Catalyst as well as preparation method and application thereof in pyridine hydrogenation reaction

Abstract

The invention provides a catalyst, a preparation method thereof and application of the catalyst in pyridine hydrogenation reaction. The pyridine hydrogenation catalyst comprises an alumina carrier and active metal loaded on the alumina carrier, the alumina carrier only contains L acid and does not contain B acid; the active metals are platinum and palladium, and the atomic ratio of platinum to palladium is (3-4): 1. The pyridine hydrogenation catalyst can show relatively high hydrogenation activity under the condition of low active metal loading capacity.

Description

Technical Field

[0001] The invention relates to a catalyst and a preparation method thereof and application of the catalyst in pyridine hydrogenation reaction, belonging to the field of pyridine hydrogenation. Background Art

[0002] Piperidine, also known as hexahydropyridine, is a very important intermediate that can be used as an intermediate for spices, organic solvents, piperidine hydrochloride analgesics, and can also be used to synthesize herbicides and plant growth regulators. In recent years, with the rapid development of the pharmaceutical, pesticide, dye, additive, rubber and other industries, the market demand for high-quality piperidine has increased sharply.

[0003] Piperidine compounds can be synthesized by chemical methods, but the synthesis route is long, the operation steps are cumbersome, the reaction conditions are also complicated, and it is difficult to apply them industrially. At the same time, some by-products are produced during the synthesis process, and a large amount of chemical solvents that are harmful to the environment are discharged, which makes it difficult to achieve large-scale production.

[0004] At present, the research on the synthesis of piperidine by catalytic hydrogenation of pyridine is mainly based on precious metal catalysts such as palladium, platinum, Ru, and Ir. In industry, the synthesis of piperidine by catalytic hydrogenation of pyridine mainly uses Ni-based catalysts and mainly adopts intermittent catalytic hydrogenation process. This traditional piperidine production process has the disadvantages of harsh hydrogenation reaction conditions, long reaction time, and easy deactivation of catalysts. At the same time, intermittent high-pressure hydrogenation is small in scale, high in cost, and highly polluting, and cannot meet the needs of industrial production. Therefore, continuous pyridine catalytic hydrogenation synthesis technology and high-efficiency catalysts have very important research significance and application value.

[0005] CN101502789A discloses a nano-ruthenium carbon-supported metal hydrogenation catalyst and a preparation method thereof. The catalyst uses activated carbon as a carrier and ruthenium as an active metal. A nano-ruthenium catalyst with high activity is prepared through pretreatment and modification. However, the mechanical stability of the catalyst is poor and the active components are easily lost during use.

[0006] CN1082121172A discloses a catalyst for hydrogenation of pyridine compounds and its application, with TiO2-C as a carrier and ruthenium as an active metal, and its loading amount is 1-3%. By modifying ruthenium and introducing a co-metal, the hydrogenation activity of the catalyst is greatly improved, so that the conversion rate of pyridine can be close to 100%. The fixed bed reaction device is adopted, the degree of continuity is high, the operation is easy, and large-scale production is easy. However, the loading amount of the precious metal is high, and the mechanical stability of TiO2-C is poor, and the service life is short.

[0007] In summary, how to obtain a low-loaded and highly active catalyst has become a key issue that needs to be urgently solved in the field of pyridine hydrogenation. Summary of the invention

[0008] In order to solve the above technical problems, the object of the present invention is to provide a catalyst and a preparation method thereof and use thereof in pyridine hydrogenation reaction, wherein the catalyst can achieve the beneficial effect of high activity at a low active metal loading.

[0009] To achieve the above-mentioned purpose, the present invention provides a catalyst, which includes an alumina carrier and an active metal loaded on the alumina carrier; the alumina carrier contains only L acid but no B acid; the active metal is platinum and palladium, and the atomic ratio of platinum to palladium is 3 to 4:1.

