Effects of ZrO 2 promoter on physic-chemical properties and activity of Co/TiO 2 –SiO 2 Fischer–Tropsch catalysts

Wu, Huatao; Yang, Yong; Suo, Haiyun; Qing, Ming; Lü, Yan; Wu, Baoshan; Xu, Jian; Xiang, Huimin; Li, Yongwang

doi:10.1016/j.molcata.2014.09.024

Cited by 37 publications

(19 citation statements)

References 46 publications

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“…It is relatively cheap, photochemically stable, non-toxic, easily UV-activated, and insoluble in most reaction environments [ 6 , 7 ]. However, its application is limited because of its narrow photocatalytic region (α < 400 nm) and its ability to absorb only a small fraction (5%) of incident solar irradiation, which results from its relatively large band gap (anatase, ~3.2 eV) [ 8 ]. Many recent studies have focused on modifying the morphology and crystalline structure of TiO 2 to improve its photocatalytic activity.…”

Section: Introductionmentioning

confidence: 99%

TiO2-ZnO Binary Oxide Systems: Comprehensive Characterization and Tests of Photocatalytic Activity

et al. 2018

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A series of TiO2-ZnO binary oxide systems with various molar ratios of TiO2 and ZnO were prepared using a sol-gel method. The influence of the molar ratio and temperature of calcination on the particle sizes, morphology, crystalline structure, surface composition, porous structure parameters, and thermal stability of the final hybrids was investigated. Additionally, to confirm the presence of characteristic surface groups of the material, Fourier transform infrared spectroscopy was applied. It was found that the crystalline structure, porous structure parameters, and thermal stability were determined by the molar ratio of TiO2 to ZnO and the calcination process for the most part. A key element of the study was an evaluation of the photocatalytic activity of the TiO2-ZnO hybrids with respect to the decomposition of C.I. Basic Blue 9, C.I. Basic Red 1, and C.I. Basic Violet 10 dyes. It was found that the TiO2-ZnO material obtained with a molar ratio of TiO2:ZnO = 9:1 and calcined at 600 °C demonstrates high photocatalytic activity in the degradation of the three organic dyes when compared with pristine TiO2. Moreover, an attempt was made to describe equilibrium aspects by applying the Langmuir-Hinsherlwood equation.

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Section: Introductionmentioning

confidence: 99%

TiO2-ZnO Binary Oxide Systems: Comprehensive Characterization and Tests of Photocatalytic Activity

et al. 2018

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“…Activity and selectivity of the catalysts, offline testing corresponding to Fig. 4.References ( 63 , 64 )…”

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confidence: 99%

Chemical imaging of Fischer-Tropsch catalysts under operating conditions

et al. 2017

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“…In the current literature, there is a large discrepancy between conditions and a manner of hydrogen chemisorption measurements, from which data are used to determine the average size of crystallites and dispersion of the metallic cobalt phase deposited on an oxide support. Although those, already old, recommendations, only in the 2015-beginning of 2016 period the much lower temperature, 293-323 K, of hydrogen chemisorption [28][29][30][31][32][33][34][35][36][37] and flow adsorption pulse and TPD methods [32][33][34][35][36][37] are used in many laboratories. The higher, 423 K, temperature of hydrogen chemisorption was also applied in the pulse method for estimation of the average size of cobalt crystallites [33].…”

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confidence: 99%

Estimation of Average Crystallites Size of Active Phase in Ceria-Supported Cobalt-Based Catalysts by Hydrogen Chemisorption vs TEM and XRD Methods

et al. 2016

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Cobalt catalysts with CeO 2 support, unpromoted and promoted with potassium were prepared by an impregnation method. Reduced catalysts were subjected to hydrogen chemisorption at different temperatures in the range of 313-453 K. Studies have shown that calculated Co crystallites size depends on the temperature of chemisorption. The average of size crystallites of the Co active phase obtained from the total and strong chemisorption data were compared with those from measurements by other techniques, TEM and XRD. The results of comparison allowed us to indicate the most suitable chemisorption temperature, different for unpromoted (383 K) and potassium-promoted (413 K) catalysts to determine the proper Co crystallites size of active phase, compatible with the crystallites size determined by the most objective method, i.e. by TEM measurements. In the case of small metal crystallites of active phase (4-5 nm) the divergence of their average size determined by hydrogen chemisorption and TEM methods and particularly by the XRD method is definitely higher than that in the case of larger crystallites (~12 nm).can significantly influence on obtained results. More than 40 years ago Bartholomew et al. [23][24][25] show that the chemisorption of hydrogen over cobalt catalysts with various supports (SiO 2 , Al 2 O 3 , C, MgO, ZSM-5, TiO 2 ) and over unsupported cobalt is activated and highly reversible. The activation was a function of the interaction of cobalt with a support or promoter. Frequently used in catalysis, potassium promoter significantly increased the adsorption activation energy for hydrogen [26]. It is also proved that some methods for determining the hydrogen uptake, i.e. flow adsorption methods such as thermal desorption and pulse methods, measure only irreversible (strong) chemisorption [23,27]. No hydrogen desorption was detected for MgOand ZSM-5-supported and low-loaded (1-3 wt.%) aluminasupported cobalt catalysts using TPD method, even though those catalysts adsorbed hydrogen when the static technique was applied [23,24]. The special case is the Co/TiO 2 system, where due to the strong metal-support interactions the stoichiometry of hydrogen chemisorption is lower than one hydrogen atom per surface cobalt atom, even in static measurements. With exception of the cobalt systems in which the strong metal-support interactions take place, the static technique was recommended for estimation of the average size of cobalt crystallites on the basis of maximal hydrogen chemisorption uptake, usually at 373 K. A good correlation with TEM measurements was found for the Co/SiO 2 , Co/γ-Al 2 O 3 and Co/C catalysts. The paper [9] also shows that the volume of chemisorbed hydrogen (including strong and weak chemisorption) on the CoRe/γ-Al 2 O 3 catalyst varies with the temperature of chemisorption, and the use of different data leads to the determination of different average size of crystallites, even though the actual crystallites size remains unchanged. They obtained the best results when the total chemisorption...

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Effects of ZrO 2 promoter on physic-chemical properties and activity of Co/TiO 2 –SiO 2 Fischer–Tropsch catalysts

Cited by 37 publications

References 46 publications

TiO2-ZnO Binary Oxide Systems: Comprehensive Characterization and Tests of Photocatalytic Activity

TiO2-ZnO Binary Oxide Systems: Comprehensive Characterization and Tests of Photocatalytic Activity

Chemical imaging of Fischer-Tropsch catalysts under operating conditions

Estimation of Average Crystallites Size of Active Phase in Ceria-Supported Cobalt-Based Catalysts by Hydrogen Chemisorption vs TEM and XRD Methods

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