Dehydration Of 1-butanol Research Articles

Catalytic Reactions of 1-Butanol over AlPO4Catalysts Induced by B2O3

A series of AlPO4–B2O3 samples containing 5–50 wt% B2O3 were prepared. Their textural properties were determined from studies of the adsorption of nitrogen at −196°C. The structural characteristics were investigated using DTA, TG, XRD and FT-IR methods. Surface acidity was determined from the adsorption of n-butylamine in non-aqueous media. The vapour-phase catalytic conversion of 1-butanol over the prepared catalysts was followed using a micro-catalytic pulse technique. The incorporation of B2O3 into AlPO4, as well as the calcination temperatures employed, led to significant changes in the textural parameters and crystallinity of the catalysts and in their surface acidity. The dehydration of 1-butanol to 1-butene and dibutyl ether (DBE) was strongly influenced by the surface acidity and the boron content of the samples.

Dehydration of 2-butanol by a sulfated zirconia/γ-alumina mixed metal oxide catalyst inside a gas chromatograph injection port

A sulfated zirconia/γ-alumina mixed metal oxide catalyst is prepared and utilized in the injection port of a gas chromatograph (GC) for the investigation of 2-butanol dehydration. A linear correlation ( R 2=0.996) is found between the areas of the chromatographed butene peaks and the concentration of 2-butanol in dichloromethane standard solutions ranging from 0.003 to 3 vol.%, the injector temperature maintained at 250 °C. The kinetics of the alcohol dehydration are studied by varying the injector temperature. The data is found to support a pseudo-first-order reaction mechanism, with two different apparent activation energies observed over two distinct temperature ranges: 15 kJ/mol for the higher temperature range (∼150–325 °C) and 46 kJ/mol for the lower temperature range (75 to ∼150 °C) studied. The lower apparent activation energy obtained at the higher injector temperatures is attributed to mass transport-limited kinetics, while the higher apparent activation energy barrier observed at the lower temperatures suggests that the surface alcohol dehydration reaction provides the rate-limiting step. Following exposure to stress conditions, the coke-deactivated catalyst surface is observed by scanning electron microscopy (SEM).

Unusual acceleration of acid-catalyzed reactions by water in the presence of Mo/Zr mixed oxides calcined at high temperatures

Various acid-catalyzed reactions, such as hydrolysis of ethyl acetate, esterification of acetic acid with ethanol, dehydration of 2-butanol, isomerization of 1-butene, and skeletal isomerization of n-butane, in the presence of Mo–Zr mixed oxides and other solid acids have been studied. MoO3/ZrO2 exhibited high activities only for the hydrolysis and esterification reactions, in which these high catalytic activities could not be explained by the acidic property of MoO3/ZrO2 alone, as shown by NH3–temperature programmed desorption (TPD) studies. It was found that the addition of water significantly accelerated the esterification and dehydration in the presence of MoO3/ZrO2 (calcined above 973 K), wheras SiO2–Al2O3 was greatly deactivated by water under similar reaction conditions. Furthermore, in the presence of water vapor, the activity of MoO3/ZrO2 for the isomerization of 1-butene did not decline, whereas SiO2–Al2O3 became inactive completely. IR measurements revealed that the water adsorbed on MoO3/ZrO2 (calcined at 1073 K) gave a sharp peak at 1628 cm−1, and that this peak gradually decreased at 423 K, while ZrO2 only or MoO3/ZrO2 (calcined at 673 K) did exhibit well-defined peaks. Since the adsorption-desorption behavior of water was in good agreement to the catalytic activity for dehydration of 2-butanol, the acceleration by water was presumably a result of the generation of acid sites by the dissociation of water molecules that are coordinated on the Mo species of MoO3/ZrO2.

Surface Characterization and Catalytic Activity of Alumina and Alumina-Supported ZnSO4 Catalysts Prepared from Different Alumina Sources

Three alumina samples were prepared from different sources including aluminium isopropoxide, aluminium chloride and aluminium nitrate, and were then used to prepare supported ZnSO4 catalysts via the impregnation method. The alumina and ZnSO4-supported samples were characterized by X-ray diffraction (XRD), FT-IR spectroscopy and nitrogen physisorption methods. Dehydration of 1-butanol and the cracking of cumene were undertaken over the prepared samples using a pulse microcatalytic technique. For a given alumina sample, the surface area and total pore volume decreased continuously with increasing ZnSO4 content. Loading alumina samples with ZnSO4 improved their dehydration and cracking activities. The source of alumina played a role in determining the surface acidity and catalyst activity of alumina and alumina-supported ZnSO4 catalysts. Impregnation of ZnSO4 on alumina samples resulted in an increase in the concentration of Lewis sites and the creation of Brönsted acid sites on their surfaces. The catalytic activity of the investigated catalysts was found to depend strongly on both the chemical composition and the type of acid site present on the catalyst surface.

