In recent years, with the rapid development of industry and the rapid increase of population, volatile organic compounds (VOCs) emissions into the air have increased dramatically, which has become the main cause of air pollution, seriously endangering human health and restricting the sustainable development of social economy. It is urgent to seek reasonable and effective control technology to solve VOCs Pollution. Catalytic combustion is a kind of treatment technology to realize high efficiency combustion of VOCs. Because of its advantages of low ignition temperature, high treatment efficiency and no secondary pollution, it shows great competitiveness in the process of VOCs purification. The core problem of catalytic combustion technology lies in the design and preparation of highly efficient and stable catalysts. Noble metal catalysts (such as Pt, PD and Au) have high catalytic activity and selectivity. However, due to the scarcity of resources and high price, these catalysts are usually supported on the support, and used as a negative catalyst for VOCs catalytic combustion. On the one hand, it can improve the dispersion of precious metals, reduce the amount of precious metals, and reduce the cost of catalysts. On the other hand, it can play a synergistic role between precious metals and supports, and improve the catalytic performance of catalysts.
1Pt catalyst
Pt catalyst has a high catalytic activity for VOCs combustion. As a supported catalyst, its activity is often affected by many factors, such as the nature of the support, particle size and Pt loading. Due to the specific surface area, pore structure, pH value and hydrophobicity of the support, the dispersion of active components, the adsorption of reactant molecules and the interaction between metal and support are usually greatly affected, which greatly determines the catalytic activity of the supported Pt catalyst; Therefore, different supports will lead to different VOCs catalytic activity of supported Pt catalyst. In many carriers, γ - Al2O3 has been widely studied and applied because of its large specific surface area, high stability and low cost. Using commercial γ - Al2O3 as the support, ordo et al. Prepared Pt / γ - Al2O3 Catalyst by impregnation method, which was used in the catalytic combustion of benzene, toluene and n-hexane respectively. It was found that the Pt / γ - Al2O3 catalyst had good catalytic combustion activity, and its complete oxidation could be realized under 200 ℃. The results show that the pH value of the support plays an important role in improving the performance of the supported Pt catalyst. Yazawa et al. Found that the supported Pt catalysts prepared with Al2O3, MgO, La2O3, ZrO2, SiO2-Al2O3 and SO42 -- ZrO2 with different pH have obvious differences in propane catalytic activity. The stronger the acid is, the better the catalyst activity is. This is due to the strong oxidation resistance of Pt on acid support, which makes Pt / SO42 -- ZrO2 Catalyst have the most excellent oxidation resistance At 227 ℃, the conversion of propane is over 80%. Compared with the conventional Al2O3 supported Pt catalyst, the supported Pt catalyst (such as Pt / H-ZSM-5 and Pt / mcm-14, etc.) prepared with molecular sieve as the support has better dispersion of Pt metal, and the porous characteristics of molecular sieve can effectively prevent the generation of by-products and the occurrence of carbon deposition, thus showing better aromatics catalytic combustion activity. As the water vapor generated by VOCs catalytic combustion is easy to agglomerate in the catalyst channel, it is easy to passivate the catalyst. Therefore, the hydrophobicity of the support plays an important role in maintaining high catalytic activity and good stability of the supported catalyst. It was found that supported Pt catalysts prepared by porous polystyrene (SDB), activated carbon and carbon aerogels as carriers exhibited excellent catalytic activity for Toluene Combustion. Among them, Pt / SDB catalyst can realize the complete oxidation of toluene under the reaction temperature of 150 ℃, which shows that porous hydrophobic support can not only inhibit the generation of by-products and the occurrence of carbon deposition, but also effectively remove the water vapor on the surface of catalyst, thus greatly improving the performance of catalyst.
1Pt catalyst
Pt catalyst has a high catalytic activity for VOCs combustion. As a supported catalyst, its activity is often affected by many factors, such as the nature of the support, particle size and Pt loading. Due to the specific surface area, pore structure, pH value and hydrophobicity of the support, the dispersion of active components, the adsorption of reactant molecules and the interaction between metal and support are usually greatly affected, which greatly determines the catalytic activity of the supported Pt catalyst; Therefore, different supports will lead to different VOCs catalytic activity of supported Pt catalyst. In many carriers, γ - Al2O3 has been widely studied and applied because of its large specific surface area, high stability and low cost. Using commercial γ - Al2O3 as the support, ordo et al. Prepared Pt / γ - Al2O3 Catalyst by impregnation method, which was used in the catalytic combustion of benzene, toluene and n-hexane respectively. It was found that the Pt / γ - Al2O3 catalyst had good catalytic combustion activity, and its complete oxidation could be realized under 200 ℃. The results show that the pH value of the support plays an important role in improving the performance of the supported Pt catalyst. Yazawa et al. Found that the supported Pt catalysts prepared with Al2O3, MgO, La2O3, ZrO2, SiO2-Al2O3 and SO42 -- ZrO2 with different pH have obvious differences in propane catalytic activity. The stronger the acid is, the better the catalyst activity is. This is due to the strong oxidation resistance of Pt on acid support, which makes Pt / SO42 -- ZrO2 Catalyst have the most excellent oxidation resistance At 227 ℃, the conversion of propane is over 80%. Compared with the conventional Al2O3 supported Pt catalyst, the supported Pt catalyst (such as Pt / H-ZSM-5 and Pt / mcm-14, etc.) prepared with molecular sieve as the support has better dispersion of Pt metal, and the porous characteristics of molecular sieve can effectively prevent the generation of by-products and the occurrence of carbon deposition, thus showing better aromatics catalytic combustion activity. As the water vapor generated by VOCs catalytic combustion is easy to agglomerate in the catalyst channel, it is easy to passivate the catalyst. Therefore, the hydrophobicity of the support plays an important role in maintaining high catalytic activity and good stability of the supported catalyst. It was found that supported Pt catalysts prepared by porous polystyrene (SDB), activated carbon and carbon aerogels as carriers exhibited excellent catalytic activity for Toluene Combustion. Among them, Pt / SDB catalyst can realize the complete oxidation of toluene under the reaction temperature of 150 ℃, which shows that porous hydrophobic support can not only inhibit the generation of by-products and the occurrence of carbon deposition, but also effectively remove the water vapor on the surface of catalyst, thus greatly improving the performance of catalyst.
