Hydrogenation catalyst, preparation method and application in citral hydrogenation

Abstract

The invention discloses a hydrogenation catalyst, a preparation method and application in citral hydrogenation. The hydrogenation catalyst comprises an active component and a composite oxide carrier, the active components comprise Pd and Ni; the composite oxide carrier is formed by compounding titanium dioxide and at least one of oxides selected from manganese oxide, magnesium oxide, aluminum oxide and silicon oxide, and is obtained through low-carbon hydrocarbon pretreatment; in the active component, the content of metal Pd is 0.5-10 wt% of that of the composite oxide carrier; and the content of the metal Ni is 0.001-1wt% of that of the composite oxide carrier. The hydrogenation catalyst provided by the invention is applied to citral hydrogenation for preparing citronellal, and not only has relatively high reaction performance, but also is good in poison resistance, long in stable operation period of the catalyst and good in recycling effect.

Description

Technical Field

[0001] The present invention relates to a catalyst, and particularly to a hydrogenation catalyst, a preparation method thereof, and an application thereof in the hydrogenation of citral. Background Art

[0002] Citronellal is one of the main components of essential oils such as eucalyptus oil and citronella oil. It has a strong, fresh, green citrus-like, slightly woody aroma and is widely used in the food, fragrance, and cosmetics industries. At the same time, citronellal is also an important intermediate for synthesizing other fragrances, such as for synthesizing hydroxycitronellal, citronellol, and menthol, etc.

[0003] The main processes for chemically synthesizing citronellal include: (1) using β-pinene as a raw material, through pyrolysis, chlorination, hydrolysis, catalytic hydrogenation, and air oxidation; this route has a complex synthesis process, low yield of citronellal, and a large amount of three wastes; (2) using citral as a raw material to prepare citronellal by hydrogenation; this process is the current mainstream synthesis route, but considering the special molecular structure of citral, it is still very challenging to prepare citronellal with high yield by hydrogenation. The reaction formula of this process and the possible side reactions are shown as follows:

[0004]

[0005] According to known literature reports, when using palladium metal as a catalyst, the hydrogenation reaction has a high selectivity for carbon-carbon double bonds and basically no selectivity for other unsaturated bonds. Based on this, using noble metal Pd as an active component for the selective hydrogenation of citral to prepare citronellal has high technical advantages and is a current research hot direction.

[0006] Patent application CN1234385A discloses a method for the selective liquid-phase hydrogenation of citral to prepare citronellal in the presence of a powdery rhodium and / or palladium catalyst and in the presence of an organic base. The highest selectivity of citronellal in this method is 94%, and the remaining products include citronellal isomers and over-hydrogenation product dihydrocitronellal. However, this method cannot achieve the reuse of the catalyst Pd / C. The catalyst loses its activity after being used once, and the activity cannot be restored even by washing the catalyst with a solvent. Marco Burgener et al. (Journal of Catalysis 228 (2004) 152 - 161) conducted a detailed study on the catalyst deactivation phenomenon that occurred during the hydrogenation of citral using Pd-based catalysts. The article pointed out that the real reason for the catalyst to lose its activity is not only related to the factor that decarbonylation decomposition produces CO and then combines with metal Pd to cause its catalytic activity to be lost, but also has an essential relationship with the self-polymerization of citral and the unsaturated hydrocarbon impurities generated by the decarbonylation reaction. However, regarding how to solve this thorny problem, the article did not give a suitable solution, so there is no technical means to refer to for this problem.

[0007] Therefore, how to improve the anti-decarbonylation reaction ability and anti-poisoning ability based on the Pd-based catalyst is particularly crucial and important. Summary of the Invention

[0008] To solve the above technical problems, the present invention provides a hydrogenation catalyst, a preparation method thereof, and an application thereof in the hydrogenation of citral. The hydrogenation catalyst provided by the present invention not only has high reaction performance in the hydrogenation of citral to prepare citronellal, but also has good anti-poisoning performance, a long stable operation period of the catalyst, and good recycling effect.

[0009] A hydrogenation catalyst includes an active component and a composite oxide support; the active component includes Pd and Ni; the composite oxide support is composed of titanium dioxide and at least one oxide selected from manganese oxide, magnesium oxide, aluminum oxide, and silicon oxide, and is pretreated with a lower hydrocarbon.

