In the present work, a series of deep eutectic solvents (DESs) based on organic amine as hydrogen bond acceptors (HBAs), and ethylene glycol (EG) as hydrogen bond donor (HBD) were prepared for the H2S absorption. Thermal decomposition temperature, HBA mass ratios, alkalinity and structure effect on absorption behavior were systematically investigated. The reaction mechanism was demonstrated by FT-IR and 1H NMR spectroscopy. The reaction equilibrium constants, Henry constant, enthalpy and entropy change were calculated based on the thermodynamic model to reveal the interactions between DESs and H2S. It is found that H2S absorption capacities of the most of DESs with HBA/HBD mass ratio of 1:4 were close to 1mol /mol at 303.15K and 0.2 bar. The absorption capacity of DESs depends on the alkalinity and structure of HBAs; Additionally, a good linear correlation between the alkalinity of HBA and the absorption equilibrium constant (lnK) of DESs to H2S was found
We built a molecular-level kinetic model for hydrocarbon catalytic cracking, incorporating the catalyst acidity as the parameter to estimate the reaction rates. The n-decane and 1-hexene co-conversion catalytic cracking process was chosen as the studying case. The reaction network was automatically generated with a computer-aided algorithm. A modified linear free energy relationship was proposed to estimate the activation energy in a complex reaction system. The kinetic parameters were initially regressed from the experimental data under various reaction conditions. On this basis, the product composition was evaluated for three catalytic cracking catalysts with different Si/Al. The Bronsted acid and Lewis acid as the key catalyst properties were correlated with the kinetic parameters. The built model can calculate the product distribution, and molecular composition at different reaction conditions for different catalysts. The sensitive study shows that it will facilitate the model-based optimization of catalysts and reaction conditions according to product demands.
Mo-based catalysts are widely used for the SO2 hydrogenation process. However, the detailed reaction mechanism is still unclear and some details should be further supplemented. In this paper, the SO2 hydrogenation processes over the Mo-based catalyst were systematically studied. Several technologies including temperature-programmed experiments, isotope-tracing experiment, FTIR spectra and switching experiment were adopted to investigate the reaction steps. The results indicated that during the SO2 hydrogena
Error-in-variables model (EVM) methods are used for parameter estimation when independent variables are uncertain. During EVM parameter estimation, output measurement variances are required as weighting factors in the objective function. These variances can be estimated based on data from replicate experiments. However, conducting replicates is complicated when independent variables are uncertain. Instead, pseudo-replicate runs may be performed where the target values of inputs for repeated runs are the same, but the true input values may be different. Here, we propose a method to estimate output-measurement variances for use in multivariate EVM estimation problems, based on pseudo-replicate data. We also propose a bootstrap technique for quantifying uncertainties in resulting parameter estimates and model predictions. The methods are illustrated using a case study involving n-hexane hydroisomerization in a well-mixed reactor. Case-study results reveal that assumptions about input uncertainties can have important influences on parameter estimates, model predictions and their confidence intervals.
The suitability of phenyl–based deep eutectic solvents (DESs) as absorbents for toluene absorption was investigated by means of thermodynamic modeling and molecular dynamics (MD). The thermodynamic models PC–SAFT and COSMO–RS were used to predict the vapor–liquid equilibrium (VLE) of DES–toluene systems. PC–SAFT yielded quantitative results even without using any binary fitting parameters. Among the DESs consisting of three different HBAs and three different HBDs (phenol, levulinic acid, ethylene glycol), [TEBAC][PhOH] was considered as the most suitable absorbent. Systems with [TEBAC][PhOH] had lowest equilibrium pressures of the considered DES–toluene mixtures, the best thermodynamic characteristics (i.e., Henry’s law constant, excess enthalpy, free energy of solvation of toluene), and the highest self–diffusion coefficient of toluene. The molecular–level mechanism was explored by MD simulations, indicating that [TEBAC][PhOH] has the strongest interaction of HBA–/HBD–toluene compared to the other DESs under study. This work provides guidance to rationally design novel DESs for efficient aromatic VOCs absorption.
The experimental and simulation results indicate that the reverse Brazil nut effect (RBNE)-Brazil nut effect (BNE) segregation inversion happens faster in the circular-bottom container than that in the flat-bottom container. The starting location of the sinkage of heavier grains at the top layer is triggered with certain randomness in the latter, whereas it first occurs at either of the lateral bottom edges in the former. The occurrence of standing-wave resonant spots of higher and lower granular temperature accelerates the RBNE-BNE transition. From the elastic collision model of single grain, the bottom with a larger angle leads to more energy transfer from the vertical direction. The simulation results of a monodisperse granular bed confirm that the circular-bottom container possesses a higher granular temperature and a lower packing density at the lateral edges of the circular bottom, whereas the flat-bottom container has a uniform standing-wave distribution with a period.
