Low-carbon olefin and method for preparing low-carbon carboxylic acid through carbonylation of alcohol of low-carbon olefin

Abstract

The invention discloses low-carbon olefin and a method for preparing low-carbon carboxylic acid through carbonylation of alcohol of the low-carbon olefin, and belongs to the field of catalytic chemistry. The method comprises the following steps: enabling raw materials containing low-carbon olefin, alcohol thereof and carbon monoxide to pass through a reactor loaded with an acidic molecular sieve catalyst, and reacting to obtain a product containing low-carbon carboxylic acid, the low-carbon olefin and the alcohol thereof are selected from at least one of ethylene, propylene, ethanol, normal propyl alcohol and isopropanol. The method uses the acidic molecular sieve as the catalyst, does not need a noble metal catalyst, has the advantages of small system corrosivity, easy product separation, less three-waste discharge and easy fixed bed process engineering, and is suitable for single-set large-scale production.

Description

Technical Field

[0001] This application relates to a method for preparing low-carbon carboxylic acids by carbonylation of low-carbon olefins and alcohols, belonging to the field of catalytic chemistry. Background Technology

[0002] Propionic acid (CH3CH2COOH) is an important chemical product and organic intermediate, widely used in synthetic plastics, pharmaceuticals, pesticides, feed, and fragrances. Due to its biocompatibility, propionic acid and its propionate salts are also commonly used as food preservatives. Currently, the main industrial production method for propionic acid is the Reppe process from BASF in Germany. This process uses nickel carbonyl as a catalyst, and ethylene, carbon monoxide, and water undergo a carbonyl synthesis reaction at a reaction temperature of 250–320℃ and a reaction pressure of 10–30 MPa to produce propionic acid in one step. The Reppe method involves high reaction pressure, and propionic acid is highly corrosive under the reaction conditions, requiring extremely sophisticated equipment. Ethanol carbonylation is another method for preparing propionic acid. The homogeneous carbonylation of ethanol is similar to the mature methanol carbonylation method, mainly using noble metal complex catalysts such as Rh and Ir, and also requiring the addition of iodide auxiliaries. In the homogeneous carbonylation of ethanol, not only are the noble metal catalysts expensive, but the reaction also produces severely corrosive iodide substances, and the reaction pressure is also high, requiring sophisticated equipment and making product separation difficult. The heterogeneous carbonylation of ethanol generally employs supported metal catalysts. The active component can be either noble metals or non-noble metals such as Zn, Pb, Sn, Cu, and Ni. While the heterogeneous carbonylation of ethanol can improve some of the problems of the homogeneous method, it still suffers from issues such as low catalyst stability, severe carbon deposition, and metal loss. Furthermore, it is difficult to avoid the addition of iodide promoters.

[0003] Isobutyric acid (CH3CH(CH3)COOH) is an important chemical product widely used in the manufacture of coatings, plasticizers, photoinitiators, fragrances, food preservatives, pesticides, and disinfectants. It is expensive and in high demand. Isobutyric acid is also recognized as a safe chemical by the Food Flavor Manufacturers Association. Industrially, isobutyric acid can be synthesized from isobutanol by oxidation with potassium permanganate in an alkaline medium followed by distillation. This process generates a large amount of waste residue and does not meet green environmental protection requirements. Alternatively, isobutyric acid can be synthesized from propylene, carbon monoxide, and water under homogeneous reaction conditions of high temperature, high pressure, and strong acids (such as concentrated sulfuric acid and hydrofluoric acid) based on the Koch carbonylation mechanism. Although the raw materials for the homogeneous Koch carbonylation method are inexpensive and readily available, the reaction conditions are harsh, the reactor materials are extremely demanding, product separation is difficult, and industrialization is challenging.

