M. Arai et al., Effects of supports in gas-phase hydrogenation of acetonitrile over supported platinum catalysts, APP CATAL A, 183(2), 1999, pp. 365-376
Gas-phase hydrogenation of acetonitrile was carried out over platinum catal
ysts using silica (SI), silica-alumina (SA), alumina (AL), and titania (TI)
as supports. The Pt/SI, Pt/SA, and Pt/AL catalysts produce triethylamine a
s the only major product while the Pt/TI catalysts produce triethylamine an
d diethylamine with a small amount of ethylamine. The Pt/SA and Pt/AL catal
ysts reduced at low temperature indicate an induction period, giving no pro
ducts at the beginning of the reaction. All the catalysts lose their activi
ty during the reaction. The initial turnover frequencies (TOF0) are larger
for the smaller degrees of platinum dispersion (D). The TOF0-D relation is
correlated by the same curve for SI-, SA- and TI-supported catalysts. The T
OF0 of Pt/AL catalysts is smaller compared with that of other catalysts. Ad
sorbed triethylamine was found to decompose at temperatures above 450 K, ev
olving hydrogen and leaving carbon-containing species, causing the inductio
n period and deactivation. The X-ray photoelectron spectroscopy Pt 4f bindi
ng energies of Pt/AL and Pt/TI catalysts were observed to be higher and low
er, respectively, compared with that of the Pt/SI catalyst. When acetonitri
le is adsorbed on Pt/AL catalyst, it is stabilized and the C-N bond is more
difficult to hydrogenate, giving a smaller TOF0 value. The adsorption of b
asic substances of amines by Pt/TI catalyst is so weak that it produces lar
ger amounts of the lower amines. (C) 1999 Elsevier Science B.V. All rights
reserved.