A method for producing propylene oxide

Abstract

The present invention relates to a method for producing propylene oxide, which comprises: (1) contacting propane with a nano-carbon-based material at 550-750°C and 0-10 MPa under anaerobic conditions to carry out a first reaction to obtain a first mixed product; (2) contacting the first mixed product with hydrogen peroxide at 30-65°C and 0.4-7 MPa in the presence of a catalyst and an optional solvent to carry out a second reaction. The method of the present invention can directly produce propylene oxide using propane and hydrogen peroxide as raw materials, and both the conversion rate of the raw materials and the selectivity of the target product are high.

Description

Technical Field

[0001] The present invention relates to a method for producing propylene oxide. Background Art

[0002] Propylene oxide, also known as propylene oxide (PO), is a major chemical raw material. It is the second largest organic chemical product among propylene derivatives, second only to polypropylene, and is among the 50 largest chemicals in the world. PO has very active chemical properties and a wide range of uses. It has a profound impact on the development of the chemical industry and the national economy and is widely used in chemical, light industry, medicine, food, textile and other industries.

[0003] At present, the industrial production of propylene oxide mainly adopts the chlorohydrin process and the co-oxidation process, and the production capacity of these two methods accounts for more than 80% of the world's total production capacity. The chlorohydrin process was applied to production earlier. This method uses chlorine and is severely corrosive. In order to improve the conversion rate, a large amount of water is added during the reaction process, so a large amount of chlorine-containing wastewater that pollutes the environment is produced after the reaction, which does not meet the requirements of green chemistry and clean production. Therefore, with the increasing demand for environmental protection, this process will eventually be eliminated. The co-oxidation process mainly uses ethylbenzene peroxide or tert-butyl hydroperoxide or isopropylbenzene peroxide as an oxygen source to indirectly oxidize propylene to PO. The co-oxidation process overcomes the shortcomings of the chlorohydrin process such as environmental pollution and equipment corrosion, and is a relatively clean production process than the chlorohydrin process, but it co-produces a large amount of cheap by-products such as styrene or tert-butyl alcohol, which are difficult to digest in the by-product market. In addition, the process is lengthy and the construction investment scale is large. The market supply and demand relationship and economic factors of by-products are the main reasons restricting its development.

[0004] The method using hydrogen peroxide as oxidant and heteroatom molecular sieve, especially titanium silicon molecular sieve, as catalyst can obtain higher propylene conversion rate and PO selectivity. This method is simple, the byproduct is mainly water, the process is clean, and it does not pollute the environment. It is a highly competitive PO production process, which meets the requirements of contemporary green chemistry and atomic economic development concepts, and is considered to be a green new process for producing PO. It is currently the most promising PO production method. However, its economic efficiency needs to be improved and the technical maturity needs to be improved. Summary of the invention

[0005] The object of the present invention is to provide a method for producing propylene oxide, which can directly produce propylene oxide using propane and hydrogen peroxide as raw materials.

[0006] In order to achieve the above object, the present invention provides a method for producing propylene oxide, which comprises:

[0007] (1) under anaerobic conditions, contacting propane with the nano-carbon-based material at 550-750° C. and 0-10 MPa to perform a first reaction to obtain a first mixed product;

[0008] (2) In the presence of a catalyst and an optional solvent, the first mixed product is contacted with hydrogen peroxide at 30-65° C. and 0.4-7 MPa to carry out a second reaction.

[0009] Optionally, in step (1), the conditions of the first reaction include: a temperature of 600-700°C, a time of 1-5 MPa, a propane volume space velocity of 1-100 h -1 .

[0010] Optionally, in step (2), the molar ratio of the first mixed product to the amount of hydrogen peroxide is 1:(0.1-2), preferably 1:(0.2-1).

[0011] Optionally, in step (2), the conditions of the second reaction include: a temperature of 35 to 60° C. and a pressure of 0.5 to 6 MPa.

[0012] Optionally, the nano-carbon-based material is prepared by a method comprising the following steps: calcining multi-walled carbon nanotubes at 200-1000° C. for 1-24 h in an atmosphere of 0.1-5% by volume ammonia.

[0013] Optionally, the catalyst contains titanium silicon molecular sieve, and the content of the titanium silicon molecular sieve is 70-100% by weight based on the total weight of the catalyst.

[0014] Optionally, the titanium silicon molecular sieve has a silicon-titanium molar ratio of 30-60 and a total specific surface area of ​​250-600m 2 / g, mesopore specific surface area is 30-100m 2 / g.

