No abstract

An optimized procedure was designed for the preparation of the microporous metal–organic framework (MOF) [Cu3(btc)2] (BTC=benzene‐1,3,5‐tricarboxylate). The crystalline material was characterized by X‐ray diffraction, optical microscopy, SEM, X‐ray photoelectron spectroscopy, N2 sorption, thermogravimetry, and IR spectroscopy of adsorbed CO. CO adsorbs on a small number of Cu2O impurities, and particularly on the free CuII coordination sites in the framework. [Cu3(btc)2] is a highly selective Lewis acid catalyst for the isomerization of terpene derivatives, such as the rearrangement of α‐pinene oxide to campholenic aldehyde and the cyclization of citronellal to isopulegol. By using the ethylene ketal of 2‐bromopropiophenone as a test substrate, it was demonstrated that the active sites in [Cu3(btc)2] are hard Lewis acids. Catalyst stability, re‐usability, and heterogeneity are critically assessed.

A series of bimetallic Fe-Ni/MgAl2O4 catalysts with Fe/Ni ratios between 0 and 1.5 have been examined for methane dry reforming at 923–1073 K, atmospheric pressure, and a CH4/CO2 ratio of 1. The evolution of the catalyst structure during H2 temperature-programmed reduction (TPR), CO2 temperature-programmed oxidation (TPO), and dry reforming is examined using time-resolved in situ X-ray diffraction (XRD). During H2-TPR up to 973 K, Fe2O3 and NiO are reduced to Fe and Ni. Higher temperatures lead to Fe-Ni alloy formation. The alloy remains stable up to 900 K under CO2-TPO and is decomposed to Ni and Fe3O4 at higher temperatures. The Fe-Ni alloy is the active phase while Fe partially segregates from the alloy forming FeO x during dry reforming. This is beneficial as it reduces the surface carbon accumulation through interaction with FeO x lattice oxygen, producing CO. Alternate CH4 and CO2 pulse experiments over Ni, Fe, and Ni-Fe samples showed that dry reforming over Fe-Ni catalysts can follow a Mars–van Krevelen mechanism. A molar Fe/Ni ratio of 0.7 provides the most active and least deactivated catalyst. All studied catalysts can be regenerated by CO2 carbon removal.

Efficient CO transformation from a waste product to a carbon source for chemicals and fuels will require reaction conditions that effect its reduction. We developed a "super-dry" CH reforming reaction for enhanced CO production from CH and CO We used Ni/MgAlO as a CH-reforming catalyst, FeO/MgAlO as a solid oxygen carrier, and CaO/AlO as a CO sorbent. The isothermal coupling of these three different processes resulted in higher CO production as compared with that of conventional dry reforming, by avoiding back reactions with water. The reduction of iron oxide was intensified through CH conversion to syngas over Ni and CO extraction and storage as CaCO CO is then used for iron reoxidation and CO production, exploiting equilibrium shifts effected with inert gas sweeping (Le Chatelier's principle). Super-dry reforming uses up to three CO molecules per CH and offers a high CO space-time yield of 7.5 millimole CO per second per kilogram of iron at 1023 kelvin.

Thermal atomic layer deposition (ALD) of platinum is usually achieved using molecular oxygen as the reactant gas and deposition temperatures in the 250−300 °C range. In this work, crystalline thin films of metallic Pt have been grown by ALD at temperatures as low as 100 °C using (methylcyclopentadienyl)trimethylplatinum (MeCpPtMe 3 ) as the Pt precursor and ozone as the reactant gas. The novel process is characterized by a constant growth rate of 0.45 Å per cycle within the 100−300 °C temperature window. The Pt films are uniform with low impurity levels and close-to-bulk resistivities even at the lowest deposition temperature. We show that the initial growth on SiO 2 surfaces is nucleation-controlled and islandlike and demonstrate the good conformality of the low-temperature ALD process by Pt deposition on anodic alumina nanopores and mesoporous silica thin films.