Characterization of Ni−Fe/MgO/Olivine Catalyst for Fluidized Bed Steam Gasification of Biomass

Abstract

Tar removal catalyst development is the main hurdle to improving the process of steam biomass gasification in a fluidized bed. A Ni/olivine catalyst has been previously developed to enhance the catalytic properties of calcined natural olivine and showed excellent performance and stability during biomass steam gasification in the fast internally circulating fluidized bed (FICFB) gasifier. However, the origin of its active phase was not well-understood. The present work explains the mechanism of formation and the nature of the active phase of the Ni/olivine catalyst, characterized before testing, after calcination, and after reduction by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), temperature-programmed reduction (TPR), and 57Fe Mössbauer spectroscopy. Two phenomena contribute to the formation of this active system: the formation of a NiO−MgO solid solution on the olivine surface during calcination and Ni−Fe alloys during the reduction, both of which are known to have beneficial effects on increasing carbon deposition resistance. The catalyst, resulting from subsequent calcination and reduction of the precursor after the impregnation of natural olivine with nickel nitrate, can be described as a Ni−Fe/MgO/olivine system. Its catalytic performances are confirmed in the steam reforming of methane and toluene as a tar model compound.

Catalytic biomass gasification: Simultaneous hydrocarbons steam reforming and CO2 capture in a fluidised bed reactor

“…As a matter of fact, the sample calcined at 1100 • C did not exhibit any catalytic activity, and only data related to the Ni/dolomite sample calcined at 900 • C are shown here. Some similar tendency has been previously obtained between Ni/olivine calcined at 1100 and at 1400 • C for methane and toluene reforming [24,25].…”

“…This interaction is known from previous works [24] to have beneficial effects on increasing carbon deposition resistance.…”

Supported Catalysts for CO2 Methanation: A Review

“…Before this study, the activity of calcined olivine supported nickel has been demonstrated in gasification [253] and steam reforming [254] of biomass. Olivine is a magnesium iron silicate with the general formula (Mg x Fe 1−x ) 2 SiO 4 and is a common Earth mineral.…”

Nickel supported on iron-bearing olivine for CO2 methanation

“…It contains (Mg x Fe 1Àx ) 2-SiO 4 as the main phase and small quantities of MgSiO 3 and FeO x species [35e37]. The interactions between supported NiO and (Mg x Fe 1Àx ) 2 SiO 4 might lead to NiOeMgO solid solution formation [36], which was reported to be helpful in enhancing Ni species dispersion and stability of the Ni/olivine [36,38,39]. More importantly, the olivine could be a source of Fe for the supported bimetallic NieFe catalysts.…”