纳米复合固体超强酸S_2O_8^(2-)/ZrO_2-Al_2O_3的制备及其催化合成乙酸苄酯

Preparation of Nanosize Superacid S_2O_8^(2-)/ZrO_2-Al_2O_3 and Catalytic Synthesis of Benzyl Acetate

采用改性技术和浸渍—沉淀法制备出纳米固体超强酸催化剂S2O82-/ZrO2-Al2O3。通过正交试验获得了催化剂制备的最佳条件。用XRD、TEM、BET、TG-DTG和化学分析等手段分析了S2O82-/ZrO2-Al2O3的晶化过程、比表面积、含硫量和热稳定性,分析结果表明这四个方面对催化剂的酸性有较大影响。500~650°C焙烧温度下制备的催化剂属纳米材料(<41 nm),有较大比表面积和较好的热稳定性。以优化的催化剂S2O82-/ZrO2-Al2O3通过正交试验得到合成乙酸苄酯的最佳条件为∶n(苄醇)∶n(乙酸)=1.3∶1.0,催化剂用量为0.8 g(以0.2 mol乙酸为准),带水剂苯用量为14 mL,反应时间为2.5 h,催化剂重复使用7次酯化率在90%以上,该催化剂具有催化活性高、不污染环境、可重复使用等特点。

Nanometer composite solid superacid catalyst S2O8^2-/ZrO2-Al2O3was prepared by modified technology and impregnation-precipitation method. The optimum preparation condition were determined by orthogonal test. The crystallization process, specific surface area, sulphur content and themal stability the S2O8^2-/ZrO2-Al2O3 were st udicd by means of XRD, TEM, BET, TG DTG and chemical analysis, the result of which showed that these four factors could affect the acid strengths of solid superaeid catalysts. The catalysts were nanosize materials when activated between 500 ℃ and 650 ℃, displaying large specific surface area and good themal stability. The optimum synthetic conditions of benzyl acetate were as follows. the molar ratio of benzyl alcohol to acetic acid was 1.3 ： 1.0,the mass of the catalyst was 0.8 g （when acetic acid was 0.2 mol）,the volume of the water removing reagent, benzene was 14 mL,and the reaction time was 2. 5 h. The catalyst exhibited good stability and the conversion of acetic acid still amounted to 90% after 7 runs. The catalyst was highly active;non-polluting and reusable.