation refining of high-grade tetrahydrofuran, a byproduct of PBAT, reducing the total unsaturated content in tetrahydrofuran from several hundred ppm to below 2 ppm, thereby meeting the requirements for raw material tetrahydrofuran in PTMEG production.

[0046] The present invention also provides a comparative example, in which a comparative catalyst is prepared. In the first stage, a comparison is made between a Raney nickel catalyst and a supported nickel catalyst. Both the Raney nickel catalyst and the supported nickel catalyst are nickel-based catalysts, but the types of promoters contained in the Raney nickel catalyst and the supported nickel catalyst are different.

[0047] Example 1

[0048] The system provides a feedstock, a Raney nickel catalyst, and a supported nickel catalyst. The feedstock is tetrahydrofuran obtained from upper-stage distillation, and the tetrahydrofuran content is 99.94% by mass, while the unsaturated component content is 398 ppm. The Raney nickel catalyst is composed of nickel, aluminum, molybdenum, and a metal additive, and the nickel content is 75.6%, the molybdenum content is 2.1%, and the metal additive content is 2%, wherein the metal additive is copper. The remainder is aluminum. The Raney nickel catalyst is granular with a particle size of 6 mm and a specific surface area of ​​50.9 square meters per gram. The supported nickel catalyst is composed of nickel oxide, molybdenum oxide, titanium oxide, aluminum oxide, and alkali metal. By mass percentage, the content of nickel oxide is 29%, the content of molybdenum oxide is 2.7%, the content of titanium oxide is 3%, and the content of alkali metal is 1%, wherein the alkali metal is sodium oxide; the remainder is aluminum oxide.

[0049] The Raney nickel catalyst is placed in a primary fixed-bed reactor to form a primary catalyst bed; the supported nickel catalyst is placed in a secondary fixed-bed reactor to form a secondary catalyst bed. The feed liquid and hydrogen are preheated and mixed in a preheating furnace to obtain a gas-liquid mixture. The gas-liquid mixture is then subjected to hydrogenation reactions sequentially in the primary and secondary catalyst beds to obtain a refined product. The hydrogenation reaction of the gas-liquid mixture in the primary catalyst bed is carried out at a temperature of 100°C, a pressure of 1.5 MPa, and a space velocity of 8 h⁻¹. -1 The hydrogenation reaction of the gas-liquid mixture in the secondary catalyst bed is carried out at a temperature of 75°C and a pressure of 1.5 MPa, with a space velocity of 8 h⁻¹. -1 The refined product, by mass percentage, contains 99.96% tetrahydrofuran, 1 ppm unsaturated matter, and includes acetaldehyde, propionaldehyde, and other unsaturated matter. The acetaldehyde component was not detected, the propionaldehyde component was not detected, and the content of other unsaturated matter was 1 ppm.

[0050] Example 2

[0051] The system provides a feedstock, a Raney nickel catalyst, and a supported nickel catalyst. The feedstock is tetrahydrofuran obtained from upper-stage distillation, and the tetrahydrofuran content is 99.94% by mass, with the unsaturated component content being 358 ppm. The Raney nickel catalyst is composed of nickel, aluminum, molybdenum, and a metal additive, and the nickel content is 60%, the molybdenum content is 1%, and the metal additive content is 1% (iron, with the remainder being aluminum) by mass. The Raney nickel catalyst is granular with a particle size of 5 mm and a specific surface area of ​​39.4 square meters per gram. The supported nickel catalyst is composed of nickel oxide, molybdenum oxide, titanium oxide, aluminum oxide, and alkaline earth metals. Based on the mass percentage of the supported nickel catalyst, the content of nickel oxide is 30.3%, the content of molybdenum oxide is 2.1%, the content of titanium oxide is 2.5%, and the content of the alkali metal is 0.9%, wherein the alkali metal is sodium oxide, and the remainder is aluminum oxide.

