Catalyst for preparing high-purity oleic acid as well as preparation method and application of catalyst

Abstract

The invention belongs to the technical field of catalysts, and discloses a catalyst for preparing high-purity oleic acid as well as a preparation method and application of the catalyst. According to the catalyst for preparing the high-purity oleic acid, a SiO2 molecular sieve serves as a carrier, Pd and Pt serve as active components, and the molar ratio of Pd to Pt is 3: 2-4: 1. According to the invention, by controlling the carrier, the active component and respective dosages, the prepared catalyst can perform selective hydrogenation on vegetable oil containing linoleic acid and / or linolenic acid to obtain high-purity oleic acid.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and particularly to a catalyst for preparing high-purity oleic acid, a preparation method thereof, and an application thereof. Background Art

[0002] There are various preparation processes for high-purity oleic acid, each having its own advantages and disadvantages. The crystallization and pressure filtration method and the rectification method are relatively commonly used methods in current industrial production, but there are problems such as high production cost, high energy consumption, and low product yield. Although the organic solvent method and the urea complexation method have good separation effects, their high costs limit their large-scale application. The enzyme hydrolysis method has the characteristics of environmental protection and high efficiency, but the problems of enzyme cost and stability still need to be solved.

[0003] Industrial hydrogenation can be considered for oleic acid preparation, that is, under the action of a catalyst, polyunsaturated fatty acids (such as linoleic acid and linolenic acid) in industrial oleic acid are partially reduced to oleic acid. However, in the actual hydrogenation process, the hydrogenation product is often saturated stearic acid rather than oleic acid. The specific reasons are as follows: 1) Influence of surface adsorption and reaction kinetics of the catalyst: During the catalytic hydrogenation process, linoleic acid or linolenic acid molecules need to be adsorbed on the surface of a metal catalyst (such as Ni, Pd, Pt) to bring the double bond into contact with active hydrogen atoms. Since linoleic acid contains two double bonds, its molecular structure is more easily strongly adsorbed on the catalyst surface, resulting in consecutive hydrogenation of the two double bonds on the catalyst surface. The intermediate product oleic acid (with one double bond) still has adsorption ability and is likely to remain on the catalyst surface during the reaction rather than desorbing into the solution. Therefore, once hydrogenation starts, the reaction tends to proceed to completion, generating fully saturated stearic acid.

[0004] 2) Influence of reaction conditions: Industrial hydrogenation usually uses high temperature, high pressure, and excessive hydrogen, which accelerate the complete progress of the reaction. Even if the first double bond is hydrogenated to form oleic acid, the high hydrogen concentration and catalyst activity in the system will still drive the rapid hydrogenation of the second double bond, inhibiting the accumulation of intermediate products.

[0005] 3) Synergistic effect of thermodynamics and kinetics: Thermodynamically, stearic acid (fully saturated) is more stable than oleic acid (monounsaturated). Kinetically, since the double bonds of polyunsaturated fatty acids (linoleic acid) are more active and the catalyst has a lower activation energy for them, the hydrogenation rate of the two double bonds is much higher than the further hydrogenation rate of the oleic acid with a single double bond. Therefore, in the continuous reaction, the complete hydrogenation rate of linoleic acid is faster, and it is difficult to accumulate the intermediate product oleic acid.

[0006] Therefore, how to selectively hydrogenate polyunsaturated fatty acids to prepare high-purity oleic acid is an urgent problem to be solved at present. Summary of the Invention

[0007] To solve the problems in the background art, the present invention provides a catalyst for preparing high-purity oleic acid, a preparation method thereof, and an application thereof. This catalyst can selectively hydrogenate linoleic acid to prepare oleic acid with a high conversion rate.

[0008] To achieve the above object, the first technical solution adopted by the present invention is: A catalyst for preparing high-purity oleic acid, which uses SiO 2 molecular sieve as a carrier, Pd and Pt as active components, and the molar ratio of Pd to Pt is 3:2 - 4:1.

[0009] By controlling the active components, the carrier, and their dosages, the present invention can selectively hydrogenate only one double bond of polyunsaturated fatty acids to prepare high-purity oleic acid. It has been verified that changing the carrier component, the active component, or the dosage will reduce the content of oleic acid in the hydrogenation reaction product and generate stearic acid.

[0010] Preferably, the active component accounts for 0.1% - 0.3% of the weight of the carrier.

[0011] The second technical solution adopted by the present invention is: A preparation method of a catalyst for preparing high-purity oleic acid, and the preparation method of this catalyst is: impregnate the carrier in an aqueous solution mixed with a Pd complex and a Pt complex, and after the impregnation is completed, dry and calcine the carrier.

[0012] Preferably, the Pd complex and the Pt complex are palladium tetrachloride and chloroplatinic acid hexahydrate respectively. Preferably, during the impregnation process, the temperature is generally controlled at room temperature to 80°C. Stirring can be carried out during the impregnation process, and the impregnation time is generally about 2 hours until the carrier fully absorbs the active components.

