This paper focuses on the fluid catalytic cracking (FCC) process and reviews recent developments in its modeling, monitoring, control, and optimization. This challenging process exhibits complex behavior, requiring detailed models to express the nonlinear effects and extensive interactions between input and control variables that are observed in industrial practice. The FCC models currently available differ enormously in terms of their scope, level of detail, modeling hypothesis, and solution approaches used. Nevertheless, significant benefits from their effective use in various routine tasks are starting to be widely recognized by the industry. To help improve the existing modeling approaches, this review describes and compares the different mathematical frameworks that have been applied in the modeling, simulation, control, and optimization of this key downstream unit. Given the effects that perturbations in the feedstock quality and other unit disturbances might have, especially when associated with frequent changes in market demand, this paper also demonstrates the importance of understanding the nonlinear behavior of the FCC process. The incentives associated with the use of advanced model-based supervision strategies, such as nonlinear model predictive control and real-time optimization techniques, are also presented and discussed.

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A series of zirconium dicarboxylate-based metal-organic frameworks (Zr MOFs) of the UiO-66 (tetrahedral and octahedral cages) or MIL-140 (triangular channels) structure type were investigated for the separation of ethane/ethylene mixtures. The adsorption, investigated both experimentally and computationally, revealed that the size and type of pores have a more pronounced effect on the selectivity than the aromaticity of the linker. The increase in pore size when changing from benzene to naphthalene (NDC) dicarboxylate ligand makes UiO-NDC less selective (1.3−1.4) than UiO-66 (1.75−1.9) within the pressure range (100−1000 kPa), while the threedimensional (3D) pores of the UiOs favor the adsorption of ethane due to the interactions between ethane with more spacers than in the case of the 1D channels of MIL-140s. The impact of the functionalization revealed a very interesting increase of selectivity when two perfluoro groups are present on the aromatic ring (UiO-66-2CF 3 ) (value of 2.5 up to 1000 kPa). Indeed, UiO-66-2CF 3 revealed a unique combination of selectivity and working capacity at high pressures. This is due to a complex adsorption mechanism involving a different distribution of the guest molecules in the different cages associated with changes in the ligand/perfluoro orientation when the pressure increases, favoring the ethane adsorption at high pressures.

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Optimization of drug delivery from drug loaded contact lenses assumes understanding the drug transport mechanisms through hydrogels which relies on the knowledge of drug partition and diffusion coefficients. We chose, as model systems, two materials used in contact lens, a poly-hydroxyethylmethacrylate (pHEMA) based hydrogel and a silicone based hydrogel, and three drugs with different sizes and charges: chlorhexidine, levofloxacin and diclofenac. Equilibrium partition coefficients were determined at different ionic strength and pH, using water (pH 5.6) and PBS (pH 7.4). The measured partition coefficients were related with the polymer volume fraction in the hydrogel, through the introduction of an enhancement factor following the approach developed by the group of C. J. Radke (Kotsmar et al., 2012;Liu et al., 2013). This factor may be decomposed in the product of three other factors , and which account for, respectively, hard-sphere size exclusion, electrostatic interactions, and specific solute adsorption. While and are close to 1, >>1 in all cases suggesting strong specific interactions between the drugs and the hydrogels. Adsorption was maximal for chlorhexidine on the silicone based hydrogel, in water, due to strong hydrogen bonding.The effective diffusion coefficients, , were determined from the drug release profiles.Estimations of diffusion coefficients of the non-adsorbed solutes = × allowed comparison with theories for solute diffusion in the absence of specific interaction with the polymeric membrane.

This work presents an enhanced model for the reactor-regenerator system of a UOP fluid catalytic cracking (FCC) unit with a high-efficiency regenerator. The model is derived from fundamental principles; relative to earlier versions, a different cracking deactivation model is considered, and the freeboard region in the regenerator vessel is also explicitly addressed. The resulting model is fitted to industrial data, using new correlations to estimate the cracking kinetic constants and other important parameters in the FCC heat balance. In the development of these correlations, only routinely available data and operating variables were considered. As demonstrated, parameter estimation allows a good agreement between the simulated results and the available industrial data. The procedure followed can, therefore, be used to adapt this model to different units of the same class. A comparison of the main features of the steady-state and the dynamic behavior of the validated model with previous results is also considered in this paper.