CN111822032B - Catalyst for synthesizing 2,5-dichlorophenol and in-situ synthesis method of 2,5-dichlorophenol - Google Patents

Catalyst for synthesizing 2,5-dichlorophenol and in-situ synthesis method of 2,5-dichlorophenol Download PDF

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CN111822032B
CN111822032B CN202010784877.XA CN202010784877A CN111822032B CN 111822032 B CN111822032 B CN 111822032B CN 202010784877 A CN202010784877 A CN 202010784877A CN 111822032 B CN111822032 B CN 111822032B
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dichlorophenol
situ synthesis
bivo
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CN111822032A (en
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王刚
张曦
丁克鸿
徐林
王根林
许越
郭玉秀
王浩
廖强
陆仁标
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NINGXIA RUITAI TECHNOLOGY CO LTD
Jiangsu Ruixiang Chemical Co Ltd
Jiangsu Yangnong Chemical Group Co Ltd
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Jiangsu Ruixiang Chemical Co Ltd
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Abstract

The invention provides an in-situ synthesis method of a catalyst for synthesizing 2,5-dichlorophenol and 2,5-dichlorophenol. The catalyst is BiVO 4 /V 2 O 5 /g‑C 3 N 4 A three-way composite catalyst. The 2,5-dichlorophenol synthesized by the ternary composite catalyst provided by the invention is prepared from BiVO simultaneously having photocatalytic performance and hydroxylation catalytic performance 4 /V 2 O 5 And a photocatalyst g-C having the property of producing hydrogen peroxide 3 N 4 The components are combined. The catalyst can be used for in-situ synthesis of oxidant hydrogen peroxide in the presence of light, water, oxygen and an auxiliary agent, so that 1,4-dichlorobenzene is further catalytically oxidized by the hydrogen peroxide to form a final product 2,5-dichlorophenol. Therefore, the 2,5-dichlorophenol catalytically synthesized by the ternary composite catalyst provided by the invention has higher selectivity and yield, and meanwhile, the catalyst in the synthesis process of 2,5-dichlorophenol can be recovered, thereby being green and environment-friendly.

Description

In-situ synthesis method of catalyst for synthesizing 2,5-dichlorophenol and 2,5-dichlorophenol
Technical Field
The invention relates to the technical field of petrochemical industry, and particularly relates to an in-situ synthesis method of a catalyst for synthesizing 2,5-dichlorophenol and 2,5-dichlorophenol.
Background
2,5-dichlorophenol is an important chemical raw material and an intermediate of pesticide, and is mainly used for synthesizing herbicide dicamba, leather mildew preventive, nitrogen fertilizer synergist and the like. Because dicamba herbicide has the advantages of low toxicity, high efficiency and the like, the demand of 2,5-dichlorophenol as a key intermediate is increased continuously, so that the production efficiency is improved, a green production process is developed, and the simplification of the production flow is particularly important.
The traditional method for synthesizing 2,5-dichlorophenol comprises the following steps: 1,2,4-trichlorobenzene hydrolysis method; 2,5-dichloroaniline diazotization hydrolysis method; 2,5-dichloroanisole alcoholysis. However, the methods have more problems and defects, such as more side reactions of 1,2,4-trichlorobenzene hydrolysis method and difficult isomerization and separation of products; 5363 diazotization hydrolysis of 2,5-dichloroaniline has the disadvantages of large waste water amount, high danger coefficient and the like. In view of these drawbacks, a direct oxidation method using 1,4-dichlorobenzene as a raw material and a peroxide as an oxidizing agent has been studied recently.
CN107129426A discloses a method for directly oxidizing 1,4-dichlorobenzene serving as a raw material to obtain 2,5-dichlorophenol under the action of an oxidant, a metalloporphyrin catalyst and a cocatalyst. The method uses an oxidation method to prepare 2,5-dichlorophenol, and is relatively green and environment-friendly. However, metalloporphyrin compounds are easily oxidized and decomposed, are not easily separated and recovered, are unstable in the reaction solution, undergo irreversible dimerization to form porphyrin multimers, and are expensive, expensive and not easily industrially produced.
