CN107649131B

CN107649131B - Methyl pyridine oxidation demethylation catalyst

Info

Publication number: CN107649131B
Application number: CN201710978084.XA
Authority: CN
Inventors: 王知彩; 钟虎; 水恒福; 任世彪; 雷智平; 潘春秀; 王晓玲
Original assignee: Anhui University of Technology AHUT
Current assignee: Anhui University of Technology AHUT
Priority date: 2017-10-18
Filing date: 2017-10-18
Publication date: 2020-09-01
Anticipated expiration: 2037-10-18
Also published as: CN107649131A

Abstract

The invention discloses a methyl pyridine oxidation demethylation catalyst, and belongs to the technical field of chemical catalysis. The catalyst is anatase type TiO₂The carrier is prepared by taking Ag doped V and Fe or Ce composite oxide as an active component; wherein, the active component V₂O₅The mass fraction of the Ag-Ag alloy is 5-20%, the molar ratio of Fe or Ce to V is 0.25-1, and the mass fraction of Ag is 0-1.5%. The preparation method of the catalyst comprises the following steps: with TiO₂The carrier is prepared by soaking ammonium metavanadate and a nitrate mixed solution of iron or cerium in the same volume, drying at 120 ℃, further soaking a silver nitrate solution, and roasting at 400-550 ℃. The catalyst is suitable for the oxidation demethylation reaction of the picoline under the condition of high airspeed, and has good catalytic activity, carbon deposition resistance and stability.

Description

Methyl pyridine oxidation demethylation catalyst

Technical Field

The invention belongs to the technical field of chemical catalysis, particularly relates to a catalyst and a preparation method thereof, and particularly relates to a methyl pyridine oxidation demethylation catalyst and a preparation method thereof.

Background

Pyridine is a heterocyclic compound which is most widely researched and applied at present, is used as an important organic synthesis intermediate and fine chemical raw material, and is widely applied. Early pyridine is mainly prepared by separating and extracting from coal tar, and has complex process and limited yield. Currently, pyridine is mainly produced by catalytic synthesis in the world, wherein the aldehyde (ketone) ammonia method is the most widely used pyridine synthesis technology. However, the aldehyde (ketone) ammonia process for synthesizing pyridine products contains a large amount of mixed picoline by-products such as 2-picoline, 3, 5-lutidine and the like, which accounts for about 1/2% of the yield of pyridine. Due to the complex composition and the great separation difficulty of the mixed picoline by-products, the application of other picolines except 3-picoline is very limited, and the treatment is difficult. Therefore, with the increase of the yield of synthesized pyridine, the utilization problem of mixed picolines is receiving general attention. The early catalytic dealkylation of heavy pyridine in coal tar is an important mixed picoline utilization way, the utilization value of a picoline byproduct can be improved, the pyridine base capacity structure can be effectively adjusted, and the pyridine production efficiency is improved.

The research and development of the catalytic dealkylation technology of the alkylpyridines mainly focuses on the middle of the last century, and mainly comprises the technologies of catalytic steam dealkylation, catalytic oxidation dealkylation, catalytic hydrogenation dealkylation and the like. Wherein, the catalytic oxidation dealkylation can be carried out under normal pressure, and has the advantages of lower economic cost, higher pyridine yield and the like. However, the technical key is the development of a catalyst with high activity, high selectivity and stability. British patent (GB 1191913) provides a process for the catalytic oxidative dealkylation of alkylpyridines, the catalyst used being a V-Cr catalyst containing promoters such as Cd, Bi, Ni or Co. According to the method, under the condition that the molar ratio of 3-methylpyridine, steam and air is 1:20:15, the conversion rate of 3-methylpyridine is 75%, and the yield of pyridine is 40.6%. Leitis et al developed a V-Mo-P catalyst with pyridine yields of 35.5%, 5.8% and 16.9% for the 2-picoline, 3-picoline and 4-picoline feedstocks, respectively, at 400 ℃. Yokoyama et al (US 4118388) provide an alkylpyridine oxidative dealkylation catalyst: v_aX_bAg_cO_dAnd X is at least one of Cr, Mo and W. The pyridine yield by using 3-methylpyridine as a raw material can reach 77%. Tsutsui studies found Al₂O₃The carrier is loaded with oxides or sulfides of active components such as Ni, Mo, Cr and the like, so that the yield and selectivity of the product can be improved, and Mg, P and the like are added to improve the thermal stability of the product. Kazuyuki also provides TiO containing vanadium₂A catalyst and a method for producing pyridine by catalyzing the oxidation of alkyl pyridine. Although numerous studies have shown that vanadium is the main active component of alkylpyridine oxidation, the selectivity and stability of the catalyst has not been effectively addressed. In recent years, studies on wavelet and the like have been carried outThe existing Ag doping can improve V₂O₅/TiO₂The demethylation activity and selectivity of the oxidation of the 3-methylpyridine are catalyzed, but the catalyst load is low, and the liquid space velocity of the 3-methylpyridine is only 0.01h^-1. Therefore, the modification of the vanadium oxide supported catalyst by adding transition metal is an important way for improving the main activity, selectivity and stability of the alkyl pyridine oxidation dealkylation catalyst.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention aims to provide a high-efficiency methyl pyridine oxidation demethylation catalyst to solve the problem of high added value utilization of a methyl pyridine byproduct in pyridine production.

