CN109012736A - A kind of composite modified titanium dioxide process for vehicle exhaust of degrading - Google Patents

Abstract

The invention relates to a method for preparing composite modified _TiO2 for degrading automobile exhaust gas, which belongs to the technical field of automobile exhaust gas treatment, and solves the problem that currently _TiO2 can only absorb ultraviolet light, is difficult to use visible light, has low degradation efficiency, and the shape of prepared _TiO2 is not easy Problems with low control and reactivity. The present invention first prepares the mixed solution of concentrated sulfuric acid and concentrated nitric acid, adds multi-walled carbon nanotubes, ultrasonically disperses, heats and stirs in an oil bath; Add titanium isopropoxide into deionized water, and add multi-walled carbon nanotubes, ultrasonically disperse; finally add copper nitrate solution and concentrated sulfuric acid, after stirring, transfer to a high-pressure reactor, and deionize the obtained product with deionized water After washing and drying, multi-walled carbon nanotubes and copper ion composite modified nano-TiO ₂ are prepared. The multi-walled carbon nanotubes and copper ion composite modified _TiO2 prepared by the invention can be used to degrade automobile exhaust, reduce physical harm to drivers and passengers, and improve driving environment quality.

Description

A preparation method of composite modified titanium dioxide for degrading automobile exhaust

technical field

The invention relates to a method for preparing composite modified titanium dioxide (TiO ₂ ) for degrading automobile tail gas, and belongs to the technical field of car tail gas treatment.

Background technique

With the continuous development of my country's national economy and the continuous improvement of highway and urban road construction, the number of motor vehicles in the country has exceeded 300 million. On the whole, affected by the rigid demand of the market, my country's motor vehicle market will continue to develop in the future. China will be in a period of rapid development. However, a large amount of harmful exhaust gas emitted by fuel vehicles during driving has caused serious harm to people's health and the natural environment. Nowadays, the more serious smog weather, the pollution of automobile exhaust is also one of the important reasons. As a developing country, my country's automobile manufacturing technology level is generally not high, so the single-vehicle emissions are relatively large, and the durability of emission control performance is low, resulting in a substantial increase in pollutant emissions. Exhaust emissions from automobiles are very harmful to human health, irritating the respiratory tract, reducing the immunity of the respiratory system, leading to an increase in the incidence of chronic bronchitis, bronchitis, dyspnea and other diseases in the exposed population, and symptoms of decreased lung function. At the same time, the amount of motor vehicle exhaust inhaled by children is twice that of adults. Long-term inhalation of these gases may cause anemia, eye diseases, nephritis, etc. Some people call the above diseases "urban children's traffic diseases". Therefore, automobile emission pollutants have attracted people's attention.

In recent years, some scholars have considered adding nano-titanium dioxide to paint and asphalt pavement, and using the photocatalytic principle of nano-titanium dioxide to purify automobile exhaust in tunnels, and some results have been achieved. Titanium dioxide is not only a semiconductor material, but also one of the popular catalysts. Its excellent photocatalytic performance, non-toxicity, chemical stability and low cost make it widely used in the field of environmental governance. For example, degrade toxic gases, purify water, deodorize, etc. However, due to the high bandgap energy of _TiO2 , it can only be excited by ultraviolet rays in sunlight, and cannot effectively use visible light, which accounts for about 45% of sunlight, for photocatalytic reactions. Therefore, it is necessary to effectively broaden the spectral response range of _TiO2 . Thus efficiently using sunlight. In addition, due to the low quantum efficiency of TiO ₂ , the separation time of photo-generated electrons and holes generated by TiO ₂ is relatively short, and it is easy to recombine. Therefore, the transfer of photo-generated electrons and holes in a short time affects the photocatalytic efficiency of TiO ₂ .