CN104591973A reports that 2,5-dichloroacetophenone is prepared by Friedel-Crafts acylation reaction of p-dichlorobenzene serving as a substrate and acetyl chloride in the presence of aluminum trichloride, then 2,5-dichlorophenyl acetate is prepared by Baeyer-Villiger oxidation reaction of the p-dichlorobenzene and peroxide in the presence of a catalyst, and finally 2,5-dichlorophenol is prepared by reflux hydrolysis of inorganic alkali solution. The method synthesizes the target object under the combination method of acylation and direct oxidation, and has certain innovation, but the method has complicated process, more organic waste liquid is generated, the total conversion rate and selectivity are reduced by multi-step reaction, and the reaction process can generate aluminum-containing waste water, so the method is not economical and environment-friendly.
US6586624 proposes a process for the oxidation of 1,4-dichlorophenol to 2,5-dichlorophenol by using vanadium derivatives (e.g. vanadium oxides, vanadates, vanadium acetylacetonate, etc.) as hydroxylation catalysts, organic or inorganic peroxides, especially hydrogen peroxide, as oxidants, which earlier proposed a direct oxidation process to produce 2,5-dichlorophenol, but at lower yields, low and large quantities of oxidants, especially hydrogen peroxide, and at a later stage, the use of concentrated aqueous hydrogen sulfite solutions to destroy unreacted hydrogen peroxide, causing considerable waste.
Meuneer L et al (Canadian Journal of Chemistry,2011,79 (7): 1179-1186.) use of nitrate ions or ferric iron as an inducer, and in the case of an air saturated solution, direct photolysis of 1,4-dichlorobenzene gave 2,5-dichlorophenol, 2,5-dichlorophenone, and the like. The method has great research significance on a green synthesis method, but has the defects of low yield and more byproducts, and simultaneously has poor reaction selectivity because of no directional catalyst and no strong oxidant.
For the above reasons, there is a need to provide a new preparation process of 2,5-dichlorophenol with high selectivity, high yield and environmental protection, so as to solve the above problems in the prior art.
Disclosure of Invention
The invention mainly aims to provide an in-situ synthesis method of a catalyst for synthesizing 2,5-dichlorophenol and 2,5-dichlorophenol, and solves the problem that the preparation process of 2,5-dichlorophenol in the prior art cannot give consideration to methods of high selectivity, high yield, environmental protection and the like.
In order to achieve the above object, according to one aspect of the present invention, there is provided a catalyst for synthesizing 2,5-dichlorophenol, the catalyst being BiVO 4 /V 2 O 5 /g-C 3 N 4 A three-way composite catalyst.
Further, the catalyst is prepared by the following method: in-situ synthesis of BiVO by taking ammonium metavanadate and bismuth nitrate as raw materials 4 /V 2 O 5 A complex; biVO (bismuth oxide) is added 4 /V 2 O 5 Complexes with g-C 3 N 4 Carrying out thermal polycondensation reaction on the precursor to form BiVO 4 /V 2 O 5 /g-C 3 N 4 A three-way composite catalyst.
Further, in situ synthesis of BiVO 4 /V 2 O 5 The method of the compound is any one selected from a hydrothermal-calcining method, a microwave-calcining method, a solid reaction-calcining method, a sol-gel/calcining method and a template-calcining method; preferably, the molar ratio of ammonium metavanadate to bismuth nitrate is 1.05 to 10, more preferably 1.05 to 6.5.
Further, g-C 3 N 4 The precursor is selected from any one or more of melamine, cyanamide, dicyandiamide, urea and thiourea; preferably, the thermal polycondensation reaction is selected from any one of a grinding-thermal polycondensation method, a high-temperature gas phase method, a solvent mixing-thermal polycondensation method, an ultrasonic dissolving-thermal polycondensation method; preferably, biVO 4 /V 2 O 5 Complexes with g-C 3 N 4 The weight ratio of the precursor is 1-6:1, more preferably 1-4:1.
According to another aspect of the present invention, there is also provided an in situ synthesis method of 2,5-dichlorophenol, comprising the steps of: s1, mixing 1,4-dichlorobenzene, the catalyst of any one of claims 1 to 4, a hydroxylation auxiliary agent and a solvent to obtain a raw material system; and S2, introducing oxygen into the raw material system, and irradiating ultraviolet light simultaneously to perform in-situ synthesis reaction to obtain 2,5-dichlorophenol.
Further, in step S1, the hydroxylation auxiliary agent is selected from oxalic acid and H 3 PO 4 Any one or more of citric acid, beta-aminoethanesulfonic acid, sulfonic acid, malonic acid, L-lactic acid, salicylic acid, 1,2,4-butanetricarboxylic acid and methanesulfonic acid; preferably, the solvent is selected from any one or more of water, dichloroethane, acetonitrile, chloroform, ethanol, acetic acid and formic acid, and the solvent necessarily contains water.
