Methanol oxidation on Fe2O3 catalysts and the effects of surface Mo.

M Bowker,E K Gibson,C Brookes,I P Silverwood

doi:10.1039/c5fd00225g

Abstract

The adsorption of methanol on haematite has been investigated using temperature programmed methods, combined with in situ DRIFTS. Model catalysts based on this material have then been made with a shell-core configuration of molybdenum oxide monolayers on top of the haematite core. These are used as models of industrial iron molybdate catalysts, used to selectively oxidise methanol to formaldehyde, one of the major chemical outlets for methanol. Haematite itself is completely ineffective in this respect since it oxidises it to CO2 and the DRIFTS shows that this occurs by oxidation of methoxy to formate at around 200 °C. The decomposition behaviour is affected by the absence or presence of oxygen in the gas phase; oxygen destabilises the methoxy and enhances formate production. In contrast, when a monolayer of molybdena is placed onto the surface by incipient wetness, and it remains there after calcination, the pathway to formate production is blocked and formaldehyde is the main gas phase product in TPD after methanol dosing.

Highlights

This paper concerns the adsorption and reaction of methanol with iron oxide and model catalysts of Mo monolayers deposited on that oxide
Due to its abundance it is relatively cheap and environmentally cleaner as it is usually mined from near the surface of the earth, little energy is wasted in separation and re ning, in contrast to the situation for precious metals. It is used in a variety of catalytic applications, such as ammonia synthesis, the aUK Catalysis Hub, Research Complex at Harwell (RCaH), Rutherford Appleton Laboratory, Harwell, Oxon, OX11 0FA, UK
That in the active phase of ammonia synthesis it is in metallic form, in FTS, it is probably carbidic, while in high temperature water-gas shi reaction (HTWGS), prepared as haematite, it is in the magnetite form during reaction

Summary

Introduction

This paper concerns the adsorption and reaction of methanol with iron oxide (haematite) and model catalysts of Mo monolayers deposited on that oxide. We report the changes in behaviour of reactivity and surface species formed when such model catalysts are fabricated using temperature programmed methods and DRIFTS.

Results

Conclusion