Computational fluid dynamics-discrete element method simulation of stirred tank reactor for graphene production

Liquid phase exfoliation(LPE)process for graphene production is usually carried out in stirred tank reactor and the interactions between the solvent and the graphite particles are important as to improve the production efficiency.In this paper,these interactions were revealed by computational fluid dynamics–discrete element method(CFD-DEM)method.Based on simulation results,both liquid phase flow hydrodynamics and particle motion behavior have been analyzed,which gave the general information of the multiphase flow behavior inside the stirred tank reactor as to graphene production.By calculating the threshold at the beginning of graphite exfoliation process,the shear force from the slip velocity was determined as the active force.These results can support the optimization of the graphene production process.

Optimal reaction conditions for pyridine synthesis in riser reactor

Pjridine has been generally synthesized by aldehydes and ammonia in a turbulent fluidized-bed reactor. In this paper, a novel riser reactor was proposed for pyridine synthesis. Experiment result showed that the yield of pyridine and 3-picoline decreased, but the selectivity of pyridine over 3-picoline increased compared to turbulent fluidized-bed reactor. Based on experimental data, a modified kinetic model was used for the determination of optimal operating condition for riser reactor. The optimal operating condition of riser reactor given by this modified model was as follows： The reaction temperature of 755 K, catalyst to feedstock ratio （CTFR） of 87, residence timeof3.8sandinitialacetaldehydesconcentrationof0.0029mol.L-1 （acetaldehydes to formaldehydes ratio by mole （ATFR） of 0.65 and ammonia to aldehydes ratio by mole （ATAR） of 0.9, water contention of 63wt% （formaldehyde solution））.

Modeling of pyridine synthesis process in a coupled fluidized bed reactor

To obtain the optimal operating conditions of a coupled reactor for pyridine synthesis,reactor modeling process is carried out in this paper.During the modeling process,the flow hydrodynamics,heat transfer behavior,inter-phase mass transfer behavior and reaction kinetics were taken into consideration consequently.Further,a regression program based on least square method was proposed to regress the model parameters.The prediction results agreed well with the experimental results with an average deviation of 5.9%.Finally,by setting suitable aim function,the optimal operating conditions of the coupled reactor for pyridine synthesis were determined.

SENP2-mediated SERCA2a deSUMOylation increases calcium overload in cardiomyocytes to aggravate myocardial ischemia/reperfusion injury

Background:Sarcoplasmic reticulum calcium ATPase 2a(SERCA2a)is a key protein that maintains myocardial Ca2+homeostasis.The present study aimed to investigate the mechanism underlying the SERCA2a-SUMOylation(small ubiquitinlike modifier)process after ischemia/reperfusion injury(I/RI)in vitro and in vivo.Methods:Calcium transient and systolic/diastolic function of cardiomyocytes isolated from Serca2a knockout(KO)and wildtype mice with I/RI were compared.SUMO-relevant protein expression and localization were detected by quantitative real-time PCR(RT-qPCR),Western blotting,and immunofluorescence in vitro and in vivo.Serca2a-SUMOylation,infarct size,and cardiac function of Senp1 or Senp2 overexpressed/suppressed adenovirus infected cardiomyocytes,were detected by immunoprecipitation,triphenyltetrazolium chloride(TTC)-Evans blue staining,and echocardiography respectively.Results:The results showed that the changes of Fura-2 fluorescence intensity and contraction amplitude of cardiomyocytes decreased in the I/RI groups and were further reduced in the Serca2a KO+I/RI groups.Senp1 and Senp2 messenger ribose nucleic acid(mRNA)and protein expression levels in vivo and in cardiomyocytes were highest at 6 h and declined at 12 h after I/RI.However,the highest levels in HL-1 cells were recorded at 12 h.Senp2 expression increased in the cytoplasm,unlike that of Senp1.Inhibition of Senp2 protein reversed the I/RI-induced Serca2a-SUMOylation decline,reduced the infarction area,and improved cardiac function,while inhibition of Senp1 protein could not restore the above indicators.Conclusion:I/RI activated Senp1 and Senp2 protein expression,which promoted Serca2a-deSUMOylation,while inhibition of Senp2 expression reversed Serca2a-SUMOylation and improved cardiac function.

Flow hydrodynamics in a gas–solid fluidized bed reactor with two reaction zones

A novel reactor with two reaction zones is proposed for pyridine synthesis.The flow hydrodynamics were investigated in experiments.Pressure taps and a PV-6D optical fiber were used to measure the pressure fluctuation and particle concentration,respectively.Hilbert–Huang analysis was adopted to distinguish the flow patterns through pressure fluctuation.Results show that the flow patterns are bubbling fluidization and fast fluidization in the regions below(reaction zone I)and above(reaction zone II)the nozzles,respectively.The radial distribution of the cluster time fraction was obtained through signal waves of the particle concentration.Analysis of the cluster time fraction revealed two radial distributions.In the region around the nozzles,the cluster time fraction ranged from 0 to 0.2 and concentrated at radial positions r/R=0–1,which resulted from unsymmetrical catalyst feeding.In reaction zone II,the cluster time fraction ranged from 0 to 0.2,and the radial distribution indicated a core–annulus structure.