Dynamics adsorption of the enhanced CH4 recovery by CO2 injection

The dynamic adsorption isotherms of CO₂-EGR were measured by using an Intelligent Gravimetric Analysis system. In the initial CO₂ injecting stage, all the injected CO₂ enters into the adsorbent and the mole fraction of CH₄ in the gas phase () is maintained at 1.0. The CH₄ recovery factor () increases. The duration of this stage (t_CD) depends on the selectivity of CO₂ over CH₄ (). An adsorbent with large has long t_CD. In the second stage, the injected CO₂ competes with CH₄ for adsorption. The cumulative of the second stage is much larger than that of the initial stage. However, decreases sharply. in the whole CO₂ injection is always larger than that before CO₂ injection, suggesting that CH₄ desorption results from the displacement of CO₂ rather than from pressure depletion.     

Novel Fe/MnK‐CNTs nanocomposites as catalysts for direct production of lower olefins from syngas

Novel Fe/MnK‐CNTs nanocomposites are developed as catalysts for direct production of lower olefins from syngas, delivering a high iron time yield of 337.2 μmol_CO· ·s^?1 with 51.3%C selectivity toward C₂?C₄ olefins under the optimal reaction conditions (270°C, 2.0 MPa, 30,000 mL h^?1 ). These catalysts are optimized by varying calcination temperature from 150 to 400°C. Multiple techniques including transmission electron microscopy, Elemental mapping, X‐ray diffraction, X‐ray photoelectron spectroscopy, H₂‐temperature‐programmed reduction, and Raman were employed to reveal the relationship between the catalyst nature and unique catalytic behavior. In particular, the resultant catalyst from the calcination temperature of 220°C exhibits the highest selectivity of C₂?C₄ olefins as well as good stability, which are enabled by the trade‐off among the effects of iron particle sizes, promoters, metal‐support interaction and support surface chemistry. Moreover, influences of reaction temperature, reaction pressure and space velocity are also investigated. © 2016 American Institute of Chemical Engineers AIChE J, 63: 154–161, 2017     

Reaction mechanism and kinetics for hydrolytic dehydrogenation of ammonia borane on a Pt/CNT catalyst

A reaction mechanism is proposed for hydrolytic dehydrogenation of ammonia borane on a Pt/CNT catalyst. A combination of thermodynamic analysis and FTIR measurement reveals that B‐containing byproducts are mainly in the form of an NH₄B(OH)₄‐B(OH)₃ mixture rather than NH₄BO₂ reported previously. The revised main reaction is , involving the B–H, B–N, and O–H bond cleavages. Isotopic experiments using D₂O instead of H₂O as reactant or introducing D₂ into the reaction atmosphere suggest the O–H bond cleavage being in the rate‐determining step, and an unfavorable occurrence of the chemisorbed H₂O dissociation (i.e., the direct O–H bond cleavage), respectively. Different reaction pathways with indirect O–H bond cleavages are analyzed, and then is suggested as the rate‐determining step. Subsequently, a Langmuir–Hinshelwood kinetic model is developed, which fits well with the experimental data. © 2016 American Institute of Chemical Engineers AIChE J, 63: 60–65, 2017     

Investigation mechanism of DEA as an activator on aqueous MEA solution for postcombustion CO2 capture

In this work, Diethanolamine (DEA) was considered as an activator to enhance the CO₂ capture performance of Monoethanolamine (MEA). The addition of DEA into MEA system was expected to improve disadvantages of MEA on regeneration heat, degradation, and corrosivity. To understand the reaction mechanism of blended MEA‐DEA solvent and CO₂, ¹³C nuclear magnetic resonance (NMR) technique was used to study the ions (MEACOO^‐, DEACOO^–, MEA, DEA, MEAH⁺, DEAH⁺, , ) speciation in the blended MEA‐DEA‐CO₂‐H₂O systems with CO₂ loading range from 0 to 0.7 mol CO₂/mol amine at the temperature of 301 K. The different ratios of MEA and DEA (MEA: DEA = 2.0:0, 1.5:0.5, 1.0:1.0, and 0:2.0) were studied to comprehensively investigate the role of DEA in the system of MEA‐DEA‐CO₂‐H₂O. The results revealed that DEA performs the coordinative role at the low CO₂ loading and the competitive role at high CO₂ loading. Additionally, the mechanism was also proposed to interpret the reaction process of the blended solvent with CO₂. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2515–2525, 2018     

