engleski

Statistička analiza specifične površine i konverzije cerija dopiranog manganom

The most prominent and recently explored use of ceria nanoparticles is the catalytic ability of metal-doped ceria and its suitability for oxidation of various pollutants. Different metal ions can penetrate the ceria lattice. However, the choice of metals and their ability to enter the lattice depends on the choice of synthesis route. Doped ceria exhibits higher catalytic activity because it has a greater oxygen storage capacity and a larger specific surface area. Numerous techniques for the synthesis of ceria and ceria- doped nanoparticles have been reported in the literature, such as mechanochemical synthesis, sol-gel, hydrothermal synthesis, precipitation, thermal decomposition, etc. In this work, pure ceria and manganese-doped ceria previously prepared by sol-gel [1], hydrothermal [2] and mechanochemical [3] synthesis were analyzed. Analysis of variance (ANOVA) was used to evaluate the influence of manganese content and synthesis method on the specific surface area and conversion ability of the prepared samples. Manganese-doped ceria nanoparticles were prepared by sol-gel, hydrothermal, and mechanochemical methods followed by thermal treatment at 500 °C for 2 hours. Four samples were obtained by each method, pure ceria and samples doped with 10%, 20% and 30% manganese. Specific surface areas were determined by N2 gas adsorption-desorption isotherms from Micromeritics ASAP2000 instrument at –196 °C. The samples were previously degassed at 100 °C under a dynamic vacuum of 7 mPa. The activities of the prepared catalysts were measured in an integral up-flow fixed bed reactor at atmospheric pressure [4]. Toluene was used as a model volatile organic compound. The catalytic oxidation of toluene was carried out under isothermal conditions and in a temperature range from 100 to 500 ºC. The toluene conversions obtained at 200 °C were used for statistical analysis. StatEase Design Expert 7.0 software was used for statistical analysis of the data obtained. Specific surface area (SSA) and toluene conversion (TC) were analyzed based on the variation of two factors, manganese content (numerical factor) and synthesis method (categorical factor). Based on the R-squared values, the analysis showed that the linear model should be used to predict the specific surface area. On the other hand, the 2FI (two-factor interaction) model was proposed for the evaluation of toluene conversion. Analysis of variance revealed statistically significant models confirmed by low p-values: 0.0103 for SSA and 0.0003 for TC (square root transformation), and high F-values: 7.5 for SSA and 31.31 for the square root of TC. The residuals in the normal plot were linear, supporting the condition that the error terms are normally distributed. Numerical optimization showed desirable results using the criteria of maximized specific surface area as well as maximized toluene conversion (Fig. 1). The most desirable Mn content is 30% for all synthesis routes. However, the optimization showed that sol-gel synthesis is the preferred method since the result obtained for toluene conversion is 94.6% desirable. Statistical analysis led to models that can easily predict the specific surface area and toluene conversion results as a function of the amount of manganese dopant and the synthesis method chosen.

statistička analiza, cerij, dopiranje manganom

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