A set of Y-type zeolites with Si/Al atomic ratios between 7–45 were studied as catalysts in the aminocyclization reaction between acrolein and ammonia to produce pyridine and 3-picoline. The catalytic activity tests at 360 °C revealed that the acrolein conversion increased in the order Z45 < ZY34 < ZY7 < ZY17, in agreement with the increase of the total acidity per gram of catalyst. In all cases, pyridine bases and cracking products (acetaldehyde and formaldehyde) were detected in the outflow from the reactor. The total yield of pyridines was inversely proportional to the total acidity for the catalysts, which presented large surface areas and micro- and mesoporosity. The selectivity towards 3-picoline was favored when using catalysts with a Brønsted/Lewis acid sites ratio close to 1. The formation of pyridine occurred more selectively over Lewis acid sites than Brønsted acid sites. The deactivation tests showed that the time on stream of the catalysts depended on the textural properties of zeolites, i.e., large pore volume and large BET area, as evidenced by the deactivation rate constants and the characterization of the spent catalysts. The physicochemical properties of the catalysts were determined by XRD, UV-vis, and Raman spectroscopies, infrared spectroscopy with adsorbed pyridine, N₂ physisorption, and SEM-EDXS. After the reaction, the spent catalysts were characterized by XRD, Raman spectroscopy, TGA, and SEM-EDXS, indicating that the uniform deposition of polyaromatic species on the catalyst surface and within the porous system resulted in the loss of activity.

Thermal and catalytic pyrolysis of waste expanded polystyrene (WEPS) was studied to obtain mainly styrene monomer, which can be recycled in the polystyrene industry. Initially, preliminary experiments were carried out in a static semi-batch glass reactor with basic catalysts and without catalysts, using toluene as solvent at 250 °C, determining their styrene yields to select the best catalyst. MgO turned out to be the best catalyst due to its stability and cost. This catalyst was characterized by XRD, BET area, SEM-EDS, Raman spectroscopy, UV–VIS, and TGA. The kinetic equation for WEPS pyrolysis in the glass reactor was determined as a first-order reaction. The heat of reaction, the Gibbs free energy change, and the entropy change were calculated. Finally, WEPS pyrolysis experiments were carried out using a rotating semi-batch steel reactor, at higher temperatures and without using solvents, evaluating the styrene yield and its performance for its possible industrial application. In this reaction, the activity remained almost constant after four catalyst regenerations. The best styrene yield was 94 wt%, which could be one of the highest reported in the literature. This result may be associated with the back-mixing obtained in the rotary reactor, in contrast to the performance observed in the static glass reactor.

In this work, the removal of Cu(II) ions from an aqueous effluent was studied using an Mg/Fe layered double hydroxide (LDH) as the adsorbent. The material was synthesized and characterized before and after the adsorption process to identify structural and morphological changes induced by copper uptake. Techniques such as X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS), ultraviolet-visible spectroscopy (UV-Vis), Raman spectroscopy, and nitrogen physisorption (BET) were employed to confirm the interaction between the metal ions and the LDH surface. The LDH-Mg/Fe exhibited a high maximum adsorption capacity of 526 mg/g, and the adsorption kinetics followed a pseudo-second-order model, achieving over 90% removal of Cu(II) within 2.5 h. The Cu(II)-loaded material was subsequently evaluated as a sustainable catalyst in two applications: (i) an organic synthesis via “click” chemistry, reaching yields of up to 85%, and (ii) the decoloration of Congo Red via a Fenton-like process, achieving a decoloration efficiency of at least 84%. These dual uses demonstrate the potential of Cu(II)-loaded LDH as a cost-effective and environmentally friendly approach to simultaneous pollutant removal and catalytic valorization.

This study investigates the influence of divalent metals—(Mg(II), Co(II), and Ni(II)) in layered double hydroxides (LDHs), with a constant trivalent Fe(III) component—on the decoloration of crystal violet and methyl blue dyes via a Fenton-type oxidation reaction. The catalysts, synthesized by co-precipitation and hydrothermal treatment, were tested in both hydroxide and oxide forms under varying agitation conditions (0 and 280 rpm). A 2² × 3 factorial design was used to analyze the effect of the divalent metal type, catalyst phase, and stirring. The Mg/Fe oxide, with the highest BET surface area (144 m²/g) and crystallite size (59.7 nm), showed superior performance—achieving up to 98% decoloration of crystal violet and 97% of methyl blue within 1 h. The kinetic analysis revealed pseudo-second-order and pseudo-first-order fits for crystal violet and methyl blue, respectively. These findings suggest that LDH-based catalysts provide a fast, low-cost, and effective option for dye removal in aqueous systems.

From 1950 to the present, plastic production and use have increased mainly because plastics possess qualities like stability, light weight, versatility, and decreasing production costs. However, most plastics are not biodegradable, and only a small portion is recycled worldwide. Bioplastics serve as an alternative if they are biodegradable and derived from residual materials, promoting a circular economy. PHB is a polymer with characteristics similar to some commercial plastics. It was discovered in the 1920s and has been examined by researchers and engineers since then due to its potential as a biodegradable bioplastic. Some microorganisms can produce PHB under controlled conditions. In this work, PHB production was analyzed using two strains, Bacillus subtilis and Bacillus megaterium, and two byproducts—whey and glycerol—as substrates and varying the culture media compositions. Both byproducts and both strains are suitable for PHB production; the absence of nitrogen and trace element sources enhances PHB yield. Additionally, bacterial growth, substrate uptake, and PHB production were modeled using logistic growth and the Luedeking–Piret models.

In this work, two crop soils were characterized: Querétaro (Bajío) and the State of Mexico (Edomex). Both states are part of the Sierra Madre Occidental, where temperate and subhumid climates are experienced. The surface soils are predominantly Leptosols in the Bajio and Andosols-Feozems in the Edomex. The dynamic mobility of water and fertilizers is associated with humic substances, mineralogical phases, metal dispersion, pore type, pore volume, and thermal behavior^{4 4} Behavior. . Both agricultural soils exhibited high porosity and surfaces with co-dispersion of Al³⁺/Si⁴⁺ and Ti⁴⁺/Fe^2+,3+ ions and mixed mineralogical phases such as montmorillonite, anorthite, quartz, magnetite, goethite, hematite, and kaolinite. On the one hand, the C/N values for the Bajio-crop and Edomex-crop soils showed values of 15 and 11, respectively. On the other hand, the Bajio-crop and Edomex-crop soils showed C/O values of 0.38 and 0.42, respectively, indicating the accumulation of organic carbon and the presence of various humic substances. Finally, the Bajio-crop soil presented a higher surface area, pore diameter, and pore volume than the Edomex-crop soil, which is associated with high adsorption and nutrient retention. On the contrary, the Edomex-crop soil presented greater thermal resistance than the Bajio-crop soil, which is associated with a better capacity for heat dissipation during irrigation processes or fertilizer application.