CN101149365A - Photocatalytic activity characterization method and device of a photocatalytic material - Google Patents

Abstract

The photocatalytic activity characterization method of the photocatalytic material is as follows: the photocatalytic material is put into a glass gas reactor and sealed, and the reaction system is cleaned with clean air; On the photocatalytic material; inject organic liquid or solution into the reaction system, preferentially use isopropanol photocatalyzed to generate acetone and carbon dioxide characterization system; use a new photocatalytic activity tester to detect the photocatalytic activity of the photocatalytic material in the mixed gas The content of isopropanol, acetone and carbon dioxide; the photocatalytic activity of the material is characterized by the amount of acetone and carbon dioxide generated, that is, the reaction speed; the photocatalytic reaction product is detected by the detector on-line in real time.

Description

Photocatalytic activity characterization method and device of a photocatalytic material

technical field

The invention relates to a method and a device for characterizing material properties, in particular to a method and a device for testing the activity of a photocatalytic material for gas-phase degradation of organic matter.

Background technique

With the development of human society, people are facing more and more serious indoor and outdoor environmental pollution problems. Relying on photocatalytic materials to use sunlight to degrade various gas phase pollutants that are harmful to the environment, and then mineralize them into harmless water and carbon dioxide is a very economical, convenient and feasible method. At present, the scientific community has attached great importance to the research of photocatalysis, and a large number of scientific researchers are engaged in research on the application of photocatalysis in environmental purification. However, at present, the price of scientific instruments used to characterize photocatalytic materials is relatively high, and many small research institutions cannot carry out relevant research work, and the efficiency of the instruments is low and has not been automated, which brings a lot of unnecessary physical labor to scientific researchers , greatly reducing the research speed of experiments. Therefore, it is very important to study an automatic high-efficiency photocatalytic activity characterization method and equipment to promote the research in the field of photocatalysis.

So far, the characterization methods and equipment for photocatalytic gas phase degradation can be summarized as follows:

1. Detection method. The chromatographic column of the gas chromatograph is used to separate various components in the mixed gas, and the amount of organic products is detected by a detector (thermal conductivity, hydrogen flame).

2. Sample injection method. Inject samples online using a four-way valve or offline using a syringe.

There are many disadvantages in using the above evaluation methods and devices:

1. High instrument price: the main component of the system - the gas chromatograph is very expensive.

2. High maintenance cost: the use of gas chromatograph requires high-purity carrier gas, and the sampling needles are all consumables, and the power of the instrument is large, which consumes electric energy.

3. Safety issues: Hydrogen gas is required to detect organic matter with a hydrogen flame detector, and there are serious safety hazards.

4. Low efficiency: The use of manual injection with four-way valve and injection needle at regular intervals will bring huge waste of labor costs and reduce the work efficiency of researchers.

5. Complex equipment: The equipment specifically includes various equipment such as gas chromatograph, four-way valve, high-purity carrier gas, high-pressure resistant glass reactor, and vacuum equipment. The structure is very complex.

Contents of the invention

Purpose of the present invention: to solve the above difficulties in the photocatalytic gas phase characterization method and equipment, provide a new photocatalytic evaluation method and create a new energy-saving, automatic high-efficiency, safe and simple device.

The technical solution of the present invention is: the photocatalytic activity characterization method for photocatalytic material is as follows,

1) Put the photocatalytic material into the glass reactor and seal it, and clean the reaction system with clean air;

2) Place the light source so that the light can pass through the quartz plate and irradiate on the photocatalytic material;

3) Use the characterization system of isopropanol photocatalysis to generate acetone and carbon dioxide, and characterize the photocatalytic activity of the photocatalytic material by the amount of isopropanol catalytic reaction into acetone and carbon dioxide; use an infrared gas analysis instrument to detect and characterize the photocatalytic material Isopropanol, acetone and carbon dioxide in the mixed gas after photocatalysis, the photocatalytic activity of the material can be characterized by the amount (speed) of carbon dioxide generated; the photocatalytic reaction product is detected by the detector on-line in real time. Among them, infrared rays with wavelengths of 2347, 1710 and 955 cm ⁻¹ are preferably used for detecting carbon dioxide, acetone and isopropanol, respectively, and are measured by non-dispersive infrared (NDIR) technology.

