Dehydration Of 1-pentanol Research Articles

Reliability of the synthesis of C10–C16 linear ethers from 1-alkanols over acidic ion-exchange resins

More-than-nine-carbon-atom-containing linear ethers such as ethyl octyl ether (EOE), di-n-pentyl ether (DNPE), di-n-hexyl ether (DNHE) or di-n-octyl ether (DNOE) increase the quality of the diesel blends making them environmentally friendly. In this work, dehydration of 1-pentanol, 1-hexanol and 1-octanol to DNPE, DNHE and DNOE, respectively, as well as the reaction between 1-octanol and ethanol to give EOE are shown to be a good path for obtaining these linear ethers. Acidic macroreticular and gel-type polystyrene-divinylbenzene (PS-DVB) ion-exchange resins have been tested as catalysts for these reactions in liquid phase at 423 K. In the dehydration reactions of 1-pentanol, 1-hexanol and 1-octanol, as a rule, selectivity to linear ether decreased with the length of the ether over macroreticular resins of high and medium DVB%. On the contrary, no differences in selectivity to DNPE, DNHE and DNOE were observed over gel-type and macroreticular resins of low DVB%. In the reaction for obtaining EOE from ethanol and 1-octanol, EOE synthesis competes with those of DNOE and diethyl ether. The best selectivity to EOE and DNOE were found in gel-type and macroreticular resins of low DVB% too. Swelling of the resin in the polar reaction medium was found to be a decisive factor to enhance the selectivity to long linear ethers. Therefore, Amberlyst 121 and CT 224 are proposed to catalyze the synthesis of these ethers; Amberlyst 70 is suggested as the best one for working above 423 K.

Kinetics of 1-Pentanol Etherification without Water Removal

The effect of water on the kinetics of the liquid-phase dehydration of 1-pentanol to di-n-pentyl ether (DNPE) and water over Amberlyst 70 is revisited. To explain the strong inhibitor effect of water, two approaches were compared. First, a model stemming from a Langmuir–Hinshelwood–Hougen–Watson (LHHW) mechanism was used, wherein the inhibitor effect of water was explained by the competitive adsorption of water and pentanol. Second, a modified Eley–Rideal (ER) model was used that includes an inhibition factor, in which a Freundlich-like function is used to explain the inhibitor effect of water by blocking the access of pentanol to the active centers. Both models fitted data quite well, although the best results were obtained with the modified ER model. The activation energy was 118.7 ± 0.2 kJ/mol for the LHHW model and 114.0 ± 0.1 kJ/mol for the modified ER one.

Conversion of 1-hexanol to di-n-hexyl ether on acidic catalysts

Conversion, selectivity and yield of 1-hexanol liquid phase dehydration to di-n-hexyl ether (DNHE) were determined at 150–190 °C on three acidic catalysts, the thermally stable resin Amberlyst 70, the perfluoroalkanesulfonic Nafion NR50 and the zeolite H-BEA-25, in a batch reactor. The highest conversion and yield were achieved on Amberlyst 70 at 190 °C, but the most selective catalyst was Nafion NR50. Good results were obtained at 190 °C on the zeolite. Apparent activation energies for the three catalysts were in the range 108–140 kJ/mol. Unlike H-BEA-25, the reaction of DNHE synthesis on Amberlyst 70 and NR50 was a bit more active but less selective than the analogous 1-pentanol dehydration to di-n-pentyl ether (DNPE).

Synergistic catalysis effect in pentanol conversion into di- n-pentyl ether on ZSM-5 supported titania catalysts synthesized by sol–gel