Further, in step S1, the catalyst is 0.1 to 7% by weight of 1,4-dichlorobenzene, preferably the catalyst is 1 to 4% by weight of 1,4-dichlorobenzene; preferably, the hydroxylation aid is 10-30% by weight of 1,4-dichlorobenzene.
Further, in step S1, the raw material system further includes a stabilizer; preferably, the stabilizer is selected from ZnSO 4 、ZnCl 2 、K 2 HPO 4 、NaNO 3 Any one or more of; preferably, the stabilizer is 0.15 to 0.5% by weight of 1,4-dichlorobenzene.
Further, in the step S2, the introduction rate of the oxygen is 60-100 mL/min; preferably, the reaction temperature of the in-situ synthesis reaction is 10-50 ℃; the reaction time is 10-20 h.
Further, in step S2, the irradiation power during the ultraviolet irradiation is 200 to 400W.
The invention provides a catalyst for synthesizing 2,5-dichlorophenol, which is BiVO 4 /V 2 O 5 /g-C 3 N 4 A three-way composite catalyst. The 2,5-dichlorophenol synthesized by the ternary composite catalyst provided by the invention is prepared from BiVO simultaneously having photocatalytic performance and hydroxylation catalytic performance 4 /V 2 O 5 And a photocatalyst g-C having the property of producing hydrogen peroxide 3 N 4 The components are combined. In the practical application process, the catalyst can be used for in-situ synthesis of oxidant hydrogen peroxide in the presence of light, water, oxygen and an auxiliary agent, so that the 1,4-dichlorobenzene is further catalytically oxidized by the hydrogen peroxide to form a final product 2,5-dichlorophenol. In the catalyst, biVO is defined as 4 /V 2 O 5 /g-C 3 N 4 Is a ternary compound, is tightly combined into a whole, and is not simple in mechanical mixing of components. BiVO 4 And V 2 O 5 The compound of (A) improves the performance of the 1,4-dichlorobenzene by directional catalysis, and is matched with g-C 3 N 4 The catalyst has better double effects of hydrogen peroxide in-situ catalytic synthesis and 2,5-dichlorophenol directional oxidation synthesis under the action of illumination.
Based on the reasons, the 2,5-dichlorophenol catalytically synthesized by the ternary composite catalyst provided by the invention has high selectivity and yield, and meanwhile, the catalyst in the synthesis process of 2,5-dichlorophenol can be recovered, so that the method is green and environment-friendly.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:
FIG. 1 shows a gas chromatogram in a GCMS detection spectrum of a product prepared in example 5 according to the present invention;
fig. 2 shows a mass spectrum in a GCMS detection spectrum of the product prepared in example 5 according to the present invention.
Detailed Description
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail with reference to examples.
As described in the background art, the method of 2,5-dichlorophenol in the prior art cannot give consideration to high selectivity, high yield, environmental protection and the like.
In order to solve the problems, the invention provides a catalyst for synthesizing 2,5-dichlorophenol, which is BiVO 4 /V 2 O 5 /g-C 3 N 4 A three-way composite catalyst.
Hydrogen peroxide (H) 2 O 2 ) Is one of the more effective oxidants for oxidizing 1,4-dichlorobenzene into 2,5-dichlorophenol, and the graphite phase nitrogenCarbon (g-C) 3 N 4 ) Is a relatively excellent hydrogen peroxide producing photocatalyst, and g-C under the synergistic effect of an oxygen auxiliary agent 3 N 4 The amount of the generated hydrogen peroxide is larger, and the method can be used for the synthetic reaction of 2,5-dichlorophenol. The inventors of the present application also found that bismuth vanadate (BiVO) 4 ) And vanadium pentoxide (V) 2 O 5 ) Both have the photocatalytic performance and the hydroxylation catalytic performance of 1,4-dichlorobenzene, and the two catalysts containing vanadium and g-C 3 N 4 And compounding to form the efficient ternary compound catalyst. Under the synergistic effect of illumination and an auxiliary agent, the catalyst can generate hydrogen peroxide in situ through photocatalysis, and further generate 2,5-dichlorophenol through catalytic oxidation of 1,4-dichlorobenzene. In addition, it is worth mentioning that BiVO 4 And V 2 O 5 The composite catalyst has compatibility, mutual inhibition of the composite catalyst is greatly weakened, and the composite catalyst is matched with each other on a Fermi level to form a heterojunction, so that the performance of producing hydrogen peroxide by photocatalysis is greatly improved. BiVO 4 And V 2 O 5 The close combination is integrated, and the performance of the 1,4-dichlorobenzene catalyst is also improved.
