Reaction Equilibrium Research Articles

Chemical speciation determines combined cytotoxicity: Examples of biochar and arsenic/chromium

As both electron donors and acceptors, biochars (BCs) may interact with multivalent metal ions in the environment, causing changes in ionic valence states and resulting in unknown combined toxicity. Therefore, we systematically investigated the interaction between BCs and Cr (Cr(III) & Cr(VI)) or As (As(III) & As(V)) and their combined cytotoxicity in human colorectal mucosal (FHC) cells. Our results suggest that the redox-induced valence state change is a critical factor in the combined cytotoxicity of BCs with Cr/As. Specifically, when Cr(VI) was adsorbed on BCs, 86.4 % of Cr(VI) was reduced to Cr(III). In contrast, As(III) was partially oxidized to As(V) with a ratio of 37.2 %, thus reaching a reaction equilibrium. Meanwhile, only As(V) was released in the cell, which could cause more As(III) to be oxidized. As both Cr(III) and As(V) are less toxic than their corresponding counterparts Cr(VI) and As(III), different redox interactions between BCs and Cr/As and release profiles between BCs and Cr/As together lead to reduced combined cytotoxicity of BP-BC-Cr(VI) and BP-BC-As(III). It suggests that the valence state changes of metal ions due to redox effects is one of the parameters to be focused on when studying the combined toxicity of complexes of BCs with different heavy metal ions.

A novel strategy for arsenic removal from acid wastewater via strong reduction processing.

Due to the high-acidic arsenic-containing wastewater pollution greatly threatening human health and ecological safety, a simple and efficient method for reducing arsenic was proposed in this paper to solve this problem. By using potassium borohydride (KBH4) as a reducing agent, the soluble arsenic was converted into the gaseous arsine (AsH3) or solid arsenic (As0) to achieve the purpose of removing arsenic in wastewater. By exploring the reaction kinetics of the arsenic removal process, it was found that the fast reaction stage (0-2min) conformed to pseudo-first-order kinetics. The removal rate of arsenic increased to over 73% in 0.5min, and reaction equilibrium was reached after 30min. Various influence factors including arsenic valence, aeration, addition method, concentrations of reducing agent, and hydrogen ion (H+) were investigated. The results showed that As(III) was easier to be removed by reduction than As(V), while adding KBH4 in multiples and aeration were both favorable to the removal of arsenic. Increased concentration of KBH4 also enhanced the removal of arsenic. Appropriate H+ concentration contributed to the arsenic removal, but excessive H+ concentration conversely has an inhibitory effect. The maximum removal rate of arsenic was 95.87%, with the maximum removal capacity of 45.50mg/g. Based on the XRD and SEM-EDS analysis of residue, amorphous arsenic (As0) with a mass ratio of more than 94.52% was generated after the reduction of soluble arsenic. Our study demonstrated that the reaction mechanism of reductive degradation is soluble arsenic with hydrogen radicals (H•) to form arsenic (As0) and arsine (AsH3) (in the molar ratio of 6:1). Although the generated solid arsenic (As0) is convenient for the soluble arsenic removal from wastewater, attention must be paid to the formation of AsH3, and strategies for AsH3 treatment should be considered.

Promoting Molecular Exchange on Rare-Earth Oxycarbonate Surfaces to Catalyze the Water–Gas Shift Reaction

It is highly desirable to fabricate an accessible catalyst surface that can efficiently activate reactants and desorb products to promote the local surface reaction equilibrium in heterogeneous catalysis. Herein, rare-earth oxycarbonates (Ln2O2CO3, where Ln = La and Sm), which have molecular-exchangeable (H2O and CO2) surface structures according to the ordered layered arrangement of Ln2O22+ and CO32- ions, are unearthed. On this basis, a series of Ln2O2CO3-supported Cu catalysts are prepared through the deposition precipitation method, which provides excellent catalytic activity and stability for the water-gas shift (WGS) reaction. Density functional theory calculations combined with systematic experimental characterizations verify that H2O spontaneously dissociates on the surface of Ln2O2CO3 to form hydroxyl by eliminating the carbonate through the release of CO2. This interchange efficiently promotes the WGS reaction equilibrium shift on the local surface and prevents the carbonate accumulation from hindering the active sites. The discovery of the unique layered structure provides a so-called "self-cleaning" active surface for the WGS reaction and opens new perspectives about the application of rare-earth oxycarbonate nanomaterials in C1 chemistry.

