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The conversion of Methyl 3‐hydroxypropionate (3‐HPM) to 1,3‐propanediol (1, 3‐PDO) is an important step in the pathway towards the longterm sustainable production of the ethylene oxide hydroesterification. However, 3‐HPM is prone to side reactions like hydroxyl β‐dehydration and low reaction efficiency, which hinders its development. This study presents the first‐ever report on highly efficient gallium‐promoted Cu/SiO2 catalysts prepared using ethanol‐assisted ammonia‐evaporation (Et‐AE) for converting 3‐HPM to 1,3‐PDO. The prepared Cu‐1Ga/SiO2 catalyst exhibited satisfactory catalytic activity and 1,3‐PDO selectivity in the hydrogenation reaction, with a conversion of 3‐HPM of 94 % and a selectivity to 1,3‐PDO of 91 %. The characterisation results show that the addition of Ga increases the specific surface area and the pore volume of the catalyst, and also increases the dispersion of the Cu species. And the promotional effect likely originates from interactions between Ga3+ and Cu0 species though enhanced ability of the latter to activate H2. In addition, the introduction of Ga into the catalyst increases the interaction between Cu and the support, making it more difficult for Cu+ to be completely reduced to Cu0. This increases the content of Cu+ in the catalyst, which is beneficial for improving the activity and stability of the catalyst. This study investigates modifying Cu catalysts to provide guidelines for obtaining high performing hydrogenation catalysts. [ABSTRACT FROM AUTHOR]

Hierarchical SAPO-34 zeolite catalysts were successfully synthesized via a one-step hydrothermal synthesis approach with the assistance of excess triethylamine (TEA). Compared with conventional SAPO-34 (SP-T3), SAPO-34 synthesized with a TEA/Al2O3 molar ratio of 9 (SP-T9) presents high catalytic performance in the ethanol dehydration reaction due to its pseudocubic morphology with abundant butterfly-like large secondary pores and slightly decreased surface acidity. Afterwards, a cost-effective and green route is developed for synthesizing hierarchical SAPO-34 catalysts by recycling waste mother liquids. In recycling processes, residual organic templates in the mother liquids are reused in the next synthesis of SAPO-34 without adding fresh templates. After three recycles of mother liquids, the synthesized SP-R3 catalyst still retains its high crystallinity, hierarchical structure, moderate acidity, and excellent catalytic performance in ethanol dehydration as compared to the initial SP-T9 catalyst. [ABSTRACT FROM AUTHOR]

Bio-based acetaldehyde production by non-oxidative dehydrogenation of ethanol is a promising alternative for the fine chemistry industry, where acetaldehyde is an important part of the synthesis chain and co-production of hydrogen. In this paper, investigations on nickel containing alumina itterbia stabilized zirconia with microwave-assisted synthesis as catalysts for the ethanol dehydrogenation process to acetaldehyde are reported. Ni–xAl2O3–(100 − x)[Zr0,97Yb0,03]O2 (x = 35 and 65 mol%) were prepared by using microwave (MW) irradiation and by traditional heating steps during sol–gel preparation. The textural properties, structure, morphology, surface and phase composition, and RedOx properties (SEM–EDX, BET N2-physisorption, TG–DTA, XRD, EPR) of the samples were compared with the effect of the microwave-assisted synthesis and the Zr:Al ratio on the ethanol dehydrogenation is reported. Two synthesis routes were compared, and it was found that microwave pretreatment of hydrogel during sol–gel synthesis favors catalytic dehydrogenation, whereas catalysts prepared by pretreatment under uniform heating perform much worse. The microwave-assisted synthesis approach turned out to be more promising in terms of selectivity to acetaldehyde in the ethanol dehydrogenation due to form nickel oxide particles with strong support interaction in noncubic coordination catalyzing the ethanol dehydrogenation and at the same time to decrease the formation of nickel aluminate phase involved in competitive dehydration reaction to ethylene. Thus, the highest obtained selectivity to acetaldehyde was ≈ 70% at 400 °C on Ni–65AZ–MW sample. [ABSTRACT FROM AUTHOR]

Introduction: In this work, some of the necessary equipment for an ethanol dehydration plant is designed to meet the country's demand. Objective: To design the heat exchangers and adsorption columns needed for 100 hL/d ethanol dehydration plant. Materials and Methods: The consumption of steam and cooling water was determined, with Aspen Hysys v10.0. The methodology for the design of the heat exchangers in Aspen EDR was established and the adsorption columns with zeolite 3A were dimensioned using equations reported in the consulted bibliography. Results and Discussion: For the maximum capacity of the plant, 100 hL/d, 248.68 kg/h of steam and 6221 kg/h of cooling water are consumed. The design of seven heat exchangers was obtained; all of them meet the requirements of the allowable pressure drop and the fouling or obstruction factor. In the case of the adsorption columns the result was that the height is 3.5 m and a diameter of 0.3 m. Conclusions: With the Aspen EDR tool heat exchangers design for the specified operating conditions were done in a simple way. Adsorption column with synthetic zeolite 3A produce dehydration ethanol with the required quality. [ABSTRACT FROM AUTHOR]

The reaction of ethanol conversion to acetone on binary cerium-zinc oxide catalysts has been studied. It has been established that the reaction products of the conversion of ethyl alcohol on binary cerium-zinc oxide catalysts are ethylene, acetaldehyde, acetone, carbon dioxide and, at high temperatures, destructive decomposition products. The highest yield of acetone is observed on samples rich in zinc at temperatures of the order of 450-550°C, while catalysts rich in cerium are active in the reaction of dehydration of ethanol to ethylene. In this work, the acid properties of cerium-zinc oxide catalysts were evaluated by their activity in the isomerization of butene-1 to trans and cis butenes-2. It was found that cerium-rich catalysts are active in butene-1 isomerization reaction. The activities of cerium-zinc oxide catalysts in the reactions of the conversion of ethanol to acetone and the isomerization of butene-1 into trans and cis butenes-2 are compared. It was found that the reaction of the conversion of ethanol to acetone proceeds on the centers of the basic nature, and the formation of ethylene proceeds on the centers of the acidic nature. [ABSTRACT FROM AUTHOR]

The aim of this study was to get insight into the pathway of the acetaldehyde formation from ethanol (the rate-limiting step in the production of 1,3-butadiene) on Cu-SBA-15 and Cu-MnSBA-15 mesoporous molecular sieves. Physicochemical properties of the catalysts were investigated by XRD, N2 ads/des, Uv-vis, XPS, EPR, pyridine adsorption combined with FTIR, 2-propanol decomposition and 2,5-hexanedione cyclization and dehydration test reactions. Ethanol dehydrogenation to acetaldehyde (without and with oxygen) was studied in a flow system using the FTIR technique. In particular, the effect of Lewis acid and basic (Lewis and BrØnsted) sites, and the oxygen presence in the gas reaction mixture with ethanol on the activity and selectivity of copper catalysts, was assessed and discussed. Two different reaction pathways have been proposed depending on the reaction temperature and the presence or absence of oxygen in the flow of the reagents (via ethoxy intermediate way at 593 K, in ethanol flow, or ethoxide intermediate way at 473 K in the presence of ethanol and oxygen in the reaction mixture). [ABSTRACT FROM AUTHOR]

Thermogravimetric analysis (TGA) was used to evaluate the thermal stability and the amount of coke deposition resulting from the deactivation of catalysts during ethanol dehydration reaction in a fixed bed continuous flow reactor. In this study, a series of catalysts containing 30% of Pd doped and pure 12-tungstophosphoric acid and its insoluble Cs2.5H0.5PW12O40 salt supported on SBA-15 were prepared. The catalytic efficiency of ethanol dehydration reaction was also evaluated. Two types of coke are identified from the TPO (Temperature programmed oxidation) profiles and assigned to the coke precursor and hard coke, respectively. The results indicate that cesium salts reduced the formation of hard coke. The amount of total coke formed was significantly reduced by supporting the catalysts on mesoporous SBA-15 molecular sieves. [ABSTRACT FROM AUTHOR]

The silanol groups present on the surface of lamellar silicates are excellent reaction sites for a varied number of chemical modifications. The conversion of these solids into zeolitic structures has shown to be an interesting synthetic alternative, once avoiding hard templating methods and producing materials with particular characteristics. In this work, a post-synthesis OSDA-free procedure was employed for the 2D–3D transformation of Na-RUB-18 lamellar silicate into mordenite zeolite. The conversion was performed at 140 °C and produced small zeolitic crystals (300–500 nm) after 12 and 24 h of crystallization. The reaction presented 65% yield (mol/mol SiO 2), producing materials with a similar Si/Al molar ratio (around 6). The 27Al MAS NMR spectra showed signals related to tetrahedrally coordinated aluminum. The N 2 adsorption/desorption isotherms confirmed the solids microporous nature and volume (0.36 and 0.43 cm3 g−1). The number of acidic sites was determined by NH 3 -TPD (976 and 848 µmol g−1), which also revealed sites with weak and moderate to strong acidity. Finally, the samples' catalytic activity was evaluated by the ethanol dehydration reaction performed at low temperature (150 °C). The synthesized materials were compared to a commercial sample and all the catalysts showed ethanol conversion around 70%, producing ethene and diethyl ether; the latter being the major product at the employed temperature. Unlike the commercial sample, the synthesized ones did not present any deactivation during the time on stream. This feature was attributed to their low-defect structure and subtle mesoporosity. [Display omitted] • Na-RUB-18 was used as precursor in OSDA-free hydrothermal conversion to MOR zeolite. • Small MOR crystals were obtained in high yield after 12 and 24 h of crystallization. • Low temperature ethanol dehydration reaction was performed over the MOR catalysts. • The synthesized MOR was twice as active as the commercial one in ethene production. • The low-defect/mesoporous structure was the key for superior catalytic activities. [ABSTRACT FROM AUTHOR]

Catalytic performance of catalysts is influenced by process conditions. In this work the influence of temperature, residence time and C2H5OH feed concentration was investigated in ethanol dehydration reaction using the response surface methodology (RSM) for γ‐Al2O3 and CeZrO2 catalysts. The γ‐Al2O3 was prepared using calcination method and CeZrO2 precipitation method. The process indicators (conversion, yield, selectivity) were modeled through the RSM method, and the equations obtained showed a good fit to the experimental data. The optimization results indicate different optimum conditions for each catalyst. For γ‐Al2O3 at 420 °C, 23.5 % of ethanol concentration and 0.65 gs/L, 0.6 molethylene/molethanol is obtained and total conversion. For CeZrO2 at 495 °C, 59 % ethanol concentration and 300 gs/L, 0.38 molethylene/molethanol is obtained and total ethanol conversion. Catalyst characterization was performed using, XRD (x‐ray diffraction), BET (Brunauer‐Emmett‐Teller surface area analysis), TPR (Temperature‐programmed reduction) and TPD (Temperature‐programmed desorption). [ABSTRACT FROM AUTHOR]

The effect of alkali metal ions (Na+ or K+) on the acid–base and catalytic properties of Zn-Mg(Zr)Si oxide systems in the process of obtaining 1,3-butadiene from ethanol was studied. It was found that the modification of Zn-MgSi oxide systems promotes an increase in the 1,3-butadiene selectivity (at temperatures ≥670 K) by reducing the number of formation sites of by-products. In the composition of Zn-ZrSi oxide systems, alkali metal cation additives lead to a decrease in the ethene and diethyl ether selectivity due to a decrease in the content of strong acid sites that are active in the ethanol dehydration reaction. [ABSTRACT FROM AUTHOR]

Dehydration reactions are important in the petroleum and petrochemical industries, especially for the feedstock production. In this work, the catalytic activity of zeolites with different acidities for the dehydration of ethanol to ethylene and diethylether is investigated by density functional calculations on cluster models of three isomorphous B, Al, and Ga substituted H-ZSM-5 zeolites. Both unimolecular and bimolecular mechanisms are investigated. Detailed reaction profiles for the dehydration reaction, assuming either a stepwise or a concerted mechanism, were calculated by using the ONIOM(MP2:M06-2X) + SCREEP method. The adsorption energies of ethanol are −21.6, −28.1, and −27.7 kcal mol−1 on H-[B]-ZSM-5, H-[Al]-ZSM-5, and H-[Ga]-ZSM-5 zeolites, respectively. The activation energies for the rate-determining step of the unimolecular concerted mechanism for the ethylene formation are 48.5, 42.6, and 43.6 kcal mol−1 on H-[B]-ZSM-5, H-[Al]-ZSM-5, and H-[Ga]-ZSM-5 zeolites, respectively. The activation energies for the ethoxy formation as the rate-determining step for the bimolecular formation of diethylether are 42.3, 40.0, and 41.1 kcal mol−1 on H-[B]-ZSM-5, H-[Al]-ZSM-5, and H-[Ga]-ZSM-5 zeolites, respectively. The results indicate that the catalytic activities for the dehydration of ethanol decrease in the order H-[Al]-ZSM-5 ~ H-[Ga]-ZSM-5 > H-[B]-ZSM-5. Besides the acid strength, the zeolite framework affects the reaction by stabilizing the reaction intermediates, leading to more stable adsorption complexes and lower activation barriers. [ABSTRACT FROM AUTHOR]

We demonstrate, on the basis of molecular dynamics simulations, the possibility of an efficient water-ethanol separation using nanoporous carbon membranes, namely, carbon nanotube membranes, nanoporous graphene sheets, and multilayer graphene membranes. While these carbon membranes are in general permeable to both pure liquids, they exhibit a counter-intuitive "self-semi-permeability" to water in the presence of water-ethanol mixtures. This originates in a preferred ethanol adsorption in nanoconfinement that prevents water molecules from entering the carbon nanopores. An osmotic pressure is accordingly expressed across the carbon membranes for the water-ethanol mixture, which agrees with the classic van't Hoff type expression. This suggests a robust and versatile membrane-based separation, built on a pressure-driven reverse-osmosis process across these carbon-based membranes. In particular, the recent development of large-scale "grapheneoxide" like membranes then opens an avenue for a versatile and efficient ethanol dehydration using this separation process, with possible application for bio-ethanol fabrication. [ABSTRACT FROM AUTHOR]

The influence of acid-base properties of MgO-Al2O3 systems obtained by the decomposition of hydrotalcites with ratio of Mg/Al = 1÷3 on their activity and selectivity in the process of ethanol conversion to 1-butanol is studied.The highest values of selectivity and specific rate of BuOH formation are achieved with ratio Mg/Al = 2 for the sample, which according to the test results is characterized by the largest number of acid and basic sites in the dehydrogenation/dehydration reactions of isopropanol. [ABSTRACT FROM AUTHOR]

[Display omitted] • Dehydration of ethanol was studied over silica-supported HPCs between 200 and 350 C°. • The XP spectra show that Pd doped HPAs consists of Cs3PW crystallites coated with Pd0.25 P W layers. • The value of Brönsted acidity has a significant impact on the coke formation. • Pd and SBA-15 improves the catalytic activity by reducing the catalysts deactivation. • After air regeneration, the catalysts regain the catalytic activity for o short time. The pure and palladium doped 12-tungstophosphoric acid - H 3 PW 12 O 40 (HPW) and its cesium salts Cs x H 3-x PW 12 O 40 (x = 1, 2, 2.25 and 2.5) were prepared and characterized by thermal analysis, FTIR, XRD, BET and XPS methods. In this paper were determined the optimal reaction temperature and the effect of palladium on the coke content during the dehydration of ethanol in the temperature range of 200−350 °C. Above 300 °C, a strong deactivation of the catalysts was caused by coke formation. The catalytic tests demonstrate that by supporting the HPW and Pd y PW (y = 0.15, 0.2 and 0.25) on mesoporous molecular sieve SBA-15 the catalytic activity in ethanol dehydration reaction was improved. Palladium doping of HPW/SBA-15 significantly decreases the formation of coke deposit. The formation of coke during the ethanol dehydration does not affect the Keggin structure which led us to conclude that such catalysts can be regenerated in air and regain their catalytic activity for a short time. [ABSTRACT FROM AUTHOR]

MgO-La 2 O 3 catalysts with different Mg/La molar ratio were synthesized by a precipitation method and a subsequent calcination and then characterized by x-ray diffraction, N 2 adsorption-desorption isotherms (at −196 °C), CO 2 - and NH 3 -thermoprogrammed desorption and x-ray photoelectronic spectroscopy. The coexistence of acid and basic sites promoted the selective transformation of ethanol into valuable products. Thus, MgO catalyst promoted the Guerbet reaction obtaining n -butanol as product while the incorporation of La 2 O 3 in the catalytic system improved the ethanol conversion notably, obtaining ethylene as the main product due to a dehydration reaction. The highest ethylene yield was obtained for the catalyst with a Mg/La molar ratio of 1. [Display omitted] • The coexistence of acid and basic sites promotes the selective transformation of ethanol. • MgO catalyst promotes the Guerbet reaction obtaining n -butanol as main product. • The presence of La 2 O 3 in Mg-La-O catalysts improves the ethanol conversion to ethylene. • The highest ethylene yield was obtained for the catalyst with a Mg/La molar ratio of 1. [ABSTRACT FROM AUTHOR]

A brand-new p -xylene (PX) production route via 2,5-hexanedione (HDO) and ethanol was put forward. And the reaction was successfully catalyzed by organic base - tetrapropylammonium hydroxide modified HZSM-5 zeolite. Under optimum condition, the conversion of 2,5-HDO and selectivity to PX was 89.6 % and 35.2 %, respectively, much higher than the patent HZSM-5 zeolite. For comparison, PX was also produced from 2,5-dimethyfuran (2,5-DMF) and ethanol or 2,5-HDO and ethylene under the same conditions. However, the PX selectivity and yield obtained from 2,5-HDO and ethanol was much poorer than that when 2,5-DMF or ethylene as reactant due to the series competitive dehydration reactions. To investigate the relationship between catalyst properties and performance, the physicochemical properties of catalysts were comprehensively characterized by XRD, N 2 adsorption-desorption isotherms, ICP, NH 3 /CO 2 -TPD, pyridine-IR, SEM, TEM and MAS NMR. Conclusion can be drawn that the appropriate acidity and hierarchical pore structure in T0.5-HZ catalyst (HZSM-5 modified by 0.5 M tetrapropylammonium hydroxide) were beneficial to high PX selectivity and yield. Among them, the acid site with weak acid site would catalyze 2,5-HDO intramolecular aldol condensation to 3-methylcyclopentenone (MCO), while strong acid site was beneficial for 2,5-DMF hydrolysis to 2,5-HDO. Thus, acid site with moderate strength was advantageous to the conversion of 2,5-HDO to 2,5-DMF. Besides, the enough amount of acid sites and suitable B/L ratio of 0.98 can satisfy the requirements of various dehydration reactions and Diels-Alder reaction between 2,5-DMF and dienophiles, enhancing PX selectivity and yield. Additionally, the hierarchical pore structure enhanced mass transfer efficiency and improved the reaction rate. The promising production for bio-based PX via 2,5-HDO and ethanol lay solid foundation for industrialized production route from lignicellulose. [Display omitted] • One-pot synthesis of PX was achieved. • Superior performance was due to suitable acid and hierarchical structure. [ABSTRACT FROM AUTHOR]

The sustainable chemistry based on acid-catalysed alcohol conversion reaction is a promising route to contribute to the de-fossilization strategies completion. In this concern, C1 and C2 alcohols are both well recognised sources for the production of ethers and olefins from sustainable sources in acid catalysed dehydration reaction pathway. Most of the literature is devoted to the investigation of pure alcohols conversion, whilst the simultaneous dehydration of alcohol in mixture can broad the product panel (contributing to the enlargement of bio-alcohols based chemistry) also elucidating the role of acidity (type and distribution) on the reaction mechanism. This paper is the first contribution analysing the role of acid sites (amount and distribution) on the simultaneous methanol/ethanol dehydration using ZSM-5 zeolites. ZSM-5 materials with different aluminium content were synthesised and used in catalytic test. The obtained results showed how Lewis acid sites are less important when dealing with ethanol (also in mixture with methanol) and how the different methylated- ethylated species formation can affect the product composition and the coke amount and composition. [Display omitted] • ZSM-5 with a different Si/Al in the range 11–50 were successfully synthesised. • Simultaneous methanol/ethanol dehydration was assessed. • Methyl ethyl ether is mainly produced at low temperature. • Methoxy species formation is inhibited in presence of ethanol. • No ethyl-substituted aromatics are formed during MeOH/EtOH simultaneous conversion. [ABSTRACT FROM AUTHOR]

Ag−ZrO2/SBA‐16 has recently been found to be efficient for catalyzing the single‐step conversion of ethanol to butene (1‐ and 2‐butene mixtures) in the presence of H2. The reaction proceeds via a cascading sequence of reactions over mixed metal and Lewis sites, with the catalyst composition tuned to selectively favor butene formation. However, the catalyst slowly deactivates when evaluated over long reaction times. In this work, we evaluated the lifetime of the Ag−ZrO2/SBA‐16 catalyst system for ethanol‐to‐butene conversion at 325 °C for up to 800 hours on stream. Several characterization techniques were used to elucidate the mechanism(s) by which catalyst deactivation occurs. Coke deposition, Ag particle sintering, and Ag0‐to‐Ag+ oxidation state change were identified to be the major causes of catalyst deactivation. Coke deposits cover primarily Lewis acid sites which are responsible for aldol condensation, Meerwein‐Ponndorf‐Verley (MPV) reduction, and dehydration reactions. Ag particle sintering and Ag oxidation state change leads to a reduction in the number of metallic Ag sites responsible for the dehydrogenation/hydrogenation steps. The fresh catalyst likely experiences hydrothermal sintering in the early stage of reaction and permanently loses some active Lewis acid sites before reaching a new structural steady state. The deactivation of Lewis acid sites leads to a decrease in overall ethanol conversion, whereas the deactivation of the metallic Ag sites decreases the butene selectivity. For catalyst regeneration, oxidative calcination (at 500 °C) followed by reduction (at 325 °C) successfully removes all the coke species on the catalyst surface and restores the metallic Ag particles of the 4Ag−4ZrO2/SBA‐16 catalysts. [ABSTRACT FROM AUTHOR]

