Asia-Pacific Journal of Chemical Engineering最新文献

Ethyl levulinate (EL) production from steam-exploded corn straw (SCS) in a cascade of reaction using a Brønsted (B) acid and a Lewis (L) acid in ethanol was studied. The entangled structure of corn straw could be obviously damaged through steam explosion when the pressure was 1.5 MPa holding 10 min. The content of cellulose can be increased from 35.9% to 46.8%, and the contents of hemicellulose and lignin were changed from 16.7% to 8.8% and 22.6% to 27.5%, respectively. EL yield was significantly increased from 10.7 to 24.6 wt% under optimal reaction conditions (L/B = 1/20 [mol/mol], 205°C, 90 min, 1.8 g of SCS, 60 mL of ethanol). According to kinetic models, the activation energies for the main and side reactions were 56.8 and 110.5 kJ mol⁻¹, respectively. It suggested that SCS was more easily to be converted to EL rather than other by-products. The highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) energy gaps (HOMO-LUMO gaps) of cellobiose over the mixed acids in ethanol were significantly reduced with frontier molecular orbital (FMO) theory. This work provides an effective strategy for EL production from agricultural waste straws.

The precise prediction of NOx generation concentration in coal-fired boilers serves as the foundational cornerstone for the judicious optimization and control of selective catalytic reduction denitrification (SCR) systems. Owing to the intricate nature of the denitrification process within SCR, there exists a temporal delay in regulating the ammonia injection rate based on the monitored data of NOx concentration at the SCR inlet. Such delays can give rise to ammonia leakage and subsequent obstruction of the air preheater. In light of this, a predictive model, CEEMDAN-LSTM-SA, is proposed as an amalgamation of data decomposition and the LSTM (long short-term memory) fusion self-attention mechanism within a deep learning network, which is introduced to forecast the NOx emission concentration at the SCR inlet of coal-fired units. To mitigate the impact of data outliers on the training effectiveness of the model, a clustering method coupled with a statistical testing strategy is initially applied to refine the dataset first. CEEMDAN data decomposition technology is leveraged to facilitate the breakdown of data, alleviating its non-stationary and intricate characteristics. Subsequently, through spectral analysis, the decomposed components are grouped and aggregated to form novel data elements, which are then subjected to prediction by the constructed LSTM-SA deep learning network. The ultimate NOx emission concentration prediction value is derived through a process of fusion. Upon scrutinizing and comparing the predictions derived from various models using coal-fired power plant data, it is evident that the performance metrics of CEEMDAN-LSTM-SA predictions exhibit a mean absolute error of 7.425, mean absolute percentage error of 2.415%, root mean square error of 9.715, R-squared (R²) value of .789, mean absolute relative error of 2.109%, and a Theil's information criterion of .016. In contrast to other models, including traditional self-attention networks, LSTM, and LSTM-SA combination networks, CEEMDAN-LSTM-SA proposed in this study demonstrates superior prediction accuracy and enhanced generalization capabilities. Consequently, this predictive model stands poised to furnish an efficacious framework for the SCR ammonia injection strategy within thermal power units.

The Soret and Dufour effects play a crucial role in various fields such as geosciences, groundwater pollutant migration, chemical reactor operations, binary alloy solidification, and isotope separation. This study focuses on examining the impact of mixed convective flow on hybrid nanofluid through an exponentially stretching sheet with Soret and Dufour effects. The flow is affected by factors like variable viscosity, radiation, viscous dissipation, and activation energy. Instead of the no-slip condition at the boundary, velocity slip, thermal slip, and concentration slip are considered. The physical problem is modeled using boundary layer theory, and flow patterns are expressed using partial differential equations (PDEs). These governing fluid flow equations are transformed into non-linearly coupled ordinary differential equations (ODEs) using exponential similarity transformations. These simplified ODEs are resolved using the MATLAB bvp4c package. The effects of physical parameters on velocity, temperature, and concentration are illustrated through figures. Additionally, the drag force coefficient and heat and mass transfer rates are calculated for various parameters and presented graphically and in tabular form. It is observed that compared to nanofluids, the drag force coefficient of hybrid nanofluids increases by up to 21.05% with various solute buoyancy parameters (δ). Also, the mass transfer rate of hybrid nanofluids can be increased by .96% by the chemical reaction rate (σ_m). A comparison of this work with previously published research has been reported.