[0015] Optionally, in step (2), the second reaction is carried out in the presence of a catalyst and a solvent; the weight ratio of the solvent to the catalyst is (10-1000):1, preferably (20-500):1.

[0016] Optionally, the solvent is selected from inorganic solvents and / or organic solvents; the inorganic solvent is deionized water; the organic solvent is selected from one or more of methanol, ethanol, n-propanol, isopropanol, tert-butanol, isobutanol, acetone, butanone and acetonitrile, preferably methanol and / or deionized water.

[0017] Optionally, the total volume space velocity of the second reaction is 1 to 1000 h -1 , preferably 5 to 500 hours -1 .

[0018] Through the above technical scheme, in the method of the present invention, by coupling the first reaction and the second reaction, it is possible to produce propylene oxide directly using propane and hydrogen peroxide as raw materials, and the first mixed product obtained by the first reaction is directly contacted with hydrogen peroxide to carry out the second reaction, the preparation process is simple and easy, and the conversion rate of the raw materials and the selectivity of propylene oxide are both high.

[0019] Other features and advantages of the present invention will be described in detail in the following detailed description. DETAILED DESCRIPTION

[0020] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0021] A first aspect of the present invention provides a method for producing propylene oxide, the method comprising:

[0022] (1) under anaerobic conditions, contacting propane with the nano-carbon-based material at 550-750° C. and 0-10 MPa to perform a first reaction to obtain a first mixed product;

[0023] (2) In the presence of a catalyst and an optional solvent, the first mixed product is contacted with hydrogen peroxide at 30-65° C. and 0.4-7 MPa to carry out a second reaction.

[0024] In the present invention, the anaerobic condition means that the first reaction is carried out in an atmosphere without oxygen, for example, it can be a nitrogen atmosphere, a helium atmosphere, a mixed atmosphere of nitrogen and helium, etc., or it can be an atmosphere formed by propane alone. In the atmosphere without oxygen, the molar ratio of the gas other than propane to propane can be (0-10):1. The method of the present invention directly uses propane and hydrogen peroxide as raw materials to produce propylene oxide. The method is simple, easy to operate, low in cost, and can produce propylene oxide with a high conversion rate and selectivity. It is particularly suitable for the industrial production of propylene oxide using propane as the initial raw material.

[0025] In a specific embodiment of the present invention, in step (1), the conditions of the first reaction include: a temperature of 600-700°C, a time of 1-5 MPa, a propane volume space velocity of 1-100 h -1 .

[0026] In a specific embodiment of the present invention, in step (2), the molar ratio of the first mixed product to the amount of hydrogen peroxide can vary within a large range, for example, it can be 1:(0.1-2), preferably 1:(0.2-1).

[0027] In a specific embodiment of the present invention, in step (2), the conditions of the second reaction include: temperature of 35-60°C and pressure of 0.5-6MPa; preferably, temperature of 40-50°C and pressure of 1-4MPa.

[0028] According to the present invention, there is no specific restriction on the devices used in the first reaction and the second reaction, and the devices used in the first reaction and the second reaction can be independently a fixed bed reactor, a moving bed reactor, a microreactor or other types of reactors. In a preferred embodiment, the first reaction is carried out in a fixed bed microreactor, and the second reaction is carried out in a slurry bed reactor. The above method can further improve the conversion rate of the raw materials and the selectivity to propylene oxide.

[0029] According to the present invention, the nano-carbon-based material is a nano-carbon-based material with good thermal stability. In a specific embodiment of the present invention, the nano-carbon-based material can be a commercial product, or a modified product obtained by modifying a commercial product. Preferably, the nano-carbon-based material is a carbon nanotube modified by ammonia nitrogen activation. In one embodiment, the modified carbon nanotube is produced by a method comprising the following steps: multi-walled carbon nanotubes are calcined at 200-1000°C, preferably 400-600°C, for 1-24h in an ammonia atmosphere of 0.1-5% by volume, preferably 1-2.5% by volume. Preferably, the carbon nanotube is a carbon nanotube. The ammonia atmosphere can also contain nitrogen and / or an inert gas, and the inert gas is well known to those skilled in the art, for example, it can be helium, argon, etc.