Based on the above, the invention provides an ingenious ternary composite catalyst, which realizes in-situ synthesis of oxidant hydrogen peroxide under the action of illumination, an auxiliary agent and a stabilizer, so that 2,5-dichlorophenol is synthesized, and the purposes of safe reaction and environmental protection are realized. The invention adopts the photocatalyst to synthesize hydrogen peroxide, saves the oxidant and improves the economic benefit; the adoption of the catalytic compatibility material avoids the mutual inhibition effect generated by the mechanical mixing and dissolving of different catalysts; the single kettle operation is adopted, so that the complicated operation steps caused by the subsequent gradual dropping of the raw materials are avoided; the method adopts a recyclable catalyst and low-pollution reagents, is green and environment-friendly, and solves the problems of great pollution and difficulty in wastewater treatment in the traditional process. Therefore, the ternary composite catalyst provided by the invention is used for catalytically synthesizing 2,5-dichlorophenol, has the effects of high selectivity, high yield, environmental protection and the like, and is obviously improved compared with the prior art.
In a preferred embodiment, the catalyst is prepared by the following method: in-situ synthesis of BiVO by taking ammonium metavanadate and bismuth nitrate as raw materials 4 /V 2 O 5 A complex; biVO (bismuth oxide) is added 4 /V 2 O 5 Complexes with g-C 3 N 4 Carrying out thermal polycondensation reaction on the precursor to form BiVO 4 /V 2 O 5 /g-C 3 N 4 A three-way composite catalyst. The in-situ synthesis is that ammonium metavanadate is used for synthesizing BiVO at the same time 4 Is also synthesized V 2 O 5 The raw material (2) and bismuth nitrate are used as raw materials, and BiVO can be generated simultaneously in the reaction process 4 And V 2 O 5 And the two are closely combined together and are BiVO 4 /V 2 O 5 Composite, rather than simple mechanical mixing. Obtaining BiVO 4 /V 2 O 5 After complexing, this is reacted with g-C 3 N 4 The precursor is subjected to thermal polycondensation reaction, so that the ternary composite catalyst with tightly combined components can be obtained.
In a preferred embodiment, biVO is synthesized in situ 4 /V 2 O 5 The method of the compound is any one selected from a hydrothermal-calcination method, a microwave-calcination method, a high-temperature solid phase method, a sol-gel/calcination method and a template-calcination method. BiVO can be synthesized in situ by adopting the method 4 /V 2 O 5 And (c) a complex. The hydrothermal-calcining method is that the precursor is mixed and stirred evenly, then transferred to a hydrothermal reaction kettle to be heated to the required temperature, the temperature is generally between 100 and 350 ℃ for reaction, and then the mixture is filtered, washed, dried and calcined at high temperature to obtain the compound. The microwave-calcining method is that the precursor is mixed and stirred evenly, then transferred to a microwave reactor for rapid reaction, the dried solid is taken out after the reaction is finished, and finally the compound is obtained by calcining in a high temperature furnace. The high-temperature solid-phase method is that at high temperature, precursors are fully mixed to enable reaction solid interfaces to be fully contacted, and then reaction nucleation is carried out through sintering or calcining treatment to generate a compound. The sol-gel/calcining process includes compounding the precursor of the synthesized product into solution with organic matter as solvent, crosslinking with polymer to obtain sol, further reaction of the sol to produce gel, stoving the gel and calcining in high temperature furnace to obtain the composite. The template agent-calcining method mainly usesThe skeleton carbon material such as carbon nano tube is added into the precursor liquid for growing the metal oxide nano particles to be used as a template agent, the nano particles with specific geometrical configurations are synthesized, the template agent is mainly selected from materials which can be chemically decomposed or physically dissolved and can not participate in the reaction, and then the composite is obtained by calcining.
