NEW PHOTOSYNTHESIS - DIRECT PHOTOCONVERSION OF BIOMASS TO MOLECULAR-OXYGEN AND VOLATILE HYDROCARBONS

The simultaneous photoevolution of molecular oxygen and volatile hydrocarbons was observed when ferric ions and other photosensitizers such as semiconducting oxides were implanted in cellulose and wood under high pressure and irradiated with near-UV and visible light. Control experiments with purified microcrystalline cellulose and lignin indicated that both of these components of wood could undergo phototransformation. However, in the case of lignin, only volatile hydrocarbons were observed. Although UV-induced structural degradation of Lignocellulosic substrates is well-known, the present studies reveal that in an inert atmosphere a novel photochemistry occurs that is qualitatively different from that which occurs in air. In an inert atmosphere the photochemistry bears a formal analogy to normal photosynthesis in that molecular oxygen is photoevolved and a reduced photoproduct, more reduced than the consumed substrate, is produced. This analogy is discussed in the context of oxidation-reduction levels of the photoproducts, the source of reductant for the photoredox reactions, and elementary theories of the photophysics and photochemistry in reaction cavities of the structured matrices in which the light-induced reactions occur.