[0004] Currently, the Reppe process for the carbonylation of ethylene to produce propionic acid requires high temperature, high pressure, and strong corrosion, resulting in harsh reaction conditions, demanding equipment, and difficult product separation. Furthermore, the oxidation of isobutanol to produce isobutyric acid not only involves high raw material costs but also generates a large amount of solid waste, which does not meet the requirements for green and environmentally friendly practices. Summary of the Invention

[0005] To address the aforementioned issues, this application provides a method for the carbonylation of low-carbon olefins and their alcohols to produce low-carbon carboxylic acids using acidic molecular sieve catalysis. This method features a metal-free catalytic system with low corrosivity, easily separable products, and minimal waste emissions.

[0006] A method for preparing low-carbon carboxylic acids by carbonylation of low-carbon olefins and their alcohols, the method comprising:

[0007] Raw materials containing low-carbon olefins and their alcohols, as well as carbon monoxide, are passed through a reactor supported by an acidic molecular sieve catalyst to react and obtain a product containing low-carbon carboxylic acids.

[0008] The low-carbon olefins and their alcohols are selected from at least one of ethylene, propylene, ethanol, n-propanol, and isopropanol;

[0009] The acidic molecular sieve catalyst is an acidic molecular sieve catalyst with a 10-membered ring channel structure.

[0010] The acidic molecular sieve catalyst is selected from at least one of the following: acidic molecular sieves with FER structure, acidic molecular sieves with MEL structure, acidic molecular sieves with MFI structure, acidic molecular sieves with MFS structure, acidic molecular sieves with MTT structure, acidic molecular sieves with TON structure, and acidic molecular sieves with MWW structure.

[0011] Optionally, when the low-carbon olefin and its alcohol are ethylene or ethanol, the corresponding low-carbon carboxylic acid product is propionic acid;

[0012] When the low-carbon olefin and its alcohol are propylene, n-propanol or isopropanol, the corresponding low-carbon carboxylic acid product is isobutyric acid.

[0013] In some embodiments, the raw materials are ethylene, carbon monoxide, and water, and the product is propionic acid. The reaction equation for the carbonylation of ethylene to propionic acid catalyzed by acidic molecular sieves is as follows:

[0014] CH2=CH2+CO+H2O=CH3CH2COOH

[0015] It will also be accompanied by side reactions such as ethylene hydration to produce ethanol and ethylene hydrogen transfer to produce other hydrocarbons.

[0016] The above-mentioned mechanism of ethylene carbonylation to propionic acid is as follows: ethylene reacts with Brønsted acid (ZEO-H) ​​on acidic molecular sieves to generate surface ethoxylate (ZEO-CH2CH3) species; carbon monoxide inserts into the surface ethoxylate to form surface propionyl (ZEO-COCH2CH3) species; propionyl reacts with water to generate propionic acid (CH3CH2COOH), which is desorbed while Brønsted acid (ZEO-H) ​​is reduced.

[0017] Surface ethoxy species can also react directly with water to generate ethanol, which then desorbs and reduces Brønsted acid.

[0018] In some embodiments, the raw materials are ethanol, carbon monoxide, and water, and the product is propionic acid. The reaction equation for the carbonylation of ethylene to propionic acid catalyzed by acidic molecular sieves is as follows:

[0019] CH3CH2OH + CO = CH3CH2COOH

[0020] Additionally, the reaction of propionic acid with ethanol produces a small amount of ethyl propionate.

[0021] CH3CH2COOH+CH3CH2OH=CH3CH2COOCH3CH2+H2O

[0022] It will also be accompanied by side reactions such as ethanol dehydration to produce ethylene and ethylene hydrogen transfer to produce other hydrocarbons.

[0023] The above-mentioned mechanism for the carbonylation of ethanol to produce propionic acid is as follows: ethanol reacts with Brønsted acid (ZEO-H) ​​on the acidic molecular sieve to generate a surface ethoxy group (ZEO-CH2CH3); carbon monoxide inserts into the surface ethoxy group to form a surface propionyl group (ZEO-COCH2CH3); the propionyl group reacts with water to generate propionic acid (CH3CH2COOH), which is desorbed while the Brønsted acid (ZEO-H) ​​is reduced.

