Harrison Silva Santana

Fatty acid esters were produced by phototransesterification of canola oil using TiO ₂ as a photocatalyst and employing either UVA or sunlight as radiation sources. Conversions of approximately 73% (±1.41) and 19% to fatty acid methyl esters (FAME) were achieved with methanol (1 TGL [triglyceride] mol:55 MeOH mol, 20% TiO ₂ w _catalyst / w _TGL , 65°C, 4 h). In contrast, ethanol resulted in a lower conversion rate of 38%. Conventional thermal methods employing acid and alkali catalysts were employed to compare their corresponding FAME contents to those generated through photocatalysis. The kinetic curves were established for temperature ranges of 25°C–65°C. This study evaluated six kinetic mathematical models, among which the second forward/fourth backward model exhibited the greatest accuracy ( R ² of 0.996). This indicates that a homogeneous system model can be applied to a heterogeneous process, given that the mass transfer to the active sites of the solid catalyst is not the rate‐limiting factor. The thermodynamic data (Δ G _328.15K = 29.98 kJ/mol, Δ G _338.15K = −6.88 kJ/mol, Δ H = 83.00 kJ/mol and Δ S = 0.27 kJ/mol K) suggest that this endothermic reaction requires temperatures of approximately 65°C to reach substantial conversion rates. These findings support the development of sustainable, low‐waste biodiesel production pathways aligned with global decarbonisation goals.

The growth in global demand for sustainable and efficient processes is one of the main factors driving the competitiveness of industrial technology. In this context, process intensification using microfluidic devices has stands out due to the inherent advantages of reduced length scale, providing enhanced heat and mass transfer efficiency, high selectivity, and superior yields in chemical processes. The ability to control process variables more precisely also enables a high level of safety, essential in situations involving toxic or explosive reagents. Moreover, the development of high-efficiency modular plants with variable production rates offers adaptability and flexibility for diverse industrial applications. This editorial presents a collection of five papers that explore the state of the art of microfluidics-based technologies for the intensification of sustainable processes, covering a range of applications from chemical synthesis to environmental treatment. One of today's most important primary chemicals, methanol, was explored in the paper by Silva et al. (2024). The authors addressed methanol synthesis in catalyst-coated microreactors, comparing different microreactor configurations with fixed-bed reactors.Numerical analysis showed that microreactors can achieve performance equivalent to traditional reactors, with significant advantages in terms of pressure drop and scaling efficiency. This study was essential for understanding how microreactors can be effectively scaled, retaining the benefits of microscale while meeting industrial production demands. TSA is presented as a valuable tool for identifying bottlenecks in biochemical processes and proposing intensification improvements without the need for complex computational modeling. This article is particularly relevant for biomedical processes, where limited access to biological samples makes optimization a crucial task. This collection of papers clearly illustrates how microfluidics is being used to intensify processes in areas such as chemical synthesis, environmental treatment, and biomedical applications, contributing to more sustainable and efficient solutions. The diversity of applications presented in the articles in this Research Topic reflects the great potential of microfluidic devices to transform industrial processes by reducing costs, enhancing safety, and optimizing resource use.We hope this Research Topic inspires new advancements and promotes collaborations between scientists and engineers to overcome current challenges and further explore the opportunities that microfluidics can offer for the intensification of sustainable processes.

The use of microreactors (MRs) in chemical and pharmaceutical industries allows for a series of advantages due to their reduced sizes regarding conventional batch reactors. In the present paper, the transposition of the reaction between 2,4‐thiazolidinedione (TZD) with p‐methoxybenzaldehyde from batch to a continuous capillary MR was carried out. The microdevice performance was evaluated experimentally and numerically by computational fluid dynamics (CFD). The batch process yielded 92% in 480 min using piperidine for equimolar reactant feed, while the pyrrolidine promoted a 100% yield in a 50 min, both using solvent ethanol. Kinetic and thermodynamic parameters of the synthesis using piperidine and pyrrolidine were also obtained from experimental data. In the transposition to flow chemistry, ethanol was also used as solvent and a product yield of 100% (140°C, pyrrolidine) was obtained for a residence time of 20 min, representing a reduction of 24 times in the reaction time. In the numerical simulations by CFD, two mathematical models were elaborated: a transient batch and a steady‐state continuous flow. Both models exhibited good agreement with experimental data. The average relative deviations of TZD conversion and the reaction yields in MRs were, respectively, 0.23% and −7.1% (78°C) and 1.7% and 1.2% (140°C).

