284640 Oxidative Coupling of Methane Over Samaria Catalysts

Monday, October 29, 2012: 10:10 AM
317 (Convention Center )
Helena Hagelin-Weaver and Trent Elkins, Chemical Engineering, University of Florida, Gainesville, FL

The oxidative coupling of methane (OCM) to C2 products, such as ethane and ethylene, was studied over supported and unsupported Sm2O3 nanoparticles.  Two different methods of Sm2O3 nanoparticle preparation were investigated, one method based on the decomposition of an oleate complex and one more conventional microemulsion method, to investigate the effects on the activity and selectivity in the OCM.  The Sm2O3 nanoparticles prepared using these methods were also deposited onto a support and compared to catalysts prepared using incipient wetness impregnation of a samarium nitrate solution onto the same support.  Two supports were selected, a commonly used porous alumina support (p-Al2O3) and a nanoparticle magnesia (n-MgO) support, to determine the influence of the support on the activity and selectivity in the oxidative coupling of methane.  The effects of the CH4:O2feed ratio (between 4:1 and 9:1) and the temperature (between 740 and 800°C) were also investigated.   

Catalyst characterizations using BET surface area analysis and transmission electron microscopy (TEM) reveal that the oleate method results in smaller Sm2O3 nanoparticles compared with the microemulsion method.  In general, the lowest CH4:O2 ratio (4:1) gives the highest CH4 conversion and the lowest C2 selectivity, while the highest CH4:O2 ratio (9:1) results in the highest C2 selectivity and lowest CH4 conversion.  When supported on p-Al2O3, the Sm2O3 nanoparticles prepared using the microemulsion method exhibit the highest C2 selectivities, while the Sm2O3 nanoparticles prepared using the oleate method yield the lowest C2 selectivities.  The Sm2O3/p-Al2O3 catalysts prepared using incipient wetness impregnation gives an intermediate C2 selectivity, but a slightly higher CH4 conversion compared to the other methods.  Supporting the Sm2O3 nanoparticles onto n-MgO results in higher CH4 conversions and C2 selectivities compared with the Sm2O3/p-Al2O3 catalysts.  Catalyst characterizations are underway to provide insight into the properties of these catalysts and how they affect the activity and selectivity in the oxidative coupling of methane.


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