阅读说明：本技术 一种光催化制备氯气的方法 (Method for preparing chlorine gas through photocatalysis ) 是由 王文中 张玲 王海鹏 于 2020-05-19 设计创作，主要内容包括：本发明公开一种光催化制备氯气的方法,包括：将光催化材料氯氧化铋分散到含氯离子水溶液中,光催化材料氯氧化铋在含氯离子水溶液中的浓度为0.1～30mg/mL,在空气氛围下经过光照进行光催化反应以生成氯气。本发明提供的光催化制备氯气的方法以光作为能源,以氯氧化铋作为催化剂,无需贵金属负载和电能输入激发,在空气氛围中即可进行反应。另外,氯氧化铋催化剂具有较高的光催化反应活性,且其制备工艺简单,原料便宜易得,适合大规模生产。(The invention discloses a method for preparing chlorine by photocatalysis, which comprises the following steps: dispersing a photocatalytic material bismuth oxychloride into a chloride ion-containing aqueous solution, wherein the concentration of the photocatalytic material bismuth oxychloride in the chloride ion-containing aqueous solution is 0.1-30 mg/mL, and performing a photocatalytic reaction under the air atmosphere by illumination to generate chlorine. The method for preparing chlorine by photocatalysis provided by the invention takes light as an energy source and takes bismuth oxychloride as a catalyst, and can carry out reaction in an air atmosphere without noble metal loading and electric energy input excitation. In addition, the bismuth oxychloride catalyst has higher photocatalytic reaction activity, the preparation process is simple, the raw materials are cheap and easy to obtain, and the bismuth oxychloride catalyst is suitable for large-scale production.)

1. A method for preparing chlorine gas through photocatalysis, which is characterized by comprising the following steps: dispersing a photocatalytic material bismuth oxychloride into a chloride ion-containing aqueous solution, wherein the concentration of the photocatalytic material bismuth oxychloride in the chloride ion-containing aqueous solution is 0.1-30 mg/mL, and performing a photocatalytic reaction under the air atmosphere by illumination to generate chlorine.

2. The method of claim 1, wherein the bismuth oxychloride is selected from the group consisting of BiOCl, Bi₃O₄Cl、 Bi₄O₅Cl₂、Bi₁₂O₁₇Cl₂、Bi₁₂O₁₅Cl₆、Bi₂₄O₃₁Cl₁₀At least one of them.

3. The method according to claim 1 or 2, wherein the aqueous solution containing chloride ions is at least one of a lithium chloride solution, a sodium chloride solution, a potassium chloride solution, a magnesium chloride solution, and a calcium chloride solution.

4. The method according to claim 3, wherein when the aqueous solution containing chloride ions is a lithium chloride solution, the concentration of lithium chloride is 1-670 g/L; when the aqueous solution containing the chloride ions is a sodium chloride solution, the concentration of the sodium chloride is 1-360 g/L; when the aqueous solution containing the chloride ions is a potassium chloride solution, the concentration of the potassium chloride is 1-342 g/L; when the aqueous solution containing the chloride ions is a magnesium chloride solution, the concentration of magnesium chloride is 1-54 g/L; when the aqueous solution containing the chloride ions is a calcium chloride solution, the concentration of the calcium chloride is 1-215 g/L.

5. The method according to any one of claims 1 to 4, wherein the pH of the aqueous solution containing chloride ions is 1.5 to 8.

6. The method according to any one of claims 1 to 5, wherein the photocatalytic material bismuth oxychloride is a layered structure and forms oxygen defects under illumination.

7. The method according to any one of claims 1 to 6, wherein the light condition is an ultraviolet lamp having a specific wavelength, an LED light source, a xenon lamp, a high-pressure mercury lamp, or sunlight.

8. The method according to any one of claims 1 to 7, wherein the chlorine gas generated by the photocatalytic reaction is present in the form of gaseous chlorine and free chlorine.

Technical Field

The invention belongs to the field of catalysis, and particularly relates to a method for preparing chlorine (Cl) by photocatalysis₂) The method of (1).

