CN115999593B

CN115999593B - Catalyst for preparing low-carbon carboxylic acid from low-carbon alcohol and application of catalyst

Info

Publication number: CN115999593B
Application number: CN202211512082.9A
Authority: CN
Inventors: 闫昊; 孟凡宇; 周鑫; 赵辉; 杨朝合; 郑子渊; 刘洋希
Original assignee: Yueyang Hengzhong New Material Co ltd; China University of Petroleum East China
Current assignee: Yueyang Hengzhong New Material Co ltd; China University of Petroleum East China
Priority date: 2022-11-29
Filing date: 2022-11-29
Publication date: 2024-05-07
Anticipated expiration: 2042-11-29
Also published as: CN115999593A

Abstract

A catalyst for preparing 2-ethylhexanoic acid by catalytic dehydrogenation of 2-ethylhexanol and application thereof. The catalyst of the application is a catalyst for preparing 2-ethylhexanoic acid by catalytic dehydrogenation of 2-ethylhexanol, wherein: the active component of the catalyst is one or more elements of Mg, ti, mn, cu, zn, zr, ni and Ce; the carrier of the catalyst is Hydroxyapatite (HAP); the mass fraction loading of the active component is 0.5% -50%. Correspondingly, the preparation method of the catalyst and the application of the catalyst in the preparation of fatty acid by dehydrogenation of long carbon chain fatty alcohol are also provided. The catalyst prepared by the application has alkali resistance and high temperature resistance, can be recycled and has good catalytic activity.

Description

Catalyst for preparing low-carbon carboxylic acid from low-carbon alcohol and application of catalyst

Technical Field

The application belongs to the technical field of chemical catalysis, and particularly relates to a catalyst for preparing carboxylic acid substances through catalytic dehydrogenation of alcohol substances.

Background

2-Ethylhexanoic acid is an important fine chemical raw material and is widely applied to industries such as medical raw materials, lubricants, rubber adhesives, oil additives, rust inhibitors, antifreezes, driers, curing agents, coatings, printing ink, glass fiber reinforced plastics and the like. In addition, the metal salts are upgrading and updating products of naphthenate, are widely applied to the plastic industry, and the esters are excellent plasticizers. In the refrigeration industry, 2-ethylhexanoic acid is used for fluorine-free refrigeration. In the rubber industry, cobalt salts thereof are useful. The said process may be used in petrochemical industry and daily chemical industry to produce various chemical extractants and hydrocarbon gelatinizer. The esters can also be used as food additives, feed additives, fish-farming bactericides and biological growth promoters for the food processing industry, agriculture and fishery, respectively.

The 2-ethylhexanoic acid is prepared by a catalytic dehydrogenation method, and the method has the advantages of simple operation, high selectivity, low equipment investment and the like, so that the method becomes a 2-ethylhexanoic acid production process adopted by a plurality of enterprises. The catalyst of the process is some metal oxides (ZnO, mgO, cuO, etc.). For example, chinese patent publication No. CN106278875A, a process for preparing isooctanoic acid, in which isooctanol is reacted with a strong base and a zinc compound is added to the reaction system. Because of the damage of strong alkalinity and high temperature conditions to the catalyst structure in the reaction process, the existing catalyst is mostly a disposable catalyst, and the subsequent regeneration and recycling are greatly limited.

Disclosure of Invention

The application aims to provide a catalyst for preparing low-carbon carboxylic acid by catalytic dehydrogenation of low-carbon alcohol. The catalyst has good catalytic performance, and can effectively improve the conversion rate of 2-ethylhexanol and the selectivity of 2-ethylhexanoic acid in alkaline environment. In particular, in a reaction system for preparing 2-ethylhexanoic acid by catalytic dehydrogenation of 2-ethyl-hexanol, the selectivity of the 2-ethylhexanoic acid is high.

