As a metamorphic product of coal, microcrystalline graphite is of ultrafine polycrystalline structure with near-isotropic and highly graphitized characteristics, which endows itself with great potential as filler for ultrafine-grain isotropic graphite (UGIG). In this work, two kinds of microcrystalline graphite based UGIG, MGG12 and MGG8, are prepared by a liquid mixing process from microcrystalline graphite filler with an average particle size of 12 and 8 mu m, respectively. For comparison, pitch coke based UGIG, PCG8, is prepared as control sample from pitch coke filler with an average particle size of 8 mu m using the same pitch binder and preparation method. Compared with PCG8, MGG12 and MGG8 exhibit many structure and property advantages such as higher density, higher graphitization degree, higher thermal conductivity, higher isotropy, lower coefficient of thermal expansion, smaller median pore diameter, lower porosity and better barrier property to molten fluoride salt. Notably, due to the smallest median pore diameter (0.431 mu m) of MGG8 among these three kinds of UGIG, the molten salt weight gain ratio of MGG8 is only 0.13 wt% under 5 atm, which is much lower than 16.1 wt% and 15.1 wt% for PCG8 and MGG12 under 4 atm, respectively. These advantages indicate that microcrystalline graphite may have advantages over pitch coke as filler for the preparation of UGIG for molten salt applications such as molten salt reactor. In addition, the relevant mechanisms are analyzed and discussed by comparison of the structural characteristics of micmcrystalline graphite and pitch coke.

The use of renewable biodiesel and additives diversifies transportation fuel supply. Combustion tests on neat ultra-low sulfur No.2 diesel (D100) and its blends with biodiesel and the n-butanol additive were conducted to investigate environmental impacts and tradeoffs in engine emission and power output. The testing results show measurable changes in power output and engine emission, particularly in diesel particulate matter (DPM) size distribution and black carbon compositions. The binary diesel-biodiesel blend D80B20 (80% D100 and 20%B100 by volume) offers reduced PM and black carbon emission, but higher NOx in engine exhaust. Comparatively the tertiary diesel-biodiesel-butanol blend B15Bu5 (80% D100, 15% B100, and 5% Bul 00 by volume) shows superior environmental tradeoff in the black carbon and NOx emission than D80B20 Both fuel blends suffer a 3.0-5.6% increase in brake-specific fuel consumption. At higher combustion temperature, the butanol-oxygenated diesel fuel produces DPMs of smaller size, higher number concentrations, greater OC fractions, and more amorphous black carbon particles. The peak DPM aerodynamic size dp(max) for D80B20 and B15Bu5 blends is 0.20-0.32 mu m, smaller than > 0.40 mu m dp(max) for D100 and the 0.30 mu m cut-off size of regular DPM fillers. For an internal combustion engine capable of accommodating biodiesel and water fraction in the fuel mixture, the B15Bu5 blend offers a viable fuel alternative according to the comparative testing results. The use of biodiesel and butanol additive in petroleum diesel can decrease the DPM emission, while the undesired NOx formation in tradeoff can be managed through optimizing the tertiary composition of petroleum diesel, biodiesel, and fuel additives.

CO2 enhanced oil recovery (EOR) is a potential way for carbon capture, utilization and storage (CCUS). However, the effect of CO2 injection is greatly influenced by the reservoir conditions. Typically, Minimum miscible pressure (MMP) is selected as one of the key parameters for the screening and evaluation of prospective CO2 flooding. Conventional slim tube test is both accurate and widely accepted but it is inefficient. Existing empirical formulas for MMPs are easy to be used but have been proved inaccurate and unreliable. Machine learning-based methods have great advantages in predicting MMP. However, only predication accuracy is discussed for most models without the screening of the main control factors and further validation of the model reliability. In this paper, a new prediction model based on support vector machine (SVM) was developed for pure/impure CO2 and crude oil system. This study was based on 147 sets of MMP data from the literature with full information on reservoir temperature, oil composition and gas composition. The main control factors were screened by several statistical methods. Unlike the conventional prediction models that verified by only prediction accuracy, learning curve and single factor control variable analysis are further validated to obtain the optimum model.

In this study, a heterogeneous magnetic acid catalyst MoO3/SrFe2O4, composed of molybdenum oxide (MoO3) supported on strontium ferrite (SrFe2O4), was synthesized and applied in the transesterification of waste cooking oil. The catalyst was characterized by acid-base titration method in order to determine Surface acidity, Thermogravimetric analysis (TGA/DTGA), X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), Energy dispersion X-ray spectroscopy (EDX) and Vibrating sample magnetometry (VSM) techniques. A central composite design of centered face 2(4) and a mathematical model were developed in order to describe the behavior of the ester content as a function of the independent variables reaction temperature, alcohol:oil molar ratio, catalyst dosage and reaction time. The mathematical model (R-2 = 0.9900) was validated and showed a relative error below 5% between the experimental and predicted values. Using linear regression methods and response surface methodology the conditions of biodiesel synthesis reaction were optimized and 95.4% conversion into esters was obtained from the use of 164 degrees C reaction temperature, 40:1 alcohol:oil molar ratio, 10% catalyst dosage and 4 h reaction time. The catalyst was recovered by an external conventional magnet and showed high reusability and stability, such the ester content remains above 84% after five runs. The development of MoO3/SrFe2O4 as a novel heterogeneous magnetic acid catalyst would provide an environmentally friendly approach to biodiesel production.

The water addition to supercritical tert-butyl methyl ether for continuous biodiesel production from rapeseed oil has been carried out to promote an essential enhancement of biodiesel yield. We developed a new biodiesel production by supercritical tert-butyl methyl ether with water and evaluated process variables influence using response surface methodology to obtain an optimum condition. We found that the optimum condition was at water addition of 25 wt%, temperature of 300 degrees C, and pressure of 20 MPa at space time of 30 min to achieve 77.39 wt% of biodiesel yield. In addition, the reaction rate constants were determined by first-order reaction model. We suggested that water addition to the supercritical tert-butyl methyl ether accelerates reaction rate and diminishes activation energy since the water acts as a catalyst for the reaction. The thermodynamic parameters were calculated using Eyring-Polanyi equation based on the transition state theory. We found that the supercritical reaction was endothermic, endergonic, and non-spontaneous.

The various microscopic processes that take place during enhanced oil-recovery upon injecting low salinity brines are quite complex, particularly for carbonate reservoirs. In this study, we characterize the in-situ microscopic responses of the organic layers deposited on flat Iceland spar calcite surface to brines of different salinity using Atomic force Microscopy (AFM). Organic layers were deposited from crude oil at the end of a twostep aging procedure. AFM topography images reveal that the organic layers remain stable in high-salinity brines and desorb upon exposure to low-salinity brines. In addition, the organic layers swell in low-salinity brines, and the stiffness of the organic layers is found to directly proportional to the brine salinity. These observations are explained in terms of 'salting-out' effects, where the affinity of organic layers to solvent molecules increases upon reducing the brine salinity. The swelling and desorption of organic materials provide access for the brine to mineral surface causing dissolution and change in wetting properties of the surface. Our results show the significance of de-stabilizing the organic layer on rock surfaces in order to design any successful improved oil recovery (IOR) strategy.