Over 218 million tonnes of oil palm trunks (OPT) waste is produced annually by Malaysian oil palm industry, which can be converted to biofuels via wet torrefaction. This study assessed the fuel characteristics of wet torrefied OPT (WT-OPT) using proximate analysis, higher heating value (HHV) analysis, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy–energy dispersive X–ray spectroscopy (SEM–EDX). Increasing wet torrefaction temperature and residence time increased the fixed carbon content and HHV of OPT. SEM–EDX revealed the presence of microspheres of 5-hydroxymethylfurfural (5-HMF) in OPT wet torrefied at 180 and 220°C for 72 h, an intermediate compound that can contribute to the HHV enhancement in WT-OPT. FTIR and EDX results revealed that higher temperature and residence time concentrate the carbon content of OPT. Wet torrefaction at 180°C for 72 h decreased the activation energy and pre-exponential factor of OPT from 301.88 to 171.70 kJ mol⁻¹ and from 4.43 × 10²⁸ to 3.25 × 10¹² s⁻¹, respectively, during pyrolysis. The estimated thermodynamic parameters, particularly the change in entropy which generally decreased by more than 140 J mol⁻¹ K⁻¹, indicated increase in stability of certain WT-OPT.

This study explores the development of environmentally sustainable, high-quality packaging materials by incorporating poly(hydroxybutyrate) (PHB) with different polymers. To accomplish this objective, pure PHB was blended with poly(ethylene glycol) (PEG) in a precise 9:1 ratio. Subsequently, this blend was further combined with 50 wt% of various polymers, namely, polycaprolactone, poly(vinylacetate), and polylactic acid (PLA), using a solvent-casting method. Further, the research investigates the multifaceted properties of these materials, including their thermal characteristics, morphological structures, mechanical strengths, barrier properties, and degradation behaviors. Among these blends, the film consisting of PHB, PEG, and PLA (PHB/PEG/PLA) emerged as a standout performer, displaying exceptional attributes. Notably, the PHB/PEG/PLA composite film exhibited remarkable thermal stability, boasting a high tensile strength of 26.6 MPa. Additionally, it demonstrated an outstanding ability to serve as a barrier against water vapors. These findings imply that the PHB/PEG/PLA composite film holds significant potential for a wide range of applications, particularly in the field of packaging and beyond.

Addressing the issue of processing fine kaolinite and quartz particles in coal slime, this study utilized molecular simulation and Density Functional Theory (DFT) to investigate the chelate adsorption characteristics of sodium dodecyl sulfate (SDS) on kaolinite surfaces. As a major clay mineral component in coal slime, kaolinite reduces coal's calorific value but holds potential for industrial and agricultural applications. The research identified distinct interactions between SDS and the tetrahedral SiO layer and octahedral AlO layer of kaolinite, in contrast to quartz, which contains only the tetrahedral SiO layer. This difference is crucial for the effective separation of kaolinite from quartz. The study focused on analyzing SDS adsorption on the (001) and (00-1) planes of kaolinite. The findings revealed strong adsorption of SDS on kaolinite surfaces, especially on the (001) plane, evidenced by significant charge transfer indicating efficient chelation. This effect results from the interaction of SDS's electron-donating atoms (such as S and O) with the metal atoms on the surface of kaolinite. Adsorption strength was quantified through adsorption energy calculations, showing a stronger interaction on the (001) surface. Experimental validations, including single mineral flotation experiments and infrared spectroscopic analysis, further corroborated the simulation outcomes. These tests demonstrated improved flotation recovery of kaolinite in the presence of SDS and with reduced particle size. Infrared analysis revealed that SDS selectively and strongly adsorbs on kaolinite surfaces, as indicated by diminished hydroxyl group stretching vibrations in the FTIR spectrum and changes in absorption peaks related to inorganic vibrations and sulfonic acid groups. The study demonstrates that SDS can selectively and effectively adsorb onto kaolinite surfaces, particularly on the (001) plane, facilitating the efficient extraction of fine kaolinite from coal slime. This research holds significant potential for enhancing the utilization of resources from coal slime in the coal industry, offering both economic and environmental benefits.

