Arkady Kustov

Aluminum-rich mesoporous MFI-type zeolite single crystals

Zeolites are crystalline materials, which are widely used as solid acid catalysts and supports in many industrial processes. Recently, mesoporous MFI-type zeolite single crystals were synthesized by use of carbon particles as a mesopore template and sodium aluminate as the aluminum source. With this technique, only zeolites, with relatively low A1 contents were reported (Si/Al ratio about 100). In this work, the preparation of aluminum-rich mesoporous MFI-type zeolite single crystals (Si/Al∼16–50( using aluminum isopropoxide as the aluminum source is reported for the first time. All samples are characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), ammonia temperature programmed desorption (NH 3 -TPD), and N 2 adsorption measurements. The obtained zeolites combine the high crystallinity and the characteristic micropores of zeolites with an intracrystalline mesopore system having mesopore volumes varying between 0.37–0.40 cm 3 /g.

Hierarchical zeolites: progress on synthesis and characterization of mesoporous zeolite single crystal catalysts

Abstract Recently, a new family of crystalline zeolitic materials was reported, the so-called mesoporous zeolite single crystals featuring individual zeolite single crystals with an additional noncrystalline mesopore system interconnected with the usual micropore system of the zeolite, resulting in a hierarchical pore size distribution. In this work, the preparation of mesoporous ZSM-12 single crystal catalysts using a new improved procedure for directly introducing carbon in the reaction mixture is reported. The microwave heating technique is also applied for the synthesis of mesoporous silicalite-1 single crystals using this direct introduction of carbon into the reaction mixture. All samples were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), temperature-programmed desorption of ammonia (NH 3 -TPD), and N 2 adsorption measurements. Additionally, the results of diffusion of n -hexadecane in conventional and mesoporous zeolites are presented. Isomerization and cracking of n- hexadecane was chosen as model test reaction for these materials. All results support that mesoporous zeolites are superior catalysts due to improved mass transport. Importantly, the mesoporous zeolites show significant improved resistance to poisoning by carbon formation.

New Insights into the Mechanism of Synergistic Effect for [CeO2–ZrO2 + H-Beta] CombiCat in NH3–SCR

NH3–SCR performance of the combined catalyst (CombiCats) prepared by mechanical mixing of CeO2–ZrO2 and H-Beta is studied in details. It was shown, that individual standard SCR activities of CeO2–ZrO2 and H-Beta are negligible, while their mixing results in the significant improvement of NOx conversion. The absence of standard SCR activity of individual components enabled us to estimate the contribution of fast SCR, NO and NH3 oxidation reactions to the overall process on CombiCat. Comparison of catalytic data obtained for layered configurations and CombiCats with various CeO2–ZrO2/H-Beta ratios also allowed us to determine the rate-limiting step and role of each component in the process.