Performance Evaluation of a Titania-coated Reticulated Foam Photocatalytic Oxidation Reactor

We have constructed and evaluated the performance of a gas-solid annular photocatalytic oxidation reactor that incorporates an alumina reticulated foam monolith element as a titania catalyst support. The reticulate occupies the annular region formed by the lamp and the outer reactor tube. Three alumina reticulates possessing different mean pore sizes and pore densities, designated as 10, 20 and 30 pores-per-inch (PPI) were employed. The reticulates were wash-coated with Degussa P25 titania. Light transmittance measurements through the reticulates showed that 30 PPI reticulate, the least optically dense element, captures the most light. Photocatalytic oxidation of dilute isopropanol (IPA) in air was chosen as the probe reaction to assess the performance of each reticulate- catalyst coating configuration. Process parameters varied were inlet IPA concentration, incident UV intensity, and mean gas residence time. For similar catalyst loadings, the 30 PPI reticulate outperformed both the 20 and 10 PPI reticulates, while the 20 PPI reticulate modestly outperformed the 10 PPI reticulate. With increasing titania coating yielding thicker titania films, general performance increases until a critical thickness is achieved. Light intensity measurements and simple forward UV intensity profile calculations reveal that reticulate performance is largely governed by the UV intensity profile. For a given reticulate, results suggest that the optimum thickness of the TiO

Some remarks on certain classes of semilattices

In this paper the concept of a∗-semilattice is introduced as a generalization to distributive∗-lattice first introduced by Speed [1]. It is shown that almost all the results of Speed can be extended to a more eneral class of distributive∗-semilattices. In pseudocomplemented semilattices and distributive semilattices the set of annihilators of an element is an ideal in the sense of Grätzer [2]. But it is not so in general and thus we are led to the definition of a weakly distributive semilattice. In§2we actually obtain the interesting corollary that a modular∗-semilattice is weakly distributive if and only if its dense filter is neutral. In§3the concept of a sectionally pseudocomplemented semilattice is introduced in a natural way. It is proved that given a sectionally pseudocomplemented semilattice there is a smallest quotient of it which is a sectionally Boolean algebra. Further as a corollary to one of the theorems it is obtained that a sectionally pseudocomplemented semilattice with a dense element becomes a∗-semilattice. Finally a necessary and sufficient condition for a∗-semilattice to be a pseudocomplemented semilattice is obtained.