Aída Luz Villa

Decomposition of nitrous oxide in excess oxygen over Co- and Cu-exchanged MFI zeolites

The decomposition of nitrous oxide on several Co- and Cu-ZSM-5 zeolite catalysts was studied in the absence and presence of excess oxygen. Also, the effect of methane addition, as well as catalyst steaming in dry and wet feeds is reported. N2O decomposition with no oxygen in the feed was proportional to metal loading on both catalysts. Co-ZSM-5 was much more resistant than Cu-ZSM-5 in excess oxygen. The tolerance of Co-ZSM-5 catalysts to excessive amounts of oxygen is high when Co2+ is stabilized in the zeolite framework and depends on the catalyst method of preparation. The presence of methane with no oxygen in the feed enhanced N2O decomposition while the addition of both methane and oxygen to the feed decreased N2O conversion on all catalysts tested. Co2+ ions stabilized by ZSM-5 framework have high hydrothermal stability in comparison to Cu2+ -exchanged ZSM-5.

Direct Synthesis of Diethyl Carbonate from CO2 and CH3CH2OH Over Cu–Ni/AC Catalyst

Cu–Ni/AC (Active carbon) catalysts were synthesized and characterized by temperature programmed reduction, X-ray diffraction, Scanning electron microscopy, chemical analysis, and N2 adsorption. Their activities (in terms of TOF) in the direct synthesis of diethyl carbonate from CO2 and CH3CH2OH were also evaluated. The presence of a Cu–Ni alloy phase may explain the significant increase in activity of bimetallic catalysts compared with monometallic samples.

Effect of the substrate and catalyst chirality on the diastereoselective epoxidation of limonene using Jacobsen-type catalysts.

Chiral and achiral Jacobsens catalysts in their homogeneous form or immobilized on Al-MCM-41 exhibit similar catalytic activity during diastereoselective epoxidation of limonene when in situ generated dimethyldioxirane is used as oxidizing agent. Experimental observations suggest that not only the catalyst chiral center but also the substrate chiral center participates in the preferential formation of most diastereomers. Remarkable turnover numbers (TON), up to 288, was achieved over the heterogeneous catalysts in comparison to their homogeneous counterparts (TON up to 46). Catalyst leaching rather than catalyst oxidative degradation was identified as the main source of catalyst deactivation during reutilization tests.

Evaluación de catalizadores Sn-MCM-41 en la producción de nopol

In this contribution the activity of Sn-MCM-41 materials obtained by hydrothermal synthesis and by chemical vapor deposition (CVD) of Sn on MCM41 with several tin precursors is shown. Sn loading and hexagonal channel ordering were obtained by atomic absorption and X ray diffraction, respectively. High activity for nopol was considerable over those materials containing Sn loadings as low as 0.08%

Synthesis at several length scales of zeolite A membranes using a continuous flow method

ABSTRACT Zeolite A membranes were synthesized in the inner side of porous TiO2 and α-Al2O3 tubular supports by a continuous method. The methodology was then used at several scales for preparing membranes on TiO2 and α-Al2O3 supports with lengths of 6, 12 and 25 cm. Formation of an homogeneous zeolite film was confirmed by XRD and SEM in all supports. Single-gas permeation experiments (He, H2, N2 and n-C3H8) indicated that Knudsen diffusion was the predominant mechanism in both supports. All the synthesized membranes present high flux and moderate selectivity to water in water–ethanol mixtures.

Oxidación alílica de monoterpenos con metaloftalocianinas

Results of allylic oxidation of limonene and a-pinene monoterpenes using silica inmovilized metallophthalocyanines as biomimetic catalyts are presented. The effect of the metal was evaluated on the production of verbenone and carvone. The following order of reactivity was observed: Fe > Co> Cr > Mn > Cu. Higher yields to verbenone, 15%, were obtained over FePcS-S and CoPcS-S.