ИСТИНА

Hierarchical micro-mesoporous materials have emerged as an important class of catalytic materials, which has significant advantages with respect to both zeolites and ordered mesoporous solids. Nowadays this class of materials involves different structural types: nanosized zeolites with mesopores in between the crystallites; delaminated zeolites; zeolitic nanosheets; mesoporous zeolites; ordered mesoporous materials with fully or partially crystalline zeolitic walls, micro-mesoporous composites and etc. The literature on these materials is growing almost exponentially and a great deal of reviews highlighting various aspects of the recent achievements in this area has appeared recently [1]. This lecture is devoted to micro-mesoporous materials obtained by zeolites recrystallization, which has been demonstrated to be a versatile tool for the tailored synthesis of mesoporous zeolites, micro-mesoporous nanocomposites and ordered mesoporous materials with zeolytic fragments in the walls [2]. The lecture will cover the recent achievements in the field of the development of this type of micro-mesoporous materials. The recrystallized materials will be classified into three distinctly different groups depending on the degree of recrystallization: i) mesoporous zeolites (RZEO-1); ii) micro-mesoporous nanocomposites (RZEO-2); iii) mesoporous materials with zeolytic fragments in the walls (RZEO-3). The first part of the lecture will be focused on the mechanism of zeolite recrystallization, which determines the main synthetic strategies leading to different types of recrystallized materials. In the second part, a comprehensive view on their structure, texture and porosity in connection with acidic and diffusion properties will be given. The third part will be devoted to the engineering of recrystallized materials for the specific catalytic applications in petrochemistry and oil refining. The specific attention will be focused on the impact of recrystallization on the improvement of the catalytic performance of zeolites and mesoporous materials in various catalytic reactions including cracking and hydrocracking of alkanes, hydroisomerization of n-alkanes, C10+ alkylaromatics dealkylation, alkylation and transalkylation of aromatics, dehydration of methanol into DME, skeletal isomerization of 1-butene, disproportionation of toluene and cumene and upgrading of bio-oils. It will be demonstrated that the choice of the optimal recrystallized material is governed by the two main factors: i)the size of reactant/product with respect to the size zeolitic micropores; ii) the acidic strength required for the specific reaction. If the reactants and products are very bulky and cannot diffuse into zeolitic micropores but strong acidity is not required, RZEO-2 and RZEO-3 are the optimal catalysts. Nanocomposite materials RZEO-2 are especially advantageous in the sequential reactions, involving transformation of large reactant in the mesopores and smaller intermediate in the micropores. In the case of the reactions demanding strong acidity, such as FCC, cumene disproportionation or biphenyl transalkylation with diisopropylbenzene, RZEO-1 is the most appropriate. In the last part of the lecture the advantages and disadvantages of micro-mesoporous materials obtained by zeolites recrystallization with respect to pure micro- and mesoporous molecular sieves and other hierarchical zeolites will be critically analyzed and the future opportunities and perspectives will be discussed.