Conservatively perturbed equilibrium in multi-route catalytic reactions

Abstract The phenomenon of conservatively perturbed-equilibrium (CPE) in multi-route catalytic reactions was studied in the plug-flow reactor (PFR). The following multi-route mechanisms were chosen for studying, i.e., the two-route mechanism with the single common intermediate, the three-route mechanism with some common steps, and the two-route mechanism with the single common step and two common intermediates. All mentioned mechanisms exhibit the CPE-phenomenon. At given rate coefficients, the mechanism with the single common intermediate showed the greater CPE-effect than the mechanism with the common steps. A special computer experiment was performed in which the kinetic characteristics of non-catalytic and catalytic reactions have been compared. In this experiment, both non-catalytic and catalytic reactions have the same overall-reactions with the given equilibrium constant. It was shown that the absolute values of extreme concentrations at the CPE-point are almost the same. In this case, it is possible to estimate the concentrations at the CPE-values for complex reactions based on similar characteristics of the corresponding simple ones.

Acid-Base Properties of Cis-Vacant Montmorillonite Edge Surfaces: A Combined First-Principles Molecular Dynamics and Surface Complexation Modeling Approach.

Montmorillonite layer edge surfaces have pH-dependent properties, which arises from the acid-base reactivity of their surface functional groups. Edge surface acidity (with intrinsic reaction equilibrium constant, pKa) is a chemical property that is affected by crystal structure. While a cis-vacant structure predominates in natural montmorillonites, prior molecular-level studies assume a centrosymmetric trans-vacant configuration, which potentially leads to an incorrect prediction of montmorillonite acid-base surface properties. We computed intrinsic acidity constants of the surface sites of a montmorillonite layer with a cis-vacant structure using the first-principles molecular dynamics-based vertical energy gap method. We evaluated pKa values for both non-substituted and Mg-substituted layers on common edge surfaces (i.e., surfaces perpendicular to [010], [01̅0], [110], and [1̅1̅0] crystallographic directions). The functional groups ≡Si(OH), ≡Al(OH2)2/≡Al(OH)(OH2), and ≡SiO(OH)Al sites on surfaces perpendicular to [010] and [01̅0] and ≡Si(OH)U, ≡Si(OH)L, ≡Al(OH2), and ≡Al(OH2)2 on surfaces perpendicular to [110] and [1̅1̅0] determine the proton reactivity of non-substituted cis-vacant edge surfaces. Moreover, the structural OH sites on edge surfaces had extremely high pKa values, which do not show reactivity at a common pH. Meanwhile, Mg2+ substitution results in an increase in pKa values at local or adjacent sites, in which the effect is limited by the distance between the sites. A surface complexation model was built with predicted pKa values, which enabled us to predict surface properties as a function of pH and ionic strength. Edge surface charge of both trans- and cis-vacant models has little dependence on Mg2+ substitutions, but the dependence on the crystal plane orientation is strong. In particular, at pH below 7, edge surfaces are positively or negatively charged depending on their orientation. Implications of these findings on contaminant adsorption by smectites are discussed.

Influence of operational parameters and kinetics analysis on photocatalytic hydrolysis of ammonia borane for H2 production used heterojunction FeTiO3/TiO2-decorated carbon nanofibers

In this work, carbon nanofibers (CNFs) decorated with heterojunction iron titanate/titanate nanoparticles (FeTiO3/TiO2 NPs) were effectively prepared using electrospinning for use as a photocatalyst in the production of hydrogen (H2) from ammonia borane (AB). The as-prepared FeTiO3/TiO2@CNFs exhibited strong photocatalytic activity for H2 release from photohydrolysis of the AB when exposed to visible light. Under visible light illumination, the observed H2 evolution over TiO2@CNFs was 0.38 mol in 14 min, whereas over FeTiO3/TiO2@CNFs it was 2.97 mol. Using FeTiO3/TiO2@CNFs, H2 generation was shown to be substantially higher under visible light irradiation (2.97 mol/14 min) than in the dark (1.87 mol/14 min). A mathematical model was used to predict the photocatalytic activity of FeTiO3/TiO2@CNFs. Different operational factors were used to verify the accuracy of the mathematical model; they included the impact of AB concentration, light intensity, reaction temperature, and catalyst dosage. The reaction rate constant and equilibrium concentration were measured experimentally and compared to those predicted by the model. A good correlation was obtained between the calculated and measured photocatalytic activity.

