Methane decomposition kinetics and reaction rate over Ni/SiO2 nanocatalyst produced through co-precipitation cum modified Stöber method

Abstract

Co-precipitation cum modified Stöber method was adopted to produce nano-Ni/SiO2 (n-Ni/SiO2) catalyst and conducted a series of methane decomposition kinetic experiments in a fixed bed pilot plant. Methane decomposition activity of n-Ni/SiO2 catalyst was quantified by considering thermodynamic deposition of carbon at a temperature range of 550–650 °C and methane partial pressure from 0.2 to 0.8 atm. The utmost methane conversion of 18.87 mmol/gcat min was obtained at 650 °C and methane partial pressure of 0.8 atm. The findings concluded that the enhancement occurred with carbon formation rate when increasing the methane partial pressure is very much evident at higher temperature such as 650 °C. However, the intensity in methane decomposition descending tendency was declined at lower reaction temperature. The effects of methane partial pressure and reaction temperature on the specific molar carbon formation rate were also examined. The calculated reaction order and activation energy were 1.40 and 61.1 kJ mol−1, respectively. The kinetic experiments showed the existence of an optimum reaction condition to achieve the highest performance of n-Ni/SiO2 catalyst in terms of methane decomposition rate. However, carbon accumulation ceases once complete catalyst deactivation occurred at certain reaction conditions such as high temperature and lower methane partial pressure. Virgin nanocatalyst and as-produced nanocarbons were studied with BET, XRD, and TEM.