Synthesis and Characterization of Fe-Substituted ZSM-5 Zeolite and Its Catalytic Performance for Alkylation of Benzene with Dilute Ethylene

Composite Photocatalysts with Fe, Co, and Ni Oxides on Supports with Tetracoordinated Ti Embedded into Aluminosilicate Gel during Zeolite Y Synthesis

Ti-aluminosilicate gels were used as supports for the immobilization of Fe, Co, and Ni oxides (5%) by impregnation and synthesis of efficient photocatalysts for the degradation of β-lactam antibiotics from water. Titanium oxide (1 and 2%) was incorporated into the zeolite network by modifying the gel during the zeolitization process. The formation of the zeolite Y structure and its microporous structure were evidenced by X-ray diffraction and N2 physisorption. The structure, composition, reduction, and optical properties were studied by X-ray diffraction, H2-TPR, XPS, Raman, photoluminescence, and UV-Vis spectroscopy. The obtained results indicated a zeolite Y structure for all photocatalysts with tetracoordinated Ti4+ sites. The second transitional metals supported by the post-synthesis method were obtained in various forms, such as oxides and/or in the metallic state. A red shift of the absorption edge was observed in the UV-Vis spectra of photocatalysts upon the addition of Fe, Co, or Ni species. The photocatalytic performances were evaluated for the degradation of cefuroxime in water under visible light irradiation. The best results were obtained for iron-immobilized photocatalysts. Scavenger experiments explained the photocatalytic results and their mechanisms. A different contribution of the active species to the photocatalytic reactions was evidenced.

Sustainable product-based approach in the production of olefins using a dual functional ZSM-5 catalyst

Investigation of the current industrial processes, such as methanol to olefin (MTO) and hexane to olefin (HTO), in terms of green and sustainable chemistry approaches in order to design the process, catalyst and reactor from the beginning in such a way as to minimize environmental pollution is compulsory. Therefore, the synthesis of a group of multifunctional catalysts, which can be used simultaneously in both industrial processes to produce a variety of products, was studied. The effect of incorporation of different metals (Fe, Mn, Zn, Ga and Al) on the strengthening of each of the products was also studied. The investigation of reactor productivity (WHSV_HTO = 25) in HTO showed that the production efficiency of propylene in microchannels is higher than the ideal value for all samples, which is a significant improvement for sustainable approaches in future technologies. Considering the overall performances, Ga-ZM showed the best performance in both processes due to the high P/E ratio. The significant effect of Ga on the increasing of propylene was confirmed in MTO at 400 °C (P/E ≃ ∞), which indicated the dramatic effect of this metal in directing the reaction mechanism to an olefin-based cycle by converting almost all ethylene to propylene by methylation.

Fenton Reaction–Unique but Still Mysterious

This study is devoted to the Fenton reaction, which, despite hundreds of reports in a number of scientific journals, provides opportunities for further investigation of its use as a method of advanced oxidation of organic macro- and micropollutants in its diverse variations and hybrid systems. It transpires that, for example, the choice of the concentrations and ratios of basic chemical substances, i.e., hydrogen peroxide and catalysts based on the Fe2+ ion or other transition metals in homogeneous and heterogeneous arrangements for reactions with various pollutants, is for now the result of the experimental determination of rather randomly selected quantities, requiring further optimizations. The research to date also shows the indispensability of the Fenton reaction related to environmental issues, as it represents the pillar of all advanced oxidation processes, regarding the idea of oxidative hydroxide radicals. This study tries to summarize not only the current knowledge of the Fenton process and identify its advantages, but also the problems that need to be solved. Based on these findings, we identified the necessary steps affecting its further development that need to be resolved and should be the focus of further research related to the Fenton process.

Metal Sites in Zeolites: Synthesis, Characterization, and Catalysis

Zeolites with ordered microporous systems, distinct framework topologies, good spatial nanoconfinement effects, and superior (hydro)thermal stability are an ideal scaffold for planting diverse active metal species, including single sites, clusters, and nanoparticles in the framework and framework-associated sites and extra-framework positions, thus affording the metal-in-zeolite catalysts outstanding activity, unique shape selectivity, and enhanced stability and recyclability in the processes of Brønsted acid-, Lewis acid-, and extra-framework metal-catalyzed reactions. Especially, thanks to the advances in zeolite synthesis and characterization techniques in recent years, zeolite-confined extra-framework metal catalysts (denoted as metal@zeolite composites) have experienced rapid development in heterogeneous catalysis, owing to the combination of the merits of both active metal sites and zeolite intrinsic properties. In this review, we will present the recent developments of synthesis strategies for incorporating and tailoring of active metal sites in zeolites and advanced characterization techniques for identification of the location, distribution, and coordination environment of metal species in zeolites. Furthermore, the catalytic applications of metal-in-zeolite catalysts are demonstrated, with an emphasis on the metal@zeolite composites in hydrogenation, dehydrogenation, and oxidation reactions. Finally, we point out the current challenges and future perspectives on precise synthesis, atomic level identification, and practical application of the metal-in-zeolite catalyst system.

Effect of H2SiF6 modification of IM-5 on catalytic performance in benzene alkylation with ethylene

IM-5 zeolite modified by H₂SiF₆ has superior activity, equivalent stability, higher DEB selectivity and a lower xylene selectivity in comparison of ZSM-5 with similar Si/Al₂ ratio. The process provides a new way to make ethylbenzene in the vapor phase.

Synergistic effect of Fe and Ga incorporation into ZSM-5 to increase propylene production in the cracking of n-hexane utilizing a microchannel reactor

Comprehensive investigation of the synergistic effect of incorporating Fe and Ga into ZSM-5 in cracking of hexane.