CN115282968B - A metal-doped self-assembly catalyst - Google Patents

Abstract

The invention relates to a transition metal doped cobalt oxide catalyst and a preparation method thereof, wherein the catalyst can promote long-chain alpha-olefin to react with synthesis gas to prepare high-carbon alcohol; by introducing the preparation of urea and transition metal, a catalyst system with proper active center concentration is obtained, the selectivity of the hydroformylation reaction of high-carbon-number olefins is remarkably improved, and the alcohol yield is improved. The scheme of the invention has the advantages of short reaction time, controllable process, difficult loss of active metal and the like, and is convenient for large-scale application and popularization.

Description

A metal-doped self-assembly catalyst

Technical field

The invention belongs to the field of catalyst preparation, and specifically relates to a catalyst that catalyzes the hydroformylation reaction of long-chain α-olefins and synthesis gas to produce higher carbon alcohols and a preparation method thereof, and particularly relates to the preparation of nonanol.

Background technique

High-carbon alcohols are important fine chemical raw materials. For example, C ₆ to C ₁₀ alcohols are called plasticizer alcohols and are used to improve the plasticity, temperature resistance and weather resistance of plastic products. The hydroformylation reaction process is one of the methods for preparing high-carbon alcohols, that is, under certain temperature and pressure conditions, using a metal complex catalyst, olefins react with synthesis gas to convert into carbonyl compounds with extended carbon chains. For example, in the synthesis of butanol/octanol, propylene is used as raw material, butyraldehyde is first obtained through hydroformylation reaction, and then butanol is obtained through hydrogenation reaction; butyraldehyde is dimerized and hydrogenated to obtain octanol product (Sichuan Chemical Industry, 2009, 12(3): 20-24). Isononanol is produced mainly through traditional processes, ExxonMobil processes, Oxeno processes and Johnson Matthey processes (Petrochemical Technology and Economics, 2018, 34(5): 59-62). Generally, C ₈ branched olefins and butene dimers are used as raw materials, and Co/Rh homogeneous catalysts are used; among them, ExxonMobil Chemical Company's Co catalytic technology is in a dominant position, and the reaction is carried out in two steps: (1) under high pressure conditions, under In the carbonylation reactor, tetracarbonyl cobalt salt is used to catalyze the hydroformylation reaction between octene and synthesis gas to generate C ₉ -aldehyde; (2) C ₉ -aldehyde is separated from the catalyst and transferred to the hydrogenation reactor for further hydrogenation to generate nonane. alcohol.

The existing hydroformylation-to-alcohol reaction process requires a two-step reaction with high reaction pressure; the homogeneous catalyst used contains toxic phosphorus ligands, and active metals are easily lost and separation is difficult.

Cobalt oxide is reported to be able to catalyze the hydroformylation-hydrogenation reaction of 1-octene to produce nonanol (Catal. Today, 2018, 309: 147-152). However, the reaction time required to produce nonanol is long and the catalyst performance is poor. Stability needs further verification. Similar studies have also shown that the catalytic performance of cobalt oxide suffers from the problems of long reaction time and low selectivity of alcohol products (Fuel, 2020, 269: 117397). Even if noble metals and alkali metals are used to modulate cobalt oxide, it still requires a long reaction time to obtain the target product (Appl. Catal. A-Gen, 2020, 602: 117735)

Based on the insufficient performance of existing catalysts, the solution of the present invention regulates cobalt oxide by doping transition metals, and better realizes the production of alcohol through the hydroformylation reaction of long-chain α-olefins and synthesis gas, with the advantages of short reaction time and high alcohol product. The advantages of high selectivity and low loss of active metals.

Contents of the invention

The invention provides a simple and rapid catalyst for synthesizing high-carbon alcohols. The catalyst of the invention has simple preparation steps, good repeatability and is easy for industrial application.

The catalyst of the invention is a one-step alcohol production catalyst with specific crystal planes and electronic effects, which can catalyze the hydroformylation reaction of C ₆ to C ₁₂ long chain α-olefins and synthesis gas. It is an iron, copper, and nickel doped cobalt oxide catalyst. .

When the iron, copper, and nickel-doped cobalt oxide catalyst used in the present invention is used to synthesize high-carbon alcohol, the catalyst is reduced to a cobalt catalytic active center during the alcohol-making reaction, and no pre-reduction procedure is required. Copper promotes the reduction of cobalt oxide and improves catalytic activity; iron promotes and improves the selectivity of alcohol products. Doping transition metals synergistically improves catalytic activity.

