This work reports on the capability of the O2-activated Cu-ZSM-5 and Cu-MOR zeolites to selectively convert methane into methanol at a temperature of 398 K. A strong correlation between (i) the activity and (ii) the intensity of the 22 700 cm-1 UV-vis band, assigned to the bis(mu-oxo)dicopper core, is found (i) as a function of the reaction temperature, (ii) as a function of the Cu loading of the zeolite, and (iii) in comparison to other Cu materials. These three lines of evidence firmly support the key role of the bis(mu-oxo)dicopper core in this selective, low-temperature hydroxylation of methane.

Increasing demand for renewable feedstock-based chemicals is driving the interest of both academic and industrial research to substitute petrochemicals with renewable chemicals from biomass-derived resources. The search towards novel platform chemicals is challenging and rewarding, but the main research activities are concentrated on finding efficient pathways to produce familiar drop-in chemicals and polymer building blocks. A diversity of industrially important monomers like alkenes, conjugated dienes, unsaturated carboxylic acids and aromatic compounds are thus targeted from renewable feedstock. In this context, on-purpose production of 1,3-butadiene from biomass-derived feedstock is an interesting example as its production is under pressure by uncertainty of the conventional fossil feedstock. Ethanol, obtained via fermentation or (biomass-generated) syngas, can be converted to butadiene, although there is no large commercial activity today. Though practised on a large scale in the beginning of the 20th century, there is a growing worldwide renewed interest in the butadiene-from-ethanol route. An alternative route to produce butadiene from biomass is through direct carbohydrate and gas fermentation or indirectly via the dehydration of butanediols. This review starts with a brief discussion on the different feedstock possibilities to produce butadiene, followed by a comprehensive summary of the current state of knowledge regarding advances and achievements in the field of the chemocatalytic conversion of ethanol and butanediols to butadiene, including thermodynamics and kinetic aspects of the reactions with discussions on the reaction pathways and the type of catalysts developed.

instance, by Venuto, Ho ¨lderich, and Jacobs for zeolite reactions, 7 or by Brunel, Corma, and Ying for the mesoporous molecular sieves; 8 however, comparison with the state-of-the-art at the end of 2001 shows that the field has rapidly expanded over the past few years.

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.

Si liquid NMR and in situ infrared spectroscopy was used to investigate the polycondensation process of tetraethyl orthosilicate (TEOS) in a concentrated aqueous solution of tetrapropylammonium hydroxide (TPAOH) at low temperatures. The composition was characterized by a molar hydrolysis ratio (H 2 O/TEOS) of 6 and a molar TPAOH/TEOS ratio of 0.37. The 29 Si NMR spectra and the infrared spectra of the samples recorded at different reaction times and temperatures were assigned to a limited number of specific silicate polyanions containing three and five rings. The structure directing action of tetrapropylammonium cations was evidenced by the formation of silicate polyanions with a curved hydrophobic SiO 2 surface, such as the bicyclic pentamer, pentacyclic octamer, and the tetracyclic undecamer. At room temperature, the polycondensation process leads to the selective formation of a species containing 33 Si atoms. It occluded a tetrapropylammonium molecule and had the same framework connectivity as in bulk MFI zeolite. This TEOS polycondensation process may be relevant for the first steps of the crystallization of MFI type zeolites.