[0010] In the active component, the content of metal Pd is 0.5-10 wt% of the composite oxide support, preferably 1-5 wt%; the content of metal Ni is 0.001-1 wt% of the composite oxide support, preferably 0.01-0.1 wt%.

[0011] As a preferred embodiment of the hydrogenation catalyst in the present invention, in the composite oxide support, the content of titanium dioxide is 10-60 wt%.

[0012] As a preferred embodiment of the hydrogenation catalyst in the present invention, the lower hydrocarbon is selected from alkanes or alkenes with 1-4 carbon atoms, preferably one or more of methane, ethane, propane, ethylene, and propylene.

[0013] As a preferred embodiment of the hydrogenation catalyst in the present invention, the conditions for the pretreatment with the lower hydrocarbon are: placing the composite oxide support in a lower hydrocarbon atmosphere, heating to 200-400 °C, and treating for 1-10 h.

[0014] A preparation method of a hydrogenation catalyst includes the following steps:

[0015] 1) Prepare the composite oxide support: compound titanium dioxide and at least one oxide selected from manganese oxide, magnesium oxide, aluminum oxide, and silicon oxide, mix well, grind into powder, and sieve.

[0016] 2) Pretreat the support: pretreat the composite oxide support with a lower hydrocarbon.

[0017] 3) Preparation of hydrogenation catalyst: Dissolve the precursors of metals Pd and Ni in water, mix with the pretreated composite oxide support, add an alkali solution, control the pH to 8 - 10, let stand at 50 - 100 °C for 10 - 20 h, filter out the solid, wash, and dry to obtain the hydrogenation catalyst;

[0018] Among them, the addition amount of the Pd precursor, calculated based on the amount of metal Pd, is 0.5 - 10 wt% of the composite oxide support, preferably 1 - 5 wt%; the addition amount of the Ni precursor, calculated based on the amount of metal Ni, is 0.001 - 1 wt% of the composite oxide support, preferably 0.01 - 0.1 wt%.

[0019] As a preferred embodiment of the preparation method in the present invention, in step 1), the mass ratio of titanium dioxide to other oxides is (10 - 60):(40 - 90).

[0020] As a preferred embodiment of the preparation method in the present invention, the particle size of the composite oxide support obtained in step 1) is 100 - 600 mesh.

[0021] As a preferred embodiment of the preparation method in the present invention, in step 2), the conditions for the low-carbon hydrocarbon pretreatment are: place the composite oxide support in a low-carbon hydrocarbon atmosphere, heat to 200 - 400 °C, and treat for 1 - 10 h;

[0022] Preferably, the low-carbon hydrocarbon is selected from alkanes or alkenes with 1 - 4 carbon atoms, preferably one or more of methane, ethane, propane, ethylene, and propylene.

[0023] As a preferred embodiment of the preparation method in the present invention, the Pd precursor is selected from one or more of palladium chloride, palladium nitrate, and palladium sulfate;

[0024] Preferably, the Ni precursor is selected from one or more of nickel chloride, nickel bromide, nickel nitrate, and nickel sulfate;

[0025] Preferably, the alkali solution is one or more of sodium hydroxide, potassium hydroxide, and ammonia water solution.

[0026] Application of a hydrogenation catalyst as described above or a hydrogenation catalyst prepared by the method as described above in the reaction of hydrogenating citral to prepare citronellal.

[0027] It is known to those skilled in the art that before the hydrogenation reaction, the hydrogenation catalyst is activated under the following conditions, for example:

[0028] Place the hydrogenation catalyst in a hydrogen atmosphere, reduce at 60 - 150 °C, preferably 100 - 120 °C, for a reduction time of 2 - 20 h, preferably 5 - 10 h.

[0029] As a method for preparing citronellal by hydrogenating citral provided by the present invention, it is specifically as follows:

[0030] In the presence of a hydrogenation catalyst, citral is hydrogenated to prepare citronellal. Among them, the dosage of the hydrogenation catalyst is 1-10 wt% of the mass of citral.

