On the basis of the review on the research progress of the novelborohydrides/amides system for hydrogen storage, the LiBH4/2LiNH2 complexsystem was selected as the object of this thesis. By means of XRD, SEM, TPD DSCanalyses and hydrogen desorption performance evaluations, the dehydrogenationreaction and the kinetic properties of the LiBH4/2LiNH2 complex system wassystematically investigated for developing the novel hydrogen storage material withhigh capacity and excellent performance. The study includes the thermodynamic andkinetic properties of the complex system in the dehydrogenation reaction and thekinetic mechanism of the dehydrogenation reaction. Furthermore, thedehydrogenation performances of the Cu- and Co-catalyzed LiBH4/2LiNH2 complexsystem were also studied and the catalysis mechanism of the Cu- and Co-catalyzedsystem was clarified.The hydrogen desorption performances and structures of LiBH4/2LiNH2complex system were systematically investigated. The results show that the post-36hmilled sample started to release hydrogen at about 190℃, and the hydrogendesorption accelerated at about 250℃. As the temperature heated up to 355℃, thehydrogen desorption finished and the total amount of hydrogen desorption was about10.8 wt% with a dehydrogenated product of Li3BN2. From SEM micrograph of thedehydrogenated sample of LiBH4/2LiNH2, the plate-like dehydrogenated productscan be distinctly seen. which suggests a 2D growth mechanism of thedehydrogenated product, namely Li3BN2. in the present study. The dehydrogenatedproduct of the LiBH4/2LiNH2 sample is composed of a large number of small thinplate-like particles with a thickness of 0.2-0.4μm. The isothermal hydrogendesorption behaviors showed that the sample achieve to full dehydrogenation in 800min at 250℃and only 250 min at 270℃. The kinetic mechamism of thedehydrogenation reaction was analyzed by using the Johnson-Mehl-Avrami （JMA）equation and a diffusion-controlled dehydrogenation kinetic mechanism wasdeduced. The high apparent activation energy （128 kJ/mol） of the sample is responsible for its high operation temperature.Then, the effects of Cu addition on the hydrogen storage performances of theLiBH4/2LiNH2 system were studied systematically. It was found that The onsettemperature for hydrogen desorption of the sample with 5wt% Cu was decreased to200℃, a～50℃reduction with respect to the undoped sample, since the startingtemperature was still at about 190℃. About 10.4 wt% of hydrogen can be releasedfrom the Cu-additive sample as it was heated up to 345℃. Differential ScanningCalorimetry （DSC） examination indicated that the melting temperature of theCu-doped sample remains unchanged, but the operating temperature for hydrogendesorption was decreased after melting. It indicates that the additive Cu facilitatedthe formation of the B-N bond and served as the nuclei sites for dehydrogenatedproducts, consequently inducing the improvement of dehydrogenation kinetics.However, the dehydrogenation temperature is still high because of the highmelting-point temperature of theα-Li3BN2H8 phase. The activation energy of thesample with Cu additive determined is about 106 kJ/mol, slightly lower than that ofthe undoped sample.The hydrogen desorption properties and mechanisms of the Co-dopedLiBH4/2LiNH2 system were further investigated. It is found that the Co-doped samplestart to dehydrogenate at 150℃and finish at about 270℃. A～85℃reduction wasattained in the starting temperature for hydrogen desorption relative to the pristinesample, indicating that Co is an effective catalyst for the dehydrogenation of theLiBH4/2LiNH2 system. XRD results revealed the presence of metallic Co before andafter dehydrogenation. Isothermal dehydrogenation showed the Co-doped samplereleased 10.4 wt% of hydrogen at 190℃within 600 min. DSC examination showedthat the melting-point temperature of the Co-doped sample was lowered to 150℃.Mechanistic analyses revealed that the introduction of metallic Co into theLiBH4/2LiNH2 system decreased the melting temperature ofαphase. catalyzed theformation of B-N bonds and facilitated nucleation and growth of the dehydrogenatedproduct. As a consequence. a lower apparent activation energy （-94.8 kJ/mol） for thesample with Co additive was obtained. This lower activation energy is responsible for the significant enhancement of the dehydrogenation kinetics. Besides, the Co-dopedsystem achieves the partial hydrogen storage and the reversible amount is about 1.4wt%.
