Reaction device for preparing isosorbide through two-step dehydration continuous reaction of sorbide

Abstract

The invention belongs to the field of chemistry and chemical engineering, and particularly relates to a reaction device for preparing isosorbide through two-step dehydration continuous reaction of sorbide. The device comprises a first-stage dehydration reactor and a second-stage dehydration reactor which are communicated, the upper part of the first-stage dehydration reactor is connected with an inlet pipeline, an outlet of the inlet pipeline extends into the bottom of the reactor, and a discharge port of the first-stage dehydration reactor is connected with a feed port of the second-stage dehydration reactor through a downward inclined connecting pipeline; the outlet of the inlet pipeline of the secondary dehydration reactor extends into the bottom of the reactor; partition plates are arranged in the first-stage dehydration reactor and the second-stage dehydration reactor; each of the first-stage dehydration reactor and the second-stage dehydration reactor is provided with a stirring component; each stirring component comprises motors respectively arranged at the upper ends of the first-stage dehydration reactor and the second-stage dehydration reactor, and stirring paddles which are connected with the lower ends of the motors and extend into the inner cavities of the reactors. According to the invention, two-step dehydration for preparing isosorbide from sorbitol can be continuously carried out, the reaction efficiency and the time space yield are improved, and the reaction cost is saved.

Description

Technical Field

[0001] The invention belongs to the field of chemistry and chemical engineering, and particularly relates to a reaction device for preparing isosorbide by continuous two-step dehydration reaction of sorbitol. Background Art

[0002] Isosorbide is the only carbohydrate diol that can be mass-produced industrially. As a new bio-based material, it is widely used in food, cosmetics, medicine, plastics and polymers. In addition, it can also be used as an intermediate in the synthesis of liquid crystal materials and is widely used in electronics, national defense and other fields.

[0003] Isosorbide can be prepared from sorbitol as a raw material, and sorbitol is dehydrated in two steps under acid catalysis to produce isosorbide. Cellulose can also be directly dehydrated by hydrogenation under the action of a bifunctional catalyst or a composite multifunctional catalyst to synthesize isosorbide in a one-step method. At present, the one-step conversion method is not as efficient as the two-step dehydration reaction of sorbitol, and the yield of isosorbide is low. In addition, the one-step conversion method also has problems such as difficulty in product purification, and it is difficult to achieve industrialization in the short term. In industry, concentrated sulfuric acid is mainly used as a catalyst, and an intermittent reactor is used to prepare isosorbide by two-step dehydration of sorbitol. Liquid acid catalysts have high catalytic activity and good selectivity, but liquid acid catalysts have the disadvantages of easy corrosion of equipment, non-reusable catalysts, and difficulty in continuous production. Therefore, improving the catalyst system and establishing a continuous production process for isosorbide are urgent problems to be solved. In order to solve this technical problem, solid acid catalysts and corresponding solid acid-catalyzed sorbitol dehydration reaction processes for preparing isosorbide have been developed, but there is no continuous production reactor suitable for solid acid catalytic reactions. Summary of the invention

[0004] In view of the problems and shortcomings in the prior art, the object of the present invention is to provide a reaction device for preparing isosorbide by a two-step dehydration continuous reaction of sorbitol.

[0005] Based on the above purpose, the present invention adopts the following technical solution: The invention provides a reaction device for preparing isosorbide by continuous two-step dehydration reaction of sorbitol, comprising a primary dehydration reactor and a secondary dehydration reactor which are connected to each other, wherein the upper part of the primary dehydration reactor is connected with an inlet pipeline, the outlet of the inlet pipeline extends into the bottom of the reactor, the discharge port of the primary dehydration reactor is connected with the feed port of the secondary dehydration reactor through a downwardly inclined connecting pipeline, the outlet of the inlet pipeline of the secondary dehydration reactor extends into the bottom of the reactor, and the discharge port of the primary dehydration reactor is higher than the feed port of the secondary dehydration reactor; partitions are arranged inside the primary dehydration reactor and the secondary dehydration reactor; the primary dehydration reactor and the secondary dehydration reactor are provided with stirring members, the stirring members comprise motors respectively arranged at the upper ends of the primary dehydration reactor and the secondary dehydration reactor, the lower end of the motor is connected with a stirring paddle extending into the inner cavity of the reactor, and the stirring shaft passes through a hole in the center of the partition; an auxiliary feeding pipe opening is opened at the top of the dehydration reactor.

