Method for preparing ferrocene by using plasma stirring technology

Abstract

The invention discloses a method for preparing ferrocene by using a plasma stirring technology, and belongs to the technical field of chemical materials. By applying high voltage or other energy sources, gas in the device is ionized to form plasma. Ions in the plasma move in an accelerated mode under the action of an electric field and collide with surrounding gas molecules, directional ion flow is generated, and ion wind is formed. The ionic wind can push surrounding gas or liquid to flow, and the stirring effect is achieved. In the plasma generation process, heat is generated, so that the local temperature rises. The temperature difference causes the density change of the fluid, so that natural convection is generated, and mixing and stirring of substances are promoted. For conductive fluid, an electromagnetic field generated by the plasma can generate electromagnetic force on charged particles in the fluid. And the electromagnetic force enables the fluid to move to realize efficient stirring. According to the method, the product purity can be improved, the purity of the obtained ferrocene is greater than or equal to 98%, the free iron content is less than or equal to 100 ppm, the granularity is 20-120 meshes, and the yield can reach 85% or above.

Description

Technical Field

[0001] The present invention belongs to the technical field of chemical materials, and particularly relates to a method for preparing ferrocene by using plasma stirring technology. Background Art

[0002] Ferrocene is an organic transition metal compound with aromatic properties. As an important organic chemical raw material and intermediate, it has wide applications in industries such as industry, agriculture, medicine, aerospace, energy conservation, and environmental protection. The purity of its products and the differences in crystal forms directly have a greater impact on the applications of the products and the quality of subsequent synthetic products. Generally, the crude ferrocene solid products separated from the synthesis reaction still contain unreacted raw materials, by-products, and impurities, etc., and must be separated and purified.

[0003] Currently, the methods for preparing ferrocene in industry mainly include the following two:

[0004] High-temperature synthesis method of iron powder and cyclopentadiene: This method needs to be carried out in a nitrogen environment above 300 °C, and ferrocene is directly formed by the reaction of iron powder and cyclopentadiene. However, the high-temperature conditions lead to high energy consumption, long reaction time (usually 6 - 8 hours), and it is easy to leave unreacted iron powder and by-products in the product, with low purity (usually ≤ 95%), and the subsequent purification process is complex.

[0005] Reaction method of ferrous chloride and sodium cyclopentadienide: Using tetrahydrofuran as a solvent, ferrous chloride anhydrous reacts with sodium cyclopentadienide at low temperature to form ferrocene. Although the reaction conditions of this method are relatively mild, tetrahydrofuran is toxic and has a low boiling point, making it difficult to recover the solvent. At the same time, the reaction yield is low, and the content of free iron in the product is relatively high, which limits its application in high-end fields.

[0006] The traditional methods generally also have the following technical bottlenecks:

[0007] Low reaction efficiency: High-temperature or low-temperature conditions lead to high energy consumption and long reaction time, restricting the production efficiency.

[0008] Insufficient product purity: Unreacted raw materials, by-products, and impurities remain seriously, and multiple steps of purification such as sublimation and recrystallization are required, increasing the cost.

[0009] Environmental protection problems: Using toxic solvents or generating a large amount of hazardous waste, which does not meet the requirements of green chemistry.

[0010] Therefore, it is of great significance to develop a high-efficiency, low-energy-consuming and environmentally friendly ferrocene preparation technology. Summary of the Invention

[0011] In view of the above situation, the present invention provides a method for preparing ferrocene by using plasma stirring technology, which can effectively solve the disadvantages of low purity, high energy consumption and low yield of ferrocene obtained in the production process.

[0012] Traditional methods for preparing ferrocene include heating iron powder and cyclopentadiene in a nitrogen atmosphere at 300 °C, or reacting anhydrous ferrous chloride with sodium cyclopentadienide in tetrahydrofuran, etc. The present invention applies plasma stirring technology to the preparation of ferrocene, considering introducing plasma stirring on the basis of these traditional methods to improve the reaction conditions and increase the reaction efficiency.

