KNO_3和KF改性Pd-Pb/Al_2O_3催化剂用于混合C_4选择加氢除炔

Pd-Pb/Al_2O_3 Catalyst Modified by KNO_3 and KF for Selective Hydrogenation of Crude C_4 to Remove Alkynes

用KNO_3和KF助剂对Pd-Pb/Al_2O_3催化剂进行改性,采用XPS,TEM,H_2-TPD等方法对改性前后的催化剂进行了表征,并考察了催化剂对混合C_4选择加氢除炔反应的选择性。实验结果表明,KF改性对Pd-Pb/Al_2O_3催化剂的选择性有明显的改善作用,而KNO_3改性的效果甚微。在保证剩余炔烃质量分数小于1.5×10^(-5)的情况下,KF改性后催化剂的1,3-丁二烯损失为2.6%,较未改性的Pd-Pb/Al_2O_3催化剂降低了0.6个百分点。XPS表征显示,KF改性的催化剂中F主要以K_3AlF_6物种形式存在,富电子的F对Pd的3d电子状态的影响可能是造成KF改性效果优于KNO_3的主要原因。

The modification of Pd-Pb/Al2O3 catalyst with KNO3 and KF was studied and used in hydrogenation of alkynes in crude C4. The catalysts before and after the modification were characterized by means of XPS, TEM and H2-TPD. The selectivities of these catalysts in the selective hydrogenation were investigated. Results showed that KF could significantly improve the selectivity of Pd-Pb/Al2O3 catalyst, while the effect of KNO3 was little. With the premises of less than 1.5 × 10 -5 （mass fraction） of residual C4 alkynes in the hydrogenated crude C4, butadiene losses over KF modified Pd-Pb/Al2O3 catalyst achieved 2.6%, which was 0.6 percentage point lower than that over the un-modified catalyst. XPS results showed that F in the KF modified catalyst existed mainly in the form of K3 AIF6 , and its effect on d-electron state of Pd was probably the key factor for the improved selectivity over the KF modified catalyst.