[0006] Furthermore, the inlet pipe of the primary dehydration reactor and the outlet pipe of the secondary dehydration reactor enter the dehydration reactor horizontally and vertically.

[0007] Furthermore, the connecting pipe connecting the discharge port of the primary dehydration reactor and the feed port of the secondary dehydration reactor is inclined downward by 10 to 15 degrees.

[0008] Furthermore, the number of baffles of the primary dehydration reactor is 3 to 5, and the number of baffles of the secondary dehydration reactor is 4 to 7; square holes are evenly arranged on the baffles; and the stirring paddle is placed between two layers of baffles.

[0009] Furthermore, the design form of the stirring paddle is a blade-shaped paddle.

[0010] Furthermore, the ratio of the diameter of the opening of the stirring paddle of the primary dehydration reactor to the diameter of the reactor is 0.15-0.35, and the ratio of the diameter of the opening of the stirring paddle of the secondary dehydration reactor to the diameter of the reactor is 0.1-0.3.

[0011] Furthermore, the height-to-diameter ratio of the primary dehydration reactor is 1.5-3, and the height-to-diameter ratio of the secondary dehydration reactor is 2-4.

[0012] Furthermore, the opening rate of the partition of the primary dehydration reactor is 28% to 33%, and the opening rate of the partition of the secondary dehydration reactor is 18% to 23%.

[0013] Furthermore, the square hole of the partition is close to one side of the inner side wall of the primary dehydration reactor and the secondary dehydration reactor.

[0014] Furthermore, the top of the dehydration reactor is also provided with an inlet and outlet valve and a vacuum valve.

[0015] The use process of the above reaction device is as follows: sorbitol enters a primary dehydration reactor through an inlet pipe, and under the action of a stirring paddle driven by a motor, sorbitol enters a secondary dehydration reactor through a reactor connecting pipe after completing primary dehydration, and under the action of a stirring paddle driven by a motor, isosorbide generated after secondary dehydration is discharged from the reaction device through an outlet pipe.

[0016] Wherein, the temperature of the primary dehydration reactor is 120~150 o C, the pressure is -0.01 to -0.05 MPa, and the residence time is 3 to 4 hours; the temperature of the secondary dehydration reactor is 150 to 190 o C, pressure is -0.05~-0.1MPa, and residence time is 2~3h.

[0017] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention can make the two-step dehydration of sorbitol to isosorbide proceed continuously, fully react under the action of the stirring paddle, realize continuous feeding and discharging of materials, improve reaction efficiency and time-space yield, and save reaction cost.

[0018] (2) Compared with the batch reactor and the kettle continuous reactor, the present invention has the best comprehensive conversion rate, which can reach 100%. In terms of isosorbide yield, the present invention has the highest yield, which is 85%.

[0019] (3) The present invention can be used for continuous production, combining the advantages of batch reactors and kettle continuous reactors. It outperforms the other two reactors in terms of comprehensive conversion rate and yield, and improves reaction efficiency and product yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The schematic diagram of the structure of the reaction device for preparing isosorbide by two-step dehydration continuous reaction of sorbitol of the present invention; Figure 2 The schematic diagram of the top view of the reaction device for preparing isosorbide by two-step dehydration continuous reaction of sorbitol according to the present invention.

[0021] In the figure: 1-primary dehydration reactor; 2-partition; 3-stirring paddle; 4-inlet pipe; 5-outlet pipe; 6-motor; 7-square hole; 8-feed pipe perforation; 9-secondary dehydration reactor. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below through embodiments in combination with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0023] Example 1 A two-step dehydration continuous reaction of sorbitol to prepare isosorbide reaction device, the schematic diagram of which is as follows Figure 1 and Figure 2 As shown, it includes a connected primary dehydration reactor 1 (height-to-diameter ratio 1.5-3) and a secondary dehydration reactor 9 (height-to-diameter ratio 2-4), the upper part of the primary dehydration reactor 1 is connected with an inlet pipe 4, the outlet of the inlet pipe 4 extends into the bottom of the reactor, the discharge port of the primary dehydration reactor 1 is connected with the feed port of the secondary dehydration reactor 9 through a connecting pipe inclined downward by 10-15 degrees, the outlet of the inlet pipe of the secondary dehydration reactor 9 extends into the bottom of the reactor, and the discharge port of the primary dehydration reactor 1 is higher than the feed port of the secondary dehydration reactor 9; the inlet pipe 4 of the primary dehydration reactor 1 and the outlet pipe 5 of the secondary dehydration reactor 9 enter the dehydration reactor horizontally and vertically.

