Effects of M-promoter (M=Y, Co, La, Zn) on Cr2O3 catalysts for fluorination of perchloroethylene

Cheng, Yongxiang; Fan, Jinglian; Xie, Zunyun; Lu, Ji-Qing; Luo, Ming

doi:10.1016/j.jfluchem.2013.08.016

Cited by 12 publications

(3 citation statements)

References 35 publications

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“…For the Cr-based catalysts for Cl/F exchange reactions, it is believed that the oxidation states of the Cr species and surface acidity are the main two factors governing the catalytic behaviors. It has been concluded that high valent Cr species such as Cr(VI) are vital for the reaction because they could be transformed to the active species such as CrO x F y [12,37], however, Cr species with low valance (e.g., Cr(III)) are inactive [38]. In the current work, the Cr 2 O 3 -R catalyst has higher surface Cr(VI) content compared to the Cr 2 O 3 -P, as evidenced by the XPS results (Table 1).…”

Section: Catalytic Testmentioning

confidence: 99%

Morphological effects of ordered Cr2O3 nanorods and Cr2O3 nanoparticles on fluorination of 2-chloro-1,1,1-trifluoroethane

et al. 2016

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Ordered Cr 2 O 3 nanorods (Cr 2 O 3 -R) and Cr 2 O 3 nanoparticles (Cr 2 O 3 -P) were prepared by a hard template method with SBA-15 and a deposition-precipitation method, respectively. These catalysts were tested for the fluorination of 2-chloro-1,1,1-trifluoroethane (HCFC-133a) to synthesize 1,1,1,2-tetrafluoroethane (HFC-134a). It was found that both catalysts were very selective, with a HFC-134a selectivity of 98 %. However, the Cr 2 O 3 -R catalyst had an area specific reaction rate of 0.012 lmol m -2 s -1 at 320°C, which was much higher than that on the Cr 2 O 3 -P (0.005 lmol m -2 s -1 ). The enhanced activity of the Cr 2 O 3 -R was attributed to its higher content of Cr(VI) species compared to that in the Cr 2 O 3 -P, which was evidenced by the hydrogen temperature-programmed reduction and X-ray photoelectron spectroscopy results. Besides, the Cr 2 O 3 -R catalyst had a higher surface acid density (0.076 mmol m -2 ) than the Cr 2 O 3 -P (0.068 mmol m -2 ), which could be another reason for its better performance.

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Section: Catalytic Testmentioning

confidence: 99%

Morphological effects of ordered Cr2O3 nanorods and Cr2O3 nanoparticles on fluorination of 2-chloro-1,1,1-trifluoroethane

et al. 2016

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“…The surface area of the single‐component oxide CrZn(0)‐O is 124.8 m 2 /g. As the Zn content increases, the surface area of the CrZn( x )‐O samples increases gradually, which suggests that the addition of Zn facilitates the high dispersion of the catalyst crystallites and, as a result, increases the BET surface area of the chromium oxide‐based catalyst . The surface area of the CrZn( x )‐F catalysts first increases and then decreases upon further increasing the Zn, and CrZn(15)‐F, with the largest surface areas of up to 139.4 m 2 /g, is the most accessible.…”

Section: Resultsmentioning

confidence: 99%

Study on the Preparation of Cr‐based Catalysts Doped by Zn using Sol–Gel Auto‐Combustion Method and Its Application for Synthesis of 1‐Chloro‐2,3,3,4,4,5,5‐heptafluorocyclopentene

Han

Zong-zhi

et al. 2017

J Chinese Chemical Soc

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High-surface-area chromium-based catalysts in the presence of a small amount of zinc were prepared via a sol-gel auto-combustion method using chromic nitrate, zinc nitrate, and citric acid. First, the auto-combustion behavior of the dried gel was investigated by derivative thermogravimetry and (DTG)-TG and infrared (IR) techniques. The results revealed that the dried gel exhibited self-propagating combustion properties. Second, the as-burnt powders were characterized by IR, X-ray diffraction (XRD), Brunauer-Emmett-Teller analysis (BET), and scanning electron microscopy (SEM). The findings showed that the gels were directly converted into CrZn-O nanoparticles with high surface area during the auto-combustion process. Third, the pre-fluorination Cr-Zn catalysts were characterized by XRD, BET, SEM, X-ray photoelectron spectroscopy (XPS), and Fourier transform (FT)-IR spectroscopy of pyridine adsorption techniques. It was found that the presence of zinc led to significant structural changes in the catalyst, the particle size was smaller, the surface area became larger, and more active sites appeared. Finally, the catalytic activities of the samples were tested for the fluorination of 1,2-dichlorohexafluorocyclopentene (1,2-F6) with anhydrous hydrogen fluoride. The obtained results indicated that the pre-fluorination activated Cr-Zn catalysts prepared by this sol-gel auto-combustion method exhibited high efficiency in the synthesis of cyclic hydrofluorocarbons.

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“…Cheng et al compared the catalytic activities of CrO x F y -supported Y, Co, La, and Zn for the fluorination of PCE and also studied the properties of the catalysts . The highest conversion was attained by La/CrO x F y , while simultaneously offering the highest selectivity (56%) for 123 .…”

Section: Hydrochlorofluorocarbons (Hcfcssecond Generation)mentioning

confidence: 99%

Fluorocarbon Refrigerants and their Syntheses: Past to Present

2020

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This Review chronicles the progress made in the field of small fluorocarbon synthesis since their invention in the early 1930s by Thomas Midgley, Jr., and his coworkers, with special focus on their application as refrigerants, foam expansion agents, aerosol propellants, and precision solvents. Divided into four generations of C1–C4 halocarbons from CFCs through HCFCs, HFCs, and HFOs, the merits and challenges of each will be discussed in the context of market demands, as well as the evolution of industrial manufacturing methods. Vital transformations, such as exchange (Swarts) fluorination, hydrodehalogenation, dehydrohalogenation, and additions (Kharasch or Prins) will feature prominently and will be discussed in detail, as well as catalysts therefor. Of the myriad of fluorocarbons described herein, the models which have reached particular commercial significance (such as chlorodifluoromethane and 1,1,1,2-tetrafluoroethane) are given special consideration as flag-bearers for the generation to which they belong. Regulatory constraints to which this industry is bound will be outlined in brief, as well as an introduction to safety designations and nomenclature put forth by the American Society for Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE). This Review includes predominantly works which can only be found in the patent literature, but should be of equal interest to both academic and industrial practitioners of the art as it centers on fundamentals of organofluorine chemistry, which could equally be applied to the synthesis of larger molecules and building blocks for other applications.

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Effects of M-promoter (M=Y, Co, La, Zn) on Cr2O3 catalysts for fluorination of perchloroethylene

Cited by 12 publications

References 35 publications

Morphological effects of ordered Cr2O3 nanorods and Cr2O3 nanoparticles on fluorination of 2-chloro-1,1,1-trifluoroethane

Morphological effects of ordered Cr2O3 nanorods and Cr2O3 nanoparticles on fluorination of 2-chloro-1,1,1-trifluoroethane

Study on the Preparation of Cr‐based Catalysts Doped by Zn using Sol–Gel Auto‐Combustion Method and Its Application for Synthesis of 1‐Chloro‐2,3,3,4,4,5,5‐heptafluorocyclopentene

Fluorocarbon Refrigerants and their Syntheses: Past to Present

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