MOCVD of rhodium, palladium and platinum complexes on fluidized divided substrates: Novel process for one-step preparation of noble-metal catalysts

Abstract

A new one‐step method, entitled fluidized‐bed metal‐organic chemical vapor deposition (FBMOCVD) of preparing highly dispersed metal‐supported catalysts is reported. The following complexes were studied and used as CVD precursors in presence of H2: [Rh(μ‐Cl)(CO)2]2, Rh(allyl)3, Rh(acac)(CO)2, Pd(allyl)(hfac), Pd(allyl)(Cp), Pt(COD)(CH3)2. (acac, acetylacetonato; hfac, hexafluoroacetylacetonato; Cp, cyclopentadienyl; COD, cyclooctadienyl). In a first approach, depositions on planar substrates were carried out to establish the best experimental conditions to obtain good‐quality deposits. X‐ray diffraction, X‐ray photo‐electron spectroscopy and electron microprobe studies were realized on the resulting thin films. Analyses of the products contained in the gas phase after and during deposition were performed by mass spectrometry and GC–MS. Finally, catalysts prepared by FBMOCVD were characterized by transmission electron microscopy–energy dispersion spectroscopy (TEM–EDS), metal‐loading determinations and specific‐surface measurements (BET). Dispersed nanosized aggregates were obtained, showing high activities in alkene hydrogenation and alcohol hydrocarbonylation. © 1998 John Wiley & Sons, Ltd.

Chemical Vapor Deposition of Iridium, Platinum, Rhodium and Palladium

“…The method resulted in the formation of pure and small palladium particles about 3 nm in size on the surface of the silica support. 64,65) As CVD allows the formation of fine particles due to homogeneous gas phase reactions of the precursors, it has become a novel alternative route to prepare catalysts.…”

“…64,106,107) Pd/Y-zeolite catalysts were prepared by introducing the vapor phase of this complex inside the Y-zeolite cavities and subsequent decomposition to metal particles by heating at 773 K in hydrogen. These catalysts were active in the methylcyclopentane conversion at 573 K. 106) Pd/SiO 2 catalysts were further prepared from (Cp)Pd(allyl) in a fluidized-bed CVD reactor.…”

“…This method allows the preparation of highly dispersed palladium aggregates (5-25 nm in size) with high activity both in alkene hydrogenation and alcohol hydrocarbonylation. 64) Recently, palladium and palladium-nickel alloy membranes were prepared on nickel-stainless steel or -alumina/-alumina porous supports. 107) The Pd(allyl)(hfac) complex is able to produce either palladium films or particles of high-purity with the assistance of hydrogen.…”

“…107) The Pd(allyl)(hfac) complex is able to produce either palladium films or particles of high-purity with the assistance of hydrogen. 64,65,102) The use of oxygen is also effective to achieve high-purity palladium films (>99 mass%Pd) from this complex. 91,108) On the other hand, Pd(Me allyl)(hfac) and Pd(Me allyl)(acac) may also produce high-purity palladium films but exclusively with the assistance of oxygen gas.…”

Coatings on ceramic powders by rotary chemical vapor deposition and sintering of the coated powders

“…There are a number of open literature publications on fabrication of catalytic nanoparticles of Pt, Pd and Rh deposited on powder supports of oxides such as Al 2 O 3 , TiO 2 and SiO 2 by FBCVD. 6) 8) In the case of nuclear materials, FBCVD is an essential technique for the deposition of multi-coatings comprising pyrolytic carbon and SiC on radioactive fuel particles for the primary containment of nuclear fission products. 9), 10) CVD techniques for ceramic particles are also useful in powder metallurgy for the preparation of sintered bulk materials with refined microstructure improving properties.…”