[0052] The Raney nickel catalyst is placed in a primary fixed-bed reactor to form a primary catalyst bed; the supported nickel catalyst is placed in a secondary fixed-bed reactor to form a secondary catalyst bed. The feed liquid and hydrogen are preheated and mixed in a preheating furnace to obtain a gas-liquid mixture. The gas-liquid mixture is then subjected to hydrogenation reactions sequentially in the primary and secondary catalyst beds to obtain a refined product. The hydrogenation reaction of the gas-liquid mixture in the primary catalyst bed is carried out at a temperature of 100°C, a pressure of 0.8 MPa, and a space velocity of 5 h⁻¹. -1 The hydrogenation reaction of the gas-liquid mixture in the secondary catalyst bed is carried out at a temperature of 40°C and a pressure of 0.8 MPa, with a space velocity of 5 h⁻¹. -1 The purified product, by mass percentage, contains 99.965% tetrahydrofuran, and the unsaturated components were not detected. The unsaturated components include acetaldehyde, propionaldehyde, and other unsaturated components. The acetaldehyde component was not detected, the propionaldehyde component was not detected, and the other unsaturated components were not detected.

[0053] Example 3

[0054] The system provides a feedstock, a Raney nickel catalyst, and a supported nickel catalyst. The feedstock is tetrahydrofuran obtained from upper-stage distillation, and the tetrahydrofuran content is 99.94% by mass, while the unsaturated component content is 386 ppm. The Raney nickel catalyst is composed of nickel, aluminum, molybdenum, and a metal additive, and the nickel content is 66.8% by mass, the molybdenum content is 1.1%, and the metal additive content is 1.7% (iron, with the remainder being aluminum). The Raney nickel catalyst is in granular form. The Raney nickel catalyst is granular, with a particle size of 7 mm and a specific surface area of ​​38.7 square meters per gram. The supported nickel catalyst is composed of nickel oxide, molybdenum oxide, titanium oxide, aluminum oxide, alkali metals, and alkaline earth metals. Based on the mass percentage of the supported nickel catalyst, the content of nickel oxide is 29.8%, the content of molybdenum oxide is 2%, the content of titanium oxide is 2.7%, the content of alkali metals is 1%, and the content of alkaline earth metals is 0.7%. The alkali metal is sodium oxide, the alkaline earth metal is calcium oxide, and the remainder is aluminum oxide.

[0055] The Raney nickel catalyst is placed in a primary fixed-bed reactor to form a primary catalyst bed; the supported nickel catalyst is placed in a secondary fixed-bed reactor to form a secondary catalyst bed. The feed liquid and hydrogen are preheated and mixed in a preheating furnace to obtain a gas-liquid mixture. The gas-liquid mixture is then subjected to hydrogenation reactions sequentially in the primary and secondary catalyst beds to obtain a refined product. The hydrogenation reaction of the gas-liquid mixture in the primary catalyst bed is carried out at a temperature of 50°C, a pressure of 0.5 MPa, and a space velocity of 6 h⁻¹. -1 The hydrogenation reaction of the gas-liquid mixture in the secondary catalyst bed is carried out at a temperature of 50°C and a pressure of 0.5 MPa, with a space velocity of 6 h⁻¹. -1 The content of tetrahydrofuran is 99.97% by mass percentage of the refined product. The unsaturated components were not detected. The unsaturated components include acetaldehyde, propionaldehyde and other unsaturated components. The acetaldehyde component was not detected. The propionaldehyde component was not detected. The other unsaturated components were not detected.

[0056] Example 4

[0057] The system provides a feedstock, a Raney nickel catalyst, and a supported nickel catalyst. The feedstock is tetrahydrofuran obtained from upper-stage distillation, and the tetrahydrofuran content is 99.94% by mass, while the unsaturated component content is 378 ppm. The Raney nickel catalyst is composed of nickel, aluminum, molybdenum, and a metal additive, and the nickel content is 75.4% by mass, the molybdenum content is 2%, and the metal additive content is 1.9%, wherein the metal additive is iron. The remainder is aluminum. The Raney nickel catalyst is granular with a particle size of 4 mm and a specific surface area of ​​41.6 square meters per gram. The supported nickel catalyst is composed of nickel oxide, molybdenum oxide, titanium oxide, aluminum oxide, and alkali metal. By mass percentage, the content of nickel oxide is 31.2%, the content of molybdenum oxide is 2.6%, the content of titanium oxide is 2.7%, and the content of alkali metal is 0.6%, wherein the alkali metal is sodium oxide.

