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A proper understanding of permeability reductions of CH4-containing coal seams after CO2 injection is essential, as coal permeability is the key parameter influencing the efficiency of enhanced coalbed methane recovery with CO2 sequestration and theoretical research on it is lacking. The main objective of this study was to accurately quantify the effects of CO2 injection on coalbed permeability. Therefore, permeability decrease coefficients and permeability rebound and recovery pressures of a binary gas (CH4 + CO2) are proposed based on the Shi–Durucan and extended Langmuir models. Then, the trends of these parameters under the influence of the main influencing factors are detailed. Specifically, the permeability decrease coefficient increased with an increase in CO2 proportion and increased rapidly when the reservoir gas pressure was low. Permeability recovery pressure decreased with an increase in CO2 proportion; the range of decrease was larger at low CO2 proportions. CO2 proportion had little effect on the permeability rebound pressure. Besides, the larger the Langmuir volume constant of CO2, the larger was the permeability decrease coefficient and permeability rebound pressure, and the smaller the permeability recovery pressure. However, the effect of the Langmuir pressure constant on these parameters was relatively weak. Finally, in light of these results, the implications of different characteristics of permeability evolution for CO2 injection pressure adjustment in the process of enhanced coalbed methane recovery with CO2 sequestration are discussed from a macroscopic perspective. The results of this study may provide a reference to select appropriate coal seams and injection pressures for CO2 sequestration.

Triphenylphosphine oxide (TPPO) and oxalyl chloride ((COCl)2) are used as novel and high-efficiency coupling reagents for the esterification of alcohols with carboxylic acids via the TPPO/(COCl)2 system at room temperature for 1 h. The reaction represents the first TPPO-promoted esterification under mild and neutral conditions with excellent yields. Furthermore, we proposed a plausible mechanism with the help of 31P NMR spectroscopy.

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Cobalt-Tetraamide-Phthalocyanine (CoTaPc) immobilized onto magnetic Fe 3 O 4 chitosan microspheres (Fe 3 O 4 / CTO) was synthesized via a simple immersion method, which is an efficient catalyst for the oxidation of cyclic ketones to lactones with O 2 /benzaldehyde as the oxidant. The CoTaPc-Fe 3 O 4 /CTO catalyst was applied for the first time in the Baeyer−Villiger (B− V) oxidation reaction. Characterization results obtained from X-ray diffraction, UV−vis, Fourier transform infrared, and scanning electron microscopy showed that the combination of CoTaPc and magnetic Fe 3 O 4 /CTO microspheres was achieved. The catalyst could be easily separated from the reaction system with an external magnet and reused several times without the remarkable loss of activity. In addition, a possible radical mechanism for the B−V oxidation in this catalytic system is proposed and verified by controlled experiments.