聚苯乙烯非均相催化加氢吸附动力学及反应动力学研究

Adsorption and Reaction Kinetic Studies of the Heterogeneous Catalytic Hydrogenation for Polystyrene

采用以表面具有贯穿大孔的二氧化硅空心微球为载体制备的负载型钯催化剂(Pd/SHMs),对聚苯乙烯(PS)在非均相加氢催化剂上的吸附及加氢反应行为进行了系统研究,得到了吸附和反应动力学模型,并对部分加氢产物进行了详细分析.结果表明随着温度的升高,PS吸附量逐渐增加,且达到饱和吸附时间也随之增长,确定了PS非均相加氢为1级反应,活化能为58.3 k J·mol-1.将不同加氢度的样品进行分离提纯分析,结果显示PS的部分加氢产物都是由较高加氢转化率(85%左右)和较低加氢转化率(25%左右)的PS组成,证明PS非均相加氢存在二次吸附和竞争吸附加氢的现象,即服从"Blocky"机理.此工作为PS催化加氢吸附及反应过程的研究奠定基础,也为理解其他聚合物在非均相催化剂上的吸附及反应行为提供帮助.

We applied silica hollow microspheres with through holes in the shell as supports to prepare Pd-based supported catalyst （Pd/SHMs） for heterogeneous catalytic hydrogenation of polystyrene （PS） and also systematically studied the adsorption and reaction behavior of PS molecules over Pd/SHMs. The dynamic adsorption and reaction models of PS molecules under different temperatures have been established and the partially hydrogenated products were also comprehensively analyzed. The result shows that both the adsorption capacity and saturation time are increased as the temperature increasing and this hydrogenation reaction is confirmed to be a first-order reaction and the activation energy is calculated to be 58.3 kJ.mol^-1. After separating and purifying three samples with different hydrogenation degrees, we further analyzed the partially hydrogenated products and the results show that they are all actually comprised of two kinds of substances with different properties, one with high hydrogenation conversion rate （ca. 85%） and the other with low hydrogenation ratio （ca. 25%）. It is proved that PS heterogeneous hydrogenation process exists secondary adsorption and competitive adsorption phenomenon, and obeys the Blocky mechanism. This work lays the foundation for PS adsorption and hydrogenation reaction and is also favorable for the understanding of the adsorption and catalytic process for other unsaturated polymers over heterogeneous catalysts.