Production process of medium-chain fatty acid and matched catalyst

Abstract

The invention discloses a production process of medium-chain fatty acid and a matched catalyst. The production process comprises the following steps: carrying out dehydrogenation reaction on medium-chain fatty alcohol under the action of a dehydrogenation catalyst to obtain medium-chain fatty aldehyde, and carrying out oxidation reaction on the medium-chain fatty aldehyde under the action of an oxidation catalyst to obtain the medium-chain fatty acid, the dehydrogenation catalyst is Cu-Zn / Zr (at) S-1, and the oxidation catalyst is Fe-Zn / Zr (at) S-1. The medium-chain fatty acid is continuously prepared by adopting a two-step process, namely the medium-chain fatty alcohol is catalyzed by adopting a dehydrogenation catalyst to dehydrogenate to generate the medium-chain fatty aldehyde, and the medium-chain fatty aldehyde is catalyzed by adopting an oxidation catalyst to oxidize to generate the medium-chain fatty acid; the dehydrogenation catalyst and the oxidation catalyst have universality, have good catalytic effects on dehydrogenation reactions of most medium-chain fatty alcohols and oxidation reactions of medium-chain fatty aldehydes, are high in conversion rate, high in selectivity and few in by-products, have high-temperature stability, and are suitable for industrial production. The large-scale long-time continuous production of the medium-chain fatty acid is facilitated.

Description

Technical Field

[0001] The present invention relates to the technical field of medium-chain fatty acid preparation, and particularly relates to a production process of medium-chain fatty acids and a supporting catalyst. Background Art

[0002] Fatty acids are a class of compounds composed of carbon, hydrogen, and oxygen. As the largest oil chemical, there are more than 3,000 derivatives, and their application scope almost covers all industrial sectors, and they are widely used in industries such as petroleum processing, rubber, plastics, mining, transportation, casting, metal processing, ink, coatings, textiles, food, medicine, daily chemical industry, etc.

[0003] Medium-chain fatty acids are fatty acids classified according to the carbon chain length and having 6-12 carbon atoms on the carbon chain, such as n-hexanoic acid, n-heptanoic acid, n-octanoic acid, isooctanoic acid, n-nonanoic acid, isononanoic acid, n-decanoic acid, octanoic acid, etc. Medium-chain fatty acids have wide applications and the annual demand is increasing year by year.

[0004] Currently, medium-chain fatty acids are usually prepared by a two-step process of dehydrogenation-oxidation of medium-chain fatty alcohols. For example, Chinese Patent Application No. 2024100236751 discloses a new process for producing isooctanoic acid and the catalyst used in this process. It adopts a dual fixed-bed coupling process and fills a Cu-Fe-Bi / SiO 2 dehydrogenation-oxidation bifunctional catalyst to catalyze the dehydrogenation of isooctanol to produce isooctanal and the oxidation of isooctanal to prepare isooctanoic acid respectively. Moreover, isooctanoic acid can be continuously produced, the reaction temperature and pressure requirements are low, the conversion rate of isooctanol is high, and the selectivity of isooctanoic acid is good. However, the catalyst in this method only has high catalytic performance in the process of dehydrogenation-oxidation of isooctanol to prepare isooctanoic acid, and has poor catalytic performance for other medium-chain fatty acids, that is, this catalyst does not have universality. When other types of medium-chain fatty acids need to be prepared, a suitable catalyst needs to be obtained again through multiple experiments, which not only reduces production efficiency but also increases production costs. Summary of the Invention

[0005] To solve the above technical problems, the present invention provides a production process of medium-chain fatty acids and a supporting catalyst. The medium-chain fatty acids are prepared by a two-step process, that is, a dehydrogenation catalyst is used to catalyze the dehydrogenation of medium-chain fatty alcohols to produce medium-chain fatty aldehydes, and an oxidation catalyst is used to catalyze the oxidation of medium-chain fatty aldehydes to produce medium-chain fatty acids. Moreover, the dehydrogenation catalyst and oxidation catalyst of the present invention have universality and have good catalytic effects on the dehydrogenation reaction of most medium-chain fatty alcohols and the oxidation reaction of medium-chain fatty aldehydes, with not only high conversion rates but also high selectivity and few by-products.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is:

[0007] In a first aspect, the present invention provides a production process for medium-chain fatty acids, comprising: dehydrogenating medium-chain fatty alcohols under the action of a dehydrogenation catalyst to obtain medium-chain fatty aldehydes, and oxidizing the medium-chain fatty aldehydes under the action of an oxidation catalyst to obtain medium-chain fatty acids;

[0008] The dehydrogenation catalyst is Cu-Zn / Zr@S-1, and the oxidation catalyst is Fe-Zn / Zr@S-1.

[0009] Further, it specifically includes the steps:

[0010] The medium-chain fatty alcohols are preheated and continuously fed into a first reaction tower filled with a dehydrogenation catalyst for dehydrogenation reaction to obtain medium-chain fatty aldehydes. The medium-chain fatty aldehydes are discharged from the bottom of the tower and condensed to obtain liquid-phase fatty aldehydes. Then, the liquid-phase fatty aldehydes are continuously fed into a second reaction tower filled with an oxidation catalyst for oxidation reaction to obtain medium-chain fatty acids. The medium-chain fatty acids are discharged from the bottom of the tower and condensed to obtain liquid-phase medium-chain fatty acids.

[0011] Further, in the process of dehydrogenating medium-chain fatty alcohols to prepare medium-chain fatty aldehydes, the reaction temperature is 150 - 350 °C, the reaction time is [not provided in the original], and the reaction pressure is 0 - 1 MPa;

[0012] In the process of dehydrogenating medium-chain fatty alcohols to prepare medium-chain fatty aldehydes, an inert gas also needs to be introduced, and the volume ratio of gaseous medium-chain fatty alcohols to the inert gas is 1:0.5 - 10.

