Continuous-flow upgrading of pentaerythritol synthesis technology via base-catalyzed aldol and Cannizzaro reactions of formaldehyde and acetaldehyde faces the challenge of effectively controlling the critical side rea...Continuous-flow upgrading of pentaerythritol synthesis technology via base-catalyzed aldol and Cannizzaro reactions of formaldehyde and acetaldehyde faces the challenge of effectively controlling the critical side reaction of hydroxymethyl acetaldehyde(HA)to the acrolein intermediate.Here,we first identified the forms of industrial formaldehyde as methane diol that easily converts to the alkaline formaldehyde under alkaline(NaOH)environment.The carbonyl group of alkaline formaldehyde induces deprotonation of acetaldehyde instead of the recognized base-hydroxyl group-induced deprotonation,and it needs to overcome only 18.31 kcal·mol^(-1)(1 kcal=4.186 kJ)energy barrier to form key intermediates of HA.The sodium solvation cage formed by NaOH hexa-coordinated formaldehyde effectively inhibits the alkalinity,thus contributing to a high energy barrier(46.21 kcal·mol^(-1))to unwanted acrolein formation.In addition,the solvation cage gradually opens to increase the alkalinity with the consumption of formaldehyde,thus facilitating the subsequent Cannizzaro reaction(to overcome 11.77 kcal·mol^(-1)).In comparison,strong alkalinity promotes the formation of acrolein(36.65 kcal·mol^(-1))to initiate the acetal side reaction,while weak alkalinity reduces the possibility of the Cannizzaro reaction(to overcome 20.44 kcal·mol^(-1)).This theoretically reveals the importance of the segmented feeding of weak and strong bases to successively control the aldol reaction and Cannizzaro reaction,and the combination of Na_(2)CO_(3) or HCOONa with NaOH improves the pentaerythritol yield by 7%to 13%compared to that of NaOH alone(70%yield)within 1 min at a throughput of 155.7 ml·min^(-1).展开更多
A new continuous-flow process for the enzymatic synthesis of optically pureγ-lactones,which are used as flavors and fragrances in the food and cosmetic industries,was developed in a three-dimensional microfluidic rea...A new continuous-flow process for the enzymatic synthesis of optically pureγ-lactones,which are used as flavors and fragrances in the food and cosmetic industries,was developed in a three-dimensional microfluidic reactor.The microchannels(175 mm in length,0.9 mm in depth,and 1.72 mL in volume)were carved precisely inside a single borosilicate glass(90 mm×75 mm×12 mm)with ultrafast femtosecond laser micromachining.The flow field analysis and reaction simulation showed that the mixing of substrates and enzymes was enhanced,allowing the adjustment of residence time in a wide window.SmCR_(V4),a carbonyl reductase with excellent catalytic activity and enantioselectivity towardγ/δ-keto acids,was employed for the asymmetric synthesis of various chiral lactones.30 mmol/L(R)-γ-decalactone(3g)can be obtained in 26 s with a space-time yield(STY)up to 16,877 g L^(-1)d^(-1),which is 14.4 times higher than the highest STY of batch reaction reported previously.This continuous-flow process was applied to the synthesis of 6 chiral lactones.In addition,the scaled-up synthesis of 3g was carried out in 6 cascade microreactors continuously for 6 h,demonstrating the feasibility and stability of the 3D continuous-flow process in enzymatic synthesis of optically pure compounds.展开更多
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 o...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-unsaturatedγ-ketoesters. A new ene reductase(ER) from Swingsia samuiensi(Ss ER) and a carbonyl reductase(Ss CR)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 and87% 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.展开更多
The selective oxidation of para-xylene(PX)to terephthalic acid(TPA)has received increasing attention due to the industrial applications of TPA.However,the oxidation of the C(sp^(3))‒H bond of PX is still a main challe...The selective oxidation of para-xylene(PX)to terephthalic acid(TPA)has received increasing attention due to the industrial applications of TPA.However,the oxidation of the C(sp^(3))‒H bond of PX is still a main challenge because of the higher bond dissociation energy.Herein,an efficient photocatalytic system for the oxidation of PX to TPA was developed by using tetrabutylammonium decatungstate(TBADT)photocatalyst using atmospheric oxygen as oxidant and 365 nm LED light irradiation.The resulting TPA product was easily separated from the post-reaction solution through simple filtration treatment with a 93.4%yield in CH3CN(37.5%1 mol L^(‒1) HCl)solvent after 19-h photocatalysis.Given the easy separation of TPA and the excellent recycling stability of TBADT,a continuous-flow photoreactor was successfully designed with promising prospect for potential industrial application.Mechanistic studies elucidated that the presence of HCl additive benefits the structural integrity of[W10O32]4−anions and the transition from excited states[W_(10)O_(32)]^(4‒*)to wO active species,leading to enhanced photooxidation performance.展开更多
In this article, polyphosphate-accumulating organisms （PAOs） from a lab-scale continuous-flow two-sludge system was isolated and identified, the different phosphorus accumulation characteristics of the isolates unde...In this article, polyphosphate-accumulating organisms （PAOs） from a lab-scale continuous-flow two-sludge system was isolated and identified, the different phosphorus accumulation characteristics of the isolates under anoxic and aerobic conditions were investigated. Two kinds of PAOs were both found in the anoxic zones of the two-sludge system, one of them utilized only oxygen as electron aeceptor, and the other one utilized either nitrate or oxygen as electron aeceptor. Of the total eight isolates, five isolates were capable of utilizing both nitrate and oxygen as electron acceptors to uptake phosphorus to some extent. And three of the five isolates showed good phosphorus accumulative capacities both under anoxic or aerobic conditions, two identified as Alcaligenes and one identified as Pseudomonas. Streptococcus was observed weak anoxic phosphorus accumulation because of its weak denitrification capacity, but it showed good phosphorus accumulation capacity under aerobic conditions. One isolates identified as Enterobacteriaceae was proved to be a special species of PAOs, which could only uptake small amounts of phosphorus under anoxic conditions, although its denitrification capacity and aerobic phosphorus accumulation capacity were excellent.展开更多
