Dissertation > Excellent graduate degree dissertation topics show

Characterization and Performance of Cr-based Catalysts for the Synthesis of CFCs Alternatives

Author: QianLin
Tutor: LuoMengFei
School: Zhejiang Normal University
Course: Physical and chemical
Keywords: Cl / F exchange reaction Gas Phase Fluorination Cr -based catalysts Tetrafluoromethane 1,1,1,2 - tetrafluoroethane
CLC: O643.36
Type: Master's thesis
Year: 2009
Downloads: 84
Quote: 0
Read: Download Dissertation

Abstract


The Montreal Protocol and its supplementary documents are limiting the use of ozone-depleting substances (ODS), chlorofluorocarbons (CFCs). Therefore, the CFCs into use or development of CFCs alternatives Fluorine Chemistry is a very important issue. The CCl 2 F 2 (CFC-12) has been widely used as a refrigerant and propellant, is the culprit that Deplete the Ozone Layer, and how the CCl 2 F 2 converted to high value-added tetrafluoromethane (CF 4 ) is one of the objectives of this study. In this thesis through the CCl 2 F 2 gas phase fluorination reaction synthesis the the CF 4 As the intermediate CClF 3 have embarked on CClF 3 gas fluorination reaction as raw material for the control experiment. In this thesis, using CrO X -Y 2 O 3 catalyst to achieve a the the CCl 2 F 2 the Pyrolysis CF 4 . In addition, the deposition prepared by precipitation the the CrO X -Al 2 O 3 catalyst for the gas phase fluorinated CClF 3 the synthesis the CF 4 . 1,1,1,2 - tetrafluoroethane (HFC-134a) is an ideal chlorofluorocarbons (CFCs) alternatives. In this thesis the precipitation the legal system prepare CrO X -Y 2 O 3 catalyst for gas fluorinated 1,1,1 - trifluoro - 2 - chloroethane (HCFC-133a) synthesis of HFC-134a. BET, XRD, Raman, UV-Vis and EPR technologies such as the structure and the surface of the catalyst phase CrO X to characterize the effects of the gas phase the the Y precursor In auxiliaries Cr-based catalyst fluoride synthesis of HCFC-133a, HFC-134a catalytic performance. 1. Prepared by deposition precipitation series calcined at different temperatures -Y the CrO X 2 O 3 catalyst, and for gas fluoride CCl 2 F 2 and CClF 3 synthesis of the CF 4 . Calcination temperature on the surface of the catalyst CrO X and using different reaction raw materials (CCl 2 F 2 , CClF 3 < / sub>) investigated CF 4 generate yield difference same CrYF catalyst. The study showed that CrYF-6 the highest activity of the catalyst, and catalytic activity CrYF-4 CrYF-6 somewhat less. The the high activity CrYO catalyst surface YCrO 4 and the CrO 3 species, because YCrO 4 CrO 3 species susceptible to the activation of the catalyst active species is formed. CrO X , CrYO-8 catalyst surface species is difficult to be the activation of YCrO 3 , and thus lower the catalytic activity. The study found that by the CCl 2 F 2 vapor phase catalytic the fluoride preparation of CF 4 , the first step reaction easily, while the second step reaction is the rate-determining step. 2. Prepared a series of different temperature roasting the CrO X -Al 2 O 3 catalyst for the gas phase fluorinated CClF 3 the synthesis the CF 4 . The best activity of the catalyst calcined at 600 ℃ under CrAlF-6 catalyst vapor phase fluorination CClF 3 synthesis of the CF 4 generate yield approximately 92% of the 400 ° C reaction temperature. The effects of the calcination temperature on the CrO X -Al 2 O 3 catalyst composition and structure. XRD, Raman and UV-Vis analysis results show that with increasing calcination temperature, the surface of the catalyst crystalline phase Cr 2 O 3 content increases. Crystalline phase Cr 2 O 3 is difficult to be activated and the formation of reactive species, thus the catalyst activity CrAlO catalyst surface Cr 2 O 3 of the content. CrAlF-6 the highest activity of the catalyst due to its the surface relative minimum Cr 2 O 3 content. The study found that carrier Al 2 O 3 3 fluoride generate AlF , and the formation of small grains AlF 3 vector conducive to obtain a higher catalytic activity. The main reason of deactivation of the catalyst may be related the catalyst surface Cr 2 O 3 content increased and the grain increases relevant. Prepared by precipitation method, a series of the CrO X-Y 2 O 3 catalyst for vapor-phase fluorination of 1,1,1 - trifluoro-2 - chloroethane (HCFC-133a) Synthesis of 1,1,1,2 - tetrafluoroethane (HFC-134a), investigated Y precursors on the catalyst surface CrO X impact. Catalysts were used Y (OH) 3 YCl 3 and Y (NO , 3 ) 3 precursor, and The turn marked CrYO-H, CrYO-Cl, and CrYO-N. The study found the highest activity CrYF-H, which is attributed to the catalyst surface CrYO-H has the highest content of Cr of 6 . High valence Cr 6 species by fluoride after easily into active species such as CrO X F Y or Cr (OH) X < / sub> F Y and other. Studies have shown that the the CrO X -Y 2 O 3 catalyst pretreatment and reaction process the some high the CrO X can be converted to CrF 3 . Catalyst CrF 3 content increased, resulting in converted to the content of the active species is relatively reduced, so the catalytic activity decreased. 4. Prepared a series of additives In the CrO X-Y 2 O 3 catalyst for vapor-phase fluorination 1,1,1 - trifluoro-2 - chloroethane> (HCFC-133a) Synthesis of 1,1,1,2 - tetrafluoroethane (HFC-134a). The study found that the increase of catalyst activity with the aid of Zn improve. Such as in the 340 ° C reaction temperature, the conversion rate of the HCFC-133a, catalyst CrYF reach 22% and close to 28% 10% In-CrYF catalyst, however, the conversion ratio of HCFC-133a. Investigated In content of the CrO X -Y 2 O 3 catalyst composition and structure affect. XRD, Raman, UV-Vis and EPR analysis results show that with increasing content of In doping, would be beneficial the CrO X-Y 2 O < / sub> catalyst surface Cr species to high valence (Cr 6 and Cr 5 ) highly dispersed formation exist. The study showed that the catalyst activity and the higher valence state of the surface of the Cr species, this is because the higher valence state Cr species of activated, after the reaction, and easy to change as a catalytic center. The studies suggest that the catalyst in the In-CrYFU InF 3 can effectively inhibit the coking of the catalyst surface.