Lamellar membranes, especially assembled by microporous framework nanosheets, have excited interest for fast molecular permeation. However, the underlying molecular dissolution behaviors on membrane surface, especially at pore entrances, remain unclear. Here, hierarchical metal-organic framework (MOF) lamellar membranes with 7 nm-thick surface layer and 553 nm-thick support layer are prepared. Hydrophilic (–NH2) or hydrophobic (–CH3) groups are decorated at pore entrances on surface layer to manipulate wettability, while –CH3 groups on support layer provide comparable, low-resistance paths. We demonstrate that molecular dissolution behaviors are determined by molecule-molecule and molecule-pore interactions, derived from intrinsic parameters of molecule and membrane. Importantly, two dissolution model equations are established: for hydrophobic membrane surface, dissolution activation energy (ES) obeys ES=Kmln[(γL-γC)μd2], while turns to ES=Kaln[(γL-γC)δeμd2] for hydrophilic one. Particularly, hydrophilic pore entrances exert strong interaction with polar molecules, thus compensating the energy consumed by molecule rearrangement, giving fast permeation (> 270 L m-2 h-1 bar-1).
In this work, we proposed a two-stage stochastic programming model for a four-echelon supply chain problem considering possible disruptions at the nodes (supplier and facilities) as well as the connecting transportation modes and operational uncertainties in form of uncertain demands. The first stage decisions are supplier choice, capacity levels for manufacturing sites and warehouses, inventory levels, transportation modes selection, and shipment decisions for the certain periods, and the second stage anticipates the cost of meeting future demands subject to the first stage decision. Comparing the solution obtained for the two-stage stochastic model with a multi-period deterministic model shows that the stochastic model makes a better first stage decision to hedge against the future demand. This study demonstrates the managerial viability of the proposed model in decision making for supply chain network in which both disruption and operational uncertainties are accounted for.
The Global Methane Pledge declared at the 2021 United Nations climate change conference (COP26) marked the world’s commitment to eradicate methane emissions. Most of these emissions are generated by the oil-gas industry, waste landfills, and agriculture sectors, and are lean in composition. This work explores the use of an intensified reactor that implements the chemical looping principle to handle lean methane emissions. A model-based framework is used to showcase the baseline performance of the proposed reactor in converting methane emissions using nickel-based oxygen carriers. Then, sensitivity analysis of the reactor performance with respect to operating conditions is performed. The reactor is subsequently optimized to minimize the methane emitted, using a dynamic program with safety and operability constraints for the alternating redox process. With the optimal cycle strategy, we demonstrate that near-complete methane conversion can be achieved by the reactor without external heating.
The rate of KCl recovery by froth flotation using low-grade carnallite is 70–85%. Herein, a novel frother, dipropylene glycol butyl ether (DPNB), was prepared to increase the flotation efficiency of KCl recovery systems. DPNB could be applied at only half the dosage of the conventional frother methyl isobutyl carbinol (MIBC) and achieve a KCl recovery rate of 94.8–98.6% with a high KCl grade (63.2–66.5%). To date, these results are the best reported for pneumatic flotation. DPNB had a 10% higher maximum dynamic stability factor compared with of MIBC; moreover, the apparent entrainment velocity of DPNB was half that of MIBC. The molecular structure of DPNB had hydroxyl and ether groups, which promoted interactions with water, thereby contributing to its excellent froth stability. DPNB is environment friendly owing to its low volatility and, thus, a promising frother for the green and highly efficient flotation of KCl/NaCl.
Oxygen, as a terminal electron acceptor, is an essential substrate in the aerobic bio-oxidation process, affecting bacterial vitality and bio-oxidation performance. In this study, a new and smart platform biotechnology of sealed-oxygen supply bioreactor (SOS-BR) was developed by improving gas pressure to significantly intensify oxygen transfer rate and resolving the formidable barriers of aerobic catalysis. In virtue of SOS-BR, the bio-productivity was greatly improved for three representative substrates (xylose, furfural, glycerol) bio-oxidation with the whole-cell catalysis of Gluconobacter oxydans. The determination of oxygen transfer coefficient (KLα) established an upgraded theoretical dynamic model for gas pressure intersification biosystem. Additionally, viscosity measurement and combined pressure control strategy explained the inflection point phenomenon of productivity and confirmed the intensify mechanism. The new strategy of significantly intensifying oxygen transfer provided insightful ideas for overcoming the subbon obstacle of obligate aerobic catalysis, and further promoted industrial practicability of bio-oxidation.
Clustering of flexible fibers in riser flows is investigated using a hybrid approach of Discrete Element Method and Computational Fluid Dynamics. Unlike spherical particles, the flexible fibers possess elongated shape, undergo significant deformation, and dissipate kinetic energies through rapid fiber deformation. The present studies show that these distinct features have significant impacts on the cluster characteristics of the fibers. An increased fiber aspect ratio leads to an increase in number and size of agglomerates, while it causes a reduction in heterogeneity of solids distribution due to the more dilute clusters with reduced packing densities. As the fibers become more flexible, the heterogeneity increases, and denser clusters are obtained. More significant effects of the fiber flexibility on the clustering are observed for the fibers with larger aspect ratios. The increased energy dissipation through the rapid fiber deformation enhances the clustering by augmenting the number and size of the agglomerates.
