Milk metabolome reveals variations on enteric methane emissions from dairy cows fed a specific inhibitor of the methanogenesis pathway

Metabolome profiling in biological fluids is an interesting approach for exploring markers of methane emissions in ruminants. In this study, a multiplatform metabolomics approach was used for investigating changes in milk metabolic profiles related to methanogenesis in dairy cows. For this purpose, 25 primiparous Holstein cows at similar lactation stage were fed the same diet supplemented with (treated, n = 12) or without (control, n = 13) a specific antimethanogenic additive that reduced enteric methane production by 23% with no changes in intake, milk production, and health status. The study lasted 6 wk, with sampling and measures performed in wk 5 and 6. Milk samples were analyzed using 4 complementary analytical methods, including 2 untargeted (nuclear magnetic resonance and liquid chromatography coupled to a quadrupole-time-of-flight mass spectrometer) and 2 targeted (liquid chromatography-tandem mass spectrometry and gas chromatography coupled to a flame ionization detector) approaches. After filtration, variable selection and normalization data from each analytical platform were then analyzed using multivariate orthogonal partial least square discriminant analysis. All 4 analytical methods were able to differentiate cows from treated and control groups. Overall, 38 discriminant metabolites were identified, which affected 10 metabolic pathways including methane metabolism. Some of these metabolites such as dimethylsulfoxide, dimethylsulfone, and citramalic acid, detected by nuclear magnetic resonance or liquid chromatography-mass spectrometry methods, originated from the rumen microbiota or had a microbial-host animal co-metabolism that could be associated with methanogenesis. Also, discriminant milk fatty acids detected by targeted gas chromatography were mostly of ruminal microbial origin. Other metabolites and metabolic pathways significantly affected were associated with AA metabolism. These findings provide new insight on the potential role of milk metabolites as indicators of enteric methane modifications in dairy cows.     

Glycine-assisted preparation of highly dispersed Ni/SiO2 catalyst for low-temperature dry reforming of methane

Ni-based catalysts have been widely studied in reforming methane with carbon dioxide. However, Ni-based catalysts tends to form carbon deposition at low temperatures (≤600 °C), compared with high temperatures. In this paper, a series of Ni/SiO₂-XG catalysts were prepared by the glycine-assisted incipient wetness impregnation method, in which X means the molar ratio of glycine to nitrate. XRD, H₂-TPR, TEM and XPS results confirmed that the addition of glycine can increase Ni dispersion and enhance the metal-support interaction. When X ≥ 0.3, these catalysts have strong metal-support interaction and small Ni particle size. The Ni/SiO₂-0.7G catalyst has the best catalytic performance in dry reforming of methane (DRM) test at 600 °C, and its CH₄ conversion is 3.7 times that of Ni/SiO₂-0G catalyst. After 20 h reaction under high GHSV (6 × 10⁵ ml/g_cat/h), the carbon deposition of Ni/SiO₂-0.7G catalyst is obviously lower than that of Ni/SiO₂-0G catalyst. Glycine-assisted impregnation method can enhance the metal-support interaction and decrease the metal particle size，which is a method to prepare highly dispersed and stable Ni-based catalyst.     

Increased hydroxyl concentration by tungsten oxide modified h-BN promoted catalytic performance in partial oxidation of methane

Hexagonal boron nitride (h-BN) as a layered inorganic nonmetallic material has been widely used. Hydrogen peroxide (H₂O₂) modification can trigger exfoliation and afford abundant B–OH active sites at edge of h-BN, which can enhance methane activation ability. Introducing tungsten oxide (WO₃) to h-BN produces a similar effect, because doping WO₃ into h-BN resulted in electron transfer to N, inducing fracture of B–N bond, resulting in N vacancy (triboron center), exposing more B sites and promoting the generation of B–OH. Significantly, the introduction of WO₃ on the modified h-BN dramatically increased the concentration of B–OH compared with the unmodified h-BN, because H₂O₂ modification weakened B–N bond. By means of XRD, TEM, XPS,EPR, FT-IR, it is proved that the high concentration of B–OH active sites contributed to activating C–H bond, thus methane conversion and CO and H₂ selectivity were significantly improved.     

Nickel‒cobalt bimetallic catalysts prepared from hydrotalcite-like compounds for dry reforming of methane

Ni–Co/Mg(Al)O alloy catalysts with different Co/Ni molar ratios have been prepared from Ni- and Co-substituted Mg–Al hydrotalcite-like compounds (HTlcs) as precursors and tested for dry reforming of methane. The XRD characterization shows that Ni–Co–Mg–Al HTlcs are decomposed by calcination into Mg(Ni,Co,Al)O solid solution, and by reduction finely dispersed alloy particles are formed. H₂-TPR indicates a strong interaction between nickel/cobalt oxides and magnesia, and the presence of cobalt in Mg(Ni,Co,Al)O enhances the metal-support interaction. STEM-EDX analysis reveals that nickel and cobalt cations are homogeneously distributed in the HTlcs precursor and in the derived solid solution, and by reduction the resulting Ni–Co alloy particles are composition-uniform. The Ni–Co/Mg(Al)O alloy catalysts exhibit relatively high activity and stability at severe conditions, i.e., a medium temperature of 600 °C and a high space velocity of 120000 mL g^?1 h^?1. In comparison to monometallic Ni catalyst, Ni–Co alloying effectively inhibits methane decomposition and coke deposition, leading to a marked enhancement of catalytic stability. From CO₂-TPD and TPSR, it is suggested that alloying Ni with Co favors the CO₂ adsorption/activation and promotes the elimination of carbon species, thus improving the coke resistance. Furthermore, a high and stable activity with low coking is demonstrated at 750 °C. The hydrotalcite-derived Ni–Co/Mg(Al)O catalysts show better catalytic performance than many of the reported Ni–Co catalysts, which can be attributed to the formation of Ni–Co alloy with uniform composition, proper size, and strong metal-support interaction as well as the presence of basic Mg(Al)O as support.     