Related Dissertations

  1. Study on Cr-based Catalysts for Vapor-phase Fluorination to Synthesis CF4 and Preparation of β-AlF3 with High Surface Area,O643.32
  2. Theoretical Study on the Mechanism and Kinetics of HFCs Degradation Reactions in Atmosphere,O643.1
  3. Studies on Extraction of Artemisinin by Tetrafluoroethane,TQ914
  4. CoMo/TiO_2-Al_2O_3HDS catalyst modification of Freon gas,O643.3
  5. The Research of Die Casting Magnesium Alloy,TG249.2
  6. Gas-Phase Synthesis of HFC-134a and HFC-125,TQ222
  7. Synthesis and Study of 2,3,5,6-tetrafluorobenzyl Alcohol,O625
  8. Preparation and Photocatalytic Properties for Water Decomposition of Titanate Photocatalyst,O643.36
  9. Multi-walled Carbon Nanotubes Au _AT_ of Pt, Au _AT_ of Pd core-shell structure of the catalyst preparation and electrochemical properties of,O643.36
  10. First- principles calculations of doped anatase titanium dioxide photocatalytic properties,O643.36
  11. The Study of Anode Catalyst Pd/C for Direct Formic Acid Fuel Cell,O643.36
  12. Pd-based cathode catalysts of direct methanol fuel cell,O643.36
  13. Study on Durability and Poisoning Resistant Performance of Pt/C and Pt/OMC Catalysts,O643.36
  14. Controllable Synthesis of Carbon Nanotubes Supported Metall Nanocatalysts and the Study on Their Electrocatalysis,O643.36
  15. Preparation and Photocatalytic Properties of Semiconductor Oxides,O643.36
  16. The Study of TWC Catalytic Removal NOx from Waste Incineration Flue Gas,O643.36
  17. Nano LaFeO 3 Controllable Synthesis and TiO 2 bridged construct composite photocatalyst,O643.36
  18. MCM-41 as aryl oxime palladium catalyst and catalytic Suzuki coupling reaction of aryl,O643.36
  19. Research of Ni-Based Catalysts for Hydrogen Generation from NaBH4 Hydrolysis,O643.36
  20. Doped Modification and Application of Titania Photocatalyst,O643.36
  21. Study on the Preparation and Photocatalytic Activity of Titanium Dioxide Nanoparticles,O643.36

CLC: > Mathematical sciences and chemical > Chemistry > Physical Chemistry ( theoretical chemistry ),chemical physics > Chemical kinetics,catalysis > Catalytic > Catalyst
© 2012 www.DissertationTopic.Net  Mobile