[0058] The Raney nickel catalyst is placed in a primary fixed-bed reactor to form a primary catalyst bed; the supported nickel catalyst is placed in a secondary fixed-bed reactor to form a secondary catalyst bed. The feed liquid and hydrogen are preheated and mixed in a preheating furnace to obtain a gas-liquid mixture. The gas-liquid mixture is then subjected to hydrogenation reactions sequentially in the primary and secondary catalyst beds to obtain a refined product. The hydrogenation reaction of the gas-liquid mixture in the primary catalyst bed is carried out at a temperature of 80°C and a pressure of 1 MPa, with a space velocity of 2 h⁻¹. -1 The hydrogenation reaction of the gas-liquid mixture in the secondary catalyst bed is carried out at a temperature of 80°C and a pressure of 1 MPa, with a space velocity of 2 h⁻¹. -1 The refined product includes the tetrahydrofuran and unsaturated compounds. The tetrahydrofuran content is 99.96% by mass percentage of the refined product. The unsaturated compounds are not detected. The unsaturated compounds include acetaldehyde, propionaldehyde and other unsaturated compounds. The acetaldehyde component is not detected. The propionaldehyde component is not detected. The other unsaturated compounds are not detected.

[0059] Example 5

[0060] The system provides a feedstock, a Raney nickel catalyst, and a supported nickel catalyst. The feedstock is tetrahydrofuran obtained from upper-stage distillation, and the tetrahydrofuran content is 99.94% by mass, with the unsaturated component content being 392 ppm. The Raney nickel catalyst is composed of nickel, aluminum, molybdenum, and a metal additive, and the nickel content is 74.3% by mass, the molybdenum content is 0.5%, the metal additive content is 3%, and the metal additive is iron, with the remainder being... The Raney nickel catalyst is granular with a particle size of 5 mm and a specific surface area of ​​50.7 square meters per gram. The supported nickel catalyst is composed of nickel oxide, molybdenum oxide, titanium oxide, aluminum oxide, and alkaline earth metals. Based on the mass percentage of the supported nickel catalyst, the content of nickel oxide is 30.1%, the content of molybdenum oxide is 2.4%, the content of titanium oxide is 2.4%, the content of the alkali metal is 0.9%, the alkali metal is sodium oxide, and the remainder is aluminum oxide.

[0061] The Raney nickel catalyst is placed in a primary fixed-bed reactor to form a primary catalyst bed; the supported nickel catalyst is placed in a secondary fixed-bed reactor to form a secondary catalyst bed. The feed liquid and hydrogen are preheated and mixed in a preheating furnace to obtain a gas-liquid mixture. The gas-liquid mixture is then subjected to hydrogenation reactions sequentially in the primary and secondary catalyst beds to obtain a refined product. The hydrogenation reaction of the gas-liquid mixture in the primary catalyst bed is carried out at a temperature of 70°C and a pressure of 1 MPa, with a space velocity of 6 h⁻¹. -1 The hydrogenation reaction of the gas-liquid mixture in the secondary catalyst bed is carried out at a temperature of 45°C and a pressure of 1 MPa, and the space velocity of the gas-liquid mixture is 6 h⁻¹. -1 The refined product includes the tetrahydrofuran and unsaturated compounds. The tetrahydrofuran content is 99.96% by mass percentage of the refined product. The unsaturated compounds are not detected. The unsaturated compounds include acetaldehyde, propionaldehyde and other unsaturated compounds. The acetaldehyde component is not detected. The propionaldehyde component is not detected. The other unsaturated compounds are not detected.

[0062] Example 6

[0063] The system provides a feedstock, a Raney nickel catalyst, and a supported nickel catalyst. The feedstock is tetrahydrofuran obtained from upper-stage distillation, and the tetrahydrofuran content is 99.94% by mass, with the unsaturated component content at 345 ppm. The Raney nickel catalyst is composed of nickel, aluminum, molybdenum, and a metal additive, and the nickel content is 73.2%, the molybdenum content is 0.5%, and the metal additive content is 1.4% by mass, consisting of copper and iron, with the remainder being aluminum. The catalyst is granular, with a Raney nickel catalyst having a particle size of 6 mm and a specific surface area of ​​55.3 square meters per gram. The supported nickel catalyst is composed of nickel oxide, molybdenum oxide, titanium oxide, aluminum oxide, alkali metals, and alkaline earth metals. Based on the mass percentage of the supported nickel catalyst, the content of nickel oxide is 29.9%, the content of molybdenum oxide is 2%, the content of titanium oxide is 1.9%, and the content of alkali metals is 0.7%, specifically sodium oxide, with the remainder being aluminum oxide.

[0064] The Raney nickel catalyst is placed in a primary fixed-bed reactor to form a primary catalyst bed; the supported nickel catalyst is placed in a secondary fixed-bed reactor to form a secondary catalyst bed. The feed liquid and hydrogen are preheated and mixed in a preheating furnace to obtain a gas-liquid mixture. The gas-liquid mixture is then subjected to hydrogenation reactions sequentially in the primary and secondary catalyst beds to obtain a refined product. The hydrogenation reaction of the gas-liquid mixture in the primary catalyst bed is carried out at a temperature of 50°C, a pressure of 0.5 MPa, and a space velocity of 8 h⁻¹. -1 The hydrogenation reaction of the gas-liquid mixture in the secondary catalyst bed is carried out at a temperature of 40°C and a pressure of 0.5 MPa, with a space velocity of 8 h⁻¹. -1 The refined product includes the tetrahydrofuran and unsaturated compounds. The tetrahydrofuran content is 99.96% by mass percentage of the refined product, the unsaturated compounds content is 1 ppm, the unsaturated compounds include acetaldehyde, propionaldehyde and other unsaturated compounds, the acetaldehyde component was not detected, the propionaldehyde component was not detected, and the content of the other unsaturated compounds is 1 ppm.

[0065] Example 7

[0066] The system provides a feedstock, a Raney nickel catalyst, and a supported nickel catalyst. The feedstock is tetrahydrofuran obtained from upper-stage distillation, and the tetrahydrofuran content is 99.94% by mass, while the unsaturated component content is 358 ppm. The Raney nickel catalyst is composed of nickel, aluminum, molybdenum, and a metal additive, and the nickel content is 66.2% by mass, the molybdenum content is 0.8%, and the metal additive content is 1.1%, wherein the metal additive is iron. The Raney nickel catalyst is granular with a particle size of 8 mm and a specific surface area of ​​35.8 square meters per gram. The supported nickel catalyst is composed of nickel oxide, molybdenum oxide, titanium oxide, aluminum oxide, and an alkali metal. By mass percentage, the nickel oxide content is 30%, the molybdenum oxide content is 1.9%, the titanium oxide content is 2%, the alkali metal content is 1% (sodium oxide), and the remainder is aluminum oxide.

[0067] The Raney nickel catalyst is placed in a primary fixed-bed reactor to form a primary catalyst bed; the supported nickel catalyst is placed in a secondary fixed-bed reactor to form a secondary catalyst bed. The feed liquid and hydrogen are preheated and mixed in a preheating furnace to obtain a gas-liquid mixture. The gas-liquid mixture is then subjected to hydrogenation reactions sequentially in the primary and secondary catalyst beds to obtain a refined product. The hydrogenation reaction of the gas-liquid mixture in the primary catalyst bed is carried out at a temperature of 80°C and a pressure of 1 MPa, with a space velocity of 6 h⁻¹. -1 The hydrogenation reaction of the gas-liquid mixture in the secondary catalyst bed is carried out at a temperature of 60°C and a pressure of 1 MPa, with a space velocity of 6 h⁻¹. -1 The refined product includes the tetrahydrofuran and unsaturated compounds. The tetrahydrofuran content is 99.96% by mass percentage of the refined product, the unsaturated compounds content is 1 ppm, the unsaturated compounds include acetaldehyde, propionaldehyde and other unsaturated compounds, the acetaldehyde component was not detected, the propionaldehyde component was not detected, and the content of the other unsaturated compounds is 1 ppm.