[0024] In some embodiments, the raw materials are propylene, carbon monoxide, and water, and the product is isobutyric acid. The reaction equation for the carbonylation of propylene to isobutyric acid catalyzed by acidic molecular sieves is as follows:

[0025] CH3-CH=CH2+CO+H2O=(CH3)2CHCOOH

[0026] It will also be accompanied by side reactions such as propylene hydration to form isopropanol and propylene hydrogen transfer to form other hydrocarbons.

[0027] The above-mentioned mechanism of propylene carbonylation to isobutyric acid is as follows: propylene reacts with Brønsted acid (ZEO-H) ​​on acidic molecular sieves to generate surface isopropoxy group (ZEO-CH(CH3)2) species; carbon monoxide inserts into the surface isopropoxy group to form surface isobutyryl group (ZEO-CO CH(CH3)2) species; isobutyryl group reacts with water to generate isobutyric acid ((CH3)2CHCOOH), which is desorbed while Brønsted acid (ZEO-H) ​​is reduced.

[0028] Surface isopropoxy species can also react directly with water to generate isopropanol, which desorbs and reduces Brønsted acid.

[0029] In some embodiments, the raw materials are propanol, carbon monoxide, and water, and the product is isobutyric acid. The reaction equation for the production of isobutyric acid by propanol carbonylation catalyzed by acidic molecular sieves is as follows:

[0030] C3H7OH + CO = (CH3)2CHCOOH

[0031] Additionally, the reaction of isobutyric acid and propanol will produce a small amount of propyl isobutyrate.

[0032] (CH3)2CHCOOH+C3H7OH=(CH3)2CHCOOC3H7+H2O

[0033] The above-mentioned mechanism of propanol carbonylation to isobutyric acid is as follows: propanol reacts with Brønsted acid (ZEO-H) ​​on the acidic molecular sieve to generate surface isopropoxy group (ZEO-CH(CH3)2) species; carbon monoxide inserts into the surface isopropoxy group to form surface isobutyryl group (ZEO-COCH(CH3)2) species; isobutyryl group reacts with water to generate isobutyric acid ((CH3)2CHCOOH) desorption and Brønsted acid (ZEO-H) ​​reduction.

[0034] The aforementioned propanols include n-propanol and isopropanol.

[0035] Optionally, the acidic molecular sieve catalyst is selected from at least one of hydrogen-form ZSM-35 molecular sieve, hydrogen-form ZSM-11 molecular sieve, hydrogen-form ZSM-5 molecular sieve, hydrogen-form ZSM-57 molecular sieve, hydrogen-form ZSM-23 molecular sieve, hydrogen-form ZSM-22 acidic molecular sieve, and hydrogen-form MCM-22 molecular sieve.

[0036] Optionally, the silicon-to-aluminum ratio (SiO2 / Al2O3) of the acidic molecular sieve catalyst is 10–200.

[0037] Preferably, the silicon-to-aluminum ratio (SiO2 / Al2O3) of the acidic molecular sieve catalyst is 20–80.

[0038] Optionally, the silicon-aluminum ratio (SiO2 / Al2O3) of the acidic molecular sieve catalyst is selected from any value or a range between 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 120, 140, 160, 180, and 200.

[0039] In some embodiments, the acidic molecular sieve catalyst is a shaped acidic molecular sieve catalyst.

[0040] In some embodiments, the shaped acidic molecular sieve catalyst contains binders such as alumina and silicon dioxide.

[0041] Optionally, the molar ratio of carbon monoxide to low-carbon olefins and their alcohols is 5:1 to 200:1.

[0042] Preferably, the molar ratio of carbon monoxide to low-carbon olefins and their alcohols is 30:1 to 100:1.

[0043] Optionally, the molar ratio of carbon monoxide to low-carbon olefins and their alcohols is selected from any value or a range between 5:1, 10:1, 20:1, 50:1, 75:1, 100:1, 125:1, 150:1, 175:1, and 200:1.

[0044] Optionally, the raw material further contains water, and the molar ratio of water to low-carbon olefins and their alcohols is 0:1 to 20:1.

[0045] Preferably, the molar ratio of water to low-carbon olefins and their alcohols is 0:1 to 5:1.

