CN107866249B - Molybdenum carbide catalyst for preparing nerol and geraniol by hydrogenating citral - Google Patents
Molybdenum carbide catalyst for preparing nerol and geraniol by hydrogenating citral Download PDFInfo
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Abstract
Molybdenum carbide catalyst for hydrogenation of citral to nerol and geraniol: the XRD diffraction spectrum of the molybdenum carbide catalyst has one of the following four characteristics according to 2 theta difference: 36-38 degrees, 41-43 degrees, 61-63 degrees and 73-75 degrees; 34-35 degrees, 37-38 degrees, 39-40 degrees, 51-53 degrees, 61-63 degrees, 69-71 degrees, 72-73 degrees, 74-75 degrees and 75-76 degrees; 36-39 degrees, 42-44 degrees, 62-65 degrees and 74-77 degrees; 25-27 degrees, 34-35 degrees, 36-37 degrees, 37-39 degrees, 39-41 degrees, 51-53 degrees, 53-54 degrees, 61-63 degrees, 68-70 degrees, 71-73 degrees, 73.5-75 degrees and 75-77 degrees.
Description
Technical Field
The invention relates to a molybdenum carbide catalyst for preparing nerol and geraniol by hydrogenating citral and application thereof.
Background
Citral (citral) is an important α, β -unsaturated aldehyde with two geometric isomers: geranial (trans, citral A) and neral (cis, citral B), wherein citral contained in the lemongrass oil is mainly citral B. The selective hydrogenation product unsaturated alcohol is nerol and geraniol (cis/trans-3, 7-dimethyl-2, 6-octadiene-l-alcohol), which are two valuable spices and medical intermediates, and the catalyst has wide application value in the industries of essence, medicine and the like (plum autumn, Liu Ying Xin, Wang Guilin, and the like, research progress of the catalyst for synthesizing nerol/geraniol by selective hydrogenation of citral [ J ]. modern chemical industry, 2007(S2):32-36.), so that researchers have attracted extensive attention and researched on the reaction of synthesizing nerol and geraniol by selective catalytic hydrogenation of citral in recent years.
The citral structure has carbonyl and double bonds, and chemical reactions such as addition, condensation, cyclization, oxidation and the like are easy to occur. The carbonyl group in the citral can be subjected to reduction, addition and condensation reactions, and can synthesize citral, nerol (nerol) and geraniol (geraniol), acetal and mercaptal, pseudoionone and ionone, cyclocitral, beta-dihydrodamascone and irone (irone), timolone and timolol, and the like. The double bond in citral can be selectively hydrogenated to obtain dihydrocitronellal, citronellal and citronellol (Qiting, Luqiqi, Li xing Yu, etc. the research on perfume synthesis using citral as raw material advances [ J ] Guangzhou chemical industry, 2014 (20)).
The hydrogenation activity of the catalyst on citral is related to the capability of the metal surface to activate C ═ C and C ═ O, and the selectivity of the catalyst on unsaturated alcohols is related to the adsorption pattern of the catalyst on reactant molecules. Therefore, in order to increase the yield of unsaturated alcohols, a catalyst is required to have not only high activity but also high selectivity to C ═ O. The active components of the catalyst for synthesizing nerol/geraniol by selective hydrogenation of citral can be divided into two main groups: one is non-noble metal, such as Ni, Co, etc.; the other is a noble metal such as Pd, Pt, Rh, Ru, etc. Different active components have different effects on the selective hydrogenation of the citral carbonyl.
The active components of the non-noble metal catalyst for selective hydrogenation of citral are mostly concentrated in metals such as Ni and Co. Ikushima and the like use mesoporous molecular sieve MCM-41 loaded Ni as a catalyst to catalyze citral hydrogenation in subcritical CO2The medium citral is hydrogenated into nerol and geraniol, and the selectivity is as high as 99%. Gieck et al examined MgCo6Ge6、MgCo4Ge6The catalytic performance of catalysts for preparing nerol and geraniol by hydrogenating citral is equal, and the catalysts are found to have very high selectivity (Gieck C, Schreyer M,
T F,et al.Synthesis,Crystal Structure,and Catalytic Properties of MgCo6Ge6[J].Chemistry,2006,12(7):1924–1930.；Gieck C,Schreyer M,
T F,et al.Crystal structure and properties of MgCo4Ge6[J].2006.). Further, Mg2Sn also shows a higher selectivity for citral hydrogenation (Claus P, Raif F, cave S, et al from monomer to material: Mg)2Sn as hydrogenation catalyst[J].Catalysis Communications,2006,7(9):618-622.)。
In recent years, the noble metal active components used for the citral carbonyl selective hydrogenation catalyst mainly comprise Ru, Rh, Pt, Ir, Os and the like. Among them, Os, Rh, Ir show high selectivity to nerol and geraniol. Os/SiO2、Rh-Ge/A12O3、Ir/SiO2、Ir/TiO2The selectivity of the catalysts to nerol and geraniol reaches 100 percent; in contrast, the selectivity of Ru metal catalysts is slightly reduced, but the activity is higher, as in Ru/A12O3、Ru/TiO2The conversion rate of the citral on the catalyst reaches 100 percent. Au/Fe2O3The catalyst has high activity and selectivity under mild conditions.