A synthetic technique based on electrospinning in conjunction with the sol–gel method and thermal treatment was employed to fabricate Pd(II)-doped SiO2/Fe2O3 nanofibers (NFs) with different Pd(II) doping amounts. These materials were evaluated for their catalytic ability in the ethanol dehydration reaction. Interestingly, the coexistence of the mixed-phase structure α-/γ-Fe2O3 indicates that the Pd(II) dopant inhibits the γ-Fe2O3-to-α-Fe2O3 phase transformation even under high-temperature thermal treatment. A higher reaction temperature is more beneficial to facilitate catalytic activity than a lower temperature. The catalytic reaction is improved upon adding Pd(II), probably due to the enhancement of the lattice oxygen mobility in the presence of Pd(II) in SiO2/Fe2O3. As the Pd(II) doping increases, the catalytic activity is gradually promoted. For 0.15 wt% Pd(II)-doped SiO2/Fe2O3 NFs produced at a reaction temperature of 670 °C, the ethanol conversion reaches a maximum value of 15.9%, and the selectivity of ethylene is 96.2%. It is inferred that a larger total proportion of active oxygen species, including lattice oxygen and surface chemisorbed oxygen, can better generate a strong catalytic reaction. [ABSTRACT FROM AUTHOR]

• Tungsten impregnated on MCF-Si rendered higher acidity than that on SBA-15. • Incipient wetness impregnation (IW) on supports provided a suitable WO 3 dispersion. • High ratio of Lewis to Bronsted plays a crucial role in the ethanol dehydration. • High green ethylene yield of 98.3% was obtained using WO 3 /MCF-Si (IW). The alternative conversion of ethanol into valuable products, such as ethylene, through catalytic ethanol dehydration becomes highly appealing due to the surplus of ethanol. This research aims to investigate the catalytic activity of WO 3 on SBA-15 and mesocellular form silica (MCF-Si), which have been prepared using different methods and utilized as catalysts in ethanol dehydration. WO 3 was impregnated on the SBA-15 and MCF-Si supports using two different methods, including incipient wetness (IW) and wetness impregnation (W). All catalysts were tested in the vapor phase of ethanol dehydration at reaction temperatures ranging from 200 to 400 °C and were characterized by powerful techniques. The findings revealed that the three-dimensional mesocellular foam structure of MCF-Si and the incipient wetness impregnation of WO 3 are the keys to obtaining a highly dispersed WO 3 catalyst with suitable acid properties. Additionally, the high Lewis to Bronsted (L/B) ratio of tungsten on silica is crucial for the catalytic dehydration of ethanol to ethylene. Among all catalysts, the WO 3 /MCF-Si (IW) exhibited the highest ethylene yield (98.3%), having an ethanol conversion of 99.6% and an ethylene selectivity of 98.7% at 400 ºC. [Display omitted] [ABSTRACT FROM AUTHOR]

This work describes the synthesis of the layered silicate magadiite and the insertion of V and/or Al (Si/V = 33 and Si/Al = 15 M ratios) by the seed-induced crystallization method (SIC), aiming at studying the influence of these heteroatoms in the ethylene production through the ethanol dehydration reaction. The preparation of these materials without contaminating phases or amorphization was observed by X-ray diffraction, and the presence of single and double rings characteristic of the magadiite structure was confirmed by FTIR. The presence of structural Al in tetrahedral and octahedral coordination was verified by 27Al-NMR, while the acid sites generated by the presence of this heteroatom were confirmed by TPD-NH 3. In addition, this work reports for the first time a quantitative study of the use of magadiite-based lamellar catalysts in the production of ethylene from ethanol. Among the catalysts studied, the ones that generated the highest ethanol conversion, selectivity and yield to ethylene were those containing only structural aluminum ([Al]-maga-(V), [Al]-maga-(Si) and [Al]-maga-(Al)). The least active and selective to ethylene was pure silicon magadiite (maga-(Si)), which presented low ethanol conversion and higher selectivity to acetaldehyde and diethylether. Worse results were obtained for the lamellar catalysts where aluminum and vanadium were together in the framework ([V,Al]-maga-(Si), [V,Al]-maga-(Al) and [V,Al]-maga-(V)). In general, these results show that layered solids can be interesting catalysts in reaction where framework acidity is needed and are stable at high temperatures even in the presence of the water produced in the reaction. Image 1 • Crystalline [Al]- and [V,Al]-magadiites were prepared by the SIC method. • The catalysts were used in the ethanol dehydration. • Ethylene was produced for the first time over layered magadiite. • [Al]-magadiite presented the highest yield to ethylene. [ABSTRACT FROM AUTHOR]

Vanadia supported on titania were prepared with increasing vanadia loadings up to 20 wt % to study the effect of the vanadia loading on catalytic reactivity. A competitive decomposition of ethanol into ethylene (dehydration) and acetaldehyde (dehydrogenation) over the catalyst occurs over the vanadia supported on TiO2. Dehydrogenation is generally favored over dehydration over a wide range of the vanadia loadings up to 20 wt % due to a lower energy barrier for the dehydrogenation channel. Both dehydration and dehydrogenation rates are enhanced in proportion to the vanadia loadings up to about 2 wt %. At higher vanadia loadings (>2 wt %), however, the dehydration rate decreases while the dehydrogenation rate saturates. X‐ray photoelectron spectroscopic analysis reveals that reduced V and Ti species are formed at the low vanadia contents and act as strong dissociative adsorption sites for H2O, while extended VOx clusters as well as three‐dimensional V2O5 islands formed at high vanadia loadings prevent the formation of such sites. Thus, the observed difference between the two reaction channels can be explained from the structural transition of the vanadia overlayers from highly dispersed small VOx clusters into larger polyvanadates or islands. At low vanadia loadings (<2 wt %), both the edge sites and the surface sites of the small VOx clusters grow in proportion to the loadings as the number of the clusters increases. Thus, both reaction channels are enhanced as well. At higher vanadia loadings (>2 wt %), however, the transformation into larger islands reduces the edge sites or the boundaries between the clusters and TiO, not the surface area. This implies that the active sites for the dehydrogenation are on the surfaces of the vanadia overlayers, while those for the dehydration are on the boundaries between the VOx and TiO2. Our results provide an additional insight into the active sites for dehydration and dehydrogenation reactions over the titania‐supported vanadia catalysts. [ABSTRACT FROM AUTHOR]

