Photocatalysis is one of the important methods to solve the current environmental pollution and energy crisis. However, the photocatalytic efficiency of most photocatalysts is still low. Improving the separation of photogenerated charges is an effective way to enhance the photocatalytic efficiency. Firstly, the paper summarizes the photocatalysis mechanism, and then reviews the effects of built⁃in electric field in semiconductor p⁃n junction, heterophase junctions, polarized surfaces and ferroelectric material polarization on separation efficiency of photogenerated charges and photocatalytic performance, based on the recent domestic and international research progress in improving the separation efficiency of photogenerated charges. Finally, the future development of built⁃in electric field in photocatalysis is prospected.
Titanium dioxide@2,5⁃Dimercapto⁃1,3,4⁃thiadiazole@silicon dioxide (TiO2@DMTD@SiO2) composite materials were synthesized by NaF hydrothermal etching combining with sol⁃gel method. The crystalline structures and morphologies were characterized by X⁃ray diffraction (XRD),Fourier transform infrared (FTIR) spectroscopy,scanning electron microscopy (SEM). The hydrophilicity of the coating was tested by the video optical contact angle, and the anticorrosion performance of the coating was evaluated by electrochemical method.The results show that contact angle of the epoxy coating with TiO2 doped nanocontainers is 71.9°,which can effectively prevent the invasion of corrosive media. Moreover, it has higher corrosion resistance than the blank epoxy coating, after immersing in 3% NaCl solution for 1 to 7 days.
Penetration is not only the technical parameters to characterize the soft and hard degree and anti⁃fatigue at medium temperature of asphalt products,but also the classification index of penetration classification system.The research results in the literature show that the logarithm of penetration is correlated with with Celsius temperature.But correlations between the logarithm and double logarithm of penetration with Celsius temperature,reciprocal of absolute temperature,are rarely studied.In order to investigate the correlations among penetration classification system,viscosity classification system and Performance Grade classification system,ten asphalt products produced by two kinds of crude oil were used to study the linear correlations between the logarithm and double logarithm of penetration with Celsius temperature and reciprocal of absolute temperature at 15, 25 and 30 ℃, respectively,as well as the linear correlation between the slope and intercept of these linear correlations.Through the comparison of correlation coefficients of referenced literatures at home and abroad for the past 80 years,it is found that the linear relationship between the logarithm of penetration and Celsius temperature does not represent the optimal linear relationship between penetration and temperature,and the linear correlation between the logarithm of penetration and reciprocal of absolute temperature is better than that between the logarithm of penetration and Celsius temperature.The correlation coefficient between the slope and intercept in the linear equation between the logarithm of penetration and the reciprocal of absolute temperature is higher.It is found that the relationship between penetration and temperature of all asphalt in the previous studies can be expressed by one equation.
Tetrathienothiophene is an important molecular unit of organic photovoltaic materials.The tetrathienoacene⁃based small molecular semiconductors, combinating a dialkylated tetrathienoacene central core with styrene end⁃capping moieties, are synthesized through Stille coupling reactions.The molecular structure of compound has been analyzed by 1H⁃NMR spectrometry.Thermogravimetric Analysis(TGA),UV⁃visible absorption spectrum(UV⁃Vis),Fluorescence emission spectrum(PL) and Electrochemical cyclic voltammetry(CV) were used to characterized the thermal properties,optical properties and electrochemical properties of the prepared compound.The compound shows UV⁃absorption peaks at 429,453 nm,and a large red shift occurs.The EHOMO=-5.57 eV was calculated by cyclic voltammetry.
In the operation process of anion exchange membrane fuel cell,water molecules are working as the transmission medium of OH-.Therefore,hygroscopic property is one of the most important performances of anion exchange membranes,in addition to conductivity and alkali resistance stability.It is also the focus of research on the improvement of anion exchange membranes.In this paper,two series of anion exchange membranes for fuel cells based on metal organic framework (MOFs) materials were prepared, and their crystal structures and morphologies were characterized by XRD and SEM.In addition,the water content,swelling degree,swelling kinetics, and mechanical properties were tested and analyzed in detail.The results show that the water content,swelling degree, and mechanical properties of the two membranes are much different. Though the swelling kinetic behavior of the two prepared membranes follow Schott's second⁃order swelling kinetic equation,but exhibit different swelling behaviors,due to the different functions of the two component of MOFs.
