Triethylene Diamine-clay Complexes as Matrices for Adsorption and Catalytic Reactions*

Complexes of 1,4-diazabicyclo [2.2.2] octane (triethylene diamine) with smectite and vermiculite were made for the purpose of exposing the internal surfaces of the clays for adsorption of gases and possible catalytic activity. When the diprotonated form of the amine saturated the exchange sites, internal surfaces of the clays were found to be available to nitrogen, ethane, and 2,4-dimethyl pentane. Proton lability in the smectites was studied with NHa, D20, and C6D6 experiments. Catalytic function was demonstrated in the conversion of acetonitrile to acetamide in the smectite. I N T R O D U C T I O N The objective of this work was to place materials within the inteflamellar spaces of layer lattice silicates such as smectite and vermiculite which would hold the sheets apart a significant amount, yet were small enough to permit interlamellar penetration by liquid or gaseous molecules for the purpose of adsorption and/or catalytic reactions. It was found that the small "cage" compound 1,4-diazabicyclo [-2.2.2] octane also called triethylene diamine (TED) fulfilled these objectives better than any of the others considered. The molecule has a bulky shape which prevents it from assuming a position parallel with the clay surface which would cover surfaces and also result in small distances between adjoining silicate layers. In addition its cationic form is divalent so each molecule neutralizes two exchange sites. When it is the exchange cation, these properties, together with its small crossectional area (28 A2), permit the internal surface of smectite and vermiculite to be available to many molecules. Results obtained in this study include X-ray and infrared absorption properties, gas adsorption isotherms, and catalytic abilities.