Modeling of metallic monolith reactor - investigation of the mass transfer limitation during catalytic oxidation of toluene

Hlapljivi organski spojevi (VOC) su toksični spojevi koji su poznati po tome da pridonose onečišćenju zraka. Stoga je od velike važnosti razvoj učinkovitih, ekonomski pristupačnih postupaka za smanjenje njihovih emisija u atmosferu. Od konvencionalnih i novijih metoda katalitička oksidacija pokazala se jednom od najatraktivnijih metoda za smanjenje emisija VOC-a, posebno u uvjetima niskih koncentracija, a katalitički sustav koji se najčešće primjenjuje za tu svrhu te za smanjenje emisija ostalih onečišćujućih tvari u atmosferu je monolitni reaktor. Cilj ovog rada je bio razvoj metalnog monolitnog katalizatora/reaktora za katalitičku oksidaciju toluena, uključujući sintezu miješanog metalnog oksida Mn-Cu u praškastom obliku, razvoj metode nanošenja katalitički aktivne komponente na metalni monolitni nosač te karakterizaciju i testiranje aktivnosti pripremljenih katalizatora. Toluen je izabran kao modelna komponenta s obzirom da je uobičajeni predstavnik aromatskih hlapljivih organskih spojeva koji se ispuštaju u okoliš iz različitih segmenata kemijske procesne industrije. Katalitička oksidacija toluena provedena je u dvije izvedbe reaktora: a) u cijevnom reaktoru s nepokretnim slojem katalizatora pri konstantnoj koncentraciji toluena (210,43 ppm), uz konstantnu masu katalizatora (0,05 g), pri različitim temperaturama (100–275 °C) i ukupnim protocima reakcijske smjese (23–138 mL/min), b) u monolitnom reaktoru također pri različitim uvjetima provedbe procesa, tj. pri konstantnoj koncentraciji toluena (210,43 ppm), uz konstantnu masu katalizatora (0,0024 g), pri različitim temperaturama (100–215 °C) te pri različitim ukupnim protocima reakcijske smjese (23–138 mL/min). U cilju detaljne analize rada reaktora primijenjenih u radu korišteni su jednodimenzijski pseudohomogeni model i model s unutarfaznom difuzijom za modeliranje cijevnog reaktora s nepokretnim slojem, dok je za modeliranje metalnog monolitnog reaktora primijenjen model koji je također uključivao međufazu difuziju. Provedena je ocjena prihvatljivosti primijenjenih modela usporedbom eksperimentalnih rezultata s teorijskim rezultatima dobivenim prema predloženim modelima te su procijenjeni parametri modela.Volatile organic compounds (VOCs) are toxic compounds recognized as important air pollutants. Therefore, the development of an efficient, economically acceptable methods to reduce their emissions into environment is highly required. Among of the existing conventional and newer methods the catalytic oxidation has proved as one of the most attractive one for the conversion of VOCs, especially at lower concentrations, whereas the catalytic system most widely used for reducing emissions into the environment is the monolithic reactor. The aim of this work was the development of a metal monolith catalyst/reactor for the catalytic oxidation of toluene, including the synthesis of mixed metal oxide of Mn-Cu in powder form, the development of methods of applying the catalytically active metal components on a monolithic carrier and characterization and testing activities prepared catalyst. Toluene was chosen as model component with respect to the common representative of aromatic volatile organic compounds that are released into the environment from various segments of the chemical process industry. The catalytic oxidation of toluene is carried out in two types of reactors: a) a tubular reactor in a fixed bed reactor at a constant concentration of toluene (210,43 ppm) and a constant weight (0,05 g), at different temperatures (100–275 °C) and the total flow of the reaction mixture (23–138 mL/min), b) in the monolithic reactor also in various conditions of the process, i.e. at a constant concentration of toluene (210,43 ppm), with a constant weight of the catalyst (0,0024 g), at different temperatures (100–215 °C) and at different total flow rates of the reaction mixture (23-138 mL/min). For the purpose of further analysis of the reactor used in the work applied as one-dimensional model pseudo-homogeneous model for modeling tubular reactor with a fixed bed, while the modeling of the metal monolithic reactor model was applied which is also included interphase diffusion. Was conducted to assess the acceptability of applied models by comparing experimental results with theoretical results obtained with the proposed model and the estimated parameters of the model