Design and preliminary test of a fluidised bed photoreactor for ethylene oxidation on mesoporous mixed SiO2/TiO2 nanocomposites under UV-A illumination

Ethylene (C2H4) is a plant hormone that has numerous effects onmany horticultural and ornamental crops. It accelerates senescence, stimulates chlorophyll loss, enhances excessive softening, promotes discoloration and browning during storage of fresh produce. Among the techniques used to remove or inhibit ethylene action during postharvest handling of fresh products (potassium-based system, high temperature catalytic oxidation, inhibition of ethylene receptors), the use of titaniumoxide (TiO2)-based materials with photocatalytic activity under ultraviolet(UV) light is one of the most promising. A fluidised-bed photoreactor(FBP) was designed to decompose ethylene in the storage room atmosphere, and the relative prototype was manufactured. Since TiO2 powder alone is not suitable for use within a fluidised bed, preliminary tests toselect the best support were performed. Alumina microspheres showeda good fluidisation behavior; its functionality was tested with differentkind of support material and actual photocatalytic activity was testedusing SiO2/TiO2-coated alumina microspheres. A reduction of approximately72% of ethylene concentration in the tested 40 ppm ethylene gas mixture was observed after 4.5 h of 36W UV light exposure. FBP resultedto be suitable to avoid the detrimental presence of C2H4 in the atmosphere surrounding fresh products within cold storage rooms.