CN107987011A - A kind of piperidines is continuously synthesizing to method - Google Patents

Abstract

The invention provides a continuous synthesis method of piperidine, which comprises the following steps: (1) distributing the catalyst in fixed-bed reactors connected in series in N sections, filling the fixed-bed reactors with nitrogen or hydrogen, and making the fixed-bed reactors The reaction pressure in the bed reactor is 1.8-4MPa, and the temperature of the fixed-bed reactor is 300-400°C by heating; At the same time, hydrogen is introduced from the hydrogen inlets of the first section to the N section of the fixed bed reactor respectively; the product is condensed through a condenser tube to obtain liquid piperidine; wherein N=2～5; the present invention adopts multi-section fixed bed continuous The hydrogenation reaction can realize the continuous production of piperidine, save the reaction time, the reactant can be recycled, the contact time between the catalyst and the reactant can be increased, and the product quality and product yield can be effectively improved.

Description

A kind of continuous synthetic method of piperidine

technical field

The invention relates to the technical field of piperidine synthesis, in particular to a continuous synthesis method of piperidine.

Background technique

Piperidine, also known as hexahydropyridine or azacyclohexane, is a colorless liquid. Has a peppery smell. Density 0.8606. Melting point -7～-9℃. The boiling point is 106°C. Soluble in water, ethanol and ether. A strong organic base that reacts with inorganic acids to form salts. Can be volatile together with steam. Piperidine is mainly used as organic synthesis raw material, pharmaceutical raw material, solvent, epoxy resin curing agent, chemical reagent, rubber vulcanizing agent, etc. At present, my country's demand for piperidine is about 4,000 tons, and it is completely dependent on imports. With the rapid development of my country's chemical industry, the demand is also increasing year by year.

There are two main production methods for piperidine, one is that furanamine or tetrahydrofuranamine is converted into piperidine under the action of high-temperature and high-pressure hydrogen and a catalyst, and the other is hydrogenation of pyridine into piperidine. In the current industrial production of pyridine hydrogenation into piperidine, the catalytic hydrogenation reaction generally adopts kettle type, which has the following disadvantages: (1) the reaction time is long and the production efficiency is low; (2) mechanical stirring will cause Uneven mixing of materials and excessive local heat release can easily lead to safety accidents; (3) Insufficient hydrogenation and insufficient pressure in the kettle will produce a series of by-products such as tetrahydropyridine, which will ultimately affect product quality and product yield. (4) The reactants of the tank reaction and the catalyst cannot be fully contacted, which affects the quality and yield of the product. Thus, developing a new synthetic method of piperidine has a good market prospect.

Contents of the invention

The object of the present invention is to provide a kind of continuous synthetic method of piperidine, adopt multi-section fixed bed continuous hydrogenation reaction, can realize the continuous production of piperidine, save reaction time, reactant can be recycled, can improve catalyst and The contact time of the reactants can effectively improve the quality of the product and the product yield.

To achieve the above object, the present invention is achieved through the following technical solutions:

A continuous synthesis method of piperidine, comprising the following steps:

(1) Pack the catalyst in the fixed-bed reactors connected in series in N sections, fill the fixed-bed reactors with nitrogen or hydrogen, make the reaction pressure in the fixed-bed reactors be 1.8-4MPa, heat the fixed-bed reactors The temperature is 300-400°C;

(2) Pyridine is preheated and vaporized and introduced once from the gas inlet of the first-stage fixed-bed reactor in a gas-phase state, and hydrogen is introduced from the hydrogen gas inlets of the first section to the N-section of the fixed-bed reactor respectively; The substance is condensed through a condenser tube to obtain liquid piperidine;

Wherein N=2～5.

Preferably, said N=3, in step (2), hydrogen is introduced from the hydrogen gas inlets of the first section, the second section, and the third section fixed-bed reactor respectively, wherein the pyridine charged with the first section, the second section The molar ratios of hydrogen charged into the second-stage and third-stage fixed-bed reactors are 1:3-4, 1:2-3, and 1:1-2, respectively.

Preferably, the catalyst is one or more of platinum carbon, palladium carbon, and Raney nickel.