[0010] The catalyst of the present invention includes an alumina carrier, so that the catalyst has strong mechanical properties and a long service life. In particular, the alumina carrier contains only L acid and no B acid. Such a catalyst is subsequently used in the pyridine hydrogenation reaction, which effectively reduces the occurrence of pyridine hydrogenation side reactions and greatly improves the yield of the target product piperidine compounds. At the same time, in the catalyst of the present invention, the active metal includes platinum and palladium at the same time, and the atomic ratio of platinum to palladium is 3 to 4:1. Compared with the existing single active metal component hydrogenation catalyst, the hydrogenation catalyst of the present invention shows higher hydrogenation activity for pyridine, which greatly improves the yield of piperidine compounds. More importantly, palladium is doped in platinum, which has a good promoting effect on the dispersion of active metals, and based on the above atomic ratio, there is a suitable interaction force between platinum and palladium active metals, thereby further increasing the dispersion of active metals and improving the utilization rate of active metal components.

[0011] In summary, the above-mentioned pyridine hydrogenation catalyst can exhibit high hydrogenation activity at a low active metal loading and is suitable for industrial production.

[0012] Furthermore, the amount of L-acid in the alumina carrier is 0.1-0.4 mmol / g (pyridine-infrared method desorption temperature 200° C.).

[0013] In some optional embodiments, the alumina carrier has a particle size of 20 to 40 mesh and a specific surface area of ​​260 m 2 / g, pore volume ≥ 0.60cm 3 / g, and an average pore size of 5 to 10 nm. Preferably, the alumina carrier has a particle size of 20 to 40 mesh and a specific surface area of ​​260 to 275 m 2 / g, pore volume of 0.60~0.65cm 3 / g, the average pore size is 6 to 8 nm.

[0014] Furthermore, based on 100% of the pyridine hydrogenation catalyst, the loading amount of platinum is 0.4-0.6 wt%.

[0015] The present invention also provides a method for preparing the aforementioned pyridine hydrogenation catalyst, which comprises: impregnating an alumina carrier in an impregnation solution containing a platinum source, a palladium source and a hydrochloric acid aqueous solution, and then drying and calcining in sequence to obtain a pyridine hydrogenation catalyst. Using a hydrochloric acid solution as a co-solvent for the palladium source can further improve the dissolution efficiency of the palladium source. At the same time, loading platinum and palladium on the alumina carrier can prevent the aggregation of platinum and palladium metal particles, thereby improving the dispersibility of the catalyst.

[0016] Furthermore, the molar concentration of the hydrochloric acid aqueous solution is 0.1 to 0.4 mol / L, for example, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L or 0.4 mol / L.

[0017] Furthermore, the platinum source is chloroplatinic acid and the palladium source is palladium chloride. The impregnation solution can be prepared by the following steps: firstly preparing a hydrochloric acid aqueous solution with a molar concentration of 0.1 to 0.4 mol / L, and then dissolving the platinum source and the palladium source in the hydrochloric acid aqueous solution to obtain the impregnation solution.

[0018] Furthermore, the impregnation is performed by an equal volume impregnation method, which can more conveniently control the loading amount of the active component. The equal volume impregnation method means that the pore volume of the carrier is consistent with the volume of the impregnation solution, and the impregnation solution can just completely enter the pores.

[0019] Furthermore, the immersion time is 12 to 24 hours. The present invention has no special requirements on the immersion temperature, and the immersion temperature can be room temperature.

[0020] Furthermore, the drying temperature is 60-120° C. and the drying time is 5-12 hours. The present invention does not have any special requirements on the drying atmosphere, for example, the drying atmosphere can be air atmosphere.

[0021] Furthermore, the calcination temperature is 400-500°C and the time is 2-5 hours. The calcination is carried out in a muffle furnace, and the material to be calcined is heated from room temperature to the calcination temperature at a heating rate of 1.5-2.5°C / min in the muffle furnace.

[0022] The present invention also provides an application of the aforementioned pyridine hydrogenation catalyst in a pyridine hydrogenation reaction. Based on the above reasons, when the pyridine hydrogenation catalyst of the present invention is applied in a pyridine hydrogenation reaction, it can exhibit high hydrogenation activity at a low active metal loading, and is suitable for industrial production.

[0023] Furthermore, the temperature of the pyridine hydrogenation reaction is 140-220°C, the hydrogen partial pressure is 2-4 MPa, the hydrogen-oil volume ratio is 300-700:1, and the liquid hourly space velocity is 1-3 h -1 .

