A process for the preparation of a heterogeneous catalyst for the production of dimethyl carbonate

Abstract

The application discloses a preparation method of a heterogeneous catalyst for preparing dimethyl carbonate, and comprises the following steps: (1) uniformly mixing red mud powder, biomass powder and plant fibers, wet granulating, drying the obtained granules, and then sintering treatment in a reducing atmosphere; after the sintering treatment, the reducing atmosphere is removed, and the temperature is continuously maintained in an air atmosphere; after the temperature is maintained, the temperature is cooled to room temperature, and a precursor is obtained; (2) ultrasonic treatment of the precursor in anhydrous ethanol; after the ultrasonic treatment, the precursor is separated and dried, and the heterogeneous catalyst is obtained. The catalyst prepared by the method has multiple types of active sites, and the plant fibers are used to introduce long channels to connect the micropores in the catalyst and increase the catalytic surface, so that the conversion rate of raw materials is effectively improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of preparation of propylene glycol, and particularly relates to a preparation method of a heterogeneous catalyst for preparing dimethyl carbonate. BACKGROUND

[0002] Dimethyl carbonate, chemical formula C3H6O3, is a colorless transparent liquid with a pungent odor, which is insoluble in water but soluble in organic solvents such as ethanol and diethyl ether. Dimethyl carbonate is a low-toxicity, environmentally friendly, and widely used chemical raw material. It contains functional groups such as carbonyl, methyl, and methoxy in its molecular structure, has multiple reaction properties, and is an important organic synthesis intermediate. It has the characteristics of safety, convenience, less pollution, and easy transportation in production. It is one of the methods for preparing dimethyl carbonate by transesterification. In this method, methanol and ethylene carbonate are converted into dimethyl carbonate and propylene glycol under the action of a catalyst. This process has attracted widespread attention and is widely used in industrial production. The ester exchange reaction generally uses alkali metal oxides, carbonates, and alcoholates as catalysts, but because it is a homogeneous reaction, it is difficult to separate and reuse the catalyst. Solid catalysts / heterogeneous catalysts can be more conveniently and completely separated from the reaction system. However, solid catalysts have low catalytic activity in practical applications, resulting in low conversion rate of raw materials, affecting reaction efficiency and product production cycle. Since the above reaction is carried out at high temperature, longer production cycle means more energy consumption. SUMMARY

[0003] In view of the above problems, the present application provides a preparation method of a heterogeneous catalyst for preparing dimethyl carbonate, which has multiple types of active sites, effectively improving the conversion rate of raw materials. In order to achieve the above purpose, the present application discloses the following technical solutions.

[0004] A preparation method of a heterogeneous catalyst for preparing dimethyl carbonate, comprising the following steps:

[0005] (1) The red mud powder, biomass powder and plant fiber are uniformly mixed, then wet granulation is carried out, and then the obtained granular material is dried and sintered in a reducing atmosphere. After completion, the reducing atmosphere is removed, and the temperature is continuously maintained in an air atmosphere. After completion, it is cooled to room temperature to obtain a precursor.

[0006] (2) The precursor is placed in anhydrous ethanol and subjected to ultrasonic treatment. After completion, the precursor is separated and dried to obtain the heterogeneous catalyst.

[0007] Further, in step (1), the mass ratio of the red mud powder, biomass powder and plant fiber is 1g: 0.1-0.14: 0.2-0.25g. The red mud contains various alkali metals, which can provide various active catalyst centers for the prepared catalyst.

[0008] Further, in step (1), the biomass powder includes at least one of wood powder, straw powder, rice husk powder and the like. Optionally, the particle size of the biomass powder is 300-500 mesh.

[0009] Further, in step (1), the length of the plant fiber is between 1-3mm. Optionally, the plant fiber includes at least one of coconut shell fiber, hemp, animal hair and the like. The plant fiber can introduce long channels to the catalyst, which is conducive to connecting the micropores therein and increasing the catalytic surface.

[0010] Further, in step (1), the particle size of the particulate matter is between 4-7mm, and other particle sizes can also be used according to actual needs, and the length of the plant fiber is proportional to the particle size of the particulate matter.

[0011] Further, in step (1), the drying temperature is 70-85℃, and the time is 40-60min, so as to reduce the moisture in the particulate matter and facilitate sintering treatment.

[0012] Further, in step (1), the reducing atmosphere includes any one of carbon monoxide, hydrogen and the like, so as to reduce the iron oxide in the red mud to elemental iron.

[0013] Further, in step (1), the sintering treatment is performed at a temperature of 700-800℃ for 1-2h. In this process, the red mud powder is vitrified to form a catalyst precursor, and the biomass powder and plant fiber are carbonized to form carbon, thereby forming a large number of micropores and long channels in the precursor.