However, noble metal catalysts have disadvantages of high cost and low resource consumption, and the search for alternatives thereof has been a trend.
Disclosure of Invention
One of the technical problems to be solved by the invention is the problem of high cost of the commonly used noble metal hydrogenation catalyst, and provides a molybdenum carbide catalyst for preparing nerol and geraniol by hydrogenating citral.
The second technical problem to be solved by the invention is the preparation method of the molybdenum carbide catalyst.
The invention aims to solve the technical problem of application of a molybdenum carbide catalyst as a catalyst in the reaction of preparing nerol and geraniol by hydrogenating citral.
In order to solve one of the above technical problems, the technical solution of the present invention is as follows: molybdenum carbide catalyst for hydrogenation of citral to nerol and geraniol: the XRD diffraction pattern of the molybdenum carbide catalyst has one of the following four characteristics:
(a) peak position: the peak 2 theta of 1a is 36-38 degrees, the peak 2 theta of 2a is 41-43 degrees, the peak 2 theta of 3a is 61-63 degrees, and the peak 2 theta of 4a is 73-75 degrees;
peak intensity ratio: 1a:2a is 1-2: 1, 1a:3a is 1.5-3: 1, 1a:4a is 1.5-3: 1;
(b) peak position: the peak 2 theta of the 1b is 34-35 degrees, the peak 2 theta of the 2b is 37-38 degrees, the peak 2 theta of the 3b is 39-40 degrees, the peak 2 theta of the 4b is 51-53 degrees, the peak 2 theta of the 5b is 61-63 degrees, the peak 2 theta of the 6b is 69-71 degrees, the peak 2 theta of the 7b is 72-73 degrees, the peak 2 theta of the 8b is 74-75 degrees, and the peak 2 theta of the 9b is 75-76 degrees;
peak intensity ratio: 1b:2 b-1-2: 1, 1b:3 b-0.2-0.6: 1, 1b:4 b-1.5-3: 1, 1b:5 b-0.8-1.5: 1, 1b:6 b-1.5-3: 1, 1b:7 b-3: 1, 1b:8 b-1-3: 1, 1b:9 b-1.5-3: 1;
(c) peak position: the peak 2 theta of 1c is 36-39 degrees, the peak 2 theta of 2c is 42-44 degrees, the peak 2 theta of 3c is 62-65 degrees, and the peak 2 theta of 4c is 74-77 degrees;
peak intensity ratio: 1c:2 c: 1.5-2.5: 1, 1c:3 c: 2.5-3.5: 1, 1c:4 c: 3-4: 1;
(d) peak position: 25-27 o for 1d peak 2 theta, 34-35 o for 2d peak 2 theta, 36-37 o for 3d peak 2 theta, 37-39 o for 4d peak 2 theta, 39-41 o for 5d peak 2 theta, 51-53 o for 6d peak 2 theta, 53-54 o for 7d peak 2 theta, 61-63 o for 8d peak 2 theta, 68-70 o for 9d peak 2 theta, 71-73 o for 10d peak 2 theta, 73.5-75 o for 11d peak 2 theta, and 75-77 o for 12d peak 2 theta;
peak intensity ratio: 1d:2d is 0.1-2: 1, 1d:3d is 0.2-2: 1, 1d:4d is 0.2-2.5: 1, 1d:5d is 0.1-1.5: 1, 1d:6d is 0.5-2: 1, 1d:7d is 0.5-2: 1, 1d:8d is 0.1-2: 1, 1d:9d is 0.5-2: 1, 1d:10d is 0.5-3: 1, 1d:11d is 0.2-2: 1, and 1d:12d is 0.5-2: 1.
To solve the second technical problem, the technical solution of the present invention is as follows: one of the above technical problems is a method for preparing a molybdenum carbide catalyst, comprising the steps of:
(1) adding organic amine into an aqueous solution of a molybdenum source, uniformly mixing, and adjusting the pH to 0.5-6.5 (for example, the pH can be specifically 0.5, 1, 0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5, 5, 6.0 or 6.5) by using acid to obtain a material I containing flocculent precipitates;
(2) carrying out heat treatment on the material I to obtain a material II;
(3) carrying out solid-liquid separation on the material II to obtain a solid material III;
(4) and roasting in an atmosphere inert to molybdenum carbide to obtain the catalyst.