Background

Cl₂As an important basic chemical raw material, the method is widely applied to the production of polyvinyl chloride (PVC), chlorine-containing disinfectants, bleaches, synthetic fibers, pesticides, various chlorides and the like. Further, Cl₂Can also be used in the fields of sewage treatment, tap water disinfection, electronic industry dry etching, metallurgy and the like. The production of chlorine is closely related to national production and industrial agricultureIs a large chemical with annual production of about 7 million tons. Chlorine production in a country is often seen as an important marker for the state of the chemical industry.

At present, Cl₂Mainly by the brine electrolysis method, which has been used for over 100 years, during which time researchers have made a number of improvements to the process, but this method still has two problems: 1. a large amount of electric energy is consumed, the chlor-alkali industry consumes more than 200TWh of electricity every year, wherein part of the electric energy is consumed by competitive reaction or ion migration, and the waste is huge; 2. the electrodes used for electrolysis are mainly ruthenium and iridium based electrodes, but ruthenium and iridium are both noble metals and are expensive. Therefore, development of a Cl which consumes less energy and does not require a noble metal₂The production method has great significance to the energy field, and can greatly reduce the industrial production cost.

Promising photocatalytic technology for Cl₂The method has the advantages of green and high-efficiency production, namely, the sunlight is used as an input energy source, and the chloride ion catalytic oxidation reaction under the mild condition is realized under the action of the photocatalyst. In Zhou Shi just et alEnergy Environ. Sci. 2011, 4, 4046Doping of BiVO with Mo is reported₄When used as a photo-anode, the chlorine ions in seawater can be oxidized into Cl by photoelectrocatalysis₂. Lican et al inCatal. Sci. Technol. 2014, 4, 2913It is proposed that chloride ions may be replaced by TiO₂The photocatalytic oxidation is carried out to HClO, and then the decomposition is carried out under the illumination to generate oxygen. Tsunehiro Tanaka et al inPhys. Chem. Chem. Phys. 2015, 17, 17995-18003The report of CO production using Ni-Al-LDH as photocatalyst₂When reducing, chloride ion can be used as a hole sacrificial agent to accelerate the reaction rate, and the detection proves that the chloride ion is oxidized into HClO, but the average yield is lower than 9 mu mol/h. Ghim Wei Ho et al inEnergy Environ. Sci.2016, 9, 3151-3160Reported therein as SiO₂/[email protected]₂In the case of a photocatalyst, chloride ions can be used as a sacrificial agent of a photo-generated carrier, and the chloride ions can be reduced into chloride ions by photo-generated electrons after being oxidized into chlorine radicals by photo-generated holes. Wu Zhu et al inAdv. Mater. 2017, 29, 1606009 Here, mpg-C formed in situ was found₃N₄the/Ag/AgCl photocatalytic material can oxidize chloride ions in a solution under illumination to form chlorine radicals, and the generation of the chlorine radicals is verified through radical capture and free electron resonance experiments. These work demonstrate the feasibility of photocatalytic chloride ion oxidation. However, the above reported oxidation process of chloride ion is a side reaction or an intermediate reaction in the photocatalytic reaction, and the yield of active chlorine is low or not detected, so that the generation of Cl by photocatalysis is urgently needed₂The reaction of (2) was studied in detail. Development of suitable non-noble metal photocatalysts and implementation of chloride ion oxidation and Cl₂Is generated as photocatalytic Cl₂Key points and difficulties in preparation.

Disclosure of Invention

The invention solves the technical problem of providing a high-efficiency photocatalysis preparation method of chlorine (Cl) aiming at the current situations that the current photocatalysis chloride ion has low oxidation efficiency and needs external bias voltage₂) Method of (1) is Cl₂Provides a new way for the preparation of the compound. The invention provides a method for preparing Cl by photocatalysis₂The method takes light as energy and bismuth oxychloride as a catalyst, does not need noble metal loading and electric energy input excitation, and can carry out reaction in the air atmosphere. In addition, the bismuth oxychloride catalyst has higher photocatalytic reaction activity, the preparation process is simple, the raw materials are cheap and easy to obtain, and the bismuth oxychloride catalyst is suitable for large-scale production.

