CN104447353B - A kind of benzene and hydroxylamine salt react the method directly preparing aniline - Google Patents

Abstract

The present invention is a kind of method that benzene reacts directly aniline processed with hydroxylamine salt, the method comprises the steps: to be separately added into acetic acid, water, hydroxylamine salt, benzene and catalyst in the normal pressure reactor with condensation reflux unit, being warming up to 70-80 DEG C, stirring the lower response time is 2-5h, obtains aniline；Wherein, volume ratio is acetic acid: water: benzene=5:5:1, and quality is than benzene: catalyst=5～20:1, mol ratio benzene: hydroxylamine salt=1:1, and described catalyst is that the vanadium dioxide catalyst that Carbon Materials supports (is called for short VO₂/ C), active component VO in this catalyst₂Account for the 3～25% of catalyst gross mass。The selectivity of aniline of the present invention is up to 99%, and yield is up to 41%, and the preparation process of catalyst is simple, with low cost, environmental friendliness, easily operate。

Description

A kind of method that directly prepares aniline by reaction of benzene and hydroxylamine salt

technical field

The invention relates to a method for directly preparing aniline by reacting benzene with hydroxylamine salt, in particular to a method for directly catalyzing the reaction of benzene and hydroxylamine salt to synthesize aniline in one step under mild reaction conditions using a vanadium dioxide catalyst supported by a carbon material.

Background technique

Aniline is an important organic chemical raw material and fine chemical intermediate. It is widely used in industries such as medicine, dyestuff, rubber, and spices. It is also the main raw material for the production of diphenylmethane diisocyanate (MDI). With the increase of MDI demand, the The demand for aniline has also increased significantly. At present, the industrial production methods of aniline are mainly catalytic hydrogenation of nitrobenzene and gas-phase ammonolysis of phenol. The first step of catalytic hydrogenation of nitrobenzene is to nitrate benzene with a mixture of concentrated nitric acid and concentrated sulfuric acid at 90-140°C to produce nitrobenzene, which is then recovered by rectification and then undergoes liquid or gas phase catalytic hydrogenation to produce aniline . This synthesis method not only consumes a lot of energy and corrodes equipment, but also produces a large amount of acid residue, NO _x waste gas and waste water containing phenol, causing serious pollution to the environment. The gas-phase ammonolysis method of phenol is to react phenol with ammonia to generate aniline at a high temperature of about 400°C. The synthesis of industrial raw material phenol mainly adopts the cumene method, that is, benzene and propylene are used as raw materials, and cumene is catalyzed by AlCl3 to synthesize cumene, and cumene is oxidized by air to generate peroxide, which decomposes in the presence of dilute _acid Finally, phenol and acetone are obtained. It can be seen that the industrial production methods of these anilines all have problems such as harsh reaction conditions, many steps, high energy consumption, high cost, low atomic utilization rate and serious environmental pollution. Therefore, in order to adapt to the green trend of global chemical production, it is urgent to develop new simple and environmentally friendly synthetic routes to aniline. In recent years, the synthesis of aniline by direct ammonification and oxidation of benzene, which changes the multi-step reaction into one step, can significantly improve the atom economy, and the by-product is hydrogen or water, which has no pollution to the environment, so it has attracted extensive attention from researchers.

Professor Hu Changwei of Sichuan University reported a method for the preparation of aniline by direct amination of benzene. The method uses ammonia water as the amination agent, hydrogen peroxide as the oxidant, and the catalyst used is Ni and Cu supported on titanium-silicon molecular sieve TS-1. , Ce, V, Ti metal catalysts (patent publication number: CN101906045). Although this method has mild reaction conditions and little environmental pollution, the carrier TS-1 is expensive, the catalyst cost is high, and the conversion rate of benzene is very low (less than 10%), and the yield of aniline is low.

Zhu Liangfang etc. used gamma-Al ₂ O ₃ as a carrier and used two or three of nickel, molybdenum, vanadium, zirconium, manganese, and cerium as active components in the one-step amination reaction of benzene (patent Publication number: CN1555921). This patent also uses ammonia water as an aminating agent and hydrogen peroxide as an oxidizing agent. Although the reaction conditions are mild, the yield of aniline is only 0.038%, and the catalyst requires multi-stage roasting, the preparation process is complicated, and hydrogen reduction activation is required before use. In addition, in order to solve the limitation of low yield of aniline using ammonia as amination agent, the research group proposed in patent 200510020505 that soluble vanadium salts (vanadyl sulfate, ammonium metavanadate, sodium metavanadate) were used as catalysts, and hydroxylamine hydrochloride One-step synthesis of aniline as an aminating agent in aqueous acetic acid. This method makes the yield of aniline reach 68%. Although the method greatly improves the yield of aniline, the soluble vanadium salt catalyst is expensive, cannot be recycled and reused, and has a high cost, thereby also limiting the industrial application of the method.