[0014] Further, in step (1), the temperature is continued to be maintained in the air atmosphere for 20-30min, so as to remove the carbon formed by carbonization of the biomass powder and plant fiber in the precursor.

[0015] Further, in step (2), the ultrasonic treatment is performed for 15-20min, and the ultrasonic power is 300-500W, so as to remove impurities in the precursor.

[0016] Further, in step (2), the drying temperature is 60-70℃, and the time is 10-15min, so as to remove residual ethanol.

[0017] Compared with the prior art, the present application has the following beneficial technical effects: the present application uses basic red mud as raw material, and after mixing with biomass powder and plant fiber, sintering treatment is carried out in a reducing atmosphere, and after completion, the reducing atmosphere is removed and the temperature is continued to be kept in an air atmosphere. In the above process, the red mud is sintered and vitrified into the main framework of the catalyst at high temperature, at the same time, sodium, potassium, calcium, aluminum and the like in the red mud form oxides attached to the main framework, providing various basic sites for the catalyst, and the iron ions provided by the iron oxide in the red mud form Lewis acid sites, which can effectively improve the catalytic activity of the catalyst and improve the conversion rate of the raw material. In addition, part of the iron oxide in the red mud is reduced to iron single substance under the action of the reducing atmosphere, so that the catalyst prepared by the present application can be recycled by magnetism. At the same time, the biomass powder and the plant fiber are carbonized in the reducing atmosphere, wherein the biomass powder can provide a large number of micropores for the catalyst, and the plant fiber can provide long channels for the catalyst, which can form a series connection with the micropores, thereby opening the closed micropores in the catalyst, exposing more catalytic surface, increasing the contact area with the reaction raw material, and improving the catalytic efficiency. DETAILED DESCRIPTION

[0018] It should be noted that the following detailed description is illustrative only and is intended to provide further description of the present application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0019] It should be noted that the terms used herein are only intended to describe specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, the singular form is intended to include the plural form unless the context clearly indicates otherwise, and furthermore, it should be understood that when the terms "comprise" and / or "include" are used in the specification, they mean that there is a presence of the features, steps, operations, devices, components and / or their combinations. The present application is further described by specific embodiments. Example 1

[0020] A method for preparing a heterogeneous catalyst for preparing dimethyl carbonate, comprising the following steps:

[0021] (1) Red mud powder, 500 mesh wood powder and 2 mm long short-cut coconut shell fiber are mixed in a mass ratio of 1 g:0.12:0.23 g in a granulator, and then water is sprayed to granulate, obtaining granular material with a particle size of 5-7 mm. Then the granular material is dried at 80℃ for 50 min, and then placed in a tube furnace, and sintered at 780℃ in a carbon monoxide atmosphere for 1.5 hours. After completion, the carbon monoxide atmosphere is removed, and the temperature is continued to be kept in an air atmosphere for 30 min, and after completion, the furnace is slowly cooled to room temperature, and the precursor is obtained.

[0022] (2) ultrasonic treatment of the precursor in anhydrous ethanol for 20 min at an ultrasonic power of 400 W, and then filtering out the precursor and drying at 60 ℃ for 15 min to obtain the heterogeneous catalyst.

[0023] The conversion rate of the catalyst prepared in this embodiment to ethylene carbonate in the process of preparing dimethyl carbonate and coproducing propylene glycol by transesterification (raw materials are anhydrous methanol and ethylene carbonate) was tested, and the test result was 76.31%. Example 2

[0024] A preparation method of a heterogeneous catalyst for preparing dimethyl carbonate, comprising the following steps:

[0025] (1) red mud powder, 300-mesh rice husk powder and 1-mm short-cut ramie were mixed in a granulator according to a mass ratio of 1 g:0.14:0.25 g, and then water granulation was performed to obtain granular materials with a particle size of 4-5 mm. Then the granular materials were dried at 85 ℃ for 40 min, and then placed in a tube furnace and sintered in a carbon monoxide atmosphere at 700 ℃ for 2 hours. After completion, the carbon monoxide atmosphere was removed, and the temperature was continued to be kept in an air atmosphere for 25 min. After completion, the furnace was slowly cooled to room temperature, and a precursor was obtained.

[0026] (2) ultrasonic treatment of the precursor in anhydrous ethanol for 15 min at an ultrasonic power of 500 W, and then filtering out the precursor and drying at 65 ℃ for 15 min to obtain the heterogeneous catalyst.

