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Abstract: In this work, an Al2O3-coated SiC foam monolith was used as the support of a Ni-based catalyst, which was applied for coupling partial oxidation and steaming reforming of methane to produce syngas or hydrogen. This monolithic catalyst showed excellent structural stability in a 900h endurance test. Its catalytic activity and stability were also excellent during the first 500h of the endurance test with a CH4 conversion (∼96%) near thermodynamic equilibrium. Subsequently, it deactivated gradually and its activity was reduced by 7% in the following 400h. This deactivation is ascribed to deposited carbon that originated from methane cracking in the upper part of the stainless steel reactor. Fresh and used catalyst samples were characterized by XRD, BET, SEM and XRF methods. The results showed that the active coating consisting of Al2O3, and the components loaded on it was partially dislodged from the SiC substrate during the reaction, but the loss of Ni loaded on the Al2O3 coating was less than the loss of Al2O3. This is ascribed to most Ni species being located on the outer surface of the monolithic support, which was more weakly corroded by the reactant flow. The shrinkage of the active coating and the sintering of nickel particles were also observed in the endurance test. Moreover, the SiC foam supported Ni-based monolithic catalyst showed a more homogeneous bed temperature distribution compared with a traditional Ni/Mg–Al spinel catalyst. [Copyright &y& Elsevier]

Abstract: The intrinsic kinetic information for the dissociation of CH4 on the fresh Ni active sites was studied by pulsing CH4 through Ni/α-Al2O3 catalyst with different Ni particles. After the elimination of the mass and heat transfer, the conversions of CH4 were controlled far below the values of the thermodynamic equilibrium in order to keep the pulse reaction in the kinetic region. The coverage degree of carbon species on Ni active site is kept less than 1 to eliminate the influence of carbon deposition on the dissociation of CH4. The plot of versus the Ni particle size exhibits a “mountain” shape. The E a and ln A for the CH4 dissociation are linearly increased with the increase in the Ni particle size, showing the compensation effect in the CH4 dissociation. This work reveals that the CH4 dissociation on fresh Ni active site of Ni particles in Ni/α-Al2O3 catalysts is a structure sensitive reaction. [Copyright &y& Elsevier]

Abstract: A Pd layer was deposited on Nafion® membrane by electroless plating in order to reduce methanol crossover. The composite membrane was characterized by using the following techniques of X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray spectrometer (EDXS) and transmission electron microscopy (TEM). Methanol crossover was determined by the electrochemical method. The experimental results indicated that Pd film was successfully deposited onto the Nafion® membrane. The methanol permeability was effectively suppressed by the Pd layer, with methanol-related current decreasing from 64mA/cm2 (J lim) to 57mA/cm2 for 1M methanol and from 267mA/cm2 to 170mA/cm2 for 5M methanol, respectively. Furthermore, by employing the novel Pd-Nafion® composite electrolyte, the performance of single fuel cell was obviously improved with a high concentration of methanol such as 5M, indicating that depositing Pd layer onto the Nafion® membrane is an effective method to suppress the methanol crossover. [Copyright &y& Elsevier]

A Cu-Zn-Al methanol catalyst combined with HZSM-5 was used for dimethyl ether (DME) synthesis from a syngas containing nitrogen, which was produced by air–partial oxidation of methane (air–POM). Air–POM occurred at 850 °C, 0.8 MPa, CH4/air/H2O/CO2 ratio of 1/2.4/0.8/0.4 over a Ni-based catalyst modified by magnesia and lanthanum oxide with 96% CH4 conversion and constantly gave syngas with a H2/CO ratio of 2/1 during a period of 450 h. The obtained N2-containing syngas was used directly for DME synthesis. About 90% CO per-pass conversion, 78% DME selectivity and 70% DME yield could be achieved during 450 h stability testing under the pressure of 5.0 MPa, the temperature of 240 °C and the space velocity of 1000 h−1. [Copyright &y& Elsevier]