In order to further increase the selectivity of the catalyst and at the same time increase the product yield, in a preferred embodiment the molar ratio of ammonium metavanadate to bismuth nitrate is 1.05 to 10, more preferably 1.05 to 6.5.
g-C 3 N 4 As long as the precursor can react with the BiVO 4 /V 2 O 5 The compound is subjected to a thermal polycondensation reaction, in a preferred embodiment, g-C 3 N 4 Precursors include, but are not limited to, any one or more of melamine, cyanamide, dicyandiamide, urea, and thiourea. Preferably, the thermal polycondensation reaction is selected from any one of a mill-thermal polycondensation method, a high-temperature gas phase method, a solvent mixing-thermal polycondensation method, and an ultrasonic dissolution-thermal polycondensation method. Wherein the grinding-thermal polycondensation method is to mix BiVO 4 /V 2 O 5 And g-C 3 N 4 Fully grinding the precursor and then carrying out g-C in a high-temperature furnace 3 N 4 And carrying out high-temperature polycondensation on the precursor to generate a ternary compound. The high-temperature gas phase method is to mix BiVO 4 /V 2 O 5 And g-C 3 N 4 The precursors are in the same high temperature furnace but have g-C sublimed at high temperature 3 N 4 The precursor forms a gas phase and adheres to BiVO 4 /V 2 O 5 And performing polycondensation on the surface to form a ternary complex. The solvent mixing-thermal polycondensation method is to mix BiVO 4 /V 2 O 5 And g-C 3 N 4 Stirring and dispersing the precursor in a solvent uniformly, filtering, washing, drying, and placing the dried solid in a high-temperature furnace for g-C 3 N 4 And carrying out high-temperature polycondensation on the precursor to generate a ternary compound. The ultrasonic dissolving-thermal polycondensation method is to mix BiVO 4 /V 2 O 5 And g-C 3 N 4 The precursor is filtered and washed after being dispersed in solvent ultrasonically and homogeneouslyWashing, drying, and g-C treating the dried solid in high-temperature furnace 3 N 4 And carrying out high-temperature polycondensation on the precursor to generate a ternary compound.
In a preferred embodiment, biVO is used for the purpose of simultaneously achieving high photocatalytic hydrogen peroxide production activity and hydroxylation oxidation activity 4 /V 2 O 5 Complexes with g-C 3 N 4 The weight ratio of the precursor is 1-6:1, more preferably 1-4:1. BiVO (bismuth oxide) is added 4 /V 2 O 5 Complexes with g-C 3 N 4 The weight ratio of the precursor is controlled within the range, so that the capability of the catalyst for producing hydrogen peroxide by photocatalysis is further improved, and the activity and the selectivity of catalyzing 1,4-dichlorobenzene to produce 2,5-dichlorophenol are better.
According to another aspect of the present invention, there is also provided an in situ synthesis method of 2,5-dichlorophenol, comprising the steps of: s1, mixing 1,4-dichlorobenzene, the catalyst, a hydroxylation auxiliary agent and a solvent to obtain a raw material system; and S2, introducing oxygen into the raw material system, and irradiating ultraviolet light simultaneously to perform in-situ synthesis reaction to obtain 2,5-dichlorophenol. As described above, by using the ternary composite catalyst provided by the invention, in the presence of light, water, oxygen and an auxiliary agent, an oxidant hydrogen peroxide can be synthesized in situ, so that 1,4-dichlorobenzene is further catalytically oxidized by hydrogen peroxide to form a final product 2,5-dichlorophenol. BiVO (BiVO) with both photocatalytic performance and hydroxylating catalytic performance 4 /V 2 O 5 And a photocatalyst g-C having the property of generating hydrogen peroxide 3 N 4 The combination increases the synergistic effect between different catalysts, and avoids the defect of mutual inhibition after the two catalysts with different properties are mechanically mixed and dissolved. BiVO 4 /V 2 O 5 Generated using an in situ method, biVO 4 /V 2 O 5 /g-C 3 N 4 Using BiVO 4 /V 2 O 5 And g-C 3 N 4 The precursor generated by thermal polycondensation is greatly improved in both physical bonding firmness and catalytic performance. Compared with the traditional synthetic method, the invention has the advantages of simplified operation and safe processAnd the method has the advantages of green and environmental protection. The ultraviolet light irradiation may be performed by a mercury vapor lamp, an ultraviolet germicidal lamp, a xenon lamp, or the like.
The specific reaction principle of the invention is as follows (preferably in the presence of a stabilizer):
Figure BDA0002621575200000051
in order to further improve the reaction efficiency and yield, in a preferred embodiment, in step S1, the hydroxylation assistant is selected from oxalic acid, H 3 PO 4 Any one or more of citric acid, beta-aminoethanesulfonic acid, sulfonic acid, malonic acid, L-lactic acid, salicylic acid, 1,2,4-butanetricarboxylic acid and methanesulfonic acid. After the hydroxylation auxiliary agents and the ternary composite catalyst are used together, under the oxidation action of hydrogen peroxide produced by a system, the catalytic oxidation activity of 1,4-dichlorobenzene is better, the reaction selectivity is better, and the yield of a target product is higher. Preferably, the solvent is selected from any one or more of water, dichloroethane, acetonitrile, chloroform, ethanol, acetic acid and formic acid, and the solvent necessarily contains water. The reaction is carried out in the solvent, and the catalytic oxidation process is more stable.
