Simple approach in understanding interzeolite transformations using ring building units

Abstract

Recently, there are two general approaches used in understanding interzeolite transformations, thermodynamically represented by framework density (FD) and kinetically by structural building units. Two types of structural building units are composite building units (CBU’s) and secondary building units (SBU’s). This study aims to examine the approaches by using interzeolite transformation data available in literature and propose a possible alternative approach. From a number of cases of zeolite transformation, the FD and CBU approach are not suitable for use. The FD approach fails in cases involving zeolite parents that have moderate or high FD’s, while CBU approach fails because of CBU’s unavailability in parent zeolites compared with CBU’s in their transformation products. The SBU approach is most likely to fit because SBU’s are units that have basic form of ring structures and closer to the state and shape of oligomeric fragments present in zeolite synthesis or dissolution cases. Thus, a new approach can be considered in understanding the interzeolite transformation, namely the ring building unit (RBU) approach. The advantage of RBU approach is RBU’s can be easily derived from all framework types, but in SBU approach there are several types of frameworks that cannot be expressed in SBU forms.