The invention provides a method for preparing chlorine gas by photocatalysis, which comprises the following steps: dispersing a photocatalytic material bismuth oxychloride into a chloride ion-containing aqueous solution, wherein the concentration of the photocatalytic material bismuth oxychloride in the chloride ion-containing aqueous solution is 0.1-30 mg/mL, and performing a photocatalytic reaction under the air atmosphere by illumination to generate chlorine. The yield of the chlorine in the method for preparing the chlorine by photocatalysis can reach 20.4 mu mol/h.

Preferably, the bismuth oxychloride is selected from BiOCl and Bi₃O₄Cl、Bi₄O₅Cl₂、Bi₁₂O₁₇Cl₂、Bi₁₂O₁₅Cl₆、Bi₂₄O₃₁Cl₁₀At least one of them.

Preferably, the aqueous solution containing chloride ions is at least one of a lithium chloride solution, a sodium chloride solution, a potassium chloride solution, a magnesium chloride solution and a calcium chloride solution.

Preferably, when the aqueous solution containing chloride ions is a lithium chloride solution, the concentration of lithium chloride is 1-670 g/L; when the aqueous solution containing the chloride ions is a sodium chloride solution, the concentration of the sodium chloride is 1-360 g/L; when the aqueous solution containing the chloride ions is a potassium chloride solution, the concentration of the potassium chloride is 1-342 g/L; when the aqueous solution containing the chloride ions is a magnesium chloride solution, the concentration of magnesium chloride is 1-54 g/L; when the aqueous solution containing the chloride ions is a calcium chloride solution, the concentration of the calcium chloride is 1-215 g/L.

Preferably, the pH of the aqueous solution containing chloride ions is 1.5-8.

Preferably, the photocatalytic material bismuth oxychloride has a layered structure and forms oxygen defects under illumination.

Preferably, the light irradiation condition is an ultraviolet lamp having a specific wavelength, an LED light source, a xenon lamp, a high-pressure mercury lamp, or sunlight.

Preferably, the chlorine gas generated by the photocatalytic reaction is in the form of gaseous chlorine and free chlorine. In an optional embodiment, the method can stop illumination and collect products after 0.1-5 h of illumination reaction, test the content of chlorine by a DPD spectrophotometer method, and use Cl₂Is expressed in terms of the form. Due to Cl₂Readily soluble and reactive with water, so Cl produced by photocatalysis in sodium chloride solution₂Some exist in the solution as free chlorine (hypochlorous acid, hypochlorite or dissolved elemental chlorine) and some exist in the gas phase as chlorine gas.

The invention has the advantages that:

1) in the present invention is Cl₂The preparation of the compound provides a new way, the reaction is only carried out under the conditions of aqueous solution containing chloride ions, catalyst and illumination, the large consumption of electric energy is avoided, and the compound has great significance to the energy field;

2) the invention takes bismuth oxychloride material as Cl₂The photocatalyst has the advantages of easy preparation of bismuth oxychloride, cheap raw materials, suitability for large-scale production and no pollutionNeeds to be loaded by noble metal, thereby greatly reducing the industrial production cost.

Drawings

FIG. 1 is a scanning electron microscope image of a catalyst sample BiOCl obtained in example 1 of the present invention;

FIG. 2 is an X-ray diffraction diagram of BiOCl of the catalyst samples obtained in example 1 and example 2;

FIG. 3 shows Cl of a catalyst sample BiOCl obtained in example 1 in sodium chloride solutions with different concentrations for 30 minutes of photocatalytic reaction₂Yield performance is plotted.

Detailed Description

The present invention is further illustrated by the following examples, which are to be understood as merely illustrative and not restrictive.