The construction of C-N bond is an important research field in modern organic synthesis. For C-N bond construction methods, the amination of olefins is the most efficient way which can synthesize multi⁃site products in one⁃step. With the development of photocatalytic redox reactions, some important breakthroughs have been made in the field of amination of alkenes. Using the photocatalytic redox reaction with visible light as a green energy source, the cheap olefin compounds can be catalyzed into biologically active amine compound intermediates. This type of reaction can be widely used in synthetic chemistry, material chemistry, medicine and other fields. Therefore, it is necessary to develop photocatalytic amination of olefins. The research progress over 5 years in five areas, including olefin amidation hydrogenation reaction, olefin amination hydrogenation reaction, olefin halogenation amination reaction, olefin amination alkoxylation reaction, and olefin amination alkylation reaction, is briefly summarized.
At present, for the low permeability fractured reservoir has not formed a perfect identification method of channeling channels, the application of the evaluation index system does not conform to the actual field, the identification method has strong limitations, there are some problems such as big error in the result of recognition at small level. In order to solve these problems, the evaluation system is constructed by deepening the characteristics, mechanism and performance of interporosity flow in low permeability fractured reservoirs, and introducing the corresponding relationship of sand body and permeability of single well and small layer, the model of channeling channel identification is established by using the method of Modulus and objective mathematical analysis and subjective and objective combination weighting. The results show that the evaluation system and the recognition result are more in line with the actual situation of the mine because of the analysis of the pressure⁃sensitive effect, the effect of starting pressure gradient and the introduction of the corresponding relation of sand body for the first time, one channeling channel has not been identified, and the identified result is basically consistent with the field practice, which proves the accuracy of the established method and can provide technical support for the development and adjustment of low permeability fractured reservoirs.
A fully coupled fluid flow and geomechanics model is proposed for ECBM and CO2 underground storage with consideration of multi⁃component multi⁃process transportation in porous media to investigate the complicated geomechanical effects, and the corresponding numerical solver is developed. The effect of geomechanical effects and injection gas components on permeability and injection/production index were also investigated. The results indicate that both effective stress effect and matrix swelling/shrinkage can significantly affect porosity and permeability, but in opposite direction. Matrix swelling induced by CO2 injection can lead to about 90% loss in permeability around injector. The increasing of Young's modulus or decreasing of matrix Langmuir strain, will induce earlier CO2 breakthrough time and lower coalbed methane recovery and CO2 sequestration amount. These results can provide better methane production prediction and support high⁃efficient productivity improvement.
Yanmuxi reservoir in Tuha shows low rock cementation, strong reservoir heterogeneity and high salinity of injected water.Long term water injection development has formed an advantage channel, and the existing technology is difficult to meet the technical requirements of deep liquid flow diversion.The compatibility of inorganic gel and surfactant was studied based on the reservoir geological and fluid characteristics of the target reservoir.The results showed that nonionic surfactant (DWS) solution had good salt resistance property.Inorganic gel (calcium silicate or magnesium silicate) has little effect on DWS solution,indicating that the displacement effect during alternate injection process and profile control will not be affected too much.When surfactant emulsifies with crude oil,"Jiamin effect" can produce additional seepage resistance and liquid flow diversion effect,so the recovery rate increases greatly.In the three combinations of inorganic gels,surfactants and nitrogen,the "inorganic gel+surfactant solution+gas" alternate injection mode exhibits higher injection pressure, and superior liquid flow diverting and expanding the volume effect.
While water exists in the waxy crude oil, gelling process of this non⁃Newtonian oil⁃water two⁃phase system not only has the properties of waxy crude oil but also its own specific characteristic as decrease of temperature. Both the gelling temperature limit and change rule of gelling strength in W/O waxy crude oil emulsion system under different emulsified water fractions, were investigated by rheological measurement. The results indicate that the characteristic gelling temperature and the strength of the gels increase with the increasing of emulsified water fraction, when the temperature decreasing at a certain rate; the gelling temperature in W/O waxy crude oil emulsion system of any given emulsified water fraction rises with the increasing of cooling rate, while the gelling strength decreased with the cooling rate rising under the constant pressure. The research results of the effect of emulsified water on the gelling characteristic for waxy crude oil at cooling process provides necessary support for the development and application of flow technology for multiphase transportation.
