Steam reforming of ethanol over skeletal Ni‐based catalysts: A temperature programmed desorption and kinetic study

Abstract

An investigation on reaction scheme and kinetics for ethanol steam reforming on skeletal nickel catalysts is described. Catalytic activity of skeletal nickel catalyst for low-temperature steam reforming has been studied in detail, and the reasons for its high reactivity for H 2 production are attained by probe reactions. Higher activity of water gas shift reaction and methanation contributes to the low CO selectivity. Cu and Pt addition can promote WGSR and suppress methanation, and, thus, improve H 2 production. A reaction scheme on skeletal nickel catalyst has been proposed through temperature programmed reaction spectroscopy experiments. An Eley-Rideal model is put forward for kinetic studies, which contains three surface reactions: ethanol decomposition, water gas shift reaction, and methane steam reforming reaction. The kinetics was studied at 300-400 C using a randomized algorithms method and a least-squares method to solve the differential equations and fit the experimental data; the goodness of fit obtained with this model is above 0.95. The activation energies for the ethanol decomposition, methane steam reforming, and water gas shift reaction are 187.7 kJ/ mol, 138.5 kJ/mol and 52.8 kJ/mol, respectively. Thus, ethanol decomposition was determined to be the rate determining reaction of ethanol steam reforming on skeletal nickel catalysts. V C 2013 American Institute of Chemical Engineers AIChE J, 60: [635][636][637][638][639][640][641][642][643][644] 2014

Kinetic study of methane reforming with carbon dioxide over NiCeMgAl bimodal pore catalyst

“…To develop a proper kinetic model, the following assumptions were made based on our experimental observations and information available in literature: There is only one type of active site for the adsorption of all species. As illustrated in previous studies for Ni‐based catalysts at similar conditions, methane, CO 2 and intermediates adsorb and react on the same type of active site. The reversibility of methane adsorption and dissociation is supported by the influence of H 2 addition to the feed gas. The methane dissociation generates adsorbed carbon and associated hydrogen atom, which is supposed to be at thermodynamic equilibrium. The adsorption and dissociation of carbon dioxide are considered as reversible (Eq. )…”

Impact of Water on Condensed Phase Ethanol Guerbet Reactions

“…We first suspected that low temperature ethanol steam re-forming (reaction 1) and the water gas shift reaction (reaction 2) 13, 14 were responsible for gas formation, but we observed no CO and little free H 2 in the product gas and no consumption of water produced in the Guerbet reactions. Reactions 2 and 4−6 above are highly favored thermodynamically at condensed-phase Guerbet reaction temperatures (150− 230°C), 17,18 and CO is a thermodynamically unfavorable product below 250°C.…”

Elucidation of metal and support effects during ethanol steam reforming over Ni and Rh based catalysts supported on (CeO2)-ZrO2-La2O3

“…However, the high cost of noble metals has shifted the attention to transition metals such as Ni, with various studies suggesting the latter metal as active for ESR given its effectiveness in catalysing C-C and C-O bond scissions. Ethanol adsorbed on Ni active sites can dehydrogenate towards acetaldehyde, followed by decomposition reactions for the formation of CH3 and CO species [25][26][27]. These methyl groups at lower temperatures desorb as CH4, with nickel's methanation activity also contributing to higher methane selectivities.…”