The effect of alkali metal modification on g-C ₃N ₄ photocatalyst was systematically studied. The density functional theory is used to explain the microscopic mechanism of different alkali metal modification on improving photocatalytic activity from the various angles of geometry and electronic structure. The results show that the binding energies of alkali metals and g-C ₃N ₄ become weaker and weaker with the increase of the number of extra-nuclear electronic layers of Li, Na, K and Rb atoms, and the influence on the structure of g-C ₃N ₄ is weaker and weaker. The electronic structure analysis shows that Li, Na, and K atoms have an activation effect on g-C ₃N ₄, and Rb atoms have a passivation effect on the surface of g-C ₃N ₄. At the same time, the adsorption of N ₂ molecules on M-g-C ₃N ₄ (M=Li, Na, K, Rb) is simulated, and the interaction mechanism between N ₂ molecules and alkali metals is understood. By analyzing the adsorption energy, structural parameters and electronic properties of N ₂ adsorption, it is found that the influence of Li and Na atoms on N ₂ adsorption is greater. The N—N bond of N ₂ is elongated, and the K and Rb atoms have little effect on N ₂. Alkali metal modified g-C ₃N ₄ is more beneficial for the adsorption of N ₂ molecules than pure g-C ₃N ₄, but as the atomic radius of the alkali metal increases, the adsorption capacity becomes weaker and weaker, and the electron transfer becomes less and less. That is to say, the ability of activating N ₂ molecule decreases in the order of Li, Na, K and Rb.

The three dimensional model of the pipe leakage in the open ground was established and the grid refinement was made to aim at the highspeed leak areas. Using CFD commercial software FLUENT 6.3 for gas pipeline leakage process was simulated. The different wind speed, the influence of the initial velocity and leak mouth shapes (round and diamond) under the condition of leak were examined. The numerical simulation results showed that the wind speed had a great influence on jet angle on gas leak. The diffusion range increased with the diffusion height. The initial velocity had a great influence on jet height. The diffusion height increased with the initial velocity increasing. The wider range of hydrogen sulfide leak was circle leak mouth. The simulation results had certain significance for long distance natural gas pipeline leakage diffusion laws awareness and accident prevention.

The heavy oil electric heat pipe tracing twodimensional unsteady model was established to analyze the influence and the laws of heavy oil pipeline safety shutdown time under the thickness of pipe insulation, the number of heating pipes and location parameters. The results show that in the case of a single tube with heat, when the pipe thickness was respectively 60, 70 mm, and 80 mm, corresponding security shutdown time was about 26, 30 h, and 34 h| in the case of double pipes heating, the change of the angle between the two tubes had the smaller impact on the safety shutdown time, and the safety shutdown time was about 36 h.

Using large pore γ-Al2O3 prepared by acid precipitation, the Ni2P(25%)/γ-Al2O3 catalyst was prepared as the support by the impregnation method. The test results of XRD, BET and mercury porosimetry show that the large pore γ-Al2O3 has preferable surface area and pore structure. After in-situ reduction，the effects of preparation conditions and reaction conditions on dehydrocracking activity of the catalyst were studied in a fixed-bed down-flow reactor with the diesel as the material. The results show that desulfurization degree of 98.2% would be attained under the optimum condition as follows: synthesis temperature of 80 ℃, pH of 8，reaction temperature of 360 ℃，reaction pressure of 4.0 MPa，liquid hourly space velocity of 1.0 h-1 and volume ratio of hydrogen to cyclohexane of 500∶1.