Synchronized Collective Proton-Assisted Electron Transfer in Solid State by Hydrogen-Bonding Ru(II)/Ru(III) Mixed-Valence Molecular Crystals.

A proton-coupled electron transfer (PCET) reaction was widely studied with isolated organic molecules and metal complexes in solution in view of the biological catalytic reaction, while studying this reaction in the crystalline or solid-state phase, which has a novel example, would give insight into the rather internal environment of proteins without solvation and a creation of new molecular materials. We tried to crystallize a hydrogen-bonded (H-bonded) coordination polymer with one-dimensional nanoporous channels, formed from redox-active RuIII complexes, [RuIII(Hbim)3] (Hbim- = 2,2'-biimidazolate monoanion). As a result, a synchronized collective PCET phenomenon was observed for the molecular nanoporous crystal by novel solid-state cyclic voltammetry (CV), which could be measured by only setting some crystals on the electrode surface. The nanoporous crystals, {[RuIII(Hbim)3]}n (1), are simultaneously induced to a synchronized collective RuIIRuIII mixed-valence state, {RuIIRuIII}n, with alternating arrays of RuII and RuIII complexes by PCET in a way of the reductive state of {RuIIRuII}n. Further, a new crystal with {RuIIRuIII}n, {[RuII(H2bim)(Hbim)2][RuIII(bim) (Hbim)2][K(MeOBz)6]}n (2), was also prepared, and the solid-state CV revealed the same electrochemical behavior of {RuIIRuIII}n with 1. The single crystal with {RuIIRuIII}n of 2 was unusually a semiconductor with 5.12 × 10-6 S/cm conductivity at 298 K by an impedance method (8.01 × 10-6 S/cm by a direct-current method at 277 K). Thus, an unprecedented electron-hopping conductor driven by a low-barrier proton transfer through a PCET mechanism (Ea = 0.30 eV) was realized in the H-bonding molecular crystal with {RuIIRuIII}n. Such studies on a PCET reaction in the crystalline state is not only worthwhile as a model of essential biological reactions without solvation, but also proposed to a new design of molecular materials to occur an electron transfer by using an intermolecular H-bond.

Characteristics of gas from the fluidized bed gasification of refuse paper and plastic fuel (RPF) and wood biomass.

Energy recovery from small and medium scale waste thermal treatment facilities in the municipalities of Japan is challenging, owing to low power generation efficiency and high economic demands. Gas Engine (GE) generation is considered an efficient resource utilization method in these facilities. In this study, new and consistent feedstock, Refuse Paper and Plastic Fuel (RPF), and wood pellets were tested in an air-blown Fluidized Bed Gasifier (FBG) for syngas utilization in a GE. With temperatures ranging from 700 to 940 °C and varying Equivalence Ratios (ER) of 0.3-0.5, some of the most important product gas characteristics were analyzed, including the Lower Heating Value (LHV) and tar concentration levels. Gas composition results revealed that the concentration tendencies varied for the product gases CO, H2, and hydrocarbons, depending on the feedstock type, whereas the same tendencies were observed for CH4 and tar concentrations. Through the ER range, the LHV of product gas for RPF and wood pellets was 3.4-5.9 MJ/Nm3. Tar concentrations decreased to 2.5-14.0 g/Nm3-dry as the ER was raised. The optimal ER for LHV performance in GE generation was approximately 0.4 for RPF and wood pellets, and remaining tar concentrations were about 5.0 g/Nm3-dry at the gasifier exit.