Chemical functionalisation of 2D materials via batch and continuous hydrothermal flow synthesis

2D materials are single or few layered materials consisting of one or several elements with a thickness of a few nanometers. Their unique, tunable physical and chemical properties including ease of chemical functionalization makes this class of materials useful in a variety of technological applications. The feasibility of 2D materials strongly depends on better synthetic approaches to improve properties, increase performance and durability and reduce costs. As such, in the synthesis of nanomaterials, hydrothermal processes are widely adopted through a precursor-product synthesis route. This method includes batch or continuous flow systems, both employing water at elevated temperatures (above boiling point) and pressures to fine tune the physical, chemical, optical and electronic properties of the nanomaterial. Both techniques yield particles with different morphology, size and surface area due to different mechanisms of particle formation. In this review, we present batch and continuous hydrothermal synthesis of a selection of 2D derivatives (graphene, MXene and molybdenum disulphide), their chemical functionalisation as an advantageous approach in exploring properties of these materials as well as the benefits and challenges of employing these processes, and an outlook for further research

New Pathways in the Synthesis of 2-Dimensional Materials

Our research focuses on designing and discovering new 2D and other (3D, 1D, 0D) advanced functional nanomaterials (utilizing a target-oriented approach) and technologies that provide effective solutions in the energy, biomedical and environmental applications

Enhancing engine oil performance using nanoparticles and bio-lubricants as additives

Optimize internal combustion engine lubrication to reduce friction and wear leading to improve fuel consumption and to reduce exhaust emission

Greener synthesis of 1,2-butylene carbonate from CO2 using graphene-inorganic nanocomposite catalyst

The synthesis of 1,2-butylene carbonate (BC) from cycloaddition reaction of 1,2-butylene oxide (BO) and carbon dioxide (CO2) was investigated using several heterogeneous catalysts in the absence of organic solvent. Continuous hydrothermal flow synthesis (CHFS) has been employed as a rapid and cleaner route for the synthesis of a highly efficient graphene-inorganic heterogeneous catalyst, ceria-lanthana-zirconia/graphene nanocomposite, represented as Ce–La–Zr/GO. The heterogeneous catalysts have been characterised using transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD) and nitrogen adsorption/desorption (BET for measuring the surface area/pore size distribution),. Ceria- lanthana-zirconia/graphene nanocomposite catalyst (Ce–La–Zr/GO) exhibited high catalytic activity as compared to other reported heterogeneous catalysts in the absence of any organic solvent with a selectivity of 76% and 64% yield of 1,2-butylene carbonate at the reaction conditions of 408 K, 75 bar in 20 h

Enhancing physicochemical properties of coconut oil for the application of engine lubrication

Engine lubricants require specific physical and chemical properties to function effectively and extend the lifespan of engines. Coconut oil (CCO) is an abundant, renewable, and environmentally friendly bio-based stock that has the potential to be a viable alternative to conventional mineral oil-based lubricants. In this study, we investigated the potential of CCO as a lubricant and formulated different blends with additives to enhance its physicochemical characteristics. Polymethylmethacrylate (PMMA), styrenated phenol (SP) and potassium hydroxide (KOH) were used as additives in varying concentrations. We evaluated the formulations for low pour point (PP), high viscosity index (VI) and total base number (TBN) using differential scanning calorimetry (DSC), viscometry, and titration methods (following ASTM D2270 and ASTM D2896–21 respectively). The formulated CCO was also tested for thermal, oxidative, and shear stability using thermogravimetric analysis and rheometry. The optimal formulation exhibited a PP reduction from 21 °C to 6 °C, improved VI from 169 to 206, and a TBN adjustment from 0 to 4.14 mg KOH g-1. The formulated CCO also exhibited superior thermal, oxidative, and shear stability compared to unformulated CCO and reference oil (15W40). Our results suggest that blending CCO with additives can effectively enhance its suitability for engine lubrication, opening up new possibilities for environmentally sustainable and renewable lubricants

