The effect of diesel oxidation catalyst(DOC) and its combination with selective catalytic reduction(SCR) system on NO2

formaldehyde and methanol emissions from a diesel/methanol engine was studied. Results show that the use of DOC in the dual fuel engine can make NO2 ratio reach the level of general diesel emissions and significantly reduce methanol emissions

but does not ideally purify formaldehyde. Under the condition of maintaining the conventional NO2 ratio level of diesel-engines

the SCR+DOC scheme can completely eliminate the formaldehyde and methanol emissions from the dual fuel engine. According to the variation of NO2 ratio in each stage

the standard Gibbs free energy change of the relevant reversible reaction at combustion temperature and exhaust temperature has been analyzed successively

and the main reactions and directions of each stage were clarified. Moreover

the possible reasons for the complete oxidation of methanol by the SCR+DOC scheme were also discussed together with related studies.