“EFECTO DEL CONTENIDO DE ÓXIDO DE LITIO EN FORMULACIONES CATALÍTICAS CoMo/Al2O3-MgO-Li2O(x) PARA LA HIDRODESULFURIZACIÓN DE DIBENZOTIOFENO”

El desarrollo de formulaciones catalíticas convencionales a base de Co(Ni)Mo usando soportes catalíticos de alúmina (Al2O3) con alta acidez han adquirido un gran interés para los investigadores, quienes han reportado la remoción de azufre (S) contenido en fracciones del petróleo, sin embargo estas formulaciones presentan el inconveniente de hidrogenar estas moléculas, lo cual disminuye la cantidad de insaturados presentes en estas fracciones del petróleo. Esto nos lleva a la modificación del catalizador convencional de Co(Ni)Mo/Al2O3 disminuyendo su acidez con la adición de magnesia (MgO), por otra parte la magnesia contenida en el soporte presenta la desventaja de baja estabilidad textural y estructural sobre todo cuando esta se expone al medio ambiente, debido a la naturaleza higroscópica de la magnesia al transformarse de MgO a Mg(OH)2 y MgCO3, lo cual lleva a un colapso en la superficie específica accesible. Motivo por el cual usando algún aditivo que puede ser un óxido alcalino que pueda promover la estabilidad estructural, textural y baja acidez de las formulaciones catalíticas convencionales que contengan magnesia. En este trabajo se propone la adición en la formulación catalítica de diferentes contenidos de un óxido alcalino, como lo es el óxido de litio Li2O de forma que se pueda encontrar cual es el contenido óptimo para obtener una buena remoción de azufre sin hidrogenar en demasía los insaturados. Estas formulaciones se caracterizaron por diferentes técnicas como, Fisisorción de N2, FTIR, Raman, DRX, SEM y UV/Vis para determinar sus propiedades texturales y estructurales. Se determinó la fuerza y cantidad de sitios básicos en la superficie de las muestras mediante la termodesorción de una molécula sonda como el CO2, seguida a través de espectroscopia IR, encontrándose un incremento ligero en la presencia de sitios básicos en las mismas. Los resultados de actividad catalítica están relacionados con la incorporación e incremento del óxido alcalino en donde se reduce la hidrogenación con cantidades menores al 5% de Li2O. Finalmente este trabajo contribuye al entendimiento del uso de soportes de baja acidez como alternativa para soportar fases activas de CoMo, los cuales preservan la hidrodesulfuración y no hidrogenan en demasía los insaturados

Relevant changes in the properties of Co(Ni)Mo/Al2O3 HDS catalysts modified by small amounts of SiO2

The changes in hydrodesulfurization activity, selectivity, dispersion, sulfidation, and extent of promotion of Co(Ni)Mo catalysts were investigated when the alumina support surface is modified by grafting 4 wt% silica. Adding SiO2 eliminates the most reactive hydroxyl groups on the alumina surface (IR band at 3775 cm 1) decreasing the possibility of generating tetrahedral Mo species difficult to sulfide in favor of octahedral ones capable of contributing to the sulfided active phase. The catalysts were evaluated in the hydrodesulfurization of 4,6-dimethyldibenzothiophene. Incorporating SiO2 to alumina increases the hydrogenation rate constant and therefore the global hydrodesulfurization rate of 4,6-dimethyldibenzothiophene and enhances the promotion of Mo by Co (or Ni). The global sulfidation of Ni is not affected by the addition of silica but the sulfidation of cobalt is significantly improved. The extent of promotion of the NiMo/Al2O3 and NiMo/SiO2/ Al2O3 catalysts was greater than the one achieved in their Co-promoted counterpartsCB-168827, beca posdoctoral otorgada por CONACyT al Dr. Adolfo Romero Galarza from DGAPA-UNAM, project PAPIIT-IN-113015. We thank Mariela Bravo-Sanchez (Universidad de Guadalajara) for her discussion about the XPS results, Ivan Puente for the TEM work, and Alberto Herrera-Gómez (CINVESTAV-Unidad Querétaro, Mexico) for providing computer program AANALYZER version 1.2

Catálisis en el Centro Conjunto de Investigación en Química Sustentable, uaem-unam*

Describimos aquí las actividades de investigación en el área de catálisis realizadas por algunas investigadoras de la Facultad de Química de la Universidad Autónoma del Estado de México, adscritas al Centro Conjunto de Investigación en Química Sustentable, uaem-unam. Se incluyen las líneas de investigación que desarrollan, las contribuciones que han generado y los logros en este campo obtenidos en los últimos años. También se presenta información sobre la infraestructura con que se cuenta en el cciqs y en la Facultad de Química para llevar a cabo investigación sobre catálisis; la importancia que tienen los trabajos de colaboración nacional e internacional, así como, la formación de recursos humanos altamente especializados en esta área. Por último, presentamos las perspectivas de investigación y desarrollo planteadas para el campo de la catálisis

Photocatalytic Degradation of the Malachite Green Dye with Simulated Solar Light Using TiO2 Modified with Sn and Eu

