Catalytic Combustion Of Xylene+Acetone Mixtures Over Mixed Oxide Catalysts

Volatile organic compounds （VOCs） are recognized as major contributors to air pollution.Alot of technologies have been developed for the destruction of VOCs, of which catalyticcombustion attracted special attention and was widely seen as one of the most effectivepollution treatment technologies for consuming less energy and creating no secondary pollution.Catalyst plays a key role for combustion efficiency. This work focused on Ni-Mn-Ce basedcatalysts, mainly concerned with its catalytic combustion ability for VOCs consist of acetoneand xylene, and with its catalytic activity under different humidity atmosphere.In this work, three series of active catalysts based on different metallic compounds wereprepared and their catalytic behavior were studied—（1） three kind of active catalystsrespectively based on metallic oxide: MnOy/Cord, NiO/Cord and CdO/Cord;（2） catalystsbased on NiMnx/SiO₂/Cord （x=0,0.25,0.5,1,2）;（3） catalysts based onMnNiCezOy/SiO₂/Cord （z=0,0.25,0.5,1）.In series （1）, the results showed that the catalytic activity of those catalysts against gaseousVOCs consist of xylene and acetone followed the order of MnOy/Cord>NiO/Cord>CdO/Cord.In series （2）, the composite oxide catalysts showed superior activities to those based onsingle Ni or Mn oxide. In NiMnx/SiO₂/Cord based catalysts, with the increase of x, theactivity increased slowly. When the ratio of Ni to Mn reached1:1, the activity ran up to aceiling level abruptly. However continuing increased x value caused the activities fallingdown.In series （3）, it was discovered that in these catalysts Ce mainly exists in the form ofCeO2, the doped Ce raised the dispersion of active ingredients, decreased their mean crystalparticle size and increased their specific surface area. The results showed that doped Ce notonly enhanced the activity of catalysts against VOCs consist of acetone and xylene, but alsoreduced the negative effect of moisture by increasing the content of Ce. With the increase ofcontent of Ce, the interaction force between H2O molecular and the surface of MnNiCezOy/Al2O3-SiO₂/Cord（z=0,0.25,0.5,1）faded down, therefore the anti-moisture ability of catalystimproved. While the content of Ce raised to a ceiling level, further increase of Ce content ledalmost no promotion to catalytic activity.