The Fabrication And Soot Catalytic Oxidation Performance Of Sepiolite Paper Catalyst

The elimination of catalytic oxidation of soot particles?PM?at lower temperatures is an important challenge facing the current solution to atmospheric composite pollution.Compared to traditional honeycomb catalysts,paper-type catalysts have the advantages of small specific gravity,high porosity,and good gas diffusion performance,which have very attractive application prospects in the elimination of soot.Sepiolite fiber is an inexpensive chain-like layered silicate mineral with strong adsorption capacity and ion exchange performance.In this paper,the sepiolite fiber was used as the matrix to construct the paper catalyst for the elimination of soot for the first time.The influences of the preparation process and the active components on the catalyst structure and soot catalytic oxidation activity were studied.Using acidified sepiolite fiber as matrix,together with a small amount of mullite fiber,polyvinyl alcohol as organic binder,sodium hexametaphosphate as dispersant,and various kinds of inorganic binders?sodium silicate,cerium sol,aluminum sol,zirconium sol?,the sepiolite fiber paper catalysts have been prepared by traditional paper-making method.The effects of processing process on the structure and catalytic activity of sepiolite fiber paper catalysts were investigated extensively.It was found that the application of sodium silicate and cerium sol as inorganic binders can generate spheroids on the surface of the matrix fibers,which was beneficial to increase the contact degree between the catalyst and soot.While agglomerates appeared in the samples using zirconium sol and aluminum sol as inorganic binders,which was unfavorable for increasing the contact degree between the catalyst and soot,and leading to reduced catalytic activity.Among all of the samples,the SFP-Si used sodium silicate as inorginc binder exhibited the best catalytic activity,in which the T_m is 398°C,T₁₀ is 345°C,T₅₀ is 398°C,T₉₀ is 420°C.The order of catalytic activities towards soot oxidation was as follows:SFP-Si>SFP-Ce>SFP-Zr>SFP-Al.The effects of weight ratio between sepiolite fibers and mullite fiber on the structure and catalytic activities of KNO₃@SFP-Si fiber paper catalyst were studied.It was found that the tensile strength increased with the increased contents of mullite fiber in the range of 0⁵0%.Meanwhile,it displayed the highest porosity of 97.89%for the sample with the contents of 20%for mullite fibers.The order of catalytic activities towards soot oxidation was as follows:SFP-1>SFP-5>SFP-2>SFP-4>SFP-3.The catalytic activities were reduced first and then enhanced with the increased amounts of mullite fibers.When the mullite fibers accounts for 10%,it has the best overall properties including good catalytic activity and mechanical properties.Various kinds of active ingredients,such as KNO₃,CeO₂,Fe₂O₃,Ce-Fe,and Ce-Fe-K,were loaded on the sepiolite fiber paper with the same composition.The loading amount was determined to be about 10 wt%.The order of catalytic activities for the sepiolite fiber paper catalysts loaded with the above active ingredients was as follows:KNO₃>Ce-Fe-K>CeO₂>Fe₂O₃>CeO₂-Fe₂O₃.It was believed that KNO₃ can effectively increase the surface fluidity and improve the catalystic activity,which was benefited to the favorable transfer of soot and active components inside the paper catalyst.When grinding with carbon black,the catalytic activity of sepiolite fiber paper catalyst loaded with CeO₂-Fe₂O₃-KNO₃ active component was improved significantly,and the T_m was 378°C.