Genesis of Brønsted Acid Sites during Dehydration of 2-Butanol on Tungsten Oxide Catalysts

In situ measurements of Brønsted acid sites (by titration with 2,6-di-tert-butyl-pyridine) and reduced centers (by UV–vis spectroscopy) were carried out on WOx–ZrO2 with catalysts at 2.9–32.3 W/nm2 in order to probe how these species form and act as active sites during 2-butanol dehydration. The rate of 2-butanol dehydration (per W-atom) on WOx–ZrO2 reached maximum values at intermediate WOx surface densities, as was also found previously for o-xylene and n-pentane isomerization. Polytungstate domains prevalent at these surface densities balance the accessibility of W6+ centers with their ability to reduce to form Brønsted acid sites via reduction with 2-butanol. In situ UV–vis spectra showed that 2-butanol reduces WOx species and that the highest density of the Brønsted acid sites formed is obtained at WOx surface densities similar to those required for maximum dehydration rates. Brønsted acid site densities were measured during 2-butanol reaction using sterically hindered 2,6-di-tert-butyl-pyridine, which titrates only Brønsted acid sites. 2-Butanol dehydration requires Brønsted acid sites that form during reaction at low concentrations (0.040 sites/W-atom) and reach their highest concentration at intermediate WOx surface densities (6.8–14.8 W/nm2). Pre-edge features in UV–vis spectra are weak for monotungstate species (<4 W/nm2) and their intensity increase is parallel to that observed in 2-butanol dehydration rates, confirming the requirement for active Hδ+ (WO3)nδ− species, formed during reaction and stabilized by polytungstate domains. Turnover rates (per Brønsted acid site) are much higher on WOx–ZrO2 than on Lewis acid sites active for 2-butanol dehydration on γ-Al2O3. 2-Butanol dehydration turnover rates (per Brønsted acid site) on SiO2-supported tungstophosphoric acid (HPW), however, are higher than those on WOx–ZrO2. The mechanism-based rate equation developed for 2-butanol dehydration and the faster secondary butene isomerization found on HPW suggest that acid sites are weaker on HPW than on WOx–ZrO2. A weaker acidity is indeed expected from the stronger conjugate base provided by the smaller WOx domains and the larger H+/W ratio in HPW clusters. Weaker acid sites allow faster product desorption and higher turnover rates from saturated surfaces during 2-butanol dehydration.

Unprecedented Acceleration Effects of Water on Acid-Catalyzed Reactions Over Molybdena-Zirconia Catalysts

Effects of water on various acid-catalyzed reactions have been studied mainly using MoO3/ZrO2. While the reaction rate of gas-phase esterification of acetic acid with ethanol and the dehydration of 2-butanol over SiO2-Al2O3 decreased significantly by the addition of water vapor in the feed gas, these reactions over MoO3/ZrO2 were found to be greatly enhanced by the presence of water. The enhancement by water was reversible and was remarkable when MoO3/ZrO2 was calcined at a temperature range of 773-1073 K. IR spectroscopy of H2O adsorbed on MoO3/ZrO2 suggests that the acceleration effect of water would be due to the generation of acidic sites from water coordinated to Mo species on the surface of MoO3/ZrO2.

Kinetic Study on 2-Methyl-1-Butanol Dehydration Catalysed by Ion Exchange Resin.

The dehydration of 2-methyl 1-butanol (2M1BOH) in the liquid phase was studied by using an ion-exchange resin, Amberlyst 15 in the H+ form. Experiments were carried out in a batch reactor with the dry resin as a catalyst. Considering the inhibition effect of water, the rate expressions based on the Langmuir-Hinshelwood model were formulated. The sorption equilibrium model between liquid and resin phases during resin swelling was included in kinetic modelling. The cross-linked ion-exchange resin was highly selective to water at the beginning of the reaction. The experimental results agreed well with the calculated ones.