[0013] Further, in the process of dehydrogenating medium-chain fatty alcohols to prepare medium-chain fatty aldehydes, the reaction temperature is at least 30 °C higher than the boiling point of the medium-chain fatty alcohols participating in the reaction and higher than the boiling point of the corresponding medium-chain fatty aldehydes.

[0014] Further, in the process of oxidizing medium-chain fatty aldehydes to prepare medium-chain fatty acids, the reaction temperature is 150 - 400 °C, the reaction time is [not provided in the original], and the reaction pressure is 0 - 1 MPa;

[0015] In the process of oxidizing medium-chain fatty aldehydes to prepare medium-chain fatty acids, an inert gas and oxygen also need to be introduced. The volume ratio of gaseous medium-chain fatty aldehydes to the mixed gas of the inert gas and oxygen is 1:0.5 - 10, and the volume ratio of the inert gas to oxygen is 1:1.

[0016] Further, in the process of oxidizing medium-chain fatty aldehydes to prepare medium-chain fatty acids, the reaction temperature is at least 30 °C higher than the boiling point of the medium-chain fatty aldehydes participating in the reaction and higher than the boiling point of the corresponding medium-chain fatty acids.

[0017] Further, in the process of dehydrogenating medium-chain fatty alcohols to prepare medium-chain fatty aldehydes or in the process of oxidizing medium-chain fatty aldehydes to prepare medium-chain fatty acids, the volume space velocity of the medium-chain fatty alcohol or medium-chain fatty aldehyde feed is 50 - 5000 h -1 。

[0018] In a second aspect, the present invention provides a catalyst for preparing medium-chain fatty acids from medium-chain fatty alcohols, comprising a dehydrogenation catalyst Cu-Zn / Zr@S-1 for dehydrogenating medium-chain fatty alcohols to obtain medium-chain fatty aldehydes and an oxidation catalyst Fe-Zn / Zr@S-1 for oxidizing medium-chain fatty aldehydes to obtain medium-chain fatty acids;

[0019] The dehydrogenation catalyst Cu-Zn / Zr@S-1 is composed of a Zr-doped S-1 support and active components Cu and Zn supported on the support, and the loading amount of Cu is 5-20% of the mass of the Zr@S-1 support, and the loading amount of Zn is 1-5% of the mass of the Zr@S-1 support;

[0020] The oxidation catalyst Fe-Zn / Zr@S-1 is composed of a Zr-doped S-1 support and active components Fe and Zn supported on the support, and the loading amount of Fe is 5-50% of the mass of the Zr@S-1 support, and the loading amount of Zn is 1-5% of the mass of the Zr@S-1 support.

[0021] In a third aspect, the present invention further provides a method for preparing a catalyst, comprising the steps of:

[0022] (1) Mixing tetrapropylammonium hydroxide solution with tetraethyl orthosilicate and zirconium propoxide precursor, and continuously stirring under hydrothermal conditions. After tetraethyl orthosilicate is completely hydrolyzed, the mixed solution is placed in a pressure reactor and left to stand at 100-200 °C for 20-30 h, and then the Zr@S-1 support is obtained through filtration, washing, drying, and calcination;

[0023] (2) Mixing and stirring the metal salt solutions of active components Cu and Zn with the Zr@S-1 support until a sludge-like mixture is formed, then first drying and calcining the mixture, and then reducing it under a hydrogen atmosphere to obtain the dehydrogenation catalyst Cu-Zn / Zr@S-1;

[0024] Or mixing and stirring the metal salt solutions of active components Fe and Zn with the Zr@S-1 support until a sludge-like mixture is formed, then first drying and calcining the mixture to obtain the oxidation catalyst Fe-Zn / Zr@S-1.

[0025] Further, in step (1), the mass ratio of tetraethyl orthosilicate to tetrapropylammonium hydroxide is 1:10-50;

[0026] The doping amount of Zr in the Zr@S-1 support prepared in step (1) is 0.5-2% of the mass of tetraethyl orthosilicate;

[0027] In step (1), the calcination temperature is 500-600 °C, and the calcination time is 3-8 h;

[0028] In step (2), the calcination temperature is 400 - 500 °C and the calcination time is 3 - 8 h;

[0029] In step (2), the reduction temperature is 250 - 350 °C and the reduction time is 1 - 3 h.

[0030] The beneficial effects of the present invention are as follows:

[0031] (1) The production process of medium-chain fatty acids provided by the present invention uses a two-step process to prepare medium-chain fatty acids, that is, a dehydrogenation catalyst is used to catalyze the dehydrogenation of medium-chain fatty alcohols to produce medium-chain fatty aldehydes, and an oxidation catalyst is used to catalyze the oxidation of medium-chain fatty aldehydes to produce medium-chain fatty acids. The dehydrogenation catalyst and the oxidation catalyst have high conversion rates for the raw material medium-chain fatty alcohols and medium-chain fatty aldehydes respectively, have high selectivity for the corresponding products medium-chain fatty aldehydes and medium-chain fatty acids, and have few by-products, which is suitable for large-scale continuous production; moreover, the dehydrogenation catalyst and the oxidation catalyst of the present invention have universality and have good catalytic effects on the dehydrogenation reactions of most medium-chain fatty alcohols and the oxidation reactions of medium-chain fatty aldehydes, and are suitable for the production of most medium-chain fatty acids;

[0032] (2) After the dehydrogenation catalyst Cu-Zn / Zr@S-1 and the oxidation catalyst Fe-Zn / Zr@S-1 for the production of medium-chain fatty acids provided by the present invention are operated at high temperature for a long time, the catalytic effects basically remain unchanged, and they have high-temperature stability, thus realizing the long-term continuous production of medium-chain fatty acids. Detailed implementation manners

[0033] The present invention provides a production process of medium-chain fatty acids and a supporting catalyst. To make the purpose, technical solution and effects of the present invention clearer and more definite, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0034] The present invention provides a catalyst for preparing medium-chain fatty acids from medium-chain fatty alcohols, including a dehydrogenation catalyst Cu-Zn / Zr@S-1 for dehydrogenating medium-chain fatty alcohols to obtain medium-chain fatty aldehydes and an oxidation catalyst Fe-Zn / Zr@S-1 for oxidizing medium-chain fatty aldehydes to obtain medium-chain fatty acids;

