(617c) Hydrogen Production From Oxidative Steam Reforming of Methanol: Total Oxidation Followed By Steam Reforming of Methanol

Hydrogen production from oxidative steam reforming of methanol: total oxidation followed by steam reforming of methanol

Dong Hyun Kim, Hyun Chan Lee, Jietae Lee

Department of Chemical Engineering, Kyungpook National University

Daegu, 702-701, Korea

The oxidative methanol steam reforming of methanol (OSRM) has been regarded as a combination of partial oxidation (POM) and steam reforming of methanol (SRM).

POM: CH₃OH + 0.5 O₂ → CO₂ + 2 H₂           (1)

SRM: CH₃OH + H₂O → CO₂ + 3 H₂                (2)

By adjusting the O₂ content, the OSRM can be made autothermal, which can make the design of the reformer very simple without heat supply or removal and would be useful in mobile hydrogen production.

Whether POM proceeds according to the equation (2) is not experimentally resolved. At low reaction temperatures where the O₂ conversion was not complete, the products were H₂O and CO₂ rather than H₂ and CO₂ [ref]. Only after the O₂ was completely consumed, the selectivity of H₂ has begun to increase[ ref]. In experiments of POM, it was very difficult to keep the catalyst bed isothermal due to the large reaction heat and poor thermal conductivities in the catalyst beds.

In the present study, we developed an isothermal reactor for OSRM using the catalyst supported on aluminum strips.  The aluminum plate was anodically oxidized to form a porous alumina layer, on which the active metal components, Cu and Zn, were impregnated. The measured temperature profiles along the bed of 6 cm during OSRM were uniform within ±1^oC in the temperature range of 200 – 300 ^oC. At any reaction temperature in the range and when the O₂ conversion is not complete, the products of OSRM were H₂O and CO₂, showing the total oxidation of methanol in the presence of O₂. It is thus experimentally shown that POM as well as OSRM are methanol combustion until all the O₂ is consumed and then SRM afterward. The reaction rates of the total oxidation were measured and a rate expression was proposed.  On the contrary to the implications in the literature, the rate of total oxidation of methanol over the Cu catalyst was observed to be much slower than the rate of SRM in the experimental conditions.