Increase in the H2 Yield Sustainability in APR of Biomass Derivates By Reduction of Pt Loading in Pt-Ni-Co Catalysts
Conventional generation of H2 is by reforming naphtha or methane (HC), non-renewable raw materials, which have high cost and high environmental impact. An alternative to cover the deficit is to increase H2 production from renewable resources derived from digestion of waste lignocellulosic biomass (CHO). The incorporation of biomass in the Refinery contributes to its transformation into Bio refinery, future target for the generation of Biofuels.
The conversion method to transform CHO derived from biomass into H2 is the catalytic reforming. By its higher thermal sensitivity and water solubility, CHO reforming is performed at lower temperatures than HC and in aqueous phase (APR). The catalysts used in APR are multimetallic Pt based and must have high loads and dispersions of the active metal.
Hydrolysis products of glucose such as alcohols can be transformed into H2 with different performance on the same catalyst. As still it has not found a catalyst suitable properties and acceptable cost for scaling. In this work we have studied the behavior of Pt catalysts with the addition of Ni and Co supported on alumina, in APR of different  alcohols. The objective of this work is increase the sustainability of this process to find the most selective to H2 and stable catalyst modifying the metal charge, using it in APR of aqueous solutions of ethylene glycol, glycerol and sorbitol. Two supported metal catalysts were prepared: a reference one with 1% Pt and a trimetallic Pt-Ni-Co. The support was γ-Al2O3 Sasol, thermally stabilized (Vp = 1.48 cm3 / g, SG = 204 m2 / g), ground to 35-80 mesh. To determine the appropriate ratio of Ni and Co to maximize hydrogen performance and reduce CH4 selectivity, different bimetallic catalysts were prepared varying the Ni:Co ratio, with a total metal loading of 6%.
The metallic phase was characterized by ICP and CO chemisorption. The dehydrogenation capacity was measured with DHC. The APR experiments were performed with 10 wt% alcohols in aqueous solutions, with 0.5 g catalyst reduced in situ in H2 1 h at 500ºC. The catalyst deactivation by coke deposition was studied by temperature programmed oxidation (TPO).
The good yield to H2 of Pt can be replaced by the Ni addition. The Ni is a high productor of H2 and CH4, which decreases the selectivity. Co helps maintain low levels of coke and methane, which is a good additive to compensate for the high activity to undesirable reactions of Ni and promote stability. The catalyst Pt(0.5)Ni(1.5)Co(4.5)/Al2O3 with 0.5 wt% Pt, 1.5 wt% Ni and 4.5 wt% Co, shows a suitable yield and selectivity to H2. At higher molecular weight of the alcohol feeded, less catalyst stability.