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The initial velocity of gas emission is one of the important indicators for identifying the risk of coal and gas outburst. The existing research has not organically combined the testing of the initial gas emission rate index of coal with the testing of the other three indicators for outburst identification (coal seam gas pressure, coal failure type, and coal solidity coefficient). The current method for measuring the initial velocity of gas emission is based on AQ 1080-2009 'Method for Measuring the Initial Velocity Index (∆p) of Coal Gas Emission'. The measurement results only reflect the difficulty of gas emission through coal particles under standard experimental conditions, without considering the in-situ environment of coal seam gas occurrence. The results cannot accurately reflect the severity of the disaster of gas emission inside the coal rock mass on site. In order to solve the above problems, the device and method for measuring the initial velocity of in-situ gas emission are proposed. The method replaces coal particles with original coal blocks, replaces methane with original gas components, increases the gas pressure, stress, and temperature environment in which the coal body is located. The method restores the in-situ environment for measurement. A in-situ gas emission initial velocity measurement experiment is conducted by use of coal samples from coal and gas outburst coal seams in a certain coal mine. The conclusions are listed as follows. ① With the simulation of gas emission process, the gas emission flow rate gradually decreases and shows a negative exponential change law with time. The gas flow rate is used to characterize the initial velocity of in-situ gas emission, then ΔpQA=7.1 mmHg, ΔpQI=2.9 mmHg. ② As the simulation of the gas emission process progresses, the gas pressure in the emission space gradually increases, and the rate of gas pressure increase gradually decreases. The gas pressure changes roughly with time in a logarithmic function relationship. The emission gas pressure is used to characterize the initial velocity of in-situ gas emission, then ΔpPA=25 mmHg, ΔpPI=26.6 mmHg, ΔpPD=11 mmHg. The measurement results can comprehensively reflect the dual pore structure of coal seams, the mechanical properties of coal bodies, the energy of gas occurrence in coal bodies, the in-situ environment of stress and temperature in coal seams, and truly reflect the degree of outburst danger in coal mines underground.

Glycerol and CO2 are largely produced as by-products in modern industry. Herein, three Ru complexes bearing air- and water-stable NHC–nitrogen–nitrogen ligands are designed as bifunctional catalysts to upcycle glycerol and CO2 simultaneously. Among them, Ru complex 2 featuring an N–H structure shows the highest efficiency with TONs up to 300 000 and 387 000 for formate and lactate, respectively. 13C labelling experiments clearly manifest that formate is primarily derived from CO2. Furthermore, in situ FTIR spectra suggest that glyceraldehyde from glycerol might serve as a key intermediate to form lactate, while DFT calculations indicate that Ru complex 2 possesses the lowest reaction barriers and can form the Ru＝N intermediate, contributing to its higher activity. [ABSTRACT FROM AUTHOR]

An innovative bitopic phosphoramidite ligand L was proficiently synthesized and subsequently employed in coordination with two distinct metal species (AgI and RhI), leading to the construction of a heterometallic coordination polymer. The catalyst showcased remarkable performance in the hydroformylation of long-chain alkenes, displaying high activity and selectivity with a minimum yield of 90% for aldehydes. Operating as a heterogeneous catalyst, it not only demonstrated outstanding efficacy in facile separation from the product but also maintained a low rhodium loss per catalytic cycle. The catalyst exhibited exceptional stability, remaining high activity and selectivity over 10 successive reuses. Moreover, the RhAgL catalysts exhibit notable isomerization effects on alkenes, which promote the preferential formation of branched aldehydes in the resulting product. The straightforward synthetic strategy employed in preparing this highly effective catalyst introduced an innovative concept for heterogeneous catalysis, offering promising prospects for advancing industrial processes. This remarkable performance indicates the catalyst's potential for sustainable and efficient chemical transformations, highlighting its significance in driving advancements in catalytic technology for a variety of applications in industry. [ABSTRACT FROM AUTHOR]

