A set of experiments was carried out to investigate the chemical stability of 5-o-caffeoylquinic acid (5-CQA) in the presence of superheated steam. A batch cylindrical reactor made of glass and isothermally operated between 398 and 499 K was used in the experiments. A high-performance liquid chromatograph equipped with a diode array detector was applied to monitor the 5-CQA concentrations. The conversions of 5-CQA were correctly reproduced with a simplified kinetic model represented by a reversible pseudofirst-order reaction of isomerization. The effect of temperature on the forward rate constant was represented by the Arrhenius equation with parameters tuned on experimental data. The heat of isomerization of 5-CQA and the equilibrium constant at 298 K were calculated by involving the integrated form of the van't Hoff equation. The observed reaction was revealed to not be detrimental for the quality of manufactured leaves and branches of mate because the content of total chlorogenic acids was not changed.

A 24 factorial design of experiments complemented with a central point was performed to examine the influence of operating factors on color strength and color fastness of polyethylene terephthalate (PET) fibers dyed with the Disperse Orange 30 dye in supercritical CO2. The effects of temperature, pressure, dyeing time and mass ratio between the dye and PET introduced in the dyeing chamber ( α ratio) were considered. An additional set of kinetic results of color strength was obtained at the optimum condition in terms of pressure at the already presented temperatures and α ratios. A significant statistical effect of all the investigated factors on the color was observed, but except for the temperature, the influence of the same variables on wash fastness was negligible ( p < 0.05). The color results expressed in terms of K/ S from 2.4 to 21.8 revealed that the use of supercritical CO2 as a solvent for the dye is a rapid and reliable alternative procedure for dyeing of PET fibers with the Disperse Orange 30 dye. The results of wash fastness currently obtained (i.e. 4.69 ± 0.18) support the use of ScCO2.

An experimental investigation to determine the specific heat, thermal conductivity and apparent density of mate leaves (Ilex paraguariensis) was carried out. The experimental method of mixtures and a quasi‐adiabatic calorimeter were used to obtain a specific heat of dry leaves close to 1780 ± 450 J/kg/K. A thermal conductivity of 0.17 ± 0.01/W/m/K was tuned on transient experimental measurements of temperature in a dry bar of mate leaves. A dynamic one‐dimensional heat transfer model was involved in this procedure of tuning. An apparent density equal to 750 ± 40 kg/m was experimentally found. The effect of moisture content on these thermophysical properties was also theoretically investigated by involving simplified models based on properties of only dry matter and water. Analogous results available in the literature support the reliability of all experimental data and equations presented in this investigation. PRACTICAL APPLICATIONS Mate manufacturing basically involves a stage of enzymatic deactivation and a process of drying that are together responsible for almost the full energy consumed in the mate industry. A detailed description of both these processes with mathematical models is a cheap and safe way to process optimization and energy saving. However, the knowledge of the specific heat, thermal conductivity and density of the processed material whose availability is limited in the literature is required for model solution.

A set of chemical kinetic and phase-transition experiments was performed to investigate the competing conversions of fumaric acid into maleic and malic acids by isomerization and hydration, respectively. The reactions were carried out in sealed stainless steel batch reactors operated up to ∼1600 kPa and jacketed with glycerol at 398, 423, 448, and 473 K. The catalyst used was 0.97 M hydrochloric acid. To avoid excessive data near equilibrium, the reaction time was reduced from 720000 to 12600 s as the temperature of the heating fluid was increased. To ensure a homogeneous reaction, the solubility of fumaric acid in water was determined in the temperature range from 293 to 473 K using a high-pressure variable-volume sapphire view cell. The variation in the species concentration with time was determined by HPLC analysis of 12 reaction mixture samples per reaction run conducted twice under identical conditions. The parameters of the Arrhenius equation for the isomerization and hydration reactions were tuned on the kinetic experimental data by applying the Simplex method of optimization (k 20 = 1.27 × 10–7 s–1, k 30 = 1.29 × 107 s–1, E a2/R = −2815 K, E a3/R = 11260 K).