Ricardo López-Medina

Shaping up operando spectroscopy: Raman characterization of a working honeycomb monolith

A new monolithic reactor for operando Raman spectroscopy studies of honeycomb-shaped catalysts has been developed to obtain complete information on these systems, considering the effect of conformation on structure–activity relationships; this is illustrated by Raman-GC monitoring of alumina-supported vanadium phosphorous oxide phases during propane ammoxidation with monolithic and powdered beds.

Tuning of Active Sites in NiNbO Catalysts for the Direct Conversion of Ethane to Acetonitrile or Ethylene

NiO nanoparticles that are highly active for the ethane activation have been prepared. These nanoparticles have been dispersed on the surface of two different Nb2O5 materials by using a novel dry nanodispersion method. This article describes the characterization and catalytic behavior of both series of catalysts as well as the nature of the active sites required for the transformation of ethane into acetonitrile and/or ethylene. It is demonstrated how such active sites present in the catalysts are obtained through this novel dry mixing method. The catalysts obtained are promising catalytic materials for both, ethane ammoxidation and oxidative dehydration (ODH) reactions.

Propane Versus Ethane Ammoxidation on Mixed Oxide Catalytic Systems: Influence of the Alkane Structure

Catalysts from three different catalytic systems, Ni–Nb–O, Mo–V–Nb–Te–O and Sb–V–O, have been prepared, characterized, and tested during both ethane and propane ammoxidation reactions, in order to obtain acetonitrile and acrylonitrile, respectively. The catalytic results show that Mo–V–Nb–Te–O and Sb–V–O catalyze propane ammoxidation but are inactive for ethane ammoxidation whereas Ni–Nb–O catalysts catalyze both, ethane and propane ammoxidation. The activity results, and the characterization of fresh and used catalysts along with some data from previous studies, indicate that the ammoxidation reaction mechanism that occurs in these catalytic systems is different. In the case of Mo–V–Nb–Te–O and Sb–V–O, two active sites appear to be involved. In the case of Ni–Nb–O catalysts, only one site seems to be involved, which underlines that the mechanism is different and take place via a different intermediate. These catalysts activate the methyl groups in ethane, on the contrary, neither ethane nor ethylene appear to adsorb on the Mo–V–Nb–Te–O and Sb–V–O active sites.Graphical Abstract

Niobiosilica Materials as Attractive Supports for Sb–V–O Catalysts

Since niobium species have been described as being able to increase the catalytic properties of the Sb–V–O catalytic system, the main objective of the present paper is to design a non ordered-mesoporous Nb-containing material useful to be used as a support for this kind of catalysts. Such a material has been used as support for Sb–V–O active phases and the catalysts have been characterized and tested for the propane ammoxidation reaction. For comparative purposes, and in order to evaluate the role of niobium species, the study has been also performed with a support without niobium. The results have shown how the incorporation of niobium species into the support matrix with the procedure described here leads to the formation of a very promising catalytic support. The Nb species incorporated into the support cooperate with vanadium species of the SbVOx active phase increasing its performance for nitrile insertion into propane. Since Nb is a common additive that improves the catalytic behavior of different catalytic systems, the mesoporous Nb-containing support described in the present paper could be useful for other catalysts and/or catalytic processes.