FORMATION AND CATALYTIC FUNCTIONALITY OF SYNTHETIC POLYMER NOBLE METAL COLLOID
FORMATION AND CATALYTIC FUNCTIONALITY OF SYNTHETIC POLYMER NOBLE METAL COLLOID
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DOI：
10.1080/00222337908056678
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发表时间：
1979-01-01
期刊：
影响因子：
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通讯作者：
HIRAI, H
中科院分区：
文献类型：
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作者：
HIRAI, H
用乙醇还原法制备了贵金属在合成聚合物中的胶体分散体。在甲醇-水混合溶剂中，在氩气或空气中回流4小时，得到均一的Rh-PVA-MeOH/H2O胶体分散溶液。金属Rh的颗粒大小分布在30~70？的狭窄范围内，平均直径为40？A。胶体Rh的形成经历了三个步骤：聚乙烯醇与Rh(III)离子的配位，甲醇还原形成小颗粒(直径8？)，小颗粒长大(直径40？)。聚乙烯吡咯烷酮(PVP)和聚甲基乙烯基醚(PMVE)可以分别代替聚乙烯醇，得到类似于Rh-PVA-MeOH/H2O的胶体分散体。用乙醇代替甲醇-水(Rh-PVP-EtOH)和用甲醇代替甲醇-水，并加入少量氢氧化钠甲醇溶液(Rh-PVP-MeOH/NaOH)，可在非水溶剂中制备胶体分散体。在Rh-PVP-EtOH和Rh-PVP-MeOH/NaOH中，Rh-PVP-EtOH和Rh-PVP-MeOH/NaOH中的Rh粒子的平均直径分别为22和9？以聚乙烯吡咯烷酮为原料，在水或非水溶剂中制备了钯、银、Os、铱、铂、金的胶体分散体。胶体分散体即使在空气中放置20天也非常稳定。在30℃常压氢压下，Rh、Pd和Ph是烯烃加氢反应的有效催化剂。钯的胶体分散体催化二烯和二烯酸酯分别高选择性地加氢生成单烯和单烯酸酯。
Colloidal dispersions of noble metals in synthetic polymers are prepared by reduction with alcohol. Reflux of a solution of rhodium(III) chloride and poly(vinyl alcohol) (PVA) in a methanol-water mixed solvent under argon or air for 4 hr gives a homogeneous solution of colloidal dispersion of rhodium (Rh-PVA-MeOH/H2O). The particle size of metallic rhodium is distributed n a narrow range of 30-70 Å, and the average diameter is 40 A. The formation of colloidal rhodium proceeds through three steps: coordination of poly(vinyl alcohol) to rhodium(III) ion, reduction with methanol to form small particles (8 Å in diameter), and growth of the small particle to large particle (40 Å in diameter). Polyvinylpyrrolidone (PVP) and poly(methyl vinyl ether) (PMVE) can be used in place of poly(vinyl alcohol) and result in colloidal dispersions, respectively, similar to Rh-PVA-MeOH/H2O. Colloidal dispersions in nonaqueous solvent can be prepared by using ethanol instead of methanol-water (Rh-PVP-EtOH) and by using methanol instead of methanol-water, with addition of small amount of methanol solution of sodium hydroxide (Rh-PVP-MeOH/NaOH). The average diameters of rhodium particles in Rh-PVP-EtOH and Rh-PVP-MeOH/NaOH are 22 and 9 Å, respectively. The colloidal dispersions of palladium, silver, osmium, iridium, platinum, and gold in aqueous or nonaqueous solvent are prepared by using polyvinylpyrrolidone. The colloidal dispersions are very stable even under air for 20 days. Those of rhodium, palladium, and platinum are effective catalysts for hydrogenation of olefins at 30°C under an atmospheric hydrogen pressure. The colloidal dispersion of palladium catalyzes highly selective hydrogenation of diene and dienoate to monoene and monoenoate, respectively.