Catalytic Dehydration of Ethanol over W/TiO2 Catalysts Having Different Phases of Titania Support

This study aims to investigate the catalytic behaviors on W/TiO2 catalysts having different phases of TiO2 towards catalytic dehydration of ethanol to higher value products including ethylene, diethyl ether, and acetaldehyde. In fact, TiO2 support with different crystalline phases can result in differences of physico-chemical properties of the catalyst. Therefore, the present work reports on the catalytic behaviors that were altered with different phases of TiO2 in catalytic ethanol dehydration to diethyl ether or ethylene as a major product. To prepare the catalysts, three different phases [anatase (A), rutile (R), and mixed phases (P25)] of TiO2 supports were impregnated with 10 wt% of tungsten (W). It was found that the W/TiO2-P25 catalyst revealed higher activity among other catalysts. At 300 °C, all catalysts can produce the diethyl ether yield of 24.1%, 22.8%, and 10.6% for W/TiO2-P25, W/TiO2-A, and W/TiO2-R catalysts, respectively. However, when the reaction temperature was increased to 400°C, ethylene is the major product. The W/TiO2-P25 and W/TiO2-A catalysts render the ethylene yield of 60.3% and 46.2%, respectively, whereas only 15.9% is obtained from W/TiO2-R catalyst. The most important parameter influencing their catalytic properties appears to be the proper pore structure, acidity, and distribution of W species. Copyright © 2020 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Production of Acetaldehyde via Oxidative Dehydrogenation of Ethanol over AgLi/SiO2 Catalysts

Three AgLi/SiO2 catalysts containing different types of silica supports [small particle size (SPS), medium particle size (MPS) and large particle size (LPS)] were prepared by incipient wetness co-impregnation techniques and tested in oxidative dehydrogenation of ethanol into acetaldehyde. The catalysts were characterized and evaluated by various characterization techniques (e.g. XRD, N2 physisorption, SEM-EDX, UV-Visible spectroscopy, H2-TPR, and CO2-TPD). This study reveals that the catalyst with the best performance is AgLi/SiO2-LPS with a yield in acetaldehyde of 76.8% at 300 °C. The results obtained with the tested catalysts are discussed, and the reasons of performance improvement caused by the presence of the dispersion of active components, the interaction between active components and silica supports, the textural properties of catalysts and reducibility, are raised. Besides, the cooperation of redox properties (Agnδ+  cluster and Ag0) and weak basic density played a pivotal role in promoting the formation of acetaldehyde from ethanol oxidative dehydrogenation. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Effect of Mo-Doped Mesoporous Al-SSP Catalysts for the Catalytic Dehydration of Ethanol to Ethylene

The catalytic dehydration of ethanol to ethylene over the mesoporous Al-SSP and Mo-doped Al-SSP catalysts was investigated. The Al-SSP catalyst was first synthesized by the modified sol-gel method and then doped with Mo by impregnation to obtain 1% Mo/Al-SSP and 5% Mo/Al-SSP catalysts (1 and 5 wt% of Mo). The final catalysts were characterized using various techniques such as XRD, N2 physisorption, SEM/EDX, TEM, and NH3-TPD. The catalytic activity for all catalysts in gas-phase ethanol dehydration reaction was determined at temperature range of 200°C to 400°C. It was found that the most crucial factor influencing the catalytic activities appears to be the acidity. The acid property of catalysts depended on the amount of Mo loading. Increased Mo loading in Al-SSP resulted in increased weak acid sites, which enhanced the catalytic activity. Besides acidity, the high concentration of Al at surface of catalyst is also essential to obtain high activity. Based on the results, the most suitable catalyst in this study is 1% Mo/Al-SSP catalyst, which can produce ethylene yield of ca. 90% at 300°C with slight amounts of diethyl ether (DEE) and acetaldehyde

Observation of Increased Dispersion of Pt and Mobility of Oxygen in Pt/g-Al2O3 Catalyst with La Modification in CO Oxidation

The study focuses on an improvement of the catalytic activity via CO oxidation for Pt/g-Al2O3 catalyst by addition of La onto the support prior to impregnation with Pt metals. The molar ratios of La/Al were varied from 0.01 to 0.15. Based on temperature-programmed desorption (TPD) of CO2, La addition apparently resulted in increased basicity of the catalysts, which is related to increasing of oxygen mobility. However, when considered the Pt dispersion measured by CO chemisorption, it was found that Pt dispersion also increased with increasing the amount of La addition up to La/Al = 0.05. It is suggested that too high amount of La addition can inhibit the dispersion Pt due to surface coverage of La. It is worth noting that the catalytic activity toward CO oxidation essentially depends on both Pt dispersion and oxygen mobility and they can be superimposed on each other. Based on this study, the Pt/g-Al2O3 catalyst with La addition of La/Al molar ratio = 0.05 showed the highest activity due to its optimal Pt dispersion and oxygen mobility leading to its highest value of turnover frequency (TOF).

Photooxidation and Virus Inactivation using TiO2(P25)–SiO2 Coated PET Film

This study chemically modified PET film surface with P25 using silicate as a binder. Different P25–binder ratios were optimized for the catalyst performance. The modified samples were analyzed by scanning electron microscopy-energy-dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy. Diffuse reflectance UV-vis spectra revealed significant reductions in the band gaps of the P25 solid precursor (3.20 eV) and the surface-modified PET–1.0Si–P25 (2.77 eV) with visible light. Accordingly, under visible light conditions, catalyst activity on the film will occur. Additionally, the film’s performance was evaluated using methylene blue (MB) degradation. Pseudo-first-order-rate constants (min−1), conversion percentages, and rates (µg.mL−1.gcat−1.h−1) were determined. The coated films were evaluated for viral Phi–X 174 inactivation and tested with fluorescence and UV-C light illumination, then log (N/N0) versus t plots (N = [virus] in plaque-forming units [PFUs]/mL) were obtained. The presence of nanosilica in PET showed a high adsorption ability in both MB and Phi–X 174, whereas the best performances with fluorescent light were obtained from PET–1.0Si–P25 and PET–P25–1.0Si–SiO2 equally. A 0.2-log virus reduction was obtained after 3 h at a rate of 4×106 PFU.mL−1.gcat−1.min−1. Additionally, the use of this film for preventing transmission by direct contact with surfaces and via indoor air was considered. Using UV light, the PET–1.0Si–P25 and PET–1.0Si–P25–SiO2 samples produced a 2.5-log inactivation after 6.5 min at a rate of 9.6×106 and 8.9×106 PFU.mL−1.gcat−1.min−1, respectively. Copyright © 2022 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).