The floc morphology was investigated in a continuous-flow reactor, in order to understand the evolution of flocs in practical flocculation and sedimentation processes in water utilities. Kaolin-humic acid suspension w...The floc morphology was investigated in a continuous-flow reactor, in order to understand the evolution of flocs in practical flocculation and sedimentation processes in water utilities. Kaolin-humic acid suspension was used as the test water, and polyaluminum chloride was chosen as the coagulant. An in-situ recognition system was applied to analyze the floc size, boundary fractal dimension, and eccentricity ratios. Particle numbers and turbidity were also determined in the sedimentation stage. At a coagulant dose of 1 mg/L as Al, the average floc size increased from 62 to 78 μm and the boundary fractal dimension was around 1.14, suggesting that flocs were compact and continuously grew during the entire flocculation process. However, with the dose increased to 5 mg/L, the average floc size decreased and stabilized at around 65 μm, with the fractal dimension of 1.20. It can be concluded that the excess coagulant doses resulted in the formation of chain-shaped, lower density, and more branched structure flocs, thereby restricting flocs’ further growth in the subsequent flocculation. Floc morphology analysis suggested that charge neutralization dominated in the initial flocculation stage, then the bridge and sweep mechanisms were dominant in the subsequent flocculation. In addition, compared with the traditional inclined plate settler, a novel V-shaped plate settler introduced in this study had an advantage in small size floc（less than 5 μm） removal. The V-shaped region could promote aggregate restructuring and re-flocculation; therefore, the V-shaped plate settler provides an alternative method for sedimentation.展开更多
Understanding the unique characteristics of continuous-flow photochemistry will lead to a paradigm shift in the way we enhance sustainability and wellbeing.In this mini-review,we first provide a succinct overview of w...Understanding the unique characteristics of continuous-flow photochemistry will lead to a paradigm shift in the way we enhance sustainability and wellbeing.In this mini-review,we first provide a succinct overview of working principles of this technique and discuss several recent synthetic protocols.Then,emphasis is given to those representative examples which address environmental issues such as indoor air pollutants and water contamination.Finally,recent progress made using this technique to deal with rising CO2 emission,solar energy utilization and biomedical equipment is described.It is believed that this mini-review could inspire more chemists to utilize this technique in their research,either in the academic or industrial field.展开更多
A continuous-flow synthesis of nitriles by Schmidt reaction has been developed.Using this procedure,a variety of aldehydes could be smoothly transformed into the desired nitriles in good to excellent yields.The mild r...A continuous-flow synthesis of nitriles by Schmidt reaction has been developed.Using this procedure,a variety of aldehydes could be smoothly transformed into the desired nitriles in good to excellent yields.The mild reaction conditions and the flowing reaction system greatly improved the safety and make the reaction easy to scale up.展开更多
The association between continuous-flow left ventricular assist devices(CF-LVADs)and gastrointestinal(GI)bleeding from angiodysplasia is well recognized.However,the association between continuous-flow biventricular as...The association between continuous-flow left ventricular assist devices(CF-LVADs)and gastrointestinal(GI)bleeding from angiodysplasia is well recognized.However,the association between continuous-flow biventricular assist devices(CF-BIVADs)and bleeding angiodysplasia is less understood.We report a case of GI bleeding from a patient with a CF-BIVAD.The location of GI bleeding was identified by nuclear red blood cell bleeding scan.The vascular malformation leading to the bleed was identified and localized on angiography and then by pathology.The intensity of bleeding,reflected by number of units of packed red blood cells needed for normalization of hemoglobin,as well as the time to onset of bleeding after transplantation,are similar to that seen in the literature for CF-LVADs and pulsatile BIVADs.While angiography only detected a dilated late draining vein,pathology demonstrated the presence of both arterial and venous dilation in the submucosa,vascular abnormalities characteristic of a late arteriovenous malformation.展开更多
In the present study,we described a continuous-flow,one-pot synthesis of asymmetrical ureas using nucleophilic addition reaction of amines to isocyanates derived from acids’Curtius rearrangement.The advantages of thi...In the present study,we described a continuous-flow,one-pot synthesis of asymmetrical ureas using nucleophilic addition reaction of amines to isocyanates derived from acids’Curtius rearrangement.The advantages of this method included broad substrate scope,high yields,rapid reaction,simplicity,extraordinary safety,and easy scale-up.展开更多
The development of efficient and sustainable methods to obtain spirocyclic compounds is of significance as these structures are widely found in pharmaceuticals and agrochemicals.Herein,we disclose an electrochemical d...The development of efficient and sustainable methods to obtain spirocyclic compounds is of significance as these structures are widely found in pharmaceuticals and agrochemicals.Herein,we disclose an electrochemical dearomative spirocyclization of N-acyl sulfonamides in a continuous-flow cell.The reaction is simple and efficient without external catalysts or supporting electrolytes and could be applied in a decagram-scale synthesis.展开更多
