Understanding the Role of Atomic Ordering in the Crystal Structures of NixSny toward Efficient Vapor Phase Furfural Hydrogenation

We have synthesized ordered NixSny nanoparticles separated by Al2O3 as highly efficient catalysts for the vapor phase hydrogenation of furfural. The NixSny-Al2O3 composite catalysts with different chemical compositions (Ni3Sn4, Ni3Sn, Ni1.5Sn, Ni3Sn2, Ni) were prepared through the layered double hydroxide (LDH) route by annealing at 800 degrees C in the presence of H-2. NixSny nanoparticles were well dispersed throughout the Al2O3 matrix indicating the high thermal stability of these materials. The effect of different concentration of Ni, Sn, and Al in the formation of NixSny-Al2O3 catalyst was investigated. The X-ray diffraction, transmission electron microscopy, and X-ray absorption fine structure analyses indicate the formation of intermetallic phases with spherical particles having an average size of 30-160 nm. The nanoparticles with different compositions were tested toward the hydrogenation of furfural, and it was found that crystal structure, atomic ordering and composition play crucial roles in the catalytic activity. DFT calculations indicate that the adsorption energy and the geometrical orientation of furfural on the surface of different NixSny-Al2O3 compounds play crucial role in the hydrogenation of furfural. Ni3Sn2-Al2O3 was found to be the most efficient catalyst with high furfural conversion (similar to 65%) and selectivity (57-62%) for furfuryl alcohol.