Characterization and evaluation of Ni/SiO2 catalysts for hydrogen production and tar reduction from catalytic steam pyrolysis-reforming of refuse derived fuel

Abstract

A series of Ni/SiO 2 catalysts have been prepared and investigated for their suitability for hydrogen production and tar reduction in a two-stage pyrolysis-reforming system, using refuse derived fuel (RDF) as the raw material. Experiments were conducted at a pyrolysis temperature of 600 ºC, and a reforming temperature of 800 ºC. The product gases were analysed by gas chromatography (GC) and the condensed fraction was collected and quantified using gas chromatography-mass spectrometry (GC-MS). The effects of the catalyst preparation method, nickel content and the addition of metal promoters (Ce, Mg, Al), were investigated. Catalysts were characterised using BET surface area analysis, temperature programmed oxidation (TPO), and scanning electron microscopy (SEM). The TPO and SEM analysis of the reacted catalysts showed that amorphous type carbons tended to be deposited over the Ni/SiO 2 catalysts prepared by impregnation, while filamentous type carbons were favoured with the sol-gel prepared catalysts. The influence of catalyst promoters (Ce, Mg, Al) added to the Ni/SiO 2 catalyst prepared by the sol-gel method was found not to be significant, as the H 2 production was not increased and the tar formation was not reduced with the metaladded catalyst. The highest H 2 concentration of 57.9 vol.% and lower tar amount produced of 0.24 mg tar /g RDF ; were obtained using the 20 wt.% Ni/SiO 2 catalyst prepared by sol-gel. On the other hand a low catalytic activity for H 2 production and higher tar produced were found for the impregnated series of catalysts, which might be due to the smaller surface area, pore size and due to the formation of amorphous carbons on the catalyst surface. Alkenes and alcohol functional groups were mainly found in the analysed tar samples, with major concentrations of styrene, phenol, indene, cresols, naphthalene, fluorene, and phenanthrene.

Catalyst Deactivation and Regeneration Processes in Biogas Tri-Reforming Process. The Effect of Hydrogen Sulfide Addition

“…From Figure 6 and the results compiled in Table 3 it can be seen that in general, very low weight losses were measured. Focusing on the left of Figure 6, there are negative peaks at low temperature, until 150 °C, attributed to the evaporation of water [31], specially detected for the Rh-Ni/Ce-Al2O3 and Ni/Zr-Al2O3 samples. Then, at increasing temperatures, these samples gain weight due to the oxidation at low temperature of the reduced Rh and Ni surface species.…”

Catalytic Pyrolysis/Gasification of Refuse Derived Fuel for Hydrogen Production and Tar Reduction: Influence of Nickel to Citric Acid Ratio Using Ni/SiO2 Catalysts

“…Also the high catalytic activity for tar cracking is observed by using the Ni/SiO 2 catalysts, compared with the blank experiment carried out with the sand bed, under the same experimental conditions. Different major tar compounds such as styrene, phenol, naphthalene and phenanthrene, have been identified in tars from the catalytic steam reforming of RDF and biomass [22,38,40,41]. The tar Class 2 includes heterocyclic aromatic compounds; within this group the most notable compound was phenol which showed the highest concentration ranging from 62 up to 613 µg phenol /g RDF (Table 4).…”

“…Researchers have grouped tar compounds into five classes, based on the molecular weight and characteristics of the identified compounds, as shown in Table 5 [38,39]. All the identified tar compounds in this work were grouped from Class 2 to Class 5; tar Class 1 is not included on Table 5 as it is always referred to as non-GC detectable compounds.…”

Influence of Ni/SiO2 catalyst preparation methods on hydrogen production from the pyrolysis/reforming of refuse derived fuel

“…The Ni/SiO 2 catalysts were tested under the same pyrolysis/reforming conditions, using RDF as raw material; with a catalyst:RDF ratio of 1:2. The experimental details have been described elsewhere [20][21][22]; however a brief description is as follows. A two-stage pyrolysis/reforming reactor was used; the pyrolysis temperature was set at 600 ºC whereas the reforming stage was carried out at 800 ºC.…”