Biodiesel is produced on a large scale as an eco‐friendly substitute and additive to fossil fuels. Catalytic homogeneous processes using strong acids, alkalis, and natural oils have been realized in industry. However, these traditional methods have several disadvantages, such as the generation of large volumes of waste, high water and reagent needs, use of hazardous reagents, high operation costs, and utilization of valuable feedstocks and catalysis, respectively. Different solutions have subsequently been investigated, such as cheap alternative feedstocks, co‐solvents and catalysts, sustainable operational conditions, advanced reactor designs and scales, and advantageous pre‐ and post‐reaction treatments. This review explores and analyzes the main aspects of current biodiesel technologies and opportunities. It also describes some advanced improvement strategies.

Methyl oleate, an example of a FAME (fatty acid methyl ester), was produced by oleic acid (OA) photoesterification with TiO₂and UVA light. Different parameters were evaluated and optimised: catalyst pretreatment, temperature (25–65 °C), catalyst loading (1–30 % w/w_OA) and oleic acid : alcohol molar ratio (1 : 3–1 : 55). Response surface quadratic methodology obtained by central composite rotational design (RSM‐CCRD) was used to evaluate the main operational conditions of the photoesterification process. A high conversion of 98 % (±0.8) at 55 °C, 20 % TiO₂(w/w_OA), and 1(OA) : 55(methanol) molar ratio was achieved. The photoesterification mechanism is furthermore proposed. The Langmuir‐Hinshelwood kinetic model considered the forward and backward reaction as first‐order fits with the best accuracy (R²of 0.997). The thermodynamic results (ΔG_338.15K=−20.75 kJ/mol, ΔH=13.75 kJ/mol, and ΔS=0.47 kJ/mol.K) indicate that the operating conditions are important, both to supply the energy requirement of the reaction, but also to increase the miscibility of the reactants.

Microfluidic devices or microdevices refer to systems with a characteristic length in the micrometer range. Systems in this size allow handling small quantities of reagents and samples, with reduced residence time, better control of chemical species concentration, high heat and mass transfers, and high surface/volume ratio. These characteristics led to the application of these microdevices in several areas, such as biological systems, energy, liquid-liquid extraction, food, agricultural sectors, pharmaceuticals, flow chemistry, microreactors, and biodiesel synthesis. Microreactors are devices that have interconnected microchannels, in which small amounts of reagents are manipulated and react for a certain period of time. The traditional characteristics of microreactors are less quantities of reagents and samples, high surface area in relation to volume (10000 m² m^-3), reduction of resistance to heat and mass transfer, reduced reaction times, and narrower residence time distributions. In recent years, several studies have been carried out on biodiesel production in microreactors that explore the influence of operating conditions, mixing and reaction yield, numbering, and especially the microdevices design. Despite all the advantages of microreactors, the literature shows that there are only a few applications on an industrial scale. Two main reasons that hinder the adoption of this technology are the scale-up to a large enough volume to deliver the necessary production capacity and the costs related to industrial manufacturing microreactors. It is often stated that large-scale production of microreactors can be easily achieved by numbering-up. However, researches show that an incredibly high number of microdevices would be needed, which results in a technical unfeasibility and a strong impact on the construction costs of the industrial system. The present review aims to show whether microreactors can replace conventional biodiesel production processes and how this replacement technology could be carried out. The current chapter was divided into the following sections: Introduction, Synthesis and Purification of Biodiesel in Microreactors, Fundamentals of CFD, and Fundamentals of Scale-up. Finally, conclusions and future perspectives are exposed.

An innovative method of alcoholic fermentation was proposed by developing a microfluidic device with millichannels filled with yeast immobilized in alginate hydrogel, manufactured by a new robotic system. We propose and build an automatic equipment consisting of a modified three‐dimensional (3D) printer with two independent systems, a module with a syringe for the injection of solutions/hydrogels and a conventional head with a fused filament fabrication mechanism. The methodology consisted of hydrogel 3D printing tests, the manufacture of millireactors with immobilized yeast and the application of the millireactors in alcoholic fermentation. The 22G needle provided the best printing accuracy in tests with hydrogel. The cells were homogeneously distributed by alginate and their concentration did not influence ethanol production. The optimal millireactor configuration was 2% alginate solution containing 25 g L⁻¹ cells, achieved average ethanol production of 11.24 ± 0.015 g L⁻¹, with productivity of 22.49 g L⁻¹ h⁻¹ and efficiency of 44%.