Effect of the Synthesis Method of MgAl2O4 and of Sn and Pb Addition to Platinum Catalysts on the Behavior in n-Butane Dehydrogenation

Hydrogenation of CO to olefins over a supported iron catalyst on MgAl2O4 spinel: effects of the spinel synthesis method

In the process of CO hydrogenation to olefins by the Fischer–Tropsch synthesis (FTO), the support is a key factor in the activity, selectivity, and thermal and chemical stability of the catalysts, and magnesium aluminate spinel (MgAl₂O₄) has recently been reported to be very effective. In this work, three methods, namely, citric acid solution combustion (MAC), EDTA sol–gel (MAG) and NH₃-coprecipitation (MAP) have been employed to prepare the spinel with detailed characterization of the structure, specific surface area, porosity, and alkalinity properties of both the as-synthesized spinel and the supported catalysts. The results showed that MAC and MAG possessed stronger basicity with more homogeneous particle sizes and narrower distribution of the pore size due to the formation of the metal-nitrate–chelate-complex. This led to a large quantity of gas being released during calcination, however, stronger interactions between the active phase and MAC resulted in lower CO conversion. The catalyst supported on MAP (CMAP) exhibited the highest CO conversion, the highest selectivity of lower olefins, the shortest induction period of reaction, and the lowest AFS chain growth probability; thus, MAP was suggested as an applicable synthetic method. Based on the CMAP catalyst, the effects of the operational conditions were investigated and a 200 hour stability test was carried out with satisfactory performance.

In the process of CO hydrogenation to olefins by the Fischer–Tropsch synthesis, the support is a key factor in the activity, selectivity, and thermal and chemical stability of the catalysts, and magnesium aluminate spinel has recently been reported to be very effective.

Colloidal synthesis of Pt–In bimetallic nanoparticles for propane dehydrogenation

Recently, Pt-based bimetallic nanoparticles have drawn much attention because of their great catalytic performance and wide applications in diverse fields. In this work, we report that bimetallic Pt–In nanoparticles with uniform size distribution and controllable composition can be synthesized through a one-step, facile colloidal approach. Various characterization tools such as XRD, TEM, XPS, and synchrotron techniques have been used to characterize the as-obtained nanoparticles. It is demonstrated that the Pt and In elements are homogeneously distributed in the whole nanoparticle. The bimetallic Pt–In nanoparticles have shown great catalytic performance, including high activity, high selectivity, and high stability, for the propane dehydrogenation reaction to produce propene, one of the most important chemicals. The excellent catalytic performance makes Pt–In bimetallic nanoparticles promising catalysts in future industrial application.

Stable platinum nanoparticles on specific MgAl2O4 spinel facets at high temperatures in oxidizing atmospheres

The development of thermally stable, nanometer-sized precious metal-based catalysts remains a daunting challenge. Such materials, especially those based on the use of costly platinum metal, are essential and, to date, non-replaceable for a large number of industrially important catalytic processes. Here we report a well-defined cuboctahedral MgAl2O4 spinel support material that is capable of stabilizing platinum particles in the range of 1-3 nm on its relatively abundant {111} facets during extremely severe aging at 800 °C in air for 1 week. The aged catalysts retain platinum dispersions of 15.9% with catalytic activities for methanol oxidation being ~80% of that of fresh ones, whereas a conventional Pt/γ-Al2O3 catalyst is severely sintered and nearly inactive. We reveal the origin of the markedly superior ability of spinel {111} facets, resulting from strong interactions between spinel surface oxygens and epitaxial platinum {111} facets, inspiring the rational design of anti-sintering supported platinum group catalysts.