In the above technical solution, the concentration of molybdenum atoms in the aqueous solution of the molybdenum source in step (1) is preferably 0.001-1.0 mol/L, and for example, the concentration of molybdenum atoms may specifically be: 0.005, 0.01, 0.04, 0.08, 0.15, 0.25, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, 0.9 or 1.0 mol/L; the molar ratio of the organic amine to the molybdenum atoms is preferably 30.0-4.0: 1, and for example, the molar ratio of the organic amine to the molybdenum atoms specifically can be: 30.0, 25.0, 20.0, 18.0, 16.0, 14.0, 12.0, 10.0, 8.0, 6.0 or 4.0; the organic amine preferably means a compound containing a carbon-nitrogen bond in the molecule and the nitrogen atom is selected from a primary amine nitrogen, a secondary amine nitrogen or a tertiary amine nitrogen. The number of carbons in the organic amine molecule is not particularly limited, and is, for example, but not limited to, C2～C10Further non-limiting examples of organic amines of (2) are aliphatic amines, C6～C10Aromatic amines, alcohol amines, alicyclic amines, etc. As more specific, non-limiting examples, the amine can be aniline, 1, 2-propanediamine, dodecylamine, 1, 6-hexanediamine, ethanolamine, diethanolamine, triethanolamine, ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and the like.
In the technical scheme, the heat treatment temperature in the step (2) is preferably 40-70 ℃, and the heat treatment time is preferably 4-24 hours.
In the above technical scheme, the skilled person knows that before the roasting in step (4), the roasting product can be dried conventionally, so that the strength of the obtained roasted product is better.
In the above technical scheme, aniline is selected as the organic amine, and steps (1), (2), (3) and (4) are sequentially performed to prepare the catalyst a, that is, the molybdenum carbide having the characteristic (a) in the XRD powder diffraction pattern.
In the technical scheme, 1, 6-hexamethylene diamine is selected as organic amine, before roasting in the step (4), the obtained material III is dispersed in water by 10-30 times of the dry weight of the material III, Ammonium Persulfate (APS) is added, the use amount of the Ammonium Persulfate (APS) can be 0.1-1.5 times of the dry weight of the material III, the pH value of the solution is adjusted to 2-3.5, and then the step (4) is carried out, so that the catalyst B can be prepared, namely the molybdenum carbide with the characteristic (B) in the XRD powder diffraction pattern.
In the above technical scheme, the organic amine is tetraethylenepentamine, and the steps (1), (2), (3) and (4) are sequentially performed to prepare the catalyst C, that is, the molybdenum carbide having the characteristic (C) in the XRD powder diffraction pattern.
In the technical scheme, aniline is selected as the organic amine, the molybdenum source aqueous solution in the step (1) further contains Cetyl Trimethyl Ammonium Bromide (CTAB), the molar ratio of CTAB to Mo atoms is 0.01-10 times, and the steps (2), (3) and (4) are continuously carried out in sequence to prepare the catalyst D, namely the molybdenum carbide with the characteristic (D) in the XRD powder diffraction pattern.
In the above technical solution, the molybdenum source is preferably a water-soluble salt of oxoacid of molybdenum.
In the above embodiment, the water-soluble salt is preferably at least one selected from the group consisting of ammonium salt, alkali metal salt, calcium salt, magnesium salt, thallium salt and zinc salt.
In the above-mentioned embodiment, the oxoacid of molybdenum is preferably at least one selected from the group consisting of orthomolybdic acid, metamolybdic acid, paramolybdic acid, dimolybdic acid and tetramolybdic acid.
By way of non-limiting example:
in the above technical scheme, the acid used for adjusting the pH in step (1) is not particularly limited, but inorganic acids are superior to organic acids from the economic point of view, and the common inorganic acids can be hydrochloric acid, sulfuric acid, nitric acid and the like; the concentration of the inorganic acid is preferably 0.1-5.0 mol/L.
In the above technical solution, the atmosphere chemically inert to molybdenum carbide used in step (4) is not particularly limited, and the atmosphere inert to molybdenum carbide may be at least one of inert gases in the periodic table of elements (such as, but not limited to, helium, argon), nitrogen, carbon monoxide and methane, or a mixture thereof, as a non-limiting example.
In the technical scheme, the roasting temperature in the step (4) is preferably 650-750 ℃, and the roasting time is 2-8 hours; further preferably, the roasting temperature is 650-750 ℃ and the roasting time is 6-16 hours.
