The production of polymers from renewable materials has arisen increasing interest because of the environmental impacts caused by conventional processes. In this context, the present manuscript investigates the step-growth polymerization of poly(ethylene 2,5-furandicarboxylate), PEF, a furanic polyester with structural similarity to poly(ethylene terephthalate), PET, using ethylene glycol (EG), and 2,5-furandicarboxylic acid (FDCA) as monomers. The polymerization is performed in two steps: direct esterification of EG and FDCA under continuous nitrogen flow, followed by the transesterification of produced diesters and oligomers under reduced pressure. In order to do that, experiments were performed at distinct reaction temperatures and using different nitrogen flow rates. Based on the obtained experimental data, a mathematical model was built and model parameters were estimated to allow for appropriate description of available data. The obtained results indicate that the rates of polymerization are highly limited by mass transfer and removal of reaction byproducts. POLYM. ENG. SCI.,

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The residence time distributions (RTDs) of continuous solution copolymerization tank reactors connected in series are evaluated experimentally to analyze features related to the fluid dynamics of this class of reactors. For this purpose, tracer step experiments are carried out in lab‐scale polymerization tank reactors to provide experimental data for analysis of the quality of mixing and evaluate associated macromixing effects. Besides, mathematical models are developed to describe the RTD data obtained experimentally. Based on a compartmental approach, perfect mixing tanks, tanks with stagnant zones, tanks with crossflow, and tanks in series with backflow models were proposed. Particularly, the analysis of the available experimental data and of mathematical models indicate that the flow features of these systems are strongly associated with the established degree of mixing, presenting significant non‐ideal flow behavior, usually neglected in most modeling and experimental studies.

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The present work discusses the mathematical modeling and the control design of the steam reforming of natural gas. The developed model comprises a set of differential and algebraic equations, based on energy and mass balances for reactions performed in a fixed catalyst bed reactor, where natural gas and water are transformed mainly into a mixture of hydrogen and carbon oxides. Normally, after removal of hydrogen and purification of the output stream, the residual gas can be also directed to the furnace to provide heat to the reactor. This is a common practice in industrial sites in order to minimize losses. As the global reactions are exothermic, the reactor temperature may reach prohibitive high values, leading to coke formation and catalyst deactivation. For this reason, a control scheme is proposed to account for regulation of the reactor outlet temperature, using residual and fuel gas streams as manipulated variables, allowing the analysis of effect of several process variables in reactor performance. The obtained results indicate that the proposed mathematical model can accurately represent the steam reforming process and that the proposed control scheme can allow for efficient operation of the reactor, even when the residual gas stream is not sufficient to reach the desired operation temperature.