Removal of NO from flue gas using UV/S2 process in a novel photochemical impinging stream reactor

A novel photochemical impinging stream reactor was developed for the first time. Removal process of NO from flue gas using sulfate radical ( ·) and hydroxyl radical (·OH) from UV‐light activation of persulfate (UV/S₂ advanced oxidation process) was investigated in the novel reactor. Experiments were conducted to evaluate the effects of S₂ concentration, solution pH, UV power, solution temperature, liquid‐gas ratio, flue gas flow, NO, SO₂,and O₂ concentrations on removal of NO. Mechanism and kinetics of NO removal were also studied. The results show that increasing UV power, solution temperature, S₂ concentration, or solution circulation rate promotes NO removal. Increasing solution pH (1.2–11.9), NO concentration or flue gas flow weakens NO removal. O₂ concentration has no significant effect on NO removal. · and ·OH were the major active species for NO removal. Absorption rate equation and kinetic parameters of NO removal were obtained. © 2017 American Institute of Chemical Engineers AIChE J, 63: 2968–2980, 2017     

The analysis of solubility,absorption kinetics of CO2 absorption into aqueous 1‐diethylamino‐2‐propanol solution

In this present work, the CO₂ absorption performance of aqueous 1‐diethylamino‐2‐propanol (1DEA2P) solution was studied with respect to CO₂ equilibrium solubility, absorption kinetics, and absorption heat. The equilibrium solubility of CO₂ in 2M 1DEA2P solution was measured over the temperature range from 298 to 333 K and CO₂ partial pressure range from 8 to101 kPa. The absorption kinetics data were developed and analyzed using the base‐catalyzed hydration mechanism and artificial neural network models (radial basis function neural network [RBFNN] and back‐propagation neural network [BPNN] models) with an acceptable absolute average deviation of 10% for base‐catalyzed hydration mechanism, 2.6% for RBFNN model and 1.77% for BPNN model, respectively. The CO₂ absorption heat of 1DEA2P was estimated to be ?43.6 kJ/mol. In addition, the ions (1DEA2P, 1DEA2PH⁺, , CO₃^2?) speciation plots of the 1DEA2P‐CO₂‐H₂O system were developed to further understand the reaction process of 1DEA2P with CO₂. Based on a comparison with conventional amines (e.g., MEA, DEA, MDEA) and alternative amines (i.e., 1DMA2P and 4‐(diethylamino)?2‐butanol [DEAB]), 1DEA2P exhibited good performance with respect to CO₂ equilibrium solubility, reaction kinetics, and CO₂ absorption heat. Meanwhile, the overall evaluation of 1DEA2P for application in CCS in terms of absorption and desorption is presented, giving helpful information for the screening of these novel amines. © 2017 American Institute of Chemical Engineers AIChE J, 63: 2694–2704, 2017     

Kinetics of CO2 absorption by aqueous 3‐(methylamino)propylamine solutions: Experimental results and modeling

Experimental data and a model for the initial kinetics of CO₂ into 3‐(methylamino)propylamine (MAPA) solutions are presented in work. MAPA has been tested as an activator for tertiary amines with encouraging results. The measurements were performed in a string of discs contactor and, as no initial kinetics data are available in literature, additional measurements were carried out and in a wetted wall column. The obtained overall mass‐transfer coefficients from both apparatuses are in reasonable agreement. To obtain values for the observed kinetic constant, , the experimental results were interpreted using a two‐film mass‐transfer model and invoking the pseudo‐first order assumption. Needed experimental values for density, viscosity, and Henry's law coefficient for CO₂ were measured and are given. The results indicate that MAPA is almost twice as fast as piperazine, eight times faster than 2‐(2‐aminoethyl‐amino)ethanol (AEEA), and 15 times faster than monoethanolamine, when comparing unloaded 1 M solutions at 25°C. The observed kinetic constant was modeled using the direct mechanism. The final expression for can be applied for any concentration and temperature within the experimental data range, and, together with the presented physical data, comprises a complete model for calculating absorption fluxes. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3792–3803, 2014     

Experimental Evaluation of the Adsorption,Diffusion, and Separation of CH4/N2 and CH4/CO2 Mixtures on Al-BDC MOF