[0030] According to the present invention, the catalyst contains titanium silicon molecular sieve, which is well known to those skilled in the art, and can be, for example, one or more of the molecular sieves having an MFI structure, a MOR structure, or a BEA structure. The content of the titanium silicon molecular sieve in the catalyst can vary within a wide range, for example, based on the total weight of the catalyst, the content of the titanium silicon molecular sieve is 70-100 wt %, preferably 40-55 wt %. The silicon-titanium molar ratio of the titanium silicon molecular sieve can also vary within a wide range, for example, it can be 15-60, preferably 20-55. The total specific surface area of ​​the titanium silicon molecular sieve is 250-600 m 2 / g, mesopore specific surface area is 25-100m 2 / g. The use of the above-mentioned titanium silicalite molecular sieve can further improve the raw material conversion rate and the selectivity of propylene oxide in the method of the present invention. Among them, titanium silicalite molecular sieve is well known to those skilled in the art and can be obtained by self-synthesis or commercial purchase, and the specific preparation method is not repeated here.

[0031] According to the present invention, in step (2), the second reaction is carried out in the presence of a catalyst and a solvent; the solvent is selected from an inorganic solvent and / or an organic solvent; the inorganic solvent may be deionized water; the organic solvent may be selected from one or more of alcohols, ketones and nitriles, for example, one or more of methanol, ethanol, n-propanol, isopropanol, tert-butanol, isobutanol, acetone, butanone and acetonitrile, preferably methanol and / or deionized water. The weight ratio of the solvent to the catalyst may vary within a wide range, for example, it may be (10 to 1000):1, preferably (20 to 500):1.

[0032] In one embodiment of the present invention, the total space velocity of the second reaction can be 1 to 1000 h -1 , preferably 5 to 500 hours -1 .

[0033] The present invention is further described below by way of examples, but the present invention is not limited thereto. The reagents used in the examples are all commercially available chemically pure reagents.

[0034] The nano-carbon material is a multi-walled carbon nanotube modified with ammonia and nitrogen (CNT is activated and modified). The specific production is as follows: the multi-walled carbon nanotube is calcined at 600° C. for 4 hours in a 1 volume % ammonia atmosphere (the balance is nitrogen) using a tubular furnace.

[0035] Titanium silicate molecular sieve (TS-1) is a molecular sieve sample produced by the method described in the prior art Zeolites, 1992, Vol. 12, pages 943-950, with a silicon-titanium molar ratio of 24 and a total specific surface area of ​​402 m 2 / g, mesopore specific surface area is 27m 2 / g.

[0036] Gas chromatography was used to analyze the contents of the various components in the obtained reaction products, and on this basis, the conversion rate of propane and the selectivity of propylene oxide were calculated using the following formulas:

[0037] Propane conversion rate = [(molar amount of propane added - molar amount of unreacted propane) / molar amount of propane added] × 100%;

[0038] Propylene oxide selectivity = [molar amount of propylene oxide produced by the reaction / (molar amount of propane added - molar amount of unreacted propane)] × 100%.

[0039] Example 1

[0040] The process of producing propylene oxide is as follows:

[0041] (1) In nitrogen atmosphere, 0.1 MPa, 600°C, propane volume space velocity of 100 h-1 Under the conditions of , propane (the molar ratio of nitrogen to propane is 1:1) is firstly passed through a fixed bed microreactor with a nano-carbon-based material as a catalyst bed to perform a first reaction to obtain a first mixed product;

[0042] (2) The first mixed product, hydrogen peroxide, methanol solvent and catalyst are placed in a slurry bed reactor at a molar ratio of the first mixed product to hydrogen peroxide of 1:1, a weight ratio of the methanol solvent to the catalyst of 50, at a temperature of 60° C., a pressure of 0.5 MPa and a total volume space velocity of 500 h / min. -1 The reaction mixture obtained after the second reaction was analyzed by gas chromatography, and the propane conversion rate and the selectivity of propylene oxide were calculated. The reaction results for 2 hours are listed in Table 1.

[0043] Example 2

[0044] Propylene oxide was produced by the same method as in Example 1, except that in step (1), the temperature was 550°C and the propane volume space velocity was 5h -1 ;

[0045] In step (2), the molar ratio of the first mixed product to hydrogen peroxide is 2:1, the weight ratio of the solvent methanol to the catalyst is 20, the reaction temperature is 40°C, the pressure is 2.5 MPa, and the total volume space velocity is 200 h -1 .

[0046] Example 3

[0047] Propylene oxide was produced by the same method as in Example 1, except that in step (1), the propane volume space velocity was 25 h -1 ;

[0048] In step (2), the molar ratio of the first mixed product to the hydrogen peroxide solution (calculated as hydrogen peroxide) is 10:1, the weight ratio of the solvent methanol to the catalyst is 40, the temperature is 50°C, the pressure is 1.5 MPa, and the total volume space velocity is 100 h -1 .

