Preparation and application of Al2O3-Pd catalyst

Abstract

The invention discloses a preparation method and application of an Al2O3-Pd catalyst, according to the method, pyridine is used as a raw material, n-dodecane is used as an internal standard, alumina supported palladium is used as a catalyst, cyclohexane is used as a solvent, catalytic hydrogenation is carried out under 1.0-3.0 MPa and 100-200 DEG C to obtain piperidine, the conversion rate is up to 99.8%, and the yield is 95% or above. Compared with the traditional rhodium-carbon catalyst, the method has the advantages of low cost and high yield. In addition, the process is mild in reaction condition, high in yield, high in product quality, few in by-product, free of peculiar smell, environmentally friendly and safe.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical reaction engineering and relates to an Al 2 O 3 -Pd catalyst preparation method and application. Background Art

[0002] The reduction products of pyridine compounds, piperidines, are not only important pharmaceutical intermediates, but also widely used in the chemical industry, especially in the production of pesticides and rubber additives. Currently, the main method for preparing piperidine derivatives is reduction through catalytic hydrogenation reaction. The reaction formula of this process is as follows:

[0003]

[0004] In the catalytic hydrogenation method, Raney nickel is an early catalyst for catalytic hydrogenation to piperidine. It has high reaction activity, but poor stability, easy to spontaneously combust and deactivate, and inconvenient to store and use. In terms of precious metals, for the hydrogenation of N-heteroaromatic compounds, supported precious metal catalysts such as Rh, Pd, Ru and Pt catalysts are generally more active than non-precious metal catalysts such as Co, Ni, Fe and Cu catalysts. At the same time, the hydrogenation reaction performance of the catalyst is improved by adjusting the surface properties of the catalyst and the reduction ability of the catalyst. Summary of the invention

[0005] In order to overcome the deficiencies of the prior art, one of the objects of the present invention is to provide a method for preparing an alumina-supported palladium catalyst.

[0006] The second purpose of the present invention is to use pyridine as a raw material and catalyze the palladium catalyst supported by aluminum oxide to obtain piperidine. The method strengthens the gas-liquid-solid three-phase mass transfer, the reaction temperature and pressure conditions are milder, the reaction time is greatly reduced, the hydrogen dosage is lower, and the selectivity is higher; at the same time, the continuous automatic operation of the process can be realized, the process energy consumption is lower, and the safety is higher. It is a greener, more efficient and safer method for preparing piperidine.

[0007] One of the purposes of the present invention is achieved in that:

[0008] The porous spherical alumina carrier is prepared by using an oil-ammonia column molding method by adding a soft template, comprising the following steps:

[0009] The uniform sol was prepared by using pseudo-boehmite, introducing a soft template, and supplemented with a small amount of surfactant CTAB and ultrasonic treatment to ensure the uniform dispersion of PS spheres. The sol was solidified in an oil-ammonia column, and after drying and calcination, a large number of pores were formed inside the alumina spheres, effectively increasing the specific surface area.

[0010] The soft template is selected from one of activated carbon, PVP, and CS+F127.

[0011] Preparation of supported Pd / Al by impregnation-reduction method 2 O 3 The catalyst comprises the following steps:

[0012] First, pipette an appropriate volume of Na 2 PdCl 4 The solution was diluted to an appropriate volume and an equal volume was used to impregnate spherical alumina with a known water absorption rate. The Na 2 PdCl 4 The solution can be fully adsorbed by the spherical alumina support and dried at 90 °C after 2 hours. A slightly excess of hydrazine hydrate is used to reduce the impregnated Na 2 PdCl 4 The spherical alumina in the solution was transferred to a 75°C oven to continue the reaction for 2 h when no obvious bubbles emerged, and then washed with deionized water until there was no Cl in the washing liquid. - Exist, dried at 90°C.

[0013] The second object of the present invention is achieved in this way:

[0014] (1) Using pyridine as a raw material, dissolving it and n-dodecane in a solvent at a certain mass concentration as a substrate solution to be hydrogenated;

[0015] (2) The substrate solution obtained in step (1) and hydrogen are input into a micro mixer at a certain molar ratio, and mixed in a micron-sized channel to form a gas-liquid microdispersed mixture. In the micro mixer, hydrogen is cut into bubbles of micron-sized particle size, which are well mixed with the substrate solution to form a microdispersed system. This state significantly enhances the heat transfer and mass transfer process of the system, enables the reaction to be carried out at a lower temperature and pressure, accelerates the reaction rate, and reduces the demand for excess hydrogen. Under mild reaction conditions, the n-pentylamine byproduct generated by the hydrogenation ring-opening reaction of pyridine is significantly reduced or no longer generated, and the selectivity of the reaction is improved.

