Stability and activity of carbon nanofiber-supported catalysts in the aqueous phase reforming of ethylene glycol

Nickel, cobalt, copper and platinum nanoparticles supported on carbon nano-fibers were evaluated with respect to their stability, catalytic activity and selectivity in the aqueous phase reforming of ethylene glycol (230 C, autogenous pressure, batch reactor). The initial surface-specific activities for ethylene glycol reforming were in a similar range but decreased in the order of Pt (15.5 h1 ) >Co(13.0 h1 ) >Ni(5.2 h1 ) while the Cu catalyst only showed low dehydrogenation activity. The hydrogen molar selectivity decreased in the order of Pt (53%)>Co(21%)>Ni (15%) as a result of the production of methane over the latter two catalysts. Over the Co catalyst acids were formed in the liquid phase while alcohols were formed over Ni and Pt. Due to the low pH of the reaction mixture, especially in the case of Co (as a result of the formed acids), significant cobalt leaching occurs which resulted in a rapid deactivation of this catalyst. Investigations of the spent catalysts with various techniques showed that metal particle growth is responsible for the deactivation of the Pt and Ni catalysts. In addition, coking might also contribute to the deactivation of the Ni catalyst.     

Doppler spectrum-based polar nephelometer

The particle scattering asymmetry parameter of an ensemble of submicrometer particles, as well as the complete scattering phase function (angular distribution), is determined by measuring the Doppler spectrum of the scattered light. No calibration is required. The monitor incorporates a 532?nm laser with long coherence length, an integrating sphere to collect the scattered light, and a heterodyne (interferometric) detection scheme. Measurements of monodisperse polystyrene latex spheres and polydisperse ammonium sulfate particles indicate that the measured value of the asymmetry parameter is generally within ±0.03 of that calculated using Mie theory.