CN115430392A - Preparation method of benzil and special Venturi ejector - Google Patents

Preparation method of benzil and special Venturi ejector Download PDF

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CN115430392A
CN115430392A CN202211062072.XA CN202211062072A CN115430392A CN 115430392 A CN115430392 A CN 115430392A CN 202211062072 A CN202211062072 A CN 202211062072A CN 115430392 A CN115430392 A CN 115430392A
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inner diameter
benzoin
reaction
length
section
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CN115430392B (en
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梅华
钱彬
王兵
魏亮
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JIANGSU NUOMENG CHEMICAL CO Ltd
Changzhou Tronly Advanced Electronic Materials Co Ltd
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JIANGSU NUOMENG CHEMICAL CO Ltd
Changzhou Tronly Advanced Electronic Materials Co Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J19/26—Nozzle-type reactors, i.e. the distribution of the initial reactants within the reactor is effected by their introduction or injection through nozzles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F23/00—Mixing according to the phases to be mixed, e.g. dispersing or emulsifying
    • B01F23/20—Mixing gases with liquids
    • B01F23/23—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids
    • B01F23/237—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids characterised by the physical or chemical properties of gases or vapours introduced in the liquid media
    • B01F23/2373—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids characterised by the physical or chemical properties of gases or vapours introduced in the liquid media for obtaining fine bubbles, i.e. bubbles with a size below 100 µm
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F25/00—Flow mixers; Mixers for falling materials, e.g. solid particles
    • B01F25/30—Injector mixers
    • B01F25/31—Injector mixers in conduits or tubes through which the main component flows
    • B01F25/312—Injector mixers in conduits or tubes through which the main component flows with Venturi elements; Details thereof
    • B01F25/3124—Injector mixers in conduits or tubes through which the main component flows with Venturi elements; Details thereof characterised by the place of introduction of the main flow
    • B01F25/31243—Eductor or eductor-type venturi, i.e. the main flow being injected through the venturi with high speed in the form of a jet
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F25/00—Flow mixers; Mixers for falling materials, e.g. solid particles
    • B01F25/30—Injector mixers
    • B01F25/31—Injector mixers in conduits or tubes through which the main component flows
    • B01F25/312—Injector mixers in conduits or tubes through which the main component flows with Venturi elements; Details thereof
    • B01F25/3125—Injector mixers in conduits or tubes through which the main component flows with Venturi elements; Details thereof characteristics of the Venturi parts
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J19/0053—Details of the reactor
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C45/00—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds
    • C07C45/27—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation
    • C07C45/32—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation with molecular oxygen
    • C07C45/37—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation with molecular oxygen of >C—O—functional groups to >C=O groups
    • C07C45/39—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation with molecular oxygen of >C—O—functional groups to >C=O groups being a secondary hydroxyl group
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F2101/00—Mixing characterised by the nature of the mixed materials or by the application field
    • B01F2101/2204—Mixing chemical components in generals in order to improve chemical treatment or reactions, independently from the specific application

Abstract

The invention discloses a preparation method of benzil, which adopts a jet loop reactor, takes benzoin and air as raw materials, acetic acid as a solvent and acid and salt as catalysts to carry out oxidation reaction; the acid is one or two of hydrochloric acid and sulfuric acid; the salt is one or more of sodium bromide, potassium bromide, sodium iodide and potassium iodide; inner diameter of the inducer opening of the venturi ejector in the jet loop reactor: nozzle inner diameter: the inner diameter of the closed air chamber: length of mixing section: the ratio of the length of the diffusion zone is 34 (1.5-4.5): (2-6): (180-280): (1550-1850), the opening angle of the diffuser section is 12-28 degrees; and the micro-positive pressure of the reaction system is controlled in the reaction process. The invention adopts a novel reactor-jet loop reactor to carry out air oxidation on benzoin to prepare benzil, and the method carries out catalytic oxidation by using a cheap catalyst, thereby having short reaction time and less air consumption.

Description

Preparation method of benzil and special Venturi ejector
Technical Field
The invention belongs to the technical field of chemical production, and particularly relates to a process method for producing benzil by adopting novel reactor equipment, namely a loop reactor.
Background
Benzil has wide functions in the production of medicines, spices and daily chemicals and is an important organic synthesis intermediate. The method for preparing benzil by oxidizing benzoin is divided into two methods by taking benzoin as a raw material: one is a non-catalytic oxidation process. The benzil synthesis method is characterized in that benzil is synthesized by using a direct oxidation method, namely benzoin and an oxidant are directly mixed in a reaction system, and the benzoin is oxidized into the benzil by using an oxidation reduction reaction principle under certain reaction conditions, but the benzil synthesis method has the problems of large oxidant consumption, violent reaction, more byproducts, serious pollution and the like.
