孤立Pt位点于Pt-Sn、Pt-Zn配位的PtSnZn有序金属间化合物选择性催化丙烷脱氢

Atomically dispersed Pt in ordered PtSnZn intermetallic with Pt-Sn and Pt-Zn pairs for selective propane dehydrogenation

随着页岩气的大规模开采,丙烷脱氢制丙烯日益重要.在本文中我们以Al_(2)O_(3)为载体,结合强静电吸附法和程序升温还原法合成了~0.9 nm PtSnZn有序金属间化合物团簇(PtSnZn/Al_(2)O_(3)).PtSnZn金属间化合物的结构形成主要受动力学控制,Pt原子被Sn和Zn完全孤立,形成Pt-Sn和Pt-Zn原子对.PtSnZn/Al_(2)O_(3)在丙烷脱氢反应中表现出优异的催化性能,丙烯选择性高达~100%,并且在长周期稳定性测试中丙烷转化率维持在40%以上.Pt Sn Zn/Al_(2)O_(3)的丙烷脱氢催化性能远远优于Pt/Al_(2)O_(3)、PtSn/Al_(2)O_(3)和PtZn/Al_(2)O_(3)催化剂.实验结果和理论计算表明Sn 5p和Zn 4s与Pt 5d轨道的杂化使得Pt d带中心远离费米能级(-2.81 eV),这在丙烷脱氢反应中会降低催化剂对丙烯的吸附能和抑制深度脱氢反应,使得PtSnZn/Al_(2)O_(3)催化剂表现出高丙烯选择性和稳定性.

With the surge of shale gas,propane dehydrogenation becomes increasingly important to synthesize propylene.Herein,a new type of ordered PtSnZn intermetallic clusters (~0.9 nm) supported on Al_(2)O_(3)was synthesized by a stepwise approach including electrostatic adsorption and temperature-programmed reduction.The structure of the Pt SnZn clusters results from a kinetically controlled process and Pt atoms in the PtSnZn clusters are well isolated by Sn and Zn with Pt-Sn and Pt-Zn pairs.The PtSnZn/Al_(2)O_(3)catalyst exhibits excellent catalytic performance for propane dehydrogenation,which achieves~100%propylene selectivity and keeps a high propane conversion (>40%) during stability testing.The catalytic performance of PtSnZn/Al_(2)O_(3)is also significantly higher than that of Pt/Al_(2)O_(3),PtSn/Al_(2)O_(3),and PtZn/Al_(2)O_(3).Experiments and theoretical calculations indicate that the Sn 5p and Zn 4s orbitals are hybridized with Pt 5d by forming Pt-Sn and Pt-Zn pairs,which leads to the d band center of Pt deviating from Fermi level (-2.81 eV).The shift of the Pt d band center significantly decreases the adsorption energy of propylene and prohibits further dehydrogenation resulting in high propylene selectivity and stability.