Adsorption equilibrium, thermodynamics, and kinetics of CH₄, N₂, and CO₂ were investigated by volumetric-chromatographic and inverse gas chromatographic (IGC) methods on the Al-BDC MOF. The binary adsorption data from the volumetric-chromatographic experiments represents that the Al-BDC MOF has a high CO₂/CH₄ selectivity ca. 11 and a CH₄/N₂ selectivity ca. 4.3 at 303 K, and appears to be a good candidate for the CH₄ separation. The initial adsorption heats of CH₄, N₂, and CO₂ on the Al-BDC MOF were determined to be 15.3, 11.5, and 32.2 kJmol^?1 by IGC method, respectively. Moreover, the micropore diffusivities of N₂, CH₄ and CO₂ in the Al-BDC MOF at 303 K were also estimated to be 1.58 × 10^?7 cm²/s, 7.04 × 10^?8 cm²/s, and 3.95 × 10^?9 cm²/s, respectively. The results indicate that micropores play a crucial role in the adsorptive separation of the CH₄/N₂ and CH₄/CO₂ mixtures, and the IGC method is a validity manner to estimate the thermodynamic and kinetic parameters of MOF adsorbents.     

Synergistic effects of sulfur poisoning and gas diffusion on polarization loss in anodes of solid oxide fuel cells

Poisoning effects of sulfur compounds on the performances of solid oxide fuel cells are non‐trivial. However, the synergistic effects of gas diffusion, adsorption, desorption and reaction in anodes are typically neglected. In this work, an analytical model is derived to quantitatively evaluate the poisoning effects of H₂S. The results show that sulfur poisoning correlates closely with inefficient gas diffusion for small anode pore size, small porosity/tortuosity, and low working temperatures. As compared with concentration polarization, H₂S‐diffusion‐induced activation polarization in thin anodes with a large is detrimental, especially for low‐temperature operations with a high H₂S concentration and a low current density. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1127–1134, 2018     

Removal of Hg0 from flue gas using two homogeneous photo‐fenton‐like reactions

Removal of Hg⁰ using two homogeneous Photo‐Fenton‐Like reactions was first investigated in a photochemical reactor. Effects of process parameters on Hg⁰ removal were studied. Free radical and reaction products were analyzed. Removal pathways of Hg⁰ were discussed. Simultaneous removal of Hg⁰, NO, and SO₂ is also studied briefly. The results show that UV power, wavelength, H₂O₂ concentration, and solution pH have great effects on Hg⁰ removal. Hg⁰, and SO₂ concentrations, solution temperature, Fe³⁺, Cu²⁺, , and concentrations also have significant effects on Hg⁰ removal. However, concentrations of CO₂, NO, O₂, Cl^?, , , SiO₂, Al₂O₃, and Fe₂O₃ only have slight effects on Hg⁰ removal. Hg⁰/NO/SO₂ can be simultaneously removed by Photo‐Fenton‐Like reactions. ·OH was captured, and / /Hg²⁺ were also detected. Removals of Hg⁰ by photochemical oxidation and ·OH oxidation play a major role, and removal of Hg⁰ by H₂O₂ oxidation only plays a secondary role in removal of Hg⁰. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1322–1333, 2015     

A novel Core–Shell structured CuIn@SiO2 catalyst for CO2 hydrogenation to methanol

CO₂ hydrogenation is one of the most promising processes in response to energy crisis and greenhouse gas emission. There is, however, still a lack of a highly efficient and sustainable catalyst for this reaction. In this study, a novel low-cost core–shell structured CuIn@SiO₂ catalyst is prepared by a solvothermal method and used for catalyzing CO₂ hydrogenation to methanol. A significant interaction exists between Cu and In, promoting Cu dispersion and reducibility, Cu₂In alloy and oxygen vacancy formation. Moreover, plenty of interfacial sites are formed between Cu₂In and In₂O₃, which further enhances CO₂ adsorption and activation. CuIn@SiO₂, therefore, shows not only a satisfactory catalytic stability due to core–shell formation but also an excellent catalytic performance. 9.8% CO₂ conversion, 78.1% CH₃OH selectivity, and 13.7 ·h⁻¹·g_cat⁻¹ CH₃OH space–time yield are obtained at the space velocity of 20,000 mL·g_cat⁻¹·h⁻¹. CuIn@SiO₂ possesses a great potential as catalyst for CO₂ hydrogenation in a moderate condition in industry. © 2018 American Institute of Chemical Engineers AIChE J, 65: 1047–1058, 2019     

