Selective hydrogenation catalyst, method for preparing the same, and use thereof

Abstract

The application discloses a selective hydrogenation catalyst and a preparation method and application thereof, and the selective hydrogenation catalyst is a core-transition metal-carbon shell three-layer structure, a reducible oxide carrier is used as the core, a transition metal is used as the middle layer, and a polymerizable carbon source is used to form the carbon shell through a polymerization reaction. Through adjustment of the calcination temperature, the composition of the carbon shell layer can be adjusted, so that the selective hydrogenation catalyst can realize a targeted catalytic hydrogenation reaction on a nitroaromatic compound containing other reducible functional groups; through adjustment of the calcination temperature, the selective catalytic hydrogenation reaction on a certain functional group of the above compound can be realized, and meanwhile, other functional groups are not hydrogenated. The selective hydrogenation catalyst preparation method is simple, can resist O2 in the environment and CO in a crude hydrogen source, and has an excellent industrial application prospect.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and in particular to a selective hydrogenation catalyst, its preparation method, and its application. Background Technology

[0002] Nitroaromatics, cinnamaldehyde, citronellol, and other raw materials, through hydrogenation reactions, yield corresponding aniline / nitrobenzene derivatives, cinnamyl alcohol, citronellol, and other fine chemicals. These are important intermediates in the production of pharmaceuticals, agricultural chemicals, dyes, pigments, and fragrances, and are essential components of fine chemical products. They have significant application value in both production and daily life.

[0003] The Béchamp process has long been widely used for the catalytic hydrogenation of nitroaromatics. This process requires large amounts of Fe, Zn, and Sn powders as reducing agents, as well as hydrochloric acid as a solvent, causing severe environmental pollution and generating large quantities of waste acid and residue. Therefore, researchers have been committed to developing environmentally friendly catalyst systems. Pt-based noble metal heterogeneous catalysts are favored due to their high catalytic hydrogenation activity, recyclability, and environmental friendliness. However, the high hydrogenation activity of Pt-based noble metals also leads to poor selectivity and the accumulation of the explosive intermediate hydroxylamine, requiring the use of vanadium, lead phosphate, and other auxiliary agents, which presents separation challenges. Furthermore, if inexpensive industrial hydrogen is used as the hydrogen source, its high CO content leads to poisoning and deactivation of Pt-based noble metals, further limiting the application of this type of catalyst in industrial production.

[0004] Currently, carbon materials have attracted considerable attention due to their low cost and simple preparation. Carbon-coated metals or metal oxides have also been reported in the literature, with preparation methods including arc welding, polymerization, and hydrothermal methods. However, existing materials of this type still suffer from poor activity, which greatly limits their application in industrial production.

[0005] In summary, the preparation of carbon-coated metal or metal oxide materials and their performance in catalytic hydrogenation reactions have received widespread attention and research, and have broad application prospects. Summary of the Invention

[0006] The purpose of this invention is to provide a selective hydrogenation catalyst to address the technical deficiencies in the prior art.

[0007] Another object of the present invention is to provide a method for preparing the above-mentioned selective hydrogenation catalyst.

[0008] Another object of the present invention is to provide the application of the above-mentioned selective hydrogenation catalyst.

[0009] The technical solution adopted to achieve the purpose of this invention is:

[0010] A selective hydrogenation catalyst, wherein the selective hydrogenation catalyst has a three-layer structure of core-transition metal-carbon shell, with a reducible oxide support as the core, a transition metal as the middle layer, and a polymerizable carbon source undergoing a polymerization reaction to form the carbon shell.

[0011] The method for preparing the selective hydrogenation catalyst includes the following steps:

[0012] Using a reducible oxide as a support, the transition metal is loaded by a wet chemical impregnation method to obtain a supported catalyst precursor. Then, a polymerizable carbon source is polymerized to form a carbon shell that coats the surface of the supported catalyst precursor. After filtration, washing, and drying, the precursor is calcined in an oxygen-free atmosphere to obtain a selective hydrogenation catalyst. The calcination temperature is 100–1000 °C.

[0013] In the above technical solution, the carbon source is a nitrogen-containing carbon source or a nitrogen-free carbon source.

