阅读说明：本技术 一种快速氧化苄基醇制苄基醛的方法 (Method for preparing benzyl aldehyde by quickly oxidizing benzyl alcohol ) 是由 纪红兵 黄丽云 张�浩 何晓辉 于 2021-08-13 设计创作，主要内容包括：本发明提供一种快速氧化苄基醇制苄基醛的方法,旨在提供一种在无催化剂的条件下快速对苄基醇进行氧化反应的方法,该方法依次包括下述步骤：1)在室温下,将苄基醇溶解有机溶剂中作为内相,次氯酸钠水溶液作为外相；2)在室温下,将所述的内相从微流体装置的注射管中注入,水相从承接管中注入,两相流体在承接管中相遇后通过剪切作用形成水包油微液滴,进行高效的氧化反应。(The invention provides a method for preparing benzyl aldehyde by quickly oxidizing benzyl alcohol, and aims to provide a method for quickly carrying out oxidation reaction on benzyl alcohol under the condition of no catalyst, which sequentially comprises the following steps: 1) dissolving benzyl alcohol in an organic solvent at room temperature to serve as an internal phase, and taking a sodium hypochlorite aqueous solution as an external phase; 2) at room temperature, the inner phase is injected from an injection tube of the microfluid device, the water phase is injected from a bearing tube, and the two-phase fluid meets the bearing tube and then forms oil-in-water micro-droplets through shearing action to perform efficient oxidation reaction.)

1. A method for preparing benzyl aldehyde by quickly oxidizing benzyl alcohol is characterized by sequentially comprising the following steps:

1) dissolving benzyl alcohol in an organic solvent at room temperature to serve as an internal phase, and taking a sodium hypochlorite aqueous solution as an external phase;

2) at room temperature, the inner phase is injected from an injection tube of the microfluid device, the outer phase is injected from a receiving tube, and the two-phase fluid meets the receiving tube and then forms oil-in-water micro-droplets through shearing action to perform efficient oxidation reaction.

2. The method of claim 1, wherein the organic solvent is one of ethyl acetate, tetrahydrofuran, pyridine, or toluene.

3. The method of claim 1, wherein the flow rate of the inner phase fluid is 30-100 μ L/min and the flow rate of the outer phase fluid is 50-150 μ L/min.

4. The method of claim 1, wherein the benzyl alcohol is used at a concentration of 0.1-0.8M and the sodium hypochlorite is used at a concentration of 5 wt% to 35 wt%.

5. The method of claim 1, wherein the controlled internal phase droplet residence time in the receiving tube is from about 10s to about 50 s.

6. The method as claimed in claim 1, wherein the micro-fluid device comprises a syringe, the front end of the syringe is inserted into a receiving tube, a square tube is disposed outside the syringe and the receiving tube, and the syringe, the receiving tube and the square tube are coaxial.

7. The method of claim 1, wherein the length of the adapter is 17-70 cm.

8. The method for preparing benzyl aldehyde by rapidly oxidizing benzyl alcohol as claimed in claim 1, wherein the front end of the injection tube (1) is tapered.

Technical Field

The invention relates to the technical field of microfluidics and organic chemistry, in particular to a method for quickly oxidizing in a droplet microfluidics device.

Background

Benzyl aldehyde is an important organic synthesis intermediate and a fine chemical product, and is widely applied to industries such as medicines, dyes, spices, resins and the like. At present, the benzyl aldehyde 'green' catalytic synthesis technology mainly comprises the following steps: toluene oxidation, aromatic ester/acid catalytic hydrogenation and benzyl alcohol liquid phase oxidation. Wherein the benzyl alcohol liquid phase oxidation method is to use hydrogen peroxide and molecular oxygen (O)₂Air) or sodium hypochlorite as an oxidizing agent to selectively oxidize benzyl alcohol to benzyl aldehyde. The method has simple process and environmental protection, and is expected to prepare the benzyl aldehyde with high yield, thereby causing wide attention of researchers.