[0024] Further, the pyridine hydrogenation catalyst is reduced at 180-220° C. for 2-4 h and at 240-320° C. for 2-4 h, and then participates in the pyridine hydrogenation reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 shows a Py-IR graph of an alumina support used in one embodiment of the present invention;

[0026] Figure 2 The EDS spectrum of the catalyst after reduction in Example 2 of the present invention is shown;

[0027] Figure 3 The TEM image of the catalyst after reduction in Example 2 of the present invention is shown;

[0028] Figure 4 shows a TEM image of the catalyst after reduction in Example 6 of the present invention;

[0029] Figure 5 The TEM image of the catalyst after reduction in Example 7 of the present invention is shown. DETAILED DESCRIPTION

[0030] In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the technical solution of the present invention is now described in detail below, but it should not be construed as limiting the applicable scope of the present invention.

[0031] (I) Alumina carrier preparation example

[0032] In an optional embodiment, the above-mentioned alumina carrier can be prepared by the following preparation method:

[0033] Deionized water, pseudo-boehmite powder, sesbania powder and concentrated nitric acid are uniformly mixed in a certain proportion and then formed on an extruder; wherein the mass ratio of deionized water to pseudo-boehmite powder is 1.2-1.3, the amount of concentrated nitric acid accounts for 4% of the weight of the mixed system, and the amount of sesbania powder accounts for 2% of the weight of the mixed system. Sesbania powder can increase the extrusion speed, and concentrated nitric acid, as a peptizing agent, can increase the carrier strength and improve the pore structure.

[0034] The formed samples were dried at room temperature, dried at 120°C for 8 h, and calcined at 550°C for 6 h. The calcined samples were crushed on a 20-40 mesh sieve to separate particles with a particle size of 20-40 mesh.

[0035] The particle size of the alumina carrier is 20-40 mesh and the specific surface area is 280m 2 / g, pore volume is 0.65cm 3 / g, average pore size is 6.7nm, and water absorption is 1.4.

[0036] The acidity of the catalyst support was tested by pyridine-infrared method: the sample was pressed into a pellet, sealed in the in-situ cell of an infrared spectrometer, heated to 400 °C and evacuated to 10 -3 Pa, constant temperature for 1h, remove gas molecules adsorbed by the sample; then the in-situ cell is cooled to room temperature, pyridine vapor is adsorbed and adsorption equilibrium is maintained for 30min, and then the in-situ cell is heated to 200℃ and evacuated to 10 - 3 Pa, and desorbed at this vacuum for 60 min, cooled to room temperature and took a spectrum with a scanning range of 1700 cm -1 -1400cm -1 , the pyridine adsorption infrared spectrum of the sample desorbed at 200℃ is obtained, as shown in Figure 1 shown.

[0037] pass Figure 1 It can be seen that the vibration band wave number is 1448cm -1 There is an absorption peak of L acid site, and the vibration band wave number is 1543cm -1 No absorption peak of B acid site was found. Figure 1 Medium 1448cm -1 The acid content of L-acid was calculated based on the area of ​​the characteristic absorption peak, and the acid content of L-acid was 0.4 mmol / g.

[0038] (II) Preparation Example and Comparative Example of Pyridine Hydrogenation Catalyst

[0039] Example 1

[0040] This embodiment provides a method for preparing a pyridine hydrogenation catalyst, which comprises the following steps:

[0041] Weigh 0.246 g of hydrochloric acid and dissolve it in a beaker, dilute it with water, and then transfer it to a 25 mL volumetric flask to prepare a hydrochloric acid aqueous solution with a concentration of 0.1 mol / L.

[0042] Weigh 0.208g of chloroplatinic acid and 0.009g of palladium chloride and dissolve them in the above hydrochloric acid aqueous solution, stir evenly to obtain an impregnation solution. Weigh 6.5g of the above alumina carrier, and use an equal volume impregnation method to impregnate the above impregnation solution and the above alumina carrier at room temperature for 12 hours, then dry the impregnated product in an air atmosphere at 80°C for 6 hours, and then place it in a muffle furnace and calcine it at a heating rate of 2°C / min to 450°C for 4 hours to obtain a pyridine hydrogenation catalyst.

