Abstract
Ex situ catalytic pyrolysis of biomass using char-supported nanoparticles metals (Fe and Ni) catalyst for syngas production and tar decomposition was investigated. The characterizations of fresh Fe-Ni/char catalysts were determined by TGA, SEM–EDS, Brunauer–Emmett–Teller (BET), and XPS. The results indicated that nanoparticles metal substances (Fe and Ni) successfully impregnated into the char support and increased the thermal stability of Fe-Ni/char. Fe-Ni/char catalyst exhibited relatively superior catalytic performance, where the syngas yield and the molar ratio of H2/CO were 0.91 Nm3/kg biomass and 1.64, respectively. Moreover, the lowest tar yield (43.21 g/kg biomass) and the highest tar catalytic conversion efficiency (84.97 wt.%) were also obtained under the condition of Ni/char. Ultimate analysis and GC–MS were employed to analyze the characterization of tar, and the results indicated that the percentage of aromatic hydrocarbons appreciably increased with the significantly decrease in oxygenated compounds and nitrogenous compounds, especially in Fe-Ni/char catalyst, when compared with no catalyst pyrolysis. After catalytic pyrolysis, XPS was employed to investigate the surface valence states of the characteristic elements in the catalysts. The results indicated that the metallic oxides (MexOy) were reduced to metallic Me0 as active sites for tar catalytic pyrolysis. The main reactions pathway involved during ex situ catalytic pyrolysis of biomass based on char-supported catalyst was proposed. These findings indicate that char has the potential to be used as an efficient and low-cost catalyst toward biomass pyrolysis for syngas production and tar decomposition.
Highlights
In recent years, biomass has attracted much attention mainly because it can be used as a renewable resource to produce various high-quality chemicals, multi-functional char-based materials, and fuel products, which can reduce the burden of relying on fossil resources, and are regarded as a meaningful way toward CO2 emissions [1,2,3,4,5,6]
Tar, which generally includes aromatic compounds with one-ring to five-rings, oxygen-containing hydrocarbons, and polycyclic aromatic hydrocarbons, is one of the main problems hindering the industrialization of pyrolysis technology, because it condenses [15,16,17]
Gamliel et al [26] performed a comparison between in situ and ex situ catalytic fast pyrolysis, and the results indicated that the ex situ catalytic fast pyrolysis produced more gases yield and aromatics in the bio-oil than in situ catalytic fast pyrolysis
Summary
Biomass has attracted much attention mainly because it can be used as a renewable resource to produce various high-quality chemicals, multi-functional char-based materials, and fuel products, which can reduce the burden of relying on fossil resources, and are regarded as a meaningful way toward CO2 emissions [1,2,3,4,5,6]. Depending on the above statement, in this study, the ex situ catalytic pyrolysis system was self-designed for investigation of biomass pyrolysis Various catalysts, such as nickel-based catalysts [27], noble-metal-based catalysts [28], transition metal catalysts [29], alkali metal catalysts [30], natural catalysts [31], zeolite catalysts [32], and carbon-supported catalysts [33] have been investigated for syngas production and tar decomposition from biomass. Char, which could be obtained from solid waste pyrolysis, may have the potential to upgrade the bio-oil quality and syngas yield This cheap and green char catalyst has received more attention on catalytic pyrolysis of biomass, it is still worth it to understand the catalytic activities and mechanisms of char or char-supported catalysts on tar decomposition and syngas production. Ex situ catalytic pyrolysis of biomass over char-supported Ni and/or Fe catalysts for syngas production and tar decomposition was investigated. The objectives of this this study were to (1) synthesize char-based catalysts by impregnation with metal (Fe and/or Ni), (2) compare the catalytic activity of char-based catalysts for syngas production and tar decomposition, and (3) discuss the catalytic mechanism of biomass over char-based catalyst
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