Uso alternativo de resíduo agroindustrial, bagaço de cana, na síntese de catalisadores pré-dimensionados para obtenção de carbono e hidrogênio via decomposição do metano

Abstract

Brazil is the world's largest sugarcane producer, generating up to 0.28 tons of bagasse for each ton processed. This bagasse is a promising source of lignocellulosic biomass, with an estimated discard of 167.9 million tons. However, it is estimated that 10 % of the discarded bagasse is not used for energy generation by mills. This work aims to valorize this residue, using it as a raw material for the manufacture of a pre-molded model used for the production of biomorphic alumina (Al2O3) ceramics by the replica method. Pre-sized ceramic materials were synthesized using sugarcane bagasse, followed by wet impregnation with 3 mass ratios of Ni: 5 % (5Ni/DrySCB_Al2O3-pd), 10 % (10Ni/DrySCB_Al2O3-pd) and 20 % (20Ni/DrySCB_Al2O3- pd). For comparison, powdered catalysts with 5 % Ni (w/w), with and without sugarcane bagasse, were synthesized in a single step: 5Ni/DryBCA_Al2O3-p and 5Ni/Al2O3-p, respectively. The catalysts were characterized by energy dispersive X-ray fluorescence spectrometry (EDX), thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), N2 physisorption at 77 K and H2 temperature-programmed reduction (TPR-H2). The catalysts were tested for the production of ordered carbon and hydrogen via methane catalytic decomposition (DCM) at 500 °C for 30 minutes. The formed carbon was characterized by TGA and transmission electron microscopy (TEM). The results indicated that the in situ synthesis of 5 % powdered catalysts resulted in the formation of difficult-to-reduce nickel species (TPR). The anchoring of NiO on the pre-sized materials allowed the easy reduction of nickel species supported on alumina. The presence of mesoporosity in the powdered catalysts was confirmed by N2 adsorption and desorption at 77 K. The pre-sized catalysts showed a low surface area due to ceramic sintering. Pre-sized and powdered catalysts showed catalytic activity when reduced at different temperatures: 600 °C and 800 °C, respectively. Among the studied catalysts, the 10Ni/DrySCB_Al2O3-pd catalyst showed the highest catalytic activity, 45 %, followed by 20Ni/DrySCB_Al2O3-pd with 44 %. Reduced at 800 °C, the synthesized powdered catalysts exhibited catalytic activity with 25 % and 4 % yield for the 5Ni/Al2O3-p and 5Ni/DrySCB_Al2O3-p catalysts, respectively. The carbonaceous materials obtained for both catalyst morphologies, pre-sized and powdered, are of the carbon nanotube type.