Post about "kinetic mechanism"
Pneumatic flocculation is a special kind of flocculation process which has its own characters and advantages in polluted river water treatment. It not only be able to enhance the removal rate of the colloids and the suspended substances but also increase the dissolved oxygen in wastewater. In recent years, there’re few attention on it, so there’re no uniform understanding on control parameters of pneumatic flocculation, and the optimized parameters existed are very different. According to those problems existed in pneumatic flocculation, experiment on treatment of polluted town river water by pneumatic flocculation was conducted, and parameters of pneumatic flocculation were optimized in laboratory, besides, kinetic mechanism of pneumatic flocculation were analyzed and discussed.According to the experiment research, the removal rate of CODcr, turbidity and total phosphorus were 68.9%,93.6%and 72.4%under the optimal conditions. The optimal coagulant dose of PFAC and PAM is 40mg/L and 0.5mg/L; the inflatable effect of microporous aeration is better than perforation aeration, for the perforation aeration, perforated pipe which has aperture of 2mm has the best inflatable effect; the optimum aeration intensity(qs) of microporous aeration is that, stage of mixing is 146.3×10-3m3(air)/(m2·min), stage of flocculation is 47.3×10-3m3(air)/(m2-min), the optimum aeration intensity(qs) of perforation aeration is that, stage of mixing is 201.2×l0-3m3(air)/(m2-min), stage of flocculation is 65.1×10-3m3(air)/(m2-min); the order of factors in influencing the treatment effect(form major to minor) is:aeration intensity→dose of PFAC→modes of aeration(bublle size)→dose of PAM. further analysis of stirring effect’s representation was performed; pneumatic flocculation can remarkably increase the dissolved oxygen in wastewater, and the dissolved oxygen of the effluent can be keeped at a certain degree; the treatment effect is not good when the return sludge is initiated; analysis of the flocs’rising phenomenon indicate that, the small aeration intensity, the properties of wastewater and the microbial action is the main reason for flocs’rising phenomenon, however, if the aeration intensity and the sludge discharge time are suitable, the flocs’rising phenomenon can be avoided; the flocs of pneumatic flocculation have good settling property, it can completely precipitated in 30min.Meanwhile, further analyses had been made on the kinetics theory. Pneumatic flocculation is different from mechanical and hydraulic flocculation, because that there is microcrystal of hydrolysate on bubble surface, redundant CO2 is blown off form water and some organic compounds are oxidized. The stirring of air bubble is a special stirring method, because the stirring intensity is different at different water depth, the shallower the bigger. Based on the previous research, further analyses and improvement had been made on S.K equation, which makes the coefficient in equation more stable, a new control parameter(qs–quantity of aeration in per unit time and per unit area) had been proposed, and the new control parameter can direct practical production better. The collision, adhesion and desorption among air bubble and flocs have been analyzed. Fractal theory which develops rapidly in study of flocs’structure in recent years has been introduced simply.In this subject, the experimental and theoretical aspects of pneumatic flocculation has been deeply researched, and related parameters have been optimized, further study on the kinetic mechanism of pneumatic flocculation has been conducted, which enrich the basic theory of the pneumatic flocculation, meanwhile, All of these have made certain contributions to the pneumatic flocculation’s application in treatment of polluted town river water.
In this paper, benzyl acetate acid was produced from benzoic acid and benzyl alcohol under microwave radiation, using sodium acid sulfate, amino sulfonic acid and p-toluenesulfonic acid as catalysts. The effects of reaction temperature, the amount of catalysts, the reaction time, and the mole ratio of the raw material were compared. The results showed that the activity of p-toluenesulfonic acid was much higher than that of the amino sulfonic acid and hydrogen sulfate sodium.In addition, benzyl acetate acid was synthesized under conventional oil bath heating, using p-toluenesulfonic acid as catalyst. The effects of the reaction temperature, the amount of catalysts, the reaction time and the mole ratio of the raw material were investigated. The optimum conditions were concluded that: reaction temperature 150℃, the amount of p-toluenesulfonic acid 1.00 g, reactants benzoic acid 0.10 mol, alcohol-acid molar ratio for 4.0:1, and reaction time 140 min.Design four factors of three level orthogonal tests, p-toluene sulfonic acid as catalyst , synthesized benzyl benzoate respectively under in microwave radiation and routine oil bath heating, and the reaction process conditions were quadratic optimization, get the optimization under microwave irradiation process conditions as follows: reaction temperature 155℃, radiation time 30 min, P-toluene sulfonic acid dosage 1.20 g, reactants benzoic acid 0.10 mol, Alcohol-acid molar ratio 4.0:1, average yield can reach 94.52%. P-toluene sulfonic acid dosage and microwave radiation time have great influence on reaction yield; the optimization under conventional oil bath heating: reaction temperature 150℃, reaction time140 min, P-toluene sulfonic acid dosage 1.00 g, Alcohol-acid molar ratio 4.0:1, average yield can reach 96.37%. Alcohol-acid mole ratio has great influence on reaction yield. It turned out that: microwave can accelerated reaction, greatly shorten the reaction time, improved the reaction rate.In this paper the reaction kinetics of benzyl benzoate was discussed. In no catalyst cases, benzoic acid concentration didn’t change with the reaction time increased, almost no esterification reaction occurring; In p-toluene sulfonic acid as catalyst, discussed reaction rate constant under different temperature, compared the activation energy and exponential factor under microwave radiation and conventional oil bath heating, get the activation energy under microwave radiation is three-tenths of that under conventional oil bath heating, and the exponential factor reduced greatly. Reaction kinetics research shows, microwave can accelerate the esterification reaction, it embodies the thermal and a thermal effect of microwave.