High-entropy alloys(HEAs)have been widely applied in the field of catalysis due to their unique physicochemical properties.Nevertheless,it still remains a big challenge to prepare HEA nanoparticles(NPs)with ultrasmall...High-entropy alloys(HEAs)have been widely applied in the field of catalysis due to their unique physicochemical properties.Nevertheless,it still remains a big challenge to prepare HEA nanoparticles(NPs)with ultrasmall particle size and uniform size distribution.Recently,Kohei Kusada and Hiroshi Kitagawa's team reported a continuous-flow reactor-based liquid-phase reduction method for the preparation of ultrafine homogeneous HEA NPs,providing an effective strategy for the rational construction of high-efficiency HEA catalysts.展开更多
A novel egg-like nanosphere was designed as a long-lived catalyst and is described as F%O4@nSiO2-NHa-Fe2O3.xBi2O3@mSiO2. The catalyst was prepared using a modified Stober method with template-free surface-protected et...A novel egg-like nanosphere was designed as a long-lived catalyst and is described as F%O4@nSiO2-NHa-Fe2O3.xBi2O3@mSiO2. The catalyst was prepared using a modified Stober method with template-free surface-protected etching. The catalyst particle consists of a magnetic Fe3O4 core as the ＂yolk＂, an inner silica shell bearing active Fe2O3＂xBi2O3 species as the ＂egg white＂, and outer mesoporous silica as the ＂egg shell＂. It exhibits an excellent performance in the catalytic reduction of nitro aromatics to corresponding anilines in a fixed-bed continuous-flow reactor. The reaction could be performed at 80 ~C and could reach complete conversion in less than I rain with only a 7% excess of hydrazine hydrate. The catalyst bed could be easily shifted between different substrates without cross-contamination because of the uniformity of the catalyst particles. This catalyst exhibited very good stability in the continuous-flow protocol. In the long-term reduction of p-nitrophenol with 0.5 mmol.min-1 productivity, it worked for more than 1,500 cycles without any catalytic activity loss.展开更多
In this paper the photolysis half-lives of the model dyes in water solutions and under ultraviolet （UV） radiation were determined by using a continuous-flow spectrophotometric method. A quantitative structure- prope...In this paper the photolysis half-lives of the model dyes in water solutions and under ultraviolet （UV） radiation were determined by using a continuous-flow spectrophotometric method. A quantitative structure- property relationship （QSPR） study was carried out using 21 descriptors based on different chemometric tools including stepwise multiple linear regression （MLR） and partial least squares （PLS） for the prediction of the photolysis half-life （t1/2） of dyes. For the selection of test set compounds, a K-means clustering technique was used to classify the entire data set, so that all clusters were properly represented in both training and test sets. The QSPR results obtained with these models show that in MLR-derived model, photolysis half-lives of dyes depended strongly on energy of the highest occupied molecular orbital （EHoMO）, largest electron density of an atom in the molecule （ED^＋） and lipophilicity （logP）. While in the model derived from PLS, besides aforementioned EHOMO and ED^＋ descriptors, the molecular surface area （Sm）, molecular weight （M-W）, electronegativity （X）, energy of the second highest occupied molecular orbital （EHoMO- 1） and dipole moment （μ） had dominant effects on logt1/2 values of dyes. These were applicable for all classes of studied dyes （including monoazo, disazo, oxazine, sulfo- nephthaleins and derivatives of fluorescein）. The results were also assessed for their consistency with findings from other similar studies.展开更多
Continuous-flow microreactors offer increased reactivity and reusability via unique reaction pathways to address a wide range of practical nanocatalysis problems.However,only limited platforms exist to employ these mi...Continuous-flow microreactors offer increased reactivity and reusability via unique reaction pathways to address a wide range of practical nanocatalysis problems.However,only limited platforms exist to employ these microreactors for versatile nanocatalytic reactions.In this work,we conformally anchored nickel oxide(Ni O)nanosheets onto quartz fibers(QFs),which exhibited a high catalytic activity using the hydrogenation of 4-nitrophenol(4-NP)as a model reaction in a batch reaction study.More importantly,we demonstrated that fiber-based QF@Ni O composites(e.g.,cotton,fabric,belt,felt)can be integrated as versatile platforms to develop microreactors for continuous-flow catalytic applications including hydrogenation reactions and dyecatalyzed degradation.This fiber-based three-dimensional(3 D)nanocatalyst architecture effectively drives continuous-flow catalytic reactions with unprecedented efficiency due to the easy diffusion of reactant molecules into the fibrous structure,allowing contact with catalytic active sites.Our approach to continuous-flow microreactor design uses surface hybridization as a guideline to immobilize nanocatalysts onto the QFs.These QF-based platforms,coupled with rational design,are expected to be applied to a wide range of nanocatalytic reactions.展开更多
