Effect of Organic Nickel Precursor on the Reduction Performance and Hydrogenation Activity of Ni/Al2O3 Catalysts

Optimization of Synthesis Conditions of Ni/SBA-15 Catalysts: Confined Nanoparticles and Improved Stability in Dry Reforming of Methane

Despite its economic and environmental advantages, the dry reforming of methane using supported Ni-based catalysts remains challenging due to problems of metal particle sintering and carbon deposition, which lead to loss in catalytic activity. In this study, different silica supports, containing 5 wt% nickel, were prepared and characterized by N2 sorption, XRD, TPR, and TEM/SEM, in addition to Raman and TGA/MS for the spent catalysts. Different synthesis conditions were thus varied, like nickel deposition method, nature of nickel precursor salt, conditions for thermal activation, and nature of support. The results showed that enhanced metal dispersion, good confinement, and efficient stabilization of the active phase inside the pores can be achieved by using a well-structured mesoporous support. Moreover, it was demonstrated that carbon resistance can be improved when small nickel particles are well confined inside the pores. The strategies that affect the final dispersion of nickel particles, their consequent confinement inside (or deposition outside) the mesopores and the resulting catalytic activity and stability include mainly the application of hydrothermal treatment to the support, the variation of the nature of nickel precursor salt, and the conditions for thermal activation. General guidelines for the preparation of suitable Ni-based catalysts highly active and stable for dry reforming of methane (DRM) are thus presented in this work.

Well-dispersed nickel nanoparticles on the external and internal surfaces of SBA-15 for hydrocracking of pyrolyzed α-cellulose

Catalysts comprising nickel supported on SBA-15 were prepared by wet impregnation and co-impregnation methods. Wet impregnation was performed by directly dispersing an Ni(NO₃)₂·6H₂O aqueous solution into SBA-15, whereas in co-impregnation, ethylene glycol (EG) was added to nickel nitrate aqueous solution prior to dispersion into SBA-15. After drying and calcination, NiO/SBA-15w and NiO/SBA-15c were produced. Later, after the reduction process, Ni/SBA-15w and Ni/SBA-15c were obtained. The prepared catalysts were evaluated for the hydrocracking of pyrolyzed α-cellulose. The TEM images revealed that the catalysts prepared by wet impregnation showed inhomogeneous distribution of nickel loading, whereas catalysts prepared by co-impregnation using EG exhibited homogeneous distribution and formed no nickel aggregates. During hydrocracking of pyrolyzed α-cellulose, Ni/SBA-15c with total acidity, nickel loading, particle size, and specific surface area of 7.27 m mol g⁻¹, 5.20 wt%, 3.17 nm, and 310.0 m² g⁻¹, respectively, exhibited the best catalytic performance compared to other prepared catalysts with 67.35 wt% conversion of liquid product with maximum selectivity in producing 13.09 wt% of 3-methyl-pentane. Moreover, Ni/SBA-15w with total acidity, nickel loading, particle size, and specific surface area of 10.87 m mol g⁻¹, 8.15 wt%, 7.01 nm, and 628.0 m² g⁻¹, respectively, produced 69.89 wt% liquid product without hydrocarbons. Study of selectivity towards the formation of liquid hydrocarbons was carried out via double step hydrocracking using Ni/SBA-15w, and 18.55 wt% of n-hexane was produced in the liquid product.

Ni/SBA-15c catalyst showed excellent catalytic activity, resistance towards coke formation, and selective production of 3-methyl-pentane in the hydrocracking of pyrolyzed α-cellulose.