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Carbon materials have emerged as a new generation of catalysts for the crucial industrial hydrogenation of nitroarenes. Activated carbon, known for its cost-effectiveness and facile modifiability, stands out among various carbon materials. This study focuses on the preparation of N and P co-doped carbons for catalysing the hydrogenation of 1-chloro-4-nitrobenzene. Comprehensive characterisation using thermal analysis (TGA-MS), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, N 2 adsorption at −196 °C, and ICP-MS was performed. The synergistic effect of N and P was evident, with co-doped carbons outperforming their mono-doped counterparts, underscoring the significance of nitrogen. N,P-codoped activated carbon emerges as a promising, active, stable, and selective metal-free catalyst for the hydrogenation of 1-chloro-4-nitrobenzene, leading to 4-chloroaniline. [Display omitted] • N,P-co-doped carbon boosts nitroarene reduction. • Enhanced activity via N,P synergy. • Stable and recyclable catalytic performance. • Superior catalytic performance to mono-doped carbon. [ABSTRACT FROM AUTHOR]

Ti Ce mixed oxides with different Ti/Ce atomic ratios have been synthesized via a solvothermal method and used as supports for platinum nanoparticles. These catalysts were tested in the preferential oxidation of CO in excess of H 2 (PROX reaction) using different feed compositions in order to simulate real conditions. Both, supports and catalysts, were characterized by a wide variety of techniques including N 2 adsorption, XRF, XRD, Raman spectroscopy, XPS, H 2 -TPR, UV–Vis and DRIFTS. The best performance was obtained with the Pt/Ti 0.9 Ce 0.1 O 2 catalyst, what was attributed to the incorporation of Ce atoms in the TiO 2 lattice. 10% at. Ce is the maximum concentration we could incorporate in the TiO 2 lattice by using the solvothermal method. [ABSTRACT FROM AUTHOR]

Steam reforming of glycerol to produce syngas or H 2 -enriched streams is a promising route that has caught the attention of many researchers around the world. This reaction is typically carried out over metal-based catalysts supported on stable materials. Herein we report a study on the effect of Sn on the catalytic properties of Pt/C in the aforementioned reaction. A series of Pt-Sn/C catalysts with different Pt:Sn ratios were prepared and characterized using ICP, H 2 -TPR, TEM and XPS techniques, and they were tested in the glycerol steam reforming reaction at 623 K and atmospheric pressure. The best performance was observed for the catalysts with low tin contents. It was found that Sn promoted oxidation reactions and inhibited methanation. Furthermore, the presence of Sn improved the stability of the catalysts when operating at harsher conditions of temperature and glycerol concentration. A promoter effect of Sn hindering platinum sintering and the formation of coke precursors is proposed as the origin of the observed behaviour. [ABSTRACT FROM AUTHOR]

Activated carbons doped with nitrogen and/or sulfur have been obtained by pyrolysis followed of steam activation of a sulfur containing polymer (polythiophene) and two nitrogen-containing polymers (polyaniline and polypyrrole). These polymers were synthesized by oxidative chemical polymerization in aqueous media of their corresponding monomers. The influence of the steam activation on the textural properties and surface chemistry of the carbons has been evaluated and their catalytic activity has been determined in the hydrogenation reaction of 1-chloro-4-nitrobenzene. The degree of conversion in the reaction depends on the development of adequate porosity in the activated carbon (which is determined by the activation conditions) together with the presence of heteroatoms that act as active catalytic sites, with S showing considerably greater effectiveness than N. A compromise between an acceptable level of doping with sulfur and an adequate porosity is necessary, which has been achieved in a carbon obtained from polythiophene pyrolyzed at 900 °C and steam activated at 800 °C for 4 h, with a specific surface area of 742 m2/g and S content of 1.71 at%. [Display omitted] • N and S containing polymers used as precursors of metal-free doped activated carbons. • S-doped carbons are more active than N-doped carbons in the catalytic hydrogenation of 1-chloro-4-nitrobenzene. • Steam activation at high temperature develops carbon porosity but removes heteroatoms. • Compromise between S-doping and developed porosity is necessary to maximize catalytic performance. • 100 % selectivity in the hydrogenation of the nitro group towards aniline in all cases. [ABSTRACT FROM AUTHOR]

Abstract: A series of pure siliceous and Zn-modified MCM-41 spheres were synthesized at room temperature, atmospheric pressure and at short reaction times. Mesoporous molecular sieves were characterized by a number of techniques: XRD, N2 adsorption, TEM, XPS and NH3–TPD. Pure siliceous MCM-41 exhibits the typical hexagonal array of well-defined pores with a mean pore diameter of 3.0nm. Addition of a small percentage of Zn (Zn/Si ratio 0.02) into the synthesis gel produces a material with increased lattice parameter (a o), pore diameter and total adsorption capacity. These results suggest the incorporation of zinc, with a larger ionic radius, into the silica framework. Unfortunately, higher zinc contents (Zn/Si ratio 0.04) produce a deterioration of the long-range order of the material, together with a decrease in the surface area and total pore volume. In this sample, the presence of small ZnO nanoparticles embedded into the silica matrix can be envisaged. From a catalytic point of view, these Zn-modified MCM-41 mesoporous molecular sieves appear as quite interesting materials to be used as a catalyst by themselves or as a support for noble metal catalysts. [Copyright &y& Elsevier]

Abstract: An impressive enhancement of the catalytic performance of platinum in the vapour phase selective hydrogenation of crotonaldehyde (2-butenal) has been achieved by modifying a ZnO support by addition of Cr(III) cations. The addition of chromium enhances the structural properties of the support (larger surface area) and increases its reducibility. The presence of chromium in the support enhanced the catalytic activity and the selectivity towards the unsaturated aldehyde in such a way that the Pt/Cr–ZnO catalyst showed the best results (in terms of yield and stability) published until now. The improved behaviour of this catalyst has been explained on the basis of the high support reducibility and a proper metal-support interaction. [Copyright &y& Elsevier]