Therefore, how to improve the absorption rate of TiO ₂ to visible light and improve the effect of TiO ₂ in degrading automobile exhaust under visible light conditions has become one of the key issues of research. Although many attempts have been made to adjust the microstructure of TiO ₂ , due to the limitations of the performance of TiO ₂ itself, the application prospect of purely relying on TiO ₂ as a photocatalyst is still subject to many restrictions. Therefore, improving the quantum yield of the photocatalytic reaction and improving the utilization rate of sunlight through modification has become a commonly used method. The common modification methods mainly include semiconductor recombination, rare earth element doping, metal ion modification, noble metal deposition, Doping with non-metallic elements, etc.

At present, people mainly prepare TiO ₂ through three methods: liquid phase, gas phase and solid phase. Each of these methods has advantages and disadvantages. _TiO2 prepared by the gas phase method has the advantages of good dispersibility, high purity, small particle size, and visible light transmittance. However, the gas-phase method also has the disadvantages of complex preparation equipment, difficulty in popularization, and high energy consumption costs. In contrast, the liquid-phase method has the advantages of simple equipment, low cost, and easy operation, and is currently the first choice in the industrial field, especially in laboratory preparation. The solid-phase method equipment has a relatively simple process, but the product quality is not high in purity and is easily polluted. It is mainly suitable for some applications that do not have strict requirements on the shape and size of TiO ₂ . As a kind of liquid phase method, the hydrothermal method dissolves and recrystallizes insoluble or insoluble substances through a high temperature and high pressure environment to realize the formation and modification of inorganic compounds. It can not only prepare single-component tiny crystals, but also prepare Two-component or multi-component special compound powder can not only carry out reactions that cannot be completed at normal temperature, but also overcome some unavoidable hard agglomeration after high temperature treatment.

Therefore, the present invention provides a method for preparing composite modified _TiO2 for degrading automobile exhaust. According to the unique advantages of the hydrothermal method, multi-walled carbon nanotubes and copper ions are used to prepare composite modified _TiO2 in good shape for photocatalysts. It is used to degrade the main components such as hydrocarbons, nitrogen oxides, carbon monoxide, and carbon dioxide in automobile exhaust, expand its light absorption band to visible light, increase the absorption rate of visible light, and improve the photocatalytic efficiency of TiO ₂ , so as to achieve its effective degradation of automobile exhaust performance and improve air quality.

Contents of the invention

(1) Technical issues

The purpose of the present invention is to provide a method for preparing composite modified _TiO2 for degrading automobile exhaust, which solves the problem that _TiO2 can only absorb ultraviolet light, is difficult to use visible light, has low degradation efficiency, is difficult to control the form of prepared _TiO2 , and has low reactivity. High problem, thus improving the photocatalytic efficiency of _TiO2 .

(2) Technical solution

In order to solve the technical problems such as the low utilization efficiency of visible light, the easy recombination of photogenerated electron-hole pairs and the poor degradation effect on automobile exhaust of TiO ₂ prepared by conventional methods. The present invention firstly selects carbon nanotubes and copper ions as dopants according to the principle of photocatalysis of _TiO2 , and then uses the composite effect of carbon nanotubes and copper ions to improve the _TiO2 photocatalytic degradation of automobiles according to the good reaction conditions of the hydrothermal method. The effect of exhaust gas provides a method for preparing composite modified _TiO2 for degrading automobile exhaust. The technical scheme of the present invention is as follows: first, prepare a mixed solution of concentrated sulfuric acid and concentrated nitric acid in a beaker, add multi-walled carbon nanotubes, ultrasonically disperse, heat and stir in an oil bath; then use reflux equipment and deionized water to wash the multi-walled carbon Nanotubes to make the pH value meet the requirements, after drying, add titanium isopropoxide into deionized water, and add the multi-walled carbon nanotubes prepared after drying treatment, ultrasonically disperse; finally add copper nitrate solution and concentrated sulfuric acid, stir After that, it was transferred to a high-pressure reactor, and after reacting for 12 hours, the obtained product was washed with deionized water, dried, and ground to prepare multi-walled carbon nanotubes and copper ion composite modified nano-TiO ₂ . The invention adopts multi-walled carbon nanotubes prepared by a hydrothermal method and copper ion composite modified TiO ₂ to further improve the degradation effect of TiO ₂ on automobile tail gas during use and improve road traffic environmental quality.

