a b s t r a c tThe physical and chemical properties of 1,4-diphenylbutadiyne (DPB) blended with carbon-supported Pd (DPB-Pd/C) in the form of pellets during hydrogenation were investigated. A thermogravimetric analyzer (TGA) was employed to measure the kinetics of the hydrogen uptake by the DPB getter pellets. The kinetics obtained were then used to develop a semi-empirical model, based on gas diffusion into solids, to predict the performance of the getter pellets under various conditions. The accuracy of the prediction model was established by comparing the prediction models with independent experimental data on hydrogen pressure buildup in sealed systems containing DPB getter pellets and subjected to known rates of hydrogen input. The volatility of the hydrogenated DPB products and its effects on the hydrogen uptake kinetics were also analyzed.Published by Elsevier B.V.

Nanoparticles of aluminum metal were generated by passing an aerosol of micrometer-scale (mean 50 μm) particles in argon through an atmospheric pressure plasma torch operated at less than 1000 W. A designed experiment was conducted to investigate the effects of plasma gas flow rate, aerosol gas flow rate, and applied power on the shape, size, and size distribution of the final particles. The size and shape of the metal particles were dramatically impacted by the operating parameters employed. At relatively low powers or at high powers and short residence times, virtually all the particles are spherical. Under other conditions, the particles had spherical heads, and virtually all had tails, some quite long. The particle size distributions also were influenced by the operating conditions. Under most conditions the size distributions were log-normal, consistent with growth by agglomeration. However, under some conditions, the population of particles above or below the mode was far too great to be consistent with a log-normal distribution. For example, the particle distributions tend to show an unusual concentration of very small particles at relatively short residence times and low aluminum feed rates. The distributions tend to show an unusual concentration of large particles at relatively long residence times and high aluminum feed rates. On the basis of the data collected, some simple models of the mechanism of nanoparticle formation were postulated which should be of value in future studies of the process.

Hydrogen spillover over macroscopic distances was demonstrated and exploited in the design of two novel catalytic reactors for 1-butene isomerization. A dual-bed reactor containing separate zones of noble metal and bimetallic catalysts yielded activities up to 2.7 times greater than that of the noble metal alone. The noble metal catalyst contained palladium supported on graphitic carbon. The bimetallic catalyst contained a base metal, either iron or cobalt, and a lanthanide metal, either cerium or praseodymium, also supported on graphitic carbon. The bimetallic catalysts by themselves had no measurable activity at the current experimental conditions. Results from a dual-bed, dual-feed reactor using the same catalysts showed dramatic activity increases relative to controls. In this reactor, the hydrocarbon never contacted the noble metal catalyst, yet substantial hydrocarbon conversion was measured. No hydrocarbon conversion was detected when blank support replaced the bimetallic catalyst or when no material at all was placed above the noble metal catalyst. In both reactors, the activity increase was attributed to hydrogen spillover. That is, molecular hydrogen adsorbed and dissociated on the noble metal catalyst. The adsorbed atomic hydrogen was then transported via surface diffusion to the bimetallic catalyst, activating those sites. The results also demonstrated that a catalytic reaction may occur at distinctly different reactive sites and that catalysts may be selected to promote specific steps within the reaction.