Adsorption/Desorption Behavior of Ethanol Steam Reforming Reactants and Intermediates over Supported Cobalt Catalysts

Abstract

The interactions of reactants and intermediates with the surfaces in ethanol steam reforming over Co catalysts supported on ZrO 2 and CeO 2 were investigated using Temperature Programmed Desorption, Thermogravimetric Analysis-Differential Scanning Calorimetry (TGA-DSC), in situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) and isotopic labeling techniques. Possible mechanistic steps are proposed that lead to acetaldehyde and acetone formation, steam reforming and coking. The role of the support versus active metal (i.e., Co) and the involvement of water in the reaction network are discussed.

Catalytic Hydrogen Production from Bioethanol

“…Thus, a catalyst on which water could more effectively dissociate to form surface-bound hydroxyl and hydrogen might be a potentially better catalyst for steam reforming reactions. On the Co/CeO 2 (111) surface, our computational work elucidates the formation of acetaldehyde and acetate intermediates and is consistent with extant experimental observations [133]. The present computational studies do not account for the generation of acetone, carbon monoxide, and methane, which are byproducts observed in experimental studies.…”

“…In addition, the outcomes from this kinetic analysis will benefit the reactor design which can promote mass and heat transfer during reaction. Based on the TPD and DRIFTS results reported in [133], a possible reaction pathway for ethanol steam reforming over Co-based catalysts is proposed by our laboratories in Fig.6. In Scheme 1, the reactant molecules (EtOH and water) diffuse from gas phase to the surface of the catalyst.…”

Steam reforming of ethanol over K promoted Co catalyst

“…5 shows IR spectra during ethanol-TPD over Co/␣-Al 2 O 3 and Co/1K/␣-Al 2 O 3 catalysts. Assignment of the adsorbed species was conducted based on the literature [26,[41][42][43][44][45][46][47][48][49][50][51][52]. When ethanol was adsorbed at 323 K, C-H stretching of CH 3 -and -CH 2 -(around 3000 cm −1 ), C-H bending of CH 3 -and -CH 2 -(1450 and 1380 cm −1 ), and C-C-O stretching (1120 and 1070 cm −1 ) vibrations peaks were observed.…”

“…7). Assignment of adsorbed species was conducted based on references [26,[41][42][43][44][45][46][47][48][49][50][51][52], and which was described in above section (see = 164 cm −1 ); then the monodentate acetate species ( as (COO) = 1548 cm −1 , s (COO) = 1360 cm −1 ; = 188 cm −1 ) was formed with increasing temperature. The monodentate acetate species peaks almost disappeared at 673 K because of the reforming reaction that occurred between acetate and water.…”

Kinetic and process study of ethanol steam reforming over Ni/Mg(Al)O catalysts: The initial steps

“…However, once the metal-support interface is lost due to blockage by CH x species (coke precursors), the demethanation of acetate becomes hindered, leading to the deactivation of the catalyst. Song et al [6][7][8] conducted similar experiments over Co catalyst supported on ZrO 2 and CeO 2 and proposed mechanistic steps starting with either molecular or dissociative adsorption of C 2 H 5 OH on the Co sites. The adsorbed C 2 H 5 OH molecules can decompose to form single C-species or dehydrate to C 2 H 4 .…”