Abstract A series of sphere-like polyelectrolyte complexes (PECs) and their homogeneous polyelectrolyte complex membranes (HPECMs) were synthesized by using sodium carboxymethyl cellulose (CMCNa) and poly(diallyldimethylammonium chloride) (PDDA). Different compositions or ionic complexation degrees (ICD) of PECs could be characterized by FT-IR spectra. The circular dichroism spectrum (CD) and field emission scanning electron microscopy (FESEM) were employed to examine the conformation and morphology of PECs, respectively. Zeta (ζ) potential was utilized to investigate the charge density of PEC particles while the surface hydrophilicity of HPECMs was studied by using contact angle (CA) meter. When subjected to ethanol dehydration, HPECMs revealed a satisfactory pervaporation performance and desired anti-trade-off phenomenon. For HPECM 0.31 and HPECM 0.57, the permeation fluxes were 2.25 kg m−2 h−1 and 2.93 kg m−2 h−1, and the water content in permeate reached up to 99.35 wt% and 99.38 wt%, with respect to 10 wt% water in feed under 70 °C. All the results indicated that small-sized and sphere-like PECs were truly in favor of enhancing the pervaporation performance in ethanol dehydration. Graphical abstract fx1 Highlights • Sphere-like polyelectrolyte complexes (PECs) were successfully synthesized. • Homogeneous polyelectrolyte complex membranes (HPECMs) could be fabricated. • The HPECMs showed excellent pervaporation performances for ethanol dehydration. • Water flux up to 2.93 kg m−2 h−1 with a separation factor of 1443. [ABSTRACT FROM AUTHOR]

The present study aims to investigate the catalytic ethanol dehydration to higher value products including ethylene, diethyl ether (DEE), and acetaldehyde. The catalysts used for this reaction were WO3/TiO2 catalysts having W loading of 13.5 wt.%. For a comparative study, the TiO2 supports employed were varied by two different preparation methods including the sol-gel and solvothermal-derived TiO2 supports, denoted as TiO2-SG and TiO2-SV, respectively. It is obvious that the different preparation methods essentially altered the physicochemical properties of TiO2 supports. It was found that the TiO2-SV exhibited higher surface area and pore volume and larger amounts of acid sites than those of TiO2-SG. As a consequence, different characteristics of support apparently affected the catalytic properties of WO3/TiO2 catalysts. As expected, both catalysts WO3/TiO2-SG and WO3/TiO2-SV exhibited increased ethanol conversion with increasing temperatures from 200 to 400°C. It appeared that the highest ethanol conversion (ca. 88%) at 400°C was achieved by the WO3/TiO2-SV catalysts due to its high acidity. It is worth noting that the presence of WO3 onto TiO2-SV yielded a remarkable increase in DEE selectivity (ca. 68%) at 250°C. In summary, WO3/TiO2-SV catalyst is promising to convert ethanol into ethylene and DEE, having the highest ethylene yield of ca. 77% at 400°C and highest DEE yield of ca. 26% at 250°C. These can be attributed to proper pore structure, acidity, and distribution of WO3. [ABSTRACT FROM AUTHOR]

Abstract: In this study, selective formation of 5-ethoxymethylfurfural (EMF) from one-pot conversion of fructose in a co-solvent of ethanol with tetrahydrofuran over green SO3H-CD carbon was investigated for the first time using an ultrasonic system. The maximum EMF yield of 74% with 100% fructose conversion was achieved in mild conditions. Moreover, the better selectivity and the longer recyclability (eight cycles) for EMF production via particular reactions such as fructose dehydration and etherification were obviously found while the formation of 5-hydroxymethylfurfual, ethyl levulinate or humins was inhibited using SO3H-CD carbon, comparing to commercial catalysts such as Amberlyst-35, SiO2-Tosic acid and Al2O3.Graphical abstract: [ABSTRACT FROM AUTHOR]

Abstract: Excellent catalytic activity of activated redbrick clay (ARB) for dehydration and highly selective conversion of cyclohexanol to cyclohexene and 1-phenylethanol to styrene is reported. The efficacy of the catalyst is compared with commercial catalysts, silica and α-Fe2O3, which performed poorly giving side products. Synergistic acidic properties and combinational Lewis and Bronsted acidic sites of ARB afforded superior performances relative to silica and α-Fe2O3 catalysts. Pyridine Fourier-transform-infrared spectra (FT-IR) and temperature-programmed desorption (NH3-TPD) measurements showed the presence of combinational Lewis and Bronsted acidic sites and a weak to mild acidic texture, which could facilitate favorable interaction between the ARB clay catalyst and the reactants (cyclohexanol and 1-phenylethanol). The physicochemical characteristics of ARB, commercial silica and α-Fe2O3 catalysts were investigated using X-ray diffraction, scanning electron microscopy, X-ray fluorescence, NH3-TPD, UV-visible diffuse reflectance spectroscopy, and pyridine FT-IR.Graphical abstract: [ABSTRACT FROM AUTHOR]

Abstract The use of biomass for production of chemicals is gaining interest because of its potential to contribute towards a reduction in greenhouse gas emissions and other environmental benefits linked to the substitution of fossil resources. But, conversely to biofuels, studies focusing on environmental impacts of biomass-derived chemicals are scarce. This paper uses life cycle assessment to evaluate the environmental sustainability of bio-ethylene from poplar produced by the following three thermo-chemical routes: direct and indirect dehydration of ethanol and production of olefins via dimethyl ether. The indirect route is the best option for most impact categories for all three allocation methods considered: system expansion, economic and energy basis. However, the dimethyl ether-to-olefins route has the lowest global warming potential. In comparison to ethylene produced bio-chemically from sugar beet, the thermo-chemical indirect route has lower impacts for all categories except human, terrestrial and freshwater toxicities. All three thermo-chemical alternatives show a significant reduction in global warming potential (up to 105% in the case of dimethyl ether-to-olefins) and depletion of fossil fuels when compared to conventional ethylene production from fossil fuels. However, the results also suggest that bio-ethylene produced by any of the three thermo-chemical routes would lead to a significant increase in most other impact categories relative to fossil fuels. Therefore, while trying to reduce greenhouse gas emissions, the overall environmental sustainability of bio-ethylene suffers from the increase in other environmental impacts. Highlights • Three thermo-chemical bio-ethylene processes are compared environmentally. • Indirect route is best for several impacts but the dimethyl ether is better for GWP. • Indirect route is better than 1st generation ethanol dehydration except for toxicities. • Net saving in GHG emissions of 44%–105% achieved compared to fossil alternatives. • However, other impacts are higher than for the fossil alternatives. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) materials have attracted great attention due to their unique physical and chemical properties derived from the dimensionality effect and modulation in their band structure. Herein, an important industrial catalytic material, gamma alumina (γ-Al 2 O 3 ) with well-defined two-dimensional nanosheet structure was fabricated by a designed crown ether induced assembly approach. The obtained γ-Al 2 O 3 nanosheets with a thickness of ∼4 nm possess high surface area (351 m 2 /g) and 16% pentacoordinate Al 3+ sites which are the main catalytic active sites for ethanol dehydration to ethylene, compared to almost no pentacoordinate Al 3+ sites for the commercial γ-Al 2 O 3 nanoparticles. Furtherly, systematical investigation reveals that the crown ether plays the key role in the assembly of nanosheet structure. As a catalyst for ethanol dehydration to ethylene, the obtained alumina nanosheets with easily-accessible surface and more active sites, exhibit a superior catalytic performance to the commercial alumina with a much higher yield at large space velocity. [ABSTRACT FROM AUTHOR]