Before the catalytic reaction of isopropanol, a certain amount of organic liquid or solution is injected into the vaporization chamber of the reaction system, and the reaction gas is circulated and completely vaporized in a closed space by a circulation pump to promote the reaction. The organic liquid and solution include alcohols, ketones and aldehydes. When isopropanol is used, the reaction products acetone and carbon dioxide can be directly detected by an infrared gas analyzer to realize real-time detection in the whole process.

Technical solution of the device:

Improvement of infrared gas sensor: The principle of infrared gas analysis instrument is that the light intensity loss of an infrared beam of known intensity in a specific wavelength range can be used to directly measure the concentration of the corresponding gas. The practical solution to achieve this task consists of infrared light source, gas The infrared receiving window of the thermopile sensor is covered with a narrow-band filter in front of it, which can pick up the infrared absorption light wave corresponding to a certain gas, so as to realize the conversion of light intensity and voltage. According to the Lambert-Beer absorption law can be Determine the concentration of the gas to be measured. Among them, the detection of carbon dioxide, acetone and isopropanol in the present invention is preferably carried out using infrared rays with wavenumbers of 2347, 1710 and 955 cm ⁻¹ respectively.

1. The photocatalytic activity characterization device of photocatalytic materials includes glass gas reactor, liquid vaporization chamber, polytetrafluoroethylene PTFE or silicone pipe, liquid vaporization chamber heater, quick connector, air filter, light source and infrared gas analyzer Composition, in which the glass reactor and the organic liquid vaporization chamber are connected in series through a gas circulation pump, and are also connected in series with an infrared gas analyzer. The quartz glass and the main body of the reactor are sealed by a rubber ring to realize the airtightness of the reactor; the sealed gas circulation pump is connected to the glass gas reactor and the infrared gas analyzer through a pipeline. Use xenon lamp, LED, ultraviolet fluorescent lamp as the light source of catalytic reaction. Among them, the xenon lamp light source can be equipped with a cut-off wavelength filter or a single wavelength filter, the LED light source can be a high-power combined LED light source, and the ultraviolet fluorescent lamp can be a black light lamp and a purple light lamp with a center wavelength of 365nm.

2. A circular glass gas reactor is used, and the two ends of the reactor are respectively an air inlet and an air outlet to realize gas circulation. The front of the reactor is made of quartz material, which can completely transmit ultraviolet and visible light above 220nm. The quartz glass and the reactor body are sealed by a rubber ring. Six adjustable clamps are used to compress the quartz plate and the reactor to achieve the airtightness of the reactor.

3. Use a gas circulation pump to promote the diffusion and circulation of reaction products. The gas circulation pump is a non-polluting, air-tight circulation pump. The gas flow rate is 1-100ml/min.

4. Use computer to collect data and realize automation. The computer is connected to the infrared gas analysis instrument through the GPIB board or serial interface, and the computer sampling, drawing and data processing and analysis are realized through LabView programming.

5. Calibration of carbon dioxide, acetone or isopropanol in the system: use carbon dioxide-free air as the balance gas, and inject a certain amount of liquid acetone or isopropanol into the closed reactor. After fully reacting and vaporizing, use a gas chromatograph to determine the concentration of acetone or isopropanol in the closed reactor. The calibration concentration is increased from small to large, and finally the correction curve is obtained, and the correction curve is used for curve fitting, and the real concentration of the substance in the system is calculated by using the correction function. And theoretically calculate the theoretical concentration to achieve calibration. When calibrating carbon dioxide, a certain amount of gaseous carbon dioxide can be injected into the system, and the calibration method is the same as above.

