Evaluation of Surface Acido‐Basic Properties of Inorganic‐Based Solids by Model Catalytic Alcohol Reaction Networks

The characterization of acido‐basic properties of the surface of inorganic solids is essential to understand the behavior of catalysts during heterogeneous catalyzed reactions. The use of alcohols as reactive probe molecules to investigate these properties has been developed since the 1970s, and in 1991, a new alcohol, 2‐methylbut‐3‐yn‐2‐ol (MBOH), was proposed. This review sums up the knowledge accumulated for 15 years on this model reaction network and compares its advantages with those of other alcohols. The operating conditions are reviewed, and deactivation phenomena are analyzed. Then, from investigations of correlations with other techniques able to reveal the acido‐basic properties of surfaces, it is concluded that MBOH appears to be the most valuable reactive probe molecule as the nature of the sites involved in the different routes of its network is unambiguous. The links that may exist between the rate of a model reaction and the thermodynamic acido‐basic properties of the surface are then discussed. It is shown that even when true kinetics parameters are available, they are not necessarily correlated to thermodynamic parameters. What can be expected from a model reaction network is to evaluate the reactivity of a surface along an acidic or a basic route. In basic sites, this reactivity may be related to the nucleophilicity of the surface or to the way the deprotonated intermediate is stabilized on the surface. It can be used to follow the modifications of a series of materials during synthesis and to identify the factors governing a reaction of practical interest.     

Preparation and Catalytic Properties of a Ru(II) Coordinated Polyimide Supported by a Ligand Containing Terpyridine Units

The synthesis of terpyridine-based polyimide catalysis for hydrosilylation reaction is outlined in this work. 5,5′′-Bis(bromomethyl)-2,2′:6′,2′′-terpyridine was polymerized with the corresponding diimide derivatives of dianhyrides to give polyimides utilizing the terpyridine unit in the main chain. The synthesis of polyimides containing Ru(II) complexes in the side chain is described. Condensation polymerization is used to synthesize the macromolecular backbone and, as a result, the Ru(II) complex was attached via coordination chemistry. The material design emphasizes the relationship between the molecular structure and supramolecular organization of these polymers. It demonstrates that terpyridyl complexes remain a versatile functionality for constructing supramolecular assemblies. The terpyridine unit may enhance the electron carrier mobility of the polymers, while the incorporation of ruthenium complexes into a conjugated polymer significantly changes the catalytic properties of the resulting polymers. The prepared polyimide-supported catalyst provides superior catalytic activity (70–79%), selectivity and stability in the hydrosilylation of acetophenone. The catalyst can be easily isolated from the reaction product, which benefits recycling. The catalysts were reused for four experiments.     

Catalytic property of Fe-Al pillared clay for Fenton oxidation of phenol by H2O2

Clay pillared with Fe-Al was synthesized as a catalyst for Fenton oxidation of phenol by hydrogen peroxide (H₂O₂). The pillaring process altered the basal space of clay, which is related to the amounts of aluminium and iron in the pillaring solution. The catalytic activity of the pillared clay was attributed to the accessible iron species, whose amount is regulated not only by the introduced iron species but also by the basal space that subsequently depends on the introduced aluminium species. The heterogeneous Fenton reaction exhibited an induction period followed by an apparent first order oxidation of phenol by H₂O₂. The induction period was proposed as an activation process of the surface iron species, which is thus enabled to complex with the reactants. The induction time (t_I) depended on temperature (T) and pH condition but irrelevant to the concentrations of phenol and H₂O₂ and the amount of catalyst. The rate of the oxidation process was evaluated with respect to the concentrations of phenol and H₂O₂, the amount of catalyst, pH and temperatures. During the catalytic reaction the trend of iron leaching showed an ascending period and a descending period, which was related to the presence of ferrous ions and ferric ions. The Fe-Al pillared was recovered through two procedures, dry powder and slurry, which have different effect on the induction period.     

Catalytic Performance of Ce1−x Ni x O2 Catalysts for Propane Oxidative Steam Reforming

The model, proposed by Peskov et al. (Catal Today 105:223, 2005) to describe kinetic oscillations observed in the N₂O + H₂ reaction on Ir(110), is used to illustrate the effect of periodic perturbation of the reactant pressures on oscillations. The attention is focused on the conversion of natural period-1 oscillations to period-1 oscillations with the imposed frequency. For this conversion, simultaneous perturbation of both reactant pressures is found to be much more efficient compared to perturbation of one of the pressures.