Synthesis and evaluation of catalytic activity of NiFe2O4 nanoparticles in a diesel engine: An experimental investigation and Multi-Criteria Decision Making approach

Exposure to gaseous and particulate matter (PM) emissions from engine combustion can result in severe human health risks. Although blending biodiesel-diesel fuel presents reduction in diesel engine emissions, mixing fuel with an oxidation catalyst with considerable oxygen storage capacity (OSC) characteristic might better reduce the harmful engine emissions. In the present study, NiFe2O4 nanoparticles were synthesized via the combustion method. X-ray diffraction analysis, Raman spectroscopy and temperature programmed reduction techniques were used to assess the structure and OSC of the nanoparticles. The data was collected using a diesel engine in fuel blends of "B20–NiFe2O4" under steady state conditions, at 25, 50 and 75% of engine full load, and at a constant engine speed of 1500 rpm. The Analysis of variance (ANOVA) approach was used to interrupt the engine outputs. The soot samples emitted from diesel engine fuel containing B20–NiFe2O4 were collected for transmission electron microscopy analysis to determine their morphology and nanostructure. NiFe2O4 nanoparticles showed spinel structure with an OSC of 13580 μmol/g. There was a considerable reduction in exhausted particles with the B20–NiFe2O4 blend. The average emission reductions for hydrocarbons, carbon monoxide, particle number, and particle mass were 44.3%, 12%, 26%, and 30%, respectively. The soot particle internal structure showed that for the B20–NiFe2O4 blend, particles were structurally arranged around the outer region of the core. Finally, the Technique for Order Performance by Similarity to Ideal Solution (TOPSIS) was performed using the experimental data (all investigated parameters) to rank the alternatives. The optimization result reveals that B20–NiFe2O4 is a good alternative for different conditions of engine loading. By using the TOPSIS ranking, the engine can be operated in the most optimal manner at 50% load using B20–NiFe2O4.