[0043] In the pyridine hydrogenation catalyst, the atomic ratio of platinum to palladium is 3:1 (theoretical calculated value). Based on 100% of the pyridine hydrogenation catalyst, the loading amount of platinum is 0.44 wt%.

[0044] The prepared pyridine hydrogenation catalyst is subjected to reduction treatment in a tubular furnace and then put into use. The reduction includes: first reducing the prepared pyridine hydrogenation catalyst at 200° C. for 2 h, and then reducing it at 400° C. for 2 h.

[0045] Example 2

[0046] This embodiment provides a method for preparing a pyridine hydrogenation catalyst, which is different from Example 1 only in that the amount of chloroplatinic acid used is 0.216 g, and the amount of palladium chloride used is 0.007 g.

[0047] In the pyridine hydrogenation catalyst thus obtained, the atomic ratio of platinum to palladium is 4:1 (theoretical calculated value). Based on 100% of the pyridine hydrogenation catalyst, the loading amount of platinum is 0.46 wt%.

[0048] Example 3

[0049] This embodiment provides a method for preparing a pyridine hydrogenation catalyst, which differs from Embodiment 2 only in that platinum is loaded first and palladium is loaded later in the impregnation treatment:

[0050] Weigh 0.208 g of chloroplatinic acid and dissolve it in the above hydrochloric acid aqueous solution, and stir evenly to obtain a chloroplatinic acid impregnation solution.

[0051] Weigh 0.009 g of palladium chloride and dissolve it in the above hydrochloric acid aqueous solution, and stir evenly to obtain a palladium chloride impregnation solution.

[0052] Weigh 6.5 g of the aforementioned alumina carrier, first use an equal volume impregnation method to impregnate the chloroplatinic acid impregnation solution and the aforementioned alumina carrier at room temperature for 12 hours, and dry the impregnated product at 80°C in an air atmosphere for 6 hours; then use an equal volume impregnation method to impregnate the palladium chloride impregnation solution and the dried product at room temperature for 12 hours, and dry the impregnated product at 80°C in an air atmosphere for 6 hours, and finally place the dried product in a muffle furnace and calcine at a heating rate of 2°C / min to 450°C for 4 hours to obtain a pyridine hydrogenation catalyst.

[0053] Example 4

[0054] This embodiment provides a method for preparing a pyridine hydrogenation catalyst, which differs from Embodiment 2 only in that palladium is loaded first and platinum is loaded later in the impregnation treatment:

[0055] Weigh 0.208 g of chloroplatinic acid and dissolve it in the above hydrochloric acid aqueous solution, and stir evenly to obtain a chloroplatinic acid impregnation solution.

[0056] Weigh 0.009 g of palladium chloride and dissolve it in the above hydrochloric acid aqueous solution, and stir evenly to obtain a palladium chloride impregnation solution.

[0057] Weigh 6.5 g of the aforementioned alumina carrier, first use an equal volume impregnation method to impregnate the palladium chloride impregnation solution and the aforementioned alumina carrier at room temperature for 12 hours, and dry the impregnated product at 80°C in an air atmosphere for 6 hours; then use an equal volume impregnation method to impregnate the chloroplatinic acid impregnation solution and the dried product at room temperature for 12 hours, and dry the impregnated product at 80°C in an air atmosphere for 6 hours, and finally place the dried product in a muffle furnace and calcine at a heating rate of 2°C / min to 450°C for 4 hours to obtain a pyridine hydrogenation catalyst.

[0058] Comparative Example 1

[0059] This comparative example provides a method for preparing a pyridine hydrogenation catalyst, which comprises the following steps:

[0060] Weigh 0.246 g of hydrochloric acid and dissolve it in a beaker, dilute it with water, and then transfer it to a 25 mL volumetric flask to prepare a hydrochloric acid aqueous solution with a concentration of 0.1 mol / L.

[0061] 0.234 g of chloroplatinic acid was weighed and dissolved in the above hydrochloric acid aqueous solution, and stirred evenly to obtain an impregnation solution.

[0062] Weigh 6.5g of the above-mentioned alumina carrier, and use an equal volume impregnation method to impregnate the above-mentioned impregnation solution and the above-mentioned alumina carrier at room temperature for 12 hours, then dry the impregnated product in an air atmosphere at 80°C for 6 hours, and then place it in a muffle furnace and calcine it at 450°C at a heating rate of 2°C / min for 4 hours to obtain a pyridine hydrogenation catalyst. Based on the pyridine hydrogenation catalyst as 100%, the loading amount of platinum is 0.5wt%.

