Abstract Syngas and hydrogen production by methane reforming of a biogas (CH4/CO2 = 2.85) using carbon dioxide was evaluated in a fixed bed reactor with a Pd-Ag membrane in the presence of a nickel catalyst (Ni 3.31% weight)/γ-Al2O3) at 773 K, 823 K, and 873 K and 1.01×105 Pa. Operation with hydrogen permeation at 873 K increased the methane conversion to approximately 83% and doubled the hydrogen yield relative to operation without hydrogen permeation. A mathematical model was formulated to predict the evolution of the effluent concentrations. Predictions based on the model showed similar evolutions for yields of hydrogen and carbon monoxide at temperatures below 823 K for operations with and without the hydrogen permeation. The hydrogen yield reached approximately 21% at 823 K and 47% at 873 K under hydrogen permeation conditions.

The liquid phase oxidation of glycerol was performed producing fine organic acids. Catalysts based on Pt, Pd and Bi supported on activated carbon were employed to perform the conversion of glycerol into organic acids at 313 K, 323 K and 333 K, under atmospheric pressure (1.0 bar), in a mechanically agitated slurry reactor (MASR). The experimental results indicated glycerol conversions of 98% with production of glyceric, tartronic and glycolic acids, and dihydroxyacetone. A yield of glyceric acid of 69.8%, and a selectivity of this compound of 70.6% were reached after 4 h of operation. Surface mechanisms were proposed and rate equations were formulated to represent the kinetic behavior of the process. Selective formation of glyceric acid was observed, and the kinetic parameter values indicated the lowest activation energy (38.5 kJ/mol) for its production reaction step, and the highest value of the adsorption equilibrium constant of the reactant glycerol (10-4 dm³/mol).

The transient behavior in a three-phase trickle bed reactor system (N2/H2O-KCl/activated carbon, 298 K, 1.01 bar) was evaluated using a dynamic tracer method. The system operated with liquid and gas phases flowing downward with constant gas flow Q G = 2.50 x 10-6 m³ s-1 and the liquid phase flow (Q L) varying in the range from 4.25x10-6 m³ s-1 to 0.50x10-6 m³ s-1. The evolution of the KCl concentration in the aqueous liquid phase was measured at the outlet of the reactor in response to the concentration increase at reactor inlet. A mathematical model was formulated and the solutions of the equations fitted to the measured tracer concentrations. The order of magnitude of the axial dispersion, liquid-solid mass transfer and partial wetting efficiency coefficients were estimated based on a numerical optimization procedure where the initial values of these coefficients, obtained by empirical correlations, were modified by comparing experimental and calculated tracer concentrations. The final optimized values of the coefficients were calculated by the minimization of a quadratic objective function. Three correlations were proposed to estimate the parameters values under the conditions employed. By comparing experimental and predicted tracer concentration step evolutions under different operating conditions the model was validated.

O principal objetivo foi a preparação e a utilização de uma argila organofílica com capacidade de promover a separação do composto fenol, encontrado em larga escala nos efluentes aquosos de indústrias petroquímicas. O trabalho consistiu no preparo de um material adsorvente, partindo de cinco tipos diferentes argilas retiradas de bacias localizadas na região nordeste do Brasil: Verde Lodo, Bofe e Chocolate, retiradas do município de Campina Grande, Boa Vista, PB; e Lagoa de Dentro e S. Jorge, do Pólo Gesseiro do Araripe, PE. As argilas in natura foram tratadas com uma solução de carbonato de sódio visando a troca dos poli-cátions existentes em suas regiões intercamadas pelo cátion sódio, em um reator de bancada, com diferentes concentrações, tempo de contato e temperatura, de acordo com um planejamento experimental 2³. Como resposta ao tratamento com carbonato de sódio, fez-se a leitura das viscosidades plásticas (cP ou mPa.s) das suspensões aquosas desse material com 4,86% em massa. Os resultados mostraram que a argila Chocolate, na melhor condição do planejamento experimental, atingiu uma viscosidade plástica de 4 mPa.s, sendo, portanto, escolhida como material adsorvente. Em seguida, este material foi submetido a um tratamento com sal quaternário de amônio em duas concentrações diferentes visando a troca catiônica de sódio por cátions amônio quaternário. Após o preparo do material adsorvente, foram realizados ensaios adsortivos de equilíbrio, sendo verificado o efeito da concentração do sal quaternário de amônio no processo adsortivo de remoção do fenol. A eficiência adsortiva, para uma relação de massa 1 g de argila organofílica e volume de solução fenólica igual a 100 mL, com concentrações iniciais entre 20 e 110 mg.L-1, foi de aproximadamente 70%.

