A priori phase prediction of zeolites: case study of the structure-directing effects in the synthesis of MTT-type zeolites.
This study first uses molecular modeling to examine the structure-directing effects of small amines that are selective for the crystallization of MTT-type zeolite phases. The optimized van der Waals interactions of these small amines are compared within the one-dimensional pore zeolites with the MTT, TON, and MTW frameworks. From these results and our previous molecular modeling studies of structure-directing agents (SDA) for MTT-type zeolites, a large number of amines or quaternary ammonium molecules are successfully predicted to be selective for MTT phases. These molecules were chosen by matching the crystallographic periodicity of the pore structure with the distances between the centers of branched groups in these molecules. These molecules vary in length and in the number of branched moieties, and a few of these molecules are polymeric or oligomeric. In test cases where the distances between the branched groups are not multiples of the pore periodicity, with few exceptions these molecules usually do not produce MTT phases. Finally, we discuss the inorganic conditions necessary for crystallization of MTT phases in borosilicate preparations with some of the diamines in this investigation.
Burton
Allen W
AW
Chevron Energy Technology Company, Richmond, California 94802, USA. buaw@chevron.com