Adsorption of ethylamine on silica-supported nickel phosphide

The adsorption of ethylamine on Ni2P/SiO2 was studied by diffuse-reflectance Fourier transform infrared (FTIR) spectroscopy, temperature-programmed desorption (TPD), and ab initio calculations. The FTIR results indicate that ethylamine is adsorbed molecularly on the freshly reduced surface, but in the form of an ethylammonium species on the fresh surface exposed to H2S. The TPD results indicate that ethylamine is held strongly, and decomposes to release ammonia at 500 K and ethylene at 883 K. The ethylammonium species is more reactive and releases ammonia at 634 K and ethylene at 622 K. Molecular orbital calculations for the adsorbed ethylamine give good agreement between experimentally observed vibrational frequencies and calculated values. These results indicate that on the freshly reduced surface ethylamine interacts through its nitrogen lone pair with Ni sites in a Lewis acid-base manner.