The application further aims to provide a catalyst for preparing 2-ethylhexanoic acid by catalytic dehydrogenation of 2-ethylhexanol, which has alkali resistance and high temperature resistance, and can obviously improve the use times and service life of the catalyst.

It is still another object of the present application to provide a method for preparing a catalyst for preparing 2-ethylhexanoic acid by catalytic dehydrogenation of 2-ethylhexanol.

The catalyst for preparing the low carbonic acid by catalytic dehydrogenation of the low carbon alcohol comprises metal elements and hydroxyapatite, wherein the metal elements comprise one or more elements of Mg, ti, mn, cu, zn, zr, ni and Ce, and the content of the metal elements is 0.5-50 wt%.

The low-carbon alcohol is saturated monoalcohol with carbon number lower than 8, and the low-carbon carboxylic acid is saturated monoacid with carbon number lower than 8.

The catalyst is especially used in the reaction system for preparing 2-ethylhexanoic acid by catalytic dehydrogenation of 2-ethylhexanol, and has good catalytic performance. Has the advantages of alkali resistance and high temperature resistance, and can be recycled.

Detailed Description

A catalyst for the catalytic dehydrogenation of 2-ethylhexanol to 2-ethylhexanoic acid according to the present application is described in further detail below. And do not limit the scope of the application, which is defined by the claims. Certain disclosed specific details provide a thorough understanding of the various disclosed embodiments. However, one skilled in the relevant art will recognize that embodiments can be practiced without one or more of the specific details, with other materials, etc.

In the description and in the claims, the terms "comprising," including, "and" containing "are to be construed as open-ended, meaning" including, but not limited to, unless the context requires otherwise.

Reference in the specification to "an embodiment," "one embodiment," "another embodiment," or "certain embodiments," etc., means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, it is not necessary for an "embodiment," "one embodiment," "another embodiment," or "certain embodiments" to refer to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. The various features disclosed in the specification may be replaced by alternative features serving the same, equivalent or similar purpose. Thus, unless expressly stated otherwise, the disclosed features are merely general examples of equivalent or similar features.

The application will be further illustrated with reference to specific examples. It is to be understood that these examples are illustrative of the present application and are not intended to limit the scope of the present application. The experimental procedures, which do not address the specific conditions in the examples below, are generally carried out under conventional conditions or under conditions recommended by the manufacturer. All percentages, ratios, proportions, or parts are by weight unless otherwise indicated.

In the present application, the concentration unit "M" of the solution represents mol/L.

The catalyst for preparing the low-carbon carboxylic acid by catalytic dehydrogenation of the low-carbon alcohol comprises metal elements and hydroxyapatite, wherein the metal elements comprise one or more elements of Mg, ti, mn, cu, zn, zr, ni and Ce, and the content of the metal elements is 0.5-50 wt%.

The content of the metal element means a ratio of the mass of the metal element to the total mass of the catalyst.

According to the catalyst disclosed by the application, metal elements are doped in a Hydroxyapatite (HAP) structure through bonding of metal M-PO _x, and in the reaction process, the contact area of an active site, a reaction substrate and alkali liquor is high due to the alkali resistance of the catalyst, so that the catalytic activity and the stability of the catalyst are improved. In addition, as active metal sites are dispersed, the atom utilization rate is improved, so that the reaction is independently completed on each dispersed site, and the selectivity is improved. The carrier itself can raise a part of alkaline sites, and has synergistic effect of co-dehydrogenation with active metal, so as to further raise reaction conversion rate.

The metallic elements in the catalyst are all in the form of oxides. The catalytic effect is good.

In certain embodiments, the metallic element comprises one or more of Cu, zn.

In certain embodiments, the metal element is present in an amount of 10wt% to 30wt%.

By regulating and controlling the chemical composition environment of the active metal, the interaction between the carrier and the active metal is enhanced, and the alkali resistance and high temperature resistance of the active metal oxide are greatly improved.

