查看更多>>摘要：Cellulose nanofibers have been widely used in membrane fabrication due to their unique structure,hydrophilicity,sustainability,facile surface modification,and low cost.In this study,the efficient combination of the precise molecular sieving characteristics of graphene oxide(GO)and the high permeability of the cellulose nanofibers(CNFs)network is demonstrated.GO nanosheets were incorporated into the CNF matrix using a facile vacuum filtration technique followed by chemical cross-linking.Cross-linking with glutaraldehyde not only resisted membrane swelling but also improved molecular selectivity.The nanofiltration performance of prepared membranes was evaluated in both aqueous and organic solutions.The optimized crosslinked membranes exhibited a pure solvent flux of 13.9 ± 1.9 Lm~(-2)h~(-1)bar~(-1)and 4.1 ± 0.35 Lm~(-2)h~(-1)bar~(-1)for water and ethanol respectively,while maintaining a rejection above 90% for Rose Bengal and Brilliant Blue dyes.
查看更多>>摘要：Hydrogen(H2)is known as an environmentally friendly and crucial source of energy and recently demands for this compound has increased globally.One of the main ways of production of this compound is the Water-Gas Shift(WGS)reaction which utilizes various catalysts based on the operating conditions of the process.This work presents the performance of a soft computing method named PSO-RBF to estimate carbon monoxide(GO)conversion in WGS reactions.In addition,decision tree analysis was also performed to extract the associated rules which provides the highest performance for the reaction(higher conversion of CO).Different active phase compositions and support types of catalysts were utilized for development of the PSO-RBF model.The developed model accounts for the intrinsic catalyst parameters for estimation of the reaction performance by including features such as surface area,calcination time and temperature.In addition,sensitivity analysis of the model predictions was also examined to identify useful patterns.The results showed that the PSO-RBF model can accurately predict the actual CO conversion data with overall R~2,AARD%,and RMSE values of 0.9977,3.93,and 0.0159,respectively.It was also observed that the decision tree model can successfully extract the rules and trends from the experimental data.The outcomes of the sensitivity analysis study revealed that the most influential parameters for the process are temperature and H2 composition in the feed stream.This work shows the capability of soft computing methods such as the PSO-RBF and decision tree approaches for estimating better catalysts and process conditions for this crucial reaction in the environmental field.2022 Institution of Chemical Engineers.Published by Elsevier Ltd.All rights reserved.
Jose Luis Solis-SanchezHeriberto Alcocer-GarciaEduardo Sanchez-Ramirez
13页
查看更多>>摘要：Levulinic acid is considered among the top twelve chemicals from biomass in terms of market potential,due to its considerable number of applications.Levulinic acid is obtained by acid hydrolysis of glucose using dilute sulfuric acid as a catalyst.Because of this,the resulting stream has an excess of water,which has an impact on energy consumption in the separation and purification process.So,it is important to analyze sustainable alternatives.Process intensification can help achieve this goal.Particularly,reactive distillation(RD)is an intensified process where is carried out the chemical reaction and distillation in a single equipment,the advantage of this reduction has a direct impact on the capital cost,and energy consumption in the last stages of separation,and environmental impact,improving the sustainability of the process.Additionally,reactive distillation positively impacts performance,and it is used to separate dilute mixtures more efficiently.Therefore,this work's objective is to implement a process intensification using a reactive distillation column to reduce energy consumption,process costs,and the final cost of Levulinic acid production.A conventional scheme is used to compare the energy,cost,environmental,and conversion impacts when using reactive distillation.The results show a total conversion of glucose to Levulinic acid using RD and similar purities are obtained when using the conventional reactor.In addition,it presents savings in the cost of the equipment by 23% and 24% in energy consumption compared to the conventional system.