In view of the large fluctuation of the gas turbine load in the distributed energy system, the current researches on Organic Rankine Cycle (ORC) pay more attention to the comparison of the thermal performance of the same heat absorption with the initial parameters, but rarely consider the impacts of decrease in both flue gas temperature and mass flow rate on system performance causing by the gas turbine load reduction. Based on the characteristic model constructed by HYSYS platform, optimization scheme of the variable working condition ORC working medium was studied using the narrow⁃point temperature difference in the heat exchanger as the constraint condition. Under the variable load condition of gas⁃fired power plants, the operating parameters of the maximum net output power of the system are optimized. The cycle performances of varies working fluids with different compositions were compared of the characteristics of heat rate, mass flow and AP. The net output of R152a system shows obvious advantages on the heat rate and mass flow rate, compared with that in the mixed working medium in the selected working condition range, while the condenser AP value and the system heat recovery rate exhibit opposite performance. This work provides a reference database for the studying of the binary non⁃azeotropic mixture of ORC system.
The galvanic corrosion behavior of magnesium alloy and Q235 steel system different Sc/Sa(negative / anode area ratio) in simulated solution of tank bottom water in Daxie oil depot was studied by immersion experiment, electrochemical test and micro morphology observation method. The impact of different Sc/Sa on corrosion rate was found out, which curve and expression were fitted. The results show that, the corrosion rate of magnesium alloy anode increases greatly with the increasing of Sc/Sa, but the increasing of corrosion rate for the negative part is not obvious. Based on the galvanic current image, the galvanic current fluctuates and decreases with time. When Sc/Sa is 1.0 or 2.0, the galvanic current decreases obviously, which does not decrease obviously when Sc/Sa is 0.5. The corrosion rate is calculated by galvanic current. It is demonstrated that the galvanic current, as well as the corrosion degree increases linearly with the increase of Sc/Sa.
The development of bottom water reservoir is affected by strong bottom water, low height of oil column, high viscosity of formation crude oil, and complex distribution of separation interlayer, etc. In order to solve the shortcomings of current conventional methods, such as large amount of multi⁃factor data analysis and application limitations, a new method based on BP neural network data mining algorithm for predicting recoverable reserves of horizontal wells in bottom water reservoir is proposed, and its reliability is analyzed by means of mathematical model. Aiming at the static and dynamic data of bottom⁃water reservoir, the effective hidden information is fully mined, and a data⁃driven model for the prediction of recoverable reserves of bottom⁃water reservoir is constructed on the basis of the establishment of basic data set. The results of practical application show that this method can realize the quantitative analysis of the influencing factors and the limit of technical parameters of horizontal well development in bottom⁃water reservoir, the maximum error of recoverable reserves prediction is less than 8%, and the fitting effect is good, which can be further applied to the research of production performance, development limit and well location design of horizontal Wells in bottom⁃water reservoir.
In order to solve the problem that large quantities of heavy crude oil imported from Venezuela cannot be transported by pipeline at normal temperature after arriving at shore，the transportation technology research was carried out aiming at some key problems such as the quick prediction of diluted heavy crude oil viscosity,the stability and uniformity evaluation of diluted heavy crude oil and the determination of safe blending proportions under different transportation conditions，and a set of analysis method for transporting diluted heavy crude oil at normal temperature based on indoor blending experiments and assisted by simulation calculation was established.Based on the statistical analysis of basic physical properties of 16 kinds of imported light crude oils ,the indoor experiments of blending Venezuela heavy crude oil with three kinds of typical light crude oil oils respectively were carried out,and quick reference tables of viscosity of diluted heavy crude oils with different blend proportions were established by these indoor experiment data. As long as the viscosity of light crude oil at 20 ℃ was known, the viscosity of diluted heavy crude oil at different blending proportions and temperatures can be quickly determined by using these quick reference tables.The stability and uniformity of diluted heavy crude oil were tested by let stand tests.These tests show that the diluted heavy crude oil samples still keep good stability and uniformity after 10 days of standing.Taking Ridong pipeline as an example,the process of transporting diluted Venezuela heavy crude oil was simulated by self⁃developed calculation program, and a kind of method to determine the safe blending proportions and feasible operation plans was proposed.These research results can also support the safety operation of pipeline of transporting diluted heavy crude oil at normal temperature.
