The effect of Mo on the morphology, crystal structure and hydrogen sorption properties of Mg/C composites prepared by reactive milling was studied. Transmission electron microscopic(TEM) observation shows that Mg/C composites prepared with the addition of Mo are of nanoscale with particle size about 20-120 nm after 3 h of milling under 1 MPaH_2. MgH_2 of tetrahedral crystal structure predominates in the materials with the geometric shape of oblique hexagonal prism. From X-ray diffraction(XRD) and hydrogen content studies, Mo and crystallitic carbon have a synergistic effect on promoting the hydrogenation rate in the reactive milling process. From differential scanning calorimetric(DSC) studies, the dehydrogenation peak temperature of the Mg/C materials with Mo is lowered to 299-340 ℃.
In order to better understand the prevailing mechanism of CO2 storage in coal and estimate CO2 sequestration capacity of a coal seam and enhanced coalbed methane recovery(ECBM) with CO2 injection into coal, we investigated the preferential adsorption of CH4 and CO2on coals. Adsorption of pure CO2,CH4 and their binary mixtures on high-rank coals from Qinshui Basin in China were employed to study the preferential adsorption behaviour. Multiple regression equations were presented to predict CH4 equilibrium concentration from equilibrium pressure and its initial-composition in feed gas. The results show that preferential adsorption of CO2 on coals over the entire pressure range under competitive sorption conditions was observed, however, preferential adsorption of CH4 over CO2on low-volatile bituminous coal from higher CH4-compostion in source gas was found at up to 10 MPa pressure. Preferential adsorption of CO2 increases with increase of CH4 concentration in source gas, and decreases with increasing pressure. Although there was no systematic investigation of the effect of coal rank on preferential adsorption, there are obvious differences in preferential adsorption of gas between low-volatile bituminous coal and anthracite. The obtained preferential adsorption gives rise to the assumption that CO2 sequestration in coal beds with subsequent CO2-ECBM might be an option in Qinshui Basins, China.
Calcium carbonate(CaCO 3) crystals in their preferred orientation were obtained in BG11 culture media inoculated with Synechocystis sp. PCC6803(inoculated BG11). In this study, the features of calcium carbonate deposition were investigated. Inoculated BG11 in different calcium ion concentrations was used for the experimental group, while the BG11 culture medium was used for the control group. The surface morphologies of the calcium carbonate deposits in the experimental and control groups were determined by scanning and transmission electron microscopy. The deposits were analyzed by electronic probe micro-analysis, Fourier transform infrared spectrum, X-ray diffraction, thermal gravimetric analysis and differential scanning calorimetry. The results show that the surfaces of the crystals in the experimental group were hexahedral in a scaly pattern. The particle sizes were micrometer-sized and larger than those in the control group. The deposits of the control group contained calcium(Ca), carbon(C), oxygen(O), phosphorus(P), iron(Fe), copper(Cu), zinc(Zn), and other elements. The deposits in the experimental group contained Ca, C, and O only. The deposits of both groups contained calcite. The thermal decomposition temperature of the deposits in the control group was lower than those in the experimental group. It showed that the CaCO 3 deposits of the experimental group had higher thermal stability than those of the control group. This may be due to the secondary metabolites produced by the algae cells, which affect the carbonate crystal structure and result in a close-packed structure. The algae cells that remained after thermal weight loss were heavier in higher calcium concentrations in BG11 culture media. There may be more calciumcontaining crystals inside and outside of these cells. These results shall be benefi cial for understanding the formation mechanism of carbonate minerals.
In order to reduce deleterious effect on environment,human health and facilities caused by original sulfides, more attention should be paid to biodesulfurization studying for fossil fuels. In this work, eight isolates were characterized by several DNA-based methods such as BOX element polymerase chain reaction( BOX-PCR), enterobacterial repetitive intergenic consensus( ERIC)-PCR and random amplification of polymorphic DNA( RAPD)-PCR. The desulfurization performance was determined by micro-coulometric method,Gibb's assay and barium sulfate test. It was found out that ERIC-PCR displays a much higher inter-strain heterogeneity compared with using BOX. The length of the primer didnot play the most important role in bacterial classification. The combination of the analysis of repetitive-sequence-based polymerase chain reaction ngerprinting and 16 S r DNA was able to provide more effective way in the separation and identification of bacteria.According to the analysis of 16 S r DNA,the more efficient desulfurization strain should belong to Klebsiella variicola.
The Mg/MoS_2 composites were prepared by ball milling under argon atmosphere,and the effect of MoS_2 on the crystal structure and hydrogen storage properties of Mg was investigated.It is found that 10 wt% of MoS_2 is sufficient to prevent particle aggregation and cold welding during the milling process.The crystallite size of Mg will remain constant at slightly less than 38.8 nm with the milling process due to the size confinement effect of MoS_2.The dehydrogenation temperature of MgH_2 is reduced to 390.4-429.4 ℃ due to the crystallite size reduction.Through fitting by Johnson-Mehl-Avrami model,it is found that Mg crystal grows by three dimension controlled by interface transformation during the process of MgH_2 decomposition.MoS_2 has a weak catalyst effect on the decomposition of MgH_2 and activation energy of 148.9 k J/mol is needed for the dehydrogenation process calculated by the Arrhenius equation.