[0014] In the above technical solution, the nitrogen-containing carbon source is dopamine hydrochloride, glutamic acid or melamine, and the nitrogen-free carbon source is glucose or tannic acid.

[0015] In the above technical solution, the reducible oxide is TiO2, CeO2, FeOx (x=1–2), Fe2O3, WO3, ZnO, CuO, ZrO or In2O3, and the TiO2 has anatase phase or a mixed phase of anatase and rutile.

[0016] In the above technical solution, the transition metal is a transition metal of type VIIIB, IB, or IIB. Preferably, the transition metal is Pd, Pt, Ru, Au, Ni, Co, or Fe.

[0017] In the above technical solution, the loading of the transition metal in the selective hydrogenation catalyst is 0.01 wt.% to 40.0 wt.%.

[0018] In the above technical solution, the mass ratio of the carbon source to the supported catalyst precursor is (0.01~20.0):1.

[0019] In the above technical solution, the polymerization coating is a stirred polymerization coating, which is carried out in a water bath or oil bath for 6 to 72 hours. The temperature of the water bath or oil bath is room temperature to 120°C, the stirring speed is 100 to 3000 r / min, and the temperature of the hydrothermal polymerization coating is [not specified].

[0020] In the above technical solution, the polymerization coating is a hydrothermal polymerization coating. The temperature of the hydrothermal polymerization coating is 80-200℃, and the time is 4-48h. The hydrothermal polymerization coating may or may not be stirred. When stirring, the stirring speed is 50-500r / min.

[0021] In the above technical solution, the drying is vacuum drying, the drying temperature is 60-120℃, and the drying time is 2-48h.

[0022] In the above technical solution, the non-oxygen atmosphere is a mixture of H2 and N2, wherein the content of H2 is 1% vol to 100% vol, and N2 is a balance gas.

[0023] Another aspect of the invention includes the application of the selective hydrogenation catalyst in the selective hydrogenation reaction of compounds containing two or more reducible functional groups.

[0024] In the above technical solution, the reducible functional groups are C=C, -NO2, C≡C, C=O, -X (X is a halogen element), -O-CH3, -C≡N, -OH and -CHO;

[0025] Preferably, when the reducible functional groups are C=O and C=C, the compound undergoing selective hydrogenation is cinnamaldehyde or citronellol.

[0026] Another aspect of the present invention also includes the application of the selective hydrogenation catalyst in the selective catalytic hydrogenation of C=C nitroaromatic hydrocarbons to prepare aniline derivatives or nitrobenzene derivatives;

[0027] When the carbon source is a polymerizable nitrogen-containing carbon source:

[0028] The calcination temperature is 100–400℃, and the hydrogenation selectivity of C=C is 100%; the calcination temperature is 500–1000℃, and the hydrogenation selectivity of -NO2 is 100%.

[0029] When the carbon source is a polymerizable, nitrogen-free carbon source:

[0030] When the calcination temperature is 100–300℃, the hydrogenation selectivity of C=C is 100%; when the calcination temperature is 400–1000℃, the hydrogenation selectivity of -NO2 is 100%.

[0031] Compared with the prior art, the beneficial effects of the present invention are:

[0032] 1. This invention proposes a method for preparing a carbon-coated selective hydrogenation catalyst with high activity and high selectivity. This catalyst is widely used in the selective hydrogenation reaction of raw materials for fine chemical products such as substituted 4-nitrophenylacetylene, 3-nitroacetylene, 3-nitrostyrene, ethyl 4-nitrocinnamate, and 4-nitrocinnamic acid.

[0033] 2. The selective hydrogenation catalyst prepared in this invention has a three-layer structure: core-transition metal-carbon shell. Specifically, a reducible oxide support forms the core, a polymerizable carbon source polymerizes to form the carbon shell, and a transition metal forms the intermediate layer. By controlling the calcination temperature, the composition of the carbon shell can be adjusted, thereby achieving targeted catalytic hydrogenation of nitroaromatic compounds containing other reducible functional groups. By controlling the calcination temperature, selective catalytic hydrogenation of a specific functional group of the compound can be achieved, while other functional groups remain unhydrogenated. This selective hydrogenation catalyst has a simple preparation method, is resistant to ambient O2 and CO in the crude hydrogen source, and has excellent prospects for industrial application. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the preparation process of the present invention.

