The aim of the project is the development of new active, selective and stable catalysts for syngas (H2+CO) production by the catalytic partial oxidation and dry reforming of methane (CH4-CPO, CH4-DR). This research project, a continuation proposal of the one approved last year, will be focused on the preparation, characterization and study of the catalytic activity of nanostructured ZrO2-supported nickel (Ni/ZrO2) systems that showed in preliminary tests a promising activity and stability for CH4-CPO. The new perspective brought to the topic deals with the adoption of new methods for the catalysts preparation and of an additional catalytic process for syngas production, i.e. the dry reforming of methane (CH4-DR), yielding syngas from carbon dioxide and methane. Special attention will be focused on the ZrO2 support structure and morphology, catalysts activation conditions (temperature, atmosphere), Ni particles size and catalysts deactivation.
Ni/ZrO2 samples at various Ni loading (0.5-10.0 wt%) will be prepared using ZrO2 supports obtained with different methods and showing distinct morphology. The characterization of the materials will be performed with several physico-chemical techniques including Atomic Adsorption, XRD, UV-vis, FESEM, FTIR, Raman, TPR and textural analyses. The catalytic activity will be tested in a flow apparatus at atmospheric pressure in steady state conditions, by changing feed ratio, reaction temperature, contact time and catalyst pre-treatment.
The combined analysis of characterization and catalytic results is expected to improve the knowledge of the relationship between composition, structure and catalytic performances of the materials.
Nickel supported systems (mainly on Al2O3) are active for CH4-CPO and CH4-DR, although they suffer from deactivation due to coke deposition. ZrO2 has been considered a good alternative to Al2O3 as a support for Ni. The Ni/ZrO2 preparation method influenced the particle size and catalytic properties of the Ni active component and affects the resistance to carbon formation. However, a full understanding of the microscopic process occurring at the surface of the Ni particles or at the interface between particles and support is still lacking. Thus, the effects of preparation method and activation procedure (atmosphere and temperature) on the size and reactivity of supported metal nanoparticles need a deeper investigation.
The new perspective brought to the topic deals with the adoption of new methods for the catalysts preparation and of an additional catalytic process to the CH4-CPO one for syngas production such as the dry reforming of methane (CH4-DR), yielding syngas from carbon dioxide and methane. The CH4-DR process is of considerable interest due to the simultaneous utilization of two major greenhouse gases, CH4 and CO2.
To this end a ZrO2 support obtained by the Surfactant Templates (ST) method will be considered for the Ni/ZrO2 samples preparation in addition to the ZrO2 supports conventionally adopted and synthesized by the precipitation methods.
Special attention will be focused on the ZrO2 support structure and morphology, catalysts activation conditions (temperature, time of stream, pre-activation atmosphere), Ni particles size and catalysts deactivation both for the CH4-CPO and CH4-DR reactions intended for reactions for syngas production.
A wide variety of surface and bulk techniques, currently applied in our research group or in collaboration with other units (Dr. Elisabetta Rombi, Dipartimento di Scienze Chimiche e Geologiche, Università di Cagliari and Dr. Maria Cristina Campa, CNR - Istituto per lo Studio dei Materiali Nanostrutturati), will be useful to characterize new Ni-based supported catalysts and to establish a correlation between structure (nature and dispersion of active sites) and catalytic activity. X-ray diffraction (XRD) will be used to study the crystalline phase of the support and the mean particle size of the Ni phase (oxide or metal), to be compared with those obtained by FESEM images. UV-vis spectroscopy will be used to investigate electronic features and FTIR will give information on dispersion, coordinative unsaturation and redox properties of the supported species and their reactivity with suitable probe-molecules (CO and NO) in situ and operando conditions. Raman Spectroscopy will throw light on the nature of the support, adsorbates and types of carbonaceous species that can form on the catalyst surface during the catalytic process. TPR will clarify the redox properties of the supported Ni species and H2/O2 titration will evaluate dispersion of the metal particles.