[0068] Comparative Example 1

[0069] The facility provides a feed liquid and a nickel-based catalyst. The feed liquid is tetrahydrofuran obtained from the upper stage distillation process. The tetrahydrofuran content is 99.94% by mass, and the content of the unsaturated component is 378 ppm. The nickel-based catalyst is composed of nickel, aluminum, and molybdenum. The nickel content is 75.4% by mass, the molybdenum content is 2%, and the remainder is aluminum. The nickel-based catalyst is granular with a particle size of 6 mm and a specific surface area of ​​56.5 square meters per gram.

[0070] The nickel-based catalyst is placed in a fixed-bed reactor to form a catalyst bed. The feed liquid and hydrogen are preheated and mixed in a preheating furnace of the fixed-bed reactor to obtain a gas-liquid mixture. The gas-liquid mixture is then subjected to a hydrogenation reaction in the catalyst bed to obtain a refined product. The hydrogenation reaction is carried out at a temperature of 100°C and a pressure of 1 MPa, and the space velocity of the gas-liquid mixture is 6 h⁻¹. -1 The refined product includes the tetrahydrofuran and unsaturated compounds. The tetrahydrofuran content is 99.96% by mass percentage of the refined product, the unsaturated compounds content is 34 ppm, the unsaturated compounds include acetaldehyde, propionaldehyde and other unsaturated compounds, the acetaldehyde content is 15 ppm, the propionaldehyde content is 10 ppm, and the other unsaturated compounds content is 9 ppm.

[0071] Comparative Example 2

[0072] The facility provides a feed liquid and a nickel-based catalyst. The feed liquid is tetrahydrofuran obtained from the upper stage distillation process. The tetrahydrofuran content is 99.94% by mass, and the content of the unsaturated component is 359 ppm. The nickel-based catalyst is composed of nickel, aluminum, molybdenum, and a metal additive. The nickel content is 74.2% by mass, the molybdenum content is 2%, and the metal additive content is 2%. The metal additive is copper, and the remainder is aluminum. The nickel-based catalyst is granular with a particle size of 6 mm and a specific surface area of ​​45.4 square meters per gram.

[0073] The nickel-based catalyst is placed in a fixed-bed reactor to form a catalyst bed. The feed liquid and hydrogen are preheated and mixed in a preheating furnace of the fixed-bed reactor to obtain a gas-liquid mixture. The gas-liquid mixture is then subjected to a hydrogenation reaction in the catalyst bed to obtain a refined product. The hydrogenation reaction is carried out at a temperature of 100°C and a pressure of 1 MPa, and the space velocity of the gas-liquid mixture is 6 h⁻¹. -1The refined product includes the tetrahydrofuran and unsaturated compounds. The tetrahydrofuran content is 99.96% by mass percentage of the refined product, the unsaturated compounds content is 12 ppm, the unsaturated compounds include acetaldehyde, propionaldehyde and other unsaturated compounds, the acetaldehyde content is 4 ppm, the propionaldehyde content is 2 ppm, and the other unsaturated compounds content is 6 ppm.

[0074] Comparative Example 3

[0075] The facility provides a feed liquid and a nickel-based catalyst. The feed liquid is tetrahydrofuran obtained from upper-stage distillation. The tetrahydrofuran content is 99.94% by mass, and the content of the unsaturated component is 370 ppm. The nickel-based catalyst is composed of nickel, aluminum, molybdenum, and a metal additive. The nickel content is 68.3% by mass, the molybdenum content is 1.9%, and the metal additive content is 1.5%. The metal additive is copper, and the remainder is aluminum. The nickel-based catalyst is granular with a particle size of 6 mm and a specific surface area of ​​29.1 square meters per gram.