The synthesis of TiZSM-5 (TiZ) catalysts using acid catalyzed sol–gel method via different molar ratios of tetra-isopropyl orthotitanate [Ti(O-i-Pr) 4] was thoroughly characterized by inductively coupled plasma optical emission (ICP-OE), X-ray diffraction (XRD), particle size analyzer, N 2 adsorption, pyridine-FTIR and ultra-violet visible (UV–vis) spectroscopy. Liquid phase dehydration of 1-pentanol to di- n-pentyl ether (DNPE) was tested for the catalysts. Characterization of TiZSM-5 catalysts clearly shows that at low loadings (up to 5 wt%) titanium atoms were on the inner surface of zeolite layers mainly in tetrahedral environment as conceived from UV–vis (248–260 nm) and IR (960 and 1123 cm −1) results besides surface texturing data that showed lower surface areas (524–480 m 2 g −1) and pore volumes (0.4955–0.4530 cm 3 g −1) as compared to the parent (587 m 2 g −1 and 0.5642 cm 3 g −1). A distortion of tetrahedral Ti species was perceived at high-titania loadings (≥10 wt%) evidencing its existence on zeolite surfaces as a distinctive anatase phase. The catalytic dehydration of 1-pentanol over 5, 10 and 15 wt% TiZ catalysts achieved 70% conversion and 10TiZ showed the highest selectivity (60%) to DNPE. This was due to enhancing Brönsted acid sites, retaining crystallinity, decreased particles size and to the relatively large BET surface area. The effect of temperature (298–523 K), time (4–16 h), titania loadings (2.5–15 wt%) as well as solvent engagement on the selectivity to DNPE was thoroughly investigated. The nano-sized TiO 2 crystals in/on 10TiZ surfaces and zeolite pore volume seem to provide excellent possibilities for diffusion of reactants and products, which of significant importance in heterogeneous catalysis.

Liquid-phase dehydrocondensation of 1-pentanol to di- n-pentyl ether (DNPE) over medium and large pore acidic zeolites

The present paper deals with the liquid-phase synthesis of di- n-pentyl ether (DNPE) by dehydration of 1-pentanol over H-Beta, H-ZSM-5, H-mordenite and H-Y zeolites. Their SiO 2/Al 2O 3 ratios were about 25 for H-Beta, 28 for H-ZSM-5, 35 for H-mordenite and 6 for H-Y. Experiments were performed in a batch reactor in the temperature range 140–180 °C at 1.6 MPa. Comparison of the catalysts behaviour shows that H-Beta is the most active and selective to DNPE, although it is less active than microporous ion-exchange resins. Kinetics of DNPE synthesis was studied. The best kinetic model for all the catalysts stems from a reaction mechanism whose rate-limiting step is the surface reaction between two 1-pentanol molecules adsorbed on adjacent sites, to yield DNPE and water both adsorbed on single site. Activation energy, on each single catalyst, was estimated to be in the range 94–118 kJ mol −1.

Supported Nafion catalyst for 1-pentanol dehydration reaction in liquid phase

Abstract Silica-supported and alumina-supported Nafion catalysts that differ in surface area and Nafion contents were prepared using an impregnation technique. Liquid-phase dehydration of 1-pentanol to produce di-n-pentyl ether was used to measure their catalytic activity. A reproducible impregnation method was found, which considers a controlled evaporation of water and alcohols and a further washing with methanol before final drying. Only silica-supported catalysts were active for the alcohol dehydration reaction. Acid capacity and 1-pentanol conversion, increased on increasing the initial amount of Nafion. Despite 1-pentanol conversion obtained for all silica-supported catalysts were lower than that obtained for commercial Nafion NR50, turnover numbers were always better for impregnated catalyst. A maximum turnover number was found for 26 wt% loading of Nafion on silica. A kinetic model in terms of compounds activities describes satisfactorily the experimental kinetic data. It is based on a mechanism in which the rate-determining step is the surface reaction between two adjacent adsorbed 1-pentanol molecules. The apparent activation energy was found to be in the range 106–128 kJ mol−1.

Experimental Study of the Chemical Equilibria in the Liquid-Phase Dehydration of 1-Pentanol to Di-n-pentyl Ether

The thermodynamic equilibrium of the liquid-phase bimolecular dehydration of 1-pentanol to di-n-pentyl ether (DNPE) and water was studied in the temperature range of 423−463 K over Amberlyst 70. Furthermore, the equilibrium position of two side reactions could be followed, DNPE decomposition to 1-pentanol and 1-pentene and isomerization of 1-pentene to 2-pentene. The etherification reaction proved to be slightly exothermic, with an enthalpy change of reaction at 298.15 K of −(3.8 ± 0.6) kJ mol-1. From this value, the standard formation enthalpy and molar entropy of DNPE were computed to be −(421.1 ± 1.2) kJ mol-1 and 473.71 J (K·mol)-1, respectively. The enthalpy changes of the reaction of DNPE decomposition to 1-pentene and 1-pentanol and 1-pentene isomerization to 2-pentene were 63.4 ± 0.9 and −19.7 ± 2.1 kJ mol-1, respectively.