In order to achieve the aim, the invention provides a methyl pyridine oxidation demethylation catalyst which is anatase TiO₂Is used as a carrier, V-Fe or V-Ce composite oxide is used as an active component, and Ag is used as a modifier. Wherein, the active component V₂O₅The mass fraction of the Ag-Ag alloy is 5-20%, the molar ratio of Fe or Ce to V is 0.25-1, and the mass fraction of Ag is 0-1.5%.

As an optimization, the active component is a V-Ce composite oxide; wherein: v₂O₅The mass fraction of (A) was 6.6%, the molar ratio of Ce to V was 0.54, and the mass fraction of Ag was 0.8%.

The invention also provides a preparation method of the catalyst, which comprises the following specific steps:

A. adding a certain amount of ammonium metavanadate (NH)₄VO₃) And oxalic acid (H)₂C₂O₄·2H₂O) preparing into mixed aqueous solution, wherein NH₄VO₃And H₂C₂O₄·2H₂The O mol is 1: 2.

B. And adding a certain amount of ferric nitrate or cerous nitrate into the mixed solution, and mixing and dissolving to obtain the active component impregnation liquid.

C. Adding titanium dioxide carrier into the active component solution, stirring, soaking for 24h, evaporating to dryness, and drying at 120 deg.C for 12 h.

D. Preparing a certain amount of silver nitrate solution, adding the titanium dioxide carrier loaded with the active component, and soaking for 24 hours. After evaporation to dryness, the mixture was dried at 120 ℃ for 12 hours.

E. And roasting the precursor subjected to Ag dipping modification for 4-7 h at 400-550 ℃ in an air atmosphere.

The catalyst provided by the invention can be used for oxidation demethylation of methylpyridine in a mixed atmosphere of water vapor and air. The reactor used is a quartz tube two-section fixed bed reactor with the inner diameter of 25mm and the length of 400 mm. The specific reaction conditions are as follows: the amount of the catalyst used was 1.0g, and the catalyst was diluted with quartz sand of equal mass. The air flow is 20ml/min, and the space velocity of the catalyst is 1.22h^-1The molar ratio of the picoline to the water vapor is 1:10, the temperature of the first-stage gasification furnace is 200 ℃, and the reaction temperature of the second-stage reaction furnace is 300 ℃.

The scientific principle of the invention is as follows:

the invention uses anatase type TiO₂The catalyst is used as a carrier, adopts a V-Fe or V-Ce composite oxide active component, and obtains the low-cost and high-load methylpyridine oxidation demethylation catalyst through Ag modification. The electron transfer capacity of vanadium oxide and the surface acid center strength of the catalyst can be modulated by doping Fe or Ce, the activation of picoline molecules is promoted, and the activity and the stability of the catalyst are improved; the Ag modification can improve the oxygen adsorption capacity of the catalyst, activate oxygen molecules to form lattice oxygen, and improve the activity and selectivity of the catalyst.

Compared with the prior art, the invention has the following beneficial effects:

1. provides a catalyst for synthesizing pyridine by oxidation and demethylation of picoline, which has higher catalytic activity and the airspeed of the picoline is 1.22h^-1Under the condition, the one-way yield of the pyridine can reach 63.0 percent at most, and the selectivity of the pyridine product can reach 78.8 percent.