The construction of high-efficiency self-supported ceramic photoelectrode based on ideal semiconductor materials is essential for achieving effective degradation of pollutants by photoelectrocatalysis (PEC) technology. Herein, a Ti₄O₇/h-BN composite ceramic photoelectrode with a unique microstructure was fabricated by a step-by-step calcination process and used in PEC water pollution remediation. The PEC activity of Ti₄O₇ ceramic photoelectrode could be enhanced by introducing hexagonal boron nitride (h-BN) nanoparticles on the surface. The most optimized Ti₄O₇/h-BN photoelectrode exhibited the decolorization rate of active brilliant blue KN-R at about 97.79% in 30 min. The PEC activities could remain stable during five degradation cycles. The excellent photoelectrocatalytic performance of Ti₄O₇/h-BN ceramic photoelectrode could be attributed to the low Tafel slope, low charge transfer resistance, large electrochemical active area, and excellent photo-generated carrier separation efficiency. A type-II heterojunction was formed between the Ti₄O₇ and h-BN, which caused more effective carrier separation and enhanced the generation of dominant active species •O²⁻ and h⁺. This work provided a mature synthesis strategy of Ti₄O₇/h-BN self-supported ceramic photoelectrodes with excellent practical application prospects to achieve superior PEC performance for water purification.

The lowered dispersibility of carboxylic acid polymers in the seawater system with high salt content results in reduced scale inhibition efficiency. To solve this problem, a series of carboxylic acid polymers containing ether groups were prepared by free radical polymerization using α-allyl glycerol ether (AG) and vinyl monomers containing different numbers of carboxylic acid groups (acrylic acid [AA], maleic acid [MA], itaconic acid [IA], and aconitic acid [ANA]) as raw materials, and their scale inhibition properties in artificial seawater were studied. The static test results demonstrate that IA-AG outperforms the other three polymers containing ether carboxylic acid in terms of scale inhibition performance, with CaCO₃ and CaSO₄ having scale inhibition rates of 95.16% and 98.73%, respectively. Furthermore, molecular dynamics (MD) simulation was employed to investigate the mechanism of scale inhibition by simulating the interaction between ether carboxylic acid polymers and the crystal surface. The results show that the order of binding energy between polymers and crystal faces is IA-AG > ANA-AG > MA-AG > AA-AG. The simulation results are in agreement with the experimental phenomena. The polymers can overcome their own deformation and adsorb on the crystal surfaces, thus inhibiting the growth of scale.

Mass transfer of bubbles is important in microalgae cultivation. In this study, aiming to improve the microalgae culturing efficiency, computational fluid dynamics (CFD) was adopted to study the influence of the aeration manners on mass transfer of bubbles within ascending columns in multi-column airlift photobioreactor (PBR) and the hydrodynamic conditions within the PBR under different aeration manners. In addition, the bubble generation time, the detachment diameter, and the average volumetric mass transfer coefficient of bubbles in ascending columns were analyzed. Furthermore, the experimental results were compared with the simulation results obtained from microalgae cultivation. The results showed that the whole aeration manner yields the lowest mixing strength and mass transfer efficiency of bubbles at an aeration rate of 0.2 vvm. Conversely, both the mixing strength of the liquid and mass transfer coefficient of bubbles were enhanced under the half and alternate aeration manners. However, the results demonstrated that the distribution of the flow field was not uniform under the half aeration manner and there were obvious high-speed and low-speed zones. In contrast, the flow field distribution in the PBR was more uniform under the alternate aeration manner, which was suitable for microalgae cultivation at high concentration. This study effectively enhanced the mixing strength and CO₂ transfer rate in the PBR.

The double-layer porous media burner is considered as an effective way to realize stable lean-burn. In order to quickly achieve a stable combustion state in a double-layer porous media burner, this work investigated the dynamic characteristics of methane/air premixed combustion in a bench-scale double-layer porous media burnspanning from ignition to stable combustion and ultimately flameout. The experimental results indicate that regulating the equivalence ratio and the inlet velocity enables the establishment of a stable flame front and the φ = 0.75 and the V_in = 0.20 m/s are the appropriate start-up conditions. The average propagation velocity of the combustion wave variation along the axial direction and ranged approximately from −0.022 to −0.078 mm/s. Moreover, the transition time to a stable combustion state is reduced by nearly 47.14% as the equivalence ratio increases from 0.60 to 0.70. During start-up stage, there are significant fluctuations in CO and NOx concentrations, but both emissions remain low during steady combustion state, with the maximum concentrations of 37.5 and 40.2 mg/m³, respectively. Furthermore, the porous media combustion exhibits a pronounced re-ignition capacity. At higher equivalence ratios, longer interruptions of premixed gas are allowed.