In another aspect, a method for preparing a catalyst for preparing a lower carboxylic acid by catalytic dehydrogenation of a lower alcohol comprises:

1) Mixing a soluble salt containing phosphorus element with a soluble solution containing metal element to obtain solution A, wherein the metal element comprises one or more elements of Mg, ti, mn, cu, zn, zr, ni and Ce;

2) Mixing a soluble salt containing calcium with the solution A, and adjusting the solution to be alkaline to obtain a mixture B;

3) Heating the mixed solution B to precipitate crystals, and washing, drying and roasting the obtained crystals to obtain the catalyst.

In the catalyst, phosphorus element solution and active metal element are mixed firstly, and then calcium element solution is mixed, the mixture is formed in one step by a hydrothermal method, HAP is formed in the crystallization process, and the active metal element is uniformly introduced into the HAP, so that the catalyst has good catalytic dehydrogenation performance and higher stability of 2-ethylhexanol.

In the step 1), the mole ratio of the phosphorus element to the metal element in the soluble salt containing the phosphorus element and the soluble solution containing the metal element is 1 (0.28-0.8). The molar ratio of the calcium element of the soluble salt of the calcium element to the phosphorus element of the soluble salt of the phosphorus element in the step 2) is 5 (3.0-3.5). In certain embodiments, in step 2), the soluble salt of the calcium-containing element is mixed with solution a, and the solution is alkaline and the pH of the mixed solution is adjusted to 12.

By controlling the pH of the mixed solution B, the conversion to n (Ca)/n (P) =1.67 of hydroxyapatite is facilitated by the hydrothermal synthesis of hydroxyapatite going through octacalcium phosphate, to amorphous calcium phosphate, to calcium deficient apatite and to hydroxyapatite, the higher the pH, the higher the OH-concentration.

In the preparation process of the catalyst, when the pH is regulated to 12, the metal salt of the active component can be ensured to be uniformly mixed in the hydroxyapatite in the form of hydroxide precipitation, and the metal oxide is formed by post-roasting. In certain embodiments, mixed solution B precipitates crystals at a temperature of 110 ℃ to 150 ℃.

In the crystallization process, the supersaturation degree of the mixed solution B is larger along with the gradual rise of the temperature; when the temperature is raised to 110-150 ℃, the supersaturation degree of the solution is raised to a metastable state, and the solution starts to crystallize attached to the active metal hydroxide particles, and the saturation degree reaches the maximum; in the middle and late stages of the reaction, the supersaturation degree of the solution is reduced, and the crystal growth is slowly ended.

In certain embodiments, the drying temperature is controlled between 75 ℃ and 110 ℃.

In certain embodiments, the firing temperature is controlled at 450 ℃.

The catalyst obtained by in-situ doping not only maintains the activity of the active metal oxide, but also improves the alkali resistance and high temperature resistance of the catalyst, and meanwhile, the active metal oxide is dispersed in the carrier HAP, so that more uniform active sites are provided for the reaction, and the conversion rate and the selectivity of the reaction are improved.

In the present application, the solubility of the phosphorus-containing element includes, but is not limited to, (NH ₄)₂HPO₄、H₃PO₄、NaH₂PO₄ and (CH ₃O)₃ PO, etc.).

Soluble salts of calcium include, but are not limited to ,Ca(NO₃)₂·4H₂O、Ca(OH)₂、CaHPO₄·2H₂O、CaO、CaCl₂ and Ca (OC ₂H₅)₂, etc.).

The soluble solution containing a metal element is usually nitrate or chloride. Nitrate is a preferable substance, has the advantages of no residual elements after decomposition, elimination of interference of anions and low price.

In certain embodiments, the lye comprises an alkali metal hydroxide. Such as sodium hydroxide, or potassium hydroxide, etc.

The catalyst obtained by the method is applied to the reaction of preparing 2-ethylhexanoic acid by catalytic dehydrogenation of 2-ethylhexanol.

