Continuous Flow Process Research Articles

Polymeric membrane with nanohybrids of Cu nanocomposites and metalloporphyrin-based nanosheets for enzyme-like catalytic degradation of Congo Red

Metalloporphyrin-based nanozymes are effective peroxidase-like catalysts for dye degradation; however, their reusability is a challenge due to the nanoscale dimensions. Membrane technology has the advantages of high efficiency, low energy consumption, and easy operation. Here, we integrate poly (vinylidene fluoride) (PVDF) membrane with nanozyme for effective decolorization of Congo Red (CR). A nanozyme (Cu@Cu-FeTCPP) is prepared by growth of copper hydroxide-copper oxide (Cu(OH)2-CuO) nanocomposites onto the metal organic framework (MOF) nanosheet consisting of tetrakis-(4-carboxyphenyl)-porphyrin iron ligands and cupric ion nodes. The functional membrane is achieved by loading Cu@Cu-FeTCPP nanozyme on the PVDF membrane surface (Cu@Cu-FeTCPP/PVDF). The as-prepared membrane shows catalytic activity for the degradation of CR. Under flow through conditions, the catalytic degradation in tangential flow plays a major role in overall decolorization of CR, far exceeding the contribution of adsorption. The membrane can rapidly catalyze the dye degradation even at different operating pressures (0.1–0.7 kPa) and feed solutions with higher CR concentrations (eg. 60 mg·L-1). Compared with the static batch catalysis and the free nanozyme catalysis, the membrane exhibits higher decolorization efficiency and outstanding reusability in the continuous flow process owing to the promoted mass transfer. After 40 min of continuous flow reaction in a feed solution containing CR (40 mg·L-1) and H2O2 (50 mM), the decolorization efficiency approaches 90% and remains above 85% after five catalytic cycles. The membrane with enzyme-mimicking ability has application prospect in wastewater treatment.

Production of higher hydrocarbon-pool from bio-ethanol for fuel applications

In a way to explore the inherent acidity and porosity properties of zeolites for the conversion of renewable biomass-derived ethanol into various fuel stocks, three types of zeolites; HZ, HY, and HB have been studied in their proton form. The studies indicated the formation of catalyst-dependent hydrocarbon composition of the product falling in gasoline and jet fuel for the specific end-use applications. The flexibility in product choice facilitated by changing the catalyst makes the present process suitable for industrial applications based on the nature of product in demand. At optimized temperature and pressure reaction conditions, HB zeolite produced >40 wt% jet fuel hydrocarbons (T = 400 °C and P = 50 bar), HZ produced 53 wt% octane gasoline (RON >100) and HY zeolite produced 25 wt% of olefins in liquid product. The novelty of the present process lies in its simple, single-step, continuous-flow vapour-phase single catalytic process operating on zeolites bearing no metal function but possessing variable pore size and other catalytic properties required for producing higher range hydrocarbons from ethanol.

Flow Optimization of Photoredox-Mediated Metal-Free Ring-Opening Metathesis Polymerization.

Photoredox-mediated metal-free ring-opening metathesis polymerization (MF-ROMP) is a convenient metal-free method to produce a variety of ROMP polymers. Transitioning MF-ROMP from a batch to a continuous flow process has yet to be demonstrated and could potentially benefit the production efficiency, safety, and modularity of reaction conditions. We designed and evaluated continuous flow and droplet flow setups and compared the results for MF-ROMP across a short series of common monomers. By using the droplet flow reactor setup, we achieved flow conversions comparable to that of batch and circumvented issues with diffusion-limited mixing and air exposure.

Structure-activity relationships of ZrO2 crystalline phases in the catalytic transfer hydrogenation of methyl levulinate with ethanol

The depletion of fossil resources is driving the research towards renewable alternatives, like lignocellulosic biomass. Therefore, the development of efficient continuous-flow processes, allowing to achieve better productivity compared to batch processes, will play a crucial role in promoting a sustainable transition. In this context, we report on the continuous-flow, gas-phase, catalytic transfer hydrogenation (CTH) of methyl levulinate and ethanol over zirconia catalysts, in particular focusing on the effect of two different crystalline phases (i.e. monoclinic, m-ZrO2, and tetragonal, t-ZrO2) on catalyst performance. An in-depth catalyst characterisation was coupled with both computational and 1H NMR relaxation studies to assess the structure-activity relationship, providing fundamental insights into the catalytic process and future catalyst optimization. The results, indicate that the higher Lewis acidity and basicity along with the lower affinity with ethanol of m-ZrO2 with respect to t-ZrO2 are responsible for the promotion of undesired oligomerisation reactions of angelica lactones responsible for catalyst deactivation.

