Comparative Study on Steam Reforming of Single- and Multicomponent Model Compounds of Biomass Fermentation for Producing Biohydrogen over Mesoporous Ni/MgO Catalyst

Abstract

Steam reforming (SR) of single model molecules (acetone, butanol, and ethanol) and a specific mixture (butanol/acetone/ethanol = 6/3/1, mass ratio) assumed as a model of biobutanol raw mixture has been researched over mesoporous Ni x /MgO catalysts (x represented nickel mole percent in Ni–Mg) at 673–873 K. The result showed reactant conversion at lower temperatures allowed ranking the three single-molecule compounds as the function of SR activity as follows: ethanol > acetone > butanol. The catalytic performance of mesoporous Ni0.12/MgO catalyst with lower Ni component containing enough active sites outperformed that of mesoporous Ni0.16/MgO catalyst which was more inclined to sinter in all SR tests of single-component compounds except at 673 K. On the contrary, the catalytic behavior of Ni0.16/MgO (richer in nickel) was superior to that of Ni0.12/MgO catalyst in SR of multicomponent compounds. Moreover, in acetone–butanol–ethanol steam reforming (ABESR), SR of ethanol suffered competition from acetone and butanol, suppressing ethanol molecule access to the limited active sites of the catalyst. As a consequence, the conversion of ethanol in SR of multicomponent compounds decreased compared to that in SR of pure ethanol.

Sol-gel synthesis of nanocrystalline MgO and its application as support in Ni/MgO catalysts for ethanol steam reforming

“…S6), confirming the lack of NiO [45,54], in agreement with the XAS results. The main reduction peak centered at 670 °C (Region 2) suggested that the nickel atoms were located on the surface or in subsurface layers associated with MgO in a nonhomogeneous solid solution [45,54]. In Region 3, after 900 °C, a small H 2 consumption signal indicated the presence of some nickel atoms in the bulk material, associated with MgO in a solid solution.…”

“…The Ni 01 P0 sample showed no reduction below 400 °C (Region 1, Fig. S6), confirming the lack of NiO [45,54], in agreement with the XAS results. The main reduction peak centered at 670 °C (Region 2) suggested that the nickel atoms were located on the surface or in subsurface layers associated with MgO in a nonhomogeneous solid solution [45,54].…”

“…In Region 3, after 900 °C, a small H 2 consumption signal indicated the presence of some nickel atoms in the bulk material, associated with MgO in a solid solution. For Ni 10 P0, the H 2 consumption evidenced above 200 °C suggested the presence of NiO, with the highest peak in Region 1 being associated with nickel on the surface or in subsurface layers [45,54]. For the samples prepared with the surfactant, NiO reduction was also observed at 450 and 430 °C for Ni 10 P1 and Ni 10 P2, respectively.…”

“…For the samples prepared with the surfactant, NiO reduction was also observed at 450 and 430 °C for Ni 10 P1 and Ni 10 P2, respectively. However, most of the nickel atoms were in the form of Ni-MgO solid solution, being reduced above 700 °C for both samples [45,54]. The reducibility of the samples also revealed the effects related to dispersion of nickel in the support (Table 3).…”

Appraisal of Ni Species Supported on Porous MgO during Ethanol Steam Reforming by XAS

“…The nickel atoms were in the form of NiMgO solid solution, being reduced above 700 °C for both samples. [12,47] For Ni 10 MgO, the nickel was completely reduced, while for the sample Ni 10 MgO-P123 prepared the nickel atoms were partially reduced. The constant consumption of H 2 in Region 3 (Figure S7), with peaks at different temperatures, indicated that various Ni species were formed because of the diffusion of nickel into the support, from the outermost layer to the subsurface layer, and then to the inner lattice.…”