Deposition precipitation derived Ni-Co active sites for enhanced dry reforming of methane performances

Dry reforming of methane (DRM) is one of the routes proposed to valorize the CO2 into high value molecules, such as syngas (H-2 + CO) by its reaction with methane. Due to thermodynamic limitation this reaction takes place at high temperatures, above 650 degrees C and in a presence of a catalyst. Ni and Co based catalysts are used in DRM, as Ni is showing good activities and Co is improving the selectivity. As the distribution of these two active sites is the key in achieving high conversions and good stability towards deactivation. In this work, bimetallic nanoparticles with various ratios (total loading of 20 wt%) were supported SBA-15 via phyllosilicate precursors. The Ni-Co bimetallic nanoparticles are obtained by activation in hydrogen. Ni-Co based materials were completely characterized in calcined and reduced phase by XRD, N2-physisorption, TPR, TEM, XPS). Only Ni and/or Co phyllosilicates are obtained indifferent of the ratio used, the deposition precipitation method is resulting in high specific surfaces of 300 m(2)g(-1). After the reduction at 700 degrees C Ni-Co NPs are obtained with sizes between 2 and 7 nm as showed by XRD, TPR with bimetallic distribution of 15Ni-5Co, 10NI-10Co and 5Ni-15Co within single NPs as analyzed by S/TEM-EDX mapping. The catalytic performances over DRM are showing the following tendency 20Ni-0Co = 15Ni-5Co > 10NI-10Co > 5Ni-15Co > 0Ni-20Co, while cobalt reach catalysts are rapidly deactivating after 2 h of reaction. Best results are showed by 15Ni-5Co with conversions of 74.5% and 79% for CH4 and CO2 respectively after 200 h of reaction. The spent catalyst showing only 29 wt% carbon and limited sintering with fewer Ni-Co NPs of similar to 13 nm observed. Such unforeseen stability is associated to the presence NPs with the shell composed majority of Ni active sites and with some Co atoms within the NPs in 15/5 catalyst formulation as shown by XPS and S/TEM-EELS mapping.