Synergy of ruthenium and cobalt in SiO2-supported catalysts on ethylene hydroformylation

Dynamic hydroformylation of ethylene at atmospheric pressure and 150 degree sC has been studied in a fixed bed reactor over ruthenium- and cobalt-conta ining SiO2-supported catalysts (1% Ru loading). Any combination of rutheniu m and cobalt precursors leads to significant improvement of hydroformylatio n activity with respect to those of monometallic catalysts. The optimal ato mic ratio of Co:Ru is estimated to be 3:1 for ideal catalytic activity. A c atalyst derived from Ru-3(CO)(12) and Co-2(CO)(8) is most active. A catalys t derived from metal carbonyls is generally more active than a catalyst pre pared from metal salts. Metal chlorides retard the preparation of active ca talysts in most cases, The catalysts studied exhibit fairly good catalytic stability. The determined rate enhancement of ethylene hydroformylation sug gests a synergy of ruthenium and cobalt, which is understood as catalysis b y bimetallic particles or ruthenium and cobalt monometallic particles in in timate contact, The synergy causes high ethylene hydrogenation activity whi le giving enhanced ethylene hydroformylation activity. Meanwhile, the poten tial of the ruthenium-based catalysts is evaluated from both catalytic perf ormances and cost by comparison with the corresponding rhodium-based ones, (C) 2001 Elsevier Science B.V. All rights reserved.