[0046] Optionally, the molar ratio of water to low-carbon olefins and their alcohols is selected from any value or a range between 0.0:1, 0.5:1, 1.0:1, 2.0:1, 3.0:1, 4.0:1, 5.0:1, 6.0:1, 7.0:1, 8.0:1, 9.0:1, 10.0:1, 12.0:1, 15.0:1, 17.5:1, and 20:1.

[0047] Optionally, the reaction temperature is 180–320°C.

[0048] Preferably, the reaction temperature is 230–280°C.

[0049] Optionally, the reaction temperature is selected from any value or a range between 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, 260°C, 270°C, 280°C, 290°C, 300°C, 310°C, and 320°C.

[0050] Optionally, the reaction pressure is 2 to 10 MPa.

[0051] Preferably, the reaction pressure is 4–6 MPa.

[0052] Optionally, the pressure of the reaction is selected from any value of 2MPa, 3MPa, 4MPa, 5MPa, 6MPa, 7MPa, 8MPa, 9MPa, 10MPa or a range between any two.

[0053] Optionally, the mass hourly space velocity (WHSV) of low-carbon olefins and their alcohols is 0.05–1.0 h⁻¹. -1 .

[0054] Preferably, the mass hourly space velocity (MSV) of the low-carbon olefins and their alcohols is 0.1–0.3 h⁻¹. -1 .

[0055] Optionally, the space velocity of the low-carbon olefins and their alcohols is selected from 0.05 h⁻¹. -1 0.1h -1 0.15h -1 0.2h -1 0.25h -1 0.3h -1 0.35h -1 0.4h -1 0.45h -1 0.5h -1 0.55h -1 0.6h -1 0.65h -1 0.7h -1 0.75h -1 0.8h -1 0.85h -1 0.9h -1 0.95h -1 1.0h -1 Any value in the range or any value between the two.

[0056] Optionally, the reactor used for the reaction is a fixed-bed reactor.

[0057] In some embodiments, the raw materials also contain components such as nitrogen, argon, helium, and hydrogen.

[0058] The beneficial effects that this application can produce include:

[0059] The method for producing low-carbon carboxylic acids by carbonylation of low-carbon olefins and alcohols provided in this application uses acidic molecular sieves as catalysts, does not require precious metal catalysts, has low system corrosivity, is easy to separate products, produces less waste, and is easy to engineer as a fixed-bed process, making it suitable for large-scale single-unit production. Detailed Implementation

[0060] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0061] The endpoints and any values ​​of the ranges disclosed in this application are not limited to the precise ranges or values, but should be understood to include those approximations of such ranges or values. For numerical ranges, the endpoint values ​​of the various ranges and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0062] Unless otherwise specified, the raw materials and catalysts used in the embodiments of this application were all purchased commercially.

[0063] Unless otherwise specified, all test methods are standard and all instrument settings are those recommended by the manufacturer.

[0064] The analysis method in the embodiments of this application is as follows:

[0065] The products and unreacted raw materials were analyzed online using an Agilent 7890B gas chromatograph, with its FID detector connected to a PLOT-Q capillary column and its TCD detector connected to a Porapak Q packed column.

[0066] In the embodiments of this application, the conversion rate and selectivity are calculated as follows:

[0067] 1) For the ethylene carbonylation reaction, both the ethylene conversion and propionic acid selectivity are calculated based on the number of carbon moles:

[0068] Ethylene conversion rate = [(molar carbon content of ethylene in feed) - (molar carbon content of ethylene in discharge)] ÷ (molar carbon content of ethylene in feed) × 100%

[0069] Propionic acid selectivity = (number of carbon moles of propionic acid in the discharge) ÷ (number of carbon moles of all products) × 100%

[0070] 2) For the carbonylation reaction of ethanol, both the ethanol conversion and propionic acid selectivity are calculated based on the number of carbon moles. Because ethanol is easily dehydrated to ethylene on acidic molecular sieves, ethylene is treated as a reactant when calculating the conversion and selectivity.

