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The hydrothermal reduction of CO 2 captured in aqueous solutions using metal reductants is a promising novel approach that achieves high yields of conversion and high selectivity, but it presents the limitation of the high temperatures needed for the reaction to take place. In this work, experiments combining several reductant metals (Zn, Al and Fe), catalysts (Pd/C, Ni, Cu, Fe 2 O 3 and Fe 3 O 4) and temperatures (200, 250 and 300 ºC) were performed to optimize the process at milder temperatures. Using Al as reductant and Pd/C as catalyst, yields as high as 38 % were obtained at 200ºC, compared with the highest yield (57 %) observed at 250 ºC. Thus a significant temperature reduction can be achieved using a suitable combination of reductant and catalyst. Using this reaction system, Pd/C as catalyst and Al as reductant, an extensive set of experiments at different times and temperatures were performed in order to determine the kinetics of the process and correlate them to a mathematical model of the process. The model correctly reproduces the experimental data with average errors lower than 5.9 %. These results demonstrate the feasibility of lower the operating temperature while maintaining the performance, when using an adequate combination of catalyst and reductant. • The hydrothermal reduction of CO2 was done with different reductants and catalysts. • Conversion to formic acid with yield up to 57 % and 100 % selectivity was achieved. • With Pd/C catalyst and Al reductant, reaction temperature was reduced to 200 ºC. • A kinetic model of the reaction was presented. [ABSTRACT FROM AUTHOR]

Abstract: Nitro blue tetrazolium (NBT) solution dosimeters were prepared and investigated based on radiation-induced reduction of NBT2+. NBT solution dosimeters containing different concentrations of NBT dye from 1 to 5 mM were prepared in a solution of ethanol. The dosimeters were irradiated with 6 MV X-ray beam at doses up to 30 Gy. The dose sensitivity of NBT solution increases strongly with increase of concentrations of NBT dye. The dose response of NBT dosimeters increases remarkably by addition of various concentrations of sodium formate (0.5, 2.5 and 5 mM). It becomes more remarkable with increasing pH value of NBT-sodium formate dosimeters. The sensitivity of the solution increased fairly with increase of irradiation temperature, therefore, the response of the solutions has to be corrected under actual processing conditions. The stability of solution dosimeters after irradiation was very high up to 30 days. [Copyright &y& Elsevier]