Dehydration of Alcohols by Microporous Niobium Silicate AM-11

The dehydration of ethanol, 1-propanol and 1-butanol has been studied at atmospheric pressure using the novel microporous niobium silicate AM-11 (Aveiro–Manchester structure number 11) in the temperature range 150–300 °C. The selectivity for alkenes increases with temperature for all three alcohols and reaches 100% for 100% conversion at 250–300 °C. At lower reaction temperatures (∼200 °C), ethers are also formed and their selectivity decreases markedly with the alcohol size.

New insights in the understanding of the behaviour and performances of bismuth molybdate catalysts in the oxygen-assisted dehydration of 2-butanol

Pure Bi 2Mo 3O 12, Bi 2Mo 2O 9, Bi 2MoO 6, MoO 3 and α-Sb 2O 4 and their mechanical mixtures were investigated in the oxygen-assisted dehydration of 2-butanol at atmospheric pressure and at low temperature (220 and 250°C). All catalysts were characterized before and after the catalytic reaction by BET surface area measurement, Raman spectroscopy, XRD and XPS. A strong parallelism is confirmed with the results obtained in the selective oxidation of olefins. In the frame of the remote control concept, α, β and γ-bismuth molybdates are able to play a dual role: donor of spillover oxygen (Oso) with respect to MoO 3, and acceptor of Oso with respect to α-Sb 2O 4. On one hand, this duality leads to mutual increase of activity when the bismuth molybdates are mixed together. In the presence of MoO 3, the α phase seems to be a stronger Oso donor than β and γ, and β has a donor strength between α and γ. On the other hand, when the Bi molybdates are reacted in the presence of a big quantity of spillover oxygen, like in a mixture with α-Sb 2O 4, they undergo a dramatic decrease of activity. The phenomenon originates from the full oxidation of the reduced Mo species to Mo 6+ induced by Oso. In parallel with other reactions involving oxygen, this confirms that the real active and selective state of molybdenum-containing oxides is that slightly reduced possessing Mo 5+.

Effect of sulfation methods on TiO 2–SiO 2 sol–gel catalyst acidity

A series of x TiO 2–SiO 2 ( x=1.7, 4.0 and 6.7 wt.% TiO 2) binary mixed oxides was prepared by a sol–gel method in acidic and basic conditions. In order to upgrade the acidic properties of the obtained solids, their sulfation was carried out in three different ways: (1) by in situ (H 2SO 4 was admixed with the gel), (2) impregnating the dried solids with aqueous solutions of H 2SO 4, and (3) by impregnating as in (2) but with (NH 4) 2SO 4. FTIR-pyridine adsorption and benzene deuteroexchange showed that the acid site strength depends on the sulfation method. The highest values of total acidity, determined by ammonia thermodesorption, correspond to the in situ sulfated samples. The obtained pore size distribution (4.0–5.0 nm) was narrow and the specific BET areas (250–350 m 2/g) were large. X-Ray diffraction, RDF, XPS spectroscopy and catalytic activity in the 2-butanol dehydration show that one step sulfated in situ TiO 2–SiO 2 sol–gel preparations resulted in catalysts with homogeneous and strong acidity.

Synthesis and Characterization of TiO2−MgO Mixed Oxides Prepared by the Sol−Gel Method

Titania−magnesia mixed oxides, with magnesia concentrations between 10 and 90 wt %, were prepared by using the sol−gel method with titanium n-butoxide and magnesium ethoxide as precursors. The mixed oxides were characterized with X-ray powder diffraction, BET nitrogen adsorption isotherms, electron spin resonance (ESR), and by testing their catalytic activity for 2-propanol and 2-butanol dehydration. Samples contained periclase, anatase, karooite (MgTi2O5), geikielite (MgTiO3), and qandilite (Mg2TiO4). The BET specific surface area varied with magnesia concentration; the samples with 50 wt % MgO had the highest area, 211 m2/g. Samples had paramagnetic centers that produced complex ESR spectra when many crystalline phases coexisted. For 2-propanol and 2-butanol decomposition, the activity and selectivity patterns of the mixed oxides were substantially different to those observed in pure TiO2 and pure MgO. This singular behavior should be a result of the structural defects created by the substitution of Mg2...