[0016] (3) The gas-liquid mixture formed in step (2) is introduced into a micro-packed bed module containing solid catalyst particles. The reaction pressure, temperature and material residence time are precisely controlled to complete the hydrogenation process.

[0017] (4) After the reaction in step (3) is completed, the product is continuously separated into gas and liquid through a gas-liquid separation module, the gas is introduced into the tail gas treatment system, and the liquid product enters the subsequent monitoring step.

[0018] The solvent for dissolving pyridine substances is an organic solvent formed by one of methanol, ethanol, toluene, tetrahydrofuran, n-hexane and cyclohexane.

[0019] The mass concentration of pyridine in the organic solvent is 2wt%-40wt%, preferably 5wt%.

[0020] The selected hydrogen to oil ratio is 300:1-500:1.

[0021] The space velocity is preferably 1.0-3.0, more preferably 1.0-2.0.

[0022] The reaction pressure is 1.0-8.0 MPa, more preferably 2.0-3.0 MPa; the reaction temperature is 25-300° C., more preferably 125-175° C.;

[0023] The solid particle catalyst is a palladium / aluminum oxide catalyst or a nickel-molybdenum / aluminum oxide catalyst.

[0024] The pyridine selectivity is greater than 99%, the yield is greater than 95%, and the selectivity is greater than 96%.

[0025] The innovative and beneficial effects of the method provided by this solution are:

[0026] (1) A porous spherical alumina carrier was prepared by introducing a pore-forming agent using an oil-ammonia column molding method, and a supported alumina palladium catalyst was prepared by an impregnation-reduction method.

[0027] (2) The selected catalyst loadings are 0.05% and 0.1%, both of which can achieve efficient reactions under milder reaction conditions, lower hydrogen usage, and lower pressure.

[0028] (3) Micro-reaction technology can accurately control reaction parameters, making it easier to achieve continuity and automation.

[0029] (4) The product selectivity reaches over 96%, and the conversion rate of pyridine reaches over 99%. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a supported spherical Pd / Al 2 O 3 The internal cross-section SEM images and element distribution of various supported catalysts before and after loading 2 Adsorption-desorption isotherms and pore size distribution. DETAILED DESCRIPTION

[0031] The present invention will be further described below in conjunction with specific implementation modes, but is not limited thereto.

[0032] Meanwhile, the experimental methods described in the following examples are conventional methods unless otherwise specified; the reagents, materials and equipment described are all commercially available unless otherwise specified.

[0033] Embodiment 1:

[0034] According to the method, a cyclohexane solution of pyridine was prepared with a mass concentration of 5%. The solution was mixed with hydrogen in a micro mixer to form a well-dispersed gas-liquid state; the mixture flowed through a 0.05% Pd / γAl2O3 ionizer containing a particle size of 1.8-2.0 mm and an activated carbon pore-forming agent. 2 O 3 (1:1) catalyst reaction column; control the reaction temperature to 150°C, the reaction pressure to 2.0MPa, and the space velocity to 1.0h -1 , hydrogen-to-oil ratio 500:1; after separation in a gas-liquid separator, the product at the lower end was collected and analyzed, the conversion rate of pyridine was 99.2%, and the selectivity of piperidine was 96.9%.

[0035] Example 2

[0036] According to the method, a cyclohexane solution of pyridine was prepared with a mass concentration of 5%. The solution was mixed with hydrogen in a micro mixer to form a well-dispersed gas-liquid state. The mixture flowed through a 0.05% Pd / θAl2O3 pore-forming agent containing a particle size of 1.1-1.2 mm and HMTA. 2 O 3 -2 catalyst reaction column; control the reaction temperature to 150°C, the reaction pressure to 2.0MPa, and the space velocity to 1.0h -1 , hydrogen-to-oil ratio of 500:1; after separation in a gas-liquid separator, the product at the lower end was collected and analyzed, the conversion rate of pyridine was 99.2%, and the selectivity of piperidine was 98.8%.

[0037] Example 3

[0038] According to the method, a cyclohexane solution of pyridine was prepared with a mass concentration of 5%. The solution was mixed with hydrogen in a micro mixer to form a well-dispersed gas-liquid state. The mixture flowed through a 0.1% Pd / γAl2O3 ionizer containing a particle size of 1.8-2.0 mm and an activated carbon pore-forming agent. 2 O 3 (1:1) catalyst reaction column; control the reaction temperature to 125°C, the reaction pressure to 2.0MPa, and the space velocity to 1.0h -1 , hydrogen-to-oil ratio of 500:1; after separation in a gas-liquid separator, the product at the lower end was collected and analyzed, the conversion rate of pyridine was 99.0%, and the selectivity of piperidine was 98.2%.

