The Layered Manganese Oxide Synthesis And Its Application For Toluene Catalytic Combustion

Volatile organic compounds?VOCs?are the major precursors to cause some air pollution problems?e.g.photochemical smog,haze?.Low temperature catalytic oxidation has gained increasing attention due to its efficient and economical way converting VOCs into harmless CO₂ and H₂O without secondary pollution.Nowadays,more and more modern factories can discharge less pollutant with lower concentration.Thus,in some cases like painting factories?e.g.automobile and furniture manufacturing etc.?,the low temperature catalytic oxidation removal of VOCs with low concentration?hundreds of ppm?and big air volume is still a great challenge.MnO_x not only has comparable activity to noble metal catalysts in the removal of VOCs,but also is inexpensive and abundant.The major results are shown as follows.?1?Three kinds of two-dimensional?2D?layered?-MnO₂?K-Ox,K-MES and K-Et?catalysts were synthesized via the redox-precipitation reaction between KMnO₄ and oxalic acid,2-?N-morpholino?ethane sulfonic acid?MES?and ethanol,respectively.Among them,K-Et had the highest concentration of oxygen vacancies,consequently highest low-temperature reducibility and lowest apparent activation energy?E_a?in toluene catalytic oxidation.The catalyst K-Et achieved an outstanding catalytic performance that T₅₀0 and T₉₀of toluene catalytic oxidation were 172 and 195?,respectively.And the conversion rate of toluene to CO₂ over K-Et at 200? maintained at ca.95%during the 42 h measurement.?2?Furthermore,by in-situ diffuse reflectance infrared Fourier transform spectroscopy?DRIFT?,the catalytic pathway of toluene on K-Et was deduced,it has confirmed that H₂O can help further decrease the E_a in toluene catalytic oxidation,accelerate the production of intermediate species and their conversion to the final products?CO₂ and H₂O?.In addition,when the SO₂ gas?the concentration was more than 100 ppm?was introduced into the reaction flue,the SO₂ gas would chemisorb on the surface of catalyst and then the accumulation phenomenon occurs.The higher the concentration of SO₂,the more serious the accumulation phenomenon is.Moreover,the accumulation phenomenon will not be alleviated with the increase of temperature,resulting in the decrease of catalyst activity and the deactivation of catalyst.?3?The K-Et are synthesized at room temperature with simple preparation and low cost.They have the advantages of high catalytic activity,good catalytic stability and unique hydrophilicity.This work shows a possibility of realizing high catalytic performance of toluene catalytic oxidation on one-component manganese oxide system.