In certain embodiments, a process for preparing 2-ethylhexanoic acid by catalytic dehydrogenation of 2-ethylhexanol comprises: the catalyst is placed in 2-ethylhexanol, strong alkali is added, the reaction is carried out in the atmosphere of nitrogen, and the reaction temperature is controlled between 200 ℃ and 250 ℃.

Strong bases include, but are not limited to, sodium hydroxide, or potassium hydroxide, and the like.

In certain embodiments, the mass ratio of catalyst to 2-ethyl octanol is 1:100 to 1:500.

In certain embodiments, the molar ratio of sodium hydroxide to 2-ethylhexanol is from 1:1.3 to 1:0.7.

In certain embodiments, the operating pressure is atmospheric after the nitrogen displacement gas is introduced.

In certain embodiments, the reaction time is from 0.5 to 2 hours.

In the reaction system, the conversion rate of the 2-ethyl Xin Jichun reaches more than 97 percent, and the selectivity is more than 94 percent.

In addition, the catalyst of the application can be repeatedly used for a plurality of times, and can maintain good catalytic performance.

Specifically, the catalytic dehydrogenation of 2-ethylhexanol to prepare 2-ethylhexanoic acid comprises:

Placing a catalyst and sodium hydroxide into an intermittent reaction kettle, adding a magneton or magnetic stirring device, sealing, filling nitrogen with certain pressure, evacuating, performing gas replacement, heating to a required temperature, adjusting a proper rotating speed, and reacting for a certain time; and after the reaction is finished, standing and cooling, then reducing the pressure in the kettle to normal pressure, adding distilled water and stirring to obtain the sodium isooctanoate aqueous solution.

Transferring the sodium isooctanoate aqueous solution into a beaker, slowly adding sulfuric acid solution under stirring for acidification, standing for layering, and separating a water phase; washing the oil phase with distilled water to obtain crude isooctanoic acid, distilling under reduced pressure to remove unreacted alcohol, and rectifying to obtain 2-ethylhexanoic acid product.

The catalyst of the present application and its catalytic effect are further described below in conjunction with specific examples. The substances used in the examples below are all chemically pure standard.

Example 1:

Synthesis of Cu in situ supported HAP catalyst

2GNH ₄H₂PO₄ and 2.51g Cu (NO ₃)₂) were mixed in 25 ml deionized water and stirred for 12h to give solution A.

6.7G of Ca (NO ₃)₂·4H₂ O) is placed in 50 ml of deionized water to be uniformly dispersed, slowly added into the solution A in a dropwise manner, then sodium hydroxide is added into the mixed solution in a dropwise manner until the PH value is=12, and stirring is continued for 12 hours, so that a solution B is obtained.

Solution B was transferred to a polytetrafluoroethylene-lined autoclave and hydrothermally crystallized at 110℃for 24h. The resulting sample was filtered through deionized water, dried at 80℃and calcined in a muffle furnace at 450℃for 2h to give the desired catalyst, designated CuO/HAP. The content of Cu element in the catalyst was 30wt%.

Example 2

Synthesis of Zn in situ supported HAP catalyst

This example method for preparing a catalyst and parameters refer to example 1 except that Cu (NO ₃)₂ in example 1 was replaced with 2.53g of Zn (NO ₃)₂), the catalyst obtained was designated as ZnO/HAP. Catalyst having a Zn content of 30wt% in example 3

Synthesis of catalyst with Ce in situ supported on HAP

This example method for preparing a catalyst and parameters refer to example 1 except that Cu (NO ₃)₂ in example 1 was replaced with 4.36g Ce (NO ₃)₂), the catalyst obtained was designated as CeO/HAP. Catalyst having Ce content of 30wt%

Example 4

Synthesis of Cu-Zn bimetallic in-situ supported HAP catalyst

The method of preparing the catalyst and parameters of this example refer to example 1 except that Cu (NO ₃)₂ was replaced with 1.26g Cu (NO ₃)₂ and 1.27g Zn (NO ₃)₂ mixture), the resulting catalyst was recorded as CuO-ZnO/hap.

