The selective reaction of one part of a bifunctional molecule is a fundamental challenge in heterogeneous catalysis and for many processes including the conversion of biomass-derived intermediates. Selective hydrogenation of unsaturated epoxides to saturated epoxides is particularly difficult given the reactivity of the strained epoxide ring, and traditional platinum group catalysts show low selectivities. We describe the preparation of highly selective Pd catalysts involving the deposition of n-alkanethiol self-assembled monolayer (SAM) coatings. These coatings improve the selectivity of 1-epoxybutane formation from 1-epoxy-3-butene on palladium catalysts from 11 to 94% at equivalent reaction conditions and conversions. Although sulphur species are generally considered to be indiscriminate catalyst poisons, the reaction rate to the desired product on a catalyst coated with a thiol was 40% of the rate on an uncoated catalyst. Interestingly the activity decreased for less-ordered SAMs with shorter chains. The behaviour of SAM-coated catalysts was compared with catalysts where surface sites were modified by carbon monoxide, hydrocarbons or sulphur atoms. The results suggest that the SAMs restrict sulphur coverage to enhance selectivity without significantly poisoning the activity of the desired reaction.

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Facet-specific growth is highly desirable for catalysts, as conversion and selectivity can be altered with increasing amounts of particular active sites. The (100) surface of a rock-salt structure is comprised of alternating oxygen anions and metal cations, similar to the (110) facet. The (111) surface differs substantially in that an ideal (111) surface would consist solely of oxygen anions or metal cations, and cannot exist as-is.However, wet chemical syntheses of MgO(111) and NiO(111) have recently been reported; theory and experiments show the (111) surface is stabilized as a hydroxylated surface. These (111) faceted metal oxides exhibit catalytic properties that differ significantly from their (100) counterparts. Here, we discuss the theory and performance of the (111) rock-salt metal oxides in catalysis, as supports, and as adsorbents.

Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) has been used for lipid analysis; however, one of the drawbacks of this technique is matrix interference peaks at low masses. Metal oxide surfaces are described here for direct, matrix-free analysis of small (MW < 1000 Da) lipid compounds, without interferences in the resulting spectra from traditional matrix background peaks. Spectra from lipid standards produced protonated and sodiated molecular ions. More complex mixtures including vegetable oil shortening and lipid extracts from bacterial and algal sources provided similar results. Mechanistic insight into the mode of ionization from surface spectroscopy, negative ion mass spectrometry, and stable isotope studies is also presented. The metal oxide system is compared to other reported matrix-free systems.

Platinum nanoparticles were grown on alumina by atomic layer deposition using either H 2 or O 2 as the second half-reaction precursor. Particle diameters could be tuned between ∼1 and 2 nm by varying between use of H 2 and O 2 and by changing the number of ALD cycles. The use of H 2 as the second precursor led to smaller Pt particle sizes. Differences in particle size were found to be related to the availability of surface hydroxyl groups, which were monitored via in situ infrared spectroscopy during Pt ALD. Temperature-programmed desorption (TPD) of CO and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) for adsorbed CO were used to characterize sites and coordination numbers of the nanoparticles. As expected, smaller nanoparticles had sites with lower average coordination numbers. The catalysts were evaluated for oxidative dehydrogenation of propane to propylene. Catalysts having the smallest Pt particles with the lowest coordination number (synthesized by one cycle of Pt ALD with H 2 ) had a C 3 H 6 selectivity of 37% at 14% conversion, whereas under the same reaction conditions the selectivity was less than 1% for larger (3.6 nm) commercial Pt catalysts at 9% conversion.