Solvent-free oxidation of benzyl alcohol with oxygen using zeolite-supported Au and Au–Pd catalysts (original) (raw)
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Journal of Porous Materials, 2014
In the present paper, nanocrystalline hierarchical ZSM-5 zeolites were successfully synthesized by the hydrothermal method in the presence of tetrapropylammonium hydroxide as a single template with the gel composition of 58SiO 2 :Al 2 O 3 :20TPAOH:1,500H 2 O. The prepared zeolite catalysts were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Nitrogen adsorption-desorption (BET), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HR-TEM) techniques. The formation of pure and highly crystalline ZSM-5 zeolite phase is confirmed by XRD. The IR vibration band at 550 cm-1 is assigned to the double 5-rings of MFI-type zeolites. N 2 adsorption-desorption isotherms showed that the synthesized product had high BET surface area and possessed composite pore structures with both micro and mesopores. The catalytic performance of hierarchical ZSM-5 zeolite was investigated in the selective oxidation of benzyl alcohol (BzOH) with hydrogen peroxide (H 2 O 2) under mild conditions. The results showed that the conversion of BzOH and the selectivity to benzaldehyde were about 94 and about 99 % respectively, when using 0.08 g ZSM-5 catalyst with acetonitrile as the solvent and H 2 O 2 as the oxidant at 90°C. This catalyst can be retrieved and reprocessed for five times without a significant loss in its activity and selectivity.
Journal of Industrial and Engineering Chemistry, 2014
Al 2 O 3 (1 : 1) systems were examined. The systems with a binder were prepared by two different methods of mixing zeolite with aluminum hydroxide. The samples were characterized by N 2 sorption (at 77 K), X-ray diffraction, 27 Al magic-angle spinning (MAS) NMR spectroscopy, temperature-programmed desorption of ammonia and adsorption of pyridine. Preparation of the zeolite catalyst with aluminium hydroxide was made by two methods: (1) mixing of powders and (2) combining appropriate pastes. Regardless of the method used for mixing there was no blocking of zeolite channels by aluminum oxide. The method of mixing zeolite with aluminium hydroxide powders promotes migration of aluminum from aluminum hydroxide/oxide to the zeolite framework. The results of n-hexane conversion showed that with Ni,H/ZSM-5 a slightly lower conversion than with H/ZSM-5 catalyst was observed that can be explained by a reduced yield of cracking products. Ni,H/ZSM-5-Al 2 O 3 (1 : 1) catalytic systems were insignificantly less efficient in n-hexane transformation than alumina free samples but at the same time they were less selective towards hydrocarbons with boiling temperatures higher than this of n-hexane, precursors of carbonaceous deposits.
Catalysis Today, 2007
Performance of Co-Al, Ni-Al, Cu-Al, Zn-Cu-Al, Mg-Fe, Co-Fe, Ni-Fe, Mn-Cr, Co-Cr, Ni-Cr, Zn-Cr and Cu-Cr hydrotalcite-like solid catalysts has been evaluated for the liquid phase oxidation of benzyl alcohol to benzaldehyde using molecular oxygen as an oxidizing agent in the absence of any solvent. The Mn and Cu containing hydrotalcite-like solids show good catalytic activity in the oxidation and hence these are promising catalysts for the solvent-free oxidation reaction.
Royal Society Open Science, 2021
Hierarchical zeolites have the potential to provide a breakthrough in transport limitation, which hinders pristine microporous zeolites and thus may broaden their range of applications. We have explored the use of Pd-doped hierarchical ZSM-5 zeolites for aerobic selective oxidation (selox) of cinnamyl alcohol and benzyl alcohol to their corresponding aldehydes. Hierarchical ZSM-5 with differing acidity (H-form and Na-form) were employed and compared with two microporous ZSM-5 equivalents. Characterization of the four catalysts by X-ray diffraction, nitrogen porosimetry, NH 3 temperature-programmed desorption, CO chemisorption, high-resolution scanning transmission electron microscopy, X-ray photoelectron spectroscopy and X-ray absorption spectroscopy allowed investigation of their porosity, acidity, as well as Pd active sites. The incorporation of complementary mesoporosity, within the hierarchical zeolites, enhances both active site dispersion and PdO active site generation. Likewi...
Catalytic deoxygenation of benzaldehyde over gallium-modified ZSM-5 zeolite
The deoxygenation of benzaldehyde has been investigated over gallium-modified ZSM-5 catalysts. In the absence of H 2 , Ga/HZSM-5 catalyzes benzaldehyde decarbonylation resulting in benzene and CO. The active sites for this reaction are the strong Brønsted acid sites. In the presence of H 2 , the main product is toluene. It is believed that Ga cationic species ðGa þ =GaH þ 2 Þ generated during H 2 reduction can promote the hydrogenation/hydrogenolysis reactions that give toluene and water. In the absence of H 2 , toluene can only be observed in transient experiments when the Ga/HZSM-5 catalysts are reduced. It is suggested that the GaH þ 2 species generated under H 2 play an important role in the hydrogenation/hydrogenolysis. However, they readily decompose to Ga + in the absence of H 2 . The addition of water to the feed modifies the catalytic activity and selectivity of Ga/HZSM-5 catalysts. On the one hand, water generates additional Brønsted acid sites from the reaction of extra-framework Ga with chemisorbed water (GaO(OH)) and with defect hydroxyls of the zeolite framework (GaOHSi). These additional sites enhance the production of benzene but decrease the production of toluene, due to a decrease in the density of reduced Ga cationic species.
Zeolite and Mixed Oxide Catalysts for VOCs Oxidation
2014
Zeolite (NaX, NaX-CeO2) and mixed oxide (Co4MnAl, NiMgMn) catalysts were tested in catalytic oxidation of volatile organic compounds (VOCs). The different kinds of catalysts proved remarkable activity in catalytic oxidation of ethanol and isopropanol respectively. The deepen comparison revealed that basic zeolite NaX-CeO2 is more suitable for oxidation of isopropanol while oxidation of ethanol is faster in a presence of the metal mixed oxides, Co4MnAl and especially NiMgMn. The results of catalytic testing were linked to certain catalysts ́ properties. Basicity/acidity and oxygen storage capacity (OSC) appeared to be the crucial parameters for selected tested alcohol oxidation. Key-Words: Ethanol, Isopropanol, Metal mixed oxide, Oxidation, and Zeolite