Example 5

Synthesis of catalyst carried on HAP by Zn impregnation method

Mixing 2g NH ₄H₂PO₄ and 6.7g Ca (NO ₃)₂·4H₂ O in 75 ml deionized water, stirring for 12h to obtain solution A, then dripping alkali solution sodium hydroxide into the solution A until pH=12, stirring for 12h to obtain solution B, transferring the solution B into an autoclave lined with polytetrafluoroethylene, performing hydrothermal crystallization at 110 ℃ for 24h, filtering the formed sample with deionized water, drying at 80 ℃ to obtain a required carrier, and recording as HAP;

Dissolving the obtained HAP and 2.53g Zn (NO ₃)₂ in 30ml deionized water, fully mixing, stirring the mixture at a constant temperature of 60 ℃ at a speed of 1000rpm to form a paste, evaporating the surface to dryness, standing the obtained paste at normal temperature for 6 hours, putting the paste into a 100 ℃ oven for drying, and roasting for 2 hours at 450 ℃ in a muffle furnace to obtain the required catalyst, wherein the required catalyst is recorded as Zn/HAP-IM, and the Zn content is 30wt% of the HAP mass fraction.

Example 6

Synthesis of catalyst loaded on active carbon by Zn impregnation method

Dissolving 2g of Active Carbon (AC) and 1.74g of Zn (NO ₃)₂) in 30ml of deionized water, fully mixing, stirring the mixture at a constant temperature of 60 ℃ at a speed of 1000rpm to form a paste, evaporating the surface to dryness, standing the obtained paste at the normal temperature for 6 hours, putting the paste into a drying oven at 100 ℃ for drying, and roasting in a muffle furnace at 450 ℃ for 2 hours to obtain the required catalyst, namely Zn/AC-IM, wherein the Zn content is 30wt% of the active carbon mass fraction.

Experimental example 1

The catalysts prepared in examples 1-4 were used in the oxidation of 2-ethylhexanol according to the following protocol: weighing a certain amount of catalyst and sodium hydroxide, adding the catalyst and sodium hydroxide into a 500ml intermittent stirring reaction kettle, adding a certain amount of 2-ethylhexanol, sealing, filling nitrogen with a certain pressure, evacuating, repeating the gas displacement for three times, setting a certain reaction temperature and stirring speed, and starting the reaction. Cooling after stopping the reaction, then reducing the pressure in the kettle to normal pressure, adding distilled water and stirring to obtain the sodium isooctanoate aqueous solution. Transferring the sodium isooctanoate aqueous solution into a beaker, slowly adding sulfuric acid solution under stirring for acidification, standing for layering, and separating a water phase; washing the oil phase with distilled water to obtain crude isooctanoic acid, distilling under reduced pressure to remove unreacted 2-ethylhexanol, and rectifying to obtain 2-ethylhexanoic acid product. The supernatant was subjected to chromatography and the results are shown in Table 1.

TABLE 1

Wherein the subscript number is active metal loading (mass percent), for example, cuO ₃₀/HAP, the loading of Cu is 30wt%, and the carrier is HAP. Reaction conditions: the reaction substrate is 180g of 2-ethylhexanol, 72g of NaOH and 1g of catalyst are added, the mol ratio of sodium hydroxide to 2-ethylhexanol is 1.3:1, the mass ratio of catalyst to 2-ethylhexanol is 1:180, the reaction temperature is 240 ℃, and the reaction time is 1h.

Experimental example 2

The experimental example catalyzes the dehydrogenation of 2-ethylhexanol with ZnO and ZnO ₃₀/HAP and a recycled catalyst. Experimental conditions reference experimental example 1, except that different catalysts were used. The ZnO and ZnO ₃₀/HAP and the recycled catalyst catalyze 2-ethylhexanol dehydrogenation results are shown in Table 2.

