Methane steam reforming catalysts development and coating over structured supports

Resumen

Hydrogen is a clean energy carrier which coupled with fuel cells can achieve high efficiencies in electricity generation. The modular characteristic of fuel cells would require compact hydrogen generators, for which the macro-scale reformers are not suitable. The compactness of the reformers can be achieved using metallic structured supports. A thin layer of well-developed conventional catalyst coating is adhered to the support using washcoating techniques. Lower pressure drops and higher overall productivities per unit volume are attained. In this work two methane reforming Ni-based catalysts (Ni Al2O3 and Ni MgO) have been prepared, characterized and washcoated on different FeCrAl structured supports: microchanneled plates and monoliths. Finally, the original catalysts and the different coatings prepared have been activity tested in different reactors. In a first stage, the Ni based catalysts have been prepared (using a wet impregnation technique) and characterized (with different techniques: XRD, XPS, N2 physisorption, LPSA and SEM). In the second stage, a pre-treatment to the FeCrAl metallic support has been developed. Metallic supports have been pre-annealed and then pre-oxidized to produce an alumina layer that protects the base metal against high temperature oxidation and which promotes the adhesion between the base metal and the catalyst coatings. In the third stage, the catalyst slurries have been prepared and characterized controlling some parameters (as the solids content and the milling time), to get catalyst coatings with specific properties (as apparent density and catalyst particle size). Once this parameters were controlled, different series of pre-oxidized FeCrAl structured supports (microchanneled foils and monoliths) have been catalyst coated. In the last stage, each Ni-based catalyst and each structured support catalyst coated series have been tested as different reaction systems: as a stack of catalyst coated microchanneled foils, as a bed of catalyst particles and as a catalyst coated monolith. The best results among all have been found with a Ni MgO coated monolith with the catalyst reduced to the nanoscale size and tested under a steam to carbon ratio of 1.5 and at a temperature of 700 ºC.