Adsorption of amines on alumina
Adsorption of amines on alumina
复制标题
胺在氧化铝上的吸附
DOI：
10.1016/0021-9517(75)90100-1
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发表时间：
1975
影响因子：
7.3
通讯作者：
J. Pašek
中科院分区：
文献类型：
--
作者：
J. Koubek;J. Volf;J. Pašek
研究了一系列脂肪胺在氧化铝上的吸附行为。较弱的键合物种进行了研究，通过测量吸附等温线的脉冲色谱技术。由吸附等温线计算了吸附量与等量吸附热的关系。采用程序升温脱附（TPD）方法研究了强化学吸附。大多数胺的研究解吸在两个步骤。吸附的空间位阻要求在伯胺系列内没有不同。乙基-、二乙基-、三乙胺系列吸附量的减少表明空间位阻效应。两个不同的区域中观察到的脂肪族伯胺的吸附量后的等排吸附热的依赖性。低于0.3 mmol/g时，吸附热的增加顺序为正丁基- <正丙基- <乙基- <甲胺，高于0.5 mmol/g时，顺序正好相反。胺-表面相互作用的类型在这两个区域中的每一个都不同。基于对不同水合表面的测量，可以得出结论，羟基在低于0.3 mmol/g的区域中形成活性位点的一部分。在0.5mmol/g以上的活性中心可能是氧离子。在低于0.1 mmol/g的覆盖率下可能发生对酸性铝离子的非常强的吸附，并且对应于TPD色谱图的第二个峰。
The adsorption of a series of aliphatic amines on alumina was investigated. The more weakly bonded species were studied by measuring the adsorption isotherms by the pulse chromatograph technique. The dependence of the isosteric heat of adsorption upon the adsorbed amount was calculated from the adsorption isotherms. The method of temperature programmed desorption (TPD) was employed in the study of strong chemisorption. Most of the amines investigated desorbed in two steps. The steric demands of adsorption do not differ within the series of primary amines. The decrease in the adsorbed amount in the series ethyl-, diethyl-, triethylamine indicates the effect of steric hindrance. Two distinct regions were observed in the dependences of the isosteric heat of adsorption of primary aliphatic amines upon the adsorbed amount. Below 0.3 mmole/g the heat of adsorption increased in the ordern-butyl- <n-propyl- < ethyl- < methylamine, while the order was exactly reversed above 0.5 mmol/g. The type of amine-surface interaction was different in each of these two regions. On the basis of measurements on variously hydrated surfaces it was possible to conclude that hydroxyl groups form a part of the active sites in the region below 0.3 mmol/g. The active sites in the region above 0.5 mmol/g were probably oxide ions. Very strong adsorption on acidic aluminum ions probably occurs at coverages below 0.1 mmol/g and corresponds to the second peak of the TPD chromatogram.