| abstract |
In purifying a gaseous unsaturated hydrocarbon stream by selectively hydrogenating more highly unsaturated hydrocarbon impurity contained therein, part of the starting stream is mixed with hydrogen in excess of the stoichiometric requirement to hydrogenate the impurity and passed over a first bed of hydrogenation catalyst, whereafter a second part of the starting stream is mixed with the hydrogen-containing product of the first catalyst and passed over a second bed of hydrogenation catalyst. Using such stepwise feed of hydrocarbon the hydrogen excess can be kept at a high enough level to limit or avoid deactivation of the catalyst, which is preferably supported palladium. |