The benzyl oxidation reaction mostly adopts transition metal catalysts (such as chromium, copper, nails and the like) and sodium hypochlorite or tert-butyl peroxide as an oxidant in published research works, the reaction is very violent and emits a large amount of heat, so that a protective measure must be taken in an experiment. The requirements in industrial production are more strict. The reaction time is generally more than a few hours, which greatly limits the industrial application value of the method, and the product is easy to be over-oxidized to generate byproducts because the reaction time is too long. In addition, the use of transition metals as catalysts has a number of disadvantages, chromium oxide catalysts have megatoxicity, nail compounds are too expensive, post-reaction treatment is troublesome, it is difficult to ensure that the synthesized products are not contaminated by heavy metals, and the like.

Disclosure of Invention

Aiming at the problems, the invention adopts the droplet microfluidic technology to rapidly carry out the oxidation reaction on benzyl alcohol under the condition of no catalyst.

A method for preparing benzyl aldehyde by quickly oxidizing benzyl alcohol sequentially comprises the following steps:

1) dissolving benzyl alcohol in an organic solvent at room temperature to serve as an internal phase, and taking a sodium hypochlorite aqueous solution as an external phase;

2) at room temperature, the inner phase is injected from an injection tube of the microfluid device, the outer phase is injected from a receiving tube, and the two-phase fluid meets the receiving tube and then forms oil-in-water micro-droplets through shearing action to perform efficient oxidation reaction.

Further, the method for preparing benzyl aldehyde by rapidly oxidizing benzyl alcohol is characterized in that the organic solvent is one of ethyl acetate, tetrahydrofuran, pyridine and toluene.

Further, in the method for preparing benzyl aldehyde by rapidly oxidizing benzyl alcohol, the flow rate of the inner phase fluid is 30-100 μ L/min, and the flow rate of the outer phase fluid is 50-150 μ L/min.

Further, in the method for preparing benzyl aldehyde by quickly oxidizing benzyl alcohol, the concentration of the benzyl alcohol is 0.1-0.8M, and the concentration of sodium hypochlorite is 5-35 wt%.

Further, in the method for preparing benzyl aldehyde by rapidly oxidizing benzyl alcohol, the residence time of the adjusted internal phase liquid drop in the adapting pipe is from 10s to 50 s.

Further, in the method for preparing benzyl aldehyde by rapidly oxidizing benzyl alcohol, the microfluidic device comprises an injection tube, the front end of the injection tube is inserted into a receiving tube, a square tube is arranged outside the injection tube and the receiving tube, and the injection tube, the receiving tube and the square tube are coaxial.

Further, in the method for preparing benzyl aldehyde by quickly oxidizing benzyl alcohol, the length of the adapting pipe is 17-70 cm.

Further, in the above method for preparing benzyl aldehyde by rapidly oxidizing benzyl alcohol, the front end of the injection tube is tapered.

Furthermore, the above-mentioned microfluidic device with a coaxial confocal structure is composed of an injection tube (Φ 550 × 950 μm), a square tube (Φ 1000 × 1200 μm) and a receiving tube (Φ 400 × 950 μm) (as shown in fig. 1), the front end of the injection tube in the reaction device is drawn into a taper shape of Φ 160 × 95 μm by a capillary drawing instrument, and the length of the receiving tube is 17-70 cm. The reactants undergo an oxidation reaction in the microchannel.

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

1. the invention can realize that the reaction does not need to add a catalyst under the condition of not using a phase transfer catalyst, and the high specific surface provided by the micro-droplets can ensure that the two-phase reaction can be rapidly carried out with high yield. (the reaction rate is nearly 100 times that of conventional stirring).

2. The invention can regulate the specific surface area of a two-phase interface and the residence time of liquid drops by regulating the flow rate of the fluid, thereby regulating the reaction efficiency. Meanwhile, the reaction efficiency can be regulated and controlled by regulating and controlling the interface concentration of two phases.

3. The method can be continuously operated in the preparation process, has mild conditions, and is suitable for industrial production.

4. The droplets produced by the present invention have a high surface area to volume ratio, thus achieving more efficient mass transfer, with conversion rates of 20% to 55% at reaction times of 10 to 60 seconds. Moreover, the process is continuous and controllable, the condition is mild, and industrial production can be realized.

Drawings

FIG. 1 is a schematic diagram of a microfluidic device for preparing two-phase microdroplets;

FIG. 2 is a high speed camera image of micro-droplets of examples 1, 2, 3, 6;

FIG. 3 is a high speed camera view of microdroplets of example 4;

FIG. 4 is a high speed camera view of microdroplets of example 5;

Detailed Description

The present invention will be described in more detail with reference to the following examples, but the scope of the present invention is not limited to the scope shown in the examples.

