WANG Hao, ZHAO Shuohan, WANG Qiulong, DU Jingxin

(State Key Laboratory of Silicate Building Materials, School of Materials and Engineering, Wuhan University of Technology, Wuhan 430070, Hubei, China)

Extended Abstract:[Background and purpose] How to deal with the styrene waste gas produced in industrial production is a challenge, in terms of environmental protection. At present, the currently available styrene treatment methods include photocatalytic oxidation, activated carbon adsorption, traditional RTO technology, condensation recovery and biological drip filtration, among which the commonly used and efficient method is to use activated carbon or molecular sieve adsorption of styrene, while the adsorption material as solid waste incineration treatment or RTO combustion furnace treatment of styrene. These processes have various problems, such as large heat accumulation and requirement of insulation materials, easy blockage after styrene crosslinking during combustion, resulting in high fuel consumption and reduced production safety.[Methods] The combination of adsorption and catalytic combustion was adopted. Microwave absorbing heating honeycomb ceramics were made from wave-absorbing heating materials as the carrier. Sol-gel method was used to prepare (CeO₂-CuO)/TiO₂ on the surface of wave-absorbing heating honeycomb ceramics for low-temperature adsorption of catalytic combustion catalysts. The styrene is adsorbed and cross-linked on surface of the honeycomb ceramics, while the honeycomb ceramics can be heated rapidly through the microwave heating. The styrene can be burned and decomposed in situ at a lower temperature through microwave heating, with the generation of harmless CO₂ and H₂O.[Results] Complexing agents, C₆H₈O₇, C₁₀H₁₄N₂Na₂O₈, C₆H₁₅NO₃, were used to complex Ce³⁺ and Cu²⁺. The effects of complexing agents on micromorphology of the coatings were studied. The adsorption and thermal decomposition of the catalysts for styrene treatment were also evaluated. Phase composition, microstructure and specific surface area of the three low temperature adsorption catalytic combustion catalysts were characterized by using X-ray diffractometer (XRD), scanning electron microscope (SEM), automatic specific surface area and porosity analyzer. CeO₂ and CuO diffraction peaks have the highest intensity at 600 ℃, without secondary phase. The catalyst coated with C₁₀H₁₄N₂Na₂O₈ as the complexing agent has uniform grain distribution, small particle size and homogeneous dispersion. These nanoparticles are stacked closely and randomly, which enriches the pore structure of the catalyst, increases the pore area of the catalyst and enables the catalyst to have more catalytic active sites. These will help to improve the adsorption capacity and microwave catalytic decomposition capacity of styrene. In the temperature range of 100–200 ℃, the catalytic conversion rate of the catalyst is better than other catalysts.[Conclusions] C₁₀H₁₄N₂Na₂O₈ has the highest adsorption efficiency for styrene and the highest catalytic conversion efficiency under microwave conditions. The catalyst particle sizes are in the range of 20–30 nm, the catalyst coating is of network structure, with large specific surface area, uniform pore size distribution and styrene adsorption efficiency of 95%. Under microwave conditions, the ignition temperature of styrene is only 90 ℃, the catalytic activity is the highest at 200 ℃, and the catalytic conversion rate reaches 90%.

Key words: microwave; styrene treatment; adsorption; catalytic combustion; sol-gel method