13C NMR studies of CO adsorbed on supported rhodium catalysts: Effects of alkali promotion

摘要: Abstract Changes in the chemical properties of silica-supported Rh catalysts on potassium promotion are observed 13 C NMR spectra adsorbed CO. Catalysts prepared by incipient wetness with 2.5% loading and Rh: K ratios 1:0, 3 : 1, 1 show relatively constant CO adsorption site character but have large changes relative populations linear, bridging, isolated dicarbonyl, metal-bound Back-bonded metal electrons produce a Gaussian peak near 275 ppm indicate transition to metallic behavior underlying at high levels. Purely electrostatic effects shown be too small cause shifts reported for IR positions. Alkali inhibits breakup particles formation dicarbonyl sites during adsorption, probably conversion surface -OH groups -OK groups.