In order to make the morphology of the catalyst more perfect, it is preferable to undergo a pre-calcination stage before calcination, comprising the following steps: heating to 250-350 ℃ from room temperature at a speed of 4-10 ℃/min, and then heating to the roasting temperature at a speed of 1-3 ℃/min.
Because the molybdenum carbide has stronger activity, is easy to contact with air to generate violent oxidation reaction, and emits a large amount of heat after spontaneous combustion, passivation treatment is required before XRD and SEM representation, and the passivation conditions are as follows: treating for 2-24 hours in an oxygen-nitrogen mixed atmosphere containing 0.5-5% by volume of oxygen at 0-50 ℃.
However, the catalyst sample for hydrogenation reaction can be directly used for hydrogenation reaction without passivation treatment, passivation can also be considered for storage and transportation safety, but due to the lower activity of the passivated catalyst, the passivated catalyst can be activated by using a methane-hydrogen-containing mixed gas before being used for hydrogenation reaction, for example, the conditions of the activation treatment are as follows: the content of methane in the methane-hydrogen mixed gas is 10-30% by volume, the treatment temperature is 550-650 ℃, and the treatment time is 2-6 hours.
The catalyst used in the hydrogenation reaction in the embodiment of the present invention is not passivated.
The technical key of the invention is the selection of the catalyst, and the technical conditions of the reaction can be reasonably determined by a person skilled in the art according to the description of the invention. By way of non-limiting example:
the amount of the catalyst can be, but is not limited to, 1-50% of the weight of the citral.
The hydrogenation reaction solvent can be 3-8 times of the weight of the citral.
The hydrogenation solvent may be toluene, tetrahydrofuran, ethanol, isopropanol, petroleum ether or their mixture.
The hydrogenation reaction temperature can be 90-130 ℃.
The reaction pressure can be 1-5 MPa.
The reaction time may be 5 to 10 hours.
To solve the third technical problem, the technical scheme of the invention is as follows: the use of a molybdenum carbide catalyst according to any of the preceding technical aspects as a catalyst in the reaction of hydrogenation of citral to nerol and geraniol.
The inventors of the present invention have surprisingly found that molybdenum carbide having an XRD powder diffraction pattern with the characteristics listed in (b) above has a better selectivity for nerol and geraniol (based on the total selectivity of nerol and geraniol); molybdenum carbide having the characteristic listed in (c) above in its XRD powder diffractogram has a higher yield of nerol and geraniol (based on the total yield of nerol and geraniol).
The temperature of the oven or the oil bath in the step (4) may specifically be: 40, 45, 50, 55, 60, 65 or 70 ℃; the reaction time may specifically be: 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, or 24 hours;
the roasting temperature in the step (4) may specifically be: 650, 675, 690, 700, 715, 725, 735, or 750 ℃; the constant-temperature calcination time may be specifically 2, 4, 6 or 8 hours.
On the basis of the scheme, the molybdate in the step (1) is ammonium molybdate, potassium molybdate, sodium molybdate or zinc molybdate.
Compared with the existing catalyst, the invention has the following advantages:
(1) the catalyst does not contain noble metal components, and has low cost, high economical efficiency and wide resource amount.
(2) Effectively expands the application range of the transition metal carbide catalyst and can replace the reaction catalyzed by noble metal.
(3) The preparation condition is simple and easy to control, the process is simplified, the cost is lower, the product quality is higher, the stability is good, the atom utilization rate is high, and the environment is friendly.
(4) The hydrogenation reaction condition is mild, and the requirements on equipment environment and operation are low.
Drawings
FIG. 1 is an XRD powder diffractogram of catalyst A used in the present invention;
FIG. 2 is an XRD powder diffractogram of catalyst B used in the present invention;
FIG. 3 is an XRD powder diffractogram of catalyst C used in the present invention;
FIG. 4 is an XRD powder diffractogram of catalyst D used in the present invention.
Detailed Description
[ example 1 ]
1. Catalyst preparation
Taking (NH) with molybdenum atom concentration of 0.07mol/L4)6Mo7O24·4H20.15L of O aqueous solution, 0.18mol of aniline is added into the solution, and 2mol/L of HCl solution is added dropwise to the solution under stirring until the pH value is 2.0 to obtain a material I;
and standing the material I at 60 ℃ for 12 hours to obtain a material II, filtering, washing a filter cake with water for three times, washing with 200mL of water each time, washing the filter cake with absolute ethyl alcohol for three times, washing with 100mL of ethanol each time, and finally vacuum-drying the filter cake at 60 ℃ for 12 hours to obtain a material III.