Kinetics of the absorption of carbon dioxide into aqueous ammonia solutions

Experiments were performed in a customized double stirred tank reactor to study the kinetics of CO₂ absorption into NH₃ solutions at concentrations ranging from 0.42 to 7.67 kmol·m^?3 and temperatures between 273.15 and 293.15 K. The results show that the reactive absorption was first order with respect to CO₂ but fractional order (1.6–1.8) with respect to ammonia. Experimental data can be satisfactorily interpreted by a termolecular mechanism using and . © 2016 American Institute of Chemical Engineers AIChE J, 62: 3673–3684, 2016     

Simultaneous removal of NO and SO2 using aqueous peroxymonosulfate with coactivation of Cu2+/Fe3+ and high temperature

A novel process on simultaneous removal of NO and SO₂ using aqueous peroxymonosulfate (PMS) with synergic activation of Cu²⁺/Fe³⁺ and high temperature in an impinging stream reactor is developed for the first time. Effects of PMS concentration, Cu²⁺/Fe³⁺ concentration, reaction temperature, solution pH, flue gas flow, liquid–gas ratio, gas components, and inorganic ions on NO/SO₂ removals were investigated. Active species and products were determined by electron spin resonance spectroscopy and ion chromatography. Removal pathways of NO/SO₂ were revealed, and mass transfer‐reaction kinetics of NO removal was studied. The optimal experimental conditions are obtained. H₂SO₄ and HNO₃ are the main products. It is found that there is a clear synergy between Cu²⁺/Fe³⁺ and high temperature for activating PMS. and ·OH are found to be the main oxidants for NO removal. NO removals belong to pseudo‐first fast reactions in the two investigated oxidation systems. Besides, the kinetic parameters are also measured. © 2016 American Institute of Chemical Engineers AIChE J, 63: 1287–1302, 2017     

Electrochemical synthesis,characterization and application of a microstructure Cu<Subscript>3</Subscript>(BTC)<Subscript>2</Subscript> metal organic framework for CO<Subscript>2</Subscript> and CH<Subscript>4</Subscript> separation

The electrochemical route is a promising and environmentally friendly technique for fabrication of metal organic frameworks (MOFs) due to mild synthesis condition, short time for crystal growth and ease of scale up. A microstructure Cu₃(BTC)₂ MOF was synthesized through electrochemical path and successfully employed for CO₂ and CH₄ adsorption. Characterization and structural investigation of the MOF was carried out by XRD, FE-SEM, TGA, FTIR and BET analyses. The highest amount of carbon dioxide and methane sorption was 26.89 and 6.63 wt%, respectively, at 298 K. The heat of adsorption for CO₂ decreased monotonically, while an opposite trend was observed for CH₄. The results also revealed that the selectivity of the developed MOF towards CO₂ over CH₄ enhanced with increase of pressure and composition of carbon dioxide component as predicted by the ideal adsorption solution theory (IAST). The regeneration of as-synthesized MOF was also studied in six consecutive cycles and no considerable reduction in CO₂ adsorption capacity was observed.     

Systematic analysis and optimization of power generation in pressure retarded osmosis: Effect of multistage design

This work presents a systematic method for analysis and optimization of specific energy production (SEP) of pressure retarded osmosis (PRO) systems employing single‐stage configuration as well as multistage design with interstage hydro‐turbines. It is shown that the SEP normalized by the draw solution feed osmotic pressure increases with the number of stages as well as a dimensionless parameter . As compared to the single‐stage PRO, the multistage arrangement not only increases flux and volume gain, but also allows a stage‐dependent, progressively decreasing hydraulic pressure, both of which contribute to enhanced SEP and power density. At the thermodynamic limit where γ_tot goes to infinity, the theoretical maximum SEP by an N‐stage PRO system is , where q_tot is the ratio of the draw solution flow rate at the outlet to the inlet on the system level. For single‐stage PRO, it is no more than π₀. For infinite number of stages, the theoretical limit becomes . SEP under realistic conditions and practical constraints on multistage design are discussed. © 2017 American Institute of Chemical Engineers AIChE J, 63: 144–152, 2018     

Ni/CaO‐Al2O3 bifunctional catalysts for sorption‐enhanced steam methane reforming