A Telescoped Continuous Flow Enantioselective Process for Accessing Intermediates of 1-Aryl-1,3-diols as Chiral Building Blocks.

A telescoped continuous flow process is reported for the enantioselective synthesis of chiral precursors of 1-aryl-1,3-diols, intermediates in the synthesis of ezetimibe, dapoxetine, duloxetine, and atomoxetine. The two-step sequence consists of an asymmetric allylboration of readily available aldehydes using a polymer-supported chiral phosphoric acid catalyst to introduce asymmetry, followed by selective epoxidation of the resulting alkene. The process is highly stable for at least 7 h and represents a transition-metal free enantioselective approach to valuable 1-aryl-1,3-diols.

Highly Scalable and Inherently Safer Preparation of Di, Tri and Tetra Nitrate Esters Using Continuous Flow Chemistry.

Nitrate esters are important organic compounds having wide application in energetic materials, medicines and fuel additives. They are synthesized through nitration of aliphatic polyols. But the process safety challenges associated with nitration reaction makes the production process complicated and economically unviable. Herein, we have developed a continuous flow process wherein polyol and nitric acid are reacted in a microreactor to produce nitrate ester continuously. Our developed process is inherently safer and efficient. The process was optimized for industrially important nitrate esters containing two, three and four nitro groups. Substrates include glycol dinitrates: 1,2-propylene glycol dinitrate (PGDN), ethylene glycol dinitrate (EGDN), diethylene glycol dinitrate (DEGDN), triethylene glycol dinitrate (TEGDN); trinitrates: trimethylolethane trinitrate (TMETN), 1,2,4-butanetriol trinitrate (BTTN); and tetranitrates: erythritol tetranitrate (ETN). The optimized process for each molecule provided yield >90 % in a short residence time of 1 min corresponding to a space time yield of >18 g/h/mL of reactor volume.

Sol–gel catalysts immobilized on stainless steel meshes for Ba2+ removal in a continuous flow process: An experimental design

Abstract This study describes the use of a continuous flow system for photocatalytic reactions employing a TiO2 sol–gel structured catalyst. The catalyst was immobilized on various stainless steel meshes to investigate the barium(II) removal. To verify its photocatalytic activity, batch tests were carried out and the results were compared to the commercial catalyst P25. Effects of thermal treatment on the structured catalyst were investigated. The continuous flow photocatalytic tests were conducted under different experimental conditions through an experimental design to verify the effect of the parameters (pH and volume flow). The results of the batch tests indicated that the TiO2 sol–gel catalyst showed very similar activity to the TiO2 P25 when used in powder suspension (32% reduction of Ba2+). In the continuous flow process, maximum adhesion of catalysts on meshes was found at a calcination temperature of 623 K. The experimental design indicated the pH as a significant parameter in the studied conditions. It was observed that at pH levels close to 7, also indicated by the study of the zero charge point and lower flow rates, it was possible to obtain ∼20% removal of Ba2+ ions, in a continuous flow reactor with a residence time of 83 min.

Innovative structural modification process of Kraft lignin using continuous-flow regime

An innovative process for the structural modification of kraft lignin (KL), followed by the incorporation of the herbicide picloram (PCL; C6H3Cl3N2O2; CAS, 1918-02-1) to obtain a nanoformulation, was developed by means of a hydroxymethylation reaction in a continuous-flow regime to reach the technological readiness level (TRL) 4. The modified KL-PCL nanoformulation obtained should be used to validate formulations for the controlled release of the herbicide in the subsequent stage (TRL5) to prove the environmental benefit of this type of formulation against a conventional formulation. It is expected that structural modification will improve properties such as surface area, adsorption, and the availability of chemical groups for interaction. The developed modification process proved to be more efficient because it was performed with a reaction time 12 times shorter on average than the same reaction already described in the literature, and the nanoformulation resulting from the continuous-flow processing showed an excellent polydispersity index compared to the batch method. The modification process, which uses flow synthesis and includes the incorporation of an agrochemical molecule, not only represents an innovative approach but also aligns with the United Nations Sustainable Development Goals.

Photothermal Aza‐Michael Addition of Divergent Amines to Vinyl Sulfones: A Method Towards Transition Metal‐ and Base‐Free Medium

AbstractA highly efficient and versatile method has been developed for the photothermal aza‐Michael addition, producing β‐amino sulfones with excellent yields. The protocol uses mild and simple conditions under the batch and continuous flow process and is suitable for synthesis, without the need for transition metal catalysts, ligands, strong acids, or bases. This sustainable approach offers a significant breakthrough in organic synthesis with potential applications in medicinal chemistry and materials science.

