Effect of Low-Cost Perovskite Based Lean NOx Trap to Reduce the NOx Emission for CRDI Engine

Abstract

Lean NOx trap (LNT) is an after-treatment technology that targets NOx emissions from an IC Engine and reduces it by using fuel as the reductant. The main mechanisms involved in this process are (i) oxidation of NO into NO2, (ii) Entrapment of NO2 over an alkali Earth metal in the form of nitrates, and (iii) Regeneration and reduction of NO2. The oxidation and reduction reactions are usually performed over rare Platinum Group Metals (PGM). The alternate cycling of operation modes helps in the regeneration and reduction stage due to the presence of unburnt hydrocarbons and carbon monoxides. These HC and CO generated during profitable operation can reduce agents similar to ammonia in SCR (Selective Catalytic Reduction). In the case of LNT, the fuel-injected for reduction imposes a penalty on the system. Cobalt-based perovskites with the chemical formula “ACoO3” (where “A” denotes Ba, Sr, etc.) show excellent absorption and reduction tendencies towards NOx and are highly suited for LNT as they have higher NO oxidation capacity. This research experimented with two different coating procedures (with and without binder) with three other perovskite catalysts–BaCoO3, SrCoO3, and Ba0.5Sr0.5CoO3. Both the coatings were tested for their adherence, and it revealed that the binder-less layer had only 4% coating loss after 2 hrs of sonication. BaCoO3 showed higher NOx absorption due to the higher electropositive nature of barium. The peak conversion efficiency attained in this experiment was 84% at a catalyst temperature of 350°C and 40% load condition.