Methane decomposition over Ni supported on palm oil fuel ash (Ni-POFA) catalyst

Abstract

The performance of Ni supported on palm oil fuel ash (Ni-POFA) catalyst was evaluated for methane decomposition reaction. The effects of Ni loading (5, 10, 15 and 20 wt.%) and gas hourly space velocity (GHSV) (5000, 7000, 15,000 and 25,000 mL/g h) were investigated at 550 °C for 6 h. The results show that increasing the Ni loading from 5 to 15 wt.% increased the initial H2 yield. However, the highest Ni loading (20 wt.% Ni) resulted in the lowest CH4 conversion and H2 yield, which has been associated to Ni particles agglomeration and formation of large filamentous carbon. The increase of GHSV from 5000 to 7000 mL/g h increased the initial CH4 conversion and initial H2 yield. Nonetheless, the catalytic performance of Ni-POFA degraded rapidly at higher GHSVs (15,000 and 25,000 mL/g h). This has been linked to a shorter contact time between CH4 gas and the catalyst at higher CH4 flow rates. The current study proposes the 15 wt.% Ni and 7000 mL/g h as the optimum Ni loading and GHSV for Ni-POFA catalyst, respectively. Under these conditions, methane decomposition performed admirably at 87.0% initial CH4 conversion and 27.0% initial H2 yield. Under the same conditions, the highest stable value of H2 production was achieved at ∼2.0% over the 6-h reaction time.