Acidic–base properties of silica–magnesia sol–gel mixed oxides: use of 2 butanol as test reaction

2-butanol dehydration was performed as a test reaction for acid–base characterization of a series of unsulfated and sulfated silica–magnesia sol–gel mixed oxides covering the 1.3–6.7% MgO composition range. The dehydration of 2-butanol over non-sulfated silica–magnesia yields a mixture of butenes in which the fraction of 2-butene (Saytzeff orientation) is 33%. High selectivity for 1-butene (Hofmann orientation) is indicative of the E1cB mechanism over sulfated silica–magnesia oxides. The acid–base properties were also investigated by ammonia and carbon dioxide TPD and FTIR spectroscopy of adsorbed pyridine. Acid–base properties are discussed as a function of magnesium content (nature, strength and amount of sites). A very good correlation between the results of test reactions and acid–base characterization methods is observed.

Acidity studies on pillared clays (PILCs) by pyridine adsorption and 1-butanol dehydration

A study was made on the acidic properties of clays, from different parent materials, pillared with aluminium or zirconium species. In conjunction with the well known method of pyridine desorption followed by infrared spectroscopy, the reaction test of 1-butanol dehydration was carried out. Also the heats of adsorption and the amounts of adsorbed pyridine, were determined by a thermogravimetry coupled with Differential Scanning Calorimetry (TG-DSC). The information on the acidic properties of the materials, obtained by the three methods, is discussed and it is concluded that the latter method (TG/DSC), although not currently used as one could expect, is sufficiently expedite and appropriate for this purpose.

Structural and surface properties of SnO2–AlPO4 catalysts in relation to their dehydration activities

Abstract Pure AlPO4 (Al/P=1) and SnO2–AlPO4 mixed catalysts containing different amounts of SnO2 were prepared at 283 K and thermally treated in air at 773 K. The catalysts were characterized using DTA and XRD techniques. The textural properties were determined from the adsorption of nitrogen at 77 K. The surface acidity was measured by the amine titration method. The dehydration of 2-propanol and 1-butanol on the prepared catalysts has been investigated using a pulse microcatalytic reactor. Significant changes in texture, surface acidity and catalytic activity were found as a result of the effect of chemical compositions. All the investigated catalysts exhibited higher dehydration activities of 2-propanol than the corresponding activities towards the dehydration of 1-butanol. No dehydrogenation products were detected by any of the investigated catalysts, under the present experimental conditions. Dehydration of alcohols is related to the surface acid density and is structurally insensitive.

Tantalum Pillared Montmorillonite: II. Acidic and Catalytic Properties

The acidic and catalytic properties of a series of Ta-PILCs synthesized with a different initial tantalum content were characterized by adsorption of gaseous probe molecules (TPD of ammonia and FTIR spectra of absorbed pyridine) and by the test reaction of 1-butanol dehydration. A large increase of acidity was noted in Ta-PILCs compared to Na-montmorillonite or tantalum oxide. Cross-linking pillars and silica layers of the clay induce stronger Lewis and new Brønsted sites. The lack of basic sites formation is evidenced by the dehydration of 1-butanol to butene selectivity (100%). The incorporation of the tantalum oxide between the montmorillonite sheets produce, within Ta-PILC, acid centers of the same nature as observed for the silicon–tantalum mixed oxides.

Modification of the Interlayer in Lanthanum–Niobium Oxide and Its Catalytic Reactions

The methods for preparation of pillared materials with ZrO2, TiO2, or SiO2in the interlayer of layered perovskite structural oxides, HLaNb2O7(HLa), were examined in detail. HLa that had been intercalated withn-amines of different carbon chain lengths was used in pillaring ZrO2.N-octyl- and decylamine were useful in the construction of the pillar. It is of critical importance to enlarge the interlayer spacing of the HLa by using filling withn-octylamine for the intercalation of the precursor of ZrO2, TiO2, or SiO2. The precursor of ZrO2or TiO2could easily be intercalated by exchange withn-octylamine. When pillaring with SiO2was done, the preparation was not as easy as pillaring with ZrO2or TiO2. The molar ratio of tetraethoxysilane (TEOS), the concentration of HCl, and the amount of ethanol was closely related in the preparation. The optimum preparation condition was a molar ratio of TEOS:ethanol:HCl (2 or 3M) of 10:5:0.5 to 1 mol of HLaNb2O7fully filled withn-octylamine at 40°C. Thus, the materials prepared (by pillaring with ZrO2, TiO2, or SiO2) were used as a catalyst in the dehydration of 1-butanol. Enhancement of activity was detected on all the pillared catalysts. It was caused by interaction between the pillaring material and the host matrix. The TiO2pillared catalyst exhibited the highest activity in hydration, followed by the ZrO2and SiO2pillared catalysts. All of the catalysts that were examined consisted of a large amount of mesopore, in which the TiO2pillared catalyst exhibited the presence of a larger ratio of mesopore, as compared with other catalysts.