Due to their relatively high specific surface area, large pore volume, high hydrothermal stability and acid and alkali resistance, carbon materials are widely used in fuel cells, sensors, adsorption separation, catalysis and other fields. Biomass is the most widespread substance on the earth. The preparation of carbon materials using biomass as a precursor is not only cheap, efficient, simple and easy to do, but also harmless to the environment, so it has become a research hotspot in recent years. In addition, so far, the application of vanadium dioxide and molybdenum dioxide catalysts supported by carbon materials in the one-step reaction of aniline from benzene and hydroxylamine salt has not been reported.

Contents of the invention

The purpose of the present invention is to provide a method for directly preparing aniline by reacting benzene with hydroxylamine salt. The method uses a carbon material-supported vanadium dioxide catalyst, which can catalyze the reaction of benzene and hydroxylamine salt in one step under mild reaction conditions. Aniline has high selectivity and reactivity, and at the same time, the preparation method of the catalyst is simple, easy to operate and low in cost.

The technical scheme adopted in the present invention is:

A method for directly preparing aniline by reacting benzene with hydroxylamine salt, the method comprising the steps of:

Add acetic acid, water, hydroxylamine salt, benzene and catalyst to the normal pressure reactor equipped with a condensing reflux device, raise the temperature to 70-80°C, and stir for a reaction time of 2-5 hours to obtain aniline;

Wherein, the volume ratio is acetic acid:water:benzene=5:5:1, mass ratio benzene:catalyst=5～20:1, molar ratio benzene:hydroxylamine salt=1:1, and the catalyst is supported by carbon material A vanadium dioxide catalyst (VO ₂ /C for short), in which the active component VO ₂ accounts for 3-25% of the total mass of the catalyst.

Described hydroxylamine salt is hydroxylamine hydrochloride or hydroxylamine sulfate.

A method for preparing a carbon material-supported vanadium dioxide catalyst, comprising the following steps

Add ammonium metavanadate and sucrose into deionized water, after dissolving, pour the solution into a hydrothermal kettle, seal it and heat treat it at 80-180°C for 6-48 hours, and finally filter and wash with hot water until the lotion is neutral and dry Afterwards, a tan solid was obtained, and the solid was carbonized at 500-900°C for 3-8 hours under a nitrogen atmosphere to finally obtain a black carbon-supported vanadium dioxide catalyst (VO ₂ /C);

Wherein, the material ratio is the molar ratio of ammonium metavanadate:sucrose=1:1-15, and 1.3-19.9 mmol of ammonium metavanadate is added to every 60 ml of deionized water.

The effects and benefits of the present invention are: the catalyst of the present invention is used for the one-step reaction of benzene and hydroxylamine salt to prepare aniline with high selectivity and reactivity, the selectivity of aniline can reach 99%, and the yield can reach 41%. Compared with the soluble vanadium salt catalyst with better catalytic performance reported in the literature, the solid catalyst provided by the invention is easy to separate from the product after the reaction, and the catalyst can be reused after centrifugation, which has a good application prospect. Compared with the traditional preparation method impregnation method of the supported catalyst, the preparation method of the catalyst involved in the present invention adopts the method of hydrothermal synthesis, the sucrose aqueous solution and the metal precursor are mixed and subjected to one-step hydrothermal treatment to obtain the precursor of the carrier and the active component at the same time, The content of the active components of the catalyst can be adjusted by adjusting the concentration of the metal precursor, and the preparation of the catalyst uses the abundant biomass resource sucrose as the precursor of the carbon carrier, and does not need to use other catalysts to catalyze the hydrolysis and polycondensation of sucrose, and the cost is low , environment-friendly, simple preparation process, easy operation, and good application and industrialization prospects.

Description of drawings

Fig. 1 is the XRD spectrogram of the catalyst prepared in Example 1 of the present invention.

detailed description

The present invention will be further described below in conjunction with specific examples, but the present invention is not limited to the following examples.

Example 1

Preparation of VO ₂ /C-1# catalyst: Dissolve 1.0g (8.5mmol) ammonium metavanadate and 6.8g (19.9mmol) sucrose in 60mL deionized water. Afterwards, it was heat treated at 120°C for 12 hours, and after cooling down to room temperature, it was filtered, washed with hot water until the washing liquid was neutral, and dried to obtain a brown catalyst precursor. The catalyst precursor was carbonized at 550° C. for ₆ hours under a nitrogen atmosphere to finally obtain a black solid. From the XRD spectrum of FIG. -073-2362) match, so the active component of the catalyst obtained is VO ₂ . Carry out thermogravimetric (TG) analysis to catalyst on SeteramSetsys16/18 thermal analyzer, it can be known that VO in the prepared catalyst accounts for ₁₅ % of the total mass of catalyst through calculation.

