不同Pt前躯体对Pt/KL催化剂芳构化性能的影响

Influences of Pt Precursors on the Aromatization Performance of Pt/KL Catalyst

为考察不同Pt前躯体对Pt/KL催化剂芳构化性能的影响,分别以Pt(NH3)4(NO3)2和Pt(NH3)4Cl2为Pt前躯体,KL分子筛为载体,制备了TN-Pt/KL和TC-Pt/KL芳构化催化剂,其对应的再生剂为R-TN-Pt/KL和R-TC-Pt/KL。采用XRD、XRF、TGA、BET、TEM、H2-TPR等分析手段对上述催化剂进行了表征,并以正庚烷为原料,在500℃、0.4MPa、MHSV=1.5h^-1、n(H2)/n(n-Heptane)=3的条件下分别对新鲜剂和再生剂的芳构化性能进行评价。结果表明:2种不同的Pt前躯体对新鲜剂上Pt的粒径、比表面积和孔体积影响不大,但TC-Pt/KL催化剂上芳构化活性中心更多,且该催化剂上的Pt2+与KL分子筛载体之间的相互作用力更强,有利于提高其芳构化活性,减缓Pt颗粒聚集长大;与新鲜剂相比,2种再生剂Pt粒径均明显增大,比表面积和孔体积也明显降低,但R-TC-Pt/KL的物化性质优于R-TN-Pt/KL;以Pt(NH3)4Cl2为前躯体制备的催化剂具有较优异的芳构化活性和稳定性,2种催化剂的再生性能均较差,TC-Pt/KL催化剂比TN-Pt/KL的再生性能略好。

To investigate the influences of different Pt precursors on the aromatization performance of Pt/KL catalyst,TN-Pt/KL and TC-Pt/KL catalysts were prepared with Pt(NH 3) 4(NO 3) 2 and Pt(NH 3) 4Cl 2 as the Pt precursors and KL molecular sieve as the carrier,respectively,while the corresponding regenerated catalysts are R-TN-Pt/KL and R-TC-Pt/KL.These catalysts were characterized by XRD,XRF,TGA,BET,TEM and H 2-TPR.Results show that Pt precursors have little effect on the particle size of Pt,surface area and pore volume of the fresh catalysts.However,TC-Pt/KL is of more aromatization active centers and stronger interaction force between Pt^2+ and KL molecular sieve.Thus,it is beneficial to improve aromatization activity and restrict the aggregation and growth of Pt particles.Compared with the fresh catalysts,the Pt particle sizes of the two regenerated catalysts are increased significantly,while the surface area and pore volume obviously are decreased.Moreover,R-TC-Pt/KL shows much better physical and chemical properties than R-TN-Pt/KL.Using n -heptane as feed,under the conditions of 500 ℃,0.4 MPa,MHSV=1.5 h^-1,n (H2)/ n ( n -Heptane)=3,the aromatization performances of fresh catalysts and regenerated catalysts were evaluated respectively.The results show that the catalysts prepared by Pt (NH 3) 4Cl2 exhibit excellent aromatization activity and stability,but both regenerated catalysts show poor catalytic performance.