Hawkins Alexander P, Zachariou Andrea, Parker Stewart F, Collier Paul, Silverwood Ian P, Howe Russell F, Lennon David
School of Chemistry, University of Glasgow, Joseph Black Building, Glasgow G12 8QQ, U.K.
UK Catalysis Hub, Research Complex at Harwell, STFC Rutherford Appleton Laboratory, Chilton, Oxon OX11 0FA, U.K.
ACS Omega. 2020 Mar 30;5(14):7762-7770. doi: 10.1021/acsomega.9b03503. eCollection 2020 Apr 14.
The techniques of quasi-elastic and inelastic neutron scattering (QENS and INS) are applied to investigate the oligomerization of propene over a ZSM-5 zeolite. Investigations are performed at low temperatures, allowing identification of the onset of the oligomerization reaction and observation of the low-energy spectral changes due to intermediate formation that are difficult to observe by optical methods. Oligomerization proceeds via formation of a hydrogen-bonded precursor by an interaction of the propene with an internal acid site followed by protonation and chain growth with protonation being the rate-limiting step. The use of quasi-elastic neutron scattering to observe changes in system mobility with temperature via the elastic window scan technique allows identification of the active temperature range where catalyst activity commences and permits targeting of the more time-consuming INS investigations to conditions of interest. From examination of the product's spectrum, the structure of the resulting oligomer is deduced to be primarily linear.
采用准弹性和非弹性中子散射技术（QENS和INS）研究丙烯在ZSM-5沸石上的齐聚反应。研究在低温下进行，从而能够确定齐聚反应的起始点，并观察到由于中间产物形成而导致的低能光谱变化，这些变化用光学方法难以观测到。齐聚反应通过丙烯与内部酸性位点相互作用形成氢键前驱体，随后进行质子化和链增长，其中质子化是限速步骤。利用准弹性中子散射通过弹性窗口扫描技术观察系统迁移率随温度的变化，能够确定催化剂活性开始的活性温度范围，并将更耗时的INS研究针对感兴趣的条件。通过对产物光谱的研究，推断所得齐聚物的结构主要为线性。
