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.