Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Metal – metal oxide or metal hydroxide
Patent
1997-08-29
2000-07-18
Niebling, John F.
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Metal, metal oxide or metal hydroxide
502339, 502344, 585275, B01J 2342, B01J 2302
Patent
active
060907460
DESCRIPTION:
BRIEF SUMMARY
SUMMARY
The invention relates to a process for producing tenside-stabilized colloids of mono- and bimetals of the group VIII and Ib of the periodic system which are isolable in the form of powder and which are soluble at a concentration of at least 100 mg atom of metal/l of water, from metal salts in the presence of strongly hydrophilic tensides with hydrotriorganoborates in THF, or with simple chemical reduction agents like hydrogen or alkali formate in water and alcohols, respectively. Furthermore, the subject matter of the invention is the use of the tenside-stabilized colloids which are produced according to this process as precursor for supported catalysts for the selective cis-hydrogenation of C--C triple bonds, for the selective hydrogenation of functional groups at the aromatic nucleus, for the selective hydrogenation of benzene to cyclohexene, for the partial oxidation of the primary alcohol functionality in carbohydrates, as well as for use as a precursor for electrocatalysts in fuel cells.
DESCRIPTION OF THE PROCESS
The use of colloidally stabilized one- and multi-metallic nanoparticles as separately isolable precursor for producing supported metal catalysts is a new, economically beneficial alternative to the traditional in situ formulation of active metal components on carrier surfaces (H. Bonnemann et al., J. Mol. Catal. 86 (1994), 129-177]. The particular characteristic of the process according to the invention is the pre-formation of colloidally stabilized metal nanoparticles, optionally having an intermetalic composition, with defined size and particle structure. The characteristics of the catalyst (activity, selectivity, lifetime) of such metal colloids which are fixed on carriers are superior to conventional, supported catalysts.
The preferred solvent in this catalyst technology is water, due to economical and ecological reasons. The subject matter of the present invention is a process which permits to stabilize mono- and bimetallic nanoparticles in the form of powder in such a way, that highly concentrated colloidal solutions of the corresponding mono- and bimetallic catalyst-precursor can be produced in water without appreciable metal precipitations. By fixation of the precursor from aqueous solution on organic or inorganic carrier materials, new heterogeneous catalysts are prepared according the invention, for. e.g. selective hydrogenations, partial oxidations, or electrocatalysts for fuel cells.
According to the state of the art, some nanometals can be stabilized colloidally in water [T. Sato, S. Kuroda, A. Takami, Y. Yonezawa, H. Hada, Appl. Organomet. Chem. 1991, 5, 261; T. Sato et al., J. Appl. Phys. 1990, 68,1297; T. Sato et al., J. Chem. Soc., Faraday Trans. 1, 1987, 83,1559; T. Sato, S. Kuroda, A. Takami, Y. Yonezawa, H. Hada, Appl. Organomet. Chem. 1991, 5, 261; J. H. Fendler, "Membrane-Mimetic Approach to Advanced Materials", Springer-Verlag, Berlin, 1994; J. S. Bradley in "Clusters and Colloids", (Ed. G. Schmid), VCH, Weinheim 1994; H. Hirai, Y. Nakao, N. Toshima, Chem. Lett. 1978, 5, 545; M. Ohtaki, M. Komiyama, H. Hirai, N. Toshima, Macromolecules 1991, 24, 5567; N. Toshima et al., J. Phys. Chem., 1991, 95, 7448; N. Toshima, T. Yonezawa, Makromol. Chem., Macromol. Symp., 1992, 59,327; N. Toshima et al., J. Phys. Chem. 1992, 96,9927; K. Torigoe, K. Esumi, Langmuir 1993, 9, 1664; J. S. Bradley et al., Chem. Mater. 1993, 5, 254; H. Hirai, Y. Nakao, N. Toshima, Chem. Lett. 1976, 9,905; M. Ohtaki, M. Komiyama, H. Hirai, N. Toshima, Macromolecules 1991, 24,5567, N. Toshima, M. Ohtaki, T. Teranishi, Reactive Polym. 1991, 15, 135; C. Larpent, F. Brisse-Le Menn, H. Patin, Mol. Catal. 1991, 65, L35; N. Toshima, T. Takahashi, Bull. Chem. Soc. Jpn. 1992, 65, 400-9].
However, the described metal colloids cannot be isolated, and they are soluble in water only at a high dilution. Therefore, they are not suitable as a catalyst precursor.
Some authors could isolate water soluble nanometal colloids in the presence of hydrophilic P- and N-donators [J. S. Bradley in "Clusters-and Colloids
REFERENCES:
patent: 5147841 (1992-09-01), Wilcoxon
Bonnemann Helmut
Brijoux Werner
Brinkmann Rainer
Richter Joachim
Ghyka Alexander G.
Niebling John F.
Studiengesellschaft Kohle MBH
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