[0035] Among them, the dehydrogenation catalyst Cu-Zn / Zr@S-1 is composed of a Zr-doped S-1 support and active components Cu and Zn supported on the support. The loading amount of Cu is 5-20% of the mass of the Zr@S-1 support, and the loading amount of Zn is 1-5% of the mass of the Zr@S-1 support. Preferably, the loading amount of Cu is 5-15% of the mass of the Zr@S-1 support, and the loading amount of Zn is 1-3% of the mass of the Zr@S-1 support. More preferably, the loading amount of Cu is 10% of the mass of the Zr@S-1 support, and the loading amount of Zn is 2% of the mass of the Zr@S-1 support.

[0036] The oxidation catalyst Fe-Zn / Zr@S-1 is composed of a Zr-doped S-1 support and active components Fe and Zn supported on the support. The loading amount of Fe is 5-50% of the mass of the Zr@S-1 support, and the loading amount of Zn is 1-5% of the mass of the Zr@S-1 support. Preferably, the loading amount of Fe is 20-30% of the mass of the Zr@S-1 support, and the loading amount of Zn is 1-3% of the mass of the Zr@S-1 support. More preferably, the loading amount of Fe is 25% of the mass of the Zr@S-1 support, and the loading amount of Zn is 2% of the mass of the Zr@S-1 support.

[0037] The preparation method of the above catalyst includes the following steps:

[0038] (1) First, weigh a certain amount of tetrapropylammonium hydroxide and dissolve it in deionized water, mix and stir evenly until the solution becomes a colorless and transparent clear solution. Subsequently, weigh a certain amount of tetraethyl orthosilicate and zirconium n-propoxide and add them to the above solution, and continuously stir at 60-100 °C for 10-15 h to completely hydrolyze tetraethyl orthosilicate. Then, put the above solution into a polytetrafluoroethylene autoclave, first stand at a constant temperature of 100-130 °C for 10-15 h, then adjust the temperature to a constant temperature of 150-180 °C and stand for 10-15 h. Then, take out the product, filter, wash, and dry it, and then calcine it in an air atmosphere at a calcination temperature of 500-600 °C for 3-8 h to obtain the Zr@S-1 support.

[0039] (2) Dissolve the precursor Cu salt and Zn salt in deionized water to obtain an active component precursor solution, and the amount of deionized water added in the active component precursor solution needs to match the saturated water absorption of the support to be added. Then, add the Zr@S-1 support prepared in step (1), continuously stir until a sludge-like mixture is formed, and then continue to stir for 3-10 h. Then, dry the mixture and calcine it in an air atmosphere at 400-500 °C for 3-8 h, and then reduce it in a hydrogen atmosphere at 250-350 °C for 1-3 h to obtain the dehydrogenation catalyst Cu-Zn / Zr@S-1.

[0040] (3) Dissolve the precursor Fe salt and Zn salt in deionized water to obtain an active component precursor solution, and the amount of deionized water added to the active component precursor solution needs to match the saturated water absorption of the carrier to be added. Then add the Zr@S-1 carrier prepared in step (1), continuously stir until a sludge-like mixture is formed, continue to stir for 3 - 10 h, then dry the mixture, and calcine it in an air atmosphere at 400 - 500 °C for 3 - 8 h to obtain the oxidation catalyst Fe-Zn / Zr@S-1.

[0041] Specifically, in the catalyst preparation method of the present invention, the mass ratio of tetraethyl orthosilicate to tetrapropylammonium hydroxide in the above step (1) is 1:10 - 50, preferably 1:10 - 30, and more preferably 1:20.

[0042] Specifically, in the catalyst preparation method of the present invention, the doping amount of Zr in the Zr@S-1 carrier prepared in the above step (1) is 0.5 - 2% of the mass of tetraethyl orthosilicate, preferably 0.5 - 1.5%, and more preferably 1%, to ensure the mechanical strength of the carrier and improve the anti-poisoning ability.

[0043] Specifically, in the catalyst preparation method of the present invention, drying in the above steps (1) and (2) means drying at 100 - 130 °C.

[0044] Specifically, in the catalyst preparation method of the present invention, the precursor Cu salt, Fe salt and Zn salt in the above steps (2) and (3) are at least one of chloride salts, acetate salts, nitrate salts, carbonate salts and sulfate salts.

[0045] The dehydrogenation catalyst and oxidation catalyst of the present invention use Zr@S-1 as the carrier. Compared with other molecular sieve carriers or oxide carriers, the Zr@S-1 carrier has both a regular pore structure and a high specific surface area, and at the same time introduces zirconium elements, enhancing the thermal stability and anti-poisoning ability of the carrier; in addition, the Zr@S-1 carrier also has good ion exchange ability, which can better disperse the active components, thereby improving the overall performance of the catalyst. These characteristics make it show higher activity and selectivity in catalytic reactions, especially suitable for the high-temperature or complex reaction environment in the process of preparing medium-chain fatty acids from medium-chain fatty alcohols in the present invention.

