A new approach is proposed to obtain the kinetic parameters of biomass pyrolysis mixed with calcium catalyst. This approach involves the optimization of least squares (LS) with the Coats-Redfern integral method to avoid mathematical biases that may appear when applying the linear regression approach. The method was applied to the TGA data of pyrolysis of corn cob and corn cob mixed with 20 or 40 % by weight of CaO or CaCO₃ under N₂ atmosphere at temperatures between 25 and 700 °C. For raw cob, r² reaches 0.997. For corn cob mixed with 20 % by weight of CaO or CaCO₃, r² reached 0.996–0.998, and for 40 % by weight, r² reached 0.836–0.957. Applying this method, the activation energy (EA) value of the raw cob pyrolysis is 58.35 kJ mol⁻¹, while the addition of CaO or CaCO₃ increases the EA to 69.33 and 66.07 kJ mol⁻¹, respectively. The method is simple to use and allows reliable values of kinetic parameters.

This paper presents the analysis of nanorefrigerant fluids to improve the thermal efficiency of a refrigeration system. Simulations in ANSYS FLUENT 15.0 were performed with mixtures of refrigerants R113, R123 and R134a, with Al2O3 nanoparticles at 1 vf% and 5 vf% (vf%, fraction volume concentration), flowing through a horizontal tube with a constant wall temperature. A mixture and the k-e turbulent models were employed to obtain results of heat transfer coefficient, temperature and pressure drop for each case. Results show an increment in thermal characteristics by adding 1 vf% and 5 vf% of Al2O3 nanoparticles to the three refrigerants selected. However, the size of the nanoparticle does not affect the thermal properties of nanofluid and the pressure drop does not show a specific pattern of behavior at different concentrations of nanoparticles. Finally, the mixture of R134a with 30 nm of mean diameter size Al2O3 at 1 vf% was selected because of its higher thermal efficiency and its favorable properties as a refrigerant.

This paper presents the results obtained from the chemical activation of bacterial nanocellulose (BCN) using fique juice as a culture medium. BNC activation (BNCA) was carried out with H₃PO₄ and KOH at activation temperatures between 500 °C to 800 °C. The materials obtained were characterized morphologically, physicochemically, superficially, and electrochemically, using scanning electron microscopy, X-ray photoelectron spectroscopy (XPS), the physisorption of gases N₂ and CO₂ at 77 K and 273 K, respectively, cyclic voltammetry, chronopotentiometry, and electrochemical impedance spectroscopy (EIS). The samples activated with H₃PO₄ presented specific surface areas (S_BET) around 780 m² g⁻¹, while those activated with KOH values presented specific surface areas between 680 and 893 m² g⁻¹. The XPS analysis showed that the P_XPS percentage on the surface after H₃PO₄ activation was 11 wt%. The energy storage capacitance values ranged between 97.5 F g⁻¹ and 220 F g⁻¹ by EIS in 1 M H₂SO₄. The samples with the best electrochemical performance were activated with KOH at 700 °C and 800 °C, mainly due to the high S_BET available and the accessibility of the microporosity. The capacitance of BNCAs was mainly improved by electrostatic effects due to the S_BET rather than that of pseudocapacitive ones due to the presence of phosphorus heteroatoms.