Surface organometallic chemistry on metals in water - Chemical modification of platinum catalyst surface by reaction with hydrosoluble organotin complexes: application to the selective dehydrogenation of isobutane to isobutene
Fz. Bentahar et al., Surface organometallic chemistry on metals in water - Chemical modification of platinum catalyst surface by reaction with hydrosoluble organotin complexes: application to the selective dehydrogenation of isobutane to isobutene, CATAL TODAY, 66(2-4), 2001, pp. 303-308
Surface organo-metallic chemistry on metals can be a new route to generate
supported bimetallic catalysts. According to previous works on Pt-Sn cataly
sts, the reaction of tetra n-butyl-tin on the reduced platinum surface lead
s to well-defined bimetallic catalysts which are very active and selective
in the dehydrogenation of isobutane into isobutene. The presence of tin not
only isolates the surface platinum atoms from each other (EXAFS) and thus
prevents a fast deactivation by decreasing the processes of C-C bond cleava
ge but also favors the regeneration processes under air. So far the catalys
t preparations were carried out either in the gas phase or in organic solut
ion (e.g. heptane). However, in order to meet the industrial criteria of pr
ocess simplicity, there is a need to carry out such catalyst preparation in
water.
In this work, Pt-Sn/Al2O3 and Pt-Sn/SiO2 catalysts was prepared by reacting
tris n-butyl-tin hydroxide on the platinum surface, in water solution unde
r atmospheric pressure of hydrogen. The kinetics of the reaction was follow
ed by measuring the amount of butane evolved as a function of time. The sol
ids obtained were characterized by CO, O-2 or H-2 chemisorption and electro
n microscopy (CTEM and EDAX). Clearly, the (n-Bu)(3)Sn(OH) reacts selective
ly on the platinum surface and not with the support, with evolution of buta
ne, leading to a bimetallic catalyst where the platinum atoms are isolated
from each other by the tin atoms. Very high selectivities (> 95%) and activ
ities were obtained for the reaction of isobutane dehydrogenation into isob
utene and it was concluded that surface organo-metallic chemistry on metal
in water can be an alternative route to prepare well-defined supported bime
tallic Pt-Sn catalysts. (C) 2001 Elsevier Science B.V. All rights reserved.