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( Caroline Mercy Andrew Swamidoss ),( Mahshab Sheraz ),( Ali Anusa ),( Sangjae Jeong ),( Young-min Kim ),( Seungdo Kima ) 한국폐기물자원순환학회(구 한국폐기물학회) 2019 ISSE 초록집 Vol.2019 No.-
This paper explored the effect of different calcination temperatures on the catalytic performance of HFC-134a conversion over Al<sub>2</sub>O<sub>3</sub>. The catalyst (Al<sub>2</sub>O<sub>3</sub>) used here was prepared by calcinating it at different temperatures, i.e. 500℃, 650℃, 700℃ and 800℃. These calcined catalysts were placed in a plug flow reactor-GC/MS system and their efficiency in decomposing HFC- 134a was investigated. It was found that Al<sub>2</sub>O<sub>3</sub>-650 (calcined at 650℃) exhibited the best decomposition rate with more than 99% decomposition lasting for 7 hours. It was followed by Al<sub>2</sub>O<sub>3</sub>-800, Al<sub>2</sub>O<sub>3</sub>-700 and the least decomposition potential by Al<sub>2</sub>O<sub>3</sub>-500. A valuable by-product trifluoroethylene (TrFE) was obtained at the expense of the HFC-134a decomposition and the yield of TrFE over a period of 18 hours was the greatest over Al<sub>2</sub>O<sub>3</sub>-650 and the least over Al<sub>2</sub>O<sub>3</sub>-500. Al<sub>2</sub>O<sub>3</sub>-800 and Al<sub>2</sub>O<sub>3</sub>-700 closely followed but the yield of TrFE started drastically declining after 8 hours. The yield of CO<sub>2</sub> was also relatively lesser over Al<sub>2</sub>O<sub>3</sub>-650 than the other calcination temperatures. It was concluded that calcinating Al<sub>2</sub>O<sub>3</sub> at 650℃ extended the lifetime of the catalyst due to greater surface area, greater number of weak acidic sites and lesser number of strong acidic sites.
( Mahshab Sheraz ),( Sangjae Jeong ),( Ali Anus ),( Caroline Mercy Andrew Swamidoss ),( Seungdo Kim ) 한국폐기물자원순환학회(구 한국폐기물학회) 2019 한국폐기물자원순환학회 심포지움 Vol.2019 No.1
The catalytic decomposition of HFC-134a was carried out with Alumina and different (wt %) of Magnesium doped alumina at 600°C reaction temperature. The catalyst were calcined at 650°C and their thermal degrading behaviour were determined by using Thermogravimetric analysis for determining the weight loss of Spent-catalysts. For decomposition test of HFC-134a used plug flow reactor connected directly to gas chromatography/mass spectrometry system. Although 99% Conversion rate was achieved and stability was more than 6 hours and less coke formation by using Mg(5)Al<sub>2</sub>O<sub>3</sub>. By the addition of Mg metal in γ-Al<sub>2</sub>O<sub>3</sub> showed crucial role but could not prevented from fluorination. However high amount of metal content can blocked the pores of catalyst and reaction was decreased rapidly. There was also the formation of valuable by-product trifluoroethylene eco-friendly gas as a result of decomposition of high GWP gas HFC-134a. The catalytic activity order of different (wt %) Mg based alumina catalyst is Mg(5)Al<sub>2</sub>O<sub>3</sub> > γ-Al<sub>2</sub>O<sub>3</sub> > Mg(20)Al<sub>2</sub>O<sub>3</sub> > Mg(30)Al<sub>2</sub>O<sub>3</sub> > Mg(70)Al<sub>2</sub>O<sub>3</sub>, respectively.
( Ali Anus ),( Sangjae Jeong ),( Mahshab Sheraz ),( Caroline Mercy Andrew Swamidoss ),( Seungdo Kim ) 한국폐기물자원순환학회(구 한국폐기물학회) 2019 한국폐기물자원순환학회 심포지움 Vol.2019 No.1
The study emphasized on the catalytic decomposition of 1,1,1,2-tetrafluoroethane by pyrolysis, hydrolysis, and oxidative pyrolysis. γ-Al2O3 which is proved to be a striking catalyst for HFC decomposition was calcined at 650°C for 2 hours and used as catalyst whereas NH3-TPD, BET analysis and XRD used for its characterization. All the experiments were conducted using a fixed bed reactor at 600°C, which is considered to be an optimal temperature for maximum conversion according to the literature. Trifluoroethylene was detected as the prime by-product with GC/MS, and about 99% of HFC-134a was decomposed by practicing the catalytic pyrolysis condition, for up to 6.8 hours. Catalyst stability was amplified when the water is introduced in the system, and it was further enhanced as water increased because of the formation of surface hydroxyl groups, which shield the alumina surface ultimately delaying catalyst deactivation. Higher catalyst life was also perceived in aerobic condition, but CO<sub>2</sub> found to be the dominant by-product for this experiment instead of trifluoroethylene. By taking these findings under consideration, the behavior of catalyst in different reaction environment is discussed and elaborated with the help of previously mentioned characterizing techniques.
Ali Anus,Mahshab Sheraz,정상재,Caroline Mercy Andrew Swamidoss,김영민,Muhammad Awais Aslam,김의건,김승도 한국화학공학회 2021 Korean Journal of Chemical Engineering Vol.38 No.6
During catalytic pyrolysis of HFC-134a over γ-alumina, the formation of HF and coke causes catalyst deactivation. Catalyst deactivation and product selectivity depend on the contact time during catalytic pyrolysis of HFC- 134a as reported in this paper. γ-Alumina calcined at 650 oC was used as the catalyst due to its higher quantity of acidic sites and larger surface area, which are crucial for catalytic pyrolysis. X-ray diffraction (XRD), scanning electron microscope- energy dispersive X-ray spectroscopy (SEM-EDS), and thermogravimetric analysis (TGA) of the catalysts were performed to determine the influence of contact time and flow rate of HFC-134a. 2mL/min of HFC-134a balanced with nitrogen to 25, 50, 100, and 200mL/min total flow rates was studied at 600 oC. 200mL/min showed a 9.4 h catalyst lifetime with a small number of by-products. Shorter contact time between HFC-134a and HF with the catalyst was found to be the key to the longer lifetime of the catalyst. The catalyst lifetime was decreased with an increase in the HFC-134a input amount. Among 2, 4, and 6mL/min input of HFC-134a, 2mL/min showed the longest catalytic activity followed by 4 and 6mL/min, respectively. Conversion of γ-alumina into AlF3 and deposition of coke were responsible for the deactivation.