Vitamin B_(1) is widely applied in the healthcare and food industry as an antineuritic and antioxidant to maintain the normal functioning of nerve conduction,the heart,and the gastrointestinal tract.This study reports...Vitamin B_(1) is widely applied in the healthcare and food industry as an antineuritic and antioxidant to maintain the normal functioning of nerve conduction,the heart,and the gastrointestinal tract.This study reports on an integrated eight-step continuous-flow synthesis of vitamin B_(1) from commercially available 2-cyanoacetamide.The proposed continuous-flow process is based on advances in chemistry,engineering,and equipment design,and affords improved performance and safety compared with batch-mode manufacturing.Several challenges were precisely investigated and controlled,including mixing,unexpected clogging,solvent switches,an exothermic reaction,and the prevention of side reactions,using various micro-channel flow reactors,mixers,separators,and continuous filters.Vitamin B_(1) was produced with a separated yield of 47.7% and high purity,with a total residence time of about 3.5 h.This eight-step continuous-flow protocol enables technology involving up to six of the key principles of green chemistry.Hence,the application of flow technology is of paramount importance for improving security,reducing waste,and,in particular,improving the efficiency of batch operations that require several days for manufacturing.展开更多
Continuous-flow microwave-assisted heating has been extensively applied in chemical engineering.A common method used for heating fluids is by using a tube in a cavity.However,it is challenging to maintain high heating...Continuous-flow microwave-assisted heating has been extensively applied in chemical engineering.A common method used for heating fluids is by using a tube in a cavity.However,it is challenging to maintain high heating efficiency owing to the temperature-dependent dielectric properties of different fluids,and the temperature of fluids is usually uneven.In this study,a multilayer ring structure is proposed based on an impedance gradient that covers a tube with a porous material inside it to achieve high heating efficiency and uniformity.A multiphysics model,including electromagnetic fields,fluid heat transfer,and free and porous media flow,was established to simulate the continuous-flow microwave heating process.The dimensions of the multilayer ring structure were optimized and manufactured.Energy utilization efficiency experiments and continuous heating experiments were conducted,which demonstrated that the proposed model achieved an efficiency>90%with different aqueous ethanol solutions,while maintaining high heating uniformity compared with other heating models.Furthermore,the effects of the tube permittivity and porosity of the porous material on the heating efficiency were investigated to demonstrate the robustness of the proposed model.展开更多
To develop technically feasible and economically favorable dynamic process control(DPC)strategies for an alternating activated sludge(AAS)system,a bench-scale continuous-flow alternating aerobic and anoxic reactor,per...To develop technically feasible and economically favorable dynamic process control(DPC)strategies for an alternating activated sludge(AAS)system,a bench-scale continuous-flow alternating aerobic and anoxic reactor,performing short-cut nitrogen removal from real domestic wastewater was operated under different control strategies for more than five months.A fixed-time control(FTC) study showed that bending-points on pH and oxidation-reduction potential(ORP)profiles accurately coincided with the major biologic...展开更多
A new analytical method is proposed for the determination of heroin based on a sequential perturbation caused by trace amounts of heroin in the Cu(Ⅱ)-catalyzed oscillating reaction between hydrogen peroxide and sodiu...A new analytical method is proposed for the determination of heroin based on a sequential perturbation caused by trace amounts of heroin in the Cu(Ⅱ)-catalyzed oscillating reaction between hydrogen peroxide and sodium thiocyanate in an alkaline medium with the aid of a continuous-flow stirred tank reactor(CSTR). The method relies on the linear relationship between the change in oscillation period of the system and the concentration of heroin, with a detecting limit of 4.0×10^(-7) mol/L. The calibration curve fits a linear equation very well when the concentration of heroin is in the range of 2.0×10^(-6)_1.2×10^(-5) mol/L(r=0.9971). This method features good precision(RSD=0.98%). The influences of temperature, injection point, flow rate and reaction variables on the oscillation period were investigated in detail and a possible mechanism of the performance of heroin in the Cu(Ⅱ)-catalyzed oscillating reaction system is also discussed. The proposed method opens a new avenue for the determination of heroin.展开更多
A continuous-flow ultrasound-assisted oxidative desulfurization(UAOD)of partially hydro-treated diesel has been investigated using hydrogen peroxide-formic acid as simple and easy to apply oxidation system.The effects...A continuous-flow ultrasound-assisted oxidative desulfurization(UAOD)of partially hydro-treated diesel has been investigated using hydrogen peroxide-formic acid as simple and easy to apply oxidation system.The effects of different operating parameters of oxidation stage including residence time(2–24 min),formic acid to sulfur molar ratio(10–150),and oxidant to sulfur molar ratio(5–35)on the sulfur removal have been studied using response surface methodology(RSM)based on Box–Behnken design.Considering the operating costs of the continuous-flow oxidation stage including chemical and electrical energy consumption,the appropriate values of operating parameters were selected as follows:residence time of 16 min,the formic acid to sulfur molar ratio of 54.47,and the oxidant to sulfur molar ratio of 8.24.In these conditions,the sulfur removal and the volume ratio of the hydrocarbon phase to the aqueous phase were 86.90%and 4.34,respectively.By drastic reduction in the chemical consumption in the oxidation stage,the volume ratio of the hydrocarbon phase to the aqueous phase was increased up to 10.Therefore,the formic acid to sulfur molar ratio and the oxidant to sulfur molar ratio were obtained 23.64 and 3.58,respectively,which lead to sulfur removal of 84.38%with considerable improvements on the operating cost of oxidation stage in comparison with the previous works.展开更多
基金funded by the National Natural Science Foundation of China(22478632)Key Scientific and Technological Project of Henan Province(242102321032).