TABLE 2

Wherein, the subscript number is active metal loading (mass percent), the suffix is cycle number, for example, znO ₃₀/HAP-1, the Zn loading is 30wt%, the carrier is HAP, and the catalyst is recycled for 1 time. Reaction conditions: 180g of 2-ethylhexanol, 72g of NaOH and 1g of catalyst are added, the molar ratio of sodium hydroxide to 2-ethylhexanol is 1.3:1, the mass ratio of catalyst to 2-ethylhexanol is 1:180, the reaction temperature is 240 ℃, and the reaction time is 1h.

Experimental example 3

The catalyst prepared in example 2 was subjected to catalytic dehydrogenation in different reaction raw materials to prepare the catalytic performance of alkyl carboxylic acid, and the results are shown in table 3. See experimental example 1 for additional conditions of the experiment.

TABLE 3 Table 3

Catalyst	Substrate(s)	Conversion (%)	Corresponding fatty acid selectivity (%)
				ZnO₃₀/HAP	2-Ethylheptanol	75.2	83.1
ZnO₃₀/HAP	2-Methyl heptanol	86.8	86.2
				ZnO₃₀/HAP	Isononol	54.1	80.1
ZnO₃₀/HAP	Decyl alcohol	40.1	44.5

Wherein the subscript number is active metal loading (mass percent), for example, znO ₃₀/HAP, the Zn loading is 30wt%, and the carrier is HAP. Reaction conditions: 180g of reaction substrate, adding sodium hydroxide and a catalyst in a corresponding proportion, wherein the molar ratio of the sodium hydroxide to the alcohol is 1.3:1, the mass ratio of the catalyst to the alcohol is 1:180, the reaction temperature is 240 ℃, and the reaction time is 1h.

It will be evident to those skilled in the art that the application is not limited to the details of the foregoing illustrative embodiments, and that the present application may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, the scope of the application being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims

1. A method for preparing 2-ethylhexanoic acid by catalytic dehydrogenation of 2-ethylhexanol comprises the steps of placing a catalyst in 2-ethylhexanol, adding sodium hydroxide, reacting in nitrogen atmosphere, and controlling the reaction temperature to be 200-250 ℃;

The catalyst comprises metal elements and hydroxyapatite, wherein the metal elements comprise one or more elements of Mg, ti, mn, cu, zn, zr, ni, ce, and the content of the metal elements is 0.5-50 wt%;

A method of preparing a catalyst comprising:

1) Mixing a soluble salt containing phosphorus element with a soluble solution containing metal element to obtain solution A, wherein the molar ratio of the phosphorus element to the metal element is 1 (0.28-0.8);

2) Dropwise adding a solution A into soluble salt containing calcium, and regulating the solution A to be alkaline until the pH value is=12 to obtain a mixed solution B;

3) And (3) carrying out hydrothermal reaction on the mixed solution B, precipitating crystals at the temperature of 110-150 ℃, washing the obtained crystals with water, drying and roasting to obtain the catalyst, wherein the roasting temperature is controlled at 450 ℃.

2. The method according to claim 1, wherein the content of the metal element is 10wt% to 30wt%.

3. The method according to claim 1, wherein the metal element comprises one or more elements of Cu, zn, ce.

4. The method according to claim 1, wherein the molar ratio of the calcium element of the soluble salt of the calcium element to the phosphorus element of the soluble salt of the phosphorus element in step 2) is 5 (3.0-3.5).

5. The method according to any one of claims 1-4, wherein: the drying temperature is controlled between 75 ℃ and 110 ℃.

6. The method according to any one of claims 1-4, wherein: the substance for adjusting the pH in step 2) includes an alkali metal hydroxide.

7. The process according to any one of claims 1 to 4, wherein the mass ratio of catalyst to 2-ethylhexanol is 1:100 to 1:500.

8. The process according to any one of claims 1 to 4, wherein the molar ratio of sodium hydroxide to 2-ethylhexanol is from 1:1.3 to 1:0.7.