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促进型铑催化剂上,测定CO吸附的IR光谱和铑的分散度,结果表明:线吸附CO的谱带基本不变,桥CO谱带红移且变宽。变化顺序为Rh-Mn>Rb-Mn-Fe-Li>Rh-Fe>Rh-Li>Rh。该变化归因于助剂对吸附CO氧端络合而形成的η~2-CO物种,并可作为活性中心亲氧能力强弱的相对尺度,Rh·Mn/SiO_2上,测量CO/H_2的IR光谱,发现了归属于甲酰基的谱带;说明甲酰基是反应中间物,并测定各催化剂活性和选择性,基于这些结果和蔡启瑞等曾提出的氢助解离乙烯酮机理,能较合理地探讨了助剂的协合催化作用,本研究再次为上述机理提供另一重要实验证据。
Promoted rhodium catalyst, the IR spectra of CO adsorbed and the dispersity of rhodium were determined. The results showed that the band of adsorbed CO was almost unchanged and the CO band of the bridge was redshifted and broadened. The changing order is Rh-Mn> Rb-Mn-Fe-Li> Rh-Fe> Rh-Li> Rh. The change is attributed to the formation of η ~ 2-CO species on the CO-binding oxygen side of the adsorbents, and can be used as a relative measure of the affinity of the active site for the affinity of oxygen. For Rh / Mn / SiO 2, CO / H 2 IR spectrum and the formyl group was found. The formyl group was the reaction intermediate and the activity and selectivity of each catalyst were determined. Based on these results and the hydrogen-assisted dissociation of ketene mechanism proposed by Cai et al. Explored the synergetic catalysis of adjuvants. This study provides another important experimental evidence for the above mechanism.