Water effect on the kinetics of 1-pentanol dehydration to di-n-pentyl ether (DNPE) on amberlyst 70

Experiments performed at 433 K and 453 K with 1-pentanol/water and 1-pentanol/DNPE (di-n-pentyl ether) clearly states the inhibiting effect of water released in the liquid-phase dehydration of 1-pentanol to DNPE on ion-exchange resin. The inhibiting effect of water was described by an empirical correction factor in the Eley–Rideal rate model deduced in a previous work. Best results were obtained with a factor including a Freundlich-like adsorption isotherm expression. The activation energy of dehydration reaction lowers slightly on splitting off the water effect, and it is 114.0 ± 0.1 kJ/mol.

Thermally stable ion-exchange resins as catalysts for the liquid-phase dehydration of 1-pentanol to di- n-pentyl ether (DNPE)

Conversion, selectivity, yield, and kinetics of the liquid-phase dehydration of 1-pentanol to di- n-pentyl ether (DNPE) were determined at 403–463 K on a recently developed sulfonated resin, Amberlyst 70, which is thermally stable up to 473 K. The behavior of Amberlyst 70 was compared with that of Nafion resin NR50, an H-Beta zeolite, and styrene-divinylbenzene resins stable up to 423 K (i.e., Amberlyst 36 and CT-224). Amberlyst 70 was found to be the most suitable catalyst for this application, showing the highest conversion and yield, with a selectivity to DNPE ⩾ 93%, despite the fact that NR50 showed the highest selectivity to ether at 423–463 K. The kinetic study reveals that a model stemming from an ER mechanism in which 1-pentanol from the liquid phase reacts with 1-pentanol adsorbed on a single center to give ether adsorbed on a single site represents data on each catalyst. The activation energy was computed to be in the range 110–120 kJ/mol on all the catalysts.

Dehydration of 1-pentanol to di- n-pentyl ether catalyzed by a microporous ion-exchange resin with simultaneous water removal

A good selectivity, more than 90%, and an excellent yield can be achieved in the DNPE synthesis by 1-pentanol dehydration at 130–155 °C using a gel-type acidic resin. It is the result of shifting the equilibrium point to DNPE formation through the removal of the formed water during the chemical reaction by distillation and reflux of the organic phase. Alkenes have been obtained as byproducts with selectivities ranging from 5 to 10% in the final product. A kinetic model in terms of compound activities describes satisfactorily the kinetic data. It is based on a mechanism in which the rate-determining step is the surface reaction between two adjacent adsorbed 1-pentanol molecules. The activation energy obtained for the dehydration reaction is 115 kJ mol −1. From the operation point of view, it has been proved that 1-pentanol dehydration can be successfully tracked by a calorimetric reactor equipped with a Fourier transform mid-infrared (FTIR) probe.

Conversion, Selectivity, and Kinetics of the Dehydration of 1-Pentanol to Di-n-Pentyl Ether Catalyzed by a Microporous Ion-Exchange Resin

Selectivity, yield, and kinetics of the liquid-phase dehydration of 1-pentanol to di-n-pentyl ether were studied experimentally over a commercial gel-type ion-exchange resin with 4% of cross-linking in the temperature range 120−150 °C at 1 MPa in a continuous stirred tank reactor. Selectivities to ether higher than 96% were obtained at all temperatures for space times greater than 5 g h mol-1. However, the obtained maximum yield is only 0.22 of 1. The best kinetic model stems from a mechanism in which 1-pentanol, adsorbed on one center, reacts with 1-pentanol from the liquid phase to give the ether adsorbed. The surface reaction is assumed to be the rate-limiting step, in which only one center takes part.

