Preparation method for 4,4'-bipyridine

Abstract

A preparation method for 4,4'-bipyridine, comprising: using pyridine as a raw material, preheating and gasifying the pyridine, then, catalyzed by a loaded Ni / HY catalyst, generating 4,4'-bipyridine vi

Description

TECHNICAL FIELD The present disclosure belongs to the field of fine chemical engineering and organic synthesis, relates to a preparation method for 4,4'-bipyridinc. and in particular to a method for preparing 4,4'-bipyridine by gas phase catalytic dehydrogenation coupling of pyridine. BACKGROUND 4,4'-bipyridine can be used for synthesizing herbicide paraquat, is an important intermediate in chemical and pharmaceutical synthesis, and can be used as a ligand of metal catalysts, a photosensitizer, an indicator for detecting metal ions and the like due to a unique chelation effect. Main synthesis methods for the 4,4'-bipyridine include the following types. (I) A hot sodium method or a low temperature sodium method: The hot sodium method includes: enabling pyridine and sodium to react under a condition of heating reflux, and then introducing a certain amount of air for oxidation to obtain the 4,4'-bipyridine. The method has a yield of less than 50% and low product purity. The low temperature sodium method is first developed by ICI and includes: enabling pyridine and a liquid ammonia solution of sodium to react at -20°C—30°C to obtain an intermediate, and then performing oxidation with air to obtain the 4,4'-bipyridine. The method has high product purity and a high pyridine utilization rate. As the sodium is used, the sodium processes have a risk of fire and explosion, thus limiting industrial production. (II) A 4-chloropyridine method: The 4,4'-bipyridine is prepared by using 4-chloropyridine as a raw material and a nickel-containing phosphine compound as a catalyst. The method has an easy reaction and a high yield. However, the raw material 4-chloropyridine has high price, and costs are high, so that the method is not suitable for industrial production. (Ill) A p-formaldehyde pyridine method: With aluminate or phosphate as a catalyst, p-formaldehyde pyridine, acetaldehyde and ammonia are subjected to a gas phase reaction in a nitrogen flow at a reaction temperature of 300°C-450°C. The raw material, p-formaldehyde pyridine, used in the method is difficult to obtain and high in cost, so that the method has no industrial value. SUMMARY The purposes of the present disclosure are to overcome the disadvantages of the prior art and provide a preparation method for 4,4'-bipyridine. The 4,4'-bipyridine is obtained by a catalytic dehydrogenation coupling reaction in one step with cheap pyridine as a raw material. The method has the advantages of being high in atom utilization rate, low in cost, simple and convenient in operation, high in safety and suitable for industrialization. The purposes of the present disclosure are realized by adopting the following technical schemes. A preparation method for 4,4'-bipyridine includes: with pyridine as a raw material, preheating and gasifying the pyridine, and then carrying out a dehydrogenation coupling reaction under a catalytic action of a loaded Ni / HY catalyst to generate 4,4'-bipyridine. Specifically, the preparation method for 4,4'-bipyridine includes: with the pyridine as the raw material, sending the pyridine into a preheater, preheating and gasifying the pyridine, and then carrying out the dehydrogenation coupling reaction under the catalytic action of the loaded Ni / HY catalyst in a fixed bed reactor filled with the loaded Ni / HY catalyst to generate the 4,4'-bipyridine. As a further preferred embodiment of the present disclosure, the preparation method for 4,4'-bipyridine further includes: dissolving the 4,4'-bipyridine in unreacted pyridine, performing distillation separation to separate the 4,4'-bipyridine and the pyridine, and recycling the pyridine. The pyridine has a liquid hourly space velocity of 0.5 g-6 g pyridine / (gcataiysfh) before the gasifying, preferably 0.5 g-2 g pyridine / (gcataiyst-h), and more preferably 2 g pyridine / (gcataiySfh). The dehydrogenation coupling reaction is carried out at a temperature of 250°C-450°C, preferably 280°C-400°C, further preferably 300°C-350°C, and most preferably 320°C; and the dehydrogenation coupling reaction is carried out at normal pressure. The loaded Ni / HY catalyst has a nickel loading amount of 5%-30%, preferably 10%-30%, and further preferably 10%. The loaded Ni / HY catalyst uses an HY molecular sieve (namely hydrogen type Y molecular sieve) as a carrier, the HY molecular sieve has a silica-alumina ratio of 5-100, and the silica-alumina ratio of the HY molecular sieve has an obvious effect on a reaction result. When the silica-alumina ratio is too low, the catalyst is easily inactivated. When the silica-alumina ratio is too high, by-products such as 2,4'-bipyridine and 2,2'-bipyridine are generated, leading to decrease of target product selectivity. Therefore, the silica-alumina ratio of the HY molecular sieve is preferably 40-60. Another purpose of the present disclosure is to provide a method for preparing the loaded Ni / HY catalyst, and the method includes: dissolving nickel nitrate hexahydrate in distilled water, adding an HY molecular sieve under stirring, performing impregnation overnight, then performing drying at 120°C, calcining at a temperature of 400°C-500°C and pressing molding, and then performing reduction