University of Patras

About: University of Patras is a education organization based out in Pátrai, Greece. It is known for research contribution in the topics: Population & Catalysis. The organization has 13372 authors who have published 31263 publications receiving 677159 citations. The organization is also known as: Panepistímio Patrón.

Performance of doped Pt/TiO2 (W6+) catalysts for combustion of volatile organic compounds (VOCs)

Abstract: The oxidation of benzene and ethylacetate, present in trace amounts in air, over Pt supported on γ-Al2O3, SiO2, TiO2 and TiO2 (W6+) carriers has been studied. It was found that doping of the TiO2 support with W6+ cations has a positive effect on the activity of Pt catalysts for benzene and ethylacetate oxidation. A maximum in activity enhancement has been observed at a W6+ content of 0.45 at% in the TiO2 support. The Pt/TiO2 (0.45 at% W6+) catalyst is over two orders of magnitude more active than the Pt/γ-Al2O3 catalyst in the case of ethylacetate oxidation and an order of magnitude more active in the case of benzene oxidation. Doping of TiO2 with W6+ cations enhances its activity for ethylacetate degradation towards smaller organic intermediates, such as ethanol, acetic acid and ethylene, and it also affects product distribution. The enhanced activity of the Pt/TiO2 (W6+) catalysts is attributed to complementary bifunctional steps occuring on sites offered by Pt metal and by the support. During oxidation of benzene-ethylacetate-water mixtures, benzene oxidation is strongly suppressed in the presence of ethylacetate, while water acts as an inhibitor for both volatile organic compounds (VOC) oxidations.

Effect of composition, environmental factors and cement-lime mortar coating on concrete carbonation

Abstract: The paper describes the physicochemical processes of concrete carbonation and presents a simple mathematical model for the evolution of carbonation in time, applicable under constant relative humidity higher than 50%. The model is based on fundamental principles of chemical reaction engineering, and uses as parameters the ambient concentration of CO2, the molar concentratrations of the carbonatable constituents, Ca(OH)2 and CSH, in the concrete volume, and the effective diffusivity of CO2 in carbonated concrete. The latter is given by an empirical function of the porosity of hardened cement paste and of relative humidity, derived from laboratory diffusion tests. The validity of the model for OPC or pozzolanic cement concretes and mortars is demonstrated by comparison of its predictions with accelerated carbonation test results obtained in an environment of controlled CO2 concentration, humidity and temperature. The mathematical model is extended to cover the case of carbonation of the coating-concrete system, for concrete coated with a cement-lime mortar finish, applied either almost immediately after the end of concrete curing or with a delay of a certain time. Parametric studies are performed to show how the evolution of carbonation depth with time is affected by cement and concrete composition (water/cement or aggregate/cement ratio, percentage OPC or aggregate replacement by a pozzolan), environmental factors (relative humidity, ambient concentration of CO2), the presence and the time of application of a lime-cement mortar coating and its composition (water/cement, aggregate/cement and lime/cement ratios of the mortar, percentage OPC or aggregate replacement by a pozzolan).