11:40
Catalysis in unconventional environments 2
Chair: Luca Salassa
11:40
20 mins
#14
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EXPERIMENTAL AND MODELLING STUDY OF METHANE DRY REFORMING IN A SPARK PLASMA REACTOR
Damjan Lašič Jurković, Andrej Pohar, Blaž Likozar
(presenter: Damjan Lasic Jurkovic)
Abstract: Over the recent years, there has been an increasing need for efficient processes for CO2 and CH4 conversion in order to reduce greenhouse gas concentrations as well as form valuable platform chemicals. Methane dry reforming (DRM) is a promising route for producing syngas from CH4 and CO2, which can be used for further synthesis of chemicals.1 DRM was carried out in a spark-plasma reactor with pin-to-pin geometry, using hollow electrodes as gas inlets in order to maximize the plasma coverage of the reagents. Different process parameters were studied, such as total gas flow rate, plasma power (by varying the input voltage) and different reagent ratios. The main products were H2 and CO, and relatively high conversions were obtained (up to 80% for CH4 and 70% for CO2). The reactor was also tested in plasma-catalytic configuration, utilizing different catalyst types, such as Ni-coated Al2O3 porous foam structured catalyst and pelletized commercial Ni/Al2O3. In addition, a three-dimensional kinetic and fluid-dynamic model was developed, taking into account the mass transfer in the form of convection and diffusion, heat-transfer and the reaction network. The reaction rate parameters were fitted to experimental data in order to achieve good model predictive power.
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12:00
20 mins
#36
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Development of a methane plasma kinetic scheme accounting for excited states in the frame of plasma-enhanced catalysis
Pierre A Maitre, Matthew S Bieniek, Panagiotis N Kechagiopoulos
(presenter: Pierre-André Maitre)
Abstract: Recent research has focused on the application of non-thermal plasma-catalysis for methane upgrading, where methane activation occurs through its collision with highly energetic electrons. The process feasibility has been demonstrated experimentally but the mechanistic details leading to enhanced performance are not yet fully understood. Several studies have suggested the higher internal energy of vibrationally excited states as key in promoting activity in the gas phase or the catalyst.
Micro-kinetic modelling is used for the study of this complex system. Building on the most elaborate published methane plasma-kinetic scheme, detail is significantly enhanced to account rigorously for the reactivity of excited states, considering reactions involving excited states, de-excitation by collisions, stepwise ionizations, etc. The developed kinetic scheme comprises an extensive set of 1011 reactions among 52 species (15 being excited states) and is the most comprehensive in methane plasma literature.
Non-catalytic 0D kinetics simulations reveal the important role of the excited states, with over 90% of methane conversion occurring through its initial vibrational excitation. Current work on extending the model with heterogeneous catalytic microkinetics aims to reveal the interaction of these excited states with the catalyst surface, with 0D global kinetic and 1D fluid simulations treating different time-scale processes.
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12:20
20 mins
#18
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METHANE-TO-ETHYLENE CONVERSION IN NANO-SECOND PULSED PLASMA
Evangelos Delikonstantis, Marco Scapinello, Georgios Stefanidis
(presenter: Evangelos Delikonstantis)
Abstract: In the preset work, non-oxidative methane coupling to ethylene in a nanosecond pulsed spark discharge is explored. It is found that operating at moderately elevated pressures (5 bar) and hydrogen cofeeding (CH4:H2=1:1), product selectivity is shifted from acetylene to ethylene that is produced as major product at high yield (~20% [1]), without use of catalyst, as shown in Fig.1 (left). A possible reaction mechanism that explains the C2 product shift in this single step process has been presented in Ref. [2]. Operating at ambient pressure, the discharge characteristics allow for acetylene formation as major product, which can be subsequently hydrogenated to ethylene by a highly selective catalyst placed in the post-plasma zone, as shown in Fig.1 (right). Such a hybrid plasma-catalytic reactor system can attain high ethylene yields at low cost since both heat and H2 required for the hydrogenation reaction are provided by methane cracking in the plasma zone itself. After establishing the optimum operating window, global ethylene yield of 26% is attained [3] in the two-step process, while 19% lower energy input is required (1642 versus 2020 kJ/molC2H4) in comparison to the single step process.
References
1. Scapinello, M., Delikonstantis, E., Stefanidis, G.D. Fuel, 2018, 222, 705–710.
2. Scapinello, M., Delikonstantis, E., Stefanidis, G.D., Chem. Eng. J. 2019, 360, 64–74.
3. Delikonstantis, E., Scapinello, M., Stefanidis, G.D., Fuel Process. Technol. 2018, 176, 33–42.
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12:40
20 mins
#76
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TiO2 NANOSHEETS AS A COMPONENT OF SELF-CLEANING BUILDING MATERIALS
M Luna, I Romero, ML Almoraima Gil, P Fornasiero, T Montini, MJ Mosquera, JJ Delgado
(presenter: Juan Jose Delgado)
Abstract: The deterioration of historic buildings and monuments has become a pressing concern in our modern society. Hundreds of chemical compounds are emitted directly or indirectly into the atmosphere due to industrial and urban activities and they strongly affects the preservation of relevant buildings. The incorporation of TiO2 in the form of nanocoatings in the materials building can avoid the degradation of the buildings or cultural heritage by mean of a photocatalysis reaction. We employed the TiO2 nanosheets to synthesize a transparent mesoporous TiO2-SiO2 photocatalytic coating[1]. This material was applied on limestone to evaluate its effectiveness in photocatalytic degradation of atmospheric pollution in buildings materials. We have varied the loading of the TiO2 nanoparticles in order to investigate the effect in the photocatalytic activity. Furthermore, of the loading factor, was evaluated the influences of the amount of F- ion present in the TiO2 nanosheets. To complete the study, we compare the obtained results of our photocatalyst with the commercial P25 photocatalyst. Our results allowed us to conclude that TiO2 nanosheet treated to remove the fluorine ions with NaOH is an excellent candidate to be use as active component of self-cleaning building materials (Figure 1). An intensive characterization by Transmission Electron Microscopy has also been carried out in order to understand the distribution of the TiO2 nanoparticles in the coating.
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