[0063] The prepared pyridine hydrogenation catalyst is subjected to reduction treatment in a tubular furnace and then put into use. The reduction includes: first reducing the prepared pyridine hydrogenation catalyst at 200° C. for 2 h, and then reducing it at 400° C. for 2 h.

[0064] Comparative Example 2

[0065] This comparative example provides a method for preparing a pyridine hydrogenation catalyst, which comprises the following steps:

[0066] Weigh 0.246 g of hydrochloric acid and dissolve it in a beaker, dilute it with water, and then transfer it to a 25 mL volumetric flask to prepare a hydrochloric acid aqueous solution with a concentration of 0.1 mol / L.

[0067] 0.055 g of palladium chloride was weighed and dissolved in the above hydrochloric acid aqueous solution, and stirred evenly to obtain an impregnation solution.

[0068] Weigh 6.5g of the aforementioned alumina carrier, and use an equal volume impregnation method to impregnate the aforementioned impregnation solution and the aforementioned alumina carrier at room temperature for 12 hours, then first dry the impregnated product in an air atmosphere at 80°C for 6 hours, and then place it in a muffle furnace and calcine it at 450°C at a heating rate of 2°C / min for 4 hours to obtain a pyridine hydrogenation catalyst. Based on the pyridine hydrogenation catalyst as 100%, the palladium loading amount is 0.5wt%.

[0069] The prepared pyridine hydrogenation catalyst is subjected to reduction treatment in a tubular furnace and then put into use. The reduction includes: first reducing the prepared pyridine hydrogenation catalyst at 200° C. for 2 h, and then reducing it at 400° C. for 2 h.

[0070] Comparative Example 3

[0071] This comparative example provides a method for preparing a pyridine hydrogenation catalyst, which comprises the following steps:

[0072] Weigh 0.246 g of hydrochloric acid and dissolve it in a beaker, dilute it with water, and then transfer it to a 25 mL volumetric flask to prepare a hydrochloric acid aqueous solution with a concentration of 0.1 mol / L.

[0073] Weigh 0.154 g of chloroplatinic acid and 0.02 g of palladium chloride, dissolve them in the above hydrochloric acid aqueous solution, and stir evenly to obtain an impregnation solution.

[0074] Weigh 6.5 g of the aforementioned alumina carrier, and use an equal volume impregnation method to impregnate the above impregnation solution and the aforementioned alumina carrier at room temperature for 12 hours. Then, the impregnation product is first dried in an air atmosphere at 80°C for 6 hours, and then placed in a muffle furnace and calcined at a heating rate of 2°C / min to 450°C for 4 hours to obtain a pyridine hydrogenation catalyst.

[0075] In the pyridine hydrogenation catalyst, the atomic ratio of platinum to palladium is 1:1 (theoretical calculated value). Based on 100% of the pyridine hydrogenation catalyst, the loading amount of platinum is 0.32 wt%.

[0076] The prepared pyridine hydrogenation catalyst is subjected to reduction treatment in a tubular furnace and then put into use. The reduction includes: first reducing the prepared pyridine hydrogenation catalyst at 200° C. for 2 h, and then reducing it at 400° C. for 2 h.

[0077] Comparative Example 4

[0078] This comparative example provides a method for preparing a pyridine hydrogenation catalyst, which comprises the following steps:

[0079] Weigh 0.246 g of hydrochloric acid and dissolve it in a beaker, dilute it with water, and then transfer it to a 25 mL volumetric flask to prepare a hydrochloric acid aqueous solution with a concentration of 0.1 mol / L.

[0080] Weigh 0.193 g of chloroplatinic acid and 0.012 g of palladium chloride, dissolve them in the above hydrochloric acid aqueous solution, and stir evenly to obtain an impregnation solution.

[0081] Weigh 6.5 g of the aforementioned alumina carrier, and use an equal volume impregnation method to impregnate the above impregnation solution and the aforementioned alumina carrier at room temperature for 12 hours. Then, the impregnation product is first dried in an air atmosphere at 80°C for 6 hours, and then placed in a muffle furnace and calcined at a heating rate of 2°C / min to 450°C for 4 hours to obtain a pyridine hydrogenation catalyst.