The other method is a catalytic oxidation method, and the benzil is prepared by using a high-efficiency catalyst and using molecular oxygen or air as an oxidant to catalyze and oxidize benzoin. It has been reported that air is used as an oxidant, toluene is used as a solvent, and Pd/SiO is used 2 The benzil is prepared by catalytically oxidizing benzoin with a catalyst at 100 ℃ for 0.75h, the yield of the benzil is 98%, the reaction condition is mild, the reaction time is short, the yield of the benzil is high, but the catalyst is expensive, the reaction cost is high, and the industrial production is not facilitated. It is also reported that the yield of the product benzil is 94 percent, the reaction time is short, the catalyst efficiency is high when the Co (Salen) complex is used as a catalyst to catalyze and oxidize benzoin to prepare benzil for 2.25 hours, but the Co (Salen) complex is complicated to prepare and the preparation period is long. In industrial production, benzil is usually employedBenzoin is synthesized by air oxidation, however, in industrial production, when cheap and easily available catalyst is used for preparing benzil by air oxidation, the problems of long reaction time, low mass transfer efficiency of air and raw material reaction liquid and the like exist.
Disclosure of Invention
The invention aims to solve the problems of long reaction time, large air consumption and the like in the current industrial production and provides a method for preparing benzil by oxidizing benzoin with air by adopting a novel reactor-jet loop reactor.
In order to achieve the aim, the invention provides a preparation method of benzil, which adopts a jet loop reactor, takes benzoin and air as raw materials, acetic acid as a solvent and acid and salt as catalysts to carry out oxidation reaction; the acid is one or two of hydrochloric acid and sulfuric acid; the salt is one or more of sodium bromide, potassium bromide, sodium iodide and potassium iodide; the inner diameter of the inlet section opening of the venturi ejector in the jet loop reactor is as follows: nozzle bore diameter: the inner diameter of the closed air chamber: length of mixing section: the ratio of the length of the diffusion zone is 34 (1.5-4.5): (2-6): (180-280): (1550-1850), the opening angle of the diffuser is 12-28 degrees; the micro-positive pressure of the reaction system is controlled to be 0.07 +/-0.01 MPa in the reaction process.
The loop reactor is a novel reactor system and particularly comprises a reaction kettle, a circulating pump, a heat exchanger and a Venturi ejector (mixer). The reaction liquid circulates in a loop at a large flow rate, is jetted at a high speed through the Venturi ejector, and forms negative pressure at the working nozzle, so that the gas participating in the reaction is sucked into the ejector to form micron-sized bubbles with large specific surface area, the gas-liquid contact is increased, the emulsification effect of gas-liquid two phases is formed, and the reaction speed of the gas-liquid two phases is greatly accelerated.
When the air oxidation of benzoin is carried out by using the loop reactor, the explosion limit problem of volatile solvent needs to be considered by adopting organic matters as the solvent, the air is continuously supplied by the mass flowmeter, and nitrogen which does not participate in the reaction and unreacted oxygen in the air are discharged out of the system through the backpressure valve, so that the proportion of the organic matters cannot be in the explosion limit range. Therefore, in practical operation, in view of production safety, a pressurized reaction system is not used, but a micro-positive pressure reaction system (absolute pressure in the system is less than 2 atm) is used, so that normal circulation and consumption of air are maintained, while in the micro-positive pressure reaction system, the dissolved amount of gas participating in the reaction is greatly reduced, and in order to accelerate the reaction speed, a gas-liquid two-phase emulsification effect is formed in the reaction kettle and is maintained in the whole pipeline. The invention makes the venturi ejector more suitable for air oxidation of benzoin by completely new design, especially aiming at the design of the mixing section and the diffusion section.
Meanwhile, aiming at benzoin air oxidation, the invention adopts a brand-new catalytic system, takes acid (hydrochloric acid/sulfuric acid/mixture of the hydrochloric acid and the sulfuric acid) and salt (NaBr/NaI/KI/KBr/mixture of more than two) as catalysts, is cheap and easy to obtain, and has better catalytic effect.
Further, the reaction temperature is controlled to be 80-90 ℃ in the oxidation reaction process, and the reaction time is controlled to be 7-10 hours; and controlling the linear velocity of the fluid at the nozzle of the Venturi ejector to be 100-150 m/s.
In some embodiments, it is preferred that the acid concentration (i.e., the concentration of the hydrochloric acid solution or sulfuric acid solution) be from 7% to 30%; the adding amount of the acid (namely the adding amount of the hydrochloric acid solution or the sulfuric acid solution) is 20 to 65 percent of the mass of the benzoin; the addition amount of the salt is 0.5-10% of the mass of the benzoin.
In some embodiments, the acid is preferably a 7% sulfuric acid solution, and the amount of the sulfuric acid solution added is 37.5% of the mass of the benzoin; the salt is potassium bromide, and the adding amount of the potassium bromide is 3.0 percent of the mass of the benzoin.
In some embodiments, it is preferred that the inner diameter of the inducer opening of the venturi ejector in the jet loop reactor is: nozzle inner diameter: the gas chamber closing-in inner diameter: length of mixed section: the ratio of the length of the diffusion section is 34: 4:230:1650, the opening angle of the diffuser section is 20.
