Abstract
The current research is focused on the study and evaluation of a new process for the hydrogen generation. Nowadays, hydrogen production is mainly based on the reforming of natural gas or naphtha. Less energy intensive and more sustainable processes for hydrogen production are appealing for both industry and consumer applications. A highly attractive route is steam reforming of bio-alcohols, in principle CO2 neutral. Costly separation processes can be avoided by splitting the process into two alternated steps (chemical-loop reforming), in the aim of achieving two separate streams of H2 and COx. Moreover, an additional advantage in terms of sustainability is the use of bio-ethanol as the source of hydrogen, instead of natural gas.The main principle of the thermochemical-loop cycle is that an oxygen-storage material is first reduced by an ethanol stream, and then re-oxidized by water, in order to produce hydrogen and restore the original oxidation state of the looping-material.The initial task of the project was to define conditions and materials that may lead to an optimized process, allowing producing a hydrogen stream that does not require any additional purification or separation treatment. Different M-modified spinel-type mixed oxides: TYPE I – MFe2O4 and TYPE II – M0.6Fe2.4Oy viz. modified ferrospinels (where M=Cu, Co, Mn, Mg, Ca and Cu/Co, Cu/Mn, Co/Mn), as potentially attractive ionic oxygen and electron carrier looping materials, were prepared via co-precipitation method and tested in terms of both redox properties and catalytic activity to generate hydrogen by oxidation with steam, after a reductive step carried out with ethanol. Particularly, the focus on the reactivity behaviour of binary/ternary materials explained by their ability to form thermodynamically stable spinel oxides which allow us to re-obtain the initial spinel phase upon cycling and in turn increase the stability of looping material itself. In addition, the research includes in-situ DRIFTS and in-situ XPS studies that allowed to extract information at molecular level and to follow surface changes within the reduction/re-oxidation processes during ethanol chemical-loop reforming. Bulk characterizations have been done using XRD, TPR/O, TEM/SEM/EDS, Magnetic measurements and Raman/Mössbauer spectroscopic techniques. Moreover, a modification of the conventional CLR process with an addition of the 3rd regeneration step (carried out with air) was done in order to increase the stability of the looping material and to overcome the deactivation problems, such as: a coke deposition/accumulation and an incomplete re-oxidation of M0 during the 2nd step.