Dynamic Estimation Method of Effective Active Site on Palladium Methane Oxidation Catalyst in Exhaust Gas of Marine Lean Burn Gas Engine

Abstract

Lean-burn gas engines have recently attracted attentions in the maritime industry, because they can reduce NOx, SOx and CO2 emissions. However, since CH4 is the main component of natural gas, the slipped methane which is the unburned methane emitted from the lean-burn gas engines likely contributes to global warming. It is thus important to make progress on exhaust aftertreatment technologies for lean-burn gas engines. Pd catalysts for CH4 oxidation is expected to provide a countermeasure for slipped methane, because it can activate at lower exhaust temperature. However, a deactivation in higher H2O concentration should be overcome, because H2O inhibits CH4 oxidation. This study was performed investigates the effects of exhaust temperature or gas composition on active Pd catalyst sites to clarify CH4 oxidation performance in the exhaust gas of lean-burn gas engines. The authors developed the method of estimating effective active sites for the Pd catalyst at various exhaust temperature. The estimation method is based on the assumption that active sites used for CH4 oxidation can be shared with that used for CO oxidation. To clarify the effects of exhaust temperature and compositions on active Pd catalyst sites, the authors developed an experimental system for the new estimation method. This paper introduces experimental results and verifications of the new method, showing that chemisorbed CO volume on a Pd/Al2O3 catalyst is increased with increasing Pd loading in 250–450 ºC, simulated as a typical exhaust temperature range of lean-burn gas engines.

Performance evaluation of methane oxidation catalyst for marine gas-engine in actual exhaust and simulated gas

“…The CO adsorption volume provides the quantity of the effective active site. 32 Therefore, these results support the findings shown in Figure 8, which indicates that the adsorbed NO volume decreases with increasing temperature. In addition, these results suggest that the low NO emission condition can affect the CH 4 oxidation activity of the catalyst.…”

“…To investigate whether NO in the exhaust gas adsorbed on the catalyst inhibited on catalyst activity, the volumetric capacity of the adsorbed NO volumetric was measured by NO-pulse adsorption using a dynamic estimation system connected to the micro-reactor, as shown in Figure 2. The system was modified from the previous study 32 and consisted of mass flow controllers, a switching unit, and a microcomputer. The switching unit comprised two 5-port 2-position valves and a constant-volume pipe.…”

“…31 Consequently, the authors revealed that the quantity of effective active sites on the Pd catalyst is related to the CH 4 oxidation performance by developing a dynamic estimation method for effective active sites of the Pd catalyst at gas-engine exhaust temperature. 32…”

“…31 Consequently, the authors revealed that the quantity of effective active sites on the Pd catalyst is related to the CH 4 oxidation performance by developing a dynamic estimation method for effective active sites of the Pd catalyst at gas-engine exhaust temperature. 32 To implement a CH 4 oxidation catalyst in a marine gas-engine, it is important to investigate the effects of both exhaust gas and exhaust temperature on the CH 4 oxidation activity by comparing the actual exhaust gas of the gas-engine with the simulated gas. In contrast, it cannot be found the research on the performance of CH 4 oxidation catalysts under actual exhaust gas conditions coincides with the wide range of load conditions of a marine gas-engine.…”

The Effect of Active Carbon from Coconut Shell as an Adsorbent on Motorcycle Exhaust Gas Emissions and Engine Performance

“…This research shows a 25% reduction in CO emissions. [7], [12], [13] investigated the use of activated carbon from agricultural waste as an adsorbent to reduce sulfur dioxide (SO2) emissions in industry. The results showed a reduction in SO2 emissions by 40%.…”