[0071] Ethanol conversion rate = [(number of carbon moles of ethanol in feed) - (number of carbon moles of ethanol and ethylene in discharge)] ÷ (number of carbon moles of ethanol in feed) × 100%

[0072] Propionic acid selectivity = (number of carbon moles of propionic acid in the discharge) ÷ (number of carbon moles of all products) × 100% Note: All products do not include ethylene generated from the dehydration of ethanol.

[0073] 3) For the propylene carbonylation reaction, both the ethylene conversion and propionic acid selectivity are calculated based on the number of carbon moles:

[0074] Propylene conversion rate = [(molar carbon content of propylene in feed) - (molar carbon content of propylene in discharge)] ÷ (molar carbon content of propylene in feed) × 100%

[0075] Isobutyric acid selectivity = (number of carbon moles of isobutyric acid in the discharge) ÷ (number of carbon moles of all products) × 100%

[0076] 4) For the propanol carbonylation reaction, the propanol conversion and isobutyric acid selectivity are calculated based on the number of carbon moles. Because propanol is easily dehydrated to propylene on acidic molecular sieves, propylene is treated as a reactant when calculating the conversion and selectivity.

[0077] Propanol conversion rate = [(molar carbon count of propanol in feed) - (molar carbon count of propanol and propylene in discharge)] ÷ (molar carbon count of propanol in feed) × 100%

[0078] Isobutyric acid selectivity = (number of carbon moles of isobutyric acid in the discharge) ÷ (number of carbon moles of all products) × 100%

[0079] Note: All products do not include propylene produced by the dehydration of propanol.

[0080] Example 1

[0081] 2g of acidic H-ZSM-35 molecular sieve catalyst (SiO2 / Al2O3 = 40, 20-40 mesh particles) was loaded into a container with an inner diameter of [missing information]. In a fixed-bed reactor, the reactor interior contains Thermocouple sheaths were used. Ethylene and carbon monoxide were fed via mass flow meters, while water was fed via a horizontal flow pump. The raw materials were mixed and preheated before entering the catalyst bed for reaction. The products were heated and analyzed online using gas chromatography. Reaction conditions, including reaction temperature (T), reaction pressure (P), molar ratio of carbon monoxide to ethylene (CO:C2H4), molar ratio of water to ethylene (H2O:C2H4), ethylene mass hourly space velocity (WHSV), and reaction results after one day (24h) of operation are shown in Table 1.

[0082] Examples 2-10

[0083] Except for the changes in catalyst and reaction conditions, the experimental steps and apparatus of Examples 2 to 10 are the same as those of Example 1. The reaction conditions and reaction results after running for one day (24 hours) are shown in Table 1.

[0084] Comparative Example 1

[0085] The catalyst in Example 1 was replaced with H-MOR silica molecular sieve (SiO2 / Al2O3 = 15), and the experimental steps and apparatus were the same as in Example 1. The reaction conditions and reaction results after one day (24h) are shown in Table 1.

[0086] Comparative Example 2

[0087] The catalyst in Example 1 was replaced with a Py / H-MOR pyridine adsorption silicate molecular sieve (SiO2 / Al2O3 = 15). Py / H-MOR was prepared by treating H-MOR at 280°C and atmospheric pressure with a mixture of pyridine and nitrogen at a flow rate of 500 ml / min for 6 hours until adsorption saturation. Other experimental procedures and apparatus were consistent with Example 1. The reaction conditions and results after one day (24 h) of operation are shown in Table 1.

[0088] Table 1. Ethylene carbonylation reaction conditions and results of Examples 1-10 and Comparative Examples 1-2

[0089]

[0090] Note: Product selectivity <0.1% means that the product is hardly generated.