We report a series of coordination cages that incorporate peptide chains at their vertices, prepared through subcomponent self‐assembly. Three distinct heterochiral tripeptide subcomponents were incorporated, each exhibiting an L−D−L stereoconfiguration. Through this approach, we prepared and characterized three tetrahedral metal‐peptide cages that incorporate thiol and methylthio groups. The gelation of these cages was probed through the binding of additional metal ions, with the metal‐peptide cages acting as junctions, owing to the presence of sulfur atoms on the peripheral peptides. Gels were obtained with cages bearing cysteine at the C‐terminus. Our strategy for developing functional metal‐coordinated supramolecular gels with a modular design may result in the development of materials useful for chemical separations or drug delivery. [ABSTRACT FROM AUTHOR]

Preset slot is an effective control measure to solve the blank zone problem appeared in the coal and rock mass hydraulic fracturing. Taking Tangkou Coal Mine as an example, RFPA software was used to analyze the crack propagation law controlled by the preset slots on the long drilling along the coal seam strata of the working face. The research shows that: all the main hydraulic fractures controlled by the multi-slot fracturing expand in the direction perpendicular to the minimum horizontal principal stress. There are some preset slots that can preferentially induce hydraulic crack propagation. As the density of the pre-slots increases, the length of the unilateral main hydraulic crack decreases and the crack opening angle increases. The length change of the longest unilateral main hydraulic crack roughly conforms to the linear relationship. The average length of the longest unilateral main hydraulic crack is 26.3 m. The average crack opening angle is 11.8°. The stable pressure of the crack propagation is 18.0 MPa. The reasonable slot density is 0.04 m, and the corresponding slot spacing is 25 m. The average pressure relief area of a single hole is 2 537 m2. The permeability of the main fracture area can be increased by 100 to 200 times.

Electrocatalytic nitrogen reduction reaction (eNRR) is a new method for sustainable NH3 production, which has attracted much attention in recent years. However, the low Faradaic efficiency due to the competitive hydrogen evolution reaction (HER) and inert N≡N triple bond activation hinders its practical application. To find highly efficient electrocatalysts with excellent activity, stability and selectivity, we have studied a series of transition metal dimers (TM2) loaded on poly triazine imide, (PTI) a crystalline carbon nitride, by density functional theory calculations. The results show that most of the metal dimers have good stability. Finally, among 26 homonuclear diatomic catalysts, Mo2@PTI, Re2@PTI, and Pt2@PTI exhibit strong capability for suppressing HER, with a favorable limiting potential of −0.53, −0.36, and −0.63 V, respectively, and hence, can be used as efficient electrocatalysts for NRR. In this study, a homonuclear diatomic eNRR catalyst was designed and screened to provide not only a theoretical basis for the experiments but also an alternative approach for sustainable synthesis of ammonia. [ABSTRACT FROM AUTHOR]

Taking Xi’an Mine as an example, it is found that the sudden drop of the atmospheric pressure causes the abnormal increase of gas emission in underground return airflow, and the abnormal gas emission usually lags behind the pressure drop of about 3-6 h. The abnormal gas emission curve is divided into three types: “polar peak”, “fluctuation” and “fluctuation + polar peak”. The basic principle of the atmospheric pressure affecting the gas concentration of return air flow in the underground mining face is analyzed. It is considered that the absolute value of the air pressure of the roadway affects the “desorption and adsorption” speed of the coal pore wall gas. The pressure gradient caused by the relative change of the air pressure of the roadway affects the gas migration velocity in the pore and fracture. Combined with the measured data, the quantitative equation of the change of the return gas concentration with the atmospheric pressure in the residual coal recovery face under the initial surface pressure is obtained. Finally, according to the influence of the atmospheric pressure drop on the gas emission, two kinds of prevention and control ideas are proposed to cut off the gas migration channel or to offset the atmospheric pressure drop.