The micro-fluidic device adopted in the following embodiment of the invention is a micro-fluidic device with a coaxial confocal structure, referring to fig. 1, and consists of an injection tube (phi 550X 950 μm), a square tube (phi 1000X 1200 μm) and a receiving tube (phi 400X 950 μm), wherein the front end of the injection tube is inserted in the receiving tube, the square tube is arranged outside the injection tube and the receiving tube, the front end of the injection tube in the reaction device is drawn into a cone with the size of phi 160X 95 μm by a capillary drawing instrument, and the length of the receiving tube is 17-70 cm. The reactants undergo an oxidation reaction in the microchannel.

Example 1

The length of the adapter tube was 17 cm as described above for the microfluidic device. 0.5g of 4-nitrobenzol was weighed out in 15ml of ethyl acetate at room temperature as the dispersed phase (internal phase). A25 wt% aqueous sodium hypochlorite solution was prepared as a continuous phase (outer phase). And respectively sucking the internal phase solution and the external phase solution by using a 10mL syringe, and respectively pumping the two-phase solution into an injection pipe and a receiving pipe at a constant flow rate by using a syringe pump to form oil-in-water drops, wherein the flow rate of the internal phase is 50 mu L/min, and the flow rate of the external phase is 150 mu L/min. The resulting droplets are shown in the high-speed camera diagram of FIG. 2 and have a particle size of 460. mu.m. The residence time of the reactants in the microchannel was about 10 seconds, and the conversion was 20% and the product selectivity of 4-nitrobenzaldehyde was 99% as determined by gas chromatography after the reaction solution was extracted with ethyl acetate.

Example 2

The length of the adapter tube was 34 cm as described above for the microfluidic device. 0.5g of 4-nitrobenzol was weighed out in 15ml of ethyl acetate at room temperature as the dispersed phase (internal phase). A25 wt% aqueous sodium hypochlorite solution was prepared as a continuous phase (outer phase). And respectively sucking the internal phase solution and the external phase solution by using a 10mL syringe, and respectively pumping the two-phase solution into an injection pipe and a receiving pipe at a constant flow rate by using a syringe pump to form oil-in-water drops, wherein the flow rate of the internal phase is 50 mu L/min, and the flow rate of the external phase is 150 mu L/min. The resulting droplets are shown in the high-speed camera diagram of FIG. 2 and have a particle size of 460. mu.m. The residence time of the reactants in the microchannel was about 20 seconds, and the conversion was 25% and the product selectivity of 4-nitrobenzaldehyde was 99% as determined by gas chromatography after the reaction solution was extracted with ethyl acetate.

Example 3

The length of the adapter tube is 70cm as described above for the microfluidic device. 0.5g of 4-nitrobenzol was weighed out in 15ml of ethyl acetate at room temperature as the dispersed phase (internal phase). A25 wt% aqueous sodium hypochlorite solution was prepared as a continuous phase (outer phase). And respectively sucking the internal phase solution and the external phase solution by using a 10mL syringe, and respectively pumping the two-phase solution into an injection pipe and a receiving pipe at a constant flow rate by using a syringe pump to form oil-in-water drops, wherein the flow rate of the internal phase is 50 mu L/min, and the flow rate of the external phase is 150 mu L/min. The resulting droplets are shown in the high-speed camera diagram of FIG. 2 and have a particle size of 460. mu.m. The residence time of the reactants in the microchannel was about 50 seconds, and the conversion, as quantified by gas chromatography after the reaction solution was extracted with ethyl acetate, was 32% and the product selectivity to 4-nitrobenzaldehyde was 99%.