[0082] In the pyridine hydrogenation catalyst, the atomic ratio of platinum to palladium is 2:1 (theoretical calculated value). Based on 100% of the pyridine hydrogenation catalyst, the loading amount of platinum is 0.41 wt%.

[0083] The prepared pyridine hydrogenation catalyst is subjected to reduction treatment in a tubular furnace and then put into use. The reduction includes: first reducing the prepared pyridine hydrogenation catalyst at 200° C. for 2 h, and then reducing it at 400° C. for 2 h.

[0084] (III) Example and Comparative Example of Synthesis of Piperidine by Hydrogenation of Pyridine

[0085] Example 5

[0086] This embodiment provides a method for synthesizing piperidine by hydrogenating pyridine, which comprises the following steps:

[0087] 0.5 L of 5 wt% raw material liquid (pyridine dissolved in cyclohexane) and 1.0 g of the catalyst prepared in Example 2 were used, hydrogen was introduced, and a catalytic hydrogenation reaction was carried out under a pressure of 3.5 MPa, a reaction temperature of 100 ° C, and a liquid hourly space velocity of 1.5 h -1 , the hydrogen-to-oil volume ratio is 500, the reaction time is 2 h, and after the reaction is completed, the reaction liquid is taken and analyzed by gas chromatography.

[0088] Example 6

[0089] This embodiment provides a method for synthesizing piperidine by hydrogenating pyridine, which comprises the following steps:

[0090] 0.5 L of 5 wt% raw material liquid (pyridine dissolved in cyclohexane) and 1.0 g of the catalyst prepared in Example 2 were used, hydrogen was introduced, and a catalytic hydrogenation reaction was carried out under a pressure of 3.5 MPa, a reaction temperature of 140° C., and a liquid hourly space velocity of 1.5 h -1 , the hydrogen-to-oil volume ratio is 500, the reaction time is 2 h, and after the reaction is completed, the reaction liquid is taken and analyzed by gas chromatography.

[0091] Example 7

[0092] This embodiment provides a method for synthesizing piperidine by hydrogenating pyridine, which comprises the following steps:

[0093] 0.5 L of 5 wt% raw material liquid (pyridine dissolved in cyclohexane) and 1.0 g of the catalyst prepared in Example 2 were used, hydrogen was introduced, and a catalytic hydrogenation reaction was carried out under a pressure of 4.0 MPa, a reaction temperature of 180° C., and a liquid hourly space velocity of 1.5 h -1 , the hydrogen-to-oil volume ratio is 500, the reaction time is 2 h, and after the reaction is completed, the reaction liquid is taken and analyzed by gas chromatography.

[0094] Example 8

[0095] This embodiment provides a method for synthesizing piperidine by hydrogenating pyridine, which comprises the following steps:

[0096] 0.5 L of 5 wt% raw material liquid (pyridine dissolved in cyclohexane) and 1.0 g of the catalyst prepared in Example 1 were used, hydrogen was introduced, and a catalytic hydrogenation reaction was carried out under a pressure of 4.0 MPa, a reaction temperature of 180° C., and a liquid hourly space velocity of 1.5 h -1 , the hydrogen-to-oil volume ratio is 500, the reaction time is 2 h, and after the reaction is completed, the reaction liquid is taken and analyzed by gas chromatography.

[0097] Example 9

[0098] This embodiment provides a method for synthesizing piperidine by hydrogenating pyridine, which comprises the following steps:

[0099] 0.5 L of 5 wt% raw material liquid (pyridine dissolved in cyclohexane) and 1.0 g of the catalyst prepared in Example 3 were used, hydrogen was introduced, and a catalytic hydrogenation reaction was carried out under a pressure of 4.0 MPa, a reaction temperature of 180° C., and a liquid hourly space velocity of 1.5 h -1 , the hydrogen-to-oil volume ratio is 500, the reaction time is 2 h, and after the reaction is completed, the reaction liquid is taken and analyzed by gas chromatography.