[0046] Based on the dehydrogenation catalyst Cu-Zn / Zr@S-1 and oxidation catalyst Fe-Zn / Zr@S-1 of the present invention, the continuous production of medium-chain fatty acids can be realized. The production process adopts a two-step method, including: the medium-chain fatty alcohol undergoes a dehydrogenation reaction under the action of the dehydrogenation catalyst Cu-Zn / Zr@S-1 to obtain medium-chain fatty aldehydes, and the medium-chain fatty aldehydes undergo an oxidation reaction under the action of the oxidation catalyst Fe-Zn / Zr@S-1 to obtain medium-chain fatty acids. The specific steps are as follows:

[0047] S1. Preheat the medium-chain fatty alcohol and pump it into the first reaction tower filled with a dehydrogenation catalyst through a transfer pump. After the medium-chain fatty alcohol is heated and vaporized at the top of the first reaction tower, it is mixed with an inert gas and enters the reaction zone of the first reaction tower, where it undergoes a dehydrogenation reaction under the action of the catalyst to obtain a gas-phase product. The gas-phase product is discharged from the bottom of the tower and, after condensation, a liquid-phase product of medium-chain fatty aldehyde and a mixed gas-phase product of inert gas and hydrogen are obtained. After the mixed gas-phase product of inert gas and hydrogen is separated, the inert gas can be recycled to the top of the tower for reuse;

[0048] S2. Pump the liquid-phase product of medium-chain fatty aldehyde obtained in step S1 into the second reaction tower filled with an oxidation catalyst through a transfer pump. After the medium-chain fatty aldehyde is heated and vaporized at the top of the second reaction tower, it is mixed with an inert gas and oxygen and enters the reaction zone of the second reaction tower, where it undergoes an oxidation reaction under the action of the catalyst to obtain a gas-phase product. The gas-phase product is discharged from the bottom of the tower and, after condensation, a liquid-phase product of medium-chain fatty acid and a mixed gas-phase product of inert gas and oxygen are obtained. The mixed gas-phase product of inert gas and oxygen can be recycled to the top of the tower for reuse.

[0049] Specifically, in step S1 above, the preheating temperature of the medium-chain fatty alcohol is lower than the boiling point of the medium-chain fatty alcohol.

[0050] Specifically, in the process of preparing medium-chain fatty aldehyde by dehydrogenation of medium-chain fatty alcohol in step S1 above, the reaction temperature is 150 - 350 °C, the reaction pressure is 0 - 1 MPa, and the volume ratio of gas-phase medium-chain fatty alcohol to inert gas is 1:0.5 - 10. Here, the volume ratio refers to the volume of medium-chain fatty alcohol after being heated and vaporized at the top of the tower to the volume of inert gas at the corresponding temperature; preferably, the reaction temperature is at least 30 °C higher than the boiling point of the medium-chain fatty alcohol participating in the reaction and higher than the boiling point of the corresponding medium-chain fatty aldehyde product; preferably, the volume ratio of gas-phase medium-chain fatty alcohol to inert gas is 1:1 - 3.

[0051] Specifically, in the process of preparing medium-chain fatty acid by dehydrogenation of medium-chain fatty aldehyde in step S2 above, the reaction temperature is 150 - 400 °C, the reaction pressure is 0 - 1 MPa, and the volume ratio of gas-phase medium-chain fatty aldehyde to the mixed gas of inert gas and oxygen is 1:0.5 - 10, and the volume ratio of inert gas to oxygen in the mixed gas of inert gas and oxygen is 1:1. Here, the volume ratio refers to the volume of medium-chain fatty aldehyde after being heated and vaporized at the top of the tower to the volume of the mixed gas of inert gas and oxygen at the corresponding temperature; preferably, the reaction temperature is at least 30 °C higher than the boiling point of the medium-chain fatty aldehyde participating in the reaction and higher than the boiling point of the corresponding medium-chain fatty acid; preferably, the volume ratio of gas-phase medium-chain fatty aldehyde to the mixed gas of inert gas and oxygen is 1:4 - 8.

[0052] Specifically, in the process of preparing medium-chain fatty aldehydes by dehydrogenation of medium-chain fatty alcohols in the above step S1 or in the process of preparing medium-chain fatty acids by oxidation of medium-chain fatty aldehydes in the above step S2, the volume space velocity of the gas-phase feeding of medium-chain fatty alcohols or medium-chain fatty aldehydes is 50-5000 h -1 , preferably, the volume space velocity is 500-1500 h -1 .

[0053] Specifically, in the above steps S1 and S2, during condensation, the condensation temperature should be higher than the melting point of the product and much lower than the boiling point of the product. Usually, normal temperature cooling water is used as the condensation medium.

[0054] The present invention does not have special restrictions on the sources of all raw materials, and they can be commercially available.

[0055] In the present invention, the reaction tower can specifically adopt a fixed-bed reactor. And during the process of loading the catalyst, the catalyst needs to be mixed evenly with the inert carrier and then jointly loaded into the catalyst fixed bed of the fixed-bed reactor. The inert carrier can specifically adopt quartz sand, silicon carbide, ceramic balls, inert alumina, etc. And the loading mass of the inert carrier accounts for 20-50% of the total mass of the catalyst and the inert carrier. Preferably, 30-40 wt% of quartz sand is adopted.

[0056] Example 1

[0057] This example provides a catalyst for preparing medium-chain fatty acids from medium-chain fatty alcohols, including a dehydrogenation catalyst Cu-Zn / Zr@S-1 for dehydrogenating medium-chain fatty alcohols to obtain medium-chain fatty aldehydes and an oxidation catalyst Fe-Zn / Zr@S-1 for oxidizing medium-chain fatty aldehydes to obtain medium-chain fatty acids. The preparation process is as follows:

[0058] (1) Weigh 0.25 Kg of tetrapropylammonium hydroxide and dissolve it in 10 L of deionized water, mix and stir evenly until the solution becomes a colorless, transparent and clear solution. Then weigh 5 Kg of tetraethyl orthosilicate and 0.18 Kg of zirconium propoxide and add them to the above solution. Continuously stir at 80 °C for 12 h to completely hydrolyze tetraethyl orthosilicate; then pour the above solution into a polytetrafluoroethylene autoclave, stand still at a constant temperature of 120 °C for 12 h, and then adjust the temperature to a constant temperature of 170 °C and stand still for 12 h; then take out the product, filter, wash, dry it at 120 °C for 12 h, and then calcine it in the air at 550 °C for 5 h to obtain the Zr-doped S-1 support;

