Effects of Carbon Formation on Catalytic Performance for CO₂ Reforming with Methane on Ni/Al₂O₃ Catalyst: Comparison of Fixed-Bed with Fluidized-Bed Reactors

Abstract

The amount of carbon formed and the H2/CO molar ratio for the carbon dioxide reforming (CDR) reaction with methane were investigated on Ni/Al2O3 catalyst using a laboratory-scale fixed-bed reactor and a bench-scale fluidized-bed reactor. A significant suppression of carbon deposition in the fluidized-bed reactor compared with the fixed-bed reactor can be mainly induced from different product gas flow patterns by the continuous circulation of catalysts in oxidizing and reducing regions. This approach also enhances the gasification rate of deposited carbon in an expanded catalyst bed by increasing the amount of water adsorbed. The higher H2/CO ratio above 1.0 in the fluidized-bed reactor is also attributed to the enhanced gasification rate of deposited carbon precursors. The differences in the conversions of CH4 and CO2 and the H2/CO ratios in the two reactors are responsible for the different competitive rates of the reverse water–gas shift (RWGS) reaction, the Boudouard reaction, and the gasification of carbon precursors.

Modifying alumina with CaO or MgO in supported Ni and Ni–Co catalysts and its effect on dry reforming of CH4

“…The Raman spectra of the Al 2 O 3 and modified-Al 2 O 3 supported Ni and Ni-Co catalysts revealed two prominent bands at $1350 cm À1 (D band) and $1588 cm À1 (G band) with a shoulder at $1617 cm À1 (D* band). The D band was attributed to structural imperfections [3,20,[62][63][64][65]. The G band was attributed to the in-plane carbon-carbon stretching vibrations of pairs of sp 2 carbons due to graphitic carbon [3,20,[62][63][64][65].…”

“…The D band was attributed to structural imperfections [3,20,[62][63][64][65]. The G band was attributed to the in-plane carbon-carbon stretching vibrations of pairs of sp 2 carbons due to graphitic carbon [3,20,[62][63][64][65]. The intensity ratio of the D and G band, I D /I G , is indicative of the ratio of the amount of disordered to graphitic carbon [3,[62][63][64]20,65].…”

Combined steam and CO2 reforming of CH4 using coke oven gas on nickel-based catalyst: Effects of organic acids to nickel dispersion and activity

“…Although the CDR reaction, which can produce syngas having a stoichiometric ratio of H 2 /CO of 1.0, seems to be an effective way to utilize CO 2 directly, it is not yet well established for an industrial application due to the negative characters of sever coke formation and catalyst deactivation and so on. Therefore, steam reforming of methane (SRM), which can produce syngas with a stoichiometric molar ratio of H 2 /CO around 3, has been received much attention due to its possible industry application [6][7][8]. In addition, the combined CDR and SRM, which is called as combined steam and CO 2 reforming with CH 4 (CSCR), has been also largely investigated as an alternative reforming reaction of SRM by producing the syngas having a molar ratio of H 2 /CO around 2, which has been known to be a proper composition for the subsequent application to the Fischer-Tropch synthesis and methanol (or dimethyl ether) synthesis reaction and so on [8].…”

“…Therefore, steam reforming of methane (SRM), which can produce syngas with a stoichiometric molar ratio of H 2 /CO around 3, has been received much attention due to its possible industry application [6][7][8]. In addition, the combined CDR and SRM, which is called as combined steam and CO 2 reforming with CH 4 (CSCR), has been also largely investigated as an alternative reforming reaction of SRM by producing the syngas having a molar ratio of H 2 /CO around 2, which has been known to be a proper composition for the subsequent application to the Fischer-Tropch synthesis and methanol (or dimethyl ether) synthesis reaction and so on [8]. The CSCR reaction is composed with the following characteristic reactions such as SRM, CDR, and water-gas shift (WGS) or reverse WGS (RWGS) reaction [4][5][6][7][8][9]; …”

“…Since the CSCR reaction is composed of SRM and CDR, CSCR reaction can easily control a molar ratio of H 2 /CO by adjusting feed compositions of CH 4 /CO 2 /H 2 O, which can produce a molar ratio of H 2 /CO about 2, and may reduce coke formation through a facile gasification of deposited cokes [8]. In addition, the byproduct gases generally contain CO 2 and CH 4 with abundant hydrogen form steel industries during a refining process of iron ores, which has been known to release a larger quantity of CO 2 in a single industry by occupying about 6% of the total released anthropogenic CO 2 [10,11].…”