Recent progress in the quantitative assessment and interpretation of photoactivity

The development of the photo-catalysis field is limited by a deficient quantitative assessment of photo-activity. The interplay between mass and momentum transport together with radiative transfer phenomena taking place at any photo-catalytic reaction or process makes complex such quantitative assessment. To reach this goal, the review studies the measurement, meaning, and analysis of three types of observables. The first family of observables has the reaction rate and closely connected observables as the turnover frequency as central pieces. The second family owns the so-called efficiency observables, starting from the photonic yield and quantum efficiency of the reaction and ending in the global efficiency of the process. Finally, the review studies kinetic constant observables. The contribution focusses on most rencet contribution analyzing these observables in terms of their (adequate) measurement conditions and physico-chemical interpretation, in order to unveil their full potential in the context of the photo-catalysis field.MCIN/AEI PID2019-105490RB-C31ERDF A way of making EuropeEuropean CommissionConsejo Nacional de Ciencia y Tecnologia (CONACyT) SENER-CONACyT 117373UGR PPJIA2019-0

Diseño de un Seminario/Laboratorio asistido por ordenador para el estudio de procesos de foto-descontaminación de efluentes gaseosos en MATLAB®

El proyecto ha desarrollado un seminario/laboratorio asistido por ordenador que incluye la simulación de un sistema de reacción para la descontaminación de corrientes gaseosas y la validación experimental a partir de medias experimentales del flujo de fotones en el sistema lámpara-reactor. Ha sido diseñado como actividad práctica de la asignatura “Ingeniería Ambiental” del Grado en Ingeniería Química de la Universidad de Granada. Estará relacionado con los contenidos que se desarrollan en el “Bloque 2: Contaminación de corrientes gaseosas” a partir del estudio y diseño de un sistema de reacción foto-catalítico para la eliminación de contaminantes en fase gas; promoviendo el desarrollo de competencias básicas, generales y específicas de la asignatura recogidas en la memoria verificada del grado. Se ha realizado el diseño completo de la actividad generando una gran variedad de material didáctico entre los que se encuentran: presentaciones/diapositivas vinculadas a la actividad, guías de desarrollo del seminario, código desarrollado en MATLAB®, guion de prácticas para la validación experimental, etc. Estos han sido diseñados para que puedan ser aplicados en formato presencial, híbrido (presencial/no presencial) o completamente virtual. Se han diseñado varias plantillas de trabajo para el estudiantado que están asociadas a distintos niveles de dificultad, lo que permitirá una relativa flexibilidad para su aplicación en otras asignaturas del Grado en Ingeniería Química. La parte final del seminario incluye la validación experimental del modelo a partir de mediciones básicas de propiedades ópticas del equipo de reacción, de modo que este proyecto ha incluido también tareas donde se han diseñado estas actividades experimentales

Análisis Pinch. Diseño vs Rediseño

Resumen El diseño de las redes de intercambio de calor es una tarea casi obligada para muchos ingenieros en un amplio número de industrias. El Análisis Pinch está formado por un conjunto de herramientas que permiten diseñar redes de intercambio para garantizar un uso eficiente de la energía dentro de las industrias de procesos; sin embargo, rediseñar una red en operación siguiendo el mismo procedimiento para cuando se diseña puede conducir a resultados poco satisfactorios, sobretodo porque se está desechando un área de intercambio por la que se ha pagado. En este trabajo se explican las bases conceptuales, así como las semejanzas y diferencias entre las metodologías recomendadas para abordar proyectos de diseño y de rediseño; haciendo uso de las herramientas del Análisis Pinch. Estas estrategias son aplicadas a una refinería de petróleo cubana y como resultado se obtienen dos variantes de solución. La primera sigue el procedimiento clásico de diseño de una red de intercambio de calor, mientras que para el rediseño de la red se utiliza el concepto de eficiencia de área de intercambio propuesto por Tjoe y Linnhoff. A este segundo enfoque se le agrega una etapa donde se aplican técnicas de optimización, lo que permite eliminar la aleatoriedad durante la búsqueda de las mejores variantes de rediseño. La alternativa seleccionada es evaluada teniendo en cuenta criterios técnicos, económicos y medioambientales. The design of the heat exchanger networks is a task almost forced for many process engineers. These projects are very important in a wide number of industries. The Pinch Analysis includes a group of tools that allow to design exchanger networks. The objective is to guarantee an efficient use of the energy inside the process industries. However, to retrofit a network in operation following the same procedure for when it is designed, it can cause bad results, because the paid exchange area gets lost.In this paper the conceptual bases are explained, as well as the similarities and differences among the methodologies recommended to approach design and retrofit projects. These strategies are applied to a Cuban refinery of petroleum and two alternatives are obtained. The first one follows the classic procedure of design of a heat exchanger networks and to retrofit the network the used method it is the proposed by Tjoe and Linnhoff. In this method, techniques of optimization are used what allows to eliminate the randomness during the search of the best variants of retrofit. The selected alternative is evaluated keeping in mind technical, economic and environmental approaches

