Performance and Regeneration of Methane Oxidation Catalyst for LNG Ships

Abstract

Liquefied natural gas (LNG) use as marine fuel is increasing. Switching diesel to LNG in ships significantly reduces air pollutants but the methane slip from gas engines can in the worst case outweigh the CO2 decrease with an unintended effect on climate. In this study, a methane oxidation catalyst (MOC) is investigated with engine experiments in lean-burn conditions. Since the highly efficient catalyst needed to oxidize methane is very sensitive to sulfur poisoning a regeneration using stoichiometric conditions was studied to reactivate the catalyst. In addition, the effect of a special sulfur trap to protect the MOC and ensure long-term performance for methane oxidation was studied. MOC was found to decrease the methane emission up to 70–80% at the exhaust temperature of 550 degrees. This efficiency decreased within time, but the regeneration done once a day was found to recover the efficiency. Moreover, the sulfur trap studied with MOC was shown to protect the MOC against sulfur poisoning to some extent. These results give indication of the possible use of MOC in LNG ships to control methane slip emissions.

A Discussion on Alternative Fuel Criteria for Maritime Transport

“…LNG is a clean, colourless, odourless, non-toxic, and noncorrosive fuel and is compatible with IMO targets (Buhaug et al, 2009;Arteconi et al, 2010;EC, 2021). LNG usage lowers different types of emissions (Lehtoranta et al, 2021) but increase greenhouse gas emissions due the methane leakage during life-cycle (Schinas & Butler, 2016;Manouchehrinia et al, 2020;Ančić et al, 2020). Besides, LNG is competitively priced with conventional fuels but has a high initial investment cost (Brynolf et al, 2014).…”

Investigation of a Second Exhaust Valve Lift to Improve Combustion in a Methane - Diesel Dual-Fuel Engine

“…However, methane requires high ignition temperatures of 600 °C, which makes complete combustion of the homogeneous air-fuel mixture difficult [14]. Due to the stability of the methane molecule, special catalysts are needed for exhaust gas aftertreatment, which have light-off temperatures of over 500 °C and thus place special demands on exhaust gas temperature management [15]. Since the global warming potential (GWP) of methane is 25 times that of carbon dioxide, it is essential that the conversion by the catalytic converter be as complete as possible [16].…”

Active Methanotrophs and Their Response to Temperature in Marine Environments: An Experimental Study

“…Methanotrophs are a subset of methylotrophs that utilize CH 4 and other C 1 compounds as the sole carbon and energy sources under aerobic conditions [7,8]. Aerobic methane oxidation in natural ecosystems is, thus, one important way to control CH 4 emissions in the atmosphere, reducing the potential of global warming [9][10][11][12]. Thus, better knowledge on the aerobic methane oxidation of natural ecosystems is of great significance to precisely characterize the emissions of CH 4 and trends of global warming.…”