Термодинамический анализ хлорирования оксида алюминия

Thermodynamic analysis of aluminum oxide chlorination is of theoretical and practical interest and is performed for the main possible reactions of interaction with chlorine. The process is possible only in the direction of decreasing (decreasing) the Gibbs energy (∆G). The condition ∆G0 determines the principal possibility of carrying out the process under specified conditions and is determined only by the initial and final state of the system. The calculated values of the Gibbs energy and the equilibrium constant in the temperature range 400 – 1000 K show that in the presence of a reducing agent, the equilibrium of reactions is shifted towards the formation of aluminum chloride. It was found that the changes in the Gibbs energy of chlorination reactions of polymorphic modifications of Al2O3 increases in the series: γ-Al2O3, Al2O3 am., δ-Al2O3, α-Al2O3. It is possible to effectively assess the basic laws of obtaining anhydrous aluminum chloride in the reacting system by evaluating the change in the ratio of the initial components. Thermodynamic analysis of Al – O – C – Cl and Al – O – C – Cl – Si – Na systems with different component ratios was performed. The latter system is a rough alumina containing sodium aluminosilicate. It is shown that the 100 % yield of the target products with the full use of chlorine corresponds to the stoichiometry of their chemical interaction. The possibility of selective chlorination of Al2O3 and SiCl4 has been determined. As calculations have shown, sodium oxide is completely converted into chloride, which makes it possible to use the residue from chlorination to obtain aluminum-silicon alloys without sodium impurities.

Adsorption-Reduction Behavior of Cr(VI) by Ferrihydrite-Fulvic Acid Complexes with Different C/Fe Mole Ratios

Ferrihydrite and fulvic acid are prevalent components of soils and can significantly influence the environmental behavior of Cr(VI) in these matrices. Prior research has investigated the sorption behavior of Cr(VI) by ferrihydrite and fulvic acid independently; however, the sorption-reduction capacity of Cr(VI) by the ferrihydrite-fulvic acid complex, which is ubiquitously present in soils, has been less explored. In this study, ferrihydrite-fulvic acid complexes (Fh-FA) with varying C/Fe mole ratios were synthesized, and the adsorption-reduction behaviors of Cr(VI) on Fh-FA were examined using batch experiments, FTIR, BET, XRD, SEM-EDS, and XPS. The results demonstrate that the pseudo-second-order kinetic model can accurately describe the adsorption process of Fh-FA on Cr(VI), which can be delineated into three stages: rapid adsorption (0-30 min), slow adsorption (30-120 min), and reaction equilibrium (>120 min). The adsorption of Cr(VI) on Fh-FA primarily occurs through chemisorption. FTIR and XPS analyses revealed that Cr(VI) is initially adsorbed by Fe-OH on the Fh-FA surface. However, as the C/Fe mole ratio of Fh-FA increases, more Fe-OH is complexed by -COOH from FA, resulting in a decrease in the adsorption capacity of Cr(VI) by Fh-FA. The number of phenolic hydroxyl groups from FA also increases, providing additional electrons to reduce Cr(VI) to Cr(III) with increasing C/Fe mole ratio. This study not only emphasizes the adsorption-reduction behavior of Cr(VI) by ferrihydrite-fulvic acid complexes but also uncovers the interplay between C/Fe mole ratios and Cr(VI) adsorption-reduction, contributing to a more comprehensive understanding of the relative roles of Fe hydroxides and natural organic matter in soil environments. These findings have significant implications for Cr(VI) management in soils, enhancing our capability to protect and sustain the environmental quality.

Regeneration of NCM622 from end-of-life lithium-ion battery cathode materials.

The boom of the electric vehicle industry significantly aggravates the demand for lithium-ion batteries (LIBs), especially the ternary cathode materials, however, the majority of end-of-life (EOL) LIBs on the market are batteries utilized in customer electronics. Here, we utilized the mixed EOL LIBs from cell phones and laptops to manufacture the LiNi0.6Co0.2Mn0.2O2 (NCM622) cathode material. A feasible, high efficiency (99.98% Co, 99.98% Ni, 99.99% Mn, and 99.99% Li), and ultra-fast leaching of EOL LIB cathodes was achieved. Thermodynamic calculations suggested that the coordination number, coordination species concentrations, and fractions have significant effects on the apparent activation energy and the equilibrium of the leaching reactions. The remanufactured NCM622 cathode material demonstrated a well-ordered layered hexagonal structure with a low Li+/Ni2+ mixing ratio, which facilitated reliable reversible capacity, low polarization, high rate capabilities (163.8 mA h g-1), and capacity retention ratio (94.3%).

