Papers by Keyword: Reaction Rate

Abstract: The process of producing active vacancies on a hydrogen-terminated diamond surface is the most important rate-limiting stage in CH₄/H₂ and CH₄/H₂/CO₂ atmospheres. Hydrogen atom and the hydroxyl group can bone to the hydrogen atom on the diamond surface and create an active vacancy. Density functional theory (DFT) was used to study the extraction reaction by two reactants both hydrogen atom and the hydroxyl group. The result indicated that the hydroxyl group could reduce the energy required for diamond surface activation. What is more, the activation rate of the surface by the hydroxyl group was livelier at low temperature, while the activation rate of the hydrogen atom predicts on the contrary. The scanning electron microscope (SEM) and Raman spectra demonstrated that the introduction of CO₂ in the CH₄/H₂ atmosphere could reduce the deposition temperature and raise the deposition rate at low temperature.

Abstract: Microfluidic chip injection photocuring is a new method for microfluidic chip fabrication. The accuracy of microfluidic chip photocuring has an important impact on the reliability of microfluidic chip. The reaction rate of photocuring system directly affects the final quality and efficiency of microfluidic chip. The rapid reaction rate of photocuring system will lead to poor feeding effect of the reaction system. The forming accuracy is affected, and the reaction rate is too slow, which will increase the forming time and affect the forming efficiency. In this paper, the conversion rate and reaction rate of different active monomers and oligomers used in the formulation system of microfluidic chips were measured on-line. The photocuring reaction kinetics of microfluidic chips was studied, and the influence of the formulation system on the photocuring reaction was explored, which laid a foundation for optimizing the formulation of microfluidic chips.

Abstract: Hydrodynamic cavitation is expected to apply to the decomposition of chemicals and the disinfection in wastewater. In this study, the effects of upstream pressure, hole diameter and shape of orifice plate on the reaction rate of I₃^- formation were investigated. The reaction rate increases with increasing upstream pressure of orifice plate. The reaction rates have maximum values, when hole diameters of orifice plate are 2.7 mm at the upstream pressure of 0.9 MPa gauge and 3.0 mm at 0.7 MPa gauge. The reaction rate increases in the order of triangle < square < hexagon < circle shaped hole of orifice plate at the same hole area.

Abstract: The adsorption capability of Cd²⁺ with δ-MnO₂ was studied in water. The results indicated: the adsorption strongly relied on pH values. At 303K, the pH values were above 6.05, adsorption percentages of Cd²⁺ were nearly 100%. When pH values were below 2.3, adsorption rates of Cd²⁺ was below 20%. The adsorption processes was completely controlled by reaction rate and diffusion factor. The reaction rate of adsorption increased with pH values and temperatures. The adsorption activated energy of Cd²⁺ was 54.66 KJ•mol ^-1 at pH value 3.28, and it was 31.98 KJ•mol ^-1 at pH value 6.05. δ-MnO₂ may be effectively desorpted after adsorption Cd²⁺ at the pH values below 2.05. The desorption rates were about 75%.

Abstract: Double-coated Mg powders with a chloride and a polymer such as HTPB(hydroxy-terminated polybutadiene),NC(nitrocellulose),PVB(polyvinylbutyral) were fabricated by physical vapor deposition and solvent evaporation,respectively.The influence of the addition and the species of the first and second coating agents on the water reaction characteristics was investigated. The results show that both the hydrogen release during the reaction with water and the reaction rate increases distinctly with the increase of the chloride.Compared with those of the raw Mg powders and Mg powders coated with the chloride, the initial reaction temperature of the double-coated Mg powders increases to different extent.Moreover,the initial reaction temperature has an increase trend with the increase of the addition of coating agents.

Abstract: Adiabatic self-heating tests had been conducted on Dafosi coal. Analysis of the relationship of temperature and reaction rate revealed that the dependence of coal sample temperature on reaction rate can be described by a third order polynomial from 40°C up to 155°C. But at a small interval of temperature, the reaction rate still conforms to the Arrhenius kinetic model. When Arrhenius equation is used to solve the kinetic parameters of the coal spontaneous combustion, the coal temperature should be processed in segment.

Abstract: Based on the pore size distribution simulation and the derivation of the effective diffusion coefficient, a mathematical model describing the mass transfer and chemical reaction in a cylindrical gas sensitive porous medium is formulated. The reaction features and the effective utilization of the gas sensitive porous medium are analyzed under different pore size distribution. The results indicate that, an increase in porosity or in the most probably pore diameter leads to a higher mass transfer rate of the target gas, while the surface chemical reaction ability decreases. Depending on the calculated value of the Thiele number, the variation of the gas sensitivity and the effective surface utilization can be analyzed. The gas sensitivity and the effective utilization coefficient of the gas sensitive porous medium can be controlled by adjusting pore structure parameters. This will be useful for the pore structure design of gas sensor and choosing the most reasonable operation conditions.

Abstract: This study aimed to investigate the influence of NaOH concentration and temperature used for cellulose extraction from sweet-bamboo leaves on the kinetics of the extraction reaction. The NaOH concentration and the temperature used for the extraction were varied and their effect was examined. It was found that the extraction rate was accelerated by either the increase of NaOH concentration or extraction temperature. The NaOH concentration affected the reaction rate constant, k, and the activation energy, E and the order of the reaction, n. Increase of NaOH concentration enhanced the reaction to move forwards, thus reducing the k and E values of the reaction and the order of the reaction, n, was changed. The correlation of the temperature and the NaOH concentration with the k value showed that at the lower NaOH concentration, the temperature influenced on the k value more significantly. The influence of the NaOH concentration on the k value was lessened with increase of the extraction temperature.

Abstract: This study evaluated the performance of a photoreactor packed with TiO2/Quartz and ZrO2/Quartz, ZnO/Quartz, initiated by UV irradiation. The experimental results showed that the concentration of VOCs increased and the degration efficiency decreased at the same residence time. Additionally, as the residence time increased, degration efficiency increased. According to the Langmuir-Hinshelwood Model’s predicted results, the reaction rate constant (kc) was 50.1, 7.2, and 3.0 ppm min-1 for TiO2/Quartz, ZrO2/Quartz and ZnO/Quartz, respectively. In contrast, the adsorption equilibrium constant (K) was 10.0, 21.9, and 2.4 ppm-1 with the previous catalyst, individually.

Abstract: In this thesis,a series of oxidation experiments on galena are conducted under different condition such as pH is 2,temperature is 50°C and 25°C.After the experiment is completed,The rate constant,reaction order，reaction reaction rate and energy of activation are also analyzed and computed.The effects of temperature and oxidized medium on lead ore oxidation speed were studied. Under the condition of 50°C, The rate of oxidation reaction is increase when concentration is 100mg/l.The higher the concentration the more sulfuric acid ion,the easier to produce sediment of lead sulfate , so the reaction will be impeded .the reaction will be extremely slow or even can’t carry on at 25°C.