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

The simultaneous photoevolution of molecular oxygen and volatile hydro carbons was observed when ferric ions and other photosensitizers such as semiconducting oxides were implanted in cellulose and wood under hi gh pressure and irradiated with near-UV and visible light. Control exp eriments with purified microcrystalline cellulose and lignin indicated that both of these components of wood could undergo phototransformati on. However, in the case of lignin, only volatile hydrocarbons were ob served. 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 differe nt from that which occurs in air. In an inert atmosphere the photochem istry bears a formal analogy to normal photosynthesis in that molecula r 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 sourc e of reductant for the photoredox reactions, and elementary theories o f the photophysics and photochemistry in reaction cavities of the stru ctured matrices in which the light-induced reactions occur.