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Porous materials are widely used in industry for applications that include chemical separations and gas scrubbing. These materials are typically porous solids, although the liquid state can be easier to manipulate in industrial settings. The idea of combining the size and shape selectivity of porous domains with the fluidity of liquids is a promising one and porous liquids composed of functionalized organic cages have recently attracted attention. Here we describe an ionic-liquid, porous, tetrahedral coordination cage. Complementing the gas binding observed in other porous liquids, this material also encapsulates non-gaseous guests—shape and size selectivity was observed for a series of isomeric alcohols. Three gaseous chlorofluorocarbon guests, trichlorofluoromethane, dichlorodifluoromethane and chlorotrifluoromethane, were also shown to be taken up by the liquid coordination cage with an affinity that increased with their size. We hope that these findings will lead to the synthesis of other porous liquids whose guest-uptake properties may be tailored to fulfil specific functions.Porous liquids promise to combine the advantages of the porosity of solids with those of the fluidity of liquids. Now, a permanently porous ionic-liquid coordination cage has been assembled that encapsulates isomers of butanol and propanol with some size and shape selectivity, as well as three gaseous chlorofluorocarbons with a size-dependent affinity.

Dichlorodifluoromethane (CFC-12) is one of the typical compounds currently studied in the problem of Freon, which is responsible for the destruction of the ozone layer and abnormal climate change. Al2O3/ZrO2 solid catalyst was prepared, and the effects of the molar ratio of Al2O3 and ZrO2, calcination temperature, calcination time, and catalyst dosage of the catalyst on the decomposition rate of CFC-12 were studied. The results showed that the best conditions for the preparation of catalyst were as follows: molar ratio of Al2O3 to ZrO2 was 1, calcination temperature was 800 ℃, calcination time was 2 h, and the amount of catalyst was 1 g. The hydrolysis rate of CFC-12 composite material could reach 98.75%. The characteristics of the catalysts were characterized by XRD, XPS, SEM, EDS, BET, CO2-TPD and NH3-TPD.

Emissions of ozone-depleting substances, including trichlorofluoromethane (CFC-11), have decreased since the mid-1980s in response to the Montreal Protocol 1 , 2 . In recent years, an unexpected increase in CFC-11 emissions beginning in 2013 has been reported, with much of the global rise attributed to emissions from eastern China 3 , 4 . Here we use high-frequency atmospheric mole fraction observations from Gosan, South Korea and Hateruma, Japan, together with atmospheric chemical transport-model simulations, to investigate regional CFC-11 emissions from eastern China. We find that CFC-11 emissions returned to pre-2013 levels in 2019 (5.0 ± 1.0 gigagrams per year in 2019, compared to 7.2 ± 1.5 gigagrams per year for 2008–2012, ±1 standard deviation), decreasing by 10 ± 3 gigagrams per year since 2014–2017. Furthermore, we find that in this region, carbon tetrachloride (CCl 4 ) and dichlorodifluoromethane (CFC-12) emissions—potentially associated with CFC-11 production—were higher than expected after 2013 and then declined one to two years before the CFC-11 emissions reduction. This suggests that CFC-11 production occurred in eastern China after the mandated global phase-out, and that there was a subsequent decline in production during 2017–2018. We estimate that the amount of the CFC-11 bank (the amount of CFC-11 produced, but not yet emitted) in eastern China is up to 112 gigagrams larger in 2019 compared to pre-2013 levels, probably as a result of recent production. Nevertheless, it seems that any substantial delay in ozone-layer recovery has been avoided, perhaps owing to timely reporting 3 , 4 and subsequent action by industry and government in China 5 , 6 . Atmospheric data and chemical-transport modelling show that CFC-11 emissions from eastern China have again decreased, after increasing in 2013–2017, and a delay in ozone-layer recovery has probably been avoided.

