First International Conference on
Unconventional Catalysis, Reactors and Applications

Zaragoza-Spain, 16-18 October 2019
15:30   Unconventional activation/energy supply methods 2
Chair: Anabela Valente
20 mins

Souad Khannyra, Mohammed Addou, Maria Jesus Mosquera (presenter: Souad Khannyra)
Abstract: Usually, building materials are exposed to an extensive range of atmospheric contaminants, including particulate matter and other components such as organic and inorganic elements, especially on urban areas. Such pollutants tend to deposit on the surface of buildings, resulting in their aesthetic and structural deterioration. The preservation of building materials may be improved by the use of photocatalysts. Specifically, the development of self-cleaning materials could be a very promising approach to mitigate the esthetical damage of building materials and to reduce the amount of contaminants. Titanium dioxide (TiO2) has attracted attention from many researchers in different fields, especially in photocatalysis area. The major limitation in developing self-cleaning materials based on TiO2 is associated to its absorption, being exclusively localized in the UV range. Different methods have been used to improve TiO2 photocatalytic activity, being one the most suitable methods the use of metals because of their high localized surface plasmon resonance. In the present work, we have developed a simple sol-gel pathway for producing Cu-TiO2/SiO2 photocatalysts with application on buildings materials. The presence of copper increased the absorption in the visible range, leading to an improvement in the photocatalytic activity of TiO2. We have varied the loading of Cu, in order to study their effect on the photocatalytic activity. The prepared sols were sprayed on three substrates with different porosity. The obtained results show that the integration of Cu (5%) in a TiO2–SiO2 network significantly improved the photoactivity of the coating. The higher loadings of Cu in a TiO2–SiO2 (10% and 15%), led to a decrease in the photocatalytic properties.
20 mins

Emine Kayahan, Mathias Jacobs, Mumin Enis Leblebici (presenter: Emine Kayahan)
Abstract: Continuous-flow photochemistry in microreactors has gained attention of researchers since this technology can provide high reaction rates by overcoming the bottlenecks of the photoreactor designs: light utilization and mass transfer limitations [1]. Recently, a novel microstructured reactor, aerosol photoreactor, proved to work extremely efficiently [2]. In aerosol photoreactors, each droplet works as a microreactor. Unlike conventional microreactors, aerosol photoreactors can also provide high throughput. The aim of this work is to design and operate an aerosol photoreactor. The design parameters are droplet size, light intensity and thickness of the reactor. Droplet size affects mass transfer, light scattering and the residence time. Droplet sizes were characterized for a nozzle and two nebulizers. The Sauter mean droplet diameter was ranged from 44 to 30 µm in a nozzle working at 5 to 20 bars. Smaller droplet sizes were generated (5-15 µm) with the nebulizers. The preliminary spectroscopic measurements (Fig.1) suggest that the droplet size has the major effect on the attenuation of light rather than the reactant concentrations. In this study, two cylindrical photoreactors with different light paths will be build and tested with a model reaction. Droplet size and light intensity will be varied. Optimum reactor dimensions and operational conditions will be presented. References 1. Leblebici, M. E., B. Van den Bogaert, G.D. Stefanidis, T. Van Gerven, Chemical Engineering Journal, 2017 310, 240–248. 2. Ioannou, G. I., T. Montagnon, D. Kalaitzakis, S. A. Pergantis, G. Vassilikogiannakis, ChemPhotoChem, 2017, 1, 173–177.
20 mins

Alba García Sanchez, Carmen García, Patricia Reñones, Elena Alfonso, Mariam Barawi, Ignacio Villar, Raul Perez Ruiz, Fernando Fresno, Marta Liras, Víctor A de la Peña O'Shea (presenter: Víctor Antonio de la Peña O'Shea)
Abstract: Photocatalytic conversion of CO2 and H2O is an interesting route to produce fuels and chemicals; this process is also known as Artificial Photosynthesis (AP). In last years, extensive efforts have been made to develop efficient catalytic systems capable of harvesting light absorption and reducing CO2 especially when using water as the electron donor. Herein, we report different strategies and modifications of photocatalysts to increase process performance. Among them, an interesting approach to improve charge separation in photocatalytic systems is the use of heterojunctions. In this line, the combination of different semiconductors with noble metal nanoparticles or organic semiconducting polymers leads to a separation of the photogenerated charge carriers to increasing their life time, facilitating charge transfer to adsorbed molecules. The main products, using bare TiO2, were CO and H2, with low concentrations of CH4. The deposition of surface plasmon nanoparticles (SP-NPs) leads to changes in the selectivity to higher electron-demanding products, such as CH4. TAS measurements confirm that this behavior is due to the electron scavenging ability of SP-NPs [2]. Organo-inorganic hybrid materials show a dramatic reactivity improvement in CO2 photoreduction, enhancing methane selectivity. Reaction pathways are not well defined for this reaction and several uncertains are still unsolved [3]. To explain this behavior a combination of in-situ NAP-XPS, FTIR, TAS spectroscopies and theoretical tools has been used, showing a more efficient light absorption and charge transfer in the hybrid photocatalyst compared with bare materials. References 1. V. A. de la Peña O’Shea, D. P. Serrano, J. M. Coronado, “Current challenges of CO2 photocatalytic reduction over semiconductors using sunlight”, in Molecules to Materials Pathway to Artificial Photosynthesis, E. Rozhkova, K. Ariga (Eds.), Springer, London, 2015. 2. L. Collado, A. Reynal, F. Fresno, M. Barawi, V. Perez Dieste, C. Escudero, J. M. Coronado, D. Serrano, J. Durrant, V. A. de la Peña O’Shea. Nat. Commun. 2018, 9, 4986 3. Fresno F.; Villar-García, I.; Collado, L.; Alfonso-Gonzalez, E.; Reñones, P.; Barawi, M.; de la Peña O’Shea, V. A Mechanistic View of the Main Current Issues in Photocatalytic CO2 Reduction” J. Phys. Chem. Lett,2018 9 7319
20 mins

Sergio Muñoz, Marek Grzelczak, Ángel Martín, María José Cocero, Roland Dittmeyer, Alexander Navarrete (presenter: Alexander Navarrete Muñoz)
Abstract: Exciting advances are being made in the development of efficient photocatalytic catalytic materials for CO2 conversion. In order to extract their full potential, it is required to efficiently collect and transport the solar energy and the reactants to the catalyst. Thus, novel reaction devices are needed that provide robustness, scalability and flexible design. We have developed a concept for a plasmonic microreactor for CO2 activation. The reactor is based on abundant materials and is capable of handling a wide range of pressures. Even beyond the supercritical state of CO2 which is beneficial for hydrogenation reactions. The last advances on this new technology are going to be presented.