Catalysis Today | 2021
Enhanced catalytic activity and stability of nanoshaped Ni/CeO2 for CO2 methanation in micro-monoliths
Abstract
Abstract Coupling inherently fluctuating renewable feedstocks to highly exothermic catalytic processes, such as CO2 methanation, is a major challenge as large thermal swings occurring during ON- and OFF- cycles can irreversible deactivate the catalyst via metal sintering and pore collapsing. Here, we report a highly stable and active Ni catalyst supported on CeO2 nanorods that can outperform the commercial CeO2 (octahedral) counterpart during CO2 methanation at variable reaction conditions in both powdered and μ-monolith configurations. The long-term stability tests were carried out in the kinetic regime, at the temperature of maximal rate (300\u2009°C) using fluctuating gas hourly space velocities that varied between 6 and 30\u2009L·h-1·gcat-1. Detailed catalyst characterization by μ-XRF revealed that similar Ni loadings were achieved on nanorods and octahedral CeO2 (c.a. 2.7 and 3.3\u2009wt. %, respectively). Notably, XRD, SEM, and HR-TEM-EDX analysis indicated that on CeO2 nanorods smaller Ni-Clusters with a narrow particle size distribution were obtained (∼ 7\u2009±\u20094\u2009nm) when compared to octahedral CeO2 (∼ 16\u2009±\u200913\u2009nm). The fast deactivation observed on Ni loaded on commercial CeO2 (octahedral) was prevented by structuring the reactor bed on μ-monoliths and supporting the Ni catalyst on CeO2 nanorods. FeCrAlloy® sheets were used to manufacture a multichannel μ-monolith of 2\u2009cm in length and 1.58\u2009cm in diameter, with a cell density of 2004 cpsi. Detailed catalyst testing revealed that powdered and structured Ni/CeO2 nanorods achieved the highest reaction rates, c.a. 5.5 and 6.2\u2009mmol CO2\u2009min-1·gNi-1 at 30\u2009L·h-1·gcat-1 and 300\u2009°C, respectively, with negligible deactivation even after 90\u2009h of fluctuating operation.