Search Results (3)

1,1,1,2-tetrafluoroethane (HFC-134a) is a potent greenhouse gas that can be degraded to produce trifluoroacetic acid (TFA), a degradation product that has an impact on aquatic ecology, so its emission has been a continuous concern worldwide. Existing studies mainly estimate the global- or national-scale emissions of HFC-134a, and there are relatively few studies on regional emissions, all of which used the top-down method. By establishing a regional-scale bottom-up emission inventory and comparing it with the regional-scale top-down estimation results, regional emissions can be verified and their emission characteristics and environmental impacts can be analysed. HFC-134 emissions were estimated for the first time in the North China Plain using the emission factor method, and spatiotemporal characteristics and environmental impacts were analysed for the period of 1995 to 2020. The results showed that the cumulative HFC-134a emissions were 88 (73–103) kt (126 Mt CO₂-eq), which have led to an increase in global radiative forcing of 1.1 × 10⁻³ (0.9 × 10⁻³–1.3 × 10⁻³) W m⁻², an increase in global surface temperature of 8.9 × 10⁻⁴ °C, and a cumulative TFA production of 7.5 (6.2–8.9) kt as of 2020. The major sources of HFC-134a emissions are the refrigeration and air conditioning sector, which involves the automotive air conditioning (MAC), industrial and commercial refrigeration, and air conditioning (ICR) sub-sectors. China joined the Kigali Amendment in 2021 to phase down HFCs and proposed the goal of carbon neutrality by 2060. The North China Plain is a region undergoing rapid economic development, with a relatively high proportion of GDP (29%) and car ownership (23%) in 2020. Additionally, HFC-134a emissions accounted for about 20% of the total emissions in China. Therefore, HFC-134a emissions and their environmental impact on the North China Plain should not be ignored. Full article

HFC-134a, one of the representative hydrofluorocarbons (HFCs) used as a coolant gas, is a known greenhouse gas with high global warming potential. Catalytic decomposition is considered a promising technology for the removal of fluorinated hydrocarbons. However, systematic studies on the catalytic decomposition of HFC-134a are rare compared to those for other fluorinated hydrocarbon gases. In this study, Ga-Al₂O₃ and S/Ga-Al₂O₃ catalysts were prepared and the change in their properties post-acid treatment was investigated by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), temperature-programmed desorption of ammonia (NH₃-TPD), in situ Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy combined with energy-dispersive X-ray spectroscopy (SEM-EDS), and X-ray photoelectron spectroscopy (XPS). The S/Ga-Al₂O₃ catalyst achieved a much higher HFC-134a conversion than Ga-Al₂O₃, which was ascribed to the promotional effect of the sulfuric acid treatment on the Lewis acidity of the catalyst surface, as confirmed by NH₃-TPD. Furthermore, the effect of hydrogen fluoride (HF) gas produced by HFC-134a decomposition on the catalyst was investigated. The S/Ga-Al₂O₃ maintained a more stable and higher HFC-134a conversion than Ga-Al₂O₃. Combining the results of the stability test and characterization, it was established that the sulfuric acid treatment not only increased the acidity of the catalyst but also preserved the partially reduced Ga species. Full article

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. Full article