Preparation Of Paper-like Microfibers Entrapped Catalyst For Trace CO And VOCs Catalytic Combustion In Gas

Catalytic oxidation is considered as the best available control technology（BACT）for the volatile organic compounds（VOCs）treatment and also widely used in CO removal.For the poor mass/heat transfer and high press drop of traditional fixed bed,a novel structured fixed-bed based on microfibers entrapped catalyst with higher contacting efficiency was fabricated to enhance the catalytic reaction rate in this paper.The preparation conditions and application performance of the microfibers entrapped catalyst were investigated according to CO oxidation and VOCs combustion for industrial applications.Firstly,paper-like stainless steel fibers entrapped catalysts were prepared from two different paths and characterized by SEM,XRD,XPS and H₂-TPR.The granular catalysts were entrapped into stainless steel fibers with three-dimensional network for all catalysts,but the active components of the Cu/Cr/Ag impregnated carbons（ASC）,such as Cu²⁺and Cr⁶⁺,were reduced to Cu⁺,Cu⁰ and Cr⁶⁺by activated carbon for directly entrapped process,respectively.MnOx were well dispersed on the Al₂O₃ and granular activated carbon（GAC）by impregnation method.The catalytic activity order of the catalysts was obtained as follow:ASC﹥Mn-GAC﹥Mn-GAC/PSSF≈Mn-Al₂O₃/PSSF﹥﹥MFE-ASC.The structured fixed-bed with Mn-GAC/PSSF catalyst exhibited a lower press drop and better stability for CO oxidation in rich hydrogen gas at higher temperature.Secondly,the performances of Mn-GAC/PSSF catalysts with different Mn loadings and calcination temperatures were investigated for CO oxidation at different reaction conditions.The results indicated that higher catalytic activity could be achieved over the catalysts by higher Mn loading with Cu dopped under thelower calcination temperature.The CO conversion over Mn-GAC/PSSF catalysts which calcinated at 500℃with 10%,20%and 30%Mn loadings were 38.8%,48.8%and 49.4%respectively.Meanwhile,the CO conversion over20%-Mn-GAC/PSSF catalyst was decreased by 3.1%with the GHSV increased from 5732 h^-1to 9553 h^-1,while it was only 9%over granular Mn-GAC catalyst.The results indicated that the mass transfer efficiency of Mn-GAC/PSSF catalyst is much higher than that of granular Mn-GAC catalyst.Furthermore,the highest CO conversion could be promoted to 94%over the 20%-Cu-Mn-GAC/PSSF（Cu/Mn=0.5）catalyst at 235℃。Then,MEK combustion was analyzed in the structured fixed-bed with Mn-Al₂O₃/PSSF catalyst.The results revealed that the Mn-GAC/PSSF catalysts were much more active than Mn-GAC granular catalyst due to the excellent mass transfer and contacting efficiency of the PSSF structure which exhibited high selectivity for MEK complete oxidation.The T₅₀ and T₉₀of 20%-Mn-GAC/PSSF catalyst were 41℃and 60℃lower than that of the 20%-Mn-GAC catalyst,respectively.Al₂O₃ was preferable for microfibrous entrapped composite materials with20%Mn loaded and calcined at 400℃.The?T₉₀ were 28℃and 3℃as the GHSV increased from 7643 to 15286,then to 22929 h^-1,20℃and 3℃as the initial concentration of MEK decreased from 1000 to 2000,then to 3000 mg·m^-3,respectivly.The results revealed that the paper like microfibers entrapped Mn based catalyst has a broad scope of application.Finally,the complete combustion kinetic of MEK over 20%-Mn-Al₂O₃/PSSF catalyst has been investigated by using Power-law rate and Mars-van Krevelen models.The results showed that the rate date could be fitted to both of the two models,the Mars-van Krevelen kinetic model was more suitable and provided an excellent prediction of the kinetic date,which suggested that the reaction mechanism was oxidation-reduction,and the surface reduction and oxidation reaction activation energies were 40.73 kJ/mol and 44.67 kJ/mol,relatively.