A rapid and convenient strategy to monitor the productivity of biomanufacturing is essential for the research in optimizing relevant bioprocesses. In this work, we have developed a fluorescein-derived probe (FL-DT) that reacts rapidly with thiol groups via 1, 4-Micheal addition reaction of the sulfhydryl to unsaturated ketone and releases fluorescence. FL-DT specifically forms fluorescent adduct with two adjacent thiols in a protein of interest (POI), making the probe a reliable tool for protein quantification. The production of xylanase fused with a short di-Cys tag was then successfully monitored and quantified with FL-DT in E. coli system under different protein expression conditions, providing useful information for optimizing the bioprocess. Our work provides a convenient and efficient strategy for POI labeling and monitoring bioproduction.
Due to its toxicity and corrosiveness, it is of enormous significance to efficiently capture and recover sulfur dioxide (SO2) from flue gas and natural gas. Herein, a new type of IL/MIL-0.7 composite was precisely designed to meet this challenge, which exhibits a high adsorption capacity for SO2 (13.17 mmol·g-1) at 298 K and 1 bar while excludes almost completely carbon dioxide (CO2) (0.27 mmol·g-1) and nitrogen (N2) (0.07 mmol·g-1). The high IAST selectivity (at least 11925) of IL/MIL-0.7 for SO2/CO2 can be achieved within the whole test pressure range. In addition, the breakthrough experiment also confirmed the excellent performance of the composite for deep removal of 2000 ppm SO2. Furthermore, the IL/MIL-0.7 composites can maintain excellent performance after four adsorption and desorption circulations and the thermostability can up to ~450 K. Therefore, this stable IL@MOF composite has the potential application as an effective adsorbent for SO2 removal from flue gas.
Oblique collisions of two spherical particles coated with a thin layer of viscous liquid are considered. Experimental measurements are performed using particle tracking velocimetry. Comprehensive experimental data for collisions with an impact angle between 0° - 60° are presented. Collisions are characterised by the Stokes’ number, the coefficient of restitution, and the rotational velocity. The experiments are compared to numerical simulations using the discrete element method (DEM). The translational velocities predicted by the simulations were in good agreement with the experiments at high Stokes’ number, where the models are dominated by the normal components. As the tangential forces become more significant (i.e. at low to medium Stokes’ number, and high collision angle), agreement between the simulations and experiments is poorer. At low Stokes’ number the translational velocities were in good agreement with the experiments, but was poorer at high Stokes’ number.
The direct Z-scheme provide a potential strategy for high efficient CO2 photoreduction, whereas the heterointerface contact resistance is significantly limited the interfacial electron transfer kinetic. Herein, we build the directional charge-transfer channels in a direct Z-scheme system over metal−organic frameworks (MOFs), that is the lattice-guided MOF-on-MOF hybrids, to facilitate CO2 photoreduction. The heteroepitaxial lattice growth along the c-axis of MIL-88B(Fe) via the high-activity (001) facet over the stable (111) facet of UiO-66-NH2. Theoretical calculations and experimental results provide the direct evidence that engineering direct Z-scheme of these MOFs hybrids can induce the electrons migration from UiO-66-NH2 to the holes of MIL-88B(Fe) by directional charge-transfer channels owing to their lattice match. This can dramatically boosts photocatalytic CO2-to-CO selectivity up to nearly 100%, with a rate of 2.26 μmol·g-1·h-1. This work demonstrates that the efficiently selective CO2 photoreduction processes can be achieved by engineering Z-scheme via lattice intergrown of MOF hybrids strategy.
CO2 methanation is one of the vital reactions to utilize CO2 and realize power to gas process. To decrease the CO2 capture cost and alleviate the hot spots during the strong exothermic methanation reaction, here, we report a coupling of CO2 capture process with in situ CO2 methanation process through a ceramic-molten carbonate (MC) dual phase membrane reactor over the Ni-based catalyst. The performance of the membrane reactor was systematically investigated and compared with the traditional fixed-bed reactor. The results show that the performance of the membrane reactor is higher than that of the fixed-bed reactor, since the produced steam through the methanation process can be partially removed through the dual-phase membrane, which promotes the reaction shift to right side. A stability test shows no obvious degradation within 32 h. These results indicate that the membrane reactor is promising for coupling CO2 capture with in situ methanation process.
Because of very high potential barrier for thermionic emission and trap-assisted charge recombination, photocatalytic reaction rate that determined by semiconductor-cocatalyst interfacial electron transfer severely deviates from linearity to the photocatalyst dosage or to the light intensity. This makes it challenging to maximize utilization of practical irradiation by referring the parameters evaluated from method used in conventional catalysis. We here develop a model and predict that photocatalytic reaction rate positively correlates to photocatalyst concentration under weak illumination while the correlation becomes negative under intense irradiation. The theoretical simulation that matches the experimental values can be used to guide maximizing photocatalytic photon utilization under various intensity of irradiation. The strong correlation can rationalize photocatalytic evaluation instead of obtaining a numerically high value by excessively lowering the denominators. To realize efficient utilization of real-time changing sunlight, we propose a reactor configuration that can optimize the amount of photocatalyst participating into the reaction.