[0059] (2) Weigh 5 Kg of the Zr@S-1 support prepared above, and weigh 1.46 Kg of Cu(NO 3 ) 2 and 0.29 Kg of Zn(NO 3 ) 2Dissolve it in 6.5 L of deionized water, and at this time, the volume of the solution just reaches the saturated water absorption capacity of the used Zr@S-1 support; then add the Zr@S-1 support to the stirring kettle containing the precursor solution, continuously stir until a sludge-like mixture is formed, and continue stirring for 6 h; then dry the mixture at 120 °C for 3 h, calcine it in air at 450 °C for 5 h, and then reduce it in a hydrogen atmosphere at 300 °C for 2 h to obtain a 10% Cu-2% Zn / Zr@S-1 dehydrogenation catalyst;

[0060] (3) Weigh 5 Kg of the above-prepared Zr@S-1 support, and dissolve 5.40 Kg of Fe(NO 3 ) 3 and 0.29 Kg of Zn(NO 3 ) 2 in 6.5 L of deionized water. At this time, the volume of the solution just reaches the saturated water absorption capacity of the used Zr@S-1 support; then add the Zr@S-1 support to the stirring kettle containing the precursor solution, continuously stir until a sludge-like mixture is formed, and continue stirring for 6 h; then dry the mixture at 120 °C for 3 h, and calcine it in air at 450 °C for 5 h to obtain a 25% Fe-2% Zn / Zr@S-1 dehydrogenation catalyst.

[0061] Example 2

[0062] This example provides a catalyst for preparing medium-chain fatty acids from medium-chain fatty alcohols, including a dehydrogenation catalyst Cu-Zn / Zr@S-1 for dehydrogenating medium-chain fatty alcohols to obtain medium-chain fatty aldehydes and an oxidation catalyst Fe-Zn / Zr@S-1 for oxidizing medium-chain fatty aldehydes to obtain medium-chain fatty acids. The difference from Example 1 is that:

[0063] In the dehydrogenation catalyst Cu-Zn / Zr@S-1 prepared in this example, the loading amount of Cu is 5% and the loading amount of Zn is 3%;

[0064] In the oxidation catalyst Fe-Zn / Zr@S-1 prepared in this example, the loading amount of Fe is 20% and the loading amount of Zn is 5%.

[0065] Example 3

[0066] This example provides a catalyst for preparing medium-chain fatty acids from medium-chain fatty alcohols, including a dehydrogenation catalyst Cu-Zn / Zr@S-1 for dehydrogenating medium-chain fatty alcohols to obtain medium-chain fatty aldehydes and an oxidation catalyst Fe-Zn / Zr@S-1 for oxidizing medium-chain fatty aldehydes to obtain medium-chain fatty acids. The difference from Example 1 is that:

[0067] In the dehydrogenation catalyst Cu-Zn / Zr@S-1 prepared in this example, the loading amount of Cu is 15% and the loading amount of Zn is 1%;

[0068] In the oxidation catalyst Fe-Zn / Zr@S-1 prepared in this example, the loading amount of Fe is 30% and the loading amount of Zn is 1%.

[0069] Example 4

[0070] In this example, isononanoic acid was prepared by using the dehydrogenation catalyst Cu-Zn / Zr@S-1 and the oxidation catalyst Fe-Zn / Zr@S-1 prepared in Example 1. The production process is as follows:

[0071] S1. Preheat isononanol to 150 °C in the raw material tank, pump it into the top of the first reaction tower filled with the dehydrogenation catalyst through a plunger pump. The raw material is vaporized by the preheater at the top of the tower and mixed with nitrogen. The volume ratio of gaseous isononanol to nitrogen is 1:2. The mixed gas enters the reaction zone of the first reaction tower. Control the volume space velocity of the gaseous isononanol raw material feed to be 1000 h -1 , the reaction temperature is 210 °C, adjust the back pressure valve, and set the pressure inside the tower to 0.25 MPa; after the reaction is completed, the gaseous product is discharged from the bottom of the tower, condensed by a coil condenser, and the cooling medium is normal temperature cooling water. After condensation, a liquid-phase product and a gaseous product are obtained. Among them, the liquid-phase product is isononanal and is collected as the raw material for step S2. The gaseous product is a mixed gas of nitrogen and hydrogen. After the mixed gas of nitrogen and hydrogen is separated, nitrogen can be recycled and reused;

[0072] S2. Pump the liquid-phase product of isononanal obtained in step S1 into the second reaction tower filled with the oxidation catalyst through a plunger pump. The raw material is vaporized by the preheater at the top of the tower and mixed with a nitrogen / oxygen mixed gas. The volume ratio of gaseous isononanal to the nitrogen / oxygen mixed gas is 1:5. The volume ratio of nitrogen to oxygen in the nitrogen / oxygen mixed gas is 1:1. The mixed gas enters the reaction zone of the second reaction tower. Control the volume space velocity of the gaseous isononanal raw material feed to be 1000 h -1 , the reaction temperature is 260 °C, adjust the back pressure valve, and set the pressure inside the tower to 0.5 MPa; after the reaction is completed, the gaseous product is discharged from the bottom of the tower, condensed by a coil condenser, and the cooling medium is normal temperature cooling water. After condensation, a liquid-phase product and a gaseous product are obtained. Among them, the liquid-phase product is isononanoic acid and is collected, and the gaseous product is a nitrogen / oxygen mixed gas. After the nitrogen / oxygen mixed gas is separated, it can be recycled and reused.

