Adsorption and catalytic properties of Fe/Cr-pillared bentonites
2012
Tomul, Fatma
This paper presents a study of the adsorption and catalytic properties of bentonites pillared with iron (Fe), chromium (Cr) and iron/chromium pillars with different Fe/Cr molar ratios and calcined at 350°C. The carbon dioxide (CO₂) and hydrogen (H₂) adsorption properties exhibited by the pillared bentonites were studied. The highest CO₂ and H₂ adsorption capacities for the Fe/Cr-pillared bentonite sample with a Fe/Cr molar ratio of 1/9 (Fe/Cr0.1–PB) were 0.691 and 0.791mmol/g, respectively. The equilibrium data for the CO₂ and H₂ adsorptions were analysed using the Freundlich, the Langmuir and the Redlich–Peterson isotherm models. The results were used to estimate the adsorption parameters and relate them to the pillar type. The results show that the CO₂ and H₂ adsorptions of the pillared samples follow different isotherm equations. The catalytic activity was evaluated for the catalytic wet peroxide oxidation of phenol. The highest catalytic activity was observed for the Fe/Cr0.1–PB sample; a 100% phenol conversion was achieved in 4h using the experimental conditions of t=30°C, pH 3.7 and mcₐₜ=5g/L. Using the same catalyst, the oxidation rate of phenol increased when the temperature was raised from 30°C to 50°C; this increase is a result of the higher H₂O₂ decomposition and OH⁻ production rates. The oxidation rate of phenol also increased when the initial pH was raised from 3.7 to 5.
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