In some embodiments, preferably, the reaction temperature is controlled to be 85 ℃ during the oxidation reaction, and the reaction time is controlled to be 8 hours; and controlling the linear velocity of the fluid at the nozzle of the Venturi ejector to be 125m/s.
The invention also provides a special Venturi ejector for preparing the benzil, the inner diameter of the opening of the inlet section of the Venturi ejector is as follows: nozzle bore diameter: the inner diameter of the closed air chamber: length of mixed section: the ratio of the length of the diffusion zone is 34 (1.5-4.5): (2-6): (180-280): (1550-1850), the opening angle of the diffuser section is 12-28 degrees.
In some embodiments, it is preferred that the venturi eductor have an inducer opening inside diameter: nozzle bore diameter: the inner diameter of the closed air chamber: length of mixing section: the ratio of the length of the diffusion section is 34: 4:230:1650, the opening angle of the diffuser section is 20.
Compared with the prior art, the invention has the following advantages:
the invention improves and designs the specification parameters of the injection loop reactor, is suitable for a micro-positive pressure environment for preparing the benzil, can effectively shorten the reaction time, reduces the using amount of air and improves the equipment productivity.
The invention uses a new catalytic system (acid (sulfuric acid or hydrochloric acid, or the mixture of the two) + salt (sodium bromide or potassium bromide or sodium iodide or potassium iodide, or the mixture of the above substances)) to carry out air oxidation catalysis of benzoin, is cheap and easy to obtain, and obtains excellent catalytic effect by matching with the use of a jet loop reactor.
Drawings
FIG. 1 is a schematic diagram of the structure of a jet loop reactor for the production of benzil according to the present invention;
FIG. 2 is a schematic structural view of the venturi ejector of FIG. 1;
in the figure, 1-reaction kettle, 2-Venturi ejector, 3-heat exchanger, 4-circulating pump, 5-gas circulating pipe, 6-inlet section, 7-mixing section, 8-diffusion section, 9-nozzle, 10-gas chamber, 101-condenser pipe and 102-back pressure valve.
Detailed Description
The present invention will be described in detail with reference to specific examples.
As shown in figure 1, the benzil production of the present invention adopts a jet loop reactor to carry out batch reaction. The loop reactor comprises a reaction kettle 1, a Venturi ejector 2, a heat exchanger 3, a circulating pump 4 and the like.
When the reactor is in operation, the circulation pump 4 is started. The reaction liquid circulates in the loop in a large flow, the venturi ejector 2 ejects at a high speed, and negative pressure is formed at the working nozzle, so that the reaction air is sucked into the venturi ejector. One side of the top of the reaction kettle 1 is provided with a branch pipe which is connected with an air inlet and can form air circuit circulation locally. The micro bubbles with large specific surface area are formed in the Venturi ejector, and the mass transfer process between gas-liquid heterogeneous reaction materials is enhanced and the reaction time is shortened by dividing and stirring the liquid flow. The lower end of the Venturi ejector is positioned below the liquid level, and the gas-liquid mixed material and the material in the reaction kettle are impacted, so that the effect of promoting dispersion and mixing is achieved, and the reaction is promoted to further proceed. The material enters the heat exchanger from the bottom end of the reaction kettle through the circulating pump 4 and enters the Venturi ejector 2 from the top end of the reaction kettle 1. The heat exchanger 3 removes or provides heat released or absorbed in the reaction process, and controls the fluctuation of the reaction temperature to +/-1 ℃.
The heat exchanger in this patent can adopt tubular heat exchanger or plate heat exchanger.
Aiming at the reaction system of the reaction micro-positive pressure, the design structure size of the Venturi ejector greatly influences the effect of mutual dispersion and contact between reaction substances, thereby finally influencing the chemical production efficiency. With reference to fig. 2, the venturi ejector of the present patent is specifically composed of an inlet section 6 in the shape of a convergent tube, a mixing section 7, a diffuser section 8, a nozzle 9 and a gas chamber 10. As shown in FIG. 1, a gas circulation pipe 5 is provided on the side of the gas chamber 1 and connected to the top gas inlet of the reaction vessel 1 to provide a gas circulation space in a local region.
Batch reaction operation sequence: dissolving raw material benzoin and a catalyst in solvent acetic acid, and adding the materials into a reaction kettle through a charging opening; the method comprises the steps of introducing air into a reactor through an air inlet until the system pressure is 1MPa, checking leakage, introducing 5 ℃ cooling water into a condensation pipe (so that the solvent acetic acid is cooled and flows back), adjusting the air flow to a certain value through a mass flow meter, adjusting a back pressure valve 102 at the rear end of the condensation pipe 101 to maintain the system gauge pressure to be 0.07 +/-0.01 MPa (in the actual reaction process, the pressure is slightly fluctuated), starting a circulating pump 4 to enable liquid in a kettle to slowly flow, heating to the reaction temperature (the heating time is about 10 min) through a heat exchanger 3, adjusting the circulating pump 4 rapidly until the flow rate reaches a certain value, and recording the flow rate as the reaction starting time.