Модернизация CVD-установки для осаждения карбида хрома на внутренних поверхностях корпуса распылителя форсунки дизельных двигателей

Fuel injector nozzle parts tend to wear out due to abrasive particles of quartz and aluminum oxide penetrating into the fuel. The hardness of quartz abrasive particles exceeds the hardness of work surfaces in 1.4 times, and that of aluminum oxide – in 2.7 times. Strengthening one part of the fuel injector nozzle does not increase the service life sufficiently, so it is necessary to harden both parts of the precision pair. The CVD method is the most promising technology of wear-resistant coating deposition on steel machine parts. It produces carbide-chrome coating with microhardness up to 19 GPa (in vacuum conditions of 100 to 0.001 Pa) at temperatures above 200°C. The analysis of available devices and the review of patents of known solutions on the coating deposition from a steam phase have shown the impossibility of using these devices for restoration of the nozzle body. In this respect, the author developed a new reactor design and a scheme of the CVD unit for the coating deposition on the inner hard-to-reach surfaces of the nozzle body. The developed CVD unit takes into account the factors affecting chromium carbide deposition: thermodynamic conditions, reagent feed, deposition duration, unit parameters, adhesion and coating properties. The CVD unit upgrade results in making chromium carbide coating on the inner surfaces of the nozzle sprayer body, achieving thermodynamic equilibrium of chemical reaction of chromium hexacarbonyl decomposition at temperatures below 200°C (below the low tempering level of 18Х2Н4ВА, 12Х2Н4А and 40ХН2МА steel), and ensuring a controlled supply of a reaction medium to hard-to-reach areas, where refractory metal coatings are formed.

Highly efficient production and purification of fructoseviaglucose isomerization by calcium chloride and triethylamine

CaCl2and Et3N promoted glucose isomerization cooperatively, the generated fructose with CaCl2 and Et3N form the α-fructofuranose complex, which shifted the reaction equilibrium towards fructose formation and precipitated fructose from the mixture.

THE CATALYSTS IMPACT ON THE TRI- AND DIETHANOLAMINE AND ETHYL OLEATE INTERACTION

Alkanolamides and ester amines are raw materials for manufacturing surfactants, detergents and cosmetics, pharmaceuticals, and dyes. We investigated the regularities of the interaction between ethyl oleate and a mixture of tri- and diethanolamines (diethanolamine content was 21 wt.%) in the presence of Brønsted and Lewis catalysts. The cation exchange resin KU-2-8, anion exchange resin AB-17-8, potassium hydroxide, nickel oxalate, cation exchange resin KU-2-8 with immobilized Ni2+ ions, cation exchange resin KU-2-8 with immobilized Ni2+ ions treated with a 0.1 M alkali solution within 1 hour, and tin (II) p-toluenesulfonate were used as catalysts. The reaction was carried out in non-stationary conditions with the formed ethanol distillation from the reaction mixture to shift the transesterification reaction equilibrium. It was established that the studied catalysts, with a few exceptions, are characterized by a relatively low rate of reagent conversion. It is shown that the effectiveness of cation exchange resin KU-2-8 in the H-form depends significantly on the temperature and, to a greater extent, on the ethyl oleate and tri- and diethanolamines molar ratio. The study of the reagent ratio influence made it possible to assume that mass transfer processes significantly affect the parameters of ethyl oleate and ethanolamines interaction. It is shown that, under the same conditions, catalytic activity similar to cation exchange resin KU-2-8 is exhibited by anion exchange resin AB-17-8 and tin (II) p-toluenesulfonate. Modifying cation exchange resin KU-2-8 by immobilized nickel ions improves its catalytic properties, and subsequent treatment of the obtained catalyst with an alkali solution even slightly reduces the conversion of ethyl oleate. It was established that nickel oxalate exhibits the highest activity as a catalyst for the reaction between ethyl oleate and tri- and diethanolamines. This effect can be explained by the high electron-accepting properties of the oxalate anion, which reduces the electron density of the Ni2+ cation. As a result, in the presence of this catalyst, the ester conversion is 21.9%. The obtained results made it possible to conclude the potential prospects of using cation exchange resin KU-2-8 in H-form and nickel oxalate as catalysts for ethyl oleate and tri- and diethanolamines interaction.