A dehydrative cross-coupling of 1-phenylethanol catalysed by sugar derived, in situ formed palladium(0) nanoparticles under acidic conditions is realised. The acidic conditions allow for use of alcohols as a feedstock in metal-mediated coupling reactions via their in situ dehydration and subsequent cross-coupling. Extensive analysis of the size and morphology of the palladium nanoparticles formed in situ showed that the zero-valent metal was surrounded by hydrophilic hydroxyl groups. EDX-TEM imaging studies using a prototype silicon drift detector provided insight into the problematic role of molecular oxygen in the system. This increased understanding of the catalyst deactivation allowed for the development of the cross-coupling methodology. A 250-12,000 fold increase in molar efficiency was observed when compared to related two-step protocols that use alternative feedstocks for the palladium-mediated synthesis of stilbenes. This work opens up a new research area in which the active catalyst is formed, stabilised and regenerated by a renewable sugar. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ethanol conversion involved several routes under chemical looping conditions. • Nickel oxide oxidises secondary products from primary ethanol conversion. • Nickel in reduced oxygen carrier catalyses ethanol dehydrogenation or de-composition. • Kinetics for catalytic and non-catalytic reactions determined at high temperature. The use of bio-ethanol in chemical looping combustion (CLC) and reforming (CLR) has the potential to produce energy and/or hydrogen and, as a negative-emissions technology (NET), to remove CO 2 from the atmosphere at low cost following the principles of bio-energy with CO 2 capture and storage (BECCS). The determination of the rate of the chemical processes involving the fuel conversion with the oxygen carrier is required for the modelling and design of a chemical looping unit. In this work, a kinetic study of ethanol conversion is performed considering a NiO-based material as the oxygen carrier. Combined experiments in TGA and fixed bed were conducted. TGA tests confirmed that the oxygen carrier was reduced by a ethanol-containing gaseous stream at temperatures higher than 773 K. An apparent reaction kinetics for the NiO reduction with ethanol was determined, which might be used in simplified fuel reactor models. However, tests performed in a fixed bed revealed that products derived of the ethanol decomposition, such as CH 4 , CO, H 2 were responsible for NiO reduction, instead of the direct reduction with ethanol. High temperature kinetics of processes involved in ethanol conversion, namely dehydration, dehydrogenation and decomposition, were determined. Both, non-catalytic and Ni-catalytic reactions were of relevance under chemical looping conditions. A reaction pathway was described to be used in detailed fuel reactor models of chemical looping units. [ABSTRACT FROM AUTHOR]

Extractive distillation using low transition temperature mixtures (LTTMs) is a promising technology to separate ethanol and water azeotrope. In this work, the separation of water and ethanol by extractive distillation using LTTMs (choline chloride/urea 1:2) as entrainer was designed and simulated in Aspen Plus. Firstly, database of ChCl/urea = 1:2 (Reline) was established in Aspen Plus. Secondly, the simulation and optimization of the conventional extractive distillation process for ethanol dehydration with Reline or ethylene glycol as entrainer were worked out. The results showed that the TAC (total annual cost) of the process with Reline as entrainer was reduce by 14.61% than that of the process with EG as entrainer. In addition, in order to reduce energy consumption in distillation, an energy-efficient extractive distillation process which combining the preconcentration section and entrainer recovery section in one column was developed. The results showed that the proposed process with Reline as entrainer could save 29.48% and 17.42% of TAC compared with the conventional extractive distillation with EG and Reline as entrainer, respectively. [ABSTRACT FROM AUTHOR]

The indicators of ethanol to ethylene catalytic dehydration process on trilobe- and ring-shaped samples of an alumina catalyst were compared at the fixed parameters: thermal agent temperature and catalyst load. Experiments were performed in a flow-through reactor of a laboratory setup and in a tubular reactor of a pilot installation. The use of the less active ring-shaped catalyst ensures higher values of ethanol conversion, ethylene yield, and catalyst performance and significantly lower hydraulic resistance, compared to the more active trilobe-shaped catalyst. This is caused by lower intensity of the heat absorption on the less active catalyst and, correspondingly, to the higher temperature in the ring bed due to higher bed porosity. [ABSTRACT FROM AUTHOR]

Lewis acidic Sn centers isolated within Beta zeolite frameworks catalyze bimolecular ethanol dehydration to diethyl ether, yet with kinetic behavior sensitive to the hydrophobic character of their confining microporous voids. Sn sites in open ((HO)-Sn-(OSi ) 3 ) and closed (Sn-(OSi ) 4 ) configurations, quantified from infrared spectra of adsorbed CD 3 CN before and after reaction, convert to structurally similar intermediates during ethanol dehydration catalysis (404 K) and revert to their initial configurations after regenerative oxidation treatments (21% O 2 , 803 K). Dehydration rate data (404 K, 0.5–35 kPa C 2 H 5 OH, 0.1–50 kPa H 2 O) measured on ten low-defect (Sn-Beta-F) and high-defect (Sn-Beta-OH) zeolites were described by a rate equation that was derived from mechanisms identified previously by density functional theory calculations and simplified using microkinetic modeling to identify kinetically-relevant pathways and intermediates. Polar hydroxyl defect groups located in the microporous environments that confine Sn sites preferentially stabilize reactive (ethanol-ethanol) and inhibitory (ethanol-water) dimeric intermediates over monomeric ethanol intermediates. As a result, equilibrium constants (404 K) for ethanol-water and ethanol-ethanol dimer formation are 3–4× higher on Sn-Beta-OH than on Sn-Beta-F, consistent with insights from single-component (302 K) and two-component (303 K, 403 K) ethanol and water adsorption measurements. Intrinsic dehydration rate constants (404 K) were identical, within error, among Sn-Beta-OH and Sn-Beta-F zeolites; thus, measured differences in dehydration turnover rates solely reflect differences in prevalent surface coverages of inhibitory and reactive dimeric intermediates at active Sn sites. The confinement of Lewis acidic binding sites within secondary microporous environments of different defect density confers the ability to discriminate surface intermediates on the basis of polarity, providing a design strategy to accelerate turnover rates and suppress inhibition by water. [ABSTRACT FROM AUTHOR]

Density functional theory calculations are combined with kinetic measurements of ethanol dehydration to diethyl ether to identify the relative catalytic contributions of structurally distinct speciations of Sn sites in zeolite Beta frameworks. The structural complexities of the Beta framework require nonstandard techniques for entropy and energy calculations, including consideration of anharmonic effects in vibrational modes, employment of quasi-harmonic densities of states methods to evaluate entropies, and use of hybrid density functionals to evaluate binding energies. Calculated energies and entropies are used to construct a microkinetic model that is iteratively refined to identify all kinetically and thermodynamically sensitive reaction steps and intermediates which are subsequently treated with the higher-level methods. The rate and equilibrium constants obtained from this tiered approach agree well with measured reaction orders in ethanol and water. Site balances provide evidence for the interconversion of Sn sites between “closed” configurations that are tetra-coordinated to the framework, open configurations formed by hydrolysis that are tri-coordinated to the framework and contain a hydroxyl ligand and proximal silanol group (“hydroxy-open”), and open tri-coordinate configurations formed by reaction with ethanol, yielding an ethoxy ligand and proximal silanol group (“ethoxy-open”). Closed, hydroxy-open, and ethoxy-open Sn sites adsorb ethanol via distinct modes and react via distinct pathways, with the consequence that prevalent dehydration pathways depend on the speciation of Sn sites under reaction conditions. The kinetic modeling indicates that, under the conditions studied (404 K, 0.5–35 kPa ethanol, 0.1–50 kPa water), bimolecular dehydration on the closed Sn site is the sole kinetically-relevant step, and ethanol, ethanol-ethanol dimers, and ethanol-water dimers are the most abundant surface intermediates. These results highlight the importance of considering the distribution of heteroatom coordination modes to zeolite frameworks under reaction conditions, as well as pathways for their interconversion in the presence of reacting molecules, to obtain more robust mechanistic and kinetic interpretations of catalytic pathways in Lewis acid zeolites. [ABSTRACT FROM AUTHOR]

