Process for the preparation of a catalyst for the synthesis of pyridine from 3-methylpyridine

Abstract

The application discloses a preparation method of a catalyst for synthesizing pyridine from 3-methylpyridine and relates to the technical field of catalysts. The catalyst comprises the following steps: ZSM-5 is used as a carrier, V2O5, CoO and Ag are used as active components, molecular sieve ZSM-5, citric acid, ammonium metavanadate, cobalt nitrate, silver nitrate and deionized water are mixed, and then are filtered, dried and calcined to obtain a supported high-efficiency catalyst; the catalyst is filled in a fixed bed, 50% 3-methylpyridine is used as raw material, and a demethylation reaction is carried out under the action of high temperature, the catalyst and air to produce pyridine. The catalyst used in the application does not need to be frequently activated, the activation frequency is low, the catalyst stability is good, the catalyst is not prone to deactivation, can continue to operate stably after activation, catalyst loss is greatly reduced, 3-methylpyridine can be efficiently converted into pyridine by using the prepared catalyst, and the dilemma of waste caused by small demand for 3-methylpyridine in the market is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of catalyst, in particular to a preparation method of a catalyst for synthesizing pyridine from 3-methylpyridine. BACKGROUND

[0002] Pyridine is an organic compound, which is a six-membered heterocyclic compound containing one nitrogen heteroatom. It can be regarded as a compound in which one (CH) of the benzene molecule is replaced by N, so it is also called nitrogen benzene. Pyridine is a colorless or slightly yellow liquid with a foul odor. Pyridine and its homologues exist in bone tar, coal tar, coal gas, shale oil and petroleum. Pyridine is an important organic synthesis intermediate and fine chemical raw material, mainly used in "three drugs" synthesis, and widely used in food additives, feed additives, fuels, daily chemical products and polymer compound preparation. It is also a common organic synthesis catalyst good solvent. At present, more than 95% of pyridine base is synthesized by catalysis with formaldehyde and ammonia as raw materials. The raw materials for synthesizing pyridine by aldehyde-ammonia method are formaldehyde, acetaldehyde and ammonia, and the products are pyridine and 3-methylpyridine. The production of 1 ton of pyridine produces about 0.5 tons of methylpyridine by-product. Compared with pyridine, the demand for methylpyridine is small, and the market price is low.

[0003] 3-methylpyridine is an organic compound with the chemical formula C6H3N, which is a colorless or yellow liquid, soluble in water, and soluble in ethanol, ether and most organic solvents. It is mainly used as a solvent and can also be used for the preparation of nicotinic acid and nicotinamide. At the same time, the mixed methylpyridine by-product composed of 3-methylpyridine is complex, difficult to separate and high in energy consumption. How to reasonably and high-value utilize a large amount of alkylpyridine by-product is an important problem that needs to be solved in the process of pyridine production. Therefore, the development of high-efficiency and stable catalyst is the key technology for the synthesis of pyridine by dealkylation of alkylpyridine.

[0004] Patent No. CN104496887A discloses a synthesis method for generating pyridine by demethylation of 3-methylpyridine. The method uses catalyst DLL or DLF to catalyze 62-64% 3-methylpyridine as raw material in a fluidized bed reactor at a reaction temperature of 520-540℃. The collected material is subjected to secondary circulation reaction, and samples are taken for inspection. When the pyridine content reaches the predetermined target, the 3-methylpyridine conversion rate reaches 70%, and the final material is collected. The catalyst after reaction enters the regenerator for activation, and the regeneration temperature is 650℃, and the activation time is 3h. This method can synthesize pyridine by demethylation of 3-methylpyridine, but the synthesis conditions are harsh, the catalyst activity is not high, and the collected liquid needs to be subjected to secondary or even multiple circulation reactions to be efficiently converted into pyridine. In addition, the catalyst needs to be activated and regenerated every time it is used, which is relatively cumbersome.

[0005] A 3-methyl pyridine preparation pyridine catalyst and its preparation method are provided in patent No. CN104492479A. The method first prepares a catalyst, and then reacts in a fixed fluidized bed at a temperature of 560 DEG C. The conversion rate of 3-methyl pyridine is 65-70%. In the synthesis method, the preparation of the catalyst requires more complex drugs, and the reaction temperature is high, which is energy-consuming.

[0006] In the current common pyridine base synthesis, the product is pyridine and 3-methyl pyridine, and about 0.5 tons of 3-methyl pyridine by-product mainly containing 3-methyl is produced per ton of pyridine. Compared with pyridine, the demand for methyl pyridine is small, and the market price is low. SUMMARY

[0007] The purpose of the present application is to provide a preparation method of a 3-methyl pyridine synthesis pyridine catalyst to solve the problems raised in the above background.

