Promoting Effects of Acid Treatment on Catalytic Performance of K-Sepiolite Clay Fibers for Soot Oxidation

In this study, sepiolite clay fibers were activated through hydrochloric acid acidification at various concentrations. The effects of different acid environments on the phase structure, morphology, and physicochemical properties of the activated sepiolite fibers were studied extensively. It was found that calcite impurities can be effectively removed when the acid concentration exceeds 1 M. Furthermore, the specific surface area of K-supported sepiolite fibers increases continuously with rising acid concentration, reaching 107.9 m2/g when the hydrochloric acid concentration is 7 M. The soot temperature-programmed oxidation (TPO) results demonstrated that K-supported sepiolite fibers acidified with 3 M HCl exhibited the highest catalytic activity, with T10 and T50 values of 323 °C and 348 °C, respectively. The 10 wt% K-supported sepiolite paper catalyst, using 3 M HCl-activated sepiolite fibers as the matrix, exhibited the lowest T50 value of 436 °C and showed excellent stability compared to all other paper catalyst samples. This study on the activation of sepiolite-based catalysts under various acidic conditions advances the development of highly active and stable mineral catalytic materials and facilitates their practical application.