Kim Sunhee, Byl Oleg, Yates John T
Department of Chemistry, Surface Science Center, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA.
J Phys Chem B. 2005 Mar 3;109(8):3499-506. doi: 10.1021/jp0405512.
The adsorption of triethylenediamine (TEDA) at 300 K is observed to occur via hydrogen bonding to isolated Al-OH groups on the surface of partially dehydroxylated high area gamma-Al(2)O(3) powder. This form of bonding results in +0.3 to +0.4% blue shifts in the CH(2) scissor modes at 1455 cm(-1) and a -0.4% red shift in the CN skeletal mode at 1060 cm(-1), compared to the gas-phase frequencies. Other modes are red shifted less than 0.1%. The isolated OH modes are red shifted by -200 to -1000 cm(-1) due to the strong hydrogen bonding association of Al-OH groups with an N atom in TEDA. Thermal desorption of adsorbed TEDA from the surface occurs in the range 300-700 K. Mass spectral and infrared studies indicate that the decomposition of TEDA occurs on Al(2)O(3) above 725 K, and that C-H bonds are broken, forming adsorbed species with N-H bonds which are stable to 1000 K or above. In contrast to adsorption at 300 K, adsorption of TEDA at 85 K results in the formation of a condensed ice of TEDA, which covers the outer surface of the porous Al(2)O(3) and which does not interact with Al-OH groups inside the porous powder due to immobility.
观察到在300 K下，三乙烯二胺（TEDA）通过与部分脱羟基的高比表面积γ-Al₂O₃粉末表面孤立的Al-OH基团形成氢键而发生吸附。与气相频率相比，这种键合形式导致1455 cm⁻¹处的CH₂剪刀式振动模式发生+0.3%至+0.4%的蓝移，以及1060 cm⁻¹处的CN骨架振动模式发生-0.4%的红移。其他模式的红移小于0.1%。由于Al-OH基团与TEDA中的N原子形成强氢键缔合，孤立的OH模式红移了-200至-1000 cm⁻¹。吸附在表面的TEDA在300 - 700 K范围内发生热脱附。质谱和红外研究表明，TEDA在725 K以上在Al₂O₃上发生分解，并且C-H键断裂，形成具有N-H键的吸附物种，这些物种在1000 K或更高温度下稳定。与300 K时的吸附情况相反，85 K时TEDA的吸附导致形成TEDA的冷凝冰，它覆盖了多孔Al₂O₃的外表面，并且由于其不移动性而不与多孔粉末内部的Al-OH基团相互作用。