The invention belongs to the technical field of catalysis, and provides a method for preparing Cl by photocatalysis₂The method of (1), comprising: dispersing a photocatalytic material bismuth oxychloride into an aqueous solution containing chloride ions, and carrying out photocatalytic reaction under the illumination condition and the air atmosphere to generate Cl₂. In some embodiments, the generated chlorine gas is present in the reaction apparatus in the form of gaseous chlorine and free chlorine.

The invention selects bismuth oxychloride as a photocatalytic material for the following reasons: 1. the bismuth oxychloride is easy to prepare, the raw materials are cheap, and the method is suitable for large-scale production; 2. the bismuth oxychloride has a proper energy band structure, and the valence band position is correct, so that the requirement of chloride ion oxidation is met; 3. the bismuth oxychloride material has a proper crystal structure, firstly, the layered structure provides conditions for chloride ion migration, and in addition, the bismuth oxychloride material can form oxygen defects under illumination, which is beneficial to improving the photocatalytic Cl₂The resulting activity.

The bismuth oxychloride catalyst is selected from BiOCl and Bi₃O₄Cl、 Bi₄O₅Cl₂、Bi₁₂O₁₇Cl₂、Bi₁₂O₁₅Cl₆、Bi₂₄O₃₁Cl₁₀At least one of them. The bismuth oxychloride catalyst is preferably BiOCl, because the preparation process of BiOCl is the simplest and is more suitable for large-scale production.

The invention also provides a preparation method of the bismuth oxychloride photocatalytic material, which comprises the steps of mixing the bismuth source and the chlorine source in a solvent, adjusting the pH of the mixture and carrying out the subsequent crystal growth process. As an example, the preparation process of the bismuth oxychloride specifically comprises the following steps:

first, a bismuth source and a chlorine source are mixed in a solvent to obtain a mixture. The order of mixing is not limited. The bismuth source may be bismuth nitrate pentahydrate, bismuth trichloride, bismuth trioxide, etc., preferably bismuth nitrate pentahydrate. The chlorine source may be lithium chloride, potassium chloride, sodium chloride, calcium chloride, ammonium chloride, hydrochloric acid, cetyltrimethylammonium chloride, 1-butyl-3-methylimidazolium chloride, etc., and preferably potassium chloride and sodium chloride. The solvent can be water, methanol, ethanol, glycol, acetone, acetonitrile, N-dimethylformamide and the like, and is preferably deionized water. The mixing can be accelerated by magnetic stirring, strong stirring, ultrasound and other methods.

The solid-to-liquid ratio of the bismuth source to the solution can be (10-100) mg: 1 mL. The atomic molar ratio of the chlorine source to the bismuth source may be (1: 1) to (10: 1), and is preferably (1: 1) to (4: 1).

The pH of the mixture is then adjusted. The pH of the mixture is first measured using a pH meter and can be adjusted to below 13 by adding acid, base, deionized water, and the like. When preparing BiOCl, the pH of the mixture of bismuth nitrate pentahydrate and potassium chloride in water meets the requirements without further adjustment. The proportion of Bi, O and Cl in the chemical formula of the photocatalytic material bismuth oxychloride can be changed by adjusting the pH of the intermediate mixture, so that BiOCl and Bi are obtained₃O₄Cl、 Bi₄O₅Cl₂、Bi₁₂O₁₇Cl₂、Bi₁₂O₁₅Cl₆、Bi₂₄O₃₁Cl₁₀And the like.

The mixture is then heated or treated at room temperature to grow crystals. The method can be carried out by room-temperature stirring, a hydrothermal method, oil bath heating, muffle furnace heat treatment and the like. Transferring the mixture into a corresponding device, and transferring the mixture into a beaker for stirring if the mixture is stirred at room temperature; if the hydrothermal method is used, transferring the mixture into a hydrothermal kettle; if oil bath heating is used, the mixture is transferred to a flask; if a muffle furnace heat treatment is used, the solids from the mixture filtered off are transferred to a crucible. The heating temperature is 10 to 200 ℃, preferably 120 to 180 ℃. The heating time is 4-48 h.