[0008] To achieve the above-mentioned purpose, the present application provides the following technical solution: a preparation method of a 3-methyl pyridine synthesis pyridine catalyst, comprising the following steps:

[0009] Step 1: preparation of supported high-efficiency catalyst

[0010] The supported catalyst ZSM-5 is the carrier, and the active components are V2O5, CoO and Ag. The molecular sieve ZSM-5, citric acid, ammonium metavanadate, cobalt nitrate, silver nitrate and deionized water are mixed, filtered, dried and calcined to prepare a supported high-efficiency catalyst.

[0011] Step 2: catalyst application

[0012] The catalyst is loaded in a fixed bed, 50% 3-methyl pyridine is used as raw material, and the demethylation reaction is carried out under the action of high temperature, catalyst and air to produce pyridine.

[0013] Further, in step 1 catalyst preparation: the active components are V2O5, CoO and Ag, wherein the mass fraction of V2O5 is 5%-20%, the amount-of-substance ratio of Co to V is 1:0.5-2.5, and the mass fraction of Ag is 0.5%-2%.

[0014] Further, in step 1, the silicon-aluminum ratio of ZSM-5 is 300.

[0015] Further, in step 1, the catalyst calcination temperature is 350-450 DEG C, and the calcination time is 4-8h.

[0016] Further, in the preparation of the catalyst, the molecular sieve ZSM-5, citric acid, ammonium metavanadate, cobalt nitrate, silver nitrate and deionized water are mixed, stirred and then left still for 20h to fully load the ions.

[0017] Further, the reaction temperature in the reaction system of step 2 is 350 DEG C.

[0018] Further, the reaction pressure in the reaction system of step 2 is low pressure, 0-40 kPa.

[0019] Compared with the prior art, the present application has the following beneficial effects:

[0020] 1. The catalyst of the present application does not need to be frequently reactivated, and has less reactivation times, better stability, and is not easy to be deactivated, so that one batch of catalyst can be continuously operated for at least 30 days, and after reactivation, the catalyst can continue to be stably operated, thereby greatly reducing catalyst loss, and using the prepared catalyst can efficiently convert 3-methylpyridine into pyridine, and solve the dilemma of waste caused by small demand of 3-methylpyridine in the market.

[0021] 2. The reaction temperature in the application is 350 DEG C, which is lower than that of similar catalysts, and is more energy-saving. DETAILED DESCRIPTION

[0022] The embodiments of the present application will be described in detail below, however, the embodiments of the present application are not limited thereto. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0023] Embodiment 1:

[0024] (1) A certain amount of molecular sieve ZSM-5, citric acid, ammonium metavanadate, cobalt nitrate, silver nitrate and deionized water were weighed according to the calculation and placed in a 2L beaker, wherein the mass fraction of V2O5 was 5%, the molar ratio of Co and V was 1:0.5, and the mass fraction of Ag was about 0.5%; after stirring for 2h, it was statically placed for 20h, and then it was filtered, dried and finally calcined at 450 DEG C for 6h to obtain the catalyst.

[0025] (2) The catalyst was pressed and screened, 20g of the catalyst was loaded into a fixed bed reaction tube, and the temperature was raised for reaction; when the temperature reached 350 DEG C, the raw material liquid (50% 3-methylpyridine) was pumped into the vaporization chamber at a certain pump speed (the vaporization temperature was 200 DEG C), the steam entered the reaction device at the lower end of the reaction tube under the action of the catalyst and air, the gas phase after reaction came out from the upper end of the reaction tube, and after condensation by the condenser tube, it entered the collection tank to obtain the collection liquid; when the collection was stable, the collection liquid was weighed and detected.

[0026] Embodiment 2:

[0027] (1) According to the calculation, a certain amount of molecular sieve ZSM-5, citric acid, ammonium metavanadate, cobalt nitrate, silver nitrate and deionized water are weighed and placed in a 2L beaker, wherein the mass fraction of V2O5 is 10%, the molar ratio of Co to V is 1:1, and the mass fraction of Ag is about 1%; after stirring for 2h, it is placed for 20h, filtered, dried, and finally calcined at 400℃ for 6h to obtain the catalyst.

[0028] (2) The catalyst is pressed and screened, 20g of the catalyst is loaded into a fixed bed reaction tube, and the temperature is raised for reaction; when the temperature reaches 350℃, the raw material liquid (50% 3-methylpyridine) is pumped into the vaporization chamber by a plunger pump at a certain pump speed (the vaporization temperature is 200℃), and the vapor enters the reaction device at the lower end of the reaction tube under the action of the catalyst and air; the gaseous phase after reaction comes out from the upper end of the reaction tube, is condensed by a condenser tube, and then enters a collection tank to obtain a collection liquid; when the collection is stable, the collection liquid is weighed and detected.