[0091] Example 11

[0092] 2g of acidic H-ZSM-35 molecular sieve catalyst (SiO2 / Al2O3 = 40, 20-40 mesh particles) was loaded into a container with an inner diameter of [missing information]. In a fixed-bed reactor, the reactor interior contains Thermocouple sheaths were used. Carbon monoxide was fed via a mass flow meter, while ethanol and water were fed via a horizontal flow pump. The raw materials were mixed and preheated before entering the catalyst bed for reaction. The products were heated and analyzed online using gas chromatography. Reaction conditions, including reaction temperature (T), reaction pressure (P), molar ratio of carbon monoxide to ethanol (CO:C2H5OH), molar ratio of water to ethanol (H2O:C2H5OH), ethanol mass hourly space velocity (WHSV), and reaction results after one day (24h) of operation are shown in Table 2.

[0093] Examples 12-20

[0094] Except for the changes in catalyst and reaction conditions, the experimental steps and apparatus of Examples 12-20 are the same as those of Example 11. The reaction conditions and reaction results after running for one day (24 hours) are shown in Table 2.

[0095] Comparative Examples 3-4

[0096] Except for the catalyst, the experimental procedures and apparatus of Comparative Examples 3 and 4 were the same as those of Example 11. The reaction conditions and reaction results after one day (24 hours) are shown in Table 2. Among them, the catalyst used in Comparative Example 3 was the same as that used in Comparative Example 1, and the catalyst used in Comparative Example 4 was the same as that used in Comparative Example 2.

[0097] Table 2. Ethanol carbonylation reaction conditions and results of Examples 11-20 and Comparative Examples 3-4

[0098]

[0099] Example 21

[0100] 2g of acidic H-ZSM-35 molecular sieve catalyst (SiO2 / Al2O3 = 40, 20-40 mesh particles) was loaded into a container with an inner diameter of [missing information]. In a fixed-bed reactor, the reactor interior contains Thermocouple sheaths were used. Propylene and carbon monoxide were fed via mass flow meters, while water was fed via a horizontal flow pump. The raw materials were mixed and preheated before entering the catalyst bed for reaction. The products were heated and analyzed online using gas chromatography. Reaction conditions, including reaction temperature (T), reaction pressure (P), molar ratio of carbon monoxide to propylene (CO:C3H6), molar ratio of water to propylene (H2O:C3H6), propylene mass hourly space velocity (WHSV), and reaction results after one day (24h) of operation are shown in Table 3.

[0101] Examples 22-30

[0102] Except for the changes in catalyst and reaction conditions, the experimental steps and apparatus of Examples 22-30 are the same as those of Example 21. The reaction conditions and reaction results after running for one day (24 hours) are shown in Table 3.

[0103] Comparative Examples 5-6

[0104] Except for the catalyst, the experimental procedures and apparatus of Comparative Examples 5 and 6 were the same as those of Example 21. The reaction conditions and reaction results after one day (24 hours) are shown in Table 3. Among them, the catalyst used in Comparative Example 5 was the same as that used in Comparative Example 1, and the catalyst used in Comparative Example 6 was the same as that used in Comparative Example 2.

[0105] Table 3. Propylene carbonylation reaction conditions and results of Examples 21-30 and Comparative Examples 5-6

[0106]

[0107] Example 31

[0108] 2g of acidic H-ZSM-35 molecular sieve catalyst (SiO2 / Al2O3 = 40, 20-40 mesh particles) was loaded into a container with an inner diameter of [missing information]. In a fixed-bed reactor, the reactor interior contains Thermocouple sheathing was used. Carbon monoxide was fed via a mass flow meter, while isopropanol and water were fed via a horizontal flow pump. The raw materials were mixed and preheated before entering the catalyst bed for reaction. The products were heated and analyzed online using gas chromatography. The reaction conditions, including reaction temperature (T), reaction pressure (P), molar ratio of carbon monoxide to propanol (CO:C3H7OH), molar ratio of water to propanol (H2O:C3H7OH), propanol mass hourly space velocity (WHSV), and the reaction results after one day (24h) of operation are shown in Table 4.

[0109] Examples 32-40

[0110] Except for the changes in catalyst and reaction conditions, the experimental steps and apparatus of Examples 32-40 are the same as those of Example 31. The reaction conditions and reaction results after running for one day (24 hours) are shown in Table 4.