[0013] Preferably, the drying temperature is 120 - 150°C.

[0014] Preferably, the calcination temperature is 500 - 900°C.

[0015] The third technical solution adopted by the present invention is: Application of a catalyst for preparing high-purity oleic acid in the continuous selective hydrogenation to prepare high-purity oleic acid.

[0016] Preferably, the preparation method of high-purity oleic acid is: using a vegetable oil containing linoleic acid and / or linolenic acid as a raw material, and carrying out a hydrogenation reaction under the action of the catalyst for preparing high-purity oleic acid.

[0017] Preferably, the raw material includes palm kernel oil oleic acid and / or soybean oil oleic acid.

[0018] Preferably, the temperature of the hydrogenation reaction is 120 - 160 °C, the hydrogen pressure is 0.1 - 0.5 MPa, and the reaction time is 1 - 4 hours.

[0019] Preferably, the temperature of the hydrogenation reaction is 120 - 160 °C, the hydrogen pressure is 0.3 MPa, and the reaction time is 2 hours.

[0020] Compared with the prior art, the present invention has the following beneficial effects: By controlling the carrier, the active ingredient, and their respective dosages, the catalyst prepared by the present invention can selectively hydrogenate vegetable oils containing linoleic acid and / or linolenic acid to obtain high-purity oleic acid with high conversion rates. Detailed implementation manners

[0021] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with specific implementation manners. It should be understood that these descriptions are exemplary and are not intended to limit the scope of the present invention. In addition, in the following descriptions, descriptions of well-known structures and technologies are omitted to avoid unnecessarily confusing the concepts of the present invention. For those not specified in the examples, conventional conditions or conditions recommended by the manufacturer are used. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0022] Example 1 Preparation and application of the catalyst Preparation of the catalyst: 1) Preparation of the solution: According to the molar ratio of 3:2 of Pd and Pt in the catalyst, palladium chloride and chloroplatinic acid hexahydrate were accurately weighed and dissolved in deionized water to prepare a 1% concentration mixed solution; 2) Impregnation process: The silica carrier (such as fumed silica or precipitated silica) was placed in the prepared mixed solution and stirred and impregnated at room temperature to 80 °C for 2 hours to allow the carrier to fully adsorb metal ions; 3) Drying: After impregnation, the carrier was taken out of the solution and dried at 120 °C to remove the solvent; 4) Calcination: The dried carrier was calcined in an inert gas atmosphere at 500 °C for 4 hours to obtain the catalyst 0.1% Pd 3 Pt 2 / SiO 2 ("0.1%" means that the active ingredient accounts for 0.1% of the weight of the carrier).

[0023] Application of the catalyst: Hydrogenation of palm kernel oil oleic acid Raw materials: Palm kernel oil fatty acid (oleic acid content 81.15%, linoleic acid 14.85%, linolenic acid 0.0%); Catalyst: 0.1% Pd 3 Pt 2 / SiO 2 ; Hydrogenation reaction conditions: The temperature range is 80 - 180 °C, as shown in Table 1 specifically, hydrogen pressure 0.3 MPa, reaction time 2 hours.

[0024] The products obtained under the above different hydrogenation conditions were detected, including the weight percentage of saturated fatty acid (C18:0), oleic acid (C18:1) and linoleic acid (C18:2) in the products, and the results are shown in Table 1.

[0025] Table 1 Results of hydrogenation of palm kernel oil fatty acid at different temperatures .

[0026] As can be seen from Table 1, after selective hydrogenation, the oleic acid content in soybean oil fatty acid increased significantly.

[0027] Example 2 Preparation and application of catalyst The preparation of the catalyst refers to Example 1, in which the molar ratio of Pd to Pt is 4:1, and the active component accounts for 0.1% of the weight of the carrier, and the obtained catalyst is 0.1% Pd 4 Pt / SiO 2 .

[0028] Application of the catalyst: Hydrogenation of soybean oil fatty acid Raw materials: Soybean oil fatty acid (oleic acid content 32.15%, linoleic acid 56.89%, linolenic acid 1.87%); Catalyst: 0.1% Pd 4 Pt / SiO 2 ; Hydrogenation reaction conditions: Temperature 80 - 180 °C, as shown in Table 2 specifically, hydrogen pressure 0.5 MPa, reaction time 2 hours.

[0029] The products obtained under the above different hydrogenation conditions were detected, including the weight percentage of saturated fatty acid (C18:0), oleic acid (C18:1), linoleic acid (C18:2) and linolenic acid (C18:3) in the products, and the results are shown in Table 2.

[0030] Table 2 Results of hydrogenation of soybean oil fatty acid at different temperatures .

