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and k 2 is directly proportional to the rate constant of the slow combustion reaction of 5-CQA, as determined by Eq. 14 . This ratio reveals that the activation energy of the investigated reaction of oxidation is close to 77046 J mol −1 . At this

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Abstract  

The activation energy values of cyclohexane dehydrogenation and hydrogenolysis on alumina supported Ni, MoOx and three NiMoOx samples of different Ni:Mo ratio have been determined. Applying these values and the activation energies determined before for thiophene hydrodesulfurization on these catalysts, the C-Cat, H-Cat and S-Cat bond strengths were calculated. The bond strengths C-Cat and S-Cat are significantly higher for the samples of higher catalytic activity [NiMo(0.35) and NiMo(0.6)] in comparison with those of the less active ones [NiMo(0.15) and Ni12]. Compensation plots between Arrhenius constants indicate equal site distribution for the three reactions.

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Kinetic data in the esterification of lactic acid with ethanol have been obtained using Preyssler acid as a catalyst. The effects of different parameters such as the alcohol:acid molar ratio, reaction temperature and catalyst concentration have been examined. The activation energy, forward and backward rate constants and equilibrium constants were calculated in the temperature of 343–358 K.

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The kinetics of the liquid-phase hydrogenation of cinnamyl alcohol over Ir/Al2O3 catalyst (d ≈ 7 nm) was investigated in toluene under mild conditions (T = 25–95 °C, hydrogen pressure = 3–8 bar and cinnamyl alcohol concentration = 0.0075–0.375 M). The kinetic results could be successfully modeled based on the assumption that the Langmuir–Hinshelwood surface reaction between competitively adsorbed cinnamyl alcohol and hydrogen is the rate determining step. The model predicts that cinnamyl alcohol requires two metallic sites to adsorb on with an adsorption constant of 1.4 M−1. The apparent activation energy of the reaction was experimentally determined to be ~26 kJ mol−1.

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Abstract  

Catalytic ozonation has recently been used as a new means of contaminant removal from water and wastewater. In this study, bone charcoal (BC), a new catalyst prepared under laboratory conditions, was used to catalyze the ozonation of humic substances (HS) in aqueous solutions. The catalytic effect of bone charcoal and the relevant parameters of this ozonation process (solution pH, temperature, scavenger effect, humic acids concentration and BC dosage) were investigated. In the catalytic ozonation experiments, the degradation kinetics was investigated. The reaction rate and the rate constant were determined. The results showed that using a BC catalyst in the ozonation of HS produced a 1.43- and 1.56-fold increase in reaction rates compared to the sole ozonation processes (SOP) under acidic and alkaline conditions, respectively. Furthermore, the applicability of heterogeneous catalytic ozonation with bone charcoal (HCOBC) to humic acid degradation was evaluated by performing comparisons with H2O2, O3, O3/H2O2 and O3/H2O2/BC processes. With the use of the Arrhenius equation, the activation energy (Ea) was calculated to be 10 kJ mol−1. The results also showed that under the different temperatures, the reaction of the catalytic ozonation of HS was defined as diffusion controlled in accordance with the activation energy. These findings suggest that the HCOBC can be applied as an efficient and feasible method for the removal of HS from water.

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Five Cu-based catalysts with different promoters (Al, Zr and Mn) were prepared by uniform coprecipitation and evaluated in a laboratory fixed bed reactor for methanol synthesis at 463–513 K and a pressure of 4 MPa. These catalysts were characterized by X-ray diffraction (XRD) and the data showed that they had similar crystal phase and copper crystallite sizes. The most active catalyst comprised fibrous particles with a ring structure. Zirconium, aluminum and manganese additives caused no evident change in the main active phase of the catalysts but gave rise to different copper crystallite sizes. The different Cu0 crystallite sizes resulted in different amounts of active sites, but the activation energies of methanol synthesis on these catalysts were all about 104 kJ/mol and turnover frequencies (TOFs) were about the same values, indicating the close relationship between methanol productivity and microstructure of Cu-based catalyst.

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Abstract  

The selective oxidation of isobutane over phosphomolybdic acid has been analyzed using a low-pressure steady-state technique. Observed products are methacrolein, 3-methyl-2-oxetanone (a lactone), acetic acid, carbon dioxide and water. These products form in two distinct fashions designated Categories 1 and 2. Category 1 is exclusively observed with methacrolein and is consistent with a Bulk-type (II) process. The lactone and acetic acid are Category 2 products and these form by the Bulk-type (I) mechanism. A kinetic analysis of the distributions shows that the activation energy for Category 1 production (methacrolein) increases with experiment number (varying from 56.9 ± 1.5 to 149 ± 4 kJ mol−1) and indicates a temperature-induced structural degradation of phosphomolybdic acid. The Category 2 products are not similarly affected and this suggests that the structural degradation is restricted to the surface of phosphomolybdic acid.

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The kinetics of the esterification of acetic acid with butanol in the presence of sulfated zirconia was studied. Several kinetic models were tested to correlate the kinetic data. The experimental data was represented by the Eley–Rideal mechanism and it is found that sulfated zirconia is suitable for this reaction since the activation energy reduced from 58.0 to 49.2 kJ/mol. The liquid phase esterification of butanol with acetic acid was carried out in a batch reactor at temperatures of 328, 333, 338 and 343 K, with an alcohol to acid molar ratio of 1. The equilibrium constants were determined in separate experiments at 328, 333, 338 and 343 K and calculated as 29.9, 29.3, 28.6 and 28.0, in order. Before these kinetic and equilibrium runs, the catalyst was prepared by impregnating zirconia with H2SO4. The prepared catalyst was characterized by thermal analysis, XRD, SEM, BET-surface area and IR analysis.

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conversion increased from 35.6 to 42.9%. The temperature dependence of the rate constant was used to calculate the activation energy of the overall reaction from the anisole conversion data. The activation energy of the overall reaction was found to be small

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BT. Activation energies for the HDS reaction were calculated from pseudo first-order rate constants and are presented in Table 4 . Arrhenius plots are presented in Fig. 2 . Activation energies for the HDS of BT were in the range of 24

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