The reactivity of spinel ferrites in the two-step methanol reforming

We investigated the feasibility of a two-step cycle approach for the catalytic production of hydrogen from methanol and water, using the spinel-type oxide CoFe2O4 as the electrons/O2- carrier. The oxidized spinel was first reduced with methanol at 420°C (first step of the cycle); products were CO, CO2, CH4, H2O, and H2 (conversion of methanol was total over the whole range of reaction time). The relative amount of each product was a function of the reaction time, because during reaction the spinel became progressively more and more reduced. An important aspect was the accumulation of coke, which formed from the very beginning of the reaction time. When the reduction was carried out at 300°C, initial methanol conversion was only 13%, but then conversion increased when the elapsed reaction period increased. At the same time, a dramatic rise in both hydrogen and CO formation was observed, suggesting that the surface reduction of the spinel led to a catalyst very active in methanol decomposition into CO and H2. The amount of coke formed was considerably less than that formed during reduction at 420°C. Moreover, the distribution of products, especially during the initial period of the reaction time, was affected by the structural features of the spinel; using different calcination temperatures for the preparation of the spinel induced morphological changes in the material, as confirmed by HE-TEM, strongly affecting crystal defectivity.1