[0024] The first-stage dehydration reactor 1 and the second-stage dehydration reactor 9 are both provided with a partition 2, which is also called a baffle plate to reduce back mixing and penetration; the first-stage dehydration reactor 1 and the second-stage dehydration reactor 9 are both provided with a stirring member, which includes a motor 6 respectively arranged at the upper end of the first-stage dehydration reactor 1 and the second-stage dehydration reactor 9, and the lower end of the motor 6 is connected to a stirring paddle 3 extending into the inner cavity of the reactor, the stirring shaft passes through the hole in the center of the partition 2 and the stirring paddle 3 is placed between the two layers of partitions 2; the top of the dehydration reactor is provided with an auxiliary feed pipe opening and a feed pipe through hole 8, and the top of the dehydration reactor is also provided with an inlet and outlet valve and a vacuum valve.

[0025] The primary dehydration reactor 1 is provided with 3 to 5 partitions 2, and the secondary dehydration reactor 9 is provided with 4 to 7 partitions 2. The partitions 2 are evenly arranged with square holes 7, and the square holes 7 of the partitions 2 are close to the inner side walls of the primary dehydration reactor 1 and the secondary dehydration reactor 9. The opening rate (area ratio) of the partition 2 of the primary dehydration reactor 1 is 28% to 33%, and the opening rate (area ratio) of the partition 2 of the secondary dehydration reactor 9 is 18% to 23%. The ratio of the opening diameter of the stirring paddle 3 of the primary dehydration reactor 1 to the reactor diameter is 0.15 to 0.35, and the ratio of the opening diameter of the stirring paddle 3 of the secondary dehydration reactor 9 to the reactor diameter is 0.1 to 0.3.

[0026] The method for preparing isosorbide by two-step dehydration continuous reaction of sorbitol using the above reaction device comprises the following steps: The sorbitol solution and the catalyst enter the primary dehydration reactor 1 through the inlet pipe 4, and the primary dehydration reaction is carried out under the stirring action of the stirring paddle 3 driven by the motor 6. The temperature of the primary dehydration reactor 1 is controlled to be 135 oC, the pressure is -0.03MPa, the residence time is 3.5 h, and after the primary dehydration reaction, sorbitol enters the secondary dehydration reactor 9 through the reactor connecting pipeline, and the secondary dehydration reaction is carried out under the stirring action of the stirring paddle 3 driven by the motor 6. The temperature of the secondary dehydration reactor 9 is controlled to be 170 o C, the pressure is -0.07 MPa, the residence time is 2.5 h, and the isosorbide generated after the secondary dehydration reaction is completed is discharged from the reaction device through the outlet pipe 5. The sorbitol conversion rate and isosorbide yield are calculated, and the results are shown in Table 1.

[0027] Comparative Example 1 In the method for preparing isosorbide using a batch reactor, sorbitol and a catalyst are loaded into the reactor. The first step of dehydration is carried out in the reactor: at 150°C, sorbitol is dehydrated through a primary reaction to obtain a primary product, and the primary product includes 1,4-anhydrosorbitol and isosorbide, and then the second step of dehydration is carried out: the temperature is kept constant at 150°C, 1,4-anhydrosorbitol is dehydrated through a secondary reaction to generate isosorbide, and a gaseous mixture of isosorbide and water is simultaneously evaporated. Isosorbide is separated from the gaseous mixture. The gaseous mixture is introduced into a condensation system, and the condensed liquid product is collected in a container, and then the product is purified to improve the purity of isosorbide. The sorbitol conversion rate and the isosorbide yield are calculated, and the results are shown in Table 1.

[0028] Comparative Example 2 The method for preparing isosorbide using a kettle continuous reactor (without internal components) is as follows: a sorbitol solution and a catalyst are mixed, heated to 80°C in a stirred kettle to melt the material, and the reactor is preheated to 150°C. The material enters the reactor and reacts at 160°C and 10kPa. The reacted material enters the separation unit from the reactor, and crude isosorbide is separated at 150°C and 30kPa. The crude isosorbide is condensed by a condenser and enters a crystallization separator. After filtering and drying, high-purity isosorbide is obtained. The whole process can realize continuous and rapid separation of the catalyst and the product, and improve the yield and purity of isosorbide. The sorbitol conversion rate and isosorbide yield are calculated, and the results are shown in Table 1.