文摘Continuous-flow upgrading of pentaerythritol synthesis technology via base-catalyzed aldol and Cannizzaro reactions of formaldehyde and acetaldehyde faces the challenge of effectively controlling the critical side reaction of hydroxymethyl acetaldehyde(HA)to the acrolein intermediate.Here,we first identified the forms of industrial formaldehyde as methane diol that easily converts to the alkaline formaldehyde under alkaline(NaOH)environment.The carbonyl group of alkaline formaldehyde induces deprotonation of acetaldehyde instead of the recognized base-hydroxyl group-induced deprotonation,and it needs to overcome only 18.31 kcal·mol^(-1)(1 kcal=4.186 kJ)energy barrier to form key intermediates of HA.The sodium solvation cage formed by NaOH hexa-coordinated formaldehyde effectively inhibits the alkalinity,thus contributing to a high energy barrier(46.21 kcal·mol^(-1))to unwanted acrolein formation.In addition,the solvation cage gradually opens to increase the alkalinity with the consumption of formaldehyde,thus facilitating the subsequent Cannizzaro reaction(to overcome 11.77 kcal·mol^(-1)).In comparison,strong alkalinity promotes the formation of acrolein(36.65 kcal·mol^(-1))to initiate the acetal side reaction,while weak alkalinity reduces the possibility of the Cannizzaro reaction(to overcome 20.44 kcal·mol^(-1)).This theoretically reveals the importance of the segmented feeding of weak and strong bases to successively control the aldol reaction and Cannizzaro reaction,and the combination of Na_(2)CO_(3) or HCOONa with NaOH improves the pentaerythritol yield by 7%to 13%compared to that of NaOH alone(70%yield)within 1 min at a throughput of 155.7 ml·min^(-1).
基金financially sponsored by the National Key Research and Development Program of China(No.2021YFC2102804)the National Natural Science Foundation of China(No.22078096)。
文摘A new continuous-flow process for the enzymatic synthesis of optically pureγ-lactones,which are used as flavors and fragrances in the food and cosmetic industries,was developed in a three-dimensional microfluidic reactor.The microchannels(175 mm in length,0.9 mm in depth,and 1.72 mL in volume)were carved precisely inside a single borosilicate glass(90 mm×75 mm×12 mm)with ultrafast femtosecond laser micromachining.The flow field analysis and reaction simulation showed that the mixing of substrates and enzymes was enhanced,allowing the adjustment of residence time in a wide window.SmCR_(V4),a carbonyl reductase with excellent catalytic activity and enantioselectivity towardγ/δ-keto acids,was employed for the asymmetric synthesis of various chiral lactones.30 mmol/L(R)-γ-decalactone(3g)can be obtained in 26 s with a space-time yield(STY)up to 16,877 g L^(-1)d^(-1),which is 14.4 times higher than the highest STY of batch reaction reported previously.This continuous-flow process was applied to the synthesis of 6 chiral lactones.In addition,the scaled-up synthesis of 3g was carried out in 6 cascade microreactors continuously for 6 h,demonstrating the feasibility and stability of the 3D continuous-flow process in enzymatic synthesis of optically pure compounds.
基金financially sponsored by the National Key Research and Development Program of China (No.2021YFC2102804)the National Natural Science Foundation of China(No.22078096)。
文摘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-unsaturatedγ-ketoesters. A new ene reductase(ER) from Swingsia samuiensi(Ss ER) and a carbonyl reductase(Ss CR)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 and87% 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.
文摘The selective oxidation of para-xylene(PX)to terephthalic acid(TPA)has received increasing attention due to the industrial applications of TPA.However,the oxidation of the C(sp^(3))‒H bond of PX is still a main challenge because of the higher bond dissociation energy.Herein,an efficient photocatalytic system for the oxidation of PX to TPA was developed by using tetrabutylammonium decatungstate(TBADT)photocatalyst using atmospheric oxygen as oxidant and 365 nm LED light irradiation.The resulting TPA product was easily separated from the post-reaction solution through simple filtration treatment with a 93.4%yield in CH3CN(37.5%1 mol L^(‒1) HCl)solvent after 19-h photocatalysis.Given the easy separation of TPA and the excellent recycling stability of TBADT,a continuous-flow photoreactor was successfully designed with promising prospect for potential industrial application.Mechanistic studies elucidated that the presence of HCl additive benefits the structural integrity of[W10O32]4−anions and the transition from excited states[W_(10)O_(32)]^(4‒*)to wO active species,leading to enhanced photooxidation performance.