[0013] To achieve the above object, the following technical solution is adopted: The present invention provides a method for preparing ferrocene by using plasma stirring technology, including the following steps:

[0014] (1) Depolymerization reaction: Dicyclopentadiene is depolymerized by high temperature to generate cyclopentadiene, and the residual liquid at the bottom of the reaction kettle is temporarily stored as hazardous waste in the hazardous waste warehouse. The whole reaction process uses plasma stirring;

[0015] (2) Negative ion synthesis: Cyclopentadiene reacts with sodium methoxide in methanol solution to generate sodium cyclopentadienide and is dissolved in methanol solution. The whole reaction process uses plasma stirring;

[0016] (3) Preparation of ferrous chloride: First, dissolve ferric chloride in methanol, add an excessive amount of iron powder, react under nitrogen protection, and then filter out the remaining iron powder to obtain a ferrous chloride solution for use. The whole reaction process uses plasma stirring;

[0017] (4) Ferrocene synthesis: Add the methanol solution of sodium cyclopentadienide to ferrous chloride, and react sodium cyclopentadienide with ferrous ions in methanol solution to generate ferrocene. The whole reaction process uses plasma stirring;

[0018] (5) Methanol recovery and purification: Heat the reaction solution obtained in step (4), distill out the solvent methanol using a distillation column, then add water to the reaction kettle, heat the material with direct steam, and use the sublimation characteristic of ferrocene (sublimation at 100 °C), under vacuum conditions, combine with a plasma heating device for gradient heating, collect the high-purity product, spray cooling water on the ferrocene gas distilled out by the distillation column to cool and crystallize ferrocene, and the ferrocene containing water is centrifuged, vacuum dried to obtain the ferrocene finished product;

[0019] (6) Methanol refining and waste liquid treatment: The crude methanol containing C5 hydrocarbons distilled out for the first time is recycled through the distillation column again, the refined methanol obtained is used as a solvent for recycling, the excess methanol is sold as a by-product, and the residual liquid at the bottom of the reaction kettle is temporarily stored as hazardous waste in the hazardous waste warehouse.

[0020] Furthermore, the plasma stirring adopts an integrated plasma generator and a stirring system.

[0021] Furthermore, for the plasma generator, an RF or microwave plasma source is selected, with a power range of 500 - 1500 W and a frequency of 13.56 MHz.

[0022] Furthermore, the stirring system is a magnetic stirring or mechanical stirring system with adjustable rotation speed and synchronized control with the plasma source.

[0023] Furthermore, the reaction kettle used in steps (1)-(5) is made of high-temperature resistant glass or quartz, and is equipped with a constant pressure dropping funnel and a condensation reflux device.

[0024] The mechanism of the stirring effect is as follows:

[0025] 1. Ion wind effect: Ions in the plasma are accelerated under the action of an electric field, collide with surrounding gas molecules, generate a directional ion flow, and form an ion wind. The ion wind can push the surrounding gas or liquid to flow, accelerate chemical reactions, improve production efficiency, and achieve a better and more reliable stirring effect;

[0026] 2. Thermal effect: Heat is generated during the generation of the plasma, resulting in a local temperature increase. The temperature difference causes density changes in the fluid, thereby generating natural convection, promoting the mixing and stirring of substances. At the same time, the thermal effect can promote the rapid completion of chemical reactions and achieve energy conservation;

[0027] 3. Electromagnetic force effect: For conductive fluids, the electromagnetic field generated by the plasma will exert an electromagnetic force on the charged particles in the fluid. The electromagnetic force causes the fluid to move, accelerates the rapid combination of chemical atomic components, achieves a safer and more reliable reaction rate, and realizes high-efficiency stirring. Different types of plasma stirring devices will be adjusted according to specific application scenarios and requirements, and use multiple methods among the above principles to achieve the high-efficiency stirring function of product mixing.