Microwave-assisted valorization of pig bristles: towards visible light photocatalytic chalcocite composite

Waste valorization for the production of valuable materials is of great importance for sustainable development. Herein, a new green methodology for the synthesis of photocatalytically active copper sulfide (Cu2S) carbon composites using pig bristles is reported. The catalyst was prepared via microwave-assisted methodology using ethylene glycol as the solvent, pig bristles as the sulfur and carbon source, and copper chloride as the metal precursor. Cu2S carbon composites (denoted as pb-Cu2S, where “pb” stands for “pig bristle”) were characterized by XRD, N2 physisorption, EDX and UV-Vis spectroscopy. In order to validate the practical utilization of pig bristle-derived chemicals, the photocatalytic degradation of methyl red using pb-Cu2S was investigated under white, blue, green and red visible light irradiation

Facile synthesis of B/g-C3N4 composite materials for the continuous-flow selective photo-production of acetone

In this work versatile boron–carbon nitride composite materials were synthesized and utilized in a sustainable process using sunlight as the energy source for the continuous-flow selective photocatalytic production of acetone from 2-propanol. It is worth highlighting that the sample preparation was carried out by an environmentally friendly strategy, without a solvent or additional reagents. Samples containing boron in 1–10 wt% were subjected to physico-chemical characterization using XRD, porosimetry, UVvisible spectroscopy, TEM, energy-dispersive X-ray spectroscopy and XPS. The reaction output was analyzed on the basis of the reaction rate, selectivity and quantum efficiency of the process. A correlation analysis between catalytic properties with two observables, the boron phase distribution in the materials and charge handling efficiency (measured using photoluminescence), rationalizes photoactivity. Such an analysis indicates that the presence of an amorphous boron metallic phase and its contact with the carbon nitride component are key to setting up a renewable and easily scalable chemical process to obtain acetone.MINECO (Spain) ENE2016-77798-C4-1-RConsejo Superior de Investigaciones Cientificas (CSIC)Secretaria de Ciencia Tecnologia e Innovacion of CDMX (SECTEI, Mexico)MINECO CTQ2016-78289-PEuropean Union (EU)RUDN University Program 5-10

A Sustainable Approach for the Synthesis of Catalytically Active Peroxidase-Mimic ZnS Catalysts

Zinc sulfides are emerging as promising catalysts in different fields such as photochemistry or organic synthesis. Nevertheless, the synthesis of ZnS compounds normally requires the utilization of toxic sulfur precursors, e.g., thiourea which is a contaminant and carcinogenic agent. As a result, new green and sustainable synthetic methodologies are needed. Herein, an innovative, simple, and cheap approach for the synthesis of ZnS carbon composites is reported. Zinc acetate dihydrate was employed as metal precursor while wasted pig bristles were employed as carbon and sulfur source. The phase and the morphology of the compounds were analyzed by XRD, XPS, SEM, and EDX and the surface area was determined by nitrogen physisorption. ZnS carbon materials showed remarkable peroxidase-like catalytic activity for two different model reactions: the liquid-phase selective oxidation of benzyl alcohol and toluene to benzaldehyde (conversions up to 63% and 29% and selectivities up to 86% and 87%, respectively) using hydrogen peroxide as oxidant under microwave irradiation

Er-W codoping of TiO2-anatase: structural and electronic characterization and disinfection capability upon UV, visible, and near-IR excitation

