The Relationship between Reaction Temperature and Carbon Deposition on Nickel Catalysts Based on Al2O3, ZrO2 or SiO2 Supports during the Biogas Dry Reforming Reaction

Abstract

The tackling of carbon deposition during the dry reforming of biogas (BDR) necessitates research of the surface of spent catalysts in an effort to obtain a better understanding of the effect that different carbon allotropes have on the deactivation mechanism and correlation of their formation with catalytic properties. The work presented herein provides a comparative assessment of catalytic stability in relation to carbon deposition and metal particle sintering on un-promoted Ni/Al2O3, Ni/ZrO2 and Ni/SiO2 catalysts for different reaction temperatures. The spent catalysts were examined using thermogravimetric analysis (TGA), Raman spectroscopy, high angle annular dark field scanning transmission electron microscopy (STEM-HAADF) and X-ray photoelectron spectroscopy (XPS). The results show that the formation and nature of carbonaceous deposits on catalytic surfaces (and thus catalytic stability) depend on the interplay of a number of crucial parameters such as metal support interaction, acidity/basicity characteristics, O2– lability and active phase particle size. When a catalytic system possesses only some of these beneficial characteristics, then competition with adverse effects may overshadow any potential benefits.

The Effect of Noble Metal (M: Ir, Pt, Pd) on M/Ce2O3-γ-Al2O3 Catalysts for Hydrogen Production via the Steam Reforming of Glycerol

“…Catalytic activation was carried out in situ (prior to catalytic testing) under a flow of high purity H 2 at 800 • C for 1 h (more details of the experimental procedure followed are given in Section 3.3 below). Figure 7 shows, for all catalysts tested herein, the influence of reaction temperature on the total conversion of C 3 H 8 O 3 (X C3H8O3 , Figure 7a), on the conversion of C 3 H 8 O 3 into gaseous products (X C3H8O3 , gaseous , Figure 7a), on the H 2 selectivity and yield (S H2 and Y H2 , respectively, Figure 7b), the selectivity to CO 2 and CO (S CO2 and S CO , Figure 7c), the selectivity to CH 4 (S CH4 , Figure 7d), and on the H 2 /CO (Figure 7e) and CO/CO 2 molar ratio ( Figure 7f); H 2 , CO 2 , CO and CH 4 were the only gaseous products identified in any significant concentrations (traces of C 2 H 4 were also identified, but not quantified), in agreement with literature reports [37,46,47,49]. It is also noted that as C 3 H 8 O 3 is thermally unstable, the extent of pyrolysis phenomena has a significant role in the GSR, for example Buffoni et al [45] reported that the thermal decomposition of glycerol could reach 30% molar at 650 • C (for a feed containing 30 wt.% glycerol) and Pompeo et al [49] 5% molar at 450 • C (for a feed containing 10 wt.% glycerol).…”

“…Moreover, Ni promotes the cleavage of C-C, O-H, and C-H bonds (in the order of O-H, -CH 2 -, C-C, -CH 3 ) [22], as well as dehydrogenation and hydrogenation [27,28]. However, despite the reporting of some very promising results [30][31][32][33][34][35], at high temperatures, Ni-based catalysts are also susceptible to carbon deposition and metal particle sintering, which unavoidably leads to their eventual deactivation [36,37].…”

Impact of small promoter amounts on coke structure in dry reforming of methane over Ni/ZrO2

“…For example, Charisiou et al report a PSD from 20 nm to 80 nm for an 8 wt% Ni/ZrO 2 catalyst characterised via STEM-HAADF. 47 The different particles observed in STEM have irregular shapes, similar to previously published literature. 48 Previous studies revealed that the nature of the support and the synthesis method have a strong impact on the observed Ni particle shapes.…”

Tuning combined steam and dry reforming of methane for “metgas” production: A thermodynamic approach and state-of-the-art catalysts

“…-Reactivity levels of Ni-La 2 O 3 -SiO 2 sample synthesized via a direct "one-pot" method during silica precipitation in absence of PEG structuring agent. [111] . Thus, on Al 2 O 3 and ZrO 2 -supported catalysts, the acidic support is proven to play a minor role in improving coke removal rather in promoting its surface accumulation since reactants are only activated on metallic sites [111] .…”