查看更多>>摘要：The overall stability of Candida rugosa lipase(CRL)was improved via immobilization onto low-cost eco-friendly carriers(agroindustrial wastes)followed by using spouted bed dryer or spray dryer.Lipase covalently immobilized on glutaraldehyde-activated rice husk proved the greatest performance,retaining 94.1% of the initial activity,followed by sugarcane bagasse(90.3%)and green coconut fiber(89.3%).On the other hand,the enzyme activity retention of CRL-lipase bioencapsulated in magnetic chitosan treated with glutaraldehyde or sodium tripolyphosphate ranged from 73.6% to 84.6%.The dried product moisture content,and water activities ranged from 4.1% and 6.5% and from _(0.2)to 0.35,respectively.After storage for six months at 5 ℃,the immobilized enzyme systems retained at least 70.0% of its initial activity(vs 18.3% retained activity for the free lipase).After ten reuse cycles,enzyme immobilized onto lignocellulosic carriers retained on average 72.7% of its initial activity.The thermostability of all immobilized derivatives was significantly improved and lipase immobilized onto rice husk showed a stabilization factor of 2_(0.4)4 at 80 ℃.The kinetic data showed that the CRL-lipase suffered alterations in catalytic behavior after the immobilization/drying,mainly a slight decrease in affinity to the substrate(↑KM).Among all the assessed immobilized lipase for aroma synthesis the rice husk immobilized lipase displayed the best result towards the production of isoamyl caprylate(62.40 g.L~(-1)).In conclusion,this report reinforces the urgent need for the economic development of eco-sustainable immobilized biocatalysts to boost the use of enzymatic technology on industrial scale,and the feasibility of the association of immobilization and drying processes to improve the enzyme-quality features.
查看更多>>摘要：In this study,the hydrodynamics characteristics of packed column with structured sinusoidal corrugated sheets packings were investigated by computational fluid dynamics(CFD)modeling and simulation method.The proposed CFD model was first validated by comparing simulation results with those of experimental data in terms of pressure drop under different inlet gas velocities.Then the effects of wave length,amplitude,angle and placement method on dry pressure drop were studied by control variable method.The relationship between F factor and pressure drop with different packing structures were investigated.The flow fields of pressure and velocity were analyzed and then used to calculate the resistance coefficient of structured packings.This simulation study can contribute to the evaluation and optimization of multiphase flow characteristics and the mass transfer performance of packed column.
查看更多>>摘要：Herein,we report the synthesis of Bi2O3 modified CaO heterogeneous catalyst for biodiesel production from low valued gurgure(Monotheca Buxifolia)seed oil to develop profitable and sustainable approach.The catalysts were analyzed by X-ray diffractometer(XRD),Brunauer-Emmett-Teller(BET),Temperature programming desorption of CO2(TPD-CO2),Field emission scanning electron microscopy(FESEM),Energy dispersive X-ray(EDX).The activity evaluation results indicated that the CaO-Bi2O3 catalyst enriched with 20 wt% Bi2O3 loading displayed an excellent catalytic performance providing biodiesel yield of 98.7% under optimum reaction parameters of oil to methanol molar ratio 1:12,65 ℃ reaction temperature in 2 hr of reaction time and catalyst loading of 6 wt%.The catalyst depicted better reusability upto six reaction cycles and hence the cost of the biodiesel could be reduced effectively.Response surface methodology(RSM)based on central composite design(CCD)was also applied to investigate the influence of reaction parameters.The statistical deign results showed good consistent with the experimental data,providing p-vale of 0.000 i.e.high level of significance of the model.Finally,it could be summarized that the synthesized catalyst demonstrated remarkable activity and durability in term of biodiesel yield using gurguray oil as a cheap and non-edible feedstock.