[0035] Figure 2 A low-magnification TEM image (40k) of catalyst B prepared in Example 2.

[0036] Figure 3 A high-magnification TEM image (400k) of catalyst B prepared in Example 2. Detailed Implementation

[0037] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0038] Example 1

[0039] A method for preparing a selective hydrogenation catalyst includes the following steps:

[0040] like Figure 1 As shown, in step 1, 410 mg of a 0.115 mmol / g PdCl2 solution was added dropwise to 10 g of TiO2 powder support, stirred until it became a slurry, aged at 60 °C for 8 h, and then dried at room temperature to obtain a supported catalyst precursor (Pd / TiO2 precursor), wherein the loading of Pd metal was 0.5 wt.%.

[0041] Step 2: Disperse 3g of the supported catalyst precursor in 600mL of Tris (tris(hydroxymethyl)aminomethane) buffer solution with pH 8.50 to obtain a suspension. Dissolve 1.5g of carbon source dopamine hydrochloride powder in 10g of deionized water to obtain an aqueous solution of dopamine hydrochloride. Add the aqueous solution of dopamine hydrochloride dropwise to the suspension while stirring vigorously at 40°C in a water bath or oil bath. After the addition is complete, continue stirring for 12h to obtain a material with a dopamine polymer shell. Filter the material, wash it three times with water and three times with alcohol, and dry it at 60-100°C for 4-12h to obtain a polymer-coated material (black powder).

[0042] Step 3: Place the polymer-coated material in a quartz boat, and place the quartz boat in a tube furnace. Introduce a mixture of 8% vol H2 and N2 gas at a flow rate of 100 mL / min into the tube furnace. Increase the temperature at a rate of 5 °C / min and calcine at 400 °C for 180 min. After calcine is completed, allow the material to cool naturally to obtain a carbon-shell-coated selective hydrogenation catalyst (finished catalyst A).

[0043] Example 2

[0044] A method for preparing a selective hydrogenation catalyst, compared with Example 1, involves raising the temperature of the calcination process in step 3 to 500°C, while keeping the other steps unchanged, to obtain a selective hydrogenation catalyst (catalyst B).

[0045] Example 3

[0046] A method for preparing a selective hydrogenation catalyst includes the following steps:

[0047] Step 1: 410 mg of PdCl2 solution with a concentration of 0.115 mmol / g was added dropwise to 10 g of TiO2 powder and stirred until it became a slurry. After aging at 60 °C for 8 h and drying at room temperature, a supported catalyst precursor (Pd / TiO2 precursor) was obtained, wherein the loading of Pd metal was 0.5 wt.%.

[0048] Step 2: Dissolve 3g of glucose in 100mL of deionized water to obtain a glucose solution. Disperse 1g of the supported catalyst precursor in the glucose solution, pour it into a polytetrafluoroethylene liner, place it in a stainless steel hydrothermal reactor, and perform a hydrothermal reaction at 120℃ for 8 hours. After natural cooling, filter, wash with water and alcohol three times each, and dry at 60-100℃ for 4-12 hours to obtain the polymer-coated material (brown powder).

[0049] Step 3: Place the polymer coating material in a quartz boat, and place the quartz boat in a tube furnace. Introduce a mixture of 8% vol H2 and N2 gas at a flow rate of 100 mL / min into the tube furnace. Increase the temperature at a rate of 5 °C / min until it reaches 300 °C and calcine for 180 min. After calcine is completed, allow it to cool naturally to obtain the selective hydrogenation catalyst (finished catalyst C).

[0050] Example 4

[0051] A method for preparing a selective hydrogenation catalyst, compared with Example 3, involves raising the temperature of the calcination process in step 3 to 400°C, while keeping the other steps unchanged, to obtain a selective hydrogenation catalyst (catalyst D).

[0052] Comparative Example 1

[0053] A method for preparing a catalyst includes the following steps:

[0054] Step 1: 410 mg of PdCl2 solution with a concentration of 0.115 mmol / g was added dropwise to 10 g of TiO2 powder and stirred until it became a slurry. After aging at 60 °C for 8 h and drying at room temperature, a supported catalyst precursor was obtained, wherein the loading of Pd metal was 0.5 wt.%.

