Vliv makrokinetických jevů na rychlost fotokatalytické redukce oxidu uhličitého

Abstract

Diploma paper is focused on photocatalytic reduction of carbon dioxide in presence of ZnS photocatalyst. The aim of the work was to put together an experimental device, to eliminate macrokinetic phenomena, to determine the dependence of CO2 photoreduction yields on volume of liquid phase for the three quartz glass tubes with different diameters and in the end to compare obtained experimental data with data from geometrically different reactor used in past. The photocatalytic reduction of carbon dioxide was performed in the stirred batch annular reactor with ZnS catalyst suspended in 0.2 M NaOH solution. Suspension was irradiated by an 8 W Hg lamp with wavelength of 254 nm which was placed into a tube from quartz glass. Supercritical-fluid grade CO2 was used as a reactant, which flowed into a reactor under pressure of 110 kPa. The optimum volume of liquid phase was determined experimentally for each tube to fulfill the condition of ideal mixing. Methane, carbon oxide and hydrogen were products of CO2 photocatalytic reduction in gas phase, methanol was product in liquid phase. Diameter of used tube had no influence on reduction yields because the tube wasn‘t submerged at optimum volume for which the macrokinetic phenomena was eliminated and reaction run in the space between the bottom of reactor and tube. The results of CO2 photocatalytic reduction obtained with tube diameter of 3.5 cm were compared with data from geometrically different reactor used in past under the same reaction conditions. It was found out that CO2 photocatalytic reduction is affected by geometry of the reactor. Results obtained in new reactor were twice higher than results from original reactor.