[0027] The conversion rate of the catalyst prepared in this embodiment to ethylene carbonate in the process of preparing dimethyl carbonate and coproducing propylene glycol by transesterification (raw materials are anhydrous methanol and ethylene carbonate) was tested, and the test result was 76.31%. Example 3

[0028] A preparation method of a heterogeneous catalyst for preparing dimethyl carbonate, comprising the following steps:

[0029] (1) red mud powder, 300-mesh rice husk powder and 1-mm short-cut ramie were mixed in a granulator according to a mass ratio of 1 g:0.14:0.25 g, and then water granulation was performed to obtain granular materials with a particle size of 4-5 mm. Then the granular materials were dried at 85 ℃ for 40 min, and then placed in a tube furnace and sintered in a carbon monoxide atmosphere at 700 ℃ for 2 hours. After completion, the carbon monoxide atmosphere was removed, and the temperature was continued to be kept in an air atmosphere for 25 min. After completion, the furnace was slowly cooled to room temperature, and a precursor was obtained.

[0030] (2) The precursor is placed in anhydrous ethanol and ultrasonically treated for 20 min with an ultrasonic power of 300 W. After the treatment, the precursor is filtered out and dried at 70 °C for 10 min to obtain the heterogeneous catalyst.

[0031] The conversion rate of the catalyst prepared in this embodiment to ethylene carbonate in the transesterification process (the raw materials are anhydrous methanol and ethylene carbonate) to produce dimethyl carbonate and propylene glycol (the process conditions are the same as in Example 1 above) was tested, and the result was 75.27%. Example 4

[0032] A method for preparing a heterogeneous catalyst for dimethyl carbonate includes the following steps:

[0033] (1) Red mud powder and 300-mesh rice husk powder were mixed evenly in a granulator at a mass ratio of 1g:0.14, and then sprayed with water to granulate, resulting in particles with a particle size between 4 and 5 mm. The particles were then dried at 85°C for 40 min and placed in a tubular furnace, where they were sintered at 700°C for 2 hours in a carbon monoxide atmosphere. After completion, the carbon monoxide atmosphere was removed, and the furnace was kept at the same temperature for 25 min in an air atmosphere. After completion, the furnace was slowly cooled to room temperature to obtain the precursor.

[0034] (2) The precursor is placed in anhydrous ethanol and ultrasonically treated for 15 minutes with an ultrasonic power of 500W. After the treatment, the precursor is filtered out and dried at 65°C for 15 minutes to obtain the heterogeneous catalyst.

[0035] The conversion rate of the catalyst prepared in this embodiment to ethylene carbonate in the process of preparing dimethyl carbonate and co-producing propylene glycol by transesterification (the raw materials are anhydrous methanol and ethylene carbonate) (the process conditions are the same as those in Example 1 above) was tested, and the result was 51.84%. Example 5

[0036] A method for preparing a heterogeneous catalyst for dimethyl carbonate includes the following steps:

[0037] (1) Red mud powder, 500-mesh wood flour, and 2mm long chopped coconut shell fibers were mixed evenly in a granulator at a mass ratio of 1g:0.12:0.23g, and then sprayed with water to granulate, resulting in particles with a diameter between 5 and 7mm. The particles were then dried at 80℃ for 50min and placed in a tube furnace, where they were sintered at 780℃ for 1.5 hours in a carbon monoxide atmosphere. After completion, the sintered particles were slowly cooled to room temperature in the furnace to obtain the precursor.

[0038] (2) The precursor was placed in anhydrous ethanol and ultrasonically treated for 20 min with an ultrasonic power of 400 W. After the treatment, the precursor was filtered out and dried at 60 °C for 15 min to obtain the heterogeneous catalyst.

[0039] The catalyst prepared in this example was tested in the process of preparing dimethyl carbonate and co-producing propylene glycol by transesterification method (raw materials were anhydrous methanol and ethylene carbonate) (the process conditions were the same as those in Example 1 above) for the conversion rate of ethylene carbonate, and the test result was 58.16%. Example 6

[0040] A preparation method of a heterogeneous catalyst for preparing dimethyl carbonate, comprising the following steps:

[0041] (1) The red mud powder and the short-cut animal hair with a length of 3 mm were mixed in a granulator at a mass ratio of 1 g:0.2 g, and then water was sprayed for granulation to obtain granular materials with a particle size of 6-7 mm. Then the granular materials were dried at 70°C for 60 min, and then placed in a tube furnace and sintered at 800°C for 1 hour in a hydrogen atmosphere. After completion, the hydrogen atmosphere was removed, and the temperature was continued to be kept at 800°C for 20 min in an air atmosphere. After completion, the furnace was slowly cooled to room temperature to obtain the precursor.

[0042] (2) The precursor was ultrasonically treated in anhydrous ethanol for 20 min at an ultrasonic power of 300 W. After completion, the precursor was filtered out and dried at 70°C for 10 min to obtain the heterogeneous catalyst.

