Session: 05-04: Methane Emissions Control
Paper Number: 110161
110161 - Increasing Si/al Molar Ratio to Improve Low Temperature Ch4 Oxidation Over Pd/lta
Natural gas vehicles (NGVs) have decreased greenhouse gas emissions compared to gasoline and diesel vehicles. The majority of natural gas emissions occur at the NGV exhaust due to unburnt methane (CH4), the main component of natural gas, leaving the tailpipe . CH4 is 25 times more potent than CO2 in impact on global warming and can be treated with CH4 oxidation catalysts (MOCs). Conventional MOCs consist of Pd/γ-Al2O3 that deactivates in the presence of H2O. Small-pore zeolites with optimized Si/Al molar ratio to tune their hydrophobicity, are a promising alternative to Pd/γ-Al2O3 . Herein, small-pore Linde Type A (LTA) zeolites were synthesized with Si/Al molar ratios of 30, 69, and ∞ . The synthesized LTA zeolites and commercial γ-Al2O3 were loaded with 1 wt.% Pd and their CH4 oxidation performance was evaluated in a packed bed micro-reactor, loaded with 100 mg catalyst pellets (250-500 μm) at 333 sccm (WHSV = 199.8 L gcat-1h-1). The catalysts were initially pretreated at 600 oC/20 min (20% O2/Ar) followed by catalytic evaluation under three consecutive CH4 oxidation cycles (1500 ppm CH4, 5% O2/Ar) from 100 to 600 oC (5 oC/min) in the absence and presence of 5% H2O. Increasing the Si/Al molar ratio of Pd/LTA from 30 to 69 led to an increase in CH4 oxidation performance under both dry and wet conditions. Specifically, Pd/LTA (69) achieved 90% CH4 conversion at the lower temperature (T90 = 360 oC) compared to Pd/LTA (30) (446 oC), Pd/LTA (∞) (414 oC), and Pd/γ-Al2O3 (366 oC) under dry conditions. Pd/LTA (69) and Pd/LTA (∞) achieved lower T90’s at 451 and 444 oC, respectively, in the presence of H2O compared to Pd/γ-Al2O3 (484 oC) and Pd/LTA (30) that did not reach 90% CH4 conversion up to 600 oC. The apparent activation energy (Eapp) and CH4, O2, H2O reaction orders for Pd/LTA (∞) and Pd/γ-Al2O3 were evaluated under dry and wet conditions. The results of this study indicate that Si/Al > 30 for Pd/LTA is required to achieve low temperature CH4 oxidation performance that surpasses that of Pd/γ-Al2O3 under both dry and wet conditions.
 D. Jiang, K. Khivantsev, Y. Wang, Acs. Catal., 10 (2020) 14304-14314.
 H.-Y. Chen, J. Lu, J.M. Fedeyko, A. Raj, Appl. Catal. A: Gen., (2022) 118534.
 B.W. Boal, J.E. Schmidt, M.A. Deimund, M.W. Deem, L.M. Henling, S.K. Brand, S.I. Zones, M.E. Davis, Chem. Mater., 27 (2015) 7774-7779.
Presenting Author: Tala Mon University at Buffalo
Presenting Author Biography: Tala’s undergraduate focused on the design of a methane recovery plant from landfill gases and the manufacturing of non-egg-based platform for influenza vaccine using SF9 insect cells. For his Master’s thesis, he explored the silencing effects of master regulatory transcription factor Foxa1/2 in human liver cancer cells and analyzed the spatial components of liver bud growth. Tala’s PhD is centered around reducing methane emissions in the exhaust gas of natural gas vehicles using zeolite supported palladium catalysts.
Increasing Si/al Molar Ratio to Improve Low Temperature Ch4 Oxidation Over Pd/lta
Technical Presentation Only