Pre-roasting and roasting the material III in a nitrogen atmosphere: the temperature is increased from 20 ℃ to 300 ℃ at the temperature increasing rate of 5 ℃/min, then is increased from 300 ℃ to 700 ℃ at the temperature increasing rate of 1 ℃/min, and is kept at the temperature of 700 ℃ for 2 hours. Then the temperature is reduced to room temperature, and the mixture is cooled for 48 hours under the protection of nitrogen, so that the needed molybdenum carbide catalyst A is obtained.
The XRD powder diffractogram is shown in fig. 1, which has the following diffraction peak positions and intensity characteristics:
peak position: 1a peak 2 theta is 37.2 degrees, 2a peak 2 theta is 42.2 degrees, 3a peak 2 theta is 61.8 degrees, 4a peak 2 theta is 74.3 degrees;
peak intensity ratio: 1a:2 a-1.75: 1, 1a:3 a-2.1: 1, 1a:4 a-2.1: 1.
2. Hydrogenation reaction
The citral catalyzed selective hydrogenation reaction was carried out in a 100mL batch autoclave with stirring. 6g of toluene (AR, a national chemical reagent) is added into the kettle as a reaction solvent, and 0.5g of catalyst A is rapidly added under the protection of nitrogen. Then 1.5g (97%, cis + trans, alatin) of the reaction raw material citral was added to the kettle, and finally 6g (AR, a national chemical reagent) of isopropanol was added and stirred to mix thoroughly. The air in the autoclave was replaced with hydrogen three times. The hydrogen pressure in the kettle is adjusted to be 3.0MPa, the heating temperature is 100 ℃, the stirring speed is 300rpm, and the reaction time is 5 hours. After the reaction, the mixture was cooled to room temperature, and 1.5g of anhydrous ethanol (AR, a chemical reagent of Chinese medicine) as an internal standard was added thereto, and the mixture was uniformly mixed, and the reaction mixture was centrifuged to obtain a supernatant, and the composition was analyzed by gas chromatography.
The chromatographic conditions were as follows:
the chromatographic type is as follows: agilent 6890N type gas chromatography, HP-5 capillary column (30m × 0.32mm × 0.25 μm), hydrogen Flame Ionization Detector (FID), and combustion gas H2The flow rate is 40mL/min, the air is combustion-supporting gas, the flow rate is 400mL/min, the protective gas is helium, and the flow rate is 1.5 mL/min. The inlet temperature was 230 ℃ and the pressure was 30 psi.
The reaction result of preparing nerol and geraniol by selective hydrogenation of a molybdenum carbide catalyst A, namely citral, is as follows: the conversion at 5 hours of reaction was 89%, the selectivity (based on the total amount of nerol and geraniol) was 37%, and the yield was 32.93%.
[ example 2 ]
1. Catalyst preparation
Taking (NH) with molybdenum atom concentration of 0.07mol/L4)6Mo7O24·4H20.15L of O aqueous solution, 0.18mol of 1, 6-hexanediamine is added into the solution, and 2mol/L of HCl solution is dripped into the solution under stirring until the pH value is 2.0 to obtain a material I;
and standing the material I at 60 ℃ for 12 hours to obtain a material II, filtering, washing a filter cake with water for three times, washing with 200mL of water each time, washing the filter cake with absolute ethyl alcohol for three times, washing with 100mL of ethanol each time, and finally vacuum-drying the filter cake at 60 ℃ for 12 hours to obtain a material III.
Suspending 3.39g of material III in 100mL of water, adding 1.45g of APS, dropwise adding a 2mol/L HCl solution while stirring until the pH value is 2.5, filtering, washing the filter cake with water three times, using 200mL of water each time, and finally drying the filter cake in vacuum at 60 ℃ for 12 hours to obtain material IIIB
Pre-roasting and roasting the material IIIB in a nitrogen atmosphere: the temperature is increased from 20 ℃ to 300 ℃ at the temperature increasing rate of 5 ℃/min, then is increased from 300 ℃ to 700 ℃ at the temperature increasing rate of 1 ℃/min, and is kept at the temperature of 700 ℃ for 2 hours. Then cooling to room temperature, and cooling for 48 hours under the protection of nitrogen to obtain the required molybdenum carbide catalyst B.
The XRD powder diffractogram is shown in fig. 2, which has the following diffraction peak positions and intensity characteristics:
peak position: peak 2 θ of 1b is 34.3 °, peak 2 θ of 2b is 37.9 °, peak 2 θ of 3b is 39.3 °, peak 2 θ of 4b is 52.1 °, peak 2 θ of 5b is 61.5 °, peak 2 θ of 6b is 69.5 °, peak 2 θ of 7b is 72.4 °, peak 2 θ of 8b is 74.6 °, and peak 2 θ of 9b is 75.6 °;
peak intensity ratio: 1b:2 b-1.2: 1, 1b:3 b-0.3: 1, 1b:4 b-2.3: 1, 1b:5 b-1.4: 1, 1b:6 b-2.3: 1, 1b:7 b-4.5: 1, 1b:8 b-1.6: 1, 1b:9 b-1.9: 1.
