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Abstract: The mechanism for catalytic wet air oxidation (CWAO) of ammonia to N2 over Ru-Cu/C catalyst is extensively studied by altering the initial pH, reaction temperature and atmosphere. It is found that N2 formation can be from the catalytically selective oxidation of ammonia or the disproportionation reaction between NH4+ and NO2−. The initial oxidation of ammonia determines the reaction mechanism, the evolution of pH and the distribution of various nitrogen species. Over-oxidation to nitrous acid lowers the pH of the solution due to dissociation of HNO2 to H+ and NO2−. With the decrease of pH, the concentration of NH4+ is increased and rapidly reacts with NO2− to form N2. The relatively lower pH also makes some nitrites be oxidized to NO3−. Enhancing the reaction of selective oxidation of ammonia to N2 increases the selectivity to N2 while limits the pH decrease and NO3− formation, since NO2− is more dominant to HNO2 at high pH and hardly oxidized to NO3−. The reaction temperature is one key factor to determine the reaction mechanism of CWAO of ammonia.Graphical Abstarct: [ABSTRACT FROM AUTHOR]

A kinetic model has been developed for the sulfidation of NiMo/AlO hydrodesulfurization (HDS) catalyst, which quantitatively establishes a relationship between the HDS activity and sulfidation conditions. The model parameters were estimated by fitting a series of experimental thiophene HDS conversion data over the catalysts sulfurized under different operations. The results show that the developed model satisfactorily predicts the HDS conversion with a total average relative deviation of less than 4 %. Moreover, parametric studies were made to validate the accuracy of the model. The comparison results show that the proposed model is fairly effective in simulating the sulfidation process. It is expected that the model will be used to guide the sulfidation research of supported Mo-based catalysts and to optimize laboratory/pilot-plant sulfiding procedures. [ABSTRACT FROM AUTHOR]

A series of CaO/AlO base catalysts with different crystal phases is prepared via thermal treatment. The as-prepared base catalysts are tested through Baeyer-Villiger oxidation of cyclohexanone to ε-caprolactone in liquid-phase using a mixture of aqueous hydrogen peroxide and benzonitrile as oxidant. The corresponding results show that the CaO/AlO catalysts with high thermal treatment temperature (e.g. 900 °C) exhibit excellent activity as well as stability. Upon these, the catalysts are characterized by TG-DTG, XRD, N-physisorption, SEM and CO-TPD techniques. The characterization results clearly suggest that such a stable and efficient catalytic performance is beneficial from the formation of calcium aluminate phase, thus overcoming one of base catalyst application barriers, that Ca or CaO species loss (leach) from CaO-based catalysts during reactions. Correspondingly, it can be inferred that the treatment of the catalysts at different temperatures results in the diverse distribution of basic strength. Furthermore, it is also demonstrated that the suitable base strength (medium strength is good for the reaction selected in the work) plays a critically role in the improvement of catalytic performance. Finally, the effects of operation conditions on catalytic activity and product selectivity are also determined and discussed. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]