Technical scheme and beneficial effects of the catalyst product of the present invention: there is an electron transfer effect between the doped metal and cobalt oxide, which promotes the reduction of cobalt oxide and improves the catalytic one-step alcohol production reaction activity. The formulation of copper, nickel, iron and urea concentrations and the selection of cobalt salts, combined with microwave and hydrothermal conditions, promote the exposure of the cobalt oxide crystal planes (111) and (220) in the material. The exposed crystal faces (111) and (220) of cobalt oxide are beneficial to hydroformylation, and (220) is beneficial to the hydrogenation of aldehyde to alcohol.

The catalyst is a transition metal TM-doped cobalt oxide material, expressed as xTM ₁ yTM ₂ -Co ₃ O ₄ , TM is a kind of transition metal iron, nickel, and copper; cobalt oxide exposes crystal planes (111) and (220); catalyst The preparation method is to introduce urea and transition metal salts, and prepare by microwave method or hydrothermal method; the catalyst prepared by microwave method has a 3D rod-shaped structure; the catalyst prepared by hydrothermal method has a layered nanosheet stack structure. The catalyst can be used in the preparation of high-carbon alcohols. The raw materials are long-chain olefins including C ₆ to C ₁₂ linear α-olefins. The target product alcohols include C ₇ to C ₁₃ alcohols, especially the production selectivity of nonanol is >40%. Specifically, the catalyst is used in the preparation of alcohol. The raw material substrate is long-chain olefins, containing α-octene, the solvent is tetrahydrofuran, the synthesis gas volume ratio is CO/H ₂ =1, and the mass ratio of the catalyst to α-octene is 5 to 20%. , the reaction temperature is 140-160 °C; the reaction pressure is 5-7 MPa, the reaction time is 4-7 h, long-chain α-olefins and synthesis gas are catalyzed by the catalyst obtained by the preparation method of the present invention to prepare alcohol. The particle size of the catalyst prepared by microwave method is 190 nm to 1.5um, with different lengths, and the specific surface area is ≥20 m ² /g; the specific surface area of the catalyst prepared by hydrothermal method is ≥ 30 m ² /g.

The catalyst preparation method includes dissolving cobalt nitrate and urea. The molar ratio of urea to cobalt nitrate is 1 to 5; the molar ratios of doped metals TM ₁ and TM ₂ to cobalt are x and y respectively, and the values of x and y are 1 to 5. between 8. Add transition metal nitrate, stir and mix to obtain a homogeneous mixed solution. The mixed solution contains 0.25~1.0 g cobalt and 0.25~0.5 g urea per 43 mL of solvent.

The mixed liquid is obtained by microwave method MW or hydrothermal method HT to obtain a solid-liquid mixture, which is cooled to room temperature, filtered, and dried to obtain a catalyst precursor. The catalyst precursor is further calcined to obtain the target catalyst. The hydrothermal crystallization temperature is 140-200 °C, and the crystallization time is 16-20 h. The reaction temperature of the microwave method is 100-180 °C, and the reaction time is 0.25-1 h.

Among them, the catalyst obtained by treating the homogeneous solution under microwave conditions is marked as TM ₁ TM ₂ -Co ₃ O ₄ -MW; the catalyst obtained by being treated under hydrothermal conditions is marked as TM ₁ TM ₂ -Co ₃ O ₄ -HT.

The catalyst can also be used to produce high-carbon aldehydes. The raw material substrate is long-chain olefins. The volume ratio of synthesis gas is CO/H ₂ =1. The mass ratio of catalyst to α-octene is 1 to 5%. The reaction temperature is 130 to 150 ° C; reaction pressure 5~7 MPa, reaction time 1~2h.

Description of the drawings

Figure 1 shows a high-magnification TEM image of the catalyst sample prepared in Example 2.

Figure 2 shows a high-magnification TEM image of the catalyst sample prepared in Example 4.

Figure 3 shows the SEM image (left) and TEM image (right) of the catalyst sample prepared in Example 2.

Figure 4 is a SEM image (left) and a TEM image (right) of the catalyst sample prepared in Example 4.

Detailed ways

The present invention will be described in detail below through examples. It is necessary to point out here that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of the present invention. Without departing from the spirit and essence of the present invention, the methods, steps or conditions of the present invention can be modified. Modifications or substitutions all fall within the scope of the present invention.

Example 1

Dissolve 2.5 g of cobalt nitrate hexahydrate, 0.0416 g of copper nitrate trihydrate, and 0.7739 g of urea in 86 mL of deionized water, and stir at room temperature for 3 h to form a homogeneous solution. The homogeneous solution was reacted under microwave conditions at 160 °C for 15 min, cooled to room temperature, filtered, dried, and calcined at 400 °C for 4 h to obtain the catalyst 2Cu-Co ₃ O ₄ -MW.

