Rafael García

Glycerol hydrogenolysis to 1,2-propanediol (1,2-PDO) was performed over activated carbon supported copper-based catalysts. The catalysts were prepared by impregnation using a pristine carbon support and thermally-treated carbon supports (450, 600, 750, and 1000 °C). The final hydrogen adsorption capacity, porous structure, and total acidity of the catalysts were found to be important descriptors to understand catalytic performance. Oxygen surface groups on the support controlled copper dispersion by modifying acidic and adsorption properties. The amount of oxygen species of thermally modified carbon supports was also found to be a function of its specific surface area. Carbon supports with high specific surface areas contained large amount of oxygen surface species, inducing homogeneous distribution of Cu species on the carbon support during impregnation. The oxygen surface groups likely acted as anchorage centers, whereby the more stable oxygen surface groups after the reduction treatment produced an increase in the interaction of the copper species with the carbon support, and determined catalytic performances.

BACKGROUND: There exists now a widely held view that the methane storage capacity on an activated carbon is not related to any of the routinely determined properties of the adsorbent, such as surface area or micropore volume. This has been confirmed and a correlation pursued with other physical and/or chemical properties of both commercially available carbons and those prepared in the laboratory. Textural characteristics (from nitrogen adsorption isotherms at 77 K) considered were BET‐equivalent specific surface area, DR micropore volume and Horvath–Kawazoe micropore size distribution. Chemical properties were evaluated using Fourier transform infrared (FTIR) spectroscopy, thermal programmed decomposition (TPD) and Boehm titrations. Both kinetic and equilibrium methane adsorption experiments were performed at 273 and 298 K and up to 3.5 MPa.RESULTS: Using phosphoric acid to activate peach stones together with additional thermal treatment enabled the production of activated carbons with 137 v/v methane adsorption capacity at 298 K.CONCLUSIONS: The presence of acidic surface functional groups has a detrimental influence on methane uptake, due to the chemical inertness of the adsorbate and/or to pore blockage of the adsorbent. Basic surface functional groups (pyrone), together with a desirable pore size distribution centered at ca 0.8 nm, are thought to be responsible for improved methane adsorption capacity on such activated carbons. Copyright © 2009 Society of Chemical Industry

BACKGROUND: A comparative study of the influence of preparation variables in the activation of pine sawdust and peach stones with phosphoric acid is presented. Adsorptive properties of these materials were tested for the clarification of apple juice and the decolorization of red wine. The main objective of this study was to identify the influence of the textural and chemical properties of activated carbons on clarification and decolorization processes.RESULTS: The role of impregnation conditions in porosity development was more important for activated carbons originating from peach stones than in those originating from pine sawdust, mainly due to their morphological differences. The amount of phosphoric acid retained on the precursors was found to be a function of the impregnation variables. Furthermore, porosity development dependence on phosphoric acid content per gram of precursor was confirmed. For both precursors, the best microporosity development was obtained at a heat treatment temperature of 450 °C. Independently of the preparation variables used, activated carbons from pine sawdust and peach stones had the same type of surface functional groups: mainly phenolic, quinonic and phosphoric ester‐like structures.CONCLUSIONS: From the results of clarifications and decolorization tests, it was confirmed that to obtain good performance in these assays, the development of mesoporosity is crucial. However, when activated carbons had similar mesoporosities, the presence of surface functional groups contributed to improved performance in clarification and decolorization process. Copyright © 2008 Society of Chemical Industry

The removal of chromium(III) in packed columns of zeolite and activated carbon has been studied. The process of Cr(III) exchange in 13X zeolite was optimized using mass transference parameters. In addition, the effects of pH, the presence of interfering ions and the anion associated with the chromium in the solution were studied. It was found that particle diameter controls the Cr(III) exchange in the zeolite, indicating that particle diffusion predominantly controls the process of Cr(III) exchange in 13X zeolite. A mixed system of zeolite and activated carbon columns increased the efficiency of chromium removal from diluted wastewater. This effect occurred due to the reduction of the organic matter (chemical oxygen demand), adsorption of chromium, and interfering ions on the activated carbon column. The activated carbon + zeolite column system emerges as an alternative method in Cr(III) removal from tannery effluents. Copyright © 2005 Society of Chemical Industry