Pyrolysis gasoline - PYGAS - is an intermediate boiling product of naphtha steam cracking with a high octane number and high aromatic/unsaturated contents. Due to stabilization concerns, PYGAS must be hydrotreated in two stages. The first stage uses a mild trickle-bed conversion for removing extremely reactive species (styrene, dienes and olefins) prior to the more severe second stage where sulfured and remaining olefins are hydrogenated in gas phase. This work addresses the reaction network and two-phase kinetic model for the first stage of PYGAS upgrading. Nonlinear estimation was used for model tuning with kinetic data obtained in bench-scale trickle-bed hydrogenation with a commercial Pd/Al2O3 catalyst. On-line sampling experiments were designed to study the influence of variables - temperature and spatial velocity - on the conversion of styrene, dienes and olefins.

We consider a mathematical framework for spatially describing accessory aquatic systems that belong to a major hydric complex like a large reservoir created by damming a river. The central purpose is to provide a precise and complete mathematical covering of short-scale or localized water bodies, with typical lengths between 1 to 10 km, that are laterally attached to the main river. Such bodies may deserve a more detailed mathematical representation due, for instance, to their tendency to develop stagnant like hydric behaviors. The proposed framework may work as an infrastructure for developing and/or installing dynamic water quality models. It can generate tetrahedrizations of the aquatic system in question by working according to a procedure which builds, successively, reliable candidates for the following entities: (a) Free Surface Triangular Mesh; (b) Submerged Terrain Triangular Mesh; (c) Three Dimensional Partition of the Domain; (d) Basic Tetrahedrization of 3D Partitions; and (e) Refinement of the Basic Tetrahedrization through a Multi-Layer Tetrahedrization Algorithm. The required input for this procedure is only composed by terrain contour data and 3D located points. We present example applications including a real scenario belonging to a recent flooded system in Brazil.

In this paper, we examine the resolution of some phase rule problems within the context of multiple chemical equilibrium reactions, using cubic equations of state and an activity coefficient model. Bubble and dew reactive surfaces, reactive azeotropic loci and reactive critical loci are generated and presented in graphical form. Also isobaric bubble and dew reactive enthalpy loci, which may be useful in the modeling of reactive distillation operations, are depicted. All the formalism here employed is developed within the coordinate transformation of Ung and Doherty, which is appropriate for equilibrium reactive or multireactive systems. The major contribution of this work is the determination of critical loci for reactive or multireactive equilibrium systems. Since it is known that for some class of chemical reactions the kinetics and product distribution exhibit high sensitivity to pressure near criticality, the present study may be useful as a predicting tool in these cases if the chemical equilibrium condition is not too far from the real phenomenon.