Coke Formation over a Nickel Catalyst under Methane Dry Reforming Conditions:  Thermodynamic and Kinetic Models

Abstract

The CO2 reforming of methane is studied over a 20 wt % Ni/USY-zeolite, and more specifically, a thermodynamic analysis of the formation of coke is used as a basis for the kinetic modeling of coke phenomena that exist under dry reforming conditions. Two thermodynamic parameters, α and β, are compared to the equilibrium constants for the CH4 decomposition and the CO disproportionation reactions and defined to determine whether coke formation is favored. This thermodynamic analysis elucidates the significance of the CO disproportionation reaction on the amount of coke deposited over the catalyst under consideration. A kinetic model with negative overall order of one, with respect to the partial pressure of carbon monoxide, is found as the most accurate prediction of the rate of coke formation. This type of kinetics strongly suggests the requirement of three adjacent free catalyst sites for the coking reaction to proceed under allowable thermodynamic conditions.

On thermodynamic equilibrium of carbon deposition from gaseous C-H-O mixtures: updating for nanotubes

“…The kinetics of nucleation and growth of soot particles in turbulent combustion flames was also numerically analyzed (Zucca et al 2006, Chernov et al 2012. A kinetic expression for the coke formation rate on a nickel catalyst was derived by Ginsburg et al (2005) and Asai et al (2008), and evidence of a prior formation of unstable carbides was presented by Kock et al (1985). Based on an elementary kinetic description presented by Bessler et al (2007) for SOFCs, a modeling study for predicting carbon deposition from reformates was also carried out (Yurkiv et al 2013).…”

“…Magnitude of the ratio indicates whether a reaction goes to the right (V i < 1) or to the left (V i > 1) or remains at equilibrium (V i = 1). A related presentation of the conditions of carbon deposition was used in an analysis for catalyzed reforming of methane (Ginsburg et al 2005), in a SOFC fueled by sewage biogas (van Herle et al 2004), and also when the fuel cell was fed with methane (Klein et al 2007). One of the similar approaches (Tsiakaras and Demin 2001) was based on consideration of the Boudouard reaction of carbon disproportionation, Equation (21).…”

Syngas from CO2 reforming of coke oven gas: Synergetic effect of activated carbon/Ni–γAl2O3 catalyst

“…To determine the influence of the presence of CO on the process, experiments in which carbon monoxide was added to the feed were conducted, the results of which are shown in Figure 5. that the higher amount of carbon deposits formed due to carbon dioxide disproportionation leads to a decrease in the catalytic activity of the catalyst for the transformation of methane [26].…”

An Overview of Response Surface Methodology Approach to Optimization of Hydrogen and Syngas Production by Catalytic Reforming of Greenhouse Gases (CH4 and CO2)

“…Thermodynamically, the dry methane reforming reaction requires temperature >500 C to be feasible [9,10]. Hence, at a temperature >500 C, coke formation and deposition on the catalyst surface is often induced mainly by methane cracking and Boudouard reactions [11,12]. The deposited coke usually lead to deactivation of the catalyst thereby reducing the activities and stability [13][14][15].…”