载体对聚硅氨烷—金属络合物催化正丙醇氧化性能的影响

EFFECT OF SUPPORTS ON CATALYTIC ACTIVITY OF POLYSILAZANE-METAL COMPLEXES IN OXYGENATION OF N-PROPANOL

1.前言 由醇类氧化脱氢,生成相应的醛和酮的反应,在工业上已有非常成熟的工艺。这一类反应的催化剂有铜,银等。但是,由于需要很高的反应温度,故这类反应常伴有CO_2、CO、H_2、羧酸、烯烃、烷烃等副产物。 我们曾发现,以SiO_2为载体的聚硅氨烷-铂络合物对甲醇、乙醇等的氧化具有较高的催化活性和选择性,在较低反应温度下,可完全生成相应的醛。但这种催化剂对正丙醇氧化的催化活性却不是很高,于100℃,5MPa下反应8h,丙醛的收率仅约为60％。 最近我们发现,负载络合物的载体对催化剂的活性有很大的影响。

Polysilazane-platinum ( or palladium ) complexes [abb. Si-N-Pt ( Pd ) ] on different supports were prepared. The supports used are SiO2, TiO2, A12O3 and MgO. The catalytic activity of the complexes prepared for the oxygena-tion of n-propanol was studied and found that the catalytic activity of Si-N-Pt ( Pd ) was greatly affected by the alkalinity of its support. The stronger the alkalinity of the support, the higher the catalytic activity of Si-N-Pt (Pd). The order of catalytic activity for Si-N-Pt on different supports appears: MgO-Si-N-Pt>Al2O3-Si-N-Pt-TiO2-Si-N-Pt>SiO2-Si-N-Pt Another important factor to affect the catalytic behavior of Si-N -Pt (Pd ) was found to be the chemical interaction between support and Si-N-Pt (Pd) which was confirmed by XPS data analysis. It was also found from XPS data that coordination bonds were formed between two nitrogen atoms and a platinum atom in Si-N-Pt complex. Alike other polymer catalysts, there is an optimum N/Pt ( Pd ) for which optimum O2 uptake rate is obtained on MgO-Si-N-Pt ( Pd ) . In this case the optimum O2 uptake rate was found to be about 0.8 ml/min for MgO-Si-N-Pt.