*Article* **Performance and Regeneration of Methane Oxidation Catalyst for LNG Ships**

**Kati Lehtoranta 1,\*, Päivi Koponen 1, Hannu Vesala 1, Kauko Kallinen 2 and Teuvo Maunula 2**

> 1 VTT Technical Research Centre of Finland, FI-02044 Espoo, Finland; paivi.koponen@vtt.fi(P.K.);hannu.vesala@vtt.fi(H.V.)

 2 Dinex, FI-41330 Vihtavuori, Finland; kki@dinex.fi (K.K.); tma@dinex.fi (T.M.)

**\***Correspondence: kati.lehtoranta@vtt.fi; Tel.: +358-20-722-5615

**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.

**Keywords:** methane slip; methane oxidation catalyst; LNG; natural gas

**Citation:** Lehtoranta, K.; Koponen, P.; Vesala, H.; Kallinen, K.; Maunula, T. Performance and Regeneration of Methane Oxidation Catalyst for LNG Ships. *J. Mar. Sci. Eng.* **2021**, *9*, 111. https://doi.org/10.3390/jmse9020111

Received: 21 December 2020 Accepted: 20 January 2021 Published: 22 January 2021

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