In the reaction process, a discharge port is used for sampling to detect whether the raw materials are completely reacted, and after the reaction is finished, the flow speed of the circulating pump 4 is immediately reduced and the temperature is rapidly reduced to the room temperature (the temperature reduction time is about 10 min). And (4) emptying the gas in the kettle and discharging the liquid in the kettle. And taking part of reaction products, and detecting the yield and selectivity of the products by adopting a liquid chromatography area normalization method.
Example 1
800g of benzoin are dissolved in 2400g of acetic acid, while adding the catalyst: 300 g of 7wt% sulfuric acid and 23.8g of potassium bromide were dissolved by stirring at 70 to 75 ℃ and the above-mentioned mixture was charged into a 5-liter loop reactor. In the material, the sulfuric acid solution accounts for 37.5 wt% of the mass ratio of the benzoin, and the bromide accounts for 3 wt% of the mass ratio of the benzoin. Introducing air into the reactor through an air inlet until the system pressure is 1MPa for leak detection, emptying after leak detection, introducing 5 ℃ cooling water into a condensation pipe (so that the solvent acetic acid is cooled and reflows), adjusting the air flow to 64L/h, adjusting a back pressure valve at the rear end of the condensation pipe to maintain the system pressure to be 0.07 +/-0.01 MPa, starting a circulating pump 4 to enable liquid in the kettle to slowly flow, raising the temperature to 85 ℃ through a heat exchanger (the temperature rise time is about 10 min), quickly adjusting the circulating pump 4 to the flow rate to 125m/s, and recording the flow rate as the reaction start time.
In the reaction process, the temperature of the reaction kettle is controlled to be 85 +/-1 ℃. The linear velocity of the fluid at the nozzle of the Venturi ejector is controlled to be 125m/s, and the detailed design size is specifically that the inner diameter D1 of the opening of the inlet section is as follows: nozzle inner diameter D2: air chamber binding off internal diameter D3: length of mixing segment L1: the ratio of the diffusion section length L2 is 38:3:4:230:1650, the opening angle alpha of the diffusion section is 20 degrees, the reaction is carried out for 8h, the flow rate of the circulating pump 4 is immediately reduced, the temperature is rapidly reduced to room temperature (the temperature reduction time is about 15 min), the product is taken out after emptying, the conversion rate of benzoin is calculated to be 99.6 percent by liquid chromatography analysis and an area normalization method, and the selectivity of benzil is 99 percent.
Example 2
800g of benzoin are dissolved in 2400g of acetic acid, while adding the catalyst: 192 g of 22% strength by weight sulfuric acid and 70 g of sodium iodide were dissolved with stirring at 70 to 75 ℃ and the above mixture was charged into a 5-liter loop reactor. In the materials, the sulfuric acid solution accounts for 24 wt% of the mass ratio of the benzoin, and the sodium iodide accounts for 8.8 wt% of the mass ratio of the benzoin. Introducing air into the reactor through an air inlet until the system pressure is 1MPa for leak detection, emptying after leak detection is finished, introducing 5 ℃ cooling water into a condensation pipe (so that the solvent acetic acid is cooled and reflows), adjusting the air flow to 64L/h, adjusting a back pressure valve positioned at the rear end of the condensation pipe to maintain the system pressure to be 0.07 +/-0.01 MPa, starting a circulating pump 4 to enable liquid in the kettle to slowly flow, raising the temperature to 85 ℃ through a heat exchanger (the temperature rise time is about 10 min), quickly adjusting the circulating pump 4 to the flow rate to 105m/s, and recording as the reaction start time.
In the reaction process, the temperature of the connecting reaction kettle is controlled to be 85 +/-1 ℃. The linear velocity of the fluid at the nozzle of the Venturi ejector is controlled to be 105m/s, and the detailed design size is specifically that the inner diameter D1 of an opening of an inlet section is as follows: nozzle inner diameter D2: air chamber binding off internal diameter D3: length of mixed segment L1: the ratio of the diffusion section length L2 is 38:2:3:190:1600, the opening angle alpha of the diffusion section is 15 degrees, the reaction is carried out for 9 hours, the flow rate of the circulating pump 4 is immediately reduced, the temperature is rapidly reduced to the room temperature (the temperature reduction time is about 15 minutes), the product is taken out after emptying, the conversion rate of benzoin is calculated to be 95.2 percent by adopting an area normalization method through liquid chromatography analysis, and the selectivity of benzil is 98.5 percent.
Example 3
800g of benzoin are dissolved in 2400g of acetic acid, while adding the catalyst: 492 g of hydrochloric acid having a concentration of 15% by weight and 52 g of sodium bromide were dissolved with stirring at 70 to 75 ℃ and the above mixture was charged into a 5-liter loop reactor. In the materials, the hydrochloric acid solution accounts for 61.5 wt% of the mass ratio of the benzoin, and the sodium bromide accounts for 6.5 wt% of the mass ratio of the benzoin. Introducing air into the reactor through an air inlet until the system pressure is 1MPa for leak detection, emptying after leak detection is finished, introducing 5 ℃ cooling water into a condensation pipe (so that the solvent acetic acid is cooled and reflows), adjusting the air flow to 64L/h, adjusting a back pressure valve positioned at the rear end of the condensation pipe to maintain the system pressure to be 0.07 +/-0.01 MPa, starting a circulating pump 4 to enable liquid in the kettle to slowly flow, raising the temperature to 85 ℃ through a heat exchanger (the temperature rise time is about 10 min), and quickly adjusting the circulating pump 4 to the flow rate to 115m/s, and recording the flow rate as the reaction start time.
