Lindlar catalysts comprising of palladium/calcium carbonate modified with lead acetate and quinoline are widely employed industrially for the partial hydrogenation of alkynes. However, their use is restricted, particularly for food, cosmetic and drug manufacture, due to the extremely toxic nature of lead, and the risk of its leaching from catalyst surface. In addition, the catalysts also exhibit poor selectivities in a number of cases. Here we report that a non-surface modification of palladium gives rise to the formation of an ultra-selective nanocatalyst. Boron atoms are found to take residence in palladium interstitial lattice sites with good chemical and thermal stability. This is favoured due to a strong host-guest electronic interaction when supported palladium nanoparticles are treated with a borane tetrahydrofuran solution. The adsorptive properties of palladium are modified by the subsurface boron atoms and display ultra-selectivity in a number of challenging alkyne hydrogenation reactions, which outclass the performance of Lindlar catalysts.

This Communication describes the synthesis of highly monodispersed 12 nm nickel nanocubes. The cubic shape was achieved by using trioctylphosphine and hexadecylamine surfactants under a reducing hydrogen atmosphere to favor thermodynamic growth and the stabilization of {100} facets. Varying the metal precursor to trioctylphosphine ratio was found to alter the nanoparticle size and shape from 5 nm spherical nanoparticles to 12 nm nanocubes. High-resolution transmission electron microscopy showed that the nanocubes are protected from further oxidation by a 1 nm NiO shell. Synchrotron-based X-ray diffraction techniques showed the nickel nanocubes order into [100] aligned arrays. Magnetic studies showed the nickel nanocubes have over 4 times enhancement in magnetic saturation compared to spherical superparamagnetic nickel nanoparticles.

The deactivation by sulfur and regeneration of a model Pt/Ba/Al2O3 NOx trap catalyst is studied by hydrogen temperature programmed reduction (TPR), X-ray diffraction (XRD), and NOx storage capacity measurements. The TPR profile of the sulfated catalyst in lean conditions at 400°C reveals three main peaks corresponding to aluminum sulfates (~550°C), "surface" barium sulfates (~650°C) and "bulk" barium sulfates (~750°C). Platinum plays a role in the reduction of the two former types of sulfates while the reduction of "bulk" barium sulfates is not influenced by the metallic phase. The thermal treatment of the sulfated catalyst in oxidizing conditions until 800°C leads to a stabilization of sulfates which become less reducible. Stable barium sulfides are formed during the regeneration under hydrogen at 800°C. However, the presence of carbon dioxide and water in the rich mixture allows eliminating more or less sulfides and sulfates, depending on the temperature and time. The regeneration in the former mixture at 650°C leads to the total recovery of the NOx storage capacity even if "bulk" barium sulfates are still present on the catalyst.

A series of 1wt%Pt/xBa/Support (Support = Al2O3, SiO2, Al2O3-5.5wt%SiO2 and Ce0.7Zr0.3O2, x = 5-30wt% BaO) catalysts was investigated regarding the influence of the support oxide on Ba properties for the rapid NOx trapping (100s). Catalysts were treated at 700°C under wet oxidizing atmosphere. The nature of the support oxide and the Ba loading influenced the Pt-Ba proximity, the Ba dispersion and then the surface basicity of the catalysts estimated by CO2-TPD. At high temperature (400°C) in the absence of CO2 and H2O the NOx storage capacity increased with the catalyst basicity: