Ethanol Dehydration Research Articles

An Effective Synthesis of Phosphated Silica (PO<sub>4</sub>/SiO<sub>2</sub>) Catalyst and its Performance for Converting Ethanol into Diethyl Ether (DEE)

Research on phosphated silica (PO4/SiO2) as a heterogeneous acid catalyst in the dehydration reaction of ethanol into diethyl ether has been carried out. The PO4/SiO2 was prepared from TEOS by a wet impregnation method with various concentrations of H3PO4 (1, 2, 3, 4 M) and calcination temperatures (400, 500, and 600 °C) to obtain it with an optimum acidity. Afterward, the catalysts were characterized by FTIR, XRD, SEM-EDX, SAA, and TG-DTA. Ethanol dehydration was run using a fixed-batch reactor with a flow of N2 gas, and GC determined the selectivity of diethyl ether. The PS-4-400 catalyst had the highest activity and selectivity in the ethanol dehydration to diethyl ether at a temperature of 225 °C, with a conversion of 58.00% and a DEE selectivity of 3.71%.

Nickel Oxide-Impregnated Phosphated Silica Catalyst: Synthesis and Application for Ethanol Dehydration into Diethyl Ether (DEE)

The synthesis, characterization, and application of a NiO-PO4/SiO2 catalyst for ethanol dehydration to diethyl ether were successfully conducted. The sol-gel method utilized TEOS as the silica source, NaHCO3 as a template, and different phosphoric acid concentrations (1, 2, and 3 M). Calcination occurred at temperatures of 400, 500, and 600 °C. The catalyst with the highest acidity underwent impregnation with 1, 2, and 3% (w/w) nickel precursor proceeded by calcination with N2 gas. Characterization techniques included FTIR, XRD, SEM-EDX, and AAS. The application of SP 2-NiO 3% catalyst as the catalyst with the highest acidity demonstrated significant activity and selectivity in diethyl ether production at 175, 200, and 225 °C temperatures, yielding 88% conversion and 5.07% diethyl ether selectivity at its optimum temperature of 225 °C.

In situ visualisation of zeolite anisotropic framework flexibility during catalysis

Zeolites exhibit framework flexibility driving their chemical and catalytic properties. Since the zeolitic pores are extremely small, a slight strain generated in the crystal induces compelling changes in shape, connectivity, accessibility, and the framework chemical properties. These modifications affected the adsorption and desorption of reactants/products and the diffusion within the channels during reaction. Using in situ 3D Bragg coherent X-ray diffraction imaging, we unveil the dynamics of the zeolite structure during catalysis, contraction and/or expansion of its framework also known as zeolite framework flexibility. We imaged three-dimensionally a single faujasite zeolite crystal during the ethanol dehydration reaction revealing anisotropic lattice dynamics simultaneously to guest molecules formation. Understanding zeolite flexibility could permit to tune zeolites properties towards potentially higher adsorption and selectivity.

Synthesis of alumina/ferric oxide nanofibers and application to catalysts for ethanol dehydration reaction by adding palladium oxide

AbstractAlumina/ferric oxide (Al₂O₃/Fe₂O₃) composite nanofibers were fabricated via electrospinning followed by heat treatment. Structural characterization revealed mesoporous morphology with high porosity and surface area and uniform dispersion of catalytically active Fe₂O₃ nanoparticles. Catalytic evaluation for ethanol dehydration demonstrated superior performance for nanofibers containing 5 wt% Fe₂O₃, attributed to their unique structural features. Further enhancement was achieved by incorporating palladium oxide (PdO), resulting in improved catalytic activity, particularly in ethylene productivity. Surface acid properties were altered with PdO addition, suggesting a role of Lewis acid sites in augmenting catalytic performance. The developed PdO/Al₂O₃/Fe₂O₃ nanofibers exhibit stable performance over multiple cycles, offering promising prospects for efficient ethanol dehydration catalysts.

Self-assembled ILs-PVA micelle nanostructure impart the pervaporation membrane with high ethanol dehydration performance

Achieving strong interaction with the targeted composition and constructing abundant transport channels is crucial to obtain the pervaporation (PV) membrane with high selectivity and flux. Here, three ionic liquids (ILs) were screened out based on their relative selectivity and capacity targeting for bioethanol dehydration by COSMO-RS. The interaction energies analysis between ILs, EtOH, and H2O suggests that the ILs can form strong hydrogen bonds with water and disrupt the hydrogen bond in the EtOH–H2O azeotropic mixture, which is beneficial for improving the selectivity. Furthermore, driven by the multiple hydrogen bonds, electrostatic interactions, and van der Waals forces, ILs could self-assemble with polyvinyl alcohol (PVA) to fabricate the PV membrane with well-ordered micelle nanostructure, as its structure was revealed by MD simulations. The formation of the ILs-PVA micelle dramatically influenced membrane surface morphology, roughness, and water contact angle, providing an extra transport channel for the membrane. The optimal membrane (at the cmc point) exhibited a superior ethanol dehydration separation factor of 1627, along with a flux of 684 g/m2h at 50 °C. It can be expected that this novel self-assembled ILs-PVA micelle nanostructure strategy will find promising applications in other azeotropic mixture separation processes, like ethanol-ethyl acetate, water-butanol, etc.

Integrated syngas biorefinery for manufacturing ethylene, acetic acid and vinyl acetate

The paper presents the design of an innovative process for manufacturing sustainable biochemicals, as acetic acid, ethylene and vinyl acetate monomer (VAM), in an integrated syngas biorefinery using renewable feedstock as biomethane and captured CO2. The work is supported by full design and simulation of six plants imbedded in a large process: syngas1 H2/CO 2:1 by catalytic partial oxidation of methane, syngas2 H2/CO 1:1 by dry methane reforming, methanol, acetic acid by carbonylation, ethylene and vinyl acetate. A key contribution is the development of a novel acetic-acid-to-ethylene process starting from syngas. This consists of catalytic hydrogenation of acetic acid (exothermic) followed by catalytic ethanol dehydration (endothermic). The thermal integration of reactors leads to low energy process and superior sustainability measures versus petrochemical and methanol-to-olefin processes. The comprehensive simulation of the integrated biorefinery allows getting consistent mass and energy balances, performing energy analysis and capital cost estimation, and finally delivering reliable sustainability measures. Based on syngas the carbon-yield, mass-yield, carbon footprint (kg CO2/kg product) and energetic requirement (MJ/kg) are 78.6%, 34.7%, 1.6 and 11.2 for ethylene, and 80.8%, 46.8%, 1.5 and 11.9 for VAM. At high biomethane price the ethylene may be costly but manufacturing the higher value VAM is fully profitable.

Zwitterionic covalent organic framework membranes for efficient liquid molecular separations

Covalent organic frameworks (COFs) featuring uniform topological structure and devisable functionality have emerged as promising membrane materials. The design and precise manipulation of COF membranes with advanced spatial structure to achieve efficient liquid molecular separations are of great necessity. Herein, zwitterionic COF membranes have been in-situ fabricated on porous polymeric substrates using an interfacial polymerization modification strategy. The continuous defect-free COF membranes with two-dimensional in-plane dominant growth can be achieved by optimizing the fabrication parameters including reaction time, monomer concentration, and catalyst concentration. Subsequent zwitterionic modification thereon not only favors the formation of hydrophilic surface but also improves the sieving capability by sheltering effect. Attributed to the synergistic contribution, the optimized zwitterionic COF membrane possesses a superior separation factor of 2839 with the water content in the permeate up to 99.7 wt%, while maintaining a comparable permeation flux of 3309 g m−2 h−1 during the ethanol dehydration process, outperforming most of other representative membranes. Furthermore, the excellent durability of the zwitterionic COF membrane in the ethanol dehydration process and its efficient separation performance towards other alcohol dehydration systems demonstrate its potential practical applications. The easy scalability of the fabrication and regulation method offers crucial guidance for the engineering of advanced COF membranes in efficient liquid molecular separations.

Preparation and optimization of nanocomposite membranes for ethanol dehydration via pervaporation by using response surface methodology

BackgroundAlcohol dehydration using pervaporation, as a fast-developing process, requires more facilitation by improving their membrane performance. MethodsGraphene oxide nanosheets (GONs) were incorporated into blend matrixes of chitosan (CS) and polyvinyl-alcohol (PVA) to prepare nanocomposite membranes (NCMs) for ethanol dehydration. The membranes' structure was evaluated using SEM and FTIR analysis and their dehydration performance was studied against membrane composition (GONs loading and the CS/PVA blending ratio) and operational variables (feed temperature and ethanol concentration) using response surface methodology. Significant FindingsSEM images revealed GONs uniform dispersion within the membrane matrix and the FTIR results revealed the hydrogen bonds formation and minor changes after GONs incorporation. The optimum NCM was selected as 50 wt. % CS/PVA blended polymer matrix loaded by 4 wt. % GONs with permeation flux (PF) and separation factor (SF) were improved by 50 % and 5-fold, to 299 g/m2h and 1142. Its PF and SF reached 418 g/m2h (45 % increment) and 652 (30 % decrement) as its temperature elevated from 50 to 70 °C. These values were measured as 311 g/m2h (25 % decline) and 1106 (66 % improvement) by increasing the feed's ethanol content from 80 to 90 wt. %.

CPAM-assisted synthesis of NaA zeolite membrane on macroporous mullite hollow fiber for ethanol dehydration by pervaporation

Due to the low transport resistance, mullite hollow fiber (HF) could be regarded as a promising support for preparation of NaA zeolite membranes. However, insufficient coverage and undesired seed penetration often occur in the seeding step of the mullite support due to the rough surfaces with ultra-large macropores (2–4 μm). This leads to poor intergrowth of the membrane layer. To solve this issue, cationic polyacrylamide (CPAM) was employed to modify the chemical and electrostatic properties of the mullite HF surface, where the electrostatic attraction between the surface and seed crystals could significantly promote the coating effect. In the seeding, the original seeds (3.2 μm) were mixed with the ball-milled seeds (0.3 μm) to improve the seed coverage, i.e., the original seed was used to block the macropores on the support surface to prevent the penetration of small seeds, while the decked ball-milled seed was used to provide sufficient active sites to induce the intergrowth of the zeolite crystals. The effects of the concentration of CPAM, mixed mass ratio of seeds, and seed concentration on the preparation of NaA zeolite membranes were systematically examined, where the separation performances were characterized by pervaporation (PV) dehydration of 90% (mass) ethanol/water mixtures at 75 °C. The results indicated that under a CPAM concentration of 0.7% (mass), an equivalent mass ratio of mixed seeds in a seed concentration of 1.0% (mass), the prepared mullite HF supported NaA zeolite membrane yielded the best PV performance, where the permeation flux and separation factor corresponded to 5.45 kg·m−2·h−1 and 10000, respectively, being sufficient for industrial applications.

Dehydration of bioethanol using novel polysulfone (PSF)/nonionic surfactants hybrid membranes

This study focuses on developing a novel polysulfone (PSF) dense hybrid membrane modified with nonionic surfactants, Tween 20 (T20) and Triton X-100 (X100), for improved pervaporation (PV) dehydration of bioethanol. The modified membranes were then examined for their ethanol dehydration performance, microscopy and spectroscopy characteristics, surface charge, mechanical and roughness properties, crystallinity structure, differential scanning calorimetry (DSC), swelling, and contact angle (CA) analysis. The free volume structure of the membranes was assessed using positron annihilation lifetime spectroscopy (PALS) and Doppler broadening spectroscopy (DBS). A significant discovery from this analysis was the semi antiplasticizing effect observed when surfactants were added to the PV membranes. The PV results revealed that incorporating 0.5 wt% T20 into PSF significantly improved the total flux and PSI of PSF/T20 to 226.35 g/m2 h and 46578 g/m2 h, respectively. Similarly, the total flux and PSI of hybrid membranes containing X100 increased to 110.19 g/m2 h and 43680 g/m2 h. Consequently, the developed PSF/T20 membranes demonstrated more significant potential for bioethanol dehydration compared to PSF/X100 membranes.

Carbon quantum dots (CQDs) incorporated dual-layer hollow fibers for pervaporative dehydration of ethanol

Pervaporative ethanol dehydration is a promising approach to concentrate ethanol from biofuel stocks. In this study, we have fabricated high performance dual-layer cellulose triacetate (CTA)/Ultem hollow fiber membranes incorporated with a small amount of superhydrophilic carbon quantum dots (CQDs) via the immiscibility induced phase separation (I2PS) method. The flow rates of the inner- and outer-layer dopes were firstly optimized. Subsequently, various small amounts of CQDs were added into the inner- and outer-layer dope solutions to explore their impacts on membrane structure and separation performance. It was found that the incorporation of a reasonably small amount of CQDs, whether to the inner or outer layer of I2PS membranes, could significantly enhance the mechanical properties and pervaporation performance by altering their structures. The most effective membrane containing 0.2 wt% CQD in the outer layer (0.2CQD_OL) demonstrated exceptional pervaporation performance. Using an 85 wt% ethanol feed solution, this membrane achieved a total flux of 4306 ± 130 g m−2h−1 (equivalent to a water permeance of 33.28 mol m−2h−1 kPa−1) and a water content of approximately 95 wt% (equivalent to a mole-based selectivity of 153) in the permeate over a 172 hr long-term test. A comparison with literature underscores the superior performance of this newly developed I2PS membrane, particularly in terms of water permeance. In summary, the CQD-embedded CTA/Ultem HF membranes demonstrate substantial potential for industrial applications in the pervaporative ethanol dehydration.

High-performance double-separation-layer pervaporation membranes for ethanol dehydration

Pervaporation membranes are used to dehydrate ethanol, but standalone sodium alginate (SA) and polyvinyl alcohol (PVA) membranes pose challenges owing to their inherent issues, such as low stability and limited separation performance. Despite employing various complex and costly membrane preparation methods to address these shortcomings, the improvement in separation performance, especially in permeate flux, remains limited. In addition, the complexity and costliness of these methods hinder their industrial applications. Herein, we developed a simple and cost-effective method to prepare high-performance pervaporation membranes. First, a SA solution was cast on the polyacrylonitrile (PAN) bottom membrane to form a SA separation layer, and subsequently a PVA separation layer was applied atop of the SA separation layer, yielding double-separation-layer PVA/SA/PAN membranes. The smooth, compact and hydrophilic SA intermediate layer apparently decreased the defects in the PVA separation layer and the presence of the PVA separation layer isolated the SA layer from the liquid feed on the outer side and inhibited the swelling of SA separation layer, leading to high selectivities and stabilities. Under operating conditions of 69°C and a feed ethanol concentration of 90 wt%, the permeate flux and separation factor of the PVA4/SA/PAN membrane are 1201 g m−2 h−1 and 5164, respectively. Notably, the pervaporation separation index (PSI) of this membrane is 79 times that of the PVA4/PAN membrane. Moreover, the membrane performance remained stable over a continuous 10-day operation at 69°C, affirming its reliability and durability. We successfully prepared a high-performance two-separation-layer pervaporation membrane for ethanol dehydration.

Preparation and catalytic evaluation of phosphated zirconia nanopowder for ethanol dehydration into diethyl ether

Research on renewable energy development is intensified nowadays, including the production of diethyl ether (DEE) as a high-value alternative fuel. This study explored the catalytic conversion of ethanol into diethyl ether using a phosphated zirconia catalyst. We examined different concentrations of phosphoric acid (1, 2, 3, and 4 M) and calcination temperatures (400, 500, and 600 °C) applied to zirconia nanopowder to evaluate their influence on the acidity of the resulting phosphated zirconia. The catalysts were characterized by FTIR, XRD, SAA, SEM-EDX Mapping, and TG-DTA. Among the catalysts tested, the PZ-2-400 catalyst, prepared with a 2 M H3PO4 concentration and calcined at 400 °C, exhibited the highest acidity value of 0.56 g/mol pyridine. When operated at the optimum temperature of 225 °C, this catalyst achieved an ethanol conversion of 80.04 % and a diethyl ether yield of 1.00 %. These findings suggest that modification of ZrO2 with phosphoric acid acts as a solid acid catalyst for diethyl ether synthesis with better activity and selectivity than unmodified ZrO2.

Beneficent impact of mixed molecular magnet/neodymium powder for facilitating ethanol dehydration in the pervaporation process

The focus of the study concerned the application of alginate membranes enriched with a mixture of Magnequench Fine Powder (MQFP) and a Molecular Magnet [Fe4(acac)6(Br-mp)2] (MM) in different proportions to improve ethanol dehydration via pervaporation. The paper concentrated on how the combined fillers affected the membranes ability to transport the ethanol/water solution components. It was observed that the integration of MM into MQFP not only improved the magnetic properties but also provided a uniform distribution of the filler in the alginate matrix. By merging the properties of two different fillers, we achieved membranes with outstanding separation process performance. This efficiency was unattainable using each filler separately, highlighting the synergistic effect of combining the two fillers. The membrane with 1 wt% MQFP and 9 wt% MM proved to be the most efficient, with the highest Pervaporation Separation Index and separation factor, reaching 40974 kg⋅m−2⋅h−1 and 12735.14, respectively.

Glycine-Modified Co-MOF Pervaporation Membrane to Enhance Water Transporting.

Cobalt-based metal-organic frameworks (Co-MOFs) with a two-dimensional layered morphology have received increasing attention for pervaporation due to their stability and hydrophilic properties. Using amino glycine (Gly) as a cross-linking agent, the Co-MOF ultrathin two-dimensional membrane doped with organic filler sodium alginate (SA) with the "brick-mixed-sand" structure was proposed. Polyacrylonitrile (PAN) was selected as the support layer of the hybrid membrane. The introduction of Gly efficiently solved the nanomaterial stacking problem and controllably adjusted the interlayer spacing between the nanosheets, which demonstrated good performance for ethanol dehydration. The results of this experimental research showed that the total flux of alcohol/water (9:1) separation by Gly-Co-MOF-SA/PAN hybrid membranes reached 1902 g m-2 h-1, which was 67% higher than that of the pure SA membranes. The "brick-mixed-sand" lamellar dense morphology of Gly-Co-MOF not only enhances membrane hydrophilicity but also provides effective channels for the rapid transport of water, which is expected to be used for the dehydration of organic solvents.

Porous Al2O3-pillared bentonite synthesized by sonochemistry and its performance as a catalyst in diethyl ether production via ethanol dehydration

Porous Al2O3-pillared bentonite synthesized by sonochemistry and its performance as a catalyst in diethyl ether production via ethanol dehydration

Enhanced ethanol dehydration performance of cationic COFs filled anionic alginate hybrid membranes

Adding charged fillers to incorporate long-range electrostatic interactions is an effective way to reduce structure defects and improve separation performance of polyelectrolyte membranes. In this study, three cationic covalent organic frameworks (COFs), TpEB, TpTGCl, and TpPy, were incorporated into anionic alginate to prepare hybrid membranes for pervaporation dehydration of ethanol. With the increase of electrostatic interaction, the decrease in the mobility of polymer chains leads to an increase in the crystallinity and selectivity. Meanwhile, the inherent hydrophilic channels of iCOFs provided additional mass transfer channels, increasing the membrane permeability. When separating a 90 wt% ethanol/water mixture at 76 °C, the hybrid membrane containing 15 wt% TpEB exhibited the highest separation performance with a permeation flux of 2460 g m-2 h-1 and a separation factor of 2110, and it also demonstrated ideal long-term stability. This work provides a new perspective for the selection of fillers in the design process of hybrid membranes in the future.

Hydrophilic 2D composite LDHs-MXene pervaporation membrane for highly efficient ethanol dehydration

Mixed matrix membranes (MMMs) demonstrate significant potential for pervaporation applications. Nevertheless, single lamella 2D materials are prone to stacking problems in membranes, resulting in unforeseen matrix inhomogeneity and defects. Here, we propose a wafer-like membrane structure designed for ethanol dehydration. This structure features a surface modification of transition metal carbides (MXenes) with layered dihydroxides (LDHs), which effectively enlarges the interlayer spacing and ameliorates the stacking issue. The LDHs-modified MXenes were then incorporated into the sodium alginate (SA) layer. The hydrophilicity, stability and morphology of the MMM were evaluated by water contact angle measurements, swelling tests and scanning electron microscopy. The experiment results indicated the hydrophilicity and stability of the MMM were effectively improved. The novel L-M@CS MMM exhibited outstanding dehydration performance for ethanol solution, with the membrane containing 0.4 wt % LDHs-modified MXenes achieving the highest permeation flux of 1377 g/(m2·h) and the optimal separation factor up to 1650.

Optimization of the bioethanol dehydration process using MgCl2 as mass separating agent

Ethanol derived from lignocellulosic sources is an important chemical that can have several uses such as biofuel that can be blended with gasoline, as sanitizer for the disinfection of surfaces, or as additive in the food, cosmetic and pharmaceutical industry. Nevertheless, its separation poses a challenge because it must be separated from water and this mixture forms an azeotrope. This research focuses on the ethanol dehydration using magnesium chloride (MgCl2) as a mass separating agent, which is an innocuous chemical used in the food industry to process Tofu. Therefore, it does not have any side effect, or it is not harmful for humans. Therefore, the use of this salt makes possible to use the purified ethanol as an additive in the food, cosmetic, or pharmaceutical industry. The proposed separation process is optimized using surrogate nonlinear models for the preconcentration and salt evaporation units. The results showed that using magnesium chloride dodecahydrate is a feasible alternative to bioethanol valorization.

Implanting Colloidal Nanoparticles into Single-Crystalline Zeolites for Catalytic Dehydration.

The encapsulation of functional colloidal nanoparticles (100 nm) into single-crystalline ZSM-5 zeolites, aiming to create uniform core-shell structures, is a highly sought-after yet formidable objective due to significant lattice mismatch and distinct crystallization properties. In this study, we demonstrate the fabrication of a core-shell structured single-crystal zeolite encompassing an Fe3O4 colloidal core via a novel confinement stepwise crystallization methodology. By engineering a confined nanocavity, anchoring nucleation sites, and executing stepwise crystallization, we have successfully encapsulated colloidal nanoparticles (CN) within single-crystal zeolites. These grafted sites, alongside the controlled crystallization process, compel the zeolite seed to nucleate and expand along the Fe3O4 colloidal nanoparticle surface, within a meticulously defined volume (1.5×107≤V≤1.3×108 nm3). Our strategy exhibits versatility and adaptability to an array of zeolites, including but not restricted to ZSM-5, NaA, ZSM-11, and TS-1 with polycrystalline zeolite shell. We highlight the uniformly structured magnetic-nucleus single-crystalline zeolite, which displays pronounced superparamagnetism (14 emu/g) and robust acidity (~0.83 mmol/g). This innovative material has been effectively utilized in a magnetically stabilized bed (MSB) reactor for the dehydration of ethanol, delivering an exceptional conversion rate (98 %), supreme ethylene selectivity (98 %), and superior catalytic endurance (in excess of 100 hours).