TY - JOUR A1 - Braun, Peter A1 - Durner, Bernhard A1 - Rabl, Hans-Peter A1 - Matysik, Frank-Michael T1 - Investigations on the decomposition of AdBlue urea in the liquid phase at low temperatures by an electrochemically induced pH shift JF - Monatshefte für Chemie N2 - Ammonia-based selective catalytic reduction (SCR) systems are the most widely used technology for reduction of nitrogen oxide emissions from lean-burn engines such as diesel engines. However, at low exhaust temperatures, the SCR process is limited by difficulties in the decomposition of the ammonia precursor urea, which is carried on-board using an aqueous solution "AdBlue". In this study, the decomposition of AdBlue urea induced by electrical current and the resulting associated pH shifts were investigated in a divided cell configuration in the liquid phase. The decomposition was found to be favored in both electrochemical compartments, anodic and cathodic, at temperatures of 60-80 degrees C compared to a reference without electrochemical treatment. In addition to the determination of ammonia contents using an ammonia sensor, IC/HPLC analyses were carried out for each sample. Different side products such as biuret, nitrate, cyanuric acid, ammelide, and others were formed. In the anodic compartment, nitrate formation could be observed due to oxidation of ammonia at the electrode surface. [GRAPHICS] . KW - Ammonia KW - Catalysis KW - CONVERSION KW - Diesel Engine KW - DOPED MN/TIO2 KW - Electrochemistry KW - HYDROLYSIS KW - In situ pH shift KW - NOX KW - OXIDATION KW - PRODUCTS KW - REMOVAL KW - SCR KW - SELECTIVE CATALYTIC-REDUCTION KW - Thermochemistry Y1 - 2019 U6 - https://doi.org/10.1007/s00706-019-02406-6 VL - 150 IS - 9 SP - 1633 EP - 1641 PB - Springer ER - TY - JOUR A1 - Braun, Peter A1 - Rabl, Hans-Peter A1 - Matysik, Frank-Michael T1 - Investigations on the Liquid-Phase Decomposition of AdBlue Urea for the Selective Catalytic Reduction Process JF - Chemie Ingenieur Technik N2 - Difficulties in decomposing AdBlue to ammonia limit the applicability of selective catalytic reduction systems at low exhaust temperatures. Investigations on the decomposition of AdBlue in the liquid phase under elevated pressure at temperatures up to 165 degrees C were carried out. Besides effects of inorganic catalysts, the impact of pH on urea decomposition was examined. After dissolution in aqueous phase, the compounds ZnO, WO3, and MoO3 were found to be effective in liquid-phase AdBlue decomposition. However, the efficiency was dropping significantly over few hours. Decomposition of AdBlue urea was also found to be favored for alkaline and acidic conditions. KW - AdBlue urea KW - Ammonia KW - DeNO(x) KW - EMISSIONS KW - HYDROLYSIS KW - KINETICS KW - Liquid-phase decomposition KW - LOW-TEMPERATURE SCR KW - MODEL KW - NOX KW - Selective catalytic reduction Y1 - 2019 U6 - https://doi.org/10.1002/cite.201800055 VL - 91 IS - 7 SP - 961 EP - 968 PB - Wiley ER -