低碱度共沉淀法制备苯选择加氢Ru-Zn催化剂

在低碱度下采用共沉淀法成功制备了非负载型Ru-Zn催化剂,用于苯选择加氢制环己烯反应.固定氢氧化钠沉淀剂的量,考察了不同氯化锌加入量对催化剂结构和催化性能的影响,采用N2吸附、X射线衍射和程序升温还原等手段对催化剂进行了表征.同时考察了选用具有最佳锌含量的Ru-Zn催化剂时搅拌速度和硫酸锌添加剂等对催化反应性能的影响,最后考察了催化剂多次使用时的反应性能.研究表明, Zn含量16.7%(质量分数)的Ru-Zn催化剂具有最佳的催化性能；在ZnSO4水溶液(0.45 mol/L)中,优化反应条件(哈氏合金釜,1200 r/min,150oC, H2压5 MPa)下反应45 min,苯转化率57%时环己烯选择性可达80%(收率超过45%).钌催化剂中ZnO晶体对于环己烯选择性达到80%非常重要.催化剂回收循环反应5次时反应性能基本不变,表明低碱度下制备的催化剂具有良好的稳定性,显示了工业化应用前景.

Ru-Zn catalysts for selective hydrogenation of benzene using coprecipitation in low alkalinity

Several unsupported Ru‐Zn catalysts were successfully prepared using the coprecipitation method under low alkaline conditions, and their catalytic performance was evaluated for the selective liq‐uid‐phase hydrogenation of benzene. The effect of the amount of ZnCl2 added to the coprecipitation solution on the physical and catalytic properties of the Ru‐Zn catalysts was studied whilst keeping the amount of the NaOH precipitant constant. The properties of the resulting catalysts were charac‐terized by N2 adsorption, X‐ray diffraction, and temperature‐programmed reduction. The effects of the stirring rate and the amount of ZnSO4 additive on the catalytic properties of the Ru‐Zn catalysts were investigated using the optimal Zn content. The recyclability of the optimal Ru‐Zn catalyst was also explored. The results revealed that the optimal Zn content for the Ru‐Zn catalysts was 16.7 wt%, and the selectivity for cyclohexene could reach up to 80%(yield>45%) when the benzene conversion was 57%in an aqueous solution of ZnSO4 (0.45 mol/L) under the optimal reaction con‐ditions (i.e., hastelloy reactor, 1200 r/min, 150 °C and 5 MPa of H2 pressure). The presence of ZnO crystals in the Ru catalysts was found to be critical to obtaining high selectivity for cyclohexene (>80%). The Ru‐Zn catalysts prepared under the low alkaline conditions also showed good stability, which indicates that they could potentially be used for industrial application.