2. The catalyst prepared by the invention is suitable for oxidation demethylation of methylpyridine under the condition of high airspeed, has good catalytic activity, carbon deposition resistance and stability, and does not deactivate after continuous reaction for 10 hours.

3. The catalyst of the invention reduces Ag loading capacity, and has low cost and simple preparation.

Detailed Description

The present invention will be described in detail with reference to examples, but the present invention is not limited to the examples.

Example 1

0.6g of NH₄VO₃And 1.3g H₂C₂O₄·2H₂Adding O into 100ml deionized water, stirring at 70 deg.C to dissolve, adding 1.0g Fe (NO) after the solution turns blue₃)₃·9H₂And O is stirred and dissolved. To the above solution was added 3.0g of TiO₂The carrier is soaked at room temperature for 24h, heated to dehydrate and dried at 120 ℃ for 12 h. Then, a solution containing 0.05g of AgNO was prepared₃The impregnation liquid of (3), the above-mentioned supported modified TiO₂An equal volume of impregnation was carried out for 24h and drying was carried out at 120 ℃ for 12 h. Finally, roasting the mixture for 5 hours at the temperature of 450 ℃ in the air atmosphere to obtain the Cat-1 catalyst (V)₂O₅Is 7.1%, the molar ratio of Fe to V is 0.48, and the mass fraction of Ag is 0.86%. ).

The evaluation of the catalyst performance was carried out in a two-stage fixed bed reactor, under the following specific reaction conditions: the amount of the catalyst used was 1.0g, and the catalyst was diluted with quartz sand of equal mass. The air flow is 20ml/min, and the space velocity of the catalyst is 1.22h^-1The molar ratio of 3-methylpyridine to water vapor was 1: 10. The temperature of the first-stage gasification furnace is 200 ℃, and the reaction temperature of the second-stage reaction furnace is 300 ℃. After 30min of reaction, a sample was taken for gas chromatography.

Example 2

0.5g of NH₄VO₃And 1.1g H₂C₂O₄·2H₂Adding O into 100ml deionized water, stirring at 70 deg.C to dissolve, adding 1.7g Fe (NO) after the solution turns blue₃)·9H₂And O is stirred and dissolved. To the above solution was added 3.0g of TiO₂The carrier is soaked at room temperature for 24h, heated to dehydrate and dried at 120 ℃ for 12 h. Then, a solution containing 0.05g of AgNO was prepared₃The impregnation liquid of (3), the above-mentioned supported modified TiO₂An equal volume of impregnation was carried out for 24h and drying was carried out at 120 ℃ for 12 h. Finally, roasting for 7 hours at 400 ℃ in air atmosphere to obtain Cat-2 catalyst (V)₂O₅The mass fraction of (A) was 5.8%, the molar ratio of Fe to V was 1.0, and the mass fraction of Ag was 0.8%. ). Method for evaluating catalytic activityThe procedure is as in example 1.

Example 3

2.5g of NH₄VO₃And 5.4g H₂C₂O₄·2H₂Adding O into 100ml deionized water, stirring at 70 deg.C to dissolve, adding 2.2g Fe (NO) after the solution turns blue₃)·9H₂And O is stirred and dissolved. To the above solution was added 3.0g of TiO₂The carrier is soaked at room temperature for 24h, heated to dehydrate and dried at 120 ℃ for 12 h. Then, 0.1g of AgNO was prepared₃The impregnation liquid of (3), the above-mentioned supported modified TiO₂An equal volume of impregnation was carried out for 24h and drying was carried out at 120 ℃ for 12 h. Finally, roasting the mixture for 4 hours at 550 ℃ in the air atmosphere to obtain the Cat-3 catalyst (V)₂O₅20.0%, the molar ratio of Fe to V was 0.25, and the mass fraction of Ag was 1.2%. ). The catalytic activity was evaluated in the same manner as in example 1.