It should be noted that the "in situ synthesis reaction" indicates that the hydrogen peroxide oxidizing agent is generated in situ in the system, and then the 2,5-dichlorophenol is synthesized by using 1,4-dichlorobenzene as the starting material under the action of the oxidizing agent and the catalyst.
For the purpose of improving the reaction efficiency and the product yield and avoiding excessive waste of reagents, in the step S1, the catalyst is preferably 0.1 to 7 percent of the weight of 1,4-dichlorobenzene, and more preferably 1 to 4 percent of the weight of 1,4-dichlorobenzene; preferably, the hydroxylation aid is 10-30% by weight of 1,4-dichlorobenzene.
In a preferred embodiment, in the step S1, the raw material system further comprises a stabilizer; preferably, the stabilizer is selected from ZnSO 4 、ZnCl 2 、K 2 HPO 4 、NaNO 3 Any one or more of them. The reaction process is more stable by using the stabilizer. Preferably, the first and second electrodes are formed of a metal,the stabilizer accounts for 0.15 to 0.5 percent of the weight of 1,4-dichlorobenzene.
In a preferred embodiment, in the step S2, the oxygen is introduced at a rate of 60 to 100mL/min; preferably, the reaction temperature of the in-situ synthesis reaction is 10-50 ℃; the reaction time is 10-20 h. More preferably, in step S2, the irradiation power during the ultraviolet light irradiation is 200 to 400W. Under the reaction conditions, the catalytic oxidation synthesis of 1,4-dichlorobenzene to produce 2,5-dichlorophenol is higher in efficiency.
The present application is described in further detail below with reference to specific examples, which should not be construed as limiting the scope of the invention as claimed.
Example 1
20g of NH 4 VO 3 Dissolve in 100mL of dilute ammonia water to obtain solution A. 39.7g of Bi (NO) 3 ) 3 Dissolved in 100mL of dilute nitric acid to give solution B. While stirring, the solution B was slowly added dropwise to the solution A, and stirred for 30min to allow the reaction to proceed sufficiently. The suspension was then centrifuged and the resulting yellow solid was washed three times with distilled water and dried in vacuo at 80 ℃. Uniformly grinding the dried yellow solid, putting the ground yellow solid into a crucible, putting the crucible into a high-temperature furnace, and calcining the yellow solid for 4 hours at 500 ℃ in the air atmosphere to obtain BiVO 4 /V 2 O 5 And (c) a complex. By ICP element analysis, bi in the catalyst accounted for 41.1%, V accounted for 20.0%, which was the target.
Example 2
20g of NH 4 VO 3 Dissolve in 100mL of hot water to give solution A. 39.7g of Bi (NO) 3 ) 3 Dissolved in 100mL of dilute nitric acid to give solution B. While stirring, the solution B was slowly added dropwise to the solution A, and stirred for 30min to allow the reaction to proceed sufficiently. And then transferring the suspension into a 500mL polytetrafluoroethylene reaction kettle, putting the reaction kettle into an electric heating constant-temperature oven, reacting for 6h at 90 ℃, taking out and cooling to room temperature, washing the obtained yellow solid with distilled water for three times, centrifuging and drying. Grinding the dried solid uniformly, putting the ground solid into a crucible, putting the crucible into a high-temperature furnace, and calcining the solid for 4 hours at 500 ℃ in the air atmosphere to obtain BiVO 4 /V 2 O 5 And (3) a compound. By ICP element analysis, bi in the catalyst accounted for 40.9%, V accounted for 20.1%, which was the target.
Example 3
On the basis of example 1, 15g of melamine and 40g of BiVO 4 /V 2 O 5 Dissolving the complex in 100mL 20% methanol water solution, ultrasonically dispersing for 30min, adding 100mL distilled water into the suspension system, centrifugally separating, and drying at 50 ℃. Grinding the dried solid for 30min, putting the ground solid into a crucible, putting the crucible into a high-temperature furnace, adjusting the heating rate to 3-5 ℃/min, and preserving the heat at 530 ℃ for 3h to obtain BiVO 4 /V 2 O 5 /g-C 3 N 4 A three-way composite catalyst. By ICP element analysis, bi in the catalyst accounted for 34.5%, V accounted for 16.9%, which was the target.
