ISSN:
1572-879X
Schlagwort(e):
RhCl3
;
Co2(CO)8
;
SiO2
;
surface‐bonded Rh+(CO)2
;
highly active Rh–Co catalyst
;
hydroformylation
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Chemie und Pharmazie
Notizen:
Abstract The preparation of a highly active bimetallic SiO2‐supported Rh–Co catalyst from RhCl3 and Co2(CO)8 (Rh:Co= 1 : 3 atomic ratio) has been studied by IR spectroscopy and ethylene hydroformylation, etc. Two steps are involved in the preparative process: (1) surface‐mediated synthesis of Rh+(CO)2/SiO2 from calcined RhCl3/SiO2; (2) impregnation of Rh+(CO)2/SiO2 with a Co2(CO)8 solution followed by H2 reduction at 623 K. The IR results of reductive carbonylation of calcined RhCl3/SiO2 have been compared to those of uncalcined RhCl3/SiO2 at 373 K. In situ IR observations, extraction results and elemental analysis suggest that approximately 50% of RhCl3 are transformed to Rh2O3 on the SiO2 surface and that calcined RhCl3/SiO2 is converted to a mixture of [Rh(CO)2Cl]2 and [Rh(CO)2O2 (Os: surface oxygen) under CO at 373 K. When this SiO2‐supported mixture was submitted to impregnation with a Co2(CO)8 solution at room temperature, IR study and elemental analysis show that [Rh(CO)2Cl]2 reacts easily with Co2(CO)8 on the surface to give RhCo3(CO)12, whereas [Rh(CO)2O2 does not react with Co2(CO)8. Catalytic study in steady‐state ethylene hydroformylation shows that a catalyst thus derived is more active than a catalyst derived from RhCo3(CO)12/SiO2 and a catalyst derived by coimpregnation of [Rh(CO)2Cl]2 and Co2(CO)8 on SiO2. This result suggests that the high rhodium dispersion of [Rh(CO)2O2 plays a crucial role in the formation of highly dispersed bimetallic Rh–Co sites.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1023/A:1019055517372
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