Development of a Continuous Flow Baldwin Rearrangement Process and Its Comparison to Traditional Batch Mode.

A new and highly efficient continuous flow process is presented for the synthesis of aziridines via the thermal Baldwin rearrangement. The process was initially explored using traditional batch synthesis techniques but suffered from moderate yields, long reaction times, and moderate diastereoselectivities. Here we demonstrate that the process can be greatly improved upon its transfer to continuous flow, which afforded the aziridine targets in high yields, short reaction times, and consistently high diastereoselectivities, with the high-throughput process rendering multigram quantities of product in short periods of time. In addition, flow processing extended the substrate scope including several examples that had failed in batch mode, thus demonstrating the value of this overlooked entry into valuable aziridine species.

N-Doped graphene fiber anchored Pd nanoparticles as a fixed-bed catalyst for continuous-flow reduction of N-containing unsaturated compounds

Catalytic fixed-bed is an efficient and facile system for scalable organic synthesis due to its continuous and fast flow operation process. As a key unit in the fixed-bed system, catalytically active packing materials are required to possess some properties, such as high activity, excellent stability, and porous packing structure. Herein, we prepare a fibrous fixed-bed catalyst by anchoring Pd nanoparticles on N-doped graphene fiber (NHG) (Pd/NGF). Due to the porous and loose packing structure, the resultant Pd/NGF catalyst can be easily filled into the continuous-flow reactor to construct a fixed-bed system with low flow resistance. The corresponding catalytic fixed-bed system exhibits a favourable flow rate (8 ​mL/min) and excellent durability toward reduction reactions of N-containing unsaturated compounds to produce aromatic amines. This work provides a new design concept of fibrous fixed-bed catalysts with dual-active components (i.e., graphene-derived active materials and metal nanoparticles) and catalytic organic synthesis in a continuous-flow process.

Multiphysics modeling of polyphenol oxidase and peroxidase inactivation in continuous-flow microwave thermal processing of coconut water

Multiphysics modeling of polyphenol oxidase and peroxidase inactivation in continuous-flow microwave thermal processing of coconut water

Development of Continuous Flow Processes to Access Pyrrolo[2,1-f][1,2,4]triazin-4-amine: An RSM for the Synthesis of Antiviral Drugs

Development of Continuous Flow Processes to Access Pyrrolo[2,1-<i>f</i>][1,2,4]triazin-4-amine: An RSM for the Synthesis of Antiviral Drugs

Cobalt-aluminum spinel supported on modified γ-alumina for peroxymonosulfate activation: Si–Al ratio of support to optimize performance and reusability

The development of cobalt-based supported catalysts with high PMS catalytic activity and stability by adjusting the composition of the support is highly desirable yet remains scarce. In the work, a series of catalysts (Co2AlO4/Al2O3-xSiO2) were prepared by impregnation and high-temperature calcination using Al2O3-xSiO2 with a low Si–Al ratio as the support. Measurement techniques such as XRD, XPS, UV-DRS, FTIR, BET, SEM and HRTEM were used to characterize textural and chemical properties (ratio of Co3+/Co2+, specific surface area, pore size, pore volume, etc.). The ratio of Co3+/Co2+ and pore volume of Co2AlO4/Al2O3-xSiO2 can be turned by controlling the ratio of Si to Al, which are closely related to the catalytic performance and reusability of the catalysts. The optimized catalyst (Co2AlO4/Al2O3-0.25SiO2) can completely degrade 10 mg/L p-nitrophenol (PNP) in 40 min in the pH range of 3–9 with excellent reusability. The effects of several reaction parameters (i.e., PMS dosage, Co2AlO4/Al2O3-0.25SiO2 dosage, reaction temperature, initial pH value, and inorganic ions) on PNP removal were comprehensively investigated. Sulfate radical (SO4•−) and singlet oxygen (1O2) are making a major contribution to the degradation of PNP. Moreover, a millimeter-scale catalyst (CoSiAl-0.25/Al2O3 pellet) was prepared by sol adsorption and high-temperature calcination method, which maintained high oxidation activity after treatment of 18 L wastewater (PNP of 10 mg/L) in a continuous flow process. The method is simple and easy to operate on a large scale, providing a new perspective on the design and preparation of cobalt-aluminum spinel catalysts for activated PMS.

Customized Production of Holey Graphene Oxides via a Continuous Flow Process.

