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Catalytic steam reforming of biomass fast pyrolysis volatiles over Ni–Co bimetallic catalysts
Laura Santamaria,Gartzen Lopez,Aitor Arregi,Maite Artetxe,Maider Amutio,Javier Bilbao,Martin Olazar 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.91 No.-
The influence of the metal selected as catalytic active phase in the two-step biomass pyrolysis-catalyticreforming strategy has been analyzed. The pyrolysis step was carried out in a conical spouted bed reactorat 500 C, whereas steam reforming was performed in afluidized bed reactor at 600 C. Ni/Al2O3,Co/Al2O3 and two bimetallic Ni-Co/Al2O3 catalysts with different metal loadings were synthesized by wetimpregnation method, and fresh and deactivated catalysts were characterized by N2 adsorption/desorption, X-ray Fluorescence (XRF), Temperature Programmed Reduction (TPR), X-Ray powderDiffraction (XRD), Temperature Programmed Oxidation (TPO), Scanning Electron Microscopy (SEM) andTransmission Electron Microscopy (TEM). Although Ni/Al2O3 and both bimetallic catalysts had similarinitial activity in terms of oxygenate conversion, (higher than 98%), the poorer metal dispersion observedin both bimetallic catalysts led to a fast decrease in conversion due to the promotion of coke formation onlarge particles. This occurred even though Ni–Co alloy formation has a positive influence by hindering theoxidation of Co0 species. The main cause for the deactivation of these catalysts is the formation of a cokewith amorphous structure. The poor initial performance of Co/Al2O3 catalyst is related to changes in theCo0 oxidation state induced by the presence of steam, which led to a fast deactivation of this catalyst.
Frictional contact analysis in a spherical roller bearing
Blanco-Lorenzo Julio,Liu Sheng,Santamaria Javier,Meehan Paul A,Vadillo Ernesto G 한국CDE학회 2023 Journal of computational design and engineering Vol.10 No.1
Numerical analyses of the roller–raceway contact have been carried out in a spherical roller bearing using frictional contact models of different complexity. The models used in the study include an implementation of Kalker’s exact contact theory named CECT (Conformal Exact Contact Theory) and detailed Finite Element models. The adequacy of the more simplified contact solutions is assessed by contrasting them with the solutions obtained with the more comprehensive models. Additionally, the use of the exact contact theory, well known in the wheel–rail application, is demonstrated in contact mechanics analyses in rolling bearings, describing relevant details of its implementation for this application. Situations with different normal loads and friction levels have been analysed, and two distinct steady equilibrium configurations of the roller have been identified.
Regenerability of a Ni catalyst in the catalytic steam reforming of biomass pyrolysis volatiles
Aitor Arregi,Gartzen Lopez,Maider Amutio,Itsaso Barbarias,Laura Santamaria,Javier Bilbao,Martin Olazar 한국공업화학회 2018 Journal of Industrial and Engineering Chemistry Vol.68 No.-
A study has been carried out of the regenerability of a commercial Ni catalyst used in the steam reforming of the volatiles from biomass pyrolysis (gases and bio-oil), determining the evolution of the reaction indices (conversion, product yields and H2 production) in successive reaction–regeneration cycles. The causes of catalyst deactivation (coke deposition and Ni sintering) have been ascertained characterizing the deactivated and regenerated catalysts by TPO, TEM, TPR and XRD. Catalyst activity is not fully recovered by coke combustion in the first cycles due to the irreversible deactivation by Ni sintering, but the catalyst reaches a pseudo-stable state beyond the fourth cycle, reproducing its behaviour in subsequent cycles.