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In this work, the Keggin-type tri- and mono-palladium-substituted silicotungstates (POMs) were constructed by the reaction of tri- and monovacant silicotungstates ([SiW9O34]10− or [SiW11O39]8−) with palladium chloride. The as-obtained potassium salts of POMs demonstrated that Pd2+ ions were incorporated into POM frameworks. Notably, Pd nanoparticles were formed when the tri-palladium-substituted Keggin-type POM salts were reduced by H2. It was found that [SiW9O34]10− anions could act as multivacant coordination ligands to effectively stabilize palladium nanoparticles. The Pd nanoparticles were catalytically active for the reductive amination of carbon dioxide, and the formylamides were achieved in high yields under mild reaction conditions with methanol as the solvent. Notably, the Pd nanocatalyst exhibited outstanding recyclability and was recycled at least eight times without any obvious loss of the catalytic activity. The characterization by HAADF-STEM revealed that Pd nanoparticles formed a stable structure with POMs. Further studies demonstrated that the N-formylation reaction proceeds by the "methyl formate" pathway, involving CO2 activation by an in situ reaction with methanol and K2CO3 to generate potassium methyl carbonate. H2 underwent heterolytic dissociation with the assistance of a base over a Pd0–SiW9 catalyst, leading to one proton bound to carbonates and the hydride on a Pd atom (Pd–H). Moreover, the coupling of potassium methyl carbonate and Pd–H species afforded methyl formate intermediates in methanol, and then the reaction of methyl formate with amines gave formamides. This catalytic system demonstrated the benefits of excellent reactivity, stability, and recyclability for the N-formylation reaction. [ABSTRACT FROM AUTHOR]

Crushed coal pillars on both sides of isolated Island working face will form multiple goafs in series, resulting in complex air leakage in goafs. Therefore, it is crucial to explore the law of coal spontaneous combustion in the goaf of the isolated Island working face. Taking the W3225 isolated working face of Qianyingzi Coal Mine as the engineering background, a reliable numerical model was established and different porosity ratios of adjacent goafs and coal pillars were set. Oxygen and methane concentration distributions in goaf were calculated to identify the zones with spontaneous combustion hazards. The following conclusions were drawn. Spontaneous combustion hazards exist in the multiple goafs, and the areas of the zones with spontaneous combustion hazards in the goaf of the working face account for a large proportion of total areas of spontaneous combustion hazards. When the porosities of adjacent goafs within 10 m on the coal pillar sides or the porosities of coal pillars are reduced, the risk of spontaneous combustion hazards of multiple goafs is reduced. When the porosities of both is reduced simultaneously, the risk of spontaneous combustion hazards in multiple goafs and coal pillars is greatly reduced. According to the simulation results, the porosities of adjacent goafs and coal pillars on both sides of the isolated working face can be reduced by means of shotcrete and grouting, which can reduce the series air leakage channel between each goaf, thus the fire prevention and extinguishing ability of the working face will be improved. Ultimately, the pressure on working face advancement can be relieved. [ABSTRACT FROM AUTHOR]

Edible mushrooms are favoured by people for their rich nutrition, medicinal value and unique flavour. The quality of postharvest mushroom decreased sharply because of its special tissue structure and physiological characteristics. Compared with other preservation technologies, packaging has been widely used in the preservation of mushrooms because of its strong preservation effect, green and convenient characteristic. This review discussed the quality deterioration of fresh mushrooms and its influencing factors, and summarised the research advances and preservation mechanism of modified atmosphere packaging (MAP), active packaging (ACP), biodegradable film packaging (BFP) and nanocomposite packaging (NCP) used to cope with the quality deterioration of fresh mushrooms. The packaging mainly maintains the quality of mushrooms and extends their shelf life by exerting antibacterial, antiviral and antioxidant, and by regulating respiration and energy metabolism, cell wall metabolism and membrane lipid metabolism. Currently, the combined packaging based on nano, active and biodegradable is getting more attention, but there is a lack of in‐depth genetic research on its preservation mechanism. Nanoemulsion‐based packaging was used in many foods; however, there is little research on the preservation of mushrooms. Based on the above packaging, the next step is to explore the intelligent packaging for edible mushrooms. This review can provide reference for further research and application of packaging preservation in mushrooms, to improve the quality of postharvest mushrooms. [ABSTRACT FROM AUTHOR]