[0073] Example 5

[0074] In this example, n-hexanoic acid was prepared by using the dehydrogenation catalyst Cu-Zn / Zr@S-1 and the oxidation catalyst Fe-Zn / Zr@S-1 prepared in Example 1. The production process is as follows:

[0075] S1. Preheat n-hexanol to 110°C in the raw material tank, pump it into the top of the first reaction tower filled with dehydrogenation catalyst through a plunger pump. The raw material is vaporized by the top preheater and mixed with nitrogen. The volume ratio of gaseous n-hexanol to nitrogen is 1:2. The mixed gas enters the reaction zone of the first reaction tower. Control the volume space velocity of the gaseous n-hexanol raw material feed to be 1000 h -1 , the reaction temperature is 180°C, adjust the back pressure valve, and set the pressure inside the tower to 0.25 MPa. After the reaction is completed, the gaseous product is discharged from the bottom of the tower, condensed by a coil condenser, and the cooling medium is normal temperature cooling water. After condensation, a liquid product and a gaseous product are obtained. Among them, the liquid product is n-hexanal and is collected as the raw material for step S2. The gaseous product is a mixed gas of nitrogen and hydrogen. After the mixed gas of nitrogen and hydrogen is separated, nitrogen can be recycled and reused;

[0076] S2. Pump the liquid n-hexanal product obtained in step S1 into the second reaction tower filled with oxidation catalyst through a plunger pump. The raw material is vaporized by the top preheater and mixed with a nitrogen / oxygen mixed gas. The volume ratio of gaseous n-hexanal to the nitrogen / oxygen mixed gas is 1:5, and the volume ratio of nitrogen to oxygen in the nitrogen / oxygen mixed gas is 1:1. The mixed gas enters the reaction zone of the second reaction tower. Control the volume space velocity of the gaseous n-hexanal raw material feed to be 1000 h -1 , the reaction temperature is 240°C, adjust the back pressure valve, and set the pressure inside the tower to 0.5 MPa. After the reaction is completed, the gaseous product is discharged from the bottom of the tower, condensed by a coil condenser, and the cooling medium is normal temperature cooling water. After condensation, a liquid product and a gaseous product are obtained. Among them, the liquid product is n-hexanoic acid and is collected, and the gaseous product is a nitrogen / oxygen mixed gas. After the nitrogen / oxygen mixed gas is separated, it can be recycled and reused.

[0077] Example 6

[0078] This example uses the dehydrogenation catalyst Cu-Zn / Zr@S-1 and oxidation catalyst Fe-Zn / Zr@S-1 prepared in Example 1 to prepare n-decanoic acid. The production process is as follows:

[0079] S1. Preheat n-decanol to 200°C in the raw material tank, pump it into the top of the first reaction tower filled with dehydrogenation catalyst through a plunger pump. The raw material is vaporized by the top preheater and mixed with nitrogen. The volume ratio of gaseous n-decanol to nitrogen is 1:2. The mixed gas enters the reaction zone of the first reaction tower. Control the volume space velocity of the gaseous n-decanol raw material feed to be 1000 h -1, the reaction temperature is 260 °C. Adjust the back pressure valve to set the pressure inside the tower to 0.25 MPa. After the reaction is completed, the gaseous product is discharged from the bottom of the tower and condensed via a coil condenser. The cooling medium is cooling water at 30 °C. After condensation, a liquid product and a gaseous product are obtained. Among them, the liquid product is n-decyl aldehyde and is collected as the raw material for step S2. The gaseous product is a mixed gas of nitrogen and hydrogen. After the mixed gas of nitrogen and hydrogen is separated, nitrogen can be recycled and reused;

[0080] S2. Pump the liquid n-decyl aldehyde product obtained in step S1 into the second reaction tower filled with an oxidation catalyst through a plunger pump. The top preheater vaporizes the raw material and mixes it with a nitrogen / oxygen mixed gas. The volume ratio of gaseous n-decyl aldehyde to the nitrogen / oxygen mixed gas is 1:5. The volume ratio of nitrogen to oxygen in the nitrogen / oxygen mixed gas is 1:1. The mixed gas enters the reaction zone of the second reaction tower. Control the volume space velocity of the gaseous feed of the n-decyl aldehyde raw material to be 1000 h -1 , the reaction temperature is 300 °C. Adjust the back pressure valve to set the pressure inside the tower to 0.5 MPa. After the reaction is completed, the gaseous product is discharged from the bottom of the tower and condensed via a coil condenser. The cooling medium is cooling water at 50 °C. After condensation, a liquid product and a gaseous product are obtained. Among them, the liquid product is n-decanoic acid and is collected. The gaseous product is a nitrogen / oxygen mixed gas, and after the nitrogen / oxygen mixed gas is separated, it can be recycled and reused.

[0081] Example 7

[0082] In this example, n-heptanoic acid is prepared using the dehydrogenation catalyst Cu-Zn / Zr@S-1 and the oxidation catalyst Fe-Zn / Zr@S-1 prepared in Example 1. The production process is as follows:

[0083] S1. Preheat n-heptanol to 150 °C in the raw material tank and pump it into the top of the first reaction tower filled with a dehydrogenation catalyst through a plunger pump. The top preheater vaporizes the raw material and mixes it with nitrogen. The volume ratio of gaseous n-heptanol to nitrogen is 1:2. The mixed gas enters the reaction zone of the first reaction tower. Control the volume space velocity of the gaseous feed of the n-heptanol raw material to be 1000 h -1 , the reaction temperature is 210 °C. Adjust the back pressure valve to set the pressure inside the packed tower to 0.25 MPa. After the reaction is completed, the gaseous product is discharged from the bottom of the tower and condensed via a coil condenser. The cooling medium is normal temperature cooling water. After condensation, a liquid product and a gaseous product are obtained. Among them, the liquid product is n-heptyl aldehyde and is collected as the raw material for step S2. The gaseous product is a mixed gas of nitrogen and hydrogen. After the mixed gas of nitrogen and hydrogen is separated, nitrogen can be recycled and reused;

[0084] S2. Pump the liquid-phase product of n-heptanal obtained in step S1 into the second reaction tower filled with an oxidation catalyst through a plunger pump. The top preheater vaporizes the raw material and mixes it with a nitrogen / oxygen mixed gas. The volume ratio of gaseous n-heptanal to the nitrogen / oxygen mixed gas is 1:5, and the volume ratio of nitrogen to oxygen in the nitrogen / oxygen mixed gas is 1:1. The mixed gas enters the reaction zone of the second reaction tower. Control the volume space velocity of the gaseous n-heptanal raw material feed to be 500 h -1 , the reaction temperature is 260 °C, adjust the back pressure valve, and set the pressure inside the tower to 0.5 MPa; after the reaction is completed, the gaseous product is discharged from the bottom of the tower and condensed by a coil condenser. The cooling medium is normal temperature cooling water. After condensation, a liquid-phase product and a gaseous product are obtained. Among them, the liquid-phase product is n-heptanoic acid and is collected, and the gaseous product is a nitrogen / oxygen mixed gas. After separation, the nitrogen / oxygen mixed gas can be recycled and reused.

