Adsorption and catalytic properties of Fe/Cr-pillared bentonites

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 0.791 mmol/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 4 h using the experimental conditions of t = 30 °C, pH 3.7 and mcat = 5 g/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.

The figures show N2-, CO2- and H2-adsorption isotherms of Fe-, Fe/Cr- and Cr-pillared-bentonites.Figure optionsDownload as PowerPoint slideHighlights
► The figures show N2-, CO2- and H2-adsorption isotherms of Fe-, Fe/Cr- and Cr-pillared-bentonites.
► Fe-, Cr- and Fe/Cr-pillared bentonites were tested as adsorbent for CO2/H2 adsorption.
► Also as catalysts for catalytic wet peroxide oxidation reaction.
► Adsorption capacity and catalytic activity are higher for the Fe/Cr0.1–PB.
► Increasing pH and temperature decreased time needed to achieve a 100% conversion.
► Iron pillars are more stable than chromium pillars.