Production and consumption of CFC-11 (trichlorofluoromethane, CCl3F), CFC-12 (dichlorodifluoromethane, CCl2F2) and CCl4 (carbon tetrachloride) are controlled under the regulations of the Montreal Protocol and have been phased out globally since 2010. Only CCl4 is still widely produced as a chemical feedstock. After 2010, emissions of CFC-11 and CFC-12 should therefore mostly originate from existing banks (e.g. from foams, mobile air conditioning units and refrigerators); however evidence has emerged of an increase in global emissions of CFC-11 in the last decade, some of which has not been fully accounted for. The motivation for this work was to assess the emissions of CFC-11, CFC-12 and CCl4 from western Europe. All countries in this region have been subject to the controls of the Montreal Protocol since the late 1980s and, as non-Article 5 Parties, have been prohibited from producing CFCs and CCl4 for dispersive use since 1996. Four different inverse modelling systems are used to estimate emissions of these gases from 2008 to 2021 using data from four atmospheric measurement stations: Mace Head (Ireland), Jungfraujoch (Switzerland), Monte Cimone (Italy) and Tacolneston (UK). The average of the four model studies found that western European emissions of CFC-11, CFC-12 and CCl4 between 2008 and 2021 were declining at 3.5 % yr-1 (2.7 % yr-1–4.8 % yr-1), 7.7 % yr-1 (6.3 % yr-1–8.0 % yr-1) and 4.4 % yr-1 (2.6 % yr-1–6.4 % yr-1), respectively. Even though the emissions were declining throughout the period, the area including northern France, Belgium, the Netherlands and Luxembourg showed consistently elevated emissions of CFC-11 compared with the surrounding regions. Emissions of CFC-12 were slightly elevated in the same region. CCl4 emissions were the highest in the south of France. France had the highest emissions of all three gases over the period 2008–2021. Emissions from western Europe (2008–2021) were on average 2.4 ± 0.4 Gg (CFC-11), 1.3 ± 0.3 Gg (CFC-12) and 0.9 ± 0.2 Gg (CCl4). Our estimated decline in emissions of CFC-11 is consistent with a western European bank release rate of 3.4 % (2.6 %–4.5 %). This study concludes that emissions of CFC-11, CFC-12 and CCl4 have all declined from 2008 to 2021 in western Europe. Therefore, no evidence is found that western European emissions contributed to the unexplained part of the global increase in atmospheric concentrations of CFC-11 observed in the last decade.

Dichlorodifluoromethane (CFC‐12) is an ozone‐depleting substance and potent greenhouse gas, which was required to be phased out after 2010 under the Montreal Protocol. CFC‐12 emissions need to be quantitatively traced. However, estimates of CFC‐12 emissions in China based on atmospheric inversions are unavailable after 2010. Here, using atmospheric observations at nine sites across China and inversion techniques, we quantify CFC‐12 emissions in China during 2011–2020 (on average 11.0 ± 0.6 Gg yr−1). The emissions derived from observations are 8.5 times larger than the previously reported inventories. Apart from emissions from eastern China revealed in previous studies, this study reveals that 71% of national total emissions were from other parts of China. Moreover, this study reconciled the global CFC‐12 emissions during 2011–2020: 28% were traced to China by this study, 9% of emissions were traced in previous studies, while 63% remain untraced, indicating the need for more regional emission inversion studies. Plain Language Summary Chlorofluorocarbons (CFCs), well known as Freon, are damaging to the stratospheric ozone layer and are potent greenhouse gases. Dichlorodifluoromethane (CFC‐12; CCl2F2) is one of the major CFCs. The production and consumption of CFC‐12 are controlled under the regulations of the Montreal Protocol and have been phased out globally since 2010. As the largest developing country and once a major producer and consumer of CFC‐12, CFC‐12 emissions in China are of great interest. In this study, we quantified emissions of CFC‐12 in China during 2011–2020 based on atmospheric observations in a network of nine sites across China. We find that the emissions derived from atmospheric inversion are 8.5 times larger than the previous emission inventories estimated using production and consumption information, suggesting unaccounted‐for emissions occurring in China. Apart from emissions from eastern China revealed in previous studies, this study reveals that 71% of national total emissions were from other parts of China. The Chinese emissions of CFC‐12 accounted for 28% of global totals from 2011 to 2020. However, there is a big gap between the total CFC‐12 emission from China, western Europe, Australia, the United States, India, and global totals, suggesting that more regional atmospheric inversion estimates are encouraged. Key Points China's Dichlorodifluoromethane (CFC‐12) emissions during 2011–2020 were quantified using atmospheric observations at nine sites across China and inverse modeling A quantitative depiction of spatial CFC‐12 emissions across China was provided by this study 28% of global CFC‐12 emissions for 2011–2020 occurred in China, according to this study