[0043] The catalyst prepared in this example was tested in the process of preparing dimethyl carbonate and co-producing propylene glycol by transesterification method (raw materials were anhydrous methanol and ethylene carbonate) (the process conditions were the same as those in Example 1 above) for the conversion rate of ethylene carbonate, and the test result was 41.53%. Example 7

[0044] A preparation method of a heterogeneous catalyst for preparing dimethyl carbonate, comprising the following steps: The red mud powder, 500 mesh wood powder and short-cut coconut shell fiber with a length of 2 mm were mixed in a granulator at a mass ratio of 1 g:0.12:0.23 g, and then water was sprayed for granulation to obtain granular materials with a particle size of 5-7 mm. Then the granular materials were dried at 80°C for 50 min, and then placed in a tube furnace and sintered at 780°C for 1.5 hours in a carbon monoxide atmosphere. After completion, the carbon monoxide atmosphere was removed, and the temperature was continued to be kept at 780°C for 30 min in an air atmosphere. After completion, the furnace was slowly cooled to room temperature to obtain the heterogeneous catalyst.

[0045] The catalyst prepared in this example was tested in the process of preparing dimethyl carbonate and co-producing propylene glycol by transesterification method (raw materials were anhydrous methanol and ethylene carbonate) (the process conditions were the same as those in Example 1 above) for the conversion rate of ethylene carbonate, and the test result was 71.49%. Example 8

[0046] A method for preparing a heterogeneous catalyst for preparing dimethyl carbonate, comprising the following steps:

[0047] (1) The red mud powder, 400 mesh straw powder and 3 mm short animal hair are mixed in a granulator according to a mass ratio of 1:0.1:0.2, and then granulated by spraying water, to obtain granular materials with a particle size of 6-7 mm. Then the granular materials are dried at 70 DEG C for 60 min, and then sintered in a tube furnace at 800 DEG C for 1 h in an air atmosphere, and then slowly cooled to room temperature in the furnace, to obtain a precursor.

[0048] (2) The precursor is ultrasonically treated in anhydrous ethanol for 20 min at an ultrasonic power of 300 W, and then filtered to obtain the precursor, and then dried at 70 DEG C for 10 min, to obtain the heterogeneous catalyst.

[0049] The conversion rate of the catalyst prepared in the embodiment to ethylene carbonate in a process for preparing dimethyl carbonate and coproducing propylene glycol by an ester exchange method (raw materials are anhydrous methanol and ethylene carbonate) is tested, and the test result is 63.92%.

[0050] The above only describes the preferred embodiments of the present application, and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a heterogeneous catalyst for dimethyl carbonate, characterized in that: Includes the following steps: (1) After mixing red mud powder, biomass powder and plant fiber evenly, wet granulation is performed. The resulting granules are then dried and sintered in a reducing atmosphere. After completion, the reducing atmosphere is removed, and the mixture is kept warm in an air atmosphere. After completion, it is cooled to room temperature to obtain the precursor. The mass ratio of red mud powder, biomass powder and plant fiber is 1g:0.1~0.14:0.2~0.25g. The biomass powder is selected from at least one of wood powder, straw powder and rice husk powder. The reducing atmosphere is selected from any one of carbon monoxide and hydrogen. The sintering temperature is 700~800℃ and the time is 1~2h. (2) The precursor is subjected to ultrasonic treatment in anhydrous ethanol. After the treatment, the precursor is separated and dried to obtain the heterogeneous catalyst.

2. The method for preparing the heterogeneous catalyst for dimethyl carbonate according to claim 1, characterized in that: In step (1), the particle size of the biomass powder is 300~500 mesh.

3. The method for preparing the heterogeneous catalyst for dimethyl carbonate according to claim 1, characterized in that: In step (1), the length of the plant fiber is between 1 and 3 mm.

4. The method for preparing the heterogeneous catalyst for dimethyl carbonate according to claim 1, characterized in that: The plant fiber is selected from at least one of coconut shell fiber and hemp fiber.

5. The method for preparing the heterogeneous catalyst for dimethyl carbonate according to claim 1, characterized in that: In step (1), the particle size of the particulate matter is between 4 and 7 mm.

6. The method for preparing the heterogeneous catalyst for dimethyl carbonate according to claim 1, characterized in that: In step (1), the drying temperature is 70~85℃ and the time is 40~60min.

7. The method for preparing the heterogeneous catalyst for dimethyl carbonate according to claim 1, characterized in that: In step (1), the temperature is maintained in the air atmosphere for 20-30 minutes.

8. The method for preparing the heterogeneous catalyst for preparing dimethyl carbonate according to any one of claims 1-7, characterized in that: In step (2), the ultrasonic treatment time is 15-20 minutes and the ultrasonic power is 300-500W.

9. The method for preparing the heterogeneous catalyst for preparing dimethyl carbonate according to any one of claims 1-7, characterized in that: In step (2), the drying temperature is 60~70℃ and the time is 10~15min.