In this study, poly(vinyl alcohol) (PVA) hybrid membranes with zeolitic imidazolate framework-90 (ZIF-90) particles were fabricated by the viscosity-driven in situ self-assembly of ZIF-90 particles in a PVA matrix and were employed for ethanol dehydration via pervaporation (PV) technology. By this method, the size-controlled and well-distributed ZIF-90 particles were successfully embedded into PVA membranes. Based on the cross-linking reactions between the ZIF-90 particles and the PVA matrix, the ZIF-90/PVA hybrid membranes demonstrated higher mechanical strength, swelling resistance, and a high separation performance for ethanol dehydration. The ZIF-90/PVA hybrid membranes were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, X-ray diffractometry, thermogravimetric analysis, a mechanical test, and water contact angle measurements. The effects of the ZIF-90 particle size, loading level, thermal treatment temperature, operation temperature, and the feed compositions of the PVA hybrid membranes on the PV performance were systematically explored. Accordingly, the hybrid membranes exhibited excellent water permeability and selectivity for water–ethanol mixture separation. Specifically, the ZIF-90/PVA hybrid membrane (M-8), which was treated thermally at 130 °C, exhibited its optimal PV performance at a flux of 268 g/(m 2 h) and a separation factor of 1379 for the PV dehydration of the 90 wt% ethanol aqueous solution at 30 °C. The ZIF-90/PVA hybrid membranes exhibited excellent potential in the PV application for ethanol dehydration. [ABSTRACT FROM AUTHOR]

Abstract: The low‐temperature dehydration of bioethanol is an environmentally benign route to ethene production. Here we compare the catalytic properties of a series of cage‐based small‐pore zeolites with different framework structures, acid strengths, and/or crystallite sizes for ethanol dehydration at 200 °C under wet conditions (H2O/EtOH=0.2). Among the zeolites studied here, nanocrystalline H‐RTH was found to be considerably more effective than H‐mordenite, the best catalyst for this reaction known to date, which can be rationalized by product shape selectivity. Whereas the acidity of this zeolite also plays a crucial role in selectively forming ethene, its nanocrystallinity is primarily responsible for the observed high catalyst durability. [ABSTRACT FROM AUTHOR]

The reactions of ethanol over TiO2 and M/TiO2 (M = Au, Pd and Au-Pd) catalysts are studied by temperature programmed desorption (TPD), in high vacuum conditions, in order to study the effects of metal nature on desorption profiles and products distribution. Ethanol reacted through dehydration (major) and dehydrogenation (minor) pathways on TiO2 and Au/TiO2 producing ethylene and acetaldehyde, with negligible hydrogen formation. On Pd/TiO2 and Au-Pd/TiO2, carbon monoxide and methane were the main products, through C-C bond cleavage, in addition to H2. TPD of ethanol on Au-Pd was almost identical to that of Pd indicating the much higher activity of Pd when compared to Au on TiO2. Ethanol desorption from all catalysts followed second order kinetics as evidenced from desorption peak shape, shift in peak temperatures with increasing initial coverages, and by data fitting of the Arrhenius plots. With increasing ethanol coverage, the activation energies calculated from the non-linear fitting of Polanyi Wigner equation as well as from leading edge analysis decreases due to repulsive lateral interactions. Both methods gave similar results (activation energy between 145 and 95 kJ/mol depending on the surface coverage), although the activation energy obtained by the leading edge method was more sensitive to surface coverage. [ABSTRACT FROM AUTHOR]

In this work, the effect of crystal facets on the catalytic behavior of γ-Al 2 O 3 was investigated by X-ray diffraction, transmission electron microscopy, temperature-programmed desorption of ethanol, solid-state 27 Al NMR, infrared spectroscopy, and ethanol dehydration reaction. A series of platelet γ-Al 2 O 3 were synthesized, in which the relative ratio of (100) facets had been systematically increased. Ethylene formation increased with increasing (100) facets, clearly demonstrating the critical role of these facets as active sites for ethanol dehydration on γ-Al 2 O 3 . This systematic approach is helpful for a better understanding of facet-dependent catalytic properties of γ-Al 2 O 3 that arise from the interaction between the supported metal and the crystal facets. [ABSTRACT FROM AUTHOR]

Zeolite-catalyzed dehydration of ethanol is an attractive economically feasible route for production of ethylene and butenes. The goal of this contribution is to monitor the intermediate species on the surface of “working” catalyst to rationalize the influence of the reaction conditions and zeolite characteristics on the dehydration pathways. With this respect the rates of diethyl ether (DEE) and ethylene formation in ethanol dehydration along with the quantification of the surface-intermediates (ethanol monomer and dimer) were simultaneously assessed under different reaction conditions in H- MFI zeolite. The reaction conditions (pressure, temperature, and ethanol conversion) control the population of surface intermediates and hence determine the dominant reaction mechanism. The results support the prevalence of dimer-assisted etherification at high ethanol pressures and enhanced contribution of ethoxide-mediated route with increasing the temperature. At high conversion, the DEE decomposition route producing ethylene was confirmed for H- MFI at 488 K along with ethoxide-mediated pathway. [ABSTRACT FROM AUTHOR]

Pervaporation membranes made from polyethersulfone (PESU), polyphenylsulfone (PPSU), polytrimethylphenylethersulfone (T-PESU) and hydrophilic PESU-co-Pluronic (H-PESU) polymers were evaluated for dehydration of ethanol and methanol. Fundamental characteristics of pore structure, free volume, d-spacing, water contact angle, water and ethanol uptakes were investigated and correlated with their dehydration performance. The H-PESU membrane shows the best ethanol dehydration performance due to its synergetic combination of the strengths from both rigid hydrophobic PESU and flexible hydrophilic Pluronic moieties. It has the highest water permeability of 0.322 mg m −1  h −1  kPa −1 which is 2–6 times higher than other three membranes because the hydrophilic Pluronic moiety may form special water transport channels. It also has a comparable mole-based selectivity of 685 due to the rigid hydrophobic PESU moiety that prevents the membrane from uncontrolled swelling. Long-term tests evidence the operating stability of both H-PESU and PESU membranes. In addition, the methanol dehydration performance of these membranes is superior to the other reported polymeric membranes. The water in the permeate can be concentrated to 86.8%. These promising preliminary results suggest that these polyarylether (PAE) membranes have great potential for ethanol and methanol dehydration. [ABSTRACT FROM AUTHOR]

Some metal-organic frameworks (MOFs) incorporate nodes that are metal oxide clusters such as Zr6O8. Vacancies on the node surfaces, accidental or by design, act as catalytic sites. Here, we report elucidation of the chemistry of Zr6O8 nodes in the MOFs UiO-66 and UiO-67 having used infrared and nuclear magnetic resonance spectroscopies to determine the ligands on the node surfaces originating from the solvents and modifiers used in the syntheses and having elucidated the catalytic properties of the nodes for ethanol dehydration, which takes place selectively to make diethyl ether but not ethylene at 473-523 K. Density functional theory calculations show that the key to the selective catalysis is the breaking of node-linker bonds (or the accidental adjacency of open/defect sites) that allows catalytically fruitful bonding of the reactant ethanol to neighboring sites on the nodes, facilitating the bimolecular ether formation through an SN2 mechanism. [ABSTRACT FROM AUTHOR]