Self‐assembly of a flexible tritopic aniline and 3‐substituted 2‐formylpyridine subcomponents around iron(II) templates gave rise to a low‐spin FeII4L4 capsule, whereas a high‐spin FeII3L2 sandwich species formed when a sterically hindered 6‐methyl‐2‐formylpyridine was used. The FeII4L4 cage adopted a new structure type with S4 symmetry, having two mer‐Δ and two mer‐Ʌ metal vertices, as confirmed by NMR and X‐ray crystallographic analysis. The flexibility of the face‐capping ligand endows the resulting FeII4L4 framework with conformational plasticity, enabling it to adapt structurally from S4 to T or C3 symmetry upon guest binding. The cage also displayed negative allosteric cooperativity in simultaneously binding different guests within its cavity and at the apertures between its faces. [ABSTRACT FROM AUTHOR]

Aryne [3 + 2] cycloaddition with nitrones generated in situ from the addition of hydroxylamines to acetylenedicarboxylates affords moderate to good yields of dihydrobenzisoxazoles. This reaction extends the current scope of aryne cycloaddition to include in situ generated nitrones and produces functionalized dihydrobenzisoxazoles with a quaternary center. Key words: nitrone, aryne, dipolar cycloaddition, reactive intermediate, dihydrobenzisoxazole. La cycloaddition [3 + 2] d'aryne a des nitrones generees in situ par l'addition d'hydroxylamines a des acetylenecarboxylates conduit a la formation avec des rendements allant de moderes a bons de dihydrobenzisoxazoles. Cette reaction prolonge la plage d'application des reactions de cycloadditions a des arynes de facon a inclure des nitrones generees in situ et a produire des dihydrobenzisoxazoles fonctionnalises avec un centre quaternaire. Mots-cles: nitrone, aryne, cycloaddition dipolaire, intermediaire reactif, dihydrobenzisoxazole. [Traduit par la Redaction], Introduction In recent years, the [3 + 2] dipolar cycloaddition of arynes with various 1,3-dipoles has become resurgent (1-7) with the development of the Kobayashi aryne precursor, (8) 2-(trimethylsilyl)aryl triflates. [...]

Es wird über robuste Reaktionsvorschriften zweier mechanistisch ungleicher C(sp3)‐Ge‐Bindungsknüpfungen ausgehend von Alkylelektrophilen und Germaniumnukleophilen berichtet. Die Germaniumreagenzien stehen nach Lithium‐auf‐Magnesium‐ bzw. Lithium‐auf‐Zink‐Ummetallierung als stabile Stammlösungen zur Verfügung. Das Germanium‐Grignard‐Reagens reagiert mit mehreren 1° und 2° Alkylelektrophilen in einem ionischen nukleophilen Austausch. Im Gegensatz dazu erfordert die Kupplung des entsprechenden Zinkreagens einen Nickelkatalysator, und jenes nimmt dann an radikalischen Bindungsknüpfungen mit 1°, 2° und selbst 3° Alkylbromiden teil. Beide Methoden umgehen das Regioselektivitätsproblem der Hydrogermylierung von Alkenen und ermöglichen die Darstellung einer breiten Palette funktionalisierter alkylsubstituierter Germane. [ABSTRACT FROM AUTHOR]

Robust procedures for two mechanistically distinct C(sp3)−Ge bond formations from alkyl electrophiles and germanium nucleophiles are reported. The germanium reagents were made available as bench‐stable solutions by lithium‐to‐magnesium and lithium‐to‐zinc transmetalation, respectively. The germanium Grignard reagent reacts with various primary and secondary alkyl electrophiles by an ionic nucleophilic displacement. Conversely, the coupling of the corresponding zinc reagent requires a nickel catalyst, which then engages in radical bond formations with primary, secondary, and even tertiary alkyl bromides. Both methods avoid the regioselectivity issue of alkene hydrogermylation and enable the synthesis of a wide range of functionalized alkyl‐substituted germanes. [ABSTRACT FROM AUTHOR]