<p>Exhaust gases from incomplete gasoline combustion are mainly unburned aliphatic and aromatic hydrocarbons. This study has investigated the performance of single-walled carbon nanotubes doped with titanium (Ti@SWNT) for reducing unburned hydrocarbons. Due to its stability at high temperatures, titanium can be a suitable and cheap substitute for platinum in catalytic converters and improve their performance. The reduction of two pollutants, butadiene, and benzopyran, from exhaust gas compounds has been evaluated by Ti@SWNT. The calculation method B3LYP based on 6–31**G + was used to optimize the geometric structure of the compounds. The reactions, mechanism, and structural and thermodynamic parameters of the reduction of butadiene to ethylene and benzopyran to o-Cresol and ethylene and finally to CO₂ and H₂O were carried out by Lanl2dz computing base. Structural calculations show that the electrical conductivity of the edges of the single-walled carbon nanotube is higher than in other places, which is a suitable place for the reaction to occur. Titanium increases the edges of the catalyst, which provides the conditions for the regeneration of unburned hydrocarbons. The doping of titanium has created a wonderful composition, and with the increase in electron transfer, absorption and reduction of unburnt hydrocarbon compounds increases. The efficiency and current density produced by this nanocatalyst is higher than its platinum counterparts. The results show that the interaction of Ti@SWNT nanocatalyst with aromatic compounds is better than that of aliphatic. The energy gap of benzopyran conversion to carbon dioxide and water is Eg_D−III = 1.62&#xa0;eV and the Gibbs free energy of this step is -32.07&#xa0;kJ.mol^− 1, which indicates the spontaneous reaction of aromatic hydrocarbons to decomposition.</p>