Dynamic analysis of a laterally loaded rectangular pile in multilayered viscoelastic soil

Rectangular piles are usually used as the foundation for many infrastructures, but there are fewer theoretical solutions for the lateral vibration. This study presents a semi-analytical methodology for the dynamic analysis of laterally loaded rectangular pile in multi-layered viscoelastic soils. The pile-soil system is modeled as a continuum, the horizontal continuous displacement model is proposed as products of the separating variables function. The coupled governing equations for rectangular pile-soil system in the frame of Euler-Bernoulli beam and modified Vlasov model are derived with the aid of Hamilton's Variation principle and calculus of variations. The physical mechanisms of soil reaction and dynamic equilibrium equation are interpreted by employing thin-layer element of soil. The dynamic responses are solved analytically and numerically by an iterative procedure. The verification and accuracy of the research are obtained thorough comparison with the relevant examples from the literatures and finite element analysis. The effects of cross-section shapes and soil stratification on the complex dynamic response are investigated and discussed in detail.

Thermodynamics of hydrogen storage: Equilibrium study of the LOHC system indole/octahydroindole

Reversible hydrogenation of indole or its derivatives could be an attractive hydrogen storage technology. Particularly for hydrogen release, the reaction equilibrium is a crucial factor determining the conditions in the respective process. This study is supposed to provide inside into this reaction equilibrium. An experimental study of the chemical equilibrium of hydrogenation/dehydrogenation reactions was performed in a stirred autoclave with n–hexane as a solvent by varying the temperature, pressure, and hydrogen:feedstock ratio. Based on the compositions in stationary state, equilibrium constants have been derived. Furthermore, thermodynamic properties of chemical reactions were derived from the equilibrium constant temperature dependence. This temperature dependence reveals that the enthalpy of reaction for the dehydrogenation of the six-membered ring is significantly larger than in the nitrogen containing five-membered ring. To get deeper insides, the molar enthalpies of formation of intermediates have been calculated using high-level quantum chemical methods. This analysis supports the observations from the equilibrium reactions. Additionally, it show that the heat of reaction for the endothermal dehydrogenation is about 2 kJ mol (H2)–1 smaller in the liquid phase than in case of a gas phase reaction.

Measurement and model of density, viscosity, and hydrogen sulfide solubility in ferric chloride/trioctylmethylammonium chloride ionic liquid

The density and viscosity of ferric chloride/trioctylmethylammonium chloride ionic liquid (rFeCl3/[A336]Cl) with different molar ratios (r = 0.1–0.8) of FeCl3 to [A336]Cl were measured at temperatures from 313.15 to 358.15 K and atmospheric pressure. The density and viscosity data were fitted by the relevant temperature variation equations, respectively. The variation of density and viscosity with temperature and r was obtained. The solubility of rFeCl3/[A336]Cl to H2S was measured at temperatures from 318.15 to 348.15 K and pressures from 0 to 150 kPa. The effects of temperature, pressure, and r on the solubility of H2S were discussed. The reaction equilibrium thermodynamic model (RETM) was used to fit the H2S solubility data, and the average relative error was less than 1.3%, indicating that the model can relate the solubility data well. And Henry's constant and chemical reaction equilibrium constant were obtained by the RETM fitting. The relationships of Henry's constant and chemical reaction equilibrium constant with temperature and r were analyzed.

Conversion of Adipic Acid to Bis-2-ethylhexyl Adipate Overcoming Equilibrium Constraints: A Laboratory Experiment

An adipic acid esterification experiment suitable for graduate students has been developed to describe the industrial manufacture of plasticizers. Students first follow the progress of the reaction with simple acid/base titration enabling measurement of the acid number. During the workup of the reaction mixture, they learn how to manage the filtration of a viscous mixture over an inert support such as Celite and practice on atmospheric and vacuum distillations. They finally learn to set a mass balance on 2-ethylhexanol using fully experimental data from their own reactions. To this end, they also learn how to retrieve from a 1H NMR spectrum the required data to evaluate the purity and the yield of bis-2-ethylhexyl adipate. These tasks corroborate basic concepts related to the tools available to shift the equilibrium in reversible reactions, at the same time providing new knowledge on mass balance calculations and 1H NMR.