[0049] Example 4

[0050] Propylene oxide was produced by the same method as in Example 1, except that in step (1), the pressure was 6 MPa, the temperature was 550°C, and the propane volume space velocity was 8 h -1 .

[0051] Example 5

[0052] Propylene oxide was produced by the same method as in Example 1, except that in step (2), the temperature of the second reaction was 30°C, the pressure was 0.45 MPa, and the molar ratio of the first mixed product to the hydrogen peroxide solution (calculated as hydrogen peroxide) was 1:1.2.

[0053] Example 6

[0054] Propylene oxide was produced by the same method as in Example 1, except that the nanocarbon-based material used in step (1) was different. The nanocarbon-based material used in this example was prepared by calcining multi-walled carbon nanotubes at 800° C. for 3 h in an ammonia atmosphere with a concentration of 3 vol%.

[0055] Comparative Example 1

[0056] Propylene oxide was produced by the same method as in Example 1, except that no nano-carbon-based material was used.

[0057] Comparative Example 2

[0058] Propylene oxide was produced in the same manner as in Example 1, except that no catalyst was used.

[0059] Comparative Example 3

[0060] Propylene oxide was produced by the same method as in Example 1, except that no nano-carbon-based material and catalyst were used.

[0061] Comparative Example 4

[0062] Propylene oxide was produced by the same method as in Example 1, except that the reaction temperature in step (1) was 400°C.

[0063] Table 1

[0064] serial number Propane conversion rate (%) Propylene oxide selectivity (%) Example 1 58 94 Example 2 31 92 Example 3 35 89 Example 4 41 83 Example 5 47 87 Example 6 39 84 Comparative Example 1 3 82 Comparative Example 2 51 2 Comparative Example 3 1 3 Comparative Example 4 14 52

[0065] It can be seen from the results of the comparative examples and the examples that the present invention can directly produce propylene oxide from propane and hydrogen peroxide, the method is simple and easy, the cost is low, and it has a high propane conversion rate and propylene oxide selectivity.

[0066] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0067] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0068] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for producing propylene oxide, the method comprising: (1) Under anaerobic conditions, propane and a nano-carbon-based material are contacted at 550-750° C. and 0-10 MPa to carry out a first reaction to obtain a first mixed product; the nano-carbon-based material is prepared by a method comprising the following steps: calcining multi-walled carbon nanotubes at 400-600° C. for 1-24 h in an ammonia atmosphere having a concentration of 1-2.5% by volume; (2) in the presence of a catalyst and an optional solvent, contacting the first mixed product with hydrogen peroxide at 30-65° C. and 0.4-7 MPa for a second reaction; the conditions of the second reaction include: a temperature of 35-60° C. and a pressure of 0.5-6 MPa; the catalyst contains titanium silicon molecular sieve, and the content of the titanium silicon molecular sieve is 70-100% by weight based on the total weight of the catalyst.

2. The method according to claim 1, wherein: In step (1), the conditions of the first reaction include: temperature of 600-700°C, time of 1-5 MPa, volume space velocity of propane of 1-100 h -1 .

3. The method according to claim 1, wherein: In step (2), the molar ratio of the first mixed product to the amount of hydrogen peroxide is 1:(0.1-2).

4. The method according to claim 3, wherein: In step (2), the molar ratio of the first mixed product to the amount of hydrogen peroxide is 1:(0.2~1).

5. The method according to claim 1, wherein: The titanium silicon molecular sieve has a silicon-titanium molar ratio of 30-60 and a total specific surface area of ​​250-600 m 2 / g, mesopore specific surface area is 30-100m 2 / g.

6. The method according to claim 1, wherein: In step (2), the second reaction is carried out in the presence of a catalyst and a solvent; the weight ratio of the solvent to the catalyst is (10-1000):

1.

7. The method according to claim 6, wherein: In step (2), the weight ratio of the solvent to the catalyst is (20-500):

1.

8. The method according to claim 6, wherein: The solvent is selected from inorganic solvents and / or organic solvents; the inorganic solvent is deionized water; the organic solvent is selected from one or more of methanol, ethanol, n-propanol, isopropanol, tert-butanol, isobutanol, acetone, butanone and acetonitrile.

9. The method according to claim 8, wherein: The solvent is methanol and / or deionized water.

10. The method according to claim 1, wherein: The total volume space velocity of the second reaction is 1 to 1000 h -1 .

11. The method according to claim 10, wherein: The total volume space velocity of the second reaction is 5 to 500 h -1 .