查看更多>>摘要：Supercapacitors(SC)are essential energy storage devices for renewable energies.In this study,activated microporous carbon spheres(AMCS)and nitrogen-doped AMCS(N-AMCS)were synthesized using a modified extended Stober method followed by CO2 activation.A high specific area(> 3400 m~2 g~(-1))was obtained for AMCS and N-AMCS,and the diameters of the sphere could be tuned from 400 nm to 1.0 μm.The SC study revealed that the AMCS and N-AMCS achieved specific capacitances of 232.75 and 263.59 F g~(-1),respectively,in 6 M potassium hydroxide(KOH).The SC pouch cells were filled with aqueous,organic,and ionic liquid electrolytes.In 1 M MeEt3NBF4 in acetonitrile,the energy densities of AMCS and N-AMCS were 27.96 and 31.20 Wh kg~(-1),respectively,at the current density of _(0.5)A g~(-1),whereas the energy densities of AMCS and N-AMCS were 69.19 and 117.69 Wh kg~(-1),respectively,in EMIMBF4.In addition,in the aqueous electrolytes,AMCS and N-AMCS had capacitance retentions of 94% and 97%,respectively,after 10,000 cycles,while the capacitance retentions of 82% and 97% were achieved with AMCS and N-AMCS,respectively,after 50,000 cycles.
查看更多>>摘要：Several technologies and synthesis routes have been implemented to produce calcium phosphates(CaPs)with distinct characteristics for biomedical applications.However,produce CaPs in a controlled way still represents a challenge.Oscillatory flow reactors(OFRs)are a technology ready to deliver in terms of mixing intensification in multiphase systems.In particular,continuous processes in OFRs improve control over the reaction conditions and can be implemented at an industrial scale.The aim of this work was to study for the first time the influence of the oscillation amplitude(x0: 4,8 and 18 mm)and frequency if: 1.9,4 and 6 Hz)as well as residence time(τ: 3.3,6.6 min)on the final CaP particles'physicochemical properties using a continuous precipitation process in a novel modular oscillatory flow plate reactor(MOFPR).Furthermore,other parameters such as the initial reagents concentration,initial Ga/P molar ratio(Ca/P = 1.67,1.33)and temperature(T = 37,54 ℃)were also assessed.The synthesized particles and overall process were compared with particles obtained using the same methodology in conventional reactors,evidencing the potential of this technology to fabricate CaPs with tailored properties for potential application as nano or microcarriers for biomedical applications.
查看更多>>摘要：Gas-liquid-solid three-phase fluidized bed has been widely used in chemical,biotechnology and environmental industries for its advantages of large inter-phase contact area,high heat/mass transfer efficiency and intense reaction process.In this work,the bidirectional sinusoidal liquid pulsed GLS fluidized bed was proposed to improve the interphase relative velocity and reaction efficiency.The effects of particle properties and pulsed liquid amplitude/frequency on the flow characteristics were studied by numerical simulations and experiments.In a complete circulation period,the average axial solids holdup is larger near the middle region of the fluidized bed and gradually decreases along the upper and lower inlets.With the increase of pulsation amplitude or period,the axial average gas holdup distribution uniformity and the liquid-solid relative velocity increase significantly.Compared with the conventional upward gas-liquid-solid fluidized bed,the bidirectional fluidized bed can further improve the liquid-solid relative velocity and reaction efficiency.The obtained studies have important implications for better design,scale-up and operation of gas-liquid-solid multiphase fluidization systems.
查看更多>>摘要：Updated methods are proposed for estimating model parameters and error-covariance matrices in stochastic differential equation(SDE)models.New expressions,based on the LAMLE(Laplace Approximation Maximum Likelihood Estimation)and LAB(Laplace Approximation Bayesian)SDE estimation methods are derived so that LAMLE and LAB can be used for systems with multi-rate data and nonstationary disturbances.The updated LAMLE method is tested using simulated data from a two-state continuous stirred tank reactor(CSTR)model.Comparisons are made with the results obtained using the continuous-time stochastic method(CTSM),confirming that the updated LAMLE algorithm provides reliable estimates for unknown model parameters,measurement noise variances,and process-error variances.In all situations tested,the updated LAMLE algorithm converged to reliable parameter and uncertainty estimates,while avoiding convergence difficulties encountered by CTSM in some situations.The updated LAMLE and LAB algorithms will be useful for parameter estimation in online models used in advanced process monitoring and control applications where multi-rate data and nonstationary disturbances are of ten encountered.Estimates of measurement noise variances and process-error variances will be helpful for state-estimator tuning.
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