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The conversion of methane or natural gas into turquoise H2 and carbon represents a promising pathway towards decarbonised energy. The pyrolysis of biogas (mainly a mixture of methane and CO2) is considered to be a negative carbon-emission technology, as the carbon source comes from biomass and the carbon is captured in solid form. In addition, the presence of CO2 in the gas mixture enables the dry reforming of methane into syngas. In this study, we show that direct biogas conversion in a fluidised catalytic reactor can produce a syngas whose composition meets the requirements for methanol synthesis or for liquid hydrocarbon production via the Fischer-Tropsch process. Confirmed by thermodynamic analysis, we show that the reaction proceeds at temperatures above 900 1C to produce carbon materials, whereas at lower temperatures the carbon is converted to CO by the Boudouard reaction. At 950 1C, very high methane and CO2 conversions are achieved (490% and 99%, respectively), accompanied by high hydrogen yield (490%) and the sequestration of carbon into a turbostratic structure. We believe that the direct catalytic reforming of biogas in a fluidised bed, when combined in series with an FTS process, could allow the production of liquid fuels with no need for costly gas separation units, in particular those implemented for CO2 capture. [ABSTRACT FROM AUTHOR]

The characterization of acid sites on solid catalysts is a key to understanding reaction mechanisms at the molecular level. This is generally done indirectly using a model probe molecule able to coordinate or be protonated on surface acid sites. For instance, Temperature Programmed Desorption (TPD) of the pyridine probe molecule followed by IR spectroscopy has become a standard method for the quantification and identification of Brønsted and Lewis acid sites found in zeolites. On the other hand, there is a lack of molecules able to be protonated on very weak Brønsted acid sites. In this work 2,6-ditert- butylpyridine is shown to be a suitable probe for characterizing weak Brønsted acidity. The proof of concept is performed on a series of Pt catalysts supported on a chlorinated alumina support (Pt--γ-Al2O3--Cl) generally used in the reforming process. In particular, we show that the area of the 1617 cm-1 vibration band is correlated to the concentration of Cl introduced into the catalyst. We also underline the relative insensitivity of pyridine as an IR probe molecule and the inadequacy of NH3 TPD for the characterization of acid sites of reforming catalysts, making 2,6-di-tert-butylpyridine a particularly important and specific probe molecule. [ABSTRACT FROM AUTHOR]