Dehydration of 1-pentanol to di- n-pentyl ether over ion-exchange resin catalysts

The dehydration reaction of 1-pentanol to di- n-pentyl ether (DNPE) and water in the liquid phase was studied at 110–180 °C and 1 MPa on sulfonic styrene–divinylbenzene (S/DVB) copolymers and the perfluoroalkanesulfonic resin NR50. S/DVB-based catalysts were macroreticular and gel-type resins both sulfonated conventionally and oversulfonated. Macroreticular resins tested include resins whose working phase in catalysis is gel phase (i.e. Amberlyst-15 and Amberlyst-35) and XN1010 whose working phase in catalysis is macropores surface. By comparing 1-pentanol conversion, selectivity to DNPE and initial reaction rates at 150 °C it is concluded that gel-type S/DVB resins that swell moderately in the reaction medium, as CT-224, are the more suitable catalysts for the reaction. NR50, which is thermally stable up to 200 °C, is the most selective catalyst tested but it is too much expensive for industrial use. Selectivity to DNPE decreases as temperature increases showing that side reaction of dehydration to 1-pentene is more sensitive to temperature. Apparent activation energies for the dehydration reaction of 1-pentanol to DNPE were found to be about 100 kJ/mol.

Kinetics of Catalytic Dehydration of 1-Pentanol

Kinetic data of 1-pentanol dehydration on γ-alumina catalyst modified by potassium hydroxide were obtained using a continuous reactor with an internal recirculation. The conversion of 1-pentanol on this catalyst in the temperature range 300 - 390 °C and space velocity 1 - 8 kg (h kg)-1 (molar fraction of water in the feed was in the range 0 - 0.56) was 50 - 98% and the selectivity with respect to 1-pentene was 50 - 84%. The following six reactions have been taken into account to describe the catalytic dehydration of 1-pantanol: direct formation of 1-pentene from 1-pentanol, formation of bis(1-pentyl) ether from 1-pentanol, disproportionation of the ether to 1-pentanol and 1-pentene, formation of 1-pentene from the ether, isomerization of 1-pentene to 2-pentene and hydrolysis of the ether to 1-pentanol. Treatment of experimental data by Langmuir-Hinshelwood models showed that the model involving adsorption of 1-pentanol accompanied by dissociation is the most suitable one.

The evaluation of ocular irritants using corneal protein profiles: Eurell, T. E. College of Veterinary Medicine, University of Illinois, Urbana, IL

Conversion, selectivity and yield of 1-hexanol liquid phase dehydration to di-n-hexyl ether (DNHE) were determined at 150–190 °C on three acidic catalysts, the thermally stable resin Amberlyst 70, the perfluoroalkanesulfonic Nafion NR50 and the zeolite H-BEA-25, in a batch reactor. The highest conversion and yield were achieved on Amberlyst 70 at 190 °C, but the most selective catalyst was Nafion NR50. Good results were obtained at 190 °C on the zeolite. Apparent activation energies for the three catalysts were in the range 108–140 kJ/mol. Unlike H-BEA-25, the reaction of DNHE synthesis on Amberlyst 70 and NR50 was a bit more active but less selective than the analogous 1-pentanol dehydration to di-n-pentyl ether (DNPE).

Formation of hexenes from 1-pentanol in the presence of cupric chloride

The dehydration of 1-pentanol in the presence of CuCl2 at 140–200‡ and a pressure of 5–80 atm, in either a CO or a N2 atmosphere, is accompanied by the formation, along with pentenes, of large amounts of hexenes (mainly cis- and trans-2-hexene).

Acidity of type Y zeolites with Ca, Sr, and Ba cations and their activity in the dehydration of 1-pentanol and the isomerization of 1-pentene

1. The acidity of 20 samples of type Y zeolites with various degrees of replacement of Na ions by Ca, Sr, and Ba cations was investigated. With increasing degree of replacement of Na by Ca and Sr cations, the acidity of type Y zeolites increases nonuniformly. A substantial increase in the acidity is observed after a 45–50% degree of exchange. The Ba-forms of zeolite showed comparatively low acidity. 2. The Ca- and Sr-forms of type Y zeolites showed similar catalytic activity in the dehydration of 1-pentanol and the isomerization of 1-pentene.

Effect of treating aluminum oxide with acetic acid on its activity in dehydration of 1-pentanol and isomerization of 1-pentene

1. After treatment with acetic acid, the catalytic activity of aluminum oxide increased as regards shift of the double bond, and hardly changed as regards dehydration of an alcohol. 2. Sodium ions are removed when aluminum oxide is treated with acetic acid. In this connection the value of its specific surface area shows little change, while the acidity increases. 3. The obtained data confirm the assumption that alcohol dehydration and olefin isomerization proceed on different sites of the catalyst surface.