2. Hydrogenation reaction
The citral catalyzed selective hydrogenation reaction was carried out in a 100mL batch autoclave with stirring. 6g of toluene (AR, a national chemical reagent) is added into a kettle to serve as a reaction solvent, 0.5g of catalyst B is rapidly added under the protection of nitrogen, and oxidation and passivation of the catalyst caused by long air exposure time are prevented. Then 1.5g (97%, cis + trans, alatin) of the reaction raw material citral was added to the kettle, and finally 6g (AR, a national chemical reagent) of isopropanol was added and stirred to mix thoroughly. And repeatedly charging and discharging hydrogen into the reaction kettle for three times to replace the oxygen in the reaction kettle. The hydrogen pressure in the kettle is adjusted to be 3.0MPa, the heating temperature is 100 ℃, the stirring speed is 300rpm, and the reaction time is 5 hours. After the reaction, the mixture was cooled to room temperature, and 1.5g of anhydrous ethanol (AR, a chemical reagent of chinese medicine) as an internal standard was added thereto, and the mixture was uniformly mixed, and the reaction mixture was centrifuged to obtain a supernatant, and the composition was analyzed by gas chromatography under the same conditions as in example 1.
The reaction result of preparing nerol and geraniol by selective hydrogenation of a molybdenum carbide catalyst B and citral is as follows: the conversion at 5 hours of reaction was 45%, the selectivity (based on the total amount of nerol and geraniol) was 77% and the yield was 34.65%.
[ example 3 ]
1. Catalyst preparation
Taking (NH) with molybdenum atom concentration of 0.07mol/L4)6Mo7O24·4H20.15L of aqueous O solution, 0.18mol of tetraethylenepentamine was added to the solution, and a 2mol/L HCl solution was added dropwise with stirring to a pH of 2.0 to obtain Compound I.
And standing the material I at 60 ℃ for 12 hours to obtain a material II, filtering, washing a filter cake with water for three times, washing with 200mL of water each time, washing the filter cake with absolute ethyl alcohol for three times, washing with 100mL of ethanol each time, and finally vacuum-drying the filter cake at 60 ℃ for 12 hours to obtain a material III.
Pre-roasting and roasting the material III in a nitrogen atmosphere: the temperature is increased from 20 ℃ to 300 ℃ at the temperature increasing rate of 5 ℃/min, then is increased from 300 ℃ to 700 ℃ at the temperature increasing rate of 1 ℃/min, and is kept at the temperature of 700 ℃ for 2 hours. Then cooling to room temperature, and cooling for 48 hours under the protection of nitrogen to obtain the required molybdenum carbide catalyst C.
The XRD powder diffractogram is shown in fig. 3, which has the following diffraction peak positions and intensity characteristics:
peak position: peak 1c 2 θ is 37.3 °, peak 2 θ is 43.2 °, peak 3c 2 θ is 63.1 °, and peak 4c 2 θ is 75.7 °;
peak intensity ratio: 1c:2 c: 2.1:1, 1c:3 c: 2.9:1, 1c:4 c: 3.5: 1.
2. Hydrogenation reaction
The citral catalyzed selective hydrogenation reaction was carried out in a 100mL batch autoclave with stirring. 6g of toluene (AR, a national chemical reagent) is added into a kettle to serve as a reaction solvent, 0.5g of catalyst C is rapidly added under the protection of nitrogen, and oxidation and passivation of the catalyst caused by long air exposure time are prevented. Then 1.5g (97%, cis + trans, alatin) of the reaction raw material citral was added to the kettle, and finally 6g (AR, a national chemical reagent) of isopropanol was added and stirred to mix thoroughly. And repeatedly charging and discharging hydrogen into the reaction kettle for three times to replace the oxygen in the reaction kettle. The hydrogen pressure in the kettle is adjusted to be 3.0MPa, the heating temperature is 100 ℃, the stirring speed is 300rpm, and the reaction time is 5 hours. After the reaction, the mixture was cooled to room temperature, and 1.5g of anhydrous ethanol (AR, a chemical reagent of chinese medicine) as an internal standard was added thereto, and the mixture was uniformly mixed, and the reaction mixture was centrifuged to obtain a supernatant, and the composition was analyzed by gas chromatography under the same conditions as in example 1.
The reaction result of preparing nerol and geraniol by selective hydrogenation of a molybdenum carbide catalyst C citral is as follows: the conversion was 86% at 5 hours, the selectivity (based on the total amount of nerol and geraniol) was 58% and the yield was 49.88%.
