Showing papers by "Fernando Cárdenas-Lizana published in 2013"
TL;DR: In this article, the gas phase hydrogenation of p-chloronitrobenzene (p-CNB) over a series of laboratory-synthesized and commercial Pd (1-10% wt) supported on activated carbon and non-reducible (SiO2 and Al2O3) and reducible (ZnO) oxides has been examined.
Abstract: 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...
107 citations
TL;DR: In this paper, a comprehensive evaluation of the catalytic applications of Au in hydrogenation, assessing the benefits relative to conventional transition metal (e.g. Pt, Pd and Ni) catalytic systems is provided.
Abstract: With increasing emphasis placed on cleaner chemical synthesis, energy efficiency and waste minimisation, the manufacture of pharmaceuticals and fine chemicals is undergoing a progressive shift from conventional stoichiometric organic processes to a harnessing of catalytic selectivity. In hydrogenation processes, gold catalysts have untapped potential in terms of selectivity in the reduction of a target functionality in multifunctional reactants. This Review provides a comprehensive evaluation of the catalytic applications of Au in hydrogenation, assessing the benefits relative to conventional transition metal (e.g. Pt, Pd and Ni) catalytic systems. Hydrogenation activity requires the formation of nanoscale Au particles that are (typically) anchored to oxide supports. The crucial catalyst structural and surface properties required to achieve enhanced hydrogenation performance in terms of rate, selectivity and stability are discussed. The synthesis procedures and characterisation methodologies directed at catalyst optimisation are evaluated. The practical application of Au catalysts is illustrated taking, as a case study, the hydrogenation of nitroaromatics, where critical features such as hydrogen adsorption/activation, structure sensitivity, metal–support interactions and active site characteristics are discussed. Commonality with the catalytic action of supported Ag is flagged with a consideration of the future outlook and direction for selective hydrogenation using Au catalysts.
86 citations
TL;DR: In this article, the authors reported a 99.9% yield of aminocompounds and high TOF (up to 61 s−1) in the liquid-phase hydrogenation of several para-substituted (-OH, -OCH3, -CH 3, -H, -Br, -Cl, -COOH and -NO2) nitroaromatics over quasi-monodispersed (ca. 3.3 nm from microscopy and CO chemisorption) Pt nanoparticles.
47 citations
TL;DR: In this paper, the gas-phase hydrodechlorination of 2,4-dichlorophenol (at 423 K) has been studied over Au/Fe2O3 prepared by deposition-precipitation.
45 citations
TL;DR: In this paper, the effect of unsupported Pd nanoparticle size in the selective C≡C semi-hydrogenation of alkynols with different alkyl chains was studied.
Abstract: We have studied the effect of unsupported Pd nanoparticle (NP) size in the selective C≡C semi-hydrogenation of alkynols with different alkyl chains, i.e., C16 in dehydroisophytol (DIP) (to isophytol (IP)) vs C1 in 2-methyl-3-butyn-2-ol (MBY) (to 2-methyl-3-buten-2-ol (MBE)). The Pd NPs were synthesized via colloidal technique with poly(N-vinyl-2-pyrrolidone) (PVP) as stabilizing agent where a range of crystal sizes (2.1–9.8 nm; confirmed by HRTEM) was generated. Both reactions show antipathetic structure sensitivity consistent with higher specific activity (TOF) over larger Pd NPs where the structure sensitivity effect is more pronounced for NPs ≤ 3.0 nm. All the Pd NPs exhibit high (≥88%) selectivity to the target alkenol product at almost complete (98%) conversion. Increased IP selectivity (SIP; XDIP=98%ca. 95%) was observed over smaller (2.1–3.0 nm) Pd NPs while ca. 98% selectivity to MBE (SMBE; XDIP=98%) is obtained irrespective of particle size. The kinetic results were consistent with a Langmuir–Hin...
35 citations
TL;DR: In this article, a comprehensive evaluation of the catalytic applications of Au in hydrogenation, assessing the benefits relative to conventional transition metal (e.g. Pt, Pd and Ni) catalytic systems is provided.
Abstract: With increasing emphasis placed on cleaner chemical synthesis, energy efficiency and waste minimisation, the manufacture of pharmaceuticals and fine chemicals is undergoing a progressive shift from conventional stoichiometric organic processes to a harnessing of catalytic selectivity. In hydrogenation processes, gold catalysts have untapped potential in terms of selectivity in the reduction of a target functionality in multifunctional reactants. This Review provides a comprehensive evaluation of the catalytic applications of Au in hydrogenation, assessing the benefits relative to conventional transition metal (e.g. Pt, Pd and Ni) catalytic systems. Hydrogenation activity requires the formation of nanoscale Au particles that are (typically) anchored to oxide supports. The crucial catalyst structural and surface properties required to achieve enhanced hydrogenation performance in terms of rate, selectivity and stability are discussed. The synthesis procedures and characterisation methodologies directed at catalyst optimisation are evaluated. The practical application of Au catalysts is illustrated taking, as a case study, the hydrogenation of nitroaromatics, where critical features such as hydrogen adsorption/activation, structure sensitivity, metal–support interactions and active site characteristics are discussed. Commonality with the catalytic action of supported Ag is flagged with a consideration of the future outlook and direction for selective hydrogenation using Au catalysts.
10 citations