[0029] Table 1 Sorbitol conversion and isosorbide yield of different solid acid catalytic reactor types Note: Comprehensive conversion rate and yield: the conversion rate and yield under continuous operation conditions after the unreacted raw materials are applied As can be seen from Table 1, from the perspective of single-pass conversion rate, the batch reactor has the highest conversion rate, reaching 99%. The single-pass conversion rate of the reactor of the present invention is between 67% and 69%, while the single-pass conversion rate of the kettle continuous reactor is between 54% and 56%. In terms of comprehensive conversion rate, the reactor of the present invention performs best, reaching 100%, followed by the batch reactor and the kettle continuous reactor, which are 99% and 99%, respectively. In terms of isosorbide yield, the reactor of the present invention has the highest yield of 85%, followed by 80% of the batch reactor, while the comprehensive yield of the kettle continuous reactor is 73%.

[0030] The batch reactor performs best in terms of single-pass conversion rate, but the reactor of the present invention performs better in terms of comprehensive conversion rate and yield, showing higher efficiency and yield. Although the single-pass conversion rate of the kettle continuous reactor is low, its comprehensive conversion rate and yield can also reach a high level according to the conversion rate and yield under continuous operation conditions, indicating that it has certain advantages in continuous production. The present invention can be produced continuously, combining the advantages of the batch reactor and the kettle continuous reactor. The reactor of the present invention performs better in terms of comprehensive conversion rate and yield than the other two reactors, improving the reaction efficiency and product yield.

Claims

1. A two-step dehydration continuous reaction device for preparing isosorbide by sorbitol, characterized in that: The invention comprises a primary dehydration reactor and a secondary dehydration reactor which are connected to each other. The upper part of the primary dehydration reactor is connected with an inlet pipe, the outlet of the inlet pipe extends into the bottom of the reactor, the discharge port of the primary dehydration reactor is connected with the feed port of the secondary dehydration reactor through a downwardly inclined connecting pipe, the outlet of the inlet pipe of the secondary dehydration reactor extends into the bottom of the reactor, and the discharge port of the primary dehydration reactor is higher than the feed port of the secondary dehydration reactor; partitions are arranged inside the primary dehydration reactor and the secondary dehydration reactor; the primary dehydration reactor and the secondary dehydration reactor are provided with stirring members, the stirring members comprise motors respectively arranged at the upper ends of the primary dehydration reactor and the secondary dehydration reactor, the lower end of the motor is connected with a stirring paddle extending into the inner cavity of the reactor, and the stirring shaft passes through the hole in the center of the partition; an auxiliary feeding pipe opening is opened at the top of the dehydration reactor.

2. The reaction device for preparing isosorbide by two-step dehydration continuous reaction of sorbitol according to claim 1, characterized in that: The connecting pipeline connecting the discharge port of the primary dehydration reactor and the feed port of the secondary dehydration reactor is inclined downward by 10 to 15 degrees.

3. The reaction device for preparing isosorbide by two-step dehydration continuous reaction of sorbitol according to claim 1, characterized in that: The number of baffles of the primary dehydration reactor is 3 to 5, and the number of baffles of the secondary dehydration reactor is 4 to 7; square holes are evenly arranged on the baffles; and the stirring paddle is placed between two layers of baffles.

4. The reaction device for preparing isosorbide by two-step dehydration continuous reaction of sorbitol according to claim 1, characterized in that: The ratio of the diameter of the stirring paddle opening of the primary dehydration reactor to the diameter of the reactor is 0.15-0.35, and the ratio of the diameter of the stirring paddle opening of the secondary dehydration reactor to the diameter of the reactor is 0.1-0.

3.

5. The reaction device for preparing isosorbide by two-step dehydration continuous reaction of sorbitol according to claim 1, characterized in that: The height-to-diameter ratio of the primary dehydration reactor is 1.5-3, and the height-to-diameter ratio of the secondary dehydration reactor is 2-4.

6. The reaction device for preparing isosorbide by two-step dehydration continuous reaction of sorbitol according to claim 3, characterized in that: The opening rate of the partition of the primary dehydration reactor is 28% to 33%, and the opening rate of the partition of the secondary dehydration reactor is 18% to 23%.

7. The reaction device for preparing isosorbide by two-step dehydration continuous reaction of sorbitol according to claim 6, characterized in that: The square hole of the partition is close to one side of the inner side wall of the primary dehydration reactor and the secondary dehydration reactor.

8. The reaction device for preparing isosorbide by two-step dehydration continuous reaction of sorbitol according to claim 1, characterized in that: The top of the dehydration reactor is also provided with an inlet and outlet valve and a vacuum valve.

Images