[0100] Example 10

[0101] This embodiment provides a method for synthesizing piperidine by hydrogenating pyridine, which comprises the following steps:

[0102] 0.5 L of 5 wt% raw material liquid (pyridine dissolved in cyclohexane) and 1.0 g of the catalyst prepared in Example 4 were used, hydrogen was introduced, and a catalytic hydrogenation reaction was carried out under a pressure of 4.0 MPa, a reaction temperature of 180° C., and a liquid hourly space velocity of 1.5 h -1 , the hydrogen-to-oil volume ratio is 500, the reaction time is 2 h, and after the reaction is completed, the reaction liquid is taken and analyzed by gas chromatography.

[0103] Comparative Example 5

[0104] This comparative example provides a method for synthesizing piperidine by hydrogenating pyridine, which comprises the following steps:

[0105] 0.5L of 5wt% raw material liquid (pyridine dissolved in cyclohexane) and 1.0g of the catalyst prepared in Comparative Example 1 were used, hydrogen was introduced, and a catalytic hydrogenation reaction was carried out under a pressure of 4.0MPa, a reaction temperature of 180°C, and a liquid hourly space velocity of 1.5h -1 , the hydrogen-to-oil volume ratio is 500, the reaction time is 2 h, and after the reaction is completed, the reaction liquid is taken and analyzed by gas chromatography.

[0106] Comparative Example 6

[0107] This comparative example provides a method for synthesizing piperidine by hydrogenating pyridine, which comprises the following steps:

[0108] 0.5L of 5wt% raw material liquid (pyridine dissolved in cyclohexane) and 1.0g of the catalyst prepared in Comparative Example 2 were used, hydrogen was introduced, and a catalytic hydrogenation reaction was carried out under a pressure of 4.0MPa, a reaction temperature of 180°C, and a liquid hourly space velocity of 1.5h -1 , the hydrogen-to-oil volume ratio is 500, the reaction time is 2 h, and after the reaction is completed, the reaction liquid is taken and analyzed by gas chromatography.

[0109] Comparative Example 7

[0110] This comparative example provides a method for synthesizing piperidine by hydrogenating pyridine, which comprises the following steps:

[0111] 0.5L of 5wt% raw material liquid (pyridine dissolved in cyclohexane) and 1.0g of the catalyst prepared in Comparative Example 3 were used, hydrogen was introduced, and a catalytic hydrogenation reaction was carried out under a pressure of 4.0MPa, a reaction temperature of 180°C, and a liquid hourly space velocity of 1.5h -1 , the hydrogen-to-oil volume ratio is 500, the reaction time is 2 h, and after the reaction is completed, the reaction liquid is taken and analyzed by gas chromatography.

[0112] Comparative Example 8

[0113] This comparative example provides a method for synthesizing piperidine by hydrogenating pyridine, which comprises the following steps:

[0114] 0.5L of 5wt% raw material liquid (pyridine dissolved in cyclohexane) and 1.0g of the catalyst prepared in Comparative Example 4 were used, hydrogen was introduced, and a catalytic hydrogenation reaction was carried out under a pressure of 4.0MPa, a reaction temperature of 180°C, and a liquid hourly space velocity of 1.5h -1 , the hydrogen-to-oil volume ratio is 500, the reaction time is 2 h, and after the reaction is completed, the reaction liquid is taken and analyzed by gas chromatography.

[0115] The test results are shown in Table 1:

[0116] Table 1

[0117]

[0118]

[0119] By comparing the data of Example 7 and Comparative Examples 5, 6, 7 and 8, it can be shown that, compared with the single-component hydrogenation catalyst, the hydrogenation catalyst modified by doping with a specific atomic ratio of the present invention exhibits higher hydrogenation activity for pyridine, and greatly improves the yield of piperidine compounds.

[0120] Furthermore, by comparing the data of Example 5, Example 6, and Example 7, it can be shown that, compared with low-temperature pyridine hydrogenation, the temperature of the pyridine hydrogenation reaction is preferably 140 to 220° C., and the yield of piperidine compounds is higher.

[0121] Furthermore, by comparing the data of Example 7, Example 9, and Example 10, it can be shown that, compared with loading platinum and palladium in sequence, it is preferred to load platinum and palladium simultaneously, and the yield of piperidine compounds is higher.