[0031] Preferably, the reaction temperature is 50-150 °C, preferably 60-100 °C; the reaction pressure is 1-10 Mpa(G), preferably 2-5 Mpa(G).

[0032] Preferably, the above hydrogenation reaction is carried out in the presence of an optional aniline-based auxiliary agent, and the dosage of the auxiliary agent is, for example, 1-50 ppm of the mass of citral, preferably 5-20 ppm;

[0033] Preferably, the aniline-based auxiliary agent is selected from one or more of p-toluidine, diphenylamine, benzidine, p-phenylenediamine, and N-nitrosodiphenylamine.

[0034] By using the hydrogenation catalyst provided by the present invention for the hydrogenation reaction of citral, the yield of the product citronellal is high, and the recycling effect of the catalyst is good, and it can still maintain a reaction selectivity of 98% after being recycled 30 times. Detailed implementation mode

[0035] The following further illustrates the present invention through specific examples. The examples described in the present invention are only for the description of the present invention and do not limit the scope of the present invention.

[0036] In the present invention, raw materials and reagents can be obtained through commercial channels without special instructions.

[0037] The main analysis methods adopted in the present invention:

[0038] Gas chromatograph: Agilent7890, chromatographic column wax (for conversion rate and selectivity determination), injection port temperature: 300 °C; split ratio 50:1; carrier gas flow rate: 52.8 ml / min; temperature programming: hold at 150 °C for 10 min, rise to 260 °C at a rate of 10 °C / min, hold for 5 min, detector temperature: 280 °C.

[0039] The following Examples 1-6 and Comparative Examples 1-5 are used to prepare different hydrogenation catalysts:

[0040]

Example 1

[0041] 1) Prepare a composite oxide support: Compound titanium dioxide and manganese oxide according to a mass ratio of 10:90, and fully mix and grind them into a powder with a particle size of 150 mesh through an air jet mill;

[0042] 2) Support pretreatment: Place the composite oxide support in an ethylene atmosphere and treat it at 250 °C for 5 h to obtain a pretreated composite oxide support;

[0043] 3) Preparation of hydrogenation catalyst: Dissolve 1.33 g of palladium chloride and 5.00 mg of nickel nitrate hexahydrate in water, mix them with 10 g of the pretreated composite oxide support, add 1 wt% NaOH solution, control the pH to 8, let it stand at 70 °C for 16 h, filter out the solid, wash, and dry to obtain the hydrogenation catalyst.

[0044]

Example 2

[0045] 1) Preparation of composite oxide support: Compound titanium dioxide and alumina in a mass ratio of 20:80, fully mix them by an air jet mill and grind them to a particle size of 200 mesh;

[0046] 2) Support pretreatment: Place the composite oxide support in a propylene atmosphere and treat it at 350 °C for 3 h to obtain a pretreated composite oxide support;

[0047] 3) Preparation of hydrogenation catalyst: Dissolve 1.00 g of palladium chloride and 50.05 mg of nickel nitrate hexahydrate in water, mix them with 10 g of the pretreated composite oxide support, add 1 wt% NaOH solution, control the pH to 8.6, let it stand at 80 °C for 18 h, filter out the solid, wash, and dry to obtain the hydrogenation catalyst.

[0048]

Example 3

[0049] 1) Preparation of composite oxide support: Compound titanium dioxide and magnesium oxide in a mass ratio of 30:70, fully mix them by an air jet mill and grind them to a particle size of 300 mesh;

[0050] 2) Support pretreatment: Place the composite oxide support in an ethylene atmosphere and treat it at 400 °C for 1 h to obtain a pretreated composite oxide support;

[0051] 3) Preparation of hydrogenation catalyst: Dissolve 1.67 g of palladium chloride and 500.49 mg of nickel nitrate hexahydrate in water, mix them with 10 g of the pretreated composite oxide support, add 1 wt% NaOH solution, control the pH to 9, let it stand at 90 °C for 20 h, filter out the solid, wash, and dry to obtain the hydrogenation catalyst.