基金Project supported by the Science and Technology Project of Heilongjiang Province (No. GA01C201-03).
文摘In this article, polyphosphate-accumulating organisms （PAOs） from a lab-scale continuous-flow two-sludge system was isolated and identified, the different phosphorus accumulation characteristics of the isolates under anoxic and aerobic conditions were investigated. Two kinds of PAOs were both found in the anoxic zones of the two-sludge system, one of them utilized only oxygen as electron aeceptor, and the other one utilized either nitrate or oxygen as electron aeceptor. Of the total eight isolates, five isolates were capable of utilizing both nitrate and oxygen as electron acceptors to uptake phosphorus to some extent. And three of the five isolates showed good phosphorus accumulative capacities both under anoxic or aerobic conditions, two identified as Alcaligenes and one identified as Pseudomonas. Streptococcus was observed weak anoxic phosphorus accumulation because of its weak denitrification capacity, but it showed good phosphorus accumulation capacity under aerobic conditions. One isolates identified as Enterobacteriaceae was proved to be a special species of PAOs, which could only uptake small amounts of phosphorus under anoxic conditions, although its denitrification capacity and aerobic phosphorus accumulation capacity were excellent.
基金supported by the National Science and Technology Major Project of Twelfth Five Years(Nos.2014ZX07201-012-2,2013ZX07201007-002)the National Innovation Team supported by the National Science Foundation of China(No.50821002)the State Key Laboratory of Urban Water Resource and Environment(Harbin Institute of Technology)(No.2012DX07)
文摘The floc morphology was investigated in a continuous-flow reactor, in order to understand the evolution of flocs in practical flocculation and sedimentation processes in water utilities. Kaolin-humic acid suspension was used as the test water, and polyaluminum chloride was chosen as the coagulant. An in-situ recognition system was applied to analyze the floc size, boundary fractal dimension, and eccentricity ratios. Particle numbers and turbidity were also determined in the sedimentation stage. At a coagulant dose of 1 mg/L as Al, the average floc size increased from 62 to 78 μm and the boundary fractal dimension was around 1.14, suggesting that flocs were compact and continuously grew during the entire flocculation process. However, with the dose increased to 5 mg/L, the average floc size decreased and stabilized at around 65 μm, with the fractal dimension of 1.20. It can be concluded that the excess coagulant doses resulted in the formation of chain-shaped, lower density, and more branched structure flocs, thereby restricting flocs’ further growth in the subsequent flocculation. Floc morphology analysis suggested that charge neutralization dominated in the initial flocculation stage, then the bridge and sweep mechanisms were dominant in the subsequent flocculation. In addition, compared with the traditional inclined plate settler, a novel V-shaped plate settler introduced in this study had an advantage in small size floc（less than 5 μm） removal. The V-shaped region could promote aggregate restructuring and re-flocculation; therefore, the V-shaped plate settler provides an alternative method for sedimentation.
基金Financial support from the National Natural Science Foundation of China(No.21771088)Zhejiang Provincial Natural Science Foundation of China(No.LY20B010005)the open research funds of JLU(2020-9)&FJIRSM,CAS(No.20170034)。
文摘Understanding the unique characteristics of continuous-flow photochemistry will lead to a paradigm shift in the way we enhance sustainability and wellbeing.In this mini-review,we first provide a succinct overview of working principles of this technique and discuss several recent synthetic protocols.Then,emphasis is given to those representative examples which address environmental issues such as indoor air pollutants and water contamination.Finally,recent progress made using this technique to deal with rising CO2 emission,solar energy utilization and biomedical equipment is described.It is believed that this mini-review could inspire more chemists to utilize this technique in their research,either in the academic or industrial field.
基金the National Natural Science Foundation of China(No.21877005)for financial support
文摘A continuous-flow synthesis of nitriles by Schmidt reaction has been developed.Using this procedure,a variety of aldehydes could be smoothly transformed into the desired nitriles in good to excellent yields.The mild reaction conditions and the flowing reaction system greatly improved the safety and make the reaction easy to scale up.
文摘The association between continuous-flow left ventricular assist devices(CF-LVADs)and gastrointestinal(GI)bleeding from angiodysplasia is well recognized.However,the association between continuous-flow biventricular assist devices(CF-BIVADs)and bleeding angiodysplasia is less understood.We report a case of GI bleeding from a patient with a CF-BIVAD.The location of GI bleeding was identified by nuclear red blood cell bleeding scan.The vascular malformation leading to the bleed was identified and localized on angiography and then by pathology.The intensity of bleeding,reflected by number of units of packed red blood cells needed for normalization of hemoglobin,as well as the time to onset of bleeding after transplantation,are similar to that seen in the literature for CF-LVADs and pulsatile BIVADs.While angiography only detected a dilated late draining vein,pathology demonstrated the presence of both arterial and venous dilation in the submucosa,vascular abnormalities characteristic of a late arteriovenous malformation.
基金National Natural Science Foundation of China(Grant No.21877005).