[0031] Example 3 Compared with Example 1, the only difference is that the percentage of the active ingredient in the carrier by weight is modified to 0.3%, and catalyst 0.3%Pd is prepared. 3 Pt 2 / SiO 2 。The final product was detected according to the hydrogenation reaction conditions in Example 1, and the results are shown in Table 3.

[0032] Table 3 Results of hydrogenation of palm kernel oil fatty acid at different temperatures 。

[0033] Comparative Example 1 Compared with Example 1, the only difference is that the carrier of the catalyst is replaced with an equal amount of Al 2 O 3 molecular sieve, and catalyst 0.1%Pd 3 Pt 2 / Al 2 O 3 is prepared. The final product was detected according to the hydrogenation reaction in Example 1, and the results are shown in Table 4.

[0034] Table 4 Results of hydrogenation of palm kernel oil fatty acid at different temperatures 。

[0035] Comparative Example 2 Compared with Example 1, the only difference is that the carrier of the catalyst is replaced with an equal amount of ZrO 2 molecular sieve, and catalyst 0.1%Pd 3 Pt 2 / ZrO 2 is prepared. The final product was detected according to the hydrogenation reaction in Example 1, and the results are shown in Table 5.

[0036] Table 5 Results of hydrogenation of palm kernel oil fatty acid at different temperatures 。

[0037] Comparative Example 3 Compared with Example 1, the only difference is that the percentage of the active ingredient in the carrier by weight is modified to 0.05%, and catalyst 0.05%Pd 3 Pt 2 / SiO 2 is prepared. The final product was detected according to the hydrogenation reaction conditions in Example 1, and the results are shown in Table 6.

[0038] Table 6 Results of hydrogenation of palm kernel oil fatty acid at different temperatures 。

[0039] Comparative Example 4 Compared with Example 1, the difference is only that the active ingredient is replaced with a single metal Pt, and the percentage of the active ingredient in the weight of the carrier is 0.1%, and the catalyst 0.1%Pd / SiO is prepared. 2 The final product was detected according to the hydrogenation reaction conditions of Example 1, and the results are shown in Table 7.

[0040] Table 7 Results of hydrogenation of palm kernel oil fatty acid at different temperatures 。

[0041] Comparative Example 5 Compared with Example 1, the difference is only that the active ingredient is replaced with a single metal Ni, and the percentage of the active ingredient in the weight of the carrier is 0.1%, and the catalyst 0.1%Ni / SiO is prepared. 2 The final product was detected according to the hydrogenation reaction conditions of Example 1, and the results are shown in Table 8.

[0042] Table 8 Results of hydrogenation of palm kernel oil fatty acid at different temperatures 。

[0043] Comparative Example 6 Compared with Example 1, the difference is only that the active ingredient is replaced with Pd and Ag with a molar ratio of 1:1 (the complex of Ag is silver nitrate), and the percentage of the active ingredient in the weight of the carrier is 0.1%, and the catalyst 0.1%PdAg / SiO is prepared. 2 The final product was detected according to the hydrogenation reaction conditions of Example 1, and the results are shown in Table 9.

[0044] Table 9 Results of hydrogenation of palm kernel oil fatty acid at different temperatures 。

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A catalyst for preparing high-purity oleic acid, characterized in that: The catalyst uses SiO2 molecular sieve as a carrier, Pd and Pt as active components, and the molar ratio of Pd to Pt is 3:2-4:

1.

2. The catalyst according to claim 1, characterized in that The active ingredient accounts for 0.1%-0.3% of the carrier weight.

3. The method for preparing a catalyst for preparing high-purity oleic acid according to claim 1 or 2, characterized in that: The preparation method of the catalyst comprises the following steps: immersing the carrier in a mixed aqueous solution of a Pd complex and a Pt complex, and drying and calcining the carrier after the immersion is completed.

4. The preparation method according to claim 3, characterized in that: The drying temperature is 120-150°C.

5. The preparation method according to claim 3, characterized in that: The calcination temperature is 500-900°C.

6. Use of the catalyst for preparing high-purity oleic acid as claimed in claim 1 or 2 in preparing high-purity oleic acid by continuous selective hydrogenation.

7. The use according to claim 6, characterized in that The method for preparing high-purity oleic acid comprises: taking vegetable oil containing linoleic acid and / or linolenic acid as raw material, and performing hydrogenation reaction under the action of the catalyst for preparing high-purity oleic acid.

8. The use according to claim 7, characterized in that The raw materials include palm kernel oil oleic acid and / or soybean oil oleic acid.

9. The use according to claim 6, characterized in that The temperature of the hydrogenation reaction is 120-160°C, the hydrogen pressure is 0.1-0.5MPa, and the reaction time is 1-4 hours.

10. The use according to claim 9, characterized in that The temperature of the hydrogenation reaction is 120-160°C, the hydrogen pressure is 0.3MPa, and the reaction time is 2 hours.