Hydrogenation of crotonaldehyde on Rh-Sn/SiO2 catalysts prepared by reaction of tetrabutyltin on prereduced Rh/SiO2 precursors

P. REYES , M.C. AGUIRRE , J.L.G. FIERRO , G. SANTORI , O. FERRETTI

JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL

ELSEVIER SCIENCE BV

Año: 2002 vol. 184 p. 431 - 444

1381-1169

Abstracts Rh and Rh-Sn/SiO2 catalysts have been prepared, characterized and used in the crotonaldehyde hydrogenation reaction. New bimetallic Rh-Sn catalysts were prepared by reaction of Sn(n-C4H9)4 over prereduced Rh-SiO2 precursor. It was observed that the temperature of the preparation reaction also plays an important role in the nature of Rh-Sn active sites. Thus, at lower temperatures , 363 K, Rh(SnBu4-x)y species remains adsorbed on the silica surface whereas at 773 K, the organometallic residue decomposes leading to Rh-Sn bimetallic catalysts. Tin addition causes a significant drop in hydrogen chemisorption capability but only a slight increase in metal particle size. Electron diffraction detected the presence of Rh0 RhSn2 and SnO2 phase for the bimetallic catalysts and Rh0 for the monometallic ones. XPS, shows  an important surface enrichment in tin suggesting that SnOx species would migrate and deposit o the metal crystals. The active sites generated upon these treatments allow the polarisation of the carbonyl group and consequently and enhancement in the selectivity to crotyl alcohol is obtained.  2002 Elsevier Science B.V. all rights reserved.