Example 4

The length of the adapter tube was 34 cm as described above for the microfluidic device. 0.5g of 4-nitrobenzol was weighed out in 15ml of ethyl acetate at room temperature as the dispersed phase (internal phase). A25 wt% aqueous sodium hypochlorite solution was prepared as a continuous phase (outer phase). And respectively sucking the internal phase solution and the external phase solution by using a 10mL syringe, and respectively pumping the two-phase solution into an injection pipe and a receiving pipe at a constant flow rate by using a syringe pump to form oil-in-water drops, wherein the flow rate of the internal phase is 80 mu L/min, and the flow rate of the external phase is 150 mu L/min. The resulting droplets are shown in the high-speed camera image of FIG. 3 and have a particle size of 540. mu.m. The residence time of the reactants in the microchannel was about 13 seconds, and the conversion was 20% and the product selectivity of 4-nitrobenzaldehyde was 99% as determined by gas chromatography after the reaction solution was extracted with ethyl acetate.

Example 5

The length of the adapter tube was 34 cm as described above for the microfluidic device. 0.5g of 4-nitrobenzol was weighed out in 15ml of ethyl acetate at room temperature as the dispersed phase (internal phase). A25 wt% aqueous sodium hypochlorite solution was prepared as a continuous phase (outer phase). And respectively sucking the internal phase solution and the external phase solution by using a 10mL syringe, and respectively pumping the two-phase solution into an injection pipe and a receiving pipe at a constant flow rate by using a syringe pump to form oil-in-water drops, wherein the flow rate of the internal phase is 50 mu L/min, and the flow rate of the external phase is 100 mu L/min. The resulting droplets are shown in the high-speed camera diagram of FIG. 4 and have a particle size of 500. mu.m. The residence time of the reactants in the microchannel was about 35 seconds, and the conversion, as quantified by gas chromatography after the reaction solution was extracted with ethyl acetate, was 33% and the product selectivity to 4-nitrobenzaldehyde was 99%.

Example 6

The length of the adapter tube was 34 cm as described above for the microfluidic device. 0.5g of 4-nitrobenzol was weighed out in 15ml of ethyl acetate at room temperature as the dispersed phase (internal phase). A35 wt% aqueous sodium hypochlorite solution was prepared as a continuous phase (outer phase). And respectively sucking the internal phase solution and the external phase solution by using a 10mL syringe, and respectively pumping the two-phase solution into an injection pipe and a receiving pipe at a constant flow rate by using a syringe pump to form oil-in-water drops, wherein the flow rate of the internal phase is 50 mu L/min, and the flow rate of the external phase is 150 mu L/min. The resulting droplets are shown in the high-speed camera diagram of FIG. 2 and have a particle size of 460. mu.m. The residence time of the reactants in the microchannel was about 20 seconds, and the conversion was 55% and the product selectivity of 4-nitrobenzaldehyde was 99% as determined by gas chromatography after the reaction solution was extracted with ethyl acetate.

Example 7

The length of the adapter tube was 34 cm as described above for the microfluidic device. 0.2g of terephthalyl alcohol was weighed out at room temperature and dissolved in 15ml of ethyl acetate as the dispersed phase (internal phase). A25 wt% aqueous sodium hypochlorite solution was prepared as a continuous phase (outer phase). And respectively sucking the internal phase solution and the external phase solution by using a 10mL syringe, and respectively pumping the two-phase solution into an injection pipe and a receiving pipe at a constant flow rate by using a syringe pump to form oil-in-water drops, wherein the flow rate of the internal phase is 50 mu L/min, and the flow rate of the external phase is 150 mu L/min. The retention time of reactants in the microchannel was about 20 seconds, and the conversion rate was 45% and the product selectivity of terephthalaldehyde was 99% by gas chromatography quantification after the reaction solution was extracted with ethyl acetate.

Example 8

The length of the adapter tube was 34 cm as described above for the microfluidic device. 0.5g of 4-methylbenzyl alcohol was weighed out at room temperature and dissolved in 15ml of ethyl acetate as dispersed phase (internal phase). A25 wt% aqueous sodium hypochlorite solution was prepared as a continuous phase (outer phase). And respectively sucking the internal phase solution and the external phase solution by using a 10mL syringe, and respectively pumping the two-phase solution into an injection pipe and a receiving pipe at a constant flow rate by using a syringe pump to form oil-in-water drops, wherein the flow rate of the internal phase is 50 mu L/min, and the flow rate of the external phase is 150 mu L/min. The residence time of the reactants in the microchannel was about 20 seconds, and the conversion was 26% and the product selectivity of 4-methylbenzaldehyde was 99% as determined by gas chromatography after the reaction liquid was extracted with ethyl acetate.