Example 4
On the basis of example 2, 15g of melamine and 40g of BiVO 4 /V 2 O 5 Dissolving the complex in 100mL 20% methanol water solution, performing ultrasonic dispersion for 30min, adding 100mL distilled water into the suspension system, performing centrifugal separation, and drying at 50 ℃. Grinding the dried solid for 30min, putting the ground solid into a crucible, putting the crucible into a high-temperature furnace, adjusting the heating rate to 3-5 ℃/min, and preserving the heat at 530 ℃ for 3h to obtain BiVO 4 /V 2 O 5 /g-C 3 N 4 A three-way composite catalyst. By ICP elemental analysis, bi in the catalyst accounted for 34.8%, V accounted for 16.7%, which was the target.
Example 5
Based on example 3, 6.5g of 1, 4-dichlorobenzene, 200mL of 20% ethanol aqueous solution, 50mL of acetonitrile, 0.26g of ternary complex catalyst, 1.2g of phosphoric acid, 0.5g of sulfonic acid, 0.01g K were sequentially added to a 500mL quartz reactor 2 HPO 4 And stirred for 30min to obtain a uniform suspension. Then introducing O into the suspension at a flow rate of 80mL/min 2 And meanwhile, placing the suspension under a 300W xenon lamp for irradiation, controlling the reaction temperature to be 25 ℃, and stirring the suspension at the rotating speed of 200 r/min for 16h. After the reaction is finished, the xenon lamp is turned off, the oxygen is stopped,the turbidity solution was heated to 58 ℃ and filtered to remove the solid catalyst, and the quantitative analysis by liquid chromatography of 1,4-dichlorobenzene and 2,5-dichlorophenol gave 1,4-dichlorobenzene with a conversion of 70.2% and a selectivity of 2,5-dichlorophenol of 89.5%.
After the product is purified, the content is more than 99.5%, GCMS analysis is adopted, spectrogram patterns are shown in figures 1 and 2, and the product is confirmed to be the target product 2,5-dichlorophenol through mass spectrum signal analysis.
Example 6
Based on example 4, 6.5g of 1, 4-dichlorobenzene, 240mL of 20% acetic acid aqueous solution, 10mL of methanol, 0.26g of ternary complex catalyst, 1.2g of phosphoric acid and 0.01g of NaNO were sequentially added to a 500mL quartz reactor 3 And stirred for 30min to obtain a uniform suspension. Then introducing O into the suspension at a flow rate of 80mL/min 2 And meanwhile, placing the suspension under a 300W xenon lamp for irradiation, controlling the reaction temperature to be 25 ℃, and stirring the suspension at the rotating speed of 200 r/min for 15h. After the reaction is finished, the xenon lamp is closed, oxygen is stopped, turbid liquid is heated to 58 ℃, solid catalyst is removed by filtration, and 1,4-dichlorobenzene and 2,5-dichlorophenol are subjected to liquid chromatography quantitative analysis, so that the conversion rate of 1,4-dichlorobenzene is 72.1%, and the selectivity of 2,5-dichlorophenol is 91.3%.
Examples 7 to 11
On the basis of example 6, the reaction time, the reaction temperature, and O were varied 2 The flow rate and the amount of the three-way catalyst, the following results were obtained:
TABLE 1
Figure BDA0002621575200000071
Figure BDA0002621575200000081
Examples 12 to 16
On the basis of example 5, the molar ratio of ammonium metavanadate to bismuth nitrate and BiVO were changed 4 /V 2 O 5 The results obtained, in terms of mass ratio to melamine, are as follows:
TABLE 2
Figure BDA0002621575200000082
Examples 17 to 20
On the basis of example 6, g-C in step (1) was varied 3 N 4 The precursor, the hydroxylation auxiliary agent, the solvent and the xenon lamp power, the obtained results are as follows:
TABLE 3
Figure BDA0002621575200000083
Comparative example 1
Omitting step (1), weighing 0.09g of purchased BiVO separately 4 、V 2 O 5 And g-C 3 N 4 The mixture was added to a quartz reactor to replace the three-way catalyst and mixed mechanically to homogeneity, the procedure was the same as in example 5, giving a conversion of 1,4-dichlorobenzene of 32.3% and a selectivity of 2,5-dichlorophenol of 46.8%.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (19)

1. The catalyst for synthesizing 2,5-dichlorophenol is characterized in that the catalyst is BiVO 4 /V 2 O 5 / g-C 3 N 4 A three-way composite catalyst; the catalyst is prepared by the following method:
in-situ synthesis of BiVO by taking ammonium metavanadate and bismuth nitrate as raw materials 4 /V 2 O 5 A complex;
subjecting the BiVO to 4 /V 2 O 5 Complexes with g-C 3 N 4 Carrying out thermal polycondensation reaction on the precursor to form the BiVO 4 /V 2 O 5 / g-C 3 N 4 A three-way composite catalyst.
