Beatriz Lorenzo

This work presents an investigation into a solvent-free esterification reaction of pentan-1-ol with propanoic acid to produce pentyl propanoate using a batch stirred-tank reactor (BSTR). The overall objective is to achieve a more sustainable and efficient reactive process. The individual effects of key variables – temperature, initial reagent ratio, and catalyst concentration – were evaluated using Lipozyme435 and compared against Amberlyst-15. Experimental data were correlated with two kinetic models: (a) a second-order reversible rate law, and (b) a Bi–Bi Ping Pong model incorporating dual-substrate inhibition, as well as an enzymatic mechanism induced by temperature and carboxylic acid concentration. The modeling reveals certain novel characteristics, which are discussed and lead to a positive evaluation. The results demonstrate a high pentyl ester conversion of 75–80% using Lipozyme435, when a stoichiometric molar ratio of alcohol/acid of 1 is used. However, under these conditions, enzyme deactivation occurred at temperatures ≥70 °C. When the alcohol/acid molar ratio was increased to 2, no loss of enzymatic activity was observed, even at the maximum tested temperature of 80 °C. Furthermore, the biocatalyst systematically developed Amberlyst-15 in reaction rate under similar conditions. Finally, reaction energy determined via a mini-scale procedure in a high-resolution calorimeter revealed an exothermic reaction enthalpy of −5.6 kJ/mol of ester produced. These findings provide a comprehensive kinetic and thermodynamic framework for improving ester synthesis under sustainable conditions.

In this work, the enzymatic synthesis of pentyl acetate obtained from acetic acid and pentan-1-ol using the commercial immobilized lipase Lipozyme^®435 was studied. Specifically, the effects of several variables of the process on the kinetics were shown, such as the initial concentration of the acetic acid, the alcohol/acid molar ratio, and the possible reuse of the enzyme, while other variables, such as temperature, agitation, and the enzyme/acid ratio were held constant. The kinetics were determined by assessing the acetic acid concentration throughout the reactive process. Experimental data were correlated with the rate equation consisting of a modified version of the Bi–Bi Ping-Pong mechanism. The results showed that when no hydrophobic solvents were used with the reagents in stoichiometric proportion, a high molar fraction of acetic acid (x_0,acid ≈ 0.50) caused the loss of enzymatic activity, achieving a conversion of only 5%. However, when there was an excess of pentan-1-ol, the reaction occurred successfully. Under optimal conditions (solvent-free conditions, x_0,alcohol/x_0,acid = 2, and x_0,acid = 0.33), it was found that the enzyme could be reused up to 10 times without a loss of activity, reaching conversions higher than 80% after 8 h. Therefore, those conditions are advantageous in terms of productivity.

This work provides density data (~1300 values) of 14 alcohols with up to five carbon atoms at p ∈ [0.1–40] MPa and T ∈ [278–358] K. The information obtained is modeled with a convenient reformulation of the Tait equation from which the volumetric coefficients, α and β, are derived both analytically and numerically. The general EoS containing α and β is also used for checking the consistency of the hypothesis on the invariability of the cited thermophysic parameters. The results obtained can be considered reliable because of the low estimated errors between the experimental data and those of the literature, which are below 0.4% for volume, while for the volumetric coefficients there is always a reference diverging 10%, or less, from the proposed model estimations. By including the averages of α and β into the general state of equation the errors increase, being <15%, compared to those based on the Tait equation. Hence, the assumption on the stability of the volumetric coefficients in this working interval is sufficient to make rough estimations of the molar volume of the selected alcohols.