Example 4

1.5g of NH₄VO₃And 3.2g H₂C₂O₄·2H₂Adding O into 100ml deionized water, stirring at 70 deg.C to dissolve, adding 2.0g Fe (NO) after the solution turns blue₃)·9H₂And O is stirred and dissolved. To the above solution was added 3.0g of TiO₂The carrier is soaked at room temperature for 24h, heated to dehydrate and dried at 120 ℃ for 12 h. Then, a solution containing 0.01g of AgNO was prepared₃The impregnation liquid of (3), the above-mentioned supported modified TiO₂An equal volume of impregnation was carried out for 24h and drying was carried out at 120 ℃ for 12 h. Finally, roasting for 4 hours at 500 ℃ in the air atmosphere to obtain the Cat-4 catalyst (V)₂O₅Is 14.3%, the molar ratio of Fe to V is 0.39, and the mass fraction of Ag is 0.1%. ). The catalytic activity was evaluated in the same manner as in example 1.

Example 5

With 1.2g Ce (NO)₃)·6H₂O instead of 1.00g Fe (NO) in example 1₃)·9H₂O, other working procedure the same as in example 1, Cat-5 catalyst (V) was prepared₂O₅The mass fraction of (A) was 6.6%, the molar ratio of Ce to V was 0.54, and the mass fraction of Ag was 0.8%. ). The catalytic activity was evaluated in the same manner as in example 1.

Example 6

With 1.8g Ce (NO)₃)·6H₂O instead of 1.7g Fe (NO) in example 2₃)·9H₂O, other operating procedure the same as in example 2, Cat-6 catalyst (V) was prepared₂O₅The mass fraction of (A) was 5.3%, the molar ratio of Ce to V was 0.98, and the mass fraction of Ag was 0.8%. ). The catalytic activity was evaluated in the same manner as in example 1.

Example 7

Using 2.5g Ce (NO)₃)·6H₂O instead of 2.2g Fe (NO) in example 3₃)·9H₂O, other working procedure the same as in example 3, Cat-7 catalyst (V) was obtained₂O₅18.1%, the molar ratio of Ce to V was 0.27, and the mass fraction of Ag was 1.1%. ). The catalytic activity was evaluated in the same manner as in example 1.

Example 8

With 2.8g Ce (NO)₃)·6H₂O instead of 2.0g Fe (NO) in example 4₃)·9H₂O, other working procedure the same as in example 4, Cat-8 catalyst (V) was prepared₂O₅Is 12.4%, the molar ratio of Ce to V is 0.50, and the mass fraction of Ag is 0.1%. ). The catalytic activity was evaluated in the same manner as in example 1.

The results of catalytic oxidative demethylation reactions of examples 1-8 are shown in Table 1

TABLE 13 reaction results of oxidative demethylation of methylpyridines

Claims

1. The methyl pyridine oxidizing and demethylating catalyst is characterized in that anatase TiO is used as the catalyst₂Is used as a carrier, V-Fe or V-Ce composite oxide is used as an active component, and Ag is used as a modifier;

wherein: active component V₂O₅The mass fraction of the Fe or Ce is 5-20%, and the molar ratio of Fe or Ce to V is 0.25-1: 1; the mass fraction of the modifier Ag is 0.1-1.5%;

the preparation of the methyl pyridine oxidation demethylation catalyst comprises the following steps:

A. reacting NH₄VO₃And H₂C₂O₄·2H₂O into a mixed aqueous solution of NH₄VO₃And H₂C₂O₄·2H₂The molar ratio of O is 1: 2;

B. adding ferric nitrate or cerous nitrate into the mixed aqueous solution, mixing and dissolving to obtain an active component solution;

C. adding a titanium dioxide carrier into the active component solution prepared in the step B, stirring, soaking, drying by distillation, and drying to obtain the titanium dioxide carrier loaded with the active component;

D. preparing a silver nitrate solution, adding the titanium dioxide carrier loaded with the active component prepared in the step C, soaking, evaporating to dryness and then drying to obtain a precursor after Ag soaking modification;

E. and D, roasting the precursor subjected to the Ag dipping modification prepared in the step D for 4-7 hours at the temperature of 400-550 ℃ in an air atmosphere.

2. The picoline oxidative demethylation catalyst of claim 1 wherein the active component is a V-Ce complex oxide; wherein: v₂O₅The mass fraction of (A) was 6.6%, the molar ratio of Ce to V was 0.54, and the mass fraction of Ag was 0.8%.

3. Use of the catalyst of claim 1 for catalyzing oxidative demethylation of picolines.