The codoping of the anatase structure with tungsten and erbium was carried out using a microemulsion preparation procedure. Tungsten and erbium single doped and pure anatase nanomaterials were also prepared. The corresponding solids were characterized using X-ray diffraction, surface area, transmission electron microscopy, X-ray photoelectron and absorption (X-ray near-edge and extended X-ray absorption) spectroscopies as well as UV–vis and photoluminescence spectroscopies. Results provided a complete structural and electronic characterization of the solids, showing the unique features generated by the copresence of tungsten and erbium at substitutional positions of the anatase structure. The disinfection capability of these single and codoped TiO2-based materials was tested against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria and under ultraviolet, visible and near infrared light excitations. The ErW-anatase solid presents significant photoactivity in the elimination of both microorganisms in the whole UV–vis-nearIR range of excitation wavelengths. The biocidal results were interpreted with the help of a kinetic modelling of the experiments and correlated with results from the physico-chemical characterization of the samples and from an electron paramagnetic resonance and optical study of the radicals species produced under illumination. This procedure indicates a different physical origin of the photoactivity for light excitation above and below ca. 500 nm

Highly active catalytic Ru/TiO2 nanomaterials for continuous production of γ-valerolactone

Green energy production from renewable sources is an attractive but challenging topic to face the likely energy crisis scenario in the future. In the current work, a series of versatile Ru/TiO2 catalysts were simply synthesized and employed in continuous flow catalytic transfer hydrogenation of industrially derived methyl levulinate biowaste (from Avantium Chemicals B.V.) to γ-valerolactone. Different analytical techniques were applied in the characterization of the as-synthesized catalysts, including XRD, SEM, EDX, TEM and XPS etc. The effects of various reaction conditions (e.g. temperature, concentration and flow rate) were investigated. Results suggested that optimum dispersion and distribution of Ru on the TiO2 surface could efficiently promote production of γ-valerolactone, with 5% Ru/TiO2 catalyst providing excelling catalytic performance and stability as compared to commercial Ru catalysts

Thermo-photo degradation of 2-propanol using a composite ceria-titania catalyst: Physico-chemical interpretation from a kinetic model

This work describes a study carried out to construct and determine a kinetic formalism for the gas-phase degradation of 2-propanol using a combined thermo-photo based process. Outstanding catalytic performance was observed for a composite ceria-titania system with respect its parent ceria and titania reference systems. Thermo-photo as well as parallel photo- and thermal-alone experiments were carried out to interpret catalytic behavior. The kinetic experiments were conducted using a continuous flow reactor free of internal and external mass-heat transfer and designed using a Box-Behnken formalism. The kinetic expression developed for the thermo-photo degradation process explicitly includes the effect of the photon absorption in the reaction rate and leads to a mathematical formula with two components having different physico-chemical nature. This fact is used to settle down a fitting procedure using two steps (two separated experimental sets of data concerning temperature, light intensity, oxygen, water and/or 2-propanol concentrations) with, respectively, four and three parameters. The kinetic formalism was validated by fitting the experimental data from these two independent experiments, rendering a good agreement with the model predictions. The parameters coming from the kinetic modelling allow an interpretation of the catalytic properties of the ceria-titania catalyst, quantifying separately its enhanced performance (with respect to its parent systems) in the photonic and thermal components for the process. The procedure is applicable to a wide variety of thermo-photo processes in order to contribute to the understanding of their physical roots

Enhancing photocatalytic performance of TiO2 in H2 evolution via Ru co-catalyst deposition

A series of ruthenium catalysts supported into pure anatase titania were tested in the photo-production of hydrogen from methanol:water mixtures under UV and visible illumination conditions. Catalysts containing 1, 2, 3 and 5 wt.% of ruthenium were subjected to a characterization study with the help of X-ray diffraction, Raman, X-ray photoelectron spectroscopy, photoluminescence, morphology as well as scanning and transmission electron microscopy. Through the measurement of the optical properties of the suspension of the catalysts and the hydrogen photo-production reaction rate we calculate the true quantum efficiency. Optimum activity is presented by the catalyst with a 3 wt.% of Ru component, which shows quantum efficiency values of ca. 3.1 and 0.6% under, respectively, UV and visible light illumination. Careful examination of the physico-chemical properties of the solid allows to establish a correlation between the ruthenium surface exposed and the quantum efficiency. The implications of such result to justify chemical activity of the ruthenium supported samples are discussed both for UV and visible illumination conditions