The present invention is characterized in that: isopropanol is selected for photocatalysis to generate acetone and carbon dioxide characterization system, the reaction process is simple, and the photocatalytic activity mechanism is convenient to explain. The infrared gas analyzer can measure isopropanol, acetone and carbon dioxide at the same time, realize automatic measurement and data analysis, and save manpower. Adaptation of an infrared gas analyzer for the measurement of isopropanol, acetone and carbon dioxide. The photocatalytic reaction under normal pressure does not require vacuum equipment. The equipment is simple, the power is small, and energy saving. Low daily maintenance costs. It does not use high-purity hydrogen, which is safe.

Description of drawings

Fig. 1 Diagram of the photocatalytic activity evaluation device for photocatalytic gas phase degradation of organic matter

When Fig. 2 a kind of photocatalytic material degrades isopropanol in photocatalytic gas phase in the device of the present invention, the concentration of isopropanol, acetone and carbon dioxide product varies with time

In the figure: 1. Light source, 2. Filter, 3. Glass reactor, 4. Photocatalytic sample, 5. Organic liquid vaporization chamber, 6. Vaporization chamber heater, 7. Gas circulation pump, 8. Infrared gas analyzer , 9, quick connector.

Detailed ways

The present invention will be further described below in conjunction with embodiment:

(1) The reaction device includes glass gas reactor, sealed gas circulation pump, liquid vaporization chamber, pipeline (polytetrafluoroethylene PTFE or silicone tube), liquid vaporization chamber heater, quick connector, air filter, light source and infrared gas Analyzer.

(2) Put the photocatalytic material into the glass reactor and seal the system. Use quick connectors to clean the reaction system with clean air at a flow rate of 100ml/min, and the cleaning time depends on the specific situation.

(3) Inject a certain amount of organic liquid or solution into the vaporization chamber of the reaction system, and start the circulation pump to circulate the reaction gas in the closed space. Start the circulating pump for 0.5-1 hour to completely vaporize the organic liquid or solution.

(4) Place the light source so that the light can pass through the quartz plate and irradiate on the photocatalytic material. Turn on the light source and click start in the computer control program at the same time.

(5) The photocatalytic reaction product is detected online in real time by an infrared gas analyzer. Use the computer to record the change of the substance amount of the reaction product with time and save it. The photocatalytic activity of photocatalytic materials can be judged by the rate of product formation.

Implementation Case 1: Photocatalytic reaction of isopropanol photodegradation to generate acetone and carbon dioxide.

First, the powder sample is spread in a circular glass tank with a diameter of 2 cm, and the circular glass tank containing the sample is placed in the reactor, and the film sample can be placed directly. Cover the quartz plate and secure the seal. Open the quick connector in the closed-circuit system, connect the air filter to the inlet valve, turn on the gas circulation pump, and use clean air to clean the reactor, pipeline, and gas chamber in the infrared gas analyzer to remove the adsorbed pollutants , this process can also optionally be purged with CO2-free air. Connect the quick connector and inject 10ul of isopropanol into the sample vaporization chamber with a syringe. Start the circulation pump to circulate for 30 minutes to completely vaporize the injected isopropanol. Turn on the infrared gas analyzer and warm it up for 30 minutes. A 300W xenon lamp is used as the light source, and a cut-off wavelength filter can be used to obtain visible light greater than a certain wavelength. Turn on the light source and click Data Acquisition on the computer at the same time. As time goes by, it can be seen from the monitor of the computer that the amount of isopropanol in the reactor is gradually decreasing, and the amount of acetone and carbon dioxide is constantly increasing. At the same time, the computer has stored the data into *.txt files, which can be exported for further processing.

Implementation Case 2: Photocatalytic reaction of photodegradation of acetaldehyde to generate carbon dioxide.

