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Abstract:This work studies Ni-based catalyst deactivation and regeneration processes in the presence of H 2 S under a biogas tri-reforming process for hydrogen production, which is an energy vector of great interest. 25 ppm of hydrogen sulfide were continuously added to the system in order to provoke an observable catalyst deactivation, and once fully deactivated two different regeneration processes were studied: a self-regeneration and a regeneration by low temperature oxidation. For that purpose, several Ni-based catalysts and a bimetallic Rh-Ni catalyst supported on alumina modified with CeO 2 and ZrO 2 were used as well as a commercial Katalco 57-5 for comparison purposes. Ni/Ce-Al 2 O 3 and Ni/Ce-Zr-Al 2 O 3 catalysts almost recovered their initial activity. For these catalysts, after the regeneration under oxidative conditions at low temperature, the CO 2 conversions achieved-79.5% and 86.9%, respectively-were significantly higher than the ones obtained before sulfur poisoning-66.7% and 45.2%, respectively. This effect could be attributed to the support modification with CeO 2 and the higher selectivity achieved for the Reverse Water-Gas-Shift (rWGS) reaction after catalysts deactivation. As expected, the bimetallic Rh-Ni/Ce-Al 2 O 3 catalyst showed higher resistance to deactivation and its sulfur poisoning seems to be reversible. In the case of the commercial and Ni/Zr-Al 2 O 3 catalysts, they did not recover their activity.

Here, a method is described for the synthesis of Linde type L (LTL) zeolite under microwave-assisted hydrothermal conditions, and its behavior as a support for heterogeneously catalyzed hydrogen production is detailed. Microwave heating reduces the reaction time and improves the quality of the LTL zeolite crystals in comparison to those obtained using conventional ovens. The size and morphology of zeolite can be fi nely modulated by the composition of the gel and reaction conditions (heating rate, static/dynamic conditions, aging, reaction time, etc). The physicochemical properties of the synthesized LTL zeolites make them appropriate catalyst supports for reforming reactions in which high hydrogen production yields are desired. Therefore, rhodium-and nickel-based bimetallic catalysts are prepared in order to be tested by dry and oxidative biogas reforming processes at 800 °C and atmospheric pressure for hydrogen production. For all the catalysts tested, except for the sodium-exchanged disc-shaped zeolite, hydrogen yields close to the predicted by the equilibrium conversion are reached.

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