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Metallization of methane (CH₄) has always been an interesting issue. Here, we report a study on the structure, metallization and superconductivity in K-doped CH₄ under pressure, based on the particle swarm optimization, density functional theory, and density functional perturbation theory. Summarizing the thermodynamical and dynamical stabilities, the electronic band structures, and the electron–phonon interaction calculations, we predicted that K-doped CH₄ in $P{2}_1∕m$ space-group is a metal and a possible superconductor in the pressure range of $70-90$ GPa. The superconducting critical temperature is about 12.7 K at 80 GPa. It was found that the charge transfer from K to CH₄ drives the metallization and mainly contributes to the electron–phonon interaction. The result confirms that CH₄ can become a metal and superconductor under the electron doping and the relative low pressure.

To explore the high-temperature superconductor at low pressures, we have investigated the crystal structures, electronic properties, and possible superconductivity in the case of methane (CH₄) doped by lithium in the pressure range of $0-100$GPa, based on the first-principles calculations. The results show that Li-intercalated CH₄ (Li_x(CH₄)${}_{1-x}$) can realize metallization and superconductivity at low pressures, even 5GPa. We find that there is a charge transfer between Li and CH₄, but the metallization is driven by the change of crystal field induce by doping instead of charge transfer. The critical temperture is predicted from 3.8K at 5GPa for LiCH₄ to 12.1K at 100GPa for Li(CH₄)₄. The low-pressure superconductivity of Li_x(CH₄)${}_{1-x}$ can be further optimized by adjusting component and pressure.

Standard enthalpies of formation (ΔH_f) were calculated with models developed using the computer program SPARC. SPARC uses computational algorithms based on chemical structure theory to calculate the ΔH_f. Molecular structures are broken into simple functional units (reactophores) with intrinsic properties. Each reactophore is analyzed and the effects of appended molecular structures are quantified through perturbation theory. The ΔH_f models have been developed using all known data for saturated and unsaturated hydrocarbons. The structures of these compounds vary from chains to conjugated rings to poly-benzoic aromatic hydrocarbons. The SPARC calculated RMS deviation of these 587 compounds is 4.50 kJ mol^-1.

Three endohedral fullerenes C₂H₂–C₆₀, C₂H₄–C₆₀, and C₂H₆–C₆₀ are investigated theoretically using density functional theory. Their electronic and structural properties are studied. The calculations suggest that the formations of these complexes are endothermic; the dopant and C₆₀ cage affect each other rarely except for the slight distortion of C₆₀ cage and compression of the hydrocarbon molecules. A small quantity of electron transfer from C₆₀ to the hydrocarbon molecule was also observed. Accordingly, C₆₀ could theoretically be a good container for some small hydrocarbon molecules.

The aerobic oxidative cleavage of styrene C=C double bonds catalyzed by simple manganese porphyrin is reported. Under the catalysis of chloro(tetraphenylporphinato)manganese, the oxidative cleavage of the carbon-carbon double bond of the styrene with air yields benzaldehyde. Our results show that the oxidative cleavage and the epoxidation of the styrene double bond are the competition reactions in the styrene-manganese porphyrin-air system. The reaction temperature decided the product distribution. Under the conditions of 0.4 MPa air and 30 ppm of chloro(tetraphenylporphinato)manganese, the styrene conversion was 20.0% and the selectivity of benzaldehyde and styrene oxide was 81.7% and 12.7% respectively when the reaction temperature was 110°C. Styrene conversion was 92.5% and the selectivity of benzaldehyde and styrene oxide was 48.1% and 41.2% respectively when the reaction temperature was 120°C.

We report a collection of lowest-energy structures of hydrocarbon molecules C_nH_m (n = 6-18, m = 0 - 2n + 2) within the wide hydrogen chemical potential range. The genetic algorithm combined with Brenner's empirical potential is applied for the search. The resultant low-energy structures are further examined by ab initio quantum chemical calculations. The lowest-energy molecules with several additional low-energy structures are classified to four groups according to their structural motifs and the phase diagram with respect to carbon atom number and hydrogen chemical potential is presented. The results provide useful information for identifying the hydrocarbon molecules in the interstellar medium as well as addressing the hydrocarbon-related nanofragment growth in experiments.

Electrical energy consumption in air conditioning systems reaches 60% to 70% of the total electric energy consumption in buildings. Therefore, saving electrical energy consumption in air conditioning systems would have a significant impact on the national electrical energy consumption. Currently, the air conditioning sectors were having a dilemma on finding the alternative substitutes for CFC and HCFC refrigerants which are proven to cause destruction of the ozone layer and contribute to the effects of global warming. This paper will discuss the problems faced by an Article 5 country similar to Indonesia in phasing-out HCFC especially in air conditioning and refrigeration sectors. This paper will also discuss the possibility to use hydrocarbon-based refrigerants, which have zero ozone depletion potential (ODP) and low global warming potential (GWP), in air conditioning sectors. Some results of field applications of this refrigerant will be reported, and in general it can be concluded that the air conditioning retrofitted with hydrocarbon refrigerant consumes 10%–20% less electrical energy. Mixture of R-290 and R-134a was also investigated. R-134a is used to reduce the flammability of R-290 and to make the saturation pressure close to R-22. The results show that at composition of 0.6 R-290/0.4 R-134a mole fractions, the mixture behave as an azeotrope refrigerant mixture and can be used for R-22 replacement. At this composition, lower flammability limit (LEL) is 3693%, which is higher than pure R-290. Hence, the refrigerant mixture can be classified as less flammable A2 class refrigerant. The performance test shows that the refrigerant mixture can be used as a drop-in refrigerant in the R-22 machine. The measurement of refrigeration capacity and compressor input work at the same chilled water temperature shows that the calculated COP of the refrigerant mixture is better than R-22's but lower than R-290's.

The existing artificial and chemical refrigerants have been phased out due to environmental concerns, and they have been replaced with environmentally friendly refrigerants. Among them, carbon dioxide, ammonia, and hydrocarbons are paid attention as next generation refrigerants, and their application has been widely expanded. Therefore, in this paper, the latest studies of flow boiling and condensation heat transfer characteristics of carbon dioxide, ammonia, and hydrocarbon are reviewed. The heat transfer characteristics of ammonia and hydrocarbon show the relatively similar trends with the conventional refrigerants compared to those of carbon dioxide. The general trends and recommendable models of flow boiling and condensation heat transfer with carbon dioxide, ammonia, and hydrocarbons are summarized.

In this paper, the window air conditioner performance with commercial LPG as a replacement of HFC134a is assessed with modified capillary lengths for charge optimization. Global Warming Potential (GWP) of commercial LPG is only three, which is neglected compared to HFC134a (1300). Flammability issues will also be reduced in charge optimization and adopting safety standards. Initially, baseline tests are conducted with HFC134a and commercial LPG in the existing system, and optimum refrigerant charge is determined. The simulation study is conducted with modified capillary lengths for charge reduction of commercial LPG. Experimental assessment is conducted for the charge optimization as per IS 1349 (Part 1) for low ambient test conditions (Domestic Test-DT and Export Test A-ETA) and high ambient test conditions (Export Test B-ETB). With the optimized capillary length and optimum charge quantity, 0.4–2.03% higher cooling capacity, 0.62–8.9% lesser power consumption, and 10.49–16.4% higher COP are achieved with commercial LPG than that of HFC134a baseline at low and high ambient test conditions, respectively.