Mild hydrogenation of quinoline - 2. A novel Rh-containing pillared layered clay catalyst

A novel highly dispersed Rh-containing catalyst (Rh, 2 wt.%) was prepared by ion-exchange of a Mg/Al/Ce pillared montmorillonite and characterized by chemical analysis, X-ray diffraction analysis and H, chemisorption. The Rh crystallites which formed were smaller than 2 run. The catalytic behavior of this Rh-containing pillared layered clay (Rh-PLC) catalyst was investigated in the mild hydrogenation of quinoline (T = 373-473 K; P-H2 = 2.0 MPa) and compared with that of a commercial 5 wt.% Rh on alumina (Rh-Al2O3) catalyst. At 373 K, both catalysts gave only partial hydrogenation to 1,2,3,4-tetrahydroquinoline (py-THQ), although with a significantly lower conversion for Rh-PLC, attributable to its micro-porous structure and steric hindrance of quinoline. However, when the temperature was increased to 473 K, Rh-PLC, unlike the commercial catalyst, was able to fully hydrogenate quinoline to decahydroquinoline, underlining the key role played by the metal particle size. (C) 2002 Elsevier Science B.V. All rights reserved.