Hierarchical Mesoporous Zeolites
Classical microporous zeolites have been a major breakthrough in petrochemical industries. Such molecular sieves have been synthesized and widely used in industry as heterogeneous catalyst due to their high ion-exchange capacity, strong acidity, high stability, and shape selectivity. To make these systems more efficient, pore size constraints have to be solved. One way to overcome these problems is by expansion of the porosity towards the mesoporous region. A possible solution came with the discovery of the ordered mesoporous materials (OMM’s) like MCM-41 and SBA-15 which have their pore sizes. However due to the amorphous nature of the OMM’s their catalytic performance and hydrothermal stability is often poor compared to zeolites. The rational design and synthesis of novel architecture materials with desired activity requires the thorough understanding of the crystallization and formation mechanism of zeolites. The increased knowledge of synthesis mechanism would improve our ability to control the properties (size, morphology, composition, etc.) and lay the basis to rational design of new materials.
Our research focuses on the understanding of the synthesis mechanism of microporous and mesoporous zeolites and silicas and the development of novel hierarchical molecular architectures. Better control of the structure in nanoscale enhances the catalytic properties of the microporous and mesoporous materials in applications such as methanol to olefins and methanol to gasoline reactions, biomass valorization and CO2 capture and utilization.
- “Mesoporous SSZ-13 Zeolite Prepared by a Dual Template Method with Improved Performance in the Methanol to Olefins Reaction”, Journal of Catalysis, 298 (2013) 27–40. >>Link>>
- “Dual template synthesis of highly mesoporous SSZ-13 zeolite with improved stability in the methanol-to-olefins reaction”, Chemical Communications, 48 (2012) 9492-9494. >>Link>>
The necessity to develop novel routes for the sustainable supply of transportation fuels and chemicals impose increasing pressure in all practical fields of science and engineering. Lignocellulosic biomass is one of the most promising renewable feedstock. Carbohydrates are the main constituents of cellulosic and hemicellulosic biomass. 5-hydroxymethylfurfural (HMF) is considered a key biorenewable intermediate for the further production of biofuels and chemicals. Although HMF can be obtained from fructose in high yield, selective transformation of glucose, the dominant sugar in cellulosic biomass, remains a challenge. The highest HMF yields were obtained for glucose dehydration by chromium (II) chloride in ionic liquids. The temporary self-organization of Cr ions into a binuclear metal complex with glucose is the essential feature of the unique reactivity of this homogeneous catalyst.
The separation of the products from the ionic liquid is difficult and thus not desired as the industrial application is concerned due to the homogeneous nature of this catalyst. Utilization of the lignocellulosic biomass requires the development of novel technologies for the selective depolymerization of polymeric carbohydrates into sugars monomers followed by their efficient conversion into platform molecules and downstream products. Similar to highly efficient petrochemical refineries, catalysts will play a central role to selectively alter or remove functionalities from renewable feedstocks at specific molecular sites in future biorefinery processes. Our research focuses on the development of heterogeneous catalytic systems capable of selectively converting the lignocellulosic biomass into platform molecules and end products.
- “Glucose Activation by Transient Cr2+ Dimers”, Angewandte Chemie International Edition, 49 (2010) 2530-2534. >>Link>>
- “Towards a Selective Heterogeneous Catalyst for Glucose Dehydration in Water: CrCl2 Catalysis in a Thin Immobilized Ionic Liquid Layer”, Chemcatchem, 3 (2011) 969-972. >>Link>>
The conventional liquid phase catalytic processes involve the use of suspended small catalyst particles. However the difficulties in recovering small catalyst particles from the reaction mixture severely limit their use in industrial applications. The use of an external magnetic field is a promising strategy to separate the suspended magnetic catalyst from the liquid system. In addition to their potential in separation, the magnetic catalyst bodies can also be used for magnetic heating. During the cycle of magnetization process the energy is transformed into heat through various loss processes (hysteresis losses, Neel and Brown relaxation). In a conventional heating system employed in chemical reactors the heat is generated externally and transferred through the reaction medium. Conversely, in magnetic heating the heat is generated locally at the catalyst body in the reactor. Thus, the magnetic heating approach provides a basis to overcome the heat transfer limitations. Besides, it prevents the formation of overheated hot zones in the reactor and provides a precise temperature control throughout the whole reactor. Presently magnetic field enhancement studies found applications in the area of fine chemical synthesis and biomedical applications such as hyperthermia by using the monometallic and bimetallic magnetic nanoparticles. In recent years methods have been established for the synthesis of nanoparticles and the magnetic field enhancement studies are now limited to the synthesis reactions in the scope of nanoparticles applied as catalysts. Our research focuses on the rational design of novel catalytic structures specifically for the externally applied magnetic field for chemical synthesis which will expand the applications towards high efficiency demanding conventional chemical transformations such as isomerization and hydrogenation reactions.
“Design and operation of a radio-frequency heated micro-trickle bed reactor for consecutive catalytic reactions”, Chemical Engineering Journal, 281 (2015) 884-891. >>Link>>
- “Design of a radio frequency heated isothermal micro trickle bed reactor”, Chemical Engineering Journal, 243 (2014) 225-233. >>Link>>
- “Structural and magnetic properties of Ni1−xZnxFe2O4 (x=0, 0.5 and 1) nanopowders prepared by sol–gel method”, Journal of Magnetism and Magnetic Materials, 348 (2013) 44-50. >>Link>>