The goal of this research was the preparation and use of organophilic clay capable of promoting the separation of phenol, found in large scale in the aqueous effluent of petrochemical industries. The studies consisted of preparing adsorbent material, based on five different types of clay taken from ponds located in the Northeast of Brazil, which are: Verde Lodo, Bofe and Chocolate, from Campina Grande, Boa Vista, PB, Brazil, and Lagoa de Dentro and S. Jorge, from Araripe's pole of plaster in PE, Brazil. In experimental scale the clays in natura were treated with a solution of sodium carbonate, to the exchange of poly-cations exist in their interlayer regions by the sodium cation, used different concentrations, temperature and time of contact, according to a experimental design 2³. In response to treatment with sodium carbonate, was reading the plastic viscosity (cP or mPa.s) of aqueous suspensions of this material with 4.86% by weight. The result showed that the Chocolate clay, in the best condition of the experimental design, has a plastic viscosity equal to 4 mPa.s and therefore was chosen as adsorbent material to continue the study. The Chocolate clay was subjected to a treatment with quaternary aµmonium salt, in two different concentrations, to cation exchange of sodium by quaternary aµmonium cations. After preparing the adsorbent material, were tested adsorptive equilibrium was verified the effect of the concentration of the quaternary aµmonium salt in the adsorptive process to removal of phenol. The adsorptive efficiency for a ratio (wt/vv) of 1 g of organophilic clay in 100 mL of phenolic solution, with initial concentrations between 20 and 110 mg.L-1, was approximately 70%.

The hydrodynamic parameters were determined for two different three-phase systems (fluidized-bed and trickle-bed) through the experimental evaluation of the dynamic residence time distribution in the gas or liquid phase. For different fluid phase flow rates the fluidized-bed system was operated with a tracer in the gas phase and in the trickle-bed with a tracer in the liquid phase. The analysis of the processes was achieved through the application of different models representing the dynamic behavior of tracers present in the gas and liquid phases with a simulation of experimental operations of the three-phase reactors. The transfer functions developed for the two systems made it possible to estimate the hydrodynamic parameters providing the gas holdup (2.22 x 10-2 to 8.42 x 10-2) and the gas phase Peclet number (54.18 to 41.20) for the fluidized-bed and the liquid holdup (0.16 to 0.25), the liquid phase Peclet number (20.37 to 4.52) and wetting efficiency (0.34 to 0.56) for the trickle-bed.

In the present work a process of catalytic wet air oxidation of lignin obtained from sugar-cane bagasse is developed with the objective of producing vanillin, syringaldehyde and p-hydroxybenzaldehyde in a continuous regime. Palladium supported on g-alumina was used as the catalyst. The reactions in the lignin degradation and aldehyde production were described by a kinetic model as a system of complex parallel and series reactions, in which pseudo-first-order steps are found. For the purpose of producing aromatic aldehydes in continuous regime, a three-phase fluidized reactor was built, and it was operated using atmospheric air as the oxidizer. The best yield in aromatic aldehydes was of 12%. The experimental results were compatible with those values obtained by the pseudo-heterogeneous axial dispersion model (PHADM) applied to the liquid phase.