And after the treatment is finished, naturally cooling the obtained reactant to room temperature, performing solid-liquid separation, such as suction filtration and centrifugal separation, to obtain bismuth oxychloride, and finally washing and drying to obtain the powdery bismuth oxychloride photocatalytic material. The drying method is not particularly limited, and known drying methods such as freeze drying, vacuum drying (for example, in a drying oven), constant temperature evaporation, and the like can be used.

The method for preparing chlorine by using the prepared photocatalytic material bismuth oxychloride specifically comprises the following steps:

dispersing the photocatalytic material bismuth oxychloride into an aqueous solution containing chloride ions. The concentration of the bismuth oxychloride is 0.1-30 mg/mL, preferably 1-5 mg/mL, and the reason is that the concentration range can not only ensure higher light energy utilization efficiency, but also prevent material waste.

The aqueous solution containing chloride ions may be at least one of a lithium chloride solution, a sodium chloride solution, a potassium chloride solution, a magnesium chloride solution and a calcium chloride solution, and is preferably a sodium chloride solution. When the aqueous solution containing the chloride ions is a lithium chloride solution, the concentration of the lithium chloride is 1-670 g/L; when the aqueous solution containing the chloride ions is a sodium chloride solution, the concentration of the sodium chloride is 1-360 g/L; when the aqueous solution containing the chloride ions is a potassium chloride solution, the concentration of the potassium chloride is 1-342 g/L; when the aqueous solution containing the chloride ions is a magnesium chloride solution, the concentration of magnesium chloride is 1-54 g/L; when the aqueous solution containing the chloride ions is a calcium chloride solution, the concentration of the calcium chloride is 1-215 g/L.

The pH value of the water solution containing the chloride ions is 1.5-8, and the pH value range can prevent the material from being corroded by acid and can reduce the using amount of acid and alkali.

Photocatalytic reaction to Cl under illumination₂. The lighting condition can be ultraviolet lamp with specific wavelength,LED light sources, xenon lamps, high-pressure mercury lamps or sunlight.

For example, the illumination is stopped after the illumination reaction is carried out for 0.1-5 h, and the product is collected. Directly filtering free chlorine in the solution to obtain filtrate, absorbing chlorine in gas phase with tail gas absorption tube, testing chlorine content in the filtrate and absorption liquid with DPD spectrophotometer method, and measuring chlorine content with Cl₂Is expressed in terms of the form.

The present invention will be described in detail by way of examples. It is to be understood that the following examples are illustrative of the present invention and are not to be construed as limiting the scope of the invention, and that certain insubstantial modifications and adaptations of the invention by those skilled in the art in light of the foregoing description are intended to be included within the scope of the invention. The specific process parameters and the like of the following examples are also only one example of suitable ranges, i.e., those skilled in the art can select the appropriate ranges through the description herein, and are not limited to the specific values exemplified below.

Example 1

The method for preparing chlorine by photocatalysis comprises the following steps:

mixing 0.97g of bismuth nitrate pentahydrate and 0.15g of potassium chloride in 30mL of deionized water to obtain a white suspension, magnetically stirring for 1h, transferring to a 50mL reaction kettle, and putting the reaction kettle into an oven to keep the temperature at 160 ℃ for 24 h; naturally cooling to room temperature after heating, filtering out a sample by using a suction filtration method, washing for 3 times by using deionized water, and then carrying out freeze drying to obtain the BiOCl photocatalytic material;

preparing an aqueous solution with the sodium chloride concentration of 75 g/L, pouring 50mL of the sodium chloride solution into a reactor with the volume of 600mL, adding 0.1g of the BiOCl photocatalytic material into the aqueous solution, and uniformly dispersing the BiOCl photocatalytic material by ultrasonic oscillation;

and (3) sealing the reactor, and then placing the reactor under a 25W ultraviolet lamp (with the wavelength of 254 nm) for reaction. After 30 minutes of reaction, the ultraviolet lamp was turned off and the solution in the reactor was filtered, and the content of free chlorine in the filtrate was found to be 10.1. mu. mol Cl₂；

And (4) changing a product collection mode, and testing the amount of chlorine in the gas phase. Bismuth oxychloride andthe dispersion operation in the solution is as in steps (1) and (2), but a gas inlet device and a tail gas absorption device are connected to the reactor. In the process of illumination reaction, air is pumped into the reactor all the time, tail gas is absorbed at the same time, and no Cl is detected in the tail gas absorption liquid₂. Illustrating the Cl formed under these conditions₂Most of which is dissolved in the reaction liquid in the reactor.