Nanostructured Al2O3/Graphene Additive in Bio-Based Lubricant: A Novel Approach to Improve Engine Performance

Personal and industrial use of internal combustion engines (ICEs) is projected to continue until 2050 and beyond. Yet demands to reduce global dependence on petrochemicals and fossil fuel-derived lubricants are increasing and environmentally necessary. New strategies for maintaining and enhancing ICE performance by reducing friction, wear, fuel consumption, and exhaust emissions will reduce the depletion of mineral and fossil fuel reserves and environmental pollution. This paper reports the tribological enhancement of nano-bio lubricants formulated using 2D nanocomposites of Al2O3/graphene as novel additives in coconut oil, whose performance as a lubricant compares favourably with the mineral-based engine oil 15W40. Structural, compositional, and morphological characterization of an Al2O3/graphene nanocomposite synthesized via thermal annealing revealed an ultra-fine particle size (<10 nm) with spherical/laminar morphology and a rich sp2 domain, exhibiting a consistent colloidal stability when formulated as nanofluid. Through the use of various characterisation techniques, including friction and wear analysis we gained valuable insight into the tribological mechanism. Our optimisation of 2D tribological system using coconut oil formulation resulted significant reductions in the coefficient of friction (28%), specific fuel consumption (8%), and exhaust pollutants (CO, SO2, and NOx) emissions. This work demonstrates the benefits of using nano-bio lubricant formulated using coconut oil and 2D based hybrids as base stock and additives, delivering solutions to global challenges such as improving fuel consumption while reducing environmental pollution; solutions that can be transferred to other areas where lubricants are a necessity

Green Process Engineering as the Key to Future Processes

Microreactors are small devices with sub-millimeter internals which have superb mass and heat transfer. Initially, they were used for reactions with very high demands on the latter, e.g. very exothermic reactions, gas-liquid reactions with interfacial transport issues, reactions with very fast kinetics which demands even faster mixing, and more. In this way, the processing window was opened widely and, also due to the minute volumes only present in the reaction zone, safe processing under otherwise hazardous conditions was enabled. This includes processing of reactions which are prone to thermal runaway and in the explosive regime. Scale-up of promising reactions and products which was hindered with conventional technology is now possible using the new equipment. This has widened the process development possibilities in chemical industry. In the last years, micro process technology was not only used for the very problematic synthetic issues which formerly had a dead-end position in industry’s process development. Rather, the scope of chemical reactions to be processed in microreactors was considerably widened by exploring new process conditions with regard to temperature, pressure, concentration, solvents, and more. This is commonly referred to as flow chemistry. This allowed to reduce the processing time-scale for many reactions to the minute range or even below which fits well to the residence times of microreactors. In addition, the process integration of several reactions in one flow to a multi-step synthesis has opened a new door in molecular diversity as well as system and process complexity. The same holds for the combination of reactions and separations in micro-flow. To achieve throughputs relevant for industrial production, smart scale-out to milli-flow units has established and supplemented the num­bering-up concept (parallelization of microchannels/-reactors operated under equal conditions). New innovations and enabling technologies need anyhow evaluation and benchmarking with conventional technology on the full-system level. Yet, microreactor technology has in the last years deepened so much into process intensification on a holistic scale that the focus increasingly is given towards the process dimension—to process design and automation, real-case applications, cost analysis, life-cycle assessment, and more. The impact on cost competitiveness and sustainability becomes well assessed. Facing this very recent scientific achievement, the special issue “Design and Engineering of Microreactor and Smart-Scaled Flow Processes” of the journal Processes aims to cover recent advances in the development of microreactor and smart-scaled flow processes towards the process level — in the sense as given above

Greener synthesis of 1, 2 butylene carbonate from CO2 using graphene-inorganic nanocomposite catalysis