Evaluation of the catalytic activity of nonanol synthesis: the mass ratio of the catalyst to the raw material 1-octene = 8.4%, the catalyst dosage is 0.1445g, the 1-octene dosage is 1.68 g, the solvent tetrahydrofuran dosage is 10.65 g, and the synthesis gas CO/H ₂ =1 , the reaction temperature is 150 °C, the reaction pressure is 7 MPa, the stirring speed is 700 rpm, and the reaction time is 4 h. The reaction results are shown in Table 1.

Example 2

Dissolve 2.5 g cobalt nitrate hexahydrate, 0.0694 g ferric nitrate nonahydrate, 0.0415 g cobalt nitrate hexahydrate, and 0.7739 g urea in 86 mL deionized water, and stir at room temperature for 3 h to form a homogeneous solution. The homogeneous solution was reacted under microwave conditions at 160 °C for 15 min, cooled to room temperature, filtered, dried, and calcined at 400 °C for 4 h to obtain the catalyst 2Fe2Cu-Co ₃ O ₄ -MW. Activity evaluation is the same as in Example 1. The reaction results are shown in Table 1.

Example 3

Dissolve 2.5 g cobalt nitrate hexahydrate, 0.0500 g nickel nitrate hexahydrate, 0.0415 g copper nitrate trihydrate, and 0.7739 g urea in 86 mL deionized water, and stir at room temperature for 3 h to form a homogeneous solution. The homogeneous solution was reacted under microwave conditions at 160 °C for 15 min, cooled to room temperature, filtered, dried, and calcined at 400 °C for 4 h to obtain the catalyst 2Ni2Cu-Co ₃ O ₄ -MW. Activity evaluation is the same as in Example 1. The reaction results are shown in Table 1.

Example 4

Dissolve 2.5 g cobalt nitrate hexahydrate, 0.0694 g ferric nitrate nonahydrate, 0.0415 g copper nitrate trihydrate, and 0.7739 g urea in 86 mL deionized water, and stir at room temperature for 3 h to form a homogeneous solution. The homogeneous solution was crystallized under hydrothermal conditions at 160 °C for 18 h, cooled to room temperature, filtered, dried, and calcined at 400 °C for 4 h to obtain the catalyst 2Fe2Cu-Co ₃ O ₄ -HT. Activity evaluation is the same as in Example 1. The reaction results are shown in Table 1.

Comparative Example 1

Dissolve 2.5 g Co(NO ₃ ) ₂ ×6H ₂ O, 0.0694 g Fe(NO ₃ ) ₃ ×9H ₂ O, and 0.7739 g CO(NH ₂ ) ₂ urea in 86 mL deionized water, and stir at room temperature for 3 h to form Homogeneous solution. The homogeneous solution was reacted under microwave conditions at 160 °C for 15 min, cooled to room temperature, filtered, dried, and calcined at 400 °C for 4 h to obtain the catalyst 2Fe-Co ₃ O ₄ -MW. Activity evaluation is the same as in Example 1. The reaction results are shown in Table 1.

Comparative Example 2

Dissolve 2.5 g Co(NO ₃ ) ₂ ×6H ₂ O, 0.0500 g Ni(NO ₃ ) ₂ ×6H ₂ O, and 0.7739 g CO(NH ₂ ) ₂ urea in 86 mL deionized water, and stir at room temperature for 3 h to form Homogeneous solution. The homogeneous solution was reacted under microwave conditions at 160 °C for 15 min, cooled to room temperature, filtered, dried, and calcined at 400 °C for 4 h to obtain the catalyst 2Ni-Co ₃ O ₄ -MW. Activity evaluation is the same as in Example 1. The reaction results are shown in Table 1.

Comparative Example 3

Dissolve 2.5 g Co(NO ₃ ) ₂ ·6H ₂ O and 0.7739 g CO(NH ₂ ) ₂ urea in 86 mL deionized water, and stir at room temperature for 3 h to form a homogeneous solution. The homogeneous solution was reacted under microwave conditions at 160 °C for 15 min, cooled to room temperature, filtered, dried, and calcined at 400 °C for 4 h to obtain a catalyst Co ₃ O ₄ -MW sample. Activity evaluation is the same as in Example 1. The reaction results are shown in Table 1.

Table 1 Catalytic activity of nonanol produced by the reaction of 1-octene and synthesis gas

Example 5

The catalyst of Example 3 was used, the activity evaluation was as in Example 1, the reaction time was 5 h, and the reaction results were shown in Table 2.

Example 6

The catalyst of Example 3 was used, and the activity evaluation was as in Example 1. The reaction time was 7 h, and the reaction results are shown in Table 2.