[0039] Example 4

[0040] According to the method, a cyclohexane solution of pyridine was prepared with a mass concentration of 5%. The solution was mixed with hydrogen in a micro mixer to form a well-dispersed gas-liquid state. The mixture flowed through a 0.1% Pd / γAl2O3 ionizer containing a particle size of 1.8-2.0 mm and a PVP pore-forming agent. 2 O3 Catalyst reaction column; control the reaction temperature to 125°C, the reaction pressure to 3.0MPa, and the space velocity to 1.0h -1 , hydrogen-to-oil ratio 500:1; after separation in a gas-liquid separator, the product at the lower end was collected and analyzed, the conversion rate of pyridine was 97.9%, and the selectivity of piperidine was 98.2%.

[0041] Example 5

[0042] According to the method, a cyclohexane solution of pyridine was prepared with a mass concentration of 5%. The solution was mixed with hydrogen in a micro mixer to form a well-dispersed gas-liquid state; the mixture flowed through a 0.1% Pd / θAl2O3 pore-forming agent having a particle size of 0.6-0.7 mm and HMTA. 2 O 3 -1 catalyst reaction column; control the reaction temperature to 150°C, the reaction pressure to 2.0MPa, and the space velocity to 1.0h -1 , hydrogen-to-oil ratio of 500:1; after separation in a gas-liquid separator, the product at the lower end was collected and analyzed, the conversion rate of pyridine was 99.8%, and the selectivity of piperidine was 99.0%.

[0043] Example 6

[0044] According to the method, a cyclohexane solution of pyridine was prepared with a mass concentration of 5%. The solution was mixed with hydrogen in a micro mixer to form a well-dispersed gas-liquid state. The mixture flowed through a 0.1% Pd / θAl2O3 pore-forming agent having a particle size of 1.1-1.2 mm and HMTA. 2 O 3 -2 catalyst reaction column; control the reaction temperature to 150°C, the reaction pressure to 2.0MPa, and the space velocity to 1.0h -1 , hydrogen-to-oil ratio of 500:1; after separation in a gas-liquid separator, the product at the lower end was collected and analyzed, the conversion rate of pyridine was 97.1%, and the selectivity of piperidine was 99.1%.

[0045] The above are only some embodiments of the present invention, and do not limit the present invention in any form. Any simple modification, equivalent changes and modifications made to the above embodiments based on the technical essence of the invention are within the scope of the technical solution of the present invention.

Claims

1. A method for preparing an Al2O3-Pd catalyst and its application, comprising the following steps: (1) Pyridine is used as a raw material and n-dodecane is used as an internal standard, which are dissolved in a solvent as a substrate solution to be hydrogenated; (2) loading alumina-supported palladium catalyst; (3) The substrate solution obtained in step (1) and hydrogen are mixed in a certain molar ratio in a micro-mixer module. (4) the gas-liquid mixture formed in step (3) is introduced into a micro-packed bed containing solid catalyst particles, and the pressure, temperature and flow rate of the reaction process are controlled to complete the hydrogenation process; (5) The product obtained after the reaction in step (4) is subjected to continuous gas-liquid separation in a gas-liquid separator to obtain piperidine.

2. The method for synthesizing piperidine by continuous liquid phase hydrogenation of pyridine according to claim 1, characterized in that: The catalyst has a carrier that uses an oil-ammonia column molding method to prepare a porous spherical alumina carrier by adding a soft template agent.

3. The method for synthesizing piperidine by continuous liquid phase hydrogenation of pyridine according to claim 1, characterized in that: The mass concentration of pyridine in the solvent is 2wt%-40wt%, preferably 5wt%.

4. The method for synthesizing piperidine by continuous liquid phase hydrogenation of pyridine in a microreactor according to claim 1, characterized in that: The reaction hydrogen-to-oil ratio is 300:1-500:

1.

5. The method for synthesizing piperidine by continuous liquid phase hydrogenation of pyridine according to claim 1, characterized in that: The reaction pressure is 1.0-8.0 MPa, more preferably 2.0-3.0 MPa.

6. The method for synthesizing piperidine by continuous liquid phase hydrogenation of pyridine according to claim 1, characterized in that: The reaction temperature is 25-300°C, more preferably 125-175°C.

7. The method for synthesizing piperidine by continuous liquid phase hydrogenation of pyridine according to claim 1, characterized in that: The solid particle catalyst is a palladium / aluminum oxide catalyst or a nickel-molybdenum / aluminum oxide catalyst.

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