Preferably, the catalyst is Raney nickel.

Preferably, in the step (1), hydrogen is charged into the fixed-bed reactor, so that the reaction pressure in the fixed-bed reactor is 2-3 MPa.

Preferably, the retention time of the fixed bed reaction is 30-150s.

Preferably, the mass ratio of the pyridine to the catalyst is 1:1-3.

The beneficial effects of the present invention are: the present invention adopts multi-stage fixed-bed continuous hydrogenation reaction, which not only saves the reaction time compared with the tank reaction, the reactants can be recycled, and the contact time between the catalyst and the reactants can be increased by connecting the fixed beds in series , to ensure that the reaction gas is in full contact with the catalyst, which can eliminate the space in the lower part of the reactor that is not filled with catalyst, and can effectively improve the product yield and product quality per unit volume and unit time of the reactor. The invention can realize continuous production, reduce reaction time, improve production continuity and safety, and is more suitable for future continuous industrial production.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the present invention Examples, not all examples. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

Example 1:

A continuous synthesis method of piperidine, comprising the following steps:

Pack 20g of Raney nickel catalyst in 3 sections of fixed bed reactor, fill nitrogen into the fixed bed reactor, make the reaction pressure in the fixed bed reactor be 2MPa, heat the fixed bed reactor temperature to be 300°C;

15g of pyridine was preheated and vaporized by the heating furnace, and introduced once from the inlet of the first-stage fixed-bed reactor in the gas phase (the feeding amount of pyridine per minute was 0.7mL), and at the same time, the hydrogen was proportionally fed from the first stage and the second stage respectively. The hydrogen gas inlet of the first section and the third section fixed bed reactor is introduced (wherein the mol ratio of the pyridine charged to the first section, the second section, and the third section fixed bed reactor is 1:4, 1:4, respectively. 1:3, 1:1), the reaction residence time is 60s. The product was condensed through a condenser tube to obtain 16 g of liquid piperidine, and a sample was taken every 6 hours. The content of piperidine was 6%, and the yield of piperidine was 6%.

Example 2:

A continuous synthesis method of piperidine, comprising the following steps:

Pack 20g of palladium catalyst in 3 sections of fixed-bed reactors, charge nitrogen into the fixed-bed reactors, make the reaction pressure in the fixed-bed reactors be 2MPa, heat the fixed-bed reactors to make the temperature 300°C;

15.05g of pyridine was preheated and vaporized by the heating furnace, and introduced once from the gas inlet of the first-stage fixed-bed reactor in the gas phase (the feeding amount of pyridine per minute was 0.7mL), and at the same time, the hydrogen was divided into three times in proportion from the first stage respectively. Section, the second section, the hydrogen gas inlet of the third section fixed-bed reactor is introduced (wherein the mol ratio of the pyridine charged with the first section, the second section, the third section fixed-bed reactor is filled with is respectively 1:3, 1:2, 1:2), the reaction residence time is 60s. The product was condensed through a condenser tube to obtain 16.25 g of liquid piperidine. A sample was taken every 6 hours on average. The content of piperidine was 3%, and the yield of piperidine was 3%.

Example 3:

A continuous synthesis method of piperidine, comprising the following steps:

Pack 25g of Raney nickel catalyst in 3 sections of fixed bed reactor, fill the fixed bed reactor with hydrogen, make the reaction pressure in the fixed bed reactor be 2.5MPa, heat the fixed bed reactor to 300°C ;

15.65g of pyridine was preheated and vaporized by the heating furnace, and introduced once from the gas inlet of the first-stage fixed-bed reactor in the gas phase (the feeding amount of pyridine per minute was 0.7mL), and the hydrogen was divided into three times in proportion from the first stage respectively. The hydrogen gas inlet of section, second section, the third section fixed-bed reactor introduces (the mol ratio of the pyridine charged and the hydrogen that the first section, second section, the third section fixed-bed reactor is filled with is respectively 1 :3, 1:2, 1:2), the reaction residence time is 60s. The product was condensed through a condenser tube to obtain 16.85 g of liquid piperidine. A sample was taken every 6 hours on average. The content of piperidine was 10%, and the yield of piperidine was 10%.

