Methanol Reforming over Cobalt Catalysts Prepared from Fumarate Precursors: TPD Investigation

Eftichia Papadopoulou,Theophilos Ioannides

doi:10.3390/catal6030033

Abstract

Temperature-programmed desorption (TPD) was employed to investigate adsorption characteristics of CH3OH, H2O, H2, CO2 and CO on cobalt-manganese oxide catalysts prepared through mixed Co-Mn fumarate precursors either by pyrolysis or oxidation and oxidation/reduction pretreatment. Pyrolysis temperature and Co/Mn ratio were the variable synthesis parameters. Adsorption of methanol, water and CO2 was carried out at room temperature. Adsorption of H2 and H2O was carried out at 25 and 300 °C. Adsorption of CO was carried out at 25 and 150 °C. The goal of the work was to gain insight on the observed differences in the performance of the aforementioned catalysts in methanol steam reforming. TPD results indicated that activity differences are mostly related to variation in the number density of active sites, which are able to adsorb and decompose methanol.

Highlights

Mixed cobalt-manganese fumarate salts are useful precursors leading to catalysts with different structure depending on the type of surrounding atmosphere during activation [1]
Activation in air leads to burn-off of the fumarate group and concomitant formation of mixed Cox Mn1 ́x Oy spinel oxides, while activation in inert gas leads to pyrolysis of the fumarate group and formation of species with lower oxidation state, such as metallic cobalt, mixed oxides of Co2+ and Mn2+ and residual carbon
Combination of in-situ XRD, H2 -TPD profile of CoMn11AFc500 (TPR) and methanol-TPR has shown that catalysts produced by pyrolysis are almost fully reduced [1]

Summary

Introduction

Mixed cobalt-manganese fumarate salts are useful precursors leading to catalysts with different structure depending on the type of surrounding atmosphere during activation [1]. Catalysts derived from pyrolysis do not need prereduction and are more active than those with an initial spinel structure in the reaction of steam reforming of ethanol or methanol [2]. State-of-the-art catalysts for steam reforming of methanol are copper-based and operate at 250–300 ̋ C, while ethanol reforming requires higher temperatures of the order of 600 ̋ C [3,4,5,6,7,8,9]. Cobalt is a less efficient catalyst than copper in the steam reforming of methanol operating at temperatures around 400 ̋ C [2]

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