(3) Beneficial effect

At present, the widely used vehicle exhaust treatment method is to purify the exhaust gas by installing an exhaust treatment device in the exhaust system of the vehicle through chemical and physical treatment methods, in addition to improving the vehicle fuel and using new energy to control the exhaust gas emission. However, some environmentally friendly vehicle energy sources are likely to affect the service life and performance of motor vehicles, and the imperfect supporting facilities of new energy vehicles have also prevented people from effectively improving their acceptance. As a new generation of high-efficiency and environmentally friendly catalysts, nanoscale photocatalysts have broad application prospects in the purification of automobile exhaust, and good research progress has been achieved. And because the nano-scale catalyst has the advantages of high selectivity, high catalytic activity and anti-poisoning, its purification and catalytic efficiency is much higher than that of traditional catalysts. This method aims to explore a method for preparing modified nano-TiO ₂ to achieve the purpose of further exerting the photocatalytic performance of TiO ₂ .

Detailed ways

The invention provides a kind of composite modified _TiO2 preparation method for degrading automobile tail gas, concrete implementation steps are as follows:

(1) Prepare 100 ml of concentrated sulfuric acid and concentrated nitric acid mixture in a beaker at a volume ratio of 3:1, add 0.5 g of multi-walled carbon nanotubes, ultrasonically disperse for 5 minutes, heat and stir in an oil bath at 120°C for 15 minutes ;

(2) Using a suction filtration device and deionized water to wash the multi-walled carbon nanotubes multiple times to make the pH value reach 6, and dry at 60°C for 12 hours;

(3) 20 milliliters of titanium isopropoxide was added to 12 milliliters of deionized water, and the dried multi-walled carbon nanotubes were added, and ultrasonically dispersed for 10 minutes;

(4) Add 8 milliliters of copper nitrate solution and 24 milliliters of concentrated sulfuric acid, after stirring for 15 minutes, transfer to a pressure reactor with a pressure of 3.5 MPa, and react for 12 hours at 200° C.;

(5) The product obtained in the reaction kettle was washed with deionized water to make the pH value reach 6, and dried at 80°C for 24 hours, and then multi-walled carbon nanotubes and copper ion composite modified nano-TiO were prepared by grinding. ₂ .

Claims (1)

1. a kind of composite modified _TiO that is used to degrade automobile tail gasPreparation method, it is characterized in that the concrete steps of this method are as follows: (1) Prepare 100 ml of concentrated sulfuric acid and concentrated nitric acid mixture in a beaker at a volume ratio of 3:1, add 0.5 g of multi-walled carbon nanotubes, ultrasonically disperse for 5 minutes, heat and stir in an oil bath at 120°C for 15 minutes ; (2) Using a suction filtration device and deionized water to wash the multi-walled carbon nanotubes multiple times to make the pH value reach 6, and dry at 60°C for 12 hours; (3) 20 milliliters of titanium isopropoxide was added to 12 milliliters of deionized water, and the dried multi-walled carbon nanotubes were added, and ultrasonically dispersed for 10 minutes; (4) Add 8 milliliters of copper nitrate solution and 24 milliliters of concentrated sulfuric acid, after stirring for 15 minutes, transfer to a pressure reactor with a pressure of 3.5 MPa, and react for 12 hours at 200° C.; (5) The product obtained in the reaction kettle was washed with deionized water to make the pH value reach 6, and dried at 80°C for 24 hours, and then multi-walled carbon nanotubes and copper ion composite modified nano-TiO were prepared by grinding. ₂ .