with hydrogen at a temperature of 450°C-550°C to obtain the loaded Ni / HY catalyst. Another purpose of the present disclosure is to provide a 4,4'-bipyridine preparation device. The device includes a preheater, a fixed bed reactor and a condenser; the fixed bed reactor includes a cylinder, the cylinder is externally provided with a sleeve, and a lower part and an upper part of the sleeve are provided with a heat conduction substance inlet and a heat conduction substance outlet, respectively; a feeding port of the preheater is separately connected with a liquid feeding pipe and an air inlet pipe, and a discharging port of the preheater is connected with a feeding port on a top of the fixed bed reactor; the fixed bed reactor is internally provided with a loaded Ni / HY catalyst, and the fixed bed reactor is provided with a temperature measuring apparatus and a pressure measuring apparatus which are used for measuring the temperature and pressure in the fixed bed reactor, respectively; and a discharging port at a bottom of the fixed bed reactor is provided with a discharging pipe, and the discharging pipe is provided with the condenser for cooling a collected reaction product. Preferably, the fixed bed reactor is a stainless steel cylinder. Preferably, a connecting pipeline of the preheater and the fixed bed reactor is provided with a gas flow meter. Preferably, the temperature measuring apparatus may be a temperature measuring apparatus commonly used in industry, such as a thermocouple; the pressure measuring apparatus may be any pressure measuring apparatus commonly used in industry, such as a pressure gauge; and the pressure in the reactor may be controlled by any method commonly used in industry in the prior art, such as control by a back pressure valve. Compared with the prior art, the present disclosure has the following beneficial effects. (1) In the present disclosure, by using the cheap pyridine as the raw material, the use of expensive raw materials is avoided, and production costs are low. (2) In the present disclosure, the use of flammable and explosive metallic sodium is avoided, and the reaction is a continuous reaction, which is safe and controllable. (3) In the present disclosure, by carrying out the catalytic dehydrogenation coupling reaction in one step using the loaded Ni / HY catalyst to obtain the 4,4'-bipyridine, the target product selectivity is high, a reaction process is simple and easy to operate, and small amounts of "three wastes" are generated. The method is environmentally friendly, and suitable for continuous industrial production of the 4,4'-bipyridine. (4) In the present disclosure, the loaded Ni / HY catalyst has a longer catalytic life, and a higher pyridine conversion rate and higher target product selectivity can be maintained even when the reaction is continuously carried out for 1000 hours under the technological conditions of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic structural diagram of a 4,4'-bipyridine preparation device. In the figure: E, preheater; R, fixed bed reactor; C, condenser; 1, liquid feeding pipe; 2, air inlet pipe; 3, gas flow meter; 4, pressure gauge; 5, back pressure valve; 6, heat conduction oil feeding pipe; 7, heat conduction oil discharging pipe; 8, thermocouple; 9, discharging pipe; and 10, sleeve. DETAILED DESCRIPTION The technical schemes of the present disclosure are further explained in combination with examples below. It should be noted that the examples are only used to provide specific embodiments and are not intended to limit the method of the present disclosure, and equipment capable of realizing the conditions of the present disclosure can be used to realize the present disclosure. Example 1 A preparation method for a loaded Ni / HY catalyst (hereinafter referred to as loaded nickel) is as follows. 20 g of nickel nitrate hexahydrate was dissolved in 200 mL of distilled water to obtain a nickel nitrate aqueous solution. 40 g of an HY molecular sieve powder (with a silica-alumina ratio of 40, a pore size of 4 nm, a specific surface area of 750 g / m2, and a sodium oxide content of 0.03%) was impregnated in the nickel nitrate aqueous solution, stirred overnight at normal temperature, dried at 120°C for 12 h, calcined at 450°C for 16 h, pressed by a tablet press and then sieved to obtain a 10 mesh-20 mesh catalyst precursor. Then, the catalyst precursor was subjected to reduction in a hydrogen flow (18 L / h) at 500°C for 12 h to obtain a loaded Ni / HY catalyst with a nickel loading amount of 10% (recorded as catalyst 1). Example 2 The HY molecular sieve powder in Example 1 was replaced with an HY molecular sieve powder (with a silica-alumina ratio of 5, a pore size of 4 nm, a specific surface area of 750 g / m', and a sodium oxide content of 0.2%), other conditions were the same as those in Example 1, and a loaded Ni / HY catalyst with a nickel loading amount of 10% was prepared (recorded as catalyst 2). Example 3 The HY molecular sieve powder in Example 1 was replaced with an HY molecular sieve powder (with a silica-alumina ratio of 20, a pore size of 4 nm, a specific surface area of 750 g / m2, and a sodium oxide content of 0.2%), other conditions were the same as those in Example 1, and a loaded Ni / HY catalyst with a nickel loading amount of 10% was prepared (recorded as catalyst 3). Example 4 The HY molecular sieve powder in Example 1 was replaced with an HY molecular sieve powder (with a silica-alumina ratio of 80, a pore size of 4 nm, a specific surface area of 750 g / m2, and a sodium oxide content of 0.03%), other conditions were the same as those in Example 1, and a loaded Ni / HY catalyst with a nickel loading amount of 10% was prepared (recorded as catalyst 4). Example 5 10 g of nickel nitrate hexahydrate was dissolved in 100 mL of distilled water to obtain a nickel nitrate aqueous solution. 