No abstract

The catalytic wet air oxidation (CWAO) of lignin, obtained from sugar-cane bagasse, was evaluated through kinetic studies of the process of aromatic aldehyde production. The operations were carried out in a high pressure mechanically stirred slurry reactor, in a semibatch way, and in the presence of a palladium catalyst supported on γ-alumina in a temperature range of 373−413 K, at a total pressure of 20 bar, where the partial pressure of oxygen varied in a range of 2−10 bar. The lignin concentration was 60.00 kg/m3 in an alkaline medium of 2 mol/L of NaOH. The lignin degradation reaction and the aromatic aldehyde buildup were described by a kinetic model quantified by a complex series/parallel reaction network.

Evaluations of the methane−carbon dioxide component of a carbon reforming process over a Ni/γ-Al2O3 catalyst were performed in a fixed-bed reactor at 1023, 1073, and 1123 K. The fitting of mass balance equations, including kinetic rate laws based on a mechanism proposition of three reaction steps, was formulated following experimental indications, where each step of the reaction system was individually evaluated. The comparison between experimental and calculated concentrations of the reactants and product effluents of the fixed-bed reactor leads to the estimation of the order of magnitude of the kinetic parameters corresponding to the reaction steps. The model was validated with the syngas selectivities evolutions at 943−1146 K.

A reforming experiment was performed using a nickel catalyst, with the goal of suggesting a mechanism for the autothermal reforming of methane (ATR), under thermally neutral conditions. To bring the process to future scale-up at a fixed-bed reactor, kinetic-operational evaluations were made while taking into account the parameters of the gas phase flow and the temperature. From these evaluations, based on conversions, yields, and selectivities, it was possible to develop a novel approach to a descriptive mathematical model of the process behavior. A thermodynamic evaluation of the ATR was performed to measure the effects of operational conditions (temperature, pressure, and composition of the feed), in relation to the established limit values of the chemical equilibrium.