José F.O. Granjo

Separation of ethanol–water mixtures by liquid–liquid extraction using phosphonium-based ionic liquids

Bio-alcohols are produced from biomass by fermentation, and distillation is commonly used to separate the alcohol from the aqueous phase. This is, however, a high energy consumption process, and alternative approaches to this separation are being pursued. In this work, the use of phosphonium-based ionic liquids (ILs) for the extraction of ethanol from fermentation broths is investigated. Ternary phase diagrams, necessary for the design and to implement an alternative liquid–liquid extraction process for the alcohol recovery, were determined for seven ionic liquids. The modelling of the equilibrium data was performed using the COSMO-RS and NRTL models; the first aiming at screening other ionic liquids not experimentally studied, and the latter aiming at designing a separation process. The gathered data indicate that phosphonium-based ionic liquids are the best yet reported to perform water–ethanol separations. Based on the most promising phase diagrams, an analysis of the alcohol and ionic liquid recovery steps was carried out and a liquid–liquid extraction stage coupled to an extractive fermentation, where the ionic liquid is continuously recycled to the fermentator and the ethanol concentration is carried out by pervaporation, is here proposed as an alternative to distillation.

A virtual platform to teach separation processes

In this article the Unit Operations and Separation Processes area of a virtual platform called LABVIRTUAL(http://labvirtual.eq.uc.pt) is presented aiming to support the autonomous study of undergraduate students engaged in a Chemical Engineering degree, especially in Portuguese‐speaking countries. The main features, subjects, computational applications, and examples in the platform are described, as well as a first assessment by the students.

Kinetic Models for the Homogeneous Alkaline and Acid Catalysis in Biodiesel Production

Abstract In this work, kinetic models were obtained from experimental data in the open literature, for both the alkaline (NaOH) and acid (H2SO4) homogeneous catalysis of the transesterification reaction, used to produce biodiesel from vegetable oils. Two approaches, designated as statistical and empirical, were adopted to obtain these models. For both catalysis types, the kinetic models obtained show average absolute errors of approximately 4%, using both empirical and statistical approaches, well within the precision of the experimental procedures. In the alkaline catalysis, kinetic models fitted better a pseudo 2nd-order reaction, while for the acid catalysis pseudo 1st-order reaction provided a best fit.

LABVIRTUAL-A platform for the teaching of chemical engineering: The use of interactive videos

This article focus on the pedagogical tools in LABVIRTUAL (http://labvirtual.eq.uc.pt), a broad scope virtual platform intended to support the learning at the undergraduate level of Chemical Engineering courses, mainly in Portuguese‐speaking countries. The platform contains fundamentals, case studies, simulators, virtual laboratories, and, recently, interactive videos for the teaching of chemical processes. The significance and impact of LABVIRTUAL are illustrated with an interactive video regarding the characterization of nanoparticles by dynamic light scattering, developed for long‐distance learning and used in the discipline of Technology of Disperse Systems. Furthermore, two questionnaires were prepared to assess the students’ response to the interactive video and the use of LABVIRTUAL in general. The results show that the interactive video is effective to prepare the laboratory work and guide the students’ self‐regulated study, but needs to be complemented with other pedagogical methods to enhance the learning outcomes. LABVIRTUAL is generally viewed as a valuable learning tool by the students of Separation Processes and Project Design, 3rd and 5th year courses, respectively, of the Masters’ degree in Chemical Engineering of the University of Coimbra, due to the synergy of pedagogical tools that complement well the face‐to‐face classroom lectures. This fact also justifies the high number of monthly visits, including from companies that use the platform as a life‐long learning tool.

Systematic Generation of Chemical Reactions and Reaction Networks subject to Energetic Constraints

Abstract This work describes the inclusion of energetic constraints in a step-wise methodology to develop kinetic models, spanning all stoichiometric consistent reaction networks. The task of generating reaction networks is formulated as a combinatorial optimization problem, identifying sets of reactions that link all species and allow a consistent flux balance analysis. The Gibbs free energy variations of the system, considered in the entire time domain, is used as the main criterion for selecting feasible candidates. This is illustrated with the α -pinene isothermal liquid isomerization.

Identifiability of the glyceride transesterification kinetics via alkaline catalysis

Abstract This study addresses the glyceride transesterification (TE) kinetics, a crucial step in bio-diesel production from vegetable oils. To overcome common limitations of the existing kinetic models, a n th order reversible model with a broader domain of application is fitted to experimental data gathered from different authors. We consider the glyceride TE employing sodium methoxide (NaOCH 3 ), and use a general four-step model building approach, including (i) structural identifiability analysis; (ii) outlier detection using a robust M-estimator; (iii) parameter estimation (PE) and subsequent construction of the respective confidence intervals; and (iv) practical identifiability analysis. The results show that although the kinetic models with five (5P) and six (6P) parameters are structurally non-identifiable, the former (5P) can be shown to be practically identifiable and fit accurately the data, with an average relative deviation (ARD) of 6.5 %.

Reconfiguration of an Oilseed Processing Plant into a Whole-crop Biorefinery

Abstract We consider the integration of biodiesel and bioethanol production processes with an existing oilseed processing industry to expand the value chain associated with the original raw materials, with multiple advantages from the economic and sustainability perspectives. This process integration task provides several opportunities for the application of systematic decision making methodologies. However, to be implemented in a significant extension, it also places many demands at the levels of the development of accurate models for the thermodynamic and kinetic description of the operations considered, and optimization based design methods for the units to be included in the processing structure. An overview of recent developments in each of these levels is considered in the first part of this work. This is followed with the presentation of an optimal design methodology for the specification of a “De Smet” horizontal solid-liquid extractor, commonly used by the industry to leach out the oil from the flakes. A comparison of the performance of the optimal design with a reference unit is given.