화학공학소재연구정보센터
Chemical Engineering & Technology, Vol.31, No.4, 575-581, 2008
The removal of copper with dialkyldithiocarbamate ligands in condensed carbon dioxide
The global kinetics of the oxidation and removal of copper(0) foil were examined in liquid and supercritical CO2 using tert-butyl peracetate (t-BuPA) as the oxidant and dialkyldithiocarbamate lithium salts (Li+R2DTC-, with R = ethyl, propyl, or n-butyl) as the chelating agent. The pressure was kept constant (at 240 bar) for all reactions as density was not found to affect the kinetics at pressures above 150 bar. Temperature was varied between 25 and 60 degrees C and the concentrations of the oxidant and chelating agents were varied to determine the observed overall reaction orders for each species. Interestingly, under our reaction conditions, the observed global reaction was independent of oxidant concentration but varied due to the R2DTC- concentration. The Et2DTC- had an observed half order reaction dependence, indicating a complex reaction mechanism while the other two R2DTC- had first order dependence suggesting diffusion limitations. Arrhenius expressions were determined by the temperature dependent kinetics of the product, Cu(R2DTC)(2), formation. The apparent activation energy, E-a, for the Et2DTC- was 66 kJ/mol, confirming a complex reaction mechanism due to its large value. The apparent activation energies for the Pr2DTC- and Bu2DTC- were 14 and 17 kJ/mol, respectively. These low energies are consistent with diffusion limitation.