Ni/CaO‐Al₂O₃ bifunctional catalysts with different CaO/Al₂O₃ mass ratios were prepared by a sol–gel method and applied to the sorption‐enhanced steam methane reforming (SESMR) process. The catalysts consisted mainly of Ni, CaO and Ca₅Al₆O₁₄. The catalyst structure depended strongly on the CaO/Al₂O₃ mass ratio, which in turn affected the CO₂ capture capacity and the catalytic performance. The catalyst with a CaO/Al₂O₃ mass ratio of 6 or 8 possessed the highest surface area, the smallest Ni particle size, and the most uniform distribution of Ni, CaO, and Ca₅Al₆O₁₄. During 50 consecutive SESMR cycles at a steam/methane molar ratio of 2, the thermodynamic equilibrium was achieved using the catalyst with a CaO/Al₂O₃ mass ratio of 6, and H₂ concentration profiles for all the 50 cycles almost overlapped, indicating excellent activity and stability of the catalyst. Moreover, a high CO₂ capture capacity of 0.44 was maintained after 50 carbonation–calcination cycles, being almost equal to its initial capacity (0.45 ). © 2014 American Institute of Chemical Engineers AIChE J, 60: 3547–3556, 2014     

NMR spectroscopic study of chemical equilibria in solutions of formaldehyde,water, and butynediol

Liquid mixtures of formaldehyde, water, and butynediol are complex reacting multicomponent systems in which formaldehyde forms oligomers both with water and butynediol. ‐ and ‐NMR spectra of these mixtures are elucidated. The species distribution of the oligomers is quantitatively determined by ‐NMR spectroscopy. The measurements cover temperatures from 293 to 366 K, overall formaldehyde mass fractions from to , and overall butynediol mass fractions from to . A mole fraction‐based and an activity‐based model of the chemical equilibrium in the studied system are developed and chemical equilibrium constants are reported. © 2017 American Institute of Chemical Engineers AIChE J, 63: 4442–4450, 2017     

Effect of substrate curvature on microstructure and gas permeability of hollow fiber MFI zeolite membranes

Literature data show that gas permeability of MFI zeolite membrane varies depending on the geometry of supports. The present work investigates the effects of the surface curvature of substrates on the microstructure and the gas permeation property of supported zeolite membranes. MFI zeolite membranes were grown on porous alumina hollow fibers with different diameters (surface curvature) by the secondary growth method. Single gas permeation and H₂/CO₂ binary gas separation from 25 to 300 were conducted to study the membrane quality. The zeolite membranes on supports of larger surface curvature have higher permeability and lower selectivity due to the presence of more inter‐crystalline gaps in the zeolite layer formed during the template removal step. The effects of the support surface curvature (and geometry) on zeolite membrane microstructure and gas permeation characteristics are semi‐quantitatively analyzed by a transport model considering both structural change and gas diffusion in micropores. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3419–3428, 2018     

Forced convection boiling in a stator–rotor–stator spinning disc reactor

Boiling of a pure fluid inside the rotor–stator cavities of a stator–rotor–stator spinning disc reactor (srs‐SDR) is studied, as a function of rotational velocity ω, average temperature driving force and mass flow rate . The average boiling heat transfer coefficient h_b increases a factor 3 by increasing ω up to 105 rad s^?1, independently of and . The performance of the srs‐SDR, in terms of h_b vs. specific energy input ?, is similar to tubular boiling, where pressure drop provides the energy input. The srs‐SDR enables operation at Wm , yielding values of h_b not practically obtainable in passive evaporators, due to prohibitively high pressure drops required. Since h_b is increased independently of the superficial vapor velocity, h_b is not a function of and the local vapor fraction. Therefore, the srs‐SDR enables a higher degree of control and flexibility of the boiling process, compared to passive flow boiling. © 2016 American Institute of Chemical Engineers AIChE J, 62: 3763–3773, 2016     

The influence of injection velocity and relaxation time on the spreading of tracers in viscoelastic liquids agitated by submerged,recirculating jets with low reynolds numbers

We provide experimental demonstration that the spread of tracer elements in a tank containing a viscoelastic liquid and agitated by a submerged jet pointing to the base of the tank can be influenced by the relaxation time of the liquid. We analyzed the temporal spreading of the boundary of a tracer‐front in two dimensions using flow visualization at early stages and found that for a given fluid, the evolution of the tracer‐front at various injection velocities follows a universal trajectory when considered on a normalized time scale of , where t is observation time, is injection velocity and is the effective diffusivity of the tracer elements in the medium. For a different fluid, at a given , the trajectory scales with the relaxation time of the fluid. The importance of relaxation time to the evolution of a tracer‐front is something previously unreported. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3132–3140, 2017