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To improve the ability of water to wet coal in the process of coal seam water injection, different ionic liquids and surfactant compound solutions were added to water. Analyses of surface tension, reverse spontaneous imbibition, and contact angle were used to optimize the different compound solutions. The results showed that when the mixture ratio of 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIm][BF4]) and sodium dodecyl sulfate (SDS) was 3:1, and the concentration of the composite solution reached 0.1 wt%, the liquid surface tension reached a minimum of 28.946 mN/m, and the contact angle between the solution and the coal sample was 41.3°, which was lower than that of any concentrations of the other composite solutions. This solution could effectively wet the coal. In addition, infrared spectroscopy showed that different concentrations of the [BMIm][BF4] and SDS composite solution had different effects on the content of functional groups in coal. Further, based on the relationship between the content of the functional groups and contact angle, the relationship between the content of ring hydroxyl and OH⋯O in the hydroxyl structure and the size of the contact angle was found to be the most significant. Based on the above findings, a new type of composite wetting agent was prepared, and the wetting mechanism between coal and the wetting agent was clarified from the perspective of functional groups. The research results have important guidance and practical significance for improving the effect of increasing moisture and reducing dust in the process of coal seam water injection.

Dimethyl ether (DME), a promising renewable energy source, has been extensively studied due to its inherent advantages. A cost-effective approach to synthesize ferrierite (ZSM-35) from geopolymer precursors was proposed in this study. The catalytic behavior of geopolymer-based ZSM-35 was evaluated in the process of methanol to dimethyl ether (MTD), and the acid sites, porosity and metal functions of catalysts were continuously optimized to improve the catalytic efficiency. The results showed that protonated catalysts were more active than original products due to their abundant weak acid, medium-strong and strong acid sites. The porosity was mainly affected by the structure of catalysts. The maximum conversion of methanol increased from 16% to 30% and then to 71%, corresponding to the conversion of amorphous geopolymer to semi-crystalline and finally to crystalline ZSM-35 zeolite. ZSM-35 zeolite was the optimal catalyst due to its SBET of 237.9 m2/g was higher than that of geopolymer of 9.3 m2/g, which provided more adequate porosity to enhance mass transfer. A series of cerium-modified catalysts were further synthesized by ion-exchange method to optimize structural and surface properties. The highest conversion of Ce-modified catalyst reached 95.78%, which may be ascribed to the abundant acid active sites, hierarchical porosity and metal functions effectively improving catalytic performance.

Disaster prevention effect of hydraulic techniques in mines depends on the migration range of water and the wetting degree of coal body. Therefore, it is of great significance to study the interaction among accumulated coal grains and water during migration and flow. First, this paper simulates the migration and wetting process of water and coal grains with an inverse spontaneous imbibition experiment. Then, theoretical and experimental results are compared to determine the optimal determination method of grain diameter as a key parameter in model. The research shows that the lower the metamorphic grade is, the more obvious the imbibition, and the grain diameter of approximately 100–297 μm produces the greatest imbibition effect. At the same time, after realizing that large grains have a dominant influence on formation of imbibition channels, the traditional mathematical model of imbibition height is improved and thus provides a theoretical guiding significance for improving hydraulic techniques.

It is of great significance to quantitatively describe the change in the permeability of the water-injected coal to improve the effect of the coal seam water injection technology. However, the current permeability model often assumes the pores of the porous medium are smooth, which is a large difference from the coarse coal matrix-pore interface. Therefore, a rough capillary bundle is used as the physical model to characterize the coal structure in this paper. Combined with fractal theory, a permeability model including the tortuosity fractal dimension and the specific surface area of the pores is established based on the traditional Kozeny-Carman equation, and the degree of influence of each factor on the permeability was obtained. Then, liquid permeability and structural parameters of the coal samples from the Daliuta Coal Mine and the Qincheng Coal Mine in China were obtained by nuclear magnetic resonance experiments, which verified the accuracy of the model. The research show that the tortuosity fractal dimension has the greatest influence on the theoretical permeability, and the theoretical permeability decreases rapidly when the tortuosity fractal dimension is between 1.05 and 1.20. Increasing the specific surface area of the pores will lead to an increase in the tortuosity fractal dimension and a decrease in the theoretical permeability. Under the different nuclear magnetic resonance experimental conditions, the theoretical permeability of the coal samples is consistent with the change in the liquid permeability and is closer to the measured value compared with the permeability models of Xu and Liu.

Circulating fluidized bed fly ash (CFBFA) was used to synthesize kaliophilite catalyst via a facile and low-energy two-step process: fabrication of amorphous CFBFA geopolymer and hydrothermal transformation of CFBFA-based geopolymer into kaliophilite. X-ray diffraction and scanning electron microscopy results demonstrated that CFBFA was successfully converted into kaliophilite with short prismatic crystals having size of ~1 μm. Temperature-programmed desorption of CO2 analysis results indicated the presence of abundant weak, medium-strength and high-strength basic sites on the kaliophilite catalyst, which were respectively assigned to hydroxyl groups, K-O ion pairs, and O2− ions. When kaliophilite was used as a heterogeneous catalyst for biodiesel production, the highest biodiesel yield of 99.2% was obtained under transesterification conditions of 5 wt% catalyst concentration, methanol:canola oil mole ratio of 15:1, reaction temperature of 85 °C, and reaction time of 6 h. The kaliophilite catalyst could be easily recovered and reused for four cycles without significant deactivation. Further, a solid base catalysis mechanism for transesterification over kaliophilite catalyst was proposed.