[0076] The nickel-based catalyst is placed in a fixed-bed reactor to form a catalyst bed. The feed liquid and hydrogen are preheated and mixed in a preheating furnace of the fixed-bed reactor to obtain a gas-liquid mixture. The gas-liquid mixture is then subjected to a hydrogenation reaction in the catalyst bed to obtain a refined product. The hydrogenation reaction is carried out at a temperature of 100°C, a pressure of 0.5 MPa, and a space velocity of 3 h⁻¹. -1 The refined product includes the tetrahydrofuran and unsaturated compounds. The tetrahydrofuran content is 99.95% by mass percentage of the refined product, the unsaturated compounds content is 11 ppm, the unsaturated compounds include acetaldehyde, propionaldehyde and other unsaturated compounds, the acetaldehyde content is 4 ppm, the propionaldehyde content is 3 ppm, and the other unsaturated compounds content is 4 ppm.

[0077] Comparative Example 4

[0078] The facility provides a feedstock and a nickel-based catalyst. The feedstock is tetrahydrofuran obtained from upper-stage distillation, and the tetrahydrofuran content is 99.94% by mass, while the unsaturated component content is 386 ppm. The supported nickel catalyst is composed of nickel oxide, molybdenum oxide, titanium oxide, aluminum oxide, and an alkali metal. The nickel oxide content is 30.2% by mass, the molybdenum oxide content is 1.8%, the titanium oxide content is 2%, the alkali metal content is 1%, the alkali metal is sodium oxide, and the remainder is aluminum oxide.

[0079] The nickel-based catalyst is placed in a fixed-bed reactor to form a catalyst bed. The feed liquid and hydrogen are preheated and mixed in a preheating furnace of the fixed-bed reactor to obtain a gas-liquid mixture. The gas-liquid mixture is then subjected to a hydrogenation reaction in the catalyst bed to obtain a refined product. The hydrogenation reaction is carried out at a temperature of 100°C and a pressure of 1 MPa, and the space velocity of the gas-liquid mixture is 6 h⁻¹. -1 The refined product includes the tetrahydrofuran and unsaturated compounds. The tetrahydrofuran content is 99.95% and the unsaturated compound content is 17 ppm, based on the mass percentage of the refined product. The unsaturated compounds include acetaldehyde, propionaldehyde, and other unsaturated compounds. The acetaldehyde content is 4 ppm, the propionaldehyde content is 7 ppm, and the other unsaturated compounds content is 6 ppm.

[0080] Table 2. Parameters and unsaturated product content of the hydrogenation reaction.

[0081]

[0082] Note: In the table, T1 represents the temperature of the hydrogenation reaction in the primary catalyst bed, P1 represents the pressure of the hydrogenation reaction in the primary catalyst bed, and S1 represents the space velocity of the gas-liquid mixture in the primary catalyst bed; T2 represents the temperature of the hydrogenation reaction in the secondary catalyst bed, P2 represents the pressure of the hydrogenation reaction in the secondary catalyst bed, and S2 represents the space velocity of the gas-liquid mixture in the secondary catalyst bed.

[0083] As can be seen from Table 1, the catalyst with added metal additives is superior to the catalyst without added metal additives under the same process conditions. This shows that the addition of metal additives helps the components to play a good synergistic role and achieve better catalytic effect.

[0084] As shown in Table 1, by comprehensively controlling temperature, pressure, and air velocity, and ensuring that the temperature does not exceed 150℃, the pressure does not exceed 5 MPa, and the air velocity does not exceed 8 h⁻¹, the system can achieve optimal performance. -1 This invention can hydrogenate and refine PBAT by-products, industrial-grade tetrahydrofuran, with a total unsaturated content of less than 2 ppm. The temperature, pressure, and space velocity used in the hydrogenation and refining process of PBAT by-products, industrial-grade tetrahydrofuran, are all relatively low, thus the invention has the advantage of low energy consumption.

