The Effect Of CeO₂-based Catalysts In The Abatement Of VOCs And CH₄/CO₂ Reforming

With the rapid development of economic and technology,issues of energy and environment has been the biggest challenge in the world.Volatile organic compounds?VOCs?as the byproducts of the industy are not only damage to the environment,but also great threat to the human health.CO₂ reforming of methane?CRM?has received much attentinon due to the effective utilization of CH₄ and CO₂?weaking the greenhouse effect and producing the syngas for Fischer-Tropsch synthesis.Ceria,with the uniqie function of storge/release oxygen,reversible transformation between Ce³⁺and Ce⁴⁺and high lattice oxygen activity,etc.,has been regarded as an important catalyst for VOCs combustion and CRM.But the catalytic activity of pure CeO₂ is quite low.In this thesis,we focus on the unique physical chemical properties of CeO₂,adopting several methods to improve the catalytic activity of CeO₂-based catalysts,such as:controlling the microstructure of nano CeO₂,loading active metal,researching the metal-ceria effect and exploring the activation of reactant molecule adsorbed on the catalysts,etc..The main innovation points and research results are shown as follows:1?The Pt/CeO₂ nanocomposites of Pt nanoparticles partially confined in the mesopores of microsized mesorprous CeO2 with Pt loading of 1.0 wt%?Pt/CeO2-MM?exhibits a excellent catalytic activity for benzene oxidation.Compared Pt nanoparticles supported on the flat surface of CeO₂ nanocubes?Pt/CeO₂-NC?,the catalytic reaction temperature of T₅₀?corresponding to the benzene conversion=50%?and T₉₀?corresponding to the benzene conversion=90%?for Pt/CeO₂-MM tremendously decrease?T₅₀=149?and?T₉₀=196?,respectively.The turnover frequency?TOF?of Pt/CeO₂-MM at 140?increases by 9.0 times as compared to that of Pt/CeO₂-NC.The tremendous enhancement in the catalytic activity is due to a novel metal support interaction in Pt/CeO₂-MM.The novel metal support interaction is theoretically studied by density function theory calculation and experimentally studied by CO-TPR,CO-TPD,H₂ pulse titration and HRTEM.The theoretical and experimental evidence reveal that the partial confinement of Pt nanoparticles in the mesopores of microsized mesoporous CeO₂ leads to a significant enhancement in the activity of the surface lattice oxygen around the interface between Pt nanoparticles and CeO₂,thus tremendously increasing the catalytic activity.2?The Pt/CeO₂ nanocomposites of Pt nanoparticles partially confined in the mesopores of microsized mesorprous CeO₂ with Pt loading of 1.0 wt%?Pt/CeO₂-MM?exhibits a highly efficient photocatalytic activity for complete oxidation of benzene with the irradiation of full solar spectrum,visible-infrared and infrared light.A novel photoactivaton process induced by hot electrons gengerated upon solar light irradiation is found to significantly enhance the solar light-driven thermocatalytic activity:Pt/CeO₂-MM exhibit high efficiency catalytic activity and durability for benzene oxidation under the irradiation of 500 W Xe lamp.Even under the visible-infrared and infrared light irradiation,Pt/CeO₂-MM alao showns efficient catalytic activity for benzene oxidation.The highly efficient photocatalytic activity aries from the solar light-driven thermocatalysis on the Pt/CeO₂ nanocomposite due to the excellent thermocatalytic activity and local heating effect by the strong surface plasmonic absorption of Pt nanoparticles in the entire solar spectrum region.in-situ FTIR in the dark and with solar light irradiation reveals that the hot electron-induced photoactivation of benzene adsorbed on the Pt nanoparticles in the Pt/CeO₂-MM plays a decisive role in the catalytic enhancement.3?A nanocomposite of Pt nanoparticles supported on mesoporous CeO₂ nanorods?Pt/CeO₂-MNR?was prepared by a facile method.The Pt/CeO₂-MNR nanocomposite exihibits highly efficient catalytic activity for CRM under the focused irradiation of full solar spectrum and visible-infrared light from a Xe lamp without using additional electric heater.Under the full solar spectrum irradiation,it produces very high production rate of H₂ and CO(5.7 mmol min^-1 g^-1,6.0 mmol min^-1 g^-1),and its solar-to-fuel efficiency is as high as 10.3%.Remarkably,even under the visible-infrared irradiation with wavelengths above 690 nm,the Pt/CeO₂-MNR nanocomposite still exihibits efficient catalytic activity with high production rate of H₂ and CO(3.3 mmol min^-1 g^-1,3.7 mmol min^-1 g^-1)and high solar-to-fuel efficiency?10.6%?.The Pt/CeO₂-MNR nanocomposite exihibts excellent catalytic durability.After irradiated for 100 h,its catalytic activity almost unchanged.The highly efficient catalytic activity of the Pt/CeO₂-MNR nanocomposite derives from a novel solar-light-driven thermocatalytic process of CRM becuase of its high thermocatalytic activity and efficient photothermal conversion due to its strong absorption in the entire solar spectrum region.4?A series of Ni/CeO₂ catalysts with different Ni content were prepared by the facil sol-gel method used Ce?NO₃?₃·6H₂O,Ni?NO₃?₂·6H₂O and C₆H₈O₇·6H₂O at 80?.Ni/CeO₂-C has a strong absorption band in the full solar spectrum,visible-infrared and infrared light and can efficiently transform the absorbed light into thermal energy.The Ni/CeO₂-C nanocomposite exhibits highly efficient catalytic activity for CRM under the focused irradiation of full solar spectrum,visible-infrared and infrared light from a Xe lamp without using additional electric heater.Under the focused full solar spectrum irradiation,Ni/CeO2-C produces very high production rate of H2 and CO(6.5mmol min^-1 g^-1,6.3 mmol min^-1 g^-1),and its solar-to-fuel efficiency is as high as 11.1%.Even under the infrared irradiation with wavelengths above 830 nm,the Ni/CeO₂-C nanocomposite still exihibits efficient catalytic activity with high production rate of H₂and CO(1.6 mmol min^-1 g^-1,2.1 mmol min^-1 g^-1)and high solar-to-fuel efficiency?4.1%?.Under a novel light-driven thermocatalysis for CRM,Ni/CeO₂-C exhibits execellent durability for light-driven thermocatalysis.