La catálisis y fotocatálisis en la Facultad de Ciencias Químicas de la Universidad Autónoma de Nuevo León

En esta contribución se describen las actividades de investigación, docencia y vinculación que se realizan en las áreas de catálisis y fotocatálisis en la Facultad de Ciencias Químicas (fcq) de la Universidad Autónoma de Nuevo León (uanl). Se presentan los inicios de investigaciones en el área de catálisis y fotocatálisis en la fcq de la uanl, que coincidió con la apertura de los posgrados de maestría y doctorado en ciencias con orientación en procesos sustentables, y la orientación en química analítica ambiental ambos en el Padrón Nacional de Posgrados de Calidad (pnpc) del Consejo Nacional de Ciencia y Tecnología (conacyt) de México. Se cuenta con diferentes tipos de investigación en catálisis y fotocatálisis, tanto en la parte de síntesis y caracterización de nuevos catalizadores, estudios en diferentes tipos de reactores catalíticos para diferentes reacciones en aplicaciones ambientales y de biocombustibles. Las vinculaciones con grupos de catálisis con diferentes universidades de México y Estados Unidos de América, así como una doble titulación con la Universidad de Isla Baleares, en España. Se han dado servicios a la industria en área de catálisis y fotocatálisis y se tienen proyectos de colaboración con la plataforma solar de Almería, en España, por parte del grupo del Laboratorio de Fotocatálisis y Electroquímica Ambiental. En los posgrados relacionados con la investigación en catálisis se vislumbra un crecimiento a corto y mediano plazo en número de estudiantes del extranjero y productos académicos con colaboración internaciona

Facile synthesis of low band gap ZnO Microstructures

Abstract In this work a simple chemical route was employed to synthesize ZnO microparticles by precipitation from aqueous solution of ZnCl2 as precursor, NaOH as oxidizing and sodium dodecyl sulfate (SDS) as surfactant. Samples of ZnO microparticles were analyzed by scanning electron microscopy (SEM), FTIR spectroscopy, Raman spectroscopy, X-Ray diffraction, UV/Vis-NIR diffusereflectance,highresolutiontransmissionelectronmicroscopy(HR-TEM),andN2 adsorption-desorption.Itwasobserved from SEM analysis that ZnO microparticles with morphologies resembling six-blade impeller with diameters in the range of 500 nm to 1 m, and sheet-like (approximately 200 nm×300 nm) were obtained through this technique. X-Ray diffraction and Raman analyses confirmed the obtaining of hexagonal wurtzite ZnO crystal structure. The calculated band gap energy was 3.19 eV, which is slightly lower than the average value reported in the literature. Specific BET area of ZnO microparticles was 26.5 m2/g. Keywords: ZnO, microstructures, band gap energy, SEM, morphology. Resumen En este trabajo se empleó un a ruta química sencilla para sintetizar micropartículas de ZnO mediante precipitación en solución acuosa de ZnCl2 como precursor, NaOH como oxidante y dodecil sulfato de sodio (SDS) como tensoactivo. Las muestras de ZnO fueron analizadas mediante microscopía de barrido electrónico (SEM), espectroscopía de FTIR, espectroscopía Raman, difracción de rayos-X, reflectancia difusa de UV/Vis-NIR, microscopía de transmisión de electrones de alta resolución (HRTEM), y mediante adsorción-desorción de N2. Se observó mediante análisis de SEM que mediante esta técnica se obtienen micropartículas de ZnO con morfologías similares a impulsores de seis-aspas con diámetros entre 500 nm y 1 m, morfologías tipo-hojas(deaproximadamente200nm×300nm).Losanálisisdedifracciónderayos-XydeRamanconfirmaronlaobtención de ZnO con estructura cristalina wurtzita hexagonal. La energía de band gap calculada fue de 3.19 eV, la cual es ligeramente menor que el valor promedio reportado en la literatura. El área superficial BET de las nanopartículas de ZnO fue de 26.5 m2/g Palabras clave: ZnO, microestructuras, energía de band gap, SEM, morfología

