Photocatalytic synthesis of vitamin b3 under uv, uv-vis and visible irradiations in water by PT loaded tio2 catalysts

Selective photocatalytic oxidation of 3-pyridinemethanol to 3-pyridinemethanal and vitamin B3 by using pristine and Pt loaded home prepared (HP) rutile and commercial TiO2 photocatalysts, under UV, UV-Vis and visible irradiations in water, was performed in friendly environmental conditions. The experiments were performed in water without using any organic solvent and by using oxygen from air as oxidant. Pristine TiO2's were used for comparison. The photocatalysts were characterized by XRD, SEM-EDAX, BET, DRS, XPS and TGA techniques. The influence of pH on reactivity of 3-pyridinemethanol oxidation and total selectivity to 3-pyridinemethanal and vitamin B3 production was studied. Under very acidic conditions (pH=2) no or low activity (depending on photocatalyst) was observed, whereas by increasing the pH from 4 to 12 very high total selectivity was achieved. The Pt loading was beneficial for selectivity whereas the reactivity was positively affected only for crystalline HP sample (Pt-HPRT-400). This sample showed good activity under visible irradiation, exhibing an about 4 times higher conversion than the other samples. The influence of the position of the benzylic group in pyridine (2-pyridinemethanol and 4-pyridinemethanol) was also studied. The results showed that to synthesize vitamin B3 in green conditions the photocatalyst should be poorly crystalline or Pt loaded. Keywords: Vitamin B3, Photocatalysis, Pt loaded TiO2, Green synthesis, pH effect