The photoactivated degradation reaction of rhodamine B (RB) was studied using P-25 TiO2 (Degussa) as catalyst. Three process variables - temperature, initial pH, and catalyst concentration - were evaluated. Temperature had a slight effect on reaction rate; however, the combined effect of pH and catalyst concentration was greater. pH affected the catalyst particle's adsorption of RB, altering the reaction rate. The concentration of the catalyst was significant only up to 0,65 g L-1. The effect of temperature was studied at optimum pH and 50ºC was found to be the optimum operational temperature. The effect of the presence of a surfactant (sodium dodecylsulfate, SDS) and ionic contaminants (Cl- and SO4-) in the reaction system was also studied. The surfactant improved the catalyst's adsorption of RB by more than 80%, increasing the degradation reaction rate as well. The ionic contaminants reduced the reaction rate.

The modeling, simulation, and dynamic optimization of an industrial reaction system for acetylene hydrogenation are discussed in the present work. The process consists of three adiabatic fixed-bed reactors, in series, with interstage cooling. These reactors are located after the compression and the caustic scrubbing sections of an ethylene plant, characterizing a front-end system; in contrast to the tail-end system where the reactors are placed after the de-ethanizer unit. The acetylene conversion and selectivity profiles for the reactors are optimized, taking into account catalyst deactivation and process constraints. A dynamic optimal temperature profile that maximizes ethylene production and meets product specifications is obtained by controlling the feed and intercoolers temperatures. An industrial acetylene hydrogenation system is used to provide the necessary data to adjust kinetics and transport parameters and to validate the approach.