Optimization of nano-sized Ni/MgAl₂O₄ catalyst synthesis by the surfactant-assisted deposition precipitation method for steam pre-reforming of natural gas

Abstract

In this work, steam pre-reforming of natural gas over magnesium aluminate-supported nickel catalysts (Ni/MgAl2O4) was studied.

Synergy Effects of Cobalt Oxides on Ni/Co-Embedded Al2O3 for Hydrogen-Rich Syngas Production by Steam Reforming of Propane

“…The optimal NCA(1) and NCA(2) showed the moderate propane conversions of 72.6%-78.1% with smaller deactivation rates of 0.27%-0.31%/h while the NCA(4) showed the lowest conversion (49.5%) due to the small amount of active cobalt metal content with its less synergetic effects, which was confirmed by TPR analysis of the CA supports ( Figure 2). However, the specific rates, defined as [converted mols of C3H8 divided by the moles of Ni and Co metals per hour], revealed the lower rate of 0.96 on the NCA(0.5) (largest metal content) with larger metal aggregates with smaller active sites [20] and higher rate of 1.37 on the…”

“…The optimal NCA(1) and NCA(2) showed the moderate propane conversions of 72.6-78.1% with smaller deactivation rates of 0.27-0.31%/h while the NCA(4) showed the lowest conversion (49.5%) due to the small amount of active cobalt metal content with its less synergetic effects, which was confirmed by TPR analysis of the CA supports ( Figure 2). However, the specific rates, defined as [converted mols of C 3 H 8 divided by the moles of Ni and Co metals per hour], revealed the lower rate of 0.96 on the NCA(0.5) (largest metal content) with larger metal aggregates with smaller active sites [20] and higher rate of 1.37 on the NCA(2) even though the metal particles on the NCA(2) were aggregated during the SRP reaction. This suggests that the Ni and Co metals have some additional synergy effects through the proper distributions of the active metallic Co nanoparticles on the NCA surfaces as well as optimal formations of the thermally stable spinel CoAl 2 O 4 and NiAl 2 O 3 phases on the bulk CA(2) support [12,32,33,37], as explained in the following section.…”

“…Moreover, the facile aggregations of Ni metals, which lead to their transformations to the less active solid-solutions such as nickel aluminates, induce lower stability of the Ni-based catalysts [12,13]. The Ni-based reforming catalysts can be modified to lessen these problems by following general methodologies: to keep the small sizes of nickel nanoparticles [14][15][16][17] for better dispersion and less aggregation, to modify the supports via addition of alkali metals, lanthanides and rare earth metals [5,[18][19][20][21][22], to decrease carbon deposition with a help of basicity of those promoters and to add a small amount of noble metals such as Ru and Rh to promote the in-situ reducibility of the Ni species through various synthetic methods [9,23]. Interestingly, compared to the monometallic Ni or Co-based catalysts, bimetallic catalysts using Ni and Co species simultaneously were reported to enhance the catalytic performances as well as produce less coke formations in various reforming processes [12,[24][25][26].…”