[0028] The beneficial effects of the present invention are as follows: By applying a high voltage or other energy sources, the gas inside the device is ionized to form a plasma. First, utilizing the ion wind effect, the ions in the plasma are accelerated under the action of an electric field, collide with the surrounding gas molecules, generate a directional ion flow, and form an ion wind. The ion wind can drive the flow of the surrounding gas or liquid, thereby achieving a stirring effect. Utilizing the thermal effect, heat is generated during the generation of the plasma, leading to a local temperature increase. The temperature difference causes a change in the density of the fluid, thereby generating natural convection and promoting the mixing and stirring of substances. Utilizing the electromagnetic force effect, for a conductive fluid, the electromagnetic field generated by the plasma will exert an electromagnetic force on the charged particles in the fluid, and the electromagnetic force causes the fluid to move, thereby achieving efficient stirring. Using this method is beneficial to improving the product purity. The obtained crystal granular ferrocene has a purity of ≥98%, a free iron content of ≤100 ppm, a particle size of 20 - 120 mesh, and a yield of over 85%. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is the reaction equation of the depolymerization reaction step of the present invention;

[0030] Figure 2 It is the reaction equation of the negative ion synthesis step of the present invention;

[0031] Figure 3 It is the reaction equation of the ferrous chloride preparation step of the present invention

[0032] Figure 4 It is the reaction equation of the ferrocene synthesis step of the present invention.

[0033] The drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation to the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0035] Unless otherwise defined, all professional and scientific terms used herein have the same meaning as those familiar to those skilled in the art. In addition, any methods and materials similar or equivalent to the described content can be applied to the present invention. The preferred implementation methods and materials described herein are only for illustrative purposes and do not limit the content of this application.

[0036] In the experimental methods of the following examples, unless otherwise specified, they are all conventional methods. Unless otherwise specified, the test materials used in the following examples are all purchased from commercial channels.

[0037] Example

[0038] A method for preparing ferrocene using plasma stirring technology includes the following steps:

[0039] (1) Depolymerization reaction: Dicyclopentadiene is depolymerized at high temperature to generate cyclopentadiene. The residual liquid at the bottom of the reaction kettle is temporarily stored in the hazardous waste warehouse as hazardous waste. Plasma stirring is used throughout the reaction process;

[0040] The reaction equation for this step is shown in Figure 1 ;

[0041] (2) Negative ion synthesis: Cyclopentadiene reacts with sodium methoxide in a methanol solution to generate sodium cyclopentadienide and dissolve it in the methanol solution. Plasma stirring is used throughout the reaction process;

[0042] The reaction equation for this step is shown in Figure 2 ;

[0043] (3) Preparation of ferrous chloride: First, dissolve ferric chloride in methanol, add an excessive amount of iron powder, react under nitrogen protection, and then filter out the remaining iron powder by pressure filtration to obtain a ferrous chloride solution for use. Plasma stirring is used throughout the reaction process;

[0044] The reaction equation for this step is shown in Figure 3 ;

[0045] (4) Ferrocene synthesis: Add the methanol solution of sodium cyclopentadienide to ferrous chloride, and react sodium cyclopentadienide with ferrous ions in the methanol solution to generate ferrocene. Plasma stirring is used throughout the reaction process;

[0046] The reaction equation for this step is shown in Figure 4 ;

[0047] (5) Methanol recovery and purification: Heat the reaction solution obtained in step (4), distill out the solvent methanol using a distillation column, then add water to the reaction kettle, heat the material with direct steam, spray cooling water on the ferrocene gas distilled out by the distillation column to cool and crystallize ferrocene, and centrifugally separate and vacuum dry the water-containing ferrocene to obtain the ferrocene product;

[0048] (6) Methanol refining and waste liquid treatment: Recycle the crude methanol containing C5 hydrocarbons distilled out for the first time through the distillation column again. The refined methanol obtained is used as a solvent for recycling, and the excess methanol is sold as a by-product. The residual liquid at the bottom of the reaction kettle is temporarily stored in the hazardous waste warehouse as hazardous waste.

[0049] The plasma stirring uses an integrated plasma generator and a stirring system. The plasma generator selects a radio frequency or microwave plasma source with a power range of 500 - 1500 W and a frequency of 13.56 MHz. The stirring system is a magnetic stirrer with adjustable speed and is synchronously controlled with the plasma source.

