Avaliação de catalisadores Ni/Al2O3 modificados com B2O3 e Cobalto na reação de reforma a seco do metano

Abstract

Dry reforming of methane (DRM) is a synthetic route for the production of syngasfrom a binary gas mixture with greenhouse gases (CH4 and CO2). This reaction has garnered significant academic interest due to it’s similarity to the production of synthesis gas from biogas reforming, which shares the same componentes, but with varying ratios of CH4 and CO2 and with renewable origin. The main challenge regarding this topic is the rapid deactivation of catalysts, primarily caused by the high production of inorganic carbon (coke) that encapsulates the active phase particles and hinders long-term conversion. In this regard, seven catalysts were planned, prepared, and evaluated following the established mixture design. These included one nickel (Ni) catalyst used as a standard, two boron trioxide (B2O3) promoted Ni catalysts, two bimetallic Ni-Cobalt (Co) catalysts, and two B2O3-promoted bimetallic catalysts, all supported on gammaalumina. The support was synthesized using the microwave-assisted combustion method, employing urea as the fuel. The metals and non-metallic promoter were introduced by coimpregnation with insipid wetness, followed for a subsequent heat treatment at 550 °C for three hours. The catalysts were structurally characterized using X-ray diffraction (XRD), Fouriertransform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-Vis), fieldemission scanning electron microscopy (FE-SEM), and energy-dispersive X-ray spectroscopy (EDS). Catalyst activation was carried out at 700 °C for one hour under a hydrogen (H2) flow. Catalytic tests were conducted in a fixed-bed catalytic unit coupled with a gas chromatograph. The materials were tested for 12 hours at a space velocity of 96 L·g-1 ·h-1 . The formed carbon was characterized by XRD and Raman spectroscopy, which revealed lower formation of crystalline carbon with a disorder degree of 1.29 for the sample with a higher amount of B2O3. The carbon content was quantified using thermogravimetric analysis (TGA), demonstrating that the insertion of B2O3 reduced the carbon amount by up to 57.7%. The results indicate high stability, improved activity, and reduced coke deposition for the catalysts containing all three components. Statistical modeling shows a strong correlation between the varied components and catalyst performance, with boron significantly reducing coke formation and cobalt providing activity and stability in terms of sintering. The proposed special cubic predictive model demonstrates high statistical significance, as evidenced by the Fisher test with an Fcalc/Ftab ratio of 41.12.