摘要
在金属催化领域,近年来人们对于高分子保护金属胶体的研究表现出很大的兴趣。高分散、窄分布金属胶体的制备研究成为众多工作者努力的目标。这在沟通分子催化与凝聚相物质催化间的联系有着重要的理论意义和应用价值。人们作出了种种努力设法获得高分散、窄分布的金属胶体。如:Bradley等报导用金属蒸汽冷凝法,Schmid等用水溶性三苯膦磺酸钠小分子配位体作为稳定剂,Esumi等用在有机溶剂中热解金属化合物的方法,Toshima等利用表面活性剂形成胶束的方法,Nagy的工作也很相似。这些工作在一定程度上取得进展。
The amphoteric polymers of polyacrylamide-co-acrylic acid were tested as the protective agents in the formation of noble metal colloids. The amphoteric polymers examined were polyacrylamide-co-acrylic acid (PAAmA), poly-N-acryloyl-pyrrolidone-co-acrylic acid (PAPA), poly-N-acryloyl-morpholine-co-acrylic acid (PAMLA ) , and poly-N-acrylol-piperidine-co-acrylic acid (PAPPA). It was found that PAPA and PAPPA showed quite good protective action in spite of the fact that their homopolymer counterparts PAP and PAPP were poor in this regard. PAPPA[28]([m] indicates that the content of the acrylic acid part in copolymer is m %) can be used successfully as protective agent for the preparation of Pd, Pt, Rh, Ru, Ag and Au colloids while PAPP leads to the precipitation of the above metals with the exception of Au. PAML was a good protective polymer, when the acrylic groups were introduced to the polymer chain the copolymer PAMLA[80] worked even better. In the case of PAAmA, the content of acrylic groups was varied by controlled hydrolysis of PAAm and the sodium salts of the copolymer PAAmNa were used as protective agents for the formation of palladium colloids. It was found that the particle size and its distribution varied with the contents of acrylic groups in the copolymer and it reached a minimum at an aerylate content of about 76%. This result is quite consistent with Thiele and von Levern's observation.The stable metallic colloids with fine particle size and narrow distribution can be formed in some cases. For example, for the formation of Pd colloids, metal particles were mostly distributed in the range of 0. 6 - 5. 6 nm with an average diameter of 2. 4 nm in the PAAmNa[76] system and in 2. 0 - 3. 0 nm with an average diameter of 2. 5 nm in the PAML system, respectively. In the system of PAMLA[80], Pt colloidal particles were in the range of 1. 0-4. 0 nm with an average diameter of 2. 0 nm and Ag particles were in 1. 3-3. 5 nm with an average diameter of 2. 9 nm, respectively. With PAPPA [28] as the protective polymer, particles were dispersed in 2. 0 - 6. 0 nm with an average diam, ter of 3. 7 nm for Pt colloid, in 1. 2 - 3. 8 nm with an average diameter of 2. 6 nm for Rh and in 2. 5 -7. 5 nm with an average diameter of 4. 7 nm for Ru, respectively. The metallic sols of Pd, Pt and Rh formed were found to be good catalysts for the hydrogenation of 1,3-COD with excellent activity and selectivity.
出处
《分子催化》
EI
CAS
CSCD
1992年第5期387-393,共7页
Journal of Molecular Catalysis(China)
关键词
胶体
金属
催化剂
保护剂
高聚物
Precious metal colloids, Amphoteric polymers, Colloidal metal catalysts.