This work reports on the synthesis of photocatalysts in thin film form of TiO2 modified with Sn, Eu as well as Sn and Eu simultaneously. The obtained films were characterized by X-Ray Photoelectron Spectroscopy, Raman Spectroscopy and Ultraviolet–Visible Spectroscopy, in order to obtain information on their chemical composition, vibrational features and optical properties respectively. Chemical composition reveal that the tin content was close to 4 at.%, whereas the europium content was approximately 1 at.%. Raman results show that the unmodified material is crystalline TiO2 in the anatase phase; the Sn addition promotes the formation of the rutile crystalline phase. Europium incorporation as a novel modifier produces TiO2 in which a mixture of both crystalline phases coexists. Optical measurements reveal that the band gap energy for all samples remains close to 3.4 eV. The photocatalytic activity was evaluated in the degradation reaction of the Malachite Green dye under simulated solar light. The most relevant result is that photocatalysts containing Sn and Eu show higher photocatalytic activity (60% of MG conversion) than the TiO2 thin film (28% of MG conversion). The main objective of this work was to investigate the changes produced in the resulting material due to Sn and Eu incorporation as well as try to correlate such changes with the corresponding catalytic activity in terms of the Malachite Green dye conversion degree.SIEA UAE

Quantification of the sulfidation extent of Mo in CoMo HDS catalyst through XPS

Background removal in X-ray photoelectron spectroscopy (XPS) spectra was carried out in Co–Mo hydrodesulfurization (HDS) catalysts supported alumina using traditional and recent methods. The sulfidation extent, expressed by the XPS area ratio AMo3d-MoS2/AMo3d-Total, which is a fundamental parameter in the performance of a hydrodesulfurization catalyst, was obtained using different methodologies. The methods include the use of the background active approach, in which the background is optimized during peak-fitting. The method allows for the use of several types of backgrounds, which proved crucial for fitting the Mo 3d-S 2s and the S 2p–Si 2p regions. Both regions contain two overlapped elements, making fundamental a distinction between them. In these cases, a slope background subtraction was used in conjunction with the Shirley-Vegh-Salvi-Castle (SVSC) method to have a clear distinction between the different strengths of backgrounds arising from the overlapped peaks Mo 3d-S 2s and S 2p–Si 2p. From the resulting fitting, the relative percentage (% rel.) of each species present in Mo and S in the catalyst CoMoAl was obtained. The results were compared with those obtained using the static (traditional) approach. With these results, the sulfidation extent, an important parameter in the performance of the HDS catalyst was determined.Adolfo-Romero Galarza thanks Consejo Nacional de Ciencia y Tecnologia (CONACyT), Mexico for their postdoctoral fellowship (ID. 1908/2010C ) . We acknowledge financial support from Direccion General de Asuntos del Personal Academico ( DGAPA) Mexico, UNAM , project PAPIIT-IN-113015 . The authors appreciate the support provided by Gustavo Gomez-Sosa (CINVESTAV-Qro.) for the acquisition of the XPS data and Alberto Herrera-Gómez (CINVESTAV-Unidad Queretaro, Mexico) for engaging in useful discussion regarding the spectra fitting and for providing computer program AANALYZER version 1.2

Efficient Removal of Hg(II) fromWater under Mildly Acidic Conditions with Hierarchical SiO2 Monoliths Functionalized with –SH Groups

In this work, novel adsorbents based on 3D hierarchical silica monoliths functionalized with thiol groups were used for the removal of Hg(II) ions from an acidic aqueous solution (pH 3.5). Silica monoliths were synthesized by using two different pluronic triblock polymers (P123 and F127) to study the effect of porous structure on their sorption capacity. Before and after functionalization by grafting with 3-mercaptopropyltrimethoxysilane (MPTMS), the monoliths were characterized by several techniques, and their Hg(II) removal potential was evaluated in batch experiments at 28 C and pH 3.5, using different initial concentrations of Hg(II) ions in water (200–500 mg L1). The thiol groups of the monoliths calcined at 550 C showed thermal stability up to 300 C (from TG/DTG). The functionalized monolith synthesized with P123 polymer and polyethylene glycol showed favorable hierarchical macro-mesopores for Hg(II) adsorption. M(P123)–SH exhibited 97% removal of Hg(II) at concentration 200 mg L1. Its maximum adsorption capacity (12.2 mmol g1) was two times higher than that of M(F127)–SH, demonstrating that the 3D hierarchical macro-mesoporosity allowing accessibility of Hg(II) to thiol groups favors the physical and chemical adsorption of Hg(II) under slightly acidic conditions