FIG. 1 is a scanning electron micrograph of BiOCl prepared in example 1 of the present invention (pH was not adjusted). As shown in FIG. 1, the photocatalyst is in the form of a sheet, and the thickness of the sheet is 150-400 nm. The XRD pattern for BiOCl of this example is shown in FIG. 2 as BiOCl (pH unadjusted).

Example 2

Adjusting the preparation method of bismuth oxychloride, adjusting the pH of the mixture in the preparation process to 6, and verifying the photocatalytic Cl of the mixture₂Generating activity. Specifically, the method for preparing chlorine by photocatalysis comprises the following steps:

mixing 0.97g of bismuth nitrate pentahydrate and 0.15g of potassium chloride in 30mL of deionized water to obtain a white suspension, adjusting the pH of the white suspension to 6 by using potassium hydroxide, magnetically stirring for 1h, transferring the white suspension into a 50mL reaction kettle, and putting the reaction kettle into an oven to keep the temperature at 160 ℃ for 24 h; naturally cooling to room temperature after heating, filtering out a sample by using a suction filtration method, washing for 3 times by using deionized water, and then carrying out freeze drying to obtain the BiOCl photocatalytic material;

preparing an aqueous solution with the sodium chloride concentration of 75 g/L, pouring 50mL of the sodium chloride solution into a reactor with the volume of 600mL, adding 0.1g of the BiOCl photocatalytic material into the aqueous solution, and uniformly dispersing the BiOCl photocatalytic material by ultrasonic oscillation;

step (3) is the same as step (3) in example 1. The yield of free chlorine was determined to be 5.6. mu. mol Cl₂；

Step (4) is the same as step (4) in example 1. No Cl was detected in the tail gas absorption solution₂Description of Cl formed under these conditions₂Most of which is dissolved in the reaction liquid in the reactor.

The XRD pattern of BiOCl produced under the condition of pH =6 in this example is labeled BiOCl (pH = 6) in fig. 2.

Example 3

The concentration of chloride ions in the reaction solution was adjusted, and the BiOCl obtained in example 1 was subjected to a photocatalytic reaction in sodium chloride solutions of different concentrations.

Preparing aqueous solution with sodium chloride concentration of 7.5g/L, 30g/L, 60g/L, 90 g/L, 120g/L, 180g/L and 360g/L, and respectively carrying out photocatalysis on the aqueous solution₂A test is generated. 50mL of the sodium chloride solution is poured into a 600mL reactor, 0.1g of the BiOCl photocatalytic material is added, and magnetic stirring is carried out after ultrasonic oscillation and dispersion. The reactor was sealed and placed under a 25W ultraviolet lamp (wavelength 254 nm) for reaction. After half an hour of reaction, the ultraviolet lamp is turned off and the solution in the reactor is filtered, and the yields of free chlorine in the filtrate are 5.4, 9.8, 9.7, 10.2, 9.5, 9.1 and 3.5 mu mol Cl respectively₂. The properties of comparative example 1 are shown in FIG. 3. It can be seen that the yield of chlorine prepared by using BiOCl photocatalysis is higher when the concentration of the sodium chloride solution is 30-180 g/L, and the reason may be that: when the concentration of sodium chloride is lower than 30g/L, the mass transfer of chloride ions is limited, and the concentration of chloride ions near the surface of the catalyst is lower, so that the catalytic efficiency is lower; when the concentration of sodium chloride is higher than 180g/L, the solubility of chlorine in the solution is reduced, more chlorine overflows into the air, and the chlorine in the solution is measured to be lower.