The explosion thermal behavior of H2/CH4/air mixtures in a closed 20 L vessel

In this work, the explosion thermal behavior of H₂/CH₄/air mixtures, at different equivalence ratios (0.6–1.6) and hydrogen volume fractions (0%–100), was investigated in a confined 20-L chamber. The parameters of explosion time and pressure, as well as the explosion heat loss were quantitatively studied and analyzed. Moreover, the dominant chain reactions of the explosion process and heat release were identified via the detailed mechanism of the Foundational Fuel Chemistry Model (FFCM1). The results indicated that an increased H₂ volume fraction in the mixtures increased the peak explosion pressure, maximum pressure rise rate and deflagration index. In addition, the explosion duration and fast-burning period were greatly shortened. Both the adiabatic flame temperature and thermal diffusivity monotonically increased with increasing H₂ volume ratio. Moreover, the enhancement effect of the H₂ ratio on the thermal diffusivity of H₂/CH₄ mixtures was more prominent for fuel-rich mixtures than for fuel-lean mixtures. The obtained quantitative results are helpful for developing measures to prevent the potential explosion accidents.     

理想石门揭煤突出预测指标实验研究

该文从煤与瓦斯突出过程能量变化的角度,提出了预测突出矿井的"理想石门揭煤"模型及相应的预测指标,通过对理想石门揭煤进行模拟实验,对理想石门揭煤突出预测指标的研究,可以定量地将矿井石门揭煤可能出现动力现象的大小分为非突出,压出及突出三种情况。     

保护层卸压瓦斯抽采及涌出规律研究

随着我国煤矿开采深度的增加，煤与瓦斯突出矿井和变出煤层的数量不断增加，利用保护层开采过程中的被保护层的卸压作用对卸压瓦斯进行强化抽采，使被保护层由高瓦斯突出危险煤层变为低瓦斯无突出危险煤层，从而实现煤与瓦斯资源的安全高效共采．系统介绍了基于分源原理的回采工作面瓦斯涌出预测方法，保护层开采及卸压瓦斯强化抽采技术的发展和工程应用．结合淮南潘一矿下保护层和谢一矿上保护层开采及卸压瓦斯强化抽采实例，将保护层工作面瓦斯涌出量预测结果与保护层工作面瓦斯涌出量实测结果进行了对比分析．研究结果表明，由于保护层开采的卸压作用，使被保护层卸压瓦斯抽采率远大于被保护层卸压瓦斯的自然排放率，导致保护层工作面瓦斯涌出量预测结果小于实际瓦斯涌出量．     

基于双相介质理论的煤层甲烷预测技术

基于双相介质理论研究了双相各向同性介质中的纵波方程，并对煤层甲烷进行地震波动方程的数值模拟．正演得到的叠后记录双相介质的反射波振幅明显弱于单相介质，表现出低频共振、高频衰减及固相位移与流相位移为反相的特性．与地震资料和实际开采资料对比吻合较好．     

中国煤层气产业对外合作政策研究

中国拥有丰富的煤层气资源，与天然气相比，煤层气的开采具有单井产量低、投资回收期长等特点。目前，中国还缺乏成熟的煤层气开发技术，需要引进外资及先进的技术和管理经验。本文通过分析国外特别是美国政府对煤层气产业的扶持政策及其成功经验，对比了中国现行的产业政策，提出了加快中国煤层气产业对外合作发展的政策建议。     

晋城地区煤层甲烷碳同位素特征及成因探讨

对取自沁水盆地南部晋城地区的煤芯样中的解吸气进行了甲烷碳同位素测定.结果表明，随着解吸过程的进行，δ¹³C₁值逐渐变重，δ¹³C₁值和解吸时间呈对数关系，δ¹³C₁值变重趋势具有先快后慢的阶段性特点.取样条件和取样时间对煤层甲烷碳同位素值有较大影响，在某一个时间点所取气样的同位素值不一定代表该井原地气体的同位素值.在采样进行同位素测定时，煤样全部解吸气体的碳同位素的平均值才能代表该井煤层气的原地气同位素值.在实际操作中，可以用罐装煤样气体解吸半量时间点所取气样的同位素值来代表全部解吸气体的同位素平均值.与煤岩热模拟实验所得到的经验公式计算结果比较，晋城地区实测的煤层甲烷碳同位素值偏轻.晋城地区煤层甲烷碳同位素的组成特点受解吸-扩散-运移过程中发生的分馏效应以及其他多种因素的共同制约.