In the reaction process, the temperature of the reaction kettle is controlled to be 85 +/-1 ℃. The linear velocity of the fluid at the nozzle of the Venturi ejector is controlled to be 115m/s, and the detailed design size is specifically that the inner diameter D1 of an opening of an inlet section is as follows: nozzle inner diameter D2: air chamber binding off internal diameter D3: length of mixed segment L1: the ratio of the diffusion section length L2 is 38:2.5:3.5:220:1700, the opening angle alpha of the diffusion section is 18 degrees, the reaction is carried out for 8 hours, the flow rate of the circulating pump 4 is immediately reduced, the temperature is rapidly reduced to room temperature (the temperature reduction time is about 15 minutes), the product is taken out after emptying, the conversion rate of benzoin is calculated to be 91.6 percent by adopting an area normalization method through liquid chromatography analysis, and the selectivity of benzil is 97.3 percent.
Example 4
800g of benzoin are dissolved in 2400g of acetic acid, while adding the catalyst: 18 400g of sulfuric acid having a concentration of 400 wt% and 35 g of potassium iodide were dissolved with stirring at 70 to 75 ℃ and the above-mentioned mixture was charged into a 5L loop reactor. In the materials, the sulfuric acid solution accounts for 50 wt% of the mass ratio of the benzoin, and the potassium iodide accounts for 4.4 wt% of the mass ratio of the benzoin. Introducing air into the reactor through an air inlet until the system pressure is 1MPa for leak detection, emptying after leak detection, introducing 5 ℃ cooling water into a condensation pipe (so that a solvent acetic acid is cooled and reflows), adjusting the air flow to 64L/h, adjusting a back pressure valve at the rear end of the condensation pipe to maintain the system pressure to be 0.07 +/-0.01 MPa, starting a circulating pump 4 to enable liquid in the kettle to slowly flow, raising the temperature to 85 ℃ through a heat exchanger (the temperature rise time is about 10 min), quickly adjusting the circulating pump 4 to the flow rate to 135m/s, and recording the flow rate as the reaction start time.
In the reaction process, the temperature of the connecting reaction kettle is controlled to be 85 +/-1 ℃. The linear velocity of the fluid at the nozzle of the Venturi ejector is controlled to be 135m/s, and the detailed design size is specifically that the inner diameter D1 of an inlet section opening is as follows: nozzle inner diameter D2: air chamber binding off internal diameter D3: length of mixing segment L1: the ratio of the length L2 of the diffusion zone is 38:3:4:250:1750, reacting for 9.5 h with the opening angle alpha of the diffusion section of 23 ℃, immediately reducing the flow rate of the circulating pump 4 and rapidly cooling to room temperature (the cooling time is about 15 min), taking the product after emptying, and calculating the conversion rate of benzoin to be 97.1% and the selectivity of benzil to be 96.5% by adopting an area normalization method through liquid chromatography analysis.
Example 5
800g of benzoin are dissolved in 2400g of acetic acid, while adding the catalyst: 13 250 g of hydrochloric acid having a concentration of wt.% and 7 g of potassium iodide were dissolved with stirring at 70 to 75 ℃ and the above mixture was charged into a 5-liter loop reactor. In the material, the sulfuric acid solution accounts for 31.3 wt% of the mass ratio of the benzoin, and the potassium iodide accounts for 0.9 wt% of the mass ratio of the benzoin. Introducing air into the reactor through an air inlet until the system pressure is 1MPa for leak detection, emptying after leak detection is finished, introducing 5 ℃ cooling water into a condensation pipe (so that the solvent acetic acid is cooled and reflows), adjusting the air flow to 64L/h, adjusting a back pressure valve positioned at the rear end of the condensation pipe to maintain the system pressure to be 0.07 +/-0.01 MPa, starting a circulating pump 4 to enable liquid in the kettle to slowly flow, raising the temperature to 85 ℃ through a heat exchanger (the temperature rise time is about 10 min), quickly adjusting the circulating pump 4 to the flow rate of 145m/s, and recording as the reaction start time.
