Macrocrystals of gamma-Mo2N were synthesized by temperature-programmed reac
tion of macrocrystalline MoO3 and NH3 or N-2/H-2 mixtures, X-ray diffractio
n analyses indicate macrocrystalline Mo2N is an aggregate of particles in c
rystallographic alignment with diameters ranging from 4.6 to 18 nm, dependi
ng on synthesis conditions. Scanning tunneling microscopy (STM) supports th
ese observed diameters. Based on diffraction data and surface area measurem
ents, it is concluded that the particles in each sample are found with a ra
nge of diameters, each flattened in the [200] direction with either an amor
phous surface phase or polycrystalline interior. The highest crystal BET su
rface area achieved is 44 m(2)/g. TGA was used to monitor the temperature-p
rogrammed reaction of MoO3 and N-2/H-2 mixtures. The lowest reduction tempe
ratures were observed in syntheses employing high H-2 concentrations and sl
ow temperature ramping rates. The rate of the Mo2N macrocrystal synthesis r
eaction was observed to be slower than the equivalent powder reaction, whic
h could possibly be attributed to the effects of solid-state diffusion. The
specific thiophene hydrodesulfurization (HDS) activity (units of mol/s m(2
)) of the Mo2N macrocrystalline catalyst at 673 K was found to be higher th
an the powder form by a factor of 2.5. Weight-specific HDS activities and r
eaction product fractions over Mo2N macrocrystal and powder catalysts were
roughly the same. An analysis of reaction products over a range of conversi
ons indicates thiophene desulfurizes to form predominantly 1-butene with sm
aller amounts of other C-4 hydrocarbons also present. (C) 1999 Academic Pre
ss.