Waste materials for activated carbon preparation and its use in aqueous-phase treatment: a review.

A facile method to fabricate high-surface area functional carbons via convenient "salt templating" is presented. Exemplarily, nitrogen- as well as nitrogen-/boron-co-doped carbons were synthesized using ionic liquids as precursors and eutectics as porogen. The porogen is easily removable with water and the porosities can be adjusted from micro- to mesoporous depending on the salt nature and amount.

“Salt Templating”: A Simple and Sustainable Pathway toward Highly Porous Functional Carbons from Ionic Liquids

Stone-fruit activated carbon (SAC) and modified versions containing acidic oxygen and basic nitrogen groups have been used to prepare palladium catalysts by wet impregnation. Carbon supports and catalysts are investigated by thermo-gravimetric analysis, TPD, oxygen chemisorption, TEM and XPS. The influence of the nature of the functional groups on the dispersion and oxidation state of palladium and its activity in hydrogen oxidation is investigated. Pd dispersion is found to increase with the basic strength of functional groups on the support. XPS reveals that introduction of amine groups in SAC results in an increased proportion of Pd0, resistant to re-oxidation. Palladium catalysts supported on activated carbon modified by diethylamine groups are found to exhibit the highest metal dispersion and greatest activity in hydrogen oxidation.

The influence of surface functionalization of activated carbon on palladium dispersion and catalytic activity in hydrogen oxidation

Vapor phase hydrogenation of nitrobenzene is reported on 1 wt.% Pd supported on hydrotalcite, MgO and γ-Al2O3 catalysts. The catalysts were prepared in the laboratory using a wet impregnation method and were characterized by XRD, BET surface area, TPR, TEM, XPS and CO chemisorption studies. The conversion of nitrobenzene was studied in the temperature region of 498–573 K and compared on all the catalysts. An impressive catalytic performance of nitrobenzene conversion was observed on hydrotalcite supported Pd catalyst. CO chemisorption and TEM results prove that palladium disperses better on hydrotalcite supports when compared with other conventional supports such as MgO and γ-Al2O3, which is responsible for the high conversion of nitrobenzene.

Hydrogenation of nitrobenzene over palladium-supported catalysts—Effect of support

The gas phase (1 atm, 453 K) hydrogenation of p-chloronitrobenzene (p-CNB) over a series of laboratory-synthesized and commercial Pd (1–10% wt) supported on activated carbon (AC) and non-reducible (SiO2 and Al2O3) and reducible (ZnO) oxides has been examined. Reaction over these catalysts generated the target p-chloroaniline (p-CAN) (via selective hydrogenation) and nitrobenzene (NB)/aniline (AN) as a result of a combined hydrodechlorination/hydrogenation. A range of Pd nanoparticles with mean sizes 2.4–12.6 nm (from HRTEM and H2/CO chemisorption) were generated. Both the p-CNB transformation rate and H2 chemisorption increased with decreasing Pd size. Residual Mo (from the stabilizer used in the synthesis of Pd colloids) suppressed activity, but this was circumvented by the use of poly(N-vinyl-2-pyrrolidone) (PVP). Pd/AC generated p-CAN and AN as principal products, Pd on SiO2 and Al2O3 exhibited hydrodechlorination character generating AN and NB, and Pd/ZnO promoted the sole formation of p-CAN at all le...

Selective Gas Phase Hydrogenation of p-Chloronitrobenzene over Pd Catalysts: Role of the Support

Two active carbons from Algerian date pits prepared by chemical activation at moderate temperature (500-600 degrees C) with H3PO4 and ZnCl2 and one commercial active carbon (from Darco) have been oxidized with air at different temperatures (300-450 degrees C) and with nitric acid in severe conditions during a short time. It has been demonstrated that air treatment generates surface oxygenated groups (XPS) that have an acidic character (simplified Boehm titration), without degrading the specific surface area (BET). Each active carbon has an optimal oxidation temperature depending on its activation procedure and corresponding to 20% in weight loss during the oxidation process. This optimal temperature achieves the highest surface oxygen content, which is directly correlated to the global acidity. It also means that when the support is loaded with 5% Pd by incipient wetness method, the catalyst exhibits the best activity for the liquid phase hydrogenation of nitrobenzene to aniline. In general, the metallic dispersion of the catalysts (CO chemisorption) remained appreciable even after oxidizing treatments. Exception is noted when nitric acid is used as oxidant while the active carbon has been prepared using zinc chloride. (c) 2005 Elsevier B.V. All rights reserved.

P. Verhasselt

Papers

Effect of oxidant treatment of date pit active carbons used as Pd supports in catalytic hydrogenation of nitrobenzene