文摘In the present study,we described a continuous-flow,one-pot synthesis of asymmetrical ureas using nucleophilic addition reaction of amines to isocyanates derived from acids’Curtius rearrangement.The advantages of this method included broad substrate scope,high yields,rapid reaction,simplicity,extraordinary safety,and easy scale-up.
基金supported by the National Natural Science Foundation of China(No.22171046)the Hundred-Talent Project of Fujian(No.50021113).
文摘The development of efficient and sustainable methods to obtain spirocyclic compounds is of significance as these structures are widely found in pharmaceuticals and agrochemicals.Herein,we disclose an electrochemical dearomative spirocyclization of N-acyl sulfonamides in a continuous-flow cell.The reaction is simple and efficient without external catalysts or supporting electrolytes and could be applied in a decagram-scale synthesis.
基金supported by the National Natural Science Foundation of China(No.22071172).
文摘High-entropy alloys(HEAs)have been widely applied in the field of catalysis due to their unique physicochemical properties.Nevertheless,it still remains a big challenge to prepare HEA nanoparticles(NPs)with ultrasmall particle size and uniform size distribution.Recently,Kohei Kusada and Hiroshi Kitagawa's team reported a continuous-flow reactor-based liquid-phase reduction method for the preparation of ultrafine homogeneous HEA NPs,providing an effective strategy for the rational construction of high-efficiency HEA catalysts.
文摘A novel egg-like nanosphere was designed as a long-lived catalyst and is described as F%O4@nSiO2-NHa-Fe2O3.xBi2O3@mSiO2. The catalyst was prepared using a modified Stober method with template-free surface-protected etching. The catalyst particle consists of a magnetic Fe3O4 core as the ＂yolk＂, an inner silica shell bearing active Fe2O3＂xBi2O3 species as the ＂egg white＂, and outer mesoporous silica as the ＂egg shell＂. It exhibits an excellent performance in the catalytic reduction of nitro aromatics to corresponding anilines in a fixed-bed continuous-flow reactor. The reaction could be performed at 80 ~C and could reach complete conversion in less than I rain with only a 7% excess of hydrazine hydrate. The catalyst bed could be easily shifted between different substrates without cross-contamination because of the uniformity of the catalyst particles. This catalyst exhibited very good stability in the continuous-flow protocol. In the long-term reduction of p-nitrophenol with 0.5 mmol.min-1 productivity, it worked for more than 1,500 cycles without any catalytic activity loss.
文摘In this paper the photolysis half-lives of the model dyes in water solutions and under ultraviolet （UV） radiation were determined by using a continuous-flow spectrophotometric method. A quantitative structure- property relationship （QSPR） study was carried out using 21 descriptors based on different chemometric tools including stepwise multiple linear regression （MLR） and partial least squares （PLS） for the prediction of the photolysis half-life （t1/2） of dyes. For the selection of test set compounds, a K-means clustering technique was used to classify the entire data set, so that all clusters were properly represented in both training and test sets. The QSPR results obtained with these models show that in MLR-derived model, photolysis half-lives of dyes depended strongly on energy of the highest occupied molecular orbital （EHoMO）, largest electron density of an atom in the molecule （ED^＋） and lipophilicity （logP）. While in the model derived from PLS, besides aforementioned EHOMO and ED^＋ descriptors, the molecular surface area （Sm）, molecular weight （M-W）, electronegativity （X）, energy of the second highest occupied molecular orbital （EHoMO- 1） and dipole moment （μ） had dominant effects on logt1/2 values of dyes. These were applicable for all classes of studied dyes （including monoazo, disazo, oxazine, sulfo- nephthaleins and derivatives of fluorescein）. The results were also assessed for their consistency with findings from other similar studies.
基金supported by the National Natural Science Foundation of China(52003043)the Shanghai Pujiang Program(20PJ1400400)the Fundamental Research Funds for the Central Universities(21D110607)。
文摘Continuous-flow microreactors offer increased reactivity and reusability via unique reaction pathways to address a wide range of practical nanocatalysis problems.However,only limited platforms exist to employ these microreactors for versatile nanocatalytic reactions.In this work,we conformally anchored nickel oxide(Ni O)nanosheets onto quartz fibers(QFs),which exhibited a high catalytic activity using the hydrogenation of 4-nitrophenol(4-NP)as a model reaction in a batch reaction study.More importantly,we demonstrated that fiber-based QF@Ni O composites(e.g.,cotton,fabric,belt,felt)can be integrated as versatile platforms to develop microreactors for continuous-flow catalytic applications including hydrogenation reactions and dyecatalyzed degradation.This fiber-based three-dimensional(3 D)nanocatalyst architecture effectively drives continuous-flow catalytic reactions with unprecedented efficiency due to the easy diffusion of reactant molecules into the fibrous structure,allowing contact with catalytic active sites.Our approach to continuous-flow microreactor design uses surface hybridization as a guideline to immobilize nanocatalysts onto the QFs.These QF-based platforms,coupled with rational design,are expected to be applied to a wide range of nanocatalytic reactions.
基金supported by the Fundamental Research Funds for the Central Universities.