In the reaction process, the temperature of the reaction kettle is controlled to be 85 +/-1 ℃. The linear velocity of the fluid at the nozzle of the Venturi ejector is controlled to be 145m/s, and the detailed design size is specifically that the inner diameter D1 of the opening of the inlet section is as follows: nozzle inner diameter D2: air chamber binding off internal diameter D3: length of mixed segment L1: the ratio of the diffusion section length L2 is 38:3.5:5.5:270:1800, the opening angle alpha of the diffusion section is 25 ℃, the reaction is carried out for 8.5 h, the flow rate of a circulating pump 4 is immediately reduced, the temperature is rapidly reduced to room temperature (the temperature reduction time is about 15 min), and after emptying, the product is taken out, the conversion rate of benzoin is calculated to be 92.3 percent and the selectivity of benzil is 98 percent by adopting an area normalization method through liquid chromatography analysis.
Example 6
800g of benzoin are dissolved in 2400g of acetic acid, while adding the catalyst: 300 g of 7wt% sulfuric acid and 23.8g of potassium bromide were dissolved by stirring at 70 to 75 ℃ and the above-mentioned mixture was charged into a 5-liter loop reactor. In the materials, the hydrochloric acid solution accounts for 37.5 wt% of the mass ratio of the benzoin, and the bromide accounts for 3 wt% of the mass ratio of the benzoin. Introducing air into the reactor through an air inlet until the system pressure is 1MPa for leak detection, emptying after leak detection is finished, introducing 5 ℃ cooling water into a condensation pipe (so that the solvent acetic acid is cooled and reflows), adjusting the air flow to 64L/h, adjusting a back pressure valve positioned at the rear end of the condensation pipe to maintain the system pressure to be 0.07 +/-0.01 MPa, starting a circulating pump 4 to enable liquid in the kettle to slowly flow, raising the temperature to 85 ℃ through a heat exchanger (the temperature rise time is about 10 min), quickly adjusting the circulating pump 4 to the flow rate to 125m/s, and recording as the reaction start time.
In the reaction process, the temperature of the reaction kettle is controlled to be 85 +/-1 ℃. The linear velocity of the fluid at the nozzle of the Venturi ejector is controlled to be 125m/s, and the detailed design size is specifically that the inner diameter D1 of the opening of the inlet section is as follows: nozzle inner diameter D2: air chamber binding off internal diameter D3: length of mixed segment L1: the ratio of the length L2 of the diffusion zone is 38:3:4:230:1650, the opening angle alpha of the diffusion section is 20 degrees, the reaction is carried out for 12 h, the flow rate of the circulating pump 4 is immediately reduced, the temperature is rapidly reduced to room temperature (the temperature reduction time is about 15 min), the product is taken out after emptying, the conversion rate of benzoin is calculated to be 100 percent by adopting an area normalization method through liquid chromatography analysis, and the selectivity of benzil is 90.1 percent.
As can be seen from the comparison of example 1 and example 6, when the reaction time is prolonged, although higher benzoin conversion rate can be obtained, the selectivity of benzil is reduced.
Example 7
800g of benzoin was dissolved in 2400g of acetic acid, while adding the mixed acid and mixed salt catalyst: 50 g of 25wt% sulfuric acid, 250 g of 10wt% hydrochloric acid, 18g of potassium bromide and 5.8 g of sodium iodide were dissolved by stirring at 70 to 75 ℃ and the mixture was charged into a 5L loop reactor. In the material, the mixed acid solution (sulfuric acid and hydrochloric acid) accounts for 37.5 wt% of the mass ratio of the benzoin, and the mixed salt (potassium bromide and sodium iodide) accounts for 3 wt% of the mass ratio of the benzoin. Introducing air into the reactor through an air inlet until the system pressure is 1MPa for leak detection, emptying after leak detection, introducing 5 ℃ cooling water into a condensation pipe (so that the solvent acetic acid is cooled and reflows), adjusting the air flow to 64L/h, adjusting a back pressure valve at the rear end of the condensation pipe to maintain the system pressure to be 0.07 +/-0.01 MPa, starting a circulating pump 4 to enable liquid in the kettle to slowly flow, raising the temperature to 85 ℃ through a heat exchanger (the temperature rise time is about 10 min), quickly adjusting the circulating pump 4 to the flow rate to 125m/s, and recording the flow rate as the reaction start time.
In the reaction process, the temperature of the reaction kettle is controlled to be 85 +/-1 ℃. The linear velocity of the fluid at the nozzle of the Venturi ejector is controlled to be 125m/s, and the detailed design size is specifically that the inner diameter D1 of the opening of the inlet section is as follows: nozzle inner diameter D2: air chamber binding off internal diameter D3: length of mixed segment L1: the ratio of the diffusion section length L2 is 38:3:4:230:1650, the opening angle alpha of the diffusion section is 20 degrees, the reaction is carried out for 8h, the flow rate of the circulating pump 4 is immediately reduced, the temperature is rapidly reduced to room temperature (the temperature reduction time is about 15 min), the product is taken out after emptying, the conversion rate of benzoin is calculated to be 94.1 percent by liquid chromatography analysis and an area normalization method, and the selectivity of benzil is 96.3 percent.