The global emission of carbon dioxide (CO2) into the atmosphere has reached an unsustainable level that has resulted in climate change and therefore there is the need to reduce the emission of CO2. However, the reduction of CO2 emission has become a global environmental challenge and the use of CO2 to produce value added chemicals could be one of the few ways of reducing CO2 emission. CO2 is recognised as an abundant, cheap, recyclable and non-toxic carbon source and thus its utilisation for the production of value-added chemicals is extremely beneficial for the chemical industry. 1,2-butylene carbonate is a valuable chemical of great commercial interest. It is an excellent reactive intermediate material used in industry for the production of plasticisers, surfactant, and polymers and can also be used as a solvent for degreasing, paint remover, wood binder resins, foundry sand binders, lubricants as well as lithium battery because of its high polarity property. Several reaction routes have been attempted for 1,2-butylene carbonate production, which was phosgene, oxidative carboxylation, direct synthesis using homogeneous catalyst and direct synthesis using a heterogeneous catalyst. The latter being the most attractive route due to the inexpensive raw material, ease of catalyst recovery and the avoidance of corrosive reagents, such as phosgene. Continuous hydrothermal flow synthesis (CHFS) has been employed as a rapid and cleaner route for the synthesis of highly efficient graphene-inorganic heterogeneous catalyst, represented as Ce–La–Zr–GO nanocomposite. The graphene-inorganic heterogeneous catalyst has been characterised using transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS), while X-ray powder diffraction (XRD) and Brunauer–Emmett–Teller (BET) methods have been used for the surface area measurements. Ceria, lanthana, zirconia doped graphene nanocomposite catalyst studies have shown high catalytic activity as compared to other reported heterogeneous catalysts in the absence of any organic solvent with a higher selectivity of 76% and 64% yield of 1,2-butylene carbonate at the reaction conditions of 408 K, 75 bar in 20 h

Greener synthesis of styrene carbonate from CO2 using graphene-inorganic nanocomposite catalysts

The global emission of carbon dioxide (CO2) into the atmosphere has reached an unsustainable level that has resulted in climate change and therefore there is the need to reduce the emission of carbon dioxide. However, the reduction of CO2 emission has become a global environmental challenge and the use of CO2 to produce value added chemicals could be one of the few ways of reducing CO2 emission. CO2 is recognised as an abundant, cheap, recyclable and non-toxic carbon source and thus its utilisation for the production of value-added chemicals is extremely beneficial for the chemical industry. Styrene carbonate is a valuable chemical of great commercial interest. It is an excellent precursor material for the production of polycarbonates and can be used as a solvent for lithium battery because of its high polarity property. Several reaction routes have been attempted for styrene carbonate production, which was phosgene, oxidative carboxylation, direct synthesis using homogeneous catalyst and direct synthesis using a heterogeneous catalyst. The latter being the most attractive route due to the inexpensive raw material, ease of catalyst recovery and the avoidance of corrosive reagents, such as phosgene and dimethyl formamide. Continuous hydrothermal flow synthesis (CHFS) has been employed as a rapid and cleaner route for the synthesis of highly efficient graphene-inorganic heterogeneous catalyst, represented as Ce–La–Zr–GO nanocomposite. The graphene-inorganic heterogeneous catalyst has been characterised using transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS), while X-ray powder diffraction (XRD) and Brunauer–Emmett–Teller (BET) methods have been used for the surface area measurements. Ceria, lanthana, zirconia doped graphene nanocomposite catalyst studies have shown high catalytic activity as compared to other reported heterogeneous catalysts in the absence of organic solvent with a higher selectivity of 68% and 60% yield of styrene carbonate at the reaction conditions of 408 K, 75 bar in 20 h

Maximizing Polypropylene Recovery from Waste Carpet Feedstock: A Solvent-Driven Pathway Towards Circular Economy

Here we propose a novel approach for the efficient recovery of polypropylene from waste carpet feedstock utilising a solvent based method operating at 160 °C. The findings contribute to advancing sustainable recycling practices for waste carpet materials and offer valuable insight into the recovery of PP which can also be utilised for other complex waste streams