文摘Vitamin B_(1) is widely applied in the healthcare and food industry as an antineuritic and antioxidant to maintain the normal functioning of nerve conduction,the heart,and the gastrointestinal tract.This study reports on an integrated eight-step continuous-flow synthesis of vitamin B_(1) from commercially available 2-cyanoacetamide.The proposed continuous-flow process is based on advances in chemistry,engineering,and equipment design,and affords improved performance and safety compared with batch-mode manufacturing.Several challenges were precisely investigated and controlled,including mixing,unexpected clogging,solvent switches,an exothermic reaction,and the prevention of side reactions,using various micro-channel flow reactors,mixers,separators,and continuous filters.Vitamin B_(1) was produced with a separated yield of 47.7% and high purity,with a total residence time of about 3.5 h.This eight-step continuous-flow protocol enables technology involving up to six of the key principles of green chemistry.Hence,the application of flow technology is of paramount importance for improving security,reducing waste,and,in particular,improving the efficiency of batch operations that require several days for manufacturing.
基金supported by the National Natural Science Foundation of China(Grant No.62001398)the National Key Research and Development Program of China(Grant No.2023YFB4603500)+1 种基金the Fundamental Research Funds of China West Normal University(Grant No.KCXTD2024-2)the Key Project of Chengdu City,China(Grant No.2024-JB00-00012-GX).
文摘Continuous-flow microwave-assisted heating has been extensively applied in chemical engineering.A common method used for heating fluids is by using a tube in a cavity.However,it is challenging to maintain high heating efficiency owing to the temperature-dependent dielectric properties of different fluids,and the temperature of fluids is usually uneven.In this study,a multilayer ring structure is proposed based on an impedance gradient that covers a tube with a porous material inside it to achieve high heating efficiency and uniformity.A multiphysics model,including electromagnetic fields,fluid heat transfer,and free and porous media flow,was established to simulate the continuous-flow microwave heating process.The dimensions of the multilayer ring structure were optimized and manufactured.Energy utilization efficiency experiments and continuous heating experiments were conducted,which demonstrated that the proposed model achieved an efficiency>90%with different aqueous ethanol solutions,while maintaining high heating uniformity compared with other heating models.Furthermore,the effects of the tube permittivity and porosity of the porous material on the heating efficiency were investigated to demonstrate the robustness of the proposed model.
文摘To develop technically feasible and economically favorable dynamic process control(DPC)strategies for an alternating activated sludge(AAS)system,a bench-scale continuous-flow alternating aerobic and anoxic reactor,performing short-cut nitrogen removal from real domestic wastewater was operated under different control strategies for more than five months.A fixed-time control(FTC) study showed that bending-points on pH and oxidation-reduction potential(ORP)profiles accurately coincided with the major biologic...
基金Supported by the Project of International Cooperation between China and U kraine(No.0 4 3- 0 5 ) and the Project ofKJCXGC- 0 1Northwest Norm al U niversityChina
文摘A new analytical method is proposed for the determination of heroin based on a sequential perturbation caused by trace amounts of heroin in the Cu(Ⅱ)-catalyzed oscillating reaction between hydrogen peroxide and sodium thiocyanate in an alkaline medium with the aid of a continuous-flow stirred tank reactor(CSTR). The method relies on the linear relationship between the change in oscillation period of the system and the concentration of heroin, with a detecting limit of 4.0×10^(-7) mol/L. The calibration curve fits a linear equation very well when the concentration of heroin is in the range of 2.0×10^(-6)_1.2×10^(-5) mol/L(r=0.9971). This method features good precision(RSD=0.98%). The influences of temperature, injection point, flow rate and reaction variables on the oscillation period were investigated in detail and a possible mechanism of the performance of heroin in the Cu(Ⅱ)-catalyzed oscillating reaction system is also discussed. The proposed method opens a new avenue for the determination of heroin.
基金the supports provided by National Iranian Oil Engineering and Construction Company(NIOEC)。
文摘A continuous-flow ultrasound-assisted oxidative desulfurization(UAOD)of partially hydro-treated diesel has been investigated using hydrogen peroxide-formic acid as simple and easy to apply oxidation system.The effects of different operating parameters of oxidation stage including residence time(2–24 min),formic acid to sulfur molar ratio(10–150),and oxidant to sulfur molar ratio(5–35)on the sulfur removal have been studied using response surface methodology(RSM)based on Box–Behnken design.Considering the operating costs of the continuous-flow oxidation stage including chemical and electrical energy consumption,the appropriate values of operating parameters were selected as follows:residence time of 16 min,the formic acid to sulfur molar ratio of 54.47,and the oxidant to sulfur molar ratio of 8.24.In these conditions,the sulfur removal and the volume ratio of the hydrocarbon phase to the aqueous phase were 86.90%and 4.34,respectively.By drastic reduction in the chemical consumption in the oxidation stage,the volume ratio of the hydrocarbon phase to the aqueous phase was increased up to 10.Therefore,the formic acid to sulfur molar ratio and the oxidant to sulfur molar ratio were obtained 23.64 and 3.58,respectively,which lead to sulfur removal of 84.38%with considerable improvements on the operating cost of oxidation stage in comparison with the previous works.
