## 4 Hierarchical Porous Composite Catalysts  
As we know, the physical properties of pores or pore channels of porous materials, such as the pore shape, pore size and pore structures, are closely related to the adsorption, diffusion and shape confinement of molecules in catalytic reactions, which will exert impact on activity, selectivity and life of the catalysts. So it is important to select, fabricate and adjust proper pore systems of the catalysts. The zeolite-based hierarchical porous materials with two or more levels of porosity have potential applications in several industrial fields [135]. These materials have been proven to be promising catalysts that combine the advantages of shape selectivity with efficient mass transport [136]. The presence of mesopores in zeolite has improved theircatalytic activities and selectivities significantly as compared to conventional zeolite catalysts in a series of catalytic reactions, such as the alkylation of benzene with ethylene over ZSM-5[137], the cracking of lager molecule 1,3,5-trisopropylbenzene and cumene [138,139],the epoxidation of alkylene over TS-1 and TS-2 [140,141], isomerization of 1,2,4-trimethylbenzene, and esterification of benzylalcohol with hexanoic acid. Most importantly, some zeolites with mesoporovosity have been used in a number of industrial processes including the cracking of heavy oil fraction over zeolite Y, the production of cumene, hydro-isomerization of alkanes over mordenite, and the synthesis of fine chemicals over Y, ZSM-5, and beta [142]. The enhanced catalytic activities are due to the reduction of diffusion path and easier access to the active site as a result of the introduction of mesopores into the zeolite framework [143,144]. Various attempts have been undertaken to synthesize composite materials which combine the structures of both zeolites and mesoporous molecular sieves, such as the recrystallization of the walls of SBA and MCM materials in the presence of molecular templates [145], the preparation of zeolite coated mesoporous aluminosilicates by using diluted clear solutions containing primary zeolite units [146], and the assembly of zeolite nanoblocks into ordered mesoporous materials [147]. The introduction of mesoporousity into zeolite materials by different approaches is another method for the synthesis of mesoporous zeolite materials [148]. The obtained mesoporous zeolites preserve the crystalline nature of the zeolite materials, and the mesoporousity in zeolite can increase accessibility to the internal surface. The post-synthesis technique is a traditional method for the generation of mesopores within zeolite crystals. Upon steaming [149], acid or base leaching [150,151] and chemical treatment, the aluminum or silicon atoms can be selectively extracted from the framework, resulting in the formation of mesopores in zeolite framework. An alternative route for the preparation of mesoporous zeolite is to introduce mesopores into zeolite crystal during the zeolite crystallization. Besides a structure-directing agent for templating the zeolite structure, an easily removable pore-filling additive in the dimension of nanoscale is also often used to create mesopores in zeolite crystal. Zeolite crystallized around hard templates such as carbon black [152], carbon nanotube [153], carbon aerogel [154], mesoporous carbon [155], wood cell [156], and organic gel [157]. Moreover, a few water soluble polymers with strong interaction with silica can be incorporated into silicate crystal during the crystallization, and then they are removed to generate moso-porosity [158,159]. Recently, [PERSON]'s group has developed a direct synthesis route to mesoporous zeolites with tunable mesoporous structure by using the amphiphilic organosilane assembled supramolecule as a mesopore-directing agent [160]. The methods mentioned above make the synthesis of mesoporous zeolite possible, constructing a new family of zeolite-based materials with multilevel of pore size distribution.