The stratospheric circulation is an important element in the climate system, but observational constraints are prone to significant uncertainties due to the low circulation velocities and uncertainties in available trace gas measurements. Here, we propose a method to calculate mean age of air as a measure of the circulation from observations of multiple trace gas species which are reliably measurable by satellite instruments, like trichlorofluoromethane (CFC-11), dichlorodifluoromethane (CFC-12), chlorodifluoromethane (HCFC-22), methane (CH4), nitrous oxide (N2O), and sulfur hexafluoride (SF6), and we show that this method works well in most of the lower stratosphere up to a height of about 25 km. The method is based on the compact correlations of these gases with mean age. Methodological uncertainties include effects of atmospheric variability, non-compactness of the correlation, and measurement related effects inherent for satellite instruments. The multi-species age calculation method is evaluated in a model environment and compared against the actual model age from an idealized clock tracer. We show that combination of the six chosen species reduces the resulting uncertainty of derived mean age to below 0.3 years throughout most regions in the lower stratosphere. Even small-scale, seasonal features in the global age distribution can be reliably diagnosed. The new correlation method is further applied to trace gas measurements with the balloon-borne Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA-B) instrument. The corresponding deduced mean age profiles agree reliably with SF6-based mean age below about 22 km and show significantly lower uncertainty ranges. Comparison between observation-based and model-simulated mean ages indicates a slow-biased circulation in the ERA5 reanalysis. Overall, the proposed mean age calculation method shows promise to substantially reduce the uncertainty in mean age estimates from satellite trace gas observations.

MgO/ZrO 2 solid base catalyst was prepared by co-precipitation method. The effects of hydrolysis temperature, water vapor concentration, total flow rate and calcination temperature of the catalyst on the decomposition rate of dichlorodifluoromethane (CFC-12) were studied. The results showed that the decomposition rate of CFC-12 could reach 98.90% by using MgO/ZrO 2 solid base as the catalyst at a hydrolysis temperature of 400 °C, a water vapor concentration of 25%, a total flow rate of 5 mL/min and a calcination temperature of 700 °C. The XRD characterization of the catalyst under different calcination temperature showed that the MgO/ZrO 2 catalyst was a solid solution. The products were tested by ion chromatography, SEM and EDS and finding that the decomposition products were main HCl, HF and CO 2 . Graphical Abstract

A human health risk assessment was performed to evaluate if a biofilter for the biological methane oxidation reduces the risk from exposure to landfill gas emissions and improves the air quality mitigating odour emissions from an aftercare landfill. Accordingly, three different scenarios of landfill gas management were defined, 9 volatile organic compounds (VOCs) (cyclohexane, n-hexane, 2-methylpentane, 3-methylpentane, benzene, xylenes, toluene, dichlorodifluoromethane, vinyl chloride) were identified and using the CALPUFF dispersion model; the pollutant concentration at eleven sensitive receptors was determined. Consequently, the risk (for cancer and non-cancer compounds) was assessed applying the methodology proposed by USEPA 2009. From one hand, to determine concentration and emission rates of VOCs and hydrogen sulphide, a sample of raw landfill gas and three air samples from the biofilter surface were collected with dynamic flux chamber method and analysed in accordance with US EPA, 1986 and USEPA TO-15, 1999. To the other hand, odour emissions were assessed based both on chemical and dynamic olfactometric measurements (EN 13725:2003). The field surveys results showed a reduction of the cancer risk on average by 79% and of the hazard quotient on average by 92%. In contrast, the results of olfactometry measurements showed a lower efficiency on odour reduction than the target value of 70%. Nonetheless, the odour concentration was always far below 300 uo E  m −3 at the biofilter surface and odour concentration never exceed 1 uo E  m −3 at the sensitive receptors.

This paper presents a numerical model describing the propagation of a step-type pressure wave of small amplitude in a bubbly medium containing the Freon-12 gas under hydrate formation conditions. The dynamics of waves in channels of constant and variable cross section is considered. The influence of surfactants on the tendency of bubble fragmentation is analyzed according to the Kelvin−Helmholtz instability mechanism.

In this work, on the basis of the equations of a bubbly liquid, a numerical simulation of the process of propagation of pressure waves of moderate amplitude, accompanied by the synthesis of gas hydrate in water with gas bubbles Freon-12, was carried out. The dynamics of plane-one-dimensional shock waves with a stepped profile, the volumetric gas content of the gas in the gas-liquid medium, and the average density of the gas hydrate are shown. The situation is considered when in the initial state of the bubble mixture hydrate formation does not occur, but when exposed to a shock wave, due to an increase in pressure in the bubbles and their fragmentation, favorable conditions for hydrate formation are created at the interface. Also, the use of gas hydrate synthesis technologies creates prerequisites for solving the problem of the greenhouse effect on the planet, and hence the climate. One of the solutions may be an increase in the interphase surface upon contact between water and hydrate-forming gas. Some theoretical calculations based on the model of gas hydration behind the pressure wave are presented.