The conversion of methane into alcohols under moderate reaction conditions is a promising technology for converting stranded methane reserves into liquids that can be transported in pipelines and upgraded to value-added chemicals. We demonstrate that a catalyst consisting of small nickel oxide clusters supported on ceria-zirconia (NiO/CZ) can convert methane to methanol and ethanol in a single, steady-state process at 723 K using O as an abundantly available oxidant. The presence of steam is required to obtain alcohols rather than CO as the product of catalytic combustion. The unusual activity of this catalyst is attributed to the synergy between the small Lewis acidic NiO clusters and the redox-active CZ support, which also stabilizes the small NiO clusters.

Methane is converted over nickel on ceria zirconia (Ni/CZ) into ethane, aromatics, and hydrogen at steady state up to the thermodynamic limit at temperatures of 350 to 500 °C. At 450 and 500 °C, traces of ethylene are also produced. Ni/NiO particles activate methane and couple the resulting surface species to hydrocarbon products. Large Ni particles are responsible for the formation of carbonaceous deposits. Furthermore, aromatics are formed on these sites. Smaller Ni/NiO particles are responsible for the formation of ethane and ethylene and appear to provide sustained activity. It is suggested that these Ni sites are too small to assemble aromatic deposits, and hence they remain active throughout the reaction.

The hydrogen sulfide composition in biogas ranges from 0 to 5% depending on the feed source to the biogas digester. To meet renewable natural gas specifications of 0–4 ppm of H2S content, technologies that remove H2S from raw biogas feeds are needed. This contribution assesses three adsorbents with similar textural and physical properties but with different amines grafted to the surface. Specifically, materials containing primary, secondary, and tertiary amines at the end of a propyl surface linker grafted on a silica support are explored. H2S adsorption isotherms and cyclic studies are presented for these materials, and it is shown that secondary amines have the best amine efficiency while tertiary amines are the most stable for H2S capture, of the materials studied. The results suggest the consideration of secondary and tertiary amines for the design of amine adsorbents suitable for H2S removal in dilute gas streams over multiple cycles.

A B S T R A C TSilica deposition on the benchmark aqueous phase reforming (APR) catalyst Pt/γ-Al 2 O 3 is studied to prevent or limit hydrolytic attack of the support under hydrothermal APR conditions, for which boehmite formation by support hydration is a known cause for catalyst deactivation. Tetraethyl orthosilicate (TEOS) is employed as a silicon source in a straightforward liquid-phase, silylation process followed by catalyst calcination and reduction. Characterization by X-ray diffraction, temperature-programmed desorption of NH 3 , infrared, 27 Al nuclear magnetic resonance and X-ray photoelectron spectroscopy of the fresh catalysts suggests that silica addition occurs preferentially on the support surface, resulting in weak Brønsted acid sites as well as in the formation of Si-O-Al linkages at the expense of specific surface Lewis acid sites. Silylation and calcination of Pt/γ-Al 2 O 3 causes partial blockage of the metal surface area (12% loss), whereas γ-Al 2 O 3 surface silica modification prior to Pt deposition makes controlled metal deposition difficult. Catalytic performance tests show the overcoated samples to be active in the APR of 5 wt% glycerol, albeit with lower H 2 production rates compared to the benchmark catalyst. Characterization of spent APR catalysts clearly demonstrates that silylation/calcination treatments effectively slows down the transformation of the γ-Al 2 O 3 support due to the formation of a Si-O-Al interface. Overall, the lifetime of the catalyst is increased three-fold as a result of the surface overcoating treatment, with repetitive recycling ultimately leading to loss of the protective silica layer.

Hierarchical micro-mesoporous MCM-22 zeolites were synthesized using hexamethyleneimine and organosilanes as structure directing agents, which enabled the formation of hierarchical zeolites with mesopores created by the voids left by the organosilanes after thermal treatment, without loss of the intrinsic microporosity of the zeolite. The addition of organosilanes to the synthesis medium reduced the incorporation of aluminum atoms into the zeolite framework, making the hierarchical zeolites more hydrophobic than the microporous MCM-22 reference material. Measurements of the contact angles between water droplets and the zeolites pressed into wafers confirmed the distinct hydrophobic character of the samples. The zeolites were used as catalysts for the liquid-phase condensation of glycerol with acetone. Diffusion of the bulky products in the purely microporous zeolites was hindered due to steric constraints. On the other hand, the hierarchical zeolites showed improved catalytic performance in the glycerol condensation reaction, due to greater access to the active acid sites and increased hydrophobicity, which helped in removing water formed in the reaction from the zeolite cavities. The zeolite synthesized with the organosilane bearing 12 carbon atoms in the alkyl chain provided glycerol conversion of 83% in 2 h, while limited conversion of 19% was obtained over the purely microporous sample. In addition to the satisfactory catalytic results observed in the glycerol condensation reaction, the one-pot synthesis procedure employed was simple and allowed the creation of hierarchical zeolites with narrow mesopore size ranges and excellent potential for the conversion of platform molecules derived from biomass sources.