EXTRACTION AND ATOMIC-ABSORPTION DETERMINATION OF TUNGSTEN (VI) WITH 2-HYDROXY-5-T-BUTYLPHENOL-4'-NITROAZOBENZENE

The complexation of tungsten (VI) with an azo compound synthesized from para-tret-butylphenol (2-hydroxy-5-Tr-butylphenol-4-nitro-asobenzene) has been studied spectrophoto¬metrically. The optimum pH values of the solution are 2.0-3.0. The maximum light absorption of the complexes in n-butanol is in the range 460-470nm, and that of the reagent at 360-370; complex formation is accompanied by a bathochromic shift. The spectrophotometric characteristics of the complex have been calculated and the composition of the complex was determined by various methods. Using the equilibrium shift and isomolar series methods it has been found that the W:R ratio is 1:2. By the Sommer method it has been found that during complex formation one proton is released from each reagent molecule. The complex stability constant βk = 9.04·108 and the complex formation reaction equilibrium constant (4.2·104) have been calculated by the method of Komar. The molar absorption coefficient is (3.44.2).104. The graduation diagram is linear at a tungsten concentration of 1.0-10 µg/ml, n-butanol has been used as an extractant. A single extraction with n-butanol 97% of tungsten as a complex is extracted. Methods of extraction-atomic-absorption and extraction-photometric determination of tungsten have been developed and the influence of a number of extraneous ions on the determination of tungsten has been revealed. The correctness of the results obtained has been controlled by analysing the State Standard Alloy Reference Materials

Medium engineering of phenylethanoid transfructosylation catalysed by yeast β-fructofuranosidase.

Tyrosol and hydroxytyrosol, by-products of olive oil production, are valuable substrates for enzymatic transglycosylation that can provide products with pharmaceutical potential. Phenylethanoid fructosides are produced from sucrose and phenylethanoids by the catalytic action of β-fructofuranosidases. This work dealt with the potential of the most abundant β-fructofuranosidase, baker's yeast invertase, for this bioconversion. The effects of sucrose and phenylethanoid concentrations were investigated with a focus on the selectivity of phenylethanoid transfructosylation and fructoside yields. For this purpose, initial rate and progress curve experiments were carried out for the initial (hydroxy)tyrosol and sucrose concentrations of 0.072-0.3M and 1-2M, respectively. Reaction courses exhibited either a maximum or plateau of fructoside yield in the range of about 10-18%. The addition of deep eutectic solvents was applied in the concentration range from 5 to 70% (v/v) to investigate the possibility of shifting the reaction equilibrium towards fructoside synthesis.

Phosphorylation-Driven Production of d-Allulose from d-Glucose by Coupling with an ATP Regeneration System.

d-Allulose is a desirable sucrose substitute with potential applications in food and health care. d-Allulose can be synthesized using d-glucose as a substrate through coupling glucose isomerase with d-allulose 3-epimerase (DAEase); however, the product yield is typically less than 20% at reaction equilibrium and thus limits its use in industrial applications. Here, a 3R-ketose phosphorylation pathway coupled with an adenosine triphosphate (ATP) regeneration system was developed for the efficient synthesis of d-allulose in Escherichia coli using d-glucose as a substrate. The l-rhamnulose kinase (RhaB) was used to break the inherent reaction equilibrium due to its substrate specificity, resulting in increases in d-allulose titer by 69.9% to 4.96 ± 0.49 g/L. By optimizing the whole cell transformation conditions and designing an ATP regeneration module, d-allulose production reached 17.62 ± 0.77 g/L from 30 g/L d-glucose with a final yield of 0.73 g/g without the addition of exogenous ATP. To evaluate the potential industrial application of this multienzyme cascade system, d-allulose was produced from cane molasses (124.16 ± 2.69 g/L glucose equivalent) with a final d-allulose titer of 62.60 ± 3.76 g/L. The present study provides a practical enzymatic approach for the economical synthesis of d-allulose.

Fluidized Bed Membrane Reactor for the Direct Dehydrogenation of Propane: Proof of Concept.

In this work, the fluidized bed membrane reactor (FBMR) technology for the direct dehydrogenation of propane (PDH) was demonstrated at a laboratory scale. Double-skinned PdAg membranes were used to selectively remove H2 during dehydrogenation tests over PtSnK/Al2O3 catalyst under fluidization. The performance of the fluidized bed membrane reactor was experimentally investigated and compared with the conventional fluidized bed reactor (FBR) by varying the superficial gas velocity over the minimum fluidization velocity under fixed operating conditions (i.e., 500 °C, 2 bar and feed composition of 30vol% C3H8-70vol% N2). The results obtained in this work confirmed the potential for improving the PDH performance using the FBMR system. An increase in the initial propane conversion of c.a. 20% was observed, going from 19.5% in the FBR to almost 25% in the FBMR. The hydrogen recovery factor displayed a decrease from 70% to values below 50%, due to the membrane coking under alkene exposure. Despites this, the hydrogen extraction from the reaction environment shifted the thermodynamic equilibrium of the dehydrogenation reaction and achieved an average increase of 43% in propylene yields.