Desorption of furfural from bimetallic Pt-Fe oxides/alumina catalysts

In this work, the desorption of furfural, which is a competitive intermediate during the production of biofuel and valuable aromatic compounds, was studied using pure alumina, as well as alumina impregnated with iron and platinum oxides both individually and in combination, using thermogravimetric analysis (TGA). The bimetallic sample exhibited the lowest desorption percentage for furfural. High-resolution transmission electron microscopy (HRTEM) imaging revealed the intimate connection between the iron and platinum oxide species on the alumina support. The mechanism of furfural desorption from the Pt-Fe/Al2O3 0.5%-0.5% sample was determined using physisorbed furfural instead of chemisorbed furfural; this mechanism involved the oxidation of the C=O group on furfural by the catalyst. The oxide nanoparticles on γ-Al2O3 support helped to stabilize the furfural molecule on the surface

Catalytic conversion of 5-hydroxymethylfurfural (5-HMF) over Pd-Ru/FAU zeolite catalysts.

We present this study on FAU-type zeolites were prepared varying the Si/Al ratio (4, 5 and 6) and crystallization time (4, 6 and 8 h) to produce a highly pure and homogeneous material with enhanced surface area values. Bimetallic Pd-Ru and Pt-Ru (0.5 wt.% of each metal) were impregnated onto the zeolites matrix by the incipient wetness impregnation method. The materials were characterized by X-ray diffraction (XRD), nitrogen physisorption, Fourier Transform Infrared spectroscopy (FT-IR), Scattering Electronic Microscopy (SEM), Scattering and Transmission Microscopy (STEM), temperature-programmed desorption (TPD), temperature-programmed desorption (TPR) and Inductively Couples Plasma- Mass Spectrometer (ICP-MS). Results indicated that using lower Si/Al ratios favored the catalytic activity. Also, the longest crystallization time had a positive effect on surface area, homogeneous particle size distribution and crystallinity. The catalytic performance in the esterification of 5-hydroxymethylfurfural (5-HMF) to produce 5-acetoxymethylfurfural (AcMF) was investigated. The maximum 5-HMF conversion of 87.28 % was achieved using pure zeolite with relation Si/Al = 5, and 8 h of crystallization. Pd-Ru supported onto same zeolite showed a conversion of 84.22 %. The highest selectivity towards AcMF of 71.29 % with pure zeolite Si/Al = 5 and 8 h of crystallization was achieved, followed by Pd-Ru/FAU with Si/Al = 5 and 8 h of crystallization, achieving 60.42 %. Finally, results shown that the interaction between the properties of zeolitic support and the metallic species, specifically Pd, had a positive effect in the catalytic process the pristine zeolite showed improved catalytic characteristics related to its acid strength

Modulation of higher-order olfaction components on executive functions in humans

The prefrontal (PFC) and orbitofrontal cortex (OFC) appear to be associated with both exec- utive functions and olfaction. However, there is little data relating olfactory processing and executive functions in humans. The present study aimed at exploring the role of olfaction on executive functioning, making a distinction between primary and more cognitive aspects of olfaction. Three executive tasks of similar difficulty were used. One was used to assess hot executive functions (Iowa Gambling Task-IGT), and two as a measure of cold executive functioning (Stroop Colour and Word Test-SCWT and Wisconsin Card Sorting Test- WCST). Sixty two healthy participants were included: 31 with normosmia and 31 with hyposmia. Olfactory abilities were assessed using the '' Sniffin ' Sticks '' test and the olfactory threshold, odour discrimination and odour identification measures were obtained. All partici- pants were female, aged between 18 and 60. Results showed that participants with hypos- mia displayed worse performance in decision making (IGT; Cohen ' s- d = 0.91) and cognitive flexibility (WCST; Cohen ' s- d between 0.54 and 0.68) compared to those with normosmia. Multiple regression adjusted by the covariates participants ' age and education level showed a positive association between odour identification and the cognitive inhibition response (SCWT-interference; Beta = 0.29; p = .034). The odour discrimination capacity was not a predictor of the cognitive executive performance. Our results suggest that both hot and cold executive functions seem to be associated with higher-order olfactory functioning in humans. These results robustly support the hypothesis that olfaction and executive mea- sures have a common neural substrate in PFC and OFC, and suggest that olfaction might be a reliable cognitive marker in psychiatric and neurologic disorders

Decision making impairment: A shared vulnerability in obesity, gambling disorder and substance use disorders?

