Mn2O3-Na3PO4/TiO2 catalyst with high anti-agglomeration and attrition resistance for fluidized-bed oxidative coupling of methane

Abstract

The fluidized-bed reactor is a preferred option for the design of an intrinsic-safety oxidative coupling of methane (OCM) process, because it permits such strongly exothermic reaction to proceed isothermally. However, the widely studied Mn-Na2WO4/SiO2 catalyst cannot meet the requirements of the fluidized-bed reaction. Ground-breaking fluid catalyst coupling high activity/selectivity with good anti-agglomeration and high attrition resistance represents a grand challenge. Herein, we report an Mn2O3-Na3PO4/TiO2 catalyst (280–355 μm) for the fluidized-bed OCM process, achieving 28.5% CH4 conversion with 70.1% C2-C3 selectivity at 760 °C for a feed gas of CH4/O2 of 5/1 while remaining unchanged within 16 h test. This catalyst shows significant fluidization behavior under OCM reaction conditions. It is found that TiO2 nanorods tangle up with each other to form an interpenetrating nano-structure thereby inducing strong mechanical strength and robustness with a low attrition index of only 2.8%. Moreover, high melting-point Na3PO4 and use of TiO2 support impart the catalyst to good anti-agglomeration because of eradication of formation of the sticky Na2Si2O5 and molten Na2WO4 (main cause for agglomeration) encountered in the Mn-Na2WO4/SiO2.