[0111] Example 41

[0112] In Example 41, the isopropanol in Example 31 was replaced with n-propanol as the feed. The experimental steps and apparatus were the same. The reaction conditions and reaction results after one day (24 hours) of operation are shown in Table 4.

[0113] Comparative Examples 7-8

[0114] Except for the catalyst, the experimental procedures and apparatus of Comparative Examples 7 and 8 were the same as those of Example 31. The reaction conditions and reaction results after one day (24 hours) are shown in Table 4. Among them, the catalyst used in Comparative Example 7 was the same as that used in Comparative Example 1, and the catalyst used in Comparative Example 8 was the same as that used in Comparative Example 2.

[0115] Table 4. Propanol carbonylation reaction conditions and results of Examples 31-41 and Comparative Examples 7-8

[0116]

[0117] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for preparing low-carbon carboxylic acids by carbonylation of low-carbon olefins and their alcohols, characterized in that, The method includes: Raw materials containing low-carbon olefins and their alcohols, as well as carbon monoxide, are passed through a reactor supported by an acidic molecular sieve catalyst to react and obtain a product containing low-carbon carboxylic acids. The low-carbon olefins and their alcohols are selected from at least one of ethylene, propylene, ethanol, n-propanol, and isopropanol; The acidic molecular sieve catalyst is an acidic molecular sieve catalyst with a 10-membered ring channel structure. The acidic molecular sieve catalyst is selected from at least one of the following: acidic molecular sieves with FER structure, acidic molecular sieves with MEL structure, acidic molecular sieves with MFI structure, acidic molecular sieves with MFS structure, acidic molecular sieves with MTT structure, acidic molecular sieves with TON structure, and acidic molecular sieves with MWW structure.

2. The method according to claim 1, characterized in that, When the low-carbon olefin and its alcohol are ethylene or ethanol, the corresponding low-carbon carboxylic acid product is propionic acid; When the low-carbon olefin and its alcohol are propylene, n-propanol or isopropanol, the corresponding low-carbon carboxylic acid product is isobutyric acid.

3. The method according to claim 1, characterized in that, The acidic molecular sieve catalyst is selected from at least one of the following: hydrogen-type ZSM-35 molecular sieve, hydrogen-type ZSM-11 molecular sieve, hydrogen-type ZSM-5 molecular sieve, hydrogen-type ZSM-57 molecular sieve, hydrogen-type ZSM-23 molecular sieve, hydrogen-type ZSM-22 acidic molecular sieve, and hydrogen-type MCM-22 molecular sieve.

4. The method according to claim 1, characterized in that, The silicon-aluminum molecular ratio (SiO2 / Al2O3) of the acidic molecular sieve catalyst is 10–200. Preferably, the silicon-to-aluminum ratio (SiO2 / Al2O3) of the acidic molecular sieve catalyst is 20–80.

5. The method according to claim 1, characterized in that, The molar ratio of carbon monoxide to low-carbon olefins and their alcohols is 5:1 to 200:

1. Preferably, the molar ratio of carbon monoxide to low-carbon olefins and their alcohols is 30:1 to 100:

1.

6. The method according to claim 1, characterized in that, The raw materials also contain water, and the molar ratio of water to low-carbon olefins and their alcohols is 0:1 to 20:1; Preferably, the molar ratio of water to low-carbon olefins and their alcohols is 0:1 to 5:

1.

7. The method according to claim 1, characterized in that, The reaction temperature is 180–320°C; Preferably, the reaction temperature is 230–280°C.

8. The method according to claim 1, characterized in that, The reaction pressure is 2–10 MPa; Preferably, the reaction pressure is 4–6 MPa.

9. The method according to claim 1, characterized in that, The mass hourly space velocity (MSV) of low-carbon olefins and their alcohols is 0.05–1.0 h⁻¹. -1 ; Preferably, the mass hourly space velocity (MSV) of the low-carbon olefins and their alcohols is 0.1–0.3 h⁻¹. -1 .

10. The method according to claim 1, characterized in that, The reactor used for the reaction is a fixed-bed reactor.

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