Step-response studies of propylene partial oxidation with oxygen over a hyd
rophobic Pd/SDB catalyst were conducted at 1000 kPa and 185 degreesC in a f
ixed-bed reactor. CO2 was found to be the only oxidation product when the f
eed contained only propylene and oxygen. CO2 formation was significantly su
ppressed by addition of steam to the feed, and this addition leads to the f
ormation of partial oxidation products: acrolein and acrylic acid. A compet
itive reaction mechanism involving water molecules is proposed to explain t
he significant influence of steam concentration on the rate of propylene ox
idation and product selectivity. (C) 2001 Elsevier Science B.V. All rights
reserved.