Microfibrous LTA Zeolite Membrane Catalyst For Catalytic Combustion Of Acetone By Chemical Vapor Deposition

There are many pharmaceutical factories and chemical factories in the developed areas in China,especially in the Yangtze River delta,Pearl River delta and beijing-tianjin-tangshan area.The volatile organic compounds(VOCs)which are emitted from these factories without purification damage environment seriously.At present,many purification technologies,such as absorption method,condensation method,adsorption method,membrane separation method,catalytic combustion method,photocatalysis and microbial degradation have been developed to deal with this problem.Among these methods,the catalytic combustion method has been paid greatly attention due to its wide application,high efficiency as well as high security.The key technique of this method is preparation of catalysts,however,conventional preparation methods like wet impregnation and hydrothermal synthesis are not so satisfactory due to their low atom utilization,severe agglomeration and poor dispersity.Therefore,it is necessary to develop new and effective method for catalysts preparation.In this work,the novel Cu/LTA/PSSF and Fe/LTA/PSSF catalysts were preliminarily prepared by chemical vapor deposition(CVD),and the characterization as well as their catalytic activity in acetone oxidation was tested to investigate the feasibility of the CVD method in the preparation of microfibrous zeolite catalysts and their application.Firstly,the preparation technique of microfibrous zeolite catalysts Cu/LTA/PSSF and their application in acetone oxidation in a structured zeolite membrane reactor were investigated.The precursor,paper-like sintered stainless steel fibers(PSSF),was prerared by wet layup papermaking and sintering process and the supports,LTA/PSSF composites,were prepared by in situ hydrothermal synthesis.The synthesized PSSF and LTA/PSSF composites were characterized by XRD,SEM and N2 adsorption and desorption isotherms.The results showed that the continuous and uniform LTA zeolite membrane was successfully synthesized on the surface of PSSF via hydrothermal synthesis,and the thickness of the zeolite membrane was about 3 ?m.The uniform CuO coating was successfully synthesized on the surface of LTA/PSSF to obtain Cu/LTA/PSSF catalysts through CVD and calcination process with copper acetylacetonate(Cu(acac)2)as precursor.The catalytic performance of Cu/LTA/PSSF catalysts was tested and the effects of copper loading,calcination process,preparation method and catalysts support were studied.The results of the XRD and SEM revealed that the average crystallite size of CuO particles loaded on the LTA/PSSF via CVD(14 nm)is smaller than their counterpart via IM(25 nm),on the other hand,the dispersion of CuO by CVD was higher than that by IM.The results illustrated that the copper loading affected catalytic activity of catalysts made by CVD.Higher performance can be reached with copper loading increasing from 1% to 10%,becauseT50 and T90 decreased by 20 ?.The catalysts prepared by IM and by CVD method have their own advantages at the same copper loading,the catalytic activity of catalyst prepared by CVD performed better than the materials prepared by IM method at the temperature higher than 285 ?(T90 at 310? for IM and 300 ? for CVD,respectively)for the conversion of acetone.In addition,the support also made a difference,the Cu/LTA/PSSF catalysts performed better than Cu/LTA granular catalysts,with T90 of 288 ? and 348 ?,respectively.Secondly,the preparation technique of microfibrous zeolite catalysts Fe/LTA/PSSF and their application in acetone oxidation in a structured zeolite membrane reactor were investigated.The uniform Fe2O3 coating was successfully synthesized on the surface of LTA/PSSF to obtain Fe/LTA/PSSF catalysts through CVD and calcination process with ferric acetylacetonate(Fe(acac)3)as precursor.The cristal structure,morphological structure,distribution of active component,pore structure,valence state of active component and reducibilityof the synthesized catalysts were characterized by XRD,SEM,EDS mapping,BET,XPS and H2-TPR,respectively.The catalytic performance of Fe/LTA/PSSF catalysts was also tested and the effects of factors like iron loading,calcination process,preparation method and cataltsts support were studied.The H2-TPR and XPS results showed that Fe3+ was the predominant oxidation state of Fe and the Fe/LTA/PSSF presented pretty good reducibility.The 10% Fe/LTA/PSSF-IM presented the highest catalytic activity according to T90.