title: Pulse radiolysis of 4,4'-bipyridyl aqueous solutions at elevated temperatures: spectral changes and reaction kinetics up to 400 degrees C.
abstract: The spectral changes as well as the reaction kinetics of the transient species of 4,4'-bipyridyl (4,4'-bpy) have been experimentally investigated by pulse radiolysis techniques up to 400 degrees C. The results show that the transient species such as OH adduct 4,4'-bpyOH*, monoprotonated electron adduct 4,4'-bpyH*, and doubly protonated electron adduct 4,4'-bpyH2+* have 15-20 nm blue shifts from room temperature to 400 degrees C. For a deaerated neutral solution of 4,4'-bpy in the presence of tert-butyl alcohol, ethanol, or NaCOOH, the doubly protonated electron adduct is the main transient species at room temperature. But at temperatures > 350 degrees C, a monoprotonated form, the N-hydro radical 4,4'-bpyH*, becomes predominant. Interestingly, at room temperature, CO2-* could not efficiently react with 4,4'-bpy, but the reaction was accelerated with increasing temperature; at 350 degrees C, this reaction completed within 2 mus. Using an alkaline solution (pH = 11.5) of 4,4'-bpy in the presence of tert-butyl alcohol, we studied the N-hydro radical 4,4'-bpyH* from room temperature to 400 degrees C at 25 MPa. An estimation of the temperature-dependent G(e(aq)-) at 25 MPa agrees with our previous result with methyl viologen as a scavenger.
authors.affiliation: Nuclear Engineering Research Laboratory, School of Engineering, The University of Tokyo, 2-22 Shirakata Shirane, Tokaimura, Nakagun, Ibaraki 319-1188, Japan.
authors.forename: Mingzhang
authors.initials: M
authors.lastname: Lin
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Katsumura
authors.forename: Hui
authors.initials: H
authors.lastname: He
authors.forename: Yusa
authors.initials: Y
authors.lastname: Muroya
authors.forename: Zhenhui
authors.initials: Z
authors.lastname: Han
authors.forename: Toyoaki
authors.initials: T
authors.lastname: Miyazaki
authors.forename: Hisaaki
authors.initials: H
authors.lastname: Kudo