Koichi Sayo

Supported gold catalysts prepared by using nano-sized gold particles dispersed in nylon-11 oligomer

Gold catalysts supported on titanium oxide (TiO 2 ) have been prepared by using nano-sized gold particle/nylon-11 oligomer composites. The composite was prepared through vapor-deposition of gold onto a nylon-11 oligomer film followed by heat treatment. The gold particles/nylon-11 oligomer composite in solution was adsorbed rapidly on the surface of TiO 2 . When the gold particles/nylon-11 oligomer composite adsorbed on TiO 2 was calcined at various temperatures in air, nano-sized gold particles were supported directly on the surface of TiO 2 without coagulation. The catalytic activity of the gold particles for oxidation of CO was measured in a flow type reactor. The catalytic activity of gold supported on TiO 2 prepared by a one-stage calcination was not so high as that of gold catalysts reported previously. This result was considered to be due to growth of the size of the gold particles during calcination. When the calcination was carried out in two stages (the first at 500 °C in vacuum, and the second at 400 °C in air), the growth of the size of the gold particles was suppressed considerably. The supported gold catalyst thus obtained showed very high activity for the oxidation of CO, with a temperature of –10 °C for 50% conversion of CO.

Dispersion of nano-sized gold particles into polymers: dependence on terminal groups of polymers and morphology of vapor-deposited gold

Dispersion of nano-sized gold particles into polymers was investigated from the viewpoint of terminal groups and molecular motion of the matrix polymers, and from morphology of vapor-deposited gold. NH 2 -terminated poly(ethylene oxide) (PEO-NH 2 ) and poly(ethylene glycol) (PEG) were used as the matrix polymers. When gold with a thickness of 20 nm was vapor-deposited onto a melt of PEO-NH 2 at 60 °C, nano-sized gold particles were smoothly dispersed into the melt. On the other hand, gold vapor-deposited on a melt of PEG formed only conglomerates. When gold with a thickness of 3 nm was vapor-deposited onto PEO-NH 2 and PEG films kept at 20 °C, it formed particulate films. The gold particles formed were not dispersed into the polymer films by heat-treatment below the melting point of the polymer. However, when the polymer films were melted by heat-treatment at 50 °C, the gold particles were dispersed only into PEO-NH 2 . When gold with a thickness of 20 nm was vapor-deposited on the polymer films, it formed conglomerates, therefore the dispersion of gold particles into both polymers was not observed even upon heat-treatment at 50 °C. Measurements of spin-spin relaxation time by solid-state 1 H NMR indicated that the molecular motion of PEO-NH 2 was restricted below the melting point. Therefore, the dispersion of the nano-sized particles occurred only above the melting point of PEO-NH 2 .