Photocatalytic oxidation of glycerol

Glycerol is a poly-alcohol with three hydroxyle groups. As a byproduct of biodiesel production, its transformation to more valuable chemicals has been important . One of the methods to produce chemicals from waste glyserol is the oxidation process. Oxidation of Glycerol brings many chemicals like dihydroxy acetone, glycolic acid, glyceraldehyde, oxalic acid and others which makes it difficult to get one product with high selectivity and yield as there is gradual oxidation of formed products as well.The literatur survey and the state of the art of glycerol oxidation shows studies are more concerned with the higher temperature and pressure catalytic processes while there are only a few studies regarding photocatalytic oxidation process. To realize the photocatalytic oxidation of glycerol, Taylor flow, which is characterized as consequent flow liquid slugs and gas bubbles, and annular film flow were used. This study is examined as three parts. In the first, zinc-oxide catalsyts doped with baryum, cerium, magnezium, platinum, silver, iron, and copper were used in Taylor Flow conditions. Additionally, commerical TiO2 and zero valent iron catalysts were used and compared to zinc oxide catalysts. In part two, reactor performances were compared with slurry bubble column and batch reactors. In the part three, flow regime, liquid flow rate, gas flow rate, and oxidant type were selected as a independent parameters to investigate glycerol oxidation. Catalyts amount was kept constant for all sets. Obtained samples were analyzed using ion chromotography and High Performance Liquid Chromotography (HPLC) to analyze formic acid glycolic acid formations. From the data, it was determined that glyceolic acid production rate is very fast in first minutes while then glycolic acid concentration is constant. It needed more time to produce formic acid. It was also concluded that formic acid is formed whether the oxidation is direct or indirect.In the study it was observed that the nano sized catalysts inside the liquid passed through the interface and stationed themselves in the gas phase which reduced the efficiency of Taylor Flow, and noted as a problem to be solved. Keywords: Glycerol oxidation, ZnO, Taylor flow reactor, annular film flow reactor, photo-catalyst,