[0052]

Example 4

[0053] 1) Preparation of composite oxide support: Compound titanium dioxide and silicon oxide in a mass ratio of 40:60, fully mix them by an air jet mill and grind them to a particle size of 500 mesh;

[0054] 2) Support pretreatment: Place the composite oxide support in a methane atmosphere and treat it at 300 °C for 10 h to obtain a pretreated composite oxide support;

[0055] 3) Preparation of the hydrogenation catalyst: Dissolve 0.67 g of palladium chloride and 0.50 mg of nickel nitrate hexahydrate in water, mix with 10 g of the pretreated composite oxide support, add 1 wt% NaOH solution, control the pH to 10, let stand at 50 °C for 10 h, filter out the solid, wash, and dry to obtain the hydrogenation catalyst.

[0056]

Example 5

[0057] 1) Preparation of the composite oxide support: Compound titanium dioxide and magnesium oxide in a mass ratio of 50:50, mix thoroughly by an air jet mill and grind to a particle size of 400 mesh;

[0058] 2) Support pretreatment: Place the composite oxide support in an ethylene atmosphere and treat it at 200 °C for 9 h to obtain a pretreated composite oxide support;

[0059] 3) Preparation of the hydrogenation catalyst: Dissolve 0.33 g of palladium chloride and 25.02 mg of nickel nitrate hexahydrate in water, mix with 10 g of the pretreated composite oxide support, add 1 wt% NaOH solution, control the pH to 9.8, let stand at 120 °C for 14 h, filter out the solid, wash, and dry to obtain the hydrogenation catalyst.

[0060]

Example 6

[0061] 1) Preparation of the composite oxide support: Compound titanium dioxide and magnesium oxide in a mass ratio of 60:40, mix thoroughly by an air jet mill and grind to a particle size of 600 mesh;

[0062] 2) Support pretreatment: Place the composite oxide support in a propane atmosphere and treat it at 400 °C for 7 h to obtain a pretreated composite oxide support;

[0063] 3) Preparation of the hydrogenation catalyst: Dissolve 0.17 g of palladium chloride and 250.24 mg of nickel nitrate hexahydrate in water, mix with 10 g of the pretreated composite oxide support, add 1 wt% NaOH solution, control the pH to 8.5, let stand at 90 °C for 20 h, filter out the solid, wash, and dry to obtain the hydrogenation catalyst.

[0064]

Comparative Example 1

[0065] Prepare the hydrogenation catalyst by a method basically the same as that in Example 3, except that the pretreatment of the support in step 2) is not carried out.

[0066]

Comparative Example 2

[0067] The hydrogenation catalyst was prepared by referring to the method substantially the same as that in Example 3, except that magnesium oxide was not added during the preparation of the support in step 1); meanwhile, the pretreatment of the support in step 2) was not carried out.

[0068]

Comparative Example 3

[0069] The hydrogenation catalyst was prepared by referring to the method substantially the same as that in Example 3, except that magnesium oxide was not added during the preparation of the support in step 1).

[0070]

Comparative Example 4

[0071] The hydrogenation catalyst was prepared by referring to the method substantially the same as that in Example 3, except that in step 1) when preparing the support, alumina and magnesium oxide with a mass ratio of 30:70 were used as raw materials; meanwhile, the pretreatment of the support in step 2) was not carried out.

[0072]

Comparative Example 5

[0073] The hydrogenation catalyst was prepared by referring to the method substantially the same as that in Example 3, except that in step 1) when preparing the support, alumina and magnesium oxide with a mass ratio of 30:70 were used as raw materials.

[0074]

Application Example

[0075] For Application Examples 1 - 6 and Comparative Application Examples 1 - 5, the hydrogenation performance of the catalysts provided in Examples 1 - 6 and Comparative Examples 1 - 5 was evaluated respectively:

[0076] Reduction of the hydrogenation catalyst: The hydrogenation catalyst was placed in a hydrogen atmosphere and reduced at 120 °C for 10 h, and after reduction activation, it was used for the hydrogenation reaction.

[0077] In a 500 ml reaction kettle, 2 g of the hydrogenation catalyst, 100 g of citral, and N - nitrosodiphenylamine accounting for 15 ppm of the mass of citral were added. The autoclave was sealed, and nitrogen and hydrogen were each replaced 3 times. Then, heating and stirring were started. When the temperature rose to 120 °C, hydrogen was filled to 1 MPa(G) and maintained for 6 h until the reaction ended.

