Grafted NiO on natural olivine for dry reforming of methane

Abstract

Natural olivine is used for gasification of biomass in a fluidised bed. Characterisations by X-ray diffraction and electron microscopies (SEM and TEM) have proved the presence of a (Mg,Fe) 2 SiO 4 structure (Mg/Fe ratio: 9/1) with a rather broad distribution in elemental composition. Temperature programmed reduction has revealed equally the presence of iron oxides outside of this structure. The nature of free iron oxides can be both modified by increasing the temperature of calcination and confirmed by measurements of magnetism. The introduction of nickel oxide upon natural olivine is obtained by impregnation with a nitrate salt. The type of interaction of nickel oxide with olivine is different depending upon the preparation method and the calcination temperature. For calcination at 1100 8C, the effects of the amount of NiO and the number of impregnation have been studied. At a high temperature of calcination (1400 8C), NiO is integrated into the olivine structure and the amount of free iron increases. Integrated NiO on olivine is non-reducible, resulting in an inactive catalyst. At lower calcination temperatures grafted NiO is formed, a species which is reduced under catalytic test conditions without aggregation of particles. A single impregnation of nickel (5.5 wt% of NiO) gives a stable catalyst activated directly under reaction conditions (CH 4 þ CO 2) yielding 96% CO and 76% H 2. Catalysts with lower amounts of NiO or a double impregnation of nickel salt lead to a less stable system. Analysis reveals that no change in olivine structure nor size of nickel deposit occurs under test conditions. Equally there are no carbon deposits formed on these catalysts. A model of the evolution of each catalytic system arising from the different preparation methods is proposed. The observed deactivation of such catalysts is attributed to the increase in the amount of free iron, which favours the oxidative properties of the catalytic system.

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].…”

Demonstration and Characterization of Ni/Mg/K/AD90 Used for Pilot-Scale Conditioning of Biomass-Derived Syngas

“…The majority of these studies have been conducted on high surface area supports, which are suitable for fixed bed reactors, but are not wellsuited for operation in a fluidized bed reactor where attrition is a concern. Corella et al and other investigators [9][10][11][12][13][14][15][16][17][18][19] have examined inexpensive materials such as naturally occurring olivine and dolomite as catalysts and guard beds for tar destruction before conditioned syngas is sent to an additional reforming reactor. Dolomite and olivine have been shown to have good tar reforming activity and can extend the lifetime of downstream catalysts, but both catalysts have relatively low activity for steam reforming of light hydrocarbons (e.g.…”

“…Dolomite also shows significant levels of attrition when it is operated in a fluidized bed reactor. Studies on the incorporation of nickel into dolomite [20][21][22] and olivine [16,[23][24][25] have also been conducted in order to produce an inexpensive catalyst with improved activity for light hydrocarbon steam reforming, and potentially eliminate the need for a downstream reforming reactor. The development of the promoted nickel catalyst used in this study has been previously described [26] and it consists of nickel (Ni) for its ability to activate hydrocarbons, magnesium oxide (MgO) to stabilize nickel crystallite size and promote steam adsorption, and potassium (K) to aid in gasification reactions.…”

Temperature profiles of alumina-supported noble metal catalysts in autothermal reforming of methane

“…In addition, several studies have been conducted on the partial oxidation and reforming of methane to synthesis gas using a fluidized bed reactor [22][23][24][25][26][27][28][29][30][31][32][33][34]. In fluidized bed reactors, since the heat transfer from the exothermic region to the endothermic zone is promoted dramatically, the hot spot formation is effectively inhibited.…”