Combustion vs. hybrid sol-gel-plasma surface design of coke-resistant Co-promoted Ni-spinel nanocatalyst used in combined reforming of CH4/CO2/O2 for hydrogen production

Abstract

In this study, Co promoted NiAl2O4 nanocatalysts were fabricated via combustion, sol-gel and hybrid sol-gel plasma methods. The prepared samples were characterized by XRD, FESEM, EDX, BET, TPR and FTIR analysis. Catalytic performance of the samples was tested in combined reforming of CH4/CO2/O2. Based on the XRD patterns, in the case of sol-gel based nanocatalysts, especially the plasma treated one, lower grown up rate of the prone plane to coke formation, exacerbated amorphous behavior and smaller crystal size was obtained. Moreover, based on the FESEM and EDX analysis, the above noted samples illustrated more uniform dispersion and finer particle size. The average particle size of the plasma utilized sample was 14.7 nm, and 94.5% of the particles were less than 20 nm. Additionally, based on the BET and TPR analysis, the noted sample exhibited the largest surface area (261 m2/g), high reducibility and strongest metal-support interaction. Moreover, the optimum reaction condition were found at GHSV = 24 l/gcat.h and CH4/CO2 = 1 and also, feed composition of CH4/CO2/O2 = 1/1/0.08. Sol-gel-plasma nanocatalyst demonstrated the best catalytic activity among the prepared samples (XCH4 at 850 °C was 96.5%). Furthermore, the results of the stability tests (during 2880 min and at 750 °C) caused deactivation in all the nanocatalysts but the sol-gel-plasma catalyst was more stable. The EDX and TG-DTG results demonstrated that the more homogeneous distribution and the lowest amount of coke deposition were obtained for the plasma treated nanocatalyst. Thus, we can conclude that sol-gel-plasma is a proper method for fabricating nanocatalysts in this process. It seems that due to the promoted catalytic performance and excellent characterizations, the sol-gel-plasma fabricated sample is a promising nanocatalyst for combined reforming of CH4/CO2/O2 to syngas.