Catalytic pyrolysis of waste plastics using low cost binder-free pelletized bentonite clay has been investigated to yield pyrolysis oils as drop-in replacements for commercial liquid fuels such as diesel and gasohol 91. Pyrolysis of four waste plastics, polystyrene, polypropylene, low density polyethylene and high density polyethylene, was achieved at a bench scale (1 kg per batch) to produce useful fuel products. Importantly, the addition of binder-free bentonite clay pellets successfully yielded liquid based fuels with increased calorific values and lower viscosity for all plastic wastes. This larger scale pyrolysis study demonstrated that use of a catalyst in powder form can lead to significant pressure drops in the catalyst column, thus slowing the process (more than 1 hour). Importantly, the use of catalyst pellets eliminated the pressure drop and reduced pyrolysis processing time to only 10 minutes for 1 kg of plastic waste. The pyrolysis oil composition from polystyrene consists of 95% aromatic hydrocarbons, while in contrast, those from polypropylene, low density polyethylene and high density polyethylene, were dominated by aliphatic hydrocarbons, as confirmed by GC-MS. FTIR analysis demonstrated that low density polyethylene and high density polyethylene oils had functional groups that were consistent with those of commercial diesel (96% similarity match). In contrast, pyrolysis-oils from polystyrene demonstrated chemical and physical properties similar to those of gasohol 91. In both cases no wax formation was observed when using the bentonite clay pellets as a catalyst in the pyrolysis process, which was attributed to the high acidity of the bentonite catalyst (low SiO₂ : Al₂O₃ ratio), thus making it more active in cracking waxes compared to the less acidic heterogeneous catalysts reported in the literature. Pyrolysis-oil from the catalytic treatment of polystyrene resulted in greater engine power, comparable engine temperature, and lower carbon monoxide (CO) and carbon dioxide (CO₂) emissions, as compared to those of uncatalysed oils and commercial fuel in a gasoline engine. Pyrolysis-oils from all other polymers demonstrated comparable performance to diesel in engine power tests. The application of inexpensive and widely available bentonite clay in pyrolysis could significantly aid in repurposing plastic wastes.

Overview of research in critical and precious metal recovery using biosorption, application to real-life wastes and uses of the metal-loaded materials.

The global bio-based chemical market is growing in size and importance. Bio-based solvents such as glycerol and 2-methyltetrahydrofuran are often discussed as important introductions to the conventional repertoire of solvents. However adoption of new innovations by industry is typically slow. Therefore it might be anticipated that neoteric solvent systems (e.g., ionic liquids) will remain niche, while renewable routes to historically established solvents will continue to grow in importance. This review discusses bio-based solvents from the perspective of their production, identifying suitable feedstocks, platform molecules, and relevant product streams for the sustainable manufacturing of conventional solvents.

Aluminium-biochar composites (Al biochars) were devised to serve as a novel heterogeneous catalyst for isomerisation of glucose to fructose to achieve sustainable biorefineries. A series of Al biochars were synthesised from waste wood biomass, by varying the Al loading (10 or 20 wt%), pyrolysis temperature (from 500 to 750 °C), and purge gas (N₂ or CO₂). Their physicochemical properties, e.g., surface area, porosity, crystalline/amorphous structure, thermal stability, elemental composition, metal speciation, and acid/base site density, can be tuned by adjusting the pyrolysis conditions. As for their catalytic activity, 21.5 mol% fructose (selectivity 73.8 mol%) can be obtained from glucose conversion over Al biochar, after only 5 min heating at 160 °C in acetone/H₂O as the medium. Such performance was comparable to those of costly advanced inorganic solid catalysts in the literature. Aluminium species in Al biochars were the major contributor of their catalytic activity, as fructose yield increased by 60% with increasing Al loading. In particular, active Al sites located on the biochar surface contributed to approximately 70% of the system activity, whilst the remainder was attributed to Al components leaching to the solution phase under hydrothermal conditions. The possible active species included Al₂O₃, Al(OH)₃, AlO(OH), and Al–O–C moieties in amorphous phases, which may facilitate glucose isomerisation via the Lewis acid-driven mechanism (i.e., 1,2-hydride shift). This is the first study synthesising Al-biochar composites for catalytic glucose isomerisation, which demonstrates the high potential of biochar as a mesoporous and simple carbon support in emerging applications beyond environmental remediation.