40 g of an HY molecular sieve powder (with a silica-alumina ratio of 40, a pore size of 4 nm, a specific surface area of 750 g / m2, and a sodium oxide content of 0.03%) was impregnated in the nickel nitrate aqueous solution and stirred overnight at normal temperature. Other conditions were the same as those in Example 1, and a loaded Ni / HY catalyst with a nickel loading amount of 5% was prepared (recorded as catalyst 5). Example 6 60 g of nickel nitrate hexahydrate was dissolved in 600 mL of distilled water to obtain a nickel nitrate aqueous solution. 40 g of an HY molecular sieve powder (with a silica-alumina ratio of 40, a pore size of 4 nm, a specific surface area of 750 g / m , and a sodium oxide content of 0.03%) was impregnated in the nickel nitrate aqueous solution and stirred overnight at normal temperature. Other conditions were the same as those in Example 1, and a loaded Ni / HY catalyst with a nickel loading amount of 30% was prepared (recorded as catalyst 6). Table 1 Loaded Ni / HY catalysts prepared in Examples 1-6 Catalyst number Nickel loading amount % Silica-alumina ratio of an HY molecular sieve Catalyst 1 10 40 Catalyst 2 10 5 Catalyst 3 10 20 Catalyst 4 10 80 Catalyst 5 5 40 Catalyst 6 30 40 Example 7 As shown in FIG. 1, a 4,4'-bipyridine preparation device includes a fixed bed reactor R, a preheater E and a condenser C. The fixed bed reactor R is a stainless steel reaction tube with an inner diameter of 2 cm, a cylinder is externally provided with a sleeve 10, and a lower part and an upper part of the sleeve 10 are provided with a heat conduction oil inlet 6 and a heat conduction oil outlet 7, respectively. A feeding port of the preheater E is separately connected with a liquid feeding pipe 1 and an air inlet pipe 2, and a discharging port of the preheater E is connected with a feeding port on a top of the fixed bed reactor R. A connecting pipeline of the preheater E and the fixed bed reactor R is provided with a gas flow meter 3. The fixed bed reactor R is internally provided with a loaded Ni / HY catalyst, the temperature in the fixed bed reactor R is measured by a thermocouple 8, the pressure is measured by a pressure gauge 4, and the pressure in the fixed bed reactor R is controlled by a back pressure valve 5. A discharging port at a bottom of the fixed bed reactor R is provided with a discharging pipe 9, and the discharging pipe 9 is provided with the condenser C for cooling a collected reaction product. An appropriate amount of inert quartz sand was loaded into a lower end of the reaction tube to serve as a support, 30 g of a catalyst precursor (10 mesh-20 mesh) was loaded into the reaction tube, and an appropriate amount of inert quartz sand was loaded into an upper end of the reaction tube to serve as a buffer. Hydrogen (flow rate 18 L / h) was introduced into the fixed bed reactor, reduction was performed in a hydrogen flow at 500°C for 12 h to obtain the loaded Ni / HY catalyst, and then cooling was performed to 200°C. Parameters are shown in Table 2. Pyridine as a raw material was introduced, heated and gasified by the preheater at 115°C, then entered into the fixed bed reactor to flow through a catalyst bed layer from top to bottom, and was subjected to a catalytic dehydrogenation coupling reaction in one step under atmospheric pressure to obtain 4,4'-bipyridine. The reaction product was discharged from a bottom of the fixed bed reactor and cooled by the condenser. Then, a reaction solution was collected for analysis. Results are shown in Table 2. Table 2 Reaction results under different conditions Catalyst number Space velocity g / (fccatalyst'h) Continuous reaction time / h Reaction temperature / °C Product selectivity / % Pyridine conversion rate / % 4,4' 2,4' 2,2' Catalyst 1 2 12 320 96.9 / 1.8 21.0 100 97.1 / 1.7 21.2 500 97.0 / 1.7 21.0 1000 97.3 / 1.5 19.8 Catalyst 1 2 12 300 97.6 / 1.6 13.4 100 97.5 / 1.5 13.6 500 97.8 / 1.5 13.4 1000 97.7 / 1.5 13.0 Catalyst 1 2 12 350 95.4 0.2 2.8 35.8 100 95.6 0.1 2.6 35.7 500 95.5 0.1 2.8 35.5 1000 95.5 0.1 2.7 35.0 Catalyst 1 0.5 12 320 94.6 / 2.8 43.5 100 94.4 / 2.7 43.5 500 94.5 / 2.5 43.0 1000 94.5 / 2.6 42.6 Catalyst 1 6 12 320 98.0 I 0.7 5.8 100 98.3 I 0.6 5.7 500 98.3 I 0.6 5.7 1000 98.2 ! 0.6 5.7 Catalyst 1 0.5 12 250 98.2 / 0.8 12.4 Catalyst 1 6 12 450 89.8 0.2 2.5 33.0 Catalyst 2 2 12 320 97.8 / 1.2 25.6 50 97.5 / 1.4 20.4 100 97.6 / 1.5 11.3 200 97.5 / 1.5 4.3 300 97.8 I 1.4 0.8 Catalyst 3 2 12 320 97.3 / 1.6 23.6 50 97.1 I 1.5 21.4 100 97.3 ! 1.5 18.3 200 97.2 I 1.5 12.3 500 97.8 ! 1.4 8.9 Catalyst 4 2 12 320 46.2 18.3 32.5 16.7 50 46.4 18.2 32.3 16.9 100 46.3 18.3 32.1 16.6 500 46.4 18.2 32.4 16.8 Catalyst 5 2 12 320 97.1 / 1.8 12.2 100 97.3 / 1.7 12.4 300 97.2 / 1.7 12.0 500 97.3 / 1.8 12.3 Catalyst 6 2 12 320 97.1 / 1.8 19.6 50 97.4 / 1.6 19.5 100 97.2 / 1.8 19.8 300 97.3 / 1.7 19.6 500 97.4 / 1.8 19.3 Note: space velocity refers to liquid hourly space velocity of pyridine before gasifying; 4,4' refers to 4,4'-bipyridine; 2,4' refers to 2,4'-bipyridine; 2,2' refers to 2,2'-bipyridine.

