Plasma-enhanced sol-gel fabrication of CoWNiAl2O4 nanocatalyst used in oxidative conversion of greenhouse CH4/CO2 gas mixture to H2/CO

Design of nanocatalysts with promoted anti-coke ability, high catalytic activity and stable performance during oxidative conversion of CH 4 /CO 2 mixture to syngas was the purpose of this study. First, NiAl 2 O 4 , WNiAl 2 O 4 and CoWNiAl 2 O 4 nanocatalysts were fabricated using sol-gel technique. Then, plasma treatment was utilized for enhancement of CoWNiAl 2 O 4 . The fresh samples were characterized by XRD, FESEM, EDX, BET, TEM and FTIR analyses. Through the 48 h time on stream performance, methane conversion was dropped by 13% and coke deposition of 17.3% occurred during the stability test of NiAl 2 O 4 . Addition of tungsten into NiAl 2 O 4 , due to its ability in upgrading the rate of coke gasification, caused quite stable performance. In contrast, lower catalytic activity was found for WNiAl 2 O 4 as a result of active sites coverage. It was made an effort to compensate the reduction of catalytic activity by cobalt addition. Smaller particle size and uniform dispersion were achieved for cobalt promoted nanocatalysts. Therefore, catalytic activity was ascended. However, for sol-gel prepared CoWNiAl 2 O 4 high efficiency was found, but higher amount of deposited coke and deactivation were detected. The novel synthesis method i.e. hybrid sol-gel plasma alongside the cobalt and tungsten promoters caused a well-designed nanocatalyst. Promoted dispersion of active phases, finer particle size, stronger metal-support interaction and high surface area were achieved for plasma-enhanced sol-gel fabricated CoWNiAl 2 O 4 . Due to these tremendous properties, X CH4 = 92% was obtained for this sample at 850 °C. A well-maintained structure and excellent dispersion were gained after 48 h TOS, as evidenced by FESEM and EDX images of used nanocatalysts. NiAl 2 O 4 was prepared by sol-gel method and used in oxidative conversion of CH 4 /CO 2 mixture to H 2 /CO. During 48 h TOS, 13% fall of X CH4 and 17.3% coke deposition was detected for that. To achievement of awesome performance, NiAl 2 O 4 was promoted by Co, W and plasma. Plasma treatment by improving the dispersion, SMSI, finer particle size and higher surface area, promoted the coke gasification. Synergetic impact of plasma, besides the superior advantageous of Co and W, caused the outstanding outcomes of sol-gel plasma fabricated CoWNiAl 2 O 4 . Lowest amount of deposited coke (7.9%), stable yield in 48 h TOS, high activity (X CH4 =92% at 850 °C) and well-maintained structure and excellent dispersion after 48 h TOS were gained for that. • Synthesis of CoWNiAl 2 O 4 nanocatalyst by hybrid sol-gel plasma method (NC5W5A (SGP)). • Uniform particles distribution and finer average particle size (28.9 nm) for NC5W5A (SGP). • Stable conversion and H 2 /CO≈ 1 for NC5W5A (SGP) during 48 h TOS at 750ºC. • Low amount of coke deposition and deactivation for NC5W5A (SGP) after 48 h TOS. • Well-maintained structure and excellent dispersion for NC5W5A (SGP) after 48 h TOS.