In this work, the role of pore arrangement of 10-ring zeolites ZSM-5, TNU-9 and IM-5 on their catalytic properties in ethanol transformation were investigated. Among all the studied catalysts, the zeolite IM-5, characterized by limited 3-dimensionality, presented the highest conversion of ethanol and the highest yields of diethyl ether (DEE) and ethylene. The least active and selective to ethylene and C 3 + products was zeolite TNU-9 with the largest cavities formed on the intersection of 10-ring channels. The catalysts varied, however, in lifetime, and their deactivation followed the order: IM-5 > TNU-9 > ZSM-5. The processes taking place in the microporous zeolite environment were tracked by IR spectroscopy and analysed by the 2D correlation analysis (2D COS) allowing for an insight into the nature of chemisorbed adducts and transition products of the reaction. The cage dimension was found as a decisive factor influencing the tendency for coke deposition, herein identified as polymethylated benzenes, mainly 1,2,4-trimethyl-benzene. [ABSTRACT FROM AUTHOR]

Herein, we report the synthesis of zeolite composites with core-shell structure via a secondary growth technique and evaluation of their catalytic performance in ethanol dehydration. In particular, SAPO-34 particles were functionalized by TPA+, followed by dispersion in ZMS-5 or silicalite-1 to form SAPO-34@ZSM-5 and SAPO-34@silicalite-1 core-shell materials showed a hierarchical porous structure consisting of both micropores and mesopores. The active sites in the developed composites were found to have a mild acidity. Compared to conventional zeolite catalysts in ethanol dehydration reaction, the silicalite-1 composites. The novel core-shell materials showed a hierarchical porous structure consisting of both micropores and mesopores. The active sites in the developed composites were found to have a mild acidity. Compared to conventional zeolite catalysts in ethanol dehydration reaction, the core-shell SAPO-34@ZSM-5 improved the selectivity toward light olefins. In addition, our catalyst test results revealed the enhancement in propylene and ethylene yield over SAPO-34@ZSM-5 and SAPO-34@siliclite-1, respectively, as compared to that of bare SAPO-34. An improved catalyst stability was also obtained for the composite materials owing to their core-shell structure. The improved catalytic performance reported in this study reveals the potential utility of the zeolite composites with core-shell structure in ethanol dehydration reaction. [ABSTRACT FROM AUTHOR]

Dehydration of ethanol to diethyl ether (DEE) was studied over Cu-Fe/ZSM-5 catalysts over the temperature range of 160 − 220 °C. Metal loaded samples were prepared by wet impregnation and characterized using specific surface area measurements, X-ray diffraction and temperature-programmed desorption of NH 3 . The presence of Fe on ZSM-5 did not change the acidity of ZSM-5 but did decrease its crystallinity. On the other hand, the presence of Cu changed the acidity of ZSM-5 and favored DEE formation. The important result of the present work is the establishment of a correlation between the moderate strength of acid sites of Cu/ZSM-5 and the formation of DEE. Low-temperatures and medium strength of acid sites favor DEE production. [ABSTRACT FROM AUTHOR]

In order to promote the selective water permeation through porous filler, hydrophilic MOF-801 crystals with superior water adsorption ability were incorporated into chitosan (CS) matrix to fabricate MOF-801/CS mixed matrix membranes (MMMs) for pervaporation dehydration of ethanol. Both the experimental and molecular simulation results confirm the selective adsorption of water molecules in MOF-801 crystals, while the free volume and the lowest energy sorption sites analyses demonstrate the subdued diffusion of ethanol molecules through MOF-801. As a result, the porous structure in MOF-801 provides additional transport pathways for water molecules, and meanwhile makes the transport pathways of ethanol molecules more tortuous, thus achieving simultaneously enhanced flux and separation factor. The optimized membrane with MOF-801 loading of 4.8 wt% exhibits the total flux of 1937 g/m 2 h and separation factor of 2156. [ABSTRACT FROM AUTHOR]

In this study, poly (vinyl alcohol) (PVA) hybrid membranes with iron-dopamine (Fe-DA) nanoparticles were fabricated by the in-situ complex cross-linking method between Fe-DA nanoparticles and the PVA matrix. Based on the molecular structure feature of DA and the chelation interaction between Fe 3+ and PVA chains, the Fe-DA/PVA hybrid membranes demonstrated superior hydrophilicity, higher mechanical strength, swelling resistance, and high separation performance for ethanol dehydration via pervaporation (PV) technology. Fe-DA/PVA hybrid membranes were characterized by a scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) spectroscopy, an X-ray diffractometer (XRD), thermo gravimetric analysis (TGA), a mechanical test, and water contact angle measurement. The effects of Fe-DA nanoparticle size, loading level, operation temperature, and the feed compositions of PVA hybrid membranes on PV performance were explored. Accordingly, the hybrid membranes exhibited excellent water permeability and selectivity for water/ethanol mixture separation. Especially, the permeability flux of the Fe-DA 30 /PVA hybrid membranes could reach 995 g/(m 2 h), and the separation factor was as high as 2980 under 90 wt% ethanol at 30 °C. The Fe-DA 30 /PVA hybrid membranes exhibited excellent potential in the PV application of ethanol dehydration. [ABSTRACT FROM AUTHOR]

Graphitic carbon nitride (g-C 3 N 4 ) is an innovative soft two-dimensional (2D) nanomaterial. Due to its lamellar structure, similar to graphite layers, g-C 3 N 4 has attracted significant interest as a new class of filler for the fabrication of novel polymeric nanocomposite membranes. In this study, highly water-selective hybrid membranes with excellent water/ethanol separation performance and superior water channels were fabricated by incorporating g-C 3 N 4 nanosheets into a poly(vinyl alcohol) (PVA) matrix. g-C 3 N 4 was synthesized via thermal oxidation “etching”, using melamine as a precursor. The ultrathin and nanoporous structures formed were characterized through transmission electron microscopy, Fourier transform infrared spectra, and X-ray diffraction. Due to the strong interfacial interactions among g-C 3 N 4 , succinic acid (Sa) and the PVA matrix, the hybrid nanocomposite membranes showed both high swelling resistance and mechanical stability. Furthermore, the addition of g-C 3 N 4 can significantly improve the membrane’s hydrophilicity and heat-resistance properties. Importantly, membrane permeability improved greatly because the ordered alignment and the regular pore structure of g-C 3 N 4 resulted in ordered water channels for rapid transportation of water molecules. The total flux and separation factor of this new membrane can reach about 6332 g/(m 2 h), and 30.7 for 90% wt.% ethanol, respectively. Compared with the cross-linked pure PVA membrane (2337 g/(m 2 h) and 11.2), the flux and separation factor can be improved simultaneously. Namely, the composite membrane can break the “trade-off effect” effectively. Furthermore, the nanocomposite membrane exhibited an excellent long-term operating stability. After operating for over 120 h with a 90 wt% ethanol/water system at 75 °C, the total flux and separation factor remained at their initial values. This is a step forward in the application in pervaporation separation processes of organic-inorganic hybrid membranes with superior properties incorporating 2D porous fillers (e.g., g-C 3 N 4 ). [ABSTRACT FROM AUTHOR]