Abstract
This paper reports the improved efficiency of 1,1,1,2-tetrafluoroethane (HFC-134a) decomposition by combined use of MgO with γ-Al2O3. While a high temperature (>900 °C) was required to achieve 90% conversion during non-catalytic pyrolysis of HFC-134a, 100% conversion of HFC-134a was achieved at 600 °C by the use of γ-Al2O3. Among the three catalysts (γ-Al2O3, MgO, and CaO) tested in this study, γ-Al2O3 showed the highest HFC-134a decomposition efficiency, followed by MgO and CaO, due to its large surface area and large amount of weak acid sites. Also with the longest lifetime among the catalysts, durability in maintaining complete decomposition of HFC-134a was shown in γ-Al2O3. The addition of MgO to γ-Al2O3 was effective in extending the lifetime of γ-Al2O3 due to the efficient interaction between HF and MgO, which can delay the deactivation of γ-Al2O3. Compared to the double bed γ-Al2O3-MgO configuration, the use of a mixed γ-Al2O3-MgO bed extended the catalyst lifetime more effectively.
Highlights
The anthropogenic impact on climate change has drawn global attention to the reduction of greenhouse gases (GHG)
Owing to the thermal stability of HFC-134a [7], the thermal decomposition of HFC-134a was initiated at temperatures higher than 600 ◦ C
The conversion efficiencies of HFC-134a over all catalysts were increased by elevating the reaction temperature from 300 to 600 ◦ C
Summary
The anthropogenic impact on climate change has drawn global attention to the reduction of greenhouse gases (GHG). Based on the identified deactivation mechanism, we attempted to improve the lifetime of the γ-Al2 O3 catalyst by the addition of MgO in the catalyst bed for the decomposition of HFC-134a This process is much more convenient, simple, and economically viable due to the low cost of MgO compared to that of γ-Al2 O3. This application is beneficial in that the HF generated as a result of the dehydrofluorination reaction of HFC-134a can be neutralized by alkali metal oxides, impeding gas-solid reaction between HF and the γ-Al2 O3 catalyst. This will prevent rapid deactivation of the main catalyst and, subsequently, extend the catalytic activity
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