[0050] The reaction kettle used in steps (1)-(5) is made of high-temperature resistant glass or quartz and is equipped with a constant pressure dropping funnel and a condensation reflux device.

[0051] The above reaction needs to strictly control the plasma power and reaction temperature to avoid side reactions (such as the oxidation of ferrocene to ferrocenium ion). The reaction system needs to be protected by inert gas throughout the process to prevent the oxidation of raw materials or products and avoid the generation of side reactions.

[0052] Comparing the preparation method of the present invention with traditional methods, the present invention has the following advantages compared with traditional methods:

[0053] The present invention can significantly shorten the reaction time through plasma stirring. The traditional method takes 6 - 8 hours, while the plasma method can be shortened to 2 - 4 hours.

[0054] The high-energy environment of the present invention can promote the thoroughness of the reaction, and the yield of ferrocene can reach more than 85%, while the traditional chemical method is about 73 - 80%.

[0055] The obtained crystalline granular ferrocene has a purity ≥ 98%, a free iron content ≤ 100 ppm, and a particle size of 20 - 120 mesh.

[0056] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

[0057] The above describes the present invention and its implementation manners. This description is not restrictive. What is shown in the drawings is only one of the implementation manners of the present invention, and the actual application is not limited to this. Generally speaking, if those of ordinary skill in the art are inspired by it and design similar ways and embodiments without creative efforts without departing from the purpose of the present invention's creation, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing ferrocene using plasma stirring technology, characterized in that: It includes the following steps: (1) Depolymerization reaction: Dicyclopentadiene is depolymerized at high temperature to generate cyclopentadiene. The residual liquid at the bottom of the reaction kettle is temporarily stored as hazardous waste in the hazardous waste warehouse. The whole reaction process uses plasma stirring; (2) Anion synthesis: Cyclopentadiene reacts with sodium methoxide in methanol solution to generate sodium cyclopentadienide and is dissolved in the methanol solution. The whole reaction process uses plasma stirring; (3) Preparation of ferrous chloride: First, dissolve ferric chloride in methanol, add an excessive amount of iron powder, react under nitrogen protection, and then filter out the remaining iron powder by pressure filtration to obtain a ferrous chloride solution for use. The whole reaction process uses plasma stirring; (4) Ferrocene synthesis: Add the methanol solution of sodium cyclopentadienide to ferrous chloride, and make sodium cyclopentadienide react with ferrous ions in the methanol solution to generate ferrocene. The whole reaction process uses plasma stirring; (5) Methanol recovery and purification: Heat the reaction solution obtained in step (4), distill out the solvent methanol using a distillation column, then add water to the reaction kettle, heat the material with direct steam, spray cooling water on the ferrocene gas distilled out by the distillation column, so that ferrocene cools and crystallizes out. The ferrocene containing water is centrifuged and vacuum dried to obtain the ferrocene finished product; (6) Methanol refining and waste liquid treatment: The crude methanol containing C5 hydrocarbons distilled out for the first time is recycled through the distillation column again. The refined methanol obtained is used as a solvent for recycling, and the excess methanol is sold as a by-product. The residual liquid at the bottom of the reaction kettle is temporarily stored as hazardous waste in the hazardous waste warehouse.

2. The method for preparing ferrocene using plasma stirring technology according to claim 1, characterized in that: The plasma stirring uses an integrated plasma generator and a stirring system.

3. The method for preparing ferrocene by using plasma stirring technology according to claim 2, wherein: For the plasma generator, a radio frequency or microwave plasma source is selected, with a power range of 500 - 1500W and a frequency of 13.56MHz.

4. The method for preparing ferrocene by using plasma stirring technology according to claim 2, wherein: The stirring system is magnetic stirring or mechanical stirring, with adjustable speed and synchronous control with the plasma source.

5. The method for preparing ferrocene using plasma stirring technology according to claim 1, characterized in that: The reaction kettle used in steps (1)-(5) is made of high-temperature resistant glass or quartz, and is equipped with a constant pressure dropping funnel and a condensation reflux device.

Images