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Φυσικοχημικός και δομικός χαρακτηρισμός υποστηριγμένων καταλυτών Ir, Rh και Ru για εφαρμογές βιομηχανικού και περιβαλλοντικού ενδιαφέροντος: καταλυτική τους αξιολόγηση στην υδρογόνωση του CO2

Betsi-Argyropoulou Ioanna-Idyli

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Summary

A major part of today’s energy derives from fossil fuels, which result in increased carbon dioxide (CO2) concentration in the atmosphere and thereby causing global warming through the greenhouse effect. In recent years, research efforts have been made to reduce CO2. Among the promising exploitation processes is CO2 hydrogenation, which is of particular interest, as it effectively reduces carbon dioxide while producing high value added chemicals and fuels, such as carbon monoxide, methane, methanol, and hydrocarbons.The aim of this thesis is the study of certain Ir, Ru, Rh based catalysts and their catalytic performance with respect to the reaction of CO2 hydrogenation. The following catalysts were characterized and tested: 1%Ir/ Al2O3, 1%Ir/ CeO2ZrO2, 1%Ir/ Al2O3CeO2ZrO2, 1%Ru/ Al2O3, 1%Ru/ CeO2ZrO2, 1%Ru/ Al2O3CeO2ZrO2, 1%Rh/ Al2O3, 1%Rh/ CeO2ZrO2, 1%Rh/ Al2O3CeO2ZrO2.Initially, experiments were carried out to characterize these catalysts. In particular, Temperature- programmed hydrogen reduction (H2-TPR) experiments were carried out, a method used to assess the hydrogen reduction capacity of the catalyst, H2 chemisprption (H2-titration) experiments to calculate the mean diameter of the spherical particles and metal dispersion in the support, and BET method experiments to measure the total surface area.The catalytic performance of the above catalysts was also studied for the reaction of hydrogenation of carbon dioxide (CO2 Hydrogenation) to methane production (methanation of CO2). For the study of the catalytic activity of each catalytic material, 0.05 g is tested in the reactor, while gas mix passes through the reactor (feedback ratio: H2/ CO2=4 and specifically 20% H2, 5% CO2, 75% Ar and a total flow rate of 50 cm3 / min or 100 cm3 / min). The reactor temperature is gradually increased to 600οC, while the reaction products are being analyzed every 30οC with on-line gas chromatography. Furthermore, the catalytic stability of the catalysts for this reaction is studied. The procedure is similar to that of the catalytic activity study, with the diffwrence that chromatograms are received every hour, for 5 hrs at a constant temperature (380οC), which was chosen as an average optimum yield value for comparison between catalysts studied.

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