Pseudoionone → 6,10-Dimethylundecan-2-one

The hydrogenation of pseudoionone was carried out in a 243-ml fix-bed reactor with heating/cooling jacket with thermoelements placed in the centre of the reactor and on the reactor wall. Pressure-control valves were provided at the entrance end the exit site of the reactor. The reactor was charged with 162 ml (73 g) of catalyst (0.5% (wt./wt.) Pd on SiO2) and 81 ml of carrier material with 1 part by volume catalyst and 2 parts by volume of carrier in the bottom third of the reactor (entrance site), 2 parts by volume of catalyst and 1 part by volume of carrier in the middle third of the reactor, and catalyst alone at the top third of the reactor (exit site). The reactor was first flushed with nitrogen. The temperature at the entrance site of the reactor was adjusted to 80° C. and substrate, pseudoionone at a rate of 0.6 kg per hour, and hydrogen at a rate of 900 NL (norm liter) per hour were fed from separate storage tanks via a static mixer to the entrance site of the reactor. The hydrogenation was carried out in an up-flow mode. The mass flow was 8.3 kg of feed per hour per kg of catalyst and the pressure was set to 150 bar. The gradient of the maximum temperature in the reactor was 210° C.→170° C. and the temperature at the reactor outlet was adjusted to 80° C. The reaction product was released over a pressure valve into a separator where excess hydrogen was separated from the liquid hydrogenation product, hexahydropseudoionone. The reaction was allowed to proceed for 250 h, with yields of hexahydropseudoionone varying from 94 to 96% over that period (as determined by GC).