118
unidirectional pore systems. Furthermore, unsuccessful attempts have been made to
reduce the inter-crystalline diffusion path by tailoring morphology and crystal size
of the zeolite.
The development of hierarchical zeolite systems might help to overcome the
above synthetic limitations and to reduce the inter-crystalline diffusion path in zeolite micropores [110–112]. Hierarchical zeolites couple within them the catalytic
features provided by the micropores and the higher diffusivity provided by the large
mesopores. However, the connectivity between the various levels of pores is vital to
maximize the benefits of interconnected hierarchy, which refers to the voids network generated within the crystal space by fragmentation of the microporous crystal. Typically, hierarchical zeolite systems, also known as micro-meso zeolites, are
extensively prepared by top-down and bottom-up approaches. The top-down
approaches are based on postsynthetic treatments and easy to scale up and experimentally simple [113, 114], as shown in Fig. 3. The concept of micro-meso zeolites
is being investigated for the development of improved catalysts for the C 4 alkylation
process.
Based on the aforementioned solid acid catalysts developed/being developed,
commercial processes are evolved. The details for the same are given in the following section.
1.1.5 Zeolite-Based Commercial C 4 Alkylation Processes: Key
Feature Requirement
Owing to rapid deactivation due to coking, it is imperative to state that methodology
for catalyst regeneration holds the key to the commercial success of the process.
Commercial processes are being developed depending on three key regeneration
methods, which are described below.
1. Cyclic regeneration: The concept of fluid catalytic cracking has been exploited
to carry out regeneration of zeolite-based catalysts. This requires zeolite with
excellent thermal stability, which is usually demonstrated by ultrastable zeolite
Fig. 3 Top-down approach to hierarchical zeolite
S. M. Pai et al.
unidirectional pore systems. Furthermore, unsuccessful attempts have been made to
reduce the inter-crystalline diffusion path by tailoring morphology and crystal size
of the zeolite.
The development of hierarchical zeolite systems might help to overcome the
above synthetic limitations and to reduce the inter-crystalline diffusion path in zeolite micropores [110–112]. Hierarchical zeolites couple within them the catalytic
features provided by the micropores and the higher diffusivity provided by the large
mesopores. However, the connectivity between the various levels of pores is vital to
maximize the benefits of interconnected hierarchy, which refers to the voids network generated within the crystal space by fragmentation of the microporous crystal. Typically, hierarchical zeolite systems, also known as micro-meso zeolites, are
extensively prepared by top-down and bottom-up approaches. The top-down
approaches are based on postsynthetic treatments and easy to scale up and experimentally simple [113, 114], as shown in Fig. 3. The concept of micro-meso zeolites
is being investigated for the development of improved catalysts for the C 4 alkylation
process.
Based on the aforementioned solid acid catalysts developed/being developed,
commercial processes are evolved. The details for the same are given in the following section.
1.1.5 Zeolite-Based Commercial C 4 Alkylation Processes: Key
Feature Requirement
Owing to rapid deactivation due to coking, it is imperative to state that methodology
for catalyst regeneration holds the key to the commercial success of the process.
Commercial processes are being developed depending on three key regeneration
methods, which are described below.
1. Cyclic regeneration: The concept of fluid catalytic cracking has been exploited
to carry out regeneration of zeolite-based catalysts. This requires zeolite with
excellent thermal stability, which is usually demonstrated by ultrastable zeolite
Fig. 3 Top-down approach to hierarchical zeolite
S. M. Pai et al.