from the conferences organized by TANGER Ltd. provisional website
The acid-base centres on the catalyst surface play important role in catalysis chemistry, influencing protons activity in reaction mechanism. The work presents the characteristics of acid–base centres on the vermiculite/α-Fe2O3 nanoparticles composites, when used as catalyst for the chemical recycling of polystyrene to styrene. The iron oxides are often used in chemical/petrochemical application as catalyst. The vermiculite is cheap natural clay mineral, which is commonly used as catalyst support. The vermiculite/α-Fe2O3 nanoparticles composites were prepared by precipitation and calcination at 500 and 700 °C. The acid-base centres on the catalyst surface were characterized by TPD (Temperature Programmed Desorption) method allowing to detect the molecules NH3 and CO2 desorbed from the surface when the surface temperature is increased. The temperature of surface and the peak from desorbed molecules suggest the strength of chemical bond between desorbed molecules and surface. Before desorption, the NH3 and CO2 are adsorbed on the surface of catalysts by chemisorption. The TPD method was supplemented with the laboratory analyses using XRD and SEM.It has been found that the vermiculite/α-Fe2O3 nanoparticles composite calcined at 500 °C has medium-strong base centres on the surface, although the pure vermiculite is a light acid and pure α-Fe2O3 is a neutral material. For this reason, it can be successfully applied to the depolymerization reaction in conversion to the styrene monomer. The calcination temperature 700 °C did not improve the basicity, but rather led to its suppression.Keywords: Vermiculite, hematite, structural properties, acid-based centres, catalyst
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