Graphene-based materials for wastes, biomass and CO2 valorization in catalysis: A technological perspective via molten salt synthesis

The exfoliation of graphite to graphene is one of the main methods of graphene production. In this paper, we provide an overview of the main molten salt methods for the exfoliation of graphite to graphene, including thermal and electrochemical exfoliation of graphite in molten salt. The fundamental mechanism of these methods is discussed in detail, along with the characterization techniques and instruments used to analyze the produced graphene. Additionally, the principles of eutectic salt mixtures, which play a crucial role in the exfoliation process, are discussed. The utilization of graphene-based materials in catalysis, particularly in the CO 2 and biomass valorization to produce sustainable fuels and chemicals, has been reviewed. The molten salt method is a simple and efficient way to produce graphene-based materials by using a molten salt medium to exfoliate the graphite. The purpose of this study is to provide a comprehensive overview of the current state of knowledge regarding the use of molten salt for the exfoliation of graphite to graphene, including their benefits and limitations

Investigating the Effect of Operational Variables on the Yield, Characterization, and Properties of End-of-Life Olive Stone Biomass Pyrolysis Products

In recent years, biomass has emerged as a promising raw material to produce various products, including hydrocarbons, platform chemicals, and fuels. However, a more comprehensive evaluation of the potential production of desirable value-added products and chemical intermediates is required. For these reasons, this study aimed to investigate the impact of various operating parameters on the pyrolysis of end-of-life olive stone, an agriculture and food industry waste, using a tubular quartz reactor operated at 773 K. The results revealed that the product compositions were comparable under batch or semi-batch nitrogen feeding conditions and with reaction times of 1 or 3 h. The product distribution and composition were significantly influenced by changes in the heating rate from 5 to 50 K min−1, while the effect of changing the biomass particle size from 0.3 to 5 mm was negligible in the semi-batch test. This work provides a comprehensive understanding of the relationship between pyrolysis operational parameters and obtained product distribution and composition. Moreover, the results confirmed the possible exploitation of end-of-life olive stone waste to produce high-added value compounds in the zero-waste strategy and biorefinery concept

A study of CO2 hydrogenation over Ni-MgAlOx catalysts derived from hydrotalcite precursors

Ni/Mg/Al mixed oxides have been prepared by decomposing corresponding layered double hydroxides of the hydrotalcite family. XRD, FTIR and UV–vis–NIR analyses show that prepared materials are constituted by a rocksalt type Mg1− xNixO solid solution with Al3+ in tetrahedral interstices of the cube close packing of oxide anions. When activated at sufficiently high temperature, they convert into optimal size supported Ni metal catalysts which show very active and selective for CO2 methanation. Catalytic data show that these materials are more active at low temperature than Ni/γ-Al2O3 catalysts, with a comparable enhanced activity with respect to Ni/ La2O3-Al2O3 ones. A role of basic oxides as activating components can be envisaged and related to the strength of the adsorption of CO2 on the “support” likely forming surface (bi)carbonates as active species. Activation energies and reactions orders have been calculated by flow reactor studies in differential reactor conditions. IR spectroscopy data show that carbon dioxide adsorbs on the reduced catalyst in the form of hydroxycarbonates, that convert at higher temperature in carbonates and strongly adsorbed linear and bridging carbonyl species on metallic nickel. The formation of surface CHx species is also eviden