Continuous flow manufacturing is an innovative technology mainly applied in the chemical and pharmaceutical industries that is progressively being adapted to the manufacturing of nanomaterials to overcome the challenge of reproducing a product with consistent characteristics at a large scale. Here, a flow photochemical system is designed and prototyped for the synthesis of holey graphene oxides (hGOs). Compared to existing methods for the synthesis of hGO, the process is fast, highly scalable, and controllable. Through a combination of rigorous data analysis using machine learning algorithms on transmission electron microscope images and systematic studies of process parameters, it is demonstrated that characteristics of the produced hGO (i.e., porosity and pore size) are remarkably reproducible to the extent that it can be predicted by empirical models of processing-property correlations. Depending on the tailored nanopore structures, the synthesized hGOs out-performed GO in a range of applications that can benefit from the nanoporous two-dimensional (2D) sheets such as in supercapacitors, gas adsorption, and nanofiltration membranes. These results are significant in offering new perspectives on the low-cost industrialization of 2D nanomaterials.

Optimization of Design Parameters for X̄ Control Charts with Independent Multiple Assignable Causes Based on Continuous Flow Processes

The economic design of control charts depends on the process shock model distribution due to difficulties from both theoretical and practical aspects. This paper pursues to develop the economic design of [Formula: see text] control chart for monitoring continuous flow processes under Bur XII shock model. The Burr XII distribution is flexible and its hazard rate can take many forms like fixed, increasing, decreasing, single mode or even U-shaped. Continuous flow processes find applications in batch processes like filtration, chemical processing, and more. A sensitivity analysis is executed and numeric examples are given to illustrate the effects of changing the parameters of the shock model distribution on the optimum values of the economic design models as discussed in this paper.

Synthesis of Dolutegravir Exploiting Continuous Flow Chemistry.

An efficient continuous flow process for the synthesis of dolutegravir, an active pharmaceutical ingredient (API) for HIV treatment, was investigated. The synthetic procedure starts from a readily available benzyl-protected pyran via six chemical transformations using continuous flow reactors. The significant advantage of this flow process includes the reduction of the overall reaction time from 34.5 h in batch to 14.5 min. The overall yield of each reaction step improved dramatically upon flow optimization. Another key feature of this synthesis is telescoping multiple steps.

Perovskite Nano-Powder and Nano-Film Catalysts in Mineralization of Aqueous Organic Contaminants through Solar Simulated Radiation

Water contamination with various contaminants, including organic species, is a global concern. Reclamation through safe, economic and technically feasible methods is imperative. Two perovskites, zinc titanate (ZnTiO3) and manganese titanate (MnTiO3), mixed with TiO2 phases, were prepared as nano-powders and nano-films. The materials were characterized and used as catalysts in photodegradation of aqueous methylene blue, a hazardous model contaminant, using solar simulated radiation. The effects of various reaction conditions on the photodegradation were examined. The kinetics indicated the suitability of using the process at various contaminant concentrations and catalyst loadings. Both powder and film catalysts completely removed the contaminant in less than 6 h. Powder and film forms of the MnTiO3 mixture were more efficient than their ZnTiO3 counterparts. In both perovskite mixtures, the films exhibited higher catalytic efficiency than the powders. The film materials exhibited high catalytic efficiency in both the continuous flow and batch processes. Water contaminated with various methylene blue concentrations can be treated by the film catalysts that can be recovered and reused with no technical difficulties. The results open new horizons for larger-scale water purification processes.

Continuous-flow synthesis of polysubstituted γ-butyrolactones via enzymatic cascade catalysis

Polysubstituted chiral γ-butyrolactones are the core structural units of many natural products and high value-added flavors and fragrances used in the food and cosmetic industry. Current enzymatic cascade synthesis of these molecules faces the problems of low enzyme activity and phase separation in batch reaction, resulting in low productivity. Herein, we report a new continuous-flow process to synthesize the optically pure Nicotiana tabacum lactone (3S,4S)-4a and whisky lactone (3R,4S)-4b from α,β-unsaturated γ-ketoesters. A new ene reductase (ER) from Swingsia samuiensi (SsER) and a carbonyl reductase (SsCR) were engineered by directed evolution to improve their activity and thermostability. The continuous-flow preparative reactions were performed in two 3D microfluidic reactors, generating (3S,4S)-4a (99% ee and 87% de) and (3R,4S)-4b (99% ee and 98% de) with space-time yields 3 and 7.4 times higher than those of the batch reactions. The significant enhancement in the productivity of enzyme cascade catalysis brought by cutting-edge continuous microfluidic technology will benefit the general multi-enzyme catalytic systems in the future.

A simplified model for the fabrication of silver nanowires in a continuous flow process and its experimental verification

A simplified model for the fabrication of silver nanowires in a continuous flow process and its experimental verification