High NO_x content in diesel exhausts represents a great environmental challenge. A number of technical approaches are suggested to solve the problem. One of them is based on the reaction of selective catalytic reduction (SCR) of NO_x in diesel exhausts by reducing gas additives, such as unsaturated hydrocarbons, propane, diesel fuel, ammonia, or urea. Recent studies showed a mixture of hydrogen and carbon oxide (products of autothermal reforming of diesel fuel) to be an efficient NO_x reducing agent. Application of this technology in the framework of Bioliquids-CHP project at the first purification stage implies the conversion of a mixture of refined pyrolysis oil and diesel fuel to synthesis gas using a part of exhaust gases. At the second purification stage, it is suggested to add the obtained synthesis gas to diesel exhausts to provide the reaction of SCR of NO_x to nitrogen. The reaction is run in a reactor with a radial catalyst bed. The optimum conditions of the reaction of synthesis gas production are as follows: О₂/С = 0.5-0.6, Н₂О/C = 1.5-1.7, GHSV=12000-15000h-1, inlet temperature 300-400°С. The optimum SCR conditions are as follows: GHSV=20000h-1, inlet temperature 250-350°С, typical inlet gas composition: 6.3% CO₂, 10-12.5% H₂O, 13.4-7.2% O₂, 1000 ppm CO, 500 ppm NO_x, 2000-3000 ppm Н₂.