[ example 4 ]
1. Catalyst preparation
Taking (NH) with molybdenum atom concentration of 0.07mol/L4)6Mo7O24·4H20.15L of O aqueous solution, wherein the molybdenum source aqueous solution also contains hexadecyl trimethyl ammonium bromide (CTAB) with the molar concentration of 0.07mol/L, 0.18mol of aniline is added into the solution, and 2mol/L of HCl solution is dropwise added into the solution under stirring until the pH value is 2.0 to obtain a material I;
and standing the material I at 60 ℃ for 12 hours to obtain a material II, filtering, washing a filter cake with water for three times, washing with 200mL of water each time, washing the filter cake with absolute ethyl alcohol for three times, washing with 100mL of ethanol each time, and finally vacuum-drying the filter cake at 60 ℃ for 12 hours to obtain a material III.
Pre-roasting and roasting the material III in a nitrogen atmosphere: the temperature is increased from 20 ℃ to 300 ℃ at the temperature increasing rate of 5 ℃/min, then is increased from 300 ℃ to 700 ℃ at the temperature increasing rate of 1 ℃/min, and is kept at the temperature of 700 ℃ for 2 hours. Then cooling to room temperature, and cooling for 48 hours under the protection of nitrogen to obtain the required molybdenum carbide catalyst D.
The XRD powder diffractogram is shown in fig. 4, which has the following diffraction peak positions and intensity characteristics:
peak position: 2 θ of peak 1d is 26.0 °,2 θ of peak 2d is 34.4 °,2 θ of peak 3d is 36.9 °,2 θ of peak 4d is 37.9 °,2 θ of peak 5d is 39.4 °,2 θ of peak 6d is 52.1 °,2 θ of peak 7d is 53.6 °,2 θ of peak 8d is 61.6 °,2 θ of peak 9d is 69.5 °,2 θ of peak 10d is 72.6 °,2 θ of peak 11d is 74.6 °, and 2 θ of peak 12d is 75.5 °;
peak intensity ratio: 1d:2d ═ 0.5:1, 1d:3d ═ 0.75:1, 1d:4d ═ 0.6:1, 1d:5d ═ 0.18:1, 1d:6d ═ 1:1, 1d:7d ═ 1.6:1, 1d:8d ═ 0.6:1, 1d:9d ═ 1.1:1, 1d:10d ═ 2:1, 1d:11d ═ 1.4:1, and 1d:12d ═ 1: 1.
2. Hydrogenation reaction
The citral catalyzed selective hydrogenation reaction was carried out in a 100mL batch autoclave with stirring. 6g of toluene (AR, a national chemical reagent) is added into a kettle to serve as a reaction solvent, 0.5g of catalyst D is rapidly added under the protection of nitrogen, and oxidation and passivation of the catalyst caused by long air exposure time are prevented. Then 1.5g (97%, cis + trans, alatin) of the reaction raw material citral was added to the kettle, and finally 6g (AR, a national chemical reagent) of isopropanol was added and stirred to mix thoroughly. And repeatedly charging and discharging hydrogen into the reaction kettle for three times to replace the oxygen in the reaction kettle. The hydrogen pressure in the kettle is adjusted to be 3.0MPa, the heating temperature is 100 ℃, the stirring speed is 300rpm, and the reaction time is 5 hours. After the reaction, the mixture was cooled to room temperature, and 1.5g of anhydrous ethanol (AR, a chemical reagent of chinese medicine) as an internal standard was added thereto, and the mixture was uniformly mixed, and the reaction mixture was centrifuged to obtain a supernatant, and the composition was analyzed by gas chromatography under the same conditions as in example 1.
The reaction result of preparing nerol and geraniol by selective hydrogenation of a molybdenum carbide catalyst D, citral, is as follows: the conversion at 5 hours of reaction was 58%, the selectivity (based on the total amount of nerol and geraniol) was 64%, and the yield was 37.12%.