2. The catalyst of claim 1, wherein the BiVO is synthesized in situ 4 /V 2 O 5 The method of the compound is any one selected from a hydrothermal-calcining method, a microwave-calcining method, a solid reaction-calcining method, a sol-gel/calcining method and a template-calcining method.
3. The catalyst according to claim 1, wherein the molar ratio of the ammonium metavanadate to the bismuth nitrate is 1.05 to 10.
4. The catalyst according to claim 3, wherein the molar ratio of the ammonium metavanadate to the bismuth nitrate is 1.05 to 6.5.
5. The catalyst of claim 1, wherein the g-C is 3 N 4 The precursor is selected from any one or more of melamine, cyanamide, dicyandiamide, urea and thiourea.
6. The catalyst according to claim 1, wherein the thermal polycondensation reaction is any one selected from a mill-thermal polycondensation method, a high-temperature gas phase method, a solvent mixing-thermal polycondensation method, and an ultrasonic dissolution-thermal polycondensation method.
7. The catalyst of claim 1, wherein the BiVO is 4 /V 2 O 5 Complexes with said g-C 3 N 4 The weight ratio of the precursor is 1 to 6.
8. The catalyst of claim 7, wherein the BiVO is BiVO 4 /V 2 O 5 Complexes with said g-C 3 N 4 The weight ratio of the precursor is 1 to 4.
9. An in-situ synthesis method of 2,5-dichlorophenol, characterized in that the in-situ synthesis method comprises the following steps:
s1, mixing 1,4-dichlorobenzene, the catalyst of any one of claims 1 to 8, a hydroxylation auxiliary agent and a solvent to obtain a raw material system;
and S2, introducing oxygen into the raw material system, and irradiating ultraviolet light at the same time to perform in-situ synthesis reaction to obtain 2,5-dichlorophenol.
10. The in situ synthesis method according to claim 9, wherein in step S1, the hydroxylation assistant is selected from oxalic acid and H 3 PO 4 Any one or more of citric acid, beta-aminoethanesulfonic acid, sulfonic acid, malonic acid, L-lactic acid, salicylic acid, 1,2,4-butanetricarboxylic acid and methanesulfonic acid.
11. The in situ synthesis method according to claim 9, wherein the solvent is selected from one or more of water, dichloroethane, acetonitrile, chloroform, ethanol, acetic acid and formic acid, and the solvent contains water.
12. The in-situ synthesis method according to claim 9, wherein in step S1, the catalyst is 0.1 to 7% by weight of 1,4-dichlorobenzene.
13. The in situ synthesis method of claim 12, wherein in step S1, the catalyst is 1~4% of the weight of 1,4-dichlorobenzene.
14. The in-situ synthesis method according to claim 12, wherein in the step S1, the hydroxylation auxiliary agent accounts for 10 to 30% of the weight of 1,4-dichlorobenzene.
15. The in situ synthesis method according to any one of claims 9 to 14, wherein in step S1, the raw material system further comprises a stabilizer.
16. The in situ synthesis method of claim 15, wherein the stabilizer is selected from ZnSO 4 、ZnCl 2 、K 2 HPO 4 、NaNO 3 Any one or more of; the stabilizer accounts for 0.15 to 0.5 percent of the weight of the 1,4-dichlorobenzene.
17. The in-situ synthesis method according to any one of claims 9 to 14, wherein in the step S2, the introduction rate of the oxygen is 60 to 100 mL/min.
18. The in-situ synthesis method according to claim 17, wherein the reaction temperature of the in-situ synthesis reaction is 10 to 50 ℃; the reaction time is 10 to 20h.
19. The in-situ synthesis method according to claim 17, wherein in the step S2, the irradiation power in the ultraviolet irradiation process is 200 to 400W.
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ZnO/BiVO4-V2O5异质结构光生电荷性质及可见光下表面光电流行为;张宇等;《物理化学学报》;20131130;第29卷(第11期);2399-2404 *

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