Example 4:

A continuous synthesis method of piperidine, comprising the following steps:

Pack 25g of Raney nickel catalyst in 3 sections of fixed-bed reactor, fill the fixed-bed reactor with hydrogen, make the reaction pressure in the fixed-bed reactor be 3MPa, heat the fixed-bed reactor to 400°C;

15.65g of pyridine was preheated and vaporized by the heating furnace, and introduced once from the gas inlet of the first-stage fixed-bed reactor in the gas phase (the feeding amount of pyridine per minute was 0.7mL), and the hydrogen was divided into three times in proportion from the first stage respectively. Section, the second section, the hydrogen gas inlet of the third section fixed-bed reactor is introduced (wherein the mol ratio of the pyridine charged with the first section, the second section, the third section fixed-bed reactor is filled with is respectively 1:4, 1:3, 1:1), the reaction residence time is 60s. The product was condensed through a condenser tube to obtain 16.88 g of liquid piperidine. A sample was taken every 6 hours on average. The content of piperidine was 15%, and the yield of piperidine was 15%.

Example 5:

A continuous synthesis method of piperidine, comprising the following steps:

Pack 30g of Raney nickel catalyst in 3 sections of fixed bed reactor, fill the fixed bed reactor with hydrogen, make the reaction pressure in the fixed bed reactor 3MPa, heat the fixed bed reactor temperature to 400°C;

15.05g of pyridine was preheated and vaporized by the heating furnace, and introduced once from the gas inlet of the first-stage fixed-bed reactor in the gas phase (the feeding amount of pyridine per minute was 0.7mL), and at the same time, the hydrogen was divided into three times in proportion from the first stage respectively. Section, the second section, the hydrogen gas inlet of the third section fixed-bed reactor is introduced (wherein the mol ratio of the pyridine charged with the first section, the second section, the third section fixed-bed reactor is filled with is respectively 1:4, 1:3, 1:2), the reaction residence time is 150s. 16.25 g of liquid piperidine was condensed through a condenser tube, and a sample was taken every 6 hours. The content of piperidine was 44%, and the yield of piperidine was 44%.

The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: it can still be described in the foregoing embodiments Modifications are made to the recorded technical solutions, or equivalent replacements are made to some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims (7)

1. a continuous synthetic method of piperidine, is characterized in that, comprises the following steps: (1) Pack the catalyst in the fixed-bed reactors connected in series in N sections, fill the fixed-bed reactors with nitrogen or hydrogen, make the reaction pressure in the fixed-bed reactors be 1.8-4MPa, heat the fixed-bed reactors The temperature is 300-400°C; (2) Pyridine is preheated and vaporized and introduced once from the gas inlet of the first-stage fixed-bed reactor in a gas-phase state, and hydrogen is introduced from the hydrogen gas inlets of the first section to the N-section of the fixed-bed reactor respectively; The substance is condensed through a condenser tube to obtain liquid piperidine; Wherein N=2～5. 2. the continuous synthetic method of piperidine according to claim 1, is characterized in that, described N=3, in step (2), hydrogen is respectively from the first section, the second section, the third section fixed-bed reactor The hydrogen gas inlet is introduced, and the molar ratios of the pyridine charged to the hydrogen charged in the first, second and third fixed-bed reactors are 1:3~4, 1:2~3, 1, respectively. :1～2. 3. the continuous synthetic method of piperidine according to claim 1, is characterized in that, described catalyst is one or more in platinum carbon, palladium carbon, Raney nickel. 4. the continuous synthetic method of piperidine according to claim 3, is characterized in that, described catalyzer is Raney nickel. 5. the continuous synthetic method of piperidine according to claim 1 is characterized in that, in described step (1), in fixed-bed reactor, fills with hydrogen, makes the reaction pressure in fixed-bed reactor be 2 ~3MPa. 6. The continuous synthesis method of piperidine according to claim 1, characterized in that, the retention time of the fixed bed reaction is 30-150s. 7. The continuous synthesis method of piperidine according to claim 1, characterized in that the mass ratio of the pyridine to the catalyst is 1:1-3.