Claims (7)
1. The application of the molybdenum carbide catalyst as a catalyst in the reaction of preparing nerol and geraniol by hydrogenating citral is as follows: the XRD diffraction pattern of the molybdenum carbide catalyst has one of the following four characteristics:
(a) peak position: 1a peak 2 theta = 36-38o2a peak 2 θ = 41-43 o3a peak 2 θ = 61-63 o4a peak 2 θ = 73-75 o；
Peak intensity ratio: 1a:2a = 1-2: 1, 1a:3a = 1.5-3: 1, 1a:4a = 1.5-3: 1;
(b) peak position: 1b peak 2 θ = 34-35o2b peak 2 θ = 37-38 o3b peak 2 θ = 39-40 o4b peak 2 θ = 51-53 o5b peak 2 θ = 61-63 o6b peak 2 θ =69 to 71 o7b peak 2 θ = 72-73 o8b peak 2 θ = 74-75 o9b peak 2 θ = 75-76 o；
Peak intensity ratio: 1b:2b = 1-2: 1, 1b:3b = 0.2-0.6: 1, 1b:4b = 1.5-3: 1, 1b:5b = 0.8-1.5: 1, 1b:6b = 1.5-3: 1, 1b:7b = 3-7: 1, 1b:8b = 1-3: 1, 1b:9b = 1.5-3: 1;
(c) peak position: 1c Peak 2 θ =36~39o2c peak 2 θ = 42-44 o3c peak 2 θ = 62-65 o4c peak 2 θ = 74-77 o；
Peak intensity ratio: 1c:2c = 1.5-2.5: 1, 1c:3c = 2.5-3.5: 1, 1c:4c = 3-4: 1;
(d) peak position: 1d peak 2 θ =25 —27o2d peak 2 θ = 34-35 o3d peak 2 θ = 36-37 o4d peak 2 θ = 37-39 o5d peak 2 θ = 39-41 o6d Peak 2 θ =51~53 o7d peak 2 θ = 53-54 o8d peak 2 θ = 61-63 o9d peak 2 θ = 68-70 o10d peak 2 θ = 71-73 o11d peak 2 θ = 73.5-75 o12d peak 2 θ = 75-77 o；
Peak intensity ratio: 1d:2d = 0.1-2: 1, 1d:3d = 0.2-2: 1, 1d:4d = 0.2-2.5: 1, 1d:5d = 0.1-1.5: 1, 1d:6d = 0.5-2: 1, 1d:7d = 0.5-2: 1, 1d:8d = 0.1-2: 1, 1d:9d = 0.5-2: 1, 1d:10d = 0.5-3: 1, 1d:11d = 0.2-2: 1, 1d:12d = 0.5-2: 1;
the preparation method of the catalyst comprises the following steps:
(1) adding organic amine into an aqueous solution of a molybdenum source, uniformly mixing, and adjusting the pH value to 0.5-2.5 with acid to obtain a material I containing flocculent precipitates; the molar ratio of the organic amine to the molybdenum atoms is 30.0-4.0: 1;
(2) carrying out heat treatment on the material I to obtain a material II;
(3) carrying out solid-liquid separation on the material II to obtain a solid material III;
(4) roasting in an atmosphere chemically inert to molybdenum carbide to obtain the catalyst; before firing, it undergoes a pre-firing stage comprising the following steps: heating to 250-350 ℃ from room temperature at a speed of 4-10 ℃/min, and then heating to the roasting temperature at a speed of 1-3 ℃/min.
2. Use according to claim 1, characterized in that the molybdenum source is a water-soluble salt of the oxoacid of molybdenum.
3. The use according to claim 2, wherein the water-soluble salt is selected from at least one of an ammonium salt, an alkali metal salt, and a magnesium salt.
4. The use according to claim 2, wherein the oxoacid of molybdenum is selected from at least one of orthomolybdic acid, metamolybdic acid, paramolybdic acid, and dimolybdic acid.
5. Use according to claim 1, characterized in that: the acid used for adjusting the pH in step (1) is selected from hydrochloric acid, nitric acid or sulfuric acid.
6. Use according to claim 1, characterized in that: the atmosphere inert to molybdenum carbide used in step (4) is selected from at least one of inert gas, nitrogen, carbon monoxide and methane or a mixture thereof.
7. Use according to claim 1, characterized in that: in the step (4), the roasting temperature is 650-750 ℃, and the roasting time is 2-8 hours.
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| CN101367521A (en) * | 2008-10-13 | 2009-02-18 | 复旦大学 | Synthesis of stephanoporate molybdenum carbide nano-wire |
| CN101829588A (en) * | 2010-05-27 | 2010-09-15 | 复旦大学 | Synthetic method of load type molybdenum carbide catalyst |
| WO2012169259A1 (en) * | 2011-06-08 | 2012-12-13 | 株式会社東芝 | Method for producing molybdenum carbide granulated powder and molybdenum carbide granulated powder |
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| CN101367521A (en) * | 2008-10-13 | 2009-02-18 | 复旦大学 | Synthesis of stephanoporate molybdenum carbide nano-wire |
| CN101829588A (en) * | 2010-05-27 | 2010-09-15 | 复旦大学 | Synthetic method of load type molybdenum carbide catalyst |
| WO2012169259A1 (en) * | 2011-06-08 | 2012-12-13 | 株式会社東芝 | Method for producing molybdenum carbide granulated powder and molybdenum carbide granulated powder |
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