Carreadores de oxigênio a base de Ni obtidos por diferentes métodos de síntese para aplicação no processo de reforma de metano com recirculação química

Abstract

Oxygen carriers containing Ni, La, Al and Mg were synthesized successfully by microwave assisted self-combustion (N6C), microwave assisted self-combustion followed by wet impregnation (N6CI) and co-precipitation (N6CP), for their application in the production of hydrogen from methane chemical recirculation systems with CO2 capture. The materials were prepared following the general formula Nix/La2O3/Al2O3/MgO, where x = 60% by weight, the remainder being related to lanthanum (8%), aluminum (30%) and magnesium (2%) oxide. The obtained solids were characterized by X-ray diffraction), temperature programmed reduction and activity through methane reforming process with chemical recirculation. Reactivity tests were conducted at 900 ºC, where the sample was initially subjected to 8 cycles of OSC (oxygen storage capacity), and finally were carried out two reaction cycles, with each cycle containing 15 pulses of methane and 15 pulses of oxygen. The results of the characterizations indicate that the methods used were appropriate for obtaining different materials with different properties. Generally, the carriers showed excellent percentage of CH4 conversion, and high hydrogen production. The carrier N6CP exhibited the best performance to syngas production with H2/CO ratio equal to 2 on the 15th pulse, as well as being appointed as being the most resistant to deactivation by coke and higher oxidation potential, consuming 100% O2 up to the 12th pulse. In turn, the N6CI lost enough performance throughout the cycles and the N6C formed larger amount of coke, revealing the peculiarities of the synthesis methods employed. According to the reaction products formed in the reduction step with CH4, it can be concluded that the most frequent reactions were catalytic cracking, reforming and combustion