[0085] Example 8

[0086] In this example, lauric acid was prepared using the dehydrogenation catalyst Cu-Zn / Zr@S-1 and the oxidation catalyst Fe-Zn / Zr@S-1 prepared in Example 1. The production process is as follows:

[0087] S1. Preheat lauryl alcohol to 200 °C in a raw material tank and pump it into the top of the first reaction tower filled with a dehydrogenation catalyst through a plunger pump. The top preheater vaporizes the raw material and mixes it with nitrogen. The volume ratio of gaseous lauryl alcohol to nitrogen is 1:2. The mixed gas enters the reaction zone of the first reaction tower. Control the volume space velocity of the gaseous lauryl alcohol raw material feed to be 1000 h -1 , the reaction temperature is 290 °C, adjust the back pressure valve, and set the pressure inside the tower to 0.25 MPa; after the reaction is completed, the gaseous product is discharged from the bottom of the tower and condensed by a coil condenser. The cooling medium is 50 °C cooling water. After condensation, a liquid-phase product and a gaseous product are obtained. Among them, the liquid-phase product is lauraldehyde and is collected as the raw material for step S2, and the gaseous product is a mixed gas of nitrogen and hydrogen. After separation of the nitrogen and hydrogen mixed gas, nitrogen can be recycled and reused;

[0088] S2. Pump the liquid-phase product of lauraldehyde obtained in step S1 into the second reaction tower filled with an oxidation catalyst through a plunger pump. The top preheater vaporizes the raw material and mixes it with a nitrogen / oxygen mixed gas. The volume ratio of gaseous lauraldehyde to the nitrogen / oxygen mixed gas is 1:5, and the volume ratio of nitrogen to oxygen in the nitrogen / oxygen mixed gas is 1:1. The mixed gas enters the reaction zone of the second reaction tower. Control the volume space velocity of the gaseous lauraldehyde raw material feed to be 1500 h -1, the reaction temperature is 260 °C. Adjust the back pressure valve to set the pressure inside the tower to 0.5 MPa. After the reaction is completed, the gaseous product is discharged from the bottom of the tower and condensed via a coil condenser. The cooling medium is 70 °C cooling water. After condensation, a liquid product and a gaseous product are obtained. Among them, the liquid product is lauric acid and is collected. The gaseous product is a nitrogen / oxygen mixed gas, and the nitrogen / oxygen mixed gas can be recycled and reused after separation.

[0089] Example 9

[0090] In this example, isooctanol was prepared using the dehydrogenation catalyst Cu-Zn / Zr@S-1 and the oxidation catalyst Fe-Zn / Zr@S-1 prepared in Example 2. The production process was the same as that in Example 4, and the oxidation temperature was controlled at 220 °C and the dehydrogenation temperature was controlled at 260 °C.

[0091] Example 10

[0092] In this example, n-nonanol was prepared using the dehydrogenation catalyst Cu-Zn / Zr@S-1 and the oxidation catalyst Fe-Zn / Zr@S-1 prepared in Example 2. The production process was the same as that in Example 4, and the oxidation temperature was controlled at 240 °C and the dehydrogenation temperature was controlled at 300 °C.

[0093] Example 11

[0094] In this example, n-octanol was prepared using the dehydrogenation catalyst Cu-Zn / Zr@S-1 and the oxidation catalyst Fe-Zn / Zr@S-1 prepared in Example 3. The production process was the same as that in Example 4, and the oxidation temperature was controlled at 240 °C and the dehydrogenation temperature was controlled at 270 °C.

[0095] Samples were taken from the dehydrogenated products obtained in the dehydrogenation step of Examples 4-11 and the medium-chain fatty acids in the oxidized products obtained in the oxidation step. Among them, samples were taken at different running times in Example 4, and samples were taken after running for 1 h in Examples 5-11. The samples were analyzed by gas chromatography, and the corresponding conversion rates and selectivities were calculated, as shown in Table 1 below.

[0096] Table 1 Catalytic reaction results of the dehydrogenation-oxidation tandem coupling process in Examples 4-11

[0097]

[0098] As can be seen from Table 1 above: The dehydrogenation catalyst Cu-Zn / Zr@S-1 and the oxidation catalyst Fe-Zn / Zr@S-1 of the present invention both exhibit excellent catalytic performance for the preparation of medium-chain fatty acids from various medium-chain fatty alcohols, showing universality. Moreover, the conversion rates of the corresponding raw material fatty alcohols and fatty aldehydes are high, and the selectivities of the corresponding products fatty aldehydes and fatty acids are high. At the same time, after long-term high-temperature operation, the catalytic effects of the dehydrogenation catalyst Cu-Zn / Zr@S-1 and the oxidation catalyst Fe-Zn / Zr@S-1 basically remain unchanged, indicating that the dehydrogenation catalyst Cu-Zn / Zr@S-1 and the oxidation catalyst Fe-Zn / Zr@S-1 also exhibit high-temperature stability in the preparation of medium-chain fatty acids from medium-chain fatty alcohols, thus realizing the long-term continuous production of medium-chain fatty acids.

[0099] It should be noted that the parts not described in the present invention can be realized by adopting or referring to the existing technologies.

[0100] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by those skilled in the art within the scope of the essence of the present invention should also fall within the protection scope of the present invention.