[0078] Then, each hydrogenation catalyst recovered by filtration was recycled and reused according to the above - mentioned same method, and the GC analysis results are shown in Table 1;

[0079] Table 1. Reaction results

[0080]

[0081] The above - mentioned is only the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the method of the present invention, several improvements and supplements can be made, and these improvements and supplements should also be regarded as the protection scope of the present invention.

Claims

1. A hydrogenation catalyst, characterized in that, A composite oxide support comprising an active component; the active component includes Pd and Ni; the composite oxide support is prepared by compounding titanium dioxide and at least one oxide selected from manganese oxide, magnesium oxide, aluminum oxide, and silicon oxide, and is pretreated with a lower hydrocarbon; In the active component, the content of metal Pd is 0.5-10 wt% of the composite oxide support, preferably 1-5 wt%; the content of metal Ni is 0.001-1 wt% of the composite oxide support, preferably 0.01-0.1 wt%.

2. The hydrogenation catalyst according to claim 1, characterized in that, In the composite oxide support, the content of titanium dioxide is 10-60 wt%.

3. The hydrogenation catalyst according to claim 1 or 2, characterized in that, The lower hydrocarbon is selected from alkanes or alkenes having 1-4 carbon atoms, preferably one or more of methane, ethane, propane, ethylene, and propylene.

4. The hydrogenation catalyst according to any one of claims 1-3, characterized in that, The conditions for the lower hydrocarbon pretreatment are: placing the composite oxide support in a lower hydrocarbon atmosphere, heating to 200-400 °C, and treating for 1-10 h.

5. A method for preparing a hydrogenation catalyst, characterized in that, Comprising the following steps: 1) Prepare the composite oxide support: Compound titanium dioxide and at least one oxide selected from manganese oxide, magnesium oxide, aluminum oxide, and silicon oxide, mix well, grind into powder, and pass through a sieve; 2) Support pretreatment: Pretreat the composite oxide support with a lower hydrocarbon; 3) Prepare the hydrogenation catalyst: Dissolve the precursors of metal Pd and Ni in water, mix with the pretreated composite oxide support, add an alkali solution, control the pH to 8-10, stand at 50-100 °C for 10-20 h, filter out the solid, wash, and dry to obtain the hydrogenation catalyst; Among them, the addition amount of the Pd precursor is calculated based on the amount of metal Pd, and is 0.5-10 wt% of the composite oxide support, preferably 1-5 wt%; the addition amount of the Ni precursor is calculated based on the amount of metal Ni, and is 0.001-1 wt% of the composite oxide support, preferably 0.01-0.1 wt%.

6. The preparation method of the hydrogenation catalyst according to claim 5, wherein In step 1), the mass ratio of titanium dioxide to other oxides is (10-60):(40-90).

7. The preparation method of the hydrogenation catalyst according to claim 5, characterized in that, The particle size of the composite oxide support obtained in step 1) is 100-600 mesh.

8. The preparation method of the hydrogenation catalyst according to any one of claims 5-7, characterized in that, In step 2), the conditions for the lower hydrocarbon pretreatment are: placing the composite oxide support in a lower hydrocarbon atmosphere, heating to 200-400 °C, and treating for 1-10 h; Preferably, the lower hydrocarbon is selected from alkanes or alkenes having 1-4 carbon atoms, preferably one or more of methane, ethane, propane, ethylene, and propylene.

9. The preparation method of the hydrogenation catalyst according to any one of claims 5-8, characterized in that, The Pd precursor is selected from one or more of palladium chloride, palladium nitrate, and palladium sulfate; Preferably, the Ni precursor is selected from one or more of nickel chloride, nickel bromide, nickel nitrate, and nickel sulfate; Preferably, the alkali solution is one or more of sodium hydroxide, potassium hydroxide, and ammonia water solution.

10. Use of a hydrogenation catalyst as described in any one of claims 1-4 or a hydrogenation catalyst prepared by the method as described in any one of claims 5-9 in the reaction of hydrogenating citral to prepare citronellal.

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