[0055] Step 2: Place the supported catalyst precursor in a quartz boat, and place the quartz boat in a tube furnace. Introduce a mixture of 8% vol H2 and N2 gas at a flow rate of 100 mL / min into the tube furnace. Set the heating rate to 5 °C / min and calcine at 300 °C for 180 min. After calcine, allow the material to cool naturally to obtain a brownish-gray catalyst powder (catalyst E).

[0056] Comparative Example 2

[0057] A method for preparing a catalyst, compared with Comparative Example 1, involves raising the temperature of the calcination process in step 2 to 400°C, while keeping the other steps unchanged, to obtain a catalyst (catalyst F).

[0058] Comparative Example 3

[0059] A method for preparing a catalyst, compared with Comparative Example 1, involves raising the temperature of the calcination process in step 2 to 500°C, while keeping the other steps unchanged, to obtain a catalyst (catalyst G).

[0060] Test case

[0061] Catalysts A, B, C, and D prepared in the examples, as well as catalysts E, F, and G prepared in the comparative examples, were evaluated for their performance under the same reaction conditions. The results are shown in Table 2. The reaction conditions were as follows: the hydrogen source was either high-purity hydrogen or a mixture of H2 and CO containing 1000 ppm CO; the reaction temperature was 40°C; the reaction pressure was 3 bar; the stir bar speed was 2500 r / min; and the reaction substrate was 3-nitrostyrene (3-NS). The reaction products were detected by Shimadzu GC-2014C chromatography using an HP-5 column (0.32 mm, 50 m). The conversion, selectivity, and TOF calculation formulas are as follows:

[0062] Conversion rate calculation formula:

[0063]

[0064] Selectivity calculation formula:

[0065]

[0066]

[0067]

[0068] TOF calculation formula

[0069]

[0070] Where time represents time, and c 3-NS,0 : Concentration of substrate 3-NS before reaction, c 3-NS,t : Concentration of substrate 3-NS after reaction, c 3-VA The concentration of the NO2 hydrogenation product 3-vinylaniline (3-VA) after the reaction, c 3-ENB The concentration of 3-nitrobenzene (3-ENB), the product of C=C double bond hydrogenation after the reaction, c 3-EA The concentration of the product after complete hydrogenation, 3-ethylaniline (i.e., the product after complete hydrogenation of both C=C and -NO2), is given by n. 3-NS,0 n: The amount of substrate 3-NS before the reaction 3-NS,t n represents the amount of substrate 3-NS after the reaction. Pd The amount of Pd element active centers in the catalyst, calculated as a total amount.

[0071] Table 2

[0072]

[0073]

[0074] Wherein: a: 0.25 mmol of 3-NS, 5 mg of catalyst, 3 min reaction time, high-purity hydrogen as the hydrogen source; b: 0.25 mmol of 3-NS, 5 mg of catalyst, 3 min reaction time, H2 and CO mixture as the hydrogen source, CO content 1000 ppm; c: 0.25 mmol of 3-NS, 10 mg of catalyst, 30 min reaction time, high-purity hydrogen as the hydrogen source; d: 0.25 mmol of 3-NS, 10 mg of catalyst, 30 min reaction time, H2 and CO mixture as the hydrogen source, CO content 1000 ppm.

[0075] Table 2 shows that, for catalysts prepared at different calcination temperatures, catalysts A and B in the examples, using the same carbon source (dopamine hydrochloride powder, a nitrogen-containing carbon source), exhibited nearly 100% selectivity for C=C hydrogenation at low temperatures (100–400°C) and nearly 100% selectivity for -NO2 hydrogenation at high temperatures (500°C–1000°C). For catalysts prepared at different calcination temperatures, catalysts C and D in the examples, using the same carbon source (glucose, a nitrogen-free carbon source), exhibited nearly 100% selectivity for C=C hydrogenation at low temperatures (100–300°C) and nearly 100% selectivity for -NO2 hydrogenation at high temperatures (400°C–1000°C). This is because nitrogen-containing carbon sources have a relatively thick carbon shell and a relatively stable structure due to the presence of nitrogen, making glucose easier to reduce. Therefore, nitrogen-free carbon sources have lower conversion temperatures. Furthermore, the results for catalysts A and B under two reaction conditions, a and b, indicate that CO does not significantly poison the catalysts.