First spread the powder sample in a pre-made circular glass tank with a diameter of 2 cm, and place the circular glass tank containing the sample in the reactor, and the film sample can be directly placed. Cover the quartz plate and secure the seal. Open the quick connector in the closed-circuit system, connect the air filter to the inlet valve, turn on the gas circulation pump, and use clean air to clean the reactor, pipeline, and gas chamber in the infrared gas analyzer to remove the adsorbed pollutants , this process can also optionally be purged with CO2-free air. Connect the quick connector, and inject 10ul of 40% acetaldehyde solution into the sample vaporization chamber with the injection needle. Start the circulation pump to circulate for 60 minutes to completely vaporize the injected acetaldehyde. Turn on the infrared gas analyzer and warm it up for 30 minutes. A 300W xenon lamp is used as the light source, and a cut-off wavelength filter can be used to obtain visible light greater than a certain wavelength. Turn on the light source and click Data Acquisition on the computer at the same time. Set up a program to detect changes in the amount of carbon dioxide in the reaction system. As time changes, the amount of carbon dioxide in the reactor can be seen from the computer monitor to gradually increase.

Claims (9)

1. A photocatalytic activity characterization method of a photocatalytic material, characterized in that: (1) Put the photocatalytic material into the glass gas reactor and seal it, and clean the reaction system with clean air; (2) Place the light source so that the light can shine on the photocatalytic material through the light-transmitting window; (3) Inject the organic liquid or solution into the reaction system, and preferentially use isopropanol to photocatalyze the characterization system to generate acetone and carbon dioxide; (4) The content of isopropanol, acetone and carbon dioxide in the mixed gas after photocatalysis of the photocatalytic material is detected by a new photocatalytic activity tester; (5) The photocatalytic activity of the material is characterized by the amount of acetone and carbon dioxide generated, that is, the reaction speed; the photocatalytic reaction product is detected online in real time by a detector. 2. The photocatalytic activity characterization method of photocatalytic material according to claim 1, characterized in that the light source used is a xenon lamp, or a xenon lamp equipped with a filter, a semiconductor light-emitting diode (LED) or an ultraviolet fluorescent lamp. 3. The photocatalytic activity characterization method of photocatalytic material according to claim 1, characterized in that the organic liquid and solution include alcohols, ketones and aldehydes. The reaction products acetone and carbon dioxide of isopropanol can be detected by infrared gas analyzer at the same time, and the photocatalytic activity of the material can be characterized by detecting the amount of carbon dioxide when using other organic substances as degradation products. 4. the photocatalytic activity characterization method of photocatalytic material according to claim 3, it is characterized in that, utilize non-spectral infrared (NDIR) to measure, detect carbon dioxide, acetone, isopropanol and select wavelength to be 2347, 1710 and 955cm respectively ^-1 for infrared. 5. The photocatalytic activity characterization method of photocatalytic material according to claim 1 or 3, is characterized in that, after a certain amount of organic liquid or solution is injected into vaporization chamber, utilize vaporization chamber heating system and gas circulation pump, The organic gas is completely vaporized and reaches adsorption equilibrium. 6. The photocatalytic activity characterization method of the photocatalytic material according to claim 5, characterized in that the diffusion of the reaction product is promoted and the flow rate of the circulating gas is 1-100ml/min. 7. The photocatalytic activity characterization method of photocatalytic material according to claim 1, is characterized in that use computer to carry out automatic data acquisition, connect with infrared gas analysis instrument by RS232, USB or GPIB board card, utilize LabView programming to realize computer sampling , drawing and data processing and analysis. 8. The photocatalytic material activity test device according to claim 1, characterized in that it comprises a glass gas reactor, a liquid vaporization chamber, a polytetrafluoroethylene tube or a silicone tube, a liquid vaporization chamber heater, a quick connector, an air filter It is composed of a device, a gas circulation pump, a light source and an infrared gas analyzer. The glass reactor and the organic liquid vaporization chamber are connected in series through the gas circulation pump, and are also connected in series with the infrared gas analyzer. 9. The test device of photocatalytic material according to claim 8, characterized in that the glass reactor is circular, and the two ends are respectively an air inlet and an air outlet to realize the circulation of gas, and the light transmission window on the front side of the reactor is Quartz material that transmits ultraviolet light and visible light above 220nm.

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