Dibenzothiophene hydrodesulfurization over P-CoMo on sol-gel alumina modified by La addition. Effect of rare-earth content

articuloAlumina-lanthana (La at 1, 3, or 5 wt%) supports were prepared by sol-gel from Al alkoxide sol where La(NO 3 ) 3 was added. Annealed (550 °C) xerogels were characterized by N 2 physisorption, thermal analysis (TG-DTA), X-ray diffraction (XRD), scanning electron microscopy- energy dispersive spectroscopy (SEM-EDS), CO 2 -adsorption studied in IR region, Raman and ultraviolet-vis (UV-vis) spectroscopies. The texture of amorphous binary matrices of high La dispersion was adequate to applications in catalysts for middle distillates hydrodesulfurization (HDS). Generally, the amount and strength of surface basic sites increased with La content in solids. Mo (at 2.8 at. nm −2 ) and Co (at Co/(Co+Mo) = 0.3) were deposited over carriers by one-pot simultaneous impregnation in the presence of PO 4 3− (P 2 O 5 /(NiO+MoO 3 ) = 0.2 mass ratio). Calcined (400 °C) Co-Mo-P impregnated precursors had decreased basicity as to that of corresponding carriers, suggesting strong La-deposited species interaction. As La content in carriers increased Mo=O Raman stretching vibrations shifted to lower wave-numbers (949 to 935 cm −1 ) suggesting octahedral molybdates coordination change to tetrahedral. Although La at the lowest concentration (1 wt%) enhanced dibenzothiophene, HDS (~38% higher as to the Al 2 O 3 -supported formulation) desulfurization was significantly diminished at augmented content. Presence of hardly sulfidable tetrahedral Mo originated during impregnation at basic conditions in pores of La-modified carriers seemed to dictate observed behavior. Rare earth content in formulations enhanced selectivity to biphenyl.: J. Escobar acknowledges financial support from IMP (Y.00105) and SENER-CONACYTHidrocarburos (115086) fund

Nanocomposite Bi/TiO2 multilayer thin flms deposited by a crossed beam laser ablation confguration

Articulo relacionado con la caracterizacion de materialesA crossed beam pulsed laser deposition confguration was used to prepare nanocomposites Bi/TiO2 thin flms on two different substrates. The multilayered system was formed by depositing TiO2 and Bi layers alternately. In order to embed the Bi nanostructures in TiO2, the subsequent TiO2 layers were synthesized using a constant number of laser pulses (3000) corresponding to a thickness of approximately 21 nm. The Bi nanostructures were deposited on the TiO2 layers alternately by irradiating the Bi target with 30, 100, 200, and 300 laser pulses. In this way, the Bi nanostructures were embedded inside the TiO2 matrix. A total of 8 samples with bismuth and one reference, with TiO2 only, were produced. Transmission Electron Microscopy (TEM) showed that nearly spherical nanoparticles (NPs) were obtained at lower number of pulses, whereas at 300 pulses a quasi-percolated nanostructured Bi flm was obtained. X-Ray Photoelectron Spectroscopy (XPS) revealed that the TiO2 layers were not afected due to the bismuth presence. Raman Spectroscopy showed vibrational features characteristic of the rutile phase for the titania layer. The Raman spectrum of the multilayer prepared using 300 laser pulses on the bismuth, suggests that the Bi layer is formed by a mixture of metallic Bi, and α-Bi2O3. The Ultraviolet–Visible Spectroscopy reveals that no substantial changes are presented in the transmittance spectra indicating similar optical properties of the diferent deposits. Finally, the photoluminescence emission spectra indicate that the substrate position in the deposition chamber afects the electronic structure of the material.A. Martínez-Chávez thanks CONACyT for the scholarship granted (No. 815785). K. Esquivel and L. Escobar thank the Engineering Faculty-UAQ for the fnancial support granted through the Attention to national problems fund and the FONDEC-UAQ-2021. We greatly appreciate the collaboration of R. Basurto in performing the XPS measurements

Hydrogen production by laser irradiation of metals in water under an ultrasonic field: A novel approach

An alternative method for hydrogen production by laser irradiation of metals in water is proposed. Metals such as Ti, Al, Mg an Al–Mg alloy and Si, were laser ablated and subjected to an ultrasonic field simultaneously to promote a displacement chemical reaction of hydrogen from water. The produced gas was characterized by gas chromatography and mass spectrometry. Molecular hydrogen was found suggesting that this procedure allows the production of H 2 of high purity. All the studied metals under laser irradiation produced H 2 and the volume rise as the laser fluence was increased following a no-linear monotonic behavior with a similar tendency. Without ultrasound the amount of hydrogen was significantly reduced. An important advantage of the proposed H 2 production method is the low amount of mass consumed which lead to maximum hydrogen production rates close to 1300 ml/min per gr of aluminumThis work was partially supported by the CONACYT (Mexico) Projects CB-240998 and SENER-CONACYT 226151. The authors thank Arturo Olalde and Albina Gutierrez for their technical assistance

As2O3 Induces Oxidative Stress in Gill, Liver, Brain and Blood of Cyprinus carpio

Artículo científicoArsenic (As) is a toxic trace element for diverse aquatic species. It is present naturally in water in diverse oxidation states and chemical species. During its biotransformation, As induces production of reactive oxygen species, eliciting oxidative stress in diverse organisms. This study aimed to evaluate As-induced toxicity in brain, liver, blood and gill of the common carp Cyprinus carpio.Secretaría de Investigación y Estudios Avanzados of the Universidad Autónoma del Estado de México (SIEA-UAEM, project UAEM 3722/2014/CID)