Introduction: Addictions are associated with decision making impairments. The present study explores decision making in Substance use disorder (SUD), Gambling disorder (GD) and Obesity (OB) when assessed by Iowa Gambling Task (IGT) and compares them with healthy controls (HC). Methods: For the aims of this study, 591 participants (194 HC, 178 GD, 113 OB, 106 SUD) were assessed according to DSM criteria, completed a sociodemographic interview and conducted the IGT. Results: SUD, GD and OB present impaired decision making when compared to the HC in the overall task and task learning, however no differences are found for the overall performance in the IGT among the clinical groups. Results also reveal some specific learning across the task patterns within the clinical groups: OB maintains negative scores until the third set where learning starts but with a less extend to HC, SUD presents an early learning followed by a progressive although slow improvement and GD presents more random choices with no learning. Conclusions: Decision making impairments are present in the studied clinical samples and they display individual differences in the task learning. Results can help understanding the underlying mechanisms of OB and addiction behaviors as well as improve current clinical treatments

Thermocatalytic degradation of lignin monomer coniferyl aldehyde by aluminum–boron oxide catalysts

Two aluminum–boron oxide catalysts were produced via a sol–gel method at pH 3 and 4 during the solution mixing step of the synthesis, these materials were employed in thermocatalytic degradation of coniferyl aldehyde (CA), which was used as a probe molecule of the lignin polymeric molecule and is comprised of the repetitive monomers coniferyl, sinapyl, and paracoumaryl. The two synthesized catalysts were mostly amorphous and mesoporous, aiding in permeability and percolation of CA. A commercial catalyst was compared (Pt/alumina at 1 wt%) with both catalysts synthesized in this work by kinetic tests by varying the CA concentration and inlet temperature. Under the same reaction conditions, the commercial catalyst showed higher activity than the aluminum–boron oxide catalysts, but the synthetic catalysts presented a wider variety of organic products than the commercial catalyst. In particular, two high-value products, isomers of eugenol and isoeugenol, were yielded in higher percentages. The experimental reaction rate data was fit to a Langmuir–Hinshelwood model, and kinetic parameters were analyzed, revealing how the adsorbed CA molecules on the catalytic surface had higher mobility with the synthesized catalyst compared with the commercial catalyst, the value of $\Delta S_{\mathrm{ads}}^{0}$ for the synthetic catalysts were $-$5.48 and $-$4.31 J/mol-K and for the commercial catalyst $-$37.17 J/mol-K

Thermocatalytic degradation of lignin monomer coniferyl aldehyde by aluminum–boron oxide catalysts

Two aluminum–boron oxide catalysts were produced via a sol–gel method at pH 3 and 4 during the solution mixing step of the synthesis, these materials were employed in thermocatalytic degradation of coniferyl aldehyde (CA), which was used as a probe molecule of the lignin polymeric molecule and is comprised of the repetitive monomers coniferyl, sinapyl, and paracoumaryl. The two synthesized catalysts were mostly amorphous and mesoporous, aiding in permeability and percolation of CA. A commercial catalyst was compared (Pt/alumina at 1 wt%) with both catalysts synthesized in this work by kinetic tests by varying the CA concentration and inlet temperature. Under the same reaction conditions, the commercial catalyst showed higher activity than the aluminum–boron oxide catalysts, but the synthetic catalysts presented a wider variety of organic products than the commercial catalyst. In particular, two high-value products, isomers of eugenol and isoeugenol, were yielded in higher percentages. The experimental reaction rate data was fit to a Langmuir–Hinshelwood model, and kinetic parameters were analyzed, revealing how the adsorbed CA molecules on the catalytic surface had higher mobility with the synthesized catalyst compared with the commercial catalyst, the value of $\Delta S_{\mathrm{ads}}^{0}$ for the synthetic catalysts were $-$5.48 and $-$4.31 J/mol-K and for the commercial catalyst $-$37.17 J/mol-K