Example 8
800g of benzoin was dissolved in 2400g of acetic acid, while adding the mixed acid and mixed salt catalyst: 100 g of sulfuric acid having a concentration of 18wt%, 200 g of hydrochloric acid having a concentration of 13 wt%, 10 g of potassium bromide and 13.8 g of sodium iodide were dissolved by stirring at 70 to 75 ℃ and the mixture was charged into a 5-liter loop reactor. In the material, the mixed acid solution (sulfuric acid and hydrochloric acid) accounts for 37.5 wt% of the mass ratio of the benzoin, and the mixed salt (potassium bromide and sodium iodide) accounts for 3 wt% of the mass ratio of the benzoin. Introducing air into the reactor through an air inlet until the system pressure is 1MPa for leak detection, emptying after leak detection is finished, introducing 5 ℃ cooling water into a condensation pipe (so that the solvent acetic acid is cooled and reflows), adjusting the air flow to 64L/h, adjusting a back pressure valve positioned at the rear end of the condensation pipe to maintain the system pressure to be 0.07 +/-0.01 MPa, starting a circulating pump 4 to enable liquid in the kettle to slowly flow, raising the temperature to 85 ℃ through a heat exchanger (the temperature rise time is about 10 min), quickly adjusting the circulating pump 4 to the flow rate to 125m/s, and recording as the reaction start time.
In the reaction process, the temperature of the reaction kettle is controlled to be 85 +/-1 ℃. The linear velocity of the fluid at the nozzle of the Venturi ejector is controlled to be 125m/s, and the detailed design size is specifically that the inner diameter D1 of an opening of an inlet section is as follows: nozzle inner diameter D2: air chamber binding off internal diameter D3: length of mixed segment L1: the ratio of the diffusion section length L2 is 38:3:4:230:1650, the opening angle alpha of the diffusion section is 20 degrees, the reaction is carried out for 8h, the flow rate of the circulating pump 4 is immediately reduced, the temperature is rapidly reduced to room temperature (the temperature reduction time is about 15 min), the product is taken out after emptying, the conversion rate of benzoin is calculated by liquid chromatography analysis and an area normalization method, and the selectivity of benzil is 97.3%.
Example 9
800g of benzoin was dissolved in 2400g of acetic acid, while adding the mixed acid and mixed salt catalyst: 180 g of sulfuric acid having a concentration of 20wt%, 120 g of hydrochloric acid having a concentration of 15wt%, 6.8g of sodium bromide and 17 g of potassium iodide were dissolved by stirring at 70 to 75 ℃ and the above-mentioned mixture was charged into a 5-liter loop reactor. In the material, the mixed acid solution (sulfuric acid and hydrochloric acid) accounts for 37.5 wt% of the mass ratio of the benzoin, and the mixed salt (potassium bromide and sodium iodide) accounts for 3 wt% of the mass ratio of the benzoin. Introducing air into the reactor through an air inlet until the system pressure is 1MPa for leak detection, emptying after leak detection is finished, introducing 5 ℃ cooling water into a condensation pipe (so that the solvent acetic acid is cooled and reflows), adjusting the air flow to 64L/h, adjusting a back pressure valve positioned at the rear end of the condensation pipe to maintain the system pressure to be 0.07 +/-0.01 MPa, starting a circulating pump 4 to enable liquid in the kettle to slowly flow, raising the temperature to 85 ℃ through a heat exchanger (the temperature rise time is about 10 min), quickly adjusting the circulating pump 4 to the flow rate to 125m/s, and recording as the reaction start time.
In the reaction process, the temperature of the connecting reaction kettle is controlled to be 85 +/-1 ℃. The linear velocity of the fluid at the nozzle of the Venturi ejector is controlled to be 125m/s, and the detailed design size is specifically that the inner diameter D1 of the opening of the inlet section is as follows: nozzle inner diameter D2: air chamber binding off internal diameter D3: length of mixing segment L1: the ratio of the diffusion section length L2 is 38:3:4:230:1650, the opening angle alpha of the diffusion section is 20 degrees, the reaction is carried out for 8h, the flow rate of the circulating pump 4 is immediately reduced, the temperature is rapidly reduced to room temperature (the temperature reduction time is about 15 min), and the product after emptying is subjected to liquid chromatography analysis, and the area normalization method is adopted to calculate that the conversion rate of benzoin is 96.9 percent and the selectivity of benzil is 96.8 percent.
Comparative example 1
800g of benzoin are dissolved in 2400g of acetic acid, while adding the catalyst: 300 g of 7wt% sulfuric acid and 23.8g of potassium bromide were dissolved by stirring at 70 to 75 ℃ and the above-mentioned mixture was charged into a 5-liter loop reactor. In the material, the hydrochloric acid solution accounts for 37.5 wt% of the mass of the benzoin, and the bromide accounts for 3 wt% of the mass of the benzoin. Introducing air into the reactor through an air inlet until the system pressure is 1MPa for leak detection, emptying after leak detection is finished, introducing 5 ℃ cooling water into a condensation pipe (so that the solvent acetic acid is cooled and reflows), adjusting the air flow to 64L/h, adjusting a back pressure valve positioned at the rear end of the condensation pipe to maintain the system pressure to be 0.07 +/-0.01 MPa, starting a circulating pump 4 to enable liquid in the kettle to slowly flow, raising the temperature to 85 ℃ through a heat exchanger (the temperature rise time is about 10 min), quickly adjusting the circulating pump 4 to the flow rate to 125m/s, and recording as the reaction start time.
