催化研究方法概述1.ppt

Py-IR spectra of the as-synthesized samples NH3TPD spectra of the as-synthesized samples * IR spectra of the as-synthesized samples in the initial stage of crystallization Wavenumber/cm-1 27Al,31P, and 29Si CP/MAS NMR spectra of as-synthesized samples(2.5h) 27Al (+38) 31P (-27.4) ≈P (4Al) 29Si (-90.5) ≈Si (4Al) 27Al,31P, and 29Si CP/MAS NMR spectra of as-synthesized samples(2.5h) 27Al 31P 29Si Changes of the Al, P and Si relative content and relative crystallinity of the as-synthesized samples with the crystallization time Fig.9 Relative proportion curve of Si/P, Si/Al and Al/P Crystallization Mechanism of SAPO-34 Fast crystallization: -~80% relative crystallinity can be achieved in 2.5h Formation of crystal, nucleus(~0.5h): -Structure arrangement of the initial gel -Condensation of the hydroxies -Si directly take part in In the initial stage(2.5h): -Only si(4Al), ~90% Si relative content of maximum -Si directly take part in and/or substitute for P In the later stage(2.5h): . -Si(3Al), Si(2Al), Si(1Al), Si(0Al) appear -Si substitute for P+Al and/or for P Similar trend of Al, P, Si relative content and the crystallinity in the initial stage(2.5h) -Deferente from that in the later stage(2.5h) The acid property of SAPO-34 depending strongly on Si content and Si distribution -Si content ∝ number of acidic sites -Si distribution ∝ acid strength distribution 由丁ZSM-5沸石属中孔分子筛(5.5 A)，尽管调变后的ZSM-5抗积碳性能好，其“择形作用” 仍不尽人意。产物分布较宽，低碳烯烃选择性不够高。我们又进一步开发了SAPO-34分子筛， 发现：由于它属于小孔沸石(4.3A)，是甲醇和二甲醚高选择性地制取低碳烯烃(特别是C2= ,C3=) 优良催化剂。以SAPO-34分子筛催化MTO反应，低碳烯烃选择性高于85wt％，乙烯选择性达 50％以上，几乎没有C5以上产物。有鉴於此，利用IR , NH3-TPD, NMR，SEM，XRD)等方法 对其合成规律，反应，表面性质进行了深入的表征。 对SAPO-34分子筛晶化过程的全面表征研究表明，可以对其晶化过程进行控制，并且晶化 过程的变化对分子筛的结构组成，催化性能影响很大。因此，对其晶化过程的控制和合成方法 的改进，可以有效控制其骨架组成分布，在分子筛表面形成一定强度和数量的酸中心，进而提 高产物中乙烯的选择性，从而达到了催化剂设计的目的。 结论 * 过渡金属氮化物研究 例子3 * Introduction ? Nitrogen and carbon