Chemical Engineering Science最新文献

Recently, biomass-derived porous carbon has gained popularity as a cathode material for Zn-ion hybrid supercapacitor (ZIHSs) due to its unique structure and heteroatoms. However, the understanding of how biomass part affects resulting carbon structure and ZIHSs performance is limited. This study utilizes cattail leaves (CLs), cattail wools (CWs), and cattail stems (CSs) as carbon sources, with each impacting carbon microstructure, morphology, specific surface area (SSA), and oxygen content. CLs-based porous carbon (CLPC) exhibits a distinct hollow tube structure with thinner walls, high oxygen content, and a large SSA, which are crucial for enhanced electrochemical performance. The aqueous Zn//CLPC ZIHSs demonstrate remarkable energy density (190 Wh kg⁻¹), specific capacity (253 mAh/g at 0.1 A/g), and cycle life (91% capacity retention over 10,000 cycles at 10 A/g). Electrochemical processes are studied through various techniques, shedding light on the relationship between cattail parts, carbon structure, and ZIHSs performance, aiding in more efficient biomass utilization.

This study evaluates the noise resilience of multi-objective Bayesian optimization (MOBO) algorithms in chemical synthesis, an aspect critical for processes like telescoped reactions and heterogeneous catalysis but seldom systematically assessed. Through simulation experiments on amidation, acylation, and S_NAr reactions under varying noise levels, we identify the qNEHVI acquisition function as notably proficient in handling noise. Subsequently, qNEHVI is employed to optimize a two-step heterogeneous catalysis for the continuous-flow synthesis of hexafluoroisopropanol. Remarkable optimization is achieved within just 29 experimental runs, resulting in an E-factor of 0.125 and a yield of 93.1%. The optimal conditions are established at 5.0 sccm and 120 °C for the first step, and 94.0 sccm and 170 °C for the second step. This research highlights qNEHVI’s potential in noisy multi-objective optimization and its practical utility in refining complex synthesis processes.

Hollow fiber ceramic membrane technology demonstrates a great potential for high performance oxygen separation from air. Upscaling of single hollow fiber membrane for membrane stacks and modules is necessary toward practical applications. However, experimental methods are very time-consuming and highly cost. Mathematical modeling is a cost-effective technique and very flexible to evaluate different upscaling strategies. In this research, built upon the experimental results of a proof-of-concept hollow fiber membrane stack, a computational fluid dynamics-based Multiphysics stack model is developed and validated. Comprehensive simulations are conducted to understand the behaviors of stacks under different operating conditions. Different designs strategies are also evaluated toward optimizations of stack performance.

Vibrated gas-fluidized beds are widely used industrially, and two main methods exist to simulate them computationally: (i) in a moving reference frame by oscillating gravity and (ii) in a stationary reference frame by moving the distributor. Further, it is unclear whether gas flow in the plenum chamber of a vibrated fluidized bed should be modeled as constant or oscillating. Here, we challenge the accuracy of different potential modeling methods by comparing with experimental results of structured bubbling because these results are deterministic, avoiding the need for comparing via statistically averaged quantities. Results show that modeling a moving distributor and moving sidewalls as physically accurately as possible is important, and modeling the system in the moving reference frame is less accurate than in the stationary reference frame, due to subtle differences. Further, it is more accurate to model the gas flow as constant rather than oscillatory in the plenum chamber.

Previous studies revealed that the addition of propane enhances the recovery of methane and the storage of carbon dioxide but, at the same time, the enclathration of propane is limited. In order to deepen the CO₂/CH₄ replacement mechanism in the presence of contained concentrations of propane, this research experimentally explores the formation of hydrates into an unstirred reactor with binary CO₂/C₃H₈ mixtures at different concentrations (from 90/10 to 80/20 vol%). The lowest pressures reached within the system, together with the thermodynamic trend of both formation and dissociation processes, allowed to explain the previously mentioned low capture of propane during replacement. The results were then explained in terms of cage occupancy and molecular diameter/cavity diameter ratio.

A concept and model of two critical Reynolds numbers Re_p,cr1 and Re_p,cr2 corresponding respectively to onsets of drag crisis and recovery are proposed. A drag model at limits of zero particle Mach and Knudsen numbers is constructed. On this basis, we develop a general drag coefficient model applicable for a spherical particle traveling in a gas by using a large number of available data derived from the previous experiments, direct numerical simulations and direct simulation Monte-Carlo methods. The scope of applicability of the proposed drag model covers all flow regimes relative to the particle characterized by particle Reynolds and Mach (or Knudsen) numbers and different particle-to-gas temperature ratios. Its comparison with two latest general drag models shows the significantly smaller relative error. Furthermore, quasi-one dimensional simulations against two supersonic nozzle gas-particle flow experiments are conducted with an in-house code to validate its accuracy in comparison with the two drag models.

The Acid-Base Flow Battery is an innovative and sustainable electrochemical storage system storing energy in the form of salinity and pH gradients. However, parasitic currents via manifolds dramatically affect system by reducing its Round-Trip Efficiency (RTE).

This work experimentally studies this phenomenon using a purposely designed methodology involving sticks placed in the manifold ducts. Various figures of merit were calculated to evaluate battery performance in the charge and discharge phases. A mathematical model was validated and applied to investigate the ionic parasitic currents. The results highlighted the importance of studying this phenomenon, as achieving a reduction in the parasitic currents caused a 25% increase in the net power and more than tripled the RTE compared to the reference configuration without sticks. Although reducing manifold diameter increases pumping losses, it was found to be anyway really beneficial for the process performance and paves the way for future, more suitable, battery designs.

With the aim of investigating the changing law of crystallization driving force of typical energetic compounds under micro-scale crystallization conditions, a thermodynamic parameter determination method based on optofluidics was proposed. Aimed at nitro, nitramine and nitrate explosives in energetic compounds, hexanitrostilbene (HNS), cyclotetramethylene tetranitramine (HMX) and pentaerythritol tetranitrate (PETN) were selected as representatives, the solubility of the three kinds of energetic compounds in their respective commonly used solvents (HNS: in DMF, DMSO, NMP; HMX: in DMF, DMSO, CYC; PETN: in DMF, DMSO, EAc) at different temperatures were determined. Furthermore, microfluidics and machine learning were combined, the solubility data of the explosives were processed using BP neural network. Moreover, the metastable zone widths of HNS, HMX and PETN in each solvent were determined using on-line Raman technique. Additionally, crystalline thermodynamic parameters such as solid–liquid interfacial tension, crystal surface entropy factor, enthalpy of dissolution and etc. were calculated for each system.

Production of sorbitol or itaconic acid from sugarcane feedstocks in energy self-sufficient biorefinery scenarios were investigated, via Aspen Plus® simulations, techno-economic and environmental assessments. Sorbitol co-produced with fructose from A-molasses had a minimum selling price (MSP) (0.81 $/kg) similar to technical-grade sorbitol market prices (0.5 to 1.1 $/kg), and an internal rate of return (IRR) of 19.65%. Sorbitol co-produced with mannitol from A-molasses had a lower MSP (0.48 $/kg), below food-grade sorbitol prices (0.58 $/kg) and a higher IRR (23.63%). Combining A-molasses with lignocelluloses for the co-production of sorbitol and mannitol increased the MSP (0.63 $/kg) above the market price and decreased the IRR (18.46%). This scenario also had greenhouse gas emissions lower than that of its A-molasses only counterpart, mainly due to the method of hydrogen production. Itaconic acid production from sugarcane feedstocks in similar scenarios was unattractive due to lower IRRs (4.49% to 11.61%).