Hydrogen applications in selective catalytic reduction of NOx emissions from diesel engines

Diesel engines have been considered as a major source in nitrogen oxide (NOx) formation worldwide. The widespread use of diesel engines in consequence of their low fuel consumption, high durability and efficiency increases NOx emissions day by day. NOx emissions from diesel engines cause unavoidable damage on environment and people health. Although so many technologies such as exhaust gas recirculation (EGR), lean burn combustion, electronic controlling fuel injection systems, etc. have been developed to control NOx emissions from diesel engines, they couldn't meet the desired reduction in NOx emissions. In any case, Selective Catalytic Reduction (SCR) as one of the most promising aftertreatment-emission control technologies is an effective solution in restriction of NOx emissions. The use of SCR systems especially in heavy-duty diesel powered vehicles has been increasing nowadays. In these systems, to use of hydrogen (H2) as a reductant or promoter have been improved the conversion efficiency especially at low exhaust temperatures. Many researchers have been focused on the use of H2 in SCR systems for controlling NOx emissions. In this study, the applications of H2 in SCR of NOx have been discussed. The studies on use of H2 in SCR of NOx emissions were examined and the effects on NOx conversions were determined. Consequently, it is confirmed that H2 is a promising and alternative reductant in SCR of NOx and it has been kept as an attracting subject for many researchers. © 2017 Hydrogen Energy Publications LL

The effects of Fe2O3 based DOC and SCR catalyst on the exhaust emissions of diesel engines

The effects of Fe2O3 based DOCs (Diesel Oxidation Catalyst) and SCR (Selective Catalytic Reduction) catalysts on the exhaust emissions of diesel engine were investigated in this experimental study. The investigated catalysts, Al2O3 – TiO2/CeO2/Fe2O3 (ATCF) and Al2O3 – Nb2O5/CeO2/Fe2O3 (ANCF), were produced with impregnation method and aged for 6 h at 600 °C. FE-SEM (Field Emission Scanning Electron Microscopy), XRD (X-Ray Diffraction), XRF (X-Ray Fluorescence) and BET (Brunauer-Emmett-Teller) Surface Area analyzes were carried out to determine the specifications of catalysts. The catalytic performances of the DOCs were tested for the oxidation of CO, HC, PM, NO while SCR catalysts were tested for SCR of NOx using NH3. An individual exhaust system was built up and mounted to the engine for tests of catalysts. An electronic control system and a software were developed to control the SCR system. After the completion of experimental setup, catalysts placed inside the exhaust system were subjected to the engine tests to determine their effects on the exhaust emissions. Tests were carried out under actual working conditions with a single cylinder direct injection diesel engine. In conclusion, the catalysts made significant decrease in pollutant emissions while brake specific fuel consumption (BSFC) increased slightly. ANCF released better conversion efficiency in all pollutant emissions compared to the ATCF. Maximum decreases in CO, HC and NOx emissions, which are resulted from ANCF catalyst, were obtained at a rate of 83.51%, 80.83% and 80.29% respectively. © 2019 Elsevier Lt

Selective catalytic reduction of NOx emissions by hydrocarbons over Ag–Pt/Al2O3 catalyst in diesel engine

Selective catalytic reduction is an application used to control NOx pollutants in diesel engines. Aqueous urea solution, commercially called AdBlue and obtained by mixing pure water and NH3, is the most commonly used reductant while the V2O5–WO3/TiO2 structure has a widespread use as catalyst in SCR technology. However, the SCR systems included AdBlue and V2O5–WO3/TiO2 structure have low NOx conversion efficiency at low exhaust gas temperatures. The use of hydrocarbons as reductant and catalysts containing silver improves the conversion efficiency of selective catalytic reduction systems at low exhaust temperatures. In this work, selective catalytic reduction of NOx emissions from diesel engines in the presence of hydrocarbons has been studied. While ethanol and biodiesel mixtures were used as hydrocarbons, the Ag–Pt/Al2O3 structure was preferred as the catalyst. Scanning electron microscope and X-ray fluorescence analyses of the catalyst produced by the impregnation method were carried out. In order to determine the NOx conversion efficiency of ethanol–biodiesel mixtures in the selective catalytic reduction system, tests were carried out at different engine loads and different exhaust gas temperatures under actual operating conditions. As a result of the tests carried out, it was concluded that the reductant, which consists of 15% biodiesel and 85% ethanol, has the highest conversion performance. © 2019, Islamic Azad University (IAU).Firat University Scientific Research Projects Management Unit: 2018-2-AP3-2964This work was supported by Mersin University Scientific Research Projects Unit (Project Code: 2018-2-AP3-2964)

Development of Fe2O3 based catalysts to control pollutant emissions in diesel engines

Exhaust after treatment systems have become a necessity to eliminate pollutant emissions as required by standard. Nowadays, DOC and SCR are widely used after treatment technologies in diesel vehicles. In this experimental study carried on DOC and SCR systems, two different catalysts as Al2O3-TiO2/Fe2O3 and Al2O3-Pt/Fe2O3 were produced with impregnation method. The catalysts were characterized by Field Emission-Scanning Electron Microscope (FE-SEM), X-ray diffraction (XRD), X-ray fluorescence (XRF) and Brauner–Emmett–Teller (BET). Each catalyst was tested as DOC and SCR in real working state to see the effect of catalyst on pollutant emissions in diesel engine. Results showed that the use catalysts as DOC led to significant decrease in CO, HC, NO and smoke emissions. The exhaust temperature rose up to 50 °C after DOC. The use of catalysts in SCR system eliminated NOx emission by high rates. Furthermore; the use of catalysts in emission control systems led to an increase in specific fuel consumption and a decrease in excess air coefficient of engine. © 201