Structural Regulation And Soot Oxidation Performance Improvement Of Sepiolite Paper Catalyst

Concerning the regeneration of diesel particulate filter（DPF）at low temperatures,it is urgent to develop new high-efficiency soot oxidation catalyst.Compared with the traditional honeycomb ceramic catalyst,the paper catalyst has the advantages of small specific gravity,high porosity and good gas diffusion capability.As the sepiolite fiber has a large specific surface area,excellent adsorption capacity and ion exchange capacity,the development of sepiolite paper catalysts with high catalytic activity and stability can provide a new way for environmental pollution control and efficient utilization of mineral resources.In this paper,the structure of sepiolite paper catalyst was adjusted by adjusting the acidification conditions of sepiolite fiber,two-step calcination temperature and loading various active components（K,Co,Ba,Ce,Mn）.The enhancement of activity and stability of the catalyst for soot oxidation was studied.The synergistic mechanism of sepiolite paper catalyst was analyzed by CO₂-TPD and XPS.First,sepiolite fibers acidified with hydrochloric acid of different concentrations（0.5-7 M）were selected as the matrix to prepare potassium-supported sepiolite fiber（paper）catalyst.Acid modification can improve the specific surface area,pore volume and pore diameter of sepiolite.As the concentration of hydrochloric acid increased,the T₅₀ of potassium supported sepiolite catalyst fiber value showes a trend of decreasing first and then increasing.K/3HS has the best activity(T₁₀=323℃,T₅₀=348℃)and cycle stability.After loading potassium nitrate on sepiolite paper prepared with acidified sepiolite as the matrix,the T₅₀ value(T₅₀=436℃)of K/3HSP is the smallest in the series sepiolite paper-type catalysts.At the same time,it is found that NO can improve the light-off activity of the K-loaded sepiolite paper catalyst(T₁₀ moves to a lower temperature).The presence of H₂O causes the loss of active components,which in turn leads to a decrease in catalytic activity.Secondly,the structure,catalytic activity and stability of sepiolite fiber paper catalyst were studied by changing the calcination temperature of sepiolite fiber paper carrier and active component.It is found that the different forms of potassium（KNO₃、K₂O and K-O-Si）in sepiolite fiber paper catalysts play a key role in the activity and stability of soot oxidation.With the increase of calcination temperature of sepiolite fiber paper carrier,the porosity and average pore size of sepiolite paper matrix gradually decrease,and k-active species are easier to enter into the structure of sepiolite fiber,forming chemical bonding（confined potassium）,resulting in the decrease of soot oxidation activity.With the increase of calcination temperature,the activity and stability of sepiolite fiber paper catalyst decreased.When the calcination temperature is 400℃,the sample shows the best activity and stability.Finally,by loading a variety of active components（K,Co,Ba,Ce,Mn）,it is found that the stability of the sepiolite fiber paper catalyst in the recycling process is:K/400SP>10K10Ba5Co/SP>10K10Ba/SP>10K5Co/SP>10Ba/SP.Free potassium in10K/400SP is higher.The introduction of Ba changes the structure of sepiolite and improve the catalytic performance of soot oxidation.Adding cobalt reduces free potassium and catalytic activity.Sepiolite fiber paper loads with potassium and Ce reduces the ignition temperature of the catalyst(T₁₀=390℃).