[0122] in, Figure 2 The EDS spectrum of the pyridine hydrogenation catalyst after reduction treatment in Example 2 of the present invention is shown. Figure 2 This indicates that the Pt element and the Pd element are uniformly loaded on the alumina carrier. Figure 3 The TEM image of the pyridine hydrogenation catalyst after reduction treatment in Example 2 of the present invention is shown. Figure 3 It can be explained that the catalyst obtained by simultaneously impregnating platinum and palladium has a smaller particle size and better catalyst dispersibility. Figure 4 The TEM image of the pyridine hydrogenation catalyst after reduction treatment in Example 6 of the present invention is shown. Figure 4 It can be seen that compared with Example 2 in which platinum and palladium are impregnated simultaneously, Example 6 first impregnates platinum and then palladium, and the particle size of the obtained catalyst is larger, which indicates that the platinum and palladium metal particles are aggregated, reducing the dispersibility of the catalyst. Figure 5 The TEM image of the pyridine hydrogenation catalyst after reduction treatment in Example 7 of the present invention is shown. Figure 5 It can be seen that compared with Example 2 in which platinum and palladium are impregnated simultaneously, Example 7 in which palladium is impregnated first and then platinum, the particle size of the obtained catalyst is also increased, which indicates that the platinum and palladium metal particles are aggregated, reducing the dispersibility of the catalyst.

[0123] Combination Figure 3-Figure 5It can be further explained that it is preferred to impregnate platinum and palladium at the same time. Regardless of whether platinum or palladium is impregnated first, the active component impregnated first forms larger particles or agglomerates on the carrier, and the active component impregnated later may be more likely to adhere to these particles, thereby increasing the particle size of the entire catalyst and reducing dispersibility. When platinum and palladium are impregnated at the same time, the active components exist in the same solution at the same time, which is conducive to the uniform dispersion of the active components.

Claims

1. A catalyst, wherein It includes an alumina carrier and an active metal supported on the alumina carrier; The alumina carrier contains only L acid but no B acid; the active metals are platinum and palladium, and the atomic ratio of the platinum to the palladium is 3 to 4:

1.

2. The catalyst according to claim 1, wherein The amount of L-acid in the alumina carrier is 0.1-0.4 mmol / g.

3. The catalyst according to claim 1, wherein The alumina carrier has a particle size of 20 to 40 meshes and a specific surface area of ​​260 to 275 m 2 / g, pore volume of 0.60~0.65cm 3 / g, the average pore size is 6 to 8 nm.

4. The catalyst according to claim 1, wherein Based on 100% of the catalyst, the loading amount of the platinum is 0.4-0.6wt%.

5. A method for preparing the catalyst according to any one of claims 1 to 4, wherein: include: The alumina carrier is impregnated in an impregnation solution containing a platinum source, a palladium source and a hydrochloric acid aqueous solution, and then dried and calcined in sequence to obtain the catalyst.

6. The method for preparing a catalyst according to claim 5, wherein: In the hydrochloric acid aqueous solution, the molar concentration of hydrochloric acid is 0.1-0.4 mol / L; Preferably, the impregnation is performed by an equal volume impregnation method; further preferably, the impregnation treatment time is 12 to 24 hours.

7. The method for preparing a catalyst according to claim 5, wherein: The drying temperature is 60-120°C and the drying time is 5-12h; Preferably, the calcination temperature is 400-500° C. and the calcination time is 2-5 hours.

8. The method for preparing a catalyst according to claim 5, wherein: The platinum source is chloroplatinic acid; the palladium source is palladium chloride.

9. Use of the catalyst according to any one of claims 1 to 4 in pyridine hydrogenation reaction.

10. The use according to claim 9, wherein: The temperature of the pyridine hydrogenation reaction is 140-220°C; Preferably, the hydrogen partial pressure of the pyridine hydrogenation reaction is 2-4 MPa; the hydrogen-oil volume ratio of the pyridine hydrogenation reaction is 300-700:1; the liquid hourly space velocity of the pyridine hydrogenation reaction is 1-3 h -1 ; Preferably, the catalyst is reduced at 180-220° C. for 2-4 h and at 240-320° C. for 2-4 h in sequence before participating in the pyridine hydrogenation reaction.

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