[0085] As can be seen from Table 1, the hydrogenation depth of commercially available Raney nickel or supported nickel cannot meet the requirements, but the catalyst and process technology described in this patent can meet them.

[0086] The long-cycle life test was conducted using the techniques described in Example 3 above, lasting for 3000 hours. After 3000 hours, the unsaturated components were still not detected, indicating a promising prospect for industrial application.

[0087] Comparative Example 3 was compared with the technical means in Example 3 of the patent "A System and Method for Preparing Polymer-Grade Tetrahydrofuran (Application No.: 202311034585.4)". It can be seen that the hydrogenation depth is insufficient when the content of unsaturated substances in the raw materials is high.

[0088] While embodiments of the present invention have been described in detail above, it will be apparent to those skilled in the art that various modifications and variations can be made to these embodiments. However, it should be understood that such modifications and variations fall within the scope and spirit of the invention as set forth in the claims. Furthermore, the invention described herein may have other embodiments and can be implemented or carried out in various ways.

Claims

1. A method for hydrogenating and purifying tetrahydrofuran, characterized in that, Specifically, the following steps are included: S0: Provides a feed liquid and a nickel-based catalyst, wherein the feed liquid comprises distilled tetrahydrofuran and unsaturated components, wherein the tetrahydrofuran content is above 99.94% and the unsaturated component content is 50-400 ppm, based on the mass percentage of the feed liquid. S1: The nickel-based catalyst includes a Raney nickel catalyst and a supported nickel catalyst. The Raney nickel catalyst is placed in a primary fixed-bed reactor to form a primary catalyst bed; the supported nickel catalyst is placed in a secondary fixed-bed reactor to form a secondary catalyst bed. The Raney nickel catalyst comprises nickel, aluminum, molybdenum, and a metal additive. Based on the mass percentage of the Raney nickel catalyst, the nickel content is 60-75%, the molybdenum content is 0.51-2%, the metal additive is at least one of iron and copper, and its content is 1-3%, with the remainder being aluminum. The supported nickel catalyst includes an active component, a support, and an additive. The active component includes nickel oxide and molybdenum oxide, the support includes titanium oxide and aluminum oxide, and the additive includes one or two of alkali metals and alkaline earth metals. S2: The raw material liquid and hydrogen are preheated and mixed in a preheating furnace to obtain a gas-liquid mixture; S3: The gas-liquid mixture is subjected to hydrogenation reaction in the primary catalyst bed and the secondary catalyst bed in sequence to obtain a purified product.

2. The method for hydrogenating tetrahydrofuran according to claim 1, characterized in that, The tetrahydrofuran is a byproduct generated during the synthesis of polybutylene terephthalate-butylene adipate.

3. The method for hydrogenating tetrahydrofuran according to claim 1, characterized in that, In step S3, the hydrogenation reaction of the gas-liquid mixture in the primary catalyst bed is carried out at a temperature of 50-100°C and a pressure of 0.2-1.5 MPa, with a space velocity of 0.5-8 h⁻¹. -1 .

4. The method for hydrogenating tetrahydrofuran according to claim 1, characterized in that, In step S3, the hydrogenation reaction of the gas-liquid mixture in the secondary catalyst bed is carried out at a temperature of 40-80°C and a pressure of 0.2-1.5 MPa, with a space velocity of 0.5-8 h⁻¹. -1 .

5. The method for hydrogenating tetrahydrofuran according to claim 1, characterized in that, The refined product includes the tetrahydrofuran and unsaturated compounds. The tetrahydrofuran content is 99.95% or more and the unsaturated compounds content is less than 2 ppm, based on the mass percentage of the refined product.

6. The method for hydrogenating tetrahydrofuran according to claim 1, characterized in that, The Raney nickel catalyst is in granular form, with a particle size of 2-8 mm and a specific surface area of ​​10-60 square meters per gram.

7. The method for hydrogenating tetrahydrofuran according to claim 1, characterized in that, The alkali metals include sodium oxide and potassium oxide, and the alkaline earth metals are calcium oxide.

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