In the reaction process, the temperature of the reaction kettle is controlled to be 85 +/-1 ℃. The linear velocity of the fluid at the nozzle of the Venturi ejector is controlled to be 125m/s, and the detailed design size is specifically that the inner diameter D1 of the opening of the inlet section is as follows: nozzle inner diameter D2: air chamber binding off internal diameter D3: length of mixed segment L1: the ratio of the length L2 of the diffusion zone is 38:3:4:100:1650, the opening angle alpha of the diffusion section is 20 degrees, the reaction is carried out for 8h, the flow rate of the circulating pump 4 is immediately reduced, the temperature is rapidly reduced to room temperature (the temperature reduction time is about 15 min), the product is taken out after emptying, the conversion rate of benzoin is calculated to be 60.2 percent by liquid chromatography analysis and an area normalization method, and the selectivity of benzil is 93.5 percent.
It can be seen from example 1 and comparative example 1 that when the length of the mixing section of the venturi ejector is reduced, the conversion of benzil is significantly reduced.
Comparative example 2 (batch reaction in reaction vessel)
16g of benzoin, 6g of sulfuric acid with the concentration of 48g and 7wt% of acetic acid and 0.5 g of potassium bromide are added into a 100ml three-mouth flask, the mass ratio of the sulfuric acid solution to the benzoin is 37.5 wt%, the mass ratio of the bromide to the benzoin is 3.1 wt%, the temperature is raised to 70-75 ℃, the mixture is stirred and dissolved, one end of the three-mouth flask is connected with an air conduit, the other end of the three-mouth flask is connected with a condenser tube, the conduit tube is inserted under the liquid level, air is introduced and the air flow is controlled to be 1.3L/h, the temperature is raised to 85 ℃, the stirring reflux reaction is carried out for 8h, a sample is analyzed by liquid chromatography, the conversion rate of the benzoin is 35.5%, and the selectivity of the benzil is 95.4%.

Claims (8)

1. The preparation method of the benzil is characterized in that a jet loop reactor is adopted, benzoin and air are used as raw materials, acetic acid is used as a solvent, and acid and salt are used as catalysts to carry out oxidation reaction; the acid is one or two of hydrochloric acid and sulfuric acid; the salt is one or more of sodium bromide, potassium bromide, sodium iodide and potassium iodide; the inner diameter of the inlet section opening of the venturi ejector in the jet loop reactor is as follows: nozzle inner diameter: the gas chamber closing-in inner diameter: length of mixing section: the ratio of the length of the diffusion zone is 34 (1.5-4.5): (2-6): (180-280): (1550-1850), the opening angle of the diffuser is 12-28 degrees; the micro-positive pressure of the reaction system is controlled to be 0.07 +/-0.01 MPa in the oxidation reaction process.
2. The preparation method according to claim 1, wherein the reaction temperature is controlled to be 80-90 ℃ and the reaction time is controlled to be 7-10 hours in the oxidation reaction process; and controlling the linear velocity of the fluid at the nozzle of the Venturi ejector to be 100-150 m/s.
3. The method according to claim 2, wherein the concentration of the acid is 7-30%; the adding amount of the acid is 20-65% of the mass of the benzoin; the addition amount of the salt is 0.5-10% of the mass of the benzoin.
4. The preparation method of claim 3, wherein the acid is 7% sulfuric acid solution, and the addition amount of the sulfuric acid solution is 37.5% of the mass of the benzoin; the salt adopts potassium bromide, and the adding amount of the potassium bromide is 3.0 percent of the mass of the benzoin.
5. The method of claim 4, wherein the inner diameter of the opening of the venturi injector inlet section in the jet loop reactor is: nozzle bore diameter: the inner diameter of the closed air chamber: length of mixed section: the ratio of the length of the diffusion section is 34: 4:230:1650, the opening angle of the diffuser section is 20.
6. The preparation method according to claim 5, wherein the reaction temperature is controlled to be 85 ℃ and the reaction time is controlled to be 8 hours during the oxidation reaction; and controlling the linear velocity of the fluid at the nozzle of the Venturi ejector to be 125m/s.
7. The utility model provides a preparation benzil special venturi ejector which characterized in that, venturi ejector's inlet section opening internal diameter: nozzle inner diameter: the inner diameter of the closed air chamber: length of mixing section: the ratio of the length of the diffusion zone is 34 (1.5-4.5): (2-6): (180-280): (1550-1850), the opening angle of the diffuser section is 12-28 degrees.
8. The venturi injector special for preparing benzil according to claim 7, wherein the inner diameter of the opening of the inlet section of the venturi injector is as follows: nozzle inner diameter: the inner diameter of the closed air chamber: length of mixed section: the ratio of the length of the diffusion section is 34: 4:230:1650, the opening angle of the diffuser section is 20.
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