[0029] Example 3:

[0030] (1) According to the calculation, a certain amount of molecular sieve ZSM-5, citric acid, ammonium metavanadate, cobalt nitrate, silver nitrate and deionized water are weighed and placed in a 2L beaker, wherein the mass fraction of V2O5 is 15%, the molar ratio of Co to V is 1:1.5, and the mass fraction of Ag is about 1.5%; after stirring for 2h, it is placed for 20h, filtered, dried, and finally calcined at 380℃ for 6h to obtain the catalyst.

[0031] (2) The catalyst is pressed and screened, 20g of the catalyst is loaded into a fixed bed reaction tube, and the temperature is raised for reaction; when the temperature reaches 350℃, the raw material liquid (50% 3-methylpyridine) is pumped into the vaporization chamber by a plunger pump at a certain pump speed (the vaporization temperature is 200℃), and the vapor enters the reaction device at the lower end of the reaction tube under the action of the catalyst and air; the gaseous phase after reaction comes out from the upper end of the reaction tube, is condensed by a condenser tube, and then enters a collection tank to obtain a collection liquid; when the collection is stable, the collection liquid is weighed and detected.

[0032] Example 4:

[0033] (1) According to the calculation, a certain amount of molecular sieve ZSM-5, citric acid, ammonium metavanadate, cobalt nitrate, silver nitrate and deionized water are weighed and placed in a 2L beaker, wherein the mass fraction of V2O5 is 20%, the molar ratio of Co to V is 1:2, and the mass fraction of Ag is about 2%; after stirring for 2h, it is placed for 20h, filtered, dried, and finally calcined at 350℃ for 6h to obtain the catalyst.

[0034] (2) The catalyst is pressed and screened, 20g of the catalyst is loaded into a fixed bed reaction tube, and the temperature is raised for reaction. When the temperature reaches 350°C, the raw material liquid (50% 3-methylpyridine) is pumped into the vaporization chamber at a certain pump speed (the vaporization temperature is 200°C). The steam enters the reaction device at the lower end of the reaction tube under the action of the catalyst and air. The gaseous phase after the reaction comes out from the upper end of the reaction tube, is condensed through the condenser tube, and then enters the collection tank to obtain the collection liquid. When the collection is stable, the collection liquid is weighed and detected.

[0035] Example 5:

[0036] (1) A certain amount of molecular sieve ZSM-5, citric acid, ammonium metavanadate, cobalt nitrate, silver nitrate and deionized water are weighed according to the calculation and placed in a 2L beaker. The mass fraction of V2O5 is 20%, the molar ratio of Co to V is 1:2.5, and the mass fraction of Ag is about 2%. After stirring for 2h, it is left to stand for 20h, filtered, dried, and finally calcined at 400°C for 6h to obtain the catalyst.

[0037] (2) The catalyst is pressed and screened, 20g of the catalyst is loaded into a fixed bed reaction tube, and the temperature is raised for reaction. When the temperature reaches 350°C, the raw material liquid (50% 3-methylpyridine) is pumped into the vaporization chamber at a certain pump speed (the vaporization temperature is 200°C). The steam enters the reaction device at the lower end of the reaction tube under the action of the catalyst and air. The gaseous phase after the reaction comes out from the upper end of the reaction tube, is condensed through the condenser tube, and then enters the collection tank to obtain the collection liquid. When the collection is stable, the collection liquid is weighed and detected.

[0038] Example 6:

[0039] (1) A certain amount of molecular sieve ZSM-5, citric acid, ammonium metavanadate, cobalt nitrate, silver nitrate and deionized water are weighed according to the calculation and placed in a 2L beaker. The mass fraction of V2O5 is 20%, the molar ratio of Co to V is 1:3, and the mass fraction of Ag is about 2%. After stirring for 2h, it is left to stand for 20h, filtered, dried, and finally calcined at 420°C for 6h to obtain the catalyst.

[0040] (2) The catalyst is pressed and screened, 20g of the catalyst is loaded into a fixed bed reaction tube, and the temperature is raised for reaction. When the temperature reaches 350°C, the raw material liquid (50% 3-methylpyridine) is pumped into the vaporization chamber at a certain pump speed (the vaporization temperature is 200°C). The steam enters the reaction device at the lower end of the reaction tube under the action of the catalyst and air. The gaseous phase after the reaction comes out from the upper end of the reaction tube, is condensed through the condenser tube, and then enters the collection tank to obtain the collection liquid. When the collection is stable, the collection liquid is weighed and detected.