Example 2

The preparation of VO ₂ /C-2# catalyst: the preparation process is the same as in Example 1, the difference is that the amount of ammonium metavanadate added is 0.39g (3.3mmol), calculated by thermogravimetric (TG) analysis in the catalyst VO2 accounted for ₄ % of the total mass of the catalyst.

Example 3

The preparation of VO ₂ /C-3# catalyst: the preparation process is the same as in Example 1, the difference is that the amount of ammonium metavanadate added is 0.60g (5.1mmol), calculated by thermogravimetric (TG) analysis in the catalyst VO2 accounted for ₆ % of the total mass of the catalyst.

Example 4

The preparation of VO ₂ /C-4# catalyst: the preparation process is the same as in Example 1, the difference is that the amount of ammonium metavanadate added is 2.0g (17.1mmol), calculated by thermogravimetric (TG) analysis in the catalyst VO2 accounted for ₂₀ % of the total mass of the catalyst.

Example 5

The reaction of benzene and hydroxylamine hydrochloride to directly produce aniline: Add 5mL of acetic acid and 5mL of water into a 100mL three-neck flask equipped with a stirring and condensing reflux device, then add 0.78g (11.25mmol) of hydroxylamine hydrochloride, and stir at 30°C until completely dissolved , add 0.1 g VO ₂ /C-1# catalyst and 1 mL (11.25 mmol, 0.89 g) of benzene in sequence, and then raise the temperature to 80° C. for 4 hours. After the reaction, cool down to room temperature. After the catalyst is centrifuged, use 30wt% NaOH solution to neutralize the reaction solution until its pH=7-8, extract the organic phase with 5mL ether, and conduct qualitative analysis with gas chromatography. Perform quantitative analysis.

Example 6

The specific reaction process is the same as in Example 5, except that the catalyst used is VO ₂ /C-2# catalyst.

Example 7

The specific reaction process is the same as in Example 5, except that the catalyst used is VO ₂ /C-3# catalyst.

Example 8

The specific reaction process is the same as in Example 5, except that the catalyst used is VO ₂ /C-4# catalyst.

Example 9

Reusability of VO ₂ /C-1# catalyst: the reaction process is the same as in Example 5, except that the catalyst used is the VO ₂ /C-1# catalyst recovered after the reaction in Example 5.

Example 10

The reaction of benzene and hydroxylamine sulfate to directly produce aniline: the specific reaction process and material ratio are the same as in Example 5, except that the hydroxylamine salt used is hydroxylamine sulfate.

Table 1 shows the reaction results of Examples 5-10 of the present invention.

Matters not covered in the present invention are known technologies.

Claims (2)

1. a method for directly producing aniline by reacting benzene with hydroxylamine salt, is characterized in that the method may further comprise the steps: Add acetic acid, water, hydroxylamine salt, benzene and catalyst to the normal pressure reactor equipped with a condensing reflux device, raise the temperature to 70-80°C, and stir for a reaction time of 2-5 hours to obtain aniline; Wherein, the volume ratio is acetic acid: water: benzene=5:5:1, mass ratio benzene:catalyst=5~20:1, molar ratio benzene:hydroxylamine salt=1:1, and the catalyst is carried by carbon material Vanadium dioxide catalyst, the active component VO in this catalyst accounts for ₃ ~ 25% of the total mass of the catalyst; The preparation method of the vanadium dioxide catalyst supported by the carbon material comprises the following steps: Add ammonium metavanadate and sucrose into deionized water, after dissolving, pour the solution into a hydrothermal kettle, seal it and heat treat it at 80-180°C for 6-48 hours, and finally filter and wash with hot water until the lotion is neutral and dry Afterwards, a tan solid is obtained, and the solid is carbonized at 500-900° C. for 3-8 hours under a nitrogen atmosphere to finally obtain a vanadium dioxide catalyst supported by a black carbon material; Among them, the material ratio is the molar ratio of ammonium metavanadate: sucrose=1:1~15, and 1.3~19.9 mmol of ammonium metavanadate is added to every 60 ml of deionized water. 2. the method for directly producing aniline by reacting benzene with hydroxylamine salt as claimed in claim 1, is characterized in that described hydroxylamine salt is hydroxylamine hydrochloride or hydroxylamine sulfate.