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Ca(OH) 2 /fly ash sorbents were characterized and tested for reactivity toward SO 2 at conditions similar to those in the bag filters in the dry and semidry flue gas desulfurization processes. The sorbents were mesoporous, and their specific surface areas linearly correlated with their specific total pore (1.7-300 nm) or mesopore (2-50 nm) volumes. The 1 h utilization of Ca in a sorbent increased, in general, with increasing fly ash content. Sorbents with Ca(OH) 2 contents larger than 33 wt % had higher weights of SO 2 captured per unit weight of sorbent than Ca(OH) 2 had alone, and the sorbent with 70 wt % Ca(OH) 2 had the maximum capture. The 1 h utilizations of Ca for the sorbents and Ca(OH) 2 increased almost linearly with increasing specific surface area or pore volumes of the sorbent. The SO 2 captured per unit surface area or pore volume of the sorbent decreased almost linearly with smaller Ca(OH) 2 content. The reactivities of the sorbents were enhanced mainly by their large specific surface areas and to a lesser degree by the reactive constituents in fly ash.

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The hydrogen oxidation reaction on Pt-black/ Nafion electrode was investigated using a rotating disk electrode and cyclic voltammetry technique. The voltammetric results demonstrated that the electrode can be prepared with good reproducibility and that Ptblack particles without direct contact with Nafion were still electrochemically active in taking part in the Hadsorption/desorption process. For hydrogen oxidation, the limiting current density was reduced by the presence of Nafion coating. The H 2 diffusion resistance in Nafion film was avoided when the film thickness was less than 0.2 lm for a Pt-black loading of 20 lg. Moreover, the uncertainties in the kinetic results were discussed.