The aim of this work was to optimize the drying process of vegetal pear and minimize energy resources (cost) under prefixed limits involving vegetal pear moisture, color, and productivity. The optimization of vegetal pear drying was made by using response surface methodology (RSM) for minimum process cost and color difference between fresh and dried samples (moisture ≤0.10 g water g d.m.⁻¹). A pilot-plant dryer was used for dehydrating vegetal pear slices (0.5 cm thickness). The tests were carried out at different air temperature (60 to 70°C), samples diameter (4 to 7 cm), and pretreatment with ascorbic acid solutions (0–0.1% w/w). The optimum drying conditions were found at air temperature of 63°C with 5-cm sample diameter and 0.075% of ascorbic acid concentration. On the optimized drying conditions, dried vegetal pear presented values with moisture content of 0.052 g water g d.m.⁻¹, color difference of 11.65, production rate of 0.0073 kg h⁻¹, and total cost of $30.58/kg dried product⁻¹

The 5-(9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboximido) isophthalic acid (DEAIA) monomer, containing a dibenzobarrelene pendant group, was synthesized by the condensation of 5-aminoisophthalic acid and 9,10-dihydroanthracene-9,10-α,β-succinic anhydride (DASA). The DEAIA monomer was reacted with four structurally different aromatic diamines to synthesize four novel polyamides. All aromatic polyamide based in the DEAIA monomer showed very good solubility in aprotic polar solvents and excellent thermal stability with onset of decomposition at 430 °C. They readily form membrane by the casting method. Moreover, the most interesting polyamide was DEAIA-6F that showed high thermal stability, good film formation, and the largest gas permeability coefficients in comparison with a reported polyhexafluoroisophthalamide, HFAISO; this confirms the advantage of inserting a dibenzobarrelene pendant group.

The efficient conversion of lignocellulosic biomass into fermentable sugars remains one of the main challenges for sustainable biorefineries. This study tested the hypothesis that dilute-acid hydrolysis of Eichhornia crassipes can be optimized to maximize fermentable sugar release while elucidating the physicochemical mechanisms governing the process. A Box–Behnken response surface design was employed to evaluate the effects of temperature (110–130 °C), sulfuric acid concentration (1–3%), and solid-to-liquid ratio (1:5–1:9) on total sugar production. Statistical analyses demonstrated that temperature was the dominant factor controlling hydrolysis, whereas acid concentration and solid-to-liquid ratio regulated catalytic selectivity and mass-transfer limitations. The quadratic model adequately described the experimental response (R2 = 0.81), and its mechanistic interpretation revealed that sugar production results from the competition between polysaccharide depolymerization and monosaccharide degradation. Experimental validation confirmed the robustness of the optimized conditions, with an average prediction error of 15% and a mean sugar concentration of 79.5 ± 6.31 g·L-1. Mass balance analysis showed an average recovery of 0.636 g of soluble sugars, corresponding to 47.1% of the theoretical structural carbohydrate potential.

Four polyimides based on bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (BTD), BTD-MIMA, BTD-HFA, BTD-FND, and BTD-TPM, with different rigid substituted diamines were synthesized. The chemical structure of the polyimides was corroborated by 1H NMR spectroscopy. These polyimides were soluble in organic solvents and presented molecular weights (Mn) between 39 and 70 KDa. BTD-MIMA, BTD-HFA, BTD-FND, and BTD-TPM showed thermal stability above 400 °C. These polyimides also presented high glass transition temperatures between 272 and 355 °C. The alicyclic moiety increased solubility compared with other rigid polyimides. Membrane films from BTD-MIMA and BTD-HFA exhibited the highest gas permeability compared to BTD-FND and BTD-TPM. The introduction of ortho-substituents in BTD-MIMA or bulky –CF3 groups in BTD-HFA, in combination with the alicyclic dianhydride fragment, prevented chain packing and enhanced macromolecular chain rigidity. In turn, there was a shift toward higher gas permeability coefficients for BTD-MIMA and BTD-HFA, with a moderate loss of CO₂/N₂ and CO₂/CH₄ selectivity, and they presented similar selectivities to those of other reported polyimides with alicyclic BTD moieties containing asymmetric fragments.