The article presents an analysis between different possible sequences for the separation of bioethanol from a typical fermentor's stream. The preconcentrator column, necessary to approach the azeotropic composition was included as a fundamental part of the sequences. Starting from a recently proposed four-column configuration in the literature, a full set of alternatives was predicted and explored in detail. Different combinations of partial and total condensers were considered so as to possibly reduce the amount of equipment. It was proved that among all the simple configurations generated, two sequences with three columns are able to consistently reduce the energy demand and the capital costs. The results obtained represent the first step for the further generation of complex configuration sequences.

In the first part of the work the dehydration of bioethanol by extractive distillation was considered to define the best simple column sequence. It was proved that among all the simple configurations generated, two sequences with three columns are able to consistently reduce the energy demand and the capital costs compare to the four-column sequence used as a reference. Then, starting from the selected simple column configurations different complex sequences were predicted. It was evidenced that thermally coupled configurations realized only a limited saving in the capital costs. The two column configuration with a vapor side stream is able to reduce the capital costs, but not all the solvent can be recovered. Its convenience is related to the trade-off between the solvent cost and the savings in the capital costs achieved. The two-column configurations with a divided wall column represent an excellent alternative for bioethanol production because their performances are not limited by the solvent recovery.

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Biobutanol is receiving great interest from both the academia and industry sectors, and some companies are already focusing on revamping bioethanol plants to produce biobutanol. The recovery of fuel grade butanol by distillation was proven not to be economically sustainable. On the other side, hybrid flowsheets, obtained with the combination of liquid−liquid extraction and distillation, were proposed as a more convenient alternative. Divided wall columns (DWCs), as one of the most promising intensified distillation alternatives, were here explored in combination with liquid−liquid extraction. A multiple-objective function, taking into account the economy, the environmental impact, and the process controllability, was defined to screen the alternatives. Among all the configurations considered, liquid−liquid extraction combined with a DWC equipped with two reboilers and a side rectifier, reached 22% and 18% reduction of the economy and environmental index, respectively. At the same time, also the controllability was improved compared to the hybrid liquid−liquid-assisted simple column distillation sequence considered as a reference.

The use of liquid enzymes for the production of biodiesel as an alternative to chemical catalysts requires significant investigation due to the lack of experimental data for the various feedstock and catalyst combinations. In this paper, reaction rates and kinetic modeling of the transesterification of castor oil with methanol using the enzyme Eversa® Transform as catalyst were investigated. Reactions were carried out for 8 hours at 35 °C with: an alcohol-to-oil molar ratio equal to 6:1, a 5 wt% of liquid enzyme solution and addition of 5 wt% of water by weight of castor oil. From the concentration data, four different reaction mechanistic models were compared to determine the mechanism that best fitted the experimental data. Mechanisms where the methanolysis and hydrolysis reactions occurred simultaneously in the system were best at describing the concentration profiles. The high methanolysis rates of glycerides obtained, indicated that transesterification dominates over hydrolysis. The mechanism among the four models proposed that gave the best fit could be simplified, eliminating the kinetic parameters with negligible effects on the reaction rates. This model was able to fit the experimental data at different reaction temperatures.