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Experimental Study of Formaldehyde Decomposition Using a Plasma - Catalyst Hybrid Reactor as a Potential Voc Removal Technique

Nemati Tamar, Amin | 2021

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 54033 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Hamzeh Louyan, Tayyebeh; Khani, Mohammad Reza
  7. Abstract:
  8. Volatile organic compounds (VOCs) has harmful environmental and health effects and appropriate processes are needed to remove them from industrial and indoor environments. In this study, formaldehyde as one of the most toxic VOCs was investigated. Various methods have been developed to remove formaldehyde, however due to the to their low removal efficiencies, secondary pollution, and low energy efficiency, development of alternative methods will be beneficial. In recent years, the use of a combination of non-thermal plasma and catalyst technologies, called plasma-catalytic hybrid reactors, has provided significant results in the fields of chemical synthesis and removal of pollutants. In the present work, conversion of formaldehyde over a commercial Ni/α-Al2O3 catalyst is investigated using a plasma-catalytic reactor system with dielectric barrier (DBD) discharge structure. In order to investigate the effect of plasma treatment on the catalyst, fresh and plasma-treated Ni/α-Al2O3 catalyst samples were characterized by using X-ray powder diffraction (XRD), Brunauer–Emmett–Teller (BET), X-ray photo-electron spectroscopy (XPS), and field emission scanning electron microscopy (FESEM). The results of catalyst characterization showed that plasma pretreatment increases the surface concentration of active Ni2+ species on the catalyst surface and has no significant effect on the specific surface area of the catalyst.The effect of initial concentration, discharge power, GHSV and bed porosity on formaldehyde removal efficiency was systematically evaluated using response surface method (RSM). The RSM study was performed by using Design-Expert software and the interactions between these parameters were also investigated. RSM analysis was performed in the formaldehyde concentration range of 100 ppm-900 ppm, discharge power of 5 W- 15 W, GHSV range of 3441 h-1-8259 h-1 and porosity range of 50%-70%. In order to investigate the role of oxygen in the formaldehyde conversion process, the RSM study was carried out by using two different carrier gases, i.e. argon and oxygen. It was shown that the most sensitive parameter in formaldehyde conversion efficiency is the gas hourly space velocity (GHSV) representing a negative effect. Initial concentration also has a negative effect and discharge power has a positive effect on the conversion. The optimal catalyst bed porosity was found to be 61%. The presence of oxygen improved complete oxidation of formaldehyde resulting in higher conversion and higher CO2 selectivity.Another set of reactor tests were run under different reaction conditions to differentiate between the effect of plasma and catalyst on the reaction progress. A mechanistic study was performed and a mechanism was proposed for formaldehyde degradation over the Ni/α-Al2O3 catalyst in an IPC reactor system. It was found that CHO radicals produced in the plasma-catalytic system has an important role on the reaction progress through interaction of CHO radicals with the catalyst surface
  9. Keywords:
  10. Reaction Mechanism ; Response Surface Methodology ; Volatile Organic Compound (VOC) ; Dielectric Barrier Discharge (DBD) ; Plasma-Catalyst Hybrid Reactor ; Formaldehyde Conversion ; Industrial Wastes

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