Ring Number of Pore Opening and Channel Dimension in Zeolites

2 Ring Number of Pore Opening and Channel Dimension in Zeolites 

The channels of zeolites are delimited by the rings formed by n T-atoms. Besides some small channel systems like 6-rings, the pore openings of zeolites contain 8-, 9-, 10-, 12-, 14-, 18-, and 20-rings. A summary of the largest rings of various zeolite structure types is presented in Table 2.6. 

The channel system in zeolites can be 1-, 2-, or 3-dimensional that is, the channels extend along one, two, three-dimensions. Table 2.6 lists the channel dimensions of zeolites ordered by decreasing number of T-atoms in the largest rings.[4] Interconnecting channel systems are separated by a double arrow ( - ). A vertical bar ( ) means that there is no direct access from one channel system to the other. A perpendicular symbol ( ) represents a direction that is perpendicular to a crystallographic plane. The number of asterisks ( ) indicates the dimensions of the channel system, e.g. 1-, 2-, or 3-dimension. A few examples are selected from Table 2.6 to illustrate the notation for crystallographic characterization of the channels. 

CAN is characterized by a 1-dimensional system of channels parallel to [001] with circular 12-ring apertures. In OFF, the main 12-ring channels are interconnected with a 

2- dimensional system of 8-ring channels, thus forming a 3-dimensional channel system. RHO is an example of a framework type containing two noninterconnecting 

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