[0041] The following table is the detection result of the above example:

[0042] Pyridine selectivity (%) Yield (%) 3-methylpyridine conversion (%) Example 1 20.23 8.1 40.06 Example 2 20.89 8.73 41.90 Example 3 40.45 20.58 50.87 Example 4 55.34 37.95 68.58 Example 5 68.78 51.85 75.39 Example 6 75.67 60.13 79.47

[0043] As can be seen from the data in the table, the selectivity of 3-methylpyridine after reaction with the self-made catalyst reaches 75%, and the yield reaches 60%.

[0044] According to the best preparation method of the catalyst obtained in the example, the catalyst stability example is verified

[0045] Example 7:

[0046] (1) According to the best preparation method of the catalyst, 20g of the catalyst is weighed and loaded into a fixed bed reaction tube for continuous reaction, and the continuous reaction time reaches 15d.

[0047] (2) According to the best preparation method of the catalyst, 20g of the catalyst is weighed and loaded into a fixed bed reaction tube for continuous reaction, and the continuous reaction time reaches 30d.

[0048] (3) According to the best preparation method of the catalyst, 20g of the catalyst is weighed and loaded into a fixed bed reaction tube for continuous reaction, and the continuous reaction time reaches 45d.

[0049] Example 7 Pyridine selectivity (%) Yield (%) 3-methylpyridine conversion (%) 15d 75.32 61.23 81.29 30d 68.63 56.36 82.12 45d 63.66 50.65 79.56

[0050] As can be seen from the data in the table, the catalyst has good stability and can be continuously operated for at least 30d, and the activity of the catalyst will decrease slightly.

[0051] The catalyst operated for 45d is activated, and the verification according to example 7 is continued.

[0052] Example 8:

[0053] After the catalyst is regenerated, the reaction is continued, and the activity of the catalyst is recorded.

[0054]

[0055] As can be seen from the data in the table, when the catalyst is activated, the previous activity can be restored and stable operation can be achieved, indicating that the catalyst has good stability and does not need to be activated frequently.

[0056] In order to solve the problem that the demand for pyridine and methylpyridine is small, and the electron cloud density of the aromatic ring of pyridine base is lower than that of benzene ring, which is not conducive to the dealkylation reaction dominated by electrophilic substitution reaction, the preparation method of the application is: preparing a supported high-efficiency catalyst, loading the catalyst into a fixed bed after preparation, using 50% 3-methylpyridine as raw material, and carrying out demethylation reaction under the action of high temperature, catalyst and air to produce pyridine.

[0057] While embodiments of the application have been shown and described, it is to be understood that the embodiments described are merely exemplary of the principles and application of the present application. Numerous modifications and adaptions can be effected without departing from the spirit and scope of the present application, which is not limited to the exact construction and arrangement described. It is intended, therefore, to cover all modifications and adaptions that fall within the scope of the claims and their equivalents.

Claims

1. A method for producing a catalyst for the synthesis of pyridine from 3-methylpyridine, characterized in that It comprises the following steps: Step 1: preparation of supported high-efficiency catalyst The supported catalyst ZSM-5 is used as a carrier, and the active components are V2O5, CoO and Ag. The molecular sieve ZSM-5, citric acid, ammonium metavanadate, cobalt nitrate, silver nitrate and deionized water are mixed, filtered, dried, and calcined to prepare the supported high-efficiency catalyst. Step 2: preparation of pyridine by using the supported high-efficiency catalyst The catalyst is loaded in a fixed bed, 50% 3-methylpyridine is used as raw material, and the demethylation reaction is carried out at high temperature, in the presence of the catalyst and air to produce pyridine. In step 1, the active components are V2O5, CoO and Ag, wherein the mass fraction of V2O5 is 5%-20%, the amount-of-substance ratio of Co to V is 1:0.5-2.5, and the mass fraction of Ag is 0.5%-2%.

2. The method for preparing a catalyst for the synthesis of pyridine from 3-methylpyridine according to claim 1, characterized in that, In step 1, the silicon-aluminum ratio of ZSM-5 is 300.

3. The method for preparing a catalyst for the synthesis of pyridine from 3-methylpyridine according to claim 1, characterized in that, In step 1, the calcination temperature of the catalyst is 350-450℃, and the calcination time is 4-8h.

4. The method for preparing a catalyst for the synthesis of pyridine from 3-methylpyridine according to claim 1, characterized in that, In the preparation of the catalyst, the molecular sieve ZSM-5, citric acid, ammonium metavanadate, cobalt nitrate, silver nitrate and deionized water are mixed, stirred and then allowed to stand for 20h to fully load the ions.

5. The method for preparing a catalyst for the synthesis of pyridine from 3-methylpyridine according to claim 1, characterized in that, In the reaction system of step 2, the reaction temperature is 350℃.

6. The method for preparing a catalyst for the synthesis of pyridine from 3-methylpyridine according to claim 1, characterized in that, In the reaction system of step 2, the reaction pressure is low, which is 0-40kPa.

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