Claims

What is claimed is:

1. A preparation method for 4,4'-bipyridine, comprising: with pyridine as a raw material, preheating and gasifying the pyridine, and then carrying out a dehydrogenation coupling reaction under a catalytic action of a loaded Ni / HY catalyst to generate 4,4'-bipyridine.

2. The preparation method for 4,4'-bipyridine according to claim 1, wherein the pyridine has a liquid hourly space velocity of 0.5 g-6 g pyridine / (gcataiyst-h) before the gasifying.

3. The preparation method for 4,4'-bipyridine according to claim 2, wherein the pyridine has a liquid hourly space velocity of 0.5 g-2 g pyridine / (gcataiysrh) before the gasifying, preferably 2 g pyridine / (gcataiySrh).

4. The preparation method for 4,4'-bipyridine according to claim 1, wherein the dehydrogenation coupling reaction is carried out at a temperature of 250°C-450°C.

5. The preparation method for 4,4'-bipyridine according to claim 4, wherein the dehydrogenation coupling reaction is carried out at a temperature of 280°C-400°C.

6. The preparation method for 4.4'-bipyridine according to claim 5, wherein the dehydrogenation coupling reaction is carried out at a temperature of 300°C-350°C.

7. The preparation method for 4,4'-bipyridine according to claim 1, wherein the loaded Ni / HY catalyst has a nickel loading amount of 5%-30%; and the loaded Ni / HY catalyst uses an HY molecular sieve as a carrier, and the HY molecular sieve has a silica-alumina ratio of 5-100.

8. The preparation method for 4,4'-bipyridine according to claim 7, wherein the loaded Ni / HY catalyst has a nickel loading amount of 10%-30%; and the HY molecular sieve has a silica-alumina ratio of 40-60.

9. The preparation method for 4,4'-bipyridine according to claim 1, further comprising: performing distillation separation to separate the 4,4'-bipyridine and the pyridine.

10. A method for preparing the loaded Ni / HY catalyst used for catalyzing the dehydrogenation coupling reaction of the pyridine to generate 4,4'-bipyridine according to claim 1, comprising: dissolving nickel nitrate hexahydrate in distilled water, adding an HY molecular sieve under stirring, performing impregnation overnight, then performing drying at 120°C, calcining at a temperature of 400°C-500°C and pressing molding, and then performing reduction with hydrogen at a temperature of 450°C-550°C to obtain the loaded Ni / HY catalyst.

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