Catalytic synergy via spillover at low temperature: the dehydration and dehydrogenation of sec-butanol in the presence of oxygen

This paper reports results concerning the dehydration-dehydrogenation of 2-butanol at low temperatures over mechanical mixtures of oxides: α-Sb 2O 4 + SnO 2 and α-Sb 2O 4 + MoO 3, where each pure oxide had been prepared separately. The temperatures of reaction were 240°C and 190°C, respectively, for the two mixtures. Both mixtures exhibited better performances than the pure oxides. The α-Sb 2O 4 + SnO 2 mixture was not active in 2-butanol dehydration. The yields and the selectivities for butene and/or methyl-ethyl-ketone obtained in the other cases were higher than the theoretical values calculated from the activities of the pure oxides. SBET, XRD and XPS measurements before and after the catalytic reaction did not indicate any change of phase or a contamination during the preparation of the mixtures or during the reaction. The synergetic effects between the phases are therefore explained by the occurrence of a ‘remote control mechanism’ acting via the migration of spillover oxygen species. These are the first instances of a remote control operating at temperatures of reaction below 250°C. The actions of spillover are the same as at high temperature: creation of new acid sites on MoO 3, regeneration (reoxidation) of the reduced deactivated redox sites on both SnO 2 and MoO 3 and inhibition of the coke formation during the reaction.

Alcohol Dehydration: Mechanism of Ether Formation Using an Alumina Catalyst

Ether formation during the dehydration of secondary alcohols, namely, 2-butanol, 3-pentanol, and 1-cyclopentylethanol, was investigated. Using the proper reaction conditions, the yield of di-2-butyl ether during the dehydration of 2-butanol on alumina can be as high as 40%. That ether is formed by adding an alcohol to the alkene is ruled out by the results from deuterium tracer studies. Results from experiments using S(+)-2-butanol suggest that the formation of di-2-butyl ether occurs by a SN2-type mechanism.

Synthesis and properties of pillared montmorillonite formed by intercalation of transition metal macrocyclic complexes

The transition metal macrocyclic complex cations M-( trans-14-diene) 2+ (M=Co, Ni, Cu and Zn) were introduced into the interlayers of a sodium montmorillonite clay. The resulting clays were calcined at various temperatures. All samples were thermally stable up to 300°C with interlayer distances of 4.9 ∼ 5.1 Å and specific surface areas of 57 ∼ 86 m 2 g −1. Both the Lewis and the Brönsted acid sites were identified by Fourier transform infrared (FTIR) measurements of adsorbed pyridine. The catalyst acidity was obtained from the temperature-programmed desorption (TPD) of ammonia. The catalytic activities in the dehydration of both 2-propanol and 2-butanol were correlated to the surface area and the strong acid amount of these intercalated clays.

1-Butanol dehydration on AlPO 4 and modified AlPO 4: catalytic behaviour and deactivation

Synthesis and physico-chemical characterization of a pure A1PO 4 and A1PO 4 modified by introduction of SO 4 2− ions (2 wt.-%) or Na + ions (0.5 wt.-%) have been carried out. The influence of these ions on A1PO 4 activity and selectivity in the 1-butanol dehydration has been investigated. The acid-base properties of these catalysts were determined by ammonia and carbon dioxide TPD and FT-IR spectroscopy of absorbed pyridine. Ion incorporation leads to a modification in the A1PO 4 acid-base properties, especially on the acid sites strength, with only very minor modification of its textural properties. Thus, Na + ions decreased the number of strong acid sites whereas SO 4 2− ions increased it. A linear relationship between those acid sites and selectivity values was found. Butenes (1-butene and 2-butenes) selectivities increased when the concentration of stronger acid sites was increased while the opposite trend was observed for dibutyl ether selectivity. The resistance to deactivation of the catalysts was examined not only in function of time on-stream in the 1-butanol dehydration but also after treatment with water or methylcyclopentane in the feed (for generating coke). Both factors negatively affected the A1PO 4 activity and the reaction temperature determined which factor was of prevailing influence. Besides, acid sites strength had an important role in the A1PO 4 deactivation.