Table 2 Alcohol-making reaction activity of catalysts under different reaction conditions

Example 7

The catalyst of Example 3 was used. Refer to Example 1 for actual activity evaluation. The raw material is 1-hexene, the reaction time is 7 h, and the products are heptanol and heptanal. The reaction results are shown in Table 3.

Example 8

Refer to Example 1 for activity evaluation. The raw material is 1-dodecene, and the products are tridecanol and tridecanal. The reaction results are shown in Table 3.

Table 3 Alcohol-making reaction activities of linear α-olefins with different carbon numbers

Example alpha-olefins Conversion rate/% Alcohol selectivity/% Aldehyde selectivity/% Example 7 1-Hexene 98.40 52.51 9.21 Example 8 1-dodecene 99.97 32.59 45.17

It can be seen from Table 1-3 that Cu doping is conducive to improving the Co ₃ O ₄ hydroformylation reaction activity, and Fe doping is conducive to improving the selectivity of the product alcohol; when 1-octene is used as the substrate, at 150 °C, At 7 MPa and 5 h, when 2Fe2Cu-Co ₃ O ₄ -HT was used as the catalyst to catalyze the hydroformylation reaction, the nonanol selectivity was the highest at 67.87%; the 2Fe2Cu-Co ₃ O ₄ -HT catalyst could effectively catalyze C ₆ to C When producing alcohol _{from 12} linear α-olefins, in particular, when 1-octene is used as the raw material, the alcohol selectivity is the highest. Alcohols with other carbon numbers (C ₇ , C ₈ , C ₉ ~ C ₁₃ ), with the carbon number As the value increases, the alcohol selectivity decreases.

Figures 1 and 2 are high-magnification transmission electron microscope (TEM) photos of the catalyst samples prepared in Example 2 and Example 4 respectively. It can be confirmed that the main exposed crystal faces of the catalyst material are (111) crystal face and (220) crystal face.

Figure 3 is a scanning electron microscope (SEM) photo and a TEM photo of the catalyst sample prepared in Example 2 (microwave method). It can be confirmed that the catalyst prepared by microwave method has a rod-like structure.

Figure 4 is an SEM photo and a TEM photo of the catalyst sample prepared in Example 4 (hydrothermal method). It can be confirmed that the catalyst prepared by hydrothermal method has a layered nanosheet stacking structure.

Claims (5)

1. A metal-doped self-assembled catalyst is characterized in that the catalyst is a transition metal TM-doped cobalt oxide material expressed as xTM ₁ yTM ₂ -Co ₃ O ₄ Wherein TM ₂ Is transition metal copper, TM ₁ Is transition metal iron or nickel; cobalt oxide exposes crystal planes (111) and (220); the catalyst preparation method comprises the steps of introducing urea and transition metal salt, and adopting a microwave method or a hydrothermal method to prepare the catalyst; wherein the catalyst prepared by the microwave method is in a rod-shaped structure; preparing a catalyst by a hydrothermal method, wherein the catalyst is in a layered nano-sheet stacking structure; the catalyst is applied to the preparation of alcohol, the raw material substrate is long-chain olefin, the catalyst contains alpha-octene, the solvent is tetrahydrofuran, and the volume ratio of the synthesis gas is CO/H ₂ =1, the mass ratio of the catalyst to the alpha-octene is 1-5%, and the reaction temperature is 140-160 ℃; the reaction pressure is 5-7 MPa, the reaction time is 4-7 h, and the long-chain olefin and the synthesis gas are catalyzed by the catalyst to prepare alcohol; long chain olefins include C ₆ ～C ₁₂ Linear alpha-olefins, target product alcohols including C ₇ ～C ₁₃ An alcohol.

2. The metal-doped self-assembled catalyst according to claim 1, wherein the catalyst prepared by a microwave method has a particle size of 190 nm-1.5 μm and a different length, and the specific surface area is not less than 20 m ² /g; hydrothermal method for preparing catalyst with specific surface area not less than 30 m ² /g。

3. A method for preparing the catalyst according to claim 1, wherein the method comprises dissolving cobalt nitrate and urea, and the molar ratio of urea to cobalt nitrate is 1-5; adding transition metal nitrate, and stirring and uniformly mixing to obtain a mixed solution; the mixed solution is subjected to a microwave method or a hydrothermal method to obtain a solid-liquid mixture, the solid-liquid mixture is cooled to room temperature, filtered and dried to obtain a catalyst precursor, and the catalyst precursor is further roasted to obtain the target catalyst.

4. The process according to claim 3, wherein the crystallization temperature by hydrothermal method is 140-200 ℃ and the crystallization time is 16-20 h.

5. The process according to claim 3, wherein the reaction temperature is 100 to 180℃and the reaction time is 0.25 to 1h.