Claims

1. A production process of medium-chain fatty acids, characterized in that: include: The medium-chain fatty alcohol undergoes a dehydrogenation reaction under the action of a dehydrogenation catalyst to obtain a medium-chain fatty aldehyde, and the medium-chain fatty aldehyde undergoes an oxidation reaction under the action of an oxidation catalyst to obtain a medium-chain fatty acid; The dehydrogenation catalyst is Cu-Zn / Zr@S-1, and the oxidation catalyst is Fe-Zn / Zr@S-1.

2. A process for producing medium-chain fatty acids according to claim 1, characterized in that: The specific steps include: After preheating, the medium-chain fatty alcohol is continuously introduced into a first reaction tower filled with a dehydrogenation catalyst for dehydrogenation reaction to obtain medium-chain fatty aldehydes, which are discharged from the bottom of the tower and condensed to obtain liquid fatty aldehydes; then the liquid fatty aldehydes are continuously introduced into a second reaction tower filled with an oxidation catalyst for oxidation reaction to obtain medium-chain fatty acids, which are discharged from the bottom of the tower and condensed to obtain liquid medium-chain fatty acids.

3. The production process of a medium-chain fatty acid according to claim 1, characterized in that: In the process of dehydrogenating medium-chain fatty alcohols to prepare medium-chain fatty aldehydes, the reaction temperature is 150-350°C and the reaction pressure is 0-1MPa; In the process of dehydrogenating medium-chain fatty alcohol to prepare medium-chain fatty aldehyde, inert gas needs to be introduced, and the volume ratio of gas phase medium-chain fatty alcohol to inert gas is 1:0.5-10.

4. A process for producing medium-chain fatty acids according to claim 3, characterized in that: In the process of preparing medium-chain fatty aldehyde by dehydrogenation of medium-chain fatty alcohol, the reaction temperature is at least 30° C. higher than the boiling point of the medium-chain fatty alcohol involved in the reaction, and higher than the boiling point of the corresponding medium-chain fatty aldehyde.

5. The production process of a medium-chain fatty acid according to claim 1, characterized in that: In the process of oxidizing medium-chain fatty aldehydes to prepare medium-chain fatty acids, the reaction temperature is 150-400°C and the reaction pressure is 0-1MPa; In the process of oxidizing medium-chain fatty aldehydes to prepare medium-chain fatty acids, inert gas and oxygen need to be introduced. The volume ratio of the gaseous medium-chain fatty aldehyde to the mixed gas of inert gas and oxygen is 1:0.5-10, and the volume ratio of inert gas to oxygen is 1:

1.

6. A process for producing medium-chain fatty acids according to claim 5, characterized in that: In the process of oxidizing medium-chain fatty aldehydes to prepare medium-chain fatty acids, the reaction temperature is at least 30° C. higher than the boiling point of the medium-chain fatty aldehydes involved in the reaction, and higher than the boiling point of the corresponding medium-chain fatty acids.

7. A process for producing medium-chain fatty acids according to any one of claims 1 to 6, characterized in that: In the process of dehydrogenating medium-chain fatty alcohols to prepare medium-chain fatty aldehydes or in the process of oxidizing medium-chain fatty aldehydes to prepare medium-chain fatty acids, the volumetric space velocity of the medium-chain fatty alcohol or medium-chain fatty aldehyde feed is 50 to 5000 h -1 .

8. A catalyst for preparing medium-chain fatty acids from medium-chain fatty alcohols, characterized in that: Including a dehydrogenation catalyst Cu-Zn / Zr@S-1 for dehydrogenation of medium-chain fatty alcohol to obtain medium-chain fatty aldehydes and an oxidation catalyst Fe-Zn / Zr@S-1 for oxidation of medium-chain fatty aldehydes to obtain medium-chain fatty acids; The dehydrogenation catalyst Cu-Zn / Zr@S-1 is composed of a Zr-doped S-1 carrier and active components Cu and Zn loaded on the carrier, wherein the loading amount of Cu is 5-20% of the weight of the Zr@S-1 carrier, and the loading amount of Zn is 1-5% of the weight of the Zr@S-1 carrier; The oxidation catalyst Fe-Zn / Zr@S-1 consists of a Zr-doped S-1 carrier and active components Fe and Zn loaded on the carrier, wherein the loading amount of Fe is 5-50% of the mass of the Zr@S-1 carrier, and the loading amount of Zn is 1-5% of the mass of the Zr@S-1 carrier.

9. The method for preparing a catalyst according to claim 8, characterized in that: Includes steps: (1) mixing tetrapropylammonium hydroxide solution with tetraethyl orthosilicate and zirconium n-propoxide precursor, and continuously stirring under hydrothermal conditions, after tetraethyl orthosilicate is completely hydrolyzed, placing the mixed solution in an autoclave, standing at 100-200° C. for 20-30 hours, filtering, washing, drying, and calcining to obtain a Zr@S-1 carrier; (2) mixing and stirring the metal salt solution of active components Cu and Zn with the Zr@S-1 carrier until a sludge-like mixture is formed, and then drying and calcining the mixture, and then reducing it under a hydrogen atmosphere to obtain a dehydrogenation catalyst Cu-Zn / Zr@S-1; Alternatively, a metal salt solution of active components Fe and Zn is mixed and stirred with the Zr@S-1 carrier until a sludge-like mixture is formed, and then the mixture is dried and calcined to obtain an oxidation catalyst Fe-Zn / Zr@S-1.

10. The method for preparing a catalyst according to claim 9, characterized in that: In the step (1), the mass ratio of tetraethyl orthosilicate to tetrapropylammonium hydroxide is 1:10-50; The doping amount of Zr in the Zr@S-1 carrier prepared in step (1) is 0.5-2% of the mass of tetraethyl orthosilicate; In the step (1), the calcination temperature is 500-600° C. and the calcination time is 3-8 hours; In the step (2), the calcination temperature is 400-500° C. and the calcination time is 3-8 hours; In the step (2), the reduction temperature is 250-350° C. and the reduction time is 1-3 hours.

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