Analysis of variable-temperature reaction profiles, measured in an isothermal packed-bed reactor (PBR) whose temperature increases during the experiment, has the potential to yield accurate and precise kinetic parameters quickly for some heterogeneous catalysts. The method is demonstrated here for a typical supported nanoparticle catalyst, 2 wt% Pd/Al2O3, in the oxidation of H2, C3H8 and CO by O2. These reactions do not exhibit major changes in activation energy as a function of conversion over the range of reaction conditions analyzed. Reliable and quantitative information about rate laws was extracted readily from the shapes and positions of these profiles, as an alternative to more laborious conventional kinetic analyses. Temperature and pressure gradients were minimized by the use of sieved catalyst particles and large amounts of inert diluent for both the catalyst and feed gas. Curve-fitting of analytical expressions with as few as two adjustable parameters results in remarkable agreement between models and data. First-order profiles are indeed kinetically-limited, without mass and heat transfer effects, while inverse-firstorder profiles deviate from kinetically-controlled behavior at intermediate-to-high conversions. The activation energy and reaction order with respect to the limiting reactant obtained from a single reaction profile (with appropriate data truncation for non-kinetic phenomena, as necessary) are at least as accurate and precise as those obtained from a conventional Arrhenius analysis conducted with data obtained under differential conditions, and are measured in a fraction of the experimental time. Information about more elaborate rate laws can be obtained by global curve-fitting of a family of such profiles recorded with different volumetric flow rates.

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Fine-pore diffusers are the most common aeration system in municipal wastewater treatment plants. Fouling is inevitable and inexorable for all types of fine-pore diffusers, and is dependent on process layout, water quality, diffuser type, and time in operation, but independent of diffuser make and model. The decline in diffuser performance, resulting in increased aeration energy footprint is reflected onto the standard oxygen transfer efficiency (SOTE, ratio of oxygen transferred to the wastewater per unit oxygen blown by the aeration system, at standard conditions, %) and the net head loss across the membrane due the friction through the orifices, also known as dynamic wet pressure or DWP. In process water, the α factor is introduced to correct for the effects of wastewater, defining αSOTE(%). These parameters vary inevitably due to the fouling phenomena, with DWP increasing with time and SOTE decreasing. To account for the effects of fouling, a fouling factor F is introduced. Previously, we showed that the DWP increase is different for different materials, indicating different material properties and response with time in operation. Another indicator of diffuser performance is hence the pressure factor Ψ (ratio of DWP for used and new diffusers). This paper presents our 2-year diffuser study results and discusses the implications of our results on aeration energy footprint.