[0076] When the same carbon source is calcined at high temperature, sp2 hybridized C disappears and oxygen-containing carbon appears. Therefore, the hydrogenation selectivity of -NO2 is close to 100%. When calcined at low temperature, sp2 hybridized C exists but no oxygen-containing carbon appears. Therefore, the hydrogenation selectivity of C=C is close to 100%.

[0077] The comparative preparation of catalysts E, F and G showed that the carbon-free materials did not exhibit this change in selectivity at different calcination temperatures, and the C=C hydrogenation selectivity was close to 100%.

[0078] The activity of catalysts varies when hydrogenation is catalyzed for different functional groups. When catalysts A, C, E, F and G all selectively catalyze the hydrogenation of C=C, catalysts A and C have a higher TOF (turnover frequency, the number of times a unit active site of a catalyst can catalyze a reaction per unit time).

[0079] If the reaction substrate is replaced with 4-nitrophenylacetylene, 3-nitrophenylacetylene, 3-nitrostyrene, ethyl 4-nitrocinnamate, 4-nitrocinnamic acid, etc., the catalytic results are the same as those described above.

[0080] The above description is only a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. The application of a selective hydrogenation catalyst in the selective catalytic hydrogenation of C=C nitroaromatic hydrocarbons to prepare aniline derivatives or nitrobenzene derivatives, characterized in that, When the carbon source is a polymerizable nitrogen-containing carbon source: When the calcination temperature is 100~400℃, the hydrogenation selectivity of C=C is 99%~100%; when the calcination temperature is 500~1000℃, the hydrogenation selectivity of -NO2 is 99%~100%. When the carbon source is a polymerizable, nitrogen-free carbon source: When the calcination temperature is 100~300℃, the hydrogenation selectivity of C=C is 99%~100%; when the calcination temperature is 400~1000℃, the hydrogenation selectivity of -NO2 is 99%~100%. The selective hydrogenation catalyst has a three-layer structure of core-transition metal-carbon shell, with a reducible oxide support as the core, a transition metal as the middle layer, and a polymerizable carbon source undergoing a polymerization reaction to form the carbon shell. The reducible oxide is TiO2, CeO2, FeO, FeO2, Fe2O3, WO3, ZnO, CuO, ZrO or In2O3, wherein the TiO2 has anatase phase or a mixed phase of anatase and rutile; The transition metal is Pd, Pt, Ru, Au, Ni, Co, or Fe.

2. The application according to claim 1, characterized in that, Includes the following steps: Using a reducible oxide as a support, the transition metal was loaded by a wet chemical impregnation method to obtain a supported catalyst precursor. Then, the polymerizable carbon source is polymerized to form a carbon shell that coats the surface of the supported catalyst precursor. After filtration, washing, and drying, it is calcined in an oxygen-free atmosphere to obtain a selective hydrogenation catalyst. The calcination temperature is 100~1000℃.

3. The application according to claim 2, characterized in that, The carbon source may be a nitrogen-containing carbon source or a nitrogen-free carbon source; the nitrogen-containing carbon source may be dopamine hydrochloride, glutamic acid or melamine, and the nitrogen-free carbon source may be glucose or tannic acid.

4. The application according to claim 2, characterized in that, The loading of the transition metal in the selective hydrogenation catalyst is 0.01 wt.%–40.0 wt.%; the mass ratio of the carbon source to the supported catalyst precursor is (0.01 ~ 20.0):

1.

5. The application according to claim 2, characterized in that, The polymer coating is either stirred polymerization coating or hydrothermal polymerization coating; When the coating is coated by stirring polymerization, the stirring polymerization coating is carried out in a water bath or oil bath, the stirring time is 6~72 h, the temperature of the water bath or oil bath is room temperature~120 ℃, and the stirring speed is 100~3000 r / min. When hydrothermal polymerization coating is used, the temperature of the hydrothermal polymerization coating is 80~200 ℃ and the time is 4~48 h. The hydrothermal polymerization coating may or may not be stirred. When stirring, the stirring speed is 50~500 r / min.

6. The application according to claim 2, characterized in that, The selective hydrogenation catalyst described herein is used in the selective hydrogenation reaction of compounds containing two or more reducible functional groups.

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